Renal transplantation increases angiotensin II receptor-mediated vascular contractility associated with changes of epigenetic mechanisms

Estrogen normalizes maternal HFD-induced vascular dysfunction in offspring by regulating ATR

Previous studies have shown that female offspring are resistant to fetal high-fat diet (HFD)-induced programming of heightened vascular contraction; however, the underlying mechanisms remain unclear. The present study tested the hypothesis that estrogen plays a key role in protecting females from fetal programming of increased vascular contraction induced by maternal HFD exposure. Pregnant rats were fed a normal diet (ND) or HFD (60% kcal from fat). Ovariectomy (OVX) and 17β-estradiol (E₂) replacement were performed on 8-week-old female offspring. Aortas were isolated from adult female offspring. Maternal HFD exposure increased angiotensin II (Ang II)-induced contractions of the aorta in adult OVX offspring, which was abrogated by E₂ replacement. The AT₁ receptor (AT₁R) antagonist losartan (10 μM), but not the AT₂ receptor (AT₂R) antagonist PD123319 (10 μM), completely blocked Ang II-induced contractions in both ND and HFD offspring. In addition, HFD exposure caused a decrease in endothelium-dependent relaxations induced by acetylcholine (ACh) in adult OVX but not OVX-E₂ offspring. However, it had no effect on sodium nitroprusside (SNP)-induced endothelium-independent aorta relaxation in any of the six groups. Maternal HFD feeding increased AT₁R, but not AT₂R, leading to an increased AT₁R/AT₂R ratio in HFD-exposed OVX offspring, associated with selective decreases in DNA methylation at the AT_1aR promoter, which was ameliorated by E₂ replacement. Our results indicated that estrogen play a key role in sex differences of maternal HFD-induced vascular dysfunction and development of hypertensive phenotype in adulthood by differently regulating vascular AT₁R and AT₂R gene expression through a DNA methylation mechanism.

Anti-Hypertensive Potential and Epigenetics of Angiotensin II type 2 Receptor (AT2R)

BACKGROUND

Renin angiotensin system (RAS) is a critical pathway involved in blood pressure regulation. Octapeptide, angiotensin II (Ang II), is a biologically active compound of RAS pathway which mediates its action by binding to either angiotensin II type 1 receptor (AT1R) or angiotensin II type 2 receptor (AT2R). Binding of Ang II to AT1R facilitates blood pressure regulation, whereas AT2R is primarily involved in wound healing and tissue remodeling.

OBJECTIVES

Recent studies have highlighted the additional role of AT2R to counterbalance the detrimental effects of AT1R. Activation of angiotensin II type 2 receptor using AT2R agonist has shown the effect on natriuresis and release of nitric oxide. Additionally, AT2R activation has been found to inhibit angiotensin converting enzyme (ACE) and enhance angiotensin receptor blocker (ARB) activity. These findings highlight the potential of AT2R as a novel therapeutic target against hypertension.

CONCLUSION

The potential role of AT2R highlights the importance of exploring additional mechanisms that might be crucial for AT2R expression. Epigenetic mechanisms, including DNA methylation and histone modification, have been explored vastly with relation to cancer, but the role of such mechanisms in the expression of AT2R has recently gained interest.

Unveiling the Role of DNA Methylation in Kidney Transplantation: Novel Perspectives toward Biomarker Identification

The burden of chronic kidney disease is dramatically rising, making it a major public health concern worldwide. Kidney transplantation is now the best treatment for patients with end-stage renal disease. Although kidney transplantation may improve survival and quality of life, its long-term results are hampered by immune- and/or non-immune-mediated complications. Thus, the identification of transplanted patients with a higher risk of posttransplant complications has become a big challenge for public health. However, current biomarkers of posttransplant complications have a poor predictive value, rising the need to explore novel approaches for the management of transplant patient. In this review we summarize the emerging literature about DNA methylation in kidney transplant complications, in order to highlight its perspectives toward biomarker identification. In the forthcoming future the monitoring of DNA methylation in kidney transplant patients could become a plausible strategy toward the prevention and/or treatment of kidney transplant complications.

No answer to the lack of specificity: mouse monoclonal antibody targeting the angiotensin II type 1 receptor AT1 fails to recognize its target

Numerous antibodies targeting G protein-coupled receptors (GPCRs) have been described as non-specific among the polyclonal antibodies against angiotensin II type 1 receptor (AT₁). We have tested the newly developed AT₁ receptor mouse monoclonal antibody for its specificity. Human embryonic kidney (HEK293) cells, which do not endogenously express AT₁ receptor, were transfected in order to overexpress a fluorescently labeled enhanced green fluorescent protein (EGFP)-tagged human AT₁ receptor. Western blot and immunofluorescence assays were performed to test the specificity of the Santa Cruz monoclonal antibody sc-57036. These results were compared to the ones obtained with the polyclonal sc-1173 anti-AT₁ receptor antibodies that have already been described as non-specific. While the positive controls using GFP antibodies detected the EGFP-tagged AT₁ receptor, both polyclonal and monoclonal anti-AT₁ receptor antibodies failed to specifically recognize the corresponding band by Western blot, as similar bands were revealed in either transfected or non-transfected cells. It also failed to detect AT₁ receptor in immunofluorescence experiments. The lack of target recognition of the monoclonal AT₁ receptor antibody in our experimental conditions suggests that this antibody could give misleading results such as misidentification of the protein. To our knowledge, no specific antibodies targeting AT₁ receptors have been developed so far and the field is thus in need of new technical developments.