Introduction: Following a traumatic brain injury (TBI), the excessive release of proinflammatory cytokines is major cause of cerebral edema that can cause permanent neuronal loss. This study examined the changes in brain concentrations of proinflammatory cytokines IL-1, IL-6, TNF-α and TGF- after different doses of estrogen or progesterone treatment in brain-injured rats at 6 and 24 h post-injury. Methods: Adult female rats were divided into 14 groups, and underwent either bilateral ovariectomy (12 groups) or sham surgery (2 groups). The hormones or vehicle were given intraperitoneally 0.5 h after TBI. Moderate TBI was induced by Marmarou method in TBI or treatment groups and brain levels of proinflammatory cytokines were measured 6 and 24 h post-injury. Results: The results indicated that high dose of estrogen (E2) and low dose of progesterone (P1) increase brain levels of IL-1 6 h post-injury by 52.8% and 79.2%, respectively compared to the vehicle. By the 24th h post-injury brain IL-1 level was reduced 27.5% and 27%, respectively compared to vehicle, when estrogen low dose (E1) and E2 were administered. Progesterone high dose treatment reduced brain level of IL-6 by 45.9% at 6 h post-injury and P1 treatment reduced IL-6 level by 20.5% at 24 h post-injury when compared to the vehicle. The brain TNF-α level was reduced by 72.5% by P2 at 6 h and 48.5% by E2 at 24 h post-injury, when compared to the vehicle. In addition, TGF- level seem to be increased by E1 up to 3.37 times at 24 h post-injury compared to the vehicle. Both doses of hormones showed increased levels of TGF- at 6 h post-injury, when compared to the vehicle. Conclusion: We conclude that progesterone and estrogen may change the levels of proinflammatory cytokines in the acute or delayed phases after TBI and this may be one of the mechanisms by which hormones reduce cerebral edema.

Keywords: TBI, IL-1, IL-6, TNF-α, TGF-, acute phase, delay phase

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