Gene expression, function and ischemia tolerance in male and female rat hearts after sub-toxic levels of angiotensin II

An antihypertensive drug-AT1 inhibitor attenuated BRCA development promoted by chronic psychological stress via Ang II/PARP1/FN1 pathway

Chronic psychological stress contributes to the occurrence of cancer and activates the renin-angiotensin system (RAS). However, the mechanisms by which RAS promotes the progression of breast cancer (BRCA) under chronic psychological stress are remain unknown. In this study, we observed elevated levels of Angiotensin II (Ang II) in both serum and BRCA tissue under chronic stress, leading to accelerated BRCA growth in a mouse model. An antihypertensive drug, candesartan (an AT1 inhibitor), effectively attenuated Ang II-induced cell proliferation and metastasis. Utilizing mass spectrometry and weighted gene co-expression network analysis (WGCNA), we identified fibronectin 1 (FN1) as the hub protein involved in chronic stress-Ang II/AT1 axis. Focal adhesion pathway was identified as a downstream signaling pathway activated during the progression of chronic stress. Depletion of FN1 significantly attenuated Ang II-induced proliferation and metastasis of BRCA cells. Poly (ADP-ribose) polymerase 1 (PARP1) was found to bind to the DNA promoter of FN1, leading to the transcription of FN1. Ang II upregulated PARP1 expression, resulting in increased FN1 levels. Recombinant FN1 partially restored the progress of BRCA malignancy induced by the Ang II/PARP1 pathway. In vivo, candesartan reversed the progressive effect of chronic psychological stress on BRCA. In clinical samples, Ang II levels in both serum and tumor tissues are higher in stressed patients compared to control patients. Serum Ang II levels were positively correlated with chronic stress indicators. In conclusion, our study demonstrated that chronic psychological stress accelerates the malignancy of BRCA, and the AT1 inhibitor candesartan counteracts these effects by suppressing the Ang II-AT1 axis and the downstream PARP1/FN1/focal adhesion pathway.

MicroRNA-451a attenuates angiotensin II-induced cardiac fibrosis and inflammation by directly targeting T-box1

Hypertension or angiotensin II (Ang II) induces cardiac inflammation and fibrosis, thus contributing to cardiac remodeling. MicroRNAs (miRNAs) are considered crucial regulators of cardiac homeostasis and remodeling in response to various types of stress. It has been reported that miR-451a is involved in regulating ischemic heart injury. However, its role in Ang II-induced cardiac fibrosis remains unknown. Cardiac remodeling was induced in mice by infusion of low-dose Ang II (490 ng/kg/min) with a minipump for 2 weeks. Echocardiography and histological examinations were performed to evaluate cardiac function and pathological changes. We observed that miR-451a expression was the most significantly downregulated in the hearts of Ang II-infused mice and in both primary cardiac myocytes and fibroblasts. Overexpression of miR-451a in mice significantly attenuated Ang II-induced cardiac fibrosis and inflammation. Conversely, knockdown of miR-451a in mice aggravated this effect. Bioinformatics analysis and a luciferase reporter assay revealed that TBX1 was a direct target of miR-451a. Mechanistically, miR-451a directly targeted TBX1 expression, which inhibited TGF-β1 production in both cardiac myocytes and fibroblasts, inactivating of TGF-β1/SMAD2/3 signaling, inhibiting myofibroblast differentiation and proinflammatory cytokine expression, and leading to attenuation of cardiac fibrosis and inflammation. In conclusion, these results indicate that miR-451a acts as a novel regulator of Ang II-induced cardiac fibrosis and inflammation by directly targeting TBX1, and may be a promising therapeutic target for treating hypertensive cardiac diseases.

Effect of Irisin on Pressure Overload-Induced Cardiac Remodeling

BACKGROUND

Irisin has been considered a prognostic factor in several cardiovascular diseases. Nevertheless, no data are available on the role of irisin in cardiac remodeling.

AIM OF THE STUDY

This study aimed to determine the potential role of irisin in cardiac remodeling and explore potential mechanisms.

METHODS

A total of 40 rats that underwent transverse abdominal aortic constriction (TAC) surgery or sham operation were divided into four groups: sham + saline (NS), sham + irisin, TAC + NS, and TAC + irisin. After 6 weeks of treatment, echocardiography was performed to assess in vivo cardiac morphology. The left ventricular myocardium was prepared and observed by pathological examination. The effect of irisin on cardiomyocyte apoptosis and the expression of oxidative stress and cardiac hypertrophy markers were observed. Then, the effect of irisin on the Akt signaling system was also detected.

RESULTS

The rats in the TAC group displayed obvious signs of cardiac dysfunction and cardiac hypertrophy, and irisin treatment could reverse these changes. Irisin could inhibit the expression of nicotinamide adenine dinucleotide phosphate oxidase 2 and xanthine oxidase in TAC rats and increase the expression of antioxidant enzymes. Furthermore, the expression of phosphorylated protein kinase B (p-Akt), phosphorylated mammalian target of rapamycin (p-mTOR), and phosphorylated glycogen synthase kinase 3β (p-GSK3β) was much higher in the cardiac remodeling groups (p <0.05 vs. sham rats). Irisin could relieve the inhibition effect and reduce the expression level of these three proteins.

