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AIM: To explore whether free radicals participate in cerebral ischemic tolerance and the up-regula-tion of p38 MAPK and ERK signaling pathways in rats induced by limb ischemic preconditioning (LIP). METHODS: A total of 128 Wistar rats with permanent occlusion of bilateral vertebral arteries were randomly divided into sham group (n=16), cerebral ischemia (CI) group (n=16), LIP+CI group (n=16), DMTU (a free radical scavenger)+LIP+CI group (n=64) and DMTU+sham group (n=16). Six rats in each group were used to observe the delayed neuronal death (DND) in hippocampal CA1 region by thionin staining at 7 d after the end of operation. Other 10 rats in each group were used to de-tect the expression of p38 MAPK and ERK in hippocampal CA1 region by immunohistochemistry and Western blot. RE-SULTS: Lethal CI resulted in obvious DND in hippocampal CA1 region. However, LIP reversed the above injurious changes, represented by the decrease in histological grade and the increase in neuronal density compared with CI group (P<0. 01). Moreover, LIP significantly up-regulated the expression of p38 MAPK and ERK in hippocampal CA1 region com-pared with CI group (P<0. 01). Administration of free radical scavenger DMTU via femoral vein before LIP partially re-versed the neuroprotective effect of LIP, and blocked the up-regulation of p38 MAPK and ERK expression in hippocampal CA1 region in rats compared with LIP+CI group (P<0. 01). CONCLUSION: Free radicals are involved in the neuropro-tection and up-regulation of p38 MAPK and ERK expression induced by LIP in rats.
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Objective To investigate the changes of neuroglobin (Ngb) expression in the CA1 hippocampus after cerebral ischemia and the effect of limb ischemic preconditioning (LIP) on it in young and aged rats. Methods SD rats aged 3 months and 21-23 months with permanently occluding bilateral vertebral arteries were randomly divided into cerebral ischemic group and LIP + cerebral ischemic group, respectively. The expression of Ngb mRNA and protein in the hippocampus were investigated by reverse transcription-polymerase chain reaction (RT-PCR) and Western blot methods. The profile of delayed neuronal death (DND) of pyramidal neurons in the hippocampus CA1 was evaluated by using thionin staining under light microscope by determining the neuronal density (ND) and histological grade (HG). Results Ngb mRNA and protein expressions were 0.16±0.02 and 0.32±0.07, 0.52±0.04 and 0.91±0.06, 0.09±0.01 and 0.22±0.08, 0.21±0.01 and 0.66± 0. 06 in young cerebral ischemia group, LIP + young cerebral ischemia group, aged cerebral ischemia group and LIP + aged cerebral ischemia group, respectively. The expressions of Ngb mRNA and protein after cerebral ischemia for 8 minutes in aged rats were decreased compared with those in the young rats which suffered an identical cerebral ischemia with the aged rats (P<0.05). LIP up-regulated Ngb mRNA and protein expressions in both young and aged rats which suffered cerebral ischemia (P<0.05). However, the up-regulation of Ngb expression in aged rats was significantly less than that in young rats (P<0.05). Neuropathological evaluation showed that ND was 38.8±10.9, 171.5±16.9, 21.2±12.2 and 102.7±15.4 in young cerebral ischemic group, LIP + young cerebral ischemic group, aged cerebral ischemic group and LIP + aged cerebral ischemic group, respectively. It showed that obvious DND of pyramidal neurons was found in young and aged rats after cerebral ischemia. Although LIP effectively protected the pyramidal neurons in the CA1 hippocampus against DND normally induced by ischemic insult, the neuroprotection of LIP for aged rats was less effective than that for young rats. Conclusions The expression of Ngb and the up-regulation effect of LIP on the expression in aged rats are significantly decreased compared to those in young rats when the rats suffer cerebral ischemia. These differences may be one of underlying reasons why the aged rats exhibit severe DND after cerebral ischemia and why the neuroprotective effect of LIP is less in the aged rats than that in the young rats.
