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Nanomaterials interact with cells and modify their function and biology. Manufacturing this ability can provide tissue-engineering scaffolds with nanostructures able to influence tissue growth and performance. Carbon nanotube compatibility with biomolecules motivated ongoing interest in the development of biosensors and devices including such materials. More recently, carbon nanotubes have been applied in several areas of nerve tissue engineering to study cell behavior or to instruct the growth and organization of neural networks. To gather further knowledge on the true potential of future constructs, in particular to assess their immune-modulatory action, we evaluate carbon nanotubes interactions with human dendritic cells (DCs). DCs are professional antigen-presenting cells and their behavior can predict immune responses triggered by adhesion-dependent signaling. Here, we incorporate DC cultures to carbon nanotubes and we show by phenotype, microscopy, and transcriptional analysis that in vitro differentiated and activated DCs show when interfaced to carbon nanotubes a lower immunogenic profile.

Background: Pharmacological inhibitors of poly(ADP-ribose) polymerase-1 (PARP-1) are currently evaluated in clinical trials for various malignancies but, interestingly, also proved of remarkable efficacy in preclinical models of autoimmune disorders including experimental autoimmune encephalomyelitis (EAE)., Objectives: The objectives of the study were to determine molecular mechanisms underlying suppression of the encephalitogenic response by these drugs; likewise, whether clinically-relevant post-treatment paradigms with PARP-1 inhibitors could prevent EAE relapses., Methods: Adopted both in vitro techniques (bone marrow-derived cultured DC) as well as in vivo models of chronic or relapsing-remitting (RR) EAE., Results: We report that two structurally unrelated PARP-1 inhibitors negatively regulated NFκB activation, as well as maturation, cytokine production and APC function of cultured mouse bone marrow-derived dendritic cells (DCs). PARP-1 inhibitors also reduced the number and APC function of DCs migrating in the draining lymph nodes of ovalbumin-immunized mice. In C57Bl mice with chronic EAE or SJL mice with RR EAE, pharmacological inhibition of PARP-1 reduced CNS DC migration and demyelination as well as neurological impairment to an extent similar to that achieved with the potent immunosuppressant cyclosporine A. Remarkably, PARP-1 inhibitors injected after the first phase of disease reduced relapse incidence and severity, as well as the spinal cord number of autoreactive Th17 cells. Under this clinically-relevant treatment paradigm, PARP inhibitors also suppressed epitope spreading of the encephalitogenic response., Conclusions: Overall, data underscore the potential relevance of PARP-1 inhibitors to MS therapy and suppression of autoimmunity.

Immune synapse formation between dendritic cells (DCs) and T cells is one of the key events in immune reaction. In immunogenic synapses, the presence of fully mature DCs is mandatory; consequently, the modulation of DC maturation may promote tolerance and represents a valuable therapeutic approach in autoimmune diseases. In the field of cell therapy, bone marrow mesenchymal stem cells (MSCs) have been extensively studied for their immunoregulatory properties, such as inhibiting DC immunogenicity during in vitro differentiation and ameliorating in vivo models of autoimmune diseases (e.g., experimental allergic encephalomyelitis). MSCs seem to play different roles with regard to DCs, depending on cell concentration, mechanism of stimulation, and accompanying immune cells. The aim of this work was to elucidate the immunogenic effects of MSC/DC interactions during DC activation (LPS stimulation or Ag loading). Human monocyte-derived DCs, bone marrow-derived MSCs, and circulating lymphocytes obtained from healthy donors, as well as the laboratory-generated influenza virus hemagglutinin-derived peptide, aa 306-318 peptide-specific T cell line were used for this study. We demonstrate that MSCs mediate inhibition of DC function only upon cell-cell contact. Despite no modification observed in cell phenotype or cytokine production, MSC-treated DCs were unable to form active immune synapses; they retained endocytic activity and podosome-like structures, typical of immature DCs. The transcriptional program induced by MSC-DC direct interaction supports at the molecular pathway level the phenotypical features observed, indicating the genes involved into contact-induced rearrangement of DC cytoskeleton.

