Pathogenesis of Alopecia Areata and Vitiligo: Commonalities and Differences.

Both alopecia areata (AA) and vitiligo are distinct, heterogenous, and complex disease entities, characterized by nonscarring scalp terminal hair loss and skin pigment loss, respectively. In AA, inflammatory cell infiltrates are in the deep reticular dermis close to the hair bulb (swarm of bees), whereas in vitiligo the inflammatory infiltrates are in the epidermis and papillary dermis. Immune privilege collapse has been extensively investigated in AA pathogenesis, including the suppression of immunomodulatory factors (e.g., transforming growth factor-ß (TGF-ß), programmed death-ligand 1 (PDL1), interleukin-10 (IL-10), α-melanocyte-stimulating hormone (α-MSH), and macrophage migration inhibitory factor (MIF)) and enhanced expression of the major histocompatibility complex (MHC) throughout hair follicles. However, immune privilege collapse in vitiligo remains less explored. Both AA and vitiligo are autoimmune diseases that share commonalities in pathogenesis, including the involvement of plasmacytoid dendritic cells (and interferon-α (IFN- α) signaling pathways) and cytotoxic CD8+ T lymphocytes (and activated IFN-γ signaling pathways). Blood chemokine C-X-C motif ligand 9 (CXCL9) and CXCL10 are elevated in both diseases. Common factors that contribute to AA and vitiligo include oxidative stress, autophagy, type 2 cytokines, and the Wnt/ß-catenin pathway (e.g., dickkopf 1 (DKK1)). Here, we summarize the commonalities and differences between AA and vitiligo, focusing on their pathogenesis.

IDO/Kynurenine; novel insight for treatment of inflammatory diseases.

Inflammation and oxidative stress play pivotal roles in pathogenesis of many diseases including cancer, type 2 diabetes, cardiovascular disease, atherosclerosis, neurological diseases, and inflammatory diseases such as inflammatory bowel disease (IBD). Inflammatory mediators such as interleukins (ILs), interferons (INF-s), and tumor necrosis factor (TNF)-α are related to an extended chance of inflammatory diseases initiation or progression due to the over expression of the nuclear factor Kappa B (NF-κB), signal transducer of activators of transcription (STAT), nod-like receptor family protein 3 (NLRP), toll-like receptors (TLR), mitogen-activated protein kinase (MAPK), and mammalian target of rapamycin (mTOR) pathways. These pathways are completely interconnected. Theindoleamine 2,3 dioxygenase (IDO) subset of the kynurenine (KYN) (IDO/KYN), is a metabolic inflammatory pathway involved in production of nicotinamide adenine dinucleotide (NAD + ). It has been shown that IDO/KYN actively participates in inflammatory processes and can increase the secretion of cytokines that provoke inflammatory diseases. Data were extracted from clinical and animal studies published in English between 1990-April 2022, which were collected from PubMed, Google Scholar, Scopus, and Cochrane library. IDO/KYN is completely associated with inflammatory-related pathways, thus leading to the production of cytokines such as TNF-α, IL-1ß, and IL-6, and ultimately development and progression of various inflammatory disorders. Inhibition of the IDO/KYN pathway might be a novel therapeutic option for inflammatory diseases. Herein, we gathered data on probable interactions of the IDO/KYN pathway with induction of some inflammatory diseases.

Effect of pharmacological modulation of the kynurenine pathway on pain-related behavior and opioid analgesia in a mouse model of neuropathic pain.

