Indoleamine 2,3-dioxygenase Levels Research Articles

Immune modulation and epigenetic therapies for enhanced outcome of treatment in triple-negative breast cancer

Triple-negative breast cancer (TNBC) is a subtype of breast cancer characterized by the absence of human epidermal growth factor receptor 2, estrogen receptor, and progesterone receptor expression. While traditional TNBC treatment primarily relies on systemic chemotherapy, epigenetic modification has an important role in immune evasion and tumor progression. Recent classifications of TNBC into “hot” and “cold” tumors, based on immune activity and mutation burden, have revealed that poor response to immune checkpoint inhibitors (ICIs) in these tumors is due to low tumor-infiltrating lymphocytes and the presence of immunosuppressive cells. Emerging treatments such as ICIs and poly(ADP-ribose) polymerase inhibitors offer promising alternatives. The tumor microenvironment (TME) shapes immune responses in TNBC, and a limited subset of patients has shown encouraging responses to ICIs in treating TNBC at both early and advanced stages. However, combination therapies face challenges, including medication interactions and side effects. Epigenetic modulators, such as histone deacetylase and DNA methyltransferase inhibitors, also show promise in reversing epigenetic changes by enhancing anti-tumor immunity in TNBC. The frequent expression of indoleamine 2,3-dioxygenase 1 (IDO1) in TNBC, which catalyzes the conversion of tryptophan to kynurenine, contributes to immune suppression in TNBC patients. High IDO1 levels impair the tumoricidal activity of natural killer cells and correlate with poor responses to anti-PD-L1 therapy, which can be improved using IDO1 inhibitors. Targeting myeloid-derived suppressor cells, regulatory T-cells, and tumor-associated macrophage, along with utilizing epigenetic mechanisms, show promise in modulating the immunosuppressive TME in TNBC. Combining these approaches with standard therapies, along with biomarker-guided patient selection, can enhance treatment efficacy. Clinical trials and preclinical models are essential for optimizing these strategies. This study emphasizes the importance of understanding the mechanisms of modulation, tumor-immune interactions, and the potential of epigenetic therapies in improving treatment outcomes in TNBC.

Protective effect and mechanism of Zuogui Jiangtang Jieyu Formula on damage to hippocampal synaptic microenvironment in rats with diabetes-related depression based on microglia-neuron crosstalk signal CD300f/TLR4

This study aims to reveal the protective effect and mechanism of Zuogui Jiangtang Jieyu Formula on the damage to hippo-campal synaptic microenvironment in rats with diabetes-related depression(DD) via regulating microglia immune receptor molecule-like family member f(CD300f)/Toll-like receptor 4(TLR4) signal. Firstly, the model of DD rats was established by a two-week high-fat diet+STZ injection+chronic mild and unpredictable stress plus isolation for 28 days. The rats were randomly divided into normal group, model group, CD300f blocker(CLM1, 2 μg·kg~(-1)) group, CD300f agonist(Fcγ, 5 μg·kg~(-1)) group, positive drug(0.18 g·kg~(-1) metformin+1.8 mg·kg~(-1) fluoxetine) group, and high-dose and low-dose(20.52 and 10.26 g·kg~(-1)) Zuogui Jiangtang Jieyu Formula groups. Depression-like behavior of rats was evaluated by open field and forced swimming experiments. The levels of blood glucose and insulin were detected by biochemical analysis. The levels of tumor necrosis factor α(TNF-α), interleukin-1β(IL-1β), indoleamine 2, 3-dioxygenase(IDO), 5-hydroxytryptamine(5-HT), and dopamine(DA) in the hippocampus were detected by enzyme-linked immunosorbent assay. The changes in the synaptic ultrastructure in hippocampal neurons of rats were observed by transmission electron microscopy. The protein expressions of CD300f, TLR4, synaptophysin(SYN), and postsynaptic density protein 95(PSD-95) in microglial cells of the hippocampus were detected by immunofluorescence and Western blot. The results indicated that compared with that in the normal group, the total movement distance in open field experiments was reduced in the model group, and the immobility time in forced swimming experiments increased, with an elevated insulin level in serum, as well as TNF-α, IL-1β, and IDO levels in the hippocampus. The 5-HT and DA levels in the hippocampus were reduced. In addition, the CD300f expression was down-regulated in microglial cells of the hippocampus, and the TLR4 expression was up-regulated. Moreover, the expression of synapse-related proteins SYN and PSD-95 in hippocampal neurons decreased, and the synaptic ultrastructure of hippocampal neurons was significantly damaged. Compared with the model group, the CD300f blocker and agonist aggravated and alleviated the above abnormal changes, respectively. High-dose and low-dose Zuogui Jiangtang Jieyu Formula could significantly improve the above depression-like beha-vior in rats, inhibit the abnormal increase of TNF-α, IL-1β, and IDO and the decrease of 5-HT and DA, effectively increase the expression of CD300f in microglial cells, and decrease the expression of TLR4. They could up-regulate the protein expression of presyna-ptic membrane SYN and postsynaptic membrane PSD-95 in hippocampal neurons and finally improve the damage to the hippocampal synaptic microenvironment. In conclusion, this research confirmed that Zuogui Jiangtang Jieyu Formula effectively alleviated the depression-like behavior and inhibited inflammatory activation of microglial cells in the hippocampus of rats with DD, and the mechanism might be related to the regulation of CD300f/TLR4 signal to alleviate the damage to hippocampal synaptic microenvironment.

