Schisandrin B decreases the sensitivity of mitochondria to calcium ion-induced permeability transition and protects against ischemia-reperfusion injury in rat hearts

Qi-Po-Sheng-Mai granule ameliorates Ach-CaCl2 -induced atrial fibrillation by regulating calcium homeostasis in cardiomyocytes

BACKGROUND

Atrial fibrillation (AF) is one of the most common arrhythmias encountered in clinical settings. Currently, the pathophysiology of AF remains unclear, which severely limits the effectiveness and safety of medical therapies. The Chinese herbal formula Qi-Po-Sheng-Mai Granule (QPSM) has been widely used in China to treat AF. However, its pharmacological and molecular mechanisms remain unknown.

PURPOSE

The purpose of this study was to investigate the molecular mechanisms and potential targets of QPSM for AF.

STUDY DESIGN AND METHODS

The AF model was induced by Ach (66 μg/ml) and CaCl2 (10 mg/kg), and the dose of 0.1 ml/100 g was injected into the tail vein for 5 weeks. QPSM was administered daily at doses of 4.42 and 8.84 g/kg, and amiodarone (0.18 g/kg) was used as the positive control. The effect of QPSM on AF was assessed by electrocardiogram, echocardiography, and histopathological analysis. Then, we employed network pharmacology with single nucleus RNA sequencing (snRNA-Seq) to investigate the molecular mechanisms and potential targets of QPSM for AF. Furthermore, high performance liquid chromatography (HPLC) method was used for component analysis of QPSM, and molecular docking was used to verify the potential targets. Using the IonOptix single cell contraction and ion synchronization test equipment, single myocyte length and calcium ion variations were observed in real time. The expression levels of calcium Transporter-related proteins were detected by western blot and immunohistochemistry.

RESULTS

Based on an Ach-CaCl2-induced AF model, we found that QPSM treatment significantly reduced atrial electrical remodeling-related markers, such as AF inducibility and duration, and attenuated atrial dilation and fibrosis. Network pharmacology identified 52 active ingredients and 119 potential targets for QPSM in the treatment of AF, and 45 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways were enriched, among which calcium pathway had the greatest impact. Using single nucleus sequencing (snRNA-seq), we identified cardiomyocytes as the most differentially expressed in response to drug treatment, with nine differentially expressed genes enriched in calcium signaling pathways. High performance liquid chromatography and molecular docking confirmed that the core components of QPSM strongly bind to the key factors in the calcium signaling pathway. Additional experiments have shown that QPSM increases calcium transients (CaT) and contractility in the individual cardiomyocyte. This was accomplished by increasing the expression of CACNA1C and SERCA2a and decreasing the expression of CAMK2B and NCX1.

CONCLUSION

The present study has systematically elucidated the role of QPSM in maintaining calcium homeostasis in cardiomyocytes through the regulation of calcium transporters, which could lead to new drug development ideas for AF.

Natural Products Targeting PI3K/AKT in Myocardial Ischemic Reperfusion Injury: A Scoping Review

This scoping review aimed to summarize the effects of natural products targeting phosphoinositide-3-kinases/serine/threonine kinase (PI3K/AKT) in myocardial ischemia-reperfusion injury (MIRI). The review details various types of natural compounds such as gypenoside (GP), gypenoside XVII (GP-17), geniposide, berberine, dihydroquercetin (DHQ), and tilianin which identified to reduce MIRI in vitro and in vivo by regulating the PI3K/AKT signaling pathway. In this study, 14 research publications that met the inclusion criteria and exclusion criteria were shortlisted. Following the intervention, we discovered that natural products effectively improved cardiac functions through regulation of antioxidant status, down-regulation of Bax, and up-regulation of Bcl-2 and caspases cleavage. Furthermore, although comparing outcomes can be challenging due to the heterogeneity in the study model, the results we assembled here were consistent, giving us confidence in the intervention's efficacy. We also discussed if MIRI is associated with multiple pathological condition such as oxidative stress, ERS, mitochondrial injury, inflammation, and apoptosis. This brief review provides evidence to support the huge potential of natural products used in the treatment of MIRI due to their various biological activities and drug-like properties.