Dysfunction of the central nervous system are accompanied by changes in tryptophan metabolism, with the kynurenine pathway (KP) being the main route of its catabolism. Recently, KP metabolites, which are collectively called kynurenines, have become an area of intense research due to their ability to directly and indirectly affect a variety of classic neurotransmitter systems. However, the significance of KP in neuropathic pain is still poorly understood. Therefore, we designed several experiments to verify changes in the mRNA levels of KP enzymes in parallel with other factors related to this metabolic route after chronic constriction injury of the sciatic nerve (CCI model) in mice. The analysis revealed an increase in, Kmo, Kynu and Haoo mRNA levels in the spinal cord on the 7th day after CCI, while Kat1, Kat2, Tdo2, Ido2 and Qprt mRNA levels remain unchanged. Subsequent pharmacological studies provided evidence that modulation of KP by single intrathecal administration of 1-D-MT, UPF468 or L-kynurenine attenuates mechanical and thermal hypersensitivity and increases the effectiveness of selected opioids in mice as measured on day 7 after CCI. Moreover, our results provide the first evidence that the injection of L-kynurenine preceded by UPF468 (KMO inhibitor) is more effective at reducing hypersensitivity in animals with neuropathic pain. Importantly, L-kynurenine also exerts an analgesic effect after intravenous injections, which is enhanced by the administration of minocycline, an inhibitor of microglial activation. Additionally, L-kynurenine administered intrathecally and intravenously enhances analgesia evoked by all tested opioids (morphine, buprenorphine and oxycodone). Overall, our results indicate that the modulation of KP at different levels might be a new pharmacological tool in neuropathy management.

Identification and characterization of tryptophan-kynurenine pathway-related genes involving lamprey (Lampetra japonica) innate immunity.

The tryptophan-kynurenine (TRP-KYN) pathway is involved in several biological functions, including immunosuppression, inflammatory response, and tumor suppression. Six TRP-KYN pathway-related genes, tryptophan 2,3-dioxygenase (TDO), indoleamine 2,3-dioxygenase 2 (IDO2), aminoadipate aminotransferase (AADAT), glutamate oxaloacetate transaminase 2 (GOT2), kynurenine monooxygenase (KMO), and kynureninase (KYNU) have been identified and cloned from the jawless vertebrate lamprey (Lampetra japonica) to gain insights into their evolution and characterization. Expression distribution showed that the key gene Lj-TDO was highly expressed in the oral gland. Real-time quantitative PCR showed that TRP-KYN pathway-related genes were significantly overexpressed after multi-stimulation. RNA interference showed that Lj-IDO2 knockdown regulated the expression of inflammatory factors. In conclusion, our study successfully clarified the ancestral features and functions of the TRP-KYN pathway, while providing valuable insights into the involvement of this pathway in the immune responses of a jawless vertebrate.

Preparation of NIn-Methyl-6-[18F]fluoro- and 5-Hydroxy-7-[18F]fluorotryptophans as Candidate PET-Tracers for Pathway-Specific Visualization of Tryptophan Metabolism.

Tryptophan (Trp) is an essential proteinogenic amino acid and metabolic precursor for several signaling molecules that has been implicated in many physiological and pathological processes. Since the two main branches of Trp metabolism-serotonin biosynthesis and kynurenine pathway-are differently affected by a variety of neurological and neoplastic diseases, selective visualization of these pathways is of high clinical relevance. However, while positron emission tomography (PET) with existing probes can be used for non-invasive assessment of total Trp metabolism, optimal imaging agents for pathway-specific PET imaging are still lacking. In this work, we describe the preparation of two 18F-labeled Trp derivatives, NIn-methyl-6-[18F]fluorotryptophan (NIn-Me-6-[18F]FTrp) and 5-hydroxy-7-[18F]fluorotryptophan (5-HO-7-[18F]FTrp). We also report feasible synthetic routes for the preparation of the hitherto unknown boronate radiolabeling precursors and non-radioactive reference compounds. Under optimized conditions, alcohol-enhanced Cu-mediated radiofluorination of the respective precursors afforded NIn-Me-6-[18F]FTrp and 5-HO-7-[18F]FTrp as application-ready solutions in radiochemical yields of 45 ± 7% and 29 ± 4%, respectively. As such, our work provides access to two promising candidate probes for pathway-specific visualization of Trp metabolism in amounts sufficient for their preclinical evaluation.

d-mannose administration improves autoimmune hepatitis by upregulating regulatory T cells.