Decidual natural killer cells dysfunction is caused by IDO downregulation in dMDSCs with Toxoplasma gondii infection

Myeloid-derived suppressor cells (MDSCs) play a crucial role in maintaining maternal-fetal tolerance by expressing some immune-suppressive molecules, such as indoleamine 2,3-dioxygenase (IDO). Toxoplasma gondii (T. gondii) infection can break the immune microenvironment of maternal-fetal interface, resulting in adverse pregnancy outcomes. However, whether T. gondii affects IDO expression in dMDSCs and the molecular mechanism of its effect are still unclear. Here we show, the mRNA level of IDO is increased but the protein level decreased in infected dMDSCs. Mechanistically, the upregulation of transcriptional levels of IDO in dMDSCs is regulated through STAT3/p52-RelB pathway and the decrease of IDO expression is due to its degradation caused by increased SOCS3 after T. gondii infection. In vivo, the adverse pregnancy outcomes of IDO−/− infected mice are more severe than those of wide-type infected mice and obviously improved after exogenous kynurenine treatment. Also, the reduction of IDO in dMDSCs induced by T. gondii infection results in the downregulation of TGF-β and IL-10 expression in dNK cells regulated through Kyn/AhR/SP1 signal pathway, eventually leading to the dysfunction of dNK cells and contributing the occurrence of adverse pregnancy outcomes. This study reveals a novel molecular mechanism in adverse pregnancy outcome induced by T. gondii infection.

1-Methyltryptophan treatment ameliorates high-fat diet-induced depression in mice through reversing changes in perineuronal nets

Depression and obesity are prevalent disorders with significant public health implications. In this study, we used a high-fat diet (HFD)-induced obese mouse model to investigate the mechanism underlying HFD-induced depression-like behaviors. HFD-induced obese mice exhibited depression-like behaviors and a reduction in hippocampus volume, which were reversed by treatment with an indoleamine 2,3-dioxygenase (IDO) inhibitor 1-methyltryptophan (1-MT). Interestingly, no changes in IDO levels were observed post-1-MT treatment, suggesting that other mechanisms may be involved in the anti-depressive effect of 1-MT. We further conducted RNA sequencing analysis to clarify the potential underlying mechanism of the anti-depressive effect of 1-MT in HFD-induced depressive mice and found a significant enrichment of shared differential genes in the extracellular matrix (ECM) organization pathway between the 1-MT-treated and untreated HFD-induced depressive mice. Therefore, we hypothesized that changes in ECM play a crucial role in the anti-depressive effect of 1-MT. To this end, we investigated perineuronal nets (PNNs), which are ECM assemblies that preferentially ensheath parvalbumin (PV)-positive interneurons and are involved in many abnormalities. We found that HFD is associated with excessive accumulation of PV-positive neurons and upregulation of PNNs, affecting synaptic transmission in PV-positive neurons and leading to glutamate-gamma-aminobutyric acid imbalances in the hippocampus. The 1-MT effectively reversed these changes, highlighting a PNN-related mechanism by which 1-MT exerts its anti-depressive effect.

Serum indoleamine 2, 3-dioxygenase and tryptophan-2, 3-dioxygenase: potential biomarkers for the diagnosis of major depressive disorder.

The objective of this study was to observe the changes in the levels of indoleamine 2, 3-dioxygenase (IDO) and tryptophan-2, 3-dioxygenase (TDO) in patients with major depressive disorder (MDD) and investigate their potential role as novel biomarkers for diagnosing MDD. A total of 55 MDD patients and 55 healthy controls (HC) were enrolled in the study. The severity of MDD was assessed using the 24-item Hamilton Depression Rating Scale (HAMD-24) before and after treatment. The serum concentrations of IDO and TDO were measured at baseline and after treatment. The correlations between the serum levels of IDO and TDO and HAMD-24 scores were evaluated using Pearson's correlation test. Receiver operating characteristic (ROC) curve analysis was used to evaluate the area under the curve (AUC) of serum levels of IDO and TDO for discriminating MDD patients from HC. The serum IDO and TDO concentrations were significantly higher in patients with MDD at baseline than in healthy controls, and decreased significantly after 2weeks or 1month of treatment. The levels of IDO and TDO were significantly positively correlated with HAMD-24 scores. Furthermore, the AUC values for IDO and TDO were 0.999 and 0.966, respectively. The study suggests that serum IDO and TDO may serve as novel biomarkers for diagnosing MDD. These findings may lead to a better understanding of the pathogenesis of MDD and the development of new therapeutic targets.

