Pentoxifylline attenuates experimental mesangial proliferative glomerulonephritis

Phosphodiesterase 4 inhibitors in diabetic nephropathy

Phosphodiesterase subtype 4 (PDE4) hydrolyzes cyclic AMP, a secondary messenger that mediates intracellular signaling, and plays key roles in inflammatory and fibrotic responses. Based on these significant anti-inflammatory effects, oral administration of PDE4 inhibitor is approved for the treatment of chronic obstructive pulmonary disease, atopic dermatitis, and psoriasis. However, PDE4 inhibition also has adverse effects, such as diarrhea, vomiting, dyspepsia, and headache. Therefore, the application of PDE4 inhibitors for chronic diseases, such as diabetes and its complications, has not yet been approved. Recent studies have reported the clinical benefits of pentoxifylline, a non-selective PDE inhibitor, in patients with kidney disease. The PDE4 inhibitor, roflumilast, also clearly ameliorates the symptoms of diabetes mellitus by improving hyperglycemia and insulin resistance. However, the beneficial effects of PDE4 inhibition on diabetic nephropathy have not yet been evaluated, and its potential mechanisms of action remain unknown. In this review, we discuss the beneficial effects of PDE4 inhibitors and their mechanisms of action using diabetes and DN models.

Intrarenal Transplantation of Hypoxic Preconditioned Mesenchymal Stem Cells Improves Glomerulonephritis through Anti-Oxidation, Anti-ER Stress, Anti-Inflammation, Anti-Apoptosis, and Anti-Autophagy

To confer further therapeutic potential and prevent some adverse effects by the mesenchymal stem cells (MSCs) transplantation, we explored the effects of locally intrarenal arterial administration of hypoxic preconditioned MSCs in the anti-Thy1.1 induced rat glomerulonephritis. Proteinuria, histochemical staining, and western blotting were used to explore the therapeutic effects and mechanisms. Locally intrarenal arterial MSCs transplantation successfully implanted the fluorescent or CD44 labeled MSCs in the nephritic glomeruli, ameliorated proteinuria, and glomerulosclerosis in nephritic rats. Hypoxic preconditioning significantly upregulated hypoxic inducible factor-1α/VEGF (HIF-1α/VEGF) in the MSCs and was more efficient than normoxic MSCs in reducing the degree of urinary protein, glomerulosclerosis, fibrosis, macrophage/monocyte infiltration, GRP78 mediated endoplasmic reticulum stress, Beclin-1/LC3-II mediated autophagy, and Bax/Bcl-2/caspase 3 mediated apoptosis. Hypoxic MSCs could further promote intranuclear nuclear factor (erythroid-derived 2, Nrf2) and reduce nuclear factor kappa B expression in nephritic kidneys. As compared to normoxic MSCs, hypoxic MSCs transplantation significantly upregulated the renal expression of anti-oxidative response elements/enzymes including glutamate-cysteine ligase catalytic subunit, glutamate-cysteine ligase modifier subunit, glutathione peroxidase, catalase, Mn, and Cu/Zn superoxide dismutase. In summary, intrarenal hypoxic preconditioning MSCs transplantation was more effective to activate hypoxic inducible factor-1α/VEGF/Nrf2 (HIF-1α/VEGF/Nrf2) signaling, preserve anti-oxidant proteins and anti-oxidative responsive element proteins, and subsequently reduce glomerular apoptosis, autophagy, and inflammation.

Emerging therapeutic strategies for minimal change disease and focal and segmental glomerulosclerosis

INTRODUCTION

Minimal change disease (MCD) and Focal and segmental glomerulosclerosis (FSGS) are two of the major causes of nephrotic syndrome (NS) in children and adults. According to KDIGO (Kidney Disease: Improving Global Outcomes) guidelines, the treatment of adult primary MCD and FSGS should be based on immunosuppressants and antiproteinuric drugs. Recently, Rituximab, a humanized monoclonal antibody (mAb) has emerged as a potential treatment for steroid or calcineurin inhibitor-dependent patients; it has however demonstrated lower efficacy in those with nephrotic syndrome that is resistant to the above indicated drugs.

AREAS COVERED

Analysis of ongoing and already completed clinical trials, retrieved from clinicaltrials.gov, clinicaltrialsregister.eu and PubMed involving new therapies for nephrotic syndrome secondary to MCD and FSGS.

EXPERT OPINION

The most promising drugs under investigation for MCD and FSGS are mAbs. We are hopeful that new therapeutic options to treat multi-drug resistant MCD and FSGS will emerge from currently ongoing studies. What appears certain is the difficulty in enrolling patients affected by orphan renal diseases and the selection of valid endpoints in clinical trials, such as kidney failure.

PDE/cAMP/Epac/C/EBP-β Signaling Cascade Regulates Mitochondria Biogenesis of Tubular Epithelial Cells in Renal Fibrosis

AIMS

Cyclic adenosine 3'5'-monophosphate (cAMP) is a universal second messenger that plays an important role in intracellular signal transduction. cAMP is synthesized by adenylate cyclases from adenosine triphosphate and terminated by the phosphodiesterases (PDEs). In the present study, we investigated the role of the cAMP pathway in tubular epithelial cell mitochondrial biogenesis in the pathogenesis of renal fibrosis.

RESULTS

We found that the cAMP levels were decreased in fibrotic kidney tissues, and replenishing cAMP could ameliorate tubular atrophy and extracellular matrix deposition. The downregulation of cAMP was mainly attributed to the increased PDE4 expression in tubular epithelial cells. The inhibition of PDE4 by PDE4 siRNA or the specific inhibitor, rolipram, attenuated unilateral ureteral obstruction-induced renal interstitial fibrosis and transforming growth factor (TGF)-β1-stimulated primary tubular epithelial cell (PTC) damage. The Epac1/Rap1 pathway contributed to the main effect of cAMP on renal fibrosis. Rolipram could restore C/EBP-β and PGC-1α expression and protect the mitochondrial function and structure of PTCs under TGF-β1 stimulation. The antifibrotic role of rolipram in renal fibrosis relies on C/EBP-β and PGC-1α expression in tubular epithelial cells. Innovation and Conclusion: The results of the present study indicate that cAMP signaling regulates the mitochondrial biogenesis of tubular epithelial cells in renal fibrosis. Restoring cAMP by the PDE4 inhibitor rolipram may ameliorate renal fibrosis by targeting C/EBP-β/PGC1-α and mitochondrial biogenesis. Antioxid. Redox Signal. 29, 637-652.

Therapeutic efficacy of pentoxifylline on proteinuria and renal progression: an update

Blood pressure control with renin-angiotensin system (RAS) blockade has remained the gold standard for treating patients with proteinuric chronic kidney disease (CKD) up to date. Nevertheless, RAS blockade slows but does not halt the progression of kidney disease, thus highlighting the need to search for additional therapeutic approaches. The nonselective phosphodiesterase (PDE) inhibitor pentoxifylline (PTX) is an old drug that exhibits prominent anti-inflammatory, anti-proliferative and anti-fibrotic activities both in vitro and in vivo. Studies in human subjects have shown that PTX monotherapy decreases urinary protein excretion, and add-on therapy of PTX to background RAS blockade additively reduces proteinuria in patients with CKD of various etiology. More recent studies find that PTX combined with RAS blockade delays the decline of glomerular filtration rate in diabetic patients with mild to moderate CKD, and reduces the risk of end-stage renal disease in diabetic and non-diabetic patients in late stage of CKD with high proteinuria levels. In this review, we update the clinical trial results of PTX as monotherapy, or in conjunction or in comparison with RAS blockade on patients with proteinuria and CKD, and propose a mechanistic scheme explaining the renoprotective activities of this drug.

Targeted delivery of celastrol to mesangial cells is effective against mesangioproliferative glomerulonephritis

Mesangial cells-mediated glomerulonephritis is a frequent cause of end-stage renal disease. Here, we show that celastrol is effective in treating both reversible and irreversible mesangioproliferative glomerulonephritis in rat models, but find that its off-target distributions cause severe systemic toxicity. We thus target celastrol to mesangial cells using albumin nanoparticles. Celastrol-albumin nanoparticles crosses fenestrated endothelium and accumulates in mesangial cells, alleviating proteinuria, inflammation, glomerular hypercellularity, and excessive extracellular matrix deposition in rat anti-Thy1.1 nephritis models. Celastrol-albumin nanoparticles presents lower drug accumulation than free celastrol in off-target organs and tissues, thereby minimizing celastrol-related systemic toxicity. Celastrol-albumin nanoparticles thus represents a promising treatment option for mesangioproliferative glomerulonephritis and similar glomerular diseases.

Mesangial cell-mediated glomerulonephritis is a frequent cause of kidney disease. Here the authors show that celastrol loaded in albumin nanoparticles efficiently targets mesangial cells, and is effective in rat models.

