Multiphasic changes in smooth muscle Ca2+ transporters during the progression of coronary atherosclerosis.

Ischemic heart disease due to macrovascular atherosclerosis and microvascular dysfunction is the major cause of death worldwide and the unabated increase in metabolic syndrome is a major reason why this will continue. Intracellular free Ca2+ ([Ca2+]i) regulates a variety of cellular functions including contraction, proliferation, migration, and transcription. It follows that studies of vascular Ca2+ regulation in reductionist models and translational animal models are vital to understanding vascular health and disease. Swine with metabolic syndrome (MetS) develop the full range of coronary atherosclerosis from mild to severe disease. Intravascular imaging enables quantitative measurement of atherosclerosis in vivo, so viable coronary smooth muscle (CSM) cells can be dispersed from the arteries to enable Ca2+ transport studies in native cells. Transition of CSM from the contractile phenotype in the healthy swine to the proliferative phenotype in mild atherosclerosis was associated with increases in SERCA activity, sarcoplasmic reticulum Ca2+, and voltage-gated Ca2+ channel function. In vitro organ culture confirmed that SERCA activation induces CSM proliferation. Transition from the proliferative to a more osteogenic phenotype was associated with decreases in all three Ca2+ transporters. Overall, there was a biphasic change in Ca2+ transporters over the progression of atherosclerosis in the swine model and this was confirmed in CSM from failing explanted hearts of humans. A major determinant of endolysosome content in human CSM is the severity of atherosclerosis. In swine CSM endolysosome Ca2+ release occurred through the TPC2 channel. We propose a multiphasic change in Ca2+ transporters over the progression of coronary atherosclerosis.

18F-NaF and 18F-FDG as molecular probes in the evaluation of atherosclerosis.

The early detection of atherosclerotic disease is vital to the effective prevention and management of life-threatening cardiovascular events such as myocardial infarctions and cerebrovascular accidents. Given the potential for positron emission tomography (PET) to visualize atherosclerosis earlier in the disease process than anatomic imaging modalities such as computed tomography (CT), this application of PET imaging has been the focus of intense scientific inquiry. Although 18F-FDG has historically been the most widely studied PET radiotracer in this domain, there is a growing body of evidence that 18F-NaF holds significant diagnostic and prognostic value as well. In this article, we review the existing literature on the application of 18F-FDG and 18F-NaF as PET probes in atherosclerosis and present the findings of original animal and human studies that have examined how well 18F-NaF uptake correlates with vascular calcification and cardiovascular risk.

Intracellular calcium increases in vascular smooth muscle cells with progression of chronic kidney disease in a rat model.

Background: Vascular smooth muscle cells (VSMCs) exhibit phenotypic plasticity, promoting vascular calcification and increasing cardiovascular risk. Changes in VSMC intracellular calcium ([Ca 2+ ] i ) are a major determinant of plasticity, but little is known about changes in [Ca 2+ ] i in chronic kidney disease (CKD). We have previously demonstrated such plasticity in aortas from our rat model of CKD and therefore sought to examine changes in [Ca 2+ ] i during CKD progression. Materials and Methods: We examined freshly isolated VSMCs from aortas of normal rats, Cy/+ rats (CKD) with early and advanced CKD, and advanced CKD rats treated without and with 3% calcium gluconate (CKD + Ca 2+ ) to lower parathyroid hormone (PTH) levels. [Ca 2+ ] i was measured with fura-2. Results: Cy/+ rats developed progressive CKD, as assessed by plasma levels of blood urea nitrogen, calcium, phosphorus, parathyroid hormone and fibroblast growth factor 23. VSMCs isolated from rats with CKD demonstrated biphasic alterations in resting [Ca 2+ ] i : VSMCs from rats with early CKD exhibited reduced resting [Ca 2+ ] i , while VSMCs from rats with advanced CKD exhibited elevated resting [Ca 2+ ] i . Caffeine-induced sarcoplasmic reticulum (SR) Ca 2+ store release was modestly increased in early CKD and was more drastically increased in advanced CKD. The advanced CKD elevation in SR Ca 2+ store release was associated with a significant increase in the activity of the sarco-endoplasmic reticulum Ca 2+ ATPase (SERCA); however, SERCA2a protein expression was decreased in advanced CKD. Following SR Ca 2+ store release, recovery of [Ca 2+ ] i in the presence of caffeine and extracellular Ca 2+ was attenuated in VSMCs from rats with advanced CKD. This impairment, together with reductions in expression of the Na + /Ca 2+ exchanger, suggest a reduction in Ca 2+ extrusion capability. Finally, store-operated Ca 2+ entry (SOCE) was assessed following SR Ca 2+ store depletion. Ca 2+ entry during recovery from caffeine-induced SR Ca 2+ store release was elevated in advanced CKD, suggesting a role for exacerbated SOCE with progressing CKD. Conclusions: With progressive CKD in the Cy/+ rat there is increased resting [Ca 2+ ] i in VSMCs due, in part, to increased SOCE and impaired calcium extrusion from the cell. Such changes may predispose VSMCs to phenotypic changes that are a prerequisite to calcification.

Epicardial Adipose Tissue Removal Potentiates Outward Remodeling and Arrests Coronary Atherogenesis.

