Synthetic retinoid Am80 ameliorates chronic graft-versus-host disease by down-regulating Th1 and Th17.

Chronic GVHD (cGVHD) is a main cause of late death and morbidity after allogeneic hematopoietic cell transplantation, but its pathogenesis remains unclear. We investigated the roles of Th subsets in cGVHD with the use of a well-defined mouse model of cGVHD. In this model, development of cGVHD was associated with up-regulated Th1, Th2, and Th17 responses. Th1 and Th2 responses were up-regulated early after BM transplantation, followed by a subsequent up-regulation of Th17 cells. Significantly greater numbers of Th17 cells were infiltrated in the lung and liver from allogeneic recipients than those from syngeneic recipients. We then evaluated the roles of Th1 and Th17 in cGVHD with the use of IFN-γ-deficient and IL-17-deficient mice as donors. Infusion of IFN-γ(-/-) or IL-17(-/-) T cells attenuated cGVHD in the skin and salivary glands. Am80, a potent synthetic retinoid, regulated both Th1 and Th17 responses as well as TGF-β expression in the skin, resulting in an attenuation of cutaneous cGVHD. These results suggest that Th1 and Th17 contribute to the development of cGVHD and that targeting Th1 and Th17 may therefore represent a promising therapeutic strategy for preventing and treating cGVHD

Comprehensive structure-function characterization of DNMT3B and DNMT3A reveals distinctive de novo DNA methylation mechanisms

Mammalian DNA methylation patterns are established by two de novo DNA methyltransferases DNMT3A and DNMT3B, which exhibit both redundant and distinctive methylation activities. However, the related molecular basis remains undetermined. Through comprehensive structural, enzymology and cellular characterization of DNMT3A and DNMT3B, we here report a multi-layered substraterecognition mechanism underpinning their divergent genomic methylation activities. A hydrogen bond in the catalytic loop of DNMT3B causes a lower CpG specificity than DNMT3A, while the interplay of target recognition domain and homodimeric interface fine-tunes the distinct target selection between the two enzymes, with Lysine 777 of DNMT3B acting as a unique sensor of the +1 flanking base. The divergent substrate preference between DNMT3A and DNMT3B provides an explanation for site-specific epigenomic alterations seen in ICF syndrome with DNMT3B mutations. Together, this study reveals crucial and distinctive substrate-readout mechanisms of the two DNMT3 enzymes, implicative of their differential roles during development and pathogenesis

Reciprocal Expression of Enteric Antimicrobial Proteins in Intestinal Graft-Versus-Host Disease

We recently demonstrated that expression of alpha-defensins, the major antimicrobial peptides produced by Paneth cells, was severely suppressed in mice with graft-versus-host disease (GVHD). In this study, we found that antibacterial lectin, regenerating islet-derived III gamma (RegIII gamma) was upregulated in villous enterocytes, thus demonstrating the reciprocal control of enteric antimicrobial proteins in GVHD. Upregulation of RegIII gamma was mediated by a mechanism independent upon radiation-induced intestinal tract damage. MyD88-mediated signaling in intestinal epithelium was required for RegIII gamma upregulation in GVHD and antibiotic therapy downregulated RegIII gamma expression. These results suggest that MyD88-mediated sensing of the intestinal microbes disregulated in GVHD induces RegIII gamma upregulation in GVHD and argue a role for RegIII gamma in the pathogenesis of GVHD. (C) 2013 American Society for Blood and Marrow Transplantation

α-Mannan induces Th17-mediated pulmonary graft-versus-host disease in mice

Allogeneic hematopoietic stem cell transplantation (HSCT) is a curative therapy for various hematopoietic disorders. Graft-versus-host disease (GVHD) and infections are the major obstacles of HSCT, and their close relationship has been suggested. Although roles of bacterial and viral infections in the pathophysiology of GVHD are well described, impacts of fungal infection on GVHD remain to be elucidated. In mouse models of GVHD, injection of a-mannan (Mn), a major component of fungal cell wall, or heat-killed Candida albicans exacerbated GVHD, particularly in the lung. Mn-induced donor T-cell polarization toward Th17 and lung-specific chemokine environment in GVHD led to accumulation of Th17 cells in the lung. The detrimental effects of Mn on GVHD depended on donor IL-17A production and host C-type lectin receptor Dectin-2. These results suggest a previously unrecognized link between pulmonary GVHD and fungal infection after allogeneic HSCT