Aims/hypothesis. Activation of the renal renin-angiotensin system has been implicated in the pathogenesis of diabetic nephropathy. Because previous in vitro studies demonstrated the angiotensin II (ang II)-mediated up-regulation of the prosclerotic transforming growth factor β1 (TGF) we studied the molecular mechanism of ang II-induced TGF-β1 gene activation. Methods. Mesangial cells were stimulated with 100 nmol/l ang II with or without inhibitors of protein kinase C (PKC) and p38 MAPK and the TGF-β1 promoter activity was determined by promoter-reporter assays. The effect of ang II on the binding of nuclear proteins to the regulatory AP-1 site B, previously shown to mediate the high glucose-response of the TGF-β1 promoter, was studied by electrophoretic mobility shift assays. Results. Ang II enhanced the activity of the TGF-β1 promoter fragment -453/+11 approximately 1.6-fold.Mutation of each of two AP-1 binding sites or inhibition of the PKC-and p38 MAPK-dependent pathways blocked the ang II-stimulated activity completely. Furthermore, ang II activated the binding of nuclear proteins to the AP-1 box B of the TGF-β1 promoter. These effects were similar to those previously observed with high glucose. Co-incubation with ang II and high glucose had no additive effect on TGF-β1 promoter activity, protein binding to the AP-1 box B or activation of p38 MAPK. Conclusion/interpretation. The findings indicate that ang II and hyperglycaemia stimulate the TGF-β1 gene activation through the same PKC-and p38 MAPK-dependent pathways by the same regulatory elements of the TGF-β1 promoter. Our data could also be relevant for e.g. hypertension-induced glomerulosclerosis. [Diabetologia (2002) 45:890-898]

By analyzing T cell responses against foreign major histocompatibility complex (MHC) molecules loaded with peptide libraries and defined self- and viral peptides, we demonstrate a profound influence of self-MHC molecules on the repertoire of alloreactive T cells: the closer the foreign MHC molecule is related to the T cell's MHC, the higher is the proportion of peptide-specific, alloreactive (“allorestricted”) T cells versus T cells recognizing the foreign MHC molecule without regard to the peptide in the groove. Thus, the peptide repertoire of alloreactive T cells must be influenced by self-MHC molecules during positive or negative thymic selection or peripheral survival, much like the repertoire of the self-restricted T cells. In consequence, allorestricted, peptide-specific T cells (that are of interest for clinical applications) are easier to obtain if T cells and target cells express related MHC molecules.

The nutrient sensing capacity of the hexosamine biosynthetic pathway (HBP) has been implicated in the development of insulin resistance of skeletal muscle. To study the molecular mechanism of the free fatty acid (FFA)-induced activation of the HBP myotubes obtained from muscle biopsies of metabolically characterized, subjects were stimulated with different fatty acids for 20 h. Incubation with the saturated fatty acids palmitate and stearate (0.5 mmol/l) resulted in a threeto fourfold increase in mRNA expression of glutamine: fructose-6-phosphate aminotransferase (GFAT), the key and rate-limiting enzyme of the hexosamine pathway. Unsaturated fatty acids or 30 mmol/l glucose had little or no effect. Palmitate increased the amount of GFAT protein nearly two-fold, and subsequently, the concentration of UDP-N-acetylglucosamine, the end product of the HBP, was 1.3-fold enhanced in the palmitate-stimulated myotubes. The nonmetabolized fatty acid bromopalmitate had no effect. The DNA binding activity of the transcription factor Sp1, a target downstream of the HBP, was increased by palmitate and completely lost after enzymatic removal of O-GlcNAc. No correlation was found between the palmitateinduced increase in GFAT protein and the insulin resistance in the respective subjects. The findings reveal a new mechanism for how FFAs induce the activation of the HBP. Diabetes 52:650 -656, 2003

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