Zhengwu Peng

Nrf2/antioxidant defense pathway is involved in the neuroprotective effects of Sirt1 against focal cerebral ischemia in rats after hyperbaric oxygen preconditioning.

Sirtuin 1 (Sirt1) is a class III histone deacetylase involved in neuroprotection induced by hyperbaric oxygen preconditioning (HBO-PC) in animal models of ischemia. However, the underlying mechanisms remain to be illustrated. In the present study, rats exposed to middle cerebral artery occlusion (MCAO) were used to establish an ischemic stroke model. The infarct volume ratio, neurobehavioral score, and expressions of Sirt1, nuclear factor erythroid 2-related factor 2 (Nrf2), heme oxygenase 1 (HO-1), and superoxide dismutase 1 (SOD1) were evaluated at 7 days after reperfusion, and the level of malondialdehyde (MDA) was used to assess oxidative stress. HBO-PC increased the expression of Sirt1 and reduced infarct volume ratio and neurobehavioral deficit in MCAO rats. Meanwhile, HBO-PC also increased expression of Nrf2, HO-1, and SOD1 and decreased MDA content. Furthermore, either Sirt1 or Nrf2 knockdown by short interfering RNA (siRNA) inhibited the expression of Nrf2, HO-1, and SOD1 and eliminated the neuroprotective effects of HBO-PC. Taken together, the results suggest that the Nrf2/antioxidant defense pathway is involved in the long lasting neuroprotective effects of Sirt1 induced by HBO-PC against transient focal cerebral ischemia.

Gastrodin ameliorates depression-like behaviors and up-regulates proliferation of hippocampal-derived neural stem cells in rats: Involvement of its anti-inflammatory action

Gastrodin (GAS), an active constituent of the Chinese herbal medicine tianma, has antidepressant-like activity in animals but no specific molecular mechanisms have been identified. In the present study, chronic unpredictable stress (CUS) was used to establish a rat depression model; The sucrose preference test, forced swim test and Morris water maze test were used to assess depression-like behaviors (anhedonia, behavioral despair, motor retardation, and poor spatial memory), and the proliferation of hippocampal stem cells was tested by BrdU immunohistochemistry. The stress and inflammatory responses were assayed by measuring IL-RA, NF-κB, and p-iκB expression by Western blot and IL-1β production by ELISA. Direct and indirect effects of GAS on NSC viable cell number were examined in vitro by WST-1 and BrdU assays. It was found that GAS (200 mg/kg daily) reversed all tested depression-like behaviors in CUS model rats and up-regulated NSCs proliferation in the hippocampus. Enhanced expression of p-iκB, NF-κB, and IL-1β by CUS was also reversed by GAS. Moreover, in vitro experiments revealed that GAS alone did not increase the viability of NSCs but protected them from IL-1β-induced damage. These results support the antidepressant and neuroprotective effects of GAS, and GAS may reduce depression-like behaviors by protecting hippocampal NSCs against the proinflammatory cytokine IL-1β.

The loss of estrogen efficacy against cerebral ischemia in aged postmenopausal female mice.

Estrogen has been shown to have neuroprotective effects in numerous experimental studies involving young and adult animals. However, several clinical trials have found that in aged postmenopausal women who received estrogen replacement therapy, there did not appear to be a reduction in the incidence of stroke. The aim of this study was to investigate the effects of physiological dosages of estrogen on aged female mice subjected to ischemia-reperfusion injury. Adult ovariectomized (OVX) female mice and 22-month-old female mice received daily subcutaneous injections of 100 μg/kg or 300 μg/kg 17β-estradiol (E2) at the back of the neck for four weeks, and the expression levels of estrogen receptor (ER) α and β in the cerebral cortex were determined using real-time PCR and Western blotting analyses. To mimic ischemic stroke, the mice received middle cerebral artery occlusion (MCAO) treatment for 1h followed by a 24-h reperfusion period. The mice were then subjected to neurological deficit testing and infarct volume evaluation. The aged mice showed higher neurological deficit scores and larger infarct volumes compared with the adult mice. Both the lower and higher physiological dosages of E2 significantly improved the neurological test scores and decreased the infarct volume in the adult mice; however, E2 showed no neuroprotective effects in the aged mice. Furthermore, the protein expression of ERα and ERβ in the cerebral cortex was significantly decreased in the aged mice compared with the adult mice, and this decrease was not rescued by E2 treatment. These results indicate that the down-regulation of ERα and ERβ in the cerebral cortex may contribute to the loss of estrogen efficacy against ischemic injury in aged females and may point to new therapies for ischemic stroke in aged postmenopausal women.

Recombinant human thioredoxin-1 promotes neurogenesis and facilitates cognitive recovery following cerebral ischemia in mice.

