key: cord-0807263-ix3nvjtg authors: San Juan, Itxaso; Bruzzone, Chiara; Bizkarguenaga, Maider; Bernardo‐Seisdedos, Ganeko; Laín, Ana; Gil‐Redondo, Rubén; Diercks, Tammo; Gil‐Martínez, Jon; Urquiza, Pedro; Arana, Eunate; Seco, Marisa; García de Vicuña, Aitor; Embade, Nieves; Mato, José M; Millet, Oscar title: Abnormal concentration of porphyrins in serum from COVID‐19 patients date: 2020-08-03 journal: Br J Haematol DOI: 10.1111/bjh.17060 sha: 4d392dc55eb9ea8fb7c87c6b91ebb57b99bf04c0 doc_id: 807263 cord_uid: ix3nvjtg COVID‐19 is an infectious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2). COVID‐19 is not only a lung disease but rather a systemic syndrome where blood alterations may play a key role (1). Severe cases show a marked variation in the red blood cell distribution width (2), which agrees well with reduced erythrocyte turnover and would function as a compensatory mechanism to maintain the circulating red blood cell and oxygen levels (3). COVID-19 is an infectious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). COVID-19 is not only a lung disease but rather a systemic syndrome where blood alterations may play a key role (1) . Severe cases show a marked variation in the red blood cell distribution width (2) , which agrees well with reduced erythrocyte turnover and would function as a compensatory mechanism to maintain the circulating red blood cell and oxygen levels (3) . This article is protected by copyright. All rights reserved and ferritin concentrations (4) . Hyperbilirubinemia is also observed in erythropoietic porphyrias (5,6) or inflammation processes and would be consistent with ineffective erythropoiesis (7) and rapid hemoglobin turnover. Autopsies of deceased COVID-19 patients have revealed that the spleen is significantly altered in size, which is a normal physiological response to anemia. Preliminary studies suggest that CD147 can bind the spike protein of SARS-CoV-2, abrogating the normal recycling of erythrocytes from the spleen into the bloodstream, selectively trapping red blood cells in the spleen and developing a form of anemia (8) . Porphyrin accumulation can occur due to pathological conditions, including severe infections or in porphyries, the latter being a set of metabolic disorders that result from the deficiency of the enzymes in the heme biosynthetic pathway or gain-of-function mutations in aminolevulinate synthase 2 (ALAS2) (5). Heme synthesis relies on the sequential action of eight enzymes, mainly expressed in liver and in erythroid cells ( Figure 1A We determined serum porphyrin levels by HPLC separation and quantification. While these measurements are more sensitive on blood, the current emergency situation precluded working with such samples. Yet, serum is also a perfect matrix to derive the porphyrin content and the Accepted Article results are largely comparable (9) . As shown in Figure 1B , the serum porphyrin profile from COVID-19 patients significantly accumulate the by-products uroporphyrin I (URO I) and coproporphyrin I (COP I) and the metabolite coproporphyrin III (COP III). This accumulation cannot be attributed to pneumonia since the COVID-neg and pre-COVID cohorts show similar levels for all porphyrins but UROI, that slightly accumulates in the COVID-neg cohort. NMR analysis showed that neither aminolevulinate nor porphobilinogen accumulate. This signature is specific for COVID-19 patients and does not match the one found in porphyrias, specifically in those where the central enzymes of the heme pathway are malfunctioning due to deleterious mutations (10, 11) . Instead, in COVID-19, it is hard to rationalize how the pathological heme shortage may affect its own regulation, while the reported hyperferritinemia may be a consequence of the inflammation process. Any case, non-productive byproducts URO I and COP I accumulate, inhibiting the central enzymes of the pathway and exacerbating heme shortage (unpublished results). This unstable scenario inevitably leads to the accumulation of porphyrins, as shown by Figure 1A (thick arrows) (12) . Incidentally, the normal levels of protoporphyrin IX (PROTO IX) suggests that SARS-CoV-2 is not directly competing with the heme group for the iron atom, as previously suggested (13) . Porphyrin accumulation in COVID-19 sera is lower than in the blood of porphyria patients, in line with the limited duration of the viral infection episode. Liver damage is often associated to mitochondrial dysfunction due to the deficient functioning of the electron transport chain (ETC) upon heme shortage (14) . Ketone bodies (acetoacetic acid, 3hydroxybutyric acid and acetone) were highly elevated in the serum of COVID-19 patients, which may be an adaptation to meet the reduced need for NADH, and consequently for acetyl-CoA, to feed into the ETC in these patients. As ketone bodies are produced from fatty acid oxidation (FAO)-derived acetyl-CoA, the increased content of triglycerides (TG) and very low-density lipoproteins (VLDL)-TG observed may also be explained as an adaptation to meet the reduced need for FAO and prevent the intrahepatic accumulation of TG in these patients. We also found elevated levels of 2-hydroxybutyric ( Figure 1D ), which is synthesized principally in the liver and released as a byproduct of glutathione synthesis by the transsulfuration pathway. An elevated concentration of the metabolite may reflect an increase of oxidative stress in COVID-19 patients. In brief, these results are compatible with impaired hepatic mitochondrial function in COVID-19, also consistent with the accumulation of porphyrins. This article is protected by copyright. All rights reserved In summary, we here report an abnormal accumulation of porphyrins associated to severe COVID-19 patients that may shed some light to understand the hematological disorder associated with this devastating disease. This article is protected by copyright. All rights reserved Hematological findings and complications of COVID-19 Incidence of thrombotic complications in critically ill ICU patients with COVID-19 Modulation of red blood cell population dynamics is a fundamental homeostatic response to disease Epidemiological and clinical characteristics of 99 cases of 2019 novel coronavirus pneumonia in Wuhan, China: a descriptive study Accepted Article 5 The porphyrias: Advances in diagnosis and treatment Modern diagnosis and management of the porphyrias Characterization of iron metabolism and erythropoiesis in erythrocyte membrane defects and thalassemia traits Unavailability of CD147 leads to selective erythrocyte trapping in the spleen Abnormal serum porphyrin levels in patients with the acquired immunodeficiency syndrome with or without hepatitis C virus infection Functional consequences of naturally occurring mutations in human uroporphyrinogen decarboxylase Repurposing ciclopirox as a pharmacological chaperone in a model of congenital erythropoietic porphyria Therapeutic potential of proteasome inhibitors in congenital erythropoietic porphyria COVID-19: Attacks the 1-Beta Chain of Hemoglobin and Captures the Porphyrin to Inhibit Human Heme Metabolism Feasibility of cellular bioenergetics as a biomarker in porphyria patients