Stimulation of neurotrophic factors and inhibition of proinflammatory cytokines by exogenous application of triiodothyronine in the rat model of ischemic stroke.

There is a positive relation between decreases of triiodothyronine (T3) amounts and severity of stroke. The aim of this study was to evaluate the effect of exogenous T3 application on levels of neurogenesis markers in the subventricular zone. Cerebral ischemia was induced by middle cerebral artery occlusion in male Wistar rats. There were 4 experimental groups: sham, ischemic, vehicle, and treatment. Rats were injected with T3 (25 μg/kg, IV injection) at 24 hours after ischemia. Animals were sacrificed at day 7 after ischemia. There were high levels of brain-derived neurotrophic factor, nestin, and Sox2 expressions in gene and protein levels in the T3 treatment group (P ≤ .05 vs ischemic group). Treatment group showed high levels of sera T3 and thyroxine (T4) but low levels of thyrotropin (TSH), tumor necrosis factor-α, and interleukin-6 (P ≤ .05 vs ischemic group) at day 4 after ischemia induction. Findings of this study revealed the effectiveness of exogenous T3 application in the improvement of neurogenesis possibly via regulation of proinflammatory cytokines.