Transient Receptor Potential Ankyrin 1 Mediates Afferent Signals in the Inflammatory Reflex

Abstract

Survival of an organism requires mechanisms to sense damaging factors in the environment. In mammals, bacterial toxins and inflammatory mediators stimulate nociceptive sensory neurons to activate protective reflexes. Whereas the vagus nerve reflex circuit that protects against damaging inflammation, termed the "inflammatory reflex," was described more than twenty years ago1,2, how the vagus nerve detects inflammation to initiate the inflammatory reflex has remained unknown. Here we show that transient receptor potential ankyrin 1 (TRPA1) in sensory vagus neurons is required to sense interleukin-1{beta} (IL-1{beta}), a central cytokine mediator of inflammation and injury. Selective activation of vagus nerve TRPA1 using optopharmacology stimulated the inflammatory reflex to inhibit innate inflammatory responses to bacterial lipopolysaccharide and IL-1{beta}. Proximity ligation assay and immunohistochemistry revealed that IL-1 receptors are co-expressed with TRPA1 in vagus sensory neurons. Whole-cell patch-clamp recordings reveal that TRPA1 is required to mediate IL-1{beta}-dependent depolarization of vagus sensory neurons. Further, TRPA1-deficient mice lack inflammatory reflex attenuation of inflammation, fail to restrain cytokine release, and have significantly enhanced lethality to bacterial sepsis. Therefore, vagus neurons expressing TRPA1 are necessary and sufficient to activate the sensory arc of the inflammatory reflex to protect against harmful inflammation.