key: cord-0975820-kebvzeg4
authors: Sipkema, Detmer; Franssen, Maurice C. R.; Osinga, Ronald; Tramper, Johannes; Wijffels, René H.
title: Marine Sponges as Pharmacy
date: 2005-03-24
journal: Mar Biotechnol (NY)
DOI: 10.1007/s10126-004-0405-5
sha: 770e5fe89399378bcc9f35a003c5a0cf3e8b1d9c
doc_id: 975820
cord_uid: kebvzeg4

Marine sponges have been considered as a gold mine during the past 50 years, with respect to the diversity of their secondary metabolites. The biological effects of new metabolites from sponges have been reported in hundreds of scientific papers, and they are reviewed here. Sponges have the potential to provide future drugs against important diseases, such as cancer, a range of viral diseases, malaria, and inflammations. Although the molecular mode of action of most metabolites is still unclear, for a substantial number of compounds the mechanisms by which they interfere with the pathogenesis of a wide range of diseases have been reported. This knowledge is one of the key factors necessary to transform bioactive compounds into medicines. Sponges produce a plethora of chemical compounds with widely varying carbon skeletons, which have been found to interfere with pathogenesis at many different points. The fact that a particular disease can be fought at different points increases the chance of developing selective drugs for specific targets.

The relationship between sponges and medicines goes back to Alexandrian physicians and was thoroughly describes by the Roman historian Plinius. Physicians used sponges that were saturated with iodine to stimulate coagulation of the blood, or with bioactive plant extracts to anesthetize patients. Sponges were soaked with pure wine and put on the left part of the chest in case of heartaches and soaked in urine to treat bites of poisonous animals. Plinius recommended the use of sponges against sunstrokes, and they were used against all kinds of wounds, bone fractures, dropsy, stomach aches, infectious diseases, and testicular tumors (Hofrichter and Sidri, 2001), or even as implants after breast operations (Arndt, 1938) . At least since the 18th century, Russian, Ukrainian, and Polish physicians have used a freshwater sponge they call Badiaga (Figure 1 ) for the treatment of patients (Nozeman, 1788). The dry powder of this sponge is rubbed on the chest or back of patients with lung diseases or on the sore places in cases of foot and leg aches (such as rheumatism (Schroder, 1942) . Oficjalski (1937) discovered that Badiaga is not really one sponge, but mixtures of several freshwater sponges that differ depending on the region. In Poland it consisted of powder of Euspongilla lacustris, Ephydatia fluviatilis, and Meyenia muelleri, while the Russian Badiaga was a mixture of Euspongilla lacustris, Ephydatia fluviatilis, Spongilla fragilis, and Carterius stepanowi. He suggested that the high iodine concentration in all sponge species gives rise to the wholesome effect of Badiaga. At present Stodal, syrup containing roasted Spongia officinalis, is used for homeopathic treatment of dry and asthmatic cough in the Western world (Stodal, 2003) .

Pharmaceutical interest in sponges was aroused in the early 1950s by the discovery of a nucleosides spongothymidine and spongouridine in the marine sponge Cryptotethia crypta Feeney, 1950, 1951) . These nucleosides were the basis for the synthesis of Ara-C, the first marine-derived anticancer agent, and the antiviral drug Ara-A (Proksch et al., 2002) . Ara-C is currently used in the routine treatment of patients with leukemia and lymphoma. One of its fluorinated derivatives has also been approved for use in patients with pan-Correspondence to: Detmer Sipkema; E-mail: detmer.sipkema@ wur.nl creatic, breast, bladder, and lung cancer (Schwartsmann, 2000) . At the same time it was revealed that certain lipid components such as fatty acids, sterols and other unsaponifiable compounds occur in lower invertebrates in a diversity far greater than that encountered among animals of higher organization (Bergmann and Swift, 1951) . These early promises have now been substantiated by an overwhelming number of bioactive compounds that have been discovered in marine organisms. More than 15,000 marine products have been described thus for (MarinLit, 1999; Faulkner, 2000 Faulkner, , 2001 Faulkner, , 2002 .

Sponges, in particular, are responsible for more than 5300 different products, and every year hundreds of new compounds are being discovered (Faulkner 2000 (Faulkner , 2001 (Faulkner , 2002 .

Most bioactive compounds from sponges can be classified as antiinflammatory, antitumor, immunosuppressive or neurosuppressive, antiviral, antimalarial, antibiotic, or antifouling. The chemical diversity of sponge products is remarkable. In addition to the unusual nucleosides, bioactive terpenes, sterols, cyclic peptides, alkaloids, fatty acids, peroxides, and amino acid derivatives (which are frequently halogenated) have been described from sponges ( Figure 2 ).

For this review we have surveyed the discoveries of products derived from marine sponges up to now, and attempted to show the variety of potential medical applications of metabolites from sponges and the mechanisms by which they interfere with the pathogenesis of human diseases. This knowledge is a prerequisite for the development of a drug from a bioactive compound. For example, many secondary metabolites inhibit growth of cancer cell lines, but this does not imply that they will be suitable as a medicine against cancer, because they may exhibit important side effects. The following sections summarize compounds by disease type and describe their mode of action, and discuss the reasons why sponges would produce these metabolites.

Antiinflammatory Compounds. Acute inflammations in the human body can result from microbial infection, physical damage, or chemical agents. The body reacts by changing the blood flow, increasing the permeability of blood vessels, and allowing the escape of cells from the blood into the tissues (Tan et al., 1999) . Chronic inflammation of the skin or joints may severely damage the body if it leads to psoriasis or rheumatic arthritis (Pope et at., 1999) . Sponges have proved to be an interesting source of antiinflammatory compounds (Table 1) .

