miR-181a and inflammation: miRNA homeostasis response to inflammatory stimuli in vivo.

Inflammatory stimuli are usually associated with homeostatic responses, which have an important function in protecting the body from excessive inflammatory damage. Previous studies reported the anti-inflammatory effect of miR-181a. The current study utilized two animal models of inflammation, induced by either lipopolysaccharides (LPS) or streptozotocin. We demonstrated that inflammatory stimuli significantly increase miR-181a expression, concurrently with inflammatory factors. In addition, the knock down of toll-like receptor 4 (TLR-4) by small interfering RNA in LPS-induced Raw264.7 cells significantly reduces the expression of both miR-181a and inflammatory factors. Furthermore, patients with inflammatory response show increased expression of miR-181a, which is strongly correlated with the expression of interleukin (IL)-1β, IL-6, and tumor necrosis factor alpha. These data indicate that the up-regulation of miR-181a may be associated with homeostatic response to inflammatory stimuli by TLR-4 pathway activation. Therefore, miR-181a may serve as a novel marker for inflammatory response.