Hyperbaric oxygen preconditioning reduces ischemia–reperfusion injury by inhibition of apoptosis via mitochondrial pathway in rat brain

This study examined the hypothesis that apoptotic inhibition via mitochondrial pathway was involved in hyperbaric oxygen preconditioning (HBO-PC)–induced neuroprotection on ischemia–reperfusion injury in rat brain. Male Sprague–Dawley rats (250∼280 g, n=144) were divided into control, middle cerebral artery occlusion (MCAO) for 90 min, and HBO-PC plus MCAO groups. HBO-PC was conducted four times by giving 100% oxygen at 2.5 atm absolute (ATA), for 1 h at 12 h intervals for 2 days. At 24 h after the last HBO-PC, MCAO was performed and at 24 h after MCAO, neurological function, brain water content, infarct volume, and cell death were evaluated. Enzymatic activity of capase-3 and −9, and expression of cytochrome c, Bcl-2 and Bax proteins were performed in the samples from hippocampus, ischemic penumbra and core of the brain cortex, respectively. HBO-PC reduced brain edema, decreased infarction volume, and improved neurological recovery. HBO-PC reduced cytoplasm cytochrome c levels, decreased caspase enzyme activity, upregulated the ratio of Bcl-2 and Bax expression, and abated the apoptosis of ischemic tissue. HBO-PC protects brain tissues from ischemia–reperfusion injury by suppressing mitochondrial apoptotic pathways.     

ZnT-1 protects HL-1 cells from simulated ischemia–reperfusion through activation of Ras–ERK signaling

Activation of ERK signaling may promote cardioprotection from ischemia-reperfusion (I/R) injury. ZnT-1, a protein that confers resistance from zinc toxicity, was found to interact with Raf-1 kinase through its C-terminal domain, leading to downstream activation of ERK. In the present study, we evaluated the effects of ZnT-1 in cultured murine cardiomyocytes (HL-1 cells) that were exposed to simulated-I/R. Cellular injury was evaluated by lactate dehydrogenase (LDH) release and by staining for pro-apoptotic caspase activation. Overexpression of ZnT-1 markedly reduced LDH release and caspase activation following I/R. Knockdown of endogenous ZnT-1 augmented the I/R-induced release of LDH and increased caspase activation following I/R. Phospho-ERK levels were significantly increased following I/R in cells overexpressing ZnT-1, while knockdown of ZnT-1 reduced phospho-ERK levels. Pretreatment of cells with the MEK inhibitor PD98059 abolished the protective effect of ZnT-1 following I/R. Accordingly, a truncated form of ZnT-1 lacking the C-terminal domain failed to induce ERK activation and did not protect the cells from I/R injury. In contrast, expression of the C-terminal domain by itself was sufficient to induce ERK activation and I/R protection. Interestingly, the C-terminal of the ZnT-1 did not have protective effect against the toxicity of zinc. In the isolated rat heart, global ischemic injury rapidly increased the endogenous levels of ZnT-1. However, following reperfusion ZnT-1 levels were found to be decreased. Our findings indicate that ZnT-1 may have important role in the ischemic myocardium through its ability to interact with Raf-1 kinase.     

Proterties of large-conductance calciumactivated potassium channel in pyramidal neurons acutely isolated from hippocampal CA1 region of adult rat

<正> Properties of large-conductance Ca~(2+) -achvated K~+ (BK_(Ca)channel were studied in ex-cised patches of pyramidal neurons from adult rat hippocampal CAl region using inside-out single channel recording technique. Activity of BK_(Ca)channel was first oborved at[Ca] = l0~(-8)M with the membrane potential of + 20 mV, and the [Ca]_i at which the channel was half activated(P_0 = 0.5)was 2 x 10~(-6)M. Conductance of single BK_(Ca) channel was approx.245 pS with symmetrical 140 mM-K~+ on bo sides of the excisedmembrane,essentially independent of membrane potentials and [Ca]_i, tested. Two exponentials, with the time constants of 2.07 ma and 14.36ms at membrane potential of + 40 mV with 5×10~(-7) M-[Ca]_i,were requied to describe the observed open distrbution of BK_(Ca) channel, sug-gesting existence of two different open channel stathes with apparently normal conductance. BK_(Ca)channel occasionally entered an apparent thirdopen channel state with a single channel current amplitude about 45% the amplitude o     

Comparison of cardioprotective and anti-inflammatory effects of ischemia pre- and postconditioning in rats with myocardial ischemia–reperfusion injury

Objective  

To compare cardioprotective and anti-inflammatory effects of ischemia preconditioning (IPC) and ischemia postconditioning (IPOC) in a rat myocardial ischemia–reperfusion injury (IRI) model.     

