Effects of schisandrin B pretreatment on tumor necrosis factor-α induced apoptosis and Hsp70 expression in mouse liver

Effects of Polyphenols on Oxidative Stress, Inflammation, and Interconnected Pathways during Spinal Cord Injury

Despite the progression in targeting the complex pathophysiological mechanisms of neurodegenerative diseases (NDDs) and spinal cord injury (SCI), there is a lack of effective treatments. Moreover, conventional therapies suffer from associated side effects and low efficacy, raising the need for finding potential alternative therapies. In this regard, a comprehensive review was done regarding revealing the main neurological dysregulated pathways and providing alternative therapeutic agents following SCI. From the mechanistic point, oxidative stress and inflammatory pathways are major upstream orchestras of cross-linked dysregulated pathways (e.g., apoptosis, autophagy, and extrinsic mechanisms) following SCI. It urges the need for developing multitarget therapies against SCI complications. Polyphenols, as plant-derived secondary metabolites, have the potential of being introduced as alternative therapeutic agents to pave the way for treating SCI. Such secondary metabolites presented modulatory effects on neuronal oxidative stress, neuroinflammatory, and extrinsic axonal dysregulated pathways in the onset and progression of SCI. In the present review, the potential role of phenolic compounds as critical phytochemicals has also been revealed in regulating upstream dysregulated oxidative stress/inflammatory signaling mediators and extrinsic mechanisms of axonal regeneration after SCI in preclinical and clinical studies. Additionally, the coadministration of polyphenols and stem cells has shown a promising strategy for improving post-SCI complications.

Time- and NADPH-Dependent Inhibition on CYP3A by Gomisin A and the Pharmacokinetic Interactions between Gomisin A and Cyclophosphamide in Rats

The traditional Chinese medicine Schisandra chinensis has remarkable protective effects against chemical-induced toxicity. Cyclophosphamide (CTX), in spite advances in chemotherapy and immunosuppressive regimes, is prone to cause severe toxicity due to its chloroacetaldehyde (CAA) metabolite produced by CYP3A. Our previous study identified that S. chinensis extract (SCE) co-administration potently decreased CAA production and attenuated liver, kidney and brain injuries in CTX-treated rats. Gomisin A (Gom A) is proved to be one of the most abundant bioactive lignans in S. chinensis with a significant CYP3A inhibitory effect. To find out whether and how Gom A participated in the chemoprevention of SCE against CTX toxicity, the Gom A-caused CYP3A inhibition in vitro as well as the pharmacokinetic interactions between Gom A and CTX in vivo were examined in this study. Using human liver microsomes, a reversible inhibition assay revealed that Gom A was a competitive inhibitor with a K_I value of 1.10 µM, and the time- and NADPH-dependent CYP3A inhibition of Gom A was observed in a time-dependent inhibition assay (K_I = 0.35 µM, k_inact = 1.96 min⁻¹). Hepatic CYP3A mRNA expression experienced a significant increase in our rat model with Gom A administration. This explained why CAA production decreased in the 0.5 h- and 6 h-pretreatment rat groups while it increased in the 24 h- and 72 h-pretreatment groups, indicating a bidirectional effect of Gom A on CYP3A-mediated CTX metabolism. The present study suggested that Gom A participates like SCE in the pharmacokinetic intervention of CTX by blocking CYP3A-mediated metabolism and reducing CAA production, and thus plays an important role in the chemopreventive activity of S. chinensis against CTX toxicity, in addition to the previously recognized protective effects. Also, the combined use of S. chinensis preparation or other drugs containing Gom A as the main component with CTX needed to be addressed for better clinical intervention.