A low-salt diet increases the expression of renal sirtuin 1 through activation of the ghrelin receptor in rats

Previous studies have shown that sirtuin 1 (Sirt1) is renoprotective; however, details regarding its distribution and functions in the kidney remain unknown. Here, we demonstrated that Sirt1 was mainly expressed in the tubulointerstitial cells of normal rat kidneys and was co-localized with aquaporin 2, indicating it may be involved in water/salt regulation. Renal Sirt1 expression increased in the non-glomerular cytoplasmic portion of the kidney after a 24-h fast, but no significant changes in Sirt1 expression occurred after water loading (50 mL/kg) or 24-h water deprivation. After consuming a low-salt (0.075%) or 60% calorie restriction diet for 7 days, Sirt1 expression in the rat kidney was significantly increased, whereas a high-salt (8%) diet did not change the level of Sirt1 expression. The low-salt diet also increased Sirt1 expression in the heart, muscle, brain, and fat tissues. The increased Sirt1 that was observed in rats on a low-salt diet was associated with increased ghrelin expression in the distal nephron, with both molecules exhibiting similar distribution patterns. An in vitro experiment suggested that ghrelin increases Sirt1 expression in cortical collecting duct cells by activating ghrelin receptors. Our study indicates that this ‘ghrelin-Sirt1 system’ may participate in regulating sodium reabsorption in the distal nephron.

Viability of randomized skin flaps-an experimental study in rats

BACKGROUND

Randomized skin flaps are extensively used in plastic surgery, but the possibility of necrosis has challenged their use. Several studies have been conducted aiming to find ways to reduce the occurrence of necrosis. We evaluated the effects of pentoxifylline (PTX) and hyaluronidase (HLD), each alone or combined, on randomized rat skin flaps.

MATERIALS AND METHODS

Fifty male Wistar rats were divided into five groups of 10 animals each: control I, control II, PTX, HLD, PTX-HLD. Substances were administered from the first to the 14th postoperative day. The necrotic area was measured on the seventh and 14th postoperative day; the animals were killed on the 14th day, when samples were collected for histologic and immunohistochemical examination.

RESULTS

On the seventh day, percentage of the necrotic area was significantly reduced in PTX, HLD, and PTX-HLD animals compared with control groups. On 14th day, percentage of the necrotic area in PTX, HDL, and PTX-HLD groups was also significantly reduced compared with control groups. PTX and PTX-HLD showed a significant reduction in dermis cellularity, V_V of macrophages, and myofibroblasts compared with control groups; PTX showed a significant enhancement of L_V of blood vessels compared with all other groups.

CONCLUSIONS

The use of each substance alone or combined increased flap viability compared with control groups. On the seventh day, PTX exhibited lower viability than HLD, whereas on the 14th day there was no difference between treated groups. PTX alone enhanced the L_V of blood vessels, whereas PTX-HLD did not. However, PTX-HLD was more effective in decreasing the dermis cellularity and macrophage V_V than HLD alone.

Anti-TGF-β Antibody, 1D11, Ameliorates Glomerular Fibrosis in Mouse Models after the Onset of Proteinuria

Fibrosis is a final common pathway leading to loss of kidney function, in which the fibrogenic cytokine, transforming growth factor β (TGF-β), plays a central role. While previous studies showed that TGF-β antagonism by various means prevents fibrosis in mouse models, clinical approaches based on these findings remain elusive. 1D11 is a neutralizing antibody to all three isoforms of TGF-β. In both adriamycin (ADR)-induced nephropathy and NEP25 podocyte ablation nephropathy, thrice-weekly intraperitoneal administration of 1D11 from the day of disease induction until the mice were sacrificed (day 14 for ADR and day 28 for NEP25), significantly reduced glomerular COL1A2 mRNA accumulation and histological changes. Consistent with our previous findings, proteinuria remained overt in the mice treated with 1D11, suggesting distinct mechanisms for proteinuria and fibrogenesis. Podocyte numbers determined by WT1 staining were significantly reduced in NEP25-model glomeruli as expected, while WT1-positive cells were preserved in mice receiving 1D11. Even when 1D11 was administered after the onset of proteinuria on day 3, 1D11 preserved WT1-positive cell numbers in glomeruli and significantly reduced glomerular scar score (2.5 ± 0.2 [control IgG] vs. 1.8 ± 0.2 [1D11], P < 0.05) and glomerular COL1A2 mRNA expression (19.3 ± 4.4 [control IgG] vs. 8.4 ± 2.4 [1D11] fold increase over the healthy control, P < 0.05). Transmission electron microscopy revealed loss of podocytes and denuded glomerular basement membrane in NEP25 mice with disease, whereas podocytes remained attached to the basement membrane, though effaced and swollen, in those receiving 1D11 from day 3. Together, these data suggest that TGF-β neutralization by 1D11 prevents glomerular fibrosis even when started after the onset of proteinuria. While overt proteinuria and podocyte effacement persist, 1D11 prevents total podocytes detachment, which might be a key event activating fibrogenic events in glomeruli.

Add-on Protective Effect of Pentoxifylline in Advanced Chronic Kidney Disease Treated with Renin-Angiotensin-Aldosterone System Blockade - A Nationwide Database Analysis

A combination therapy of pentoxifylline with an angiotensin converting enzyme inhibitor (ACEI) or an angiotensin II receptor blocker (ARB) decreased proteinuria or glomerular filtration rate decline in early chronic kidney disease (CKD). Whether adding pentoxifylline to ACEI/ARB provides additional benefits on outcome is unclear in CKD stage 5 patients who have not yet received dialysis (CKD 5 ND). A prospective cohort study was conducted based on the Taiwan National Health Insurance Research Database. From January 1, 2000 to June 30, 2009, we enrolled 14,117 CKD 5 ND with serum creatinine levels >6 mg/dL and hematocrit levels <28% and who have been treated with ACEI/ARB. All patients were divided into pentoxifylline users and nonusers. Patient follow-up took place until dialysis, death before initiation of dialysis or December 31, 2009. Finally, 9,867 patients (69.9%) required long-term dialysis and 2,805 (19.9%) died before dialysis. After propensity score-matching, use of pentoxifylline was associated with a lower risk for long-term dialysis or death in ACEI/ARB users (HR, 0.94; 95% CI, 0.90–0.99) or ARB users (HR, 0.91; 95% CI, 0.85–0.97). In conclusion, pentoxifylline exhibited a protective effect in reducing the risk for the composite outcome of long-term dialysis or death in ACEI/ARB treated CKD 5 ND.

Nitric oxide synthase in diabetic rat testicular tissue and the effects of pentoxifylline therapy

Diabetes is known to be associated with erectile dysfunction, retrograde ejaculation, level of testicular hormone, and a decrease in semen quality, respectively. In this project, we aimed to investigate at the molecular level, the effects of NOS on testes pathology in diabetes and examine the effects of pentoxifylline on healing. A total of 50 Wistar albino male rats were divided into five groups: Group I control; Group II only diabetes; Group III and IV diabetes + pentoxifylline; Group V only pentoxifylline. Group III rats received 50 mg/kg/day pentoxifylline during two months. In comparison, Group IV rats received saline in the first month followed by 50 mg/kg/day of pentoxifylline for the following month. NOS expression in testicular tissue was assessed using qRT-PCR, western blot, and immunohistochemistry. The mean seminiferous tubule diameter, Johnsen's testicular biopsy score, and serum testosterone levels decreased compared to controls. In contrast, the number of apoptotic cells, the levels of nNOS, iNOS and eNOS mRNA, and protein increased when compared to the control. Upon pentoxifylline therapy NOS decreased suggesting that it contributes to this damage and treatment with pentoxifylline may be effective in reversing this damage.

Effect of pentoxifylline in proteinuric chronic kidney disease: a systematic review and meta-analysis

AIM

The aim of this study was to assess the effect of pentoxifylline on proteinuria and renal function in chronic kidney disease (CKD) treatment.

METHODS

We systematically searched PubMed, EMBASE, the Cochrane Library and ClinicalTrials.gov for randomized and non-randomized controlled trials comparing pentoxifylline to placebo, no treatment or renin-angiotensin system blockade in proteinuric CKD patients. The outcomes concerning proteinuria, renal function, blood pressure and adverse events were extracted.

RESULTS

Twelve trials with 613 participants were identified. Pentoxifylline significantly decreased proteinuria [weighted mean difference (WMD) -0.60 g/day (95 % CI -0.84 to -0.36); p < 0.001] compared to placebo or no-treatment groups, but the decrease was not significant [WMD: 0.10 g/day (-0.34 to 0.54); p = 0.66] compared to captopril treatment. The decrease of glomerular filtration rate was significantly less [WMD: 3.67 ml/min (2.71-4.62); p < 0.001] in the pentoxifylline group than in the controls. There was no significant difference in serum creatinine [WMD: -0.03 mg/dl (-0.10 to 0.03); p = 0.28], diastolic blood pressure [WMD: 0.94 mmHg (-0.74 to 2.61); p = 0.27] and adverse events [RR: 0.89 (0.60 to 1.32); p = 0.56].

CONCLUSIONS

Pentoxifylline may decrease proteinuria and protect renal function in patients with CKD. Further studies are needed to confirm this result.

