Cyclooxygenase-2 (COX-2) inhibition limits abnormal COX-2 expression and progressive injury in the remnant kidney

The Effect of Increasing Concentrations of Omega-3 Fatty Acids from either Flaxseed Oil or Preformed Docosahexaenoic Acid on Fatty Acid Composition, Plasma Oxylipin, and Immune Response of Laying Hens

BACKGROUND

There is a lack of nutrition guidelines for the feeding of omega-3 polyunsaturated fatty acids (PUFA) to laying hens. Knowledge as to whether the type and concentrations of α-linolenic acid (ALA) and/or docosahexaenoic acid (DHA) in the diet can make a difference to the birds' immune responses when subjected to a lipopolysaccharide (LPS) challenge is limited.

OBJECTIVES

The study was designed to determine the potential nutritional and health benefits to laying hens when receiving dietary omega-3 PUFA from either ALA or DHA.

METHODS

A total of 80 Lohmann LSL-Classic (white egg layer, 20 wk old) were randomly assigned to 1 of 8 treatment diets (10 hens/treatment), provided 0.2%, 0.4%, 0.6%, or 0.8% of total dietary omega-3 PUFA, provided as either ALA-rich flaxseed oil or DHA-enriched algal biomass. After an 8-wk feeding period, the birds were challenged with Escherichia coli-derived LPS (8 mg/kg; i.v. injection), with terminal sample collection 4 h after challenge. Egg yolk, plasma, liver, and spleen samples were collected for subsequent analyses.

RESULTS

Increasing dietary omega-3 supplementation yielded predictable responses in egg yolk, plasma, and liver fatty acid concentrations. Dietary intake of ALA contributed mainly to ALA-derived oxylipins. Meanwhile, eicosapentaenoic acid- and DHA-derived oxylipins were primarily influenced by DHA dietary intake. LPS increased the concentrations of almost all the omega-6 PUFA-, ALA-, and DHA-derived oxylipins in plasma and decreased hepatic mRNA expression of COX-2 and 5-LOX (P < 0.001) involved in the biosynthesis of oxylipins. LPS also increased mRNA expression of proinflammatory cytokine IFN-γ and receptor TLR-4 (P < 0.001) in the spleen.

CONCLUSIONS

These results revealed that dietary intake of ALA and DHA had unique impacts on fatty acid deposition and their derived oxylipins and inflammatory responses under the administration of LPS in laying hens.

Dual sEH/COX-2 Inhibition Using PTUPB-A Promising Approach to Antiangiogenesis-Induced Nephrotoxicity

Kidney injury from antiangiogenic chemotherapy is a significant clinical challenge, and we currently lack the ability to effectively treat it with pharmacological agents. Thus, we set out to investigate whether simultaneous soluble epoxide hydrolase (sEH) and cyclooxygenase-2 (COX-2) inhibition using a dual sEH/COX-2 inhibitor PTUPB could be an effective strategy for treating antiangiogenic therapy-induced kidney damage. We used a multikinase inhibitor, sorafenib, which is known to cause serious renal side effects. The drug was administered to male Sprague-Dawley rats that were on a high-salt diet. Sorafenib was administered over the course of 56 days. The study included three experimental groups; 1) control group (naïve rats), 2) sorafenib group [rats treated with sorafenib only (20 mg/kg/day p.o.)], and 3) sorafenib + PTUPB group (rats treated with sorafenib only for the initial 28 days and subsequently coadministered PTUPB (10 mg/kg/day i.p.) from days 28 through 56). Blood pressure was measured every 2 weeks. After 28 days, sorafenib-treated rats developed hypertension (161 ± 4 mmHg). Over the remainder of the study, sorafenib treatment resulted in a further elevation in blood pressure through day 56 (200 ± 7 mmHg). PTUPB treatment attenuated the sorafenib-induced blood pressure elevation and by day 56, blood pressure was 159 ± 4 mmHg. Urine was collected every 2 weeks for biochemical analysis. After 28 days, sorafenib rats developed pronounced proteinuria (9.7 ± 0.2 P/C), which intensified significantly (35.8 ± 3.5 P/C) by the end of day 56 compared with control (2.6 ± 0.4 P/C). PTUPB mitigated sorafenib-induced proteinuria, and by day 56, it reduced proteinuria by 73%. Plasma and kidney tissues were collected on day 56. Kidney histopathology revealed intratubular cast formation, interstitial fibrosis, glomerular injury, and glomerular nephrin loss at day 56 in sorafenib-treated rats. PTUPB treatment reduced histological features by 30%-70% compared with the sorafenib-treated group and restored glomerular nephrin levels. Furthermore, PTUPB also acted on the glomerular permeability barrier by decreasing angiotensin-II-induced glomerular permeability to albumin. Finally, PTUPB improved in vitro the viability of human mesangial cells. Collectively, our data demonstrate the potential of using PTUPB or dual sEH/COX-2 inhibition as a therapeutic strategy against sorafenib-induced glomerular nephrotoxicity.

Multitarget molecule, PTUPB, to treat diabetic nephropathy in rats

BACKGROUND AND PURPOSE

Diabetic nephropathy is a common complications related to high morbidity and mortality in type 2 diabetes. We investigated the action of the dual modulator, PTUPB, a soluble epoxide hydrolase and cyclooxygenase-2 inhibitor against diabetic nephropathy.

EXPERIMENTAL APPROACH

Sixteen-week-old type 2 diabetic and proteinuric obese ZSF1 rats were treated with vehicle, PTUPB or enalapril for 8 weeks. Measurements were made of epoxyeicosatrienoic acids, thromboxane B2 (TBX2 ) and prostaglandin E2 (PGE2 ) in the kidney of these and lean ZSF1 rats along with their blood pressure.

KEY RESULT

Obese ZSF1 rats were diabetic with fivefold higher fasting blood glucose levels and markedly higher HbA1c levels compared with lean ZSF1 rats. PTUPB nor enalapril reduced fasting blood glucose or HbA1c but alleviated the development of diabetic nephropathy. In PTUPB-treated obese ZSF1 rats, glomerular nephrin expression was preserved. Enalapril also alleviated diabetic nephropathy. Diabetic renal injury in obese ZSF1 rats was accompanied by renal inflammation with six to sevenfold higher urinary MCP-1 (CCR2) level and renal infiltration of CD-68 positive cells. PTUPB and enalapril significantly reduced urinary MCP-1 levels and renal mRNA expression of cytokines. Both PTUPB and enalapril lowered blood pressure. PTUPB but not enalapril decreased hyperlipidaemia and liver injury in obese ZSF1 rats.

CONCLUSION AND IMPLICATIONS

Overall, the dual modulator PTUPB does not treat hyperglycaemia but can effectively alleviate hypertension, diabetic nephropathy, hyperlipidaemia and liver injury in type 2 diabetic rats. Our data further demonstrate that the renal actions of PTUPB are comparable with a current standard diabetic nephropathy treatment.

Celecoxib alleviates pathological cardiac hypertrophy and fibrosis via M1-like macrophage infiltration in neonatal mice

Cardiac hypertrophy is an adaptive response to all forms of heart disease, including hypertension, myocardial infarction, and cardiomyopathy. Cyclooxygenase-2 (COX-2) overexpression results in inflammatory response, cardiac cell apoptosis, and hypertrophy in adult heart after injury. However, immune response-mediated cardiac hypertrophy and fibrosis have not been well documented in injured neonatal heart. This study showed that cardiac hypertrophy and fibrosis are significantly attenuated in celecoxib (a selective COX-2 inhibitor)-treated P8 ICR mice after cryoinjury. Molecular and cellular profiling of immune response shows that celecoxib inhibits the production of cytokines and the expression of adhesion molecular genes, increases the recruitment of M1-like macrophage at wound site, and alleviates cardiac hypertrophy and fibrosis. Furthermore, celecoxib administration improves cardiac function at 4 weeks after injury. These results demonstrate that COX-2 inhibition promotes the recruitment of M1-like macrophages during early wound healing, which may contribute to the suppression of cardiac hypertrophy and fibrosis after injury.

