Epidermal growth factor receptor tyrosine kinase‐mediated signalling contributes to diabetes‐induced vascular dysfunction in the mesenteric bed

Abstract

1 In order to characterize the roles of tyrosine kinases (TKs) and epidermal growth factor receptor (EGFR) in diabetes-induced vascular dysfunction, we investigated the ability of a chronic administration of genistein, a broad-spectrum inhibitor of TKs and AG1478, a specific inhibitor of EGFR TK activity to modulate the altered vasoreactivity of the perfused mesenteric bed to common vasoconstrictors and vasodilators in streptozotocin (STZ)-induced diabetes in rats. 2 The vasoconstrictor responses induced by norepinephrine (NE), endothelin-1 (ET-1) and angiotensin II (Ang II), were significantly increased, whereas vasodilator responses to carbachol and histamine were significantly reduced in the perfused mesenteric bed of STZ-induced diabetic rats in comparison with healthy rats. Treatment of diabetic animals with genistein or AG1478 produced a significant normalization of the altered agonist-induced vasoconstrictor and vasodilator responses without affecting blood glucose levels. In contrast, neither inhibitor had any effect on the vascular responsiveness of control (nondiabetic) animals. Treatment of diabetic animals with diadzein, an inactive analogue of genistein, did not affect the vasoconstrictor and vasodilator responses in control or diabetic animals. Phosphorylated EGFR levels were markedly raised in the mesenteric bed from diabetic animals and were normalized upon treatment with AG1478 or genistein. 3 These data suggest that activation of TK-mediated pathways, including EGFR TK signalling are involved in the development of diabetic vascular dysfunction.

Advanced glycation end product (AGE) receptor 1 suppresses cell oxidant stress and activation signaling via EGF receptor

“…Rather, the AGER1 effects on EGFR activity appear to be AGE͞ROS-specific. In fact, AGER1-mediated inhibition of AGE-induced EGFR activation (32,33) was restored by R1 siRNA. Furthermore, AGE-induced intracellular ROS generation was inhibited in AGER1-overexpressing cells, supporting the pivotal role of AGER1 in this interaction.…”

“…A possible dependence of EGFR responsiveness on the level of EGFR vs. R1 cell surface availability was suggested during EGFR and AGER1 single expression and coexpression studies. These data may point to a potential explanation for the low efficacy of AGER1 (12) under conditions of sustained ROS generation [e.g., in diabetes, when EGFR expression and activity might be expected to be elevated (32,33)]. …”

Angiotensin-(1–7) prevents diabetes-induced cardiovascular dysfunction

“…The perfused mesenteric bed was constricted by perfusion with KH solution containing NE (10 Ϫ5 M). After a steady level of precontraction was established, successive doses of carbachol (1 and 10 nmol), histamine (10 and 100 nmol), or SNP (0.1, 1.0, and 10 nmol) were given at regular intervals (7). The vasodilator response is expressed as the percentage of the precontraction induced by NE (10 Ϫ5 M).…”

“…Successive doses of the agonists NE or ET-1 were given at regular intervals to establish the vasoconstrictor responses (in mmHg) (7). The vasoconstrictor effects of NE (10 Ϫ8 , 10 Ϫ7 , and 10 Ϫ6 M), ET-1 (10 Ϫ10 , 10 Ϫ9 , and 10 Ϫ8 M), or ANG II (10 Ϫ9 , 10 Ϫ8 , and 10 Ϫ7 M) were tested in the isolated segments of the carotid or renal artery.…”

“…Vascular reactivity of the mesenteric bed and renal and carotid arteries to vasoactive agents was studied as described by us previously (5,7). Briefly, the mesenteric artery was cannulated and perfused with Krebs-Henseleit (KH) solution (at 37°C), oxygenated with 95% O 2-5% CO2, delivered at a constant flow rate of 6 ml/min using a multichannel masterflex peristaltic pump.…”