Semisynthesis of 22,25-Epoxylanostane Triterpenoids: Structure Revision and Protective Effects against Oxygen-Glucose Deprivation/Reoxygenation Injury in H9c2 Cells

22,25-Epoxylanostane triterpenoids indicated protective effects against oxygen-glucose deprivation/reoxygenation (OGD/R)-induced myocardial injury in a previous study. In order to discover potent cardioprotective agents, 20 22,25-epoxylanostane triterpenoids, including inonotsuoxides A and B, ganodercochlearins A and B, were synthesized from inotodiol (1). The structures of inonotsuoxide B and ganodercochlearin A are revised as 22R,25-epoxylanosta-8-en-3β,24R-diol (6) and 22S,25-epoxylanosta-7,9(11)-dien-3β,24R-diol (12) respectively, based on synthesis, spectroscopic data analysis, and X-ray crystallography. Compounds 13-16 and 22 showed potential protective activity against OGD/R-induced injury in H9c2 cells at a concentration of 20 μM. After OGD/R treatment, the most active compounds 13 and 22 at 5 μM increased cell viability by 11.4% and 6.4% respectively, whereas the positive control diazoxide was 14.9% at 100 μM. Flow cytometric analysis and JC-1 staining assay revealed that 13 suppressed OGD/R-induced apoptosis and the mitochondrial membrane potential in H9c2 cells. Compound 13 may serve as a potential lead cardioprotective agent for further development.

Schisandrin B Attenuates Diabetic Cardiomyopathy by Targeting MyD88 and Inhibiting MyD88-Dependent Inflammation

Diabetes manifests as chronic inflammation and leads to the development diabetic cardiomyopathy (DCM). Targeting key proteins in inflammatory signaling may provide new therapy for DCM. In this study, the authors explore the pharmacological effects and mechanisms of Schisandrin B (Sch B), a natural compound with anti-inflammatory activity against DCM. It is shown that Sch B prevents high-level glucose (HG)-induced hypertrophic and fibrotic responses in cultured cardiomyocytes. RNA sequencing and inflammatory qPCR microarray show that Sch B mainly affects myeloid differentiation primary response 88 (MyD88)-dependent inflammatory gene expression in HG-challenged cardiomyocytes. Further studies indicate that Sch B directly binds to and inhibits MyD88 activation, but does not alter MyD88-independent Toll-like receptor signaling in vivo and in vitro. Inhibiting or silencing MyD88 is associated with reduced levels of HG-induced inflammatory cytokines and myocardial injuries in vitro. Treatment of type 1 and type 2 diabetic mice with Sch B protects heart function, reduces myocardial injuries, and decreases secretion of inflammatory cytokines. Cardiomyocyte-specific MyD88 knockout also protects mice against cardiac inflammation and injury in type 1 diabetic mice. In conclusion, these studies show that cardiomyocyte MyD88 plays an apathogenetic role in DCM and Sch B specifically targets MyD88 to reduce inflammatory DCM.

Mitochondrial Damage in Myocardial Ischemia/Reperfusion Injury and Application of Natural Plant Products

Ischemic heart disease (IHD) is currently one of the leading causes of death among cardiovascular diseases worldwide. In addition, blood reflow and reperfusion paradoxically also lead to further death of cardiomyocytes and increase the infarct size. Multiple evidences indicated that mitochondrial function and structural disorders were the basic driving force of IHD. We summed up the latest evidence of the basic associations and underlying mechanisms of mitochondrial damage in the event of ischemia/reperfusion (I/R) injury. This review then reviewed natural plant products (NPPs) which have been demonstrated to mitochondria-targeted therapeutic effects during I/R injury and the potential pathways involved. We realized that NPPs mainly maintained the integrality of mitochondria membrane and ameliorated dysfunction, such as improving abnormal mitochondrial calcium handling and inhibiting oxidative stress, so as to protect cardiomyocytes during I/R injury. This information will improve our knowledge of mitochondrial biology and I/R-induced injury's pathogenesis and exhibit that NPPs hold promise for translation into potential therapies that target mitochondria.

