Rab4A-directed endosome traffic shapes pro-inflammatory mitochondrial metabolism in T cells via mitophagy, CD98 expression, and kynurenine-sensitive mTOR activation

Activation of the mechanistic target of rapamycin (mTOR) is a key metabolic checkpoint of pro-inflammatory T-cell development that contributes to the pathogenesis of autoimmune diseases, such as systemic lupus erythematosus (SLE), however, the underlying mechanisms remain poorly understood. Here, we identify a functional role for Rab4A-directed endosome traffic in CD98 receptor recycling, mTOR activation, and accumulation of mitochondria that connect metabolic pathways with immune cell lineage development and lupus pathogenesis. Based on integrated analyses of gene expression, receptor traffic, and stable isotope tracing of metabolic pathways, constitutively active Rab4AQ72L exerts cell type-specific control over metabolic networks, dominantly impacting CD98-dependent kynurenine production, mTOR activation, mitochondrial electron transport and flux through the tricarboxylic acid cycle and thus expands CD4+ and CD3+CD4-CD8- double-negative T cells over CD8+ T cells, enhancing B cell activation, plasma cell development, antinuclear and antiphospholipid autoantibody production, and glomerulonephritis in lupus-prone mice. Rab4A deletion in T cells and pharmacological mTOR blockade restrain CD98 expression, mitochondrial metabolism and lineage skewing and attenuate glomerulonephritis. This study identifies Rab4A-directed endosome traffic as a multilevel regulator of T cell lineage specification during lupus pathogenesis.

Serum procalcitonin has no significance in the diagnosis of periprosthesis joint infection before total hip and knee replacement

Background

Currently, there is no "gold standard" for early diagnosing PJI. The diagnosis of periprosthetic joint infection (PJI) is a challenging problem in the clinic. As we know, many serum markers have been used in the early diagnosis of PJI. The aim of this study was to validate the value of PCT in the diagnosis of PJI.

Methods

A retrospective review of 77 patients with revision arthroplasties from January 2013 to July 2020 was conducted. PJI was defined using the modified Musculoskeletal Infection Society (MSIS) criteria combined with follow-up results. Besides medical history, clinical and laboratory data was gathered. Preoperative blood was taken for serum PCT and other biomarkers measurement. Receiver operating characteristic (ROC) curves were generated to evaluate the biomarkers' diagnostic performance and optimal cut-off value.

Results

Forty-one patients were identified as the PJI group (27 hips and 14 knees), while thirty-six patients were identified as the aseptic loosening (AL) group (33 hips and 3 knees). The AUCs for C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), Platelets (PLT), Fibrinogen (FIB), and Procalcitonin (PCT) were 0.845 (95% CI 0.755-0.936, p < 0.001), 0.817 (95% CI 0.718-0.916, p < 0.001), 0.728 (95% CI 0.613-0.843, p < 0.001), 0.810 (95% CI 0.710-0.910, p < 0.001) and 0.504 (95% CI 0.373-0.635, p = 0.950), respectively. Higher Area under the Curve (AUC) values were obtained for the combinations of PCT and CRP (AUC = 0.870) (95% CI, 0.774-0.936), PCT and ESR (AUC = 0.817) (95% CI, 0.712-0.896), PCT and PLT (AUC = 0.731) (95% CI, 0.617-0.825), PCT and FIB (AUC = 0.815) (95% CI, 0.710-0.894). The serum PCT indicated a sensitivity of 19.51% and a specificity of 83.33% for diagnosing PJI. When the optimal cut-off value for PCT was set as 0.05 ng/ml, its positive and negative likelihood ratios were 57.1% and 47.6%, respectively.

Conclusion

In conclusion, serum PCT appeared to be no reliable biomarker in differentiating PJI from aseptic loosening before revision arthroplasties. However, PCT combined with other biomarkers further increases the diagnostic accuracy.