Biochemical mechanism underlying hypertriglyceridemia and hepatic steatosis/hepatomegaly induced by acute schisandrin B treatment in mice

Background

It has been demonstrated that acute oral administration of schisandrin B (Sch B), an active dibenzocyclooctadiene isolated from Schisandrae Fructus (a commonly used traditional Chinese herb), increased serum and hepatic triglyceride (TG) levels and hepatic mass in mice. The present study aimed to investigate the biochemical mechanism underlying the Sch B-induced hypertriglyceridemia, hepatic steatosis and hepatomegaly.

Methods

Male ICR mice were given a single oral dose of Sch B (0.25–2 g/kg). Sch B-induced changes in serum levels of biomarkers, such as TG, total cholesterol (TC), apolipoprotein B48 (ApoB 48), very-low-density lipoprotein (VLDL), non-esterified fatty acid (NEFA) and hepatic growth factor (HGF), as well as hepatic lipids and mass, epididymal adipose tissue (EAT) and adipocyte size, and histological changes of the liver and EAT were examined over a period of 12–120 h after Sch B treatment.

Results

Serum and hepatic TG levels were increased by 1.0–4.3 fold and 40–158% at 12–72 h and 12–96 h, respectively, after Sch B administration. Sch B treatment elevated serum ApoB 48 level (up to 12%), a marker of exogenous TG, but not VLDL, as compared with the vehicle treatment. Treatment with Sch B caused a time-/dose-dependent reduction in EAT index (up to 39%) and adipocyte size (up to 67%) and elevation in serum NEFA level (up to 55%). Sch B treatment induced hepatic steatosis in a time-/dose-dependent manner, as indicated by increases in total vacuole area (up to 3.2 fold vs. the vehicle control) and lipid positive staining area (up to 17.5 × 10³ μm²) in liver tissue. Hepatic index and serum HGF levels were increased by 18–60% and 42–71% at 12–120 h and 24–72 h post-Sch B dosing, respectively. In addition, ultrastructural changes, such as increase in size and disruption of cristae, in hepatic mitochondria were observed in Sch B-treated mice.

Conclusion

Our findings suggest that exogenous sources of TG and the breakdown of fat storage in the body contribute to Sch B-induced hypertriglyceridemia and hepatic steatosis in mice. Hepatomegaly (a probable hepatotoxic action) caused by Sch B may result from the fat accumulation and mitochondrial damage in liver tissue.

Heat shock proteins 27 and 70 contribute to the protection of Schisandrin B against d-galactosamine-induced liver injury in mice

Schisandrin B is a hepatoprotective component isolated from a traditional Chinese herb, Schisandra chinensis (Turcz.) Baill. This study determined the effect of Schisandrin B on d-galactosamine -induced liver injury and the role of heat shock proteins 27 and 70 against liver injury in mice. Acute liver injury was induced by intraperitoneal injection of d-galactosamine to mice, and Schisandrin B was given orally. The protein and gene expression of heat shock proteins 27 and 70 were detected by western blot and real-time quantitative polymerase chain reaction, respectively. Liver tissues were subjected to histological evaluation, and the activities of alanine aminotransferase and aspartate aminotransferase in the serum were measured. Pretreatment of Schisandrin B significantly attenuated d-galactosamine-induced liver injury in mice. This result was evidenced by improved alteration of histopathological hepatic necrosis and reduced alanine aminotransferase and aspartate aminotransferase activities in the serum. The hepatoprotective effect was accompanied with overexpression of heat shock proteins 27 and 70 both at the protein and mRNA levels. However, the aforementioned actions of Schisandrin B were all markedly suppressed by the heat shock protein inhibitor quercetin. Heat shock proteins 27 and 70 were involved in the protective effect of Schisandrin B against d-galactosamine-induced liver injury in mice.

