Yuzo Suzuki

Increased serum kynurenine/tryptophan ratio correlates with disease progression in lung cancer

BACKGROUND Indoleamine 2,3-dioxygenase (IDO) catalyzes the rate-limiting step of tryptophan (Trp) degradation along the kynurenine (Kyn) pathway. By depleting tryptophan, IDO is considered to be a fundamental immune escape mechanism for tumor cells. However, IDO expression in lung cancer has not been explored thoroughly. Thus, the present study investigated IDO activity determined by serum Trp and Kyn concentrations in lung cancer and the correlation between the IDO activity and clinical parameters. METHOD The concentrations of Trp and Kyn were measured simultaneously by liquid chromatography/electrospray ionization tandem mass spectrometry (LC-ESI/MS/MS) in the sera of 123 patients with lung cancer and 45 healthy controls. The IDO activity was estimated by calculating the serum Kyn-to-Trp ratio (Kyn/Trp ratio). RESULTS Trp concentrations were significantly lower in patients with lung cancer than in healthy controls (62.6+/-15.8microM vs. 71.1+/-11.8microM, respectively; p=0.0007), while Kyn concentrations were significantly higher in patients compared with the controls (2.82+/-1.17microM vs. 2.30+/-0.56microM, respectively; p=0.0036). The IDO activity determined by the Kyn/Trp ratio was significantly higher in the patients than in the controls (47.1+/-21.3 vs. 32.9+/-9.10, respectively; p<0.0001). In addition, patients in the advanced stages of lung cancer had significantly lower Trp concentrations and higher IDO activity than those in the early stages (p=0.0058 and p=0.0209, respectively). CONCLUSIONS IDO activity was increased in lung cancer patients, and higher IDO activity was associated with more advanced stages. These results suggest that increased IDO activity is involved in disease progression of lung cancer, possibly through its immunosuppressive effect.

Intravenous Immunoglobulin Therapy for Refractory Interstitial Lung Disease Associated with Polymyositis/Dermatomyositis

Interstitial lung disease (ILD) associated with polymyositis/dermatomyositis (ILD-PM/DM), including amyopathic dermatomyositis (ADM), is recognized as an important condition because it frequently causes death, despite intensive therapy with high-dose corticosteroid and immunosuppressive agents, such as cyclosporine A and cyclophosphamide. Intravenous immunoglobulin therapy (IVIG) has shown efficacy for myopathy associated with PM/DM, but its usefulness for ILD-PM/DM is unclear. This study was designed to investigate the efficacy of IVIG for refractory ILD-PM/DM. A review was made of medical charts of five patients (2 men and 3 women) who were treated with IVIG for refractory ILD-PM/DM resistant to high-dose corticosteroid and cyclosporine A and/or cyclophosphamide. One patient had acute ILD-PM and four patients had acute ILD-ADM. Of the five patients, one patient with ILD-PM and one patient with ILD-ADM survived. No adverse reactions were seen due to IVIG treatment. There were no critical differences in the clinical parameters and clinical courses between survivors and nonsurvivors. IVIG treatment is safe and could be an effective salvage therapy for refractory ILD-PM/DM in certain cases, suggesting that further controlled trials are worthwhile.

Mouse Lung CD103+ and CD11bhigh Dendritic Cells Preferentially Induce Distinct CD4+ T-Cell Responses

