Background and Purpose:
Microparticles (MPs, ~ size between 0.1-1mm) are lipid encased containers, and are involved in intercellular communication and regulate inflammation. Stroke increases brain derived MP (BDMP) secretion which induces neuroinflammation. Milk fat globule-EGF factor-8 (MFGE8) promotes apoptotic cell clearance and limits pathogenic antigen cross presentation. In this study, we investigate whether BDMP affects stroke-induced neuroinflammation; whether MFGE8 treatment reduces stroke or BDMP-induced neuroinflammation and improves functional outcome after stroke.
Method:
1) BDMPs were extracted from ischemic brain 24h after dMCAo by ultracentrifugation. 2) Adult (8 months) male C57BL/6J mice were subjected to dMCAo and were injected via tail vein 3h after stroke with: A) PBS (n=5/group); B) +BDMP(1.5х10
8
,n=6/group); C)+MFGE8 (Lactadherin, 400ug/kg, n=5/group); D) +BDMP+MFGE8 (n=6/group). A battery of neurological function outcomes and immunostaining were performed. Blood plasma was used for Western blot assay.
Result: 1)
Compared with the Stroke+PBS control group, Stroke+BDMP significantly increases inflammatory factor expression in the circulation, increases lesion volume, neurological deficits, blood brain barrier (BBB) leakage, microglial activation, and inflammatory cell infiltration (CD45, microglia/macrophage, Neutrophils) and inflammatory factor (TNFα, IL6, IL1β) expression in brain, and increases axon/white matter (WM) damage; 2) Compared to Stroke+PBS and Stroke+BDMP groups, Stroke+MFGE8 and Stroke+BDMP+MFGE8 mice exhibited significantly improved neurological outcome; decreased lesion volume and BBB leakage, reduced axon/WM damage, and decreased inflammatory cell infiltration and inflammatory factor expression in the ischemic border, respectively. MFGE8 treatment significantly increased anti-inflammatory factor (IL10) expression in ischemic brain, and decreased IL1β expression in circulation compared to Stroke+PBS and Stroke+BDMP groups, respectively.
Conclusion:
BDMP increases neuroinflammation and induces worse brain damage after stroke. MFGE8 treatment reduces stroke and BDMP-induced neurological deficits possibly via its anti-inflammatory effects.