No abstract available.
Diabetic Nephropathies* ; Renin-Angiotensin System*

A growing body of evidence indicates that epithelial-mesenchymal transition (EMT) of human peritoneal mesothelial cells (HPMC) may play an important role in the development and progression of peritoneal fibrosis during long-term peritoneal dialysis (PD) leading to failure of peritoneal membrane function. Here, we review our own observations and those of others on the mechanisms of EMT of HPMC and suggest potential therapeutic strategies to prevent EMT and peritoneal fibrosis during long-term PD. We found that high glucose and H2O2 as well as transforming growth factor-beta1 (TGF-beta1) induced EMT in HPMC and that high glucoseinduced EMT was blocked not only by inhibition of TGF-beta1 but also by antioxidants or inhibitors of mitogen-activated protein kinases (MAPK). Since MAPKs are downstream target molecules of reactive oxygen species (ROS), these data suggest that high glucose-induced generation of ROS and subsequent MAPK activation mediate high glucose-induced EMT in HPMC. We and others also observed that bone morphogenetic protein-7 (BMP-7) prevented EMT in HPMC. Glucose degradation products (GDP) were shown to play a role in inducing EMT. Involvement of a mammalian target of rapamycin (mTOR) in TGF-beta1-induced EMT has also been proposed in cultured HPMC. A better understanding of the precise mechanisms involved in EMT of HPMC may provide new therapeutic strategies for inhibiting peritoneal fibrosis in long-term PD patients.
Epithelial Cells/*pathology ; Fibrosis ; Humans ; Mesoderm/*pathology ; Peritoneal Dialysis/*adverse effects ; Peritoneum/*pathology

BACKGROUND: 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin (TCDD: dioxin) is a potent environmental toxicant that alters various cell function. Both reactive oxygen species (ROS) and mitogen-activated protein kinases (MAPK) mediate dioxin-induced cytotoxicity. Since dioxin was shown to increase renal cell fibronectin secretion in a dose-dependent manner and ROS and MAPK also play roles in fibronectin upregulation in renal cells, the present study examined whether ROS and/or MAPK activation play a role in dioxin-induced fibronectin upregulation in tubular epithelial cells. METHODS: Madin-Darby canine kidney (MDCK) cells were cultured with minimum essential medium (MEM) containing 10% fetal bovine serum. Growth arrested and synchronized MDCK cells by serum deprivation were stimulated with dioxin 1 nM in the presence or absence of extracellular signal-regulated protein kinase (ERK) inhibitor PD98059 50 microM, p38 MAPK inhibitor 100 nM, trolox 500 microM, or taurine 500 microM for up to 48 hours. Dichlorofulorescein (DCF)-sensitive cellular ROS was measured by FACScan and fibronectin in the media and cellular MAPK by a Western blot analysis. RESULTS: Dioxin 1 nM significantly increased cellular ROS and fibronectin in MDCK cells. Antioxidants, trolox and taurine, effectively inhibited dioxin-induced cellular ROS and fibronectin secretion. Dioxin increased phosphorylation of ERK at 5 minutes and P38 MAPK at 48 hours. Dioxin did not affect c-Jun NH2-terminal kinase (JNK) activation for up to 48 hours. Both PD98059 and p38 MAPK inhibitor suppressed dioxin-induced fibronectin secretion by MDCK cells. CONCLUSION: These data suggest that dioxin increases fibronectin secretion by renal distal tubular epithelial cells through ROS and MAPK (ERK and p38 MAPK) and this may lead to renal fibrosis.
Antioxidants ; Blotting, Western ; Epithelial Cells ; Fibronectins* ; Fibrosis ; Kidney ; Madin Darby Canine Kidney Cells* ; Mitogen-Activated Protein Kinases* ; p38 Mitogen-Activated Protein Kinases ; Phosphorylation ; Phosphotransferases ; Protein Kinases ; Reactive Oxygen Species* ; Taurine ; Up-Regulation

Administration of captopril, a scavenger of oxygen derived radicals as well as an inhibitor of angiotensin converting enzyme, has been an efficient way of treating diabetic proteinuria. In the present study, we evaluate whether captopril can ameliorate diabetic proteinuria as an effect on oxidative stress in streptozotocin- induced diabetic rats (STZR). At four weeks after the injection of streptozotocin (50 mg/kg, i.v.), STZR (n = 5) exhibited microalbuminuria. The rate of urinary albumin excretion was 0.5 +/- 0.1 and 2.6 +/- 0.3 mg/24hr in age-matched control rats (CR; n = 5) and STZR, respectively. Compared to CR, STZR also showed an extremely increased rate of urinary lipid peroxides (LPO) excretion, an index of oxygen derived radicals generation. The respective values for CR and STZR were 0.6 +/- 0.3 and 6.9 +/- 0.6 mumol/24 hr. Significant amelioration of urinary albumin and LPO excretion rate by the treatment of insulin (2 U/day) suggests that these are associated with the diabetic state induced by streptozotocin rather than a direct effect of streptozotocin. Chronic administration of captopril, which did not cause any discernible effect on CR, significantly reduced the urinary albumin excretion rate and decreased LPO excretion in STZR. The urinary albumin excretion rate was significantly correlated with the LPO excretion rate (p = 0.0004). These results suggest that oxidative stress can be responsible for diabetic microalbuminuria, and captopril could diminish the lipid peroxidation and ameliorate the microalbuminuria in diabetic rats.
Albuminuria/*drug therapy ; Animal ; Blood Glucose/analysis ; Captopril/pharmacology/*therapeutic use ; Diabetes Mellitus, Experimental/metabolism ; Diabetic Nephropathies/*drug therapy/metabolism ; Insulin/pharmacology ; Lipid Peroxidation/*drug effects ; Male ; Rats ; Rats, Sprague-Dawley ; Support, Non-U.S. Gov't

