Sevelamer hydrochloride versus aluminum hydroxide: effect on serum phosphorus and lipids in CAPD patients.

BACKGROUND: Dietary phosphorus restriction, oral administration of phosphorus binders, and dialysis are the main strategies to control hyperphosphatemia in patients with stage 5 chronic kidney disease. Aluminum hydroxide (AH) and calcium carbonate, the most commonly used phosphorus binders, have serious disadvantages, such as aluminum toxicity and hypercalcemia. Sevelamer hydrochloride (SH) is a relatively new nonabsorbed calcium- and aluminum-free phosphorus binder. The present study was designed to evaluate the efficacy of SH in the control of hyperphosphatemia and its effect, compared to AH, on serum lipid parameters in patients on continuous ambulatory peritoneal dialysis (CAPD). METHODS: 30 stable patients on CAPD were included in an open-label, randomized crossover study. After a 2-week phosphorus binder washout period, 15 patients (group I) were administered SH for 8 weeks and in the remaining patients (group II), AH was introduced (phase A). After a new 2-week washout period, patients crossed over to the alternate agent for another 8 weeks (phase B). RESULTS: There were similar reductions in serum phosphorus levels over the course of the study with both agents: by 1.18 +/- 0.07 mg/dL (0.38 +/- 0.03 mmol/L) with SH and by 1.25 +/- 0.15 mg/dL (0.40 +/- 0.05 mmol/L) with AH in phase A (p = NS), and by 1.35 +/- 0.25 mg/dL (0.43 +/- 0.08 mmol/L) with AH and by 1.23 +/- 0.80 mg/dL (0.39 +/- 0.25 mmol/L) with SH in phase B (p = NS). Moreover, SH administration was associated with a 10.5% +/- 9.4% and a 20.1% +/- 6.8% fall in total cholesterol (p < 0.05) and low-density Lipoprotein cholesterol (p < 0.001) in phase A, and 11.9% +/- 7.2% (p < 0.05) and 21.5% +/- 2.4% (p < 0.001), respectively, in phase B. In both phases of the study, AH administration was not followed by a significant change in serum lipid parameters. CONCLUSION: Sevelamer hydrochloride is a well-tolerated alternative to calcium- or aluminum-containing phosphorus binder in the control of serum phosphorus in CAPD patients. Furthermore, SH improves the lipid profile in these patients.

Protective effect of urate oxidase on uric acid induced-monocyte apoptosis.

Uremic patients have a higher risk of infection and malignancy than normal subjects. Previous studies have deomonstrated that monocytes isolated from uremic patients display an increased apoptosis rate compared to normal subjects; furthermore uremic plasma can increase apoptosis rates on U937, a human monocytic cell line. In several pathological conditions, precipitation of uric acid crystals can lead to renal insufficiency or acute renal failure by different mechanisms. In recent studies uric acid has been shown to induce inflammatory response from monocytes and it has been suggested to be involved in cell dysfunction. Rasburicase is a new recombinant urate oxidase developed to prevent and treat hyperuricaemia in patients with cancer or renal failure; it degrades uric acid to allantoin, a less toxic and more soluble product. In the present study, we aimed at determining whether uric acid may be a factor affecting U937 apoptosis, and whether urate oxidase may reduces or even prevent uric acid induced cell apoptosis. Hoechst staining and internucleosome ledder fragmentation of DNA showed that uric acid increased the percentage of apoptotic cells comparing to the control and that when the U937 cells were incubated with uric acid and urate oxidase the percentage of apoptosis significantly decreased (from 43+/-7% to 19+/- 3%, p<0.05). Also, the activity of caspase-8 and caspase-3 showed the same trend (caspase 3: from 2.7+/-0.53 to 1.6+/-0.42; caspase-8: from 2.2+/-0.43 to 1.3+/-0.57). A reduction of intracellular reduced glutathione (GSH) concentration was found in uric acid treated cells while the addition of urate oxidase in the uric acid incubated cells decreased the GSH extrusion. The concentration of TNF-alpha was increased in the sample incubated with uric acid comparing to the control. Uric acid is an inducer of apoptosis on U937 cell line, and therefore it may be a component of the mosaic of uremic toxins both in acute and chronic renal disease. We can hypothesize that uric acid might be directly involved in the apoptotic process trough the activation of both death receptor and mitochondrial-mediated pathways. We have, also, demonstrated that urate oxidase is able to prevent at least in part, the effect of uric acid on U937 apoptosis. This effect might be a result of different mechanisms of action.

Rasburicase therapy in acute hyperuricemia and renal dysfunction.

Neoplastic disorders may be complicated by acute renal failure (ARF). Different tumors may cause ARF: solid tumors involving the kidney, solid tumors not of hematological origin and not primarily involving the kidney or, more frequently, rapidly developing hematological tumors. The pathogenesis of ARF is different depending on the type of cancer, but the most frequent clinical feature is the acute tumor lysis syndrome, characterized by hyperuricemia, hyperphosphatemia, hyperkalemia, hypocalcemia and acute, frequently oliguric, ARF. The presence of a neoplastic disorder and associated acute illness may sometimes lead to the presence of immunodysfunction, septic complications and multiple organ dysfunction. In these settings patients develop systemic inflammation and diffuse endothelial damage, related to different mediators. Among these substances, in cancer patients, high circulating levels of uric acid are a common finding. Hyperuricemia is caused by the increase of purine metabolism, which is result of the increased cellular turnover or the aggressive cancer chemotherapy regimens that worsen cell lysis and release of purine metabolites. Even if hyperuricemia is not the first insult to the kidney, its development might represent a concomitant factor aggravating other previous or simultaneous insults. The most efficient therapy for lowering uric acid is rasburicase, a recombinant form of urate oxidase, a nonhuman proteolytic enzyme that oxidizes uric acid to allantoin. It is efficacious in reducing serum uric acid levels with associated diuresis more effectively and much faster than allopurinol, and to correct renal dysfunction more rapidly than allopurinol.