A recent study revealed that d-mannose suppressed immunopathology in mouse models of autoimmune diabetes and airway inflammation and increased the proportion of regulatory T cells (Tregs) in mice. We investigated the effect of d-mannose on liver injury in murine autoimmune hepatitis (AIH) models induced by concanavalin A (ConA) and α-galactosylceramide (GalCer). Mouse models of AIH were created by intraperitoneal injection of GalCer or intravenous injection of ConA. Drinking water was supplemented with d-mannose and biochemically and pathologically examined over time. The administration of d-mannose to AIH model mice significantly reduced liver injury and reduced inflammatory cytokine expression. In addition, Tregs among splenocytes and intrahepatic lymphocytes were significantly increased by the administration of d-mannose. These results indicate that treatment with d-mannose reduced the inflammatory response in the liver and suppressed liver damage by increasing Tregs.

Metabolic Reconfiguration Activates Stemness and Immunomodulation of PDLSCs.

Periodontal ligament derived stem cells (PDLSC) are adult multipotent mesenchymal-like stem cells (MSCs) that can induce a promising immunomodulation to interact with immune cells for disease treatment. Metabolic reconfiguration has been shown to be involved in the immunomodulatory activity of MSCs. However, the underlying mechanisms are largely unknown, and it remains a challenging to establish a therapeutic avenue to enhance immunomodulation of endogenous stem cells for disease management. In the present study, RNA-sequencing (RNA-seq) analysis explores that curcumin significantly promotes PDLSC function through activation of MSC-related markers and metabolic pathways. In vitro stem cell characterization further confirms that self-renewal and multipotent differentiation capabilities are largely elevated in curcumin treated PDLSCs. Mechanistically, RNA-seq reveals that curcumin activates ERK and mTOR cascades through upregulating growth factor pathways for metabolic reconfiguration toward glycolysis. Interestingly, PDLSCs immunomodulation is significantly increased after curcumin treatment through activation of prostaglandin E2-Indoleamine 2,3 dioxygenase (PGE2-IDO) signaling, whereas inhibition of glycolysis activity by 2-deoxyglucose (2-DG) largely blocked immunomodulatory capacity of PDLSCs. Taken together, this study provides a novel pharmacological approach to activate endogenous stem cells through metabolic reprogramming for immunomodulation and tissue regeneration.

Metabolic Stress and Immunity: Nutrient-Sensing Kinases and Tryptophan Metabolism.

The tryptophan catabolizing enzyme indoleamine 2,3-dioxygenase (IDO-1) has gained major attention due the immunoregulatory nature of this pathway. Both depletion of tryptophan concentrations as well as the accumulation of downstream metabolites are relevant for the mediation of the manifold consequences of increased tryptophan metabolism. Increased tryptophan catabolism is indicative for several chronic inflammatory disorders such as infections, autoimmune diseases or cancer. Low tryptophan availability is likely to be involved in the manifestation of a variety of comorbidities such as anemia, cachexia, depression and neurocognitive disturbances.Several nutrient sensing kinases are implicated in the downstream effects of dysregulated tryptophan metabolism. These include mechanisms that were conserved during evolution but have gained special features in multicellular eukaryotes, such as pathways regulated by eukaryotic translation initiation factor 2 (eIF-2)-alpha kinase (GCN2, also named general control nonderepressible 2 kinase), 5'-adenosine monophosphate (AMP)-activated protein kinase (AMPK) and target of rapamycin (TOR).The interplay between IDO-1 and above-mentioned pathway seems to be highly context dependent. A better understanding of the crosstalk is necessary to support the search for druggable targets for the treatment of inflammatory and autoimmune disorders.

The efficacy of indoximod upon stimulation with pro-inflammatory cytokines in triple-negative breast cancer cells.

