Obesity and heterozygous endothelial overexpression of prepro-endothelin-1 modulate responsiveness of mouse main and segmental renal arteries to vasoconstrictor agents

Investigating the Cardiovascular Benefits of Dapagliflozin: Vasodilatory Effect on Isolated Rat Coronary Arteries

Dapagliflozin, a sodium-glucose co-transporter 2 (SGLT2) inhibitor, is an antidiabetic medication that reduces blood glucose. Although it is well known that dapagliflozin has additional benefits beyond glycemic control, such as reducing blood pressure and lowering the risk of cardiovascular events, no sufficient research data are available on the direct effect of dapagliflozin on cardiovascular function. Thus, in this study, we investigated the direct vascular effect of dapagliflozin on isolated rat coronary arteries. The left descending coronary arteries of 13-week-old male Sprague Dawley rats were cut into segments 2-3 mm long and mounted in a multi-wire myography system to measure isometric tension. Dapagliflozin effectively reduced blood vessel constriction induced by U-46619 (500 nM) in coronary arteries regardless of the endothelium. Treatment with an eNOS inhibitor (L-NNA, 100 μM), sGC inhibitor (ODQ, 5 μM), or COX inhibitor (indomethacin, 3 μM) did not affect the vasodilation induced by dapagliflozin. The application of a Ca2+-activated K+ channel (KCa) blocker (TEA, 2 mM), voltage-dependent K+ channel (KV) blocker (4-AP, 2 mM), ATP-sensitive K+ channel blocker (KATP) glibenclamide (3 μM), and inward-rectifier K+ channel (KIR) blocker (BaCl2, 30 μM) did not affect the dapagliflozin-induced vasodilation either. The treatment with dapagliflozin decreased contractile responses induced by the addition of Ca2+, which suggested that the extracellular Ca2+ influx was inhibited by dapagliflozin. Treatment with dapagliflozin decreased the phosphorylation level of the 20 kDa myosin light chain (MLC20) in vascular smooth muscle cells. In the present study, we found that dapagliflozin has a significant vasodilatory effect on rat coronary arteries. Our findings suggest a novel pharmacologic approach for the treatment of cardiovascular diseases in diabetic patients through the modulation of Ca2+ homeostasis via dapagliflozin administration.

The impact of obesity on ocular hemodynamics and choroidal thickness

Background

Obesity affects microvascular structures. The effect of obesity on the ocular vascular system can be evaluated by changes in the choroidal thickness (CT) and retrobulbar blood flow (RBF).

Objectives

To evaluate the CT and RBF parameters in obese patients with various body mass index (BMI) values and compare these parameters with normal weight, healthy subjects.

Design

A prospective study.

Methods

The study included 102 eyes of 102 female patients. Patients were divided into three groups according to BMI as group 1 with a BMI of 18.5-24.99 (n = 32), normal weight group; group 2 with a BMI of 30-34.99 (n = 35), as obese class I; and group 3 with a BMI of 35-39.99 (n = 35), as obese class II. The peak systolic velocity (PSV), end-diastolic velocity (EDV), resistive index, and pulsatility index values of the central retinal artery (CRA) and ophthalmic artery (OA) were evaluated with color Doppler ultrasonography. CT was measured at the subfoveal area and at 500-µm intervals nasal and temporal to the fovea up to a distance of 1500 µm by using the enhanced depth imaging technique of optical coherence tomography. Intraocular pressure (IOP) was measured with a Goldmann applanation tonometry.

Results

There was a significant difference in IOP values within the groups with the highest values in group 3 (17.6 ± 2.1 mmHg) and the lowest in group 1 (12.4 ± 1.7 mmHg). The CT in groups 2 and 3 was found to be statistically significantly lower than that in group 1 at all measurement points (p < 0.001). There was a statistically significant negative correlation between CT at all measurement points and BMI (p < 0.001). The mean CRA PSV, EDV, and OA EDV values were statistically significantly lower in each obese group than those values in group 1 (p < 0.001). The OA PSV values were significantly lower in group 3 (36.5 ± 5.9 cm/s) than those in group 2 (43.8 ± 4 cm/s) and group 1 (44.6 ± 5.2 cm/s) (p < 0.001). Also, significant associations were found between BMI and CRA PSV, CRA EDV, and OA PSV values (p < 0.001).