No abstract available.
Peritoneal Fibrosis

E-cadherin is a cell adhesion molecule that is expressed abundantly in the kidney. However, the expression pattern in various renal epithelial cells is not well established. The purpose of this study was to determine the cellular localization along the nephron segments in the rat kidney. Kidneys from adult Sprague Dawley rats were fixed in 4% paraformaldehyde and processed for immunohistochemistry. Bumetanide-sensitive Na+/K+/2Cl- cotransporter (BSC1), thiazide-sensitive Na+/Cl- cotransporter (TSC), calbindin D28k, and H+-ATPase were used to identify the thick ascending, distal convoluted stubule, connecting tubule, and collecting duct, respectively. In the rat kidney, Ecadherin was expressed mainly in the basolateral domain of the collecting duct and papillary surface epithelial cells. The expression level of E-cadherin changed gradually in the connecting tubule and became moderate in the distal convoluted tubule, thick ascending limb, and loop of Henle. The S1 and S2 segment of the proximal tubule showed weak immunoreactivity. However, E-cadherin was not expressed in the S3 segment of the proximal tubule in the rat kidney. These results suggest that E-cadherin is a major adhesion molecule in the collecting duct and papillary surface epithelium, and that E-cadherin may play a critical role in maintaining the epithelial polarity of these nephron segments.
Adult ; Animals ; Cadherins ; Calcium-Binding Protein, Vitamin D-Dependent ; Cell Adhesion ; Epithelial Cells ; Epithelium ; Extremities ; Formaldehyde ; Humans ; Immunohistochemistry ; Kidney ; Loop of Henle ; Nephrons ; Polymers ; Rats ; Rats, Sprague-Dawley

Oxidative stress defined as outbalanced generation of reactive oxygen species (ROS) than the existing antioxidative defense mechanisms plays an important role in tissue injury. Ischemia/reperfusion accompanied during organ transplantation is well- established oxidative stress-induced tissue injury. We hypothesized that oxidative stress may also play a role in the development and progression of chronic allograft nephropathy (CAN), since that ROS are major signaling molecules of growth factors and cytokines [platelet-derived growth factors, transforming growth factor-beta1 (TGF-beta1) ] upregulated in the kidney of CAN, that ROS in turn upregulate TGF-beta1, and that mycophenolic acid may inhibit features of CAN [proliferation and extracellular matrix (ECM) accumulation in vascular smooth muscle cells and glomerular mesangial cells] through inhibiting cellular ROS. Cellular ROS activate signal transduction cascade (protein kinase C, mitogen-activated protein kinases, and janus kinases) and transcription factors (nuclear factor-kappa B, activated protein-1, specificity protein 1, and signal transducers and activators of transcription) leading to regulation of genes and proteins involved in cellular proliferation, ECM remodeling, and apoptosis accompanied in CAN. This review is intended to provide an overview of oxidative stress in renal allograft nephropathy.
Chronic Disease ; Humans ; Kidney Diseases/*etiology ; Kidney Transplantation/*adverse effects ; *Oxidative Stress ; Research Support, Non-U.S. Gov't

Chronic inflammation has been proposed as one of the main molecular mechanisms of aging and age-related diseases. Although evidence in humans is limited, short-term calorie restriction (CR) has been shown to have anti-inflammatory effects in aged experimental animals. We reported on the long-term treatment of daumone, a synthetic pheromone secreted by Caenorhabditis elegans in an energy deficient environment, extends the life-span and attenuates liver injury in aged mice. The present study examined whether late onset short-term treatment of daumone exerts anti-inflammatory effects in the livers of aged mice. Daumone was administered orally at doses of 2 or 20 mg/kg/day for 5 weeks to 24-month-old male C57BL/6J mice. Increased liver macrophage infiltration and gene expression of proinflammatory cytokines in aged mice were significantly attenuated by daumone treatment, suggesting that short-term oral administration of daumone may have hepatoprotective effects. Daumone also dose-dependently suppressed tumor necrosis factor-alpha (TNF-alpha)-induced nuclear factor-kappaB (NF-kappaB) phosphorylation in HepG2 cells. The present data demonstrated that short-term treatment of daumone has anti-inflammatory effects in aged mouse livers possibly through suppression of NF-kappaB signaling and suggest that daumone may become a lead compound targeting aging and age-associated diseases.
Administration, Oral ; Aging ; Animals ; Caenorhabditis elegans ; Child, Preschool ; Cytokines ; Gene Expression ; Hep G2 Cells ; Humans ; Inflammation* ; Liver ; Macrophages ; Male ; Mice* ; NF-kappa B ; Pheromones ; Phosphorylation ; Tumor Necrosis Factor-alpha

