key: cord-1029151-jrfll22j
authors: Ghashghaeinia, Mehrdad; Mrowietz, Ulrich
title: Human erythrocytes, nuclear factor kappaB (NFκB) and hydrogen sulfide (H(2)S) – from non-genomic to genomic research
date: 2021-09-24
journal: Cell cycle
DOI: 10.1080/15384101.2021.1972557
sha: 8af85a94cfccb1b12d24c192ed38b0a9e81872fe
doc_id: 1029151
cord_uid: jrfll22j

Enucleated mature human erythrocytes possess NFĸBs and their upstream kinases. There is a negative correlation between eryptosis (cell death of erythrocytes) and the amount of NFĸB subunits p50 and Rel A (p65). This finding is based on the fact that young erythrocytes have the highest levels of NFĸBs and the lowest eryptosis rate, while in old erythrocytes the opposite ratio prevails. Human erythrocytes (hRBCs) effectively control the homeostasis of the cell membrane permeable anti-inflammatory signal molecule hydrogen sulfide (H(2)S). They endogenously produce H(2)S via both non-enzymic (glutathione-dependent) and enzymic processes (mercaptopyruvate sulfur transferase-dependent). They uptake H(2)S from diverse tissues and very effectively degrade H(2)S via methemoglobin (Hb-Fe(3+))-catalyzed oxidation. Interestingly, a reciprocal correlation exists between the intensity of inflammatory diseases and endogenous levels of H(2)S. H(2)S deficiency has been observed in patients with diabetes, psoriasis, obesity, and chronic kidney disease (CKD). Furthermore, endogenous H(2)S deficiency results in impaired renal erythropoietin (EPO) production and EPO-dependent erythropoiesis. In general we can say: dynamic reciprocal interaction between tumor suppressor and oncoproteins, orchestrated and sequential activation of pro-inflammatory NFĸB heterodimers (RelA-p50) and the anti-inflammatory NFĸB-p50 homodimers for optimal inflammation response, appropriate generation, subsequent degradation of H(2)S etc., are prerequisites for a functioning cell and organism. Diseases arise when the fragile balance between different signaling pathways that keep each other in check is permanently disturbed. This work deals with the intact anti-inflammatory hRBCs and their role as guarantors to maintain the redox status in the physiological range, a basis for general health and well-being.

Under physiological conditions, the autooxidation of about 1-3% of the total body hemoglobin (ferrous Hb/HbFe 2+ ) results in the generation of methemoglobin (metHb/HbFe 3+ ). Different organs such as liver, kidney, and brain produce the signal molecule hydrogen sulfide (H 2 S). The cellular H 2 S biogenesis, that is, desulfuration of cysteine or homocysteine, is primarily accomplished by three enzymes: Cystathionine b-synthase (CBS), γ-cystathionase (CSE), and mercaptopyruvate sulfur transferase (MST) [1] [2] [3] . hRBCs does possess MST, but not the other two H 2 S-producing enzymes [4] . While H 2 O flow through cell membrane is accelerated by aquaporins [5] , the transmembrane diffusion of hydrophobic H 2 S requires no facilitator and its permeability coefficient is still 10.000 times higher than that of water [6] . Based on this property, H 2 S can exhibit broad toxicity effects or function as a signal molecule in a concentration-dependent manner. Besides the endogenously produced nitric oxide (NO) and carbon monoxide (CO), the cell membrane permeable H 2 S [7,8] plays an important role as a gaseous signaling molecule in biological and physiological processes. H 2 S regulates several biological and physiological processes, for instance: it shows anti-thrombotic effects [9] , protects vascular tissues from atherogenic disease [10] , enhances blood flow which protects against vascular ischemia [11] and inhibits glucose consumption and uptake. For reviews, see [12, 13] .