Epidermolysis-Bullosa-Associated Squamous Cell Carcinomas Support an Immunosuppressive Tumor Microenvironment: Prospects for Immunotherapy.

Cutaneous squamous cell carcinomas (SCCs) are a major complication of some subtypes of epidermolysis bullosa (EB), with high morbidity and mortality rates and unmet therapeutic needs. The high rate of endogenous mutations and the fibrotic stroma are considered to contribute to the pathogenesis. Patients with dystrophic EB (DEB) and Kindler EB (KEB) have the highest propensity for developing SCCs. Another patient group that develops high-risk SCCs is immunosuppressed (IS) patients, especially after organ transplantation. Herein, we interrogate whether immune checkpoint proteins and immunosuppressive enzymes are dysregulated in EB-associated SCCs as an immune resistance mechanism and compare the expression patterns with those in SCCs from IS patients, who frequently develop high-risk tumors and sporadic SCCs, and immunocompetent (IC) individuals. The expression of indoleamine 2,3-dioxygenase (IDO), programmed cell death protein-1 (PD-1), programmed cell death ligand-1 (PD-L1), T cell immunoglobulin and mucin-domain-containing protein-3 (TIM-3), lymphocyte activation gene-3 (LAG-3), and inflammatory infiltrates (CD4, CD8, and CD68) was assessed via immunohistochemistry and semi-quantitative analysis in 30 DEB-SCCs, 22 KEB-SCCs, 106 IS-SCCs, and 100 sporadic IC-SCCs. DEB-SCCs expressed significantly higher levels of IDO and PD-L1 in tumor cells and PD-1 in the tumor microenvironment (TME) compared with SCCs from IC and IS individuals. The number of CD4-positive T cells per mm2 was significantly lower in DEB-SCCs compared with IC-SCCs. KEB-SCCs showed the lowest expression of the exhaustion markers TIM-3 and LAG-3 compared with all other groups. These findings identify IDO, PD-1, and PD-L1 to be increased in EB-SCCs and candidate targets for combinatory treatments, especially in DEB-SCCs.

Prognostic value of indoleamine 2, 3-dioxygenase-1 expression in glial tumors.

<p>Gliomas are the most common primary malignant central nervous system tumors in adults, exhibiting a poor prognosis. Indoleamine 2, 3-dioxygenase-1 (IDO-1) has important functions in cancer immunotherapy due to its role in escaping cancer cells from the immune system. In this study we purposed to evaluate the correlation between IDO-1 expression and clinicopathological parameters in gliomas, and whether IDO-1 can be a prognostic marker.</p>. <p>n=75 patients in total, n=25 patients with low grade glial tumors (LGG, grade 1-2), n=25 patients with high grade glial tumors (HGG, grade 3-4), and n=25 persons with normal brain tissue as control group were included in this study. IDO-1 expression was categorized by using immunohistochemical staining in biopsy specimens as high (H) and low (L) groups among the patients with gliomas. We used a 95% percent confidence interval and p &lt;0.05 to analyze the association between the degree of IDO-1 expression, clinicopathological characteristics, and survival rates in glioma patients.&nbsp;</p>. <p>In HGG, IDO-1 levels were higher than in control brain tissue and LGG (p&lt; 0.001). The mean overall survival (OS) was longer in the L-IDO-1 group (64.53 &plusmn; 3.34) in months (95% CI: 57.969-71.098) compared to the H-IDO-1 group (43.74 &plusmn; 4.36) in months, (95% CI: 35.218-52.330) (p&lt; 0.05).</p>. <p>IDO-1 expression is an in&shy;de&shy;pendent prognostic biomarker to predict&nbsp;<br>OS and progression in HGG. IDO-1 can be&nbsp;evaluated as an alternative instrument for precision medicine in the treatment of gliomas.</p>.

Interferon-γ priming enhances the therapeutic effects of menstrual blood-derived stromal cells in a mouse liver ischemia-reperfusion model.

