100% Oxygen Inhalation Protect Organs Injury In Septic Animals By Mediating Serum HMGB1

Sepsis, the SIRS (systemic inflammatory response syndrome) induced by severe infection, is a major cause of death in the ICU patients. Despite great advances have been made in the mechanism and developing the measures for improving the treatment outcome, the mortality for sepsis remains approximately 20-50% [1]. Because its mechanism is not clear, there is lack of accurate or available method for assessing the patients with sepsis and there is no effective treating measures up to now. When the body has hypoxia or will have hypoxia, oxygen inhalation can increase the oxygen concentration of inspired gas, and then raise the partial pressure of oxygen in the alveolus, elevate the blood oxygen level of the arterial blood by facilitating diffusion as well as improve the oxygen supply in the tissues. We call it oxygen therapy. Hyperoxia therapy is the oxygen therapy in which the inspired concentration of oxygen is higher than 21%, and it is widely used clinically. As is known, hyperoxia therapy may induce oxygen toxicity. However, recent studies found that early 100% oxygen therapy can significantly protect the organ function and increase the survival rate in various kinds of animal model with shock [2-4]. It is reported that hyperoxia therapy with proper conditions can decrease the inflammation and infection[5, 6]. Our team also find that reasonable 100% oxygen inhalation can significantly improve the survival rate of the mice with zymosan-induced MODS. High mobility group box 1 (HMGB1) is liberated from the immune cells and acts as a late pro-inflammatory cytokine. It plays an important role in sepsis. More recently, attention has been paid to the relation of HMGB1 with sepsis. However, there is controversy over the relationship between HMGB1 and the severity of sepsis. We here constructed the animal model with lipopolysaccharide (LPS)-induced sepsis to observe the effect of 100% oxygen inhalation on the organs injury and mortality in septic animals, to analyze its relationship with serum HMGB1, and to clarify the role of HMGB1 in the effect of 100% oxygen inhalation on sepsis.PartⅠThe effect of 100% oxygen inhalation on organ injury and mortality in septic mouseObjective: To prove the protection of 100% oxygen inhalation on LPS-induced sepsis in mouse.Methods: Fifty male Kunming mouse were randomly divided into Control and Hyperoxygen groups with n=25 in each group. The animals in Control group were treated with LPS intraperitoneally (dissolved by saline, 50mg·kg-1). The animals in Hyperoxygen group were treated with LPS intraperitoneally (dissolved by saline, 50mg·kg-1), then 2 hours of 100% oxygen inhalation was given at 4 hours and 12 hours after LPS administration respectively. Mortality at 24 hours after LPS injecton was detected in two groups, and five survival animals were killed, the heart, lung, liver and kidney were immediately removed. The specimens were fixed in 4% formaldehyde for 12-24 hours, embedded in paraffin, sectioned for 5μm in thickness, and stained with hematoxylin and eosin (H&E). Histological changes were examined and scored according to the pathologic scoring system.Results: Mortality rate in Hyperoxygen group was 24%, lower than that in Control group with the mortality of 52%(P < 0.05). The pathologic scores of heart, lung, liver and kidney were lower in Hyperoxygen group than in Control group (P < 0.05). The results above mentioned suggest that reasonable 100% oxygen inhalation can protect the organs injury and decrease the mortality of LPS-induced sepsis in mouse.PartⅡThe correlation of serum HMGB1 to the severity of sepsis in ratObjective: To prove that serum HMGB1 levels is correlated to the severity of sepsis in rats.Methods: Two hundred and fourty male SD rats were randomly divided into 4 groups with n=60 in each group: LPS-4 group: the animals were treated with LPS 4 mg/kg (i. p.); LPS-8 group: the animals were treated with LPS 8 mg/kg (i. p.); LPS-16 group: the animals were treated with LPS 16 mg/kg (i. p.); Control group: the animals were treated with the same volume of the vehicle (saline). Another 5 animals without administration with LPS or normal saline was used as a control for all the above 4 groups. Five ml of blood sample from 5 animals in each group was drawn from heart under anesthesia by intraperitoneally injected pentobarbital sodium (50 mg/kg) at 2, 4, 8, 16, 24, 32 and 48 hours after LPS or vehicle injection, centrifuged, and stored at -20℃. The level of serum HMGB1 was measured at the above time points. The serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), cardiac troponin I (cTnI), creatinine (CRE) and blood urea nitrogen (BUN) were measured at the above time points. After drawing blood sample at the above time points, the animals were killed, and the heart, lung, liver and kidney were immediately removed. The specimens were fixed in 4% formaldehyde for 12-24 hours, embedded in paraffin, sectioned for 5μm in thickness, and stained with hematoxylin and eosin (H&E). Histological changes were examined and scored according to the pathologic scoring system. The correlation of serum HMGB1 to the levels of biochemical indicators and histopathologic scores were analyzed.Results:The level of HMGB1 has a positive, high correlation with the abnormal changes of serum cTnI (r = 0.693, P < 0.05), ALT (r = 0.374, P < 0.05), AST (r = 0.447, P <0.05), CRE (r = 0.503, P < 0.05) and BUN (r = 0.512, P < 0.05) as well as the pathologic scores of heart(rs = 0.755, P < 0.05), lung (rs = 0.758, P < 0.05), liver (rs = 0.789, P < 0.05) and kidney (rs = 0.796, P < 0.05).PartⅢHMGB1 takes part in the mechanism of protection of 100% oxygen inhalation in septic mouseObjective: To investigate whether HMGB1 takes part in the mechanism of protection of 100% oxygen inhalation against organs injury in septic mouse. Methods: Fifty male Kunming mouse were randomly divided into Control and Hyperoxygen groups with n=25 in each group. The animals in Control group were treated with LPS intraperitoneally (dissolved by saline, 50mg·kg-1). The animals in Hyperoxygen group were treated with LPS intraperitoneally (dissolved by saline, 50mg·kg-1), then 2 hours of 100% oxygen inhalation was given at 4 hours and 12 hours after LPS administration respectively. Five ml of blood sample from 5 animals in each group was drawn from heart under anesthesia by intraperitoneally injected pentobarbital sodium (50 mg/kg) at 24 hours after LPS administration. Serum HMGB1 levels were detected. Results: The level of serum HMGB1 was significantly higher in Control group than in Hyperoxygen group (P<0.05), suggesting that HMGB1 may take part in the mechanism of the protection of 100% oxygen inhalation against organs injury in septic mouse.Conclusion1. 100% oxygen inhalation can protect the organs injury and decrease the mortality in LPS-induced septic mouse.2. The level of serum HMGB1 is highly correlated with the severity of sepsis in a rat model, and therefore could be a potential indicator for judging the severity of sepsis in patients.3. HMGB1 may take part in the mechanism of the protection of 100% oxygen inhalation against organs injury in septic mouse.