Activation of ErbB2 and Downstream Signalling via Rho Kinases and ERK1/2 Contributes to Diabetes-Induced Vascular Dysfunction

Abstract

Diabetes mellitus leads to vascular complications but the underlying signalling mechanisms are not fully understood. Here, we examined the role of ErbB2 (HER2/Neu), a transmembrane receptor tyrosine kinase of the ErbB/EGFR (epidermal growth factor receptor) family, in mediating diabetes-induced vascular dysfunction in an experimental model of type 1 diabetes. Chronic treatment of streptozotocin-induced diabetic rats (1 mg/kg/alt diem) or acute, ex-vivo (10−6, 10−5 M) administration of AG825, a specific inhibitor of ErbB2, significantly corrected the diabetes-induced hyper-reactivity of the perfused mesenteric vascular bed (MVB) to the vasoconstrictor, norephinephrine (NE) and the attenuated responsiveness to the vasodilator, carbachol. Diabetes led to enhanced phosphorylation of ErbB2 at multiple tyrosine (Y) residues (Y1221/1222, Y1248 and Y877) in the MVB that could be attenuated by chronic AG825 treatment. Diabetes- or high glucose-mediated upregulation of ErbB2 phosphorylation was coupled with activation of Rho kinases (ROCKs) and ERK1/2 in MVB and in cultured vascular smooth muscle cells (VSMC) that were attenuated upon treatment with either chronic or acute AG825 or with anti-ErbB2 siRNA. ErbB2 likley heterodimerizes with EGFR, as evidenced by increased co-association in diabetic MVB, and further supported by our finding that ERK1/2 and ROCKs are common downstream effectors since their activation could also be blocked by AG1478. Our results show for the first time that ErbB2 is an upstream effector of ROCKs and ERK1/2 in mediating diabetes-induced vascular dysfunction. Thus, potential strategies aimed at modifying actions of signal transduction pathways involving ErbB2 pathway may prove to be beneficial in treatment of diabetes-induced vascular complications.

The dual targeting of EGFR and ErbB2 with the inhibitor Lapatinib corrects high glucose-induced apoptosis and vascular dysfunction by opposing multiple diabetes-induced signaling changes

“…In MVB isolated from non-diabetic, diabetic or diabetic rats treated chronically with Lapatinib, vascular responsiveness to norephinephrine (NE) were measured as described by us previously [18]. For acute (ex vivo) drug treatments of the diabetic MVB, either Lapatinib (10 À5 or 10 À6 M ) or BAY (10 À5 or 10 À6 M) was added to the perfusate 30 min prior to the vasoactive agent (NE) similar to that described by us previously [18].…”

“…injection of STZ (55 mg/kg body weight) and rats with a blood glucose concentration above 250 mg/dl (approx. 14 mmol/l) were declared diabetic as in the previous studies [11,12,14,18].…”

“…In a micro-array based gene expression study of diabetic mesenteric vasculature, we showed that diabetes inducedelevation in EGFR gene expression was also accompanied by an elevation in ErbB2 gene expression [15] and this resulted in enhanced ErbB2 phosphorylation [18]. Pharmacological inhibition of ErbB2 signaling via chronic treatment with the selective inhibitor, AG825, was able to correct diabetesinduced abnormal reactivity in the mesenteric vascular bed (MVB) [18] and carotid artery [13].…”

“…Pharmacological inhibition of ErbB2 signaling via chronic treatment with the selective inhibitor, AG825, was able to correct diabetesinduced abnormal reactivity in the mesenteric vascular bed (MVB) [18] and carotid artery [13]. Thus evidence from pharmacological inhibition of either receptor alone now suggests that both EGFR and ErbB2 receptors are important mediators of diabetes-induced vascular complications with recent data from our laboratory showing that EGFR and ErbB2 actually mediate vascular dysfunction in type 1 diabetes by forming heterodimers that signal in concert via a ERK1/2-rhokinase-dependent pathway [18]. However, the precise downstream effectors of EGFR-ErbB2 heterodimer signaling in diabetes-induced vascular dysfunction have not been fully characterized.…”

Diabetic cardiomyopathy: Role of epidermal growth factor receptor tyrosine kinase

“…Reportedly, EGFR phosphorylation is down-regulated in the liver, but up-regulated in the kidney and gastric mucosa as well as in the kidney/coronary/mesenteric bed micro-vascular system following experimentally induced diabetes [13–17]. Numerous studies focusing on the role of EGFR in the pathogenesis of diabetic nephropathy and micro-vascular dysfunction in diabetes have been carried out [11–13, 17,18], and clearly show detrimental effects of EGFR phosphorylation on the development of diabetic nephropathy and micro-vascular dysfunction, which, generally speaking, was mediated by increased endoplasmic reticulum (ER) stress and oxidative stress as well as decreased autophagy [11], as outlined in Fig. 1.…”