Altered expression of NDST-1 messenger RNA in puromycin aminonucleoside nephrosis.

ABSTRACT

Sulfated portions of glycosaminoglycan (GAG) side chains in heparan sulfate proteoglycan (HSPG) are thought to play an important role in charge-dependent selectivity of glomerular filtration against plasma proteins. Heparan sulfate N-acetylglucosamine N-deacetylase/adenosine 3'-phosphate 5'-phosphosulfate unsubstituted glucosamine N-sulfotransferase (NDST) is the key enzyme regulating sulfation of GAG chains. In this study we investigated transcriptional expression of NDST-1, 1 of 4 isozymes of NDST, in glomeruli of rats with puromycin aminonucleoside (PAN) nephrosis. Nephrosis was induced in rats with a single intraperitoneal injection of 150 mg/kg PAN. On days 10 and 35, expression of NDST-1 messenger RNA (mRNA) in glomeruli was analyzed with the use of Northern-blot analysis. Immunohistochemical studies were also performed with the use of monoclonal antibodies that react specifically with the N-sulfated portion of the GAG chain of HSPG and agrin, a major core protein of HSPG in glomerular basement membrane (GBM). In addition, we studied the expression of NDST-1 mRNA in cultured glomerular epithelial cells (GECs) and glomerular mesangial cells in the presence of PAN. On day 10, when significant proteinuria developed, the ratios of glomerular expression of NDST-1 mRNA against glyceraldehyde-phosphate dehydrogenase mRNA in PAN-treated rats were decreased to 48% +/- 6% of those in controls (P<.05). Immunohistochemical studies revealed that staining for N-sulfated GAG chains of HSPG on GBM was markedly reduced on day 10 in PAN-treated rats but that staining for agrin was unchanged. In contrast, on day 35, when PAN-treated rats recovered from proteinuria, we noted no differences in glomerular expression of NDST-1 mRNA and staining intensity for N-sulfated GAG chains on GBM between PAN-treated rats and controls. Incubation of GECs for 24 hours in the presence of 50 ng/mL PAN resulted in the reduction of the expression of NDST-1 mRNA (67% +/- 12% of those in controls, P<.05). In summary, we found alteration of the expression of NDST-1 mRNA, accompanying a loss of N-sulfated GAG chains of HSPG on GBM without changes in the core protein agrin, in the course of PAN nephrosis. These data suggest an important role for this enzyme in heparan sulfate assembly in GBM and GEC and in the pathogenesis of proteinuria in PAN nephrosis.