One hundred years ago, sophisticated experiment on animals provided the first evidence of fast H 2 S detoxification via its metabolism. The practice of a fast administered single dose of 10 ml of a 77 mmol/l Na 2 S solution was always lethal, whereas dogs that received a five-fold dose over a period of 20 minutes survived and showed no obvious damage [14] . Mammalian tissues (e.g. heart, kidney, brain, and intestine) as well as human erythrocytes are able to produce H 2 S. Under physiological conditions, ~30% of the short-lived H 2 S exists in a non-dissociated form and ~70% in its hydrogen sulfide anion (H 2 S HS − ). It is important to note that: a) the completion of net acid efflux by the H 2 S/HS − follows the same principle as that of CO 2 /HCO 3 − in the Jacobs-Stewart cycle (see Figure 1b ) due to the lack of extracellular hydration and intracellular dehydration, the net acid efflux in Cl − /HS − /H 2 S cycle is faster than Cl − /HCO 3 − /H 2 CO 3 cycle, c) HS − is a very good substrate for the anion exchanger 1 (AE1) and d) H 2 S possesses a very high permeability coefficient in human erythrocytes [15] . The atomic structure of CO allows it to solely bind Fe 2+ with its two unpaired electrons [16] . Therefore, all of the spectral work with CO and heme proteins employs the native (reduced) forms. NO is able to bind both Fe 2+ [18, 19] . The very high lipid and water solubility of H 2 S allows quick passage through the alveolar membrane, which is the best condition for achieving an almost perfect equilibrium between blood and alveolar air. Human alveolar air measurements showed negligible free H 2 S, indicating very low blood concentration [18] . [20] , c) ~1% of the circulating hRBCs (~200-300 billion cells) are cleared per day and replaced by erythropoiesis, and d) that ~3.7 million (3.7 x 10 6 ) cell-free, intact and respiratory competent mitochondria circulating per ml of blood plasma [21] , those organelles apart from hRBCs contribute to the degradation of H 2 S, maintain human plasma concentration of H 2 S clearly below a µM range under physiological conditions.

Ankyrin-containing proteins including IĸBs act as specific protein-protein interactors [22] [23] [24] . The prevailing opinion is that cellular activation via numerous stimuli initiates IĸB-α phosphorylation, its subsequent dissociation from and abolition of its inhibitory effect on NFĸB; and these events precede the IĸB-α proteolytically degradation. However, this does not reflect the sequence of events. In fact, the IĸB-α phosphorylation and its subsequent degradation enables NFĸB release, which rapidly translocates into the nucleus [25] to drive the expression of genes, for eample, IL-8 expression [26] . The dual function of the chemokine IL-8 includes pathogen elimination by recruitment of neutrophils and being causative in several inflammatory diseases. Both IL-4 and human erythrocytes can curb IL-8 effects. IL-4 functions as an endogenous inhibitor of IL-8 expression [27] and hRBCs reduces the bioavailability of IL-8 substantially by acting as a sink for IL-8 [28-30]. Steffan et al. were the first to show a direct link between the synergistic effects of PKC-and Ca 2+ -dependent phosphatase calcineurin on the regulation of IĸB-α phosphorylation and pointed to the necessity of the existence of an IĸB-α kinase (IKK) [25, 31] . In the meantime, the existence of IKKs [32,33], but also of an IKK kinase, have been proven [34] .

Human erythrocytes (hRBCs) possess the main members of the canonical NFĸB pathway [35 -37] . Virtually all publications on erythrocytes´ NFĸBs available to date originate from our laboratory, which demonstrate a reciprocal relationship between age and abundance of NFĸBs in hRBCs; the NFĸB protein abundance is highest in young and lowest in aged erythrocytes. There is a positive correlation between cell volume, and a negative correlation between eryptosis (cell death of erythrocytes) and the amount of NFĸB subunits p50 and p65. This finding is based on the fact that young erythrocytes have the highest cell volume and the lowest eryptosis rate, while in old erythrocytes the opposite ratio prevails [36] .

