The mechanism of curcumin post-treatment relieving lung injuries by regulating miR-21/TLR4/NF-κB signalling pathway

Objective To investigate the mechanism by which curcumin prevents lung injury in a rat model of limb ischaemia-reperfusion injury. Methods Rats were randomized into four groups ( n = 20): control group (sham group); ischaemia-reperfusion group (I/R group); curcumin group (I/R+Cur group); and inhibitor of agomir-21 group (I/R+Cur+antagomir-21 group). At 3 h after reperfusion, lung tissues were collected for histopathology and immunohistochemistry to determine the apoptosis index (AI). Lung injury score (LIS) and lung wet/dry (W/D) ratio were determined. Lung microRNA-21 (miR-21) mRNA levels were measured using reverse transcription–polymerase chain reaction. Toll-like receptor 4 (TLR4) and nuclear factor kappa-B p65 (NF-κB p65) protein levels were measured by Western blot analysis. Tumour necrosis factor (TNF)-α and interleukin (IL)-1β levels were determined by enzyme-linked immunosorbent assays. Results In the I/R group, the W/D, LIS, AI, miR-21 mRNA, TLR4, NF-κB p65, TNF-α and IL-1β were significantly increased and the PaO 2 was decreased compared with the sham group. Evidence of lung injury was observed in the I/R group and this was alleviated in the I/R+Cur group. An inhibitor of miR-21 (antagomir-21) reversed the protective effects of curcumin. Conclusion Curcumin post-treatment can alleviate the lung injuries induced by limb ischaemia-reperfusion via downregulating the levels of miR-21 mRNA