BACKGROUND: Pericoronary epicardial adipose tissue (cEAT) serves as a metabolic and paracrine organ that contributes to inflammation and is associated with macrovascular coronary artery disease (CAD) development. Although there is a strong correlation in humans between cEAT volume and CAD severity, there remains a paucity of experimental data demonstrating a causal link of cEAT to CAD. The current study tested the hypothesis that surgical resection of cEAT attenuates inflammation and CAD progression. METHODS: Female Ossabaw miniature swine (n = 12) were fed an atherogenic diet for 8 months and randomly allocated into sham (n = 5) or adipectomy (n = 7) groups. Both groups underwent a thoracotomy, opening of the pericardial sac, and placement of radioopaque clips to mark the proximal left anterior descending artery. Adipectomy swine underwent removal of 1 to 1.5 cm2 of cEAT from the proximal artery. After sham or adipectomy, CAD severity was assessed with intravascular ultrasonography. Swine recovered for an additional 3 months on an atherogenic diet, and CAD was assessed immediately before euthanasia. Artery sections were processed for histologic and immunohistochemical analysis. RESULTS: Severity of CAD as assessed by percent stenosis was reduced in the adipectomy cohort compared with shams; however, plaque size remained unaltered, whereas larger plaque sizes developed in sham-operated swine. Adipectomy resulted in an expanded arterial diameter, similar to the Glagov phenomenon of positive outward remodeling. No differences in inflammatory marker expression were observed. CONCLUSIONS: These data indicate that cEAT resection did not alter inflammatory marker expression, but arrested CAD progression through increased positive outward remodeling and arrest of atherogenesis.

Repeat cross-sectional data on the progression of the metabolic syndrome in Ossabaw miniature swine.

Ossabaw miniature swine were fed an excess calorie, atherogenic diet for 6, 9, or 12 months. Increased body weight, hypertension, and increased plasma cholesterol and triglycerides are described in Table 1. For more detailed interpretations and conclusions about the data, see our associated research study, "Biphasic alterations in coronary smooth muscle Ca(2+) regulation during coronary artery disease progression in metabolic syndrome" McKenney-Drake, et al. (2016) [1].

Biphasic alterations in coronary smooth muscle Ca(2+) regulation in a repeat cross-sectional study of coronary artery disease severity in metabolic syndrome.

BACKGROUND AND AIMS: Coronary artery disease (CAD) is progressive, classified by stages of severity. Alterations in Ca(2+) regulation within coronary smooth muscle (CSM) cells in metabolic syndrome (MetS) have been observed, but there is a lack of data in relatively early (mild) and late (severe) stages of CAD. The current study examined alterations in CSM Ca(2+) regulation at several time points during CAD progression. METHODS: MetS was induced by feeding an excess calorie atherogenic diet for 6, 9, or 12 months and compared to age-matched lean controls. CAD was measured with intravascular ultrasound (IVUS). Intracellular Ca(2+) was assessed with fura-2. RESULTS: IVUS revealed that the extent of atherosclerotic CAD correlated with the duration on atherogenic diet. Fura-2 imaging of intracellular Ca(2+) in CSM cells revealed heightened Ca(2+) signaling at 9 months on diet, compared to 6 and 12 months, and to age-matched lean controls. Isolated coronary artery rings from swine fed for 9 months followed the same pattern, developing greater tension to depolarization, compared to 6 and 12 months (6 months = 1.8 ± 0.6 g, 9 months = 5.0 ± 1.0 g, 12 months = 0.7 ± 0.1 g). CSM in severe atherosclerotic plaques showed dampened Ca(2+) regulation and decreased proliferation compared to CSM from the wall. CONCLUSIONS: These CSM Ca(2+) regulation data from several time points in CAD progression and severity help to resolve the controversy regarding up-vs. down-regulation of CSM Ca(2+) regulation in previous reports. These data are consistent with the hypothesis that alterations in sarcoplasmic reticulum Ca(2+) contribute to progression of atherosclerotic CAD in MetS.

Effect of High-Calcium Diet on Coronary Artery Disease in Ossabaw Miniature Swine With Metabolic Syndrome.

BACKGROUND: Calcium is a shortfall essential nutrient that has been a mainstay of osteoporosis management. Recent and limited findings have prompted concern about the contribution of calcium supplementation to cardiovascular risk. A proposed mechanism is through the acceleration of coronary artery calcification. Determining causality between calcium intake and coronary artery calcification has been hindered by a lack of sensitive methodology to monitor early vascular calcium accumulation. The primary study aim was to assess the impact of high calcium intake on coronary artery calcification using innovative calcium tracer kinetic modeling in Ossabaw swine with diet-induced metabolic syndrome. Secondary end points (in vitro wire myography, histopathology, intravascular ultrasound) assessed coronary disease. METHODS AND RESULTS: Pigs (n=24; aged ≈15 months) were fed an atherogenic diet with adequate calcium (0.33% by weight) or high calcium (1.90% from calcium carbonate or dairy) for 6 months. Following 5 months of feeding, all pigs were dosed intravenously with (41)Ca, a rare isotope that can be measured in serum and tissues at a sensitivity of 10(-18) mol/L by accelerator mass spectrometry. Kinetic modeling evaluated early coronary artery calcification using (41)Ca values measured in serial blood samples (collected over 27 days) and coronary artery samples obtained at sacrifice. Serum disappearance of (41)Ca and total coronary artery (41)Ca accumulation did not differ among groups. Secondary end points demonstrated no treatment differences in coronary artery disease or function. CONCLUSION: There was no detectable effect of high calcium diets (from dairy or calcium carbonate) on coronary artery calcium deposition in metabolic syndrome swine.