Oxidative stress, inflammation, dysfunctional redox homeostasis and autophagy cause age-associated diseases

Aging and age-associated diseases (AADs) are growing risk factors in societies worldwide. During aging, there is an accumulation of excessive oxygen free radicals [reactive oxygen species (ROS)] and nitrogen free radicals [reactive nitrogen species (RNS)] due to dysfunctional mitochondria, dysregulated catalytic activities of cytochrome P450 (CYP), nicotinamide adenine dinucleotide (NAD) phosphate [NADP(H)] oxidase (NOX), cyclooxygenases, and nitric oxide synthases (NOS) over the threshold of physiological levels, creating oxidative stress (OS). Excessive ROS and RNS oxidize, break, denature, and sometimes cause aggregations of key cellular components including DNA, proteins, and lipids. Normally, these denatured molecules and their aggregates are eliminated by autophagy (AP) and ubiquitin-proteosome system (UPS). However, these two proteostatic mechanisms are impaired as age progresses. As a result, these abnormal molecules turn into damage-associated molecular patterns (DAMPs), recognized as non-self by immune cells, leading to systemic chronic inflammation (SCI), which together with OS are the major causes of aging and AADs. Therefore, instead of trying to prevent and cure AADs individually, the logical approach should be the restoration of redox homeostasis by the nuclear factor erythroid 2-related factor 2 (Nrf2) pathway which can prevent the damaging effect of OS and the upregulation of AP and UPS to eliminate DAMPs, and together they attenuate SCI to lessen the effect of inflammation. The central regulators, adenosine monophosphate-activated protein kinase (AMPK), sirtuin 1 (SIRT1), and Sestrins, synergistically control the restoration of the redox homeostasis by activating Nrf2, the upregulation of AP-UPS, and the inhibition of SCI. The activation of these central regulators can be achieved by exercise, caloric restriction (CR), and intakes of certain CR mimetic natural compounds. Consequently, the activations of these regulators may lead to the prevention and/or attenuation of the AADs.