Mechanism of chimeric vaccine stimulation of indoleamine 2,3-dioxygenase biosynthesis in human dendritic cells is independent of TGF-β signaling

Lipopolysaccharide-Induced Immunological Tolerance in Monocyte-Derived Dendritic Cells

Bacterial lipopolysaccharides (LPS), also referred to as endotoxins, are major outer surface membrane components present on almost all Gram-negative bacteria and are major determinants of sepsis-related clinical complications including septic shock. LPS acts as a strong stimulator of innate or natural immunity in a wide variety of eukaryotic species ranging from insects to humans including specific effects on the adaptive immune system. However, following immune stimulation, lipopolysaccharide can induce tolerance which is an essential immune-homeostatic response that prevents overactivation of the inflammatory response. The tolerance induced by LPS is a state of reduced immune responsiveness due to persistent and repeated challenges, resulting in decreased expression of pro-inflammatory modulators and up-regulation of antimicrobials and other mediators that promote a reduction of inflammation. The presence of environmental-derived LPS may play a key role in decreasing autoimmune diseases and gut tolerance to the plethora of ingested antigens. The use of LPS may be an important immune adjuvant as demonstrated by the promotion of IDO1 increase when present in the fusion protein complex of CTB-INS (a chimera of the cholera toxin B subunit linked to proinsulin) that inhibits human monocyte-derived DC (moDC) activation, which may act through an IDO1-dependent pathway. The resultant state of DC tolerance can be further enhanced by the presence of residual E. coli lipopolysaccharide (LPS) which is almost always present in partially purified CTB-INS preparations. The approach to using an adjuvant with an autoantigen in immunotherapy promises effective treatment for devastating tissue-specific autoimmune diseases like multiple sclerosis (MS) and type 1 diabetes (T1D).

Contradictory roles of lipid metabolism in immune response within the tumor microenvironment

Complex interactions between the immune system and tumor cells exist throughout the initiation and development of cancer. Although the immune system eliminates malignantly transformed cells in the early stage, surviving tumor cells evade host immune defense through various methods and even reprogram the anti-tumor immune response to a pro-tumor phenotype to obtain unlimited growth and metastasis. The high proliferation rate of tumor cells increases the demand for local nutrients and oxygen. Poorly organized vessels can barely satisfy this requirement, which results in an acidic, hypoxic, and glucose-deficient tumor microenvironment. As a result, lipids in the tumor microenvironment are activated and utilized as a primary source of energy and critical regulators in both tumor cells and related immune cells. However, the exact role of lipid metabolism reprogramming in tumor immune response remains unclear. A comprehensive understanding of lipid metabolism dysfunction in the tumor microenvironment and its dual effects on the immune response is critical for mapping the detailed landscape of tumor immunology and developing specific treatments for cancer patients. In this review, we have focused on the dysregulation of lipid metabolism in the tumor microenvironment and have discussed its contradictory roles in the tumor immune response. In addition, we have summarized the current therapeutic strategies targeting lipid metabolism in tumor immunotherapy. This review provides a comprehensive summary of lipid metabolism in the tumor immune response.

ALK5 i II Accelerates Induction of Adipose-Derived Stem Cells toward Schwann Cells through a Non-Smad Signaling Pathway

Schwann cells (SCs) are likely to be a vital component of cell-based therapies for nerve regeneration. There are various methods for inducing SC-like cells (SCLCs) from adipose-derived stem cells (ADSCs), but their phenotypic and functional characteristics remain unsatisfactory. Here, we report a novel efficient procedure to induce SCLCs by culturing ADSCs with ALK5 inhibitor (ALK5 i) II, a specific inhibitor of activin-like kinase 5 (ALK5) (transforming growth factor-β receptor 1 (TGFβR1)) that is also known as Repsox. The resultant cells that we named "modified SCLCs (mSCLCs)" expressed SC-specific genes more strongly than conventional SCLCs (cSCLCs) and displayed a neurosupportive capacity in vitro, similarly to genuine SCs. Regarding the mechanism of the mSCLC induction by ALK5 i II, knockdown of Smad2 and Smad3, key proteins in the TGFβ/Smad signaling pathway, did not induce SC markers. Meanwhile, expression of multipotent stem cell markers such as Sex-determining region Y- (SRY-) box 2 (Sox2) was upregulated during induction. These findings imply that ALK5 i II exerts its effect via the non-Smad pathway and following upregulation of undifferentiated cell-related genes such as Sox2. The procedure described here results in highly efficient induction of ADSCs into transgene-free and highly functional SCLCs. This approach might be applicable to regeneration therapy for peripheral nerve injury.

LPS enhances CTB-INSULIN induction of IDO1 and IL-10 synthesis in human dendritic cells

Autoantigen-specific immunotherapy promises effective treatment for devastating tissue specific autoimmune diseases like multiple sclerosis (MS) and type 1 diabetes (T1D). Because activated dendritic cells (DCs) stimulate the differentiation of autoreactive T cells involved in the initiation of autoimmunity, blocking the activation of DCs may be an effective strategy for inhibiting tissue specific autoimmunity. Following this approach, immature DCs were shown to remain inactive after treatment with chimeric fusion proteins composed of the cholera toxin B subunit adjuvant linked to autoantigens like proinsulin (CTB-INS). Mass spectrometer analysis of human DCs treated with CTB-INS suggest that upregulation of the tryptophan catabolic enzyme indoleamine 2, 3-dioxygenase (IDO1) is responsible for inhibiting DC activation thereby resulting in a state of immunological tolerance within the DC. Here we show that the fusion protein CTB-INS inhibits human monocyte derived DC (moDC) activation through stimulation of IDO1 biosynthesis and that the resultant state of DC tolerance can be further enhanced by the presence of residual E. coli lipopolysaccharide (LPS) present in partially purified CTB-INS preparations. Additional experiments showed that LPS enhancement of DC tolerance was dependent upon stimulation of IDO1 biosynthesis. LPS stimulation of increased levels of IDO1 in the DC resulted in increased secretion of kynurenines, tryptophan degradation products known to suppress DC mediated pro-inflammatory T cell differentiation and to stimulate the proliferation of regulatory T cells (Tregs). Further, the presence of LPS in CTB-INS treated DCs stimulated the biosynthesis of costimulatory factors CD80 and CD86 but failed to upregulate maturation factor CD83, suggesting CTB-INS treated DCs may be maintained in a state of semi-activation. While treatment of moDCs with increasing amounts of LPS free CTB-INS was shown to increase DC secretion of the anti-inflammatory cytokine IL-10, the presence of residual LPS in partially purified CTB-INS preparations dramatically increased IL-10 secretion, suggesting that CTB-INS may enhance DC mediated immunological tolerance by stimulating the proliferation of anti-inflammatory T cells. While the extraction of LPS from bacterial generated CTB-INS may remove additional unknown factors that may contribute to the regulation of IDO1 levels, together, our experimental data suggest that LPS stimulates the ability of CTB-INS to induce IDO1 and IL-10 important factors required for establishment of a state of functional immunological tolerance in human DCs. Regulation of the ratio of LPS to CTB-INS may prove to be an effective method for optimization of readily available "off the shelf" CTB-INS mediated immune-therapy for tissue specific autoimmune diseases including type 1 diabetes.