Schisandrin B (Sch B) is the most abundant, active dibenzocyclooctadiene derivative isolated from the fruit of Schisandra chinensis (FS), a traditional Chinese herb clinically used for the treatment of viral and chemical hepatitis. 1)A recent study from our laboratory has demonstrated that long-term treatment with Sch B was able to enhance mitochondrial antioxidant status and the resistance to Ca 2ϩ -induced mitochondrial permeability transition (PT) in an ageindependent manner in various rat organs including the heart and brain.2) The Sch B-induced enhancement of mitochondrial protective parameters in the heart was associated with the protection against myocardial ischemia/reperfusion (I/R) injury in both young and middle-aged rats.2) Given that the maintenance of mitochondrial antioxidant status and structural integrity is crucial for cell survival, 3) Sch B has been proposed to be used as a universal cell protectant against tissue damage caused by endogenous and exogenous oxidants. 2)While the protection of Sch B against I/R injury has been demonstrated in the heart, 2,4) it is still unclear whether Sch B treatment can produce any beneficial effect on cerebral I/R injury.In the present study, we investigated the effect of longterm treatment with Sch B on cerebral I/R injury in rats. To elucidate the biochemical mechanism involved in the cerebroprotection against I/R injury, cerebral mitochondrial antioxidant status as well as mitochondrial structural integrity were assessed in control and Sch B-treated rats, without or with I/R challenge. MATERIALS AND METHODS ChemicalsReduced glutathione (GSH), oxidized glutathione, glutathione reductase, cytochrome c, a-tocopherol (a-TOC), cyclosporin A (Cs A) and 2,3,5-triphenyl tetrazolium chloride (TTC) were purchased from Sigma Chemical Co. (St. Louis, MO, U.S.A.). All other chemicals were of analytical grade. Solvents used for HPLC were of HPLC grade.Herbal Material Dried FS was imported from mainland China. It was authenticated and supplied by a commercial dealer (Lee Hoong Kee Ltd.) in Hong Kong. Sch B was purified from the petroleum ether extract of FS, with the purity being higher than 95% as determined by HPLC analysis. 5)Animal Care Adult female Sprague-Dawley rats (8-10 weeks; 200-250 g) were maintained under a 12-h dark/light cycle at about 22°C, and allowed food and water ad libitum. Experimental protocols were approved by the Research Practice Committee at the Hong Kong University of Science & Technology.Drug Treatment Animals were randomly divided into groups, with five animals in each. In the Sch B treatment groups, rats were intragastrically administered with Sch B (dissolved/suspended in olive oil) at a daily dose of 1, 10 or 30 mg/kg from day 1 to day 15 of the experiment. This dosage regimen was found to be effective in protecting against myocardial ischemia/reperfusion injury in rats.2) Sch B-untreated animals received the vehicle (i.e. olive oil) only. The rat model of cerebral I/R injury was modified from that of Ischikawa and Konishi.6) Phenobarbita...

This study examined the effects of (-)schisandrin B [(-)Sch B] on MAPK and Nrf2 activation and the subsequent induction of glutathione antioxidant response and cytoprotection against apoptosis in AML12 hepatocytes. Pharmacological tools, such as cytochrome P-450 (CYP) inhibitor, antioxidant, MAPK inhibitors and Nrf2 RNAi, were used to delineate the signalling pathway. (-)Sch B caused a time-dependent activation of MAPK in AML12 cells, particularly the ERK1/2. The MAPK activation was followed by an enhancement in Nrf2 nuclear translocation and the eliciting of a glutathione antioxidant response. Reactive oxygen species arising from a CYP-catalysed reaction with (-)Sch B seemed to be causally related to the activation of MAPK and Nrf2. ERK inhibition by U0126 or Nrf2 suppression by Nrf2 RNAi transfection almost completely abrogated the cytoprotection against menadione-induced apoptosis in (-)Sch B-pre-treated cells. (-)Sch B pre-treatment potentiated the menadione-induced ERK activation, whereas both p38 and JNK activations were suppressed. Under the condition of ERK inhibition, Sch B treatment did not protect against carbon tetrachloride-hepatotoxicity in an in vivo mouse model. In conclusion, (-)Sch B triggers a redox-sensitive ERK/Nrf2 signalling, which then elicits a cellular glutathione antioxidant response and protects against oxidant-induced apoptosis in AML12 cells.

Herba Cistanches (Cistanche deserticola Y. C. Ma) is a 'Yang-invigorating' tonic herb in Chinese medicine. Preliminary chemical analysis indicated that β-sitosterol (BS) is one of the chemical constituents in an active fraction of Herba Cistanches. To investigate whether BS is an active ingredient of Herba Cistanches, the effects of BS on H9c2 cells and rat hearts were examined. The results indicated that BS stimulated the mitochondrial ATP generation capacity in H9c2 cells, which was associated with the increased production of mitochondrial reactive oxygen species. BS also stimulated mitochondrial state 3 and state 4 respiration, with the resultant decrease in coupling efficiency. BS produced an up-regulation of cellular glutathione redox cycling and protected against hypoxia/reoxygenation-induced apoptosis in H9c2 cells. However, the protective effect of BS against myocardial ischemia/reperfusion injury was seen in female but not male rats ex vivo. The cardioprotection afforded by BS was likely mediated by an up-regulation of mitochondrial glutathione redox cycling in female rat hearts. In conclusion, the ensemble of results suggests that BS is an active ingredient of Herba Cistanches. The gender-dependent effect of BS on myocardial protection will further be investigated.