CuZn superoxide dismutase deficiency: culprit of accelerated vascular aging process

Aging-Induced Impairment of Vascular Function: Mitochondrial Redox Contributions and Physiological/Clinical Implications

Significance: The vasculature responds to the respiratory needs of tissue by modulating luminal diameter through smooth muscle constriction or relaxation. Coronary perfusion, diastolic function, and coronary flow reserve are drastically reduced with aging. This loss of blood flow contributes to and exacerbates pathological processes such as angina pectoris, atherosclerosis, and coronary artery and microvascular disease. Recent Advances: Increased attention has recently been given to defining mechanisms behind aging-mediated loss of vascular function and development of therapeutic strategies to restore youthful vascular responsiveness. The ultimate goal aims at providing new avenues for symptom management, reversal of tissue damage, and preventing or delaying of aging-induced vascular damage and dysfunction in the first place. Critical Issues: Our major objective is to describe how aging-associated mitochondrial dysfunction contributes to endothelial and smooth muscle dysfunction via dysregulated reactive oxygen species production, the clinical impact of this phenomenon, and to discuss emerging therapeutic strategies. Pathological changes in regulation of mitochondrial oxidative and nitrosative balance (Section 1) and mitochondrial dynamics of fission/fusion (Section 2) have widespread effects on the mechanisms underlying the ability of the vasculature to relax, leading to hyperconstriction with aging. We will focus on flow-mediated dilation, endothelial hyperpolarizing factors (Sections 3 and 4), and adrenergic receptors (Section 5), as outlined in Figure 1. The clinical implications of these changes on major adverse cardiac events and mortality are described (Section 6). Future Directions: We discuss antioxidative therapeutic strategies currently in development to restore mitochondrial redox homeostasis and subsequently vascular function and evaluate their potential clinical impact (Section 7). Antioxid. Redox Signal. 35, 974-1015.

Brain-based mechanisms of late-life depression: Implications for novel interventions

Late-life depression (LLD) is a particularly debilitating illness. Older adults suffering from depression commonly experience poor outcomes in response to antidepressant treatments, medical comorbidities, and declines in daily functioning. This review aims to further our understanding of the brain network dysfunctions underlying LLD that contribute to disrupted cognitive and affective processes and corresponding clinical manifestations. We provide an overview of a network model of LLD that integrates the salience network, the default mode network (DMN) and the executive control network (ECN). We discuss the brain-based structural and functional mechanisms of LLD with an emphasis on their link to clinical subtypes that often fail to respond to available treatments. Understanding the brain networks that underlie these disrupted processes can inform the development of targeted interventions for LLD. We propose behavioral, cognitive, or computational approaches to identifying novel, personalized interventions that may more effectively target the key cognitive and affective symptoms of LLD.

An Overview on Current Issues and Challenges of Endothelial Progenitor Cell-Based Neovascularization in Patients with Diabetic Foot Ulcer

Diabetic foot ulcer's impaired wound healing, which leads to the development of chronic non-healing wounds and ultimately amputation, is a major problem worldwide. Although recently endothelial progenitor cell-derived cell therapy has been used as a therapeutic intervention to treat diabetic wounds, thereby promoting neovascularization, the results, however, are not satisfactory. In this article, we have discussed the several steps that are involved in the neovascularization process, which might be impaired during diabetes. In addition, we have also discussed the reported possible interventions to correct these impairments. Thus, we have summarized neovascularization as a process with a coordinated sequence of multiple steps and thus, there is the need of a combined therapeutic approach to achieve better treatment outcomes.