Manoalide, one of the first sesterterpenoids to be isolated from a marine sponge (Luffariella variabilis), was found to be an antibiotic (De Silva and Scheuer, 1980) and an analgesic (Mayer and Jacobs, 1988 ). In addition, its antiinflammatory properties have been studied extensively (Bennet et al., 1987) . The antiinflammatory action is based on the irreversible inhibition of the release of arachidonic acid from membrane phospholipids by preventing the enzyme phospholipase A 2 from binding to the membranes (Glaser et al., 1989) . A rise in the intracellular arachidonic acid concentration would lead to upregulation of the synthesis of inflammation mediators as prostaglandins and leukotrienes (Figure 3) . Phospholipase A 2 inhibition has been recorded for many sesterterpenes from sponges of the order Dictyoceratida, but also for bis-indole alkaloids such as topsentin (Jacobs et al., 1994) . The mechanism by which they affect the inflammation process is different from commonly used nonsteroidal antiinflammatory drugs. Only a few sponge-derived terpenoids have been found to inhibit lipoxygenase, another enzyme that is involved in the inflammatory response (Carroll et al., 2001) .

The antiinflammatory sponge products are selective inhibitors of specific enzymes of a range of diseases, like psoriasis or rheumatic arthritis. The currently used nonsteroidal antiinflammatory drugs often fail to control the disease and present important side effects such as risk of gastrointestinal bleeding and renal complications (De Rosa, 2002) . These are caused by unselective inhibition of cyclooxygenases, some of which are also involved in the promotion of the production of the natural mucus that protects the gastrointestinal tract (Bjarnason et al., 1993) . Antitumor Compounds. A number of isolated sponge compounds are inhibitors of protein kinase C (PKC). PKC inhibitors have attracted interest worldwide, as there is evidence that too high levels of PKC enzyme are involved both in the pathogenesis of arthritis and psoriasis (owing to regulation of phospholipase A 2 activity), and in tumor development (Bradshaw et al., 1993; Yoshiji et al., 1999) . PKC is believed to be the receptor protein of tumor-promoting phorbol esters, and PKC inhibitors prevent binding of carcinosarcoma cells to the endothelium (B. Liu et al., 1991) . Glycosylation of the receptors, and especially the presence of fucose residues, plays an important role in the binding of carcinosarcoma cells and leukocytes to the receptors in the endothelium (Springer and Lasky, 1991) .

Fucosyltransferase inhibitors, such as the octaand nonaprenylhydroquinone sulfates that were isolated from a Sarcotragus sp. (Wakimoto et al., 1999) , may therefore be promising candidates for controlling inflammatory processes such as arthritis or for combating tumor growth.

In addition to PKC inhibitors and fucosyl transferase inhibitors, numerous anticancer molecules with a different mode of action have been discovered in marine sponges (Table 2) . These compounds can be divided in 3 classes:

(1) nonspecific inhibitors of cell growth; (2) specific inhibitors of cancer cells; and (3) inhibitors of cancer cells of a certain type of cancer (as the aforementioned PKC inhibitors).

Many nonspecific cell growth inhibitors have been discovered in sponges. They are valuable for treating cancer under certain conditions, but they also affect the division of healthy cells. Therefore, their applications are limited, depending on their specific characteristics. The cytoskeleton is an interesting target for cancer therapy, as the microtubules and microfilaments are involved in cellular organization during cell division. A number of adociasulfates (triterpenoid hydroquinones) from a Haticlona sp. were the first inhibitors of the kinesin motor protein to be discovered. These toxins are believed to inhibit the protein by binding to the microtubule binding site, ''locking up'' the proteinÕs motor function, and thereby blocking cell division (Blackburn et al., 1999) . In addition to these triterpenoid hydroquinones, a number of potent microtubule-interfering compounds have been discovered in marine sponges, such as halichondrin B (Bai et al., 1991) , spongistatin (Bai et al., 1993) , discodermolide (Ter Haar et al., 1996) , laulimalide (Moobeny et al., 1999), peloruside A (Hood et al., 2002) , and dictyostatin (Isbrucker et al., 2003) . Other metabolites, such as latrunculin A from Latrunculia magnifica (Coue et al., 1987) and swinholide A from Theonella swinhoei (Bubb et al., 1998), disrupt the polymerization of actin. Actin which is the key element of the microfilaments, and it can block many cellular processes including cell division. Spongiacidin B (Inaba et al., 1998) and fascaplysin (Soni et al., 2000) are examples of sponge-derived metabolites that inhibit cell division by inhibition of cyclin-dependent kinase 4, which leads to arrest of cells in the G1 phase. Other metabolites, such as mycalamide (Burres and Clement, 1989) and aragusterol (Fukuoka et al., 2000) , disturb cell division by inhibition of protein synthesis. Neoamphimedine (De Guzman et al., 1999) and elenic acid (Juagdan et al., 1995) inhibit the development of tumors by blocking topoisomerase II, the nuclear enzyme which makes transient DNA breaks that are required for replication (L.F. Liu and Chen, 1994) .

