Possible involvement of intracellular angiotensin II receptor in high-glucose-induced damage in renal proximal tubular cells.

BACKGROUND: Recent studies have identified high glucose as a potent stimulus for the intracellular synthesis of angiotensin II. However, the exact roles of angiotensin II and angiotensin II type 1 receptor blockers (ARB) in high-glucose-induced renal tubular function remain unclear. METHODS: N-Acetyl-beta-glucosaminidase (NAG), angiotensin II and 8-hydroxy-2'-deoxyguanosine (8-OHdG) concentrations in renal proximal tubular epithelial cells (RPTECs) with or without high glucose/ARB were determined using a modified commercial procedure. The changes of p22phox and cytoplasmic inhibitory kappa B (IkB) protein levels in RPTECs were measured using Western blotting. RESULTS: High-glucose treatment (4x10-2 mol/L) significantly increased NAG release, angiotensin II concentrations in cell lysates and 8-OHdG and p22phox protein levels compared with those in regular glucose medium (1.75x10(-2) mol/L). ARBs (candesartan, olmesartan or valsartan; 1x10(-9)-10(-7) mol/L) showed a significant reduction in high-glucose-induced NAG, 8-OHdG and p22phox protein levels in RPTECs. Significant decreases of cytoplasmic IkB protein levels were observed in the high-glucose-treated group in RPTECs. ARBs markedly reversed high-glucose-induced reduction of IkB protein levels in RPTECs. CONCLUSIONS: ARBs reduce high-glucose-induced oxidative stress in RPTECs possibly via blockade of intracellular as well as extracellular AT1 receptor signaling, which possibly protects renal tubular cell function during diabetic nephropathy.

Cisplatin-induced macroautophagy occurs prior to apoptosis in proximal tubules in vivo.

BACKGROUND: Autophagy is an intracellular bulk degradation process induced by cell starvation. Autophagy was recently reported to be induced by various stresses such as hypoxia, ischemia/reperfusion, toxins, and denatured proteins, and to affect cell survival and death. Light chain 3-II (LC3-II) is specifically located on double membrane-bound autophagosomes that envelop disused proteins or organelles. METHOD: Transgenic mice in which green fluorescent protein (GFP) was fused to LC3 (LC3-GFP) were administered cisplatin (20 mg/kg). After euthanasia at times between 0 and 72 h, kidneys were excised for immunohistochemical analyses. Microscopic examinations of the generated NRK-52E cell lines stably transfected with LC3-GFP, and Western blot analyses of NRK-52E cells, were undertaken after cisplatin treatment with or without autophagy inhibitors and beclin 1 small interfering RNA (siRNA). RESULTS: Autophagosomes increased in the proximal tubular cells of transgenic mice from 12 h after cisplatin injection (20 mg/kg). The time course for this was faster than those for tubular necrosis and apoptosis. Autophagosomes also increased in NRK-52E cells after cisplatin treatment, with the time course for this being faster than that for apoptosis. When autophagy was suppressed by autophagy inhibitors or beclin 1 siRNA, the level of apoptosis was also suppressed. CONCLUSION: Autophagy occurs in proximal tubular cells after cisplatin treatment and is involved in cell death in renal tubular injury. Our data suggest that autophagy is a kind of cell damage index and that cells with activated autophagy will be scavenged by apoptosis.

Effects of angiotensin II type 1 receptor blocker on albumin-induced cell damage in human renal proximal tubular epithelial cells.

BACKGROUND/AIMS: Proteinuria is not merely a marker of chronic nephropathies, but may also be involved in the progression to end-stage renal failure. We investigated the effect of angiotensin II type 1 receptor blockers (ARBs) on albumin-induced cell damage in human renal proximal tubular epithelial cells (RPTEC). METHODS: The N-acetyl-beta-D-glucosaminidase (NAG) and 8-hydroxy-2'-deoxyguanosine (8-OHdG) levels in the medium after albumin treatment with ARBs were determined by commercially available kits. The levels of p22(phox) protein in RPTEC were measured using Western blotting after albumin treatment with ARBs. Angiotensin II concentrations in cell media and cell lysates were assayed with a commercially available kit. RESULTS: Human albumin (0.1-10 mg/ml) dose-dependently increased NAG release and olmesartan or valsartan (10(-9)-10(-7) mol/l) showed a significant reduction on albumin (1 mg/ml)-induced NAG release in RPTEC. Albumin treatment (1 mg/ml) showed significant increases in p22(phox) protein levels in RPTEC and ARBs significantly decreased albumin-induced p22(phox) protein levels. Significant increases in 8-OHdG levels were observed in the albumin (1 mg/ml)-treated group and ARBs markedly reduced albumin-induced 8-OHdG levels in RPTEC. Human albumin dose-dependently increased angiotensin II concentrations in both cell media and lysates. CONCLUSION: These observations suggest renal tubular cell-protective properties of ARBs related to decreased oxidative stress during proteinuria.

Magnetic resonance imaging of palindromic rheumatism.

