Advanced glycated albumin impairs protein degradation in the kidney proximal tubules cell line LLC-PK1

Cell Mol Biol (Noisy-le-grand). 1998 Nov;44(7):1051-60.

Abstract

Advanced glycation end-products (AGEs) are assumed to play a major role in the genesis of diabetic nephropathy and other diabetic complications. We studied the potential effect of AGEs on protein turnover and lysosomal proteinase activities in LLC-PK1 cells, a pig kidney proximal tubules cell line. Advanced glycated bovine serum albumin (AGE-BSA) was used as a model of AGEs and its action was compared to that of nonglycated BSA. AGE-BSA but not BSA (50 micromol/l) induced a significant increase in cell volume (BSA: 4870.6 +/- 74.8 fl, AGE-BSA: 5718.0 +/- 20.7 fl, p<0.01). Protein degradation rate was decreased by 13.8% after 48 hrs. incubation with AGE-BSA (p<0.01) while protein synthesis increased by 19,1%, (p<0.01). After incubation with AGE-BSA but not BSA activities of lysosomal cathepsins (B, L+B and H) decreased in a time- and dose-dependent fashion. This decline was neither caused by a shift in lysosomal pH outside the optimal range for cathepsins, nor by a direct inhibitory effect of AGEs modified proteins or peptides but most probably by inhibition of cathepsin B expression as measured by RT-PCR. It is supposed that impaired protease activities participated in decreased protein breakdown and cell enlargement. For the first time our data provide the evidence that AGEs induce hypertrophy of LLC-PK1 cells due to decreased protein breakdown resulting from reduced lysosomal proteinase activities with a concomitant stimulation of protein synthesis.

MeSH terms

  • Animals
  • Cathepsin B / antagonists & inhibitors
  • Cathepsin B / genetics
  • Cathepsins / metabolism
  • Cell Count / drug effects
  • Cell Size
  • Glycation End Products, Advanced / pharmacology*
  • Glycosylation
  • Hydrogen-Ion Concentration
  • Kidney Tubules, Proximal / cytology
  • Kidney Tubules, Proximal / drug effects
  • Kidney Tubules, Proximal / metabolism*
  • LLC-PK1 Cells
  • Lysosomes / enzymology
  • Proteins / metabolism*
  • Reverse Transcriptase Polymerase Chain Reaction / methods
  • Serum Albumin, Bovine / pharmacology*
  • Swine

Substances

  • Glycation End Products, Advanced
  • Proteins
  • advanced glycation end products-bovine serum albumin
  • Serum Albumin, Bovine
  • Cathepsins
  • Cathepsin B