Rac Inhibition Reverses the Phenotype of Fibrotic Fibroblasts

Abstract

BackgroundFibrosis, the excessive deposition of scar tissue by fibroblasts, is one of the largest groups of diseases for which there is no therapy. Fibroblasts from lesional areas of scleroderma patients possess elevated abilities to contract matrix and produce α−smooth muscle actin (α-SMA), type I collagen and CCN2 (connective tissue growth factor, CTGF). The basis for this phenomenon is poorly understood, and is a necessary prerequisite for developing novel, rational anti-fibrotic strategies.Methods and FindingsCompared to healthy skin fibroblasts, dermal fibroblasts cultured from lesional areas of scleroderma (SSc) patients possess elevated Rac activity. NSC23766, a Rac inhibitor, suppressed the persistent fibrotic phenotype of lesional SSc fibroblasts. NSC23766 caused a decrease in migration on and contraction of matrix, and α−SMA, type I collagen and CCN2 mRNA and protein expression. SSc fibroblasts possessed elevated Akt phosphorylation, which was also blocked by NSC23766. Overexpression of rac1 in normal fibroblasts induced matrix contraction and α−SMA, type I collagen and CCN2 mRNA and protein expression. Rac1 activity was blocked by PI3kinase/Akt inhibition. Basal fibroblast activity was not affected by NSC23766.ConclusionRac inhibition may be considered as a novel treatment for the fibrosis observed in SSc.

Sticking it to Scleroderma: Potential Therapies Blocking Elevated Adhesive and Contractile Signaling

“…These findings are consistent with data revealing that neutrophils and macrophages use Rac for the NADPH oxidases 1, 2 and 3 [79,80]. Recently, we found that Rac is constitutively activated in SSc fibroblasts and that pharmacological inhibition of Rac1 reverses the phenotype of lesional SSc fibroblasts [81]. In this latter study, Rac1 was shown to act by PI3 kinase/Akt; rac inhibition reduced the enhanced Akt phosphorylation observed in SSc fibroblasts [81].…”

Regulation of valve endothelial cell vasculogenic network architectures with ROCK and Rac inhibitors

“…Several studies have demonstrated the unique attributes of VECs compared to vascular-derived endothelial cells (Butcher et al, 2004Hinton and Yutzey, 2011;Poggio et al, 2011;Xu et al, 2009Xu et al, , 2010Yang et al, 2008) and this study identified a new set of functional differences between the two. Both cell types formed complex networks, but in this work the VECs formed networks that were visibly and measurably different, and appeared to branch more.…”

“…Several studies have demonstrated the unique attributes of valve endothelial cells (VECs) compared to vascular-derived endothelial cells (ECs) including their transduction of angiogenic stimuli. Additional sources of differences include the valve cells' physiological predisposition toward endothelial to mesenchymal transdifferentiation during valvulogenesis and their distinct mechanical environment Hinton and Yutzey, 2011;Poggio et al, 2011;Xu et al, 2009Xu et al, , 2010Yang et al, 2008). Further, key differences between ECs and VECs arise in the expression of genes and proteins that regulate blood vessel development, angiogenesis, adhesion, migration, and cell fate in in vitro comparisons (Butcher et al, 2004.…”

“…It was also reported that flow-dependent VEC orientation was independent of PI3K, a downstream effector of Rac1, despite its known role in regulating vascular endothelial cell organization in response to flow and during angiogenesis (Butcher et al, 2004;Holmes et al, 2007). Given the importance of ROCK and Rac1 in regulating endothelial cell motility and organization during angiogenesis (Hoang et al, 2004), as well as the atypical nature of VEC responses to various angiogenic stimuli (Xu et al, 2009;Yang et al, 2008), and the potential impact of a VEC-specific anti-angiogenic therapy for the treatment of CAVD (Hakuno et al, 2010), there is compelling motivation for further study of the effects of ROCK and Rac1 inhibition on vasculogenic network formation by heart valve cells.…”

Autoimmune mechanisms of scleroderma and a role of oxidative stress

“…Scleroderma fibroblasts possess high Rac activity and a Rac inhibitor suppressed fibrotic phenotype of scleroderma fibroblasts. 69 Myofibroblasts represent activated and contractile phenotypes which exist in fibrotic lesions. Myofibroblasts express α-SMA, and can produce various cytokines, growth factors and chemokines.…”