Lysophosphatidic acid receptor 1 (LPA1) contributes to
brain injury following transient focal
cerebral ischemia. However, the mechanism remains unclear. Here, we investigated whether
nucleotide-binding oligomerization domain-like receptor family pyrin domain containing 3 (NLRP3)
inflammasome activation might be an underlying mechanism involved in the pathogenesis of
brain injury associated with LPA1 following ischemic challenge with transient
middle cerebral artery occlusion (tMCAO). Suppressing LPA1 activity by its antagonist attenuated NLRP3 upregulation in the penumbra and ischemic core regions, particularly in ionized
calcium-binding adapter molecule 1 (Iba1)-expressing cells like macrophages of mouse after tMCAO challenge. It also suppressed NLRP3
inflammasome activation, such as caspase-1 activation,
interleukin 1β (IL-1β) maturation, and apoptosis-associated speck-like
protein containing a caspase recruitment domain (ASC) speck formation, in a post-ischemic brain. The role of LPA1 in NLRP3
inflammasome activation was confirmed in vitro using
lipopolysaccharide-primed bone marrow-derived macrophages, followed by LPA exposure. Suppressing LPA1 activity by either pharmacological antagonism or genetic knockdown attenuated NLRP3 upregulation, caspase-1 activation, IL-1β maturation, and IL-1β secretion in these cells. Furthermore, nuclear factor-κB (NF-κB),
extracellular signal-regulated kinase 1/2 (ERK1/2), and p38 were found to be LPA1-dependent effector pathways in these cells. Collectively, results of the current study first demonstrate that LPA1 could contribute to ischemic
brain injury by activating NLRP3
inflammasome with underlying effector mechanisms.