D-4F increases microRNA-124a and reduces neuroinflammation in diabetic stroke rats

D-4F is an apolipoprotein-A1 mimetic peptide that promotes anti-inflammatory effects. MicroRNA-124 is the most abundant brain-specific microRNA and has anti-inflammatory effects. In this study, we investigated the therapeutic efficacy and mechanisms of D-4F treatment of stroke in type one diabetes mellitus (T1DM) rats. Male Wistar rats were induced with T1DM, subjected to embolic middle cerebral artery occlusion and treated with PBS or D-4F (1 mg/kg i.p.) at 2, 24 and 48 hours after stroke (n=8/group). A battery of function tests, brain blood barrier (BBB) integrity, white matter changes and microRNA expression were evaluated in vivo and in vitro. D-4F treatment in T1DM-stroke rats significantly improves functional outcome, decreases BBB leakage, increases tight junction protein expression, decreases white matter damage and inflammatory factor expression, while increasing anti-inflammatory M2 macrophage polarization in the ischemic brain. D-4F significantly increases microRNA-124a expression, and decreases matrix metalloproteinase-9, tumor necrosis factor-α and toll-like receptor-4 gene expression in the ischemic brain, and in primary cortical neuronal and microglial cultures. Inhibition of microRNA-124 in cultured primary cortical neurons and microglia attenuates D-4F induced anti-inflammatory effects and M2 macrophage polarization. D-4F treatment of T1DM-stroke increases microRNA-124 expression, promotes anti-inflammatory effects and M2 macrophage polarization, which may contribute to D-4F-induced improvement in neurological function, and BBB and white matter integrity.