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Cryoinjury successfully induces cardiac hypertrophy and fibrosis in P8 ICR mice

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COX-2 inhibition alleviates cardiac hypertrophy and fibrosis after cryoinjury

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MCP-1 significantly increases in COX-2 inhibition

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COX-2 inhibition improves cardiac repair in P8 ICR mice by recruiting M1-like macrophages

The Blockade of TACE-Dependent EGF Receptor Activation by Losartan-Erlotinib Combination Attenuates Renal Fibrosis Formation in 5/6-Nephrectomized Rats Under Vitamin D Deficiency

Chronic kidney disease (CKD) has been considered a major public health issue. In addition to cardiovascular diseases and infections, hypovitaminosis D has been considered a non-traditional aggravating factor for CKD progression. Interstitial fibrosis is a hallmark of CKD strongly correlated with deterioration of renal function. Transforming growth factor β (TGF-β) is the major regulatory profibrotic cytokine in CKD. Many injurious stimuli converge on the TGF-β pathway, which has context-dependent pleiotropic effects and interacts with several related renal fibrosis formation (RFF) pathways. Epidermal growth factor receptor (EGFR) is critically involved in CKD progression, exerting a pathogenic role in RFF associated with TGF-β-related fibrogenesis. Among others, EGFR pathway can be activated by a disintegrin and a metalloproteinase known as tumor necrosis factor α-converting enzyme (TACE). Currently no effective therapy is available to completely arrest RFF and slow the progression of CKD. Therefore, we investigated the effects of a double treatment with losartan potassium (L), an AT1R antagonist, and the tyrosine kinase inhibitor erlotinib (E) on the alternative pathway of RFF related to TACE-dependent EGFR activation in 5/6-nephrectomized rats under vitamin D deficiency (D). During the 90-day protocol, male Wistar rats under D, were submitted to 5/6 nephrectomy (N) on day 30 and randomized into four groups: N+D, no treatment; N+D+L, received losartan (50 mg/kg/day); N+D+E, received erlotinib (6 mg/kg/day); N+D+L+E received losartan+erlotinib treatment. N+D+L+E data demonstrated that the double treatment with losartan+erlotinib not only blocked the TACE-dependent EGF receptor activation but also prevented the expression of TGF-β, protecting against RFF. This renoprotection by losartan+erlotinib was corroborated by a lower expression of ECM proteins and markers of phenotypic alteration as well as a lesser inflammatory cell infiltrate. Although erlotinib alone has been emerging as a renoprotective drug, its association with losartan should be considered as a potential therapeutic strategy on the modulation of RFF.

Metformin arrests the progression of established kidney disease in the subtotal nephrectomy model of chronic kidney disease

Metformin, an AMP-activated protein kinase (AMPK) activator, has been shown in previous studies to reduce kidney fibrosis in different models of experimental chronic kidney disease (CKD). However, in all of these studies, the administration of metformin was initiated before the establishment of renal disease, which is a condition that does not typically occur in clinical settings. The aim of the present study was to investigate whether the administration of metformin could arrest the progression of established renal disease in a well-recognized model of CKD, the subtotal kidney nephrectomy (Nx) model. Adult male Munich-Wistar rats underwent either Nx or sham operations. After the surgery (30 days), Nx rats that had systolic blood pressures of >170 mmHg and albuminuria levels of >40 mg/24 h were randomized to a no-treatment condition or to a treatment condition with metformin (300 mg·kg−1·day−1) for a period of either 60 or 120 days. After 60 days of treatment, we did not observe any differences in kidney disease parameters between Nx metformin-treated and untreated rats. However, after 120 days, Nx rats that had been treated with metformin displayed significant reductions in albuminuria levels and in markers of renal fibrosis. These effects were independent of any other effects on blood pressure or glycemia. In addition, treatment with metformin was also able to activate kidney AMPK and therefore improve mitochondrial biogenesis. It was concluded that metformin can arrest the progression of established kidney disease in the Nx model, likely via the activation of AMPK.

Chondroitin sulfate degradation and eicosanoid metabolism pathways are impaired in focal segmental glomerulosclerosis: Experimental confirmation of an in silico prediction

Introduction: Focal segmental glomerulosclerosis (FSGS), the most common primary glomerular disease, is a diverse clinical entity that occurs after podocyte injury. Although numerous studies have suggested molecular pathways responsible for the development of FSGS, many still remain unknown about its pathogenic mechanisms. Two important pathways were predicted as candidates for the pathogenesis of FSGS in our previous in silico analysis, whom we aim to confirm experimentally in the present study. Methods: The expression levels of 4 enzyme genes that are representative of "chondroitin sulfate degradation" and "eicosanoid metabolism" pathways were investigated in the urinary sediments of biopsy-proven FSGS patients and healthy subjects using real-time polymerase chain reaction (RT-PCR). These target genes were arylsulfatase, hexosaminidase, cyclooxygenase-2 (COX-2), and prostaglandin I2 synthase. The patients were sub-divided into 2 groups based on the range of proteinuria and glomerular filtration rate and were compared for variation in the expression of target genes. Correlation of target genes with clinical and pathological characteristics of the disease was calculated and receiver operating characteristic (ROC) analysis was performed. Results: A combined panel of arylsulfatase, hexosaminidase, and COX-2 improved the diagnosis of FSGS by 76%. Hexosaminidase was correlated with the level of proteinuria, while COX-2 was correlated with interstitial inflammation and serum creatinine level in the disease group. Conclusion: Our data supported the implication of these target genes and pathways in the pathogenesis of FSGS. In addition, these genes can be considered as non-invasive biomarkers for FSGS.

Effect of Combined Treatment of Ketorolac and Remote Ischemic Preconditioning on Renal Ischemia-Reperfusion Injury in Patients Undergoing Partial Nephrectomy: Pilot Study

We evaluated postoperative renal function in patients with/without combined therapy of ketorolac and remote ischemic preconditioning during partial nephrectomy. Sixteen patients were randomly allocated to either the ketorolac combined with RIPC group (KI, n = 8) or control group (n = 8). The KI group received both remote ischemic preconditioning before surgery and intravenous ketorolac of 1 mg/kg before renal artery clamping. Renal parameters were measured before induction, after anesthesia induction, and 2, 12, 24, 48, and 72 h after renal artery declamping. Acute kidney injury was assessed by Acute Kidney Injury Network criteria. The estimated glomerular filtration rate decreased in both groups, but then increased significantly at 48 h and 72 h after declamping only in the KI group compared to 24 h (p = 0.001 and p = 0.016). Additionally, it was higher at 48 h and 72 h after declamping in the KI group compared to the control group (p = 0.025 and p = 0.044). The incidence of acute kidney injury was significantly reduced in the KI group (13%) compared to the control group (83%) (p = 0.026). FE_Na was markedly increased at 2 h after declamping, and recovered in both groups, but it was more significant at 12 h after declamping in the KI group (p = 0.022). Urinary N-acetyl-1-β-D-glucosoaminidase and serum neutrophil gelatinase-associated lipocalin were similar (p = 0.291 and p = 0.818). There is a possibility that combined therapy of ketorolac and remote ischemic preconditioning prior to ischemia may alleviate renal dysfunction and reduce the incidence of acute kidney injury in patients undergoing partial nephrectomy.

Oxylipin profiling of human plasma reflects the renal dysfunction in uremic patients

INTRODUCTION

Nearly all the enzymes that mediate the metabolism of polyunsaturated fatty acids (PUFAs) are present in the kidney. However, the correlation of renal dysfunction with PUFAs metabolism in uremic patients remains unknown.

OBJECTIVES

To test whether the alterations in the metabolism of PUFAs reflect the renal dysfunction in uremic patients.

METHODS

LC-MS/MS-based oxylipin profiling was conducted for the plasma samples from the uremic patients and controls. The data were analyzed by principal component analysis (PCA) and orthogonal partial least squares-discriminant analysis (OPLS-DA). The receiver operating characteristic (ROC) curves and the correlation of the estimated glomerular filtration rate (eGFR) with the key markers were evaluated. Furthermore, qPCR analysis of the whole blood cells was conducted to investigate the possible mechanisms. In addition, a 2nd cohort was used to validate the findings from the 1st cohort.

RESULTS

The plasma oxylipin profile distinguished the uremic patients from the controls successfully by using both PCA and OPLS-DA models. 5,6-Dihydroxyeicosatrienoic acid (5,6-DHET), 5-hydroxyeicosatetraenoic acid (5-HETE), 9(10)-epoxyoctadecamonoenoic acid [9(10)-EpOME] and 12(13)-EpOME were identified as the key markers to discriminate the patients from controls. The excellent predictive performance of these four markers was validated by ROC analysis. The eGFR significantly correlated with plasma levels of 5,6-DHET and 5-HETE positively but with plasma 9(10)-EpOME and 12(13)-EpOME negatively. The changes of these markers may account for the inactivation of cytochrome P450 2C18, 2C19, microsome epoxide hydrolase (EPHX1), and 5-lipoxygenase in the patients.