Schisandrin B protects PC12 cells against oxidative stress of neurodegenerative diseases

Increasing evidence places Schisandrin B (Sch B) at an important position in nerve protection, indicating that Sch B might play a positive role in the therapy of neurodegenerative diseases. However, there is little information on it. Our studies showed that pretreatment with Sch B could reduce lactate dehydrogenase, malondialdehyde, and reactive oxygen species release and significantly increase the cell viability and the superoxide dismutase level. Sch B (10 μM) markedly inhibited cell apoptosis, whereas LY294002 (20 μM), a phosphatidylinositol-3 kinase inhibitor, blocked the antiapoptotic effect. More importantly, Sch B (10 μM) increased the phosphoprotein kinase B/protein kinase B (Akt) and B-cell lymphoma-2/Bcl-2 associated X protein ratios on preincubation with cells for 2 h, which was then inhibited by LY294002 (20 μM). Results indicate that Sch B can protect PC12 cells from apoptosis by activating the phosphatidylinositol-3 kinase/Akt signaling pathway and may emerge as a potential drug for neurodegenerative diseases.

The Lignan-containing Extract of Schisandra chinensis Berries Inhibits the Growth of Chlamydia pneumoniae

The purpose of this study was to investigate the effect and selectivity of an extract of Schisandra chinensis berries against Chlamydia pneumoniae and C. trachomatis. Among the ethnopharmacological uses of the extract from Schisandrae fructus are cough and pneumonia. Therefore we focused on respiratory pathogens. The extract completely inhibited the growth of C. pneumoniae strain CV6 at 250 μg/mL concentration. The inhibition of C. pneumoniae and C. trachomatis growth was dose dependent and established with three different strains. The extract inhibited C. pneumoniae production of infectious progeny in a dose dependent manner. Chlamydia selectivity was elucidated with growth inhibition measurements of three other respiratory bacterial species. A pure compound found in Schisandra chinensis berries, schisandrin B at 20.0 μg/mL concentration inhibited the growth of both C. pneumoniae and C. trachomatis. The extract was found to be non-toxic to the human host cells. These findings highlight the potential of the extract from Schisandra chinensis berries as a source for antichlamydial compounds.

Schisandrin B attenuates acetaminophen-induced hepatic injury through heat-shock protein 27 and 70 in mice

BACKGROUND AND AIM

Schisandrin B is an active component isolated from Schisandra chinensis (TurcZ.) Baill. that is widely used as an antihepatotoxic agent. Schisandrin B has significant hepatoprotective effect against chemical and immunological liver injury. This study aimed to investigate the effect of Schisandrin B on the expression of 27- and 70-kDa heat-shock protein (HSP) and its role in protection against acetaminophen-induced liver injury in mice.

METHODS

After the mice were pretreated, Western blot and real-time quantitative polymerase chain reaction were used to detect the protein and gene expression of HSP27 and HSP70, respectively; the liver tissues were subjected to histological evaluation, and alanine aminotransferase and aspartate aminotransferase activities in the serum were measured.

RESULTS

Oral administration of Schisandrin B increased the expression of HSP27 and HSP70 in a time- and dose-dependent manner. The inducing effect of Schisandrin B on HSP27 and HSP70 was also confirmed by real-time quantitative polymerase chain reaction. In the acetaminophen-induced liver injury mouse model, the prior oral administration of Schisandrin B (200 mg/kg) three times in 24 h markedly alleviated liver injury as indicated by the amelioration of histopathological hepatic necrosis and the reduction of alanine aminotransferase and aspartate aminotransferase activities in the serum. However, the earlier actions of Schisandrin B were all suppressed significantly by Quercetin, a known HSP inhibitor.

CONCLUSION

The hepatic cytoprotective action of Schisandrin B against acetaminophen-induced liver injury is mediated, at least in part, by the induction of HSP27 and HSP70 in mice.

