Regional TNFα mapping in the brain reveals the striatum as a neuroinflammatory target after ventricular fibrillation cardiac arrest in rats

Cardiac arrest (CA) triggers neuroinflammation that could play a role in a delayed neuronal death. In our previously established rat model of ventricular fibrillation (VF) CA characterized by extensive neuronal death, we tested the hypothesis that individual brain regions have specific neuroinflammatory responses, as reflected by regional brain tissue levels of tumor necrosis factor (TNF)alpha and other cytokines. In a prospective study, rats were randomized to 6 min (CA6), 8 min (CA8) or 10 min (CA10) of VF CA, or sham group. Cortex, striatum, hippocampus and cerebellum were evaluated for TNF alpha and interleukin (IL)-1 alpha, IL-1 beta, IL-2, IL-4, IL-6, IL-10, IL-12 and interferon gamma at 3 h, 6 h or 14 d after CA by ELISA and Luminex. Immunohistochemistry was used to determine the cell source of TNF alpha. CA resulted in a selective TNF alpha response with significant regional and temporal differences. At 3 h after CA, TNF alpha-levels increased in all regions depending on the duration of the insult. The most pronounced increase was observed in striatum that showed 20-fold increase in CA10 vs. sham, and 3-fold increase vs. CA6 or CA8 group, respectively (p < 0.01). TNF alpha levels in striatum decreased between 3 h and 6 h, but increased in other regions between 3 h and 14 d. TNF alpha levels remained twofold higher in CA6 vs. shams across brain regions at 14 d (p < 0.01). In contrast to pronounced TNF alpha response, other cytokines showed only a minimal increase in CA6 and CA8 groups vs. sham in all brain regions with the exception that IL-1 beta increased twofold in cerebellum and striatum (p < 0.01). TNF alpha colocalized with neurons. In conclusion, CA produced a duration-dependent acute TNF alpha response, with dramatic increase in the striatum where TNF alpha colocalized with neurons. Increased TNF alpha levels persist for at least two weeks. This TNF alpha surge contrasts the lack of an acute increase in other cytokines in brain after CA. Given that striatum is a selectively vulnerable brain region, our data suggest possible role of neuronal TNF alpha in striatum after CA and identify therapeutic targets for future experiments. This study was approved by the University of Pittsburgh IACUC 1002340A-3. (C) 2014 Elsevier Ireland Ltd. All rights reserved.