Proteomic Analysis Reveals the Protective Effects of Yiqi Fumai Lyophilized Injection on Chronic Heart Failure by Improving Myocardial Energy Metabolism

Yiqi Fumai lyophilized injection (YQFM) is the recombination of Sheng mai san (SMS).YQFM has been applied clinically to efficaciously and safely treat chronic heart failure (CHF). However, the mechanism of YQFM is still not fully elucidated. The purpose of our study was to investigate the protective mechanism of YQFM against abdominal aortic coarctation (AAC) in rats by proteomic methods. After YQFM treatment, the cardiac function were obviously meliorated. One hundred and fifty-seven important differentially expressed proteins (DEPs) were identified, including 109 in model rat compared with that in control rat (M:C) and 48 in YQFM-treated rat compared with that in model rat (T:M) by iTRAQ technology to analyze the proteomic characteristics of heart tissue. Bioinformatics analysis showed that DEPs was mainly involved in the body’s energy metabolism and was closely related to oxidative phosphorylation. YQFM had also displayed efficient mitochondrial dysfunction alleviation properties in hydrogen peroxide (H₂O₂)-induced cardiomyocyte damage by Transmission Electron Microscope (TEM), Metabolic assay, and Mitotracker staining. What’s more, the levels of total cardiomyocyte apoptosis were markedly reduced following YQFM treatment. Furthermore, Western blot analysis showed that the expressions of peroxisome proliferator activated receptor co-activator-1α(PGC-1α) (p < 0.01 or p < 0.001), perixisome proliferation-activated receptor alpha (PPAR-α) (p < 0.001)and retinoid X receptor alpha (RXR-α) were upregulated (p < 0.001), PGC-1α as well as its downstream effectors were also found to be upregulated in cardiomyocytes after YQFM treatment(p < 0.001).These results provided evidence that YQFM could enhance mitochondrial function of cardiomyocytes to play a role in the treatment of CHF by regulating mitochondrial biogenesis-related proteins.

Schisandrin B Ameliorates Myocardial Ischemia/Reperfusion Injury Through Attenuation of Endoplasmic Reticulum Stress-Induced Apoptosis

Schisandrin B (Sch B), an active composition isolated from the fruit of Schisandra chinensis, has been proved to possess antiinflammatory, antioxidant and anti-endoplasmic reticulum (ER) stress effects in many rodent tissues. However, the exact mechanism of cardioprotective effect of Sch B still needs more study. Here, we detected the effects of Sch B on myocardial ischemia/reperfusion (I/R) injury rats. I/R injury model in this study was established by left anterior descending coronary artery ligation for 40 min followed by 1 h of reperfusion. Male healthy rats were randomly divided into five groups: the sham, I/R, Sch B (20 mg/kg) + I/R, and Sch B (40 mg/kg) + I/R, Sch B (80 mg/kg) + I/R, with 10 rats in each group. We showed that Sch B treatment significantly protected against myocardial I/R injury, as demonstrated by the decrease in the percentage of infarct formation assessed by 2,3,5-triphenyl tetrazolium chloride (TTC) staining in representative heart tissue slices, comparing with the I/R control group. The levels of creatine kinase (CK), lactate dehydrogenase (LDH), malondialdehyde (MDA), and total superoxide dismutase (T-SOD) were tested. The ER stress-related proteins such as C/EBP homologous protein (CHOP), activating transcription factor 6 (ATF6), and (PKR)-like ER kinase (PERK) were further measured by western blot, and their messenger RNA levels were measured by real-time PCR. The apoptosis of heart tissue cells was also tested through the expressions of caspase-9, caspase-3, Bcl-2, and Bax proteins. Collectively, these results revealed that Sch B exerts protection role on myocardial I/R injury through decreasing oxidative reaction, suppressing ATF6 and PERK pathway, and attenuating ER stress-induced apoptosis.

Cardioprotection and natural polyphenols: an update of clinical and experimental studies

Mechanisms involved in ischemia–reperfusion injury.

