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Atrial natriuretic peptide (ANP), the principal member of the natriuretic factor family of peptides, primarily a product of the atria in the adult heart, is also expressed in the fetal ventricles. A minority of ventricular impulse-conducting cells and myocytes exposed to extreme tension retain the capacity to produce ANP in the adult. The number and distribution of ANP-expressing cells increases dramatically when the ventricle is pressure loaded and hypertrophied, as in the case of chronic hypertension. Coregulation of hypertrophy and ANP expression has established this peptide as a marker of myocardial hypertrophy and of the activation of the fetal gene program, typical of this condition. However, a coordinated reduction of hypertension and ANP expression while hypertrophy persists indicates that the hemodynamic state overrules hypertrophy in controlling ANP expression in hypertensive rat hearts. Under these circumstances, reduced activity of the cardiac-restricted transcription factor GATA-4 (a regulator of both hypertrophy and ANP expression) correlated with ANP downregulation but not with hypertrophy, which remained unchanged. Therefore, maintenance of cardiac hypertrophy in essential hypertension may not be dependent solely on GATA activity: it seems that additional factors may be involved. It is suggested that cell size and ANP production are autonomous features of the myocyte in the hypertensive heart and, although governed by similar mechanisms, the two features may be manifested independently.

Gonadotropin-releasing hormone (GnRH) analogues are used for the treatment of breast, prostate, and ovarian cancer. These analogues exert their antitumor effects indirectly by inhibiting the pituitary-gonadal axis, as well as by direct inhibition of proliferation of human breast cancer cells. However, the molecular mechanisms mediating these direct antiproliferative effects are not fully understood. We found that normal and malignant human breast tissue express two forms of the neuropeptide GnRH. Quantitative reverse transcription-PCR shows that mRNA encoding the GnRH-I and GnRH-II peptides are overexpressed in cancerous versus normal tissues obtained from the same patients. To elucidate the function of these peptides in breast cancer cells, we used the atlas human cDNA expression arrays technology and studied the differentially regulated genes after GnRH treatment of MCF-7 cells. We found that a wide range of GnRH-I or GnRH-II concentrations (0.1-10 nM) inhibit the expression of mRNA encoding the 60S acidic ribosomal phosphoproteins, P1 and P2. These results were confirmed by quantitative reverse transcription-PCR, as well as Western blot analysis and immunofluorescence staining. The P1 and P2 proteins interact with elongation factors EF1 and EF2, and the level of their phosphorylation is one of the regulatory mechanisms for the overall rate of protein elongation. Thus, reduced expression of P1 and P2 proteins can affect the rate of protein translation, thereby decreasing proliferation rate of cells. Our studies may therefore suggest a putative mechanism for the direct antiproliferative effect of GnRH in breast cancer cells.

Inflammatory destruction of insulin-producing beta cells in the pancreatic islets is the hallmark of insulin-dependent diabetes mellitus, a spontaneous autoimmune disease of non-obese diabetic mice resembling human juvenile (type I) diabetes. Histochemical analysis of diabetic pancreata revealed that mononuclear cells infiltrating the islets and causing autoimmune insulitis, as well as local islet cells, express the CD44 receptor; hyaluronic acid, the principal ligand of CD44, is detected in the islet periphery and islet endothelium. Injection of anti-CD44 mAb 1 hr before cell transfer of diabetogenic splenocytes and subsequently on alternate days for 4 weeks induced considerable resistance to diabetes in recipient mice, reflected by reduced insulitis. Contact sensitivity to oxazolone was not influenced by this treatment. A similar antidiabetic effect was observed even when the anti-CD44 mAb administration was initiated at the time of disease onset: i.e., 4-7 weeks after cell transfer. Administration of the enzyme hyaluronidase also induced appreciable resistance to insulin-dependent diabetes mellitus, suggesting that the CD44-hyaluronic acid interaction is involved in the development of the disease. These findings demonstrate that CD44-positive inflammatory cells may be a potential therapeutic target in insulin-dependent diabetes.

Objective: To create monoclonal anti-endothelial cell antibodies (mAECA) from a patient with Takayasu arteritis to evaluate their ability to activate human umbilical vein endothelial cells (HUVEC), and to characterize the mechanism of EC activation., Methods: A panel of mAECA was generated from peripheral blood lymphocytes of a patient with Takayasu arteritis, using Epstein-Barr virus transformation. Activity against macrovascular EC (HUVEC) and microvascular EC (human bone marrow EC immortalized by SV40) antigens was detected by enzyme-linked immunosorbent assay. Inhibition studies were used to select the monoclonal antibodies (mAECA) which share the same EC epitope binding specificity as the total IgG-AECA from the Takayasu arteritis patient. The binding of the mAECA to human aortic EC was studied by immunohistochemistry. The secretion levels of interleukin-6 (IL-6) and von Willebrand factor (vWF) were determined, to serve as markers for EC activation. The activated EC were examined for the adherence of a monocytic cell line (U937), as well as for expression of vascular cell adhesion molecule 1, intercellular adhesion molecule 1, and E-selectin. In addition, nuclear extracts of the mAECA-treated EC were analyzed for the induction of translocation of nuclear factor kappaB (NF-kappaB), using a specific NF-kappaB oligoprobe in an electrophoretic mobility shift assay., Results: Six mAECA were selected, the mixture of which produced 100% inhibition of binding of the original IgG (from the patient with Takayasu arteritis) to HUVEC. All mAECA possessed high activity against macrovascular EC, but none had significant antimicrovascular EC activity. The mAECA, but not normal human IgG, had anti-human aortic EC activity. Four of the 6 mAECA activated EC, manifested by increased IL-6 and vWF secretion. The 4 mAECA induced EC expression of adhesion molecules and increased adhesion of U937 monocytic cells to EC. In addition, these mAECA stimulated the nuclear translocation of the NF-kappaB transcription factor., Conclusion: Our findings suggest that AECA may directly stimulate EC in Takayasu arteritis through elevation of adhesion molecule expression associated with NF-kappaB activation and adhesion of monocytes, and may therefore play a pathogenic role in the development of the vasculopathy in Takayasu arteritis.