Pentoxifylline Attenuates Proteinuria in Anti-Thy1 Glomerulonephritis via Downregulation of Nuclear Factor-κB and Smad2/3 Signaling

Anti-Thy1 glomerulonephritis is a rat nephritis model closely simulating human mesangial proliferative glomerulonephritis. It affects primarily the mesangium, yet displays substantial proteinuria during the course. This study investigated the molecular signals underlying proteinuria in this disease and the modulation of which by the known antiproteinuric agent, pentoxifylline. Male Wistar rats were randomly divided into a control group and nephritic groups with or without treatment with IMD-0354 (an IκB kinase inhibitor), SB431542 (an activin receptor-like kinase inhibitor) or pentoxifylline. Kidney sections were prepared for histological examinations. Glomeruli were isolated for mRNA and protein analysis. Urine samples were collected for protein and nephrin quantitation. One day after nephritis induction, proteinuria developed together with ultrastructural changes of the podocyte and downregulation of podocyte mRNA and protein expression. These were associated with upregulation of tumor necrosis factor (TNF)-α and transforming growth factor (TGF)-β/activins mRNAs and activation of nuclear factor (NF)-κB p65 and Smad2/3. IMD-0354 attenuated proteinuria on d 1, whereas SB431542 decreased proteinuria on d 3 and 5, in association with partial restoration of downregulated podocyte mRNA and protein expression. Pentoxifylline attenuated proteinuria and nephrinuria through the course, plus inhibition of p-NF-κB p65 (d 1) and p-Smad2/3 (d 5) and partial reversal of downregulated podocyte mRNA and protein. Our data show that the pathogenesis of proteinuria in anti-Thy1 glomerulonephritis involves TNF-α and TGF-β/activin pathways, and the evolution of this process can be attenuated by pentoxifylline via downregulation of NF-κB and Smad signals and restoration of the podocyte component of the glomerular filtration barrier.

Cyclic nucleotide signalling in kidney fibrosis

Kidney fibrosis is an important factor for the progression of kidney diseases, e.g., diabetes mellitus induced kidney failure, glomerulosclerosis and nephritis resulting in chronic kidney disease or end-stage renal disease. Cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) were implicated to suppress several of the above mentioned renal diseases. In this review article, identified effects and mechanisms of cGMP and cAMP regarding renal fibrosis are summarized. These mechanisms include several signalling pathways of nitric oxide/ANP/guanylyl cyclases/cGMP-dependent protein kinase and cAMP/Epac/adenylyl cyclases/cAMP-dependent protein kinase. Furthermore, diverse possible drugs activating these pathways are discussed. From these diverse mechanisms it is expected that new pharmacological treatments will evolve for the therapy or even prevention of kidney failure.

Stereological comparison of the effects of pentoxifylline, captopril, simvastatin, and tamoxifen on kidney and bladder structure after partial urethral obstruction in rats

Purpose

Limited studies have shown antifibrotic effects of pentoxifylline, captopril, simvastatin, and tamoxifen. No comparisons are available of the effects of these drugs on prevention of renal and bladder changes in partial urethral obstruction (PUO).

Materials and Methods

The rats were divided into six groups (n=7). The sham-operated rats (group I) only underwent laparotomy and did not receive any treatments. The PUO groups (group II-VI) received normal saline (PUO+NS), pentoxifylline (100 mg/kg/d; PUO+PEN), captopril (35 mg/kg/d; PUO+CAP), simvastatin (15 mg/kg/d; PUO+SIM), or tamoxifen (10 mg/kg/d; PUO+TAM) by gavage for 28 days. Then, the volume and/or length of the kidney components (tubules, vessels, and fibrous tissue) and the bladder components (epithelial and muscular layers, fibrous tissue, fibroblast and fibrocyte number) were quantitatively evaluated on the microscopic sections by use of stereological techniques.

Results

The volume of renal and bladder fibrosis was significantly ameliorated in the PUO+PEN group, followed by the PUO+CAP, PUO+SIM, and PUO+TAM groups. Also, the volume and length of the renal tubules and vessels and bladder layers were more significantly protected in the PUO+PEN group, followed by the PUO+CAP, PUO+SIM, and PUO+TAM groups.

Conclusions

Treatment of PUO with PEN was more effective in the prevention of renal and bladder fibrosis and in the preservation of renal and bladder structures.

Carboplatin-induced Fanconi-like syndrome in rats: amelioration by pentoxifylline

INTRODUCTION

Carboplatin is a congener of cisplatin used in the treatment of ovarian, head and neck and small-cell lung cancer. However, the clinical efficacy of carboplatin is marred by the development of ROS-dependent nephrotoxicity. The pathophysiological damage inflicted upon the kidney by carboplatin closely resembles to that of Fanconi syndrome.

AIMS AND OBJECTIVES

The present study aimed at inducing Fanconi-like syndrome in rats by administration of carboplatin. Objectives of the study involved evaluation of biochemical parameters coherent to Fanconi-like syndrome. Further, an attempt was made to evaluate the potential therapeutic effect of pentoxifylline in this condition.

RESULTS

The results of the study demonstrated that the urinary excretion profile of carboplatin treated rats closely resembled to that of patients suffering from Fanconi-like condition. Pentoxifylline was able to ameliorate this nephrotoxic condition as suggested by the change in levels of membrane bound ATPases, MDA and GSH. The urinary levels of tyrosine and cysteine correlate well with that of Fanconi-like condition in animals and humans.

CONCLUSION

In lieu of these observations, our study suggested that carboplatin-induced renovascular damage resembles to Fanconi-like condition which can be mitigated by pentoxifylline.

Effect of add-on pentoxifylline on proteinuria in membranous glomerulonephritis: a 6-month placebo-controlled trial

BACKGROUND

Membranous glomerulonephritis (MGN) may cause proteinuria as the main complication and is a strong risk factor for end-stage renal disease. Current therapeutic regimens provide only partial renoprotection. Data derived from both animal and human studies provide a scientific basis for the use of pentoxifylline as an antiproteinuric agent.

OBJECTIVE

This study was designed to evaluate the antiproteinuric effect of add-on pentoxifylline therapy in non-diabetic patients with MGN.

STUDY DESIGN

This was a double-blind, placebo-controlled trial.

SETTING

Non-diabetic patients with histologically proven MGN and urinary protein excretion (UPE) > 500 mg/24 h, entered a 6-month study period. Enrolled patients were selected from a university and three private clinics.

INTERVENTION

Patients were assigned to one of the two treatment groups: pentoxifylline 400 mg two or three times a day, or matching placebo.

MAIN OUTCOME MEASURES

Baseline and follow-up assessments included estimated glomerular filtration rate (eGFR) and UPE. Differences in the changes in variables within the placebo and pentoxifylline treatment groups during the study period were assessed using Friedman's test.

RESULTS

Treatment with pentoxifylline for 6 months resulted in a significant reduction of mean UPE (p < 0.001) along with a slight, non-significant increase of eGFR, in comparison to the mean UPE and eGFR increase in the placebo group.

CONCLUSION

This study showed that add-on therapy of pentoxifylline in MGN was beneficial, and could be considered as a potential new therapeutic indication for the drug in such kidney diseases.

Pentoxifylline for diabetic kidney disease

BACKGROUND

Diabetic kidney disease (DKD) is associated with increased morbidity and mortality, mostly relating to cardiovascular complications. The relevance of inflammation in the pathogenesis of DKD has been investigated in recent years, and it has been shown that inflammatory markers are higher in people with DKD compared with the wider population. Pentoxifylline is a methylxanthine phosphodiesterase inhibitor with favourable anti-inflammatory effects and immunoregulatory properties. The anti-inflammatory effects conferred by pentoxifylline may be beneficial in the management of DKD.

OBJECTIVES

To assess the benefits and harms of pentoxifylline for treating people with DKD.

SEARCH METHODS

We searched the Cochrane Renal Group's specialised register (January 2012), CENTRAL (Issue 12, 2011), MEDLINE, EMBASE and four Chinese biomedical literature databases (CBM-disc, 1979 to July 2009), Chinese Science and Technique Journals Database (VIP, until July 2009), China National Knowledge Infrastructure (CNKI, until July 2009) and WanFang database (until July 2009).

SELECTION CRITERIA

All randomised controlled trials (RCTs) and quasi-RCTs studying the benefits and harms of pentoxifylline for DKD.

DATA COLLECTION AND ANALYSIS

Data were extracted independently by two authors. Meta-analyses were performed when more than one study provided data on a comparable outcome in sufficiently similar patients. Results of dichotomous outcomes were expressed as risk ratios (RR) with 95% confidence intervals (CI). Mean differences (MD) were calculated to assess the effects of treatment where outcomes were expressed on continuous scales, and standardised mean differences (SMD) calculated where different scales were used. Data was pooled using the random effects model. Adverse effects were assessed using descriptive techniques and where possible, risk differences (RD) with 95% CI.

