[Effects of docosahexaenoic acid on inflammation-associated cytokines in blood and pulmonary tissue of rats with severe scald injury].

Objective: To observe the effects of docosahexaenoic acid (DHA) on the expressions of TNF-α, IL-6, and leukotriene B4 (LTB4) in serum and expression of NF-κB in pulmonary tissue of rats with severe scald injury.

Methods: One hundred and sixty SD rats were divided into sham injury (A), sham injury+DHA (B), scald (C), and scald+DHA (D) groups according to the random number table, with 40 rats in each group. Rats in groups A and B were sham injured, while rats in groups C and D were inflicted with 30% TBSA full-thickness scald on the back. Rats in groups B and D were injected with 0.5 mg/mL DHA solution with the dosage of 1 mL/kg via tail vein 5 minutes post injury, while rats in groups A and C with normal saline solution 1 mL/kg. At post injury hour (PIH) 3, 6, 12, 24, and 48, pulmonary tissue and abdominal aorta blood were collected from 8 rats in each group. The serum levels of TNF-α, IL-6, and LTB4 were determined with ELISA, and the protein expression of NF-κB p65 in pulmonary tissue was determined with Western blotting. Data were processed with analysis of variance of factorial design and LSD-t test.

Results: (1) The serum levels of TNF-α and IL-6 of rats in group A were similar to those of group B at each time point (with tTNF-α values from 0.223 to 0.947, tIL-6 values from 0.767 to 2.084, P values above 0.05). Compared with those of group A, the serum levels of TNF-α and IL-6 of rats in groups C and D were significantly higher at each time point (with tTNF-α values from 11.800 to 40.357, tIL-6 values from 10.334 to 39.321, P values below 0.01). The serum levels of TNF-α and IL-6 of rats in group D were significantly lower than those of group C at each time point (with tTNF-α values from -17.643 to -8.331, tIL-6 values from -21.596 to -6.332, P values below 0.01). The serum levels of TNF-α and IL-6 in groups C and D both showed a trend of increase earlier and decrease later, and they peaked at PIH 12, respectively (360.4 ± 13.2), (306.8 ± 7.2) pg/mL and (265.4 ± 12.3), (230.5 ± 2.2) pg/mL. (2) The serum level of LTB4 in group A was similar to that of group B at each time point (with t values from 0.787 to 1.096, P values above 0.05). The serum level of LTB4 was significantly higher in groups C and D than in group A at each time point (with t values from 7.501 to 38.962, P values below 0.01). The serum level of LTB4 in group D was obviously lower than that of group C at each time point (with t values from -19.244 to -2.532, P values below 0.01). The serum level of LTB4 in groups C and D both showed a trend of increase earlier and decrease later, and it peaked at PIH 12, (4.59 ± 0.29) and (2.85 ± 0.32) ng/mL respectively. (3) The protein expression of NF-κB p65 in pulmonary tissue in group A was similar to that of group B at each time point (with t values from 0.847 to 1.256, P values above 0.05). The protein expression of NF-κB p65 was significantly higher in groups C and D than in group A at each time point (with t values from 15.167 to 98.074, P values below 0.01). The protein expression of NF-κB p65 in group D was obviously lower than that of group C at each time point (with t values from -37.190 to -14.415, P values below 0.01). The protein expression of NF-κB p65 in groups C and D both showed a trend of increase earlier and decrease later, and it peaked at PIH 12, respectively 4.46 ± 0.12 and 2.94 ± 0.21.

Conclusions: Parenteral supply of DHA to rats with severe scald injury can reduce the levels of TNF-α, IL-6, and LTB4 in serum and decrease the expression of NF-κB in pulmonary tissue, thus alleviating the inflammation response.