Beneficial effects of schisandrin B on the cardiac function in mice model of myocardial infarction

The fruit of Schisandra chinensis has been used in the traditional Chinese medicine for thousands of years. Accumulating evidence suggests that Schisandrin B (Sch B) has cardioprotection effect on myocardial ischemia invitro. However, it is unclear whether Sch B has beneficial effects on continuous myocardial ischemia in vivo. The aim of the present study was to investigate whether Sch B could improve cardiac function and attenuate myocardial remodeling after myocardial infarction (MI) in mice. Mice model of MI was established by permanent ligation of the left anterior descending (LAD) coronary artery. Then the MI mice were randomly treated with Sch B or vehicle alone. After treatment for 3 weeks, Sch B could increase survival rate, improve heart function and decrease infarct size compared with vehicle. Moreover, Sch B could down-regulate some inflammatory cytokines, activate eNOS pathway, inhibit cell apoptosis, and enhance cell proliferation. Further in vitro study on H9c2 cells showed similar effects of Sch B on prevention of hypoxia-induced inflammation and cell apoptosis. Taken together, our results demonstrate that Sch B can reduce inflammation, inhibit apoptosis, and improve cardiac function after ischemic injury. It represents a potential novel therapeutic approach for treatment of ischemic heart disease.

Schisandrin B exhibits anti-inflammatory activity through modulation of the redox-sensitive transcription factors Nrf2 and NF-κB

Schisandrin B (SB), a dibenzocyclooctadiene derivative isolated from Schisandra chinensis and used commonly in traditional Chinese medicine for the treatment of hepatitis and myocardial disorders, has been recently shown to modulate cellular redox balance. Since we have shown that cellular redox plays an important role in the modulation of immune responses, the present studies were undertaken to study the effects of SB on activation and effector functions of lymphocytes. SB altered the redox status of lymphocytes by enhancing the basal reactive oxygen species levels and altering the GSH/GSSG ratio in lymphocytes. It also induced nuclear translocation of redox sensitive transcription factor Nrf2 and increased the transcription of its dependent genes. SB inhibited mitogen-induced proliferation and cytokine secretion by lymphocytes. SB also significantly inhibited mitogen-induced upregulation of T cell costimulatory molecules and activation markers. It was observed that SB inhibited mitogen-induced phosphorylation of c-Raf, MEK, ERK, JNK, and p38. It suppressed IκBα degradation and nuclear translocation of NF-κB in activated lymphocytes. Anti-inflammatory effects of SB were significantly abrogated by the inhibitors of Nrf2 and HO-1, suggesting the involvement of this pathway. Similar anti-inflammatory effects of SB on lymphocyte proliferation and cytokine secretion were also observed in vivo. To our knowledge, this is the first report showing that the anti-inflammatory effects of SB are mediated via modulation of Nrf2 and NF-κB in lymphocytes.

Co-treatment with Shengmai San-derived herbal product ameliorates chronic ethanol-induced liver damage in rats

Wei Kang Su (WKS) is an antioxidant-enriched herbal product manufactured on the basis of Shengmai San, a well-known traditional Chinese herbal formula. In the present study, we investigated the effects of WKS co-treatment on chronic ethanol toxicity in rats. WKS co-treatment protected against chronic ethanol-induced hepatotoxicity, as evidenced by the suppression of plasma enzyme activities and reactive oxygen metabolite levels, as well as the inhibition of hepatic mitochondrial malondialdehyde production in chronic ethanol-intoxicated rats. The hepatoprotection afforded by WKS co-treatment in chronic ethanol-intoxicated rats was associated with a reversal of altered hepatic mitochondrial antioxidant status and adenosine triphosphate (ATP) generation capacity, as well as heat shock protein 25/70 production. Therefore, WKS may offer the prospect of preventing ethanol-associated liver damage by increasing the resistance of mitochondria to oxidative stress.

