Reducing Effect of IL-32α in the Development of Stroke Through Blocking of NF-κB, but Enhancement of STAT3 Pathways

Neuroinflammation is important for the development of several neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, and stroke. Since changes of cytokine level are critical for neuroinflammation in the brain, we investigated whether IL-32 alpha overexpression could change neuroinflammation and, thus, affect stroke development. Middle cerebral artery occlusion (MCAO) induced development of ischemia, and ischemic neuronal cell death were reduced in IL-32 alpha-overexpressing transgenic mice (IL-32 alpha mice) brain through the decreased release of neuroinflammatory cytokines (IL-6, IL-1 beta, TNF-alpha) and activation of astrocytes, but enhancement of anti-neuroinflammatory cytokines (IL-10). Reactive oxygen species generation and lipid peroxidation as well as expression of inducible nitric oxide and cyclooxygenase-2 were also reduced in the IL-32 alpha mice brain. Nuclear factor-kappa B (NF-kappa B), a critical transcriptional factor regulating neuroinflammation, was much lower, but activation of signal transducer and activator of transcription 3 (STAT3), which plays a crucial role in cell survival and proliferation, was much higher in IL-32 alpha-overexpressing mice brain compared to those of wild-type mice brain. These results suggest that IL-32 alpha can prevent cerebral ischemia damage via upregulation of anti-neuroinflammatory cytokine expression and STAT3 activation, but downregulation of neuroinflammatory cytokines and NF-kappa B activation.