Mesenchymal stem cells (MSCs) have been used in liver transplantation and have certain effects in alleviating liver ischemia-reperfusion injury (IRI) and regulating immune rejection. However, some studies have indicated that the effects of MSCs are not very significant. Therefore, approaches that enable MSCs to exert significant and stable therapeutic effects are worth further study. To enhance the therapeutic potential of human menstrual blood-derived stromal cells (MenSCs) in the mouse liver ischemia-reperfusion (I/R) model via interferon-γ (IFN-γ) priming. Apoptosis was analyzed by flow cytometry to evaluate the safety of IFN-γ priming, and indoleamine 2,3-dioxygenase (IDO) levels were measured by quantitative real-time reverse transcription polymerase chain reaction, western blotting, and ELISA to evaluate the efficacy of IFN-γ priming. In vivo, the liver I/R model was established in male C57/BL mice, hematoxylin and eosin and TUNEL staining was performed and serum liver enzyme levels were measured to assess the degree of liver injury, and regulatory T cell (Treg) numbers in spleens were determined by flow cytometry to assess immune tolerance potential. Metabolomics analysis was conducted to elucidate the potential mechanism underlying the regulatory effects of primed MenSCs. In vitro, we established a hypoxia/reoxygenation (H/R) model and analyzed apoptosis by flow cytometry to investigate the mechanism through which primed MenSCs inhibit apoptosis. Transmission electron microscopy, western blotting, and immunofluorescence were used to analyze autophagy levels. IFN-γ-primed MenSCs secreted higher levels of IDO, attenuated liver injury, and increased Treg numbers in the mouse spleens to greater degrees than untreated MenSCs. Metabolomics and autophagy analyses proved that primed MenSCs more strongly induced autophagy in the mouse livers. In the H/R model, autophagy inhibitors increased the level of H/R-induced apoptosis, indicating that autophagy exerted protective effects. In addition, primed MenSCs decreased the level of H/R-induced apoptosis via IDO and autophagy. Further rescue experiments proved that IDO enhanced the protective autophagy by inhibiting the mammalian target of rapamycin (mTOR) pathway and activating the AMPK pathway. IFN-γ-primed MenSCs exerted better therapeutic effects in the liver I/R model by secreting higher IDO levels. MenSCs and IDO activated the AMPK-mTOR-autophagy axis to reduce IRI, and IDO increased Treg numbers in the spleen and enhanced the MenSC-mediated induction of immune tolerance. Our study suggests that IFN-γ-primed MenSCs may be a novel and superior MSC product for liver transplantation in the future.

Indoleamine 2,3-dioxygenase level and oxidative stress parameters in the serum of patients with chronic renal failure

Indoleamine 2,3-dioxygenase (IDO) is a tryptophan-degrading enzyme belonging to the kynurenine pathway. IDO activity has been suggested as a biomarker for diagnosis of chronic kidney disease. The aim of the study was to estimate the level of IDO, urea, creatinine, uric acid, phosphate, calcium, albumin, MDA, GSH, and activity of peroxidase, catalase, arylesterase in the serum of chronic renal failure (CRF) patients treated with dialysis compared to the healthy control group. The results showed a significant increment in IDO level in patients compared with the control. Linear regression analysis using the Pearson correlation coefficient showed that increased IDO level correlates positively with urea, creatinine, uric acid, phosphate, MDA level and peroxidase activity whereas negatively with albumin, calcium, glutathione level, catalase activity and glomerular filtration rate. We concluded that IDO level might be a possible marker of oxidative stress and inflammation in patients with CRF. Keywords: 3-dioxygenase, biochemical parameters, correlation analysis, indoleamine 2, renal failure, serum

CANLI DONÖR KARACİĞER NAKLİNİN ÖNGÖRÜSEL BİYOBELİRTEÇLERİ

Objective: Liver transplantation using a living donor (LDLT) is currently the most popular method used in the worldwide. Appropriate biomarkers that predict graft status should be used to detect early post-transplant complications that may lead to a rejection reaction. Material and Method: The study involved a total of 44 liver recipients and 44 liver donors, from whom preoperative blood samples were taken and immunoassay and spectrophotometric studies were carried out. The levels of serum neopterin, interferon-gamma (IFN- y), indoleamine-2,3 dioxygenase (IDO), and -glutathione S transferase (a-GST) were assessed using an enzyme-linked immunosorbent test. The activity of glutathione reductase (GR) and glucose-6-phosphate dehydrogenase (G6PD) in erythrocytes was measured using spectrophotometry. Result and Discussion: “Neopterin, IDO, and G6PD levels were significantly higher in the recipient group than in the donor group. The differences in gender and blood groups were statistically insignificant. The rejection reaction developed in 25% of patients and none survived. These findings may facilitate the identification of novel predictive biomarkers for the diagnosis of acute rejection reactions after LDLT. The clinical use of novel non-invasive biomarkers may provide time and cost advantages.

Effects of rubiadin-3-methyl ether on the immune properties of hUC-MSCs

Mesenchymal stem cells (MSCs) have become an effective tool for treating immune-related diseases due to their multilineage potential and immunomodulatory capabilities. One of the main factors contributing to their immunomodulatory capabilities is the IDO cascade, which was chosen as the main subject in this research. The IDO-Kyn-AHR-CYP cascade was chosen to evaluate the immunomodulatory properties of treated MSCs, with expression levels of the key gene IDO (indoleamine 2,3-dioxygenase) selected as the screening criterion. Cultured human umbilical cord MSCs (hUC-MSCs) were treated with different natural bioactive compounds. Preliminary results indicated that Rubiadin-3-methyl ether, an anthraquinone derivative isolated from the roots of Morinda longissima, was able to significantly induce IDO2 expression in UC-MSCs but not CYPs. This is the first study to show a link between Rubiadin-3-methyl ether and IDO2 in hUC-MSC. More research is needed to determine whether human UC-MSCs primed with Rubiadin-3-methyl ether have any significant benefits for treating immune-related diseases and disorders.