Retrobulbarly collected whole blood, the subsequent isolation of erythrocytes from the homozygous NFĸB-p50 deficient and congenic wild-type C57BL/6 and their subsequent incubation in Ringer solution enabled to demonstrate a direct correlation between NFĸB-p50 deficiency and increased eryptosis [38] . Additional biological/ physiological effects were: a) significant increase of white blood cell (WBCs) count and b) considerable weight loss in NFĸB-p50 deficient mice. The former indicates systemic inflammation in NFĸB-p50 deficient mice and the latter observation offers a possibility to treat obesity with NFĸB inhibitors provided their bioavailability is sufficient [39, 40] . It is known that NFĸB-p50 homodimers are refractory to inflammation while NFĸB heterodimers (e.g. RelA-p50 subunits) have an inflammatory function [41] . This is why impaired p50-p50 activation is associated with dysregulated inflammation and chronic inflammatory diseases.

The generation of a reduced form of glutathione (GSH), an intracellular antioxidant, is the result of two concerted ATP-consuming reactions conducted by 1) γ-glutamylcysteine synthetase (γ-GCS) and 2) GSH synthetase (GS) [42, 43] . (Reaction 1): L-glutamate + L-cysteine + ATP → γ-L-glutamyl-L-cysteine + ADP + P i (Reaction 2): γ-glutamyl -L-cysteine + L-glycine + ATP → GSH + ADP + P i The first reaction is, however, feedback inhibited by GSH [44] , see also Figure 2 . In nucleated cells, GSH and NO, respectively, are able to inhibit IKK-b activity by reversible S-glutathionylation or S-nitrosylation, which ultimately impairs NFĸB activation [45, 46] . Protein kinase C-alpha (PKC-α) phosphorylates NFĸB-p65 subunits [47] and this is associated with NFĸB-dependent induction of γ-GCS and intracellular GSH de novo biosynthesis [48] . Interestingly, addition of exogenous NO donor DETA/NO results in NO-mediated release of "free" intracellular zinc, zincdependent increase of γ-GCS expression and GSH synthesis [49] . This could be a new IKK-NFĸB-independent, NO-dependent pro-survival pathway connecting redox potential of a cell with intracellular "free" zinc concentration. Human erythrocytes (hRBCs) possess functional endothelial nitric oxide synthase (eNOS) (L-Arginine + O 2 + eNOS → L-Citrulline + NO) [50,51] and much more important is the fact that pro-survival NO and pro-eryptotic Ca 2 + keep each other in check [52] . Under physiological conditions one portion of the abundant serum albumin binds to NO, forming a relatively long-lived albumin-NO-adduct (~7 µM S-nitrosothiol) and thus functioning as a sink for NO, while free NO with a plasma concentration of ~3 nM serves predominantly to maintain the vascular tone [53] , see also [57] . [Ca 2+ ] i directly impairs the transmembrane equilibrium distribution of the phospholipids, that is, their inward translocation from the outer to the inner leaflet of erythrocytes' plasma membrane. For instance, [Ca 2+ ] i of ~50 and ≥200 nM affect the inward translocation of phosphatidylethanolamine and acidic phosphatidylserine (PS), respectively [58] , a process directly related to Ca 2+ -dependent inhibition of aminophospholipid translocase (or flippase) activity. A sustained cytosolic calcium elevation [Ca 2+ ] i concomitantly promotes the activity of the phospholipid scramblase which then unspecifically initiates bidirectional PS translocation on both sides of the plasma membrane. In contrast to internalized PS, PS externalization or depletion is associated with a cell-type independent weakening of the plasma membrane Ca 2+ -ATPase (PMCA)-mediated Ca 2+ -efflux [59,60]. The following reviews illustrate Ca 2+ transporting systems, for example, PMCA and the Ca 2+activated K + channel, known as Gardos channel [61-63]: In view of the antagonistic roles of NO and Ca 2+ [52] and association of early eryptosis with the removal/translocation of PS from the inner to the outer leaflet of the bilayer plasma membrane, it is not surprising that intact hRBCs maintain their [Ca 2+ ] i as low as possible and as much as necessary (see Figure 3) .

