Vasodilator agents modulate rat glomerular mesangial cell growth and collagen synthesis

Targeting inflammation in diabetic nephropathy: a tale of hope

INTRODUCTION

Diabetic nephropathy (DN) is the leading cause of chronic kidney disease (CKD) and end-stage renal disease (ESRD). Beyond the new anti-diabetic drugs that possess markedly cardiovascular and renal protective effects, no novel direct therapies for DN have become available on the market in the last twenty years. Recently well-designed clinical trials for the treatment of DN, with attractive pathogenetic rationale, e.g. bardoxolone and atrasentan, were canceled or stopped because of safety concerns or lack of reaching the end points, respectively.

AREAS COVERED

In this review, we focus on the involvement of inflammation in the pathogenesis of DN. We update information from recent experimental and clinical studies that reported beneficial effects of several agents targeting chemokines, cytokines, transcription factors and kinases as well as several compounds with anti-inflammatory properties on DN.

EXPERT OPINION

Inflammation plays a key role in the DN progression. Preclinical studies have identified several anti-inflammatory molecules that effective decrease albuminuria and/or proteinuria. However, limited clinical trials in humans have been performed to confirm these results. Inhibitors of CCL2/CCR2, IL-1β and JAK/STAT pathways, and Nrf2 inducers are promising therapeutic options to improve the renal outcome of patients with DN, but appropriate clinical trials are necessary.

Effect of pentoxifylline on microalbuminuria in diabetic patients: a randomized controlled trial

Background. Pentoxifylline is a nonspecific phosphodiesterase inhibitor with anti-inflammatory properties. Human studies have proved its antiproteinuric effect in patients with glomerular diseases, but this study was designed to assess the effects of add-on pentoxifylline to available treatment on reduction of microalbuminuria in diabetic patients without glomerular diseases. Methods. In a double-blind placebo-controlled, randomized study we evaluated the influence of pentoxifylline on microalbuminuria in type 2 diabetic patients. 40 diabetic patients with estimated glomerular filtration rate (eGFR) of more than 60 mL/min/1.73 m(2) in eight weeks and microalbuminuria were randomized to two groups which will receive pentoxifylline 1200 mg/day or placebo added to regular medications for 6 months. albuminuria; eGFR was evaluated at three- and six-month follow-up period. Results. Baseline characteristics were similar between the two groups. At six months, the mean estimated GFR and albuminuria were not different between two groups at 3- and 6-month follow-up. Trend of albumin to creatinine ratio, systolic and diastolic blood pressure, and eGFR in both groups were decreased, but no significant differences were noted between two groups (P value > 0.05). Conclusion. Pentoxifylline has not a significant additive antimicroalbuminuric effect compared with placebo in patients with type 2 diabetes with early stage of kidney disease; however, further clinical investigations are necessary to be done.

Novel effective drugs for diabetic kidney disease? or not?

INTRODUCTION

Diabetes mellitus is increasingly common worldwide and is expected to affect 592 million people by 2035. The kidney is often involved. A key goal in treating diabetes is to reduce the risk of development of kidney disease and, if kidney disease is already present, to delay the progression to end-stage renal disease (ESRD). This represents a social and ethical issue, as a significant proportion of patients reaching ESRD in developing countries do not have access to renal replacement therapy.

AREAS COVERED

The present review focuses on novel therapeutic approaches for diabetic nephropathy (DN), implemented on the basis of recent insights on its pathophysiology, which might complement the effects of single inhibition of the renin-angiotensin-aldosterone system (RAAS), the cornerstone of renoprotective interventions in diabetes, along with glycemic and blood pressure control.

EXPERT OPINION

Although a plethora of new treatment options has arisen from experimental studies, the number of novel renoprotective molecules successfully implemented in clinical practice over the last two decades is disappointingly low. Thus, new investigational strategies and diagnostic tools - including the appropriate choice of relevant renal end points and the study of urinary proteome of patients - will be as important as new therapeutic interventions to fight DN. Finally, in spite of huge financial interests in replacing the less expensive ACE inhibitors and angiotensin II receptor blockers with newer drugs, any future therapeutic approach has to be tested on top of - rather than instead of - optimal RAAS blockade.

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.

Potential new treatments for diabetic kidney disease

Antifibrotic agents, antioxidant agents, ET-a receptor antagonists, and a few other agents with nonspecific or multifaceted mechanisms of action have been evaluated and progressed to small clinical studies in human subjects. Although there are limited data at the present time, these early evaluations have produced some favorable results that at least warrant further investigation. There is certainly not enough compelling evidence to justify the routine use of any of these products specifically for DKD at the moment; however, more well-controlled and adequately powered studies in several hundred patients will help determine which of these may have a place in the DKD treatment armamentarium of the future.

