cGAS restricts colon cancer development by protecting intestinal barrier integrity.

The DNA-sensing enzyme cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS) regulates inflammation and immune defense against pathogens and malignant cells. Although cGAS has been shown to exert antitumor effects in several mouse models harboring transplanted tumor cell lines, its role in tumors arising from endogenous tissues remains unknown. Here, we show that deletion of cGAS in mice exacerbated chemical-induced colitis and colitis-associated colon cancer (CAC). Interestingly, mice lacking cGAS were more susceptible to CAC than those lacking stimulator of interferon genes (STING) or type I interferon receptor under the same conditions. cGAS but not STING is highly expressed in intestinal stem cells. cGAS deficiency led to intestinal stem cell loss and compromised intestinal barrier integrity upon dextran sodium sulfate-induced acute injury. Loss of cGAS exacerbated inflammation, led to activation of STAT3, and accelerated proliferation of intestinal epithelial cells during CAC development. Mice lacking cGAS also accumulated myeloid-derived suppressive cells within the tumor, displayed enhanced Th17 differentiation, but reduced interleukin (IL)-10 production. These results indicate that cGAS plays an important role in controlling CAC development by defending the integrity of the intestinal mucosa.

Protein Arginine Methyltransferase 5 in T Lymphocyte Biology.

Protein arginine methyltransferase 5 (PRMT5) is the major methyltransferase (MT) catalyzing symmetric dimethylation (SDM). PRMT5 regulates developmental, homeostatic and disease processes in vertebrates and invertebrates, and a carcinogenic role has been observed in mammals. Recently, tools generated for PRMT5 loss of function have allowed researchers to demonstrate essential roles for PRMT5 in mouse and human lymphocyte biology. PRMT5 modulates CD4+ and CD8+ T cell development in the thymus, peripheral homeostasis, and differentiation into CD4+ helper T lymphocyte (Th)17 cell phenotypes. Here, we provide a timely review of the milestones leading to our current understanding of PRMT5 in T cell biology, discuss current tools to modify PRMT5 expression/activity, and highlight mechanistic pathways.

Regulation of Recombinase Rag-1 Expression by Female Sex Steroids in Treg and Th17 Lymphocytes: Role of Oncostatin M.

The effect of estradiol (E2), progesterone (P4), and oncostatin M (OSM) on the differentiation of CD4+ T cells to T regulatory (Treg) lymphocytes and T helpers 17 (Th17) was investigated. The possibility of revision of the T cell receptor in these subpopulations by evaluating the expression of RAG-1 recombinase was also studied. E2 at concentrations characteristic of pregnancy trimester I, but no P4 or OSM, increased the Treg level. Combination of sex steroids with OSM increased the percent of CD4+FOXP3+ cells and enhanced RAG-1 expression in these cells, thus promoting the development of immune tolerance during pregnancy. In the study of Th17, such effect of the hormones and OSM was not detected.

Improvement of the resistance against early Mycobacterium tuberculosis-infection in the absence of PI3Kγ enzyme is associated with increase of CD4+IL-17+ cells and neutrophils.

Given the impossibility to study the lung immune response during Mycobacterium tuberculosis-latent infection, and consequently, the mechanisms that control the bacterial load, it is reasonable to determine the activation of local immunity in the early phase of the infection. The phosphatidylinositol-3-kinase gamma enzyme (PI3Kγ) is involved in the leukocyte recruitment, phagocytosis and cellular differentiation, and therefore, it is considered a promising target for the development of immunotherapies for chronic inflammatory diseases. Mice genetically deficient in PI3Kγ (PI3Kγ-/-) or WT (Wild Type) were evaluated 15 days post-infection. The enzyme deficiency improved the resistance against infection, increased the frequency of CD4+IL-17+ cells, the production of IL-17 as well as the gene and protein expression of molecules associated with Th17 cell differentiation and neutrophil recruitment. Our findings show, for the first time, the participation of the PI3Kγ in vivo in the M. tuberculosis-infection, and suggest an association of Th17 cells with protection in the early phase of tuberculosis.

