Caveolae are specialized membrane microdomains expressing the scaffolding
protein caveolin-1. We recently demonstrated the presence of caveolae in human airway smooth muscle (ASM) and the contribution of
caveolin-1 to intracellular
calcium ([Ca(2+)](i)) regulation. In the present study, we tested the hypothesis that
caveolin-1 regulates ASM contractility. We examined the role of
caveolins in force regulation of porcine ASM under control conditions as well as TNF-α-induced airway
inflammation. In porcine ASM strips, exposure to 10 mM methyl-β-
cyclodextrin (CD) or 5 μM of the
caveolin-1 specific scaffolding domain inhibitor
peptide (CSD) resulted in time-dependent decrease in force responses to 1 μM ACh. Overnight exposure to the
cytokine TNF-α (50 ng/ml) accelerated and increased
caveolin-1 expression and enhanced force responses to ACh. Suppression of
caveolin-1 with
small interfering RNA mimicked the effects of CD or CSD. Regarding mechanisms by which caveolae contribute to contractile changes, inhibition of MAP
kinase with 10 μM
PD98059 did not alter control or TNF-α-induced increases in force responses to ACh. However, inhibiting RhoA with 100 μM
fasudil or 10 μM
Y27632 resulted in significant decreases in force responses, with lesser effects in TNF-α exposed samples. Furthermore, Ca(2+) sensitivity for force generation was substantially reduced by
fasudil or
Y27632, an effect even more enhanced in the absence of
caveolin-1 signaling. Overall, these results indicate that
caveolin-1 is a critical player in enhanced ASM contractility with airway
inflammation.