Conclusion

Obesity may predispose to eye pathologies by changing the ocular vascular circulation.

Association of choroidal structure and body mass index in an adult population

PURPOSE

To determine the relation of choroidal structural parameters and body mass index (BMI) in an adult population.

METHODS

About 144 eyes of 144 healthy individuals were incorporated. There were four groups according to BMI values: Group 1 (⩽18.5), group 2 (18.6-24.9), group 3 (25.0-29.9), and group 4 (30.0-34.9). The enhanced depth imaging optical coherence tomography images were binarized using Image-J software. Choroidal thickness (CT), circumscribed choroidal area (CCA), luminal area (LA), stromal area (SA), and choroidal vascularity index (CVI) were calculated.

RESULTS

Mean subfoveal, nasal, and temporal CT were lower in group 4 rather than group 1 (p = 0.032, p = 0.001, and p < 0.001, respectively). Mean nasal and temporal CT also showed a decrease in group 4 as compared to group 2 (p = 0.04 and p = 0.039). Mean CCA and LA were decreased in group 4 in comparison to group 3 (p = 0.001 and p = 0.001), group 2 (p < 0.001 and p < 0.001), and group 1 (p = 0.001 and p < 0.001). Mean SA showed a decrease only in group 3 rather than group 2 (p = 0.021) and group 1 (p = 0.008). Mean CVI was decreased in group 3 and group 4 in comparison to group 1 (p < 0.001 and p < 0.001) and group 2 (p = 0.002 and p < 0.001).

CONCLUSION

Increased BMI percentile was associated with a decrease in CT and structural parameters.

Endothelin: 30 Years From Discovery to Therapy

Discovered in 1987 as a potent endothelial cell-derived vasoconstrictor peptide, endothelin-1 (ET-1), the predominant member of the endothelin peptide family, is now recognized as a multifunctional peptide with cytokine-like activity contributing to almost all aspects of physiology and cell function. More than 30 000 scientific articles on endothelin were published over the past 3 decades, leading to the development and subsequent regulatory approval of a new class of therapeutics-the endothelin receptor antagonists (ERAs). This article reviews the history of the discovery of endothelin and its role in genetics, physiology, and disease. Here, we summarize the main clinical trials using ERAs and discuss the role of endothelin in cardiovascular diseases such as arterial hypertension, preecclampsia, coronary atherosclerosis, myocardial infarction in the absence of obstructive coronary artery disease (MINOCA) caused by spontaneous coronary artery dissection (SCAD), Takotsubo syndrome, and heart failure. We also discuss how endothelins contributes to diabetic kidney disease and focal segmental glomerulosclerosis, pulmonary arterial hypertension, as well as cancer, immune disorders, and allograft rejection (which all involve ET_A autoantibodies), and neurological diseases. The application of ERAs, dual endothelin receptor/angiotensin receptor antagonists (DARAs), selective ET_B agonists, novel biologics such as receptor-targeting antibodies, or immunization against ET_A receptors holds the potential to slow the progression or even reverse chronic noncommunicable diseases. Future clinical studies will show whether targeting endothelin receptors can prevent or reduce disability from disease and improve clinical outcome, quality of life, and survival in patients.

Mitoprotection preserves the renal vasculature in porcine metabolic syndrome

NEW FINDINGS

What is the central question of this study? We hypothesized that chronic mitoprotection would decrease renal vascular remodelling and dysfunction in swine metabolic syndrome. What is the main finding and its importance? This study shows that experimental metabolic syndrome exerts renal microvascular and endothelial cell mitochondrial injury, which were attenuated by mitoprotection, underscoring the contribution of mitochondrial injury to the pathogenesis of metabolic syndrome-induced vascular damage.