Mouse lung dendritic cells (LDCs) have been recently shown to contain two major subpopulations: CD103(+) CD11b(low or negative) (CD103(+) LDCs) and CD103(-) CD11b(high) LDCs (CD11b(high) LDCs). Although several studies have demonstrated functional differences between them, it is unclear whether the subpopulations induce distinct T helper (Th) cell responses. The present study was conducted to examine whether CD103(+) and CD11b(high) LDCs preferentially generate different Th responses. Naive DO11.10 CD4(+) T cells were primed with CD103(+) or CD11b(high) LDCs obtained from normal BALB/c mice. The primed CD4(+) T cells were restimulated, and their cytokine secretions were assessed. The expression of intracellular cytokines and the mRNA levels of chemokine receptors were also measured. We found that the CD4(+) T cells primed with CD103(+) LDCs secreted significantly larger amounts of IFN-γ and IL-17A, whereas those primed with CD11b(high) LDCs released significantly higher levels of IL-4, IL-6, and IL-10. Intracellular cytokine assay showed that CD103(+) LDCs induced greater frequencies of CD4(+) T cells producing IFN-γ and IL-17A, whereas CD11b(high) LDCs were more efficient at inducing CD4(+) T cells producing IL-4 and IL-10. The mRNA levels of CXCR3 and CCR5, which are expressed preferentially in Th1 cells, were significantly higher in CD4(+) T cells primed with CD103(+) LDCs. The mRNA levels of CXCR4 and CCR4, which are expressed primarily in Th2 cells, were significantly greater in those primed with CD11b(high) LDCs. These data suggest that mouse CD103(+) LDCs predominantly elicit Th1 and Th17 responses, whereas CD11b(high) LDCs primarily provoke a Th2 response under the steady state.

Serum Indoleamine 2,3-Dioxygenase Activity Predicts Prognosis of Pulmonary Tuberculosis

ABSTRACT Tuberculosis (TB) continues to be a major health problem, and there are few biomarkers for predicting prognosis. Indoleamine 2,3-dioxygenase (IDO), a potent immunoregulatory molecule, catalyzes the rate-limiting step of tryptophan (Trp) degradation in the kynurenine (Kyn) pathway. An increase in IDO activity determined by the serum Trp/Kyn ratio has been shown to be associated with poor prognosis in cancers and bacteremia. In TB, however, there are no studies measuring serum IDO activity to determine its clinical significance. We evaluated serum IDO activity with 174 pulmonary TB (PTB) patients and 85 controls, using liquid chromatography/electrospray ionization tandem mass spectrometry. IDO activity was estimated by calculating the serum Kyn-to-Trp ratio. PTB patients had significantly higher Kyn concentrations and IDO activity and significantly lower Trp concentrations (P < 0.0001, P < 0.0001, and P < 0.0001, respectively) than the controls. Of 174 PTB patients, 39 (22.4%) died. The patients who died had significantly higher concentrations of Kyn and significantly lower Trp concentrations, resulting in significantly higher IDO activity (P < 0.0001, P < 0.0001, and P < 0.0001, respectively). In a receiver operating characteristic (ROC) analysis, serum IDO activity had the highest area under the curve (0.850), and this activity was an independent prognostic factor in multivariate analysis. These results suggest that serum IDO activity can be used as a novel prognostic marker in PTB.

Drug Lymphocyte Stimulation Test in the Diagnosis of Adverse Reactions to Antituberculosis Drugs

BACKGROUND Tuberculosis (TB) is a worldwide infectious disease. Recently, standard therapy has become very effective for treating patients with TB; however, as a result of this powerful regimen, serious side effects have become an important problem. The aim of this prospective study was to evaluate the usefulness of the drug lymphocyte stimulation test (DLST) to determine anti-TB drugs causing side effects. METHOD Four hundred thirty-six patients with TB were admitted to our hospital for treatment between January 2002 and August 2007. DLST was performed in patients who had certain adverse drug reactions during TB treatment. The causative drug was identified by the drug provocation test (DPT). The tested drugs were mainly isoniazid (INH), rifampin (RIF), ethambutol (EMB) and pyrazinamide (PZA). RESULTS Of 436 patients, 69 patients (15.8%) had certain adverse drug reactions to anti-TB drugs. Of the 261 agents that underwent the DLST and DPT, 28 agents (10.7%) in 20 patients (28.9%) were positive by DLST, and 67 agents (25.7%) in 46 patients (66.6%) were identified as causative drugs by DPT. The sensitivity of DLST was only 14.9% for all drugs (INH, 14.3%; RIF, 13.6%; EMB, 14.3%; PZA, 0%). CONCLUSIONS DLST offers little contribution to the detection of causative agents in patients with adverse anti-TB drug reactions.

