Expression of endothelin type B receptors (EDNRB) on smooth muscle cells is controlled by MKL2, ternary complex factors, and actin dynamics

The endothelin type B receptor (ET_B or EDNRB) is highly plastic and is upregulated in smooth muscle cells (SMCs) by arterial injury and following organ culture in vitro. We hypothesized that this transcriptional plasticity may arise, in part, because EDNRB is controlled by a balance of transcriptional inputs from myocardin-related transcription factors (MRTFs) and ternary complex factors (TCFs). We found significant positive correlations between the TCFs ELK3 and FLI1 versus EDNRB in human arteries. The MRTF MKL2 also correlated with EDNRB. Overexpression of ELK3, FLI1, and MKL2 in human coronary artery SMCs promoted expression of EDNRB, and the effect of MKL2 was antagonized by myocardin (MYOCD), which also correlated negatively with EDNRB at the tissue level. Silencing of MKL2 reduced basal EDNRB expression, but depolymerization of actin using latrunculin B (LatB) or overexpression of constitutively active cofilin, as well as treatment with the Rho-associated kinase (ROCK) inhibitor Y27632, increased EDNRB in a MEK/ERK-dependent fashion. Transcript-specific primers indicated that the second EDNRB transcript (EDNRB_2) was targeted, but this promoter was largely unresponsive to LatB and was inhibited rather than stimulated by MKL2 and FLI1, suggesting distant control elements or an indirect effect. LatB also reduced expression of endothelin-1, but supplementation experiments argued that this was not the cause of EDNRB induction. EDNRB finally changed in parallel with ELK3 and FLI1 in rat and human carotid artery lesions. These studies implicate the actin cytoskeleton and ELK3, FLI1, and MKL2 in the transcriptional control of EDNRB and increase our understanding of the plasticity of this receptor.

Adipokine Profiling in Adult Women With Central Obesity and Hypertension

Central obesity and hypertension are common risk factors for the metabolic syndrome, cardiovascular and renal diseases. Studies have shown that it is more difficult to control blood pressure and prevent end-organ damage in obese individuals with hypertension compared to their non-obese counterparts, especially among women. Obese females have a 6 times higher risk of developing hypertension than non-obese females while obese males are at a 1.5 times higher risk of developing hypertension, compared to their non-obese counterparts. Indeed, the inter-relationship between obesity and hypertension is unclear. Adipokines have been proposed to play a mediating role in the relationship between obesity and hypertension and are involved in the pathogenesis of metabolic diseases. Therefore, this study sought to determine the role of adipokines (adiponectin, plasminogen activator inhibitor-1, leptin, and tumor necrosis factor-α) in hypertensive Hong Kong Chinese women with central obesity. A total of 387 women aged 58 ± 11 years who were examined with a 2 × 2 factorial design for central obesity (waist circumference ≥ 80 cm) and hypertension (blood pressure ≥ 140/90 mmHg), were recruited from a pool of 1,492 Hong Kong Chinese adults who were previously screened for metabolic syndrome. Subjects with hyperglycemia, hypertriglyceridemia, and dyslipidemia were excluded to eliminate confounding effects. Our findings revealed that hypertensive women with central obesity had a lower anti-inflammatory status (adiponectin) and a higher pro-inflammatory status (TNF-α) than obese alone or hypertensive alone women. Also, women with central obesity had higher circulatory PAI-1 and leptin concentrations than their non-obese counterparts. We conclude that obesity may shift toward a more pro-inflammatory state and may become more severe in the presence of hypertension or vice versa.

Pro-contractile effects of perivascular fat in health and disease

Perivascular adipose tissue (PVAT) is now recognized as an active player in vascular homeostasis. The expansion of PVAT in obesity and its possible role in vascular dysfunction have attracted much interest. In terms of the regulation of vascular tone and blood pressure, PVAT has been shown to release vasoactive mediators, for instance, angiotensin peptides, reactive oxygen species, chemokines and cytokines. The secretory profile of PVAT is altered by obesity, hypertension and other cardiovascular diseases, leading to an imbalance between its pro-contractile and anti-contractile effects. PVAT adipocytes represent an important source of the mediators, but infiltrating immune cells may become more important under conditions of hypoxia and inflammation. This review describes recent advances in the effects of PVAT on the regulation of vascular tone, highlighting the evidence for a pro-contractile action in health and disease. The role of the endothelium, vascular smooth muscle, immune cells and probably perivascular nerves in PVAT function is also discussed.

LINKED ARTICLES

This article is part of a themed section on Molecular Mechanisms Regulating Perivascular Adipose Tissue - Potential Pharmacological Targets? To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.20/issuetoc.

Markers of oxidative stress in obese men with and without hypertension

OBJECTIVES

The aim of our study was to investigate if the 24-hour excretion of the urinary markers for oxidative stress to DNA and RNA, measured as 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) and 8-oxo-7,8-dihydro-guanosine (8-oxoGuo), respectively, were increased in obese individuals with or without hypertension compared to lean controls.

METHODS

A total of 63 obese hypertensive men (obeseHT), 40 obese normotensive men (obeseNT) and 27 lean normotensive men (leanNT) were included in the study. Body mass index (BMI) was between 20.0 and 24.9 kg/m² in leanNT participants and ≥30 kg/m² in obese participants. Hypertension was defined as a mean 24-hour systolic ambulatory blood pressure (AMBP) ≥ 130 mmHg or a mean 24-hour diastolic AMBP ≥80 mmHg and normotension as mean 24-hour AMBP <130/80 mmHg. Twenty-four hour urinary 8-oxoGuo and 8-oxodG excretion (nmol/24 h) were measured by a validated liquid chromatography-tandem mass spectrometry method (UPLC-MS/MS).

RESULTS

Urinary 8-oxoGuo excretion was (median and [interquartile range]) 30.8 [27.8-32.2] nmol/24 h in leanNT, 36.8 [31.3-40.2] nmol/24 h in obeseNT and 40.6 [31.7-48.5] nmol/24 h in obeseHT. The difference was statistically significant (p = .002) and post hoc tests showed a significant difference between leanNT and obeseHT (p = .001) as well as obeseNT (p = .002), whereas the two obese groups did not differ (p = .6). No statistically significant differences in 8-oxodG concentrations were observed between the three groups (p = .3).

CONCLUSION

The measurement of urinary excretion of 8-oxoGuo suggests that obesity in men, but not hypertension, is associated with increased oxidative damage to RNA.