Mitochondrial fission inhibition protects against hypertension induced by angiotensin II.

Mitochondrial dysfunction has been implicated in various types of cardiovascular disease including hypertension. Mitochondrial fission fusion balance is critical to mitochondrial quality control, whereas enhanced fission has been reported in several models of cardiovascular disease. However, limited information is available regarding the contribution of mitochondrial fission in hypertension. Here, we have tested the hypothesis that inhibition of mitochondrial fission attenuates the development of hypertension and associated vascular remodeling. In C57BL6 mice infused with angiotensin II for 2 weeks, co-treatment of mitochondrial fission inhibitor, mdivi1, significantly inhibited angiotensin II-induced development of hypertension assessed by radiotelemetry. Histological assessment of hearts and aortas showed that mdivi1 inhibited vessel fibrosis and hypertrophy induced by angiotensin II. This was associated with attenuation of angiotensin II-induced decline in mitochondrial aspect ratio seen in both the endothelial and medial layers of aortas. Mdivi1 also mitigated angiotensin II-induced cardiac hypertrophy assessed by heart weight-to-body weight ratio as well as by echocardiography. In ex vivo experiments, mdivi1 inhibited vasoconstriction and abolished the enhanced vascular reactivity by angiotensin II in small mesenteric arteries. Proteomic analysis on endothelial cell culture media with angiotensin II and/or mdivi1 treatment revealed that mdivi1 inhibited endothelial cell hypersecretory phenotype induced by angiotensin II. In addition, mdivi1 attenuated angiotensin II-induced protein induction of periostin, a myofibroblast marker in cultured vascular fibroblasts. In conclusion, these data suggest that mdivi1 prevented angiotensin II-induced hypertension and cardiovascular remodeling via multicellular mechanisms in the vasculature.

Adipocyte Phenotype Flexibility and Lipid Dysregulation.

The prevalence of obesity and associated cardiometabolic diseases continues to rise, despite efforts to improve global health. The adipose tissue is now regarded as an endocrine organ since its multitude of secretions, lipids chief among them, regulate systemic functions. The loss of normal adipose tissue phenotypic flexibility, especially related to lipid homeostasis, appears to trigger cardiometabolic pathogenesis. The goal of this manuscript is to review lipid balance maintenance by the lean adipose tissue's propensity for phenotype switching, obese adipose tissue's narrower range of phenotype flexibility, and what initial factors account for the waning lipid regulatory capacity. Metabolic, hypoxic, and inflammatory factors contribute to the adipose tissue phenotype being made rigid. A better grasp of normal adipose tissue function provides the necessary context for recognizing the extent of obese adipose tissue dysfunction and gaining insight into how pathogenesis evolves.

Targeting mitochondrial fission as a potential therapeutic for abdominal aortic aneurysm.

AIMS: Angiotensin II (AngII) is a potential contributor to the development of abdominal aortic aneurysm (AAA). In aortic vascular smooth muscle cells (VSMCs), exposure to AngII induces mitochondrial fission via dynamin-related protein 1 (Drp1). However, pathophysiological relevance of mitochondrial morphology in AngII-associated AAA remains unexplored. Here, we tested the hypothesis that mitochondrial fission is involved in the development of AAA. METHODS AND RESULTS: Immunohistochemistry was performed on human AAA samples and revealed enhanced expression of Drp1. In C57BL6 mice treated with AngII plus ß-aminopropionitrile, AAA tissue also showed an increase in Drp1 expression. A mitochondrial fission inhibitor, mdivi1, attenuated AAA size, associated aortic pathology, Drp1 protein induction, and mitochondrial fission but not hypertension in these mice. Moreover, western-blot analysis showed that induction of matrix metalloproteinase-2, which precedes the development of AAA, was blocked by mdivi1. Mdivi1 also reduced the development of AAA in apolipoprotein E-deficient mice infused with AngII. As with mdivi1, Drp1+/- mice treated with AngII plus ß-aminopropionitrile showed a decrease in AAA compared to control Drp1+/+ mice. In abdominal aortic VSMCs, AngII induced phosphorylation of Drp1 and mitochondrial fission, the latter of which was attenuated with Drp1 silencing as well as mdivi1. AngII also induced vascular cell adhesion molecule-1 expression and enhanced leucocyte adhesion and mitochondrial oxygen consumption in smooth muscle cells, which were attenuated with mdivi1. CONCLUSION: These data indicate that Drp1 and mitochondrial fission play salient roles in AAA development, which likely involves mitochondrial dysfunction and inflammatory activation of VSMCs.

Endothelial cell-derived extracellular vesicles alter vascular smooth muscle cell phenotype through high-mobility group box proteins.

