Aging and Parkinson's Disease: Inflammaging, neuroinflammation and biological remodeling as key factors in pathogenesis

In order to better understand the pathogenesis of Parkinson's Disease (PD) it is important to consider possible contributory factors inherent to the aging process, as age-related changes in a number of physiological systems (perhaps incurred within particular environments) appear to influence the onset and progression of neurodegenerative disorders. Accordingly, we posit that a principal mechanism underlying PD is inflammaging, i.e. the chronic inflammatory process characterized by an imbalance of pro- and anti-inflammatory mechanisms which has been recognized as operative in several age-related, and notably neurodegenerative diseases. Recent conceptualization suggests that inflammaging is part of the complex adaptive mechanisms ("re-modeling") that are ongoing through the lifespan, and which function to prevent or mitigate endogenous processes of tissue disruption and degenerative change(s). The absence of an adequate anti-inflammatory response can fuel inflammaging, which propagates on both local (i.e.- from cell to cell) and systemic levels (e.g.- via exosomes and other molecules present in the blood). In general, this scenario is compatible with the hypothesis that inflammaging represents a hormetic or hormetic-like effect, in which low levels of inflammatory stress may prompt induction of anti-inflammatory mediators and mechanisms, while sustained pro-inflammatory stress incurs higher and more durable levels of inflammatory substances, which, in turn prompt a local-to-systemic effect and more diverse inflammatory response(s). Given this perspective, new treatments of PD may be envisioned that strategically are aimed at exerting hormetic effects to sustain anti-inflammatory responses, inclusive perhaps, of modulating the inflammatory influence of the gut microbiota.