Pentoxifylline and propentofylline prevent proliferation and activation of the mammalian target of rapamycin and mitogen activated protein kinase in cultured spinal astrocytes

Astrocyte activation is an important feature in many disorders of the central nervous system, including chronic pain conditions. Activation of astrocytes is characterized by a change in morphology, including hypertrophy and increased size of processes, proliferation, and an increased production of proinflammatory mediators. The xanthine derivatives pentoxifylline and propentofylline are commonly used experimentally as glial inhibitors. These compounds are generally believed to attenuate glial activity by raising cyclic AMP (cAMP) levels and inhibiting glial tumor necrosis factor (TNF) production. In the present study, we show that these substances inhibit TNF and serum-induced astrocyte proliferation and signaling through the mammalian target of rapamycin (mTOR) pathway, demonstrated by decreased levels of phosphorylated S6 kinase (S6K), commonly used as a marker of mTOR complex (mTORC) activation. Furthermore, we show that pentoxifylline and propentofylline also inhibit JNK and p38, but not ERK, activation induced by TNF. In addition, the JNK antagonist SP600125, but not the p38 inhibitor SB203580, prevents TNF-induced activation of S6 kinase, suggesting that pentoxifylline and propentofylline may regulate mTORC activity in spinal astrocytes partially through inhibition of the JNK pathway. Our results suggest that pentoxifylline and propentofylline inhibit astrocyte activity in a broad fashion by attenuating flux through specific pathways.

Molecular targets for treatment of kidney fibrosis

Renal fibrosis is the culmination of processes driven by signaling pathways involving transforming growth factor-β family of cytokines, connective-tissue growth factor, nuclear factor κB, Wnt/β-catenin, Notch, and other growth factors. Many studies in experimental animal models have directly targeted these pathways and demonstrated efficacy in mitigating renal fibrosis. However, only a small fraction of these approaches have been attempted in human and even fewer have been successfully translated to clinical use for patient with kidney diseases. Drugs with proven efficacy for treatment of kidney diseases and tissue fibrosis exert some of their effects by interfering with components of these pathways. This review considers key molecular mediators of renal fibrosis and their potential as targets for treatment of renal fibrosis.

Therapeutic effects of umbilical cord blood-derived mesenchymal stem cell transplantation in experimental lupus nephritis

Mesenchymal stem cells (MSCs) have been shown to possess immunomodulatory properties. Systemic lupus erythematosus is an autoimmune disease that results in nephritis and subsequent destruction of renal microstructure. We investigated whether transplantation of human umbilical cord blood-derived MSCs (uMSCs) is useful in alleviating lupus nephritis in a murine model. It was found that uMSCs transplantation significantly delayed the development of proteinuria, decreased anti-dsDNA, alleviated renal injury, and prolonged the life span. There was a trend of decreasing T-helper (Th) 1 cytokines (IFN-γ, IL-2) and proinflammatory cytokines (TNF-α, IL-6, IL-12) and increasing Th2 cytokines (IL-4, IL-10). The in vitro coculture experiments showed that uMSCs only inhibited lymphocytes and splenocytes proliferation but not mesangial cells. Long-term engraftment of uMSCs in the kidney was not observed either. Together, these findings indicated that uMSCs were effective in decreasing renal inflammation and alleviating experimental lupus nephritis by inhibiting lymphocytes, inducing polarization of Th2 cytokines, and inhibition of proinflammatory cytokines production rather than direct engraftment and differentiating into renal tissue. Therapeutic effects demonstrated in this preclinical study support further exploration of the possibility to use uMSCs from mismatched donors in lupus nephritis treatment.

Prolonged administration enhances the renoprotective effect of pentoxifylline via anti-inflammatory activity in streptozotocin-induced diabetic nephropathy

The beneficial effects of pentoxifylline (PTX), which has an anti-inflammatory and renoprotective effect in diabetic nephropathy, are not completely understood. This study investigates whether prolonged administration of PTX (40 mg/kg, per oral) is effective in streptozotocin-induced diabetic nephropathy. The amount of urinary protein was higher in the diabetic rats than in the control rats. The amount remained unchanged after 4 weeks and decreased after 8 weeks of PTX treatment. Accumulation of monocyte chemoattractant peptide-1 (MCP-1) and mouse monoclonal anti-monocyte/macrophage antibody (ED-1) positive cells was higher in untreated diabetic rats than in the control rats. PTX administration ameliorated the urinary MCP-1 excretion and interstitial infiltration of ED-1 positive cells at 4 weeks. Further, in diabetic rats, administration of PTX for 4 weeks inhibited the renal inflammatory reaction, and when administration for 8 weeks, it prevented proteinuria. These findings support the hypothesis that prolonged administration enhances the protective effects of PTX.

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.

The role of the alpha-1 adrenoceptor in modulating human mesangial cell matrix production

BACKGROUND

The sympathetic nervous system is frequently activated in hypertension and may modify various aspects of renal function. Whether modulation of the sympathetic nervous system directly influences the development of renal fibrosis is yet to be established. The current study investigates the role of the alpha-1 adrenoceptor on human mesangial cell scarring.

METHODS

Human mesangial cells were injured with macrophage-conditioned medium (MPCM) and treated with doxazosin for 1 or 3 days.

