Objective:To explore the protective effect of methylene blue (MB) on myocardial injury in sepsis and its possible signaling pathway.Methods:A total of 32 female Wistar rats were randomly divided into sham operation group, sepsis model group, MB prevention group, and MB treatment group, with 8 rats in each group. The MB prevention group was injected with 15 mg/kg MB in the peritoneal cavity 6 hours before modeling; the other 3 groups were injected with 4 mL/kg saline in the peritoneal cavity. The sepsis model was established by cecal ligation puncture (CLP); the sham operation group was only subjected to an exploratory incision without ligation or puncture of the caecum. The MB treatment group was injected with 15 mg/kg MB in the peritoneal cavity 0.5 hours after modeling; the other 3 groups were injected with 4 mL/kg saline in the peritoneal cavity. Peripheral blood and myocardial tissue were collected from each group at 6 hours and 12 hours after modeling. Histological changes in the myocardial tissue were observed under the microscope; the levels of serum cardiac troponin I (cTnI), MB isoenzyme of creatine kinase (CK-MB), tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) were detected by enzyme-linked immunosorbent assay (ELISA); and the expressions of inducible nitric oxide synthase (iNOS), light chain 3 (LC3), and p62 in the myocardial tissue were detected by Western blotting.Results:Under light microscopy, no obvious abnormalities were found in the myocardium of the sham operation group; the myocardium of the sepsis model group showed obvious inflammatory changes; the myocardium of the MB prevention group showed mild inflammatory changes at 6 hours after modeling, severe inflammatory changes at 12 hours but less severe than the sepsis model group; the myocardium of the MB treatment group showed more obvious inflammatory changes at 6 hours after modeling but less severe than the MB prevention group at 12 hours after modeling, and the inflammatory changes at 12 hours after modeling were alleviated but more severe than the 6 hours after modeling in MB prevention group. Compared with the sham operation group, the levels of cTnI, CK-MB, TNF-α and IL-6 in the MB prevention group at 6 hours and 12 hours after modeling were not significantly changed; compared with the sepsis model group, the cTnI, CK-MB, TNF-α and IL-6 levels in the MB treatment group at 6 hours and 12 hours after modeling were significantly lower [cTnI (ng/L): 175.03±12.26, 411.24±21.20 vs. 677.79±43.95 at 6 hours of modeling, 159.52±6.44, 412.46±32.94 vs. 687.61±55.09 at 12 hours of modeling; CK-MB (ng/L): 8.38±0.49, 16.87±1.41 vs. 24.87±1.74 at 6 hours of modeling, 7.94±0.30, 16.66±2.03 vs. 25.02±7.29 at 12 hours of modeling; TNF-α (ng/L): 26.98±3.31, 46.95±3.74 vs. 112.60±6.64 at 6 hours of modeling, 31.31±5.83, 90.97±5.14 vs. 149.30±4.67 at 12 hours of modeling; IL-6 (ng/L): 40.86±4.48, 128.90±3.14 vs. 248.90±12.76 at 6 hours of modeling, 80.13±7.94, 190.40±9.56 vs. 288.90±6.01 at 12 hours of modeling; all P < 0.05]. Western blotting showed that compared with the sham operation group, the protein expressions of iNOS, LC3, and p62 in the sepsis model group were significantly higher at 6 hours and 12 hours after modeling; compared with the sepsis model group, the protein expressions of iNOS, LC3, and p62 in the MB treatment group and MB prevention group were significantly lower at 6 hours and 12 hours after modeling (iNOS/GAPDH: 0.38±0.04, 0.60±0.04 vs. 0.77±0.04 at 6 hours of modeling; 0.38±0.02, 0.66±0.04 vs. 0.79±0.05 at 12 hours of modeling; LC3/GAPDH: 0.13±0.07, 0.42±0.07 vs. 1.05±0.16 at 6 hours of modeling; 0.08±0.02, 0.25±0.03 vs. 0.48±0.09 at 12 hours of modeling; p62/GAPDH: 0.17±0.05, 0.44±0.10 vs. 1.19±0.07 at 6 hours of modeling; 0.07±0.00, 0.28±0.08 vs. 0.69±0.02 at 12 hours of modeling; all P < 0.05). Conclusion:MB can reduce myocardial oxidative stress by inhibiting iNOS expression and mitochondrial autophagy in septic rats, thereby alleviating myocardial damage in sepsis, and has protective effect on myocardial damage in sepsis.

Objective:To explore the application value of regional oxygen saturation (rSO 2) level in the prognosis evaluation of patients with acute lower limb ischemia (ALLI). Methods:Retrospective analysis of clinical data of 82 ALLI patients admitted to the ICU of Xinjiang Uygur Autonomous Region People's Hospital from June 2021 to June 2022. The subjects were divided into event group and non-event group according to the incidence of adverse events during the follow-up. The general clinical data of the two groups were compared. Multiple stepwise linear regression was used to analyze the independent related factors of rSO 2. Multivariate Cox regression was used to analyze independent risk factors of adverse events. Receiver operating characteristic (ROC) curve was used to obtain the optimal cut-off value of rSO 2 prediction adverse events. The subjects were divided into high-value group and low-value group according to the optimal cut-off value. Kaplan-Meier curve was used to analyze the difference in survival rate between groups during the follow-up. Results:A total of 82 ALLI patients were included in this study, and the incidence of adverse events during follow-up was 25.6% (21 cases). The rSO 2 of four periods and maximum, minimum, average and ankle-brachial index in the event group were significantly lower than those in the non-event group. The troponin I, troponin T, myoglobin, creatine kinase, C-reactive protein, and lactate in the event group were significantly higher than those in the non event group ( P?0.05). Multiple stepwise linear regression analysis showed that: C-reactive protein ( β=-0.320, P=0.002), lactate ( β=-0.262, P=0.009), troponin Ⅰ ( β=-0.230, P=0.025), and smoking history ( β=-0.211, P=0.034) were all independent predictors of rSO 2. Multivariate Cox regression analysis showed that 24 h rSO 2 (mean) was an independent influencing factor for adverse events in ALLI patients (adjusted HR=0.67, 95% CI:0.54-0.83, P<0.001). The 24 h rSO 2 (mean) was good in predicting the incidence of adverse events at 30, 60, and 90 days in ALLI patients (AUC were 0.934, 0.867 and 0.823), and the corresponding optimal cut-off values of rSO 2 were 59.36, 59.03 and 59.03. The sensitivity and specificity to predict adverse events in ALLI patients were 85.7% and 85.3% when the 24 h rSO 2 (mean) was 59.36 as the best cut-off value. According to the optimal cut-off , the subjects were divided into high value group (rSO 2>59.36%, 59 cases) and low value group (rSO 2≤59.36%, 23 cases), Kaplan Meier survival curve analysis showed that there was significant difference in event free survival between the two groups ( P<0.001), the high value group significantly better than the low value group. Conclusion:The 24 h rSO 2 (mean) is an independent influencing factor for adverse events in ALLI patients, and has good predictive value for prognosis.