CONCLUSION

The alterations in plasma metabolic profile reflect the renal dysfunction in the uremic patients.

Simultaneous activation of innate and adaptive immunity participates in the development of renal injury in a model of heavy proteinuria

Protein overload of proximal tubular cells (PTCs) can promote interstitial injury by unclear mechanisms that may involve activation of innate immunity. We investigated whether prolonged exposure of tubular cells to high protein concentrations stimulates innate immunity, triggering progressive interstitial inflammation and renal injury, and whether specific inhibition of innate or adaptive immunity would provide renoprotection in an established model of massive proteinuria, adriamycin nephropathy (ADR). Adult male Munich-Wistar rats received a single dose of ADR (5 mg/kg, iv), being followed for 2, 4, or 20 weeks. Massive albuminuria was associated with early activation of both the NF-κB and NLRP3 innate immunity pathways, whose intensity correlated strongly with the density of lymphocyte infiltration. In addition, ADR rats exhibited clear signs of renal oxidative stress. Twenty weeks after ADR administration, marked interstitial fibrosis, glomerulosclerosis, and renal functional loss were observed. Administration of mycophenolate mofetil (MMF), 10 mg/kg/day, prevented activation of both innate and adaptive immunity, as well as renal oxidative stress and renal fibrosis. Moreover, MMF treatment was associated with shifting of M from the M1 to the M2 phenotype. In cultivated NRK52-E cells, excess albumin increased the protein content of Toll-like receptor (TLR) 4 (TLR4), NLRP3, MCP-1, IL6, IL-1β, Caspase-1, α-actin, and collagen-1. Silencing of TLR4 and/or NLRP3 mRNA abrogated this proinflammatory/profibrotic behavior. Simultaneous activation of innate and adaptive immunity may be key to the development of renal injury in heavy proteinuric disease. Inhibition of specific components of innate and/or adaptive immunity may be the basis for future strategies to prevent chronic kidney disease (CKD) in this setting.

Transforming growth factor-β1 and phosphatases modulate COX-2 protein expression and TAU phosphorylation in cultured immortalized podocytes

OBJECTIVE AND DESIGN

The aim of this study is to elucidate TGF-β1 signaling pathways involved in COX-2 protein induction and modulation of TAU protein phosphorylation in cultured podocytes.

MATERIALS, TREATMENT AND METHODS

In vitro cultured immortalized podocytes were stimulated with TGF-β1 in presence and absence of pharmacologic inhibitors for various signaling pathways and phosphatases. Then, COX-2 protein expression, as well as P38MAPK, AKT and TAU phosphorylation levels were evaluated by western blot analysis.

RESULTS

TGF-β1 induction of COX-2 protein levels was completely blocked by pharmacologic inhibitors of phosphatases, P38 MAPK, or NF-қB pathways. Time course experiments showed that TGF-β1 activated p38 MAPK after 5 min of stimulation. Interestingly, podocyte co-incubated with TGF-β1, high glucose and/or PGE2 showed strong increase in p38 MAPK and AKT phosphorylation as well as COX- 2 protein expression levels. Levels of phosphorylated AKT were further reduced and levels of phosphorylated p38 were increased when PGE2 was added to the culture media. Interestingly, selective phosphatases inhibitors completely abrogated PGE2-induced P38 MAPK and TAU phosphorylation. Also, inhibition of phosphatases reversed TGF-β1-induced COX-2 protein expression either alone or when incubated with high glucose or PGE2.

CONCLUSION

These data suggest TGF-β1 mediates its effect in podocyte through novel signaling mechanisms including phosphatases and TAU protein phosphorylation.

IL-36α Regulates Tubulointerstitial Inflammation in the Mouse Kidney

IL-36α, a member of the IL-1 family, is a crucial mediator of inflammatory responses. We previously found that IL-36α was overexpressed in injured distal tubules (DTs); however, its pathological function remains unclear. Herein, unilateral ureter obstruction (UUO) or folic acid (FA) injection was performed in mouse kidneys to assess the role of IL-36α in kidney injury. IL-36α mRNA and protein expression significantly increased in the kidneys within 24 h after UUO. IL-36α localized to dilated DTs. IL-36α expression significantly correlated with the progression of tubulointerstitial cell infiltration and tubular epithelium cell death in UUO kidneys and with renal dysfunction in FA-induced acute kidney injury mice. At 24 h after UUO, IL-36α⁺ DT epithelial cells showed loose intercellular digitations. IL-1RL2, an IL-36α receptor protein, localized to podocytes, proximal tubules, and DTs in the healthy kidney. IL-1RL2 was expressed in interstitial cells and platelets or extended primary cilia of DT epithelial cells in UUO kidneys. IL-36α stimulation promoted the production of IL-6 and Prss35, an inflammatory cytokine and collagen remodeling-associated enzyme, respectively, in cultured NIH3T3 fibroblasts. UUO-treated IL-36α-knockout (KO) mice showed milder kidney injury features than wild-type (WT) mice did. In UUO kidneys from IL-36α-KO mice, the expression of genes associated with inflammatory response and sensory perception was significantly different from that in WT mice. Altogether, our data indicate an association between intrarenal IL-36α overexpression and the progression of tubulointerstitial inflammations and morpho-functional alterations of DT epithelial cells. IL-36α may be a novel kidney injury marker useful for evaluating DT damages.

Cyclooxygenase 2: protein-protein interactions and posttranslational modifications

Numerous studies implicate the cyclooxygenase 2 (COX2) enzyme and COX2-derived prostanoids in various human diseases, and thus, much effort has been made to uncover the regulatory mechanisms of this enzyme. COX2 has been shown to be regulated at both the transcriptional and posttranscriptional levels, leading to the development of nonsteroidal anti-inflammatory drugs (NSAIDs) and selective COX2 inhibitors (COXIBs), which inhibit the COX2 enzyme through direct targeting. Recently, evidence of posttranslational regulation of COX2 enzymatic activity by s-nitrosylation, glycosylation, and phosphorylation has also been presented. Additionally, posttranslational regulators that actively downregulate COX2 expression by facilitating increased proteasome degradation of this enzyme have also been reported. Moreover, recent data identified proteins, located in close proximity to COX2 enzyme, that serve as posttranslational modulators of COX2 function, upregulating its enzymatic activity. While the precise mechanisms of the protein-protein interaction between COX2 and these regulatory proteins still need to be addressed, it is likely these interactions could regulate COX2 activity either as a result of conformational changes of the enzyme or by impacting subcellular localization of COX2 and thus affecting its interactions with regulatory proteins, which further modulate its activity. It is possible that posttranslational regulation of COX2 enzyme by such proteins could contribute to manifestation of different diseases. The uncovering of posttranslational regulation of COX2 enzyme will promote the development of more efficient therapeutic strategies of indirectly targeting the COX2 enzyme, as well as provide the basis for the generation of novel diagnostic tools as biomarkers of disease.

Innate And Adaptive Immunity are Progressively Activated in Parallel with Renal Injury in the 5/6 Renal Ablation Model

The mechanisms triggering renal inflammation in chronic kidney disease (CKD) are unclear. We performed a detailed analysis of the time course of innate and adaptive immunity activation in the 5/6 renal ablation (Nx) model. Munich-Wistar rats undergoing Nx were studied 15, 60 and 120 days after ablation. Hypertension, albuminuria, creatinine retention, interstitial expansion and infiltration by macrophages and T-lymphocytes were already evident 15 days after Nx. PCR-array was used to screen for altered gene expression, whereas gene and protein expressions of TLR4, CASP1, IL-1β and NLRP3 were individually assessed. Tlr4, Tlr5, Lbp, Nlrp3, Casp1, Irf7 and Il1b were already upregulated 15 days after Nx, while activation of Tlr2, Tlr7, Tlr9, Nod2, Tnf and Il6 was seen after 60 days post-ablation. The number of genes related to innate or adaptive immunity grew steadily with time. These observations indicate that parallel activation of innate and adaptive immunity antecedes glomerular injury and involves a growing number of intricate signaling pathways, helping to explain the difficulty in detaining renal injury in Nx as CKD advances, and, stressing the need for early treatment. Additionally, these findings may contribute to the search of therapeutic targets specific for advanced phases of CKD.