BACKGROUND: Indoleamine 2,3-dioxygenase (IDO) inhibition has received much attention in cancer immunotherapy due to its role in immune escape in cancer cells. Additionally, changes in the pro-inflammatory cytokine levels can affect tumor growth and metastasis as well as the effectiveness of immunotherapy. The purpose of this study was for the first time to determine the effects of indoximod as an IDO inhibitor on triple-negative breast cancer (TNBC) and to assess the link between the efficacy of indoximod and IFN-γ or TNF-α stimulation. METHODS: The cytotoxic and apoptotic effects of indoximod alone or IFN-γ or TNF-α induction to mimic an inflammatory environment were evaluated by WST-1, Annexin V, cell cycle analysis, and acridine orange (AO)/ethidium bromide (EtBr) staining. Furthermore, the expression levels of IDO1 and PD-L1 expression were analyzed by RT-PCR. RESULTS: Our results demonstrated that indoximod significantly decreased the TNBC cell viability through apoptotic cell death (p < .05). The combination of indoximod and TNF-α was more effective than indoximod and IFN-γ stimulation or indoximod alone in TNBC cells. Additionally, PD-L1 expression level was significantly up-regulated after treatment with indoximod and TNF-α or IFN-γ combinations (p < .05). CONCLUSIONS: Indoximod exhibited a therapeutic potential in TNBC cells and pro-inflammatory cytokines could affect the effectiveness of indoximod. However, further studies are required to identify the role of the IDO-associated signaling pathways, the molecular mechanisms of indoximod induced apoptotic cell death, and the relationship between IDO inhibition by IDO inhibitors and pro-inflammatory cytokine levels.

Inhibition of antigen-specific immune responses by co-application of an indoleamine 2,3-dioxygenase (IDO)-encoding vector requires antigen transgene expression focused on dendritic cells.

We have previously shown that particle-mediated epidermal delivery (PMED) of plasmids encoding ß-galactosidase (ßGal) under control of the fascin-1 promoter (pFascin-ßGal) yielded selective production of the protein in skin dendritic cells (DCs), and suppressed Th2 responses in a mouse model of type I allergy by inducing Th1/Tc1 cells. However, intranasal challenge of mice immunized with pFascin-ßGal induced airway hyperreactivity (AHR) and neutrophilic inflammation in the lung. The tryptophan-catabolizing enzyme indoleamine 2,3-dioxygenase (IDO) has been implicated in immune suppression and tolerance induction. Here we investigated the consequences of co-application of an IDO-encoding vector on the modulatory effect of DNA vaccination by PMED using pFascin-ßGal in models of eosinophilic allergic and non-eosinophilic intrinsic airway inflammation. IDO-encoding plasmids and pFascin-ßGal or pCMV-ßGal were co-applied to abdominal skin of BALB/c mice without, before or after sensitization with ßGal protein. Immune responses in the lung were analysed after intranasal provocation and airway reactivity was determined by whole body plethysmography. Co-application of pCMV-IDO with pFascin-ßGal, but not pCMV-ßGal inhibited the Th1/Tc1 immune response after PMED. Moreover, AHR in those mice was attenuated following intranasal challenge. Therapeutic vaccination of ßGal-sensitized mice with pFascin-ßGal plus pCMV-IDO slightly suppressed airway inflammation and AHR after provocation with ßGal protein, while prophylactic vaccination was not effective. Altogether, our data suggest that only the combination of DC-restricted antigen and ubiquitous IDO expression attenuated asthma responses in mice, most probably by forming a tryptophan-depleted and kynurenine-enriched micromilieu known to affect neutrophils and T cells.

Increased indoleamine 2,3-dioxygenase activity and expression in prostate cancer following targeted immunotherapy.

