Guanhua Du

Baicalein exerts neuroprotective effects in 6-hydroxydopamine-induced experimental parkinsonism in vivo and in vitro

Baicalein, a flavonoid obtained from the root of Chinese medicinal herb Scutellaria baicalensis, has been shown to exert a protective effect on neurons against several neuronal insults. The aim of this study was to explore the neuroprotective effect of baicalein in 6-hydroxydopamine (6-OHDA)-induced experimental parkinsonism in vitro and in vivo. In in vitro experiments, we found that baicalein (0.5, 5 microg/mL) could significantly ameliorate the 6-OHDA-induced SH-SY5Y cell apoptosis from 31.56% in the 6-OHDA group to 18.90%, 21.61% respectively, and also promote neurite outgrowth of PC12 cell. In in vivo experiments, baicalein had no effect on apomorphine (APO)-induced rotations, but it could significantly attenuate muscle tremor of 6-OHDA-lesioned rats. The burst frequency and amplitude are 13.43%, 35.18% compared to 6-OHDA group. Moreover, baicalein treatment could also increase tyrosine hydroxylase (TH)-positive neurons to 265.52% of the 6-OHDA group. The neuroprotective action of baicalein was coincident with an attenuated astroglial response within the substantia nigra. Neuroprotective effect of baicalein as demonstrated by the increasing the number of dopaminergic neurons may have been, in part, caused by anti-apoptotic, pro-differentiation and anti-inflammatory mechanisms of baicalein. Therefore, baicalein can be a promising candidate for prevention or treatment of Parkinsons disease, owing to its anti-apoptotic, pro-differentiation and anti-inflammatory action.

Cardioprotective effect of salvianolic acid A on isoproterenol-induced myocardial infarction in rats.

The present study was designed to evaluate the cardioprotective potential of salvianolic acid A on isoproterenol-induced myocardial infarction in rats. Hemodynamic parameters and lead II electrocardiograph were monitored and recorded continuously. Cardiac marker enzymes and antioxidative parameters in serum and heart tissues were measured. Assay for mitochondrial respiratory function and histopathological examination of heart tissues were performed. Isoproterenol-treated rats showed significant increases in the levels of lactate dehydrogenase, aspartate transaminase, creatine kinase and malondialdehyde and significant decreases in the activities of superoxide dismutase, catalase and glutathione peroxidase in serum and heart. These rats also showed declines in left ventricular systolic pressure, maximum and minimum rate of developed left ventricular pressure, and elevation of left ventricular end-diastolic pressure and ST-segment. In addition, mitochondrial respiratory dysfunction characterized by decreased respiratory control ratio and ADP/O was observed in isoproterenol-treated rats. Administration of salvianolic acid A for a period of 8 days significantly attenuated isoproterenol-induced cardiac dysfunction and myocardial injury and improved mitochondrial respiratory function. The protective role of salvianolic acid A against isoproterenol-induced myocardial damage was further confirmed by histopathological examination. The results of our study suggest that salvianolic acid A possessing antioxidant activity has a significant protective effect against isoproterenol-induced myocardial infarction.

Pinocembrin protects rat brain against oxidation and apoptosis induced by ischemia-reperfusion both in vivo and in vitro.

Pinocembrin is one of the flavonoids at the highest concentration in propolis. In this study, we investigated the neuroprotective effect of pinocembrin on ischemia/reperfusion and ischemia/reperfusion-like insults. Protection by pinocembrin was studied at the in vivo level using a model of middle cerebral artery occlusion and reperfusion in rats. Pinocembrin was administrated at the start of reperfusion. Pinocembrin markedly increased rat viability, reduced infarct volumes and neurological deficit scores in all treatment groups. Primary cortical neuronal cultures were subjected to oxygen-glucose deprivation/reoxygenation, a model of ischemia/reperfusion-like injury, and treated with pinocembrin at the start of reoxygenation. Neuronal survival rates were increased, LDH release was decreased and both neurite length and apoptosis were alleviated when pinocembrin was present during reoxygenation, and this protection was associated with the reduction of reactive oxygen species, nitric oxide and neuronal nitric oxide synthase (nNOS) and inducible NOS (iNOS), and an increase of glutathione. Moreover, DNA laddering was decreased in treatment groups of pinocembrin. Caspase-3 protein was down-regulated and PARP degradation was alleviated after pinocembrin treatments. Our results suggest that pinocembrin may be a novel therapeutic strategy to reduce cerebral ischemia/reperfusion injury, and may act by the anti-oxidative and anti-apoptotic effects.