Selective cyclooxygenase-2 inhibitor use and progression of renal function in patients with chronic kidney disease: a single-center retrospective cohort study

Background

The use of selective COX-2 (sCOX-2) inhibitors with acute kidney injury, salt water retention, and cardiovascular events have been correlated in subjects with normal kidney function, but sCOX-2 inhibitor use concerning the progression of chronic kidney disease (CKD) remains uncertain.

Objectives

To determine the progression of renal function and electrolyte abnormalities among CKD patients after using sCOX-2 inhibitors during short- and long-term periods.

Methods

The study employed a retrospective cohort design comprising all types of CKD patients with and without sCOX-2 inhibitors (celecoxib and etoricoxib). Data collected included medical data, estimated glomerular filtration rate (eGFR), and serum electrolytes at 3 and 6 months between January 2009 and January 2014. Subjects attended the outpatient clinic and were then followed up until discontinuation of the drugs at years 1 and 2 until May 2016.

Results

Ninety-two CKD patients on sCOX-2 inhibitors and 92 CKD patients without sCOX-2 inhibitors were included. The sCOX-2 inhibitor group showed more decline in eGFR than the control group at 3 and 6 months of follow-up (–8.27±9.75 vs –1.64±6.05 mL/min/1.73 m², P<0.001 and –12.36±6.48 vs –4.31±5.11 mL/min/1.73 m², P=0.001, respectively) and at 1 and 2 years of follow-up after subjects discontinued sCOX-2 (–6.84±10.34 vs –1.61±8.93 mL/min/1.73 m², P=0.004 and –10.26±10.19 vs –5.12±8.61 mL/min/1.73 m², P=0.005, respectively). In addition, the sCOX-2 inhibitor group had significantly more increased serum potassium during the study follow-up than the control group.

Conclusion

The sCOX-2 inhibitors are associated with an increased risk for rapid eGFR decline and hyperkalemia in both the short term and in the long term after sCOX-2 inhibitors were terminated in the setting of a community-based CKD population. For CKD patients, these results suggest that sCOX-2 inhibitors should be closely monitored and chronic exposure to any sCOX-2 inhibitors should be avoided.

TNFα up-regulates COX-2 in chronic progressive nephropathy through nuclear accumulation of RelB and NF-κB2

OBJECTIVE

The pathogenesis of progressive nephropathies involves inflammatory factors. The inhibition of cyclooxygenase-2 (COX-2) can limit renal damage and inflammation. However, the mechanism of up-regulation of COX-2 in nephropathy is poorly defined.

MATERIALS AND METHODS

Here we found that tumor necrosis factor alpha (TNFα) was involved in expression of COX-2 in normal rat kidney (NRK) cell line.

RESULTS

TNFα stimulated COX-2 production in a time-dependent manner in NRK cells by inducing nuclear accumulation of RelB and nuclear factor kappa B2 (NF-κB2) and their association with COX-2 gene promoter. Depletion of IκB-inducing kinase alpha, a positive regulator of activation of p100 processing to active p52, attenuated TNFα-induced COX-2 production. Furthermore, TNFα induced COX-2 production and nuclear import in anti-thymocyte serum (ATS) nephropathy.

DISCUSSION AND CONCLUSION

These data suggest that TNFα-RelB/p52 pathway may be involved in the early stages of renal damage, in part by stimulating COX-2 and inflammatory responses.

Circadian CLOCK Mediates Activation of Transforming Growth Factor-β Signaling and Renal Fibrosis through Cyclooxygenase 2

The circadian rhythm regulates blood pressure and maintains fluid and electrolyte homeostasis with central and peripheral clock. However, the role of circadian rhythm in the pathogenesis of tubulointerstitial fibrosis remains unclear. Here, we found that the amplitudes of circadian rhythm oscillation in kidneys significantly increased after unilateral ureteral obstruction. In mice that are deficient in the circadian gene Clock, renal fibrosis and renal parenchymal damage were significantly worse after ureteral obstruction. CLOCK-deficient mice showed increased synthesis of collagen, increased oxidative stress, and greater transforming growth factor-β (TGF-β) expression. TGF-β mRNA expression oscillated with the circadian rhythms under the control of CLOCK-BMAL1 heterodimers. The expression of cyclooxygenase 2 was significantly higher in kidneys from CLOCK-deficient mice with ureteral obstruction. Treatment with a cyclooxygenase 2 inhibitor celecoxib significantly improved renal fibrosis in CLOCK-deficient mice. Taken together, these data establish the importance of the circadian rhythm in tubulointerstitial fibrosis and suggest CLOCK/TGF-β signaling as a novel therapeutic target of cyclooxygenase inhibition.

Role of COX-2/mPGES-1/prostaglandin E2 cascade in kidney injury

COX-2/mPGES-1/PGE2 cascade plays critical roles in modulating many physiological and pathological actions in different organs. In the kidney, this cascade is of high importance in regulating fluid metabolism, blood pressure, and renal hemodynamics. Under some disease conditions, this cascade displays various actions in response to the different pathological insults. In the present review, the roles of this cascade in the pathogenesis of kidney injuries including diabetic and nondiabetic kidney diseases and acute kidney injuries were introduced and discussed. The new insights from this review not only increase the understanding of the pathological role of the COX-2/mPGES-1/PGE2 pathway in kidney injuries, but also shed new light on the innovation of the strategies for the treatment of kidney diseases.

Celecoxib offsets the negative renal influences of cyclosporine via modulation of the TGF-β1/IL-2/COX-2/endothelin ET(B) receptor cascade

Endothelin (ET) signaling provokes nephrotoxicity induced by the immunosuppressant drug cyclosporine A (CSA). We tested the hypotheses that (i): celecoxib, a selective cyclooxygenase-2 (COX-2) inhibitor, counterbalances renal derangements caused by CSA in rats and (ii) the COX-2/endothelin ET(B) receptor signaling mediates the CSA-celecoxib interaction. Ten-day treatment with CSA (20 mg/kg/day) significantly increased biochemical indices of renal function (serum urea, creatinine), inflammation (interleukin-2, IL-2) and fibrosis (transforming growth factor-β₁, TGF-β₁). Histologically, CSA caused renal tubular atrophy along with interstitial fibrosis. These detrimental renal effects of CSA were largely reduced in rats treated concurrently with celecoxib (10 mg/kg/day). We also report that cortical glomerular and medullary tubular protein expressions of COX-2 and ET(B) receptors were reduced by CSA and restored to near-control values in rats treated simultaneously with celecoxib. The importance of ET(B) receptors in renal control and in the CSA-celecoxib interaction was further verified by the findings (i) most of the adverse biochemical, inflammatory, and histopathological profiles of CSA were replicated in rats treated with the endothelin ETB receptor antagonist BQ788 (0.1 mg/kg/day, 10 days), and (ii) the BQ788 effects, like those of CSA, were alleviated in rats treated concurrently with celecoxib. Together, the data suggest that the facilitation of the interplay between the TGF-β1/IL-2/COX-2 pathway and the endothelin ET(B) receptors constitutes the cellular mechanism by which celecoxib ameliorates the nephrotoxic manifestations of CSA in rats.

HuR and other turnover- and translation-regulatory RNA-binding proteins: implications for the kidney

The posttranscriptional regulation of gene expression occurs through cis RNA regulatory elements by the action of trans factors, which are represented by noncoding RNAs (especially microRNAs) and turnover- and translation-regulatory (TTR) RNA-binding proteins (RBPs). These multifactorial proteins are a group of heterogeneous RBPs primarily implicated in controlling the decay and translation rates of target mRNAs. TTR-RBPs usually shuttle between cellular compartments (the nucleus and cytoplasm) in response to various stimuli and undergo posttranslational modifications such as phosphorylation or methylation to ensure their proper subcellular localization and function. TTR-RBPs are emerging as key regulators of a wide variety of genes influencing kidney physiology and pathology. This review summarizes the current knowledge of TTR-RBPs that influence renal metabolism. We will discuss the role of TTR-RBPs as regulators of kidney ischemia, fibrosis and matrix remodeling, angiogenesis, membrane transport, immunity, vascular tone, hypertension, and acid-base balance as well as anemia, bone mineral disease, and vascular calcification.