It is undisputed that changes in [Ca 2+ ] i are associated with changes in cell functions [64] . into three classes: cPKCs (α, βI, βII, and γ), novel, that is, nPKCs (d, e, η, and θ), and atypical, that is, aPKCs (ζ and iota (i)). The first class being Ca 2+ , PS, and DAG-dependent; the second being Ca 2+independent but PS-and DAG-dependent, and the third class being Ca 2+ -and DAG-independent but acidic phospholipids and ceramides dependent. hRBCs possess four cytosolic isoforms of PKCs: alpha, zeta, mu, and iota, of which only PKC-α with membrane translocation capability [72, 73] , that is, induction of eryptosis [74, 75] . Using chelerythrine as a specific PKC-α inhibitor, we were able to show a direct correlation between the costunolide-induced GSH-depletion and PKC-α activation in hRBCs [76] , a phenomenon also observed in nucleated mammalian cells. Thus, it is not astonishing that the capacity of hRBCs to synthesize ~2 mM of the pro-survival [GSH] i [77,78] exceeds the rate GSH turnover by 150fold [79] to avoid a PKC-α mediated induction of erythrocytes death (eryptosis). Furthermore, H 2 S can be endogenously produced in the presence of GSH [80, 81] . GSH is a linchpin of cellular defense protecting both prokaryotic [82] and eukaryotic cells [83, 84] including hRBCs from biotic and abiotic stresses. In nucleated mammalian cells, PKC-α activation drives the pro-survival machinery [85] [86] [87] , and its inhibition commonly triggers apoptosis in these cells [88, 89] . In addition to this, respiratory diseases of viral [90] and bacterial [91] origin are associated with PKC-α activation. It is to note that intact hRBCs are actively involved in bacterial [92] and viral clearance from circulation [93-98], for reviews see [99, 100] . The message is clear: specific PKC-α inhibitors, for exmaple, the bioactive molecule chelerythrine [101-104], as a natural product of plant origin can dose-dependently cause a pro-apoptotic effect in nucleated cells, thus creating a hostile environment for intracellular parasites including viruses and simultaneously can create a pro-survival effect in enucleated hRBCs [76] . Therefore, hRBCs in combination with PKC-α inhibitors (e.g., chelerythrine) should be a promising approach to treat COVID-19 [105] . PKC-α as the upstream kinase of the NFĸB signaling pathway as well as NFĸB itself, represent a link between nucleated and enucleated mammalian cells, which can be designated as: "NFĸB, from non-genomic to genomic research".

Obesity-and psoriasis-associated chronic lowgrade inflammation and NFĸB activation are two sides of the same coin that perpetuate each other. It is known that NFĸB is a positive physiological regulator of glycolysis [106] , for review see [107] . The following review clearly illustrates the relationship between the anti-inflammatory effects of insulin and the pro-inflammatory effects of glucose with NFĸB as a common target [108] . Interestingly, glucose uptake is negatively correlated with in adipose tissue up-regulation of H 2 S system. As already mentioned, a negative correlation exists between the intensity of inflammatory diseases and endogenous H 2 S levels. Psoriasis is directly associated with low serum H 2 S levels [109] , for review, see [110] . Diminished adipose tissue H 2 S has been observed in obesity. H 2 S inhibits the expression of highly proinflammatory IL-8 in human keratinocytes and shows potential for psoriasis treatment [111] . In addition, hRBCs function as a sink for IL-8, thus minimizing the deleterious effects of NFĸB-mediated IL-8 expression. Recently, Mezouari et al. demonstrated that H 2 S enhances the secretion of the glucoregulatory hormone glucagon-like peptide 1 and improves glucose clearance in mice [112] , for review see [113] . In addition to these, endogenous H 2 S deficiency in patients with chronic kidney disease (CKD) is associated with impaired renal erythropoietin (EPO) production and EPO-dependent erythropoiesis [114] . Taken together, the role of antiinflammatory hRBCs to regulate H 2 S homeostasis and to maintain its physiological concentration in the blood as well as to function as a sink for a many inflammatory cytokines and chemokines, is essential for maintaining cellular health as the basis for general health and well-being.