MAIN RESULTS

We identified 17 studies that included a total of 991 participants with DKD which met our inclusion criteria. Overall, the methodological quality of included studies was low: 4/17 reported the method of randomisation, 13/17 did not; no study described the method of random allocation; 4/17 studies were considered to be at high risk of bias and 13/17 were considered to have unclear risk for incomplete outcome data reporting; 9/17 studies were at low risk bias and in 8/17 the risk of bias was unclear for selective outcome reporting.Compared with placebo, pentoxifylline significantly reduced serum creatinine (SCr) (MD -0.10 mg/dL, 95% CI -0.17 to -0.03), albuminuria (SMD -2.28, 95% CI -3.85 to -0.70) and overt proteinuria (MD -428.58 µg/min, 95% CI -661.65 to -195.50), but there was no difference in creatinine clearance (CrCl) (MD -5.18 mL/min, 95% CI -15.55 to 5.19). When compared with routine treatment alone, pentoxifylline did not significantly reduce SCr (MD 0.00 mg/dL, 95% CI -0.06 to 0.07) or blood pressure (systolic (SBP): MD -0.28 mm Hg, 95% CI -2.20 to 1.63; diastolic (DBP): MD -0.15 mm Hg, 95% CI -1.44 to 1.14), but did significantly reduce albuminuria (SMD 0.62, 95% CI 0.18 to 1.07) and proteinuria (MD 0.46 g/24 h, 95% CI 0.17 to 0.74). There was no significant difference in SCr (MD 0.00 mg/dL, 95% CI -0.08 to 0.07), albuminuria (MD -8.79 µg/min, 95% CI -27.18 to 9.59), proteinuria (MD -0.01 g/24 h, 95% CI -0.03 to 0.01) or blood pressure (SBP: MD 1.46 mm Hg, 95% CI -0.57 to 3.50; DBP: MD 1.37 mm Hg, 95% CI -0.23 to 2.98) between pentoxifylline and the active comparator (captopril or clonidine/methyldopa) for patients with type 1 and type 2 DKD. CrCl was significantly increased when pentoxifylline was compared to clonidine/methyldopa (MD 10.90 mL/min, 95% CI -1.40 to 20.40) but not with captopril (MD 3.26 mL/min, 95% CI -1.05 to 7.59). No data were available on the incidence of end-stage kidney disease (ESKD), time to ESKD, quality of life, or all-cause mortality. The adverse events of pentoxifylline were mild; no serious adverse events were reported in any of the included studies.

AUTHORS' CONCLUSIONS

From the available evidence, pentoxifylline seems to offer some beneficial effects in renal function improvement and reduction in albuminuria and proteinuria, with no obvious serious adverse effects for patients with DKD. However, most studies were poorly reported, small, and methodologically flawed. Evidence to support the use of pentoxifylline for DKD was insufficient to develop recommendations for its use in this patient population. Rigorously designed, randomised, multicentre, large scale studies of pentoxifylline for DKD are needed to further assess its therapeutic effects.

Endothelin signaling via guanine exchange factor C3G in renal glomerular mesangial cells

The guanine nucleotide exchange factor C3G is one of the mediators of endothelin-1 (ET-1) intracellular signaling cascades and is vital for kidney development and homeostasis. The aim of the current study was to analyze the specificity of ET-1-induced signaling via C3G in rat glomerular mesangial cells (GMC) and to investigate the biological significance of C3G during mesangioproliferative glomerulonephritis. In GMC, C3G expression was increased (1) in vivo after induction of the anti-Thy1 model of glomerulonephritis and (2) in cell culture experiments after fetal bovine serum incubation. To examine the consequences of C3G up-regulation, adenovirus-mediated gene transfer of C3G into cultured glomerular cells was done, and the GTP loading of the small G proteins Rap1 and R-Ras was analyzed. Overexpression of C3G in mesangial cells resulted in enhanced activation of Rap1, but failed to affect the GTP-bound status of R-Ras in ET-1-stimulated cells. C3G overexpression led to significant changes in GMC spreading and migration patterns in response to ET-1 stimulation and increased stress fiber formation, which was mimicked by Rap1A overexpression. Together, these findings suggest (1) the existence of regulatory mechanisms resulting in disease-related up-regulation of C3G in GMC and (2) that an increase in the C3G protein level may contribute to the resolution stage of mesangioproliferative glomerulonephritis by reducing GMC sensitivity to ET-1, modulating cellular motility, and actin dynamics.

Dipyridamole suppresses high glucose-induced osteopontin secretion and mRNA expression in rat aortic smooth muscle cells

BACKGROUND

Diabetic patients are frequently afflicted with medial artery calcification, a predictor of cardiovascular mortality. Diabetes induced the expression of osteopontin in arterial vasculature, which is an indicator of disease progression in artery calcification and vascular stiffness. Signal transduction and strategies that suppress high glucose-induced osteopontin expression in arterial vascular smooth muscle cells is investigated.

METHODS AND RESULTS

The incubation of rat aortic smooth muscle cells under high glucose concentration increased osteopontin protein secretion and mRNA expression. Treatment with dipyridamole decreased high glucose-induced osteopontin expression and secretion. Dipyridamole decreased glucose-induced osteopontin through inhibition of phosphodiesterase, thereby increasing intracellular levels of adenosine-3',5'-cyclic monophosphate (cAMP) and guanosine-3',5'-cyclic monophosphate (cGMP), and increased thioredoxin expression to inhibit the reactive oxygen species (ROS) system. Induction of osteopontin was reversed when cells were pretreated with N-[2-bromocinnamyl(amino)ethyl]-5-isoquinolinesulfonamide (H89, cAMP-dependent protein kinase inhibitor), KT5823 (cGMP-dependent protein kinase inhibitor), or dinitrochlorobenzene (thioredoxin reductase inhibitor). The antioxidant, N-acetyl-L-cysteine, suppressed glucose-induced osteopontin expression by decreasing ROS concentration. Both H89 and KT5823 downregulated thioredoxin expression.

CONCLUSIONS

These results suggest a novel effect for dipyridamole to suppress high glucose-induced osteopontin protein secretion and mRNA expression. Dipyridamole has antioxidant properties and a phosphodiesterase inhibitor activity, which might be useful to ameliorate diabetic vasculopathy and its cardiovascular complications.

Phosphodiesterase inhibitors in the management of autoimmune disease

Phophodiesterases inhibitors (PDEis) act by inhibiting the catabolism of cyclic nucleotides, cAMP and cGMP, which are ubiquitously expressed in cells of the immune system. Increased levels of cAMP and/or cGMP have been reported to decrease the activity of pro-inflammatory TH1 cells, attenuate experimental autoimmune encephalomyelitis and experimental arthritis. PDE5i like Sildenafil improves endothelial dysfunction and vascular remodelling in patients with pulmonary artery hypertension and refractory secondary Raynaud's phenomenon, with a potential to cause disease modification in the former. Studies in animal models of fibrosis suggest that these drugs have anti-fibrotic effect and may be potentially useful in conditions like scleroderma. They also have been shown to have renoprotective effect in animal models. The emerging trends make it necessary to exploit the full therapeutic potential of this class of drugs in various autoimmune diseases like rheumatoid arthritis, scleroderma, profibrotic conditions and PAH.

Pathogenic perspectives for the role of inflammation in diabetic nephropathy

Diabetes and its complications have become a public health problem. One of the most important complications is diabetic nephropathy, which is nowadays the main cause of chronic renal failure. In spite of our greater understanding of this complication, the intimate mechanisms leading to the development and progression of renal injury are not well understood. New perspectives in activated innate immunity and inflammation appear to be relevant factors in the pathogenesis of diabetes. Moreover, different inflammatory molecules, including adipokines, Toll-like receptors, chemokines, adhesion molecules and pro-inflammatory cytokines, may be critical factors in the development of microvascular diabetic complications, including nephropathy. This new pathogenic perspective leads to important therapeutic considerations, with new pathogenic pathways becoming important therapeutic targets that can be translated into clinical treatments for diabetic nephropathy.

Inhibition of tubulointerstitial fibrosis by pentoxifylline is associated with improvement of vascular endothelial growth factor expression

AIM

Recent information indicates that pentoxifylline (PTX) has the ability to suppress inflammation and profibrotic cell proliferation. In this study, we investigated the effect of PTX on tubulointerstitial fibrosis and the expression of vascular endothelial growth factor (VEGF) in a rat model of obstructive nephropathy.

METHODS

Wistar rats with left ureteral ligation were divided into control and PTX-treated groups. The histopathologic degree of tubulointerstitial fibrosis was scored with PAS and Masson-stained sections. The protein and mRNA for vascular endothelial growth factor (VEGF) were semiquantitatively measured with immunohistochemistry and RT-PCR. The protein for transforming growth factor beta1 (TGFbeta1) and hypoxia-induced factor 1 alpha (HIF-1alpha) was determined by Western blot.

RESULTS

Compared with the control group, PTX treatment reduced fibrosis scores at d 7 and d 14 (P<0.05). The reduction was accompanied by inhibited expression of transforming growth factor-beta 1 (TGFbeta1), a key cytokine in tubulointerstitial fibrogenesis (P<0.01). Meanwhile, VEGF protein and mRNA in the kidney were increased in the PTX-treated group compared with the control group (P<0.01). PTX up-regulated expression of VEGF mRNA in a dose- and time-dependent manner in cultured HK-2 cells (P<0.01). However, expression of HIF-1alpha (a key transcription factor for VEGF gene expression) was unchanged by PTX treatment. PTX prolonged the half-life of VEGF mRNA by a 1.07-fold increase.

CONCLUSIONS

PTX inhibited tubulointerstitial fibrosis in a rat model of obstructive nephropathy while preventing loss of VEGF. PTX up-regulated expression of VEGF mRNA through stabilization of its mRNA in cultured renal tubular epithelial cells.

Preservation of peritoneal morphology and function by pentoxifylline in a rat model of peritoneal dialysis: molecular studies

BACKGROUND

High-glucose (HG) content of dialysate accelerated peritoneal fibrosis. We investigated in vitro mechanisms and the in vivo potential of pentoxifylline (PTX) to prevent this fibrogenic process.