Long-term treatment with shengmai san-derived herbal supplement (Wei Kang Su) enhances antioxidant response in various tissues of rats with protection against carbon tetrachloride hepatotoxicity

Wei Kang Su (WKS) is a commercial herbal product based on a Chinese herbal formula, Shengmai San. Here, we investigated the effects of long-term treatment with WKS on mitochondrial antioxidant status and functional ability, as well as heat shock protein (Hsp) 25/70 production, in various tissues of rats. WKS treatment enhanced mitochondrial antioxidant status and ATP generation capacity, as well as Hsp 25/70 production in various rat tissues. WKS treatment suppressed plasma reactive oxygen metabolite levels and protected against carbon tetrachloride hepatotoxicity in rats. Long-term WKS treatment may prevent diseases by enhancing the resistance of mitochondria to oxidative stress.

Effects of Adaptogens on the Central Nervous System and the Molecular Mechanisms Associated with Their Stress-Protective Activity

Adaptogens were initially defined as substances that enhance the "state of nonspecific resistance" in stress, a physiological condition that is linked with various disorders of the neuroendocrine-immune system. Studies on animals and isolated neuronal cells have revealed that adaptogens exhibit neuroprotective, anti-fatigue, antidepressive, anxiolytic, nootropic and CNS stimulating activity. In addition, a number of clinical trials demonstrate that adaptogens exert an anti-fatigue effect that increases mental work capacity against a background of stress and fatigue, particularly in tolerance to mental exhaustion and enhanced attention. Indeed, recent pharmacological studies of a number of adaptogens have provided a rationale for these effects also at the molecular level. It was discovered that the stress-protective activity of adaptogens was associated with regulation of homeostasis via several mechanisms of action, which was linked with the hypothalamic-pituitary-adrenal axis and the regulation of key mediators of stress response, such as molecular chaperons (e.g., HSP70), stress-activated c-Jun N-terminal protein kinase 1 (JNK1), Forkhead box O (FOXO) transcription factor DAF-16, cortisol and nitric oxide.

Adaptogens exert a stress-protective effect by modulation of expression of molecular chaperones

Adaptogens are medicinal plants that augment resistance to stress, and increase concentration, performance and endurance during fatigue. Experiments were carried out with BALB/c mice taking ADAPT-232 forte, a fixed combination of three genuine (native) extracts of Eleutherococcus senticocus, Schisandra chinensis and Rhodiola rosea, characterised for the content of active markers eleutherosides, schisandrins, salidroside, tyrosol and rosavin and in doses of about 30, 90 and 180 mg/kg for seven consecutive days followed by forced swimming test to exhaustion. ADAPT-232 forte strongly augments endurance of mice, increasing the time taken to exhaustion (TTE) in a dose-dependent manner from 3.0+/-0.5 to 21.1+/-1.7 min, approximately seven fold. Serum Hsp72 was measured by EIA both in normal and stressful conditions before and after swimming test. Repeated administration of adaptogen dose dependently increases basal level of Hsp72 in serum of mice from 0.8-1.5 to 5.5-6.3 pg/ml. This effect is even stronger than the effect of stress, including both physical (swimming) and emotional impacts: 3.2+/-1.2 pg/ml. Cumulative effect of stress and adaptogen was clearly observed in groups of animals treated with adaptogen after swimming to exhaustion, when serum Hsp72 increased to 15.1+/-1 pg/ml and remained at almost the same level during the 7 days. It can be concluded that adaptogens induce increase of serum Hsp72, regarded as a defense response to stress, and increase tolerance to stress (in our model combination of physical and emotional stresses). It can be suggested that increased tolerance to stress induced by adaptogen is associated with its stimulation of expression of Hsp70 and particularly with Hsp72 production and release into systemic circulation, which is known as a mediator of stress response involved in reparation of proteins during physical load. Our studies suggest that this could be one of the mechanisms of action of plant adaptogens.

