miR-19a-3p and miR-19b-3p Promote Microglia Activation Associated With Neuroinflammation.

Neuroinflammation, driven by microglia activation and the production of pro-inflammatory cytokines, has been implicated in several neurological diseases and neuropathic pain. MicroRNAs (miRNAs) have emerged as important regulators of neuroinflammatory processes. Prior studies identified elevated levels of circulating miR-19a and miR-19b in individuals living with chronic pain following spinal cord injury (SCI). In this study, we wanted to determine whether miR-19a and miR-19b have a direct effect on microglia activation, specifically pro-inflammatory activation, associated with neuroinflammation. Microglia were activated by inflammatory stimuli in the presence of miR-19a or miR-19b mimics, and assessed for the expression of cytokines, chemokines, and effector molecules. The results show that miR-19a or miR-19b mimics increased the expression of pro-inflammatory cytokines, chemokines, and effector molecules in microglia. The results also showed decreased expression of suppressor of cytokine signaling (SOCS) proteins, namely SOCS1 and SOCS3, in activated microglia with miR-19a and miR-19b mimics. Additionally, enhanced signaling through the NFκB and Jak pathways was observed with increased NFkB-p65 and JAK1 phosphorylation in the presence of miR-19a and miR-19b mimics. Further results show that miR-19a and miR-19b inhibitors reversed these effects on activated microglia. Overall, our results demonstrate that miR-19a or miR-19b increased the expression of pro-inflammatory cytokines, chemokines, and effector molecules in activated microglia. These results indicate that miR-19a and miR-19b can enhance microglia activation and associated inflammatory responses, which may have implications for conditions associated with neuroinflammation.