Schisandrin B protects against myocardial ischemia/reperfusion injury via the PI3K/Akt pathway in rats

The natural medicinal monomer, schisandrin B (Sch B), has been shown to exert cardioprotective effects; however, the underlying mechanisms of these effects remain to be fully elucidated. Therefore, the aim of the present study was to investigate whether Sch B attenuated myocardial ischemia/reperfusion (I/R) injury via the phosphoinositide 3‑kinases (PI3K)/Akt signaling pathway. To confirm this, I/R models were established in rats by ligation of the left anterior descending coronary artery. A group of animals were administered with Sch B (60 mg/kg, lavage) and/or the PI3K inhibitor, LY294002 (0.3 mg/kg, intraperitoneal). Myocardial infarct size, myocardial infarct serum markers, myocardial apoptotic index and the expression of Akt were measured in each group. The results demonstrated that the administration of Sch B reduced the size of the myocardial infarct, and this effect was eliminated following LY294002 treatment. In addition, the administration of Sch B decreased the apoptotic index and the serum markers of myocardial infarction. Sch B administration also increased the expression of phosphorylated Akt, and Sch B treatment decreased the B‑cell lymphoma 2 (Bcl‑2)‑like protein 4/Bcl‑2 ratio and the expression of cleaved caspase‑3. Therefore, Sch B may protect myocardial tissue from I/R injury via the PI3K/Akt signaling pathway in rats.

Protective effects on myocardial infarction model: delivery of schisandrin B using matrix metalloproteinase-sensitive peptide-modified, PEGylated lipid nanoparticles

Purpose

Schisandrin B (Sch B) is clinically applied for the treatment of hepatitis and ischemic disease. However, its clinical efficacy is limited due to the poor solubility and low bioavailability. This study aimed to develop matrix metalloproteinase (MMP)-sensitive peptide-modified, polyethylene glycol (PEG)-modified (PEGylated) solid lipid nanoparticles (SLNs) for loading Sch B (MMP-Sch B SLNs), and to evaluate the therapeutic effect in the myocardial infarction model.

Methods

PEG lipid and MMP-targeting peptide conjugate were synthesized. MMP-Sch B SLNs were prepared by solvent displacement technique. The physicochemical properties and pharmacokinetics of SLNs were investigated. In vivo effects on infarct size was evaluated in rats.

Results

The successful synthesis of lipid-peptide conjugate was confirmed. MMP-Sch B SLNs had a particle size of 130 nm, a zeta potential of 18.3 mV, and a sustained-release behavior. Higher heart drug concentration and longer blood circulation times were achieved by Sch B loaded SLNs than the drug solution according to the pharmacokinetic and biodistribution results. The best therapeutic efficacy was exhibited by MMP-Sch B SLNs by reducing the infarction size to the greatest extent.

Conclusion

The modified SLNs may be a good choice for delivery of Sch B for the treatment of myocardial infarction.

Effects and mechanisms of compound Chinese medicine and major ingredients on microcirculatory dysfunction and organ injury induced by ischemia/reperfusion

Microcirculation dysfunction and organ injury after ischemia and reperfusion (I/R) result from a complex pathologic process consisting of multiple links, with metabolism impairment in the ischemia phase and oxidative stress in the reperfusion phase as initiators, and any treatment targeting a single link is insufficient to cope with this. Compound Chinese medicine (CCM) has been applied in clinics in China and some Asian nations for >2000years. Studies over the past decades revealed the protective and therapeutic effect of CCMs and major ingredients on I/R-induced microcirculatory dysfunction and tissue injury in the heart, brain, liver, intestine, and so on. CCM contains diverse bioactive components with potential for energy metabolism regulation; antioxidant effect; inhibiting inflammatory cytokines release; adhesion molecule expression in leukocyte, platelet, and vascular endothelial cells; and the protection of thrombosis, albumin leakage, and mast cell degranulation. This review covers the major works with respect to the effects and underlying mechanisms of CCM and its ingredients on microcirculatory dysfunction and organ injury after I/R, providing novel ideas for dealing with this threat.

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.

