Evidences of Biological Functions of Biliverdin Reductase A in the Bovine Epididymis
JOURNAL OF CELLULAR PHYSIOLOGY
Authors: D'Amours, Olivier; Frenette, Gilles; Caron, Patrick; Belleannee, Clemence; Guillemette, Chantal; Sullivan, Robert
Abstract
Epididymal sperm binding protein 1 (ELSPBP1) is secreted by the epididymal epithelium via epididymosomes and is specifically transferred to dead spermatozoa during epididymal transit. We identified biliverdin reductase A (BLVRA) as a partner of ELSPBP1 by immunoprecipitation followed by tandem mass spectrometry. Pull down assays showed that these two proteins interact in the presence of zinc ions. The BLVRA enzyme is known to convert biliverdin to bilirubin, both of which possess antioxidant activity. Assessment by real-time RT-PCR showed that BLVRA is highly expressed in the caput and the corpus epididymis, but is expressed at lower levels in the testis and the cauda epididymis. It is primarily found in the soluble fraction of the caput epididymal fluid, is barely detectable in the cauda fluid, and is detectable to a lesser extent in the epididymosome fraction of both caput and cauda fluids. Immunocytometry on epididymal sperm showed that BLVRA is found on all sperm recovered from the caput region, whereas it is undetectable on cauda sperm. Biliverdin and bilirubin are found in higher concentrations in the caput epididymal fluid, as measured by mass spectrometry. Lipid peroxidation was limited by 1M of biliverdin, but not bilirubin when caput spermatozoa were challenged with 500M H2O2. Since immature spermatozoa are a source of reactive oxygen species, BLVRA may be involved in the protection of maturing spermatozoa. It is also plausible that BLVRA is implicated in haemic protein catabolism in the epididymal luminal environment. J. Cell. Physiol. 231: 1077-1089, 2016. (c) 2015 Wiley Periodicals, Inc.
Genetic Variations in Bilirubin Metabolism Genes and Their Association with Unconjugated Hyperbilirubinemia in Adults
ANNALS OF HUMAN GENETICS
Authors: Chiddarwar, Ashish S.; D'Silva, Selma Z.; Colah, Roshan B.; Ghosh, Kanjaksha; Mukherjee, Malay B.
Abstract
Objective: The present study was undertaken to investigate the genotype and allele frequencies of the variants in the four bilirubin metabolism genes (UGT1A1, OATP2, HMOX1, and BLVRA) and their association with hyperbilirubinemia. Material and Methods: Genotyping of 17 genetic variants was performed in 115 adults with hyperbilirubinemia and 150 controls by PCR-RFLP, GeneScan analysis, and direct DNA sequencing. Results: Genetic polymorphisms of the UGT1A1 promoter, specifically the T-3279G phenobarbital-responsive enhancer module and (TA) 7 dinucleotide repeat, as well as the intron and coding region variants of the OATP2, HMOX1, and BLVRA genes, were significantly higher among the cases than the controls. Further, nearly 82% of the cases showed the presence of significantly four or more variants as compared to 37% of the controls (P < 0.0001) and the mean total serum bilirubin levels also increased according to the number of variants co-expressed. Conclusions: This study demonstrates that polymorphisms in the bilirubin metabolism genes had a significant effect on bilirubin levels and could be genetic risk factors for hyperbilirubinemia.