Schisandrin B from Schisandra chinensis reduces hepatic lipid contents in hypercholesterolaemic mice

The effects of schisandrin B (Sch B) on liver and serum lipid contents were investigated in mice with experimentally-induced hypercholesterolaemia. Hypercholesterolaemia was induced either by oral administration of a cholesterol/bile salts mixture (2/0.5 g kg(-1)) for four days or by feeding a high fat/cholesterol/bile salts (10/1/0.3%, w/w) diet for seven days. Daily co-administration of Sch B (50-200 mg kg(-1), i.g.) for four or six days, respectively, decreased hepatic total cholesterol (TC) and triglyceride (TG) levels (by up to 50% and 52%, respectively) in hypercholesterolaemic mice. Sch B treatment also increased hepatic indices (14-84%) in hypercholesterolaemic mice. The results indicated that Sch B treatment could decrease hepatic TC and TG levels, and increase liver weight, in mouse models of hypercholesterolaemia. Fenofibrate treatment (100 mg kg(-1)) produced effects similar to those of Sch B on the hepatic index and lipid levels of hypercholesterolaemic mice.

Biochemical basis of the "Qi-invigorating" action of Schisandra berry (wu-wei-zi) in Chinese medicine

Schisandra berry or Wu-Wei-Zi, meaning the "the fruit of five tastes" in Chinese, is a commonly used herb in traditional Chinese medicine (TCM). Based on the "Five-Element" theory in TCM, while the "five tastes" of Schisandra berry refer to its influence on the five visceral organs in the body, ancient Chinese herbalists specifically trumpeted the berry's beneficial effect on the "Qi" of the five visceral organs. "Qi" is a Chinese term used as a broad description of energy-dependent body functions. Over the past ten years, our laboratory has attempted to define the biochemical properties of Schisandra berry in regard to its purported "Qi-invigorating" properties. We have found, for the first time, an ability of Schisandra berry to fortify mitochondrial antioxidant status, thereby offering the body a generalized protection against noxious challenges both of internal and external origin. Given the indispensable role of the mitochondrion in generating cellular energy, the linking of Schisandra berry to the safeguarding of mitochondrial function provides a biochemical explanation for its "Qi-invigorating" action.

Schisandrin B induced antioxidant response is partly mediated by cytochrome P-4502E1 catalyzed reaction in mouse liver

In order to explore the role of cytochrome P-450 (CYP) 2E1 in schisandrin B (Sch B)-induced antioxidant and heat shock responses, the effects of Sch B treatment on hepatic mitochondrial glutathione antioxidant status (mtGAS) and heat shock protein (Hsp)25/70 expression were compared between wild-type and cyp2e1 knock-out C57B/6N mice. Cyp2e1 knock-out mice exhibited a significantly smaller degree of Sch B-induced enhancement in hepatic mtGAS when compared with the wild-type counterpart. But Hsp25/70 expression induced by Sch B was not affected. Sch B-induced enhancement of mtGAS was corroborated by the increase in hepatic mitochondrial antioxidant capacity, as assessed by in vitro measurement of oxidant production, with the enhancing effect being slightly reduced in the knock-out mice. Using liver microsomes prepared from wild-type and knock-out mice as a source of CYP, Sch B was found to be a good co-substrate for the CYP-catalyzed reaction, with the rate of NADPH oxidation observable in microsomes prepared from knock-out mice being slower. The CYP-catalyzed reaction with Sch B was associated with a concomitant production of oxidant species, with the extent of oxidant production being reduced in cyp2e1 knock-out mouse microsomes. Taken together, the results indicate that CYP2E1 is partly responsible for the hepatic metabolism of Sch B that may trigger the antioxidant response in vivo.

(–)Schisandrin B is more potent than its enantiomer in enhancing cellular glutathione and heat shock protein production as well as protecting against oxidant injury in H9c2 cardiomyocytes

Effects of schisandrin B enantiomers ((+)Sch B and (-)Sch B) treatment on cellular reduced glutathione (GSH) level and heat shock protein (Hsp)25/70 production were investigated in H9c2 cardiomyocytes. (+)Sch B and (-)Sch B at 6.25 muM produced a time-dependent and biphasic change in cellular GSH level and Hsp25/70 production, with the stimulatory effect of (-)Sch B being more potent. The GSH- and Hsp-enhancing effects were accompanied by a parallel cytoprotection against xanthine oxidase/xanthine-induced toxicity, with the biphasic time course of (+)Sch B- or (-)Sch B-induced protection being superimposed with that of the increase in GSH level but not Hsp25/70 production. The results indicate that (-)Sch B produces more potent enhancing effects on cellular GSH and Hsp production as well as protection against oxidative injury than (+)Sch B in cardiomyocytes.