ABSTRACT

The metabolic syndrome (MetS) induces intrarenal microvascular disease, which may involve mitochondrial injury. The mitochondrial cardiolipin-targeting peptide elamipretide (ELAM) improves the microcirculation in post-stenotic kidneys, but its ability to attenuate MetS-induced renal vascular damage is unknown. We hypothesized that chronic treatment with ELAM would decrease renal vascular remodelling and function in swine MetS. Pigs were studied after 16 weeks of diet-induced MetS, MetS treated for the last 4 weeks with daily injections of ELAM (0.1 mg kg^-1 ), and lean control (Lean) animals (n = 6 each). Single-kidney regional perfusion, blood flow and glomerular filtration rate were measured with multi-detector computed tomography (CT). Peritubular capillary (PTC) endothelial cell (EC) mitochondrial density and cardiolipin content were assessed in situ, as were PTC-EC apoptosis and oxidative stress. The spatial density of PTCs (Haematoxylin and Eosin staining) and renal microvessels (micro-CT), and renal artery endothelial function (organ bath) were characterized. Regional perfusion and serum creatinine were preserved in MetS pigs, but renal blood flow and glomerular filtration rate were higher compared with Lean. Mitochondrial density and cardiolipin content were diminished in MetS PTC-ECs, but improved in ELAM-treated pigs, as did PTC density. Elamipretide also attenuated PTC-EC oxidative stress and apoptosis. Furthermore, ELAM improved renal microvascular density, decreased microvascular remodelling and restored endothelial nitric oxide expression and endothelium-dependent relaxation of renal artery segments. In conclusion, MetS-induced mitochondrial alterations might contribute to renal PTC and microvascular loss and might impair renal artery endothelial function in pigs. Mitoprotection with ELAM preserved a hierarchy of renal vessels, underscoring its potential to ameliorate renal vascular injury in MetS.

Endothelial overexpression of endothelin-1 modulates aortic, carotid, iliac and renal arterial responses in obese mice

Endothelin-1 (ET-1) is essential for mammalian development and life, but it has also been implicated in increased cardiovascular risk under pathophysiological conditions. The aim of this study was to determine the impact of endothelial overexpression of the prepro-endothelin-1 gene on endothelium-dependent and endothelium-independent responses in the conduit and renal arteries of lean and obese mice. Obesity was induced by high-fat-diet (HFD) consumption in mice with Tie-1 promoter-driven, endothelium-specific overexpression of the prepro-endothelin-1 gene (TET^het) and in wild-type (WT) littermates on a C57BL/6N background. Isometric tension was measured in rings (with endothelium) of the aorta (A), carotid (CA) and iliac (IA) arteries as well as the main (MRA) and segmental renal (SRA) arteries; all experiments were conducted in the absence or presence of L-NAME and/or the COX inhibitor meclofenamate. The release of prostacyclin and thromboxane A2 was measured by ELISA. In the MRA, TET^het per se increased contractions to endothelin-1, but the response was decreased in SRA in response to serotonin; there were also improved relaxations to acetylcholine but not insulin in the SRA in the presence of L-NAME. HFD per se augmented the contractions to endothelin-1 (MRA) and to the thromboxane prostanoid (TP) receptor agonist U46619 (CA, MRA) as well as facilitated relaxations to isoproterenol (A). The combination of HFD and TET^het overexpression increased the contractions of MRA and SRA to vasoconstrictors but not in the presence of meclofenamate; this combination also augmented further relaxations to isoproterenol in the A. Contractions to endothelin-1 in the IA were prevented by endothelin-A receptor antagonist BQ-123 but only attenuated in obese mice by BQ-788. The COX-1 inhibitor FR122047 abolished the contractions of CA to acetylcholine. The release of prostacyclin during the latter condition was augmented in samples from obese TET^het mice and abolished by FR122047. These findings suggest that endothelial TET^het overexpression in lean animals has minimal effects on vascular responsiveness. However, if comorbid with obesity, endothelin-1-modulated, prostanoid-mediated renal arterial dysfunction becomes apparent.

