A profile of pro-inflammatory cytokine expression in human Delta-1-induced monocyte-derived Langerhans cell-like dendritic cells after stimulation with Toll-like receptor ligands

Monocyte-derived Langerhans cell-like dendritic cells （Mo-LCs） are involved in epidermal disorders such as psoriasis in murine models. However, the roles of Mo-LCs in the pathogenesis of psoriasis in humans remain unclear. Also, the contribution of notch ligand delta-like 1 （DLL-1）, expressed on keratinocytes, to Mo-LC functions requires clarification. Here, we established a new method of stimulating Mo-LCs derived from CD14＋ monocytes with immobilized human DLL-1 to generate induced Mo-LCs （DI（＋）Mo-LCs）. The DI（＋）Mo-LCs were compared to the dendritic cells derived from monocytes （Mo-DCs） cultured with interleukin-4 （IL-4） and granulocyte-macrophage colony-stimulating factor （GM-CSF）, and M1 macrophages （Mφ） derived from monocytes cultured with GM-CSF. The DI（＋）Mo-LCs were found to produce significant amounts of IL15, IL23A, and interferon-β （IFNB1） in response to the Toll-like receptor （TLR）3 agonist Polyinosinic-polycytidylic acid （Poly（I:C）） or TLR4 agonist lipopolysaccharide （LPS） despite their low expression of tumor necrosis factor （TNF）. In conclusion, we have established a new method to generate DI（＋）Mo-LCs. We have also discovered that DI（＋）Mo-LCs have a unique capacity for producing IL15 and IL23A, which are related to the pathogenesis of psoriasis. Our data contribute to a better understanding of the roles of Mo-LCs in epidermal defense and pathogenesis

CCR6+ MCAM+ Th17 Cell Numbers Increase in Patients with Psoriasis and Correlate with Disease Severity

Psoriasis is a chronic immune-mediated disease in which the interleukin (IL)-23/IL-17 axis plays a key role in the inflammatory cascade. We recently reported that co-expression of CCR6 and melanoma cell adhesion molecule (MCAM) in effector memory CD4 T cells (TEM) of peripheral blood might be a useful marker for T helper (Th) 17 cells. In this study, we monitored changes in TEM expressing CCR6 and MCAM using the Psoriasis Area and Severity Index (PASI) score during anti-tumor necrosis factor (TNF) therapy. We also studied CCR6+ MCAM+ Th17 cells histologically in skin biopsy samples from psoriasis patients. In psoriasis patients treated with anti-TNF therapy, the PASI score and the percentage of CCR6+ MCAM+ TEM cells in the blood changed almost in parallel. In immunohistochemical analyses, the proportions of IL-17+ T cells and MCAM+ T cells in the lesional skin of severely psoriatic patients were significantly higher than in mildly psoriatic patients (P<0.05), and the number of IL17+ T cells correlated with the PASI score (r=0.400, P<0.05). Taken together, these results indicate that CCR6+ MCAM+ Th17 cells in peripheral blood and lesional skin might play an important role in the pathology of psoriasis

Regulatory Effect of IL-4 on Early Th17 Differentiation from Naive T Cells into Stem Cell Memory Th17 Precursors via Modulation of CD31 and CCR6 Expression

Although antigen-specific T helper （Th） cells are developed from naive T cells, human Th17 cells are not derived from naive CD4+ T cells unlike murine cells. Therefore, the source of human Th17 cells has remained unresolved. In this study, we assessed the early differentiation pathway of human Th17 cells from CD31+ thymic naive T cells into stem cell memory CCR6+ Th17 precursors and the regulation of this process by cytokines. Peripheral blood mononuclear cells were isolated from healthy volunteers. We found that only CD31- CCR6+ naive type CD4+ T cells had the ability to produce IL-17A in response to Th17-inducing stimuli. A cell tracking assay using CD31+ CCR6- cells labeled with carboxyfluorescein diacetate succinimidyl ester revealed that CD31- CCR6+ Th17 precursors were derived from CD31+ CCR6- thymic naive T cells. CD31 is known to suppress IL-17 production by interfering with downstream T cell receptor （TCR） signaling molecules including Lck, which is essential for IL-17 production. The inactive form of Lck was much higher in CD31+ T cells than CD31- T cells after TCR stimulation. In experiments of cytokine-mediated modulation of Th17 cell differentiation, IL-4 suppressed the conversion of CD31+ CCR6- naive T cells into CD31- CCR6+ Th17 precursors by upregulating CD31 expression and suppressing CCR6 expression. In conclusion, CD31- CCR6+ Th17 precursors could be sourced from CD31+ CCR6- naive T cells, and IL-4 regulated the early Th17 differentiation. Our findings provide novel insights into the regulation of differentiation of naive CD4+ T cells into Th17 cells in humans. Furthermore, our results may provide hints for further elucidation of the differentiation process of Th17 cells and of the pathology of Th17 cell-related diseases

Transfer and Enzyme-Mediated Metabolism of Oxidized Phosphatidylcholine and Lysophosphatidylcholine between Low- and High-Density Lipoproteins

Oxidized low-density lipoprotein (oxLDL) and oxidized high-density lipoprotein (oxHDL), known as risk factors for cardiovascular disease, have been observed in plasma and atheromatous plaques. In a previous study, the content of oxidized phosphatidylcholine (oxPC) and lysophosphatidylcholine (lysoPC) species stayed constant in isolated in vivo oxLDL but increased in copper-induced oxLDL in vitro. In this study, we prepared synthetic deuterium-labeled 1-palmitoyl lysoPC and palmitoyl-glutaroyl PC (PGPC), a short chain-oxPC to elucidate the metabolic fate of oxPC and lysoPC in oxLDL in the presence of HDL. When LDL preloaded with d13-lysoPC was mixed with HDL, d13-lysoPC was recovered in both the LDL and HDL fractions equally. d13-LysoPC decreased by 50% after 4 h of incubation, while d13-PC increased in both fractions. Diacyl-PC production was abolished by an inhibitor of lecithin-cholesterol acyltransferase (LCAT). When d13-PGPC-preloaded LDL was incubated with HDL, d13-PGPC was transferred to HDL in a dose-dependent manner when both LCAT and lipoprotein-associated phospholipase A2 (Lp-PLA2) were inhibited. Lp-PLA2 in both HDL and LDL was responsible for the hydrolysis of d13-PGPC. These results suggest that short chain-oxPC and lysoPC can transfer between lipoproteins quickly and can be enzymatically converted from oxPC to lysoPC and from lysoPC to diacyl-PC in the presence of HDL