Posttransplant prophylactic intravenous immunoglobulin in kidney transplant patients at high immunological risk: a pilot study

The effects of posttransplant prophylactic intravenous immunoglobulin (IVIg) were investigated in renal transplant recipients at high immunological risk. Thirty-eight deceased-donor kidney transplant recipients with previous positive complement-dependent cytotoxicity crossmatch (n=30), and/or donor-specific anti-HLA antibodies (n=14) were recruited. IVIg (2 g/kg) was administrated on days 0, 21, 42 and 63 with quadruple immunosuppression. Biopsy-proven acute cellular and humoral rejection rates at month 12 were 18% and 10%, respectively. Glomerulitis was observed in 31% and 60% of patients at months 3 and 12, respectively, while allograft glomerulopathy rose from 3% at month 3 to 28% at 12 months. Interstitial fibrosis/tubular atrophy increased from 18% at day 0 to 51% and 72% at months 3 and 12 (p<0.0001). GFR was 50 +/- 17 mL/min/1.73 m(2) and 48 +/- 17 mL/min/1.73 m(2) at 3 and 12 months. PRA decreased significantly after IVIg (class I: from 18 +/- 27% to 5 +/- 12%, p<0.01; class II: from 25 +/- 30% to 7 +/- 16%, p<0.001). Patient and graft survival were 97% and 95%, respectively and no graft was lost due to rejection (mean follow-up 25 months). In conclusion, prophylactic IVIg in high-immunological risk patients is associated with good one-year outcomes, with adequate GFR and a profound decrease in PRA level, but a significant increase in allograft nephropathy.

Role of P-glycoprotein in cyclosporine cytotoxicity in the cyclosporine-sirolimus interaction

Cyclosporine nephrotoxicity remains a major side effect in solid organ transplantation, and can be exacerbated by concomitant administration of sirolimus. Cyclosporine and sirolimus are P-glycoprotein (Pgp) substrates. We hypothesized that the Pgp activity level may affect cyclosporine cytotoxicity by interfering with the ability of Pgp to remove cyclosporine from within tubular cells, and that an interaction between cyclosporine and sirolimus on Pgp function may explain the enhancement of cyclosporine nephrotoxicity by sirolimus. Cyclosporine cytotoxicity was evaluated in primary cultures of normal human renal epithelial cells (HRECs) by cell viability and cytotoxicity assays. Verapamil, quinine, PSC833, and PGP-4008 were used as Pgp inhibitors. Rhodamine-123 (R-123), a fluorescent substrate of Pgp, was used to assess Pgp-mediated transport. Cellular cyclosporine concentration was measured by high-performance liquid chromatography coupled to tandem mass spectrometry. Pgp expression and function were confirmed in HRECs and cyclosporine and sirolimus were shown to be Pgp inhibitors in this model. Verapamil-induced inhibition of Pgp led to a significant increase in cellular concentration of cyclosporine (P<0.05). Cyclosporine exerted a concentration-dependent cytotoxic effect on HRECs that was significantly increased by inhibition of Pgp activity. Sirolimus exerted an inhibitory effect on R-123 efflux in HRECs and increased cellular cyclosporine concentrations in a dose-dependent manner. These data demonstrate that Pgp plays a critical role in protecting renal epithelial cells from cyclosporine toxicity. The inhibitory effect of sirolimus on Pgp-mediated efflux and the cellular concentration of cyclosporine could explain the exacerbation of cyclosporine nephrotoxicity observed clinically.