Inhibitory effects of Schisandra chinensis extract on acne-related inflammation and UVB-induced photoageing

CONTEXT

Schisandra chinensis (Turcz.) Baill. (Schisandraceae) fruit extract (SFE) has been reported to induce non-specific tissue protection against inflammation in vivo. However, the effects of SFE on Propionibacterium acnes-stimulated acne and UVB-irradiated photoageing have yet to be investigated.

OBJECTIVE

To systematically investigate the effects of SFE against P. acnes and photoageing in vitro.

MATERIALS AND METHODS

Qualitative and quantitative analyses of SFE were performed by HPLC. SFE concentrations from 2.5 to 50 μg/mL were tested. Specifically, ELISA was used to examine the levels of pro-inflammatory cytokines in THP-1 cells as well as of collagen I and matrix metalloproteinases-1 in HDF cells. The anti-bacterial effect of SFE was determined using the microdilution broth method. Glutathione and malondialdehyde levels were examined using the colorimetric and TBA methods, respectively. The degree of ageing was determined by cytochemical staining.

RESULTS

SFE significantly inhibited P. acnes growth (MIC 0.5 mg/mL) and 50 μg/mL of SFE suppressed the production of interleukin-1β, interleukin-8 and tumour necrosis factor α, by 59.67%, 62.69% and 68.30%, respectively, in P. acnes-stimulated THP-1 cells. Additionally, 10 μg/mL of SFE suppressed photoageing in UVB-exposed fibroblasts by decreasing metalloproteinase levels by 88.4%, inducing collagen by 58.4% and activating the anti-oxidant defence system, by limiting lipid peroxidation by 51.1% and increasing glutathione production by 34.1% (2.5 μg/mL SFE).

DISCUSSION AND CONCLUSION

These results indicated that SFE could significantly ameliorate the inflammatory state in P. acnes-stimulated THP-1 and UVB-irradiated HDF cells, suggesting its potential as a novel agent for acne therapy and photoageing prevention.

Schizandrin protects primary rat cortical cell cultures from glutamate-induced apoptosis by inhibiting activation of the MAPK family and the mitochondria dependent pathway

Glutamate-induced excitotoxicity has been implicated in a variety of neuronal degenerative disorders. In the present study, we investigated the possible neuroprotective effects of schizandrin against apoptosis of primary cultured rat cortical cells induced by glutamate. Glutamate (10 μM) administered for 24 h decreased the expression of Bcl-2 and Bcl-X(L) protein, whereas increased the expression of Bax, Bak, apoptosis inducing factor (AIF), endonuclease G (Nodo G) and endoplasmic reticulum (ER) stress of caspase-12. Pretreatment with schizandrin (100 μM) before glutamate treatment increased the Bcl-X(L) and Bcl-2 expression and decreased Bax, Bak, AIF, Nodo G and caspase-12 compared with those only treated with glutamate. Furthermore, glutamate-induced phosphorylation of JNK, p38 and ERK mitogen-activated protein kinases (MAPK), and these effects were attenuated by schizandrin (100 μM) treatment. These results suggest that schizandrin possesses the neuroprotective effects. The molecular mechanisms of schizandrin against glutamate-induced apoptosis may involve the regulation of Bcl-2 family proteins expression, and ER stress through blocking the activation of JNK, ERK and p38 MAPK.

Mitochondrial decay in ageing: 'Qi-invigorating' schisandrin B as a hormetic agent for mitigating age-related diseases

1. The mitochondrial free radical theory of ageing (MFRTA) proposes a primary role for mitochondrial reactive oxygen species (ROS) in the ageing process. The reductive hot spot hypothesis of mammalian ageing serves as a supplement to the MFRTA by explaining how the relatively few cells that have lost oxidative phosphorylation capacity due to mitochondrial DNA mutations can be toxic to the rest of the body and result in the development of age-related diseases. 2. Schisandrin B (SchB), which can induce both a glutathione anti-oxidant and a heat shock response via redox-sensitive signalling pathways, is a hormetic agent potentially useful for increasing the resistance of tissues to oxidative damage. The enhanced cellular/mitochondrial anti-oxidant status and heat shock response afforded by SchB can preserve the structural and functional integrity of mitochondria, suggesting a potential role for SchB in ameliorating age-related diseases. 3. Future studies will focus on investigating whether SchB can produce the hormetic response in humans.