A 44-year-old man with intermittent asymmetric migratory oligoarthritis lasting the recent decade was admitted to our hospital. Considerable specific biomarkers for rheumatoid arthritis such as anti-agalactosyl IgG antibody are all negative. He was diagnosed as palindromic rheumatism (PR). Although hand X-rays showed no remarkable findings, hand magnetic resonance imaging (MRI) detected pannus and bone erosion. PR is defined as the disease characterized by short-lasting attacks of acute oligoarthritis, without radiographic changes. To our knowledge, the findings of MRI for PR have not been previously described. We propose that MRI findings in patients with PR is useful tool to distinguish PR from rheumatoid arthritis (RA) or other RA related diseases.

Coexisting primary hyperparathyroidism and sarcoidosis in a patient with severe hypercalcemia.

A 75-year-old woman was admitted to our hospital because of general fatigue. She had suffered from sarcoidosis during her 40s with remission, but subsequently she experienced progression of hypercalcemia and renal dysfunction for 7 years. On admission, she showed marked hypercalcemia (up to 15.5 mg/dl) and renal failure (serum creatinine 2.5 mg/dl). Plasma intact PTH level was elevated (up to 190 pg/ml), and thyroid ultrasonography and (99m) Tc-MIBI scintigraphy detected a parathyroid mass, which was surgically removed and histologically confirmed to be a parathyroid adenoma. However, even after surgery her serum calcium remained elevated, but subsequent administration of glucocorticoid for sarcoidosis completely normalized her hypercalcemia. The simultaneous occurrence of primary hyperparathyroidism and sarcoidosis is rare, and our data suggest that high plasma PTH and 1,25(OH)D exerted an additive effect on the occurrence of severe hypercalcemia.

Angiotensin II receptor blocker inhibits tumour necrosis factor-alpha-induced cell damage in human renal proximal tubular epithelial cells.

AIM: We investigated the effect of angiotensin II (AII) type 1 (AT1) and angiotensin II type 2 (AT2) receptor blockers on tumour necrosis factor alpha (TNF-alpha)-induced cell damage in human renal proximal tubular epithelial cells (RPTEC). METHODS: The lactate dehydrogenase (LDH) and N-acetyl-beta-glucosaminidase (NAG) release into the medium after TNF-alpha treatment in RPTEC were determined using modified commercial procedures. In addition, the levels of caspase 3/7 activity in RPTEC were measured after TNF-alpha treatment with AlphaTau1 or AT2 receptor blockers. Finally we investigated the change of p22phox protein levels after TNF-alpha with AlphaTau1 or AT2 receptor blockers in RPTEC. RESULTS: Tumour necrosis factor alpha (10(-8) mol/L) significantly increased LDH and NAG release into the medium from RPTEC. AlphaTau1 receptor blockers, olmesartan and valsartan (10(-9)-10(-6) mol/L) showed a significant reduction on TNF-alpha-induced LDH and NAG release in RPTEC. AT2 receptor blocker, PD123319 (10(-7)-10(-5) mol/L) also decreased TNF-alpha-induced LDH and NAG release in RPTEC. Blockade of both AlphaTau1 and AT2 receptor indicated additional reduction on TNF-alpha-induced LDH and NAG release. TNF-alpha (10(-8) mol/L) treatment showed small but significant increases of caspase 3/7 activity in RPTEC, and AT1 and AT2 receptor blockers (10(-8) mol/L) comparably decreased TNF-alpha-induced caspase 3/7 activity. Significant increases of p22phox protein levels were observed in TNF-alpha-treated group in RPTEC. However, only AlphaTau1 (10(-8) mol/L) but not AT2 (10(-5) mol/L) receptor blocker significantly decreased TNF-alpha-induced p22phox protein levels. CONCLUSION: The present study demonstrates that TNF-alpha induces renal tubular cell damage in RPTEC and AT1/AT2 receptor blockers showed cytoprotective effects probably via at least partly different mechanism.

Increased amount of the angiotensin-converting enzyme (ACE) mRNA originating from the ACE allele with deletion.

The insertion/deletion (I/D) polymorphism in intron 16 of the angiotensin-converting enzyme (ACE) gene is involved in the development of cardiovascular diseases. We compared the ACE mRNA expression originating from the allele with a deletion (D allele) and that from the allele with an insertion (I allele) in human white blood cells from ID heterozygotes. We identified the mRNA from the I allele by using the G2215A polymorphism that lies in exon 15 and that was linked to the I/D polymorphism. RNA samples were obtained from 12 healthy heterozygotes of both I/D and G2215A, and every insertion was shown to be linked to 2215G. ACE mRNA was amplified by the reverse transcription/polymerase chain reaction (RT-PCR) method with an end-labeled antisense primer. The PCR products were digested with HaeII and separated by electrophoresis, and the relative radioactivities of the 2215A and 2215G bands were measured on an auto-image analyzer. The results showed that, in every cases, the intensity of the 2215A product (D allele origin) was higher than that of the 2215G product (I allele origin). The mean ratio of 2215A to 2215G was 1.79 (1.11-2.62). Thus, the D allele leads to higher expression of the ACE mRNA and may affect the renin-angiotensin system in local regions.