Yong Gu

Caveolin‐1 regulates nitric oxide‐mediated matrix metalloproteinases activity and blood–brain barrier permeability in focal cerebral ischemia and reperfusion injury

J. Neurochem. (2012) 120, 147–156.

Interaction of free radicals, matrix metalloproteinases and caveolin-1 impacts blood-brain barrier permeability.

Free radicals play an important role in cerebral ischemia-reperfusion injury. Accumulations of toxic free radicals such as reactive oxygen species (ROS) and reactive nitrogen species (RNS) not only increase the susceptibility of brain tissue to ischemic damage but also trigger numerous molecular cascades, leading to increased blood-brain barrier (BBB) permeability, brain edema, hemorrhage and inflammation, and brain death. Activating matrix metalloproteinases (MMPs) is a key step in BBB disruption. MMPs are proteolytic zinc-containing enzymes responsible for degradation of the extracellular matrix around cerebral blood vessels and neurons. Free radicals can activate MMPs and subsequently induce the degradations of tight junctions (TJs), leading to BBB breakdown in cerebral ischemia-reperfusion injury. Recent studies revealed that caveolin-1, a membrane integral protein located at caveolae, can prevent the degradation of TJ proteins and protect the BBB integrity by inhibiting RNS production and MMPs activity. The interaction of caveolin-1 and RNS forms a positive feedback loop which provides amplified impacts on BBB dysfunction during cerebral ischemia-reperfusion injury. Here, we reviewed the recent progress in the interactions of RNS, caveolin-1 and MMPs. Current evidence indicates that the interactions of RNS, caveolin-1 and MMPs are critical signal pathways in BBB disruption and infarction enlargement during cerebral ischemia-reperfusion injury.

Herbal Medicines for Ischemic Stroke: Combating Inflammation as Therapeutic Targets

Stroke is a debilitating disease for which limited therapeutic approaches are available currently. Thus, there is an urgent need for developing novel therapies for stroke. Astrocytes, endothelial cells and pericytes constitute a neurovascular network for metabolic requirement of neurons. During ischemic stroke, these cells contribute to post-ischemic inflammation at multiple stages of ischemic cascades. Upon ischemia onset, activated resident microglia and astrocytes, and infiltrated immune cells release multiple inflammation factors including cytokines, chemokines, enzymes, free radicals and other small molecules, not only inducing brain damage but affecting brain repair. Recent progress indicates that anti-inflammation is an important therapeutic strategy for stroke. Given a long history with direct experience in the treatment of human subjects, Traditional Chinese Medicine and its related natural compounds are recognized as important sources for drug discovery. Last decade, a great progress has been made to identify active compounds from herbal medicines with the properties of modulating post-ischemic inflammation for neuroprotection. Herein, we discuss the inflammatory pathway in early stage and secondary response to injured tissues after stroke from initial artery occlusion to brain repair, and review the active ingredients from natural products with anti-inflammation and neuroprotection effects as therapeutic agents for ischemic stroke. Further studies on the post-ischemic inflammatory mechanisms and corresponding drug candidates from herbal medicine may lead to the development of novel therapeutic strategies in stroke treatment.

Efficacy and safety of Suanzaoren decoction for primary insomnia: a systematic review of randomized controlled trials

BackgroundInsomnia is a widespread human health problem, but there currently are the limitations of conventional therapies available. Suanzaoren decoction (SZRD) is a well known classic Chinese herbal prescription for insomnia and has been treating people’s insomnia for more than thousand years. The objective of this study was to evaluate the efficacy and safety of SZRD for insomnia.MethodsA systematic literature search was performed for 6 databases up to July of 2012 to identify randomized control trials (RCTs) involving SZRD for insomniac patients. The methodological quality of RCTs was assessed independently using the Cochrane Handbook for Systematic Reviews of Interventions.ResultsTwelve RCTs with total of 1376 adult participants were identified. The methodological quality of all included trials are no more than 3/8 score. Majority of the RCTs concluded that SZRD was more significantly effective than benzodiazepines for treating insomnia. Despite these positive outcomes, there were many methodological shortcomings in the studies reviewed, including insufficient information about randomization generation and absence of allocation concealment, lack of blinding and no placebo control, absence of intention-to-treat analysis and lack of follow-ups, selective publishing and reporting, and small number of sample sizes. A number of clinical heterogeneity such as diagnosis, intervention, control, and outcome measures were also reviewed. Only 3 trials reported adverse events, whereas the other 9 trials did not provide the safety information.ConclusionsDespite the apparent reported positive findings, there is insufficient evidence to support efficacy of SZRD for insomnia due to the poor methodological quality and the small number of trials of the included studies. SZRD seems generally safe, but is insufficient evidence to make conclusions on the safety because fewer studies reported the adverse events. Further large sample-size and well-designed RCTs are needed.