Promotion of skin wound healing using hypoimmunogenic epidermal cell sheets

ObjectiveThe physiological process of wound healing is dynamic, continuous, and intricate. Nowadays, full-thickness burn wounds are treated by autologous skin transplantation. Unfortunately, when substantial burns develop, there are fewer donor sites accessible, making it difficult to satisfy the requirement for large-scale skin transplants and increasing the risk of patient mortality. This study investigated the possibility of using a newly created hypoimmunogenic epidermal cell sheet to heal skin wounds. MethodsTransfection with lentivirus was used to generate Keratinocytes (KCs) that overexpress Indoleamine 2,3-Dioxygenase (IDO). Western blotting and quantitative polymerase chain reaction were used to measure IDO levels. To evaluate the function of IDO+ keratinocytes, CCK-8 and Transwell assays were performed. In cell sheet induction media, KCs and Fibroblasts (FBs) were cultured to yield epidermal cell sheets. The full-thickness skin excisions of BALB/c mice were transplanted with epidermal cell sheets. To assess the tumorigenicity of IDO+ keratinocytes, BALB/c nude mouse xenograft models were also used. CD3 and CD31 immunofluorescence labeling of wound tissue on day 12 to identify T lymphocyte infiltration and capillary development. ELISA measurement of IL-1 and TNF-α concentrations. ResultsIDO + keratinocytes dramatically enhanced the expression levels of IDO mRNA and protein, as well as the amount of kynurenine in the conditioned media of IDO+ keratinocytes, compared to the Control and NC groups. CD8+ T cell apoptosis was considerably greater in the IDO group than in the Control and NC groups. Nevertheless, the proliferation and migratory capabilities of IDO+ keratinocytes were not substantially different from those of the Control and NC groups. In vitro cultivation of the hypoimmunogenic epidermal cell sheet was effective. In vivo transplantation experiments demonstrated that IDO+ epidermal cell sheets can effectively promote wound healing without tumorigenicity, and IDO+ epidermal cell sheets may promote wound healing by decreasing the expression levels of inflammatory factors (TNF and IL-1) in wound tissue, decreasing CD3+ T lymphocytes, and increasing infiltration and new capillaries in wound tissue. ConclusionIn this study, we successfully constructed the hypoimmunogenic epidermal cell sheet and demonstrated that the hypoimmunogenic epidermal cell sheet could accelerate wound healing.

Breast cancer progression and kynurenine pathway enzymes are induced by hexachlorobenzene exposure in a Her2-positive model.

Breast cancer is one of the leading cancers among women worldwide. Given the evidence that pesticides play an important role in breast cancer, interest has grown in pesticide impact on disease progression. Hexachlorobenzene (HCB), an aryl hydrocarbon receptor (AhR) ligand, promotes triple-negative breast cancer cell migration and invasion. Estrogen receptor β (ERβ) inhibits cancer motility, while G protein-coupled ER (GPER) modulates the neoplastic transformation. Tryptophan is metabolized through the kynurenine pathway by indoleamine-2,3-dioxygenase (IDO) and tryptophan-2,3-dioxygenase (TDO), with kynurenine signaling activation often predicting worse prognosis in cancer. In this context, we examined the HCB (0.005; 0.05; 0.5 and 5μM) effect on LM3 cells, a human epidermal growth factor receptor 2 (HER2)-positive breast cancer model. Results show that HCB increases IDO and TDO mRNA levels and promotes cell viability, proliferation and migration through the AhR pathway. Moreover, HCB boosts mammosphere formation, vascular endothelial growth factor and cyclooxygenase-2 expression and reduces IL-10 levels. For some parameters, U-shaped or inverted U-shaped dose-response curves are shown. HCB alters ER levels, reducing ERβ while increasing GPER. These results demonstrate that exposure to environmentally relevant concentrations of HCB up-regulates the kynurenine pathway and dysregulates ERβ and GPER levels, collaborating in HER2-positive breast cancer progression.