Suppression of oxidative stress in endothelial progenitor cells promotes angiogenesis and improves cardiac function following myocardial infarction in diabetic mice

Myocardial infarction is a major contributor to morbidity and mortality in diabetes, which is characterized by inadequate angiogenesis and consequent poor blood reperfusion in the diabetic ischemic heart. The aim of the present study was to investigate the effect that oxidative stress in endothelial progenitor cells (EPCs) has on cardiac angiogenesis in diabetic mice. EPCs derived from diabetic mice revealed reductions in superoxide dismutase (SOD) expression levels and activity compared with those from normal mice. An endothelial tube formation assay showed that angiogenesis was markedly delayed for diabetic EPCs, compared with normal controls. EPCs subjected to various pretreatments were tested as a cell therapy in a diabetic mouse model of myocardial infarction. Induction of oxidative stress in normal EPCs by H₂O₂ or small interfering RNA-mediated knockdown of SOD reduced their angiogenic activity in the ischemic myocardium of the diabetic mice. Conversely, cell therapy using EPCs from diabetic mice following SOD gene overexpression or treatment with the antioxidant Tempol normalized their ability to promote angiogenesis. These results indicate that decreased expression levels of SOD in EPCs contribute to impaired angiogenesis. In addition, normalization of diabetic EPCs by ex vivo SOD gene therapy accelerates the ability of the EPCs to promote angiogenesis and improve cardiac function when used as a cell therapy following myocardial infarction in diabetic mice.

Free radical biology of the cardiovascular system

Most cardiovascular diseases (CVDs), as well as age-related cardiovascular alterations, are accompanied by increases in oxidative stress, usually due to increased generation and/or decreased metabolism of ROS (reactive oxygen species; for example superoxide radicals) and RNS (reactive nitrogen species; for example peroxynitrite). The superoxide anion is generated by several enzymatic reactions, including a variety of NADPH oxidases and uncoupled eNOS (endothelial NO synthase). To relieve the burden caused by this generation of free radicals, which also occurs as part of normal physiological processes, such as mitochondrial respiratory chain activity, mammalian systems have developed endogenous antioxidant enzymes. There is an increased usage of exogenous antioxidants such as vitamins C and E by many patients and the general public, ostensibly in an attempt to supplement intrinsic antioxidant activity. Unfortunately, the results of large-scale trails do not generate much enthusiasm for the continued use of antioxidants to mitigate free-radical-induced changes in the cardiovascular system. In the present paper, we review the clinical use of antioxidants by providing the rationale for their use and describe the outcomes of several large-scale trails that largely display negative outcomes. We also describe the emerging understanding of the detailed regulation of superoxide generation by an uncoupled eNOS and efforts to reverse eNOS uncoupling. SIRT1 (sirtuin 1), which regulates the expression and activity of multiple pro- and anti-oxidant enzymes, could be considered a candidate molecule for a 'molecular switch'.

Manganese superoxide dismutase expression in endothelial progenitor cells accelerates wound healing in diabetic mice

Amputation as a result of impaired wound healing is a serious complication of diabetes. Inadequate angiogenesis contributes to poor wound healing in diabetic patients. Endothelial progenitor cells (EPCs) normally augment angiogenesis and wound repair but are functionally impaired in diabetics. Here we report that decreased expression of manganese superoxide dismutase (MnSOD) in EPCs contributes to impaired would healing in a mouse model of type 2 diabetes. A decreased frequency of circulating EPCs was detected in type 2 diabetic (db/db) mice, and when isolated, these cells exhibited decreased expression and activity of MnSOD. Wound healing and angiogenesis were markedly delayed in diabetic mice compared with normal controls. For cell therapy, topical transplantation of EPCs onto excisional wounds in diabetic mice demonstrated that diabetic EPCs were less effective than normal EPCs at accelerating wound closure. Transplantation of diabetic EPCs after MnSOD gene therapy restored their ability to mediate angiogenesis and wound repair. Conversely, siRNA-mediated knockdown of MnSOD in normal EPCs reduced their activity in diabetic wound healing assays. Increasing the number of transplanted diabetic EPCs also improved the rate of wound closure. Our findings demonstrate that cell therapy using diabetic EPCs after ex vivo MnSOD gene transfer accelerates their ability to heal wounds in a mouse model of type 2 diabetes.