Young-Sun Kang

Aldosterone induces myocardial fibrosis and vascular inflammation via proinflammatory and profibrotic cytokines. The effect of spironolactone on renal inflammation and renal function was investigated in type 2 diabetic rats. For define the molecular mechanism of spironolactone, the effect of spironolactone on the synthesis of monocyte chemotactic peptide-1 (MCP-1) and its upstream transcription factor, NF-kappaB, was evaluated in cultured mesangial cells and proximal tubular cells. There were no changes in blood glucose concentration or BP after spironolactone treatment. Spironolactone treatment significantly reduced urinary albumin excretion and ameliorated glomerulosclerosis. Urinary levels of MCP-1 were significantly increased concurrently with renal expression of MCP-1, macrophage migration inhibitory factor, and macrophage infiltration. Spironolactone treatment significantly inhibited urinary excretion of MCP-1 as well as renal MCP-1 and migration inhibitory factor expression and macrophage infiltration. In addition, aldosterone induced upregulation of MCP-1 expression and NF-kappaB transcriptional activity in cultured cells, and spironolactone reduced both NF-kappaB activation and MCP-1 synthesis. Furthermore, NF-kappaB inhibition abolished aldosterone-induced MCP-1 production. Overall, these findings suggest that aldosterone-induced NF-kappaB activation leads to activation of proinflammatory cytokines, ultimately leading to renal injury in this model. These data suggest that mineralocorticoid blockade may be a potential therapeutic target in diabetic nephropathy.

Vanilloid receptor 1 (VR1), a ligand-gated ion channel activated by vanilloids, acid, and heat, is a molecular detector that integrates multiple modes of pain. Although the function and the biophysical properties of the channel are now known, the regions of VR1 that recognize ligands are largely unknown. By the stepwise deletion of VR1 and by chimera construction using its capsaicin-insensitive homologue, VRL1, we localized key amino acids, Arg-114 and Glu-761, in the N- and C-cytosolic tails, respectively, that determine ligand binding. Point mutations of the two key residues resulted in a loss of sensitivity to capsaicin and a concomitant loss of specific binding to [(3)H]resiniferatoxin, a potent vanilloid. Furthermore, changes in the charges of the two amino acids blocked capsaicin-sensitive currents and ligand binding without affecting current responses to heat. Thus, these two regions in the cytoplasmic tails of VR1 provide structural elements for its hydrophilic interaction with vanilloids and might constitute a long-suspected binding pocket.

Human aminoacyl-tRNA synthetases (ARSs) are normally located in cytoplasm and are involved in protein synthesis. In the present work, we found that human methionyl-tRNA synthetase (MRS) was translocated to nucleolus in proliferative cells, but disappeared in quiescent cells. The nucleolar localization of MRS was triggered by various growth factors such as insulin, PDGF, and EGF. The presence of MRS in nucleoli depended on the integrity of RNA and the activity of RNA polymerase I in the nucleolus. The ribosomal RNA synthesis was specifically decreased by the treatment of anti-MRS antibody as determined by nuclear run-on assay and immunostaining with anti-Br antibody after incorporating Br-UTP into nascent RNA. Thus, human MRS plays a role in the biogenesis of rRNA in nucleoli, while it is catalytically involved in protein synthesis in cytoplasm.

Mammalian aminoacyl tRNA synthetases form a macromolecular protein complex with three non-enzymatic cofactors. Among these factors, p43 is also secreted to work as a cytokine on endothelial as well as immune cells. Here we investigated the activity of p43 in angiogenesis and determined the related mediators. It promoted the migration of endothelial cells at low dose but induced their apoptosis at high dose. p43 at low concentration activated extracellular signal-regulating kinase, which resulted in the induction and activation of matrix metalloproteinase 9. In contrast, p43 at high concentration activated Jun N-terminal kinase, which mediated apoptosis of endothelial cells. These results suggest that p43 is a novel cytokine playing a dose-dependent biphasic role in angiogenesis.