Schisandrin B-induced increase in cellular glutathione level and
protection against oxidant injury are mediated by the enhancement of
glutathione synthesis and regeneration in AML12 and H9c2 cells
Affiliations: Department of Biochemistry, The Hong Kong University
of Science & Technology, Clear Water Bay, Hong Kong SAR, China
Note: [] Address for correspondence: Dr. Kam Ming Ko, Department of
Biochemistry, The Hong Kong University of Science & Technology, Clear
Water Bay, Hong Kong, China. Tel.: +1 852 2358 7298; Fax: +1 852 2358 1552;
E-mail: [email protected]
Abstract: To define the relative role of reduced glutathione (GSH) synthesis
and regeneration in schisandrin B (Sch B)-induced increase in cellular GSH
level and the associated cytoprotection against oxidative challenge, the
effects of L-buthionine-[S,R]-sulfoximine (BSO, a specific inhibitor of
γ-glutamate cysteine ligase (GCL)) and
1,3-bis(2-chloroethyl)-1-nitrourea (BCNU, a specific inhibitor of glutathione
reductase (GR)) treatments or their combined treatment were examined in control
and Sch B-treated AML12 and H9c2 cells, without and/or with menadione
intoxication. Both BSO and BCNU treatments reduced cellular GSH level in AML12
and H9c2 cells, with the effect of BSO being more prominent. The GSH-enhancing
effect of Sch B was also suppressed by BSO and BCNU treatments, with the effect
of the combined treatment with BSO and BCNU being semi-additive. While Sch B
treatment increased the GR but not GCL activity in AML12 and H9c2 cells, it
increased the cellular cysteine level. BSO treatment also suppressed the Sch
B-induced increase in GR activity. BSO or BCNU treatment per se did not cause
any detectable cytotoxic effect, as assessed by lactate dehydrogenase leakage,
but the combined treatment with BSO and BCNU was cytotoxic, particularly in
H9c2 cells. The cytotoxic effect of BSO and BCNU became more apparent following
the menadione challenge. The cytoprotection afforded by Sch B pretreatment was
partly suppressed by BSO or BCNU treatment, or completely abrogated by the
combined treatment with BSO and BCNU. In conclusion, the results indicate that
the cytoprotective action of Sch B is causally related to the increase in
cellular GSH level, which is likely mediated by the enhancement of GSH
synthesis and regeneration.