Cerebral ischemia (CI) can induce loss of hippocampal neurons, causing cognitive dysfunction such as learning and memory deficits. In adult mammals, the hippocampal dentate gyrus contains neural stem cells (NSCs) that continuously generate newborn neurons and integrate into the pre-existing networks throughout life, which may ameliorate cognitive dysfunction following CI. Recent studies have demonstrated that recombinant human thioredoxin-1 (rhTrx-1) could promote proliferation of human adipose tissue-derived mesenchymal stem cells and angiogenesis. To investigate whether rhTrx-1 also regulates hippocampal neurogenesis following CI and its underlying mechanisms, adult mice were subjected to bilateral common carotid arteries occlusion (BCCAO) to induce CI and treated with rhTrx-1 before reperfusion. Mice treated with rhTrx-1 showed shortened escape latencies in Morris water maze by 30 days and improvements in spatial memory demonstrated by probe trial test. Enhanced NSCs proliferation was observed at day 14, indicated by BrdU and Ki67 immunostaining. Doublecortin (DCX)(+) cells were also significantly increased following rhTrx-1 treatment. Despite increases in BrdU(+)/NeuN(+) cells by day 30, the double-labeling to total BrdU(+) ratio was not affected by rhTrx-1 treatment. The promotive effects of rhTrx-1 on NSCs proliferation and differentiation were further confirmed in in vitro assays. Western blot revealed increased ERK1/2 phosphorylation after rhTrx-1 treatment, and the ERK inhibitor U0126 abrogated the effects of rhTrx-1 on NSCs proliferation. These results provide initial evidence that rhTrx-1 effects neurogenesis through the ERK signaling pathway and are beneficial for improving spatial learning and memory in adult mice following global CI.

Anti-depressive mechanism of repetitive transcranial magnetic stimulation in rat: the role of the endocannabinoid system.

Repetitive transcranial magnetic stimulation (rTMS) to treat depression has been thoroughly investigated in recent years. However, the underlying mechanisms are not fully understood. In this study, a chronic unpredictable mild stress (CUMS) paradigm was applied to male Sprague Dawley rats. Then rTMS was performed for 7 consecutive days, and the anti-depressive effects were evaluated by the sucrose preference test (SPT), the forced swimming test (FST), and the open-field test (OFT). Hippocampal cannabinoid type I receptor (CB1) expression was measured, and the expression levels of brain-derived neurotrophic factor (BDNF), Bcl-2, and Bax and the number of bromodeoxyuridine (BrdU)-positive cells were also investigated. These parameters were also observed after the selective CB1 receptor antagonist AM251 was used as a blocking agent. The results showed that CUMS induced a significant decrease in sucrose preference, a significant increase in immobility time in the FST, and a significantly decreased horizontal distance in the OFT. In addition, reduced hippocampal CB1 receptor, BDNF, and Bcl-2/Bax protein expression levels in CUMS rats, as well as decreased cell proliferation were also observed in the dentate gyrus. Meanwhile, rTMS treatment up-regulated cell proliferation; elevated CB1 receptor, BDNF, and Bcl-2/Bax expression levels in the hippocampus; and ameliorated depressive-like behaviors. All of these beneficial effects were abolished by AM251. These results indicate that rTMS increases BDNF production and hippocampal cell proliferation to protect against CUMS-induced changes through its effect on CB1 receptors.

Rosmarinic acid ameliorates PTSD-like symptoms in a rat model and promotes cell proliferation in the hippocampus.

Rosmarinic acid (RA) is an important component of Chinese herbal medicine treatments and has been demonstrated to exert therapeutic effects in mood disorders. The present study was designed to assess the effects of RA on post-traumatic stress disorder (PTSD)-like symptoms, hippocampal cell proliferation and phosphorylation extracellular regulated protein kinases (pERK1/2) expression. We found that administration of RA (10mg/kg) alleviated PTSD-like symptoms in rats exposed to an enhanced single prolonged stress (ESPS) paradigm and restored hippocampal proliferation and pERK1/2 expression. Interestingly, the effects of RA were inhibited by the blockage of the ERK signaling. These data support the use of RA for treating PTSD and indicate that the ERK1/2 signaling cascade may play a critical role in the therapeutic efficacy of RA in treating such conditions.

Sertraline promotes hippocampus-derived neural stem cells differentiating into neurons but not glia and attenuates LPS-induced cellular damage.

Sertraline is one of the most commonly used antidepressants in clinic. Although it is well accepted that sertraline exerts its action through inhibition of the reuptake of serotonin at presynaptic site in the brain, its effect on the neural stem cells (NSCs) has not been well elucidated. In this study, we utilized NSCs separated from the hippocampus of fetal rat to investigate the effect of sertraline on the proliferation and differentiation of NSCs. The study demonstrated that sertraline had no effect on NSCs proliferation but it significantly promoted NSCs to differentiate into serotoninergic neurons other than glia cells. Furthermore, we found that sertraline protected NSCs against the lipopolysaccharide-induced cellular damage. These data indicate that sertraline can promote neurogenesis and protect the viability of neural stem cells.

Ziprasidone ameliorates anxiety-like behaviors in a rat model of PTSD and up-regulates neurogenesis in the hippocampus and hippocampus-derived neural stem cells.