Nitric oxide synthetase inhibitors, such as the imidazole alkaloid Na amine D that was isolated from the calcareous sponge Leucetta cf. chagosensis (Dunbar et al., 2000) , are not involved in growth inhibition of cancer cells, but may prevent events in the early phases of tumorigenesis. Nitric oxide could participate in the tumorigenesis by mediating DNA Fig. 3 . Inflammatory cascade inside the cell. Phospholipase A 2 (PLA 2 ) catalyzes the release of membrane-bound arachidonic acid (AA) to free arachidonic acid. Arachidonic acid is converted to leukotrienes and prostaglandins by lipoxygenase (LOX) and cyclooxygenase-2 (COX-2), respectively. Spongederived antiinflammatory molecules are mainly inhibitors of PLA 2 or LOX, while nonsteroidal antiinflammatory drugs inhibit COX-2, but also the constitutive COX-1. damage and support tumor progression through the induction of angiogenesis (Lala and Orucevic, 1998) . However, inhibition of nitric oxide synthetase may also affect other physiologic processes in which nitric oxide is involved, such as intracellular or transcellular messaging, and it is involved in regulation of the immunogenic respons by T lymphocytes. Agelasphin (KRN7000) from Agelas mauritianus (E. Kobayashi et al., 1995) has been found to stimulate the immune system by activation of dendritic and natural killer T (NKT) cells. The NKT cell level is lower in the blood of patients with cancer or autoimmune disease, such as type 1 diabetes (Shimosaka, 2002) , and in mice it was shown that tumors could be rejected by stimulation of the immune system by agelasphin (Yamaguchi et al., 1996) . The activity of other compounds is more specific toward tumor cells. Multidrug resistance in human carcinoma cells caused by overexpression of two kinds of membrane glycoproteins is reversed by agosterol A from the marine sponge Spongia sp. It has been suggested that an altered cytosolic pH plays a role in drug resistance. Vascular (H + ) AT-Pase (v-ATPase) is an enzyme involved in many cellular processes that are often upregulated in cancer cells, such as acidic vesicular organelle formation, which is a response to radiation injury or manipulation of the pH to decrease entry of chemotherapeutics into the cells (Martinez-Zaguilan et al., 1999). Salicylihamide A was isolated from a Haliclona sp. as a selective inhibitor of v-ATPase and has been shown to be 60-fold more cytotoxic to certain cancer cells than to their normal noncancerous counterparts (Erickson et al., 1997). The first natural 6-hydroximino-4-en-3-one steroids were isolated from Cinachyrella spp. (Rodriguez et al., 1997) and are examples of molecules that can be deployed against a specific type of cancer. They displayed high affinity to aromatase (Holland et al., 1992), which is the rate-limiting enzyme that catalyzes the conversion of androgens to estrogens ( Figure 4 ). Blockade of this step allows treatment of hormone-sensitive breast cancer that is dependent on estrogen (Lonning et al., 2003) . A peculiar fact about the 6-hydroximi no-4-en-3-one steroids is that they were chemically synthesized before they were even discovered in nature.

In addition, many more compounds that displayed growth inhibition activity of tumor cell lines have been isolated (Table 2) Immunosuppressive Compounds. In addition to their potential for treatment of cancer, nitric oxide synthetase inhibitors downregulate T-cells are, suppressing the immune system, and they diminish the fierceness of migraine attacks (Griffith and Gross, 1996). Immune system suppression is desired in cases of hypersensitivity to certain antigens (e.g., allergies) or organ transplantations. Patients who receive a donor organ need life-long medication to prevent rejection by the immune system, and for that reason it is extremely important that these medicines are very specific suppressors. Therefore there is a continuous demand for new immunosuppressives. A number of new molecules with immunosuppressive activity, which interfere at different points of the immune response have been discovered in marine sponges (Table 3; Figure 5 ).

Three polyoxygenated sterols from a Dysidea sp. from Northern Australia are selective immunosuppressive compounds that inhibit the binding of interleukin 8 (IL-8), a cytokine that attracts neutrophils into an area of tissue injury, to the IL-8 receptor (Leone et al., 2000) . The simplexides from the Caribbean sponge Plakortis simplex are a group of immunosuppressive glycolipids that inhibit proliferation of activated T cells by a noncytotoxic mechanism (Costantino et al., 1999). Pateamine A, from a Mycale sp., inhibits the production of IL-2 (Romo et al., 1998) and thereby the activation of resting T cells and B cells to a lesser extent. Contignasterol from Petrosia contignata (Burgoyne and Andersen, 1992) inhibits allergen-induced histamine release from rat mast cells (Takei et al., 1994) and from guinea-pig lung tissue in vitro (Bramley et al., 1995) , and the activation of eosinophils into airways in guinea-pigs and could be used to treat asthma (Langlands et al., 1995) .

Cardiovascular Agents. In addition to regulators of the white blood cells, a number of spongederived molecules have been found to interfere with other blood-related diseases such as thrombosis, atherosclerosis, or diabetes ( Table 4 ). The process of blood coagulation is triggered by a complex proteolytic cascade that leads to the formation of fibrin. Thrombin is a serine protease that cleaves a peptide fragment from fibrinogen, which then leads to the generation of fibrin, a major component of blood clots (Shuman et al., 1993) . Cyclotheonarnide A, Callyspongynic acid, isolated from Callyspongia truncata, is an a-glucosidase inhibitor (Nakao et al., 2002) . a-Glucosidase inhibitors interfere with the hydrolysis of glycogen, keeping the glucose concentration in the blood at a lower level, and can be used to treat patients with diabetes (Lebovitz, 1992) .

