Intracellular protons accelerate aging and switch on aging hallmarks in mice

Histone modifications as molecular drivers of cardiac aging: Metabolic alterations, epigenetic mechanisms, and emerging therapeutic strategies

Cardiac aging represents a complex pathophysiological process characterized by progressive metabolic recombination and functional dedifferentiation of cardiac cellular components. Despite advancements in cardiovascular medicine, a critical research gap persists in understanding the precise epigenetic mechanisms that drive age-related cardiac dysfunction. This comprehensive review elucidates the pivotal role of histone modifications-including methylation, acetylation, and phosphorylation-in orchestrating the molecular landscape of cardiac aging. Significant gaps remain in our understanding of site-specific histone modification impacts on cardiac function, the intricate crosstalk between different histone marks, and their integration with metabolic alterations that characterize the aging myocardium. Current evidence reveals a dynamic epigenetic signature in aged cardiac tissue, typically featuring increased transcriptional activation markers alongside decreased repressive marks, though context-dependent variations exist. This review explores how histone modifications influence critical pathways governing mitochondrial dysfunction, DNA damage repair, inflammation, and fibrosis in aging hearts. Innovative therapeutic approaches targeting specific histone-modifying enzymes promise to mitigate age-related cardiac deterioration, potentially revolutionizing treatment paradigms for cardiovascular diseases in aging populations. Addressing these knowledge gaps requires multidimensional approaches that integrate epigenomics with functional assessment of cardiac performance.

Heterochromatin loss as a determinant of progerin-induced DNA damage in Hutchinson-Gilford Progeria

Hutchinson-Gilford progeria is a premature aging syndrome caused by a truncated form of lamin A called progerin. Progerin expression results in a variety of cellular defects including heterochromatin loss, DNA damage, impaired proliferation and premature senescence. It remains unclear how these different progerin-induced phenotypes are temporally and mechanistically linked. To address these questions, we use a doxycycline-inducible system to restrict progerin expression to different stages of the cell cycle. We find that progerin expression leads to rapid and widespread loss of heterochromatin in G1-arrested cells, without causing DNA damage. In contrast, progerin triggers DNA damage exclusively during late stages of DNA replication, when heterochromatin is normally replicated, and preferentially in cells that have lost heterochromatin. Importantly, removal of progerin from G1-arrested cells restores heterochromatin levels and results in no permanent proliferative impediment. Taken together, these results delineate the chain of events that starts with progerin expression and ultimately results in premature senescence. Moreover, they provide a proof of principle that removal of progerin from quiescent cells restores heterochromatin levels and their proliferative capacity to normal levels.