The Co-occurrence of Chronic Hepatitis B and Fibrosis Is Associated With a Decrease in Hepatic Global DNA Methylation Levels in Patients With Non-alcoholic Fatty Liver Disease

Global DNA hypomethylation has been reported in patients with chronic hepatitis B (CHB) and non-alcoholic fatty-liver disease (NAFLD). However, the global DNA methylation profile of patients with concurrent NAFLD and CHB (NAFLD + CHB) is still unclear. We aimed to detect the hepatic global DNA methylation levels of NAFLD + CHB patients and assess the associated risk factors. Liver biopsies were collected from 55 NAFLD patients with or without CHB. The histological characteristics of the biopsy were then assessed. Hepatic global DNA methylation levels were quantified by fluorometric method. The hepatic global DNA methylation levels in NAFLD + CHB group were significantly lower than that in NAFLD group. Participants with fibrosis showed lower levels of hepatic global DNA methylation than those without fibrosis. Participants with both CHB and fibrosis had lower levels of hepatic global DNA methylation than those without either CHB or fibrosis. The co-occurrence of CHB and fibrosis was significantly associated with a reduction in global DNA methylation levels compared to the absence of both CHB and fibrosis. Our study suggests that patients with NAFLD + CHB exhibited lower levels of global DNA methylation than patients who had NAFLD alone. The co-occurrence of CHB and liver fibrosis in NAFLD patients was associated with a decrease in global DNA methylation levels.

Rab4A inactivation in T cells blocks mTOR activation, pro-inflammatory lineage development, and disease pathogenesis in lupus-prone mice

Introduction

Expression of Rab4A is increased in T cells of patients and mice with SLE. Overexpression of Rab4A forms a positive feedback loop with mTOR that can be blocked with therapeutic efficacy in SLE. To determine the impact of this gene on disease development, the triple-congenic lupus-prone Sle1.2.3 mouse strain (TC) have been backcrossed with C57Bl/6 wild-type (WT) mice that carry floxed Rab4AQ72L (TC-FL) alleles or lack Rab4A in T cells (TC-KO).

Methods

Proteinuria was assessed by the Bradford assay. Splenocytes were examined by flow cytometry. Autoantibody production was measured by ELISA.

Results

TC mice had increased proteinuria over age and sex-matched WT controls. Deletion of Rab4A in T cells reduced proteinuria ≥ 50% in female TC-KO mice relative to TC-FL mice at 21 or 40 weeks of age. Similar trends were noted in male mice. The production of antinuclear and antiphospholipid antibodies was reduced in TC-KO mice as compared to TC-FL and parental TC controls.

Immunophenotyping unveiled a 45% depletion of CD4+ T cells and 50% expansion of CD8+ T cells in female TC-KO mice relative to TC-FL controls. CD38 expression was reduced on CD4+ T cells of TC-KO mice by 51% and 48% relative to TC and TC-FL controls. CD38 expression was also reduced on CD8+ T cells but not on CD19+ B cells. mTORC1 activity was reduced by 36% in CD4 T cells, but not in CD8 T cells or B cells of TC-KO mice. Along these lines, overexpression of Rab4A activated mTORC1, reduced expression of CD4, and increased expression of CD38 in Jurkat cells.

Conclusion

These findings reveal an opposite influence of Rab4A on endosomal recycling of CD4 and CD38 that facilitates mTORC1 activation and thus causes pro-inflammatory T-cell lineage specification and triggers autoimmunity in SLE.

Sirolimus in patients with clinically active systemic lupus erythematosus resistant to, or intolerant of, conventional medications: a single-arm, open-label, phase 1/2 trial

BACKGROUND

Patients with systemic lupus erythematosus have T-cell dysfunction that has been attributed to the activation of the mammalian target of rapamycin (mTOR). Rapamycin inhibits antigen-induced T-cell proliferation and has been developed as a medication under the generic designation of sirolimus. We assessed safety, tolerance, and efficacy of sirolimus in a prospective, biomarker-driven, open-label clinical trial.

METHODS

We did a single-arm, open-label, phase 1/2 trial of sirolimus in patients with active systemic lupus erythematosus disease unresponsive to, or intolerant of, conventional medications at the State University of New York Upstate Medical University (Syracuse, NY, USA). Eligible participants (aged ≥18 years) had active systemic lupus erythematosus fulfilling four or more of 11 diagnostic criteria defined by the American College of Rheumatology. We excluded patients with allergy or intolerance to sirolimus, patients with life-threatening manifestations of systemic lupus erythematosus, proteinuria, a urine protein to creatinine ratio higher than 0·5, anaemia, leucopenia, or thrombocytopenia. Patients received oral sirolimus at a starting dose of 2 mg per day, with dose adjusted according to tolerance and to maintain a therapeutic range of 6-15 ng/mL. Patients were treated with sirolimus for 12 months. Safety outcomes included tolerance as assessed by the occurrence of common side-effects. The primary efficacy endpoint was decrease in disease activity, assessed using the British Isles Lupus Assessment Group (BILAG) index and the Systemic Lupus Erythematosus Disease Activity Index (SLEDAI). Blood samples of 56 matched healthy individuals were obtained as controls for immunobiological outcomes monitored at each visit. The primary efficacy endpoint was assessed in all patients who completed 12 months of treatment, and all patients who received at least one dose of treatment were included in the safety analyses. This trial is registered with ClinicalTrials.gov, number NCT00779194.