A comparative study of chronic kidney disease in dogs and cats: induction of cyclooxygenases

The present study investigated whether renal cyclooxygenase (COX) induction is associated with the severity of chronic kidney disease (CKD) in dogs and cats. The collected kidneys were examined histopathologically and immunohistochemically. The immunoreactivities of COX-1 and COX-2 were evaluated quantitatively, and the correlations to the plasma creatinine concentrations, glomerular size, glomerulosclerosis, interstitial fibrosis, and interstitial cell infiltration were evaluated statistically. Immunoreactivities for COX-1 were heterogeneously observed in the medullary distal tubules and collecting ducts; no correlations with the severity of renal damage were detected. Immunoreactivities for COX-2 were heterogeneously observed in the macula densa (MD) regions. In dogs, the percentage of COX-2-positive MD was significantly correlated with the glomerular size. In cats, glomeruli with COX-2-positive MD had significantly higher sclerosis scores than those with COX-2-negative MD. In conclusion, renal COX-2 is induced in canine and feline CKD, especially in relation to the glomerular changes.

Renal effects of prolonged high protein intake and COX2 inhibition on hypertensive rats with altered renal development

Cyclooxygenase 2 (COX2) is involved in regulating renal hemodynamics after renal ablation. It is also known that high protein intake (HPI) leads to a deterioration of renal function when there is preexisting renal disease and that there are important gender differences in the regulation of renal function. This study tested the hypothesis that the role of COX2 in regulating renal function and the renal hemodynamic effects elicited by HPI are enhanced when nephrogenesis is altered during renal development. It was also expected that the role of COX2 and the effects elicited by HPI are age and sex dependent. Newborn Sprague-Dawley rats were treated with an AT1 ANG II receptor antagonist during the nephrogenic period (ARAnp). Experiments were performed at 3–4 and 10–11 mo of age. Arterial pressure was elevated ( P < 0.05) at both ages and in both sexes of ARAnp-treated rats. Renal COX2 expression was only elevated ( P < 0.05) at 10–11 mo of age in both sexes of ARAnp-treated rats. COX2 inhibition induced greater renal vasoconstriction in male and female hypertensive than in normotensive rats at both ages. HPI did not induce glomerular filtration rate (GFR) in the youngest hypertensive rats and in the oldest female hypertensive rats. However, the GFR decreased during HPI (0.63 ± 0.07 to 0.19 ± 0.05 ml/min) in the oldest male hypertensive rats. The HPI-induced increment in proteinuria was greater ( P < 0.05) in male (99 ± 22 mg/day) than in female (30 ± 8 mg/day) hypertensive rats. These results show that COX2 plays an important role in the regulation of renal function when renal development is altered and that prolonged HPI can lead to a renal insufficiency in males but not in females with reduced nephron endowment.

Cyclooxygenase 2 promotes parathyroid hyperplasia in ESRD

Hyperplasia of the PTG underlies the secondary hyperparathyroidism (SHPT) observed in CKD, but the mechanism underlying this hyperplasia is incompletely understood. Because aberrant cyclooxygenase 2 (COX2) expression promotes epithelial cell proliferation, we examined the effects of COX2 on the parathyroid gland in uremia. In patients with ESRD who underwent parathyroidectomy, clusters of cells within the parathyroid glands had increased COX2 expression. Some COX2-positive cells exhibited two nuclei, consistent with proliferation. Furthermore, nearly 78% of COX2-positive cells expressed proliferating cell nuclear antigen (PCNA). In the 5/6-nephrectomy rat model, rats fed a high-phosphate diet had significantly higher serum PTH levels and larger parathyroid glands than sham-operated rats. Compared with controls, the parathyroid glands of uremic rats exhibited more PCNA-positive cells and greater COX2 expression in the chief cells. Treatment with COX2 inhibitor celecoxib significantly reduced PCNA expression, attenuated serum PTH levels, and reduced the size of the glands. In conclusion, COX2 promotes the pathogenesis of hyperparathyroidism in ESRD, suggesting that inhibiting the COX2 pathway could be a potential therapeutic target.

Immunohistochemical examination of cyclooxygenase-2 and renin in a KK-A(y) mouse model of diabetic nephropathy

The renin-angiotensin system plays a central role in the pathological mechanisms of diabetic nephropathy and is regulated by renal expression of cyclooxygenase-2 (COX-2). In the present study, the kidneys of diabetic KK-A(y) mice, a model of human type 2 diabetes, were investigated histologically and immunohistochemically at 8, 12, 16, and 20 weeks of age, and changes in renal lesions and expression of COX-2 and renin were evaluated quantitatively. Glomerular damage, characterized by expansion of mesangial matrices and nodular lesions, was observed in the kidneys of these mice. The glomerular sclerosis score gradually increased with age and was significantly higher than those of age-matched control C57BL/6 mice at 12, 16, and 20 weeks of age. Although mild tubulointerstitial damage was observed, there was no significant change in the interstitial fibrosis score. These findings were considered early diabetic nephropathy changes. COX-2-positive signals were consistently detected in the macula densa cells of the thick ascending limbs in all KK-A(y) mice, with a slightly higher score observed at 8 weeks of age. No COX-2-positive signals were detected in C57BL/6 mice. Renin-positive signals were commonly detected in the juxtaglomerular arterioles, and the scores in KK-A(y) mice increased at 16 weeks and decreased at 20 weeks of age. The present study demonstrated activation of renal COX-2 and renin expression in diabetic KK-A(y) mice at different stages. This finding suggests that these two enzymes contribute to the development and progression of diabetic nephropathy via different mechanisms.

Upregulation of fibronectin expression by COX-2 is mediated by interaction with ELMO1

Engulfment and cell motility 1 (ELMO1), a bipartite guanine nucleotide exchange factor (GEF) for the small GTPase Rac 1, was identified as a susceptibility gene for glomerular disease. Here, we reported that ELMO1 interacted with COX-2 in human mesangial cells. Furthermore, we identified ELMO1 as a posttranslational regulator of COX-2 activity. We demonstrated that COX-2 cyclooxygenase activity increased fibronectin promoter activity. The protein-protein interaction between ELMO1 and COX-2 increased the cyclooxygenase activity of COX-2 and, correspondingly, fibronectin expression. We also found that ET625, the dominant negative form of ELMO1 lacking Rac1 activity, interacted with COX-2, increased cyclooxygenase activity of COX-2 and enhanced COX-2-mediated fibronectin upregulation. To further rule out Rac1 as an ELMO1-mediated regulator of COX-2 activity, we employed the constitutive active Rac1, Rac1(Q63E), and demonstrated that Rac1 signaling has no effect on COX-2-mediated fibronectin promoter activity. These results suggest that ELMO1 contributes to the development of glomerular injury through serving as a regulator of COX-2 activity. The interaction of ELMO1 with COX-2 could play an important role in the development and progression of renal glomerular injury.

Mechanical stretch and prostaglandin E2 modulate critical signaling pathways in mouse podocytes

Elevated glomerular capillary pressure (Pgc) and hyperglycemia contribute to glomerular filtration barrier injury observed in diabetic nephropathy (DN). Previous studies showed that hypertensive conditions alone or in combination with a diabetic milieu impact podocyte cellular function which results in podocyte death, detachment or hypertrophy. The present study was aimed at uncovering the initial signaling profile activated by Pgc (mimicked by in vitro mechanical stretch), hyperglycemia (high glucose (HG), 25mM d-glucose) and prostaglandin E(2) (PGE(2)) in conditionally-immortalized mouse podocytes. PGE(2) significantly reduced the active form of AKT by selectively blunting its phosphorylation on S473, but not on T308. AKT inhibition by PGE(2) was reversed following either siRNA-mediated EP(4) knockdown, PKA inhibition (H89), or phosphatase inhibition (orthovanadate). Podocytes treated for 20min with H(2)O(2) (10(-4)M), which mimics reactive oxygen species generation by cells challenged by hyperglycemic or enhanced Pgc conditions, significantly increased the levels of active p38 MAPK, AKT, JNK and ERK1/2. Interestingly, stretch and PGE(2) each significantly reduced H(2)O(2)-mediated AKT phosphorylation and was reversed by pretreatment with orthovanadate while stretch alone reduced GSK-3beta inhibitory phosphorylation at ser-9. Finally, mechanical stretch alone or in combination with HG, induced ERK1/2 and JNK activation, via the EGF receptor since AG1478, a specific EGF receptor kinase inhibitor, blocked this activation. These results show that cellular signaling in podocytes is significantly altered under diabetic conditions (i.e., hyperglycemia and increased Pgc). These changes in MAPKs and AKT activities might impact cellular integrity required for a functional glomerular filtration barrier thereby contributing to the onset of proteinuria in DN.

