IQGAP1-dysfunction leads to induction of senescence in human vascular smooth muscle cells

An evaluation of the role of miR-361-5p in senescence and systemic ageing

Senescent cells are key regulators of ageing and age-associated disease. MicroRNAs (miRs) are a key component of the molecular machinery governing cellular senescence, with several known to regulate important genes associated with this process. We sought to identify miRs associated with both senescence and reversal by pinpointing those showing opposing directionality of effect in senescence and in response to senotherapy. Cellular senescence phenotypes were assessed in primary human endothelial cells following targeted manipulation of emergent miRNAs. Finally, the effect of conserved target gene knockdown on lifespan and healthspan was assessed in a C. elegans system in vivo. Three miRNAs (miR-5787, miR-3665 and miR-361-5p) demonstrated associations with both senescence and rejuvenation, but miR-361-5p alone demonstrated opposing effects in senescence and rescue. Treatment of late passage human endothelial cells with a miR-361-5p mimic caused a 14 % decrease in the senescent load of the culture. RNAi gene knockdown of conserved miR-361-5p target genes in a C. elegans model however resulted in adverse effects on healthspan and/or lifespan. Although miR-361-5p may attenuate aspects of the senescence phenotype in human primary endothelial cells, many of its validated target genes also play essential roles in the regulation or formation of the cytoskeletal network, or its interaction with the extracellular matrix. These processes are essential for cell survival and cell function. Targeting miR-361-5p alone may not represent a promising target for future senotherapy; more sophisticated approaches to attenuate its interaction with specific targets without roles in essential cell processes would be required.

Aging Hallmarks and the Role of Oxidative Stress

Aging is a complex biological process accompanied by a progressive decline in the physical function of the organism and an increased risk of age-related chronic diseases such as cardiovascular diseases, cancer, and neurodegenerative diseases. Studies have established that there exist nine hallmarks of the aging process, including (i) telomere shortening, (ii) genomic instability, (iii) epigenetic modifications, (iv) mitochondrial dysfunction, (v) loss of proteostasis, (vi) dysregulated nutrient sensing, (vii) stem cell exhaustion, (viii) cellular senescence, and (ix) altered cellular communication. All these alterations have been linked to sustained systemic inflammation, and these mechanisms contribute to the aging process in timing not clearly determined yet. Nevertheless, mitochondrial dysfunction is one of the most important mechanisms contributing to the aging process. Mitochondria is the primary endogenous source of reactive oxygen species (ROS). During the aging process, there is a decline in ATP production and elevated ROS production together with a decline in the antioxidant defense. Elevated ROS levels can cause oxidative stress and severe damage to the cell, organelle membranes, DNA, lipids, and proteins. This damage contributes to the aging phenotype. In this review, we summarize recent advances in the mechanisms of aging with an emphasis on mitochondrial dysfunction and ROS production.

Role of a small GTPase Cdc42 in aging and age-related diseases

A small GTPase, Cdc42 is evolutionarily one of the most ancient members of the Rho family, which is ubiquitously expressed and involved in a wide range of fundamental cellular functions. The crucial role of Cdc42 includes regulation of the actin cytoskeleton, cell polarity, morphology and migration, endocytosis and exocytosis, cell cycle, and proliferation in many different cell types. Many studies have provided compelling yet contradicting evidence that Cdc42 dysregulation plays an important role in cellular and tissue aging. Furthermore, Cdc42 is a critical factor in the development and progression of aging-related pathologies, such as neurodegenerative and cardiovascular disorders, diabetes type 2, and aging-related disorders of the joints and bones, and the inhibition of the Cdc42 demonstrates potentially significant therapeutic and anti-aging effects in animal models of aging and disease. However, regulation of Cdc42 expression and activity is very complex and depends on many factors, such as the origin and complexity of the tissues, hormonal status, etc. Therefore, this review is focused on current advances in understanding the underlying cellular and molecular mechanisms associated with Cdc42 activity and regulation of senescence in different cell types since they may provide a foundation for novel therapeutic strategies and targeted drugs to reverse the aging process and treat aging-associated disorders.

A common signature of cellular senescence; does it exist?

Cellular senescence is a stress response, which can be evoked in all type of somatic cells by different stimuli. Senescent cells accumulate in the body and participate in aging and aging-related diseases mainly by their secretory activity, commonly known as senescence-associated secretory phenotype-SASP. Senescence is typically described as cell cycle arrest. This definition stems from the original observation concerning limited cell division potential of human fibroblasts in vitro. At present, the process of cell senescence is attributed also to cancer cells and to non-proliferating post-mitotic cells. Many cellular signaling pathways and specific and unspecific markers contribute to the complex, dynamic and heterogeneous phenotype of senescent cells. Considering the diversity of cells that can undergo senescence upon different inducers and variety of mechanisms involved in the execution of this process, we ask if there is a common signature of cell senescence. It seems that cell cycle arrest in G0, G1 or G2 is indispensable for cell senescence; however, to ensure irreversibility of divisions, the exit from the cell cycle to the state, which we call a GS (Gero Stage), is necessary. The DNA damage, changes in nuclear architecture and chromatin rearrangement are involved in signaling pathways leading to altered gene transcription and secretion of SASP components. Thus, nuclear changes and SASP are vital features of cell senescence that, together with temporal arrest in the cell cycle (G1 or/and G2), which may be followed by polyploidisation/depolyploidisation or exit from the cell cycle leading to permanent proliferation arrest (GS), define the signature of cellular senescence.