Redox and mTOR-dependent regulation of plasma lamellar calcium influx controls the senescence-associated secretory phenotype

Cardiac cell senescence: molecular mechanisms, key proteins and therapeutic targets

Cardiac aging, particularly cardiac cell senescence, is a natural process that occurs as we age. Heart function gradually declines in old age, leading to continuous heart failure, even in people without a prior history of heart disease. To address this issue and improve cardiac cell function, it is crucial to investigate the molecular mechanisms underlying cardiac senescence. This review summarizes the main mechanisms and key proteins involved in cardiac cell senescence. This review further discusses the molecular modulators of cellular senescence in aging hearts. Furthermore, the discussion will encompass comprehensive descriptions of the key drugs, modes of action and potential targets for intervention in cardiac senescence. By offering a fresh perspective and comprehensive insights into the molecular mechanisms of cardiac senescence, this review seeks to provide a fresh perspective and important theoretical foundations for the development of drugs targeting this condition.

Senescent cardiac fibroblasts: A key role in cardiac fibrosis

Cardiac fibroblasts are a cell population that controls the homeostasis of the extracellular matrix and orchestrates a damage response to maintain cardiac architecture and performance. Due to these functions, fibroblasts play a central role in cardiac fibrosis development, and there are large differences in matrix protein secretion profiles between fibroblasts from aged versus young animals. Senescence is a multifactorial and complex process that has been associated with inflammatory and fibrotic responses. After damage, transient cellular senescence is usually beneficial, as these cells promote tissue repair. However, the persistent presence of senescent cells within a tissue is linked with fibrosis development and organ dysfunction, leading to aging-related diseases such as cardiovascular pathologies. In the heart, early cardiac fibroblast senescence after myocardial infarction seems to be protective to avoid excessive fibrosis; however, in non-infarcted models of cardiac fibrosis, cardiac fibroblast senescence has been shown to be deleterious. Today, two new classes of drugs, termed senolytics and senostatics, which eliminate senescent cells or modify senescence-associated secretory phenotype, respectively, arise as novel therapeutical strategies to treat aging-related pathologies. However, further studies will be needed to evaluate the extent of the utility of senotherapeutic drugs in cardiac diseases, in which pathological context and temporality of the intervention must be considered.

Regulation and role of calcium in cellular senescence

Cellular senescence is a state of stable cell proliferation arrest accompanied by a distinct secretory program impacting the senescent cell microenvironment. This phenotype can be induced by many stresses, including telomere shortening, oncogene activation, oxidative or genotoxic stress. Cellular senescence plays a key role in the organism throughout life, with beneficial effects at a young age for instance in embryonic development and wound healing, and deleterious effects during aging and in aging-related diseases. In the last decade calcium and calcium signaling have been established as critical factors in the implementation and regulation of cellular senescence. In this review we will present and discuss the main discoveries in this field, from the observation of an increased intracellular calcium concentration in senescent cells to the identification of calcium-binding proteins, calcium channels (TRP, ITPR, …) and MERCs (mitochondria-endoplasmic reticulum contact sites) as key players in this context.

Cellular senescence: the good, the bad and the unknown

Cellular senescence is a ubiquitous process with roles in tissue remodelling, including wound repair and embryogenesis. However, prolonged senescence can be maladaptive, leading to cancer development and age-related diseases. Cellular senescence involves cell-cycle arrest and the release of inflammatory cytokines with autocrine, paracrine and endocrine activities. Senescent cells also exhibit morphological alterations, including flattened cell bodies, vacuolization and granularity in the cytoplasm and abnormal organelles. Several biomarkers of cellular senescence have been identified, including SA-βgal, p16 and p21; however, few markers have high sensitivity and specificity. In addition to driving ageing, senescence of immune and parenchymal cells contributes to the development of a variety of diseases and metabolic disorders. In the kidney, senescence might have beneficial roles during development and recovery from injury, but can also contribute to the progression of acute kidney injury and chronic kidney disease. Therapies that target senescence, including senolytic and senomorphic drugs, stem cell therapies and other interventions, have been shown to extend lifespan and reduce tissue injury in various animal models. Early clinical trials confirm that senotherapeutic approaches could be beneficial in human disease. However, larger clinical trials are needed to translate these approaches to patient care.