Up-regulated TGF-beta mRNA expression in splenic T cells of high IgA-prone mice: a murine model of IgA nephropathy with glomerulosclerosis

BACKGROUND/AIMS: Recently, we established a high serum IgA-prone inbred (HIGA) mouse strain as a murine model of spontaneous IgA nephropathy by selective mating of high serum IgA ddY mice, and found that they showed enhanced production of glomerular extracellular matrix components with increased expression of TGF-beta mRNA and protein in the kidneys. In this study, we examined the roles of lymphocytes in the development of high serum IgA in this strain. METHODS: We performed flow cytometric analyses of T and B cells in splenic mononuclear cells (SMNCs) from these mice using BALB/c mice as normal controls. We also compared serum TGF-beta1 concentrations and TGF-beta mRNA expression levels in the B-cell-depleted (T-cell-rich) fraction of SMNCs in these mice. RESULTS: HIGA mice showed significantly fewer CD3-positive cells compared with BALB/c mice when young, but not when aged. The CD4/CD8 ratio of HIGA mice was lower than that of BALB/c mice, but this difference was not significant. Although the number of B220-positive cells did not vary significantly, the ratio of surface IgA-positive B cells was significantly increased in both young and adult HIGA mice. The B-cell-depleted SMNCs from HIGA mice exhibited higher levels of expression of TGF-beta and TGF-beta1 mRNA than controls from a young age, which were maintained throughout life, but there were no differences in PDGF, MCP-1 or bFGF expression between these two strains. In contrast to local mRNA expression, serum TGF-beta1 concentration was decreased in HIGA mice compared with BALB/c controls. CONCLUSION: These findings suggest that the mating procedure performed to establish HIGA mice selected for a unique phenotype of local up-regulation of TGF-beta production in the kidneys, as well as T cells that may contribute to both the early and consistently high serum IgA expression and enhanced production of renal extracellular matrix components in HIGA mice. Additionally, TGF-beta1 may act locally, not systemically, in a paracrine or autocrine manner.     

Occurrence and some properties of a protein-like inhibitor of dopamine beta-hydroxylase in rat liver.

Evidence of endogenous inhibitors of dopamine β-hydroxylase [3, 4-dihydroxyphenylethylamine, ascorbate:O₂ oxidoreductase (hydroxylating), EC 1.14.2.1] (DBH) in rat liver was obtained. At least two kinds of endogenous inhibitors were present in the 105,000 g supernatant of rat liver homogenate and their molecular weights were shown to be about 40,000 and 1200 by gel filtration.The higher molecular weight inhibitor was partially purified by ammonium sulfate fractionation, column chromatography of Sephadex G-100 or Sephadex G-200, and DEAE-Sephadex(A-25) treatment. The activity of this inhibitor was not diminished by boiling for 5 min, but was lost completely when the inhibitor was treated with trypsin, suggesting that it may be a protein. The inhibition of DBH by this protein-like inhibitor in the liver was completely protected by the addition of N-ethylmaleimide, indicating that it may contain functional sulfhydryl groups. The inhibition by this protein-like inhibitor was of the noncompetitive type with both the substrate and with ascorbic acid, one of the cofactors in this reaction.