An analysis of high glucose and glucosamine-induced gene expression and oxidative stress in renal mesangial cells

Renal mesangial cells play an important role in the development of diabetic kidney disease. We have previously demonstrated that some of the effects of high glucose on mesangial extracellular matrix (ECM) protein expression are mediated by the hexosamine biosynthesis pathway (HBP) in which fructose-6-phosphate is converted to glucosamine-6-phosphate by the rate-limiting enzyme glutamine:fructose-6-phosphate amidotransferase (GFAT). Using Affymetrix murine expression U430 2.0 oligochips, we examined the global effects of high glucose (HG) and glucosamine (GlcN) on mRNA expression of a mouse mesangial cell line (MES-13). We sought to determine the portion of mRNA expression in MES-13 cells, which is mediated both by high glucose and glucosamine, i.e., via the HBP. Of the 34,000 genes on the chip, approximately 55.7 - 60.8% genes are detected in MES-13 cells. Culturing MES-13 cells for 48 h with HG alters the expression of approximately 389 genes at our preset threshold levels (at least 2-fold change) where 263 genes are up-regulated and 126 genes are down-regulated. GlcN also increases the expression of 106 genes and decreases 94 genes during the same period of incubation. Seventy-two genes in the chip are commonly regulated by HG and GlcN, in which 33 genes are up and 39 genes are down. The mRNA level of thioredoxin interacting protein (TXNIP), an inhibitor of thioredoxin activity, is maximally increased approximately 18.8 and 9.9-fold respectively by HG and GlcN. The differential expression of several genes found in the microarray analysis is further validated by real-time quantitative PCR. Significant biological processes commonly targeted by HG and GlcN are the TXNIP-thioredoxin system, oxidative stress, endoplasmic reticulum (ER) stress, extracellular matrix genes, and interferon-inducible genes. Stable overexpression of TXNIP in MES-13 cells increases glucose and glucosamine-mediated ECM gene expression and oxidative stress. We conclude from these results that the HBP mediates several effects of high glucose on mesangial cell metabolism, which promotes reactive oxygen species generation to cause cellular oxidative stress, ECM gene expression and apoptosis.