Transforming growth factor beta1 and aldosterone

Four-week inhibition of the renin-angiotensin system in spontaneously hypertensive rats results in persistently lower blood pressure with reduced kidney renin and changes in expression of relevant gene networks

AIMS

Prevention of human hypertension is an important challenge and has been achieved in experimental models. Brief treatment with renin-angiotensin system (RAS) inhibitors permanently reduces the genetic hypertension of the spontaneously hypertensive rat (SHR). The kidney is involved in this fascinating phenomenon, but relevant changes in gene expression are unknown.

METHODS AND RESULTS

In SHR, we studied the effect of treatment between 10 and 14 weeks of age with the angiotensin receptor blocker, losartan, or the angiotensin-converting enzyme inhibitor, perindopril [with controls for non-specific effects of lowering blood pressure (BP)], on differential RNA expression, DNA methylation, and renin immunolabelling in the kidney at 20 weeks of age. RNA sequencing revealed a six-fold increase in renin gene (Ren) expression during losartan treatment (P < 0.0001). Six weeks after losartan, arterial pressure remained lower (P = 0.006), yet kidney Ren showed reduced expression by 23% after losartan (P = 0.03) and by 43% after perindopril (P = 1.4 × 10-6) associated with increased DNA methylation (P = 0.04). Immunolabelling confirmed reduced cortical renin after earlier RAS blockade (P = 0.002). RNA sequencing identified differential expression of mRNAs, miRNAs, and lncRNAs with evidence of networking and co-regulation. These included 13 candidate genes (Grhl1, Ammecr1l, Hs6st1, Nfil3, Fam221a, Lmo4, Adamts1, Cish, Hif3a, Bcl6, Rad54l2, Adap1, Dok4), the miRNA miR-145-3p, and the lncRNA AC115371. Gene ontogeny analyses revealed that these networks were enriched with genes relevant to BP, RAS, and the kidneys.

CONCLUSION

Early RAS inhibition in SHR resets genetic pathways and networks resulting in a legacy of reduced Ren expression and BP persisting for a minimum of 6 weeks.

Differential Role of Aldosterone and Transforming Growth Factor Beta-1 in Cardiac Remodeling

Angiotensin II, a major culprit in cardiovascular disease, activates mediators that are also involved in pathological cardiac remodeling. In this context, we aimed at investigating the effects of two of them: aldosterone (Ald) and transforming growth factor beta-1 (TGF-β1) in an in vivo model. Six-week-old male wild-type (WT) and TGF-β1-overexpressing transgenic (TGF-β1-TG) mice were infused with subhypertensive doses of Ald for 2 weeks and/or treated orally with eplerenone from postnatal day 21. Thehearts' ventricles were examined by morphometry, immunoblotting to assess the intracellular signaling pathways and RT qPCR to determine hypertrophy and fibrosis marker genes. The TGF-β1-TG mice spontaneously developed cardiac hypertrophy and interstitial fibrosis and exhibited a higher baseline phosphorylation of p44/42 and p38 kinases, fibronectin and ANP mRNA expression. Ald induced a comparable increase in the ventricular-heart-weight-to-body-weight ratio and cardiomyocyte diameter in both strains, but a less pronounced increase in interstitial fibrosis in the transgenic compared to the WT mice (23.6% vs. 80.9%, p < 0.005). Ald increased the phosphorylation of p44/42 and p38 in the WT but not the TGF-β1-TG mice. While the eplerenone-enriched chow partially prevented Ald-induced cardiac hypertrophy in both genotypes and interstitial fibrosis in the WT controls, it completely protected against additional fibrosis in transgenic mice. Ald appears to induce cardiac hypertrophy independently of TGF-β1, while in the case of fibrosis, the downstream signaling pathways of these two factors probably converge.

Corticosteroid-binding Globulin (SERPINA6) Establishes Postpubertal Sex Differences in Rat Adrenal Development

Encoded by SerpinA6, plasma corticosteroid-binding globulin (CBG) transports glucocorticoids and regulates their access to cells. We determined how CBG influences plasma corticosterone and adrenal development in rats during the pubertal to adult transition using CRISPR/cas9 to disrupt SerpinA6 gene expression. In the absence of CBG, total plasma corticosterone levels were ∼80% lower in adult rats of both sexes, with a greater absolute reduction in females than in males. Notably, free corticosterone and adrenocorticotropic hormone were comparable between all groups. Between 30 and 90 days of age, wild-type female rats showed increases in adrenal weight and the size of the corticosterone-producing region, the zona fasciculata (zf), in tandem with increases in plasma CBG and corticosterone concentrations, whereas no such changes were observed in males. This sex difference was lost in rats without CBG, such that adrenal growth and zf expansion were similar between sexes. The sex-specific effects of CBG on adrenal morphology were accompanied by remarkable changes in gene expression: ∼40% of the adrenal transcriptome was altered in females lacking CBG, whereas almost no effect was seen in males. Over half of the adrenal genes that normally exhibit sexually dimorphic expression after puberty were similarly expressed in males and females without CBG, including those responsible for cholesterol biosynthesis and mobilization, steroidogenesis, and growth. Rat adrenal SerpinA6 transcript levels were very low or undetectable. Thus, sex differences in adrenal growth, morphology and gene expression profiles that emerge during puberty in rats are dependent on concomitant increases in plasma CBG produced by the liver.

