Reduction of rat brain CD8+ T‐cells by levodopa/benserazide treatment after experimental stroke

The activation of inflammatory cascades in the ischemic hemisphere impairs mechanisms of tissue reorganization with consequences for recovery of lost neurological function. Recruitment of T‐cell populations to the post‐ischemic brain occurs and represents a significant part of the inflammatory response. This study was conducted to investigate if treatment with levodopa, potentially acting as an immunomodulator, affects the T‐cell accumulation in the post‐ischemic brain. Male Sprague–Dawley rats were subjected to transient occlusion of the middle cerebral artery (tMCAO) for 105 min followed by levodopa/benserazide treatment (20 mg/kg/15 mg/kg) for 5 days initiated on day 2 post‐stroke. One week after tMCAO, T‐cell populations were analysed from brains, and levels of interleukin (IL)‐1β, chemokine (C‐X‐C motif) ligand 1, IL‐4, IL‐5, interferon gamma and IL‐13 were analysed. After levodopa/benserazide treatment, we found a significant reduction of cytotoxic T‐cells (CD3⁺CD8⁺) in the ischemic hemisphere together with reduced levels of T‐cell‐associated cytokine IL‐5, while other T‐cell populations (CD3⁺, CD3⁺CD4⁺, CD3⁺CD4⁺CD25⁺) were unchanged compared with vehicle‐treated rats. Moreover, a reduced number of cells was associated with reduced levels of intercellular adhesion molecule 1, expressed in endothelial cells, in the infarct core of levodopa/benserazide‐treated animals. Together, we provide the first evidence that dopamine can act as a potential immunomodulator by attenuating inflammation in the post‐ischemic brain.