Pentoxifylline reduces nephrotoxicity associated with cyclosporine in the rat by its rheological properties

Hemorheology in kidney transplantation: A role for cardiovascular risk?

Uremic patients undergoing dialysis (HD) present a cardiovascular risk of death 10-20 fold higher than general population, but also kidney transplantation keeps considerable cardiovascular burden.Hemorheologic profile alterations have been described in HD; comprehensive data on kidney transplant recipients (KT) are missing. Aim of our study is to characterize the hemorheological profile in KT, and to compare these data with HD and healthy volunteers (HV).We investigated 47 HV, 90 HD and 108 KT.We confirm hemorheological alterations in HD. KT, when compared to HD, normalizes many parameters: plasma viscosity, whole blood viscosity at 1-Hz and 200-Hz shear rate, erythrocyte aggregation index and yield stress. KT show a markedly lower erythrocyte deformability (ED). We found no differences among hemorheological parameters between the different classes of immunosuppressive drugs used.In conclusion, HD show various hemorheological defects; this could support the high incidence of cardiovascular complications. KT improves most hemorheological alterations; nevertheless, ED is reduced in KT, maintaining a detrimental injury at microcirculatory level and leading to the progression of fibrosis till to end-stage injury. Impaired ED in KT could also contribute to progression of interstitial fibrosis and tubular atrophy (IF/TA) in grafts.

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.

Evaluation of nephrotoxic effects of mycotoxins, citrinin and patulin, on zebrafish (Danio rerio) embryos

Citrinin (CTN) and patulin (PAT) are fungal secondary metabolites which are found in food and feed and showed organotoxicity in mature animals. In this study zebrafish embryos were applied to investigate the developmental toxicity of CTN and PAT on embryonic kidney. In the presence of CTN and PAT, the gross morphology of kidneys from embryos with green fluorescent kidney (wt1b:GFP) was not apparently altered. Histological analysis of CTN-treated embryos indicated cystic glomerular and tubular lesions; a disorganized arrangement of renal cells was also found in the PAT-treated group. From the view point of renal function, dextran clearance abilities of embryos exposed to CTN and PAT were significantly reduced. The damaged renal function caused by CTN could be partially rescued by the administration of pentoxifylline, suggesting the reduction of glomerular blood flow contributes to CTN-induced renal dysfunction. Additionally, CTN induced the expression of proinflammation genes, including COX2a, TNF-α and IL-1β, but failed to modify the levels and distribution of wt1a transcript and Na(+)/K(+)-ATPase protein. In summary, CTN and PAT caused profound nephrotoxicity in histological structure and biological function of zebrafish embryos; the inflammatory pathway and blood rheology may involve in CTN-induced renal impairment.

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.

Pentoxifylline attenuates the increase in whole blood viscosity after transfusion

BACKGROUND

Pentoxifylline improves tissue oxygenation and intestinal blood flow in models of haemorrhagic shock, and it has been used for the treatment of intermittent claudication due to its beneficial effects on haemorheology. We investigated the effects of pentoxifylline on whole blood viscosity during packed red-blood cell transfusion in critically ill adult patients.

METHODS

Twenty critically ill patients were randomly assigned to one of two groups (pentoxifylline group: n = 11, placebo group: n = 9) and prospectively studied. Forty-five minutes before and during the packed red-blood cell transfusion (10 ml min(-1)) over a period of 80 min, 1.5 mg kg(-1) . h(-1) pentoxifylline or placebo were administered intravenously. Haematocrit, plasma fibrinogen concentration, total protein concentration, whole blood viscosity (at a shear rate of 10 s(-1), 50 s(-1), and 100 s(-1)) and plasma viscosity were measured.

RESULTS

After the packed red-blood cell transfusion, haematocrit levels increased significantly in both groups (pentoxifylline group: from 26.1 +/- 2.8% to 33.0 +/- 3.2; placebo group: from 24.4 +/- 3.3% to 32.6 +/- 2.6%; means +/- standard deviation). Compared to baseline, whole blood viscosity increased in both groups at all shear rates after the transfusion, but the increase was significantly less in the pentoxifylline group (26 +/- 15% vs. 49 +/- 14%, 23 +/- 11% vs. 39 +/- 12%, and 22 +/- 11% vs. 35 +/- 12% for the pentoxifylline vs. placebo groups at shear rates of 10 s(-1), 50 s(-1), and 100 s(-1), respectively). Plasma viscosity, total protein concentration, and fibrinogen concentration remained unchanged and no significant differences among groups were observed.

