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      Diabetes-Induced Renal Vascular Dysfunction Is Normalized by Inhibition of Epidermal Growth Factor Receptor Tyrosine Kinase


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          Contribution of receptor tyrosine kinase activation to development of diabetes-induced renal artery dysfunction is not known. We investigated the ability of a chronic administration of genistein, a broad-spectrum inhibitor of tyrosine kinases (TKs), and AG1478, a specific inhibitor of epidermal growth factor receptor (EGFR) TK activity, to modulate the altered vasoreactivity of isolated renal artery ring segments to common vasoconstrictors in streptozotocin-induced diabetes. In diabetic renal artery, the vasoconstrictor responses induced by norepinephrine, endothelin-1 and angiotensin II were significantly increased. Inhibition of TKs or the EGFR pathway did not affect the agonist-induced vasoconstrictor responses in the non-diabetic control animals. However, inhibition of TKs by genistein or EGFR TK by AG1478 treatment produced a significant normalization of the altered agonist-induced vasoconstrictor responses without affecting blood glucose levels. Treatment with diadzein, an inactive analogue of genistein, did not affect the vasoconstrictor responses in the diabetic animals. Western blotting showed that phosphorylated EGFR protein levels were increased in vehicle-treated diabetic animals. In renal arteries from AG1478-treated diabetic animals, EGFR protein levels were similar to non-diabetic control animals. These data suggest that activation of TK-mediated pathways, including the EGFR TK signalling pathway, are involved in the development of diabetic vascular dysfunction in the renal artery.

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          Most cited references 26

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          The metalloprotease Kuzbanian (ADAM10) mediates the transactivation of EGF receptor by G protein–coupled receptors

          Communication between different signaling pathways enables cells to coordinate the responses to diverse environmental signals. Activation of the transmembrane growth factor precursors plays a critical role in this communication and often involves metalloprotease-mediated proteolysis. Stimulation of G protein–coupled receptors (GPCR) transactivates the EGF receptors (EGFRs), which occurs via a metalloprotease-dependent cleavage of heparin-binding EGF (HB-EGF). However, the metalloprotease mediating the transactivation remains elusive. We show that the integral membrane metalloprotease Kuzbanian (KUZ; ADAM10), which controls Notch signaling in Drosophila, stimulates GPCR transactivation of EGFR. Upon stimulation of the bombesin receptors, KUZ increases the docking and activation of adaptors Src homology 2 domain–containing protein and Gab1 on the EGFR, and activation of Ras and Erk. In contrast, transfection of a protease domain–deleted KUZ, or blocking endogenous KUZ by morpholino antisense oligonucleotides, suppresses the transactivation. The effect of KUZ on shedding of HB-EGF and consequent transactivation of the EGFR depends on its metalloprotease activity. GPCR activation enhances the association of KUZ and its substrate HB-EGF with tetraspanin CD9. Thus, KUZ regulates the relay between the GPCR and EGFR signaling pathways.
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            Preclinical and clinical evaluations of ABX-EGF, a fully human anti-epidermal growth factor receptor antibody.

            The epidermal growth factor receptor (EGFR) is a transmembrane glycoprotein, with an extracellular ligand-binding domain and intracellular tyrosine kinase domain. Ligand binding induces EGFR dimerization and autophosphorylation on several tyrosine residues in the intracellular domain, leading to mitogenic signal transduction. EGFR overexpression correlates with a poor prognosis and is often associated with malignant transformation in a variety of epithelial cancers. ABX-EGF is a high-affinity (dissociation constant K(D) = 5 x 10(-11) M) fully human IgG2 monoclonal antibody against human EGFR. ABX-EGF binds EGFR and blocks receptor binding of EGF and transforming growth factor-alpha, inhibiting EGFR tyrosine phosphorylation and tumor cell activation. ABX-EGF prevents tumor formation and eradicates large, established A431 tumors in xenograft models. Tumor growth inhibition occurs at relatively low doses, without concomitant chemotherapy or radiotherapy. When combined with chemotherapeutic agents, ABX-EGF has resulted in additive antitumor activity. A Phase I clinical trial has demonstrated activity in several tumor types, and the results from a Phase II trial for renal cell cancer also showed modest activity. Therapy was generally well tolerated without statistically significant adverse events. Monoclonal antibody blockade of EGFR represents a new and exciting direction in cancer therapy.
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              Putative pathophysiological role of growth factors and cytokines in experimental diabetic kidney disease.

               A Flyvbjerg (2000)
              The development of diabetic nephropathy in patients with Type I (insulin-dependent) and Type II (non-insulin-dependent) diabetes mellitus is still a huge clinical problem associated with increased morbidity and mortality. The mechanisms underlying the development of diabetic kidney disease are extremely complex and yet not completely understood. Among many potential pathogenic mechanisms responsible for the development of diabetic kidney disease, various growth factors have been suggested to be important players. In particular, growth hormone (GH)/insulin-like growth factors (IGFs), transforming growth factor beta (TGF-beta), vascular endothelial growth factor (VEGF) and epidermal growth factor (EGF) have measurable effects on the development of experimental diabetic kidney disease through complex intra-renal systems. Recent findings that these growth factors might initiate the early diabetic renal changes have provided insight into processes that might be relevant for future development of new drugs useful in the treatment of diabetic kidney disease. As will appear from the present review, enhanced understanding of the cellular mechanisms responsible for the development of diabetic kidney disease has already allowed the design of specific antagonists of pathophysiologically increased growth factors. Recent studies have shown that treating experimental diabetic models with such antagonists is followed by renoprotection.

                Author and article information

                J Vasc Res
                Journal of Vascular Research
                S. Karger AG
                August 2005
                29 July 2005
                : 42
                : 4
                : 284-291
                aDepartment of Pharmacology and Toxicology, Faculty of Medicine, Kuwait University, Safat, Kuwait; bCentre for Genome-based Therapeutics, Welsh School of Pharmacy, Cardiff University, Cardiff, UK
                85904 J Vasc Res 2005;42:284–291
                © 2005 S. Karger AG, Basel

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                Page count
                Figures: 7, References: 40, Pages: 8
                Research Paper


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