title: Inducible headkidney cytochrome P450 contributes to endosulfan immunotoxicity in walking catfish Clarias gariepinus.
abstract: The effect of endosulfan metabolites on fish immune system is not well known. It is also not clear whether endosulfan accumulates in fish immune organs and undergoes metabolic biotransformation in situ. In the present study we investigated the role of headkidney (HK), an important fish immune organ on endosulfan metabolism and the long term effects of endosulfan metabolites on the fish immune system. C. gariepinus (walking catfish) were exposed to 2.884ppb of endosulfan (1/10th LC50) for 30d followed by their maintenance in endosulfan-free water for 30d for recovery. Endosulfan induced time-dependent reduction in the HK somatic index and histo-pathological changes in renal and hemopoietic components of the organ. At cellular level, exposure to endosulfan led to death of HK leucocytes. Gas-liquid-chromatography documented the presence of both α- and β-isomers of endosulfan along with the toxic metabolite endosulfan sulfate (ESS) in the HK of exposed fishes. We report that β-endosulfan accumulates more readily in the HK. Depuration studies suggested the persistence of ESS in the HK. Enzyme-immunoassay and qPCR results demonstrated direct relationship between cytochrome P450 1A (CYP1A) expression and ESS levels in the HK. Pre-treatment of HKL with CYP1A specific inhibitor α-Naphthoflavone (ANF) led to reduction in CYP1A mRNA, protein levels, and inhibited ESS formation together implicating the role of CYP1A on endosulfan metabolism. When the exposed fish were transferred to endosulfan-free water ('recovered fish') it was observed that after 30d of recovery period the concentration of endosulfan and its metabolite in the HK were significantly reduced, compared to 30-d exposed fish. We also observed improvement in HK histo-architecture but no significant recovery in HKL number and viability. Collectively, our findings suggest that HK plays an important role in endosulfan metabolism. We propose that endosulfan induces the activation of CYP1A in HK which led to the generation of persistent metabolite, ESS, resulting in immunotoxicity.
authors: Immunobiology Laboratory, Department of Zoology, University of Delhi, Delhi 110 007, India.
authors: Usha
authors: U
authors: Kumari
authors: Immunobiology Laboratory, Department of Zoology, University of Delhi, Delhi 110 007, India.
authors: Nidhi
authors: N
authors: Srivastava
authors: Immunobiology Laboratory, Department of Zoology, University of Delhi, Delhi 110 007, India.
authors: Asha
authors: A
authors: Shelly
authors: Immunobiology Laboratory, Department of Zoology, University of Delhi, Delhi 110 007, India.
authors: Preeti
authors: P
authors: Khatri
authors: Pesticide Toxicology and Soil Microbial Ecology Laboratory, Department of Zoology, University of Delhi, Delhi 110 007, India.
authors: Sarat
authors: S
authors: N
authors: Pesticide Toxicology and Soil Microbial Ecology Laboratory, Department of Zoology, University of Delhi, Delhi 110 007, India.
authors: Dileep Kumar
authors: DK
authors: Singh
authors: Immunobiology Laboratory, Department of Zoology, University of Delhi, Delhi 110 007, India. Electronic address: shibnath1@yahoo.co.in.
authors: Shibnath
authors: S
authors: Mazumder
mesh_terms: D000818:Animals; D001711:Biotransformation; D002397:Catfishes / Q000378:metabolism*; D065607:Cytochrome P-450 Enzyme Inhibitors / Q000378:metabolism; D003577:Cytochrome P-450 Enzyme System / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D004726:Endosulfan / Q000031:analogs & derivatives / Q000378:metabolism / Q000633:toxicity*; D007118:Immunoassay; D007668:Kidney / Q000166:cytology / Q000378:metabolism / Q000473:pathology; D007962:Leukocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D008297:Male; D012333:RNA, Messenger / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D014874:Water Pollutants, Chemical / Q000737:chemistry / Q000378:metabolism / Q000633:toxicity*
chemical_list: D065607:Cytochrome P-450 Enzyme Inhibitors; D012333:RNA, Messenger; D014874:Water Pollutants, Chemical; C544689:endosulfan sulfate; D003577:Cytochrome P-450 Enzyme System; D004726:Endosulfan
keywords: CYP1A; Clarias gariepinus; Endosulfan; Headkidney