Long-acting β2 agonist (LABA) with a long-acting muscarinic receptor antagonist (LAMA) promotes human airway smooth muscle (HASM) relaxation and circumvents β2 adrenergic receptor tachyphylaxis

To fill the gap in the knowledge between clinical studies and pre-clinical mechanistic studies using combined LABA/LAMA therapy, we hypothesized that the combination is more effective in attenuating excitation-contraction (E-C) coupling compared to either LAMA or LABA alone in human airway smooth muscle (HASM) cells. In primary HASM and human precision-cut lung slices (hPCLS) obtained from non-diseased donors, we show that the combination of umeclidinium (LAMA) and vilanterol (LABA) robustly attenuated carbachol-induced E-C coupling markers, compared to that induced by either compound individually. The effective concentrations of umeclidinium or vilanterol that attenuated E-C coupling signaling events were significantly decreased when the agents were combined as compared to dosing of either alone. In HASM cells treated overnight with albuterol to induce β₂AR desensitization, umeclidinium or the umeclidinium-vilanterol combination attenuated carbachol-induced E-C coupling signaling. Furthermore, the umeclidinium-vilanterol combination showed little change in the ability to dilate pre-constricted hPCLS in the presence of albuterol-induced β₂AR desensitization compared to relaxation to vilanterol alone, which was significantly attenuated by albuterol-induced desensitization. Our data suggest that targeting G_αq and G_αi signaling through muscarinic receptor antagonism serves as an effective therapy for obstructive lung diseases, even in the face of β₂AR tachyphylaxis.