An Overview of l-Amino Acid Oxidase Functions from Bacteria to Mammals: Focus on the Immunoregulatory Phenylalanine Oxidase IL4I1.

l-amino acid oxidases are flavin adenine dinucleotide-dependent enzymes present in all major kingdom of life, from bacteria to mammals. They participate in defense mechanisms by limiting the growth of most bacteria and parasites. A few mammalian LAAOs have been described, of which the enzyme "interleukin-4 induced gene 1" (IL4I1) is the best characterized. IL4I1 mainly oxidizes l-phenylalanine. It is a secreted enzyme physiologically produced by antigen presenting cells of the myeloid and B cell lineages and T helper type (Th) 17 cells. Important roles of IL4I1 in the fine control of the adaptive immune response in mice and humans have emerged during the last few years. Indeed, IL4I1 inhibits T cell proliferation and cytokine production and facilitates naïve CD4⁺ T-cell differentiation into regulatory T cells in vitro by limiting the capacity of T lymphocytes to respond to clonal receptor stimulation. It may also play a role in controlling the germinal center reaction for antibody production and limiting Th1 and Th17 responses. IL4I1 is expressed in tumor-associated macrophages of most human cancers and in some tumor cell types. Such expression, associated with its capacity to facilitate tumor growth by inhibiting the anti-tumor T-cell response, makes IL4I1 a new potential druggable target in the field of immunomodulation in cancer.

KLK5 induces shedding of DPP4 from circulatory Th17 cells in type 2 diabetes.

OBJECTIVE: Increasing plasma levels and activity of dipeptidyl peptidase-4 (DPP4 or CD26) are associated with rapid progression of metabolic syndrome to overt type 2 diabetes mellitus (T2DM). While DPP4 inhibitors are increasingly used as anti-hyperglycemic agents, the reason for the increase in plasma DPP4 activity in T2DM patients remains elusive. METHODS: We looked into the source of plasma DPP4 activity in a cohort of 135 treatment naive nonobese (BMI < 30) T2DM patients. A wide array of ex vivo, in vitro, and in silico methods were employed to study enzyme activity, gene expression, subcellular localization, protease identification, surface expression, and protein-protein interactions. RESULTS: We show that circulating immune cells, particularly CD4+ T cells, served as an important source for the increase in plasma DPP4 activity in T2DM. Moreover, we found kallikrein-related peptidase 5 (KLK5) as the enzyme responsible for cleaving DPP4 from the cell surface by directly interacting with the extracellular loop. Expression and secretion of KLK5 is induced in CD4+ T cells of T2DM patients. In addition, KLK5 shed DPP4 from circulating CD4+ T helper (Th)17 cells and shed it into the plasma of T2DM patients. Similar cleavage and shedding activities were not seen in controls. CONCLUSIONS: Our study provides mechanistic insights into the molecular interaction between KLK5 and DPP4 as well as CD4+ T cell derived KLK5 mediated enzymatic cleavage of DPP4 from cell surface. Thus, our study uncovers a hitherto unknown cellular source and mechanism behind enhanced plasma DPP4 activity in T2DM.

Lysyl Oxidase 3 Is a Dual-Specificity Enzyme Involved in STAT3 Deacetylation and Deacetylimination Modulation.

In mammalian cells, histone deacetylase (HDAC) and Sirtuin (SIRT) are two families responsible for removing acetyl groups from acetylated proteins. Here, we describe protein deacetylation coupled with deacetylimination as a function of lysyl oxidase (LOX) family members. LOX-like 3 (Loxl3) associates with Stat3 in the nucleus to deacetylate and deacetyliminate Stat3 on multiple acetyl-lysine sites. Surprisingly, Loxl3 N-terminal scavenger receptor cysteine-rich (SRCR) repeats, rather than the C-terminal oxidase catalytic domain, represent the major deacetylase/deacetyliminase activity. Loxl3-mediated deacetylation/deacetylimination disrupts Stat3 dimerization, abolishes Stat3 transcription activity, and restricts cell proliferation. In Loxl3-/- mice, Stat3 is constitutively acetylated and naive CD4+ T cells are potentiated in Th17/Treg cell differentiation. When overexpressed, the SRCR repeats from other LOX family members can catalyze protein deacetylation/deacetylimination. Thus, our findings delineate a hitherto-unknown mechanism of protein deacetylation and deacetylimination catalyzed by lysyl oxidases.

