Protective effect of n-butanol extract of Cremanthodium humile on myocardial injury induced by hypobaric hypoxia in mice

Abstract

Objective To determine the protective effect of n-butanol extract of Cremanthodium humile (BECH) on myocardial damage induced by hypobaric hypoxia (HH) in mice. Methods Fifty clean-grade BALB/c male mice were divided into (n=10): hypoxia model group, acetazolamide group, low-, medium-and high-dose BECH groups (125, 250 and 500 mg/kg) for normobaric confinement hypoxia experiments to determine the optimal dose of administration. Another 30 mice were divided into (n=10): acute decompression group, acetazolamide group and BECH administration group for the survival rate of the best administered dose in decompression hypoxia tolerance experiment. Fifty-two mice were divided into (n=13) normal control group, HH group, acetazolamide group and BECH administration group. BECH or acetazolamide was given intragastrically (i.g.) for 5 consecutive days, then the mice of the normal control group was placed at the local altitude, and those in the other groups were exposed to a simulated altitude of 8 000 m for 24 h in a hypobaric hypoxia chamber. After blood samples were harvested from the eyeball, all mice were sacrificed immediately. Histopathological changes in mouse myocardium were observed with HE staining. The serum activities of CK, AST and c-TnI were determined. The contents and levels of ROS, CAT, MDA, SOD, LD, LDH, GSH-Px and T-AOC in myocardial tissue were measured. Western blotting was used to detect the expression of Nrf-2, HO-1, Bax, Bcl-2 and cleaved Caspase-3 proteins in myocardial tissues. Results Compared with the hypoxia model group, BECH treatment significantly prolonged the survival time of mice in normobaric confinement hypoxia, especially the high-dose administration; the treatment also significantly reduced the mortality of mice in acute decompression. Significantly increased levels of ROS (P < 0.05) and MDA, CAT, LD and LDH (P < 0.01), decreased levels of SOD, GSH-Px and T-AOC(P < 0.01), up-regulation of Nrf-2, HO-1, Bax and cleaved Caspase-3 (P < 0.05, P < 0.01) and down-regulation of Bcl-2 (P < 0.05) in the myocardial tissues were observed in the mice from the HH model group than those in the control group. While, BECH treatment significantly attenuated myocardial tissue oxidative stress damage in mice under hypobaric hypoxic environment (P < 0.01), decreased the amount of LD and the activity of LDH (P < 0.01), increased the levels of SOD, GSH-Px and T-AOC(P < 0.01), up-regulated the protein levels of Nrf-2, HO-1 amd Bcl-2(P < 0.05, P < 0.01), down-regulated those of Bax and cleaved Caspase-3 (P < 0.05, P < 0.01), and reduced the Bax/Bcl-2 ratio in myocardial tissue. Conclusion BECH inhibits oxidative stress, improves energy metabolism, suppresses cell apoptosis via activating the Nrf-2/HO-1 signaling pathway, and then ameliorates HH-induced myocardial tissue injury.

Keywords

• cremanthodium humile
• n-butanol extract
• hypobaric hypoxia
• myocardial injury
• oxidative stress