Preventive effects of COX-2 inhibitor, celecoxib on renal tubular injury induced by shock wave lithotriptor

Our study was designed to investigate the protective effect of the COX-2 inhibitor, celecoxib, on renal tubules against shock wave lithotripsy (SWL). Sprague-Dawley rats were randomly divided into three groups: sham, control, and COX-2 groups. The control group was administrated normal saline. The COX-2 group was administered celecoxib (10 mg/kg). After administration for 1 week, the control and COX-2 groups received 1,000 shock waves. Before and after SWL, 24-h urine was collected. CCr was measured to assess renal function. To determine the renal tubular injury, N-acetyl glucosaminidase (NAG) and beta-2 microglobulin levels in urine were quantified. The COX-2 gene expression was compared between the three groups. Prior to SWL, all groups had similar levels of NAG and beta-2 microglobulin. After SWL, all groups showed similar CCr. Compared with the sham group, control and COX-2 groups produced increase of NAG and beta-2 microglobulin excretion. However, NAG and beta-2 microglobulin excretions were significantly lower in the COX-2 group than control group. The COX-2 gene expression did not increase in the sham group. However, the COX-2 gene expression was significantly increased in the control group, which was prevented by celecoxib in COX-2 group. Biochemical findings supported a renal protective effect of celecoxib on SWL. This study suggests that celecoxib would be useful prior and after SWL because of renal protective effects.

Rapamycin has dual opposing effects on proteinuric experimental nephropathies: is it a matter of podocyte damage?

BACKGROUND

In clinical renal transplantation, an increase in proteinuria after conversion from calcineurin inhibitors to rapamycin has been reported. In contrast, there are studies showing a nephro-protective effect of rapamycin in proteinuric diseases characterized by progressive interstitial inflammatory fibrosis.

METHODS

Because of the contradictory reports concerning rapamycin on proteinuria, we examined proteinuria and podocyte damage markers on two renal disease models, with clearly different pathophysiological mechanisms: a glomerular toxico-immunological model induced by puromycin aminonucleoside, and a chronic hyperfiltration and inflammatory model by mass reduction, both treated with a fixed high rapamycin dose.

RESULTS

In puromycin groups, rapamycin provoked significant increases in proteinuria, together with a significant fall in podocin immunofluorescence, as well as clear additional damage to podocyte foot processes. Conversely, after mass reduction, rapamycin produced lower levels of proteinuria and amelioration of inflammatory and pro-fibrotic damage. In contrast to the puromycin model, higher glomerular podocin and nephrin expression and amelioration of glomerular ultrastructural damage were found.

CONCLUSIONS

We conclude that rapamycin has dual opposing effects on subjacent renal lesion, with proteinuria and podocyte damage aggravation in the glomerular model and a nephro-protective effect in the chronic inflammatory tubulointerstitial model. Rapamycin produces slight alterations in podocyte structure when acting on healthy podocytes, but it clearly worsens those podocytes damaged by other concomitant injury.

Omega-3 fatty acid supplementation attenuates oxidative stress, inflammation, and tubulointerstitial fibrosis in the remnant kidney

Significant reduction of renal mass initiates a series of hemodynamic and nonhemodynamic events which lead to proteinuria, glomerulosclerosis, tubulointerstitial injury, and end-stage renal failure. Lipid mediators derived from fatty acids participate in regulation of renal hemodynamic and nonhemodynamic processes that influence progression of renal disease. Composition of cellular fatty acids and hence related signaling responses are influenced by their dietary contents. Consumption of omega-3 fatty acids (O-3FA) has proven effective in mitigating atherosclerosis. We tested the hypothesis that O-3FA supplementation may retard progression and attenuate upregulation of pathways involved in oxidative stress, inflammation, and fibrosis in rats with renal mass reduction. Sprague-Dawley rats were subjected to 5/6 nephrectomy [chronic renal failure (CRF)] and randomly assigned to the untreated and O-3FA-treated (0.3 g.kg(-1).day(-1) by gastric gavage for 12 wk) groups. Sham-operated rats served as controls. The untreated CRF rats exhibited proteinuria, hypertension, azotemia, upregulations of renal tissue NAD(P)H oxidase, MCP-1, COX-2, PAI-1, TGF-beta, Smad2, alpha-smooth muscle actin, fibronectin, and hepatocyte growth factor, activation of ERK1/2 and NF-kappaB, downregulation of Smad7, intense mononuclear leukocyte infiltration, tubulointerstitial fibrosis, and glomerulosclerosis. O-3FA supplementation significantly lowered COX-2, NAD(P)H oxidase (NOX-4, gp91(phox), p47(phox), p22(phox)), PAI-1, TGF-beta, connective tissue growth factor, alpha-smooth muscle actin, fibronectin, Smad2, and MCP-1, raised Smad7, and attenuated ERK1/2 and NF-kappaB activation, tubulointerstitial fibrosis, and inflammation. Thus, long-term O-3FA supplementation can reduce or reverse upregulation of prooxidant, proinflammatory, and profibrotic pathways and attenuate tubulointerstitial fibrosis in the remnant kidney.

Dietary soy protein selectively reduces renal prostanoids and cyclooxygenases in polycystic kidney disease

Increasing evidence in human chronic kidney disease and in animal models indicates the potential utility of dietary soy protein in the treatment of this disorder. A model in which a beneficial soy protein effect has been consistently demonstrated is the Han:SPRD-cy rat model of polycystic kidney disease. Therefore, since dietary soy protein alters renal hemodynamics and prostanoid production, the effects of dietary soy protein on renal prostanoids and related rate-limiting enzymes were examined. Normal and diseased weanling rats were given diets containing casein or soy protein for 7 wk. At 10 wk of age, renal levels of thromboxane B(2) (TXB(2), stable metabolite of TXA(2)), prostaglandin E(2) (PGE(2)) and 6-keto PGF(1alpha) (stable metabolite of PGI(2)) and activities of cyclooxygenase 1 (COX1) and COX2 were elevated in diseased compared to normal kidneys. Soy protein feeding resulted in 49% lower in vitro steady-state levels of TXB(2), and 76% less 6-keto PGF(1alpha) produced by COX1 activity in diseased kidneys, while not altering these parameters in normal kidneys. It also resulted in 47% less TXB(2) and 36% lower 6-keto PGF(1alpha) produced by COX2 activity in diseased kidneys. The relative effect of soy protein feeding on COX2 activity was in the order of TXB(2) > 6-keto PGF(1alpha) > PGE(2). Diseased kidneys had elevated protein and mRNA levels of cytosolic phospholipase A(2) (cPLA(2)) and COX1 and lower levels of COX2. Dietary soy protein attenuated the protein levels of cPLA(2) in diseased kidneys, and reduced COX2 mRNA expression in both normal and diseased kidneys. Dietary soy protein therefore reduced the levels of specific renal prostanoids, cPLA(2) and COX enzymes in this model of polycystic kidney disease, a model in which soy protein has been demonstrated to reduce disease progression.

Nephro-protective effect of Kangqianling decoction on chronic renal failure rats

ETHNOPHARMACOLOGICAL RELEVANCE

Kangqianling decoction (KQL), the modified formulation of a classical Chinese prescription named Taohongsiwu decoction, was clinically employed to treat renal fibrosis in chronic renal failure.

AIM OF THE STUDY

The present study was designed to examine whether KQL has a protective effect on renal function in association with transforming growth factor-beta (TGF-beta), angiotensin II (Ang II), tumor necrosis factor-alpha (TNF-alpha), nuclear factor-kappaB (NF-kappaB) in rats with 5/6 renal ablation (Nx)-induced chronic renal failure.

RESULTS

In renal function deterioration progression, the high expression of serum creatinine (Scr), 24-h urine protein and systolic blood pressure were markedly (P<0.05 or P<0.01) restored by KQL, respectively, at 4 and 8 weeks. The increasing expressions of renal Ang II (P<0.05), angiotensin II1-receptor (AT1R) (P<0.05), TNF-alpha (P<0.05), NF-kappaB (P<0.001) and urine TGF-beta1 (P<0.05) were reduced by the treatment of KQL. Immunohistochemical study further confirmed the nephro-protective activity of KQL as compared to the control and Sham group.

CONCLUSIONS

The results indicate that KQL is able to protect renal function via ameliorating experimental rat renal failure as found in these renal functional parameters.

