Mechanism of ulinastatin in reducing lung inflammatory injury in rats with hemorrhagic shock

Abstract

To investigate the effect of ulinastatin on the inflammatory mediators and their signaling pathways miR-146a/TLR4/NF-κB in rats with hemorrhagic shock. Seventy-two SD rats were randomly assigned into shock without resuscitation group (SR group, n=24), acetated Ringer's solution resuscitation group (AR group, n=24) and ulinastatin treatment group (n=24). In all the 3 groups hemorrhagic shock models were established by femoral artery bleeding (with the mean arterial pressure maintained at 30-40 mmHg) without resuscitation (in SR group) or with resuscitation (in AR and ulinastatin groups) using acetated Ringer's solution for 30 min at 60 min after the onset of shock. At 1, 4, and 6 h after the shock onset or immediately after shock if the rats died, the lung tissues were taken for measurement of mRNA expressions of miR-146a, tumor necrosis factor-α (TNF-α), interleukin-1 (IL-1), IL-4, IL-6 and IL-10 using real-time quantitative PCR and the protein expressions of TLR4, MyD88, IκB-α, p-IκB-α, NF-κB p65, IRAK4, p-IRAK4 (Thr345, Ser346), p-IRAK4 (Thr342) and TRAF6 using Western blotting. The lung histopathology of the rats was examined under optical microscope with HE staining. Compared with the SR group, the rats in the AR group showed slightly alleviated inflammatory infiltration in the lung tissues with significantly increased mRNA levels of miR-146a, IL-4 and IL-10 (P < 0.05) and protein expressions of IκB-α, p-IRAK4 (Thr342) and p-IRAK4 (Thr345, ser346) (P < 0.05), and decreased mRNA levels of TNF-α, IL-1 and IL-6 (P < 0.05) and protein expressions of TLR4, MyD88, NF-κB p65, p-IκB-α, IRAK-4 and TRAF6 (P < 0.05). Compared with those in AR group, the rats in ulinastatin group showed further alleviation of inflammatory lung tissue injury, with increased mRNA levels of miR-146a, IL-4 and IL-10 (P < 0.01) and protein expressions of IκB-α, p-IRAK4 and p-IRAK4 (P < 0.01) and decreased mRNA levels of TNF-α, IL-1 and IL-6 (P < 0.01) and protein expressions of TLR4, MyD88, NF-κB p65, p-IκB-α, IRAK-4 and TRAF6 (P < 0.01). Ulinastatin combined with acetated Ringer's solution resuscitation alleviates lung inflammations in rats with hemorrhagic shock possibly by enhancing miR-146a expression to regulate TLR4/NF-κB signaling pathway through a negative feedback mechanism and thus modulate the balance of pro-inflammatory and anti-inflammatory factors.