Cellular senescence is characterized by proliferation and migration exhaustion, senescence-associated secretory phenotype (SASP), and oxidative stress. Senescent vascular smooth muscle cells (VSMCs) contribute to cardiovascular diseases and atherosclerotic plaque instability. Since there are no unanimously agreed senescence markers in human VSMCs, to improve our knowledge, we looked for new possible senescence markers. To this end, we first established and characterized a model of replicative senescence (RS) in human aortic VSMCs. Old cells displayed several established senescence-associated markers. They stained positive for the senescence-associated β-galactosidase, showed a deranged proliferation rate, a dramatically reduced expression of PCNA, an altered migratory activity, increased levels of TP53 and cell-cycle inhibitors p21/p16, and accumulated in the G1 phase. Old cells showed an altered cellular and nuclear morphology, downregulation of the expression of LMNB1 and HMGB1, and increased expression of SASP molecules (IL1β, IL6, IL8, and MMP3). In these senescent VSMCs, among a set of 12 manually selected long non-coding RNAs (lncRNAs), we detected significant upregulation of PURPL and NEAT1. We observed also, for the first time, increased levels of RRAD mRNA. The detection of modulated levels of RRAD, PURPL, and NEAT1 during VSMC senescence could be helpful for future studies on potential anti-aging factors.

Senescence and mitochondrial dysfunction are two major indicators of aging. Mitochondria are potential drivers of aging phenotypes and dysfunctional mitochondria are associated with several age-related diseases. There is evidence that senescence induces changes in mitochondrial structure, dynamics, and function. Moreover, senescent vascular smooth muscle cells (VSMCs) are present in atherosclerotic plaques and contribute to their instability. The anti-atherosclerotic effects of simvastatin are well known, but recently other benefits, such as promoting mitochondrial quality and senostatic effects, have been hypothesized. We aimed to analyze simvastatin's senostatic effects in senescent VSMCs. We established and characterized mitochondrial dysfunction in doxorubicin-induced senescent VSMCs (doxorubicin) or VSMCs serially passaged to induce replicative senescence (old). We observed in both senescent models few typical senescence markers such as altered cell morphology, cell cycle inhibitors, laminB1, an accumulation of dysfunctional mitochondria characterized by reduced mitochondrial membrane potential (MMP) and respiration, accumulation of reactive oxygen species (ROS), and an altered mitochondria morphology. Down-regulation of TFAM and TOM70 expression was observed only in old cells suggesting a reduction of mitochondrial biogenesis. Next, we investigated whether simvastatin could ameliorate age-associated phenotypes in senescent VSMCs. Simvastatin 0.1 μM reduces the senescence-associated secretory phenotype (SASP) and ROS production and improves mitochondrial respiration in doxorubicin and old VSMCs. Interestingly, the effects of simvastatin on mitochondrial respiration and SASP were replicated by using a siRNA for the hydroxy-methyl-glutaryl-coenzyme A (HMG-CoA) reductase, and abolished by adding mevalonic acid, suggesting that these effects are mediated through the inhibition of HMG-CoA reductase. Our results suggest that simvastatin controls SASP and exerts potentially beneficial therapeutic effects by ameliorating senescence-induced mitochondrial dysfunction in senescent VSMCs.

Cigarette smoke (CS) is a risk factor for inflammatory diseases, such as atherosclerosis. CS condensate (CSC) contains lipophilic components that may represent a systemic cardiac risk factor. To better understand CSC effects, we incubated mouse and human aortic smooth muscle cells (SMCs) with CSC. We evaluated specific markers for contractile [i.e., actin, aortic smooth muscle (ACTA2), calponin-1 (CNN1), the Kruppel-like factor 4 (KLF4), and myocardin (MYOCD) genes] and inflammatory [i.e., IL-1β, and IL-6, IL-8, and galectin-3 (LGALS-3) genes] phenotypes. CSC increased the expression of inflammatory markers and reduced the contractile ones in both cell types, with KLF4 modulating the SMC phenotypic switch. Next, we performed a mass spectrometry-based differential proteomic approach on human SMCs and could show 11 proteins were significantly affected by exposition to CSC (FC ≥ 2.7, p ≤ 0.05). These proteins are active in signaling pathways related to expression of pro-inflammatory cytokines and IFN, inflammasome assembly and activation, cytoskeleton regulation and SMC contraction, mitochondrial integrity and cellular response to oxidative stress, proteostasis control via ubiquitination, and cell proliferation and epithelial-to-mesenchymal transition. Through specific bioinformatics resources, we showed their tight functional correlation in a close interaction niche mainly orchestrated by the interferon-induced double-stranded RNA-activated protein kinase (alternative name: protein kinase RNA-activated; PKR) (EIF2AK2/PKR). Finally, by combining gene expression and protein abundance data we obtained a hybrid network showing reciprocal integration of the CSC-deregulated factors and indicating KLF4 and PKR as the most relevant factors.

Vascular smooth muscle cell (SMC) phenotypic switching, from a contractile to a synthetic state, impacts on atherosclerotic plaque development. While traditional cigarette (TC) smoke is a known driver of cardiovascular disease, the effects of alternative nicotine delivery systems, i.e. electronic cigarettes (E-cigs) and tobacco heating products (THPs), on SMC behavior remains poorly understood. We evaluated the effects of water-soluble components collected in aqueous extracts (AEs) from TC, E-cig, and THP smoke, on human aortic SMC (HASMC) phenotypic switch. HASMCs were treated for 48 h with the three AEs. Gene expression and protein abundance profiles were assessed to evaluate cell phenotypic modulation, proliferation, migration, extracellular matrix remodeling, and inflammatory responses. Label-free MS/MS proteomic analysis and wound healing assays were also used to further characterize cellular responses. Different AEs induced distinct gene expression and protein patterns, but all seemed to induce a hybrid contractile-synthetic phenotype. TC and THP extracts increased MMP3 expression, whereas E-cig AE downregulated MMPs. E-cig extracts, although reducing inflammatory cytokines, enhanced HASMC proliferation and migration, bona fide by upregulating PCNA, RAC1, and ROCK2, thus suggesting an increased vascular remodeling. Proteomic analysis indicated mitochondrial dysfunction and redox imbalances further advising about distinct, harmful effects of AEs on vascular health and atherosclerotic lesion progression. Our findings revealed complex differential molecular effects of TC, E-cig, and THP AEs on HASMC biology, emphasizing the necessity for further research to assess their actual long-term cardiovascular implications.

Long non-coding RNAs (lncRNAs) have emerged as key regulators of cellular senescence by transcriptionally and post-transcriptionally modulating the expression of many important genes involved in senescence-associated pathways and processes. Among the different lncRNAs associated to senescence, Senescence Associated Long Non-coding RNA (SALNR) was found to be down-regulated in different cellular models of senescence. Since its release in 2015, SALNR has not been annotated in any database or public repository, and no other experimental data have been published. The SALNR sequence is located on the long arm of chromosome 10, at band 10q23.33, and it overlaps the 3' end of the HELLS gene. This investigation helped to unravel the mystery of the existence of SALNR by analyzing publicly available short- and long-read RNA sequencing data sets and RT-PCR analysis in human tissues and cell lines. Additionally, the expression of HELLS has been studied in cellular models of replicative senescence, both in silico and in vitro. Our findings, while not supporting the actual existence of SALNR as an independent transcript in the analyzed experimental models, demonstrate the expression of a predicted HELLS isoform entirely covering the SALNR genomic region. Furthermore, we observed a strong down-regulation of HELLS in senescent cells versus proliferating cells, supporting its role in the senescence and aging process.