Housefly (Musca domestica) is an important medical insect and its larva is an ideal high protein food source. We isolated from housefly larvae the polypeptides hydrolyzed by neutral protease (PHNP), and investigated the protective effect of PHNP on hydrogen peroxide (H₂O₂)-induced oxidative damage in HepG2 cells. Cells exposed to H₂O₂ showed a marked decrease in proliferation and intracellular superoxide dismutase (SOD) activity, and a significant increase in reactive oxygen species (ROS) level and malondialdehyde (MDA) content. H₂O₂ also caused apoptosis and mitochondrial dysfunction including mitochondrial fragmentation and the loss of mitochondrial membrane potential. Pretreatment with PHNP at concentrations of 2.5, 5, 10 μg/mL blocked these H₂O₂-induced cellular events in a dose-dependent manner. The effect of PHNP at 10 μg/mL is equal to that of ascorbic acid at 10 μM. In summary, PHNP has a protective effect against H₂O₂-induced oxidative injury in cells due to its ability to decrease intracellular ROS and elevate antioxidant enzyme activities.
Keywords: 2′,7′-dichlorofluorescein; 2′,7′-dichlorofluorescein-diacetate; 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide; Antioxidant activity; Apoptosis; BSA; DCF; DCFH-DA; DMEM; Dulbecco’s modified Eagle’s medium; FITC; Housefly larva; MDA; MMP; MTT; Oxidative damage; PBS; PBST; PEF; PHNP; PI; ROS; Reactive oxygen species; Rh123; SOD; TBA; TRITC; VC; Vitamin C; WST-1; bovine serum albumin; fluorescein isothiocyanate; malondialdehyde; mitochondrial membrane potential; phosphate buffered solution; phosphate buffered solution/Tween 20; polypeptides hydrolyzed by neutral protease; propidium iodide; protein-enriched fraction; reactive oxygen species; rhodamine 123; superoxide dismutase; tetraethyl rhodamine isothiocyanate; thiobarbituric acid; water-soluble tetrazolium salt (sodium salt of 4-[3-(4iodophenyl)-2-(4-nitrophenyl)-2H-5-tetrazolio]-1,3-benzene disulfonate).
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