Glomerulosclerosis is characterized by progressive extracellular matrix accumulation and glomerular cell loss. The role of glomerular cell apoptosis in glomerulosclerosis was investigated in the rat remnant kidney model and in human glomerular diseases. We identified apoptotic cells in the glomeruli, tubules and interstitium in the remnant kidney by electron microscopy. DNA fragmentation, which is a biochemical characteristic of apoptosis, was detected by in situ nick end-labeling of fragmented DNA with terminal deoxynucleotidyl transferase and biotinylated deoxyuridine triphosphate. Fragmented DNA in the glomeruli and tubules increased with the progression of glomerulosclerosis in the remnant kidney model. This finding was also demonstrated in other glomerular sclerotic lesions such as IgA and lupus nephritis. The number of cells positive for nick end-labeling in the glomerulus significantly correlated with the degree of glomerulosclerosis and the deterioration of renal function. These results indicate that apoptosis is, at least in part, involved in the cell deletion of various glomerular diseases leading to sclerosis.

Objective. To determine the expression of interleukin‐6 (IL‐6), IL‐11, leukemia inhibitory factor (LIF), and oncostatin M (OSM) and their major cellular sources in the joints of rheumatoid arthritis (RA) patients, as well as the correlation of circulating levels of these IL‐6‐type cytokines and C‐reactive protein (CRP). Methods. Messenger RNA (mRNA) and protein levels for IL‐6, IL‐11, LIF, and OSM were determined by using reverse transcription‐polymerase chain reaction and enzyme‐linked immunosorbent assay, respectively. Results. Cells isolated from the synovium of RA patients expressed mRNA for IL‐6, IL‐11, LIF, and OSM at higher levels than did synovial cells from osteoarthritis (OA) patients, and spontaneously released greater quantities of these proteins in culture. Fibroblast cell lines derived from RA synovium were able to produce IL‐6, IL‐11, and LIF, but not OSM, when stimulated with IL‐1 and tumor necrosis factor α. OSM was found to be produced spontaneously by synovial tissue macrophages. IL‐6, IL‐11, LIF, and OSM were present in synovial fluid from the RA patients; levels of IL‐6, LIF, and OSM were present in significantly greater quantities in RA patients than in OA patients. However, only IL‐6 was significantly elevated in the serum of RA patients and correlated with the serum CRP level, while other IL‐6‐type cytokines were not detected. Conclusion. IL‐6, IL‐11, LIF, and OSM are all produced in large amounts at the site of disease activity, but IL‐6 derived from synovial fibroblasts may be the major hormone‐like mediator that induces the hepatic synthesis of acute‐phase proteins in RA.

Advanced protein glycation has been proposed as a major factor in the development of diabetic nephropathy. Advanced glycation end products (AGEs) have altered the structure of extracellular matrix component and impaired self association in vitro. To elucidate the role of AGEs in the progression of diabetic nephropathy, the present study was undertaken to localize glomerular AGEs immunohistochemically. Ultrastructural changes of the mesangial matrix were analyzed with high resolution scanning electron microscopy. No glomerular AGEs staining was noted in normal control kidney specimens, or in tissue from glomerulonephritis patients without diabetes mellitus. The mesangium showed a positive AGEs staining in advanced stages of diabetic nephropathy, and the most characteristic finding was the strong AGEs staining in nodular lesions. By high resolution scanning electron microscopy, control and diabetic mesangial matrices revealed a meshwork structure composed of fine fibrils (10 nm in width) and numerous pores (12 to 13 nm in diameter). In the nodular lesions, however, loosening of the meshwork was significant, and the diameter of the pores was enlarged (approximately 24 nm). This study provides the first immunohistochemical evidence that AGEs are localized in diabetic glomeruli, most notably to nodular lesions. Advanced glycation might play a role in the progression of diabetic nephropathy through impairment of the assembly of matrix proteins in vivo.

Abnormalities in the hypothalamo-pituitary-adrenal axis in spontaneously hypertensive rats (SHR) during development of hypertension were investigated using in vivo and in vitro methods. Plasma ACTH responses to hemorrhage and ether stress were significantly smaller in 7-week-old SHR than in age-matched Wistar-Kyoto rats (WKY), while plasma corticosterone baseline levels and its response to stress were greater in SHR than in WKY. There was no significant difference in the plasma ACTH response to ether stress between bilaterally adrenalectomized SHR and WKY replaced with a 25% corticosterone pellet for 6 days. Adrenalectomy prevented the development of hypertension in SHR; however, corticosterone replacement restored hypertension. Plasma ACTH showed a smaller response to iv CRH injection in SHR than in WKY, while the ACTH response to arginine vasopressin was not different between SHR and WKY. CRH concentrations in the median eminence, posterior pituitary, and cerebral cortex were lower in SHR than in WKY, while the CRH concentration in the median eminence was not different in SHR and WKY when they were adrenalectomized with or without corticosterone replacement. Basal in vitro CRH release from hypothalamic tissue was reduced in SHR, while CRH release in response to 56 mM KCl was not different in SHR and WKY. These results suggest that adrenocortical function is enhanced in young SHR, that reduced ACTH response to stress and exogenous CRH in SHR may be ascribed to higher plasma corticosterone levels, and that corticosterone is essential for the development of hypertension in SHR.