(287) Anoctamin-1 Cl- channel in nociception: inhibition by T16[inh]-A01 and activation by an N-aroylaminothiazole and capsaicin

Abstract

Anoctamin 1 (ANO1 or TMEM16A) Ca2+−gated Cl− channels of nociceptor sensory neurons are emerging as important molecular components of peripheral pain transduction. At physiological intracellular Cl− concentrations ([Cl−]i) sensory neuronal Cl− channels, such as ANO1, are excitatory. ANO1 channels are directly activated by an N-aroylaminothiazole (E-act). At physiological [Cl−]i (40mM), E-act (10μM) direct activation of ANO1 increased current sizes (in voltage-clamp) and action potential firing (in current-clamp) recorded using whole-cell electrophysiology of mouse dorsal root ganglia (DRG) sensory neurons. Nocifensive responses of mice hind paws were also dramatically induced by subcutaneous injections of E-act (5mM), which was attenuated by co-injection of ANO1-inhibitor T16A[inh]-A01 (1.3mM). ANO1 channels are also activated by intracellular Ca2+ ([Ca2+]i) from sensory neuronal TRPV1 (transient-receptor-potential vallinoid 1) ion channels and other noxicant receptors. At physiological [Cl−]i, capsaicin (15μM)-induced action potential firing was diminished by co-application with ANO1-inhibitor T16A[inh]-A01 (20μM) To not disrupt TRPV1 carried-Ca2+ activation of ANO1 in DRG neurons. (To not disrupt TRPV1 carried-Ca2+ activation of ANO1 in DRG neurons, ANO1 modulation of capsaicin-induced action potentials was measured by perforated-patch (Amphotericin−B) current-clamp technique). Under conditions of low [Cl−]i (10mM), ANO1 actions were reversed. Specifically, E-act did not trigger action potentials; however, capsaicin-induced action potential firing was inhibited by co-application of E-act, but was unaffected by co-application of T16A[inh]-A01. Nocifensive responses of mice hind paws were dramatically induced by subcutaneous injections of E-actcapsaicin (50μM). The nocifensive responses were attenuated by co-injection with T16A[inh]-A01 (1.3mM). In summary, an ANO1-activator induced [Cl−]i-dependent sensory neuronal action potentials and mouse nocifensive behaviors; thus, direct ANO1 activation can induce pain perception. ANO1-inhibition attenuated capsaicin-triggering of action potentials and capsaicin-induced nocifensive behaviors. The results indicate that sensory neuronal ANO1 facilitates TRPV1 triggering of action potentials, resulting in enhanced nociception and inhibition of ANO1 could be a novel means of inducing analgesia.