Combination of mild hypothermia with neuroprotectants has greater neuroprotective effects during oxygen-glucose deprivation and reoxygenation-mediated neuronal injury

Co-treatment of neuroprotective reagents may improve the therapeutic efficacy of hypothermia in protecting neurons during ischemic stroke. This study aimed to find promising drugs that enhance the neuroprotective effect of mild hypothermia (MH). 26 candidate drugs were selected based on different targets. Primary cultured cortical neurons were exposed to oxygen-glucose deprivation and reoxygenation (OGD/R) to induce neuronal damage, followed by either single treatment (a drug or MH) or a combination of a drug and MH. Results showed that, compared with single treatment, combination of MH with brain derived neurotrophic factor, glibenclamide, dizocilpine, human urinary kallidinogenase or neuroglobin displayed higher proportion of neuronal cell viability. The latter three drugs also caused less apoptosis rate in combined treatment. Furthermore, co-treatment of those three drugs and MH decreased the level of reactive oxygen species (ROS) and intracellular calcium accumulation, as well as stabilized mitochondrial membrane potential (MMP), indicating the combined neuroprotective effects are probably via inhibiting mitochondrial apoptosis pathway. Taken together, the study suggests that combined treatment with hypothermia and certain neuroprotective reagents provide a better protection against OGD/R-induced neuronal injury.

Calycosin-7-O-β-d-glucoside regulates nitric oxide /caveolin-1/matrix metalloproteinases pathway and protects blood–brain barrier integrity in experimental cerebral ischemia–reperfusion injury

ETHNOPHARMACOLOGY RELEVANCE Astragali Radix (AR) has been used for thousands years to treat ischemic stroke. Calycosin and its glycoside form calycosin-7-O-β-D-glucoside (CG) are two representative isoflavones in Astragali Radix. However, its neurological effects and related molecular mechanisms are largely unknown. The present study aims to evaluate the neuroprotective effects of CG on blood-brain barrier (BBB) integrity of ischemic brain tissue and explore the relevant signaling mechanisms. MATERIAL AND METHOD Male adult Sprague-Daweley rats were subjected to 2 h of middle cerebral artery occlusion (MCAO) plus 24 h or 14 days of reperfusion. CG (26.8 mg/kg) was intraperitoneally administered into the rats at 15 min before onset of ischemia. The neuroprotective effects of CG were evaluated by measuring infarct volume, histological damage and BBB permeability. Furthermore, the effects of CG on scavenging nitric oxide (NO), and modulating matrix metalloproteinases (MMPs) and caveolin-1 (cav-1) were investigated with in vitro cultured brain microvascular endothelial cells treated with NO donor or oxygen-glucose deprivation (OGD) and/or in vivo rat model of MCAO cerebral ischemia-reperfusion injury. RESULTS CG treatment significantly reduced infarct volume, histological damage and BBB permeability in the in vivo MCAO ischemia-reperfusion rat model. CG treatment remarkably inhibited the expression and activities of MMPs, and secured the expression of cav-1 and tight junction proteins in the microvessels isolated from ischemic rat cortex. Furthermore, CG was revealed to scavenge NO, inhibit the activities of MMP-2 and MMP-9, and attenuate cell death in the in vitro cultured brain microvascular endothelial cells under OGD condition. CONCLUSION CG could protect BBB integrity in experimental cerebral ischemia-reperfusion injury via regulating NO/cav-1/MMPs pathway.

Ginkgo biloba extract (EGb761) inhibits mitochondria-dependent caspase pathway and prevents apoptosis in hypoxia-reoxygenated cardiomyocytes.

BackgroundEGb761 is a standard extract from the leaves of Ginkgo biloba (Yinxing) containing ginkgo-flavone glycosides and terpenoid. The flavonoid components of EGb761 scavenge free radicals and protect myocardia from ischemia-reperfusion injury. The present study aims to determine the effects of the active compounds of EGb761 on mitochondria-dependent caspase pathway.MethodsCardiomyocytes were exposed to 24 hours of hypoxia and four hours of reoxygenation, and pretreated with EGb761, bilobalide and quertcetin. By using immunoblot, immunofluorescent, biochemical and flow cytometry techniques, we compared the effects of EGb761 and its representative constituents including quercetin and bilobalides on regulating mitochondria-dependent caspases signal pathway and apoptotic cell death in the hypoxia-reoxygenated cardiomyocytes.ResultsPretreatment with EGb761 significantly inhibited the release of cytochrome c from mitochondria, the expression of caspase-3, cleavage activities of caspases and attenuated apoptotic cell death. The effects of quercetin on the release of cytochrome c, the cleavage activities of caspases and cell death were similar to those of EGb761 but better than those of bilobalide.ConclusionThe antioxidant constituents of EGb761 such as quercetin contribute to the cardioprotective effects of EGb761 and inhibit the mitochondria-dependent caspase pathway. It is possible that the mitochondria-dependent caspase pathway may be one of the molecular targets of EGb761 against myocardial ischemia-reperfusion injury.