Effects of the kynurenine pathway on the osteogenic differentiation of periodontal ligament stem cells

Objective: To explore the effect of kynurenine pathway on the osteogenic differentiation of periodontal ligament stem cells (PDLSC). Methods: Unstimulated saliva samples were collected from 19 patients with periodontitis (periodontitis group) and 19 periodontally healthy individuals (health group) in Nanjing Stomatological Hospital, Affiliated Hospital of Medical School, Nanjing University from June to October of 2022. Contents of kynurenine and the metabolites in saliva samples were analyzed by ultra-performance liquid chromatography-tandem mass spectrometry. The expressions of indoleamine 2, 3-dioxygenase (IDO) and aryl hydrocarbon receptor (AhR) were further detected by immunohistochemistry in gingival tissues. The PDLSC used in this study were isolated from extracted teeth for orthodontic treatment in Nanjing Stomatological Hospital, Affiliated Hospital of Medical School, Nanjing University from July to November of 2022. Experiments were then conducted using the cells by incubating with (kynurenine group) or without kynurenine (control group) in vitro. Seven days later, alkaline phosphatase (ALP) staining and assays of ALP activity were performed. Real-time fluorescence quantitative PCR (RT-qPCR) was utilized to detect the expressions of osteogenic related genes ALP, osteocalcin (OCN), runt-related transcription factor 2 (RUNX2), collagen type-Ⅰ (COL-Ⅰ) as well as the kynurenine pathway-associated genes AhR, cytochrome P450 family (CYP) 1A1, CYP1B1. Western blotting was used to detect the expression levels of RUNX2, osteopontin (OPN) and AhR proteins on day 10 and alizarin red staining was performed to observe the formation of mineral nodules on day 21 in control group and kynurenine group. Results: Salivary concentrations of kynurenine [8.26 (0, 19.60) nmol/L] and kynurenic acid [11.4 (3.34, 13.52) nmol/L] were significantly higher in the periodontitis group than in the health group [0.75(0, 4.25) nmol/L, 1.92(1.34, 3.88) nmol/L] (Z=-2.84, P=0.004; Z=-3.61, P<0.001). The expression levels of IDO (18.33±2.22) and AhR (44.14±13.63) in gingival tissues of periodontitis patients were significantly higher than that of the health group (12.21±2.87, 15.39±5.14) (t=3.38, P=0.015; t=3.42, P=0.027). In vitro, the ALP activity of PDLSC in the kynurenine group (291.90±2.35) decreased significantly compared with the control group (329.30±19.29) (t=3.34, P=0.029). The mRNA expression levels of ALP, OCN and RUNX2 in the kynurenine group (0.43±0.12, 0.78±0.09, 0.66±0.10) were decreased compared with the control group (1.02±0.22, 1.00±0.11, 1.00±0.01) (t=4.71, P=0.003; t=3.23, P=0.018; t=6.73, P<0.001), while the levels of AhR and CYP1A1 were increased in the kynurenine group (1.43±0.07, 1.65±0.10) compared with those in the control group (1.01±0.12, 1.01±0.14) (t=5.23, P=0.006; t=6.59, P<0.001). No significant difference was observed in COL-Ⅰ and CYP1B1 mRNA levels between groups. The protein levels of OPN, RUNX2 (0.82±0.05, 0.87±0.03) were reduced and that of AhR (1.24±0.14) was increased in the kynurenine group compared with those in the control group (1.00±0.00, 1.00±0.00, 1.00±0.00) (t=6.79, P=0.003; t=7.95, P=0.001; t=3.04, P=0.039). Conclusions: Over-activated kynurenine pathway in periodontitis patients can promote upregulation of AhR and suppress the osteogenic differentiation of PDLSC.

Perioperative IDO-1 dynamic changes in NSCLC patients.

e20532 Background: Indoleamine 2,3-dioxygenase (IDO) is an enzyme that is involved in the metabolism of tryptophan, an essential amino acid. It is known to play a role in the regulation of the immune system, and has been linked to perioperative immune status. Specifically, IDO has been shown to be upregulated in the perioperative period, leading to an increased risk of infection and other complications. This is thought to be due to the increased production of kynurenine, a metabolite of tryptophan, which has been associated with immunosuppression. Additionally, IDO has been linked to increased levels of inflammation and oxidative stress, which can further contribute to the risk of complications during surgery. Thus, understanding the role and dynamic changes of IDO in the perioperative period is important for optimizing patient outcomes. Methods: Patients with non-small cell lung cancer (NSCLC) who underwent surgery were enrolled in this study prospectively. Peripheral blood at different time points: preoperative, post anesthesia, post-vascular incision, post-tumor resection, and 3 days after surgery. The serum tryptophan and kynurenine were measured, and the kynurenine to tryptophan (K:T) ratio was used as an indicator of IDO activity. Paired Wilcoxon test was used to identify the significant difference of IDO activity at five different time points. The Kaplan–Meier log-rank test was used to assess the correlation between overall survival (OS), progression-free survival (PFS), and IDO activity. Results: A total of 46 patients were enrolled in this study. The median follow-up time was 24.7 (range: 0.9 – 35.3) months. No patients died during the follow-up time. The PFS at 2 years was 76% (95% CI, 76%-100%). In all patients, IDO activity was not correlated significantly with better PFS. Surgical procedure does not affect levels of plasma IDO at any pathological stage in NSCLC significantly. The level of serum IDO of post-vascular incision was significantly correlated with that of 3 days after surgery (R2 = 0.7, P &lt; 0.05). The level of preoperative level of serum kynurenine was significantly correlated with that of post-vascular incision and post-tumor resection (R2 = 0.7/0.73, P &lt; 0.05). Conclusions: Surgical procedure does not have a significant effect on the serum IDO levels during the perioperative period. The perioperative levels of serum IDO are not correlated with the surgical prognosis of NSCLC, thus alternative markers are needed to better predict the surgical prognosis of NSCLC patients.