For adequate supply of the organism with molecular oxygen, hRBCs divert 20% of the uptaken glucose to Rapoport and Luebering glycolytic shunt [115] , for review see [107] . In this process erythrocyte 2,3-bisphosphoglycerate (2,3-BPG) plays a central role. It negatively regulates hemoglobin oxygen (O 2 ) binding affinity, facilitates O 2 release from oxyhemoglobin [116] improving tissue oxygenation. H 2 S regulates 2,3-BPG production and it exists a reciprocal correlation between H 2 S concentration and 2,3-BPG production. H 2 S level increases during normoxic and decreases during hypoxic conditions [117] . This ensures maximum O 2 uptake in the lungs and maximum O 2 release in the peripheral tissues. It is to note that the reduced form of glutathione (GSH), glycolytic, and pentose phosphate pathways positively regulate H 2 S production in hRBCs [80] . hRBCs possess an active and functional endothelial nitric oxide synthase (eNOS) and are a major source of NO (hRBC-eNOS → NO production), contributing to the circulating NO pool [50, 118] . The ability of hRBCs to take up endothelium-derived NO, thereby limiting NO available for vasodilation: Fe 2+ -HbO 2 (oxy-Hb) + NO → Fe 3+ -Hb (metHb) + NO 3 − , does not invalidate our statement just described. The localization of homodimeric hRBC-eNOS at the cytoplasm leaflet preferentially increase local metHb concentration which in turn acts like a shield to protect NO molecules -produced by hRBC-eNOS -from scavanging by oxyhemoglobin (oxy-Hb). This allows NO molecules not only to leave the erythrocytes but also to interact with their targets located in the immediate vicinity of hRBC-eNOS. Another important aspect is that metHb molecules generated in this process can now be used to clear sulfide via MetHbcatalyzed oxidation of H 2 S to thiosulfate and polysulfides. It is to note that high concentration of NO impairs dimer stability of eNOS as well as its activity and this loss of dimer (eNOS monomerization) can be reversed by thioredoxin/thioreductase system [119] . These sophisticated and coordinated processes curtail exuberant NO production in vivo. The following work illustrates in a very compact form the physical and chemical properties of NO and its physiological roles [120] . NO inhibits erythrocyte cell death (eryptosis) [52] and reduction of NO bioavailability has been observed in several diseases, for example, in sickle cell anemia [121] . Recently, we observed systemic inflammation and enhanced rate of eryptosis in NFĸB-p50 (p50) deficient mice [38] . It is known that NFĸB-p50 homodimers are refractory to inflammation while NFĸB heterodimers (e.g. NFĸB-p65-p50 subunits) have an inflammatory function [41] . NFĸB-p65 (p65) activity is regulated by several reversible post-translational modification mechanisms. p65 is activated by phosphorylation [122] or acetylation [123] and inhibited by deacetylation [123, 124] . To date, there is no single publication that has investigated the influence of H 2 S on NFĸBs in hRBCs. We tend to believe that H 2 S with its anti-inflammatory properties exerts an inhibitory effect on p65 and positively regulates p50. We will clarify this experimentally in the near future. In nucleated cells, publications on the influence of H 2 S on NFĸBs are contradictory. According to several publications, H 2 S-mediated p65 sulfhydration can lead to its activation and inhibition. These inconsistencies are rather due to a lack of standardized methods for determining H 2 S concentration.

Human erythrocytes (hRBCs) are a mobile organ that traverse our entire organism. They are involved in innumerable biological and physiological processes, are directly involved in virus and bacterial elimination from circulation, maintain the concentrations of many signaling molecules and antioxidants in physiological range, possess transcription factors such as NFĸBs and their upstream kinases and act as a sink for many inflammatory cytokines and chemokines, thus minimizing their deleterious effects. Therefore, treatment of many pathological diseases without considering hRBCs, is myopic and not an adequate remedy.

