Effect of omega-3 polyunsaturated fatty acids supplementation on traumatic brain injury in a rat model

Objective To investigate the effects of omega-3 polyunsaturated fatty acids (ω-3 PUFA) supplementation on brain edema, autophagy response and neurobehavioral outcome after traumatic brain injury (TBI) in rats and the related mechanisms. Methods TBI rat models were established using Feeney's method. Seventy-two SD rats were divided into 4 groups using random number table: sham operation group, TBI group, ω-3 PUFA supplementation group (TBI+ ω-3 group) and autophagy inhibitor 3-methyladenine group (TBI+ 3-MA group) (all n=18), each group was further divided into 3 sub-groups (n=6) corresponding to 3 time points (days 1, 3, and 7 after TBI). On each of the 3 time points, we measured rat behavioral outcomes with modified neurologic severity score (mNSS) tests; brain water content was measured with wet-dry weight method. The mRNA and protein expressions of autophagy-related factors (LC3-Ⅱ and Beclin-1) in TBI cerebral cortex were determined by immunohistochemistry staining, reverse transcription-polymerase chain reaction and Western blot on day 3 after TBI. Results Compared with the sham group, on days 1, 3, and 7 after injuary, the TBI group, the TBI+ ω-3 group, and the TBI+ 3-MA group had significantly higher mNSS scores (TBI group: 12.42±0.27 vs.1.34±0.32, 12.07±0.27 vs. 1.16±0.29, 10.22±0.39 vs. 1.22±0.30; TBI+ ω-3 group: 12.05±0.23 vs. 1.34±0.32, 11.38±0.21 vs. 1.16±0.29, 8.20±0.21 vs. 1.22±0.30; TBI+ 3-MA group: 11.93±0.20 vs. 1.34±0.32, 11.09±0.19 vs. 1.16±0.29, 7.93±0.17 vs. 1.22±0.30; all P=0.00) and brain water content [TBI group: (79.82±0.61)% vs. (71.87±0.43)%, (83.04±0.42)% vs. (72.13±0.53)%, (75.12±0.72)% vs. (71.78±0.38)%; TBI+ ω-3 group: (76.81±0.63)% vs. (71.87±0.43)%, (79.39±0.59)% vs. (72.13±0.53)%, (73.86±0.38)% vs. (71.78±0.38)%; TBI+ 3-MA group: (75.98±0.49)% vs. (71.87±0.43)%, (77.14±0.46)% vs. (72.13±0.53)%, (72.24±0.37)% vs. (71.78±0.38)%; all P=0.00]. The mRNA and protein expressions of LC3-Ⅱ and Beclin-1 in the brain were also significantly higher on day 3 in the TBI group, the TBI+ ω-3 group, and the TBI+ 3-MA group (all P=0.00). Compared with the TBl group, on day 3 and day 7 after injury, the TBI+ ω-3 group and the TBI+ 3-MA group had significantly lower mNSS scores (TBI+ ω-3 group: 11.38±0.21 vs. 12.07±0.27, P=0.04, 8.20±0.21 vs. 10.22±0.39, P=0.01; TBI+ 3-MA group: 11.09±0.19 vs. 12.07±0.27, P=0.01, 7.93±0.17 vs. 10.22±0.39, P=0.00). On days 1, 3, and 7, compared with the TBI group, the TBI+ ω-3 group and the TBI+ 3-MA group had significantly lower brain water content [TBI+ ω-3 group: (76.81±0.63)% vs. (79.82±0.61)%, P=0.04, (79.39±0.59)% vs. (83.04±0.42)%, P=0.01, (73.86±0.38)% vs. (75.12±0.72)%, P=0.03; TBI+ 3-MA group: (75.98±0.49)% vs. (79.82±0.61)%, P=0.01, (77.14±0.46)% vs. (83.04±0.42)%, P=0.00, (72.24±0.37)% vs. (75.12±0.72)%, P=0.02]. On day 3, the TBI+ ω-3 group and the TBI+ 3-MA group had significantly reduced LC3-Ⅱ and Beclin-1 mRNA expression compared with the TBI group (TBI+ ω-3 group: P=0.04, P=0.01; TBI+ 3-MA group: P=0.01, P=0.00) and protein expression (TBI+ ω-3 group: P=0.01, P=0.03; TBI+ 3-MA group: both P=0.00). Conclusion ω-3 PUFA supplementation could markedly reduce brain edema and improve neurological functions after TBI, showing a neuroprotective effect, possibly through inhibiting TBI-induced autophagy responses. Key words: Traumatic brain injury; Omega-3 polyunsaturated fatty acids; Autophagy; Neuroprotection