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AIM To observe whether limb ischemic preconditioning (LIP) could attenuate pyramidal neuronal apoptosis of the CA1 hippocampus and brain edema evoked by brain ischemia in rats. METHODSSeventy-two rats whose bilateral vertebral arteries occluded permanently were randomly assigned into 6 groups: sham, LIP(bilateral femoral arteries were clamped for 10 min, 3 times, in a 10-min interval), brain ischemic insult, LIP+brain ischemic insult, DMSO+LIP+brain ischemic insult and SB 203580+LIP+brain ischemic insult groups. Assays for neuronal apoptosis were performed using TUNEL staining. The percentage of wet over dry tissue weight of the brain was measured by weighing method. RESULTS There were almost no TUNEL-positive cells in the CA1 hippocampus in either sham or LIP group. Clear TUNEL-positive pyramidal neurons of the CA1 hippocampus and increase in brain water content were detected in rats subjected to brain ischemic insult. But the number of TUNEL-positive cells and the increase in brain water content were significantly decreased in LIP+brain ischemic insult group compared with that in brain ischemic insult group, indicated that LIP prevented the occurrence of apoptosis of pyramidal neurons of the CA1 hippocampus and brain edema induced by brain ischemic insult. Pretreatment with SB 203580, an inhibitor of mitogen activated protein kinase p38(p38 MAPK), significantly increased the number of TUNEL-positive cells and brain water in SB 203580+LIP+brain ischemic insult group compared with that in DMSO+LIP+brain ischemic insult group, indicated that SB 203580 blocked the protection of LIP against neuronal apoptosis in the CA1 hippocampus and brain edema. CONCLUSION LIP could attenuate pyramidal neurons apoptosis of the CA1 hippocampus and brain edema evoked by brain ischemia, which maybe related to the activation of p38 MAPK.
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AIM To explore the role of superoxide dismutase (SOD) in the p38 mitogen-activated protein kinase (MAPK) mediated brain ischemic tolerance induced by limb ischemic preconditioning (LIP). METHODS The Wistar rats with permanent occlusion of the bilateral vertebral arteries were subjected to occlude the bilateral femoral arteries for 10 min, 3 times, at an interval of 10 min to get the LIP, then global brain ischemia was induced immediately by occluding the bilateral common carotid arteries for 8 min. SB 203580 (100 μmol·L-1, in a volume of 25 μL), an inhibitor of p38 MAPK, was intraventricularly injected 30 min before LIP in SB 203580+LIP+brain ischemia group. Xanthinoxidase and thiomalonylurea methods were used to determine SOD activity and malondialdehyde (MDA) content of the hippocampus, respectively. Thionin staining was used for observing histological changes of the hippocampus. RESULTS LIP significantly prevented the decrease of SOD activity, the increase of MDA content and the delayed neuronal death in the CA1 hippocampus induced by the brain ischemia. SB 203580 pretreatment evidently blocked the protective effect of LIP against the delayed neuronal death and the modulation on SOD activity and MDA content. CONCLUSIONSOD may play an important role served as a downstream molecule of p38 MAPK in the induction of brain ischemic tolerance by LIP.
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AIM: The present study was designed to observe the effect of [D- Arg1, D- Trp7,9, Leu11] - substance P (spantide), a non- selective antagonist of NK receptors, on the up- regulation of nitric oxide synthase (NOS) induced by formalin test. METHODS: Formalin (5%, 0.2 mL) was subcutaneously injected into the plantar side of the right hind paw to produce persistent pain and hyperalgesia. The pain response was determined by spontaneous flinch reflex test. NOS expression was examined using NADPH- d histochemical staining. Spantide was intrathecally injected via L5 - L6 intervertebral space 5 min prior to the formalin injection. RESULTS: Injection of formalin resulted in a characteristic behavioral response consisting of vigorous scratching, biting, licking and lifting of the injected hind paw from the box' s bottom. Following these behavioral responses, the NOS expression was up- regulated in the pericentral canal region of the L5 segment of the spinal cord. Pre- treatment with spantide depressed the spontaneous flinches of the injected paw in the second phase of the formalin test. At the same time, the upregulation of NOS was substantially inhibited. CONCLUSION: It might be concluded that substance P played an important role in the up - regulation of NOS in the pericentral canal region of the spinal cord in the formalin test.