FINDINGS

Between March 9, 2009, and Dec 8, 2014, 43 patients were enrolled, three of whom did not meet eligibility criteria. 11 of the 40 eligible patients discontinued study treatment because of intolerance (n=2) or non-compliance (n=9). SLEDAI and BILAG disease activity scores were reduced during 12 months of treatment in 16 (55%) of 29 patients who completed treatment. Mean SLEDAI score decreased from 10·2 (SD 5·6) at enrolment to 4·8 (4·5) after 12 months of treatment (p<0·001) and the mean total BILAG index score decreased from 28·4 (12·4) at enrolment to 17·4 (10·7) after 12 months of treatment (p<0·001). The mean daily dose of prednisone required to control disease activity decreased from 23·7 mg (SD 9·6) to 7·2 mg (2·3; p<0·001) after 12 months of treatment. Sirolimus expanded CD4⁺CD25⁺FoxP3⁺ regulatory T cells and CD8⁺ memory T-cell populations and inhibited interleukin-4 and interleukin-17 production by CD4⁺ and CD4^-CD8^- double-negative T cells after 12 months. CD8⁺ memory T cells were selectively expanded in SRI-responders. Patient liver function and lymphocyte counts were unchanged. Although HDL-cholesterol (Z=-2·50, p=0·012), neutrophil counts (Z=-1·92, p=0·054), and haemoglobin (Z=-2·83, p=0·005) were moderately reduced during treatment, all changes occurred within a range that was considered safe. Platelet counts were slightly elevated during treatment (Z=2·06, p=0·0400).

INTERPRETATION

These data show that a progressive improvement in disease activity is associated with correction of pro-inflammatory T-cell lineage specification in patients with active systemic lupus erythematosus during 12 months of sirolimus treatment. Follow-up placebo-controlled clinical trials in diverse patient populations are warranted to further define the role of mTOR blockade in treatment of systemic lupus erythematosus.

FUNDING

Pfizer, the National Institutes of Health, and the Central New York Community Foundation.

[Influence of social support and coping style on chronic post-traumatic stress disorder after floods]

OBJECTIVE

To explore the long-term prognosis and influence of social support and coping style of patients with post-traumatic stress disorder (PTSD) after suffering from floods.

METHODS

Patients suffered PTSD due to Dongting lake flood in 1998 were selected through cluster random sampling. PTSD scale civilian version (PCL-C) was used to examine and diagnose the participants in this study. PTSD was then evaluated by the social support rating scale (SSRS) and the simple coping style questionnaire (SCSQ).

RESULTS

Among all the 120 subjects, 14(11.67%) of them were diagnosed as having PTSD. Compared with the rehabilitation group, scores on subjective support, objective support, total social support and positive coping, total of coping style from the non-rehabilitation group all appeared significant low (P<0.05). Data from the multivariate logistic regression showed that social support (OR=0.281, 95% CI: 0.117-0.678) and coping style (OR= 0.293, 95% CI: 0.128-0.672) were protective factors of the chronic PTSD after the floods while disaster experience (OR=1.626, 95%CI: 1.118-2.365) appeared as a risk factor.

CONCLUSION

Chronic PTSD developed after the floods called for attention. Better social support, positive coping style could significantly improve the long-term prognosis of patients with PTSD after the floods.

Quantitative proteomic analysis of formalin-fixed, paraffin-embedded clear cell renal cell carcinoma tissue using stable isotopic dimethylation of primary amines

Background

Formalin-fixed, paraffin-embedded (FFPE) tissues represent the most abundant resource of archived human specimens in pathology. Such tissue specimens are emerging as a highly valuable resource for translational proteomic studies. In quantitative proteomic analysis, reductive di-methylation of primary amines using stable isotopic formaldehyde variants is increasingly used due to its robustness and cost-effectiveness.

Results

In the present study we show for the first time that isotopic amine dimethylation can be used in a straightforward manner for the quantitative proteomic analysis of FFPE specimens without interference from formalin employed in the FFPE process. Isotopic amine dimethylation of FFPE specimens showed equal labeling efficiency as for cryopreserved specimens. For both FFPE and cryopreserved specimens, differential labeling of identical samples yielded highly similar ratio distributions within the expected range for dimethyl labeling. In an initial application, we profiled proteome changes in clear cell renal cell carcinoma (ccRCC) FFPE tissue specimens compared to adjacent non–malignant renal tissue. Our findings highlight increased levels of glyocolytic enzymes, annexins as well as ribosomal and proteasomal proteins.