The protective roles of mitochondrial ATP-sensitive potassium channels during hypoxia–ischemia–reperfusion in brain

The role of ATP-sensitive potassium (K_ATP) channels in cerebral ischemia–reperfusion has been well documented. K_ATP channel openers protect neuron by mimicking ischemic preconditioning. However, the different protection between the mitochondrial and sarcolemma K_ATP openers has been seldom studied. In the experiment, we investigated the effects of K_ATP channel openers diazoxide and pinacidil on the hypoxia–ischemia–reperfusion in cultured hippocampal neurons and gerbil brain. The cultured hippocampal neurons and gerbil brain were pretreated with diazoxide or pinacidil before oxygen-glucose deprivation (OGD) and cerebral ischemia–reperfusion, respectively. Survival rate, apoptosis rate and lactate dehydrogenase (LDH) releasing after the reperfusion were subsequently detected. Then the subunits mRNA was detected by RT-PCR. The survival rate and LDH content in diazoxide group increased more than that in pinacidil group (86.21 ± 2.73% vs. 78.59 ± 1.94%, P < 0.05; 133.29 ± 15.00 U/L vs. 193.47 ± 3.39 U/L, P < 0.01). The apoptosis rate in diazoxide group decreased significantly more than that in pinacidil group (23.82 ± 0.14% vs. 37.05 ± 0.67%, P < 0.01). Diazoxide pretreatment increased the expression of Kir6.1 mRNA obviously. The results suggested that mitoK_ATP channels opener diazoxide played a major protective role on cerebral ischemia–reperfusion. Furthermore, diazoxide might become a new treatment for cerebral ischemia diseases through increasing the expression of Kir6.1 mRNA.     

The effect of erythropoietin on endometrial edema during ischemia–reperfusion injury in rats

This experimental study examined the effect of erythropoietin (Epo) in a rat model and particularly in an ischemia–reperfusion protocol. The potential beneficial effect of Epo was studied pathologically using endometrial edema (EE) lesions. Endometrial edema was evaluated 60 min after reperfusion (Groups A and C) and 120 min after reperfusion (Groups B and D) in rats. Epo was administered only in Groups C and D. Epo administration non-significantly increased the EE scores by 0.05 (p = 0.9315). Reperfusion non-significantly increased the EE scores by 0.15 (p = 0.6508). Epo administration and reperfusion together non-significantly increased the EE scores by 0.027 (p = 0.8898). Epo administration, reperfusion, and their interaction reduced the EE scores from significant to non-significant levels. Perhaps a study time longer than 2 h or a higher Epo dose could result in complete resolution of the endometrial edema formed as a result of the ischemia–reperfusion injury in this rat model.     

Inhibition of excitatory neurotransmitter–nitric oxide signaling pathway by inhalational anesthetics

Primary cultures of cerebral neurons of Sprague–Dawley rats increased cyclic GMP production in response to the stimulation of excitatory amino acids, including N-methyl-d-aspartate, quisqualate, kainate and (±)-1-aminocylopentane-trans-1,3-dicarboxylic acid. This increased cyclic GMP production was significantly inhibited by halothane or isoflurane at clinically relevant concentrations (0.5–2%). This inhibition was reversible by treatment with l-arginine, the substrate of nitric oxide synthase. However, the increase of cyclic GMP production stimulated by sodium nitroprusside, an activator of soluble guanylate cyclase, was not inhibited by halothane or isoflurane. Neither halothane nor isoflurane affected the basal cyclic GMP production.Activation of the excitatory amino acid neurotransmitter-stimulated nitric oxide–guanylate cyclase signaling pathway increases intracellular cyclic GMP content in neurons. Our results suggest that halothane or isoflurane inhibited this signaling pathway stimulated by selective agonists of each subtype of receptors for excitatory amino acid neurotransmitters. This inhibition may be involved in mechanisms of anesthesia and analgesia. The site(s) of the inhibition is (are) proximal to the activation of neuronal nitric oxide synthase.     