Compounds. Keramidine, isolated from an Agelas sp. (Nakamura et al., 1984) , is an example of a number of neurosuppressive compounds that have been isolated from marine sponges (Table 5) . It is a serotonergic receptor antagonist and blocks serotonin-mediated neural communication. Several different serotonin receptors have been identified. They are related to (1) platelet aggregation, and may therefore be useful against thrombosis (Ruomei et al., 1996) (Lundberg, 1995; Edgar et al., 2002) . In addition to the above-mentioned centrally acting muscle relaxants, which mediate neuromuscular communication, peripherally acting muscle relaxant may be used for local muscle relaxation. They are applied for relief of strokes, or during intubations and surgery (Frakes, 2001). 1-Methylguanosine from Tedania digitata (Quinn et al., 1980 ) and xestospongin C, which was isolated from a Xestospongia sp. (Gafni et al., 1997) , are examples of muscle relaxants that discovered in sponges (Table 5 ). Xestospongin C is a potent inhibitor of the inositol 1,4,5-triphosphate (IP 3 ) receptors and the endoplasmic-reticulum Ca 2+ pumps (De Smet et al., 1999) and inhibits IP 3 -induced increase in the oscillatory contraction of muscles (Miyamoto et al., 2000) . ß-Adrenoreceptor agonists, such as S1319 isolated from a Dysidea sp. (Suzuki et al., 1999) , have utero-relaxant properties, which can be therapeutically used for the preterm delivery of infants (Dennedy et al., 2002) , and are widely used as antiasthmatic drugs (Suzuki et al., 1999) . However, owing to their low selectivity ßadrenoreceptor agonists may have severe side effects such as arterial hypertension, corony heart disease, and tachycardia (Borchard, 1998) . Therefore, there is continued interest in finding more selective ß-adrenoreceptor agonists such as S1319.

Antiviral Compounds. Sponges are also a rich source of compounds with antiviral properties (Table 6). The high number of HIV-inhibiting compounds discovered does not reflect greater potential of sponges to fight AIDS compared with other viral diseases, but rather the interest of many researchers. The strong focus on screening for anti-HIV activity has led to discovery of numerous compounds, but the mechanism of inhibition is still poorly characterized. Papuamides C and D (Ford et al., 1999), haplosamates A and B (Qureshi and Faulkner, 1999) , and avarol (Muller et al., 1987) , which has also been patented as antipsoriasis , are examples of HIV-inhibiting compounds from different sponges. Avarol is one of the few compounds for which the mechanism by which it inhibits progression of HIV infection is more or less known. In vitro and animal data indicate that avarol combines useful properties of an increased humoral immune response, as IgG and IgM production is significantly increased, and interference with the posttranscriptional processes of viral infection (Muller et al., 1987) . Avarol inhibits HIV by almost completely blocking the synthesis of the natural UAG suppressor glutamine transfer tRNA. Synthesis of this tRNA is upregulated after viral infection, and it is important for the synthesis of a viral protease, which is necessary for viral proliferation . Low concentrations of only 0.9 and 0.3 lM avarol resulted in 80% and 50% inhibition of virus release from infected cells, respectively , while (Figure 6 ), were very potent inhibitors of HIV reverse transcriptase. This enzyme has a key role in the early stages of HIV infection and is a specific target for antiviral drugs, as it is responsible for converting the viral genomic RNA into proviral double-stranded DNA, which is subsequently integrated into the host chromosomal DNA (Loya and Hizi, 1990 ). In addition to their applications to treat diabetes, a-glucosidase inhibitors, such as callyspongymc acid, are potentially broad-based antiviral agents.

They disturb protein glycosylation and cause some viral envelope proteins to be misfolded, which leads to arrest of these proteins within the endoplasmic reticulum, where protein folding takes place. It has been demonstrated that alteration of the glycosylation pattern of HIV, hepatitis B virus, and bovine viral diarrhea virus by a-glucosidase inhibitors attenuates viral infectivity (Ratner et al., 1991; Mehta et al., 1998).

A very different class of virus inhibitors that has been found in many different sponges are 2¢-5¢ oligoadenylates (2-5A), which are involved in the interferon-mediated response against a wide range of viruses in mammals. The antiviral action is based on the activation of a latent endoribonuclease that prevents viral replication by degradation of its mRNA as well as cellular RNA (Kelve et al., 2003) . For many other antivirals, the mechanism of inhibition is still unclear, but they are active against range of viruses. Hamigeran B from Hamigera tarangaensis, for example, showed 100 % in vitro inhibition against both the herpes and polio viruses (Wellington et al., 2000) , and the weinbersterols A and B from Petrosia weinbergi exhibited in vitro activity against feline leukemia virus, mouse influenza virus, and mouse corona virus (Sun et al., 1991; Koehn et al., 1991) .

In general, antiviral molecules from sponges do not give protection against viruses, but they may result in drugs to treat already infected persons. In addition, broad-based antiviral agents such as 2-5A and a-glucosidase inhibitors may be useful in cases of sudden outbreaks of (unfamiliar) viruses like SARS and Ebola.

Antimalarial Compounds. Several sponge-derived antimalarial compounds have been discovered during the last decade (Table 7) . New antimalarial drugs are needed to cope with the increasing number of multidrug-resistant Plasmodium strains that cause malaria. Plasmodium falciparum has become resistant against chloroquinone, pyrimethamine, and sulfadoxine (Bwijo et al., 2003) . Kalihinol A from a Acanthella sp. (Miyaoka et al., 1998 ) and a number of terpenoid isocyanates, isothiocyanates, and isonitriles from Cymbastela hooperi (Konig et al., 1996) display selective in vitro antimalarial activity against P. falciparum. Also a number of free carboxylic acids from Diacarnus levii were used as precursors to yield new cyclic norditerpene peroxides after esterification. These epidioxy-substituted norditerpenes and norsesterterpenes displayed selective activity against both chloroquine-sensitive and chloroquine-resistant P. falciparum strains (DÕ Ambrosio et al., 1998). The manzamines, the most promising antimalarial compound, have been discovered in a number of sponges (Sakai et al., 1986; Ang et al., 2000; Youssaf et al., 2002) . It has been suggested that the antimalarial effect of manzamine A is due to an enhanced immune response (Ang et al., 2001) .

