Expression of thymosin beta in the rat brain following transient global ischemia

Abstract

Thymosin beta (T beta) isoforms play an important role in the organization of the cytoskeleton by sequestering G-actin during development of the mammalian brain. In this study, we examined changes in the expression of T beta 4 and T beta 15 after transient global ischemia. T beta 15 mRNA increased gradually in the dentate gyrus (DG) of the hippocampal formation from 3 h after reperfusion and peaked 9 h later. Similarly, a significant increase in T beta 4 mRNA level was observed in the DG 12 h after reperfusion. T beta 4 and T beta 15 proteins were found in different cell types in control brains; T beta 15 was expressed in a subset of doublecortin (DCX)-positive cells in the DG, whereas T beta 4-IR was observed in DG neurons and nearby microglial cells. After ischemia, T beta 15-IR was found in DG neurons and T beta 4-IR in the reactivated microglial cells. Interestingly, T beta 15-IR accumulated in the nuclei of CA1 neurons, which are vulnerable to ischemic insults. These results suggest that T beta 4 and T beta 15 function in different cellular contexts during ischemia-induced responses. (c) 2006 Elsevier B.V. All rights reserved.