Increasing Cardiomyocyte Atrogin-1 Reduces Aging-Associated Fibrosis and Regulates Remodeling in Vivo.

The muscle-specific ubiquitin ligase atrogin-1 (MAFbx) has been identified as a critical regulator of pathologic and physiological cardiac hypertrophy; it regulates these processes by ubiquitinating transcription factors [nuclear factor of activated T-cells and forkhead box O (FoxO) 1/3]. However, the role of atrogin-1 in regulating transcription factors in aging has not previously been described. Atrogin-1 cardiomyocyte-specific transgenic (Tg+) adult mice (α-major histocompatibility complex promoter driven) have normal cardiac function and size. Herein, we demonstrate that 18-month-old atrogin-1 Tg+ hearts exhibit significantly increased anterior wall thickness without functional impairment versus wild-type mice. Histologic analysis at 18 months revealed atrogin-1 Tg+ mice had significantly less fibrosis and significantly greater nuclei and cardiomyocyte cross-sectional analysis. Furthermore, by real-time quantitative PCR, atrogin-1 Tg+ had increased Col 6a4, 6a5, 6a6, matrix metalloproteinase 8 (Mmp8), and Mmp9 mRNA, suggesting a role for atrogin-1 in regulating collagen deposits and MMP-8 and MMP-9. Because atrogin-1 Tg+ mice exhibited significantly less collagen deposition and protein levels, enhanced Mmp8 and Mmp9 mRNA may offer one mechanism by which collagen levels are kept in check in the aged atrogin-1 Tg+ heart. In addition, atrogin-1 Tg+ hearts showed enhanced FoxO1/3 activity. The present study shows a novel link between atrogin-1-mediated regulation of FoxO1/3 activity and reduced collagen deposition and fibrosis in the aged heart. Therefore, targeting FoxO1/3 activity via the muscle-specific atrogin-1 ubiquitin ligase may offer a muscle-specific method to modulate aging-related cardiac fibrosis.

Reduced cleavage of von willebrand factor by ADAMTS13 is associated with microangiopathic acute kidney injury following trauma.

Acute kidney injury (AKI) is common after trauma, but contributory factors are incompletely understood. Increases in plasma von Willebrand Factor (vWF) with concurrent decreases in ADAMTS13 are associated with renal microvascular thrombosis in other disease states, but similar findings have not been shown in trauma. We hypothesized that molecular changes in circulating vWF and ADAMTS13 promote AKI following traumatic injury. VWF antigen, vWF multimer composition and ADAMTS13 levels were compared in plasma samples from 16 trauma patients with and without trauma-induced AKI, obtained from the Prehospital Air Medical Plasma (PAMPer) biorepository. Renal histopathology and function, vWF and ADAMTS13 levels were assessed in parallel in a murine model of polytrauma and haemorrhage. VWF antigen was higher in trauma patients when compared with healthy controls [314% (253-349) vs. 100% (87-117)] [median (IQR)], while ADAMTS13 activity was lower [36.0% (30.1-44.7) vs. 100.0% (83.1-121.0)]. Patients who developed AKI showed significantly higher levels of high molecular weight multimeric vWF at 72-h when compared with non-AKI counterparts [32.9% (30.4-35.3) vs. 27.8% (24.6-30.8)]. Murine plasma cystatin C and vWF were elevated postpolytrauma model in mice, with associated decreases in ADAMTS13, and immunohistologic analysis demonstrated renal injury with small vessel plugs positive for fibrinogen and vWF. Following traumatic injury, the vWF-ADAMTS13 axis shifted towards a prothrombotic state in both trauma patients and a murine model. We further demonstrated that vWF-containing, microangiopathic deposits were concurrently produced as the prothrombotic changes were sustained during the days following trauma, potentially contributing to AKI development.

The Pathobiological Basis for Thrombotic Complications in COVID-19: a Review of the Literature.

Purpose of Review: COVID-19 has rapidly evolved into a global pandemic infecting over two hundred and forty-four million individuals to date. In addition to the respiratory sequelae and systemic infection that ensues, an alarming number of micro and macrovascular thrombotic complications have been observed. This review examines the current understanding of COVID-19-associated thrombotic complications, potential mechanisms, and pathobiological basis for thromboses development. Recent Findings: The endothelium plays a major role in the process due to direct and indirect injury. The immune system also contributes to a pro-thrombotic environment with immune cell dysregulation leading to excessive formation of cytokines, also called cytokine storm, and an eventual promotion of a hypercoagulable environment, known as immunothrombosis. Additionally, neutrophils play an important role by forming neutrophil extracellular traps, which are shown to be pro-thrombotic and further enhanced in COVID-19 patients. A disruption of the fibrinolysis system has also been observed. Summary: Multiple pathways likely contribute synergistically to form a pro-thrombotic milieu. A better understanding of these factors and the complex interplay between them will lead to the improvement of diagnostic and therapeutic interventions.

