Effects Of Delayed Administration Of Guanosine On Ischemic Stroke And Related Mechanisms

Objective:Several in vitro and in vivo studies have revealed the acute neuroprotective effects of guanosine on cerebral ischemia, but it remains unclear whether delayed administration of guanosine (24h after ischemic stroke) will influence the outcome of stroke. We aimed to investigate the effects of delayed guanosine treatment on infarct volume and behavior following photothrombotic (PT) stroke of mice.Materials and Methods:Focal cerebral ischemia was induced by photothrombosis in C57/B6J mice. Intraperitoneal administration of guanosine (8mg/kg) or equal volume of saline was given 24h post-stroke and daily for 7 consecutive days. Behavioral tests were performed 1 day before PT and 1,3,7,14,28 days after PT. Behavioral tests includes modified neurological severity scale (mNSS), Rotrod test, Corner test, and Cylinder test. On day 7 post-stroke, mice were decapitated for Nissl staining, and the infarct volume was calculated.Results:The baseline behavior score of the two groups were identical. PT induced significant neurological deficits on day 1 post-stroke while no obvious difference was observed between guanosine- and saline-teated mice. During day 3 and 28, neurological function showed gradual spontaneous recovery. Guanosine promotes neurological recovery from day 14 compared to vehicle (saline) though no significant difference was detected on day 3 and 7 post-stroke. The infarct volume of the two groups showed no significant difference.Conclusion:Delayed administration of guanosine did not influence the neurological outcome or infarct volume in acute phase of cerebral infarction, but promotes the long-term recovery.Objective:To investigate whether delayed administration of guanosine will promote neurogenesis and angiogenesis following mice photothrombotic stroke and to determine the alteration of BDNF, VEGF expressions after treatment.Materials and Methods:Focal cerebral ischemia was induced by photothrombosis in C57/B6J mice. Intraperitoneal administration of guanosine (8mg/kg) or equal volume of saline was given 24h post-stroke and daily for 7 consecutive days. Neurogenesis and angiogenesis were evaluated by co-labelling bromo-deoxyuridine (BrdU) with doublecortin (DCX), neuronal nuclei (NeuN) and von Willebrand factor (vWF) immunohistochemically in subventricular zone of lateral ventricle and subgranular zone of dentate gyrus. Brain-derived neurotrophic factor (BDNF) and vascular endothelial growth factor (VEGF) levels in the ipsilesional brain at day 7,14 and 28 post-stroke were detected by western blot.Results:Guanosine significantly increased the number of BrdU+ and BrdU+/DCX+ cells in both subventricular zone and subgranular zone at all time points, the number of Brdu+/NeuN+ cells in the peri-infarction region at days 14 and 28 post-stroke and microvessel density in the peri-infarction region at day 28 post-stroke compared to the vehicle group. The BDNF and VEGF levels in the ipsilesional brain were also significantly elevated.Conclusion:Delayed administration of guanosine at 24h post-stroke enhances neurogenesis and angiogenesis, increases BDNF and VEGF levels, which likely contribute to long-term functional recovery after stroke.Objective: To investigate whether delayed administration of guanosine influences on the activation of astrocytes and microglia.Materials and Mediods: Focal cerebral ischemia was induced by photothrombosis in C57/B6 J mice.Intraperitoneal administration of guanosine(8mg/kg) or equal volume of saline was given 24 h post-stroke and daily for 7 consecutive days.Immunofluorescence was performed to count the number of astrocytes and microglia.Fluorescent quantitative PCR was conducted to determine the mRNA levels of cytokines including Ml markei's(iNOS?CD16?IL-l??CD32 and M2 markers(CD206?IL-10?Argl?Yml).Results: Compared to vehicle, guanosine significantly increase the number of GFAP+cells in sub ventricular zone but significantly decrease the number of GFAP+ and Iba-1+ cells in peri-infarct zone. The mRNA levels of Ml and M2 markers in the ischemic hemisphere were significantly down-regulated and up-regulated by guanosine, respectively.Conclusions: Delayed administration of guanosine after ischemic stroke suppresses the activation of astrocytes and microglia, and promotes the alternativc activation of microglia, which may contribute to long-term functional recovery after stroke.