Arctigenin functions as a selective agonist of estrogen receptor ß to restrict mTORC1 activation and consequent Th17 differentiation.

Arctigenin was previously proven to inhibit Th17 cell differentiation and thereby attenuate colitis in mice by down-regulating the activation of mechanistic target of rapamycin complex 1 (mTORC1). The present study was performed to address its underlying mechanism in view of estrogen receptor (ER). The specific antagonist PHTPP or siRNA of ERß largely diminished the inhibitory effect of arctigenin on the mTORC1 activation in T cell lines and primary CD4+ T cells under Th17-polarization condition, suggesting that arctigenin functioned in an ERß-dependent manner. Moreover, arctigenin was recognized to be an agonist of ERß, which could bind to ERß with a moderate affinity, promote dissociation of ERß/HSP90 complex and nuclear translocation and phosphorylation of ERß, and increase the transcription activity. Following activation of ERß, arctigenin inhibited the activity of mTORC1 by disruption of ERß-raptor-mTOR complex assembly. Deficiency of ERß markedly abolished arctigenin-mediated inhibition of Th17 cell differentiation. In colitis mice, the activation of ERß, inhibition of mTORC1 activation and Th17 response by arctigenin were abolished by PHTPP treatment. In conclusion, ERß might be the target protein of arctigenin responsible for inhibition of mTORC1 activation and resultant prevention of Th17 cell differentiation and colitis development.

Human Th17 Cells Lack HIV-Inhibitory RNases and Are Highly Permissive to Productive HIV Infection.

UNLABELLED: Human immunodeficiency virus (HIV) infects and depletes CD4(+) T cells, but subsets of CD4(+) T cells vary in their susceptibility and permissiveness to infection. For example, HIV preferentially depletes interleukin-17 (IL-17)-producing T helper 17 (Th17) cells and T follicular helper (Tfh) cells. The preferential loss of Th17 cells during the acute phase of infection impairs the integrity of the gut mucosal barrier, which drives chronic immune activation-a key determinant of disease progression. The preferential loss of Th17 cells has been attributed to high CD4, CCR5, and CXCR4 expression. Here, we show that Th17 cells also exhibit heightened permissiveness to productive HIV infection. Primary human CD4(+) T cells were sorted, activated under Th17- or Th0-polarizing conditions and infected, and then analyzed by flow cytometry. Th17-polarizing cytokines increased HIV infection, and HIV infection was disproportionately higher among Th17 cells than among IL-17(-) or gamma interferon-positive (IFN-γ(+)) cells, even upon infection with a replication-defective HIV vector with a pseudotype envelope. Further, Th17-polarized cells produced more viral capsid protein. Our data also reveal that Th17-polarized cells have diminished expression of RNase A superfamily proteins, and we report for the first time that RNase 6 inhibits HIV. Thus, our findings link Th17 polarization to increased HIV replication. IMPORTANCE: Our study compares the intracellular replicative capacities of several different HIV isolates among different T cell subsets, providing a link between the differentiation of Th17 cells and HIV replication. Th17 cells are of key importance in mucosal integrity and in the immune response to certain pathogens. Based on our findings and the work of others, we propose a model in which HIV replication is favored by the intracellular environment of two CD4(+) T cell subsets that share several requirements for their differentiation: Th17 and Tfh cells. Characterizing cells that support high levels of viral replication (rather than becoming latently infected or undergoing cell death) informs the search for new therapeutics aimed at manipulating intracellular signaling pathways and/or transcriptional factors that affect HIV replication.

JAK inhibition induces silencing of T Helper cytokine secretion and a profound reduction in T regulatory cells.