Pan-cancer analysis of IDO1 transcriptome expression and its impact on outcome in patients treated with immune checkpoint inhibitors.

2614 Background: The immunosuppressive tumor microenvironment (TME) is a major component of resistance to immune checkpoint inhibitors (ICIs). Tryptophan catabolism is recognized as a metabolic pathway leading to immunosuppression and indoleamine 2,3-dioxygenase 1 (IDO1), an enzyme catabolizing tryptophan to kynurenine, has been investigated as a potential target. Analyzing the association of IDO1 and immune molecules in the TME could better elucidate the role of IDO1 as an immunotherapeutic strategy. Thus, we performed pan-cancer transcriptome analysis of IDO1 according to cancer types and immune molecules in the TME and evaluated survival outcomes in patients treated with ICIs based on IDO1 expression levels. Methods: Comprehensive transcriptome analysis of IDO1 and selected immune molecules in 514 patients with advanced solid tumors at the Moores Cancer Center at the University of California San Diego was performed. The rate of “High” (75-100 percentile), “Intermediate” (25-74), and “Low” (0-24) IDO1 RNA expression in each cancer type was calculated (rank compared to 735 controls). Univariate and multivariate analyses of the odds ratio (OR) for high IDO1 expression based on factors such as immune checkpoints, cancer types, microsatellite instability (MSI), and tumor mutational burden (TMB) were conducted. Additionally, progression-free survival (PFS) and overall survival (OS) from the time of ICI therapy based on IDO1 expression was compared by the Kaplan-Meier method. Multivariate analysis of survival outcomes was performed using the Cox proportional hazards model. Results: Overall, 91 of 514 patients (17.7%) were classified into “High”, 228 (44.4%) into “Intermediate”, and 195 (37.9%) into “Low” IDO1 RNA expression. High IDO1 expression was seen in uterine (54.2%), ovarian (37.2%), and lung cancer (25.0%). In multivariate analysis, high STAT1 and CD40 expression, ovarian cancer, and uterine cancer were correlated with high IDO1 expression. In patients treated with ICIs (N = 217), “High” IDO1 expression (N = 49) was associated with better PFS (HR = 0.57, 95%CI: 0.40-0.83, p = 0.003) and OS (HR = 0.52, 95%CI: 0.47-0.83, p = 0.006) than “Intermediate/Low” IDO1 expression (N = 168). Multivariate analysis incorporating age, sex, IDO1, PD-1, PD-L1, PD-L2, CTLA-4, LAG3, cancer types, TMB, and MSI revealed that IDO1 (HR = 0.28, 95%CI: 0.11-0.69, p = 0.006) and PD-1 (HR = 0.24, 95%CI: 0.09-0.65, p = 0.005) are independent predictive factors for longer OS. Conclusions: IDO1 RNA levels are high in &gt;25% of uterine, ovarian, and lung cancers but differ from patient to patient between and within tumor types. High IDO1 levels correspond with longer PFS and OS from start of ICI therapy. These results suggest the importance of patient selection through pan-cancer molecular analysis and the potential role of IDO1 as a predictive marker for ICI therapy.

The tryptophan-metabolizing enzyme indoleamine 2,3-dioxygenase 1 regulates polycystic kidney disease progression.

Autosomal dominant polycystic kidney disease (ADPKD), the most common monogenic nephropathy, is characterized by phenotypic variability that exceeds genic effects. Dysregulated metabolism and immune cell function are key disease modifiers. The tryptophan metabolites, kynurenines, produced through indoleamine 2,3-dioxygenase 1 (IDO1), are known immunomodulators. Here, we study the role of tryptophan metabolism in PKD using an orthologous disease model (C57BL/6J Pkd1RC/RC). We found elevated kynurenine and IDO1 levels in Pkd1RC/RC kidneys versus wild type. Further, IDO1 levels were increased in ADPKD cell lines. Genetic Ido1 loss in Pkd1RC/RC animals resulted in reduced PKD severity, as measured by cystic index and percentage kidney weight normalized to body weight. Consistent with an immunomodulatory role of kynurenines, Pkd1RC/RC;Ido1-/- mice presented with significant changes in the cystic immune microenvironment (CME) versus controls. Kidney macrophage numbers decreased and CD8+ T cell numbers increased, both known PKD modulators. Also, pharmacological IDO1 inhibition in Pkd1RC/RC mice and kidney-specific Pkd2-knockout mice with rapidly progressive PKD resulted in less severe PKD versus controls, with changes in the CME similar to those in the genetic model. Our data suggest that tryptophan metabolism is dysregulated in ADPKD and that its inhibition results in changes to the CME and slows disease progression, making IDO1 a therapeutic target for ADPKD.

