Background  Marine casualties often die from hypothermia and related complications after prolonged immersion in seawater, and lungs are one of the important organs vulnerable to hypothermia injury, but there is a relative lack of researches on acute lung injury (ALI) caused by hypothermia.

  Objective  To investigate the changes of cold-induced RNA-binding protein (CIRP) in rats with hypothermic ALI and its possible mechanism.

  Methods  An animal model of hypothermic ALI was constructed, and 40 male adult SD rats were randomly divided into control group (0 h, n=8) and experimental group (n=32). The experimental groups were immersed in low-temperature seawater for 12 h, 16 h, 20 h, and 24 h (n=8). The contents of IL-6, IL-1β and CIRP were detected by ELISA. HE staining, TUNEL staining and CIRP immunohistochemical staining were performed on lung tissue. The expression of CIRP mRNA was detected by qRTPCR.

  Results  Compared with the control group, the experimental groups had different degrees of lung injury, and pathological sections showed thickening or structural damage of the alveolar wall, hemorrhage in the alveolar cavity, and infiltration of neutrophils and lymphocytes. Compared with the control group, the expression of IL-6 in the serum of the 16 h, 20 h and 24 h experimental groups increased, and IL-1β in the serum of the 20 h and 24 h experimental groups also increased, the differences were statistically significant (all P<0.01). Compared with the control group, the expression of CIRP in serum of rats in each experimental group increased significantly (P<0.05 in 12 h, 16 h, 20 h groups, P<0.01 in 24 h group); TUNEL results showed that there were different degrees of apoptosis in the lung tissue of rats in each experimental group (P<0.01). According to the expression level of inflammatory factors, low temperature seawater immersion for 24 hours was selected as the best time to establish the model. Immunohistochemical staining and qRT PCR showed that the expression of CIRP in lung tissue increased in the 24 hours group.

  Conclusion  The expression of CIRP in lung tissue and peripheral serum increases with time in the rat model of hypothermic ALI, suggesting that CIRP is closely related to hypothermic ALI. And CIRP is consistent with the levels of inflammatory cytokines IL-1 β and IL-6, so it is speculated that CIRP may play a role in promoting the release of inflammatory cytokines. This study preliminarily confirms the correlation between CIRP in lung tissue region and overall with hypothermic ALI.