BACKGROUND: We previously found that PD-L1 expression is increased on tumor cells following vaccination treatments that lead to increased tumor-specific T cells that secrete IFNγ. Indoleamine 2,3-dioxygenase (IDO) is another IFNγ inducible gene that has potent immunosuppressive effects. There have been reports of IDO expression in prostate cancer; however, it is unknown whether IDO expression might similarly increase in prostate tumors following T-cell-based immunotherapy. METHODS: Blood samples from normal male blood donors (n = 12) and patients with different stages of prostate cancer (n = 89), including patients with metastatic, castration-resistant prostate cancer treated with a DNA vaccine and/or pembrolizumab, were evaluated for IDO activity by kynurenine and tryptophan levels. Metastatic tissue biopsies obtained pre- and post-treatments were evaluated for IDO expression. IDO suppression of vaccine-induced T-cell function was assessed by ELISPOT. RESULTS: Overall, IDO activity was increased in patients with more advanced prostate cancer. This activity, and IDO expression as detected immunohistochemically, increased following treatment with either a DNA vaccine encoding the prostatic acid phosphatase (PAP) tumor antigen or PD-1 blockade with pembrolizumab. Increased IDO activity after treatment was associated with the absence of clinical effect, as assessed by lack of PSA decline following treatment. Increased antigen-specific T-cell response, as measured by IFNγ release, to the vaccine target antigen was detected following in vitro stimulation of peripheral blood cells with 1-methyltryptophan. CONCLUSIONS: These findings suggest that IDO expression is a mechanism of immune evasion used by prostate cancer and that future clinical trials using T-cell-based immune strategies might best include IDO inhibition.

Molecular and functional characterization of the indoleamine 2,3-dioxygenase in grass carp (Ctenopharyngodon idella).

Indoleamine 2,3-dioxygenase (IDO) is a kind of dioxygenase that can catalyze the degradation of levo-tryptophan (L-Trp) and plays key roles in immune tolerance. In this study, the IDO gene was cloned and functionally characterized from grass carp (gcIDO). The results showed that gcIDO overexpressed in GCO cells could catalyze the degradation of L-Trp through the L-Trp - kynurenine pathway, and this activity could be promoted by δ-aminolevulinic acid (ALA) while inhibited by levo-1-methyl tryptophan (L-1MT). Moreover, gcIDO was constitutively expressed in various tissues, and its expression could be significantly up-regulated by LPS and Poly (I:C) in peripheral blood leukocytes (PBLs). Furthermore, recombinant TGF-ß1 of grass carp could up-regulate the expression of IDO, TGF-ß1, CD25, and Foxp3 in PBLs, indicating that the TGF-ß1/IDO pathway is present in fish. In the soybean meal induced enteritis (SBMIE) model, the expression of gcIDO in the intestine was up-regulated significantly, demonstrating that gcIDO may play an immunoregulatory role in SBMIE. Taken together, these data suggest that the IDO plays multiple roles in the immunity of fish.

FoxP3 and IDO in Canine Melanocytic Tumors.

Human melanoma is one of the deadliest forms of cancer, with poor prognosis and high resistance to chemotherapy and radiotherapy. The discovery of immunosuppressive mechanisms in the human melanoma microenvironment led to the use of new prognostic markers and to the development of immunotherapies targeting immune checkpoint molecules. Immunoescape mechanisms in canine melanoma have not yet been investigated, and no such immunotherapy has been tested. The aim of this study was to provide preliminary data on the expression of transcription factor forkhead box protein P3 (FoxP3) and indoleamine 2,3-dioxygenase (IDO) in primary canine melanocytic tumors and to investigate their prognostic role. Formalin-fixed, paraffin-embedded samples from 74 canine melanocytic tumors (26 oral melanomas, 23 cutaneous melanomas, and 25 cutaneous melanocytomas) were retrospectively evaluated by immunohistochemistry to explore the expression of FoxP3 and IDO. An increased risk of death due to melanoma was associated with a higher number of FoxP3+ cells per high-power field (FoxP3+/HPF), a higher percentage of CD3+ cells that were also FoxP3+ infiltrating and surrounding the tumor (%FoxP3), and a higher number of IDO+ cells/HPF (IDO+/HPF). A prognostic value for FoxP3 and IDO is suggested by our study, with optimal cutoffs of 14.7 FoxP3+ cells/HPF, 6.1 IDO+ cells/HPF, and 12.5% FoxP3+ cells. Both markers were also associated with tumor type. Multivariable analysis identified IDO+/HPF ( P < .001) as an independent prognostic marker. Even though stratification by diagnosis caused a loss of significance, results from the present study suggest a prognostic role for IDO and FoxP3, possibly related to the establishment of an immunosuppressive microenvironment.