RESULTS

alpha-1 Adrenoceptor antagonist doxazosin of 2 micromol/l reduced fibronectin protein in MPCM-injured female mesangial cells by 31 +/- 1.03% (P < 0.001) and by 9.5 +/- 0.3% (P = 0.01) in male mesangial cells. The differential response between sexes was significant (P = 0.004). alpha-1B Adrenoceptors were detected in human mesangial cells by reverse transcription-polymerase chain reaction with expression in female cells being 87% higher than in males (P = 0.04). Injury with MPCM reduced alpha-1B adrenoceptor mRNA expression in both cell types. Doxazosin had no effect on the protein levels of transforming growth factor-beta (TGF-beta) or interleukin-1beta (IL-1beta), however, a small reduction in tumour necrosis factor-alpha (TNF-alpha) levels was observed. Doxazosin had no effect on the modulators of matrix turnover matrix metalloproteinases MMP3, MMP9 and tissue inhibitor of matrix metalloproteinases (TIMP-1), although a significant reduction in tissue plasminogen activator (tPA); (36.5 +/- 2.6%, P < 0.001) was observed. Doxazosin caused an up-regulation of kallikrein expression, both at mRNA and protein levels. Co-treatment with the bradykinin B2 receptor antagonist HOE140 was able to attenuate the effects of doxazosin treatment on fibronectin levels.

CONCLUSION

These data suggest that inhibition of alpha-1B adrenoceptors in mesangial cells exerts an anti-fibrotic effect in a sex-specific manner via modulation of the kallikrein-kinin/plasminogen activator system.

YC-1-inhibited proliferation of rat mesangial cells through suppression of cyclin D1-independent of cGMP pathway and partially reversed by p38 MAPK inhibitor

This study was designed to investigate the effect of 1-benzyl-3-(5'-hydroxymethyl-2'-furyl) indazole (YC-1), a guanylate cyclase activator, upon the proliferation of rat mesangial cells and its underlying mechanism. YC-1 inhibited cell proliferation and DNA synthesis in a dose- and time-dependent manner. Flow cytometry cell-cycle studies revealed that YC-1 prevented the entry of cells from G1 into S phase. The expression of cyclin D1 and the kinase activity of cyclin D1/cyclin-dependent kinase (CDK)4 were lower within YC-1-treated cells, revealed by Western blotting, Northern blotting and kinase assays. YC-1 did not increase the intracellular cGMP concentration in mesangial cells. Inhibitors of soluble guanylate cyclase, protein kinase G, or protein kinase A also did not reverse the inhibitory effect elicited by YC-1, while co-treatment with p38 mitogen-activated protein kinase (MAPK) inhibitor could partially reverse the suppressive effect. YC-1 inhibited proliferation of mesangial cells and induced cell-cycle arrest by the reduction of cyclin D1 synthesis and cyclin D1/CDK4 kinase activity. This effect acts partially through p38 MAPK signal transduction activation and is independent of cGMP-signaling pathways.

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.

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.

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.

Renoprotective Effect of Angiotensin-Converting Enzyme Inhibitor Combined with α1-Adrenergic Antagonist in Spontaneously Hypertensive Rats with Renal Ablation

To assess the renal benefits of combined angiotensin-converting enzyme inhibition and alpha(1)-adrenergic antagonism, we studied the antihypertensive and renoprotective effects of temocapril (TMP) alone and in combination with doxazosin (DOX) in spontaneously hypertensive rats (SHR)/Izumo rats with renal ablation. Five-Sixths-nephrectomized rats were assigned to receive TMP (10 mg/kg/day) (TMP group), TMP plus DOX (2 mg/kg/day) (TMP+DOX group), or vehicle (control group) orally for 12 weeks. Both systolic blood pressure (SBP) and urinary excretion of albumin (UalbV) in the control group progressively increased during the experimental period and were significantly higher than in sham-operated rats. Treatment with either TMP or TMP plus DOX had similar antihypertensive effects in this rat model. Twelve weeks after initiation of treatment, the SBP values in the control, TMP, and TMP+DOX groups were 265+/-8, 157+/-4, and 163+/-3 mmHg, respectively, in comparison with 233+/-4 mmHg in sham-operated rats (p<0.0001 control vs. sham, p<0.001 TMP vs. control, p<0.001 TMP+DOX vs. control). UalbV, serum creatinine (Scr), blood urea nitrogen (BUN), and heart weight/body weight (HW/BW) ratio were significantly lower in the TMP and TMP+DOX groups than in the control group (UalbV: p<0.05; Scr: p<0.01; [BUN, HW/BW ratio]: p<0.0001; and [UalbV, Scr, BUN, HW/BW ratio]: p<0.0001 vs. control, respectively). The index of glomerular sclerosis (IGS) and relative interstitial volume (RIV) were significantly lower in the TMP+DOX group than in the control group (IGS: p<0.05; RIV: p<0.01). Especially, UalbV, IGS, and RIV were significantly better in the TMP+DOX group than in the TMP group ([IGS, RIV]: p<0.05; UalbV: p<0.01). These results suggest that simultaneous administration of TMP and DOX provides greater renoprotective effects than administration of TMP alone.

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.

