Annexin A1 upregulates hematoma resolution via the FPR2/p-ERK(1/2)/DUSP1/CD36 signaling pathway after germinal matrix hemorrhage.

Germinal matrix hemorrhage (GMH) is one of the leading causes of morbidity and mortality in preterm infants in the United States, with little progress made in its clinical management. Blood clots disrupting normal cerebrospinal fluid circulation and absorption after germinal matrix hemorrhage are key contributors towards post-hemorrhagic hydrocephalus development. n-formyl peptide receptor 2 (FPR2), a G-protein-coupled receptor, has been associated with the activation of p-ERK1/2, which in turn promotes the transcription of the DUSP1 gene, which may play a role in CD36 signaling. CD36 scavenger, a transmembrane glycoprotein, plays an essential role in microglia phagocytic blood clot clearance after GMH. FPR2's role in blood clot clearance after hemorrhagic stroke is unknown. We hypothesize that FPR2 activation by FPR2 agonist Annexin A1 (AnxA1) will enhance hematoma resolution via the upregulation of the CD36 signaling pathway, thereby improving short- and long-term neurological outcomes. Bacterial collagenase (0.3 U) was infused intraparenchymally into the right hemispheric ganglionic eminence in P7 rat pups to induce GMH. AnxA1 and FPR2 Inhibitor (Boc2) were given at 1-h post-GMH via intranasal administration. FPR2 CRISPR was given 48-h prior to GMH induction. Short-term neurological deficits were assessed using negative geotaxis test. Hematoma volume was assessed using hemoglobin assay. Protein expression was assessed using western blots. Long-term neurocognitive deficits and motor coordination were assessed using Morris water maze, rotarod, and foot fault tests. We have demonstrated that AnxA1 treatment enhances hematoma resolution and improved short and long-term outcomes. Lastly, FPR2 agonist AnxA1 treatment resulted in the upregulation of the FPR2/p-ERK(1/2)/DUSP1/CD36 signaling pathway.