Survival of lymphocytes is not restricted by IDO-expressing fibroblast from rheumatoid arthritis patients.

Objective: Rheumatoid arthritis (RA) is characterized by expansion of fibroblast-like synoviocytes (FLS) in inflamed joints and activation of lymphocytes. Tryptophan (trp) is an essential amino acid indispensable for the biosynthesis of proteins and critical for survival of lymphocytes. Indoleamine 2,3-dioxygenase (IDO) that initiates the degradation of trp and tryptophanyl-tRNA synthetase (TTS) essential for tryptophan synthesis, regulate trp bioavailability. Here, we tested the hypothesis that triggered by cytokines, enhanced IDO activity modulate regulatory function of otherwise non-tolerogenic FLS isolated from RA patients. Materials and methods: IDO and TTS mRNA expression were evaluated by RT-PCR. IDO enzymatic activity was confirmed using HPLC. Resting or PHA-activated PBMC from healthy volunteers and RA patients were co-cultured with IDO expressing untreated (FLSC) or IFNγ-treated (FLSIFNγ) RA FLS. Lymphocyte survival and proliferation were evaluated by flow cytometry analysis and tritiated thymidine incorporation, respectively. Results: RA FLSIFNγ produce functionally active IDO and constitutively express TTS. RA FLSC and FLSIFNγ increased survival of resting lymphocytes in both studied groups, and decreased proliferation of healthy, but not RA, PBMC. Only FLSIFNγ diminished survival of activated CD3+CD4-, but not CD3+CD4+, healthy T cells and similar tendency was observed in rheumatoid cells. Importantly, IDO inhibitor, 1-methyl-DL-tryptophan (1-MT), failed to reverse this effect. PBMC, irrespective of their state (resting versus activated) or origin (healthy or RA), expressed high level of TTS mRNA. Conclusions: We suggest that RA FLS express functionally active IDO but control survival and expansion of healthy cells in IDO-independent mechanism and exert weaker, if any, suppressive effect on rheumatoid cells.

Characterization of the In Vitro Chlamydia pecorum Response to Gamma Interferon.

Chlamydia pecorum is an important intracellular bacterium that causes a range of diseases in animals, including a native Australian marsupial, the koala. In humans and animals, a gamma interferon (IFN-γ)-mediated immune response is important for the control of intracellular bacteria. The present study tested the hypotheses that C. pecorum can escape IFN-γ-mediated depletion of host cell tryptophan pools. In doing so, we demonstrated that, unlike Chlamydia trachomatis, C. pecorum is completely resistant to IFN-γ in human epithelial cells. While the growth of C. pecorum was inhibited in tryptophan-deficient medium, it could be restored by the addition of kynurenine, anthranilic acid, and indole, metabolites that could be exploited by the gene products of the C. pecorum tryptophan biosynthesis operon. We also found that expression of trp genes was detectable only when C. pecorum was grown in tryptophan-free medium, with gene repression occurring in response to the addition of kynurenine, anthranilic acid, and indole. When grown in bovine kidney epithelial cells, bovine IFN-γ also failed to restrict the growth of C. pecorum, while C. trachomatis was inhibited, suggesting that C. pecorum could use the same mechanisms to evade the immune response in vivo in its natural host. Highlighting the different mechanisms triggered by IFN-γ, however, both species failed to grow in murine McCoy cells treated with murine IFN-γ. This work confirms previous hypotheses about the potential survival of C. pecorum after IFN-γ-mediated host cell tryptophan depletion and raises questions about the immune pathways used by the natural hosts of C. pecorum to control the widespread pathogen.