SIRT1 Acts as a Modulator of Neointima Formation Following Vascular Injury in Mice

Rationale: Vascular smooth muscle cell (VSMC) proliferation and migration are crucial events involved in the pathophysiology of vascular diseases. Sirtuin 1 (SIRT1), a class III histone deacetylase (HDAC), has been reported to have the function of antiatherosclerosis, but its role in neointima formation remains unknown. Objective: The present study was designed to investigate the role of SIRT1 in the regulation of neointima formation and to elucidate the underlying mechanisms. Methods and Results: A decrease in SIRT1 expression was observed following carotid artery ligation. smooth muscle cell (SMC)–specific human SIRT1 transgenic (Tg) mice were generated. SIRT1 overexpression substantially inhibited neointima formation after carotid artery ligation or carotid artery wire injury. In the intima of injured carotid arteries, VSMC proliferation (proliferating cell nuclear antigen (PCNA)–positive cells) was significantly reduced. SIRT1 overexpression markedly inhibited VSMC proliferation and migration and induced cell cycle arrest at G1/S transition in vitro. Accordingly, SIRT1 overexpression decreased the induction of cyclin D1 and matrix metalloproteinase-9 (MMP-9) expression by treatment with serum and TNF-&agr;, respectively, whereas RNAi knockdown of SIRT1 resulted in the opposite effect. Decreased cyclin D1 and MMP-9 expression/activity were also observed in injured carotid arteries from SMC-SIRT1 Tg mice. Furthermore, 2 targets of SIRT1, c-Fos and c-Jun, were involved in the downregulation of cyclin D1 and MMP-9 expression. Conclusions: Our findings demonstrate the inhibitory effect of SIRT1 on the VSMC proliferation and migration that underlie neointima formation and implicate SIRT1 as a potential target for intervention in vascular diseases.

Neuroprotective effect of baicalein against MPTP neurotoxicity: Behavioral, biochemical and immunohistochemical profile

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) causes the damage of dopaminergic neurons as seen in Parkinsons disease (PD). Oxidative stress has been implicated in the pathogenesis of PD. Baicalein, isolated from the traditional Chinese herbal medicine Huangqin (Scutellaria baicalensis Georgi), has been shown to have antioxidant effects. Here we investigated the effect of baicalein on MPTP-induced neurotoxicity in mice. Pretreatment with baicalein for a week was followed by challenge with MPTP for 4 consecutive days; the subsequent behavioral, biochemical and immunohistochemical manifestations in mice were determined and compared to those in untreated mice and mice challenged only with MPTP. The present study showed that baicalein could improve the abnormal behavior in MPTP-treated mice. The protective effect may be caused by increasing the levels of DA and 5-HT in the striatum, increasing the counts of dopaminergic neurons, inhibiting oxidative stress and the astroglia response. These results suggest that baicalein possesses potent neuroprotective activity and may be a potential anti-Parkinsons disease drug that is worthy of further study.

Pinocembrin prevents glutamate-induced apoptosis in SH-SY5Y neuronal cells via decrease of bax/bcl-2 ratio

