Advanced glycated albumin impairs protein degradation in the kidney proximal tubules cell line LLC-PK1.
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.
Sebeková
K
K
Clinic of Pharmacotherapy, Institute of Preventive and Clinical Medicine, Bratislava, Slovakia.
Schinzel
R
R
Ling
H
H
Simm
A
A
Xiang
G
G
Gekle
M
M
Münch
G
G
Vamvakas
S
S
Heidland
A
A
D000818:Animals; D002401:Cathepsin B / Q000037:antagonists & inhibitors / Q000235:genetics; D002403:Cathepsins / Q000378:metabolism; D002452:Cell Count / Q000187:drug effects; D048429:Cell Size; D017127:Glycation End Products, Advanced / Q000494:pharmacology*; D006031:Glycosylation; D006863:Hydrogen-Ion Concentration; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D018374:LLC-PK1 Cells; D008247:Lysosomes / Q000201:enzymology; D011506:Proteins / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D012710:Serum Albumin, Bovine / Q000494:pharmacology*; D013552:Swine
D017127:Glycation End Products, Advanced; D011506:Proteins; C081628:advanced glycation end products-bovine serum albumin; D012710:Serum Albumin, Bovine; D002403:Cathepsins; D002401:Cathepsin B