CD4(+) T cells maintain cancer surveillance and immune tolerance. Chronic inflammation has been proposed as a driver of clonal evolution in myeloproliferative neoplasms (MPN), suggesting that T cells play an important role in their pathogenesis. Treatment with JAK inhibitors (JAKi) results in improvements in MPN-associated constitutional symptoms as well as reductions in splenomegaly. However, effects of JAKi on T cells in MPN are not well established and the baseline immune signature remains unclear. We investigated the frequency and function of CD4(+) T cell subsets in 50 MPN patients at baseline as well as during treatment with either ruxolitinib or fedratinib in a subset. We show that CD4(+)  CD127(low)  CD25(high)  FOXP3(+) T regulatory cells are reduced in MPN patients compared to healthy controls and that this decrease is even more pronounced following JAKi therapy. Moreover, we show that after 6 months of treatment the number of T helper (Th)-17 cells increased. We also describe a functional 'silencing' of T helper cells both in vivo and in vitro and a blockade of pro-inflammatory cytokines from these cells. This profound effect of JAKi on T cell function may underlay augmented rates of atypical infections that have been reported with use of these drugs.

The p38 mitogen-activated protein kinase cascade modulates T helper type 17 differentiation and functionality in multiple sclerosis.

The p38 mitogen-activated protein kinase cascade is required for the induction of a T helper type 17 (Th17) -mediated autoimmune response, which underlies the development and progression of several autoimmune diseases, such as experimental autoimmune encephalomyelitis, the animal model of multiple sclerosis (MS). However, the contribution of p38 phosphorylation to human Th cell differentiation has not been clarified. Here we demonstrate that the p38 signalling pathway is implicated in the generation of Th17 lymphocytes from human CD4(+)  CD27(+)  CD45RA(+) naive T cells, both in healthy donors and in patients affected by the relapsing-remitting form of MS. Our data also indicate that p38 activation is essential for interleukin-17 release from central memory lymphocytes and committed Th17 cell clones. Furthermore, CD4(+) T cells isolated from individuals with relapsing-remitting MS display an altered responsiveness of the p38 cascade, resulting in increased p38 phosphorylation upon stimulation. These findings suggest that the p38 signalling pathway, by modulating the Th17 differentiation and response, is involved in the pathogenesis of MS, and open new perspectives for the use of p38 inhibitors in the treatment of Th17-mediated autoimmune diseases.

Beyond ecto-nucleotidase: CD39 defines human Th17 cells with CD161.

CD39/ENTPD1 is a prototypic member of the ectonucleoside triphosphate diphosphohydrolase (ENTPDase) family on cell surface. CD39 has been reported to be a marker of regulatory immune cells and catalyzes extracellular hydrolysis of nucleotides to generate AMP and, in tandem with CD73, adenosine. We have recently found in addition that co-expression of CD39 and CD161 by human CD4(+) T cells may become a biomarker of human Th17 cells. CD39 and CD161 have direct interactions that are further linked with acid sphingomyelinase (ASM). Upon activation of CD39 and CD161, the molecular interactions boost ASM bio-activity, which generates cellular ceramide to further mediate downstream signals inclusive of STAT3 and mTOR. We suggest modulation of human Th17 responsiveness by CD39 and CD161 and describe novel molecular mechanisms integrating elements of both extracellular nucleotide and sphingolipid homeostasis that are pivotal in the control of human Th17 cells and which could have therapeutic potential.

Differential Effects of Calcineurin and Mammalian Target of Rapamycin Inhibitors on Alloreactive Th1, Th17, and Regulatory T Cells.