Antibiotics and Fungicides. With respect to antibiotics and fungicides, similar multiresistance problems have concerned physicians for a long time. Many new molecules with antibiotic properties are discovered every year, but in marine sponges their ubiquity is remarkable (Table 8 ). An early screening by Burkholder and Ruetzler (1969) revealed that 18 of 31 sponges tested showed antimicrobial effects, of which some were very strong against a range of gram-positive and gram-negative bacteria. The added value of some new sponge-derived antibiotics was shown by the inhibitory effect of arenosclerins A-C from Arenosclera brasiliensis on 12 antibioticresistant bacteria isolated from a hospital (Torres et al., 2002) . Fungicides that are currently used are less diverse than antimicrobials, and the use of many of them is restricted because of toxic effects to humans, animals, and plants (Nakagawa and Moore, 1995; Rahden-Staron, 2002) . It remains to be demonstrated whether antifungals like topsentiasterols D and E from Topsentia sp. (Fusetani et al., 1994) , acanthosterol sulfates I and J from an Acanthodendrilla sp. (Tsukamoto et al., 1998) or the macrolide leucascandrolide A from the calcareous sponge Leucascandra caveolata (DÕAmbrosio et al., 1996) will have different characteristics than the fungicides that are currently used, but the fact that they are produced by eukaryotic organism (if not produced by a symbiont) may imply that they are less toxic to other nonfungal eukaryotes.

Antifouling Compounds. A last class of bioactive compounds from marine sponges are antifouling molecules (Table 9 ). They are not associated with the development of new drugs, but could be environmentally friendly substitutes for chemical antifoulants. Biofouling organisms such as blue mussels, barnacles, and macroalgae cause serious problems to shipÕs hulls, cooling systems of power plants, and aquaculture materials (Holmes, 1970; Houghton, 1978) . Long-term use of chemical antifoulants has led to increased concentrations of tributyltin and its current replacements in coastal sediments (Konstantinou and Albanis, 2004) and to mortality and change of sex of nontarget organisms (Katranitsas et al., 2003) . Natural marine antifouling molecules have recently been reviewed (Fusetani, 2004) and may provide less toxic and more specific antifouling activity. Sponge-derived antifouling molecules have been found to inhibit the settlement of barnacle larvae (Okino et al., 1995; (Sera et al., 1999) .

Ecologic Role of Sponge Metabolites. Such an extensive collection of sponge-derived bioactive compounds raises the question of why sponges produce so many metabolites that can be useful to treat our human diseases. The huge number of different secondary metabolites discovered in marine sponges and the complexity of the compounds and their biosynthetic pathways (and corresponding kilobases of DNA for the programming of their synthesis) can be regarded as an indication of their importance for survival. An obvious example of the benefits of their secondary metabolites for the sponge itself, is the presence of antifouling products. To safeguard their water-pumping capacity, sponges cannot tolerate biofilm formation or settlement of barnacles or bryozoans on their surface (Proksch, 1994) , The level of cytotoxicity of some sponge products is high enough to even create a bare zone around the sponge (Thompson, 1985) that is maintained by the emission of a mucus containing the toxins (Sullivan et al., 1981) . This allows the conquest of densely populated rocks or corals and competition with faster growing organisms, but it is striking that the sponge can selectively use its poisons without self-destruction.

Secondary metabolites can protect the organism against predation, which is especially important for physically unprotected sessile organisms like sponges (Becerro et al., 1997) . Relatively few animals, such as the hawksbill turtle and some highly evolved teleost fishes (Meylan, 1990) , are largely dependent on sponges for their diet. Also some nudibranches feed on sponges and even manage to use the spongeÕs metabolites for their own chemical defence (Pawlik et al., 1988) . However, these spongivores represent only a tiny fraction of the animals inhabiting the seas. Secondary metabolites can also protect their producers against bacteria, fungi, or parasites (Davies, 1992). In sponges the role of the chemical constituents is clouded by the complexity of the sponge-symbiont relationship (Dumdei et al., 1998). Many different bacterial species permanently inhabit sponges and contribute considerably to the total sponge biomass (Wilkinson, 1978) . It has been suggested that the growth of ''useful'' microorganisms may be under control of the sponge host and serve as source of food or supply other metabolic products (Muller et al., 1981) . However, it has also been found that associated bacteria might be the actual producers of a number of compounds that Table 8 . have been isolated from sponges. Oscillatoria spongelia, a cyanobacterial symbiont that can constitute up to 40% of Dysidea herbacea, is the producer of antimicrobial polybrominated biphenyl ethers and might keep the sponge free of other bacteria (Unson, et al., 1994) . For many products it is not yet known whether they are produced by the sponge or by a symbiont. It is clear, however, that sponges are responsible for the production of a rich arsenal of ''chemical weapons.'' Their early appearance in evolution has given them a lot of time for the development of an advanced chemical defense system. It is interesting to note that the synthesis of secondary metabolites is regulated depending on conditions that the sponge experiences. Specimens of Crambe crambe in wellilluminated regions grow faster than their counterparts exposed to darker conditions, but the specimens in the dark are better defended as they accumulate higher concentrations of cytotoxic metabolites (Turon et al., 1998) . Another example is the production of halichondrin B by Lissodendoryx sp., which varies seasonally, with depth, and with the condition of the sponge. Halichondrin B yields could be enhanced by an order of magnitude during serial cloning, suggesting a defensive response to damage (Battershill et al., 2002) . The ability to stimulate the production of secondary metabolites by sponges is an important consideration when one wants to harvest compounds from sponges for the production of potential new medicines.