METHODS

For human peritoneal mesothelial cell (HPMC) culture, a normal-glucose (NG, 5.5 mM) or HG (138 mM) medium was established through pilot experiments. The rat peritoneal dialysis (PD) model consists of four groups (n = 8): group 1, intraperitoneal (IP) HG (4.25%) solution; group 2, as group 1 plus daily IP PTX (4 mg/in 1 h); group 3, IP PTX and group 4 as control.

RESULTS

In HPMC culture, PTX significantly prevented HG-stimulated gene and protein production of collagen and transforming growth factor-beta1 (TGF-ss1) (reduction rate of 72-81%). The p38 mitogen-activated protein kinase (MAPK) pathway was activated significantly in HG-treated HPMCs. Blockade of p38 MAPK by SB203580 (25 microM) or PTX (300 microg/ml) resulted in an effective suppression of collagen and TGF-ss1 gene expression in HG-cultured HPMCs. In PD experimental animals, peritoneal thickness and collagen expression in the peritoneum were significantly increased in HG-treated rats, and was attenuated by PTX (P < 0.01). Impaired peritoneal ultrafiltration (1.9 +/- 0.5 ml versus 2.4 +/- 0.4 ml, P < 0.05) and stimulated proinflammatory IL-6, MCP-1 and TGF-beta1 activation were observed in HG-treated rats. PTX well preserved the functional characteristics of peritoneum and cytokine profiles.

CONCLUSIONS

These in vitro and in vivo data suggest that PTX may have therapeutic benefits for the prevention or retardation of peritoneal fibrosis.

Effects of Pentoxifylline on Differentiation, Maturation, and Function of Human CD14+ Monocyte-derived Dendritic Cells

Pentoxifylline (PTX) is a nonspecific phosphodiesterase inhibitor which has potent immunoregulatory and antiinflammatory effects. Although its immunomodulation property has been recognized, it is not clear whether PTX could affect dendritic cells (DCs), the most efficient antigen-presenting cells. The purpose of this study was to determine whether PTX could suppress DC differentiation, maturation, and its associated functions. Immature DCs (iDCs) were generated from human peripheral blood mononuclear cell CD14+ monocytes cultured with granulocyte macrophage colony stimulating factor and interleukin-4 for 5 days. PTX concentration-dependently suppressed the expression of iDC differentiation markers including CD54, CD80, CD86, and human leukocyte antigen-DR. In addition, PTX also inhibited DC maturation marker CD83 expression after stimulating DCs with lipopolysaccharide. Furthermore, PTX inhibited the antigen-uptake ability of DCs when tested by fluorescein isothiocyanate-dextran endocytosis assay. PTX significantly reduced the production of TNF-alpha and IFN-gamma in mature DCs (mDCs). Consequently, PTX-treated mDCs showed a reduced activity of mDC-induced T-cell allostimulation and proliferation by mixed-lymphocyte reaction (MLR) assay. Therefore, PTX significantly inhibits CD14+ monocyte-derived DC differentiation, maturation, antigen-uptake ability of iDCs, and antigen-presentation ability of mDCs possibly due to the suppression of TNF-alpha and IFN-gamma production. These results suggested that inhibitory effects of PTX on DCs may contribute its antiinflammatory and immunoregulatory functions.

Inflammation and diabetic nephropathy

Diabetic nephropathy has become the main cause of renal failure, but unfortunately the intimate mechanisms leading to the development and progression of renal injury are not yet fully known. Activated innate immunity and inflammation are relevant factors in the pathogenesis of diabetes. Moreover, different inflammatory molecules, including chemokines, adhesion molecules, and proinflammatory cytokines, may be critical factors in the development of microvascular diabetic complications, including nephropathy. This new pathogenic perspective leads to important therapeutic considerations, with new pathogenic pathways becoming important therapeutic targets that can be translated into clinical treatments for diabetic nephropathy.

Blocking of Akt/NF-kappaB signaling by pentoxifylline inhibits platelet-derived growth factor-stimulated proliferation in Brown Norway rat airway smooth muscle cells

The proliferation of airway smooth muscle cells (ASMC) can cause airway hyperresponsiveness (AHR). It has been reported that platelet-derived growth factor (PDGF) can stimulate the proliferation of ASMC through phosphatidylinositol 3-kinase (PI3 K) signaling pathway, which can activate Akt protein. Activated-Akt can activate downstream signal protein [p70S6 K, nuclear factor (NF)-kappaB, and extracellular signal regulated kinase (ERK)], increasing the cyclin D1 level and suppressing the transcription of p27Kip1 to enable cell cycle entry. This investigation demonstrated that pentoxifylline (PTX) inhibited the PDGF-stimulated proliferation of ASMC by suppressing activation of the Akt/NF-kappaB pathway. ASMC were treated with PTX for 48 h, which attenuated the PDGF-stimulated proliferation of ASMC. PTX and wortmannin, a PI3 K inhibitor, not only inhibited the PDGF-activated phosphorylation of Akt but also suppressed p70S6 K expression and IkappaBalpha degradation, inhibiting nuclear translocation and the DNA binding activity of NF-kappaB. However, PTX did not influence the phosphorylation of ERK1/2. The suppression of p70S6 K by rapamycin did not influence cyclin D1 expression in PDGF-stimulated cells. These data reveal that the down-regulation of the Akt/NF-kappaB signaling pathway by PTX inhibited the proliferation of ASMC. PTX may provide information on the pathogenesis of asthma.

Honokiol, a small molecular weight natural product, alleviates experimental mesangial proliferative glomerulonephritis

Glomerulonephritis (GN) is still the most common cause of end-stage renal disease. Accumulation of glomerular macrophages, proliferation of mesangial cells, and deposition of extracellular matrix proteins are pathobiological hallmarks of GN. Pharmacological interventions that can inhibit these insults may be beneficial in the retardation of the progression of GN. Honokiol originally isolated from Magnolia officinalis, shows antioxidative, anti-inflammatory, and antiproliferative activities in a variety of inflammation models. In this study, we first investigated the in vivo effects of honokiol on rat anti-Thy1 nephritis. Anti-Thy1 nephritis was induced in Wistar rats by injecting mouse anti-rat Thy1 antibodies intravenously. Nephritic rats were randomly assigned to receive honokiol (2.5 mg/kg, twice a day) or vehicle and were killed at various time points. Glomerular histology and immunohistopathology and urine protein excretion were studied. Western blotting was conducted for markers of proliferation. Adhesion molecules, chemokine, and extracellular matrix gene expression were evaluated by Northern blotting. Honokiol-treated nephritic rats excreted less urinary protein and had lower glomerular cellularity and sclerosis. The increased intraglomerular proliferating cell nuclear antigen and Akt phosphorylation in nephritic rats could be abolished by the treatment of honokiol. Honokiol also alleviated glomerular monocyte chemoattractant protein-1 and intracellular adhesion molecule-1, similar to type I (alpha1) collagen and fibronectin mRNA levels of nephritic rats. These results indicate that honokiol may have therapeutic potential in mesangial proliferative GN.

Pentoxifylline ameliorates proteinuria through suppression of renal monocyte chemoattractant protein-1 in patients with proteinuric primary glomerular diseases

Proteinuria (albuminuria) reflects dysfunction of the glomerular permeability barrier in which inflammatory cytokines play a key role. Pentoxifylline (PTX) is a phosphodiesterase inhibitor that possesses potent anti-inflammatory and immunomudulatory effects. This study evaluated the effectiveness of PTX to reduce proteinuria and inflammatory mediators in patients with proteinuric primary glomerular diseases. Seventeen patients with primary glomerular diseases, a persistent spot proteinuria exceeding 1.5 g/g creatinine (Cr) and a glomerular filtration rate between 24 and 115 ml/min/1.73 m(2) were treated with PTX 400 mg twice daily for 6 months. Before and after the treatment, serum Cr, plasma renin activity and aldosterone concentrations, plasma and urinary tumor necrosis factor (TNF)-alpha, interleukin-1beta and monocyte chemoattractant protein (MCP)-1, as well as urinary protein and Cr were measured. PTX significantly reduced urinary protein excretion, along with an increase of serum albumin. A significant correlation existed between the basal urinary protein/Cr and the basal urinary MCP-1/Cr ratios. PTX lowered the urinary MCP-1/Cr ratio, and the percent reduction of urinary protein/Cr ratio correlated directly with the precent decrease of urinary MCP-1/Cr ratio after PTX treatment. There was no significant change in blood pressure, renal function, biochemical parameters, plasma renin activity and aldosterone concentrations, or plasma TNF-alpha and MCP-1 levels during the study. In conclusion, administration of PTX 800 mg per day is safe and effective for reducing proteinuria in patients with proteinuric primary glomerular diseases. This beneficial effect occurs in close association with a reduction of urinary MCP-1 excretion.

Therapeutics in renal disease: the road ahead for antiproliferative targets

Discovery into the molecular basis of renal disease is occurring at an unprecedented rate. With the advent of the NIH Roadmap, there is a greater expectation of translating this knowledge into new treatments. Here, we review the therapeutic strategy to preserve renal function in proliferative renal diseases by directly inhibiting the mitogenic pathways within renal parenchymal cells that promote G0 to G1/S cell-cycle phase progression. Reductionist methodologies have identified several antiproliferative molecular targets, and promising preclinical testing of leading small-molecule drugs to modulate these targets has now led to landmark clinical trials. Yet, this advancement into targeted therapy highlights important differences between the therapeutic goals of molecular nephrology versus molecular oncology and, by extension, the poorly understood role of alternative target activity in drug efficacy. Systems research to clarify these issues should accelerate the development of this promising therapeutic strategy.