CONCLUSIONS

These results suggest that pentoxifylline is effective in attenuating the increase in whole blood viscosity after a transfusion of packed red-blood cells. Plasma viscosity is not influenced by pentoxifylline.

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.

Reversal of acute tacrolimus-induced renal vasoconstriction by theophylline in rats

OBJECTIVE

To determine whether theophylline, a nonselective adenosine receptor antagonist and phosphodiesterase inhibitor, reverses the acute declines in renal blood flow and glomerular filtration rate induced by high-dose tacrolimus in rats.

DESIGN

Prospective, randomized, placebo-controlled experimental study.

SETTING

University-based basic science research laboratory.

SUBJECTS

Adult male Sprague-Dawley rats.

INTERVENTIONS

After mechanical ventilation and instrumentation under isoflurane and nitrous oxide anesthesia, animals received either tacrolimus 0.5 mg/kg intravenously or vehicle and 1 hr later either theophylline 4 mg/kg intravenously or vehicle.

MEASUREMENTS AND MAIN RESULTS

By using radiolabeled microspheres, renal blood flow was measured in three groups: control (n = 5), tacrolimus plus vehicle (n = 6), and tacrolimus plus theophylline (n = 6) at four time points-baseline and 60, 75, and 90 mins after tacrolimus or vehicle (the latter two time points being 15 and 30 mins after theophylline or vehicle, respectively). Whole blood tacrolimus and serum theophylline concentrations were measured. In a separate group of animals, by using (51)Cr-EDTA, glomerular filtration rate was measured in two groups: tacrolimus plus vehicle (n = 5) and tacrolimus plus theophylline (n = 5) at baseline and over two consecutive 20-min time periods beginning 61 mins posttacrolimus. Urine flow rate also was measured. Following tacrolimus, both renal blood flow and glomerular filtration rate declined in parallel by approximately 33% and 50% from baseline after 75 and 90 mins, respectively (p <.05 by two-way repeated-measures analysis of variance). Theophylline completely reversed these tacrolimus-induced decreases in renal blood flow and glomerular filtration rate. Urine flow rate also increased in response to theophylline.

CONCLUSIONS

Low-dose theophylline reverses tacrolimus-induced declines in renal blood flow and glomerular filtration rate observed in an acute model of tacrolimus toxicity. Theophylline's effect in chronic toxicity remains to be determined.

Beneficial effect of serotonin 5-HT2-receptor antagonism on renal blood flow autoregulation in cyclosporin-treated rats

Renal blood flow (RBF) autoregulation reappears in postischemic rat kidneys during serotonin (5-HT2) antagonism. The aim of the present study was to analyze whether 5-HT2 antagonism can ameliorate impaired RBF autoregulation in rats treated with 20 mg/kg per d cyclosporin A during 10 d. Autoregulation of RBF was assessed during stepwise lowering of renal perfusion pressure from 110 to 70 mmHg by gradual compression of the aorta. Autoregulation was lost in the cyclosporin A-treated rats. During administration of the 5-HT2 antagonist ritanserin (0.6 mg/kg intravenous bolus, followed by 1.2 mg/kg per h intravenous infusion during 1 h), autoregulation acutely reappeared. Intrarenal bolus injections of a selective 5-HT2-agonist, 2,5 dimethoxy-4-iodoamphetamine hydrochloride, elicited a significantly stronger renal vasocontraction in cyclosporin A-treated rats than in control rats. This finding was also observed with serotonin after nitric oxide-synthase blockade. These results (1) show the importance of 5-HT2-receptor-mediated vasoconstriction in the suppression of vasodilatory autoregulation of RBF in experimental cyclosporin A-induced renal dysfunction and (2) demonstrate that the complete loss of RBF autoregulation is not due to damage of the vascular smooth muscle cells.