Regulation of vascular endothelial (VE) growth factor (VEGF)–induced permeability is critical in physiological and pathological processes. We show that tyrosine phosphorylation of VEGF receptor 2 (VEGFR2) at Y951 facilitates binding of VEGFR2 to the Rous sarcoma (Src) homology 2-domain of T cell–specific adaptor (TSAd), which in turn regulates VEGF-induced activation of the c-Src tyrosine kinase and vascular permeability. c-Src was activated in vivo and in vitro in a VEGF/TSAd-dependent manner, and was regulated via increased phosphorylation at pY418 and reduced phosphorylation at pY527. Tsad silencing blocked VEGF-induced c-Src activation, but did not affect pathways involving phospholipase Cγ, extracellular regulated kinase, and endothelial nitric oxide. VEGF-induced rearrangement of VE–cadherin–positive junctions in endothelial cells isolated from mouse lungs, or in mouse cremaster vessels, was dependent on TSAd expression, and TSAd formed a complex with VE-cadherin, VEGFR2, and c-Src at endothelial junctions. Vessels in tsad−/− mice showed undisturbed flow and pressure, but impaired VEGF-induced permeability, as measured by extravasation of Evans blue, dextran, and microspheres in the skin and the trachea. Histamine-induced extravasation was not affected by TSAd deficiency. We conclude that TSAd is required for VEGF-induced, c-Src-mediated regulation of endothelial cell junctions and for vascular permeability.
Abstract Aim Periodontitis is a chronic inflammatory disease, characterized by irreversible destruction of tooth‐supporting tissue including alveolar bone. We recently reported mucin 4 ( MUC 4) and matrix metalloproteinase 7 ( MMP 7) as highly associated with periodontitis in gingival tissue biopsies. The aim of this study was to further investigate the levels of MUC 4 and MMP 7 in saliva and gingival crevicular fluid ( GCF ) samples of patients with periodontitis. Materials and Methods Saliva and GCF samples were collected from periodontitis patients and healthy controls. The levels of MUC 4, MMP 7, and total protein concentrations were analysed using ELISA or Bradford assay. Results MUC 4 levels were significantly lower in saliva and GCF from periodontitis patients relative to healthy controls. MMP 7 levels were significantly higher in saliva and GCF from periodontitis patients. Multivariate analysis revealed that MUC 4 was significantly associated with periodontitis after adjusting for age and smoking habits and, moreover, that the combination of MUC 4 and MMP 7 accurately discriminated periodontitis from healthy controls. Conclusions MUC 4 and MMP 7 may be utilized as possible novel biomarkers for periodontitis.
Mast cells are important mediators of normal angiogenesis, and participate in normal would healing, i.e. processes involved in pancreatic islet engraftment. The aim of the study was to evaluate if mast cells are present in islet grafts. For this purpose, male normoglycaemic Wistar-Furth rats were either untreated or syngeneically implanted with 250 islets under the renal capsule. The animals were killed 1 month later, and the kidneys and endogenous pancreas were removed, fixed and embedded in paraffin. The distribution of mast cells was studied in Alcian Blue stained sections. Mast cells were rarely encountered in endogenous islets, but were frequent in the renal capsule adjacent to islet grafts. Mast cells interspersed between graft endocrine cells were as rare as in the endogenous pancreas. We conclude that mast cells may contribute to the engraftment after islet transplantation.
Previous experiments have demonstrated that neuronal cells within pancreatic islets survive the isolation procedure and constitute an integral part of transplanted pancreatic islets. The aim of the present study was to investigate to what extent immunosuppressive drugs affects the acute survival of intra-islet neurons after pancreatic islet transplantation. For this purpose, C57BL/6 mice were syngeneically transplanted with 250 islets under the renal capsule. The animals were treated for 7 consecutive days with subcutaneous injections of cyclosporin, tacrolimus or vehicle. After this, the animals were killed and the grafts were removed, fixed and stained for the presence of the neuron-specific protein PGP 9.5. The number of nerves were then morphologically quantitated. No differences between the experimental groups were seen, and the number of nervous elements were approximately 5 per mm2 in all animals. It is concluded that immunosuppressive treatment does not affect the acute survival of graft neurons after experimental islet transplantation.