Ziprasidone, a widely used atypical antipsychotic drug, has been demonstrated to have therapeutic effects in patients with post-traumatic stress disorder (PTSD), but its underlying mechanisms remain poorly understood. One possible explanation is that the neuroprotective and neurogenetic actions of ziprasidone can attenuate the neuronal apoptosis which occurs in the hippocampus. To test this hypothesis, the present study was designed to assess the effects of ziprasidone treatment on anxiety-like behaviors, hippocampal neurogenesis, and in vivo/in vitro expression of pERK1/2 and Bcl-2 in male Sprague-Dawley rats. The methodology involved 3 different experiments, and the investigations also included the assessment of U0126 interference in ziprasidone treatment. It was found that the in vivo, administration of ziprasidone not only reversed the anxiety-like behaviors in rats that exposed to an enhanced single prolonged stress paradigm, but also restored the proliferation and the protein expression of pERK1/2 and Bcl-2 in the hippocampus of these rats. Also, mild concentrations of ziprasidone promoted the in vitro proliferation of hippocampal-derived neural stem cells (NSCs) and increased the levels of pERK1/2 and Bcl-2 in NSCs. Interestingly, the observed effects of ziprasidone were inhibited by U0126. These data support the use of ziprasidone for the treatment of PTSD and indicate that the changes in the ERK1/2 signaling cascade may play a critical role in the pathophysiology of PTSD and its treatment modalities. Further investigations are needed to elucidate the detailed signal cascades involved in the pathophysiology of stress-related disorders, and confirm the efficacy of ziprasidone in anti-PTSD treatment.

Microinjection of sanguinarine into the ventrolateral orbital cortex inhibits Mkp-1 and exerts an antidepressant-like effect in rats

We investigated the antidepressant effects of bilateral intra-the ventrolateral orbital cortex (VLO) administration of sanguinarine (SA), a selective mitogen-activated protein kinase phosphatase-1 (Mkp-1) inhibitor, in rats that had been subjected to a forced swimming test (FST) which is a classic animal model of depression. The expression of Mkp-1 and activation of ERK (ratio of phosphor-ERK to ERK) were also examined by immunoblotting. A single bilateral intra-VLO infusion of SA (2.5, 5 or 10 μg/0.5 μl per side) significantly reduced immobility time in the FST in dose-dependent fashion, as compared to vehicle-treated controls. A similar antidepressant effect was also observed in rats systemically administered fluoxetine, a classic antidepressant. The effects observed in the FST could not be attributed to non-specific increases in activity as neither microinjection of SA into the VLO nor fluoxetine treatment altered the behavior of the rats during the locomotion test. In addition, a decrease in the expression of Mkp-1 and a correlative increase in ERK activation were involved in the antidepressant effects of the bilateral SA administration into the VLO. The results indicated that Mkp-1 within the VLO is involved in the process of depression and may be a potential target for therapeutic action of antidepressant treatment.

The effects of Insulin Pre-Administration in Mice Exposed to Ethanol: Alleviating Hepatic Oxidative Injury through Anti-Oxidative, Anti-Apoptotic Activities and Deteriorating Hepatic Steatosis through SRBEP-1c Activation

Alcoholic liver disease (ALD) has become an important liver disease hazard to public and personal health. Oxidative stress is believed to be responsible for the pathological changes in ALD. Previous studies have showed that insulin, a classic regulator of glucose metabolism, has significant anti-oxidative function and plays an important role in maintaining the redox balance. For addressing the effects and mechanisms of insulin pre-administration on ethanol-induced liver oxidative injury, we investigated histopathology, inflammatory factors, apoptosis, mitochondrial dysfunction, oxidative stress, antioxidant defense system, ethanol metabolic enzymes and lipid disorder in liver of ethanol-exposed mice pretreatment with insulin or not. There are several novel findings in our study. First, we found insulin pre-administration alleviated acute ethanol exposure-induced liver injury and inflammation reflected by the decrease of serum AST and ALT activities, the improvement of pathological alteration and the inhibition of TNF-α and IL-6 expressions. Second, insulin pre-administration could significantly reduce apoptosis and ameliorate mitochondrial dysfunction in liver of mice exposed to ethanol, supporting by decreasing caspases-3 activities and the ratio of Bax/Bcl-2, increasing mitochondrial viability and mitochondrial oxygen consumption, inhibition of the decline of ATP levels and mitochondrial ROS accumulation. Third, insulin pre-administration prevented ethanol-mediated oxidative stress and enhance antioxidant defense system, which is evaluated by the decline of MDA levels and the rise of GSH/GSSG, the up-regulations of antioxidant enzymes CAT, SOD, GR through Nrf-2 dependent pathway. Forth, the modification of ethanol metabolism pathway such as the inhibition of CYP2E1, the activation of ALDH might be involved in the anti-oxidative and protective effects exerted by insulin pre-administration against acute ethanol exposure in mice. Finally, insulin pre-administration deteriorated hepatic steatosis in mice exposed to ethanol might be through SRBEP-1c activation. In summary, these results indicated that insulin pre-administration effectively alleviated liver oxidative injury through anti-inflammatory, anti-oxidative and anti-apoptotic activities but also deteriorated hepatic steatosis through SRBEP-1c activation in mice exposed to ethanol. Our study provided novel insight about the effects and mechanisms of insulin on ethanol-induced liver injury.