BACKGROUND: Previously, we had reported the role of tacrolimus (TAC) versus sirolimus (SRL) on the generation of regulatory T cells (Tregs) in primary MLR assays with SRL, demonstrating a uniquely supportive effect. However, the mechanisms associated with their actions on alloreactive human T cells are not fully understood. Therefore, we tested whether TAC and SRL differentially affect already alloactivated human CD4 T-cell subsets. METHODS: Alloreactive CD4CD45RA/CD45RO T cells generated in 9-day MLR were cocultured with anti-CD3 and autologous antigen presenting cells plus interleukin (IL)-2 in presence of TAC, SRL, or both, and the Tregs generated after another 5 to 6 days were phenotypically, molecularly, and functionally characterized. RESULTS: Tacrolimus significantly and SRL modestly inhibited interferon (IFN)-γ (Th1) and IL-17 (Th17)-producing cells. At clinical therapeutic concentrations, SRL, however, significantly increased forkhead/winged helix transcription factor P3 (FOXP3) Tregs, whereas TAC inhibited this T-cell population dose dependently and significantly. When used in combination, TAC and SRL had additive effects on inhibition of IFN-γ- and IL-17-producing cells. This was in contrast to the ability of SRL to reverse TAC-mediated inhibition of FOXP3-expressing cells. Proinflammatory cytokines (IL-1ß, IL-6, and tumor necrosis factor-α) added to cultures caused significant decrease in FOXP3 Tregs that was again reversed by SRL. Sirolimus-derived Tregs were phenotypically normal, anergic to allostimulation, and suppressed proliferation of allogeneic effector T-cells. CONCLUSIONS: Thus, although TAC inhibits all alloreactive T cells, SRL promotes the differentiation and expansion of donor-specific Tregs without secondary reprogramming to IFN-γFOXP3 and IL-17FOXP3 Treg subsets. These results, although performed in an artificial in vitro model, add clinically applicable information on how these agents affect T-cell subpopulations.

The methylcytosine dioxygenase Tet2 promotes DNA demethylation and activation of cytokine gene expression in T cells.

Epigenetic regulation of lineage-specific genes is important for the differentiation and function of T cells. Ten-eleven translocation (Tet) proteins catalyze 5-methylcytosine (5 mC) conversion to 5-hydroxymethylcytosine (5 hmC) to mediate DNA demethylation. However, the roles of Tet proteins in the immune response are unknown. Here, we characterized the genome-wide distribution of 5 hmC in CD4(+) T cells and found that 5 hmC marks putative regulatory elements in signature genes associated with effector cell differentiation. Moreover, Tet2 protein was recruited to 5 hmC-containing regions, dependent on lineage-specific transcription factors. Deletion of Tet2 in T cells decreased their cytokine expression, associated with reduced p300 recruitment. In vivo, Tet2 plays a critical role in the control of cytokine gene expression in autoimmune disease. Collectively, our findings suggest that Tet2 promotes DNA demethylation and activation of cytokine gene expression in T cells.

Metabolic programming and PDHK1 control CD4+ T cell subsets and inflammation.

Activation of CD4+ T cells results in rapid proliferation and differentiation into effector and regulatory subsets. CD4+ effector T cell (Teff) (Th1 and Th17) and Treg subsets are metabolically distinct, yet the specific metabolic differences that modify T cell populations are uncertain. Here, we evaluated CD4+ T cell populations in murine models and determined that inflammatory Teffs maintain high expression of glycolytic genes and rely on high glycolytic rates, while Tregs are oxidative and require mitochondrial electron transport to proliferate, differentiate, and survive. Metabolic profiling revealed that pyruvate dehydrogenase (PDH) is a key bifurcation point between T cell glycolytic and oxidative metabolism. PDH function is inhibited by PDH kinases (PDHKs). PDHK1 was expressed in Th17 cells, but not Th1 cells, and at low levels in Tregs, and inhibition or knockdown of PDHK1 selectively suppressed Th17 cells and increased Tregs. This alteration in the CD4+ T cell populations was mediated in part through ROS, as N-acetyl cysteine (NAC) treatment restored Th17 cell generation. Moreover, inhibition of PDHK1 modulated immunity and protected animals against experimental autoimmune encephalomyelitis, decreasing Th17 cells and increasing Tregs. Together, these data show that CD4+ subsets utilize and require distinct metabolic programs that can be targeted to control specific T cell populations in autoimmune and inflammatory diseases.

JAK/STAT/PKCδ molecular pathways in synovial fluid T lymphocytes reflect the in vivo T helper-17 expansion in psoriatic arthritis.

