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Therapeutic Gases for Neurological Disorders
Published in Sahab Uddin, Rashid Mamunur, Advances in Neuropharmacology, 2020
R. Rachana, Tanya Gupta, Saumya Yadav, Manisha Singh
When the upregulation of heme oxygenase 1 protein occurs, an increase in biliverdin also occurs. This biliverdin molecule is then reduced into the antioxidant and anti-nitrosative molecule, bilirubin by the activity of an enzyme biliverdin reductase. This is another mechanism which is also seen to have shown neuroprotective effects (Calabrese et al., 2007).
Carbon Monoxide Poisoning, Methemoglobinemia, and Sulfhemoglobinemia
Published in Harold R. Schumacher, William A. Rock, Sanford A. Stass, Handbook of Hematologic Pathology, 2019
In the absence of environmental CO, the blood of adults contains about 1% COHb. This represents about 80% of the total body CO; the rest probably is sequestered in myoglobin and cytochromes. This amount of CO is produced endogenously. The predominant origin is the degradation of heme by the rate-limiting heme oxygenase/cytochrome P-450 complex, which produces CO and biliverdin. Further degradation of biliverdin to bilirubin by biliverdin reductase enables one molecule of hemoglobin to generate one molecule of CO and one molecule of biliverdin.
Heme Oxygenase-1 in Kidney Health and Disease
Published in Shamim I. Ahmad, Handbook of Mitochondrial Dysfunction, 2019
Pu Duann, Elias A. Lianos, Pei-Hui Lin
Heme oxygenase (HO) was initially identified as a liver microsomal protein with activity to degrade heme to bilirubin (1). HO is the rate-limiting enzyme that catalyzes the degradation of heme to equimolar quantities of carbon monoxide (CO), iron and biliverdin (Figure 1). Biliverdin is subsequently reduced to bilirubin by biliverdin reductase (BVR) (2). Heme is pro-oxidant and synthesized in the mitochondria. In physiology, significant amount of heme could arise from the destruction of aged red blood cells, and therefore should be tightly controlled. Two major HO isoforms exist. HO-2 is constitutively active, whereas HO-1 is inducible.
HMOX1 Promotes Ferroptosis Induced by Erastin in Lens Epithelial Cell through Modulates Fe2+ Production
Published in Current Eye Research, 2023
Shengjie Liao, Mi Huang, Yanli Liao, Chao Yuan
HMOX1 could metabolize heme into carbon monoxide, iron, and biliverdin. Biliverdin is subsequently converted to bilirubin by biliverdin reductase. To observe which by-products mediate the synergistic effect with erastin, CORM2, FeSO4, and bilirubin were added into HMOX1 knock-out cell medium with erastin. Figure 6(A) showed that CORM2 and bilirubin could not aggravate the cytotoxic effect of erastin in HMOX1 knock-out cells. Adding FeSO4 increase the sensitivity of the HLECs to erastin significantly. Then HMOX1 expression vector or empty vector were transiently transfected into HMOX1 knock-out cells, and cell viability and iron level were detected after 24 h treatment of erastin. Figure 6(B) showed that HMOX1 overexpression significantly decreased cell viability after erastin treatment. Indeed, total iron level increased when cells transfected with HMOX1 expression vector which could further increase after erastin treatment (Figure 6(C)). These data implied that iron liberated from heme by HMOX1 is a pivotal by-product that mediates the sensitivity elevation of erastin in HLECs.
Inhibitory Effects of Bilirubin on Colonization and Migration of A431 and SK-MEL-3 Skin Cancer Cells Compared with Human Dermal Fibroblasts (HDF)
Published in Cancer Investigation, 2021
Javad Saffari-Chaleshtori, Ali Shojaeian, Esfandiar Heidarian, Sayed Mohammad Shafiee
Bilirubin is a tetrapyrrole and an endogenous catabolic product that is formed during heme catabolism. After lysis of the erythrocytes in the spleen and liver, macrophages remove the hemoglobin and separate the heme group. Subsequently, heme oxygenase converts heme to biliverdin that in turn is converted to unconjugated bilirubin by biliverdin reductase. Unconjugated bilirubin combines with glucuronic acid to form conjugated bilirubin in the liver and is then excreted in bile (11). The normal level of (unconjugated) bilirubin under physiological conditions is around 0.2 mg/dl (3.42 µM) (12). Bilirubin is a lipophilic compound and tends to cross the blood-brain barrier (13). This compound, at high concentrations, can exert neurotoxic effects and therefore induce severe complications in neurons (14). Neonatal jaundice is the most common cause of bilirubinemia. The genetic causes of this condition include Gilbert-Meulengracht, Crigler-Najjar, and Rotor syndrome (12). Serum bilirubin concentrations lower than 12–14 mg/dl are tolerable while higher levels lead to mental retardation especially in neonates (15). However, the mutation in the UDP-glycuronyltransferase gene causes a natural increase in bilirubin up to 1–3 mg/dl (17–51 µM) in Gilbert-Meulengracht syndrome (16).
Immunohistochemical localization of heme oxygenase-1 and bilirubin/biopyrrin of heme metabolites as antioxidants in human placenta with preeclampsia
Published in Hypertension in Pregnancy, 2020
Michiko Miya, Aikou Okamoto, Takashi Nikaido, Rie Tachimoto-Kawaguchi, Tadao Tanaka
An increase in reactive oxygen species (ROS) levels beyond the antioxidant capacity of the body causes oxidative stress. This increase in ROS levels is related to the etiology and pathophysiology of various diseases (5). The body (cells) produces antioxidants that protect it against oxidative damage caused by ROS. Heme oxygenase (HO) is an enzyme that catalyzes the region-specific oxidative degradation of iron protoporphyrin (heme) to biliverdin, iron, and carbon monoxide (CO). Biliverdin is subsequently reduced to bilirubin (BR) by biliverdin reductase. BR generates several hydrophilic metabolites called biopyrrins (BPn) upon oxidation and these can be detected using the anti-bilirubin monoclonal antibody (24G7). BPn are immediately excreted in urine because of their hydrophilic properties. The urinary concentration of BPn is known as an oxidative stress marker that reflects the degree of oxidative stress (6).