CONCLUSIONS

Irisin treatment could significantly improve cardiac remodeling by inhibiting oxidative stress via attenuating the Akt signaling activation.

Cardiac adaptation to hypertension in adult female Dahl salt-sensitive rats is dependent on ovarian function, but loss of ovarian function does not predict early maladaptation

Aim of study was to examine experimentally the adult female hypertensive heart in order to determine the role of ovary function in the response of the heart to salt-dependent hypertension. Dahl salt-sensitive rats, age 12 weeks, with/without ovariectomy were fed a standard (0.3% NaCl) or high-salt diet (8%) for 16 weeks. Mean arterial blood pressure monitored noninvasively in conscious state increased significantly by high salt. Echocardiography was performed at baseline and endpoint. Heart function and molecular changes were evaluated at endpoint by left ventricle catheterization, by sirius red staining for collagen and by gene expression using quantitative RT-PCR for selected genes. At endpoint, significant concentric hypertrophy was present with high salt. Increase in relative wall thickening with high salt compared to normal diet was more pronounced with intact ovaries (0.33 ± 0.02 and 0.57 ± 0.04 vs. 0.29 ± 0.00 and 0.46 ± 0.03) as was the reduction in midwall fractional shortening (20 ± 0.6 and 14 ± 2 vs. 19 ± 0.9 and 18 ± 1). Ovariectomy increased stroke volume and decreased the ratio of mitral peak velocity of early filling (E) to early diastolic mitral annular velocity (E') (E/E' ratio) when compared to hearts from intact rats. High salt increased expression of collagen I and III genes and perivascular collagen in the heart slightly, but % interstitial collagen by sirius red staining remained unchanged in intact rats and decreased significantly by ovariectomy. Added volume load but not deterioration of function or structure characterized the nonfailing hypertensive heart of salt-sensitive females ovariectomized at mature age when compared to corresponding intact females.

Salt loading exacerbates diastolic dysfunction and cardiac remodeling in young female Ren2 rats

OBJECTIVE

Recent data would suggest pre-menopausal insulin resistant women are more prone to diastolic dysfunction than men, yet it is unclear why. We and others have reported that transgenic (mRen2)27 (Ren2) rats overexpressing the murine renin transgene are insulin resistant due to oxidative stress in insulin sensitive tissues. As increased salt intake promotes inflammation and oxidative stress, we hypothesized that excess dietary salt would promote diastolic dysfunction in transgenic females under conditions of excess tissue Ang II and circulating aldosterone levels.

MATERIALS/METHODS

For this purpose we evaluated cardiac function in young female Ren2 rats or age-matched Sprague-Dawley (SD) littermates exposed to a high (4%) salt or normal rat chow intake for three weeks.

RESULTS

Compared to SD littermates, at 10weeks of age, female Ren2 rats fed normal chow showed elevations in left ventricular (LV) systolic pressures, LV and cardiomyocyte hypertrophy, and displayed reductions in LV initial filling rate accompanied by increases in 3-nitrotyrosine content as a marker of oxidant stress. Following 3weeks of a salt diet, female Ren2 rats exhibited no further changes in LV systolic pressure, insulin resistance, or markers of hypertrophy but exaggerated increases in type 1 collagen, 3-nitrotryosine content, and diastolic dysfunction. These findings occurred in parallel with ultrastructural findings of pericapillary fibrosis, increased LV remodeling, and mitochondrial biogenesis.

CONCLUSION

These data suggest that a diet high in salt in hypertensive female Ren2 rats promotes greater oxidative stress, maladaptive LV remodeling, fibrosis, and associated diastolic dysfunction without further changes in LV systolic pressure or hypertrophy.

Postnatal overfeeding in rats leads to moderate overweight and to cardiometabolic and oxidative alterations in adulthood

In contrast to the masses of data on obesity, few data are available concerning the cardiometabolic and oxidative consequences of moderate overweight. The model of postnatal overfeeding (OF) induces an increase in body weight at weaning that remains during adult life. Litters of Wistar rats were either maintained at 12 pups (normal-fed group, NF), or reduced to 3 pups at birth in order to induce OF. At 6 months of age, metabolic parameters, circulating oxidative stress and aortic and coronary vasoreactivity were assessed. Cardiac susceptibility to ischemia-reperfusion injury was also evaluated ex vivo as were markers of cardiac remodeling. OF led to an increase in body weight at weaning (+50%); the increase in body weight persisted throughout adult life, but was less marked (+10%). Significant increases in plasma levels of fasting glucose, insulin and leptin were found in OF rats. An increase in both plasma hydroperoxides and cardiac superoxide dismutase activity and a decrease in plasma ascorbate were found in OF rats. Vasoreactivity was not modified, but ex vivo, after 30 min of ischemia, isolated hearts from OF rats showed lower recovery of coronary flow along with a greater release of LDH. Studies on heart tissues showed an increase in collagen content and increased expression and activity of MMP-2. Our findings show that moderate overweight in adult rats, induced by postnatal overfeeding, leads to both metabolic and oxidative disturbances as well as a higher susceptibility to cardiac injury after ischemia ex vivo, which may be explained, at least in part, by ventricular remodeling.