Serum indoleamine 2,3-dioxygenase level and diagnostic value in patients with rosacea

Background: Indoleamine 2,3-dioxygenase (IDO), an enzyme in the first step of tryptophan catabolism, plays a role in the pathogenesis of various malignancies and inflammatory diseases. Although its pathogenesis is unclear, vascular dysregulation and chronic inflammation are the most common culprits for rosacea. Objectives: The aim of this study is to evaluate the relationship between IDO and rosacea and whether there is a correlation with disease severity. Methods: Fifty-two patients with rosacea and 29 healthy volunteers were recruited. The patients were grouped according to severity stage, period, and subtype of the disease. Serum IDO levels were measured with enzyme-linked immunosorbent assay. Results: Serum IDO levels were significantly higher in the patients with rosacea compared to the healthy controls (P < 0.001) and were significantly higher in the patients in remission period and with papulopustular type rosacea compared to the controls (P = 0.002 and P = 0.001, respectively). The serum IDO levels of the female rosacea patients were higher than those of the healthy female controls (P < 0.001). When the diagnostic value of the parameter was investigated, it was observed that the serum IDO level has high sensitivity (83.3%) and specificity (76.1%), with a cutoff value of 47.1 ng/mL for female rosacea patients. Conclusion: IDO was found to increase in rosacea patients. With the high specificity and sensitivity observed, especially in female patients, IDO may be a supporting parameter in the diagnosis of rosacea.

Aberrant NAD synthetic flux in podocytes under diabetic conditions and effects of indoleamine 2,3-dioxygenase on promoting de novo NAD synthesis

Nicotinamide adenine dinucleotide (NAD) is an essential coenzyme in the kidney. The first step in de novo NAD synthesis is regulated by indoleamine 2,3-dioxygenase (IDO), a tryptophan-catabolizing enzyme. Here, we investigated NAD synthetic flux and NAD levels in podocytes under diabetic conditions. We also studied the effects of IDO overexpression on NAD synthetic flux and high glucose (HG)-induced podocyte injury. NAD synthetases in the de novo, Preiss-Handler and salvage pathways were analyzed using in vivo single-nucleus RNA sequencing datasets (GSE131882) of control and diabetic kidney disease (DKD). The mRNA levels of these NAD synthetases were measured in vitro in HG-treated podocytes. The effects of IDO on NAD synthesis were examined by transducing cultured podocytes with an adenovirus encoding IDO, and apoptosis, podocyte markers and mobility were investigated. Cellular transcriptome analysis revealed that control podocytes had relatively low levels of NAD synthetases. In DKD podocytes, de novo NAD synthetase levels were further downregulated. IDO levels were virtually undetectable and did not increase in DKD. In vitro experiments confirmed aberrant de novo NAD synthetic flux and decreased IDO levels in HG-treated podocytes. Overexpression of IDO promoted NAD de novo synthesis, reduced NAD-bypass metabolic enzyme, increased NAD content and recovered podocyte injury markers under diabetic conditions. Taken together, our findings suggest that the de novo NAD synthetic flux is aberrant in DKD, and IDO promotes de novo NAD synthesis and NAD levels, as well as alleviates injury in HG-treated podocytes.

Expression of tolerogenic dendritic cells in the small intestinal tissue of patients with celiac disease

Tolerogenic dendritic cells (tolCDs) play an important role in the regulation of inflammation in autoimmune diseases such as celiac disease (CeD). Dendritic cells express CD207, CD11c, and CD103 on their surface. In addition to the receptors mentioned above, tolCDs can express the immune-regulating enzyme indoleamine 2,3-dioxygenase (IDO). This study aimed to determine the mRNA and protein expression of CD11c, CD103 and CD207 markers, and also IDO gene expression in intestinal tissues of CeD patients in comparison to the healthy individuals. Duodenal biopsies were collected from 60 CeD patients and 60 controls. Total RNA was extracted and gene expression analysis was performed using Real-time PCR SYBR® Green method. Additionally, biopsy specimens were paraffinized and protein expression was evaluated using immunohistochemistry (IHC) for expression of CD11c+, CD207+and CD103+. Gene expression levels of CD11c (P = 0.045), CD103 (P < 0.001), CD207 (P < 0.001) and IDO (P = 0.01) were significantly increased in CeD patients compared to the control group. However, only CD103 protein expression was found to be significantly higher in CeD patients in comparison to the control group (P < 0.001). The result of this study showed that the expresion levels of CD11c, CD103, CD207 and IDO markers were higher in CeD patients compared to the controls, indicating the effort of dendritic cells to counterbalance the gliadin-triggered abnormal immune responses in CeD patients.