Looking to the sustained psoriatic arthritis (PsA) joint as a model of local human inflammation, this study was designed to assess the T lymphocyte signal transduction pathways potentially involved in this chronic immune-mediated inflammatory process, as characterized by direct ex vivo analysis of T helper (Th)-17 T effector (Teff) cell phenotypes in synovial fluid (SF) and peripheral blood (PB) of clinically active PsA patients. The reverse-phase protein arrays (RPPA) technique was employed to identify STAT3, STAT1, JAK1, JAK2, PKCδ and ERK1/2 phosphoprotein levels on total T cell lysates in SF samples of PsA patients. Frequencies of T CD4(+)IL-17A-F(+) and T CD4(+)IL-23R(+) Th17 cells were quantified in SF and matched PB of PsA patients by flow cytometry and compared with PB of healthy controls (HC). Increased levels of JAK1, STAT3, STAT1 and PKCδ phosphoproteins were found in SF T cells of PsA patients, compared with PB of HC. The expansion of T CD4(+)IL-17A-F(+) cells, as well as of T CD4(+) cells expressing IL-23Rp19 (T CD4(+) IL-23R(+)), considered as the pathogenic phenotype of effector Th17 cells, was found to be confined to the joints of PsA patients, as the frequencies of both populations were significantly higher in SF than in matched PB, or in PB of HC. In conclusion, T lymphocyte signal transduction pathway mapping revealed an enhanced activation of JAK1/STAT3/STAT1 and PKCδ phosphoproteins that may drive the local inflammatory process, characterized by the in vivo expansion of T CD4(+)IL-17A-F(+) and T CD4(+)IL-23R(+) Th17 Teff cells in SF of clinically active joints of PsA patients.

AMPKα1 deficiency amplifies proinflammatory myeloid APC activity and CD40 signaling.

AMPK is a serine/threonine kinase that regulates energy homeostasis and metabolic stress in eukaryotes. Previous work from our laboratory, as well as by others, has provided evidence that AMPKα1 acts as a negative regulator of TLR-induced inflammatory function. Herein, we demonstrate that AMPKα1-deficient macrophages and DCs exhibit heightened inflammatory function and an enhanced capacity for antigen presentation favoring the promotion of Th1 and Th17 responses. Macrophages and DCs generated from AMPKα1-deficient mice produced higher levels of proinflammatory cytokines and decreased production of the anti-inflammatory cytokine IL-10 in response to TLR and CD40 stimulation as compared with WT cells. In assays of antigen presentation, AMPKα1 deficiency in the myeloid APC and T cell populations contributed to enhanced IL-17 and IFN-γ production. Focusing on the CD154-CD40 interaction, we found that CD40 stimulation resulted in increased phosphorylation of ERK1/2, p38, and NF-κB p65 and decreased activation of the anti-inflammatory Akt -GSK3ß-CREB pathway in DCs deficient for AMPKα1. Our data demonstrate that AMPKα1 serves to attenuate LPS and CD40-mediated proinflammatory activity of myeloid APCs and that AMPKα1 activity in both APC and T cells contributes to T cell functional polarization during antigen presentation.

The steroidogenic enzyme Cyp11a1 is essential for development of peanut-induced intestinal anaphylaxis.