Diabetic vasculopathy: macro and microvascular injury.

PURPOSE OF REVIEW: Diabetes is a common and prevalent medical condition as it affects many lives around the globe. Specifically, type-2 Diabetes (T2D) is characterized by chronic systemic inflammation alongside hyperglycemia and insulin resistance in the body, which can result in atherosclerotic legion formation in the arteries and thus progression of related conditions called diabetic vasculopathies. T2D patients are especially at risk for vascular injury; adjunct in many of these patients heir cholesterol and triglyceride levels reach dangerously high levels and accumulate in the lumen of their vascular system. RECENT FINDINGS: Microvascular and macrovascular vasculopathies as complications of diabetes can accentuate the onset of organ illnesses, thus it is imperative that research efforts help identify more effective methods for prevention and diagnosis of early vascular injuries. Current research into vasculopathy identification/treatment will aid in the amelioration of diabetes-related symptoms and thus reduce the large number of deaths that this disease accounts annually. SUMMARY: This review aims to showcase the evolution and effects of diabetic vasculopathy from development to clinical disease as macrovascular and microvascular complications with a concerted reference to sex-specific disease progression as well.

New insights into immunomodulation via overexpressing lipoic acid synthase as a therapeutic potential to reduce atherosclerosis.

Atherosclerosis is a systemic chronic inflammatory disease. Many antioxidants including alpha-lipoic acid (LA), a product of lipoic acid synthase (Lias), have proven to be effective for treatment of this disease. However, the question remains whether LA regulates the immune response as a protective mechanism against atherosclerosis. We initially investigated whether enhanced endogenous antioxidant can retard the development of atherosclerosis via immunomodulation. To explore the impact of enhanced endogenous antioxidant on the retardation of atherosclerosis via immune regulation, our laboratory has recently created a double mutant mouse model, using apolipoprotein E-deficient (Apoe-/-) mice crossbred with mice overexpressing lipoic acid synthase gene (LiasH/H), designated as LiasH/HApoe-/- mice. Their littermates, Lias+/+Apoe-/- mice, served as a control. Distinct redox environments between the two strains of mice have been established and they can be used to facilitate identification of antioxidant targets in the immune response. At 6 months of age, LiasH/HApoe-/- mice had profoundly decreased atherosclerotic lesion size in the aortic sinus compared to their Lias+/+Apoe-/- littermates, accompanied by significantly enhanced numbers of regulatory T cells (Tregs) and anti-oxidized LDL autoantibody in the vascular system, and reduced T cell infiltrates in aortic walls. Our results represent a novel exploration into an environment with increased endogenous antioxidant and its ability to alleviate atherosclerosis, likely through regulation of the immune response. These outcomes shed light on a new therapeutic strategy using antioxidants to lessen atherosclerosis.

Doxorubicin Exposure Causes Subacute Cardiac Atrophy Dependent on the Striated Muscle-Specific Ubiquitin Ligase MuRF1.

Background Anthracycline chemotherapeutics, such as doxorubicin, are used widely in the treatment of numerous malignancies. The primary dose-limiting adverse effect of anthracyclines is cardiotoxicity that often presents as heart failure due to dilated cardiomyopathy years after anthracycline exposure. Recent data from animal studies indicate that anthracyclines cause cardiac atrophy. The timing of onset and underlying mechanisms are not well defined, and the relevance of these findings to human disease is unclear. Methods and Results Wild-type mice were sacrificed 1 week after intraperitoneal administration of doxorubicin (1-25 mg/kg), revealing a dose-dependent decrease in cardiac mass ( R2=0.64; P<0.0001) and a significant decrease in cardiomyocyte cross-sectional area (336±29 versus 188±14 µm2; P<0.0001). Myocardial tissue analysis identified a dose-dependent upregulation of the ubiquitin ligase, MuRF1 (muscle ring finger-1; R2=0.91; P=0.003) and a molecular profile of muscle atrophy. To investigate the determinants of doxorubicin-induced cardiac atrophy, we administered doxorubicin 20 mg/kg to mice lacking MuRF1 (MuRF1-/-) and wild-type littermates. MuRF1-/- mice were protected from cardiac atrophy and exhibited no reduction in contractile function. To explore the clinical relevance of these findings, we analyzed cardiac magnetic resonance imaging data from 70 patients in the DETECT-1 cohort and found that anthracycline exposure was associated with decreased cardiac mass evident within 1 month and persisting to 6 months after initiation. Conclusions Doxorubicin causes a subacute decrease in cardiac mass in both mice and humans. In mice, doxorubicin-induced cardiac atrophy is dependent on MuRF1. These findings suggest that therapies directed at preventing or reversing cardiac atrophy might preserve the cardiac function of cancer patients receiving anthracyclines.