Azathioprine (Aza), 6-Mercaptopurine (6-MP) and 6-Thioguanine (6-TG) are thiopurine drugs widely used as immunosuppressants/anti-inflammatory agents in organ transplantation and chemotherapy. Aza is well tolerated and effective in modifying the course of MS. Here we investigated the action of 6-MP on human dendritic cells (DCs). We described for the first time that 6-MP impairs in vitro differentiation of DCs, has an inhibitory effect during DC activation processes inducing a functionally less immunogenic phenotype. Moreover, 6-MP significantly reduces DC IL-23 production and CCR7 expression, at the same time induces IL-10 augmentation. All these findings add a novel action mechanism in Aza immune modulation., (Copyright 2009 Elsevier B.V. All rights reserved.)

Background: The mechanisms by which human dendritic cells (DCs) activate a TH1-polarizing or TH2-polarizing program are still partially unclear., Objective: Study of the mechanisms responsible for the TH1/TH2-polarizing activity of human circulating myeloid DCs before and after ligation of their Toll-like receptors (TLRs)., Methods: IL-4 and IFN-gamma production by CD4+ T cells was assessed in cocultures with myeloid DCs before or after TLR triggering. Expression of Jagged-1 and Delta-4 Notch ligands and of GATA-3 and T-box expressed in T cells transcription factors was evaluated by real-time quantitative PCR. Signal transducer and activator of transcription 4 and 6 phosphorylation was assessed by flow cytometry. Knockdown of Jagged-1 or Delta-4 was performed by transfection of DCs with appropriate silencing mRNAs., Results: Myeloid immature DCs constitutively expressed Jagged-1, which induces in CD4+ T cells a TH2 polarization, as shown by Jagged-1 gene silencing. The TH2 polarization associated with high GATA-3/T-box expressed in T cells ratio and was at least partially dependent on the early induction of IL-4. Maturation of DCs by TLR ligation resulted in the reduction of Jagged-1 and upregulation of Delta-4, which was at least in part responsible for the polarization of CD4+ T cells to the TH1 phenotype., Conclusion: CD4+ T-cell responses are usually characterized by a prevalent TH2 phenotype unless TLRs are triggered on DCs by microbial components.

Poly(ADP-ribose) (PAR) polymerase (PARP)-1 is a nuclear enzyme regulating protein that functions by targeting PAR chains. Besides its classic role in DNA repair, PARP-1 is emerging as a key transcriptional regulator in different cell types including the immune ones. In this study, we investigated the role of PARP-1 in human dendritic cell (DC) function. We report that both PARP-1 mRNA and protein levels significantly increased during in vitro DC differentiation from monocytes. Of note, inhibitors of PARP-1 such as phenanthridinone and thieno[2,3-c]isoquinolin-5-one reduced expression of CD86 and CD83 in a concentration-dependent manner, having no effects on expression of CD80 and HLA-DR in mature DCs. In the same cultures, PARP-1 inhibitors also reduced production of IL-12 and IL-10. Addition of exogenous IL-12 to the culture medium partially restored CD86 expression in DCs exposed to PARP-1 inhibitors. In line with the role of PAR formation in NF-kappaB-dependent transactivation, we also report that phenanthridinone and thieno[2,3-c]isoquinolin-5-one impaired NF-kappaB and AP-1 subunit DNA binding activity in cellular extract of activated DCs. Finally, we show that PARP-1 inhibitors reduced the T cell allostimulatory activity of mature DCs, and that this reduction was prevented when DCs matured in the presence of PARP-1 inhibitors plus IL-12. Of note, nonproliferating T cells exposed to PARP-1 inhibitor-challenged DCs could undergo efficient proliferation when exposed to a subsequent activation stimulus such as anti-CD3 plus anti-CD-28. Together, data provide evidence for a key role of PARP-1 and poly ADP-ribosylation in DC immunocompetence and underscore the relevance of PARP-1 inhibitors to treatment of immune disorders.