Detection of biliverdin reductase activity

Protective activity of purpurin against d-galactosamine and lipopolysaccharide-induced hepatorenal injury by upregulation of heme oxygenase-1 in the RBC degradation cycle

Acute liver failure, associated with oxidative stress and sustained inflammation is the major clinical manifestation of liver diseases with a high mortality rate due to limited therapeutic options. Purpurin is a bioactive compound of Rubia cordifolia that has been used in textile staining, as a food additive, and as a treatment of multiple chronic and metabolic diseases associated with inflammation and oxidative stress. The present work aimed to investigate the protective efficacy of purpurin against hepatorenal damage. Thirty-six female albino rats were equally assigned into six groups. Purpurin was administered orally once a day for 6 days at doses of 05, 10, and 20 mg/kg, respectively. Intraperitoneal injection of lipopolysaccharide (50 μg/kg) was administered to the animals on 6th day evening, 1 h after d-galactosamine (300 mg/kg) administration to induce hepatorenal injury. The results revealed that purpurin alleviated alterations in serological and hematological parameters as well as restored histoarchitectural and cellular integrity of the liver and kidney. Purpurin restored superoxide dismutase, catalase, glutathione reductase, glutathione peroxidase, and glutathione content in hepatorenal tissues. Accompanied by the diminution of increased bilirubin and biliverdin, purpurin also diminished total cholesterol, triglyceride, and lipid peroxidation in hepatorenal tissues. Purpurin markedly attenuated the elevation of CYP2E1, restored glutathione-S-transferase, and prevented DNA damage in hepatorenal tissues. Purpurin reduced iron overload by reducing heme depletion and recycling of ferritin and hemosiderin. It also reinforced biliverdin reductase, heme oxygenase-1 to employ hepatorenal protection by regulating antioxidant enzymes and other pathways that produced NADPH. Thus, it may be concluded that purpurin has protective potential against acute hepatorenal injury.

Biliverdin Reductase A Attenuates Hepatic Steatosis by Inhibition of Glycogen Synthase Kinase (GSK) 3β Phosphorylation of Serine 73 of Peroxisome Proliferator-activated Receptor (PPAR) α

Non-alcoholic fatty liver disease is the most rapidly growing form of liver disease and if left untreated can result in non-alcoholic steatohepatitis, ultimately resulting in liver cirrhosis and failure. Biliverdin reductase A (BVRA) is a multifunctioning protein primarily responsible for the reduction of biliverdin to bilirubin. Also, BVRA functions as a kinase and transcription factor, regulating several cellular functions. We report here that liver BVRA protects against hepatic steatosis by inhibiting glycogen synthase kinase 3β (GSK3β) by enhancing serine 9 phosphorylation, which inhibits its activity. We show that GSK3β phosphorylates serine 73 (Ser(P)⁷³) of the peroxisome proliferator-activated receptor α (PPARα), which in turn increased ubiquitination and protein turnover, as well as decreased activity. Interestingly, liver-specific BVRA KO mice had increased GSK3β activity and Ser(P)⁷³ of PPARα, which resulted in decreased PPARα protein and activity. Furthermore, the liver-specific BVRA KO mice exhibited increased plasma glucose and insulin levels and decreased glycogen storage, which may be due to the manifestation of hepatic steatosis observed in the mice. These findings reveal a novel BVRA-GSKβ-PPARα axis that regulates hepatic lipid metabolism and may provide unique targets for the treatment of non-alcoholic fatty liver disease.