Objective: To investigate whether or not mild hypothermia can inhibit the expression and release of interleukin-3 (IL-3) in septic mice and whether it has a protective effect on septic mice.
Methods: According to random number table method, 120 male C57BL/6 mice were divided into sham operation group (Sham group), sepsis normal temperature group (NT group) and sepsis mild hypothermia group (HT group), with 40 mice in each group. The acute septic mice model was established by cecal ligation and puncture (CLP) method. In the HT group, body temperature decreased to 32-34 centigrade at 1 hour after CLP and was maintained for 8 hours, followed by rewarming slowly to 36-38 centigrade. In the NT group, mice were resuscitated after CLP and body temperature was maintained at 36-38 centigrade throughout the experimental periods, while in Sham group, the cecum was not ligated or punctured and resuscitated routinely. The average arterial pressure (MAP) of 20 mice in each group was monitored for 12 hours after CLP, and the survival time was observed for 4 days. The serum of remaining mice was collected at 12 hours after CLP, and the mice were killed for organ tissues. The serum levels of IL-3, interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) were determined by enzyme linked immunosorbent assay (ELISA). Western blotting was used to detect IL-3 protein expression in spleen and lung tissues. The pathological changes of lung and liver tissues were observed under microscope and the semi-quantitative scoring was performed.
Results: MAP of NT group and HT group decreased after CLP with the prolongation of time. MAP (mmHg, 1 mmHg = 0.133 kPa) of HT group at 10 hours and 12 hours after CLP were significantly higher than those of NT group (10 hours: 74.4±12.4 vs. 62.9±7.2, 12 hours: 68.4±3.7 vs. 57.5±9.6, both P < 0.01). Compared with Sham group, serum levels of IL-3, IL-6 and TNF-α in NT group and HT group were significantly increased at 12 hours after CLP [IL-3 (ng/L): 2.21±0.87, 0.18±0.04 vs. 0, IL-6 (ng/L): 51.22±18.65, 24.68±6.20 vs. 1.36±0.34, TNF-α (ng/L): 101.43±38.60, 72.15±25.12 vs. 14.49±5.17, all P < 0.01]. IL-3 protein expressions of spleen and lung tissues in NT group and HT group were significantly increased compared to those in Sham group (IL-3/β-actin: spleen tissue 0.200±0.039, 0.135±0.023 vs. 0.090±0.023, lung tissue 0.085±0.009, 0.056±0.009 vs. 0.039±0.005, all P < 0.01). The serum levels of IL-3, IL-6 and TNF-α were significantly lower in HT group than those in the NT group [IL-3 (ng/L): 0.18±0.04 vs. 2.21±0.87, IL-6 (ng/L): 24.68±6.20 vs. 51.22±18.65, TNF-α (ng/L): 72.15±25.12 vs. 101.43±38.60, all P < 0.01]. The expressions of IL-3 protein in HT group were significantly lower than those in NT group (IL-3/β-actin: spleen tissue 0.135±0.023 vs. 0.200±0.039, lung tissue 0.056±0.009 vs. 0.085±0.009, both P < 0.01). The lung tissue injury and liver tissue injury scores in HT group were significantly lower than those in NT group (lung tissue injury score: 4.00±1.41 vs. 6.67±2.16, P = 0.03, liver tissue injury score: 3.83±1.47 vs. 7.17±2.14, P = 0.01). Compared to NT group, the 4-day survival rate of HT group was significantly improved (50% vs. 30%, P < 0.01).
Conclusions: Mild hypothermia can significantly inhibit the expression and release of IL-3 in septic mice, attenuate organ injury, and protecte septic mice.