Key points Summary Transforming growth-factor- (TGF-) and RhoA/Rho-kinase are independently implicated in the airway hyper-responsiveness associated with asthma, but how these proteins interact is not fully understood We examined the effects of pre-treatment with TGF- on expression and activity of RhoA, Rho-kinase and ARHGEF1, an activator of RhoA, as well as on bradykinin induced contraction, in airway smooth muscle TGF- enhanced bradykinin-induced RhoA translocation, Rho-kinase dependent phosphorylation, and contraction, but partially suppressed BK-induced RhoA activity GTP content) TGF- enhanced the expression of ARHGEF1, while a siRNA against ARHGEF1 and a RhoGEF inhibitor prevented the effects of TGF- on RhoA and Rho-kinase activity and contraction, respectively ARHGEF1 expression was also enhanced in airway smooth muscle from asthmatic patients and OVA-sensitized mice ARHGEF1 is a key TGF- target gene, an important regulator of Rho-kinase activity and is therefore a potential therapeutic target for the treatment of asthmatic airway responsiveness Abstract Transforming growth factor- (TGF-), RhoA/Rho-kinase and Src-family kinases (SrcFK) have independently been implicated in airway hyper-responsiveness, but how they interact in order to regulate airway smooth muscle contractility is not fully understood. We found that TGF- pre-treatment enhanced acute contractile responses to bradykinin (BK) in isolated rat bronchioles, and inhibitors of RhoGEFs (Y16) and Rho-kinase (Y27632), but not the SrcFK inhibitor PP2 prevented this enhancement. In cultured human airway smooth muscle cells (hASMC), TGF- pre-treatment enhanced the protein expression of the Rho guanine nucleotide exchange factor ARHGEF1, MLC20, MYPT-1 and the actin-severing protein
Key points Summary Transforming growth-factor- (TGF-) and RhoA/Rho-kinase are independently implicated in the airway hyper-responsiveness associated with asthma, but how these proteins interact is not fully understood We examined the effects of pre-treatment with TGF- on expression and activity of RhoA, Rho-kinase and ARHGEF1, an activator of RhoA, as well as on bradykinin induced contraction, in airway smooth muscle TGF- enhanced bradykinin-induced RhoA translocation, Rho-kinase dependent phosphorylation, and contraction, but partially suppressed BK-induced RhoA activity content) TGF- enhanced the expression of ARHGEF1, while a siRNA against ARHGEF1 and a RhoGEF inhibitor prevented the effects of TGF- on RhoA and Rho-kinase activity and contraction, respectively ARHGEF1 expression was also enhanced in airway smooth muscle from asthmatic patients and OVA-sensitized mice ARHGEF1 is a key TGF- target gene, an important regulator of Rho-kinase activity and is therefore a potential therapeutic target for the treatment of asthmatic airway Abstract Transforming growth factor- (TGF-), RhoA/Rho-kinase and Src-family kinases (SrcFK) have independently been implicated in airway hyper-responsiveness, but how they interact in order to regulate airway smooth muscle contractility is not fully understood. We found that TGF- pre-treatment enhanced acute contractile responses to bradykinin (BK) in isolated rat bronchioles, and inhibitors of RhoGEFs (Y16) and Rho-kinase (Y27632), but not the SrcFK inhibitor PP2 prevented this enhancement. In cultured human airway smooth muscle cells (hASMC), TGF- pre-treatment enhanced the protein expression of the Rho guanine nucleotide exchange factor ARHGEF1, MLC20, MYPT-1 and the actin-severing protein GTP responsiveness