Inflammation in the pathogenesis of neurodegenerative diseases

INTRODUCTION: Neurodegenerative diseases are common chronic disorders that are associated with progressive damage to the nervous system. The role of the immune system in the development of neurodegenerative diseases was confirmed by data on the activation of microglia, the presence of an imbalance in the composition and phenotype of peripheral immune cells, and the presence of humoral immunity disorders and intestinal microbiota dysbiosis in patients with this pathology.

DISCUSSION: Inflammation has been observed to play a key role in the pathogenesis of diseases associated with progressive damage to the nervous system. The article analyzes the mechanisms in the development of “subclinical” chronic inflammation that leads to development of old-age-related diseases, including neurodegenerative pathology. At least three groups of factors associated with old age play a role in the formation of a proinflammatory status: mitochondrial dysfunction, development of an age-related proinflammatory status of the immune system, and chronic stress. Mitochondrial dysfunction is primarily associated with disruption of mitophagy processes: failure of quality control mechanisms as a result of disruption of mitophagy processes leads to the accumulation of terminally damaged mitochondria, which become a threat to cell survival. Inadequate removal of damaged mitochondria leads to hyperactivation of inflammatory signaling pathways and subsequently to chronic systemic inflammation and the development of inflammatory diseases. A high level of deletions in the mitochondrial genetic apparatus that accumulates with age inevitably leads to increased formation of reactive oxygen species, which in turn are assumed as one of the leading activators of the cytosolic NLRP3 protein, the primary component of inflammasomes. Increased inflammasome formation eventually leads to caspase-1-dependent production of proinflammatory interleukins. Age-related inflammatory imbalance is associated with the fact that the immune system, the main protective mechanism characterized by the inflammatory response, copes with constant antigenic attacks. However, over time, upon reaching a certain threshold, the reaction of the immune system becomes excessive, characterized by increased production of coagulation factors, proinflammatory cytokines, acute phase proteins of inflammation, prostaglandins, and leukotrienes.

CONCLUSIONS: Immunological changes that develop during chronic (long-term) stress are the result of a disruption of the homeostatic connection between the neuroendocrine and immune systems, leading to the formation of an inflammatory background that complements the “proinflammatory status” that develops as a result of age-related changes in the immune system and disruption of mitophagy mechanisms.