Scleroderma fibroblasts demonstrate enhanced activation of Akt (protein kinase B) in situ

Abstract

Recent studies suggest that, in addition to activation and hypersecretion of matrix components, fibroblasts from patients with systemic sclerosis (SSc) are relatively resistant to apoptosis. Transforming growth factor-β (TGF)-β is strongly implicated in the pathogenesis of SSc and we and others have shown that TGF-β can activate Akt, a kinase with potent anti-apoptotic effects. To determine whether Akt was activated in SSc, we quantified phospho-Akt expression in skin fibroblasts in vitro by western blot analysis and a functional kinase assay. In addition, the relative proportion of fibroblasts containing activated Akt in was quantified by immunohistochemistry on skin sections in situ. Analysis of Akt phosphorylation of skin fibroblasts in vitro suggested increased phosphorylation of Akt, and evaluation of skin sections by immunohistochemistry revealed significantly higher percentages of fibroblasts that stained for phospho-Akt compared with controls (78% ± 14.0% vs 13% ± 9%, p < 0.001). In addition, co-incident staining of phospho-Akt and α-smooth muscle actin was observed in some fibroblasts. These findings indicate that Akt is activated in situ in skin fibroblasts from patients with SSc. Akt activation may contribute to resistance to apoptosis, selection of disease-inducing fibroblasts, and, possibly, myofibroblasts.