Non-phenacetin analgesics and analgesic nephropathy: clinical assessment of high users from a case-control study

BACKGROUND

A recent large-scale case-control study on analgesic nephropathy (SAN) [1] found no increased risk of end-stage renal disease (ESRD) in users of combined or single formulations of phenacetin-free analgesics. In a subgroup of 22 high users, however, a dose-dependent increased risk was found, which raised the question if these patients presented or not with analgesic nephropathy (AN).

METHODS

The individual questionnaires of this subgroup of high users were reviewed, and the total lifetime intake of different types of analgesics was calculated. For evidence of AN, the following data were considered: (1) the amount and type of analgesics consumed, (2) the cause of ESRD, as diagnosed by the nephrologist in charge of the patient and (3) renal imaging and other relevant laboratory data.

RESULTS

This group of ESRD patients consumed on average 7.8 kg of antipyretic analgesics (range 30.8-2.7 kg) over an average of 21.5 years (range 35-6 years). Single analgesics were exclusively used by 12 patients (54.5%) and combined analgesics by 5 patients (22.7%), while 5 patients used both. None of the patients was diagnosed as having AN, and a review of the questionnaires did not disclose evidence suggestive of AN. The possibility that, irrespective of AN, the analgesic (ab)use contributed to the progression of existing renal diseases cannot be answered in the absence of well-defined criteria. The data supporting the existence of such an analgesic-associated nephropathy (AAN) are, however, not consistent and most likely due to confounding by indication.

CONCLUSION

In a group of ESRD patients with high use of non-phenacetin analgesics, no evidence of AN was found. There is no evidence that (ab)use of analgesics or NSAIDs other than phenacetin leads to a pathologically or clinically defined renal disease that could be named AN or AAN.

Effect of exercise on cardiac tissue oxidative and inflammatory mediators in chronic kidney disease

BACKGROUND

Chronic renal failure (CRF) results in diminished physical activity and increased risk of cardiovascular disease (CVD). CVD risk factors are raised by sedentary life style and ameliorated by physical fitness in the general population. Accordingly, exercise improves hypertension, endothelial dysfunction, insulin resistance, dyslipidemia, inflammation and oxidative stress in high-risk populations. This study was designed to explore the effect of exercise on oxidative and inflammatory mediators in the left ventricle (LV) of CRF rats.

METHODS AND RESULTS

One week after 5/6 nephrectomy female rats were housed in either regular cages or cages equipped with running wheels for 4 weeks. Sham-operated rats housed in regular cages served as controls. Sedentary CRF rats exhibited azotemia, hypertension, anemia, oxidative stress, activation of NF-kappaB and upregulations of reactive oxygen species-generating enzyme, NAD(P)H oxidase, MCP-1, cyclooxygenase-2 (COX-2), and PAI-1 in LV. The CRF rats assigned to the exercise group ran 6.8 +/- 0.7 km/day and 72 +/- 8 min/day. Voluntary exercise reversed NF-kappaB activation and lowered NAD(P)H oxidase, PAI-1, MCP-1 and COX-2 abundance, increased LV mass by raising myofibrillar proteins and ameliorated anemia without affecting renal function or arterial pressure.

CONCLUSIONS

CRF resulted in upregulation of prooxidant/proinflammatory pathways in LV. These changes were ameliorated by exercise, which indicates the potential cardiovascular benefit of exercise in renal insufficiency.

PGE(2) induces COX-2 expression in podocytes via the EP(4) receptor through a PKA-independent mechanism

Cyclooxygenase-2 (COX-2)-dependent prostaglandin E(2) (PGE(2)) synthesis correlates with the onset of proteinuria and increased glomerular capillary pressure (P(gc)) glomerular disease models. We previously showed that an in vitro surrogate for P(gc) (cyclical mechanical stretch) upregulates the expression of both COX-2 and the PGE(2) responsive E-Prostanoid receptor, EP(4) in cultured mouse podocytes. In the present study we further delineate the signaling pathways regulating podocyte COX-2 induction. Time course experiments carried out in conditionally-immortalized mouse podocytes revealed that PGE(2) transiently increased phosphorylated p38 MAPK levels at 10 min, and induced COX-2 protein expression at 4 h. siRNA-mediated knockdown of EP(4) receptor expression, unlike treatment with the EP(1) receptor antagonist SC 19220, completely abrogated PGE(2)-induced p38 phosphorylation and COX-2 upregulation suggesting the involvement of the EP(4) receptor subtype. PGE(2)-induced COX-2 induction was abrogated by inhibition of either p38 MAPK or AMP activated protein kinase (AMPK), and was mimicked by AICAR, a selective AMPK activator, and by the cAMP-elevating agents, forskolin (FSK) and IBMX. Surprisingly, neither PGE(2) nor FSK/IBMX-dependent p38 activation and COX-2 expression were blocked by PKA inhibitors or mimicked by 8-cPT-cAMP a selective EPAC activator, but were instead abrogated by Compound C, suggesting the involvement of AMPK. These results indicate that in addition to mechanical stretch, PGE(2) initiates a positive feedback loop in podocytes that drives p38 MAPK activity and COX-2 expression through a cAMP/AMPK-dependent, but PKA-independent signaling cascade. This PGE(2)-induced signaling network activated by increased P(gc) could be detrimental to podocyte health and glomerular filtration barrier integrity.

Eicosanoids and renal damage in cardiometabolic syndrome

BACKGROUND

Obesity, hypertension and Type 2 diabetes are major contributing factors to the increase in the number of patients that have chronic kidney disease. The clustering of visceral obesity and cardiovascular risk factors has been designated metabolic syndrome or cardiometabolic syndrome. Cardiometabolic syndrome is associated with a complex systemic inflammatory state that has been implicated in medically important complications, including endothelial dysfunction. Inflammation, endothelial dysfunction and insulin resistance are interrelated and have reciprocal relationships that link cardiovascular and metabolic diseases. Ultimately, cardiometabolic syndrome increases the risk for cardiovascular events and end-organ damage. Although the number of patients with cardiometabolic syndrome is escalating, therapeutic approaches have not been developed that provide protection to the kidney.

OBJECTIVE

The objective of this review is to provide an overview of the contribution of eicosanoids to renal damage in cardiometabolic syndrome.

RESULTS/CONCLUSION

Eicosanoids are altered in cardiometabolic syndrome and contribute to the progression of renal injury. The antihypertensive and anti-inflammatory actions of epoxides and soluble epoxide hydrolase inhibitors make these attractive eicosanoid therapeutic targets for chronic kidney disease in patients with cardiometabolic syndrome.

Dietary soy protein reduces early renal disease progression and alters prostanoid production in obese fa/fa Zucker rats

With the rising incidence of obesity and the metabolic syndrome, obesity-associated nephropathy also has increased. One of the earliest pathologies in the development of this nephropathy is glomerular hyperfiltration and hypertrophy. Dietary soy protein (SP) ameliorates disease progression in several models of renal disease, and vegetable sources of protein, as compared to animal sources of protein, alter renal hemodynamics. Therefore, the effect of dietary SP on early renal disease and prostanoid production was examined in the obese fa/fa Zucker rat. Rats, 6 weeks of age, were given diets containing 17% protein from either SP or egg white (EW) for 8 weeks. Feed consumption and body and kidney weights were significantly greater in fa/fa rats as compared to lean rats. The fa/fa rats also had 139% more proteinuria and kidneys with 43% larger glomeruli. SP feeding did not alter body weights or proteinuria but did result in 6% lower kidney weights (g/100 g body weight) and 16% smaller glomeruli in fa/fa rats. Cyclooxygenase activity as determined by 6-keto prostaglandin F(1alpha) (6-keto PGF(1alpha)) synthesis was lower in fa/fa rats given SP-based diets as compared to those given EW-based diets. Ratios of renal thromboxane (TX) B(2)/6-keto PGF(1alpha) and PGE(2)/6-keto PGF(1alpha) were higher, while TXB(2)/PGE(2) levels were not different in rats given SP diets as compared to those given EW diets, also indicating that dietary SP reduced renal 6-keto PGF(1alpha) levels. These findings suggest that attenuation of early glomerular hypertrophy in young obese fa/fa rats by dietary SP may be mediated by the lower levels of 6-keto PGF(1alpha) since this would be expected to reduce glomerular hyperfiltration.