Nephroprotective effects of pentoxifylline in experimental myoglobinuric acute renal failure

The nephroprotective effects of pentoxifylline, a methylxantine, were studied in glycerol-induced acute renal failure. Glycerol treated rats exhibited collecting duct and medullary ascending limb dilation and casts, with focal tubular damage, confined mainly to the superficial cortex. In the interstitium focal mononuclear infiltration was observed. In some glomeruli there was swelling of mesangial spaces and mesangial cells. Pentoxifylline injected to glycerol pretreated rats exerted a protective effect. Only few groups of proximal tubules in the subcapsulary region of renal cortex showed necrosis and tubulorhexis. There were not leukocyte infiltrations or vascular congestion. Morphometric analysis showed increased surface area fraction of tubular lumen in rats treated with glycerol (p < 0.01) compared to those in controls. Intratubular cast formations in rats treated with glycerol alone were significantly higher than in rats given pentoxifylline in addition to glycerol. Kidney cortex ectopeptidases (APA, APN and DPP IV) were not significantly changed after glycerol administration. Serum creatinine and blood urea were markedly increased in glycerol treated rats, however, pentoxifylline reduced significantly their levels. This study in glycerol-induced acute renal failure showed a marked renal morphologic and functional protection by pentoxifylline.

Dipyridamole inhibits in vitro renal fibroblast proliferation and collagen synthesis

Fibroblasts are universally recognized in situations of tubulointerstitial injury, where their presence has been shown to be a marker of disease progression. The objective of this study was to determine whether the functions of fibroblasts relevant to fibrogenesis can be modified in vitro with dipyridamole. Cells were obtained from obstructed rat renal tissue and characterized on the basis of immunohistochemical findings. Fibroblasts constituted all of the cells from passage 3. Functional parameters were measured in cells cultured with 1, 5, and 50 micromol/L dipyridamole and compared to basal parameters of cells grown in Dulbecco's modified Eagle's medium plus 10% fetal calf serum (control). Northern-blot analysis indicated that dipyridamole decreased procollagen alpha1(I) messenger ribonucleic acid expression (P <.05, 50 micromol/L vs control), results that were reflected in a reduction in total collagen secretion as measured on the basis of hydroxyproline incorporation (P <.001, 50 micromol/L vs control). Mitogenesis, as measured on the basis of incorporation of tritiated thymidine, was decreased in a dose-dependent fashion by dipyridamole. Likewise, 50 micromol/L dipyridamole reduced cell-population growth to 16.8% +/- 2.1% of basal growth over 3 days (P <.001 vs control). Effects of dipyridamole on population growth were prevented by coincubation with a protein kinase G inhibitor peptide (P <.001 vs 50 micromol/L dipyridamole; P = not significant vs control). No such effect was observed with inhibitors for protein kinase A (H-89) and protein kinase C (bisindolylmaleimide I). Consistent with a protein kinase G-dependent mechanism, immunofluorescence staining indicated that dipyridamole increased basal expression of the inducible form of nitric oxide synthase. In conclusion, the results of this study demonstrate that at clinically relevant concentrations, dipyridamole inhibits profibrotic activities of renal fibroblasts. Effects on mitogenesis are mediated through a cyclic guanosine monophosphate-protein kinase G effector pathway.

Dipyridamole inhibits TGF-beta-induced collagen gene expression in human peritoneal mesothelial cells

BACKGROUND

Peritoneal matrix accumulation is characteristic of peritoneal fibrosis (PF). Continuous ambulatory peritoneal dialysis (CAPD) patients who had persistent transforming growth factor-beta (TGF-beta) in their drained effluent had an increased risk of PF. We previously reported that TGF-beta stimulates the expression of types I and III collagen mRNA in cultured human peritoneal mesangial cells (HPMCs), which may predispose them to develop PF. Pharmacological interventions to attenuate TGF-beta-stimulated matrix accumulation in HPMC may have therapeutic potential for the treatment of PF. The SMAD family and the extracellular signal-regulated protein kinase (ERK1/2, p44/p42) pathways have been shown to participate in TGF-beta signaling. Our current study identified these signal pathways in HPMCs and investigated the molecular mechanisms involved in the inhibitory effects of dipyridamole on TGF-beta-induced collagen gene expression in HPMCs.

METHODS

HPMCs were cultured from human omentum by an enzyme digestion

METHOD

Expression of collagen alpha1(I) mRNA was determined by Northern blotting. The SMAD proteins and the ERK1/2 activity were determined by Western blotting.

RESULTS

TGF-beta-stimulated collagen alpha1(I) mRNA expression of HPMC was inhibited by dipyridamole in a dose-dependent manner. Smad2 and ERK1/2 were activated in response to TGF-beta; however, TGF-beta had little effect on the protein expression of Smad4. The addition of PD98059, which blocked activation of ERK1/2, suppressed TGF-beta-induced collagen alpha1(I) mRNA expression in a dose-dependent manner. At a concentration that inhibited collagen gene expression (17 microg/mL), dipyridamole suppressed ERK1/2 activation by TGF-beta. In contrast, the same concentration of dipyridamole had no effect on TGF-beta-induced activation of Smad2.

CONCLUSION

Dipyridamole inhibits TGF-beta-induced collagen gene expression in HPMC through modulation of the ERK pathway. Our study of dipyridamole may provide therapeutic basis for clinical applications in the prevention of PF.