The vascular endothelium and smooth muscle form adjacent cellular layers that comprise part of the vascular wall. Each cell type can regulate the other's structure and function through a variety of paracrine effectors. Extracellular vesicles (EVs) are released from and transit between cells constituting a novel means of cell-cell communication. Here, we characterized the proteome of EVs released from each vascular cell type and examined the extent to which these vesicles participate in endothelial-vascular smooth muscle cell (VSMC) communication. EVs were collected by ultracentrifugation from media of rat aortic endothelial and smooth muscle cells cultured under serum-free conditions. Vesicle morphology, size and concentration were evaluated by transmission electron microscopy and nanoparticle tracking analysis. Western blot as well as shot gun proteomic analyses revealed sets of proteins common to both endothelial- and smooth muscle-derived EVs as well as proteins unique to each vascular cell type. Functionally, endothelial-derived EVs stimulated vascular cell adhesion molecule-1 (VCAM-1) expression and enhanced leukocyte adhesion in VSMCs while smooth muscle EVs did not elicit similar effects in endothelial cells (ECs). EVs from ECs also induced protein synthesis and senescence in VSMCs. Proteomic analysis of VSMCs following exposure to EC-derived EVs revealed upregulation of several proteins including pro-inflammatory molecules, high-mobility group box (HMGB) 1 and HMGB2. Pharmacological blockade HMGB1 and HMGB2 and siRNA depletion of HMGB1 in smooth muscle cells attenuated VCAM-1 expression and leukocyte adhesion induced by EC EVs. These data suggest that EC-derived EVs can enhance signalling pathways which influence smooth muscle cell phenotype.

Mitochondrial Fission Mediates Endothelial Inflammation.

Endothelial inflammation and mitochondrial dysfunction have been implicated in cardiovascular diseases, yet, a unifying mechanism tying them together remains limited. Mitochondrial dysfunction is frequently associated with mitochondrial fission/fragmentation mediated by the GTPase Drp1 (dynamin-related protein 1). Nuclear factor (NF)-κB, a master regulator of inflammation, is implicated in endothelial dysfunction and resultant complications. Here, we explore a causal relationship between mitochondrial fission and NF-κB activation in endothelial inflammatory responses. In cultured endothelial cells, TNF-α (tumor necrosis factor-α) or lipopolysaccharide induces mitochondrial fragmentation. Inhibition of Drp1 activity or expression suppresses mitochondrial fission, NF-κB activation, vascular cell adhesion molecule-1 induction, and leukocyte adhesion induced by these proinflammatory factors. Moreover, attenuations of inflammatory leukocyte adhesion were observed in Drp1 heterodeficient mice as well as endothelial Drp1 silenced mice. Intriguingly, inhibition of the canonical NF-κB signaling suppresses endothelial mitochondrial fission. Mechanistically, NF-κB p65/RelA seems to mediate inflammatory mitochondrial fission in endothelial cells. In addition, the classical anti-inflammatory drug, salicylate, seems to maintain mitochondrial fission/fusion balance against TNF-α via inhibition of NF-κB. In conclusion, our results suggest a previously unknown mechanism whereby the canonical NF-κB cascade and a mitochondrial fission pathway interdependently regulate endothelial inflammation.

Postprandial activation of leukocyte-endothelium interaction by fatty acids in the visceral adipose tissue microcirculation.

High-fat diet (HFD)-induced obesity is associated with accumulation of inflammatory cells predominantly in visceral adipose depots [visceral adipose tissue (VAT)] rather than in subcutaneous ones [subcutaneous adipose tissue (SAT)]. The cellular and molecular mechanisms responsible for this phenotypic difference remain poorly understood. Controversy also exists on the overall impact that adipose tissue inflammation has on metabolic health in diet-induced obesity. The endothelium of the microcirculation regulates both the transport of lipids and the trafficking of leukocytes into organ tissue. We hypothesized that the VAT and SAT microcirculations respond differently to postprandial processing of dietary fat. We also tested whether inhibition of endothelial postprandial responses to high-fat meals (HFMs) preserves metabolic health in chronic obesity. We demonstrate that administration of a single HFM or ad libitum access to a HFD for 24 h quickly induces a transient P-selectin-dependent inflammatory phenotype in the VAT but not the SAT microcirculation of lean wild-type mice. Studies in P-selectin-deficient mice confirmed a mechanistic role for P-selectin in the initiation of leukocyte trafficking, myeloperoxidase accumulation, and acute reduction in adiponectin mRNA expression by HFMs. Despite reduced VAT inflammation in response to HFMs, P-selectin-deficient mice still developed glucose intolerance and insulin resistance when chronically fed an HFD. Our data uncover a novel nutrient-sensing role of the vascular endothelium that instigates postprandial VAT inflammation. They also demonstrate that inhibition of this transient postprandial inflammatory response fails to correct metabolic dysfunction in diet-induced obesity.-Preston, K. J., Rom, I., Vrakas, C., Landesberg, G., Etwebe, Z., Muraoka, S., Autieri, M., Eguchi, S., Scalia, R. Postprandial activation of leukocyte-endothelium interaction by fatty acids in the visceral adipose tissue microcirculation.

Vascular ADAM17 (a Disintegrin and Metalloproteinase Domain 17) Is Required for Angiotensin II/ß-Aminopropionitrile-Induced Abdominal Aortic Aneurysm.