The mechanism of myocardial fibrosis is ameliorated by myocardial infarction-associated transcript through the PI3K/Akt signaling pathway to relieve heart failure

OBJECTIVE

This study aimed to investigate the role of long noncoding RNA (LncRNA) myocardial infarction-associated transcript (MIAT) in a heart failure (HF) model in vivo and in vitro by regulating the PI3K/Akt signaling pathway.

METHODS

We established HF models in vivo and in vitro and evaluated the collagen content of these models and other factors.

RESULTS

We found that when LncRNA MIAT was silenced, vascular endothelial growth factor, phosphorylated protein kinase B (Akt), and phosphorylated phosphoinositide 3-kinase (PI3K) mRNA and protein levels were significantly downregulated, which suggested that MIAT activated the PI3K/Akt signaling pathway. Akt and PI3K expression was not significantly changed. We also found that when LncRNA MIAT was silenced, collagen expression was significantly downregulated. This finding suggested that MIAT promoted myocardial fibrosis during the development of HF. The levels of inflammatory factors were also significantly reduced with silencing of LncRNA MIAT. This finding suggested that MIAT promoted the expression of inflammatory factors in myocardial fibrosis by activating the PI3K/Akt signaling pathway.

CONCLUSION

This study indicates that silencing LncRNA MIAT may improve myocardial fibrosis and alleviate HF through the PI3K/Akt signaling pathway, which may be helpful for patients with HF to obtain a better therapeutic effect.

Induction of LOX by TGF-β1/Smad/AP-1 signaling aggravates rat myocardial fibrosis and heart failure

This study aims to evaluate the efficacy of lysyl oxidase (LOX) inhibition in regulating rat myocardial fibrosis and chronic heart failure (CHF) and to validate the regulation of LOX by TGF-β1/Smad2/3 signaling in this process. A rat model of CHF was established by abdominal aortic coarctation. The renin-angiotensin-aldosterone system (RAAS) indexes (PRA, ACE2, Ang II, and ALD), cardiac function indicators (LVEF, LVFS, SAP, DAP, and LVEDP), ventricular remodeling- and fibrosis-related indicators (hydroxyproline, collagen deposition,and MMP-2/9), and morphological changes of myocardial tissues were examined. Rat cardiac fibroblasts (RCFs) were used in vitro assays. CHF patients showed increased LOX activity, accompanied by activated RAAS and TGF-β1. Furthermore, inhibition of LOX by β-aminopropionitrile (BAPN) mitigated the RAAS activation and attenuated cardiac dysfunction, ventricular remodeling, myocardial fibrosis, and collagen deposition in CHF rats. Moreover, TGF-β1 signaling diminished the LOX inhibition-mediated antiheart failure effect. Further assays showed that TGF-β1/Smad2/3 signaling increased expression of c-jun (AP-1 transcription factor subunit), which transcriptionally induced LOX expression. Additionally, BAPN abrogated the TGF-β1-mediated increase in cell proliferation and levels of MMP-2/9 and collagen I/III in RCFs. In conclusion, LOX can be induced by TGF-β1/Smad/AP-1 signaling and LOX inhibition attenuates rat myocardial fibrosis and CHF.

Strength training attenuates post-infarct cardiac dysfunction and remodeling

Post-myocardial infarction (MI) exercise has been employed to improve cardiac function. However, most studies have focused on endurance training (Et). Although Et has been reported to preserve cardiac function, evidence suggests that Et increases left ventricle (LV) interior dimensions as a result of albumin-induced plasma expansion. In contrast, strength training (St) induces concentric cardiac hypertrophy and improved cardiac function without causing ventricular dilation. Therefore, the purpose of this study was to investigate the effects of St on cardiac function and remodeling in rats with MI. MI was surgically induced in 7-week-old rats via ligation of the coronary artery. Survivors were assigned to two experimental groups, MI-Sed (No exercise; n = 9), MI-St (St; n = 10), with a Sham group (no MI, no St; n = 9). MI-St rats began training 1-week post-MI by climbing a ladder with weights for 10 weeks. Echocardiographic measurements were performed prior to, and following exercise training, while in vivo LV hemodynamic analysis was conducted at the end of the experimental period. Our data revealed that St induced shortening of the LV end-diastolic dimension in the MI-St group compared with the MI-Sed group (P < 0.05). The peak velocities of contraction (+ dP/dt max) and relaxation (- dP/dt max) were significantly greater in the MI-St group than the MI-Sed group (P < 0.05). These training effects contributed to the improved fractional shortening (%FS). Our results demonstrate that St may be beneficial for post-MI by attenuating LV dilation and concomitant cardiac dysfunction associated with MI.

