No abstract

study, spontaneous, long-term remission was observed in approximately 15% of patients. 4 In 2007, eculizumab (Soliris ®

In addition to the Trk tyrosine kinase receptors, neurotrophins also bind to a second receptor, p75, a member of the tumor necrosis factor receptor superfamily. Several signaling pathways have been implicated for p75 in the absence of Trk receptors, including induction of NF-B and c-Jun kinase activities and increased production of ceramide. However, to date, the mechanisms by which the p75 receptor initiates intracellular signal transduction have not been defined. Here we report a specific interaction between p75 and TRAF6 (tumor necrosis factor receptor-associated factor-6) after transient transfection in HEK293T cells. The interaction was ligand-dependent and maximal at 100 ng/ml of nerve growth factor (NGF). Other neurotrophins also promoted the association of TRAF6 with p75 but to a lesser extent. The binding of TRAF6 was localized to the juxtamembrane region of p75 by co-immunoprecipitation and Western blotting. To assess the functional significance of this interaction, we have tested responses in cultured Schwann cells that express p75 and TRAF6. An NGF-mediated increase in the nuclear localization of the p65 subunit of NF-B could be blocked by the introduction of a dominant negative form of TRAF6 in Schwann cells. These results indicate that TRAF6 can potentially function as a signal transducer for NGF actions through the p75 receptor.

Paroxysmal nocturnal hemoglobinuria (PNH) is a debilitating and life-threatening disease in which lysis of PNH red blood cells frequently manifests with chronic hemolysis, anemia, and thrombosis. Renal damage in PNH is associated with chronic hemosiderosis and/or microvascular thrombosis. We determined the incidence of renal dysfunction or damage, defined by stages of chronic kidney disease (CKD), in a large cohort of PNH patients and evaluated the safety and efficacy of the complement inhibitor eculizumab in altering its progression. Renal dysfunction or damage was observed in 65% of the study population at baseline with 21% of patients with later stage CKD or kidney failure (glomerular filtration rate [GFR] 60 ml/min/1.73 m 2 ; Stage 3, 4, or 5). Eculizumab treatment was safe and well-tolerated in patients with renal dysfunction or damage and resulted in the likelihood of improvement as defined as categorical reduction in CKD stage (P < 0.001) compared with baseline and to placebo (P 5 0.04). Improvement in renal function was more commonly seen in patients with baseline CKD Stages 1-2 (67.1% improvement, P < 0.001) although improvement was also observed in patients with CKD Stages 3-4 (P 5 0.05). Improvements occurred quickly and were sustained for at least 18 months of treatment. Patients categorized at CKD Stages 3-5 did not worsen during treatment with eculizumab. Overall, 40 (21%) of 195 patients who demonstrated renal dysfunction or damage at baseline were no longer classified as such after 18 months of treatment. Administration of eculizumab to patients with renal dysfunction or damage was well tolerated and was usually associated with clinical improvement. Am. J. Hematol. 85:553-559, 2010. V