Interrelationship between nitric oxide and prostaglandins in bovine granulosa cells

It is well recognized that prostaglandins of the E (PGE) and F (PGF) series play an important role in ovarian physiology; in addition, nitric oxide (NO) has been recently demonstrated to be an important mediator of granulosa cell function. There is now evidence for a biologic relationship between PGs and the NO biosynthetic pathway. The aim of this study was to investigate the relationship between NO and PGE2 and PGF2alpha in bovine granulosa cells. Granulosa cells collected from small (<5mm) and large (>8mm) follicles were treated with the NO donor S-nitroso-N-acetylpenicillamine (SNAP) or with indomethacin, an inhibitor of PGs synthesis, and PGE2 and PGF2alpha were quantified; in addition, the effects of PGE2 PGF2alpha and indomethacin on steroidogenesis and NO production were determined. The highest concentration of SNAP inhibited (P < 0.001) PGE2 production in cells from both kinds of follicles, while the lowest dose was effective only in cells from small follicles. The highest concentration of SNAP inhibited and stimulated (P < 0.001) PGF2alpha production in cells from small and large follicles, respectively. Progesterone (P4) production was stimulated by PGE2 and inhibited by PGF2alpha (P < 0.001) in cells from both types of follicles. Estradiol 17beta (E2) secretion was inhibited in cells from small and stimulated in those from large follicles by PGE2 (P < 0.05), while PGF2alpha was stimulatory in cells from both kinds of follicles (P < 0.001). P4 production by cells from small follicles was inhibited and stimulated by those from large follicles by indomethacin (P < 0.001), which also increased E2 output in cells from small follicles (P < 0.001). NO production was inhibited by both PGE2 and PGF2alpha except at the lowest concentration, which was stimulatory (P < 0.001). Indomethacin stimulated (P < 0.001) NO production. Taken together, the present data suggest a cross-talk between NO and PGs biosynthetic pathways, which needs to be further clarified.

Dipyridamole inhibits PDGF-stimulated human peritoneal mesothelial cell proliferation

BACKGROUND

It has been proposed that proliferation of human peritoneal mesothelial cells (HPMCs) accompanied by collagen synthesis may contribute to the development of peritoneal fibrosis (PF) in patients of long-term continuous ambulatory peritoneal dialysis (CAPD). However, the precise molecular mechanism regulating HPMC proliferation has never been reported. Dipyridamole has been reported to have potential as an antiproliferative and antifibrotic agent. We investigated the mechanism and effect of dipyridamole in regulation of HPMC proliferation.

METHODS

HPMCs were cultured from human omentum by an enzyme digestion

METHOD

Cell proliferation was measured by the methyltetrazolium assay and intracellular cAMP was measured using an enzyme immunoassay kit. Cell-cycle distribution of HPMC was analyzed by flow cytometry. Extracellular signal-regulated protein kinase (p44/p42 ERK) activity and expressions of cell-cycle proteins (cyclin D(1), CDK4, pRB and p27(Kip1)) were determined by Western blotting.

RESULTS

The addition of DP suppressed PDGF-stimulated HPMC proliferation by cell-cycle arrest at the G1 phase. The antimitogenic effect of dipyridamole was mediated through the cAMP pathway. PDGF (25 ng/mL) increased the ERK1/2 activity of HPMC within 15 minutes, which maximized at 30 minutes, and the pretreatment with dipyridamole (17 microg/mL) substantially reduced the ERK response to PDGF by approximately 78.5%. PDGF induced elevated protein levels of cyclin D(1), but the CDK4 protein level did not change. Dipyridamole and DBcAMP had no effect on the levels of cyclin D(1) and CDK4 in PDGF-stimulated HPMC. PDGF decreased p27(Kip1) and induced pRB phosphorylation of HPMC. In contrast, dipyridamole prevented PDGF-induced p27(Kip1) degradation and attenuated PDGF-stimulated pRB phosphorylation.

CONCLUSION

Dipyridamole appears to inhibit PDGF-stimulated HPMC proliferation through attenuated ERK activity, preservation of p27(Kip1), and decreased pRB phosphorylation. Thus, dipyridamole may have therapeutic efficacy to prevent or alleviate PF.

Dipyridamole inhibits human peritoneal mesothelial cell proliferation in vitro and attenuates rat peritoneal fibrosis in vivo

BACKGROUND

Peritoneal fibrosis (PF) is one of the most serious complications after long-term continuous ambulatory peritoneal dialysis (CAPD). Proliferation of human peritoneal mesothelial cells (HPMC) and matrix over-production are regarded as the main processes predisposing to PF. Dipyridamole (DP) has been reported to have potential as an antiproliferative and antifibrotic agent. We thus investigated the effect of DP in inhibiting proliferation and collagen synthesis of HPMC. A rat model of peritonitis-induced PF was also established to demonstrate the in vivo preventive effect of DP.