Insights on Localized and Systemic Delivery of Redox-Based Therapeutics.

Reactive oxygen and nitrogen species are indispensable in cellular physiology and signaling. Overproduction of these reactive species or failure to maintain their levels within the physiological range results in cellular redox dysfunction, often termed cellular oxidative stress. Redox dysfunction in turn is at the molecular basis of disease etiology and progression. Accordingly, antioxidant intervention to restore redox homeostasis has been pursued as a therapeutic strategy for cardiovascular disease, cancer, and neurodegenerative disorders among many others. Despite preliminary success in cellular and animal models, redox-based interventions have virtually been ineffective in clinical trials. We propose the fundamental reason for their failure is a flawed delivery approach. Namely, systemic delivery for a geographically local disease limits the effectiveness of the antioxidant. We take a critical look at the literature and evaluate successful and unsuccessful approaches to translation of redox intervention to the clinical arena, including dose, patient selection, and delivery approach. We argue that when interpreting a failed antioxidant-based clinical trial, it is crucial to take into account these variables and importantly, whether the drug had an effect on the redox status. Finally, we propose that local and targeted delivery hold promise to translate redox-based therapies from the bench to the bedside.

111In-DANBIRT In Vivo Molecular Imaging of Inflammatory Cells in Atherosclerosis.

Atherosclerosis-related morbidity and mortality remain a global concern. Atherosclerotic disease follows a slow and silent progression, and the transition from early-stage lesions to vulnerable plaques remains difficult to diagnose. Inflammation is a key component of the development of atherosclerotic plaque and consequent life-threatening complications. This study assessed 111In-DANBIRT as an in vivo, noninvasive SPECT/CT imaging probe targeting an inflammatory marker, Lymphocyte Function Associated Antigen-1 (LFA-1), in atherosclerotic plaques. Methods. Selective binding of 111In-DANBIRT was assessed using Sprague-Dawley rats exposed to filtered air and ozone (1 ppm) by inhalation for 4 hours to induce a circulating leukocytosis and neutrophilia in peripheral blood. After 24 hours, whole blood was collected and incubated with radiolabeled DANBIRT (68Ga-DANBIRT and 111In-DANBIRT). Isolated cell component smeared slides using cytospin technique were stained with Wright-Giemsa stain. Apolipoprotein E-deficient (apoE-/-) mice were fed either a normal diet or a high-fat diet (HFD) for 8 weeks. Longitudinal SPECT/CT imaging was performed 3 hours after administration at baseline, 4, and 8 weeks of HFD diet, followed by tissue harvesting for biodistribution, serum lipid analysis, and histology. 3D autoradiography was performed in both groups 24 hours after administration of 111In-DANBIRT. Results. Increased specific uptake of radiolabeled DANBIRT by neutrophils in the ozone-exposed group was evidenced by the acute immune response due to 4-hour ozone exposure. Molecular imaging performed at 3 hours using SPECT/CT imaging evidenced an exponential longitudinal increase in 111In-DANBIRT uptake in atherosclerosis lesions in HFD-fed mice compared to normal-diet-fed mice. Such results were consistent with increased immune response to vascular injury in cardiovascular and also immune tissues, correlated by 24 hours after administration of 3D autoradiography. Histologic analysis confirmed atherosclerotic disease progression with an increased vascular lesion area in HFD-fed mice compared to normal-diet-fed mice. Conclusion. 111In-DANBIRT is a promising molecular imaging probe to assess inflammation in evolving atheroma and atherosclerotic plaque.

Post-translationally modified muscle-specific ubiquitin ligases as circulating biomarkers in experimental cancer cachexia.

Cancer cachexia is a severe wasting syndrome characterized by the progressive loss of lean body mass and systemic inflammation. Up to 80% of cancer patients experience cachexia, with 20-30% of cancer-related deaths directly linked to cachexia. Despite efforts to identify early cachexia and cancer relapse, clinically useful markers are lacking. Recently, we identified the role of muscle-specific ubiquitin ligases Atrogin-1 (MAFbx, FBXO32) and Muscle Ring Finger-1 in the pathogenesis of cardiac atrophy and hypertrophy. We hypothesized that during cachexia, the Atrogin-1 and MuRF1 ubiquitin ligases are released from muscle and migrate to the circulation where they could be detected and serve as a cachexia biomarker. To test this, we induced cachexia in mice using the C26 adenocarcinoma cells or vehicle (control). Body weight, tumor volume, and food consumption were measured from inoculation until ~day 14 to document cachexia. Western blot analysis of serum identified the presence of Atrogin-1 and MuRF1 with unique post-translational modifications consistent with mono- and poly- ubiquitination of Atrogin-1 and MuRF1 found only in cachectic serum. These findings suggest that both increased Atrogin-1 and the presence of unique post-translational modifications may serve as a surrogate marker specific for cachexia.