The effect of mycophenolate mofetil on podocytes in nephrotoxic serum nephritis.

Mycophenolate mofetil (MMF) is applied in proteinuric kidney diseases, but the exact mechanism of its effect on podocytes is still unknown. Our previous in vitro experiments suggested that MMF can ameliorate podocyte damage via restoration of the Ca2+-actin cytoskeleton axis. The goal of this study was to characterize podocyte biology during MMF treatment in nephrotoxic serum (NTS) nephritis (NTN). NTN was induced in three-week old wild-type mice. On day 3, half of the mice were treated with MMF (100 mg/kgBW/d p.o.) for one week. On day 10, we performed proteomic analysis of glomeruli as well as super-resolution imaging of the slit diaphragm. For multiphoton imaging of Ca2+ concentration ([Ca2+]i), the experimental design was repeated in mice expressing podocyte-specific Ca2+ sensor. MMF ameliorated the proteinuria and crescent formation induced by NTS. We identified significant changes in the abundance of proteins involved in Ca2+ signaling and actin cytoskeleton regulation, which was further confirmed by direct [Ca2+]i imaging in podocytes showing decreased Ca2+ levels after MMF treatment. This was associated with a tendency to restoration of podocyte foot process structure. Here, we provide evidence that MPA has a substantial direct effect on podocytes. MMF contributes to improvement of [Ca2+]i and amelioration of the disorganized actin cytoskeleton in podocytes. These data extend the knowledge of direct effects of immunosuppressants on podocytes that may contribute to a more effective treatment of proteinuric glomerulopathies with the least possible side effects.

Strong hypoxia reduces leptin synthesis in purified primary human trophoblasts.

INTRODUCTION: Oxygen availability severely affects placental function. During placental hypoxia, stabilization of hypoxia inducible factors (HIFs) affects transcription, and leptin gene expression concomitantly increases in vivo and in vitro. However, a causal relationship is uncertain. METHODS: We investigated the effect of oxygen availability on HIF-1 alpha (HIF1A) and leptin regulation in primary human trophoblasts isolated from six normal term placentae cultured at 0.1%, 1%, 3%, and 8% oxygen for 6 h, 24 h and 48 h. Gene expressions of leptin (LEP), leptin receptors (LEPR), HIF1A, insulin receptor (INSR) and further genes relevant in hypoxia (VEGFA, EPO, NOS2) or apoptosis (BCL2, BAX, Tp53) were examined. Leptin, HIF1A, INSR, phospho-AKT/AKT (insulin receptor signaling), caspase 3 and cleaved caspase 3 (apoptosis) proteins were measured. RESULTS: A hypoxic reaction with stabilization of HIF1A protein as well as up-regulation of HIF1A and VEGFA gene expressions, but without any hint for apoptosis, was present at 0.1% and 1% oxygen. However, leptin protein concentration (cell supernatants) peaked at 8% oxygen (normoxia) and was significantly reduced at 0.1% oxygen. There was no significant correlation between leptin and HIF1A, neither on the gene nor on the protein level. DISCUSSION: Elevated leptin gene expression in hypoxic placentas may not originate from trophoblasts, but from other placental cells, or from interaction of trophoblasts with other cells. Not only fetal hyperleptinemia, but also fetal hypoleptinemia under hypoxic conditions is conceivable. Strategies to prevent leptin dysregulation during pregnancy should be elucidated to protect the offspring from fetal programming of leptin resistance and adiposity in later life.

Considering laparoscopic salvage options--is pre-emptive omentectomy necessary in paediatric peritoneal patients?

BACKGROUND: In paediatric peritoneal dialysis patients, pre-emptive omentectomy is discussed controversially and literature provides only little data concerning this issue. Our aim was to evaluate the rate of omentum-majus-related problems in our patients, in whom omentectomy was generally not performed. Furthermore, we were interested in the success rates of laparoscopic adhesiolysis. PATIENTS AND METHODS: Between 09/2006 and 03/2008, we regularly saw 18 peritoneal dialysis patients in whom we retrospectively analysed medical records to determine the rate of catheter-related complications. In addition, we evaluated the success rates of laparoscopic adhesiolysis. RESULTS: During 355 dialysis months in 18 patients, we observed 7 omentum-majus-related obstructions in 6 patients (1/50.7 PM). The median age of the patients affected was 9 years, median filling volume at the time of the obstruction was 671 ml/m (2). Laparoscopic adhesiolysis was successful in 4 out of 7 episodes. In 3 cases, the catheter lumen was plugged by necrotic portions of the omentum and the catheters had to be replaced. CONCLUSION: Our data confirm omentum-majus-related catheter obstruction as a major cause of catheter dysfunction. However, in comparison to literature, it remains unclear to which extent omentectomy can reduce the incidence of catheter obstruction in general (including e. g. obstruction due to coagulation). Thus, the decision to perform an omentectomy should be taken individually after careful consideration. In case of omentum-majus-associated obstruction, early but not late laparoscopic intervention proved to be a successful, minimally invasive technique to restore catheter function.