Shinpoong Pharmaceutical Co., Ltd.

Ischemic preconditioning (IPC) provides neuroprotection against subsequent severe ischemic insults by specific mechanisms. We tested the hypothesis that IPC attenuates post-ischemic neuronal death in the gerbil hippocampal CA1 region (CA1) throughout hypoxia inducible factor-1α (HIF-1α) and its associated factors such as vascular endothelial growth factor (VEGF) and nuclear factor-kappa B (NF-κB). Lethal ischemia (LI) without IPC increased expressions of HIF-1α, VEGF, and p-IκB-α (/and translocation of NF-κB p65 into nucleus) in CA1 pyramidal neurons at 12 h and/or 1-day post-LI; thereafter, their expressions were decreased in the CA1 pyramidal neurons with time and newly expressed in non-pyramidal cells (pericytes), and the CA1 pyramidal neurons were dead at 5-day post-LI, and, at this point in time, their immunoreactivities were newly expressed in pericytes. In animals with IPC subjected to LI (IPC/LI)-group), CA1 pyramidal neurons were well protected, and expressions of HIF-1α, VEGF, and p-IκB-α (/and translocation of NF-κB p65 into nucleus) were significantly increased compared to the sham-group and maintained after LI. Whereas, treatment with 2ME2 (a HIF-1α inhibitor) into the IPC/LI-group did not preserve the IPC-mediated increases of HIF-1α, VEGF, and p-IκB-α (/and translocation of NF-κB p65 into nucleus) expressions and did not show IPC-mediated neuroprotection. In brief, IPC protected CA1 pyramidal neurons from LI by upregulation of HIF-1α, VEGF, and p-IκB-α expressions. This study suggests that IPC increases HIF-1α expression in CA1 pyramidal neurons, which enhances VEGF expression and NF-κB activation and that IPC may be a strategy for a therapeutic intervention of cerebral ischemic injury.

Ischemic preconditioning (IPC) is induced by exposure to brief durations of transient ischemia, which results in ischemic tolerance to a subsequent longer or lethal period of ischemia. In the present study, the effects of IPC (2 min of transient cerebral ischemia) were examined on immunoreactivity of platelet‑derived growth factor (PDGF)‑BB and on neuroprotection in the gerbil hippocampal CA1 region following lethal transient cerebral ischemia (LTCI; 5 min of transient cerebral ischemia). IPC was subjected to a 2‑min sublethal ischemia and a LTCI was given 5‑min transient ischemia. The animals in all of the groups were given recovery times of 1, 2 and 5 days and change in PDGF‑BB immunoreactivity was examined as was the neuronal damage/death in the hippocampus induced by LTCI. LTCI induced a significant loss of pyramidal neurons in the hippocampal CA1 region 5 days after LTCI, and significantly decreased PDGF‑BB immunoreactivity in the CA1 pyramidal neurons from day 1 after LTCI. Conversely, IPC effectively protected the CA1 pyramidal neurons from LTCI and increased PDGF‑BB immunoreactivity in the CA1 pyramidal neurons post‑LTCI. In conclusion, the results demonstrated that LTCI significantly altered PDGF‑BB immunoreactivity in pyramidal neurons in the hippocampal CA1 region, whereas IPC increased the immunoreactivity. These findings indicated that PDGF‑BB may be associated with IPC‑mediated neuroprotection.

Calbindin D-28K (CB), a Ca²⁺-binding protein, maintains Ca²⁺ homeostasis and protects neurons against various insults. Hyperthermia can exacerbate brain damage produced by ischemic insults. However, little is reported about the role of CB in the brain under hyperthermic condition during ischemic insults. We investigated the effects of transient global cerebral ischemia on CB immunoreactivity as well as neuronal damage in the hippocampal formation under hyperthermic condition using immunohistochemistry for neuronal nuclei (NeuN) and CB, and Fluoro-Jade B histofluorescence staining in gerbils. Hyperthermia (39.5 ± 0.2°C) was induced for 30 minutes before and during transient ischemia. Hyperthermic ischemia resulted in neuronal damage/death in the pyramidal layer of CA1-3 area and in the polymorphic layer of the dentate gyrus at 1, 2, 5 days after ischemia. In addition, hyperthermic ischemia significantly decreaced CB immunoreactivity in damaged or dying neurons at 1, 2, 5 days after ischemia. In brief, hyperthermic condition produced more extensive and severer neuronal damage/death, and reduced CB immunoreactivity in the hippocampus following transient global cerebral ischemia. Present findings indicate that the degree of reduced CB immunoreactivity might be related with various neuronal damage/death overtime and corresponding areas after ischemic insults.