Mitochondria and aging

The role of oxidative stress in the development of knee osteoarthritis: A comprehensive research review

Knee osteoarthritis (KOA) is one of the most common degenerative diseases, and its core feature is the degeneration and damage of articular cartilage. The cartilage degeneration of KOA is due to the destruction of dynamic balance caused by the activation of chondrocytes by various factors, with oxidative stress playing an important role in the pathogenesis of KOA. The overproduction of reactive oxygen species (ROS) is a result of oxidative stress, which is caused by a redox process that goes awry in the inherent antioxidant defence system of the human body. Superoxide dismutase (SOD) inside and outside chondrocytes plays a key role in regulating ROS in cartilage. Additionally, synovitis is a key factor in the development of KOA. In an inflammatory environment, hypoxia in synovial cells leads to mitochondrial damage, which leads to an increase in ROS levels, which further aggravates synovitis. In addition, oxidative stress significantly accelerates the telomere shortening and ageing of chondrocytes, while ageing promotes the development of KOA, damages the regulation of redox of mitochondria in cartilage, and stimulates ROS production to further aggravate KOA. At present, there are many drugs to regulate the level of ROS, but these drugs still need to be developed and verified in animal models of KOA. We discuss mainly how oxidative stress plays a part in the development of KOA. Although the current research has achieved some results, more research is needed.

Therapeutic Strategies for Mitochondrial Dysfunction and Oxidative Stress in Age-Related Metabolic Disorders

Mitochondria are complex, intercellular organelles present in the cells and are involved in multiple roles including ATP formation, free radicals generation and scavenging, calcium homeostasis, cellular differentiation, and cell death. Many studies depicted the involvement of mitochondrial dysfunction and oxidative damage in aging and pathogenesis of age-related metabolic disorders and neurodegenerative diseases. Remarkable advancements have been made in understanding the structure, function, and physiology of mitochondria in metabolic disorders such as diabetes, obesity, cardiovascular diseases, and stroke. Further, much progress has been done in the improvement of therapeutic strategies, including lifestyle interventions, pharmacological, and mitochondria-targeted therapeutic approaches. These strategies were mainly focused to reduce the mitochondrial dysfunction caused by oxidative stress and to retain the mitochondrial health in various diseases. In this chapter, we have highlighted the involvement of mitochondrial dysfunction in the pathophysiology of various disorders and recent progress in the development of mitochondria-targeted molecules as therapeutic measures for metabolic disorders.

Age-Specific Gene Expression Profiles of Rhesus Monkey Ovaries Detected by Microarray Analysis

The biological function of human ovaries declines with age. To identify the potential molecular changes in ovarian aging, we performed genome-wide gene expression analysis by microarray of ovaries from young, middle-aged, and old rhesus monkeys. Microarray data was validated by quantitative real-time PCR. Results showed that a total of 503 (60 upregulated, 443 downregulated) and 84 (downregulated) genes were differentially expressed in old ovaries compared to young and middle-aged groups, respectively. No difference in gene expression was found between middle-aged and young groups. Differentially expressed genes were mainly enriched in cell and organelle, cellular and physiological process, binding, and catalytic activity. These genes were primarily associated with KEGG pathways of cell cycle, DNA replication and repair, oocyte meiosis and maturation, MAPK, TGF-beta, and p53 signaling pathway. Genes upregulated were involved in aging, defense response, oxidation reduction, and negative regulation of cellular process; genes downregulated have functions in reproduction, cell cycle, DNA and RNA process, macromolecular complex assembly, and positive regulation of macromolecule metabolic process. These findings show that monkey ovary undergoes substantial change in global transcription with age. Gene expression profiles are useful in understanding the mechanisms underlying ovarian aging and age-associated infertility in primates.

Life-history Constraints on the Mechanisms that Control the Rate of ROS Production

The quest to understand why and how we age has led to numerous lines of investigation that have gradually converged to consider mitochondrial metabolism as a major player. During mitochondrial respiration a small and variable amount of the consumed oxygen is converted to reactive species of oxygen (ROS). For many years, these ROS have been perceived as harmful by-products of respiration. However, evidence from recent years indicates that ROS fulfill important roles as cellular messengers. Results obtained using model organisms suggest that ROS-dependent signalling may even activate beneficial cellular stress responses, which eventually may lead to increased lifespan. Nevertheless, when an overload of ROS cannot be properly disposed of, its accumulation generates oxidative stress, which plays a major part in the ageing process. Comparative studies about the rates of ROS production and oxidative damage accumulation, have led to the idea that the lower rate of mitochondrial oxygen radical generation of long-lived animals with respect to that of their short-lived counterpart, could be a primary cause of their slow ageing rate. A hitherto largely under-appreciated alternative view is that such lower rate of ROS production, rather than a cause may be a consequence of the metabolic constraints imposed for the large body sizes that accompany high lifespans. To help understanding the logical underpinning of this rather heterodox view, herein I review the current literature regarding the mechanisms of ROS formation, with particular emphasis on evolutionary aspects.

Effects of aging on articular cartilage homeostasis

This review is focused on aging-related changes in cells and extracellular matrix of the articular cartilage. Major extracellular matrix changes are a reduced thickness of cartilage, proteolysis, advanced glycation and calcification. The cellular changes include reduced cell density, cellular senescence with abnormal secretory profiles, and impaired cellular defense mechanisms and anabolic responses. The extracellular and cellular changes compound each other, leading to biomechanical dysfunction and tissue destruction. The consequences of aging-related changes for joint homeostasis and risk for osteoarthritis are discussed. This article is part of a Special Issue entitled "Osteoarthritis".