Endoplasmic reticulum stress and NOD-like receptor protein 3 involves in intestinal mucosal injury induced by severe heat stroke / 中华急诊医学杂志

ABSTRACT

Objective:To observe whether endoplasmic reticulum stress and NOD-like receptor protein 3 (NLRP3) inflammasome activation were involved in severe heat stroke induced intestinal mucosal injury and to investigate the potential protective effect of the endoplasmic reticulum stress inhibitor 4-phenylbutyric acid (4-PBA).Methods:Thirty male BALB/c mice were randomly (random number) assigned to 3 groups the control group, heat stroke group (HS), and 4-PBA pretreatment group (4-PBA+HS, 4-PBA 120 mg/kg, intraperitoneal injection). Mice in the control group were placed at room temperature, while mice in the HS group and 4-PBA+HS group were placed in a prewarmed chamber [temperature (35.5±0.5) °C, humidity (60.0±5.0)%]. A rectal temperature (Tc) that reached 42 °C was considered to indicate severe heat stroke. The concentrations of malondialdehyde (MDA) and superoxide dismutase (SOD) in intestinal homogenate were analyzed by a colorimetric method, serum interleukin-1β (IL-1β) and interleukin-18 (IL-18) were assessed by ELISA, intestinal histopathology was evaluated by hematoxylin and eosin (HE) staining, intestinal ultrastructure was observed by electron microscopy, and the protein expression of GRP78, CHOP, NLRP3 and cleaved caspase-1 were analyzed by Western blot. Data were statistically analyzed by ANOVA test and LSD- t multiple comparison test if homogeneous variance, or analyzed by Welch test and Dunnett's T3 multiple comparison test if heterogeneous variance. Results:The concentration of MDA in the HS group was increased ( t=14.243, P<0.01), while SOD was decreased compared with that in the control group ( t=7.781, P<0.01), and the concentrations of serum IL-1β and IL-18 were significantly elevated ( t=12.664, P<0.01; t=16.240, P<0.01). Under light microscopy, extensive destruction of small intestinal villi and inflammatory cell infiltration were observed in the intestines of mice with severe heat stroke. Transmission electron microscopy showed that endoplasmic reticulum structures were significantly expanded, and mitochondria were vacuolated in the intestines of mice with severe heat stroke. Compared with those in the control group, the protein expression levels of GRP78, CHOP, NLRP3 and cleaved caspase-1 in the small intestine were elevated in the HS group ( t=14.824, P <0.01; t=12.667, P<0.01; t=9.298, P<0.01; and t=6.588, P=0.001). Compared with those in the HS group, mice in the 4-PBA pretreatment group exhibited reduced concentrations of MDA ( t=9.167, P<0.01), increased SOD ( t=6.077, P<0.01) , and reduced serum IL-1β and IL-18 levels ( t=4.889, P= 0.001; t=5.693, P<0.01). In addition, 4-PBA pretreatment significantly alleviated the pathological disruption and ultrastructural damage to small intestine tissues. Moreover, 4-PBA pretreatment reduced GRP78, CHOP , NLRP3 and cleaved caspase-1 protein expression ( t=9.080, P<0.01; t=7.152, P<0.01; t=4.249, P=0.005; t=3.650, P=0.011). Conclusions:Endoplasmic reticulum stress and NLRP3 inflammasome are involved in intestinal mucosal injury induced by severe heat stroke. 4-PBA plays a protective role by alleviating endoplasmic reticulum stress and NLRP3 inflammasome activation.