Marine sponges produce an enormous array of antitumor, antiviral, antiinflammatory, immunosup-pressive, antibiotic, and other bioactive molecules that can affect the pathogenesis of many human diseases. The relationship between the chemical structures of the secondary metabolites from sponges and the diseases they affect is usually not obvious. Different components affect the targeted disease by different mechanisms (e.g., microtubule stabilization or interaction with DNA to combat tumors). Moreover, inhibitors of transcription may be effective against both cancer and viral diseases. To make things more complex, there are many relations between, for instance, inflammation, cancer, and viral infections via the immune system, which plays a key role in certain responses of the body to these diseases. Chronic inflammation of the lungs by cigarette smoke often leads to lung cancer (Ohwada et al., 1995) and cervical and liver cancer can follow chronic inflammation caused by papilloma viruses (Smith-McCune et al., 1996) and hepatitis B and C viruses, respectively (Zhu et al., 1997) . In addition, limited activity testing (e.g., only on cell growth inhibition and not on antiviral properties) yields an incomplete overview of the actual properties of the metabolites. Finally, for many bioactive molecules from sponges, the exact mode of action and their origin (sponge or symbiont) are still unclear. Most bioactive metabolites from sponges are inhibitors of certain enzymes, which often mediate or produce mediators of intracellular or intercellular messengers involved in the pathogenesis of a disease. As this is usually a cascade of reactions inside the cell or tissue, many enzymes in the cascade are targets for potential therapy. The different enzymes in the cascade can be structurally completely different proteins; therefore, it is not surprising that a wide range of metabolites can be used for the treatment of one disease. This applies in particular to a complex disease, such as cancer, which is affected by so many different factors. Furthermore, antiviral molecules also appear to encamps a wide array of chemical structures, such as peptides, lipids, alkaloids, sterols, oligonucleotides, and a phenolic macrolide. A similar diverse pattern is observed for antibacterial and immunosuppressive metabolites. Most compounds that display antiinflammatory activity are sesterterpenoids. Nevertheless, in these cases the activity of the sponge metabolites is concentrated on certain steps; for instance, most antiinflammatory compounds act against phospholipase A 2 .

The potency of sponge-derived medicines lies in the fact that each of these thousands of metabolites and their derivatives has its own specific dose-related inhibitory effect, efficacy, and potential (diminished) side effects that determine its suitability for medicinal use. In addition, the skeleton or active core of these molecules may be used as a vehicle to develop derivatives with their own specific efficacy and side effects. Therefore, the most important challenge in transforming bioactive molecules into medicines is now to screen the treasurehouse of sponge metabolites and select those that display a specific mode of action with the desired characteristics against a disease. An important question for the future remains how to actually prepare the potential novel drugs on a large scale. 

La girolline, nouvelle substance antitumorale extraite de lÕé ponge, Pseudaxinyssa cantharella n sp (Axinellidae). C R Acad Sci

Cytotoxic peptides hemiasterlin, hemiasterlin A and hemiasterlin B induce mitotic arrest and abnormal spindle formation

In vivo antimalarial activity of the bcarboline alkaloid manzamine A

Immunemediated parasite clearance in mice infected with Plasmodium berghei following treatment with manzamine A

Antimalarial activity of sesquiterpenes from the marine sponge Acanthella klethra

Agosterol A, a novel polyhydroxylated sterol acetate reversing multidrug resistance from a marine sponge Spongia sp

Absolute stereochemistry of halichlorine; a potent inhibitor of VCAM-1 induction

Die Rohstoffe des Tierreichs 1, 2 Hä lfte

Halichondrin B and homohalichondrin B, marine natural products binding in the vinca domain of tubulin: discovery of tubulin-based mechanism of action by analysis of differential cytotoxicity data

Spongistatin 1, a highly cytotoxic, sponge-derived, marine natural product that inhibits mitosis, microtubule assembly, and the binding of vinblastine to tubulin

A chemical ecology of sponges in culture

Multiple functions for secondary metabolites in encrusting marine invertebrates

Differential effects of manoalide on secreted intracellular phospholipases

The isolation of a new thymine pentoside from sponges

Contributions to the study of marine products, 32: the nucleosides of sponges, I

Contributions to the study of marine products, 30: Component acids of lipids of sponges, I

Polycyclic guanidine alkaloids from the marine sponge Crambe crambe and Ca ++ channel blocker activity of crambescidin 816

Side effects of nonsteroidal anti-inflammatory drugs on the small and large intestine in humans

Adociasulfates 1-6, inhibitors of kinesin motor proteins from the sponge Haliclona (aka Adocia) sp

Pharmacological properties of b-adrenoreceptor blocking drugs

Peloruside A, a novel antimitotic agent with paclitaxel-like microtabule-stabilizing activity

Marine fouling and offshore structures

Hennoxazoles, bioactive bisoxazoles from a marine sponge

Aragusterol A: a potent antitumor marine steroid from the Okinawan sponge of the genus, Xestospongia

Spongiacidins A-D, new bromopyrrole alkaloids from Hymeniacidon sponge

Tubulin polymerizing activity of dictyostatin 1, a polyketide of marine sponge origin

Topsentin, a unique phosphohpase A 2 inhibitor

Presented at the Japan-US Seminar on Bioorganic Marine Chemistry

Crambescidins: new antiviral and cytotoxic compounds from the sponge Crambe crambe

Elenic acid, an inhibitor of topoisomerase II, from a sponge, Plakinastrella sp

Latruncutin, a new 2-thiazolidinone macrolide from the marine sponge Latrunculia magnifica