Relationship between an increased serum kynurenine/tryptophan ratio and atherosclerotic parameters in hemodialysis patients

Essential amino acid tryptophan (Trp) is mainly catabolized by indoleamine 2,3‐dioxygenase, which leads to the formation of kynurenine (Kyn). In this study, we reexamined whether an increased indoleamine 2,3‐dioxygenase activity, as estimated by the Kyn/Trp ratio (μM/mM), is associated with atherosclerotic parameters in hemodialysis (HD) patients. Serum Trp and Kyn were measured in 243 HD patients by liquid chromatography/electrospray ionization tandem mass spectrometry. We measured carotid artery intima‐medial thickness, brachial‐ankle pulse wave velocity, ankle‐brachial pressure index, and the cardio‐ankle vascular index. Log‐transformed Kyn/Trp ratio was significantly correlated with log‐transformed time on HD (ρ=0.28, P<0.01), log‐transformed highly sensitive C‐reactive protein (ρ=0.20, P<0.01), and peripheral total lymphocyte count (ρ=−0.13, P<0.05). A significant association was found between log‐transformed Kyn/Trp ratio and mean carotid artery intima‐medial thickness (ρ=0.18, P<0.01). Mean carotid artery intima‐medial thickness was significantly higher in the lowest quartile of Kyn/Trp ratio (<165) (0.62±0.12 mm) when compared with the highest quartile (≥304) (0.68±0.15 mm) (P<0.01). Ankle‐brachial pressure index was lower in the second quartile (1.01±0.20), the third quartile (1.01±0.19), and the fourth quartile (1.03±0.15) compared with that in the first quartile (1.09±0.13) (P<0.05). It follows from these findings that the Kyn/Trp ratio increases with time on HD, and is associated with advanced atherosclerotic changes in chronic HD patients.

Serum activity of indoleamine 2,3-dioxygenase predicts prognosis of community-acquired pneumonia.

OBJECTIVES Indoleamine 2,3-dioxygenase (IDO) catalyzes the rate-limiting step of tryptophan (Trp) degradation in the kynurenine (Kyn) pathway. By depleting Trp, IDO plays a critical role in inducing immune suppression and tolerance. The aim of present study was to investigate serum IDO activity, determined by Kyn-to-Trp ratio (Kyn/Trp ratio), in community-acquired pneumonia (CAP) and to examine its clinical significance. METHODS This study subjects consisted of 129 consecutive patients with CAP and 64 healthy controls. The concentrations of Kyn and Trp were measured simultaneously by liquid chromatography/electrospray ionization tandem mass spectrometry. RESULTS The CAP patients had significantly higher Kyn concentrations and significant lower Trp concentrations than the controls (p < 0.0001 and p < 0.0001, respectively). Accordingly, IDO activity was significantly higher (2.4-fold) in the patients than in the controls (p < 0.0001). IDO activity correlated well with PSI (Pneumonia Severity Index) and CURB65 (p = 0.0005 and p < 0.0001, respectively). Moreover, the IDO activity and Kyn concentration were significantly higher in the nonsurvivors and were found to predict mortality in multivariate analysis. CONCLUSIONS IDO activity was increased in CAP, and this activity was associated with the severity and outcome of this disease. These results suggest that IDO activity can predict prognosis of CAP.

Indoleamine 2,3-dioxygenase in the pathogenesis of tuberculous pleurisy.