Chronic schisandrin B treatment improves mitochondrial antioxidant status and tissue heat shock protein production in various tissues of young adult and middle-aged rats

The effects of chronic schisandrin B (Sch B) treatment (10 mg/kg/dayx15) on mitochondrial antioxidant status and sensitivity to Ca2+-induced permeability transition, as well as tissue heat shock protein (Hsp)25/70 production were examined in various tissues (brain, heart, liver, skeletal muscle) of young adult and middle-aged female rats. Age-dependent impairment in mitochondrial antioxidant status, as assessed by levels/activities of antioxidant components (reduced glutathione, alpha-tocopherol, Se-glutathione peroxidase and Mn-superoxide dismutase) and the extent of reactive oxygen species generation in vitro, was observed in brain, heart, liver and skeletal muscle tissues. While tissue Hsp25 levels remained relatively unchanged with aging, the Hsp70 level was increased in both brain and heart tissues of middle-aged rats. Chronic Sch B treatment was able to enhance mitochondrial antioxidant status and the resistance to Ca2+-induced mitochondrial permeability transition in an age-independent manner in various tissues of rats. However, Hsp25 and Hsp70 levels were only increased in young adult rats. The Sch B-induced enhancement of mitochondrial protective parameters in the heart was associated with the protection against myocardial ischemia-reperfusion injury in both young adult and middle-aged rats. The results suggest that chronic Sch B treatment may be beneficial for reversing the mitochondrial changes with aging and enhancing the heat shock response.

Structural determinants of schisandrin B which enhance mitochondrial functional ability and glutathione status as well as heat shock protein expression in rat hearts and H9c2 cells

Using an ex vivo model of isolated-perfused rat hearts and cultured H9c2 cells, the structure-activity relationships of schisandrin B (Sch B), and analogs lacking either the methylendioxy group or cyclooctadiene ring, schisandrin A (Sch A) and dimethyl diphenyl bicarboxylate (DDB), respectively, were investigated. Pretreatment with Sch B, but not with Sch A or DDB, protected against myocardial ischemia-reperfusion (I-R) injury in rats. Although Sch B pretreatment largely prevented H9c2 cells from menadione-induced cytotoxicity, Sch A pretreatment produced only a marginal protection. However, DDB pretreatment did not cause any detectable effect. The myocardial and cellular protection afforded by Sch B pretreatment correlated with increases in mitochondrial ATP generation capacity and/or reduced glutathione level as well as heat shock protein (Hsp)25/70 expression, under both control and oxidative stress conditions. The results indicate that the methylenedioxy group and the cyclooctadiene ring are important structural determinants of Sch B in enhancing mitochondrial functional ability and glutathione status, as well as tissue Hsp 25/70 expression, thereby protecting the myocardium against I-R injury.

Role of cytochrome P-450 in schisandrin B-induced antioxidant and heat shock responses in mouse liver

In order to explore the role of cytochrome P-450 (P-450) in schisandrin B (Sch B)-induced antioxidant and heat shock responses, the effect of 1-aminobenzotriazole (ABT, a broad spectrum inhibitor of P-450) on hepatic mitochondrial glutathione antioxidant status (mtGAS) and heat shock protein (Hsp)25/70 expression was examined in Sch B-treated mice. The non-specific and partial inhibition of cytochrome P-450 (P-450) by ABT pretreatment significantly caused a protraction in the time-course of Sch B-induced enhancement in hepatic mitGAS and Hsp25/70 expression in mice. Using mouse liver microsomes as a source of P-450, Sch B, but not dimethyl diphenyl bicarboxylate (a non-hepatoprotective analog of Sch B), was found to serve as a co-substrate for the P-450-catalyzed NADPH oxidation reaction, with a concomitant production of oxidant species. Taken together, the results suggest that oxidant species generated from P-450-catalyzed reaction with Sch B may trigger the antioxidant and heat shock responses in mouse liver.

