Faculty Bibliography

BACKGROUND:The purpose of this study was to test the hypothesis that decreased dietary intake of Vitamin D contributes to Vitamin D deficiency in end-stage renal disease (ESRD) patients on hemodialysis (HD). METHODS:We performed a cross-sectional study of 58 hemodialysis outpatients from two Mount Sinai Medical Center (MSMC)-affiliated outpatient HD units in New York City and 648 outpatients at MSMC with CKD stages I-IV. Serum 25(OH)D concentrations were measured from August 2010 to July of 2011 in recruited hemodialysis patients (n=58) and linked with results of dietary and lifestyle surveys. The Mount Sinai Data Warehouse (electronic medical record) was used to capture 25(OH) Vitamin D levels for outpatients with CKD stages I-IV who had Vitamin D testing during the same time period. RESULTS:The prevalence of Vitamin D insufficiency/deficiency in the HD cohort was 96.6%. Mean (SD) and median (IQR) 25(OH)D concentrations were 15.65 (6.82) and 13.55 (10.15) ng/mL, respectively. Dietary surveys showed a median weekly Vitamin D intake of 1044 IU (IQR=808, vs. a recommended weekly allowance of 4200 IU) and specific avoidance of foods containing both Vitamin D and phosphorus. In contrast, mean and median 25(OH)D concentrations in patients with CKD stages I-IV were 25.66 (13.44) and 23.60 (15.48) ng/mL (p<0.001 vs. HD patients). CONCLUSIONS:Vitamin D deficiency is more prevalent in HD patients than in pre-dialysis patients with CKD and is associated with decreased dietary intake of Vitamin D. Dialysis restrictions imposed to reduce dietary phosphorus intake likely contributes to the development of hypovitaminosis D in ESRD patients.

BACKGROUND:Memory T-cells are mediators of transplant injury, and no therapy is known to prevent the development of cross-reactive memory alloimmunity. Activated vitamin D is immunomodulatory, and vitamin D deficiency, common in hemodialysis patients awaiting transplantation, is associated with a heightened alloimmune response. Thus, we tested the hypothesis that vitamin D3 supplementation would prevent alloreactive T-cell memory formation in vitamin D-deficient hemodialysis patients. METHODS AND FINDINGS/RESULTS:We performed a 12-month single-center pilot randomized, controlled trial of 50,000 IU/week of cholecalciferol (D3) versus no supplementation in 96 hemodialysis patients with serum 25(OH)D<25 ng/mL, measuring effects on serum 25(OH)D and phenotypic and functional properties of T-cells. Participants were randomized 2:1 to active treatment versus control. D3 supplementation increased serum 25(OH)D at 6 weeks (13.5 [11.2] ng/mL to 42.5 [18.5] ng/mL, p<0.001) and for the duration of the study. No episodes of sustained hypercalcemia occurred in either group. Results of IFNγ ELISPOT-based panel of reactive T-cell assays (PRT), quantifying alloreactive memory, demonstrated greater increases in the controls over 1 year compared to the treatment group (delta PRT in treatment 104.8+/-330.8 vs 252.9+/-431.3 in control), but these changes in PRT between groups did not reach statistical significance (p = 0.25). CONCLUSIONS:D3 supplements are safe, effective at treating vitamin D deficiency, and may prevent time-dependent increases in T-cell alloimmunity in hemodialysis patients, but their effects on alloimmunity need to be confirmed in larger studies. These findings support the routine supplementation of vitamin D-deficient transplant candidates on hemodialysis and highlight the need for large-scale prospective studies of vitamin D supplementation in transplant candidates and recipients. TRIAL REGISTRATION/BACKGROUND:Clinicaltrials.gov NCT01175798.

Acute graft-versus-host disease (GvHD) is a serious complication of allogeneic hematopoietic cell transplantation (allo-HCT) that results from donor allogeneic T cell attack on host tissues. Based on previous work implicating immune cell-derived C3a and C5a as regulators of T cell immunity, we examined the effects of locally produced C3a and C5a on murine T cell-mediated GvHD. We found that total body irradiation, a conditioning regimen required to permit engraftment of allo-HCT, caused upregulation and activation of alternative pathway complement components by recipient APCs. Allo-HCT with decay accelerating factor-null (Daf1(-/-)) host BM and Daf1(-/-) donor lymphocytes led to exacerbated GvHD outcome and resulted in splenic and organ-infiltrating T cell expansion. T cells deficient in C3a receptor (C3aR) and/or C5a receptor (C5aR) responded weakly in allogeneic hosts and exhibited limited ability to induce GvHD. Using a clinically relevant treatment strategy, we showed that pharmacological C5aR blockade reduced GvHD morbidity. Our data mechanistically link APC-derived complement to T cell-mediated GvHD and support complement inhibition as a therapeutic strategy for GvHD in humans.

Brain-derived neurotrophic factor (BDNF) regulates neuronal differentiation, synaptic plasticity, and morphology, and modest changes in BDNF levels results in complex behavioral phenotypes. BDNF levels and intracellular localization in neurons are regulated by multiple mechanisms, including use of distinct promoters, mRNA and protein transport, and regulated cleavage of proBDNF to mature BDNF. Sortilin is an intracellular chaperone that binds to the prodomain of BDNF to traffic it to the regulated secretory pathway. However, sortilin binds to numerous ligands and plays a major role in mannose 6-phosphate receptor-independent transport of lysosomal hydrolases utilizing motifs in the intracellular domain that mediate trafficking from the Golgi and late endosomes. Sortilin is modified by ectodomain shedding, although the biological implications of this are not known. Here we demonstrate that ADAM10 is the preferred protease to cleave sortilin in the extracellular stalk region, to release the ligand binding sortilin ectodomain from the transmembrane and cytoplasmic domains. We identify sortilin shedding at the cell surface and in an intracellular compartment. Both sortilin and BDNF are trafficked to and degraded by the lysosome in neurons, and this is dependent upon the sortilin cytoplasmic tail. Indeed, expression of the sortilin ectodomain, which corresponds to the domain released after shedding, impairs lysosomal targeting and degradation of BDNF. These findings characterize the regulation of sortilin shedding and identify a novel mechanism by which sortilin ectodomain shedding acts as a regulatory switch for delivery of BDNF to the secretory pathway or to the lysosome, thus modulating the bioavailability of endogenous BDNF.

BACKGROUND:Patients with diffuse large B-cell lymphoma (DLBCL) who are not cured by initial therapy sometimes experience disease-free survival after autologous stem cell transplantation. Chemotherapy responsiveness before transplantation is a major predictor of outcome. Patients not responding to second-line regimens may receive third-line therapy in the hopes of achieving response, but outcome data are limited. PATIENTS AND METHODS/METHODS:We identified patients with relapsed or refractory DLBCL at Weill Cornell Medical Center for whom data on responses to second-line chemotherapy were available. RESULTS:A total of 74 patients with relapsed or refractory DLBCL who underwent second-line chemotherapy between 1996 and 2007 were identified. Of these patients, 27 (36%) did not respond. The median overall survival of nonresponding patients was 4 months, and only 1 patient (4%) survived for 1 year. The choice of third-line aggressive chemotherapy instead of less intensive approaches did not confer a survival benefit. CONCLUSION/CONCLUSIONS:Our data demonstrate that patients with recurrent DLBCL not responding to second-line chemotherapy demonstrate dismal outcomes. Trials of novel regimens should be prioritized as management strategies for these patients. Our data provide an important benchmark in the evaluation of the potential clinical value of such approaches.