To elucidate the effect of nitric oxide (NO) on the blood flow of the pancreatic islets, the NO synthase inhibitor NG-nitro-L-arginine (N-arg; 25 mg/kg BW) was administered iv to rats 10 min before pancreatic blood flow was measured with a nonradioactive microsphere technique. In male Sprague-Dawley rats, N-arg induced a marked decrease in islet blood flow (16 +/- 4 vs. 44 +/- 8 microliters/min.g pancreas; P < 0.001) and a less pronounced decrease in whole pancreatic blood flow (0.27 +/- 0.04 vs. 0.43 +/- 0.06 ml/min.g; P < 0.05), leading to a markedly decreased fractional islet blood flow (5.5 +/- 0.9% vs. 10.3 +/- 1.3%; P < 0.02). In a second experiment, injection of D-glucose (300 mg/kg BW, iv) in male Sprague-Dawley rats induced a selective increase in islet blood flow (P < 0.05). Such an increase has previously been shown to be mediated by a vagal cholinergic mechanism. Administration of N-arg to these rats resulted in decreased pancreatic (P < 0.05), islet (P < 0.001), and fractional (P < 0.001) islet blood flow, which did not differ from those observed in normoglycemic rats after treatment with N-arg. Furthermore, we studied the mechanism behind the previously described increase in islet blood perfusion, mediated by the vagus nerve, in F1-hybrids of the GK (Goto-Kakizaki) rat, a spontaneous animal model of noninsulin-dependent diabetes mellitus. Administration of N-arg to female GK rats resulted in decreases in islet (P < 0.001), pancreatic (P < 0.01), and fractional islet blood flow (P < 0.001) to the levels observed in female Wistar rats treated in parallel. These data are consistent with the possibility that NO is an important physiological regulator of islet blood flow. Furthermore, the vagally dependent high levels of islet blood flow demonstrated in the GK rat appear to be mediated by a mechanism involving NO.
Worldwide there is massive increase in the prevalence of type 2 diabetes and the International Diabetes Federation predicts that in 20 years some 600 million people worldwide will be afflicted. In the U.S. alone, the annual cost for diabetes care is an astonishing $245 billion, of which 97% is targeted to type 2 diabetes. Hence, it is immediately apparent that there is an urgent need to find new strategies capable of preventing and treating this disease.
Loss of pancreatic islet function is a central hallmark in the progression of type 2 diabetes, and β-cell failure and dysfunction may even precede the advent of hyperglycemia. Most efforts to date have been put toward understanding the changes that occur in pancreatic islets in type 2 diabetes by in vitro studies of the endocrine cells, mainly the β-cells and the α-cells. However, what is often forgotten is that in the much more complex situation of in vivo these endocrine cells intercommunicate with the rest of the body by endocrine, neural, and paracrine signals. Endothelial cells in different organs substantially vary in their gene expression and thereby in their phenotype depending on signals from the surrounding parenchyma. In the islets of Langerhans, the endothelial cell phenotype differs from the rest of the pancreas by being exposed to vascular endothelial growth factor-A from the β-cells (1,2). However, the endothelial cells …
The aim of the study was to investigate how an acute increase in functional demand for insulin release affected islet blood perfusion in anesthetized rats.We measured total pancreatic and islet blood flow with differently colored microspheres before and 30 minutes after a 50% partial pancreatectomy.The blood glucose concentrations increased in the animals subjected to partial pancreatectomy. The fact that serum insulin concentrations remained unaffected implies that the islets in fact doubled their output of insulin to maintain the same degree of insulinemia. Still, pancreatic islet blood flow was the same as in the sham-operated animals. Likewise, the number of perfused pancreatic islets and the flow distribution between individual islets were not influenced by the partial pancreatectomy.We conclude that the acute demand for insulin secretion induced by a 50% partial pancreatectomy is not necessarily associated with an acute increase in islet blood perfusion. These findings suggest that basal islet blood flow is high enough to allow for short-term changes in hormone release without simultaneous changes in blood perfusion.
