IL-1β enhances β2-adrenergic receptor expression in human airway epithelial cells by activating PKC

Protein kinase C (PKC)-activated signal transduction pathways regulate cell growth and differentiation in many cell types. We have observed that interleukin (IL)-1 beta upregulates beta (2)-adrenergic receptor (beta (2)-AR) density and beta2-AR mRNA in human airway epithelial cells (e.g., BEAS-2B). We therefore tested the hypothesis that PKC-activated pathways mediate IL-1 beta -induced beta -AR upregulation. The role of PKC was assessed from the effects of 1) the PKC activator phorbol 12-myristate 13-acetate (PMA) on beta -AR density, 2) selective PKC inhibitors (calphostin C and Ro-31-8220) on beta -AR density, and 3) IL-1 beta treatment on the cellular distribution of PKC isozymes. Recombinant human IL-1 beta (0.2 nM for 18 h) increased beta -AR density to 213% of control values (P < 0.001). PMA (1 <mu>M for 18 h) increased beta -AR density to 225% of control values (P < 0.005), whereas Ro-31-8220 and calphostin C inhibited the IL-1<beta>-induced upregulation of beta -AR in dose-dependent fashion. PKC isozymes detected by Western blotting included alpha, beta II, epsilon, mu, zeta, and lambda/iota. IL-1 beta increased PKC-mu immunoreactivity in the membrane fraction and had no effect on the distribution of the other PKC isozymes identified. These data indicate that IL-1 beta -induced beta -AR upregulation is mimicked by PKC activators and blocked by PKC inhibitors and appears to involve selective activation of the PKC-mu isozyme. We conclude that signal transduction pathways activated by PKC-mu upregulate beta (2)-AR expression in human airway epithelial cells.