Protective effect of schisandrin B against cyclosporine A-induced nephrotoxicity in vitro and in vivo

Schisandrin B (Sch B) is an active ingredient of the fruit of Schisandra chinensis. It has many therapeutic effects arising from its tonic, sedative, antitussive and antiaging activities and is also used in the treatment of viral and chemical hepatitis. The aim of this study was to investigate the protective effects of Sch B on cyclosporine A (CsA)-induced nephrotoxicity in mice and HK-2 cells (a human proximal tubular epithelial cell line). After gavage with Sch B (20 mg/kg) or olive oil (vehicle), mice received CsA (30 mg/kg) by subcutaneous injection once daily for four weeks. Renal function, histopathology, and tissue glutathione (GSH) and malondialdehyde (MDA) levels were evaluated after the last treatment. The effects of Sch B on CsA-induced oxidative damage in HK-2 cells were investigated by measuring cell viability, the release of lactate dehydrogenase (LDH), the level of reactive oxygen species (ROS), and the cellular GSH and ATP concentrations. Cellular apoptosis was assessed by flow cytometry. Treatment with Sch B in CsA-treated mice significantly suppressed the elevation of blood urea nitrogen (BUN) and serum creatinine levels and attenuated the histopathological changes. Additionally, Sch B also decreased renal MDA levels and increased GSH levels in CsA-treated mice. Using an in vitro model, Sch B (2.5, 5 and 10 μM) significantly increased the cell viability and reduced LDH release and apoptosis induced by CsA (10 μM) in HK-2 cells. Furthermore, Sch B increased the intracellular GSH and ATP levels and attenuated CsA-induced ROS generation. In conclusion, Sch B appears to protect against CsA-induced nephrotoxicity by decreasing oxidative stress and cell death.

Prooxidant-induced glutathione antioxidant response in vitro and in vivo: a comparative study between schisandrin B and curcumin

We investigated whether two naturally-occurring prooxidants, namely, schisandrin B (Sch B) and curcumin, and a synthetic prooxidant, menadione, can invariably elicit cyto/hepatoprotective responses against oxidant-induced injury. Results showed that (-)Sch B (a potent enantiomer of Sch B, 15 μM), curcumin (7.5 μM) and menadione (2 μM) induced a similar extent of reactive oxygen species production in AML12 cells. The relative potencies of cytoprotection in vitro were in a descending order of curcumin>menadione>(-)Sch B, which were parallel to the extent of stimulation in cellular reduced glutathione level. We further examined their hepatoprotection in vivo. Pretreatment with Sch B (800 mg/kg) and curcumin (737 mg/kg), but not menadione (344 mg/kg), protected against CCl(4) toxicity, with the degree of protection afforded by Sch B being much larger than that of curcumin. The attenuated hepatoprotection afforded by curcumin may be attributed to its low bioavailability in vivo. This postulation is supported by the findings that intraperitoneal injections of Sch B (400 mg/kg) and curcumin (368 mg/kg) and the long term, low dose treatment with Sch B (20 mg/kg/d×15) and curcumin (18 mg/kg/d×15) induced glutathione antioxidant response and hepatoprotection to similar extents in vivo. The inability of menadione to induce hepatoprotection may be related to its extensive intestinal metabolism and/or hepatotoxicity. Taken together, prooxidants can invariably induce the glutathione antioxidant response and confer cytoprotection in vitro. Whether or not the prooxidant can produce a similar response in vivo would depend on its bioavailability and potential toxic effect.

Schisandra chinensis fruit extract attenuates albuminuria and protects podocyte integrity in a mouse model of streptozotocin-induced diabetic nephropathy

ETHNOPHARMACOLOGICAL RELEVANCE

Schisandra chinensis fruit is widely used in Chinese medicine for the treatment of hepatic, renal, heart, cerebrovascular and infectious diseases.