METHODS

HPMC was cultured from human omentum by an enzyme digestion

METHOD

Cell proliferation was measured by the methyltetrazolium assay. Intracellular cAMP was measured using an enzyme immunoassay (EIA) kit. Total collagen synthesis was measured by (3)H-proline incorporation assay. Expression of collagen alpha1 (I) and collagen alpha 1 (III) mRNAs was determined by Northern blotting. The rat model of peritonitis-induced PF was developed by adding dextran microbeads (Cytodex, 8 mg/1 mL volume) to a standardized suspension (3 x 10(9)) of Staphylococcus aureus. DP was administrated via intravenous infusion (4 mg in 1 h) daily for seven days. Macroscopic grading of intraperitoneal adhesions and histological analyses of peritoneal thickness and collagen expression were performed.

RESULTS

Addition of DP to HPMC cultures suppressed serum-stimulated cell proliferation and collagen synthesis. The antimitogenic and antifibrotic effects of DP appear to be predominantly mediated through the cAMP pathway, as DP increased intracellular cAMP in a dose-dependent manner. The macroscopic grade of intraperitoneal adhesion and peritoneal thickness were both significantly increased in animals treated with Cytodex plus S. aureus; on the other hand, DP attenuated these fibrotic changes with statistical significance (P < 0.01). Analysis of gene expression of collagen alpha 1 (I) and alpha1 (III) in the peritoneal tissue of experimental animals yielded similar results.

CONCLUSIONS

This study suggests that dipyridamole may have therapeutic potential in treating peritoneal fibrosis.

Effects of pentoxifylline, pentifylline and gamma-interferon on proliferation, differentiation, and matrix synthesis of human renal fibroblasts

BACKGROUND

Kidneys that progress to end-stage renal failure are almost invariably characterized by the presence of tubulointerstitial fibrosis. Therapeutic interventions to halt the progressive deterioration of renal function are still limited. Pentoxifylline, pentifylline, and gamma-interferon have shown a potential benefit in the treatment of fibrotic processes in the skin and lung. Thus, the aim of the present study was the analysis of potential anti-fibrotic effects of these substances on human kidney fibroblasts in vitro.

METHODS

Primary renal fibroblasts were established from human kidney biopsies and were studied in addition to two renal fibroblast cell lines. Cells were first growth arrested by withdrawal of fetal calf serum (FCS) and subsequently stimulated with 10% FCS in the presence of different concentrations of pentoxifylline (PTX), pentifylline (PTF), or gamma-interferon (IFN-gamma). Fibroblast proliferation was determined by bromodeoxyuridine incorporation and cell counts. Northern and western blot hybridizations for basic fibroblast growth factor (FGF)-2 and transforming growth factor (TGF)-beta1 were performed to analyse inhibitory effects. The effects of all three substances on matrix synthesis were evaluated by immunoblot analyses and ELISA for collagen type I and fibronectin after stimulation with TGF-beta1. Finally, differentiation into myofibroblasts was examined by double immunofluorescence staining for alpha-smooth-muscle actin and Hoechst dye H33258.

RESULTS

PTX and PTF resulted in a dose- and time-dependent inhibition of proliferation in all fibroblast lines (maximum 78.9+/-6.2% at 500 microg/ml PTX). Conversely, IFN-gamma had only modest effects on fibroblast proliferation, resulting in a maximum of 36.0+/-6.1% inhibition at 500 U/ml. Northern blot hybridizations determined that FGF-2 mRNA levels in fibroblasts were decreased up to 73.7 and 91.5% by PTX (1000 microg/ml) and PTF (100 microg/ml), whereas IFN-gamma led to a reduction of 46.2% at 1000 U/ml, indicating that the inhibitory effects of all three substances may be mediated through inhibition of FGF-2 synthesis. These findings were corroborated by immunoblot analyses where again PTX and PTF had the strongest inhibitory effects. No change in TGF-beta1 mRNA levels was noted. Synthesis of cellular and secreted collagen type I was robustly inhibited by PTX and PTF, whereas IFN-gamma exerted the strongest inhibitory effect on fibronectin synthesis and secretion. In addition, IFN-gamma down-regulated the expression of alpha-smooth-muscle actin up to 73.3% (at 1000 U/ml) whereas PTX and PTF resulted in a down-regulation of up to 49.7+/-1.8 and 80.0+/-4.4% (at 1000 and 100 microg/ml) respectively. PTF was in all experiments about 10 times more potent than equimolar concentrations of PTX.

CONCLUSIONS

PTX and PTF exerted robust inhibitory effects on fibroblast proliferation, extracellular matrix synthesis, and myofibroblastic differentiation. Conversely, IFN-gamma caused strong inhibition of fibronectin synthesis and alpha-smooth-muscle cell actin expression but had only weak inhibitory influences on fibroblast proliferation and collagen type I synthesis. Inhibitory effects of all three substances on proliferation may be mediated through inhibition of FGF-2 synthesis.

Pentoxifylline inhibits human peritoneal mesothelial cell growth and collagen synthesis: effects on TGF-beta

BACKGROUND

Prevention or treatment of peritoneal fibrosing syndrome has become an important issue in patients on continuous ambulatory peritoneal dialysis (CAPD). Recent evidence has suggested that mesothelial stem cell proliferation and matrix over-production predispose the development of peritoneal fibrosis. We investigated whether pentoxifylline (PTX) affects human peritoneal mesothelial cell (HPMC) growth and collagen synthesis.

