Reactivation of optic nerve head astrocytes by TGF-beta2 and H2O2 is accompanied by increased Hsp32 and Hsp47 expression.

PURPOSE

Histologic studies have previously demonstrated increased expression of small heat shock proteins (Hsps) in reactive optic nerve head (ONH) astrocytes of patients with glaucoma. Transforming growth factor (TGF)-beta2 and hydrogen peroxide (H(2)O(2)) are known to induce ONH astrocyte reactivation. The goal of the present study was to determine whether new potentially involved Hsps, such as Hsp32, -47, -60, and -70, are expressed in the reactivation process of ONH astrocytes mediated by TGF-beta2 and H(2)O(2).

METHODS

Cultured human ONH astrocytes were treated with 1.0 ng/mL TGF-beta2 for up to 48 hours. In addition, the cells were exposed to 100, 200, or 400 microM H(2)O(2) for 1 hour. Expression of Hsp32, -47, -60, and -70 was examined by immunohistochemistry, real-time PCR, and Western blot analyses.

RESULTS

Treatment with TGF-beta2 increased Hsp32 after 4 and 6 hours, whereas Hsp47 was upregulated after treatment with TGF-beta2 for 12, 24, and 48 hours. Exposure of the cells to H(2)O(2) could increase both Hsp32 and -47. No significant effects on the expression of Hsp60 and -70 were observed after treatment of the cells with TGF-beta2 or H(2)O(2).

CONCLUSIONS

TGF-beta2 increased Hsp32 after short-term treatment and Hsp47 after longer periods in cultured human ONH astrocytes. H(2)O(2) increased both Hsp32 and -47 levels. No effects on Hsp60 and -70 levels were induced by TGF-beta2 and H(2)O(2). These results may provide further insights into the cellular stress responses of reactive human ONH astrocytes. Further extensive studies are needed to examine the potential roles of Hsps in the ONH of glaucomatous eyes.