Beyond water channel: Aquaporin-4 in adult neurogenesis

Aquaporin-4 (AQP4) is a key molecule for maintaining water and ion homeostasis associated with neuronal activity in the central nervous system, but the roles of AQP4 in adult neurogenesis remain largely unexplored. Based on preliminary evidences over the past years, AQP4 appears to emerge as an important player regulating the multiple steps of adult neurogenesis. In this mini-review, we discuss the recent findings that reveal a specific functional role of AQP4 in regulating the adult neurogenesis, including proliferation of neural progenitors/neural stem cells, fate specification and differentiation, neuronal migration, and the potential mechanisms. Further studies on the regulation of AQP4 in promoting neurogenesis will lead to better understanding of the signaling mechanisms of adult neurogenesis and potentially provide an opportunity to develop AQP4 as new drug target for neurogenesis.

Glibenclamide Improves Survival and Neurologic Outcome After Cardiac Arrest in Rats.

Objectives:Glibenclamide confers neuroprotection in animal models as well as in retrospective clinical studies. This study determines whether glibenclamide improves outcome after cardiac arrest in rats. Design:Prospective randomized laboratory study. Setting:University research laboratory. Subjects:Male Sprague-Dawley rats (n = 126). Interventions:Rats successfully resuscitated from 8-minute asphyxial cardiac arrest were randomized to glibenclamide or vehicle group. Rats in the glibenclamide group were intraperitoneally administered glibenclamide with a loading dose of 10 &mgr;g/kg at 10 minutes and a maintenance dose of 1.2 &mgr;g at 6, 12, 18, and 24 hours after return of spontaneous circulation, whereas rats in the vehicle group received equivalent volume of vehicle solution. Measurements and Main Results:Survival was recorded every day, and neurologic deficit scores were assessed at 24, 48, and 72 hours and 7 days after return of spontaneous circulation (n = 22 in each group). Results showed that glibenclamide treatment increased 7-day survival rate, reduced neurologic deficit scores, and prevented neuronal loss in the hippocampal cornu ammonis 1 region. To investigate the neuroprotective effects of glibenclamide in acute phase, we observed neuronal injury at 24 hours after return of spontaneous circulation and found that glibenclamide significantly decreased the rate of neuronal necrosis and apoptosis. In addition, glibenclamide reduced the messenger RNA expression of tumor necrosis factor-&agr; and monocyte chemoattractant protein-1 in the cortex after return of spontaneous circulation. Furthermore, the sulfonylurea receptor 1 and transient receptor potential M4 heteromers, the putative therapeutic targets of glibenclamide, were up-regulated after cardiac arrest and cardiopulmonary resuscitation, indicating that they might be involved in neuroprotective effect of glibenclamide. Conclusions:Glibenclamide treatment substantially improved survival and neurologic outcome throughout a 7-day period after return of spontaneous circulation. The salutary effects of glibenclamide were associated with suppression of neuronal necrosis and apoptosis, as well as inflammation in the brain.

Caveolin-1 is essential for protecting against binge drinking-induced liver damage through inhibiting reactive nitrogen species

Caveolin‐1 (Cav‐1) is known to participate in many diseases, but its roles in alcoholic liver injury remain unknown. In the present study, we aimed to explore the roles of Cav‐1 in protecting hepatocytes from ethanol‐mediated nitrosative injury. We hypothesized that Cav‐1 could attenuate ethanol‐mediated nitrosative stress and liver damage through regulating epidermal growth factor receptor/signal transducer and activator of transcription 3/inducible nitric oxide synthase (EGFR/STAT3/iNOS)‐signaling cascades. Ethanol‐fed mice had time‐ and dose‐dependent increases of Cav‐1 in serum and liver with peak increase at 12 hours. Compared to wild‐type mice, Cav‐1 deficiency mice revealed higher expression of iNOS, higher levels of nitrate/nitrite and peroxynitrite, and had more serious liver damage, accompanied with higher levels of cleaved caspase‐3 and apoptotic cell death in liver, and higher levels of alanine aminotransferase and aspartate aminotransferase in serum. Furthermore, the results revealed that the ethanol‐mediated Cav‐1 increase was in an extracellular signal‐regulated kinase–dependent manner, and Cav‐1 protected hepatocytes from ethanol‐mediated apoptosis by inhibiting iNOS activity and regulating EGFR‐ and STAT3‐signaling cascades. In agreement with these findings, clinical trials in human subjects revealed that serum Cav‐1 level was time dependently elevated and peak concentration was observed 12 hours after binge drinking. Alcohol‐induced liver lesions were negatively correlated with Cav‐1 level, but positively correlated with nitrate/nitrite level, in serum of binge drinkers. Conclusions: Cav‐1 could be a cellular defense protein against alcoholic hepatic injury through inhibiting reactive nitrogen species and regulating EGFR/STAT3/iNOS‐signaling cascades. (Hepatology 2014;60:687–699)