METHODS

HPMC was cultured from human omentum by an enzymic disaggregation method. Cell proliferation was assayed using a methyltetrazolium uptake method. Cell cycle analysis was performed by flow cytometry. Collagen synthesis was measured by 3H-proline incorporation into pepsin-resistant, salt-precipitated collagen. Prostaglandins and cAMP were determined by enzyme immunoassay. Northern blot analysis was used to determine mRNA expression.

RESULTS

Our data show that PTX inhibited serum-stimulated HPMC growth and collagen synthesis in a dose-dependent manner. Cell cycle analysis showed that PTX arrested the HPMCs in the G1 phase. PTX decreased the procollagen alpha1 (I) mRNA expression either stimulated by serum or transforming growth factor-beta (TGF-beta). PTX did not alter prostaglandins synthesis but dose-dependently increased intracellular cAMP level. PTX, the same as 3-isobutyl-l-methylxanthine, could potentiate prostaglandin E1 (PGE1) increased cAMP levels of HPMC. The antimitogenic and antifibrogenic effects of PTX on HPMC were reversed by N-[2]-((p-Bromocinnamyl)amino)ethyl]-5-isoquinolinesulfonamide (H-89). Therefore, the mechanism of these effects may be due to the phospodiesterase inhibitory property of PTX.

CONCLUSIONS

These data suggest that PTX may have a role in treating peritoneal fibrosing syndrome.

Doxazosin inhibits retinoblastoma protein phosphorylation and G(1)-->S transition in human coronary smooth muscle cells

Previous studies have demonstrated that the alpha(1)-adrenergic receptor antagonist doxazosin (Dox) inhibits multiple mitogenic signaling pathways in human vascular smooth muscle cells. This broad antiproliferative activity of Dox occurs through a novel mechanism unrelated to its blocking the alpha(1)-adrenergic receptor. Flow cytometry demonstrated that Dox prevents mitogen-induced G(1)-->S progression of human coronary artery smooth muscle cells (CASMCs) in a dose-dependent manner, with a maximal reduction of S-phase transition by 88+/-10.5% in 20 ng/mL platelet-derived growth factor and 1 micromol/L insulin (P+I)-stimulated cells (P<0.01 for 10 micromol/L Dox versus P+I alone) and 52+/-18.7% for 10% FBS-induced mitogenesis (P<0.05 for 10 micromol/L Dox versus 10% FBS alone). Inhibition of G(1) exit by Dox was accompanied by a significant blockade of retinoblastoma protein (Rb) phosphorylation. Hypophosphorylated Rb sequesters the E2F transcription factor, leading to G(1) arrest. Adenoviral overexpression of E2F-1 stimulated quiescent CASMCs to progress through G(1) and enter the S phase. E2F-mediated G(1) exit was not affected by Dox, suggesting that it targets events upstream from Rb hyperphosphorylation. Downregulation of the cyclin-dependent kinase inhibitory protein p27 is important for maximal activation of G(1) cyclin/cyclin-dependent kinase holoenzymes to overcome the cell cycle inhibitory activity of Rb. In Western blot analysis, p27 levels decreased after mitogenic stimulation (after P+I, 43+/-1.8% of quiescent cells [P<0.01 versus quiescent cells]; after 10% FBS, 55+/-7.7% of quiescent cells [P<0. 05 versus quiescent cells]), whereas the addition of Dox (10 micromol/L) markedly attenuated its downregulation (after P+I, 90+/-8.3% of quiescent cells [P<0.05 versus P+I alone]; after 10% FBS, 78+/-8.3% of quiescent cells [P<0.05 versus 10% FBS alone]). Furthermore, Dox inhibited cyclin A expression, an E2F regulated gene that is essential for cell cycle progression into the S phase. The present study demonstrates that Dox inhibits CASMC proliferation by blocking cell cycle progression from the G(0)/G(1) phase to the S phase. This G(1)-->S blockade likely results from an inhibition of mitogen-induced Rb hyperphosphorylation through prevention of p27 downregulation.

Selenium stimulates estradiol production in bovine granulosa cells: possible involvement of nitric oxide

Reduction in fertility is well known to be possibly related to selenium deficiencies, even if target organ for selenium action is, at present, unclear. The present study was aimed to examine whether selenium directly influences granulosa cells. Bovine granulosa cells from different size follicles were used to investigate the effect of selenium (5 ng/ml), with or without bovine follicle-stimulating hormone (bFSH) (100 ng/ml), on proliferation and steroidogenesis. In addition, we sought to determine if selenium modulates the production of nitric oxide, which is known to play an important role in ovarian activity. Our data demonstrate that selenium significantly (P < 0.001) stimulates the proliferation of the cells from small follicles; moreover, it further potentiates the stimulatory effect of the gonadotropin in the same cells. Furthermore, selenium significantly (P < 0.01) augments E2 output by cells from both kinds of follicles. bFSH increases E2 production (P < 0.01) by cells from large follicles, whereas it exerts a stimulatory (P < 0.01) effect only in the presence of selenium in the cells from the small ones. The production of nitric oxide is significantly increased (P < 0.001) by bFSH, but only in cells from small follicles. Selenium inhibits (P < 0.001) nitric oxide production in cells from both kinds of follicles and significantly decreases (P < 0.001) bFSH-induced nitric oxide production in cells from the small ones. We conclude that selenium acts on granulosa cells by modulating their proliferation and E2 synthesis; moreover, its effect could be mediated, at least in part, through an inhibition of nitric oxide.

