Proteomic Analysis and Identification of Intestinal FBP as a Predictor of Gut Dysfunction During Heatstroke in Mice

Heat stress combined with lipopolysaccharide induces pulmonary microvascular endothelial cell glycocalyx inflammatory damage in vitro

Heat stroke is a life-threatening disease with high mortality and complications. Endothelial glycocalyx (EGCX) is essential for maintaining endothelial cell structure and function as well as preventing the adhesion of inflammatory cells. Potential relationship that underlies the imbalance in inflammation and coagulation remains elusive. Moreover, the role of EGCX in heat stroke-induced organ injury remained unclear. Therefore, the current study aimed to illustrate if EGCX aggravates apoptosis, inflammation, and oxidative damage in human pulmonary microvascular endothelial cells (HPMEC). Heat stress and lipopolysaccharide (LPS) were employed to construct in vitro models to study the changes of glycocalyx structure and function, as well as levels of heparansulfate proteoglycan (HSPG), syndecan-1 (SDC-1), heparansulfate (HS), tumor necrosis factor-α (TNF-α), interleukin (IL)-6, Von Willebrand factor (vWF), endothelin-1 (ET-1), occludin, E-selectin, vascular cell adhesion molecule-1 (VCAM-1), and reactive oxygen species (ROS). Here, we showed that heat stress and LPS devastated EGCX structure, activated EGCX degradation, and triggered oxidative damage and apoptosis in HPMEC. Stimulation of heat stress and LPS decreased expression of HSPG, increased levels of SDC-1 and HS in culture supernatant, promoted the production and release of proinflammation cytokines (TNF-α and IL-6,) and coagulative factors (vWF and ET-1) in HPMEC. Furthermore, Expressions of E-selection, VCAM-1, and ROS were upregulated, while that of occludin was downregulated. These changes could be deteriorated by heparanase, whereas they meliorated by unfractionated heparin. This study indicated that EGCX may contribute to apoptosis and heat stroke-induced coagulopathy, and these effects may have been due to the decrease in the shedding of EGCX.

Proteomic identification of hippocalcin and its protective role in heatstroke-induced hypothalamic injury in mice

Heatstroke is a devastating condition that is characterized by severe hyperthermia and central nervous system dysfunction. However, the mechanism of thermoregulatory center dysfunction of the hypothalamus in heatstroke is unclear. In this study, we established a heatstroke mouse model and a heat-stressed neuronal cellular model on the pheochromocytoma-12 (PC12) cell line. These models revealed that HS promoted obvious neuronal injury in the hypothalamus, with high pathological scores. In addition, PC12 cell apoptosis was evident by decreased cell viability, increased caspase-3 activity, and high apoptosis rates. Furthermore, 14 differentially expressed proteins in the hypothalamus were analyzed by fluorescence two-dimensional difference gel electrophoresis and identified by matrix-assisted laser desorption ionization time-of-flight mass spectrometry. Expression changes in hippocalcin (HPAC), a downregulated neuron-specific calcium-binding protein, were confirmed in the hypothalamus of the heatstroke mice and heat-stressed PC12 cells by immunochemistry and western blot. Moreover, HPAC overexpression and HPAC-targeted small interfering RNA experiments revealed that HPAC functioned as an antiapoptotic protein in heat-stressed PC12 cells and hypothalamic injury. Lastly, ulinastatin (UTI), a cell-protective drug that is clinically used to treat patients with heatstroke, was used in vitro and in vivo to confirm the role of HPAC; UTI inhibited heat stress (HS)-induced downregulation of HPAC expression, protected hypothalamic neurons and PC12 cells from HS-induced apoptosis and increased heat tolerance in the heatstroke animals. In summary, our study has uncovered and demonstrated the protective role of HPAC in heatstroke-induced hypothalamic injury in mice.

Cryptdin-2 predicts intestinal injury during heatstroke in mice

Intestinal injury-induced bacterial translocation and endotoxemia are important in the pathophysiological process of heatstroke. However, the underlying mechanism remains to be fully elucidated. Previous studies using 2D-gel electrophoresis found that defensin-related cryptdin-2 (Cry-2), an intestinal α-defensin, is upregulated in intestinal tissues during heatstroke in mice, and that treatment with ulinastatin, a multivalent enzyme inhibitor, reduced heat-induced acute lung injury. To investigate the association between Cry-2 and heat stress (HS)-induced intestinal injury and the probable protective role of ulinastatin, the present study examined the intestinal expression of Cry-2 via histopathologic analysis and reverse transcription-quantitative polymerase chain reaction analysis in mice with heatstroke. The heat-stressed mice were exposed to different core temperatures and cooling treatments, and intestinal pathological changes and Chiu scores were determined. Chemical markers of intestinal injury, serum and intestinal concentrations of diamine oxidase (DAO) and D-lactic acid (D-Lac), and serum and intestinal concentrations of Cry-2 were also determined. Correlations were analyzed using Spearman's correlation analysis. It was found that HS upregulated the expression of Cry-2, and the serum and intestinal concentrations of Cry-2 were correlated with the severity of HS-induced intestinal damage, indicated by pathology scores and concentrations of DAO and D-lac. Ulinastatin protected the intestines from HS-induced injury and downregulated the expression of Cry-2, which was also correlated with the extent of intestinal injury. Therefore, ulinastatin administration may be beneficial for patients with heatstroke, and Cry-2 may be a novel predictor of HS-induced intestinal injury.

