PIWIL2 drives stroke progression via modulation of NF-κB signaling.

PIWILs are RNA-binding proteins whose role in ischemic stroke remains poorly defined. Here, we investigated the contribution of PIWILs to post-ischemic neuroinflammation by using a mouse model of 1 h transient middle cerebral artery occlusion (tMCAo), followed by 6 or 24 h of reperfusion. Brain tissues, blood, and peripheral organs were collected to assess PIWIL expression, inflammatory responses, and brain damage. PIWIL1 and PIWIL2 were significantly upregulated in the cortex and striatum at 24 h post-ischemia, with PIWIL2 also increased in blood and peripheral tissues. Immunofluorescence analyses revealed cell-type-specific localization of PIWILs in neurons, astrocytes, and endothelial cells. Notably, siRNA-mediated silencing of PIWIL2 significantly reduced infarct volume. PIWIL2 silencing also attenuated NF-κB-p65 and phospho-IκBα levels in the peri-infarct cortex but not in the striatum, indicating region-specific modulation of NF-κB signaling and differentially reprogrammed systemic chemokine profiles, with selective upregulation of CCL3, CCL5, and CXCL13 and downregulation of CCL2, CCL17, CCL20, and CXCL1. Mechanistically, PIWIL2 interacted with IKKα and promoted activation of the NF-κB pathway, leading to RelA- and RelB-dependent transcriptional regulation of pro-inflammatory chemokines. Together, these findings identify PIWIL2 as an upstream regulator of NF-κB-dependent neuroinflammation that exacerbates ischemic brain injury and suggest PIWIL2 as a promising therapeutic target targeting post-stroke inflammatory damage.