Abstract TP116: Immuno-Modulatory Micro RNAs and Adipokine Lipocalin-2 in Aged and Post-Stroke Rat Brains

Abstract

Aging and dysregulated immuno-regulatory molecules amplify the stroke incidence, and poor post-stroke outcome. Adipokine imbalance is linked to inflammation and cerebro-vascular diseases, emphasizing a need to better understand the adipokines in aging and post-stroke brains. Lipocalin2 (LCN2) is an acute response adipokine involved in immune functions and apoptosis. MicroRNAs modulate genes involved in the immune response, aging, and stroke. We examined the role of LCN2 in aging and post-stroke brain, and examined if microRNAs regulate LCN2 expression and function. Proteomic profiling was used to examine the expression of adipokines in pre- and post-stroke brains of 3 and 12 months rats. Stroke was induced by middle cerebral artery occlusion. Immunohistochemistry, real-time PCR, and biochemical analysis were employed. LCN2 was downregulated by SiRNA using cat-ionic lipid-particle transfection. MTT assay and TMRE staining detected cell viability and mitochondrial potential. Immunomodulatory miRNAs were identified using profiler qPCR arrays. MicroRNA target prediction software identified the microRNAs able to modulate the expression of LCN2. LCN2 levels were significantly elevated in the brains of older naïve rats, and in ipsilateral brains of both young and older rats during the acute phase of ischemia/re-perfusion. Circulating plasma LCN2 levels were increased as a result of aging and ischemic stroke. LCN2 was predominantly expressed in neurons of ischemic brain. LCN2 mRNA levels correlated with protein levels. Under oxygen glucose deprivation - in vitro ischemia, LCN2 decreased mitochondrial potential and augmented neuronal apoptosis. However, silencing of LCN2 by siRNA caused a significant reduction in LCN2 levels, and an increase in neuronal cell viability. Mechanistic studies in post-stroke brain identified down regulation of microRNAs 125, 138, and 383 that target 3’-UTR of LCN2. MicroRNA 138 and 383 were also decreased significantly in response to aging. This inverse correlation between these microRNAs and LCN2 expression strongly indicated miRNA-mediated regulation of LCN2. Potential downregulation of LCN2 by immunomodulatory miRNAs 125 and 383 may attenuate pro-inflammatory status, and may improve post-stroke outcome.