ABSTRACT
It is well known that a brief anoxia or hypoxia episodes can render brain resistant to a subsequent ischemia. Recent investigations indicate that mechanisms of such stimulated endogenous neuroprotection are related to the family of hypoxia-inducible factors (HIF), however there are still little data available on the role of HIF family members in hippocampus-a brain structure, highly sensitive to oxygen deficiency. We have used the model of cultured hippocampal slices and single-cell quantitative RT-PCR to study HIF-1α and HIF-3α mRNA expression following triple 5-min mild anoxia, 30-min oxygen-glucose deprivation and their combination. We also tested the effects of HIF prolyl-hydroxylase inhibition with 2,4-pyridinedicarboxylic acid diethyl ester pre-treatment followed by a 30-min oxygen-glucose deprivation. It was found that neuronal damage induced by oxygen-glucose deprivation was accompanied by a significant decrease in both HIF-1α and HIF-3α mRNA levels in CA1 but not CA3 neurons. Anoxia preconditioning did not affect cell viability and HIF mRNA levels but applied before oxygen-glucose deprivation prevented neuronal damage and suppression of HIF-1α and HIF-3α mRNA expression. It was also found that effects of the prolyl-hydroxylase inhibitor were similar to anoxia preconditioning. These results suggest that anoxia preconditioning increases anti-ischemic neuronal resistance which to a certain extent correlates with the changes of HIF-1α and HIF-3α expression.
Subject(s)
CA1 Region, Hippocampal/enzymology , CA1 Region, Hippocampal/physiopathology , Hypoxia-Inducible Factor 1, alpha Subunit/antagonists & inhibitors , Hypoxia-Ischemia, Brain/therapy , Ischemic Preconditioning/methods , Procollagen-Proline Dioxygenase/antagonists & inhibitors , Transcription Factors/antagonists & inhibitors , Animals , Animals, Newborn , Brain Infarction/enzymology , Brain Infarction/physiopathology , Brain Infarction/therapy , CA1 Region, Hippocampal/drug effects , Disease Models, Animal , Hypoxia/enzymology , Hypoxia/physiopathology , Hypoxia/therapy , Hypoxia-Inducible Factor 1, alpha Subunit/genetics , Hypoxia-Ischemia, Brain/enzymology , Hypoxia-Ischemia, Brain/physiopathology , Organ Culture Techniques , Procollagen-Proline Dioxygenase/metabolism , Rats , Rats, Wistar , Transcription Factors/genetics , Up-Regulation/physiologyABSTRACT
Diabetic patients show impaired brain functions, although underlying mechanisms remain unclear. Little is known as well about early diabetes-related changes in a brain tissue. To investigate them we analyzed the reaction of astroglial cells in the hippocampus of rats rendered diabetic by a single injection of streptozotocin (STZ). Astrocyte count, size and shape as well as levels of glial fibrillary acidic protein (GFAP) and S100b protein were assessed 3, 7 and 14 days after the STZ injection using immunohistochemistry, immuno-enzyme assay and computer-assisted image analysis. The reduced GFAP-positive cell count was found on day 3 when these cells were significantly smaller and less arborized with respect to the control. This tendency reversed on day 7 when more numerous GFAP-positive cells grew in size and became more ramified. S100b-positive cell count changes followed a contrasting pattern, elevating on days 3 and 7 and dropping on day 14. The level of cytoskeletal GFAP changed in parallel with GFAP expression revealed by immunocytochemistry, while cytosolic GFAP level started to increase only 7 days after the STZ injection. At the same time S100b level experienced an elevation on day 3 reaching the peak on day 7 and decreasing afterwards. These results suggest that the reaction of astroglial cells may be the earliest response of the brain tissue to an altered glucose metabolism playing presumably the critical role in the mechanisms underlying diabetes-related impairments of brain functions.
