Overexpression of miR-146a Might Regulate Polarization Transitions of BV-2 Cells Induced by High Glucose and Glucose Fluctuations

Abstract

Microglia are critical in neuroinflammation. M1/M2 polarization transitions of microglial phenotypes determine the states of neuroinflammation and are regulated by multiple pathways, including miRNAs and other epigenetic regulations. This study investigated the polarization transitions of microglia induced by high glucose and glucose fluctuations, and the role of miR-146a in regulating M1/M2 polarization transitions of microglia. BV-2 cells were cultured with 25 mmol/L glucose, 75 mmol/L glucose, and 25 mmol/L−75 mmol/L glucose fluctuation for 48 h. BV-2 cells overexpressing miR-146a were generated using a lentiviral vector. Quantitative real-time polymerase chain reaction (qRT-PCR) was used to measure mRNA expression of miR-146a, CD11b, iNOS, Arg-1, IRAK1, TRAF6, and NF-κB. Immunofluorescence was used to measure CD11b expression. Western blot was used to measure protein expression of CD11b, iNOS, and Arg-1. Compared with those in the 25 mmol/L glucose control group, expression of CD11b, iNOS, TNF-α, and IL-6 in the 75 mmol/L glucose or glucose fluctuation groups of cultured BV-2 cells were significantly increased, while Arg-1 and IL-10 was significantly decreased. These effects were reversed by overexpression of miR-146a. Furthermore, expression of IRAK1, TRAF6, and NF-κB was significantly increased in the high glucose and glucose fluctuation groups; this was reduced after miR-146a overexpression. In sum, high glucose and glucose fluctuations induced polarization transitions from M1 to M2 phenotype in BV-2 cells. Overexpression of miR-146a might protect BV-2 cells from high glucose and glucose fluctuation associated with M1/M2 polarization transitions by downregulating the expression of IRAK1, TRAF6, and NF-κB.

<p>Exosomes Derived from MicroRNA-146a-5p-Enriched Bone Marrow Mesenchymal Stem Cells Alleviate Intracerebral Hemorrhage by Inhibiting Neuronal Apoptosis and Microglial M1 Polarization</p>

“…It has been reported that downregulating the expression of IRAK1 by miR-146a increases M2 polarization in BV-2 cells. 41 In another study, NFAT5 suppresses the macrophage M2 phenotype. 47 Thus, it can be assumed that BMSCs-miR -146a-5p-Exos administration elevates microglial M2 polarization by suppressing the expression of IRAK1 and NFAT5.…”

“…We then identified two critical miR-146a-5p targets upregulated after ICH with pro-inflammatory and macrophages/microglia polarizationmodulated properties: IRAK1 and NFAT5. 40,41 IRAK1 is a kinase that belongs to interleukin-1 receptor-associated kinase (IRAK) family, mediating inflammatory responses in multiple pathological processes. 42 It contributes to the activation of NF-κB signaling pathway which is a wellknown inflammation signaling pathway.…”

“…MiR-146a-5p targeted IRAK1 inhibiting microglia M1 polarization in ICH echo findings from a previous study. 41 NFAT5, a novel member of Rel homology domain (RHD) proteins (Rel family), plays different roles in neurons, astrocytes, microglia, and other cell types in the central nervous system. 43,44 A number of studies suggest that NFAT5 can be activated by inflammatory stimuli induction and participates in neuroinflammation.…”

Glycemic Variability and CNS Inflammation: Reviewing the Connection

“…The interactions between various brain cell types and the brain microvessel endothelial cells, often termed the neurovascular unit (NVU), are critical to maintaining CNS function. A growing body of the literature has described the impact of diabetes on components of the NVU, including: astrocytes, which are less populous and disconnected from endothelial cells [ 50 ]; pericytes, which are similarly diminished and retracted [ 51 ]; oligodendrocytes, which are decreased in number and short-lived [ 52 ]; microglia, which are abnormally polarized [ 53 ]; and endothelial cells, which are rendered less dense and more permeable [ 54 , 55 , 56 ]. However, very little is known about the impact of glycemic variability on the integrity of the NVU.…”

“…Exposure to chronic hyperglycemia has been associated with activation of microglia [ 84 ]. Furthermore, when studying the mouse microglial BV-2 cell line, exposure to glucose fluctuations resulted in increased markers of metabolic stress leading to apoptosis and/or autophagy [ 85 ] as well as leading to shifts in microglial polarization to the inflammatory M1 phenotype [ 53 ].…”