The tolerogenic peptide hCDR1 immunomodulates cytokine and regulatory molecule gene expression in blood mononuclear cells of primary Sjogren's syndrome patients.

Primary Sjogren's syndrome (pSS) is an autoimmune disease characterized by lymphocytic infiltration of exocrine glands. We investigated whether the tolerogenic peptide, hCDR1, that ameliorates lupus manifestations would have beneficial effects on pSS as well. The in vitro effects of hCDR1 on gene expression of pro-inflammatory cytokines and regulatory molecules were tested in peripheral blood mononuclear cells (PBMC) of 16 pSS patients. hCDR1, but not a control peptide, significantly reduced gene expression of IL-1ß, TNF-α, MX-1 and BlyS and up-regulated immunosuppressive (TGF-ß, FOXP3) molecules in PBMC of pSS patients. hCDR1 did not affect gene expression in patients with rheumatoid arthritis and anti-phospholipid syndrome. Further, hCDR1 up-regulated the expression of Indoleamine 2,3-dioxygenase (IDO) via elevation of TGF-ß. IDO inhibition led to a significant decrease in the expression of FOXP3 which is crucial for the induction of T regulatory cells. Thus, hCDR1 is potential candidate for the specific treatment of pSS patients.

Indoleamine-2,3-dioxygenase in murine and human systemic lupus erythematosus: Down-regulation by the tolerogeneic peptide hCDR1.

וֹndoleamine-2,3-dioxygenase (IDO) plays a role in immune regulation. Increased IDO activity was reported in systemic lupus erythematosus (SLE). We investigated the effects of the tolerogenic peptide hCDR1, shown to ameliorate lupus manifestations, on IDO gene expression. mRNA was prepared from splenocytes of hCDR1- treated SLE-afflicted (NZBxNZW)F1 mice, from blood samples of lupus patients, collected before and after their in vivo treatment with hCDR1 and from peripheral blood mononuclear cells (PBMC) of patients incubated with hCDR1. IDO gene expression was determined by real-time RT-PCR. hCDR1 significantly down-regulated IDO expression in SLE-affected mice and in lupus patients (treated in vivo and in vitro). No effects were observed in healthy donors or following treatment with a control peptide. Diminished IDO gene expression was associated with hCDR1 beneficial effects. Our results suggest that the hCDR1-induced FOXP3 expressing regulatory T cells in lupus are not driven by IDO but rather by other hCDR1 regulated pathways.

Role of the indoleamine-2,3-dioxygenase/kynurenine pathway of tryptophan metabolism in behavioral alterations in a hepatic encephalopathy rat model.

BACKGROUND: This study aims to explore the role of indoleamine-2,3-dioxygenase (IDO)/kynurenine (KYN) pathway of tryptophan (TRY) metabolism in behavioral alterations observed in hepatic encephalopathy (HE) rats. METHODS: Expression levels of proinflammatory cytokines were tested by QT-PCR and ELISA, levels of IDOs were tested by QT-PCR and Western blot, and levels of 5-hydroxytryptamine (5-HT), KYN, TRY, 3-hydroxykynurenine (3-HK), and kynurenic acid (KA) in different brain regions were estimated using HPLC. Effects of the IDO direct inhibitor 1-methyl-L-tryptophan (1-MT) on cognitive, anxiety, and depressive-like behavior were evaluated in bile duct ligation (BDL) rats. RESULTS: Increased serum TNF-α, IL-1ß, and IL-6 levels were shown in rats 7 days after BDL, and these increases were observed earlier than those in the brain, indicating peripheral immune activation may result in central upregulation of proinflammatory cytokines. Moreover, BDL rats showed a progressive decline in memory formation, as well as anxiety and depressive-like behavior. Further study revealed that IDO expression increased after BDL, accompanied by a decrease of 5-HT and an increase of KYN, as well as abnormal expression of 3-HK and KA. The above results affected by BDL surgery were reversed by IDO inhibitor 1-MT treatment. CONCLUSION: Taken together, these findings indicate that (1) behavioral impairment in BDL rats is correlated with proinflammatory cytokines; (2) TRY pathway of KYN metabolism, activated by inflammation, may play an important role in HE development; and (3) 1-MT may serve as a therapeutic agent for HE.