Characterization of the enzymic capacity for cysteine desulphhydration in liver and kidney of the rat

Vascular endothelium expresses 3-mercaptopyruvate sulfurtransferase and produces hydrogen sulfide

Production of H2S by 3-mercaptopyruvate sulphurtransferase

Sulfide oxidation by a noncanonical pathway in red blood cells generates thiosulfate and polysulfides

Discovery of the aquaporins and development of the field

No facilitator required for membrane transport of hydrogen sulfide

Solubility and permeation of hydrogen sulfide in lipid membranes

Why can hydrogen sulfide permeate cell membranes?

The anti-thrombotic effect of hydrogen sulfide is partly mediated by an upregulation of nitric oxide synthases

Decreased endogenous production of hydrogen sulfide accelerates atherosclerosis

Hydrogen sulfide stimulates xanthine oxidoreductase conversion to nitrite reductase and formation of NO

Hydrogen sulfide and the liver

Hydrogen sulfide and endothelial dysfunction: relationship with nitric oxide

THE FATE OF SULFIDES IN THE BLOOD

Transport of H2S and HS(-) across the human red blood cell membrane: rapid H2S diffusion and AE1-mediated Cl(-)/HS(-) exchange

The carbon monoxide-binding pigment of liver microsomes. I. Evidence for its hemoprotein nature

Reactions of ferric hemoglobin and myoglobin with hydrogen sulfide under physiological conditions

Whole tissue hydrogen sulfide concentrations are orders of magnitude lower than presently accepted values

Hydrogen sulfide cytoprotective signaling is endothelial nitric oxide synthase-nitric oxide dependent

The life-span of the red cell in men

Blood contains circulating cell-free respiratory competent mitochondria

Functional role of proteins containing ankyrin repeats

Ankyrin domains across the tree of life

Large Ankyrin repeat proteins are formed with similar and energetically favorable units

Regulation of IkB alpha phosphorylation by PKC-and Ca(2+)--dependent signal transduction pathways

Role of NF-kappaB-mediated interleukin-8 expression in intraocular neovascularization

IL-4 inhibits the expression of IL-8 from stimulated human monocytes

Red blood cells are a sink for interleukin 8, a leukocyte chemotaxin

Interleukin 8 released after acute myocardial infarction is mainly bound to erythrocytes

The human erythrocyte inflammatory peptide (chemokine) receptor. Biochemical characterization, solubilization, and development of a binding assay for the soluble receptor

Dynamic phosphorylation of RelA on Ser42 and Ser45 in response to TNFalpha stimulation regulates DNA binding and transcription

Protein kinase C and calcineurin synergize to activate IkappaB kinase and NF-kappaB in T lymphocytes

Protein kinase Calpha (PKCalpha) acts upstream of PKCtheta to activate IkappaB kinase and NF-kappaB in T lymphocytes

NAK is an IkappaB kinase-activating kinase

The NFkB pathway inhibitors Bay 11-7082 and parthenolide induce programmed cell death in anucleated Erythrocytes

Age sensitivity of NFkappaB abundance and programmed cell death in erythrocytes induced by NFkappaB inhibitors

Potential roles of the NFkappaB and glutathione pathways in mature human erythrocytes

Association between nuclear factor of kappa B (NFkappaB) deficiency and induction of eryptosis in mouse erythrocytes

Pharmaceutical composition containing Bay 11-7082, parthenolide or a combination thereof for the treatment of obesity or cardiovascular diseases

Pharmacological targeting of glucose-6-phosphate dehydrogenase in human erythrocytes by Bay 11-7082, parthenolide and dimethyl fumarate

Differential activation of NF kappa B/RelA-p50 and NF kappa B/p50-p50 in control and alcohol-drinking rats subjected to carrageenin-induced pleurisy

Transport and direct utilization of gamma-glutamylcyst(e)ine for glutathione synthesis

Glutathione synthesis and turnover in the human erythrocyte: alignment of a model based on detailed enzyme kinetics with experimental data

