Anti-inflammatory effects of miR-21 in the macrophage response to peritonitis

Abstract

We investigated the role of microRNA-21 in the macrophage response to peritonitis; microRNA-21 expression increases in peritoneal macrophages after lipopolysaccharide stimulation but is delayed until 48 hours after cecal ligation and puncture. MicroRNA-21-null mice and bone marrow-derived cell lines were exposed to cecal ligation and puncture or lipopolysaccharide, and survival, microRNA-21 levels, target messenger RNAs and proteins, and cytokines were assayed. Macrophages were also transfected with microRNA-21 mimics and antagomirs, and similar endpoints were measured. Survival in microRNA-21-null mice was significantly decreased after lipopolysaccharide-induced peritonitis but unchanged after cecal ligation and puncture compared with similarly treated wild-type mice. MicroRNA-21 expression, tumor necrosis factor-α, interleukin 6, and programmed cell death protein 4 levels were increased after lipopolysaccharide addition in peritoneal cells. Pelino1 and sprouty (SPRY) messenger RNAs were similarly increased early, whereas programmed cell death protein 4 messenger RNA was decreased after lipopolysaccharide, and all microR-21 target messenger RNAs were subsequently decreased by 24 hours after lipopolysaccharide. Transfection with mimics and antagomirs led to appropriate responses in microRNA-21 and tumor necrosis factor-α. Knockdown of microRNA-21 in bone marrow-derived cells showed increased tumor necrosis factor-α and decreased interleukin 10 in response to lipopolysaccharide. Target proteins were unaffected by knockdown as was extracellular signal-regulated kinase; however, the nuclear factor κB p65 subunit was increased after lipopolysaccharide in the microRNA-21 knockout cells. In contrast, there was little change in these parameters after cecal ligation and puncture induction between null and wild-type mice. MicroRNA-21 is beneficial to survival in mice following lipopolysaccharide peritonitis. Overexpression of microRNA-21 decreased tumor necrosis factor-α secretion, whereas suppression of microRNA-21 expression increased tumor necrosis factor-α and interleukin 6, and decreased interleukin 10 levels after lipopolysaccharide. Protein targets of microRNA-21 were not different following suppression of microRNA-21. Nuclear factor κB was increased by suppression of microRNA-21. These findings demonstrate microRNA-21 is beneficial in modulating the macrophage response to lipopolysaccharide peritonitis and an improved understanding of the anti-inflammatory effects of microRNA-21 may result in novel, targeted therapy against peritonitis and sepsis.

The predictive value of microRNA‐21 for sepsis risk and its correlation with disease severity, systemic inflammation, and 28‐day mortality in sepsis patients

“…MiR‐21 is ubiquitously expressed in multiple organs such as heart and kidney, which participates in the processes of inflammation process and organ malfunction associated with sepsis . For instance, overexpression of miR‐21 reduces TNF‐α level, while the inhibition of miR‐21 upregulates TNF‐α and IL‐6 levels .…”

“…The present study disclosed that miR‐21 relative expression in sepsis patients was lower than that in HCs, and miR‐21 was with a good value for predicting reduced sepsis risk (AUC: 0.801, 95% CI: 0.758‐0.844). The possible explanations might be that: (a) MiR‐21 suppressed the release of macrophage cytokines (such as TNF‐α and IL‐6) via downregulating NF‐κB signaling, thus dampening inflammation and sepsis risk . (b) MiR‐21 might protect multiple organs (such as lung, kidney, and heart) from damage via reducing cell apoptosis and proinflammatory cytokines, thereby, alleviating organ injury and lowering sepsis risk …”

“…MiR-21 is ubiquitously expressed in multiple organs such as heart and kidney, which participates in the processes of inflammation process and organ malfunction associated with sepsis. [14][15][16][17] For instance, overexpression of miR-21 reduces TNF-α level, while the inhibition of miR-21 upregulates TNF-α and IL-6 levels. 16 Another study exhibits that knockdown of miR-21 facilitates the expression of programmed cell death protein 4 and phosphatase and tensin homolog deleted on chromosome 10, which results in an elevation in apoptosis and exacerbation of LPS-induced septic acute kidney injury.…”

Role of microRNA-21 in atherogenesis.

“…al., who recently reported that the deficiency of miR-21 increases LPSinduced IL-6 formation via NF-B activation [244]. Further studies are required to examine the effect of NF-B inhibition on cytokine production in miR-21-KO macrophages.…”

“…The role of miR-21 in LPS-induced inflammation has been a subject of intense investigation of late. Recently my mentor, in collaboration with others, showed that miR-21 protects from LPS-induced peritonitis [244]. However, the contribution of miR-21 in regulating TLR4 signaling in the context of atherosclerosis has not been examined.…”