Intra-renal angiotensin II/AT1 receptor, oxidative stress, inflammation, and progressive injury in renal mass reduction

Significant reduction of renal mass triggers a chain of events that result in glomerular hypertension/hyperfiltration, proteinuria, glomerulosclerosis, tubulointerstitial injury, and end-stage renal disease. These events are mediated by a constellation of hemodynamic, oxidative, and inflammatory reactions that are, in part, driven by local AT1 receptor (AT1r) activation by angiotensin II (Ang II). Here we explored the effects of 5/6 nephrectomy with and without AT1r blockade (losartan for 8 weeks) on AT1r and AT2r and Ang II-positive cell count, pathways involved in oxidative stress and inflammation [NAD(P)H oxidase, nuclear factor kappaB (NFkappaB), 12-lipooxygenase, cyclooxygenase (COX)-1, COX-2, monocyte chemoattractant protein (MCP)-1, plasminogen activator inhibitor (PAI)-1, renal T cell, and macrophage infiltration] as well as renal function and structure. The untreated group exhibited hypertension, deterioration of renal function and structure, reduced or unchanged plasma renin activity, aldosterone concentration, marked up-regulations of AT1r (250%), Ang II-expressing cell count (>20-fold), NAD(P)H oxidase subunits (gp91(phox,) p22(phox), and P47(phox); 20-40%), COX-2 (250%), 12-lipooxygenase (100%), MCP-1 (400%), and PAI-1 (>20-fold), activation of NFkappaB, and interstitial infiltrations of T cells and macrophages in the remnant kidneys. AT1r blockade attenuated the biochemical and histological abnormalities, prevented hypertension, and decelerated deterioration of renal function and structure. Thus, the study demonstrated a link between up-regulation of Ang II/AT1r system and oxidative stress, inflammation, hypertension, and progression of renal disease in rats with renal mass reduction.

Exacerbation of albuminuria and renal fibrosis in subtotal renal ablation model of adiponectin-knockout mice

OBJECTIVE

Obesity is recognized increasingly as a major risk factor for kidney disease. We reported previously that plasma adiponectin levels were decreased in obesity, and that adiponectin had defensive properties against type 2 diabetes and hypertension. In this study, we investigated the role of adiponectin for kidney disease in a subtotal nephrectomized mouse model.

METHODS AND RESULTS

Subtotal (5/6) nephrectomy was performed in adiponectin-knockout (APN-KO) and wild-type (WT) mice. The procedure resulted in significant accumulation of adiponectin in glomeruli and interstitium in the remnant kidney. Urinary albumin excretion, glomerular hypertrophy, and tubulointerstitial fibrosis were significantly worse in APN-KO mice compared with WT mice. Intraglomerular macrophage infiltration and mRNA levels of vascular cell adhesion molecule (VCAM)-1, MCP-1, tumor necrosis factor (TNF)-alpha, transforming growth factor (TGF)-beta1, collagen type I/III, and NADPH oxidase components were significantly increased in KO mice compared with WT mice. Treatment of APN-KO mice with adenovirus-mediated adiponectin resulted in amelioration of albuminuria, glomerular hypertrophy, and tubulointerstitial fibrosis and reduced the elevated levels of VCAM-1, MCP-1, TNF-alpha, TGF-beta1, collagen type I/III, and NADPH oxidase components mRNAs to the same levels as those in WT mice.

CONCLUSIONS

Adiponectin accumulates to the injured kidney, and prevents glomerular and tubulointerstitial injury through modulating inflammation and oxidative stress.

Selective COX-2 inhibition markedly slows disease progression and attenuates altered prostanoid production in Han:SPRD-cy rats with inherited kidney disease

Selective cyclooxygenase-2 (COX-2) inhibitors appear to have beneficial renoprotective effects in most, but not all, renal disease conditions. The objective of our study was to examine the effects of COX-2 inhibition in a rat model of polycystic kidney disease. Four-week-old Han:SPRD-cy rats were given a standard rodent diet containing NS-398 (3 mg.kg body wt(-1).day(-1)) or a control diet without NS-398 for 7 wk. In diseased rats, selective COX-2 inhibition resulted in 18% and 67% reduction in cystic expansion and interstitial fibrosis, respectively, but no change in renal function. NS-398 also ameliorated disease-associated pathologies, such as renal inflammation, cell proliferation, and oxidant injury (by 33, 38, and 59%, respectively). Kidney disease was associated with elevated renal COX-1 and COX-2 enzyme activities, and NS-398 blunted the increase in COX-2 enzyme activity (as indicated by 21 and 28% lower renal thromboxane B2 and PGE2 levels, respectively). NS-398 reduced urinary excretion of prostanoid metabolites in diseased rats. In summary, COX-2 inhibition attenuated renal injury, reduced the elevated renal COX-2 activity, and ameliorated disease-related alterations in prostanoid production in this rat model of chronic renal disease.

Role of renal cortical cyclooxygenase-2 expression in hyperfiltration in rats with high-protein intake

Renal cortical cyclooxygenase-2 (COX-2) is restricted to the macula densa and adjacent cortical thick ascending limbs (MD/cTALH). Renal cortical COX-2 increases in response to diabetes and renal ablation, both of which are characterized by hyperfiltration and reduced NaCl delivery to the MD due to increased proximal NaCl reabsorption. High-protein intake also induces hyperfiltration and decreases NaCl delivery to the MD due to increased NaCl reabsorption proximally. We investigated whether high protein induces cortical COX-2 and whether cortical COX-2 contributes to high protein-induced hyperfiltration and increased intrarenal renin biosynthesis. Cortical COX-2 increased after protein loading but decreased after protein restriction. COX-2 inhibition attenuated high protein-induced hyperfiltration but had no effect on high protein-induced intrarenal renin elevation. Therefore, induction of cortical COX-2 contributed to high protein-induced hyperfiltration but not intrarenal renin elevation. In the kidney cortex, neuronal nitric oxide synthase (nNOS) is also localized to the MD, and interactions between intrarenal nNOS and COX-2 systems have been proposed. Cortical COX-2 elevation seen in salt restriction was blocked by nNOS inhibiton. Cortical nNOS expression also increased after protein loading, and inhibition of nNOS activity completely reversed high protein-induced cortical COX-2 elevation and hyperfiltration. These results indicate that NO is a mediator of high protein-induced cortical COX-2 elevation and suggest that both intrarenal nNOS and COX-2 systems appear to regulate afferent arteriolar tone and subsequent hyperfiltration seen in high-protein intake.

Therapeutic Potential of (-)-Epigallocatechin 3-O-Gallate on Renal Damage in Diabetic Nephropathy Model Rats

Previous investigations have demonstrated that green tea polyphenols and partially hydrolyzed guar gum as dietary fiber have antioxidative and hypolipidemic activity, respectively, supporting their reduction of risk factors in the course of diabetic nephropathy via a hypoglycemic effect and ameliorating the decline of renal function through their combined administration to rats with subtotal nephrectomy plus streptozotocin (STZ) injection. As a further study, we examined whether (-)-epigallocatechin 3-O-gallate (EGCg), the main polyphenolic compound, could ameliorate the development of diabetic nephropathy. Rats with subtotal nephrectomy plus STZ injection were orally administrated EGCg at doses of 25, 50, and 100 mg/kg body weight/day. After a 50-day administration period, EGCg-treated groups showed suppressed hyperglycemia, proteinuria, and lipid peroxidation, although there were only weak effects on the levels of serum creatinine and glycosylated protein. Furthermore, EGCg reduced renal advanced glycation end-product accumulation and its related protein expression in the kidney cortex as well as associated pathological conditions. These results suggest that EGCg ameliorates glucose toxicity and renal injury, thus alleviating renal damage caused by abnormal glucose metabolism-associated oxidative stress involved in renal lesions of diabetic nephropathy.

Update on cyclooxygenase-2 inhibitors

Nonsteroidal anti-inflammatory drugs represent the most commonly used medications for the treatment of pain and inflammation, but numerous well-described side effects can limit their use. Cyclooxygenase-2 (COX-2) inhibitors were initially touted as a therapeutic strategy to avoid not only the gastrointestinal but also the renal and cardiovascular side effects of nonspecific nonsteroidal anti-inflammatory drugs. However, in the kidney, COX-2 is constitutively expressed and is highly regulated in response to alterations in intravascular volume. COX-2 metabolites have been implicated in mediation of renin release, regulation of sodium excretion, and maintenance of renal blood flow. This review summarizes the current state of knowledge about both renal and cardiovascular side effects that are attributed to COX-2 selective inhibitors.