Xuebijing injection attenuates pulmonary injury by reducing oxidative stress and proinflammatory damage in rats with heat stroke

The present study aimed to investigate the protective effect of Xuebijing injection (XBJ) on lung injury in heat-stroke rats and the underlying mechanisms. In total, 54 rats were randomly assigned to non-thermal, saline vehicle and XBJ groups. The rectal temperature (Tc), mean arterial pressure (MAP) and respiratory rate (RR) of the rats were recorded. The time-point of heat stroke and the time of survival were assessed, and indicators of arterial blood gas were regularly measured from 0 to 60 min. The concentration of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and IL-10 was also determined. At the end of the experiment, lung tissue was harvested for histopathological analysis. Inducible nitric oxide synthase (iNOS) and superoxide dismutase (SOD) expression was measured by immunohistochemistry. Terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling was used to measure apoptosis. XBJ pretreatment prolonged the decline of clinical characteristics, as demonstrated by increases in Tc, MAP, RR and indicators in arterial blood gas in rats under heat stress. The time until heat stroke and the survival time in the Saline group were shorter than in rats treated with XBJ. The expression of iNOS in lung tissue and the concentration of TNF-α, IL-1β and IL-10 in the bronchoalveolar lavage fluid of rats treated with saline was higher than in rats with XBJ pre-treatment. Contrarily, SOD expression in rats treated with saline was decreased compared with that in rats treated with XBJ. Moreover, the apoptotic rate in the lung tissues of rats with saline treatment was higher than that in rats treated with XBJ. In conclusion, XBJ delayed the development of heat stroke and increased the survival time in rats under heat-stress by ameliorating pulmonary failure and acute lung injury. The underlying mechanisms of this effect may be the reduction of inflammatory cytokines as well as attenuation of oxidative stress and apoptosis by XBJ.

Xuebijing injection alleviates liver injury by inhibiting secretory function of Kupffer cells in heat stroke rats

OBJECTIVE

To evaluate the effects of Xuebijing (XBJ) injection in heat stroke (HS) rats and to investigate the mechanisms underlying these effects.

METHODS

Sixty anesthetized rats were randomized into three groups and intravenously injected twice daily for 3 days with 4 mL XBJ (XBJ group) or phosphate buffered saine (HS and Sham groups) per kg body weight. HS was initiated in the HS and XBJ groups by placing rats in a simulated climate chamber (ambient temperature 400C, humidity 60% ). Rectal temperature, aterial pressure, and heart rate were monitored and recorded. Time to HS onset and survival were determined, and serum concentrations of tumor necrosis factor (TNF)-alpha interleukin (IL)-1beta, IL-6, alanine-aminotransferase (ALT), and aspartate-aminotransferase (AST) were measured. Hepatic tissue was harvested for pathological examination and electron microscopic examination. Kupffer cells (KCs) were separated from liver at HS initiation, and the concentrations of secreted TNF-a, IL-beta and IL-6 were measured.

RESULTS

Time to HS onset and survival were significantly longer in the XBJ than in the HS group. Moreover, the concentrations of TNF-alpha, IL-1beta, IL-6, ALT and AST were lower and liver injury was milder in the XBJ than in the HS group. Heat-stress induced structural changes in KCs and hepatic cells were more severe in the HS than in the XBJ group and the concentrations of TNF-alpha, IL-beta and IL-6 secreted by KCs were lower in the XBJ than in the HS group.

CONCLUSION

XBJ can alleviate HS-induced systemic inflammatory response syndrome and liver injury in rats, and improve outcomes. These protective effects may be due to the ability of XBJ to inhibit cytokine secretion by KCs.

Effects of propofol on damage of rat intestinal epithelial cells induced by heat stress and lipopolysaccharides

Gut-derived endotoxin and pathogenic bacteria have been proposed as important causative factors of morbidity and death during heat stroke. However, it is still unclear what kind of damage is induced by heat stress. In this study, the rat intestinal epithelial cell line (IEC-6) was treated with heat stress or a combination of heat stress and lipopolysaccharide (LPS). In addition, propofol, which plays an important role in anti-inflammation and organ protection, was applied to study its effects on cellular viability and apoptosis. Heat stress, LPS, or heat stress combined with LPS stimulation can all cause intestinal epithelial cell damage, including early apoptosis and subsequent necrosis. However, propofol can alleviate injuries caused by heat stress, LPS, or the combination of heat stress and LPS. Interestingly, propofol can only mitigate LPS-induced intestinal epithelial cell apoptosis, and has no protective role in heat-stress-induced apoptosis. This study developed a model that can mimic the intestinal heat stress environment. It demonstrates the effects on intestinal epithelial cell damage, and indicated that propofol could be used as a therapeutic drug for the treatment of heat-stress-induced intestinal injuries.