Regulation of gamma-glutamyl-cysteine synthetase by nonallosteric feedback inhibition by glutathione

Dynamic redox control of NF-kappaB through glutaredoxin-regulated S-glutathionylation of inhibitory kappaB kinase beta

Nitric oxide represses inhibitory kappaB kinase through S-nitrosylation

PKC alpha phosphorylates cytosolic NF-kappaB/p65 and PKC delta delays nuclear translocation of NF-kappaB/p65 in U1242 glioblastoma cells

Nuclear factor kappa B dependent induction of gamma glutamylcysteine synthetase by ionizing radiation in T98G human glioblastoma cells

Nitric oxide-mediated protection of endothelial cells from hydrogen peroxide is mediated by intracellular zinc and glutathione

Red blood cells express a functional endothelial nitric oxide synthase

Evidence for the presence of L-arginine-nitric oxide pathway in human red blood cells: relevance in the effects of red blood cells on platelet function

Trifluoperazine-Induced suicidal erythrocyte death and S-Nitrosylation inhibition, reversed by the nitric oxide donor sodium nitroprusside

Nitric oxide circulates in mammalian plasma primarily as an S-nitroso adduct of serum albumin

Why NO?

Biological roles of nitric oxide

Physiological [Ca2 +]i level and pump-leak turnover in intact red cells measured using an incorporated Ca chelator

L-type Ca2+ channels: a new player in the regulation of Ca2+ signaling, cell activation and cell survival in immune cells

Ion regulation of phosphatidylserine and phosphatidylethanolamine outside-inside translocation in human erythrocytes

Phosphatidylserine externalization in caveolae inhibits Ca2+ efflux through plasma membrane Ca2+-ATPase in ECV304

Purification of the (Ca2+-Mg2+)-ATPase from human erythrocyte membranes using a calmodulin affinity column

The plasma membrane Ca(2)+ ATPase and the plasma membrane sodium calcium exchanger cooperate in the regulation of cell calcium

The plasma membrane calcium pump: new ways to look at an old enzyme

The Gardos channel: a review of the Ca2+-activated K+ channel in human erythrocytes

Sensitivity of CaM Kinase II to the frequency of Ca2+ Oscillations

Intracellular Ca(2+) signaling and Ca(2+) microdomains in the control of cell survival, apoptosis and autophagy

Regulation of cell death: the calcium-apoptosis link

Roles of calcium ions in the membrane binding of C2 domains

Roles of ionic residues of the C1 domain in protein kinase C-alpha activation and the origin of phosphatidylserine specificity

Calcium stimulates self-assembly of protein kinase C alpha in vitro

Activation of the PKC-isotypes α, β1, γ, δ, and ε by phorbol esters of different biological activities

Reversible exposure of the pseudosubstrate domain of protein kinase C by phosphatidylserine and diacylglycerol

Protein kinase C isoforms in human erythrocytes

Protein kinase C in the human erythrocyte. Translocation to the plasma membrane and phosphorylation of bands 4.1 and 4.9 and other membrane proteins

Protein kinase C mediates erythrocyte "programmed cell death" following glucose depletion

Protein kinase C activation induces phosphatidylserine exposure on red blood cells †

The specific PKC-alpha inhibitor chelerythrine blunts costunolide-induced eryptosis

Mechanisms of ascorbic acid recycling in human erythrocytes

The concentration of glutathione in human erythrocytes is a heritable trait

Glutathione biosynthesis in human erythrocytes. I. Identification of the enzymes of glutathione synthesis in hemolysates

Sulfur reduction by human erythrocytes

A source of hydrogen sulfide and a mechanism of its release in the brain

Glutathione in bacteria

The central role of glutathione in the pathophysiology of human diseases

Inevitable glutathione, then and now

Protein kinase C alpha-mediated phosphorylation of PIM-1L promotes the survival and proliferation of acute myeloid leukemia cells

LPA1 receptor activation induces PKCalpha nuclear translocation in glioblastoma cells

