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Hyperglycemia‐Induced Inhibition of the Angiotensin II Type 1 Receptor Pathway in the Vascular Endothelium
Author(s) -
Hoffmann Brian R.,
Haspula Dhanush
Publication year - 2020
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.2020.34.s1.05930
Subject(s) - angiotensin ii , medicine , endocrinology , receptor , endothelium , glycosylation , chemistry , endothelial stem cell , renin–angiotensin system , biochemistry , blood pressure , in vitro
Hyperglycemia, associated with diabetes, is known to damage blood vessels and contribute to negative cardiovascular health outcomes. However, the etiology behind the negative influence of the exposure to prolonged elevated glucose on endothelial cells is not yet fully understood. Our laboratories’ previous study identified changes in endothelial cell surface glycosylation resulting from hyperglycemia. One such modified protein was the Angiotensin II type 1 receptor (AT 1 R), which was N‐glycosylated adjacent to the active site. Activation of AT 1 R by angiotensin II (AngII) at subpressor doses is associated with positive endothelial cell growth, proliferation, and tube formation. However, AngII binding to the Angiotensin II type 2 receptor (AT 2 R), has been shown to elicit opposing effects. The objective of this study was to further investigate the effects of this hyperglycemia‐induced glycosylation of AT 1 R. A two‐week high glucose treatment (25 mM) of rat cardiac microvascular endothelial cells (RCMVECs) displayed impaired function by tube formation analysis (TFA) in comparison to a normal glucose treatment (4.5 mM). The decrease tube formation was further exacerbated by the addition of a subpressor dose of AngII. To further test the influence of hyperglycemia‐induced AT 1 R N‐glycosylation on signaling we treated RCMVECs with the PNGaseF enzyme for N‐glycosylation removal at the cell surface in combination with functional assays and AngII treatment under varying glycemic conditions. The efficacy of this treatment was tested through TFA and measurements of ERK1/2 activation through phosphorylation (known contributor to AT 1 R signaling). We observed a decrease in tube length, tube area, and number of branch points in a high glucose environment plus Ang‐II and were able to recover functionality with the addition of PNGaseF. While normal glucose treated cells had shown ERK1/2 activation, no observable increases in ERK1/2 were observed in response to AngII in the high glucose conditions. In the high glucose plus AngII treatment group we also observed a significant decrease in Vegfr2 gene expression compared to the normal glucose plus AngII treatment group. Further analysis is currently underway to further validate this mechanism of AT 1 R signaling impairment, but the data we have so far lead us to believe that hyperglycemia‐induced glycosylation blocks the AT 1 R active site to decrease functionality. It is possible that the hyperglycemia‐induced glycosylation of AT 1 R inhibits AngII binding, allowing for a higher rate of binding in the AT 2 R to further impair endothelial cell functionality. Support or Funding Information Support for this project has been provided by the National Institutes of Health National Institute of Diabetes and Digestive and Kidney Diseases (K01‐DK105043 to BRH) and the Department of Biomedical Engineering at the Medical College of Wisconsin and Marquette University.