Effects of age and caloric restriction in the vascular response of renal arteries to endothelin-1 in rats

Cardiovascular alterations are the most prevalent cause of impaired physiological function in aged individuals with kidney being one the most affected organs. Aging-induced alterations in renal circulation are associated with a decrease in endothelium-derived relaxing factors such as nitric oxide (NO) and with an increase in contracting factors such as endothelin-1(ET-1). As caloric restriction (CR) exerts beneficial effects preventing some of the aging-induced alterations in cardiovascular system, the aim of this study was to analyze the effects of age and caloric restriction in the vascular response of renal arteries to ET-1 in aged rats. Vascular function was studied in renal arteries from 3-month-old Wistar rats fed ad libitum (3m) and in renal arteries from 8-and 24-month-old Wistar rats fed ad libitum (8m and 24m), or subjected to 20% caloric restriction during their three last months of life (8m-CR and 24m-CR). The contractile response to ET-1 was increased in renal arteries from 8m and 24m compared to 3m rats. ET-1-induced contraction was mediated by ET-A receptors in all experimental groups and also by ET-B receptors in 24m rats. Caloric restriction attenuated the increased contraction to ET-1 in renal arteries from 8m but not from 24m rats possibly through NO release proceeding from ET-B endothelial receptors. In 24m rats, CR did not attenuate the aging-increased response of renal arteries to ET-1, but it prevented the aging-induced increase in iNOS mRNA levels and the aging-induced decrease in eNOS mRNA levels in arterial tissue. In conclusion, aging is associated with an increased response to ET-1 in renal arteries that is prevented by CR in 8m but not in 24m rats.

Constrictor prostanoids and uridine adenosine tetraphosphate: vascular mediators and therapeutic targets in hypertension and diabetes

Vascular dysfunction plays a pivotal role in the development of systemic complications associated with arterial hypertension and diabetes. The endothelium, or more specifically, various factors derived from endothelial cells tightly regulate vascular function, including vascular tone. In physiological conditions, there is a balance between endothelium-derived factors, that is, relaxing factors (endothelium-derived relaxing factors; EDRFs) and contracting factors (endothelium-derived contracting factors; EDCFs), which mediate vascular homeostasis. However, in disease states, such as diabetes and arterial hypertension, there is an imbalance between EDRF and EDCF, with a reduction of EDRF signalling and an increase of EDCF signalling. Among EDCFs, COX-derived vasoconstrictor prostanoids play an important role in the development of vascular dysfunction associated with hypertension and diabetes. Moreover, uridine adenosine tetraphosphate (Up4 A), identified as an EDCF in 2005, also modulates vascular function. However, the role of Up4 A in hypertension- and diabetes-associated vascular dysfunction is unclear. In the present review, we focused on experimental and clinical evidence that implicate these two EDCFs (vasoconstrictor prostanoids and Up4 A) in vascular dysfunction associated with hypertension and diabetes.

Endothelin XIII

Twenty-five years ago, a groundbreaking paper from Tsukuba University in Japan was published, identifying the sequence of the endothelin gene and peptide (Nature 332, 411-415, 1988). This work opened the way for the discovery of the endothelin receptors and the development of orally active endothelin receptor antagonists (ERAs). Today, ERAs are part of medical therapy of patients around the world for the treatment of pulmonary arterial hypertension. Since the discovery of endothelin, about 1000 papers per year have been published, with more than 27,000 articles available today. Many important and break-through findings presented in the endothelin conferences have been published in the conferences' proceedings. Endothelin XIII is the proceedings of the Thirteenth International Conference on Endothelin, held at Tokyo Campus of Tsukuba University, Japan, in September 2013. At the conference, the 25th anniversary of endothelin's discovery was celebrated and articles produced from data presented at the conference are compiled in this Special Issue of Life Sciences. Endothelin XIII includes more than fifty articles, including review articles by experts in the field and numerous original research articles. As the Editors of this special issue, we are proud to present Endothelin XIII and wish the field continued growth for the benefit of patients and for the advancement of biomedical science.