Pinocembrin is the most abundant flavonoids in propolis, and has been proven to have antioxidant, antibacterial and anti-inflammatory property. To assess the protective effects of pinocembrin on neurons, SH-SY5Y neuronal cells were pretreated with pinocembrin for 2 h followed by co-treatment with glutamate (2 mM) for 12 h. Cell viability was determined by(3,4,5-dimethylthiazol-2-yl)-2,5-diphenylte-trazolium bromide assay, and apoptosis was confirmed by cell morphology, capillary zone electrophoresis and flow cytometry assay. Cell morphology was evaluated with Hoechst33258/PI dye. Treatment with pinocembrin (10(-5), 10(-6), 10(-7) mol/l) increased cell viability dose-dependently, inhibited LDH release and attenuated apoptosis. Intracellular free [Ca(2+)] was increased after glutamate exposure, and this increase was attenuated in cells treated with pinocembrin. bax mRNA expression increased remarkably following glutamate exposure and pinocembrin treatment manifested a reduction effect. bcl-2 mRNA expression changes were not detected in groups with or without pinocembrin. Western blotting results indicated that pinocembrin treatment reduced the expression of Bax and had no effect on Bcl-2, thus decreased the Bax-Bcl-2 ratio, which is in consistent with the gene expression result. Pinocembrin could also down-regulate the expression of p53 protein, and inhibit the release of cytochrome c from mitochondria to cytosol. Thus we conclude that pinocembrin exerts its neuroprotective effects in glutamate injury model partly by inhibiting p53 expression, thus Bax-Bcl-2 ratio, and the release of cytochrome c.

Neuroprotective effects of tetramethylpyrazine on hydrogen peroxide-induced apoptosis in PC12 cells.

In the present study, we investigated the effects of tetramethylpyrazine (TMP) on hydrogen peroxide (H2O2)‐induced apoptosis in PC12 cells. The apoptosis in H2O2‐induced PC12 cells was accompanied by a decrease in Bcl‐2/Bax protein ratio, release of cytochrome c to cytosol and the activation of caspase‐3. TMP not only suppressed the down‐regulation of Bcl‐2, up‐regulation of Bax and the release of mitochondrial cytochrome c to cytosol, but also attenuated caspase‐3 activation and eventually protected against H2O2‐induced apoptosis. These results indicated that TMP blocked H2O2‐induced apoptosis by the regulation of Bcl‐2 family members, suppression of cytochrome c release, and caspase cascade activation in PC12 cells.

Pinocembrin protects against β-amyloid-induced toxicity in neurons through inhibiting receptor for advanced glycation end products (RAGE)-independent signaling pathways and regulating mitochondrion-mediated apoptosis.

BackgroundIt is known that amyloid-β peptide (Aβ) plays a pivotal role in the pathogenesis of Alzheimers disease (AD). Interaction between Aβ and the receptor for advanced glycation end products (RAGE) has been implicated in neuronal degeneration associated with this disease. Pinocembrin, a flavonoid abundant in propolis, has been reported to possess numerous biological activities beneficial to health. Our previous studies have demonstrated that pinocembrin has neuroprotective effects on ischemic and vascular dementia in animal models. It has been approved by the State Food and Drug Administration of China for clinical use in stroke patients. Against this background, we investigated the effects of pinocembrin on cognitive function and neuronal protection against Aβ-induced toxicity and explored its potential mechanism.MethodsMice received an intracerebroventricular fusion of Aβ25-35. Pinocembrin was administrated orally at 20 mg/kg/day and 40 mg/kg/day for 8 days. Behavioral performance, cerebral cortex neuropil ultrastructure, neuronal degeneration and RAGE expression were assessed. Further, a RAGE-overexpressing cell model and an AD cell model were used for investigating the mechanisms of pinocembrin. The mechanisms underlying the efficacy of pinocembrin were conducted on target action, mitochondrial function and potential signal transduction using fluorescence-based multiparametric technologies on a high-content analysis platform.ResultsOur results showed that oral administration of pinocembrin improved cognitive function, preserved the ultrastructural neuropil and decreased neurodegeneration of the cerebral cortex in Aβ25-35-treated mice. Pinocembrin did not have a significant effect on inhibiting Aβ1-42 production and scavenging intracellular reactive oxygen species (ROS). However, pinocembrin significantly inhibited the upregulation of RAGE transcripts and protein expression both in vivo and in vitro, and also markedly depressed the activation of p38 mitogen-activated protein kinase (MAPK)-MAPKAP kinase-2 (MK2)-heat shock protein 27 (HSP27) and stress-activated protein kinase (SAPK)/c-Jun N-terminal kinase (JNK)-c-Jun pathways and the downstream nuclear factor κB (NFκB) inflammatory response subsequent to Aβ-RAGE interaction. In addition, pinocembrin significantly alleviated mitochondrial dysfunction through improving mitochondrial membrane potential and inhibiting mitochondrial oxidative stress, and regulated mitochondrion-mediated apoptosis by restoration of B cell lymphoma 2 (Bcl-2) and cytochrome c and inactivation of caspase 3 and caspase 9.ConclusionsPinocembrin was shown to infer cognitive improvement and neuronal protection in AD models. The mechanisms of action of the compound were illustrated on RAGE-dependent transduction inhibition and mitochondrion protection. It appears to be a promising candidate for the prevention and therapy of AD.

