Kir4.1 is coexpressed with stemness markers in activated astrocytes in the injured brain and a Kir4.1 inhibitor BaCl2 negatively regulates neurosphere formation in culture.

Astrocytes are activated in response to brain damage. Here, we found that expression of Kir4.1, a major potassium channel in astrocytes, is increased in activated astrocytes in the injured brain together with upregulation of the neural stem cell markers, Sox2 and Nestin. Expression of Kir4.1 was also increased together with that of Nestin and Sox2 in neurospheres formed from dissociated P7 mouse brains. Using the Kir4.1 blocker BaCl2 to determine whether Kir4.1 is involved in acquisition of stemness, we found that inhibition of Kir4.1 activity caused a concentration-dependent increase in sphere size and Sox2 levels, but had little effect on Nestin levels. Moreover, induction of differentiation of cultured neural stem cells by withdrawing epidermal growth factor and fibroblast growth factor from the culture medium caused a sharp initial increase in Kir4.1 expression followed by a decrease, whereas Sox2 and Nestin levels continuously decreased. Inhibition of Kir4.1 had no effect on expression levels of Sox2 or Nestin, or the astrocyte and neuron markers glial fibrillary acidic protein and ß-tubulin III, respectively. Taken together, these results indicate that Kir4.1 may control gain of stemness but not differentiation of stem cells.

A Parkinson's disease gene, DJ-1, regulates astrogliosis through STAT3.

In the injured brain, astrocytes become activated and increase GFAP expression; a phenomenon termed as astrogliosis. Previously, we have reported that DJ-1, a Parkinson's disease gene, positively regulates astrogliosis in the injured brain. Moreover, STAT3 is known to play a key role in the regulation of astrogliosis. The purpose of this study was to evaluate whether DJ-1 regulates astrogliosis, via STAT3 activation. The results of this study reveal that DJ-1 is a positive regulator of STAT3 activation, the most important mediator of astrogliosis. In brain slice cultures obtained from wild-type (WT) mice, STAT3 was activated, as demonstrated by its phosphorylation to pSTAT3, within 3 h, and GFAP expression was increased within 2 days after slice preparation. Interestingly, levels of pSTAT3 and GFAP in DJ-1 knockout brain slice were attenuated compared with that of WT. STAT3 inhibitors, DPP (5 µM) and S3I-201 (50 µM), reduced expression of BDNF, GDNF, and GFAP. However, the STAT3 inhibitors did not affect mRNA levels of Sox9, another important regulator of astrogliosis. Additionally, Sox9 siRNAs did not affect STAT3 phosphorylation. These results indicate that STAT3 and Sox9 may be the independent targets of DJ-1.