| Objective Infection is a main cause of multi-organ-dysfunction, senility is an independent risk factor of poor outcome in sepsis related MODS. Different study on the pathogenesis and development of MODS came to different explanations. The serum interleukin-6 level is a strong predictor of bad outcome in sepsis. Nuclear factor-kappa B is a main regulatory factor of IL-6 transcription in sepsis. In this study, we aimed at researching the sequence and severity of organ injury and establishing some early warning index of sepsis related MODS of elderly (MODSE). We also tried to study the possible role of age related NF-kB binding activity changing in initiation of sepsis related MODSE. Materials and methods:1. Survival study: Young (8 weeks old) and aged(18 months old) KunMing mice were divided into 3 groups respectively and received three kind of surgery : (1) 100% length of cecum were ligated and were punctured twice with a 21G needle .(2) 50% length of cecum were ligated and were punctured once with a 21G needle. (3) The sham operation mice were only received cecum exploration. The survival rate and life quality measurements (body temperature, weight loss, motor activity, fluid and food intake) of different group were monitored at different time in succedent five days.2. Study on sequence and severity of organ injury in sepsis: young and aged mice were received modified CLP surgery and divided into two groups respectively according to the sacrificing time (4 or 8 hours after surgery), body temperature, cardiac function, arterial blood gas, serum level of GLU, BUN, Cr, ALT, AST and IL-6 were measured at thesacrificing time, organs were removed to measure the MPO level and wet/dry ratio. A scoring system was applied for histological examination of lung injury.3. Study on age related changing of IL-6 expression and NF-kB binding activity in early stage of sepsis: Young and aged mice were received modified CLP surgery sacrificed at 4 hours after surgery. Blood and tissues of heart, lung and liver were collected. Serum concentration of IL-6 was determined with ELISA, IL-6 protein levels in different organ were measured with Westernblot assay. The levels of IL-6 mRNA in heart, lung and liver were determined by semi-quantity RT-PCR. The NF-kB binding activity was measured by means of EMS A.4. Statistical analysis: Data were expressed as means ± SE. The unpaired t-test was applied to assess age related differences of measured variables, The ANOVA was used to analyze differences in CLP related serum biomarks and organ injury indexes at different time point. Statistical significance was set at p<0.05. All the variables were analyzed by STAT7.0 software.Results:1. After the treatment of traditional CLP surgery, both aged and young micewere died in 48 hours, no statistical significance of age related survivalrate difference was observed. Age related survival rate difference wasobserved in the mice treated by modified CLP surgery (p<0.05) , Whileaged mice showed 30% of survival at 96 hours after surgery and allyoung mice survived 5 days after surgery. Age related differences of lifequality indexes were also found in the mice treated by modified CLPsurgery, but only body temperature is associated with survival.2. Modified CLP surgery was applied to observe age related difference inorgan injury sequence and severity of sepsis. The aged mice showedhypo-dynamic phase of circulation at 8 hours after surgery. Theimpainnent of LV function was more significant than young mice. Neitheraged nor young mice exhibited elevation of liver injury index i.e. AST,ALT. And the liver MPO level and wet/dry ratio were not changed in 8 hours after surgery. Both aged and young mice showed elevation of pathology score, MPO level and wet/dry ratio of the lung. These indexes were much higher in aged mice than in young ones. The abnormalities of blood gas indexes were earlier and more obvious in aged mice than young ones. The serum IL-6 concentrations were higher in aged mice than young ones at each time point after surgery. Among all organ injury variables of aged mice, only pulmonary pathology score was correlative with body temperature.3. Aged mice showed higher serum IL-6 concentration than young ones at four hours post modified CLP surgery. Westernblot analysis revealed that age related difference of IL-6 protein level was only found in lung tissue at 4 hours post surgery. The result of RT-PCR analysis showed that both liver and lung expressed high level of IL-6mRNA, but age related difference were only revealed in lung tissue. Aged mice were also showed enhancing NF-kB binding activity than young ones in lung tissue by means of EMS A.Conclusions:1. Comparing with the traditional CLP model, the modified CLP model was more suitable to reveal the age related changing in the process of sepsis related MODS initiation.2. The severity of hypothermia is a warning index of sepsis induced MODS in elderly (MODSE) and a prognostic factor of poor outcome in elderly.3. During sepsis, the lung is more vulnerable than other organs in MODSE related organ injury, and the severity of inflammation in the lung of elderly at early stage of sepsis could be used to predict a worse outcome.4. The age related elevation of plasma IL-6 concentration may explain the clinical phenomena that old age is risk factor of poor outcome in sepsis related MODSE. With the same infection burden, the function of circulation is more severely impaired because of higher serum inflammatory cytokines level in elderly.
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