β2-Microglobulin exacerbates neuroinflammation, brain damage, and cognitive impairment after stroke in rats

β2-Microglobulin (β2M), a component of the major histocompatibility complex class I molecule, is associated with aging-related cognitive impairment and Alzheimer's disease. Although upregulation of β2M is considered to be highly related to ischemic stroke, the specific role and underlying mechanistic action of β2M are poorly understood. In this study, we established a rat model of focal cerebral ischemia by occlusion of the middle cerebral artery. We found that β2M levels in the cerebral spinal fluid, serum, and brain tissue were significantly increased in the acute period but gradually decreased during the recovery period. RNA interference was used to inhibit β2M expression in the acute period of cerebral stroke. Tissue staining with 2,3,5-triphenyltetrazolium chloride and evaluation of cognitive function using the Morris water maze test demonstrated that decreased β2M expression in the ischemic penumbra reduced infarct volume and alleviated cognitive deficits, respectively. Notably, glial cell, caspase-1 (p20), and Nod-like receptor pyrin domain containing 3 (NLRP3) inflammasome activation as well as production of the inflammatory cytokines interleukin-1β, interleukin-6, and tumor necrosis factor-α were also effectively inhibited by β2M silencing. These findings suggest that β2M participates in brain injury and cognitive impairment in a rat model of ischemic stroke through activation of neuroinflammation associated with the NLRP3 inflammasome.