The mechanism of angiotensin II binding downregulation by high glucose in primary renal proximal tubule cells.
The renin-angiotensin system plays an important role in the development of diabetic nephropathy. However, the mechanism of ANG II receptor regulation in the renal proximal tubule in the diabetic condition has not been elucidated. Thus we investigated the signal pathways involved in high-glucose-induced downregulation of ANG II binding in primary cultured renal proximal tubule cells. Twenty-five millimolar glucose, but not mannitol and L-glucose, induced downregulation of the AT(1) receptor (AT(1)R) because of a significant decline in maximal binding with no significant change in the affinity constant. Twenty-five millimolar glucose also decreased AT(1)R mRNA and protein levels. The 25 mM glucose-induced increase in the formation of lipid peroxides was prevented by antioxidants, protein kinase C (PKC) inhibitors, or L-type calcium channel blockers. These agents also blocked 25 mM glucose-induced downregulation of (125)I-ANG II binding. In addition, 25 mM glucose increased transforming growth factor (TGF)-beta1 secretion, and anti-TGF-beta antibody significantly blocked 25 mM glucose-induced downregulation of (125)I-ANG II binding. Furthermore, the 25 mM glucose-induced increase in TGF-beta1 secretion was inhibited by PKC inhibitors, L-type calcium channel blockers, or antioxidants. In conclusion, high glucose may induce downregulation of (125)I-ANG II binding via a PKC-oxidative stress-TGF-beta signal cascade in primary cultured rabbit renal proximal tubule cells.
Park
Soo Hyun
SH
Hormone Research Center, Department of Veterinary Physiology, College of Veterinary Medicine, Chonnam National University, Kwangju 500-757, Korea.
Han
Ho Jae
HJ
D000804:Angiotensin II / Q000378:metabolism* / Q000494:pharmacology; D000818:Animals; D000959:Antihypertensive Agents / Q000494:pharmacology; D000975:Antioxidants / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002273:Carcinogens / Q000494:pharmacology; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D015870:Gene Expression / Q000502:physiology; D005947:Glucose / Q000494:pharmacology*; D007093:Imidazoles / Q000494:pharmacology; D007457:Iodine Radioisotopes; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000378:metabolism*; D015227:Lipid Peroxidation / Q000187:drug effects; D019808:Losartan / Q000494:pharmacology; D009543:Nifedipine / Q000494:pharmacology; D016877:Oxidants / Q000494:pharmacology; D018384:Oxidative Stress / Q000502:physiology; D011493:Protein Kinase C / Q000378:metabolism; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology; D012333:RNA, Messenger / Q000032:analysis; D011817:Rabbits; D011869:Radioligand Assay; D044140:Receptor, Angiotensin, Type 1; D011945:Receptors, Angiotensin / Q000235:genetics / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D016212:Transforming Growth Factor beta / Q000378:metabolism; D014662:Vasoconstrictor Agents / Q000378:metabolism* / Q000494:pharmacology
D000959:Antihypertensive Agents; D000975:Antioxidants; D002121:Calcium Channel Blockers; D002273:Carcinogens; D007093:Imidazoles; D007457:Iodine Radioisotopes; D016877:Oxidants; D011500:Protein Synthesis Inhibitors; D011725:Pyridines; D012333:RNA, Messenger; D044140:Receptor, Angiotensin, Type 1; D011945:Receptors, Angiotensin; D016212:Transforming Growth Factor beta; D014662:Vasoconstrictor Agents; D000804:Angiotensin II; C073402:PD 123319; D011493:Protein Kinase C; D009543:Nifedipine; D005947:Glucose; D019808:Losartan; D013755:Tetradecanoylphorbol Acetate