The mitomiR/Bcl-2 axis affects mitochondrial function and autophagic vacuole formation in senescent endothelial cells

Abstract

During senescence, cells undergo distinctive biochemical and morphological changes and become dysfunctional. MiRNAs are involved in the senescence process and specific miRNAs can localize to mitochondria (mitomiRs). We hypothesized that part of the typical alterations of senescence may depends on mitomiRs deregulation. Therefore, we thoroughly explored the phenotype of human endothelial cells undergoing replicative senescence (sHUVECs) and observed elongated/branched mitochondria, accumulation of autophagic vacuoles (AVs), increased ROS and IL-1β production and reduced expression of Bcl-2 compared to younger cells (yHUVECs). Despite these pro-apoptotic features, sHUVECs are more resistant to serum deprivation, conceivably due to development of pro-survival strategies such as upregulation of Bcl-xL and Survivin. We demonstrate that mitomiR-181a, -34a, and -146a, are overexpressed and localize to mitochondria in sHUVECs compared with yHUVECs and that they: i) down-regulate Bcl-2, ii) induce permeability transition pore opening and activation of caspase-1 and 3, iii) affect sensitivity to apoptosis and iv) promote the conversion of LC3-I to LC3-II. Overall, we document for the first time that some mitomiRs can act as mediators of the multiple but functionally linked biochemical and morphological changes that characterize aging cells and that they can promote different cellular outcomes according to the senescence status of the cell.

Mitochondrial MiRNA in Cardiovascular Function and Disease

“…Several studies have documented that some mitomiRs promote mitochondrial dysfunction via Bcl-2 downregulation [98,99]. Bcl-2 is an antioxidant and antiapoptotic mitochondrial protein and regulates mitochondrial fission/fusion [100,101].…”

“…The mitomiR-induced Bcl-2 deregulation may lead to a state of dysfunctional mitochondria, increased oxidative stress, chronic low-grade inflammation, and increased apoptosis rates in angiogenesis-related diseases. Giuliani et al found that mitomiR-181a, -34a, and -146a, were upregulated and localized to mitochondria and downregulated Bcl-2 in human aging endothelial cells [98]. Further, overexpression of these mitomiRs was found to decrease Bcl-2 expression, leading to mitochondrial permeability transition pore opening, activation of caspase-1 and 3, and cell apoptosis [98].…”

“…Giuliani et al found that mitomiR-181a, -34a, and -146a, were upregulated and localized to mitochondria and downregulated Bcl-2 in human aging endothelial cells [98]. Further, overexpression of these mitomiRs was found to decrease Bcl-2 expression, leading to mitochondrial permeability transition pore opening, activation of caspase-1 and 3, and cell apoptosis [98]. MitomiRs has been demonstrated to inhibit angiogenesis and vascularization [102]; however, the molecular mechanisms involved in mitomiRs-inhibited angiogenesis, with particular emphasis on those associated with cardiovascular disease, need further investigation.…”

The Protective Role of Bioactive Quinones in Stress-induced Senescence Phenotype of Endothelial Cells Exposed to Cigarette Smoke Extract

“…Cell viability, total cellular and mitochondrial ROS levels and mitochondrial Permeability transition pore (mPTP) opening were evaluated as previously described [ 26 , 27 ]. Flow cytometry coupled with appropriate fluorescent probes was conducted on a Guava EasyCyte flow cytometer equipped with GuavaSoft 2.7 software and an excitation source at 488 nm (Merck Millipore, Darmstadt, Germany).…”

The Experimental Pathology at Ancona: 50 Years of Exciting and Pioneering Research on Human Pathology

“…Under the guidance of Prof. Maria Rita Rippo, the research group has also highlighted mechanisms of resistance to programmed cell death of senescent cells and on those that regulate the differentiation of mesenchymal stromal cells (MSCs) which show alterations in their proliferative and differentiating capacity in elderly [77]. In particular, for the first time we suggested and demonstrated that mito-miRs (mitochondria resident or associated to mitochondrial membranes) are modulated and can control expression of Bcl-2 family members and the oxidative and energetic status in aging cells thus contributing to their resistance to pro-apoptotic stimuli, pro-inflammatory phenotype and altered autophagy [29,30,67]. Furthermore, our group demonstrated that FasL, whose circulating levels decrease progressively during aging [36], is modulated in post-menopausal women [37] and play a pivotal role in bone homeostasis inhibiting MSCs differentiation in adipocytes and inducing their proliferation [66].…”