Role of keratinocyte growth factor in the pathogenesis of autosomal dominant polycystic kidney disease

BACKGROUND

Previous studies have shown that the expression and distribution of keratinocyte growth factor (KGF), also known as FGF-7 (fibroblast growth factor-7) or HBGF-7 (heparin-binding growth factor-7), may be implicated in kidney cyst formation and expansion. However, there are no data on KGF expression in human autosomal dominant polycystic kidney disease (ADPKD) tissue, and it is unknown whether it affects ADPKD cyst-lining epithelial cell epithelial cell proliferation.

METHODS

The expression and distribution of KGF and KGF receptor (KGFR) mRNA in ADPKD cystic and normal kidney tissues were examined using quantitative real-time polymerase chain reaction (PCR) and in situ hybridization. KGF and KGFR protein expression in the above tissues was analysed by immunohistochemistry and western blot. The effect of KGF on cyst-lining epithelial cell proliferation was assessed by MTT assay, and its effect on the cyst-lining epithelial cell cycle was analysed by flow cytometry. The effect of KGF on cyclin D1 and P21(wafl) gene expression in cyst-lining epithelial cells was also determined.

RESULTS

KGF and KGFR mRNA expression in ADPKD cysts was higher than in normal kidney tissues. KGF and KGFR protein expression was also higher in ADPKD cysts and was localized to cyst-lining epithelial cells, tubular and interstitial cells. In vitro experiments revealed that KGF promoted cyst-lining epithelial cell proliferation, and decreased the ratio of G0/G1 phase but increased that of S phase. In response to KGF, the expression of the cyclin D1 gene in cyst-lining epithelial cells increased markedly while P21(wafl) expression decreased.

CONCLUSIONS

KGF and KGFR expression was upregulated in ADPKD kidney tissues. KGF stimulated the proliferation of cyst-lining epithelial cell in vitro by regulating the expression of cyclin D1 and P21(wafl) genes. KGF may play a role in pathogenesis of ADPKD.

Peritoneal fibrosing syndrome: pathogenetic mechanism and current therapeutic strategies

Peritoneal dialysis (PD) has been established as a main renal replacement therapy for approximately 20 years. However, long-term peritoneal exposure to high glucose and other unphysiologic contents in the PD solution may potentiate the development of peritoneal fibrosing syndrome (PFS) in PD patients. PFS is composed of a wide spectrum of peritoneal alterations, which has been observed in PD patients. Molecular studies have shown that the fibrogenic effect of peritoneal mesothelial cells and the accompanying accumulation of extracellular matrix in the peritoneum are key events leading to PFS. In this review, we highlight the impact of PFS and its pathogenetic factors, including bioincompatible PD solution, multidisciplinary inflammatory mediators, and stimulatory cytokines in the peritoneal cavity. Current therapeutic strategies based on both clinical and basic evidence for the prevention or treatment of PFS are also reviewed.

Enhancing cGMP in experimental progressive renal fibrosis: soluble guanylate cyclase stimulation vs. phosphodiesterase inhibition

cGMP serves as the main second messenger of nitric oxide (NO). Antifibrotic effects of enhancing renal cGMP levels have recently been documented in experimental acute anti-Thy-1 glomerulonephritis. The present study compares the effects of the cGMP production-increasing soluble guanylate cyclase (sGC) stimulator BAY 41-2272 with those of the cGMP degradation-limiting phosphodiesterase inhibitor pentoxifylline (PTX) in a progressive model of renal fibrosis. At 1 wk after induction of anti-Thy-1-induced chronic glomerulosclerosis (cGS), rats were randomly assigned to groups as follows: cGS, cGS + BAY 41-2272 (10 mg x kg body wt(-1) x day(-1)), or cGS + PTX (50 mg x kg body wt(-1) x day(-1)). BAY 41-2272 and PTX reduced systolic blood pressure significantly. At 16 wk, tubulointerstitial expressions of sGC mRNA and NO-induced cGMP synthesis were increased in untreated cGS animals, whereas their glomerular activity was depressed compared with normal controls. Tubulointerstitial and glomerular cGMP production in response to NO were significantly enhanced in animals treated with BAY 41-2272, but not in those treated with PTX. BAY 41-2272 administration resulted in marked reductions of glomerular and tubulointerstitial histological matrix accumulation, expression of TGF-beta1 and fibronectin, macrophage infiltration, and cell proliferation as well as improved renal function. In contrast, only moderate and nonsignificant renoprotective changes were observed in the cGS + PTX group. In conclusion, increasing renal cGMP production through BAY 41-2272 significantly improved renal NO-cGMP signaling and limited progression in anti-Thy-1-induced chronic renal fibrosis, whereas inhibition of cGMP degradation by PTX was only moderately effective. The findings indicate that pharmacological enhancement of renal cGMP levels by sGC stimulation represents a novel and effective antifibrotic approach in progressive kidney disorders.

Pentoxifylline Attenuates Tubulointerstitial Fibrosis by Blocking Smad3/4-Activated Transcription and Profibrogenic Effects of Connective Tissue Growth Factor

Pentoxifylline (PTX) is a potent inhibitor of connective tissue growth factor (CTGF), but its underlying mechanism is poorly understood. Here, it was demonstrated that PTX inhibited not only TGF-beta1-induced CTGF expression but also CTGF-induced collagen I (alpha1) [Col I (alpha1)] expression in normal rat kidney fibroblasts (NRK-49F) and alpha-smooth muscle actin expression in normal rat kidney proximal tubular epithelial cells (NRK-52E). Furthermore, PTX attenuated tubulointerstitial fibrosis, myofibroblasts accumulation, and expression of CTGF and Col I (alpha1) in unilateral ureteral obstruction kidneys. The mechanism by which PTX reduced CTGF in NRK-49F and NRK-52E was investigated. Activation of Smad3/4 was essential for TGF-beta1-induced CTGF transcription, but PTX did not interfere with TGF-beta1 signaling to Smad2/3 activation and association with Smad4 and their nuclear translocation. However, PTX was capable of blocking activation of TGF-beta1-induced Smad3/4-dependent reporter as well as CTGF promoter, suggesting that PTX affects a factor that acts cooperatively with Smad3/4 to execute transcriptional activation. It was found that PTX increased intracellular cAMP and caused cAMP response element binding protein phosphorylation. The protein kinase A antagonist H89 abolished the inhibitory effect of PTX on Smad3/4-dependent CTGF transcription, whereas dibutyryl cAMP and forskolin recapitulated the inhibitory effect. In conclusion, these results indicate that PTX inhibits CTGF expression by interfering with Smad3/4-dependent CTGF transcription through protein kinase A and blocks the profibrogenic effects of CTGF on renal cells. Because of the dual blockade, PTX potently attenuates the tubulointerstitial fibrosis in unilateral ureteral obstruction kidneys.

Adenovirus-mediated bcl-2 gene transfer inhibits renal ischemia/reperfusion induced tubular oxidative stress and apoptosis

Ischemia/reperfusion induces oxidative injury to proximal and distal renal tubular cells. We hypothesize that Bcl-2 protein augmentation with adenovirus vector mediated bcl-2 (Adv-bcl-2) gene transfer may improve ischemia/reperfusion induced renal proximal and distal tubular apoptosis through the mitochondrial control of Bax and cytochrome C translocation. Twenty-four hours of Adv-bcl-2 transfection to proximal and distal tubular cells in vitro upregulated Bcl-2/Bax ratio and inhibited hypoxia/reoxygenation induced cytochrome C translocation, O(2) (-) production and tubular apoptosis. Intra-renal arterial Adv-bcl-2 administration with renal venous clamping augmented Bcl-2 protein of rat kidney in vivo in a time-dependent manner. The maximal Bcl-2 protein expression appeared at 7 days after Adv-bcl-2 administration and the primary location of Bcl-2 augmentation was in proximal and distal tubules, but not in glomeruli. With a real-time monitoring O(2) (-) production and apoptosis analysis of rat kidneys, ischemia/reperfusion increased renal O(2) (-) level, potentiated proapoptotic mechanisms, including decrease in Bcl-2/Bax ratio, increases in caspase 3 expression and poly-(ADP-ribose)-polymerase fragments and subsequent proximal and distal tubular apoptosis. However, Adv-bcl-2 administration significantly enhanced Bcl-2/Bax ratio, decreased ischemia/reperfusion induced O(2) (-) amount, inhibited proximal and distal tubular apoptosis and improved renal function. Our results suggest that Adv-bcl-2 gene transfer significantly reduces ischemia/reperfusion induced oxidative injury in the kidney.