BACKGROUND: Cytochrome P450, family 11, subfamily A, polypeptide 1 (Cyp11a1), a cytochrome P450 enzyme, is the first and rate-limiting enzyme in the steroidogenic pathway, converting cholesterol to pregnenolone. Cyp11a1 expression is increased in activated T cells. OBJECTIVES: We sought to determine the role of Cyp11a1 activation in the development of peanut allergy and TH cell functional differentiation. METHODS: A Cyp11a1 inhibitor, aminoglutethimide (AMG), was administered to peanut-sensitized and challenged mice. Clinical symptoms, intestinal inflammation, and Cyp11a1 levels were assessed. The effects of Cyp11a1 inhibition on T(H)1, T(H)2, and T(H)17 differentiation were determined. Cyp11a1 gene silencing was performed with Cyp11a1-targeted short hairpin RNA. RESULTS: Peanut sensitization and challenge resulted in diarrhea, inflammation, and increased levels of Cyp11a1, IL13, and IL17A mRNA in the small intestine. Inhibition of Cyp11a1 with AMG prevented allergic diarrhea and inflammation. Levels of pregnenolone in serum were reduced in parallel. AMG treatment decreased IL13 and IL17A mRNA expression in the small intestine without affecting Cyp11a1 mRNA or protein levels. In vitro the inhibitor decreased IL13 and IL17A mRNA and protein levels in differentiated T(H)2 and T(H)17 CD4 T cells, respectively, without affecting GATA3, retinoic acid-related orphan receptor γt (RORγt), or T(H)1 cells and IFNG and T-bet expression. Short hairpin RNA-mediated silencing of Cyp11a1 in polarized T(H)2 CD4 T cells significantly decreased pregnenolone and IL13 mRNA and protein levels. CONCLUSION: Cyp11a1 plays an important role in the development of peanut allergy, regulating peanut-induced allergic responses through effects on steroidogenesis, an essential pathway in T(H)2 differentiation. Cyp11a1 thus serves as a novel target in the regulation and treatment of peanut allergy.

Indoleamine 2,3-dioxygenase is differentially expressed by different white blood cell populations of rhesus macaques (Macaca mulatta).

BACKGROUND: Indoleamine 2,3-dioxygenase (IDO) is involved in immune processes such as transplant and fetal rejection, autoimmunity, cancer, and infection; however, its expression in rhesus macaques has not been fully addressed. METHODS: Indoleamine 2,3-dioxygenase mRNA and protein in the white blood cells (WBCs) of Chinese rhesus macaques were examined by RT-PCR, western blotting, real-time RT-PCR, and flow cytometry. RESULTS: Both IDO protein and mRNA could be readily detected in WBCs or peripheral blood mononuclear cells (PBMCs) of normal rhesus macaques. IDO+ cell frequency was the highest among CD14(+) mononuclear cells, followed by CD56(+) cells and DCs. No difference in the frequency of IDO+ cells between CD4(+) and CD8(+) T cells; however, Th17 cells have higher frequency of IDO+ cells than Th1 cells, with Th2 cells the lowest. Toll-like receptor (TLR) stimulation significantly increased IDO protein level in CD14(+) , CD56(+) , CD1c(+) , CD11c(+) , and CD123(+) myeloid cells. CONCLUSION: Rhesus macaques express IDO differentially in their leukocyte subsets and are suitable for IDO-related pathophysiological studies.

Cathepsin K is involved in development of psoriasis-like skin lesions through TLR-dependent Th17 activation.

Cathepsins (CTSs) are lysosomal cysteine proteases that play an important role in the turnover of intracellular proteins and extracellular proteins, such as the degradation of extracellular matrices and the processing of antigenic proteins. A CTS inhibitor, NC-2300, not only suppresses bone erosion by inhibition of cathepsin K (CTSK), but also ameliorates paw swelling at inflamed joints in adjuvant-induced arthritis in rats. It has been demonstrated that the amelioration of joint inflammation by NC-2300 is mediated by the downregulation of cytokine expression in dendritic cells, which are essential for Th17 activation. In this work, we studied the role for CTSs in the pathogenesis of psoriasis-like lesion in K5.Stat3C mice, a mouse model of psoriasis, in which Th17 contributes to lesion development similar to psoriasis. Psoriatic lesions expressed increased levels of Ctsk and Ctss mRNA compared with uninvolved skin and normal control skin. Similarly, the epidermis and dermis in K5.Stat3C mice demonstrated increased CTSK activities, which were sensitive to NC-2300. Topical treatment with NC-2300 significantly ameliorated 12-O-tetradecanoylphorbol-13-acetate-induced psoriasis-like lesions in K5.Stat3C mice, and downregulated the expression of IL-12, IL-23, and Th17 cytokines. In vitro experiments revealed that TLR7 activation of bone marrow-derived myeloid dendritic cells led to increase in IL-23 at mRNA and protein levels, which were downregulated by NC-2300. These results suggest that CTSK plays a role in development of psoriatic lesions through TLR7-dependent Th17 polarization.