AIM OF THE STUDY

To investigate the effects of Schisandra chinensis fruit extract (SE) on albuminuria and podocyte injury as well as the underlying mechanism in the mouse model of streptozotocin (STZ)-induced diabetic nephropathy and in cultured mouse podocyte cells.

MATERIALS AND METHODS

SE was orally administrated in STZ-induced diabetic nephropathy mice for 7 weeks, at a daily dose of 5g/kg body weight. The urinary albumin/creatinine ratio and urine albumin excretion rate were measured at the 6th and 9th week of the experiment. The extent of glomerulosclerosis and extracellular matrix deposition were determined by periodic acid-silver methenamine and Masson's trichrome staining. The amount of podocytes and the integrity of the slit diaphragm were detected by immunohistological staining of podocyte markers, Wilms' tumor 1 and nephrin. Alpha-smooth muscle actin, E-cadherin and plasminogen activator inhibitor-1 were measured by western blot and immunohistological staining to evaluate the level of epithelial-to-mesenchymal transition (EMT). Real-time reverse transcription PCR was used to detect the mRNA level of E-cadherin, alpha-SMA and snail in cultured podocyte cells.

RESULTS

Treatment with SE significantly decreased the urine albumin excretion rate and urinary albumin/creatinine ratio. In addition, SE attenuated glomerulosclerosis and protected against podocyte loss and integrity of the slit diaphragm. Furthermore, SE effectively prevented the EMT of podocytes caused by diabetic nephropathy.

CONCLUSIONS

Our studies suggest that SE might be beneficial for diabetic nephropathy. The effects of SE on attenuating albuminuria and glomerulosclerosis are possibly mediated by preserving podocyte integrity through suppressing EMT.

Schisandrin B elicits a glutathione antioxidant response and protects against apoptosis via the redox-sensitive ERK/Nrf2 pathway in H9c2 cells

This study investigated the signal transduction pathway involved in the cytoprotective action of (-)schisandrin B [(-)Sch B, a stereoisomer of Sch B]. Using H9c2 cells, the authors examined the effects of (-)Sch B on MAPK and Nrf2 activation, as well as the subsequent eliciting of glutathione response and protection against apoptosis. Pharmacological tools, such as cytochrome P-450 (CYP) inhibitor, antioxidant, MAPK inhibitor, and Nrf2 RNAi, were used to delineate the signaling pathway. (-)Sch B caused a time-dependent activation of MAPK in H9c2 cells, with the degree of ERK activation being much larger than that of p38 or JNK. The MAPK activation was followed by an increase in the level of nuclear Nrf2, an indirect measure of Nrf2 activation, and the eliciting of a glutathione antioxidant response. The activation of MAPK and Nrf2 seemed to involve oxidants generated from a CYP-catalyzed reaction with (-)Sch B. Both ERK inhibition by U0126 and Nrf2 suppression by Nrf2 RNAi transfection largely abolished the cytoprotection against hypoxia/reoxygenation-induced apoptosis in (-)Sch B-pretreated cells. (-)Sch B pretreatment potentiated the reoxygenation-induced ERK activation, whereas both p38 and JNK activations were suppressed. Under the condition of ERK inhibition, Sch B treatment did not protect against ischemia/reperfusion injury in an ex vivo rat heart model. The results indicate that (-)Sch B triggers a redox-sensitive ERK/Nrf2 signaling, which then elicits a cellular glutathione antioxidant response and protects against hypoxia/reoxygenation-induced apoptosis in H9c2 cells. The ERK-mediated signaling is also likely involved in the cardioprotection afforded by Sch B in vivo.

