Background and purpose
The Arp2/3 multiprotein complex regulates branched polymerisation of the actin cytoskeleton and may contribute to collagen synthesis and fibrogenesis in the lung. Experimental approach: Expression of Arp2/3 components was assessed in human lung fibroblasts and in the bleomycin-induced pulmonary fibrosis model in mice. The Arp2/3 complex was repressed with the allosteric inhibitor CK666 and with interfering RNAs targeting the ARP2, ARP3 and ARPC2 subunits (siARP2, siARP3 and siARPC2) in CCD-16Lu human lung fibroblasts in vitro. Mice received daily intraperitoneal injections of CK666 from the 7th to the 14th day after tracheal bleomycin instillation. Key
Purpose
The Arp2/3 multiprotein complex regulates branched polymerisation of the actin cytoskeleton and may contribute to collagen synthesis and fibrogenesis in the lung. Experimental approach: Expression of Arp2/3 components was assessed in human lung fibroblasts and in the bleomycin-induced pulmonary fibrosis model in mice. The Arp2/3 complex was repressed with the allosteric inhibitor CK666 and with interfering RNAs targeting the ARP2, ARP3 and ARPC2 subunits (siARP2, siARP3 and siARPC2) in CCD-16Lu human lung fibroblasts in vitro. Mice received daily intraperitoneal injections of CK666 from the 7th to the 14th day after tracheal bleomycin instillation. Key
Results
Expression of Arp2/3 complex subunits mRNAs was increased in fibroblasts treated with TGF-β1 and in the lungs of bleomycin-treated mice compared with controls. In vitro, CK666 and siARPC2 inhibited cell growth and TGF-β1-induced α-smooth muscle actin (ACTA2) and collagen-1 (COL1) expression. CK666 also decreased ACTA2 and COL1 expression in unstimulated cells. CK666 reduced Akt phosphorylation and repressed phospho-GSK3β, β-catenin and MRTF-A levels in unstimulated fibroblasts. In vivo, CK666 reduced levels of both procollagen-1 and insoluble collagen in bleomycin-treated mice.