PURPOSE: Proliferation, migration, and the accumulation of extracellular matrix (ECM) protein of vascular smooth muscle cells (VSMC) play roles for transplant arteriosclerosis. We have previously reported that carvedilol (CA) inhibits the proliferation and the migration of VSMCs. The present study examined the effects of CA on platelet-derived growth factor (PDGF)-induced collagen synthesis in VSMC and the roles of reactive oxygen species (ROS), extracellular signal- regulated protein kinase (ERK), and p38 mitogen-activated protein kinase (p38 MAPK). METHODS: Primary cultured rat VSMCs were obtained from aorta of Sprague-Dawley rats. Growth arrested and synchronized cells were pretreated with CA (10 nM~10micrometer) at 1 hour before the addition of PDGF 10 ng/ml. Collagen synthesis was measured by 3[H]-proline incorporation, ROS by flow cytometry using ROS-sensitivedichlorofluorescein (DCF) dye, and the activation of ERK andp38 MAPK by Western blot analysis. RESULTS: PDGF significantly increased collagen synthesis by 2.0-fold, intracellular ROS by 1.6-fold, the activation of ERK 1/2 and p38 MAPK by 4.2-fold and 3.9-fold compared to control, respectively. CA above 1micrometer inhibited PDGF-induced collagen synthesis. CA also inhibited DCF-sensitive ROS and the activation of ERK and p38 MAPK. All pharmacological inhibitors of ROS, ERK, and p38 MAPK effectively inhibited PDGF-induced collagen synthesis. CONCLUSION: These data suggest that CA inhibit PDGF-induced collagen synthesis possibly through inhibiting intracellular ROS and ERK 1/2 and p38 MAPK activation.
Animals ; Aorta ; Arteriosclerosis ; Blotting, Western ; Collagen* ; Extracellular Matrix ; Flow Cytometry ; Muscle, Smooth, Vascular* ; p38 Mitogen-Activated Protein Kinases ; Platelet-Derived Growth Factor ; Protein Kinases ; Rats* ; Rats, Sprague-Dawley ; Reactive Oxygen Species ; Signal Transduction*

BACKGROUND: Vascular smooth muscle cell (VSMC) proliferation plays an important role in the development and progression of chronic allograft vasculopathy as in atherosclerosis. We already reported that mycophenolic acid (MPA) inhibited VSMC proliferation, cellular reactive oxygen species (ROS) and mitogen-activated protein kinases (MAPK) in human VSMCs. In this study, we examined further molecular mechanisms involved in the anti-proliferative effect of MPA in rat VSMCs. METHODS: Primary rat VSMCs were stimulated with PDGF-BB 10 ng/mL in the presence or absence of MPA and various kinds of cell signaling inhibitors. Cell proliferation was assessed by [H3]- thymidine incorporation, NAD(P)H oxidase subunits mRNA expression by RT-PCR, dichlorofluorescein- sensitive cellular ROS by FACS, and the activation of PDGF receptor-beta (Tyr 751), rac1, and MAPK by Western blot analysis. RESULTS: PDGF increased cell proliferation and cellular ROS, activation of PDGF receptor-beta (Tyr 751), rac1, expression of p22phox and MOX1 mRNA, ERK 1/2, and p38 MAPK, compared to control. MPA inhibited up-regulation of rac1 phosphorylation, p22phox and MOX1 mRNA expression, cellular ROS, and phosphorylation of ERK 1/2 and p38 MAPK. However, MPA did not affect PDGF receptor-beta (Tyr 751) activation. Wortmannin, diphenyleniodonium (DPI), trolox, and NAC, each inhibited PDGF- induced ERK 1/2 and p38 MAPK activation. PD98059 and p38 MAPK inhibitor also inhibited PDGF-induced cell proliferation. CONCLUSION: These results suggest that MPA inhibits PDGF-induced VSMC proliferation through inhibiting NAD(P)H oxidase-dependent cellular ROS leading to ERK 1/2 and p38 MAPK activation.
Allografts ; Animals ; Atherosclerosis ; Blotting, Western ; Cell Proliferation ; Humans ; Mitogen-Activated Protein Kinases ; Muscle, Smooth, Vascular* ; Mycophenolic Acid* ; NADPH Oxidase ; p38 Mitogen-Activated Protein Kinases ; Phosphorylation ; Rats ; Reactive Oxygen Species ; RNA, Messenger ; Thymidine ; Up-Regulation