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There is increasing evidence that the sodium-calcium exchanger (NCX) subtypes, NCX1, NCX2 and NCX3 play an important role in intracellular calcium homeostasis/dysregulation following cerebral ischemia. In the present study we examined NCX1, NCX2 and NCX3 protein levels in the rat hippocampus at 3, 6, 12, 18, 24 and 48 h following a 3 min and 8 min duration of global cerebral ischemia. We observed that NCX1 protein levels were significantly increased by 22.3% and 20.6% at the 6 and 12 h respective time points following a 3 min duration of global ischemia, while NCX2 and NCX3 protein levels remained relatively constant. Following a 8 min duration of global ischemia, NCX1 protein levels remained relatively constant, while NCX2 protein levels were down-regulated by 6.9%, 10.8%, 14.4% and 10.3% at the 6, 18, 24 and 48 h respective time points, and NCX3 protein levels were up-regulated by 22.1% at the 18 h time point. Taken together, our results show that NCX subtype protein expression is sensitive to cerebral ischemia, and indicates that changes in NCX activity may be playing an important role in calcium maintenance and neuronal outcome following ischemia.

We previously reported that cyclophilin A protein is up-regulated in cortical neuronal cultures following several preconditioning treatments. In the present study, we have demonstrated that adenoviral-mediated over-expression of cyclophilin A in rat cortical neuronal cultures can protect neurons from oxidative stress (induced by cumene hydroperoxide) and in vitro ischemia (induced by oxygen glucose deprivation). We subsequently demonstrated that cultured neurons, but not astrocytes, express the recently identified putative cyclophilin A receptor, CD147 (also called neurothelin, basigin and EMMPRIN), and that administration of purified cyclophilin A protein to neuronal cultures induces a rapid but transient phosphorylation of the extracellular signal-regulated kinase (ERK) 1/2. Furthermore, administration of purified cyclophilin A protein to neuronal cultures protects neurons from oxidative stress and in vitro ischemia. Interestingly, we detected up-regulation of cyclophilin A mRNA, but not protein in the hippocampus following a 3-min period of sublethal global cerebral ischemia in the rat. Despite our in vivo findings, our in vitro data show that cyclophilin A has both intracellular- and extracellular-mediated neuroprotective mechanisms. To this end, we propose cyclophilin A's extracellular-mediated neuroprotection occurs via CD147 receptor signalling, possibly by activation of ERK1/2 pro-survival pathways. Further characterization of cyclophilin A's neuroprotective mechanisms may aid the development of a neuroprotective therapy.

We previously reported that peroxiredoxin 2 (PRDX2) and Cu/Zn superoxide dismutase 1 (SOD1) proteins are up-regulated in rat primary neuronal cultures following erythropoietin (EPO) preconditioning. In the present study, we have demonstrated that adenovirally mediated overexpression of PRDX2 in cortical neuronal cultures can protect neurons from in vitro ischemia (oxygen-glucose deprivation) and an oxidative insult (cumene hydroperoxide) but not glutamate excitotoxicity. We have also demonstrated that adenovirally mediated overexpression of SOD1 in cortical neuronal cultures protected neurons only against the oxidative insult. Interestingly, we did not detect up-regulation of PRDX2 or SOD1 protein in the rat hippocampus following exposure to either 3 min or 8 min of global cerebral ischemia. Further characterization of PRDX2's neuroprotective mechanisms may aid in the development of a neuroprotective therapy.

In order to investigate protein function in rat primary cortical neuronal cultures, we modified an adenoviral vector expression system and assessed the strength and specificity of the cytomegalovirus (CMV), rous sarcoma virus (RSV), and rat and human synapsin 1 (SYN1) promoters to drive DsRed-X expression. We also incorporated the woodchuck post-transcriptional regulatory element (WPRE) and a CMV promoter-enhanced green fluorescent protein (EGFP) reporter cassette. We observed that the RSV promoter activity was strong in neurons and moderate in astrocytes, while the CMV promoter activity was weak-to-moderate in neurons and very strong in astrocytes. The rat and human SYN1 promoters exhibited similar but weak activity in neurons, despite inclusion of the WPRE. We confirmed that the WPRE enhanced RSV promoter-mediated DsRed-X expression in a time-dependent fashion. Interestingly, we observed very weak SYN1-mediated DsRed-X expression in astrocytes and HEK293 cells suggesting incomplete neuronal-restrictive behavior for this promoter. Finally, using our adenoviral expression system, we demonstrated that RSV promoter-mediated Bcl-X(L) overexpression attenuated neuronal death caused by in vitro ischemia and oxidative stress.

In this study, we investigated the efficacy of pre- and 2 h post-ischemic magnesium treatment with different durations of modest hypothermia (35 degrees C) induced immediately or 2 h following global cerebral ischemia in rats. In experimental group 1, rats received an intravenous loading dose (LD) of 360 micromol/kg MgSO4 immediately before ischemia followed by a 48 h intravenous infusion (IVI) at 120 micromol/kg/h. Immediately post-ischemia, body temperature was lowered to 35 degrees C for 6 h or maintained at 37 degrees C. In experimental group 2, 2 h after ischemia, rats received the MgSO4 LD/IVI and/or had their body temperature lowered to 35 degrees C for 6, 12 or 24 h. In experimental group 1, ischemic rats receiving 6 h of modest hypothermia demonstrated 9.4% CA1 neuronal survival, whereas rats treated with magnesium alone or magnesium and 6 h of modest hypothermia demonstrated 5.1% and 37.9% neuronal survival, respectively. In experimental group 2, ischemic rats receiving 6, 12 or 24 h of modest hypothermia demonstrated 6.1, 5 and 43% CA1 neuronal survival, respectively. Rats treated with magnesium and 6, 12 or 24 h of modest hypothermia demonstrated 8.1, 9 and 76% neuronal survival, respectively. Our findings demonstrate that post-ischemic treatment with a 24 h duration of modest hypothermia and magnesium is more effective than either treatment used alone.