Additive antiproteinuric effect of pentoxifylline in patients with type 2 diabetes under angiotensin II receptor blockade: a short-term, randomized, controlled trial

Despite the beneficial effects of blockade of the renin-angiotensin system in diabetic nephropathy (DN), albuminuria and progression of renal disease are not completely halted by these agents. Therefore, it is necessary to explore potential antiproteinuric and renoprotective effects of innovative therapeutic approaches. This study tested the hypothesis that the combination of pentoxifylline (PTF) with angiotensin II receptor blockers in normotensive patients with type 2 diabetes produces an additive antiproteinuric effect. Sixty-one patients with DN and residual albuminuria despite treatment with the recommended doses of ARB for >1 yr were randomly assigned to receive the addition of 1200 mg of PTF daily (n = 30) or to a control group (n = 31). Baseline characteristics were similar between groups, and correlation analysis showed a significant association between urinary albumin excretion (UAE) and urinary TNF-alpha (R = 0.53, P < 0.001). After 4 mo, albuminuria showed a significant decrease in patients who received PTF, from 900 mg/24 h (466 to 1542 mg/d) to 791 mg/24 h (309 to 1400 mg/d; P < 0.001), whereas no significant changes were observed in the control group: 920 mg/24 h (450 to 1489 mg/d) at baseline, and 900 mg/24 h (428 to 1800 mg/d) at the end of the study. The mean percentage variation of UAE in the treatment and control groups was -16.7 and 5.5%, respectively (between-group comparison, P < 0.001). This additive antiproteinuric effect was not dependent on changes in BP or metabolic control. However, both serum and urinary levels of TNF-alpha also decreased in patients who received PTF, from 6.4 pg/ml (2.1 to 9.7) and 16 pg/mg (8 to 29) at baseline to 4.6 pg/ml (0.4 to 9) and 14.2 pg/mg (3 to 26) at the end of the study, respectively (P < 0.01), without significant variations in control patients. Moreover, regression analysis at the end of the study showed a correlation between the change in UAE and the change in urinary TNF-alpha in patients who were treated with PTF (R = 0.49, P < 0.001). In conclusion, administration of PTF to patients who have type 2 diabetes and are under long-term treatment with an ARB produces a significant additive antiproteinuric effect associated with a reduction of urinary TNF-alpha excretion.

Role of non-selective adenosine receptor blockade and phosphodiesterase inhibition in cisplatin-induced nephrogonadal toxicity in rats

1. It is well documented that cisplatin (CDDP) treatment increases the expression of adenosine A(1) receptors in both kidney and testes. However, the effect of adenosine at these receptors is controversial. Adenosine A(1) receptors have been documented to be involved in either cytoprotection or aggravation of nephrotoxicity. The aim of the present study was to examine the effect of the non-selective adenosine receptor inhibitor theophylline and the phosphodiesterase inhibitor pentoxifylline on CDDP-induced renal and testicular toxicity. 2. Male Wister rats were divided into six groups. Two control groups received plain drinking water and a third control group received theophylline 0.8 mg/mL in the drinking water for 2 weeks. One group of animals drinking plain water was injected intraperitoneally (i.p.) with pentoxifylline 50 mg/kg per day for 2 weeks. The remaining groups were treated in the same manner and received single dose of CDDP 7 mg/kg, i.p., 1 week after starting theophylline and pentoxifylline treatment and all animals were killed 1 week after CDDP treatment. 3. Rats treated with CDDP developed nephrotoxicity, as demonstrated by increased kidney and testes weight as a percentage of total bodyweight, blood urea nitrogen and serum creatinine levels and decreased serum calcium and albumin levels. In addition, CDDP treatment resulted in an increase in the production of malondialdehyde (MDA) and decreases in total nitrate/nitrite levels, as well as depletion of reduced glutathione (GSH) content and glutathione peroxidase (GPX) activity in both the kidney and testes. Administration of theophylline in the drinking water to CDDP-treated rats resulted in exacerbation of the indices of nephrotoxicity, depletion of GSH content and GPX activity levels, with increased MDA production and platinum accumulation in both the kidney and testes. However, pentoxifylline administration reduced CDDP-induced biochemical changes and reduced platinum accumulation in both organs. Histopathological examination of the kidney revealed that CDDP treatment produced multifocal tubular atrophy, atypical reparative changes of the tubular epithelium and marked tubular necrosis. Animals treated with the theophylline/CDDP combination showed extensive widespread damage with intratubular calcification. However, pentoxifylline treatment ameliorated the overt changes induced by CDDP treatment. 4. Theophylline exacerbates the deleterious effects of CDDP on rat kidney and testes. However, pentoxifylline alleviates CDDP-induced renal and testicular toxicity.

The effects of pentoxifylline on diabetic renal changes in streptozotocin-induced diabetes mellitus

The aim of the study was to investigate the effects of pentoxifylline on the renal growth, the epidermal growth factor receptor expression, and renal total nitric oxide content in streptozotocin-induced diabetic rats. Adult male Wistar albino rats were randomly divided into three groups: normal control (the N group), diabetic nephropathy (the DN group), and diabetic nephropathy treated with pentoxifylline at the dosage of 20 mg x kg(-1) x d(-1), intraperitoneally (the group DNP). Diabetes was induced by injection of streptozotocin intraperitoneally. The kidney wet weight (KWW) and dry weight (KDW), fractional kidney weight (FKW), glomerular volume (VG), renal tissue protein (RTP) contents, and renal tissue total nitric oxide (NO) production were determined after the rats were sacrificed on 10th day. There was a significant increase in KWW and KWD in the DNP and DN groups when compared to the N group (p=0.000 for the DNP group, p = 0.000 and p < 0.01 for the DN group). In the DN group, FKW was increased for both wet and dry kidney weight (p<0.05 and p=0.001, respectively) while in the DNP group there was increase in FKW only for dry kidney weight. VG was increased in both two diabetic groups (p<0.05), but this increase was less prominent in the rats treated with pentoxifylline. RTP was significantly decreased in the DNP group when compared with the values in the DN group (p < 0.05). Immunohistochemically epidermal growth factor receptor expression was increased in diabetic rats, and it was not affected by pentoxifylline treatment. In diabetic rats renal content of total NO was decreased (p<0.05 for the DNP group, p<0.01 for the DN group). In conclusion, the results provide that pentoxifylline may have some beneficial effects on renal changes in streptozotocin-induced diabetic rats.

The renoprotective potential of pentoxifylline in chronic kidney disease

Current interventions with proven efficacy, such as glycemic and blood pressure control, dietary protein restriction, and angiotensin II blockade, slow the progression of chronic kidney disease (CKD); however, whether long-term cessation of CKD progression is possible remains unclear. Because of the pathogenetic complexity of this condition, multidrug interventions with the least adverse effects should be investigated as the next step in attempts to stop CKD progression. Pentoxifylline, a non-selective phosphodiesterase inhibitor with indiscernible toxicity, exerts potent inhibitory effects against cell proliferation, inflammation, and extracellular matrix accumulation, all of which play important roles in CKD progression. Pentoxifylline monotherapy markedly reduces proteinuria in patients with membranous nephropathy. Moreover, limited human studies have proven pentoxifylline efficacy in reducing proteinuria in patients with diabetes receiving angiotensin-converting enzyme inhibitors, and in patients with nephrotic syndrome secondary to lupus nephritis despite immunosuppressive therapy. Further clinical trials are necessary to examine whether pentoxifylline can improve renal outcomes in patients receiving interventions of proven efficacy.

Review Article. Pentoxifylline: A potential therapy for chronic kidney disease

Almost all forms of chronic kidney disease progressing to end-stage kidney failure are characterized by diffuse fibrosis, a final common pathway converging from multiple pathogenetic networks regardless of the initial injury. Four principal interventions including glycaemic and blood pressure control, dietary protein restriction, and angiotensin II blockade have been proven to slow progression of diabetic and/or non-diabetic chronic kidney disease. However, the ultimate solution to halt disease progression in the long term is still pending. Because of the pathogenetic complexity of kidney disease, multidrug intervention with the least side-effects should, without doubt, be the next step to stop kidney disease progression. Animal and cellular studies have demonstrated the rationale for pentoxifylline (i.e. its effects against cell proliferation, inflammation, and extracellular matrix accumulation) in the treatment of chronic kidney disease induced by immune- or non-immune-mediated mechanisms. Limited human studies have proven its efficacy in reducing proteinuria in patients with diabetes receiving angiotensin-converting enzyme inhibitors, and in patients with nephrotic syndrome refractory to conventional immunosuppressive therapy. Moreover, monotherapy with pentoxifylline markedly reduces proteinuria in patients with membranous nephropathy. Further studies are required to examine whether pentoxifylline can improve the renal outcome in patients receiving interventions with proven efficacy.

Effects of pentoxifylline in adriamycin-induced renal disease in rats

Tumor necrosis factor-alpha (TNF-alpha) is a mediator of inflammation in human and animal renal disease. Pentoxiphylline (PTX) is an inhibitor of TNF-alpha. In this study we examined the effects of PTX on TNF-alpha, proteinuria, nitrite production, and apoptosis in an experimental model of Adriamycin (ADR) nephropathy in rats. Rats were divided into four groups: untreated Wistar rats (controls), PTX treatment alone, ADR treatment alone to induce nephropathy, and ADR treatment followed by PTX. ADR treatment followed by PTX treatment prevented the increase in serum TNF-alpha levels and proteinuria in rats with ADR-nephropathy ( P<0.05). Urine nitrite levels were significantly increased in the ADR-induced nephropathy group and the increase was prevented in the ADR-induced nephropathy group when they also received PTX. The urine nitrite levels were not different between the PTX-treated group and the untreated control rats. PTX prevented the rise of serum TNF-alpha in ADR nephropathy rats and a decrease in proteinuria, urine nitrite, and apoptosis in the renal tissue. These findings suggest a beneficial anti-inflammatory effect of PTX.