Conclusion

Our study establishes isotopic amine dimethylation as a versatile tool for quantitative proteomic analysis of FFPE specimens and underlines proteome alterations in ccRCC.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1768-x) contains supplementary material, which is available to authorized users.

Comprehensive metabolome analyses reveal N-acetylcysteine-responsive accumulation of kynurenine in systemic lupus erythematosus: implications for activation of the mechanistic target of rapamycin

Systemic lupus erythematosus (SLE) patients exhibit depletion of the intracellular antioxidant glutathione and downstream activation of the metabolic sensor, mechanistic target of rapamycin (mTOR). Since reversal of glutathione depletion by the amino acid precursor, N-acetylcysteine (NAC), is therapeutic in SLE, its mechanism of impact on the metabolome was examined within the context of a double-blind placebo-controlled trial. Quantitative metabolome profiling of peripheral blood lymphocytes (PBL) was performed in 36 SLE patients and 42 healthy controls matched for age, gender, and ethnicity of patients using mass spectrometry that covers all major metabolic pathways. mTOR activity was assessed by western blot and flow cytometry. Metabolome changes in lupus PBL affected 27 of 80 KEGG pathways at FDR p < 0.05 with most prominent impact on the pentose phosphate pathway (PPP). While cysteine was depleted, cystine, kynurenine, cytosine, and dCTP were the most increased metabolites. Area under the receiver operating characteristic curve (AUC) logistic regression approach identified kynurenine (AUC = 0.859), dCTP (AUC = 0.762), and methionine sulfoxide (AUC = 0.708), as top predictors of SLE. Kynurenine was the top predictor of NAC effect in SLE (AUC = 0.851). NAC treatment significantly reduced kynurenine levels relative to placebo in vivo (raw p = 2.8 × 10^-7, FDR corrected p = 6.6 × 10^-5). Kynurenine stimulated mTOR activity in healthy control PBL in vitro. Metabolome changes in lupus PBL reveal a dominant impact on the PPP that reflect greater demand for nucleotides and oxidative stress. The PPP-connected and NAC-responsive accumulation of kynurenine and its stimulation of mTOR are identified as novel metabolic checkpoints in lupus pathogenesis.

Low birth weight is associated with lower respiratory tract infections in children with hand, foot, and mouth disease

BACKGROUND

Low birth weight (LBW) might be a risk factor for acquiring lower respiratory tract infections (LRTIs) associated with disease related complications in early childhood. HFMD, a frequent viral infection in southern China, is a leading cause of lower respiratory tract infections in children. We analyzed whether LBW is a risk factor for children with HFMD to develop lower respiratory tract infections.

METHODS

A total of 298 children with HFMD, admitted to a hospital in Qingyuan city, Guangdong province, were recruited. Demographic data and clinical parameters such as serum glucose level and inflammatory markers including peripheral white blood cell count, serum C-reactive protein, and erythrocyte sedimentation rate were routinely collected on admission. Birth weight data were derived from birth records.

RESULTS

Mean birth weight (BW) was 167 g lower in patients with HFMD and LRTIs as compared to patients with solely HFMD (p = 0.022) and the frequency of birth weight below the tenth percentile was significantly higher in patients with HFMD and LRTIs (p = 0.002).

CONCLUSIONS

The results of the study show that low birth weight is associated with a higher incidence of lower respiratory tract infections in young children with HFMD.

Mechanistic target of rapamycin activation triggers IL-4 production and necrotic death of double-negative T cells in patients with systemic lupus erythematosus

