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)-1β upregulates β2-adrenergic receptor (β2-AR) density and β2-AR mRNA in human airway epithelial cells (e.g., BEAS-2B). We therefore tested the hypothesis that PKC-activated pathways mediate IL-1β-induced β-AR upregulation. The role of PKC was assessed from the effects of 1) the PKC activator phorbol 12-myristate 13-acetate (PMA) on β-AR density, 2) selective PKC inhibitors (calphostin C and Ro-31-8220) on β-AR density, and 3) IL-1β treatment on the cellular distribution of PKC isozymes. Recombinant human IL-1β (0.2 nM for 18 h) increased β-AR density to 213% of control values ( P < 0.001). PMA (1 μM for 18 h) increased β-AR density to 225% of control values ( P < 0.005), whereas Ro-31-8220 and calphostin C inhibited the IL-1β-induced upregulation of β-AR in dose-dependent fashion. PKC isozymes detected by Western blotting included α, βII, ε, μ, ζ, and λ/ι. IL-1β increased PKC-μ immunoreactivity in the membrane fraction and had no effect on the distribution of the other PKC isozymes identified. These data indicate that IL-1β-induced β-AR upregulation is mimicked by PKC activators and blocked by PKC inhibitors and appears to involve selective activation of the PKC-μ isozyme. We conclude that signal transduction pathways activated by PKC-μ upregulate β2-AR expression in human airway epithelial cells.