BACKGROUND Pleural fluid is a frequent manifestation in pulmonary diseases, such as lung cancer and infectious diseases, including pulmonary tuberculosis (TB). The enzyme indoleamine 2,3-dioxygenase (IDO) catalyses tryptophan through the kynurenine pathway, and is considered a crucial immunoregulatory molecule mediating immune tolerance. Recent studies have shown IDO activity to be a novel prognostic factor not only in cancer patients but also in those with infectious diseases, including pneumonia and pulmonary TB. However, no studies have measured and determined the clinical significance of IDO activity in pleural fluid. METHODS We enrolled 92 patients, including 34 with tuberculous pleurisy (TBP), 36 with malignant pleuritis and 15 with parapneumonic effusions. IDO activity was evaluated using liquid chromatography/electrospray ionisation tandem mass spectrometry, and was estimated by calculating kynurenine-to-tryptophan ratio. RESULTS Pleural fluid from patients with TBP had significantly higher kynurenine concentrations and significantly lower tryptophan concentrations, resulting in significantly higher IDO activity compared with pleural effusion or serum from non-tuberculous pleuritis (all P < 0.001). Pleural tissue from TBP showed enhanced IDO expression in epithelioid granuloma regions by immunohistochemistry. CONCLUSIONS These results suggest that IDO is strongly involved in the pathogenesis of TBP.

Mouse CD11bhigh Lung Dendritic Cells Have More Potent Capability to Induce IgA than CD103+ Lung Dendritic Cells In Vitro

Lung dendritic cells (LDCs) are primary antigen-presenting cells that develop IgA-producing plasma cells in the lung through class switch recombination (CSR) in naive B cells. Recently, the major LDC subsets were found to comprise CD103(-)CD11b(high) LDCs (CD11b(high) LDCs) and CD103(+)CD11b(low or negative) LDCs (CD103(+) LDCs), but their abilities to induce IgA production have not been defined. Under T cell-dependent (T-D) and T cell-independent (T-ID) conditions, we compared the abilities of these two LDC populations to induce IgA. CD11b(high) or CD103(+) LDCs obtained from BALB/c mice were cocultured with naive IgD(+) B cells in the presence of LPS, with or without anti-CD40 monoclonal antibody (mAb) (i.e., T-D and T-ID coculture conditions, respectively). Under both T-D and T-ID conditions, CD11b(high) LDCs induced significantly greater amounts of IgA production, together with a significantly higher mRNA expression of activation-induced cytidine deaminase, than did CD103(+) LDCs. However, the protein expression of a proliferation-inducing ligand, B cell-activating factor of the tumor necrosis family, or retinaldehyde dehydrogenase-1 did not differ between the two LDC subsets. CD11b(high) LDCs displayed a significantly greater capacity to secrete IL-6 and IL-10 in response to LPS, with or without anti-CD40 mAb. Moreover, the IgA production induced by CD11b(high) LDCs in T-D coculture was attenuated by neutralizing both IL-6 and IL-10. These findings suggest that, of the two major LDCs, CD11b(high) LDCs more efficiently induce IgA than do CD103(+) LDCs, possibly through their potent capacity to produce IgA-inducing cytokines.

Association of Increased Indoleamine 2, 3‐Dioxygenase With Impaired Natural Killer Cell Activity in Hemodialysis Patients

Indoleamine 2, 3‐dioxygenase (IDO) suppresses adaptive immune response. However, there was no study to examine whether IDO activity is associated with immune parameters in dialysis patients. In this study, we estimated serum IDO activity by the kynurenine/tryptophan ratio (KTR), and compared KTR with natural killer (NK) cell activity, soluble interleukin‐2 receptor (sIL‐2R) and serum levels of trace elements such as selenium (Se) and zinc (Zn) that affect T‐cell function in 28 hemodialysis (HD) patients (age: 72 ± 13 years old, time on HD: 79 ± 89 months). NK cell activity was decreased in 35.7% of the patients. KTR values were almost 10‐times higher in HD patients (380.81 ± 385.46 mM/M) than those in the referred controls (32.9 ± 9.10 mM/M). KTR was lower in patients with impaired NK cell activity than those without (279 ± 111 vs. 565 ± 603 mM/M, P = 0.07). There was no relationship between KTR and sIL‐2R and Zn, while KTR was significantly and negatively correlated with serum Se levels that can impair cellular immunity (r = −0.41, P < 0.05). Our findings suggest that increased IDO activity with Se deficiency may be associated with impaired NK cell function in HD patients.