Schisandrin B-induced glutathione antioxidant response and cardioprotection are mediated by reactive oxidant species production in rat hearts

To investigate the involvement of reactive oxidant species (ROS), presumably arising from cytochrome P-450 (CYP)-catalyzed metabolism of schisandrin B (Sch B), in triggering glutathione antioxidant response, Sch B induced reduced nicotinamide adenine dinucleotide phosphate (NADPH)-dependent and CYP-catalyzed reaction and associated ROS production were examined in rat heart microsomes. Sch B analogs were also studied for comparison. Using rat heart microsomes as a source of CYP, Sch B and schisandrin C (Sch C), but not schisandrin A and dimethyl diphenyl bicarboxylate (an intermediate compound derived from the synthesis of Sch C), were found to serve as co-substrate for the CYP-catalyzed NADPH oxidation reaction, with concomitant production of ROS. The stimulation of CYP-catalyzed NADPH oxidation reaction and/or ROS production by Sch B or Sch C correlated with the increase in mitochondrial reduced glutathione level and protection against ischemia/reperfusion (I/R) injury in rat hearts. The involvement of ROS in Sch B-induced cardioprotection was further confirmed by the suppressive effect produced by N-acetylcysteine or alpha-tocopherol pretreatment. Taken together, these results suggest that Sch B-induced glutathione antioxidant response and cardioprotection may be mediated by ROS arising from CYP-catalyzed reaction.

Dietary lignans: physiology and potential for cardiovascular disease risk reduction

The present review of the literature on lignan physiology and lignan intervention and epidemiological studies was conducted to determine if lignans decrease the risks of cardiovascular disease in Western populations. Five intervention studies using flaxseed lignan supplements indicated beneficial associations with C-reactive protein, and a meta-analysis that included these studies also suggested lignans have a lowering effect on plasma total and low-density lipoprotein cholesterol. Three intervention studies using sesamin supplements indicated possible lipid- and blood pressure-lowering associations. Eleven human observational epidemiological studies examined dietary intakes of lignans in relation to cardiovascular disease risk. Five showed decreased risk with either increasing dietary intakes of lignans or increased levels of serum enterolactone (an enterolignan used as a biomarker of lignan intake), five studies were of borderline significance, and one was null. The associations between lignans and decreased risk of cardiovascular disease are promising, but they are yet not well established, perhaps due to low lignan intakes in habitual Western diets. At the higher doses used in intervention studies, associations were more evident.

Cardioprotection of sevoflurane postconditioning by activating extracellular signal-regulated kinase 1/2 in isolated rat hearts

AIM

The activation of extracellular signal-regulated kinase (ERK)1/2 protects against ischemic-reperfusion injury. Whether ERK1/2 mediates the cardioprotection of sevoflurane postconditioning is unknown. We tested whether sevoflurane postconditioning produces cardioprotection via an ERK1/2-dependent mechanism.

METHODS

In protocol 1, Langendorff-perfused Sprague-Dawley rat hearts (n=84, 12 per group), with the exception of the Sham group, were subjected to 30 min ischemia followed by 90 min reperfusion and were assigned to the untreated (control) group, followed by 4 cycles of ischemic postconditioning (25 s of each), 3% (v/v) sevoflurane postconditioning (for 5 min and 10 min of washout), and the PD98059 solvent DMSO (<0.2%), ERK1/2 inhibitor PD98059 (20 micromol/L), and Sevo+PD administration. Left ventricular hemodynamics and coronary flow at 30 min of equilibrium were recorded at 30, 60, and 90 min of reperfusion, respectively. Acute infarct size was measured by triphenyltetrazolium chloride staining. The configuration of mitochondria was observed by an electron microscope. Western blot analysis was used to determine the contents of cytosolic and mitochondrial cytochrome c at the end of reperfusion. In protocol 2, after 15 min of reperfusion, the expression of total and phosphorylated forms of ERK1/2 and its downstream target p70S6K was determined by Western blotting.

RESULTS

No differences in baseline hemodynamics were observed among the experimental groups (P>0.05). After reperfusion, compared with the control group, sevoflurane postconditioning and ischemic postconditioning significantly(P<0.05) improved functional recovery and largely (P<0.05) decreased myocardial infarct size (22.9%+/-4.6% and 21.2%+/-3.8%, vs 39.4%+/- 5.7%, both P<0.05). Sevoflurane-mediated protection was abolished by PD98059.

CONCLUSION

Anesthetic postconditioning by sevoflurane effectively protects against reperfusion damage by activating ERK1/2 in vitro.