Okinonellins A and B, two novel furanosesterterpenes, which inhibit cell division of fertilized starfish eggs, from the marine sponge Spongionella sp

The effects of a copper-based antifouling paint on mortality and enzymatic activity of a nontarget marine organism

Sponge (2Õ,5Õ)oligoadenylate synthetase activity in the whole sponge organism and in a primary cell culture

Marine natural products, XII: on the chemical constituents of the Okinawan marine sponge Hymeniacidon aldis

Penaresidin A and B, two novel azetidine alkaloids with potent actomyosin ATPase activating activity from the Okinawan marine sponge Penares sp

KRN7000, a novel immunomodulator, and its antitumor activity

Callystatin A, a potent cytotoxic polyketide from the marine sponge, Callyspongia truncata

New antiviral sterol disulfate ortho esters from the marine sponge Petrosia weinbergi

Effects of arenastatin A and its synthetic analogs on microtubule assembly

Novel potent antimalarial diterpene isocyanates, isothiocyanates, and isonitriles from the tropical marine sponge Cymbastela hooperi

Worldwide occurrence and effects of anifouling paint booster biocides in the aquatic environment: a review. Environment Int

Multiple defensive roles for triterpene glycosides from two Carribean sponges

Selective inhibition of formation of suppressor glutamine tRNA in Moloney murine leukemia virus-infected NIH-3T3 cells by avarol

Halichlorine, an inhibitor of VCAM-1 induction from the marine sponge Halichondria okadai Kadata

Role of nitric oxide in tumor progression: lessons from experimental tumors

Functional localization of specific receptors mediating gastrointestinal motor correlates of vomiting

Effects of IZP-94005 on eosinophil number and eosinophul peroxidase activity in lung lavage fluid from sensitized guenea pigs

Oral antidiabetic agents: the emergence of a-glucosidase inhibitors

Polyoxygenated Dysidea sterols that inhibit the binding of [I 125 ] IL-8 to the human recombinant IL-8 receptor type A

Lipoxygenase metabolites of arachidonic and linoleic acids modulate the adhesion of tumor cells to endothelium via regulation of protein kinase C

DNA topoisomerases: essential enzymes and lethal targets

Development of aromatase inhibitors and their pharmacologic profile

The inhibition of human immunodeficiency virus type 1 reverse transcriptase by avarol and avarone derivatives

Methods and applications of stress research

A marine literature database maintained by the Marine Chemistry Group

pH and drug resistance, I: functional expression of plasmalemmal V-type H + -ATPase in drug-resistant human breast carcinoma cell lines

Molecular basis for the inhibition of human athrombin by the macrocyclic peptide cyclotheonamide A

Bioactive marine metabolites, VII: structures of discodermins B, C, and D, antimicrobial peptides from the marine sponge Discodermia kiiensis

Manoalide: an antiinflammatory and analgesic marine natural product

Glucosidase inhibitors as potential broad based anti-viral agents

Nutritional characteristics of the sponges in the diet of the hawksbill turtle

Xestospongin C, a selective and membrane-permeable inhibitor of IP 3 receptor, attenuates the positive inotropic effect of a-adrenergic stimulation in guinea-pig papillary muscle

Antimalarial activity of kalahinol A and new relative diterpenoids from the Okinawan sponge, Acanthella sp

Laulimalide and isolaulimalide, new paclitaxel-like microtubule-stabilizing agents

Cell biological aspects of HIV-1 infection: effects of the anti-HIV-1 agent avarol

Lectin, a possible basis for symbiosis between bacteria and sponges

Potent antileukemic activity of the novel cytostatic agent avarone and its analogues in vitro and in vivo

Influence of the antileukemic and anti-human immunodeficiency virus agent avarol on selected immune responses in vitro and in vivo

Verwendung von avarol oder dessen derivaten zur bekä mpfung von entzü ndlichen systemischen und dermatologischen erkrankungen

Preand postsynaptic serotonergic manipulations in an animal model of depression

Cytotoxic effects of postharvest fungicides, ortho-phenylphenol, thiabendazole and imazalil, on isolated rat hepatocytes

Keramadine, a novel antagonist of serotonergic receptors isolated from the Okinawan sea sponge Agelas sp

Callyspongynic acid, a polyacetylenic acid which inhibits a-glucosidase, from the marine sponge Callyspongia truncata

Oceanapiside, an antifungal bis-a,x-amino alcohol glycoside from the marine sponge Oceanapia phillipensis

Pateamine: a potent cytotoxin from the New Zealand marine sponge, Mycale sp

Verhandeling over de inlandsche zoetwater-spongie, eene huisvesting der Maskers van puistenbijteren

Pharmazeutische Zentralhalle fü r Deutschland

Effect of cigarette smoke on the mRNA and protein expression of carcinoembryonic antigen (CEA), a possible chemoattractant for neutrophils in human bronchioloalveolar

Antifouling kalihinenes from the marine sponge Acanthella cavernosa

New antifouling kalihipyrans from the marine sponge Acanthella cavernosa

Defensive chemicals of the Spanish dancer nudibranch Hexabranchus sanguineus and its egg ribbons: macrolides derived from a sponge diet

Discorhabdin D an antitumor alkaloid from the sponges Latrunculia brevis and Prianos sp

Alkaloids from the antarctic sponge Kirkpatrickia varialosa, part 1: variolin B, a new antitumour and antiviral compound

Abroad-spectrum antifungal from the marine sponge Hyrtios erecta

Marine sponge bis(indole) alkaloids that displace ligand binding to a 1 -adrenergic receptors

