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The present invivo study was designed to elucidate the toxic effect of lead on oxidative stress, Na+K+ATPase and mitochondrial electron transport chain activity of the brain of Clarias batrachus. The fish were exposed to 10 and 20% of the derived 96 h LC50 value, 37.8 and 75.6 mg L−1, respectively, and sampled on 20, 40 and 60 days. Exposure of fish brain to lead demonstrated an increased production of reactive oxygen species, increased lipid peroxidation, loss of protein thiol groups in synaptosomal fraction with the decreased activity of Na+K+ATPase, partial inactivation of mitochondrial electron transport chain activity and energy depletion. However, no change in protein carbonyl content in synaptosomal fraction was observed due to lead exposure. Concluding the results of our investigation we suggest that lead exposure induces oxidative stress in the brain of Clarias batrachus and the decline in Na+K+ATPase activity was presumeably mediated by the combined action of lipid peroxidation and deficient mitochondrial electron transport chain activity. [ABSTRACT FROM AUTHOR]

Background/Aims Vasoactive intestinal peptide (VIP) has emerged as a promising agent for treatment of inflammatory bowel disease; however, its impact in ulcerative colitis (UC) targeting colonic mitochondrial dysfunction for maintenance of colon epithelial tract remains uninvestigated. Methods Two working models are as follows. In vivo model: DSS was administered in C57BL/6J mice @ 3.5%/gm body weight for three cycles of 5 days each (5 days gap in between each cycle); i.p. dose of VIP @ 0.5 nmol/mouse/day was administered for next 10 days. Posttreatment mice were sacrificed and isolated mitochondria were utilized for experimentation. In vitro model: to substantiate in vivo findings and accurately identify the reactive species involved in progression of UC, HT29 MTX-E12 mucosal model depicting semi-wet interface as in colon, was subjected to DSS (5%) treatment for 6 days followed by VIP (10 nM) treatment for 4 days in presence and absence of O2 •- scavenger superoxide dismutase (SOD; 20 mM) or •OH scavenger dimethyl sulfoxide (DMSO; 20 mM) or H2O2 scavenger catalase (CAT; 50 μg/mL) or nitric oxide (NO) scavenger L-NAME (100 μM) or ONOO- scavenger cum nitric oxide synthase inhibitor MEG (0.5 mM). Results In vivo: treatment with VIP reduced clinical and histopathological severity of DSS-induced colitis with partial recovery of inhibited mitochondrial respiratory complexes, altered mitochondrial membrane potential and lowered ATP generation. Amelioration of mitochondrial oxidative stress variables were also observed following VIP treatment. In vitro: treatment with VIP restored mitochondrial dysfunction and its efficacy proved at par with SOD and DMSO indicating involvement of O2 •- and •OH in the process. However, other free radical scavengers/inhibitors like CAT, L-NAME and MEG proved ineffective indicating non-involvement of H2O2, NO and ONOO- in the process. Conclusions VIP can act as potent anticolitogenic agent by virtue of its free radical scavenging property as it restored colonic mitochondrial function that contributed in maintenance of colon epithelial lining following exogenous VIP treatment. [ABSTRACT FROM AUTHOR]

Nickel is a potential neurotoxic pollutant inflicting damage in living organisms, including fish, mainly through oxidative stress. Previous studies have demonstrated the impact of nickel toxicity on mitochondrial function, but there remain lacunae on the damage inflicted at mitochondrial respiratory level. Deficient mitochondrial function usually affects the activities of important adenosinetriphosphatases responsible for the maintenance of normal neuronal function, namely Na + K + ATPase, as explored in our study. Previous reports demonstrated the dysfunction of this enzyme upon nickel exposure but the contributing factors for the inhibition of this enzyme remained unexplored. The main purpose of this study was to elucidate the impact of nickel neurotoxicity on mitochondrial respiratory complexes and Na + K + ATPase in the piscine brain and to determine the contributing factors that had an impact on the same. Adult Clarias batrachus were exposed to nickel treated water at 10% and 20% of the 96 h LC50 value (41 mg.l -1 ) respectively and sampled on 20, 40 and 60 days. Exposure of fish brain to nickel led to partial inhibition of complex IV of mitochondrial respiratory chain, however, the activities of complex I, II and III remained unaltered. This partial inhibition of mitochondrial respiratory chain might have been sufficient to lower mitochondrial energy production in mitochondria that contributed to the partial dysfunction of Na + K + ATPase. Besides energy depletion other contributing factors were involved in the dysfunction of this enzyme, like loss of thiol groups for enzyme activity and lipid peroxidation-derived end products that might have induced conformational and functional changes. However, providing direct evidence for such conformational and functional changes of Na + K + ATPase was beyond the scope of the present study. In addition, immunoblotting results also showed a decrease in Na + K + ATPase protein expression highlighting the impact of nickel neurotoxicity on the expression of the enzyme itself. The implication of the inhibition of mitochondrial respiration and Na + K + ATPase dysfunction was the neuronal death as evidenced by enhanced caspase-3 and caspase-9 activities. Thus, this study established the deleterious impact of nickel neurotoxicity on mitochondrial functions in the piscine brain and identified probable contributing factors that can act concurrently in the inhibition of Na + K + ATPase. This study also provided a vital clue about the specific areas that the therapeutic agents should target to counter nickel neurotoxicity., (Copyright © 2018 SETOX & Institute of Experimental Pharmacology and Toxicology, SASc.)

Several studies on mitochondrial functions following brief exposure (5-15 min) to dopamine (DA) in vitro have produced extremely variable results. In contrast, this study demonstrates that a prolonged exposure (up to 2 h) of disrupted or lysed mitochondria to DA (0.1-0.4 mM) causes a remarkable and dose-dependent inhibition of complex I and complex IV activities. The inhibition of complex I and complex IV activities is not prevented by the antioxidant enzyme catalase (0.05 mg/ml) or the metal-chelator diethylenetriaminepentaacetic acid (0.1 mM) or the hydroxyl radical scavengers like mannitol (20 mM) and dimethyl sulphoxide (20 mM) indicating the non-involvement of *OH radicals and Fenton's chemistry in this process. However, reduced glutathione (5 mM), a quinone scavenger, almost completely abolishes the DA effect on mitochondrial complex I and complex IV activities, while tyrosinase (250 units/ml) which catalyses the conversion of DA to quinone products dramatically enhances the former effect. The results suggest the predominant involvement of quinone products instead of reactive oxygen radicals in long-term DA-mediated inactivation of complex I and complex IV. This is further indicated from the fact that significant amount of quinones and quinoprotein adducts (covalent adducts of reactive quinones with protein thiols) are formed during incubation of mitochondria with DA. Monoamine oxidase A (MAO-A) inhibitor clorgyline also provides variable but significant protection against DA induced inactivation of complex I and complex IV activities, presumably again through inhibition of quinoprotein formation. Mitochondrial ability to reduce tetrazolium dye 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) in presence of a respiratory substrate like succinate (10 mM) is also reduced by nearly 85% following 2 h incubation with 0.4 mM DA. This effect of DA on mitochondrial function is also dose-dependent and presumably mediated by quinone products of DA oxidation. The mitochondrial dysfunction induced by dopamine during extended periods of incubation as reported here have important implications in the context of dopaminergic neuronal death in Parkinson's disease (PD).