Role of neuroinflammation in neurodegenerative diseases (Review)

Abstract

Neurodegeneration is a phenomenon that occurs in the central nervous system through the hallmarks associating the loss of neuronal structure and function. Neurodegeneration is observed after viral insult and mostly in various so-called 'neurodegenerative diseases', generally observed in the elderly, such as Alzheimer's disease, multiple sclerosis, Parkinson's disease and amyotrophic lateral sclerosis that negatively affect mental and physical functioning. Causative agents of neurodegeneration have yet to be identified. However, recent data have identified the inflammatory process as being closely linked with multiple neurodegenerative pathways, which are associated with depression, a consequence of neurodegenerative disease. Accordingly, pro‑inflammatory cytokines are important in the pathophysiology of depression and dementia. These data suggest that the role of neuroinflammation in neurodegeneration must be fully elucidated, since pro‑inflammatory agents, which are the causative effects of neuroinflammation, occur widely, particularly in the elderly in whom inflammatory mechanisms are linked to the pathogenesis of functional and mental impairments. In this review, we investigated the role played by the inflammatory process in neurodegenerative diseases.

Figure 1

Sources of neuroinflammation. Aging, metabolic diseases and viral infections are sources of inflammation that can affect vessels and neurons, leading to neurodegeneration. SVD, small vessel disease.

Figure 2

Relationship between microglial activation and neuronal death. Microglial activation may result in the release of neurotoxicity or neuroprotection. The increase of neurotoxic molecules favours neuroinflammation or neuronal death leading to neurodegeneration. ROS, reactive oxygen species.