No augmentation of indoleamine 2,3-dioxygenase (IDO) activity through belatacept treatment in liver transplant recipients.

Belatacept is a second-generation cytotoxic T lymphocyte antigen (CTLA)-4 immunoglobulin (Ig) fusion protein approved for immunosuppression in renal transplant recipients. It was designed intentionally to interrupt co-stimulation via CD28 by binding to its ligands B7·1 and B7·2. Experimental evidence suggests a potential additional mechanism for CTLA-4 Ig compounds through binding to B7 molecules expressed on antigen-presenting cells (APCs) and up-regulation of indoleamine 2,3-dioxygenase (IDO), an immunomodulating enzyme that catalyzes the degradation of tryptophan to kynurenine and that down-regulates T cell immunity. So far it remains unknown whether belatacept up-regulates IDO in transplant recipients. We therefore investigated whether belatacept therapy enhances IDO activity in liver transplant recipients enrolled in a multi-centre, investigator-initiated substudy of the Phase II trial of belatacept in liver transplantation (IM103-045). Tryptophan and kynurenine serum levels were measured during the first 6 weeks post-transplant in liver transplant patients randomized to receive either belatacept or tacrolimus-based immunosuppression. There was no significant difference in IDO activity, as indicated by the kynurenine/tryptophan ratio, between belatacept and tacrolimus-treated patients in per-protocol and in intent-to-treat analyses. Moreover, no evidence was found that belatacept affects IDO in human dendritic cells (DC) in vitro. These data provide evidence that belatacept is not associated with detectable IDO induction in the clinical transplant setting compared to tacrolimus-treated patients.

Prognostic value of tumor infiltrating lymphocyte subsets in breast cancer depends on hormone receptor status.

PURPOSE: Interaction between immune-regulatory proteins and tumor infiltrating lymphocytes (TILs) is complex, and their associations may have significant clinical implications. This study was designed to evaluate the relationships between immunomodulatory proteins and TIL subsets and their impact on prognosis in breast cancer. METHODS: 377 invasive breast cancer cases were selected, and immunohistochemistry was performed for HLA-A, HLA-ABC, and indoleamine 2,3-dioxygenase (IDO); CD4+, CD8+, and FOXP3+ T cells were counted in intratumoral and stromal areas for both absolute numbers as well as their ratios. RESULTS: While HLA-ABC and HLA-A expressions showed a positive correlation with CD8+ and FOXP3+ TIL infiltration, IDO expression showed a negative correlation with FOXP3+/CD4+ and FOXP3+/CD8+ T cell ratios. Expressions of HLA-ABC, HLA-A, and IDO shared an association with negative estrogen receptor status. Infiltration of CD4+, CD8+, and FOXP3+ TILs was significantly higher in tumors with high histologic grade, negative hormone receptor status, HER2 amplification, high Ki-67 index, and p53 overexpression. In survival analyses, increased CD4+ TIL infiltration was associated with better prognosis of the patients while other TIL subset infiltration and expression of immunomodulatory proteins had no prognostic significance. In subgroup analyses, high CD4+ TIL infiltration was revealed as an independent good prognostic factor in hormone receptor-negative subgroup while high FOXP3+/CD8+ T cell ratio was found to be an independent adverse prognostic factor in hormone receptor-positive subgroup, especially in luminal A subtype. CONCLUSION: CD4+ TIL subset and FOXP3+/CD8+ T cell ratio have different prognostic significance in breast cancer according to hormone receptor status.