[Rapamycine and mTOR inhibitors: from bench to bedside]

Rapamycin is a macrocyclic lactone with antifungal and antibiotic properties isolated from Streptomyces hygroscopicus during the 70's. Studies of rapamycin properties in yeast led to the discovery of TOR (Target Of Rapamycin) and its mammalian analogue, mTOR. mTOR is a central regulator of cell growth and proliferation in response to environmental stimuli such as growth factors or nutrients. There are two proteins that have been shown to be regulated by mTOR in response to a broad range of mitogenic stimuli. The translation regulation induced by mTOR is mediated by the p70 S6 kinase activation and the 4E-BP1 inhibition. Both proteins participate in the regulation of translation process and growth in cells stimulated by either mitogens or hormones. Antiproliferative effects of rapamycin and analogues have been demonstrated on numerous cell types, explaining the development of these drugs in clinical practice: as immunosuppressive drugs in solid organ transplantation, in oncology for the treatment of various types of cancer, and for the prevention of restenosis after coronary angioplasty. Rapamycin is a potent immunosuppressive drug used in solid organ transplantation for the prevention of acute rejection. In oncology these antiproliferative effects are evaluated in several types of cancers. Rapamycin is now widely used for coating stents to reduce post-stenting restenosis phenomenon after coronary angioplasty. Finally, rapamycin is now evaluated in various diseases characterized by proliferative disorders.

[Pharmacology of mycophenolate mofetil: recent data and clinical consequences]

New insights have been recently obtained about pharmacokinetic and pharmacodynamic characteristics of mycophénolate mofetil (MMF). One of the already described MPA metabolite, the acylglucuronide of MPA may be both active and responsible for some side-effects. Glucuronidation is mediated by at least two uridine diphosphate glucuronosyltransferase (UGT) forms, namely UGT1A8 and UGT1A10 whose variability could explain the inter- and intra-individual variability of MMF metabolism. MPA pharmacokinetic data in dialyzed patients or in patients with chronic renal failure are now available. After renal transplantation, MPA levels vary between immediate post-transplant period, at three months and at two years. The target enzyme is inosine monophosphate dehydrogenase (IMPDH). The genes of the two IMPDH isoforms have been cloned. The bicyclic ring system of MPA packs underneath the hypoxanthine ring of IMPDH, thereby trapping this covalent intermediate of the enzymatic reaction. After renal transplantation, a randomized trial has shown that clinical efficacy is correlated with MPA AUC but side effects are correlated with MMF dosage. When associated with cyclosporine, there is a significant decrease of MPA level. Better knowledge of MMF metabolism, of variability factors and target levels to reach in clinical practice should allow a better use of MMF.

[Mechanisms of essential arterial hypertension]

Despite a very simple haemodynamic equation of blood pressure (cardiac output multiplied by systemic vascular resistances), the precise mechanisms of essential hypertension are still unknown. Blood pressure level is determined by many physiologic systems which are submitted to complex interactions; the 2 main anomalies associated with hypertension are a primitive defect in renal excretion of sodium and an excessive rise of vascular tone. Hypertension is probably a polygenic disease, with several abnomalies in these systems interacting with a particular environment. Genetic data have recently reinforced this concept by demonstrating a link between hypertension and particular alleles of candidate genes in some population groups.

Mesalazine-induced lupus

We report a case of lupus induced by mesalazine therapy taken for over a year for Crohn's disease. The patient had polyarthritis, alopecia, lymphoneutropenia, antinuclear factors, anti-histone antibodies, anti-Sm and anti-RNP. Discontinuation of mesalazine was followed by rapid resolution of the joint manifestations, alopecia and lymphoneutropenia; the anti-histone antibodies fell to undetectable levels and the titers of the other auto-antibodies decreased gradually.

[Renal venous thrombosis: a forgotten complication of acute pyelonephritis]

BACKGROUND

Renal vein thrombosis, long recognized as a classical complication of acute pyelonephritis, has become exceptional since the advent of antibiotics.

CASE REPORT

An 85-year-old woman was hospitalized for acute Escherichia coli nephritis. Computed tomography with contrast agent injection was performed due to clinical improvement after an 8-day course of antibiotics and demonstrated purulent urine collection on an obstructive calicial stone as well as homolateral thrombosis of the renal vein. Duplex Doppler confirmed the diagnosis. Pulmonary embolism was evidenced by pulmonary scintigraphy. The clinical course was satisfactory after urine drainage and efficacious antibiotics.

CONCLUSION

Renal vein thrombosis remains a severe though uncommon complication of acute pyelonephritis. Computed tomography with iodine, contrast agent or duplex Doppler allows noninvasive diagnosis.