Association of Papillary Thyroid Carcinoma with Primary Aldosteronism

Objective The association of primary aldosteronism (PA) with thyroid disease has already been suggested. The aim of this study was to examine the presence of PA in patients with papillary thyroid carcinoma (PC) and to characterize such PC patients with PA. Methods We examined the presence of PA in 81 consecutive patients with PC, whose random sitting blood pressure (BP) was ≥140/90 mmHg in the office (n= 68), who had an incidental adrenal tumor or adrenal enlargement (n=9), or who showed hypokalemia (n=4). Thirty-one of these 81 patients had been treated with anti-hypertensive drugs. The plasma aldosterone concentration (PAC) and plasma renin activity (PRA) were first measured before operation in 16 patients and after operation in 65 patients. PA was diagnosed according to the guidelines of the Japan Endocrine Society. Results Forty patients with PC with a random PAC/PRA ratio of over 200 were subjected to a further study (12 of these patients had been treated with anti-hypertensive drugs). Ultimately, 15 patients with PC were diagnosed with PA. Adrenal venous sampling was done in 9 out of 15 patients with PC associated with PA. No patients were diagnosed as having unilateral lesions. Among the 15 patients, white-coat hypertension was observed in 5 patients, and normotension was observed in 1 patient. Conclusion These findings suggest that the prevalence of PA may be high among patients with PC. An active examination is needed to detect PA, as its signs and symptoms may be mild in patients with PC associated with hypertension.

Quantitative Serum Proteomic Analysis of Essential Hypertension Using iTRAQ Technique

Essential hypertension (EH) is a risk factor for some severe diseases. This study aimed to screen out serum special proteins and seek interaction between them, which would provide new therapeutic targets and elucidate the comprehensive pathophysiological mechanism for EH. Patients with EH (Group A, n = 47) and healthy controls (HC) (Group B, n = 47) were recruited in this study. Serums from the two groups were analyzed with isobaric tags for relative and absolute quantitation coupled two-dimensional liquid chromatography followed by electrospray ionization-tandem mass spectrometry technique, while the candidate special proteins were verified with ELISA and western blot. A total of 404 proteins were identified, of which 30 proteins were upregulated (>1.2-fold, p < 0.05) and 81 proteins were downregulated (<0.833-fold, p < 0.05) compared with HC group. With GO, KEGG analysis, and literature retrieval, 4 proteins, cathepsin G, transforming growth factor beta-1, hyaluronidase-1, and kininogen-1, were found jointly involved in the renin-angiotensin-aldosterone system and kallikrein-kinin system. The profiles of these 4 candidate proteins were confirmed with ELISA and western blot. The concentration variation of these 4 proteins could better predict the occurrence and illustrate the pathophysiological mechanism of EH. And their discovery may help pave the way for exploring new therapies of EH.

Aldosterone-to-Renin Ratio Is Associated With Reduced 24-Hour Heart Rate Variability and QTc Prolongation in Hypertensive Patients

Aldosterone is considered to exert direct effects on the myocardium and the sympathetic nervous system. Both QT time and heart rate (HR) variability (HRV) are considered to be markers of arrhythmic risk and autonomous dysregulation. In this study, we investigated the associations between aldosterone, QT time, and HRV in patients with arterial hypertension.We recruited 477 hypertensive patients (age: 60.2 ± 10.2 years; 52.3% females) with a mean systolic/diastolic 24-hour ambulatory blood pressure monitoring (ABPM) value of 128 ± 12.8/77.1 ± 9.2 mmHg and with a median of 2 (IQR: 1-3) antihypertensive agents. Patients were recruited from the outpatient clinic at the Department of Internal Medicine of the Medical University of Graz, Austria. Blood samples, 24-hour HRV derived from 24-hour blood pressure monitoring (ABPM) and ECG's were obtained. Plasma aldosterone and plasma renin concentrations were measured by means of a radioimmunoassay. Twenty-four-hour urine specimens were collected in parallel with ABPM.Mean QTc was 423.3 ± 42.0 milliseconds for males and 434.7 ± 38.3 milliseconds for females. Mean 24H-HR and 24H-HRV was 71.9 ± 9.8 and 10.0 ± 3.6 bpm, respectively. In linear regression analyses adjusted for age, sex, body mass index, ABPM, and current medication, aldosterone to active renin ratio (AARR) was significantly associated with the QTc interval, a marker for cardiac repolarization abnormalities (mean = 426 ± 42.4 milliseconds; β-coefficient = 0.121; P = 0.03) as well as with the 24-hour heart rate variability a surrogate for autonomic dysfunction (median = 9.67 [IQR = 7.38-12.22 bpm]; β-coefficient = -0.133; P = 0.01).In hypertensive patients, AARR is significantly related to QTc prolongation as well as HRV. Further studies investigating the effects of mineralocorticoid receptor blocker and aldosterone synthase inhibitors on QTc and HRV are warranted.