Oxytocin (OT), a neurohypophyseal hormone synthesized in the paraventricular and supraoptic nuclei of the hypothalamus, has been reported to have an anti- inflammatory effect. However, its role in acute lung injury (ALI) has never been investigated. The aim of this study was to explore the therapeutic effects and potential mechanism action of OT on lipopolysaccharide (LPS)-induced ALI. Mice were treated with OT 30 min before the intraperitoneal injection of LPS. After 2 h, the effects of OT on lung histopathological changes, lung wet/dry (W/D) ratio, myeloperoxidase (MPO) activity, levels of inflammatory cytokines in the bronchoalveolar lavage fluid (BALF), and expression of inflammation proteins were detected. The results showed that OT significantly reduced LPS-induced pathological injury, W/D ratio, MPO activity, and the levels of interleukin (IL)-1β, IL-18 and IL-6. Further, OT also inhibited LPS-induced Toll-like receptor 4 expression and NLR family pyrin domain containing 3 inflammasome activation. OT receptor antagonist (L-368,899) was given 90 min before injecting OT to further demonstrate the role of OT in LPS-induced ALI. The results showed OT could not alleviate the aforementioned inflammatory reactions after administering L-368,899. In conclusion, the present results indicated that OT could reduce inflammatory responses of LPS-induced ALI.
Ventilator has been widely used for life support, but ventilator-induced lung injury (VILI) is still a major problem. Oxidative stress has been considered as a key contributor for VILI, but the specific mechanism remains unclear. The expression of NLRP3 inflammasome in cells and inflammatory factors in the supernatant were measured. Mitochondrial ROS and TRPM2 channel currents were investigated using flow cytometry and Patch-clamp technique, respectively. TRPM2-/and NLRP3-/mice were used for animal experiments. Lung tissues were stained by HE and the wet-dry ratio, bronchoalveolar lavage fluid (BALF) protein, MPO (marrow peroxidase), NLRP3 inflammasome were also investigated. Knockdown of NLRP3 or Caspase-1 or treatments with SS-31 or YVAD inhibited the expression of the NLRP3 inflammasome, and reduced IL-1b and IL-18 levels in cell supernatant. These treatments suppressed the production of ROS and lowered the TRPM2 channel currents, but Rotenone exerted an opposite effect. Hightidal volume ventilation significantly increased the levels of IL-1b, IL-18, NLRP3 inflammasome, wet-dry ratio of lung, MPO and BALF protein. However, these parameters were down-regulated in TRPM2-/and NLRP3-/mice. These parameters were suppressed in TRPM2-/and NLRP3-/mice indicate that oxidative stress might promote VILI through activating NLRP3 inflammasome and TRPM2 channel.
Mechanical ventilation is an indispensable life-support treatment for acute respiratory failure in critically ill patients, which is generally believed to involve uncontrolled inflammatory responses. Oxytocin (OT) has been reported to be effective in animal models of acute lung injury. However, it is not clear whether Oxytocin has a protective effect on ventilator-induced lung injury (VILI). Therefore, in this study, we aimed to determine whether OT can attenuate VILI and explore the possible mechanism of this protection. To this end, a mouse VILI model was employed. Mice were pretreated with OT 30 min before the intraperitoneal injection of saline or nigericin and ventilation for 4 h, after which they were euthanized. Pathological changes, lung wet/dry (W/D) weight ratio, myeloperoxidase (MPO) activity, the levels of inflammatory cytokines [i.e., interleukin (IL)-1β, IL-6, and IL-18] in lung tissues and bronchoalveolar lavage fluid (BALF), and expression of NLRP3, Toll-like receptor 4 (TLR4), caspase-1, nuclear factor (NF)-κB, and GSDMD in lung tissues were measured. OT treatment could reduce pathological injury, the W/D ratio, and MPO activity in VILI mice. Our data also indicated that OT administration alleviated the expression of TLR4/My-D88 and the activation of NF-κB, NLRP3, and caspase-1 in lung tissues from the VILI mice model. Furthermore, OT also decreased the levels of IL-1β, IL-6, and IL-18 in the bronchoalveolar lavage fluid. Moreover, the OT administration may alleviate the activation of GSDMD partially through its effects on the NLRP3-mediated pathway. Collectively, OT exerted a beneficial effect on VILI by downregulating TLR4-and NLRP3-mediated inflammatory pathways.
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