11-secosteroids from the marine sponge Aplysilla glacialis

Haines GK III (1999) C/EBPb in rheumatoid arthritis: correlation with inflammation, not disease specifity

Defensive roles for secondary metabolites from marine sponges and sponge-feeding nudibranchs

Drugs from the seas-current status and microbiological implications

Isolation and synthesis of 1-methylisoguanisine, a potent pharmacologically active constituent from the marine sponge Tedania digitata

Haplosamates A and B: new steroidal sulfamate esters from two haplosclerid sponges

The inhibitory effect of the fungicides captan and captafol on eukaryotic topoisomerases in vitro and lack of recombinagenic activity in the wing spot test of Drosophila melanogaster

Petrosaspongiolides M-R: new potent and selective phospholipase A 2 inhibitors from the New Caledonian marine sponge Petrosaspongia nigra

Axinellins A and B: new proline-containing antiproliferative cyclopeptides from the Vanuatu sponge Axinella carteri

Haligramides A and B, two new cytotoxic hexapeptides from the marine sponge Haliclona nigra

Inhibition of HIV and SIV infectivity by blockade of aglucosidase activity

Isolation and synthesis of the first natural 6-hydroximino 4-en-3-one-steroids from the sponges Cinachyrella spp

Total synthesis and immunosuppressive activity of (-)-pateamine A and related compounds: implementation of a b-lactambased macrocyclization

Mololipids, a new series of anti-HIV bromotyramine-derived compounds from a sponge of the order Verongida

Quantitative measurement of various 5-HT receptor antagonists on platelet activation induced by serotonin

Mycalolide, a novel actin depolymerizing agent

Manzamin A, a novel antitumor alkaloid from a sponge

A new neurotoxic amino acid from the Micronesian marine sponge Dysidea herbacea

Pharmacological properties of the potent epileptogenic amino acid dysiherbaine, a novel glutamate receptor agonist isolated from the marine sponge Dysidea herbacea

Tedanolide: a potent cytotoxic macrolide from the Caribbean sponge Tedania ignis

Die Verwendung der Susswasserschwamme in der Ukraine

Avarol restores the altered prostaglandin and leukotrin metabolism in monocytes infected with human immunodeficiency virus type 1

Marine organisms and other novel natural sources of new cancerdrugs

A new epidioxy sterol as an antifouling substance from a Palauan marine sponge, Lendenfeldia chondrodes

Role of NKT cells and a-galactosyl ceramide

Two unique pentacyclic steroids with cis C/D ring junction from Xestospongia bergquistia Fromont, powerful inhibitors of histamine release

Highly selective tripeptide thrombm inhibitors

Induction of apoptosis by HPV 16E7: implications for cin and cervical cancer

Inhibition of cyclin-dependent kuiase 4 (Cdk4) by frascaplysin, a marine natural product

Sticky sugars for selectins

Eryloside F, a novel penasterol disaccharide possessing potent thrombin receptor antagonist activity

Antimicrobial constituents of the sponge Siphonodictyon coralliphagum

Weinbersteroldisulfates A and B, antiviral steroid sulfates from the sponge Petrosia weinbergi

S1319: A novel ß 2 -adrenoceptor agonist from a marine sponge Dysidea sp

Effect of contignasterol on histamine release induced by antiimmunoglobulin E from rat peritoneal mast cells

Cellular and molecular mechanisms of inflammation and thrombosis

Discodermolide, a cytotoxic marine agent that stabilizes microtubules more potently than taxol

Exudation of biologically-active metabolites in the sponge Aplysina fistularis, I: biological evidence

Antibacterial activity against resistant bacteria and cytotoxicity of four alkaloid toxins isolated from the marine sponge Arenosclera brasiliensis

Ceratinamides A and B: new antifouling dibromotyrosine derivatives from the marine sponge Pseudoceratina purpurea

Pseudoceratidine: a new antifouling spermidine derivative from the marine sponge Pseudoceratina purpurea

Acanthosterol sulfates A-J: ten new antifungal steroidal sulfates from a marine sponge Acanthodendrilla sp

Growth dynamics and mortality of the encrusting sponge Crambe crambe (Poecilosclerida) in contrasting habitats: correlation with population structure and investment in defence

A brominated secondary metabolite synthesized by the cyanobacterial symbiont of a marine sponge and accumulation of the crystalline metabolite in the sponge tissue

Axinellamines A-D, novel imidazo-azolo-imidazole alkaloids from the Australian marine sponge Axinell asp

Octa-and nonaprenylhydroquinone sulfates, inhibitors of a1,3-fucosyltransferase VII, from an Australian marine sponge Sarcotragus sp

Chemistry of sponges, 19: Novel bioactive metabolites from Hamigera tarangaensis

Microbial associations in sponges, III: ultrastructure of the in situ associations in coral reef sponges

BRS1, a C30 bis-amino, bis-hydroxy polyunsaturated lipid from an Australian calcareous sponge that inhibits protein kinase C

Enhancing effects of (2S,3S,4R)-1-O-(alpha-D-galactopyranosyl)-2-(N-hexacosanoylamino)-1,3,4-octadecanetriol (KRN7000) on antigen-presenting function of antigen-presenting cells and antimetastatic activity of KRN7000-pretreated antigen-presenting cells

Protein kinase C lies on the signaling pathway for vascular endothelial growth factor-mediated tumor development and angiogenesis

34-Oxamanzamines, novel biocatalytic and natural products from rnanzamine producing Indo-Pacific sponges

Selective inhibition by procubol of vascular cell adhesion molecule 1 (VCAM-1) expression in human vascular endothelial cells

The relationship of hepatitis history and pathological diagnosis of primary liver cancer