Protection by borneol on cortical neurons against oxygen-glucose deprivation/reperfusion: involvement of anti-oxidation and anti-inflammation through nuclear transcription factor κappaB signaling pathway

Borneol, a terpene and bicyclic organic compound found in several species, can easily penetrate the blood-brain barrier (BBB) and helps the absorption of many agents through BBB in the brain, but there has been no study about its direct action on neurons in the CNS. In the present study, we used an in vitro ischemic model of oxygen-glucose deprivation followed by reperfusion (OGD/R) to investigate the neuroprotective effects of borneol and the related mechanisms. We demonstrated that borneol reversed OGD/R-induced neuronal injury, nuclear condensation, intracellular reactive oxygen species (ROS) generation, and mitochondrial membrane potential dissipation. The elevation of nitric oxide (NO), the increase of inducible nitric oxide synthase (iNOS) enzymatic activity and the upregulation of iNOS expression were also attenuated by borneol. The inhibition of caspase-related apoptotic signaling pathway was consistently involved in the neuroprotection afforded by borneol. Meanwhile, borneol inhibited proinflammatory factor release and IκBα degradation, and blocked nuclear transcription factor κappaB (NF-κB) p65 nuclear translocation induced by OGD/R. On the other hand, borneol did not show obvious effect on the inhibition of phospho-IKKα activation. Furthermore, it failed to affect the OGD/R-induced enhanced level of phospho-SAPK/JNK. In conclusion, our study indicated that borneol protects against cerebral ischemia/reperfusion injury through multifunctional cytoprotective pathways. The mechanisms of this reversal from OGD/R may be involved in the alleviation of intracellular ROS and iNOS/NO pathway, inhibition of inflammatory factor release and depression of caspase-related apoptosis. Among these effects, the inhibition of IκBα-NF-κB and translocation signaling pathway might play a significant role in the neuroprotection of borneol.

The characteristics of therapeutic effect of pinocembrin in transient global brain ischemia/reperfusion rats

AIMS The therapeutic effect of pinocembrin, together with the therapeutic time window, in the transient global cerebral ischemia/reperfusion (I/R) rats was investigated. MAIN METHODS Adult male Sprague-Dawley rats were subjected to global cerebral ischemia for 20 min by four-vessel occlusion. Pinocembrin (1 and 5mg/kg) was administrated intravenously 30 min before ischemia and 30 min, 2h, 6h after reperfusion, respectively. Neurological scores, brain edema and histological examination by Nissl staining were employed to assess the neuronal injury after ischemia and the neuroprotection by pinocembrin. The activities of superoxide dismutase (SOD), myeloperoxidase (MPO) and the content of malondialdehyde (MDA) in brain tissue were tested by colorimetric assays. Alterations of neurotransmitters were determined by a high performance liquid chromatography-electrochemical method. KEY FINDINGS Pinocembrin significantly ameliorated neurological deficits and brain edema, and alleviated the degree of hippocampal neuronal loss at 24h after global cerebral I/R with a broad therapeutic time window. It was found that treatment with pinocembrin reduced the compensatory increase of SOD activity and decreased the MDA level and MPO activity in a dose-dependent manner. The metabolic balance between excitatory and inhibitory amino acids was modulated by pinocembrin treatment. SIGNIFICANCE These findings suggest that pinocembrin provides neuroprotection against global cerebral ischemic injury with a wide therapeutic time window, which may be attributed to its antioxidative, antiinflammatory and antiexcitotoxic effects.