Pentoxifylline suppresses renal tumour necrosis factor-alpha and ameliorates experimental crescentic glomerulonephritis in rats

BACKGROUND

Crescentic glomerulonephritis is a rapidly progressive form of glomerulonephritis, but treatment remains non-specific. The methylxanthine derivative pentoxifylline (PTX) is a clinically available phosphodiesterase inhibitor with anti-inflammatory and immunoregulatory activities. This study examined whether PTX has beneficial effects in a rat model of anti-glomerular basement membrane (GBM) crescentic glomerulonephritis.

METHODS

Experimental crescentic glomerulonephritis was induced in Wistar rats by intravenous injection of rabbit anti-rat GBM serum and treated with either vehicle (phosphate-buffered saline) or PTX (0.1 g/kg/day) intravenously on a daily basis. Groups of six animals were euthanized at days 3, 7, 14 or 28 after induction of disease. Effects of PTX on renal function, histology and expression of cytokines, chemokines and adhesion molecules were determined.

RESULTS

Compared with the vehicle-treated nephritic rats, PTX treatment beginning at the start of the nephritis significantly suppressed mRNA expression of tumour necrosis factor (TNF)-alpha, but not interleukin-1 beta, throughout the course of nephritis. Moreover, PTX decreased renal mRNAs for intercellular adhesion molecule-1 (ICAM-1), monocyte chemoattractant protein-1 (MCP-1), regulated on activation, normal T-cell expressed and secreted (RANTES) and osteopontin (OPN) at all time points examined. These effects were associated with a significant inhibition of macrophage and T-cell infiltration, a reduction of 24-h urinary protein excretion (50-75%, P<0.05), an improvement of histological damage including glomerular crescent formation (60-70%, P<0.01) and a decrease of cortical mRNAs for type I (alpha 1) collagen and fibronectin. The efficacy of PTX could also be seen, though to a lesser extent, in rats with established nephritis.

CONCLUSIONS

PTX is an effective anti-inflammatory and immunomodulatory agent capable of suppressing rat crescentic glomerulonephritis. Inhibition of renal TNF-alpha, ICAM-1, RANTES, MCP-1 and OPN expression may be a mechanism whereby PTX suppresses progressive renal injury in rat crescentic glomerulonephritis.

Expression of CX3CL1/fractalkine by mesangial cells in vitro and in acute anti-Thy1 glomerulonephritis in rats

BACKGROUND

Mesangial cells (MCs) can promote glomerular macrophage accumulation in glomerulonephritis through production of a variety of chemokines. This study investigated the potential of MCs to synthesize CX3CL1/fractalkine, a CX3C chemokine, both in vitro and in acute anti-Thy1 glomerulonephritis in rats.

METHODS

Anti-Thy1 glomerulonephritis was induced in Wistar rats by a single injection of mouse anti-rat Thy1.1 antibody intravenously. Glomerular mRNAs for CX3CL1/fractalkine, CCL2/monocyte chemoattractant protein (MCP)-1, and their cognate receptors, CX3CR1 and CCR2, were determined by northern blot analysis or reverse-transcription polymerase chain reaction. CX3CL1/fractalkine mRNA and protein expression in vivo was localized by in situ hybridization and immunohistochemistry. Monocytes/macrophages and activated MCs were detected by immunohistochemistry. Regulation of CX3CL1/fractalkine expression in cultured MCs was determined by northern and western blot analysis.

RESULTS

After induction of anti-Thy1 disease, glomerular CX3CL1/fractalkine mRNA was significantly up-regulated, peaking at 2 h and sustaining into day 5 of the nephritis. A corresponding increase in urinary CX3CL1/fractalkine protein was evident after day 1 of the nephritis, but became more prominent during the MC proliferative phase (days 3-5). Meanwhile, induction of glomerular CCL2/MCP-1 mRNA and urinary CCL2/MCP-1 protein occurred within 24 h, and was barely detectable after day 3 of the nephritis. Urinary CCL2/MCP-1, but not CX3CL1/fractalkine, correlated with glomerular macrophage accumulation (r = 0.936, P<0.01) and glomerular CCR2 mRNA expression (r = 0.965, P<0.01). In contrast, only urinary CX3CL1/fractalkine coincided temporally to glomerular mRNA for CX3CR1 (r = 0.809, P < 0.01). Combined in situ hybridization and immunohistochemistry revealed that activated MCs were a major source for CX3CL1/fractalkine mRNA and protein during days 3-5 of the nephritis. Incubation of cultured MCs with tumour necrosis factor (TNF)-alpha, interleukin (IL)-1beta, platelet-derived growth factor (PDGF)-AB or basic fibroblast growth factor (bFGF) significantly up-regulated CX3CL1/fractalkine mRNA and protein expression. This cytokine- and growth factor-stimulated CX3CL1/fractalkine expression could be abolished by the nuclear factor-kappaB inhibitors, curcumin and MG132.

CONCLUSIONS

Our data demonstrate that activated MCs are a source for the augmented glomerular CX3CL1/fractalkine expression during the proliferative phase of acute anti-Thy1 glomerulonephritis. Up-regulation of MC CX3CL1/fractalkine by TNF-alpha, IL-1beta, PDGF-AB and bFGF is mediated, at least in part, via the nuclear factor-kappaB signalling pathway. The differential expression of CCL2/MCP-1 and CX3CL1/fractalkine may sequentially recruit distinct subsets of monocytes to the glomerulus during acute anti-Thy1 glomerulonephritis.

Pentoxifylline Inhibits Platelet-Derived Growth Factor-Stimulated Cyclin D1 Expression in Mesangial Cells by Blocking Akt Membrane Translocation

Pentoxifylline (PTX) is a potent inhibitor of mesangial cell proliferation, but its underlying mechanism is poorly understood. Here, we demonstrate that in platelet-derived growth factor (PDGF)-stimulated mesangial cells, PTX causes G1 arrest by down-regulation of cyclin D1 expression, which subsequently attenuates Cdk4 activity. In vivo, PTX similarly reduces cyclin D1 expression in mesangial cells of rats with acute Thy1 glomerulonephritis. The mechanism by which PTX reduces cyclin D1 is also investigated. PTX blocks Akt but not phosphatidylinositol 3-kinase (PI3K) activation in response to PDGF and abrogates cyclin D1 induction by PI3K, suggesting an effect of PTX on Akt itself. Indeed, PTX is capable of blocking the membrane translocation of Akt, and enforced targeting of Akt to cell membrane prevents the inhibition of Akt and cyclin D1 by PTX. Because PTX is known to increase intracellular cAMP levels by inhibiting phosphodiesterase, the role of protein kinase A (PKA) in these events is investigated. The PKA antagonist N-[2-(4-bromocinnamylamino)ethyl]-5-isoquinoline (H89) abolishes cell proliferation effects of PTX and restores cyclin D1 expression as well as Akt membrane translocation and activation by PDGF, whereas dibutyryl cAMP and forskolin recapitulate the functions of PTX in mesangial cells. In conclusion, our results indicate that PTX, acting through PKA, interferes with PDGF signaling to Akt activation by blocking Akt membrane translocation, thereby inhibiting cyclin D1 expression and mesangial cell proliferation.

Pentoxifylline modulates intracellular signalling of TGF-beta in cultured human peritoneal mesothelial cells: implications for prevention of encapsulating peritoneal sclerosis

BACKGROUND

Peritoneal matrix accumulation is a major characteristic of encapsulating peritoneal sclerosis (EPS), which is a serious complication in long-term peritoneal dialysis (PD) patients. We reported previously that TGF-beta stimulates collagen gene expression in cultured HPMC, and is attenuated by pentoxifylline (PTX). The SMAD family and the mitogen-activated protein kinase (MAPK) (ERK1/2, JNK and p38(HOG)) pathways have been shown to participate in TGF-beta signalling. However, how PTX modulates the intracellular signalling downstream to TGF-beta remains undetermined in HPMC. In this study, we explored these signalling pathways in HPMC, and investigated the molecular mechanisms involved in the inhibitory effects of PTX on TGF-beta-induced collagen gene expression in HPMC.

METHODS

HPMC was cultured from human omentum by an enzyme digestion method. The expression of collagen alpha1(I) mRNA was determined by northern blotting, while the SMAD proteins and the MAPK kinase activity were determined by western blotting.

RESULTS

TGF-beta-stimulated collagen alpha1(I) mRNA expression of HPMC was inhibited by PTX. The Smad2, ERK1/2 and p38(HOG) pathways were activated in response to TGF-beta. However, TGF-beta displayed no activation of the JNK pathway in HPMC. The addition of PD98059 and SB203580, which blocked the activation of ERK1/2 and p38(HOG), respectively, suppressed the TGF-beta-induced collagen alpha1(I) mRNA expression. At a concentration (300 micro g/ml) that inhibited the collagen gene expression, PTX suppressed the ERK1/2 and p38(HOG) activation by TGF-beta. In contrast, PTX had no effect on the TGF-beta-induced activation of Smad2, under the same concentration.

CONCLUSION

PTX inhibits the TGF-beta-induced collagen gene expression in HPMC through modulating the ERK1/2 and p38(HOG) pathways. Our study of PTX may provide the therapeutic basis for clinical applications in the prevention of EPS.