Angiotensin II (Ang II) has been implicated in the pathogenesis of the vascular injury associated with hypertension and diabetes mellitus. Increased vascular permeability is an important early manifestation of endothelial dysfunction and the pathogenesis of atherosclerosis. How Ang II contributes to endothelial dysfunction and promotes an increase in vascular permeability is unknown but is classically attributed to its pressor actions. We demonstrate that human vascular smooth muscle cells express abundant mRNA for vascular permeability/endothelial growth factor. Vascular permeability factor is a 34- to 42-kD glycoprotein that markedly increases vascular endothelial permeability and is a potent endothelial mitogen. Ang II potently induced a concentration-dependent (maximal, 10(-7) mol/L) and time-dependent increase in vascular permeability factor mRNA expression by human vascular smooth muscle cells that was maximal after 3 hours and diminished by 24 hours. Ang II-induced vascular permeability factor mRNA expression by human vascular smooth muscle cells was inhibited by the specific Ang II receptor antagonist losartan (DuP 753), confirming that this is an Ang II receptor subtype 1-mediated event. These results describe a new action of Ang II on human vascular smooth muscle, notably the induction of vascular permeability factor mRNA expression. The wide spectrum and potent activity of vascular permeability factor suggest a novel mechanism whereby Ang II could locally and directly influence the permeability, growth, and function of the vascular endothelium independent of changes in hemodynamics.

Hyperglycemia is an independent risk factor for the development of diabetic microvascular disease. Vascular permeability factor (VPF)/vascular endothelial growth factor (VEGF) is a potent cytokine family that induces angiogenesis and markedly increases endothelial permeability. VPF is produced by many cell types, including vascular smooth muscle (VSM) cells, and has been implicated in the pathogenesis of neovascularization and endothelial dysfunction in diabetes. This study used cultured human VSM cells to study the regulation of VPF production and determine whether elevated glucose concentrations, per se, are a sufficient stimulus for increased VPF production by human cells. In human VSM cells, high extracellular glucose concentrations (20 mmol/l) increased VPF mRNA expression within 3 h (3-fold vs. glucose 5 mmol/l) and significantly increased VPF peptide production within 24 h (1.5-fold) in a time- and glucose concentration-dependent manner. The high glucose-induced increase in VPF mRNA expression was rapidly reversed after normalizing the extracellular glucose concentration and was specific for a high D-glucose concentration, as these effects were not reproduced by osmotic control media containing elevated concentrations of mannitol or L-glucose. High glucose concentrations activate protein kinase C (PKC) in human VSM cells, and PKC inhibitors (H-7 or chelerythrine chloride) or PKC downregulation each prevented the glucose-induced increases in VPF mRNA expression by human VSM cells. In conclusion, high glucose concentrations directly increase VPF mRNA expression and peptide production by human VSM cells via a PKC-dependent mechanism. These results demonstrate a cellular mechanism, whereby hyperglycemia could directly contribute to the development of endothelial dysfunction and neovascularization in diabetes.

Summary Transforming growth factor P (TGF-P) comprises a group of multifunctional regulatory proteins, whose effects include stimulation of extracellular matrix formation and modification of immune function. The presence of TGF-P, and TGF-P2 in invasive breast carcinomas has been determined and related to pathological features, the presence of fibronectin and tenascin and lymphocyte/macrophage infiltration, using immunohistochemistry. Differences were observed in the extent of reactivity within the same carcinoma and between tumours stained with an antibody detecting TGF-P, and one detecting TGF-P, plus TGF-132, the latter having a higher level of reactivity. Prominent reactivity for TGF-P, was associated with lymph node metastasis, (0.02> P> 0.01), increased detection of cellular fibronectin, fine stromal fibronectin staining, more prominent reactivity for tenascin (0.02 > P> 0.01), the presence of tumour-associated macrophage infiltration and altered ratios of CD4 and CD8 lymphocyte populations, with CD8 lymphocytes predominating. These associations were not observed for carcinomas showing prominent staining with antibody detecting TGF-P2 as well as TGF-p,. The findings indicate that TGF-P, may have a role in invasion and metastasis of breast carcinomas.

1. Endothelial dysfunction and vascular smooth muscle cell (VSMC) proliferation are key events in the pathogenesis of atherosclerosis. Vascular permeability factor (VPF), an endothelial-cell-specific multifunctional cytokine, was recently described, and has the potential to contribute to the development of endothelial dysfunction. The present study determines whether cultured human VSMCs express mRNA for VPF and whether VPF mRNA expression is influenced by human VSMC proliferation. 2. A 204 bp cDNA fragment, specific for all known variants of VPF mRNA, was cloned and used to demonstrate that human VSMCs express abundant quantities of VPF mRNA, whereas human endothelial cells do not. VPF mRNA levels were markedly diminished in non-proliferating human VSMCs. In contrast, when human VSMCs were stimulated to proliferate by exposure to serum, there was a rapid 6.6-fold increase (P < 0.01 versus time 0 h) in VPF mRNA expression, which was maximal at 3 h and persisted beyond 24 h. The magnitude of the VPF mRNA response in human VSMCs was dependent on the serum concentration. 3. Platelet-derived growth factor also increased VPF mRNA expression by human VSMCs, thus confirming that recognized growth factors for VSMCs also potently influence the VPF gene. 4. In conclusion, VPF mRNA is expressed by human VSMCs, the magnitude of VPF expression being temporally related to the proliferation of human VSMCs and the potency of the growth-promoting stimulus. We propose that VPF produced by proliferating human VSMCs could act as a paracrine hormone to powerfully influence the permeability and growth of the overlying vascular endothelium.(ABSTRACT TRUNCATED AT 250 WORDS)

The expression of transforming growth factor beta 1 (TGF-beta 1) mRNA has been determined in 16 breast carcinomas using in situ hybridization and compared with TGF-beta protein as detected by antibodies against TGF-beta 1 and TGF-beta 1 plus TGF-beta 2. Digoxigenin-labelled riboprobes were used, with alkaline phosphatase and immunogold silver detection systems. TGF-beta 1 mRNA was only detected in carcinomas in which TGF-beta 1 protein was found (9 of 16 cases) and not in those with prominent reactivity for TGF-beta 2. RNA preservation was poor in two other cases in which TGF-beta 1 protein had been detected. In general, those tumours with greater numbers of cells labelled for TGF-beta 1 mRNA had prominent reactivity for TGF-beta 1 protein. The mRNA was localized to cancer cells with no labelling of stromal cells, although in a small number of cases scanty staining for TGF-beta 1 protein had been observed in stromal cells. The incidence of detection of TGF-beta 1 mRNA is lower than the published data from Northern analysis studies of breast carcinomas, suggesting that only higher levels of TGF-beta 1 mRNA expression are being detected by in situ hybridization. However, this approach has provided useful information about the cellular sites of expression of TGF-beta 1 in breast carcinomas.