Protective effects of adenosine on the diabetic myocardium against ischemia–reperfusion injury: Role of calpain

Myocardial ischemia/reperfusion injury (I/RI) is the principal cause of mortality and morbidity in diabetic patients undergoing cardiac surgery. However, there is no specific measure available to protect diabetic hearts in this clinical setting. Our clinical studies showed that adenosine pre-treatment or post-treatment and adding adenosine to cardioplegia solution had significant myocardial protective effects in patients undergoing cardiac surgery. However, the specific protective effects and mechanisms of adenosine in diabetic myocardial I/RI are not clear. Calpain is an important proteolytic enzyme in the myocardium. Studies show that the activation of calpain is an injury factor in not only the diabetic myocardium but also myocardial I/RI progression. We therefore hypothesize that adenosine play a protective role in diabetic myocardial I/RI through the inhibition of calpain.     

Different properties of single voltage-dependent potassium channels in adult rat pyramidal neurons acutely dissociated from CAI and CA3 regions of hippocampus

<正> Previous whole-cell study has showed that delayed rectifier current inCA1 pyramidal neurons is smaller than that in CA3 neurons in rat(Klee R.et al,J.Neurophysiol,1995,74:1982).Here we investigated the dif-ferences of Ca~(2+)-independent,4-AP-insensitive and TEA-sensitive voltage-dependent single K~+ channel between acutely isolated CA1 and CA3pyramidal neurons of adult rat hippocampus using cell-attached and inside-out configurations.During a given depolarizing step of 300 ms,thechanneIs didn’t show machtivation in both types of cells.     

Higenamine regulates Nrf2-HO-1-Hmgb1 axis and attenuates intestinal ischemia–reperfusion injury in mice

Inflammation Research - Intestinal ischemia and reperfusion (IR) syndrome is a life-threatening dilemma caused by diverse events. Higenamine (HG), an active ingredient of Aconiti Lateralis Radix...     

Inhibition of TGF-β1 promotes functional recovery after spinal cord injury

Trauma to the spinal cord initiates a series of cellular and biochemical processes that damage both neurons and glia. TGF-β and its receptors are expressed around the injury site following a spinal cord injury. Here, we report that the intrathecal administration of a neutralizing antibody to TGF-β1 in rats with thoracic spinal cord contusion results in a significant enhancement of the locomotor recovery. The inhibition of TGF-β1 suppresses glial scar formation and upregulates microglia/macrophage activation after the injury, presumably providing a favorable environment for restoration of the neural network. Rats treated with the anti-TGF-β1 antibody exhibited a mild enhancement of growth and/or preservation of axons in the injured spinal cord caudal to the site of contusion. These results support the possibility of using TGF-β1 inhibitors in the treatment of human spinal cord injuries.     

Inhibition of VTA neurons activates the centrally projecting Edinger–Westphal nucleus: Evidence of a stress–reward link?

The primary site of urocortin 1 (Ucn1) expression in the brain is the centrally projecting Edinger–Westphal nucleus. The EWcp is innervated by dopaminergic neurons of the ventral tegmental area (VTA). To investigate whether activity of EWcp is regulated by the VTA, we investigated the effects of local pharmacological inhibition of VTA activity on the induction of Fos immunoreactivity in the EWcp of male C57BL/6J mice. A unilateral intracranial administration of the GABA agonist muscimol aimed at the VTA resulted in increased number of Fos-positive cells in the EWcp. This induction was lower than that produced by an intraperitoneal injection of 2.5 g/kg of ethanol. To investigate whether inhibition of dopaminergic neurons was responsible for induction of Fos, a second experiment was performed where the dopamine agonist quinpirole was unilaterally injected targeting the VTA. Injections of quinpirole also significantly induced Fos in the EWcp neurons. The induction occurred only on the side of the EWcp ipsilateral to the VTA injection. These results indicate that activity of EWcp is inhibited by tonic activity of dopaminergic VTA neurons, and that unilateral projections of VTA onto Ucn1-containing EWcp neurons provide a link between systems regulating approach and avoidance behaviors.     

Inhibition of nuclear factor-κB by 6-O-acetyl shanzhiside methyl ester protects brain against injury in a rat model of ischemia and reperfusion

Background  

Recent studies have demonstrated an inflammatory response associated with the pathophysiology of cerebral ischemia. The beneficial effects of anti-inflammatory drugs in cerebral ischemia have been documented. When screening natural compounds for drug candidates in this category, we isolated 6-O-acetyl shanzhiside methyl ester (ND02), an iridoid glucoside compound, from the leaves of Lamiophlomis rotata (Benth.) Kudo. The objectives of this study were to determine the effects of ND02 on a cultured neuronal cell line, SH-SY5Y, in vitro, and on experimental ischemic stroke in vivo.