Angiotensin II (AngII)-activated epidermal growth factor receptor has been implicated in abdominal aortic aneurysm (AAA) development. In vascular smooth muscle cells (VSMCs), AngII activates epidermal growth factor receptor via a metalloproteinase, ADAM17 (a disintegrin and metalloproteinase domain 17). We hypothesized that AngII-dependent AAA development would be prevented in mice lacking ADAM17 in VSMCs. To test this concept, control and VSMC ADAM17-deficient mice were cotreated with AngII and a lysyl oxidase inhibitor, ß-aminopropionitrile, to induce AAA. We found that 52.4% of control mice did not survive because of aortic rupture. All other surviving control mice developed AAA and demonstrated enhanced expression of ADAM17 in the AAA lesions. In contrast, all AngII and ß-aminopropionitrile-treated VSMC ADAM17-deficient mice survived and showed reduction in external/internal diameters (51%/28%, respectively). VSMC ADAM17 deficiency was associated with lack of epidermal growth factor receptor activation, interleukin-6 induction, endoplasmic reticulum/oxidative stress, and matrix deposition in the abdominal aorta of treated mice. However, both VSMC ADAM17-deficient and control mice treated with AngII and ß-aminopropionitrile developed comparable levels of hypertension. Treatment of C57Bl/6 mice with an ADAM17 inhibitory antibody but not with control IgG also prevented AAA development. In conclusion, VSMC ADAM17 silencing or systemic ADAM17 inhibition seems to protect mice from AAA formation. The mechanism seems to involve suppression of epidermal growth factor receptor activation.

Caveolin-1 Deletion Prevents Hypertensive Vascular Remodeling Induced by Angiotensin II.

It has been proposed that membrane microdomains, caveolae, in vascular cells are critical for signal transduction and downstream functions induced by angiotensin II (AngII). We have tested our hypothesis that caveolin-1 (Cav1), a major structural protein of vascular caveolae, plays a critical role in the development of vascular remodeling by AngII via regulation of epidermal growth factor receptor and vascular endothelial adhesion molecule-1. Cav1-/- and control Cav+/+ mice were infused with AngII for 2 weeks to induce vascular remodeling and hypertension. On AngII infusion, histological assessments demonstrated medial hypertrophy and perivascular fibrosis of aorta and coronary and renal arteries in Cav1+/+ mice compared with sham-operated Cav1+/+ mice. AngII-infused Cav1+/+ mice also showed a phenotype of cardiac hypertrophy with increased heart weight to body weight ratio compared with control Cav1+/+ mice. In contrast, Cav1-/- mice infused with AngII showed attenuation of vascular remodeling but not cardiac hypertrophy. Similar levels of AngII-induced hypertension were found in both Cav1+/+ and Cav1-/- mice as assessed by telemetry. In Cav1+/+ mice, AngII enhanced tyrosine-phosphorylated epidermal growth factor receptor staining in the aorta, which was attenuated in Cav1-/- mice infused with AngII. Enhanced Cav1 and vascular endothelial adhesion molecule-1 expression was also observed in aorta from AngII-infused Cav1+/+ mice but not in Cav1-/- aorta. Experiments with vascular cells further provided a potential mechanism for our in vivo findings. These data suggest that Cav1, and presumably caveolae, in vascular smooth muscle and the endothelium plays a critical role in vascular remodeling and inflammation independent of blood pressure or cardiac hypertrophy regulation.

Interleukin-19 decreases leukocyte-endothelial cell interactions by reduction in endothelial cell adhesion molecule mRNA stability.

Vascular endothelial cell (EC) inflammation is a key event in the pathogenesis of multiple vascular diseases. We tested the hypothesis that interleukin-19 (IL-19), an anti-inflammatory Th2 interleukin, could have a direct anti-inflammatory effect on ECs to decrease inflammation. IL-19 can significantly decrease tumor necrosis factor (TNF)-α-driven intracellular adhesion molecule (ICAM)-1 and vascular cell adhesion molecule (VCAM)-1 mRNA and protein abundance in cultured human coronary artery ECs (P < 0.01). IL-19 treatment of ECs, but not monocytes, significantly reduced monocyte adhesion to EC monolayers (P < 0.01). In vivo, systemic administration of IL-19 could significantly reduce TNF-α-induced leukocyte rolling and adhesion in wild-type mice as assayed by intravital microscopy (P < 0.05). IL-19 does not reduce TNF-α-stimulated NF-κB activation in ECs but does decrease serine phosphorylation and cytoplasmic translocation of the mRNA stability factor HuR and significantly reduces stability of ICAM-1 and VCAM-1 mRNA (P < 0.01). These data are the first to report that IL-19 can reduce leukocyte-endothelial cell adhesion and the first to propose reduction in HuR-mediated mRNA stability of ICAM-1 and VCAM-1 as a mechanism. Expression of IL-19 by ECs may represent a protective mechanism to promote resolution of the vascular response to inflammation. Function of IL-19 outside of the immune system is a novel concept, suggesting that resident vascular cells can adopt a Th2 phenotype, and has important ramifications for numerous inflammatory diseases.