Reversal of efflux of an anticancer drug in human drug-resistant breast cancer cells by inhibition of protein kinase Calpha (PKCalpha) activity

Enhancement of parthenolide-induced apoptosis by a PKC-alpha inhibition through heme oxygenase-1 blockage in cholangiocarcinoma cells

PKC-alpha inhibitor MT477 slows tumor growth with minimal toxicity in in vivo model of non-Ras-mutated cancer via induction of apoptosis

Conventional protein kinase C-alpha (PKC-alpha) and PKC-beta negatively regulate RIG-I antiviral signal transduction

PKC-dependent phosphorylation of eNOS at T495 regulates eNOS coupling and endothelial barrier function in response to G+ -toxins

Consequences of dysregulated complement regulators on red blood cells

Human erythrocytes selectively bind and enrich infectious HIV-1 virions

Glycophorin is the reovirus receptor on human erythrocytes

Chemical structure of attachment sites for viruses on human erythrocytes

The site of bluetongue virus attachment to glycophorins from a number of animal erythrocytes

Attachment of influenza C virus to human erythrocytes

Partial characterization of the human erythrocyte receptor for rabbit haemorrhagic disease virus

Human erythrocytes bind and inactivate type 5 adenovirus by presenting Coxsackie virus-adenovirus receptor and complement receptor 1

Regulation of circulating immune complexes by complement receptor type 1 on erythrocytes in chronic viral liver diseases

Phorbol ester stimulates a protein kinase C-mediated agatoxin-TKsensitive calcium permeability pathway in human red blood cells

In vitro and in vivo activity of protein kinase C inhibitor chelerythrine chloride induces tumor cell toxicity and growth delay in vivo

Protein kinase C inhibitor chelerythrine attenuates partial unilateral ureteral obstruction induced kidney injury in neonatal rats

Chelerythrine is a potent and specific inhibitor of protein kinase C

Coronavirus disease 2019 (COVID-19), human erythrocytes and the PKC-alpha/-beta inhibitor chelerythrine -possible therapeutic implication

Cancer: NF-kappaB regulates energy metabolism

Proliferating tumor cells mimick glucose metabolism of mature human erythrocytes

Antiinflammatory effects of insulin and the pro-inflammatory effects of glucose

Psoriasis is associated with low serum levels of hydrogen sulfide, a potential anti-inflammatory molecule

Hydrogen sulfide and dermatological diseases

Hydrogen sulfide inhibits IL-8 expression in human keratinocytes via MAP kinase signaling

The protective role of hydrogen sulfide against obesity-associated cellular stress in blood glucose regulation

H2S-releasing drugs: anti-inflammatory, cytoprotective and chemopreventative potential

Endogenous H2S production deficiencies lead to impaired renal erythropoietin production

Metabolism of 2,3-diphosphoglycerate and glycolysis in human red blood cells under the influence of dipyridamole and inorganic sulfur compounds

Reciprocal binding of oxygen and diphosphoglycerate by human hemoglobin

Hydrogen Sulfide Is a Regulator of Hemoglobin Oxygen-Carrying Capacity via Controlling 2,3-BPG Production in Erythrocytes

Endothelial nitric oxide synthase in red blood cells: key to a new erythrocrine function?

Dual-Track clearance of circulating bacteria balances rapid restoration of blood sterility with induction of adaptive immunity

The physiological role of nitric oxide

Sickle cell disease vasculopathy: a state of nitric oxide resistance

Activation of NF-kappa B in vivo is regulated by multiple phosphorylations

Duration of nuclear NF-kappaB action regulated by reversible acetylation

SIRT1 activators suppress inflammatory responses through promotion of p65 deacetylation and inhibition of NF-kappaB activity

MG designed the project and mainly wrote the manuscript. All figures were made by MG. All authors read, discussed, improved, and approved the final version of the manuscript.

The authors declare that no competing financial interests or otherwise exist.

http://orcid.org/0000-0002-1740-594X