NOS2 and Huntington disease: Human post-mortem brain tissues and animal models of PD, AD, and HD consistently exhibit the presence of activated microglia, and the increased expression of pro-inflammatory and neurotoxic factors, including TNF-α, IL-6, iNOS, and gp91phox in the striatum and hippocampus, which may exacerbate neuronal loss in these brain areas [43,44,45,46,47].