Pyroptotic Neuronal Cell Death Mediated by the AIM2 Inflammasome

TLDR

The CNS actively participates in innate immune responses to infection and injury. Neuronal pyroptosis involves ASC oligomerization, caspase‑1 activation, plasma‑membrane pore formation, and IL‑1β release. Embryonic cortical neurons express a functional AIM2 inflammasome that triggers caspase‑1–dependent pyroptosis, which can be inhibited by probenecid or Brilliant Blue FCF via pannexin‑1 blockade, and is activated by CSF from TBI patients, indicating a potential therapeutic target for CNS injury.

Abstract

The central nervous system (CNS) is an active participant in the innate immune response to infection and injury. In these studies, we show embryonic cortical neurons express a functional, deoxyribonucleic acid (DNA)-responsive, absent in melanoma 2 (AIM2) inflammasome that activates caspase-1. Neurons undergo pyroptosis, a proinflammatory cell death mechanism characterized by the following: (a) oligomerization of apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC); (b) caspase-1 dependency; (c) formation of discrete pores in the plasma membrane; and (d) release of the inflammatory cytokine interleukin-1 β (IL-1 β). Probenecid and Brilliant Blue FCF, inhibitors of the pannexin1 channel, prevent AIM2 inflammasome-mediated cell death, identifying pannexin1 as a cell death effector during pyroptosis and probenecid as a novel pyroptosis inhibitor. Furthermore, we show activation of the AIM2 inflammasome in neurons by cerebrospinal fluid (CSF) from traumatic brain injury (TBI) patients and oligomerization of ASC. These findings suggest neuronal pyroptosis is an important cell death mechanism during CNS infection and injury that may be attenuated by probenecid.