Immunopathogenesis of neurodegenerative diseases: current therapeutic models of neuroprotection with special reference to natural products.

Parkinson disease (PD) and Alzheimer disease (AD) are neurodegenerative processes whose frequency is dramatically increasing in the western world. Both diseases share a common pathogenic denominator characterized by an exaggerated activation of the systemic and cerebral immune system, respectively. For instance, lipopolysaccharides in PD and amyloid beta in AD trigger microglia and astrocytes to release reactive oxygen species (ROS) and proinflammatory cytokines. Infiltrating peripheral T cells once activated in the central nervous system also contribute to the neurodegenerative process. Besides innovative biotherapy, nutraceuticals or functional foods are currently investigated for their neuroprotective activities. Especially, vitamin D and polyphenols, seem to be promising therapeutic tools for inhibiting ROS formation and arresting cytokine-mediated neuroinflammation in PD and AD.