Hepatoprotective mechanism of schisandrin B: role of mitochondrial glutathione antioxidant status and heat shock proteins

In this study, the time course of schisandrin B- (Sch B-) induced changes in hepatic mitochondrial glutathione antioxidant status (mtGAS) and heat shock protein (HSP) 25/70 induction was examined to study their differential roles in the hepatoprotection afforded by Sch B pretreatment against carbon tetrachloride (CCl(4)) toxicity in mice. Dimethyl diphenyl bicarboxylate (DDB), a nonhepatoprotective analog of Sch B, was also included for comparison. The results indicate that Sch B treatment (2 mmol/kg) produced maximum enhancement in hepatic mtGAS and increases in both hepatic HSP 25 and HSP 70 levels at 24 h after dosing. While the extent of hepatoprotection afforded by Sch B pretreatment against CCl(4) was found to correlate inversely with the elapsed time postdosing, the protective effect was associated with the ability to sustain mtGAS and/or HSP 70 levels in a CCl(4)-intoxicated condition. On the other hand, DDB (2 mmol/kg) treatment, which did not sustain mtGAS and HSP 70 level, could not protect against CCl(4) toxicity. Abolition of the Sch B-mediated enhancement of mtGAS by buthionine sulfoximine/phorone did not completely abrogate the hepatoprotective action of Sch B. The results indicate that Sch B pretreatment independently enhances mtGAS and induces HSP 25/70 production, particularly under conditions of oxidative stress, thereby protecting against CCl(4) hepatotoxicity.

Hepatoprotective action of schisandrin B against carbon tetrachloride toxicity was mediated by both enhancement of mitochondrial glutathione status and induction of heat shock proteins in mice

In the present study, we investigated the differential role of the mitochondrial glutathione status and induction of heat shock proteins (HSPs) 25/70 in protecting against carbon tetrachloride (CCl_4) hepatotoxicity in schisandrin B (Sch B)-pretreated mice. The time-course of Sch B-induced changes in these hepatic parameters were examined. Dimethyl diphenyl bicarboxylate (DDB), a non-hepatoprotective analog of Sch B, was studied for comparison. Sch B treatment (2 mmol/kg) produced maximal enhancement in hepatic mitochondrial glutathione status as well as increases in hepatic HSP 25/70 levels at 24 h post-dosing. The stimulatory effect of Sch B then gradually subsided, but the activities of hepatic mitochondrial glutathione reductase (GR) and glutathione S-transferases (GST) as well as the level of HSP 25 remained relatively high even at 72 h post-dosing. CCl_4 challenge caused significant impairment in mitochondrial glutathione status and a decrease in HSP 70 level, but the HSP 25 level was significantly elevated. While the extent of hepatoprotection afforded by Sch B pretreatment against CCl_4 was found to inversely correlate with the time elapsed after the dosing, the protective effect was associated with the ability of Sch B to maintain the mitochondrial glutathione status and/or induce further production of HSP 25 in CCl_4-intoxicated condition. On the other hand, DDB treatment (2 mmol/kg), which did not increase mitochondrial GSH level and GST activity or induce further production of HSP 25 after CCl_4 challenge, could not protect against CCl_4 toxicity. The results suggest that the enhancement of mitochondrial glutathione status and induction of HSP 25/70 may contribute independently to the hepatoprotection afforded by Sch B pretreatment.