Pentoxifylline attenuates experimental mesangial proliferative glomerulonephritis

BACKGROUND

Accumulation of glomerular macrophages, proliferation of mesangial cells (MCs), and deposition of extracellular matrix proteins are pathobiological hallmarks of glomerulonephritis. We previously reported that a clinically available nonselective inhibitor of cyclic 3',5'-nucleotide phosphodiesterase, pentoxifylline (PTX), inhibits proliferation of cultured rat MCs, as well as collagen production by these cells. In this study, we investigated the in vivo effects of PTX on rat anti-Thy1 disease, a model of mesangial proliferative nephritis.

METHODS

Anti-Thy1 nephritis was induced in Sprague-Dawley rats by injecting mouse anti-rat Thy1 antibodies intravenously. Nephritic rats were randomly assigned to receive PTX (0.1 g/kg/day) or vehicle (phosphate-buffered saline) and were sacrificed at various time points. Paraffin kidney sections were stained with hematoxylin and periodic acid-Schiff reagents for glomerular histology. Frozen kidney sections were stained by monoclonal antibodies against proliferating cell nuclear antigen, ED-1, and alpha-smooth muscle actin and were visualized by color development from a horseradish peroxidase reaction. Monocyte chemoattractant protein-1 (MCP-1), intercellular adhesion molecule-1 (ICAM-1), and various extracellular matrix mRNAs were analyzed by Northern blotting. Urine protein concentrations were determined by Lowry's method.

RESULTS

Nephritic rats treated with PTX excreted less urinary protein on day 5 of nephritis than vehicle-treated nephritic rats. In periodic acid-Schiff-stained kidneys from PTX-treated nephritic rats, there was attenuation of both glomerular cellularity and glomerular sclerosis compared with vehicle-treated nephritic rats. PTX decreased the augmented glomerular mRNA levels of MCP-1 and ICAM-1 at two hours and on day 1 of nephritis. Immunoreactive staining showed that PTX reduced the number of proliferating glomerular macrophages on days 1, 2, and 3, but not at two hours of nephritis, compared with vehicle-treated nephritic rats. On day 5, PTX decreased the number of activated proliferating MCs and attenuated the glomerular mRNA levels of type I (alpha1), type III (alpha1), and type IV (alpha1) collagen and fibronectin compared with vehicle-treated nephritic rats.

CONCLUSION

The administration of PTX to rats with anti-Thy1 disease reduces accumulation and proliferation of glomerular macrophages, attenuates proteinuria, suppresses activation and proliferation of MCs, and ameliorates glomerular sclerosis. These results suggest that PTX may have a suppressive effect in acute phases or relapses of mesangial proliferative glomerulonephritis.

Doxazosin inhibits proliferation and migration of human vascular smooth-muscle cells independent of alpha1-adrenergic receptor antagonism

Proliferation and migration of vascular smooth-muscle cells (VSMCs), stimulated by a variety of growth factors, play a critical role in the pathogenesis of vascular diseases. We found unexpectedly that doxazosin, an alpha1-adrenergic-receptor antagonist, inhibits serum-stimulated proliferation of cultured human VSMCs. Subsequent experiments systematically investigated inhibitory effects of doxazosin on mitogenesis stimulated in VSMCs by platelet-derived growth factor (PDGF), epidermal growth factor, and G protein-coupled receptor agonists thrombin and angiotensin II. Doxazosin attenuated the stimulation of DNA synthesis for each of these ligands with median inhibitory concentrations (IC50s) from 0.3 to 1 microM. PDGF-AB (1 nM) increased cell number; doxazosin inhibited this response by 70-80%. Prazosin, a related alpha1-receptor antagonist, had similar but less potent effects on inhibiting mitogenesis in these cells. Doxazosin and prazosin inhibited PDGF-AB-stimulated and insulin-like growth factor (IGF-I)-stimulated migration of VSMCs by approximately 40-50%. These effects of doxazosin were likely unrelated to alpha1-receptor blockade because pretreatment of cells with phenoxybenzamine, an irreversible alpha1 antagonist, did not change the capacity of doxazosin to inhibit of PDGF-stimulated mitogenesis. Also, doxazosin inhibited PDGF-stimulated DNA synthesis in NIH 3T3 cells, which do not express alpha1 receptors. These results suggest that doxazosin is a potent inhibitor of VSMC proliferation and migration through a mechanism unrelated to alpha1-receptor antagonism.

Can pentoxifylline prevent renal disease?

The characteristics of pentoxifylline(Trental) suggest that it is an ideal agent to be used as adjunct in the therapy of chronic proliferative glomerulonephritides. Theoretical considerations suggest that pentoxifylline should also protect against and even ameliorate tubulo-interstitial fibrosis of affected kidneys.