title: Arsenic-induced alteration in intracellular calcium homeostasis induces head kidney macrophage apoptosis involving the activation of calpain-2 and ERK in Clarias batrachus.
abstract: We had earlier shown that exposure to arsenic (0.50 μM) caused caspase-3 mediated head kidney macrophage (HKM) apoptosis involving the p38-JNK pathway in Clarias batrachus. Here we examined the roles of calcium (Ca(2+)) and extra-cellular signal-regulated protein kinase (ERK), the other member of MAPK-pathway on arsenic-induced HKM apoptosis. Arsenic-induced HKM apoptosis involved increased expression of ERK and calpain-2. Nifedipine, verapamil and EGTA pre-treatment inhibited the activation of calpain-2, ERK and reduced arsenic-induced HKM apoptosis as evidenced from reduced caspase-3 activity, Annexin V-FITC-propidium iodide and Hoechst 33342 staining. Pre-incubation with ERK inhibitor U 0126 inhibited the activation of calpain-2 and interfered with arsenic-induced HKM apoptosis. Additionally, pre-incubation with calpain-2 inhibitor also interfered with the activation of ERK and inhibited arsenic-induced HKM apoptosis. The NADPH oxidase inhibitor apocynin and diphenyleneiodonium chloride also inhibited ERK activation indicating activation of ERK in arsenic-exposed HKM also depends on signals from NADPH oxidase pathway. Our study demonstrates the critical role of Ca(2+) homeostasis on arsenic-induced HKM apoptosis. We suggest that arsenic-induced alteration in intracellular Ca(2+) levels initiates pro-apoptotic ERK and calpain-2; the two pathways influence each other positively and induce caspase-3 mediated HKM apoptosis. Besides, our study also indicates the role of ROS in the activation of ERK pathway in arsenic-induced HKM apoptosis in C. batrachus.
authors.affiliation: Immunobiology Laboratory, Department of Zoology, University of Delhi, Delhi 110 007, India.
authors.forename: Chaitali
authors.initials: C
authors.lastname: Banerjee
authors.forename: Ramansu
authors.initials: R
authors.lastname: Goswami
authors.forename: Soma
authors.initials: S
authors.lastname: Datta
authors.forename: R
authors.initials: R
authors.lastname: Rajagopal
authors.forename: Shibnath
authors.initials: S
authors.lastname: Mazumder
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D001151:Arsenic / Q000633:toxicity*; D002118:Calcium / Q000502:physiology*; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology; D002154:Calpain / Q000378:metabolism*; D002397:Catfishes; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D006706:Homeostasis / Q000187:drug effects* / Q000502:physiology; D007424:Intracellular Fluid / Q000187:drug effects / Q000201:enzymology; D007527:Isoenzymes / Q000378:metabolism; D007668:Kidney / Q000187:drug effects / Q000201:enzymology; D008264:Macrophages / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology*
chemical_list: D007527:Isoenzymes; D048049:Extracellular Signal-Regulated MAP Kinases; D002154:Calpain; D001151:Arsenic; D002118:Calcium