The mechanistic target of rapamycin (mTOR) is recognized as a sensor of mitochondrial dysfunction and effector of T cell lineage development; however, its role in autoimmunity, including systemic lupus erythematosus, remains unclear. In this study, we prospectively evaluated mitochondrial dysfunction and mTOR activation in PBLs relative to the Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) during 274 visits of 59 patients and 54 matched healthy subjects. Partial least square-discriminant analysis identified 15 of 212 parameters that accounted for 70.2% of the total variance and discriminated lupus and control samples (p < 0.0005); increased mitochondrial mass of CD3(+)/CD4(-)/CD8(-) double-negative (DN) T cells (p = 1.1 × 10(-22)) and FOXP3 depletion in CD4(+)/CD25(+) T cells were top contributors (p = 6.7 × 10(-7)). Prominent necrosis and mTOR activation were noted in DN T cells during 15 visits characterized by flares (SLEDAI increase ≥ 4) relative to 61 visits of remission (SLEDAI decrease ≥ 4). mTOR activation in DN T cells was also noted at preflare visits of SLE patients relative to those with stable disease or healthy controls. DN lupus T cells showed increased production of IL-4, which correlated with depletion of CD25(+)/CD19(+) B cells. Rapamycin treatment in vivo blocked the IL-4 production and necrosis of DN T cells, increased the expression of FOXP3 in CD25(+)/CD4(+) T cells, and expanded CD25(+)/CD19(+) B cells. These results identify mTOR activation to be a trigger of IL-4 production and necrotic death of DN T cells in patients with SLE.

Attention deficit and hyperactivity disorder scores are elevated and respond to N-acetylcysteine treatment in patients with systemic lupus erythematosus

OBJECTIVE

To investigate whether attention deficit hyperactivity disorder (ADHD) may serve as a marker of neuropsychiatric disease and as a target for N-acetylcysteine (NAC) treatment in patients with systemic lupus erythematosus (SLE).

METHODS

The ADHD Self-Report Scale (ASRS) was used to assess 49 patients with SLE and 46 matched healthy control subjects. Twenty-four of the patients with SLE were randomized to receive either placebo, NAC at a dosage of 2.4 gm/day, or NAC at a dosage of 4.8 gm/day. Disease activity was evaluated monthly using the British Isles Lupus Assessment Group (BILAG) index, the Systemic Lupus Erythematosus Disease Activity Index (SLEDAI), the Fatigue Assessment Scale (FAS), and the ASRS, before and during the 3-month treatment period and after a 1-month washout period.

RESULTS

The cognitive/inattentive (ASRS part A), hyperactivity/impulsive (ASRS part B), and combined (total) ASRS scores were increased in patients with SLE compared with control subjects (mean ± SEM 17.37 ± 1.03 [P = 3 × 10(-7) ], 14.51 ± 0.89 [P = 2 × 10(-4) ], and 31.92 ± 1.74 [P = 8 × 10(-7) ], respectively, versus 10.41 ± 1.02, 9.61 ± 1.21, and 20.02 ± 1.98, respectively. ASRS part A scores correlated with SLEDAI (r = 0.53, P < 0.0001) and BILAG scores (r = 0.36, P = 0.011). ASRS total scores also correlated with SLEDAI (r = 0.45, P = 0.0009) and BILAG scores (r = 0.31, P = 0.025). ASRS part A (r = 0.73, P < 0.0001), ASRS part B (r = 0.47, P = 0.0006), and ASRS total scores (r = 0.67, P < 0.0001) correlated with the FAS score. Relative to the scores in placebo-treated patients, ASRS total scores were reduced in SLE patients treated with NAC dosages of 2.4 gm/day and 4.8 gm/day combined (P = 0.037). ASRS part A scores were reduced by NAC dosages of 2.4 gm/day (P = 0.001) and 4.8 gm/day (P < 0.0001) as well as by NAC at dosages of 2.4 gm/day and 4.8 gm/day combined (P = 0.001).

CONCLUSION

In patients with SLE, elevated ASRS scores reveal previously unrecognized and clinically significant symptoms of ADHD that respond to NAC treatment.

Prenatal exposure to cigarette smoke alters later-life antitumor cytotoxic T-lymphocyte (CTL) activity via possible changes in T-regulatory cells

Epidemiological studies suggest that maternal smoking increases the incidence in the progeny of certain childhood cancers. Our previous study in mice demonstrated the feasibility of such an association by demonstrating that prenatal exposure to cigarette smoke (CS) elevated the incidence of transplanted tumors and reduced cytotoxic T-lymphocyte (CTL) activity in juvenile male offspring. The current study extends these findings by investigating the relationship between CS-induced CTL suppression and effects on regulators of effector T-cell activity, such as T-regulatory (Treg; CD4+ CD25+ Foxp3+) cells and transforming growth factor (TGF)-β. Results here demonstrate that in utero exposure to CS, at a maternal particle concentration of 15 mg/m3 (4 h/d, 5 d/wk), significantly reduced ex vivo CTL activity of whole splenocytes (and isolated CD8+ cells) against tumor cells both before and after injection of prenatally exposed mice with EL4 lymphoma cells. In contrast, prenatal CS exposure significantly increased levels of thymic Treg cells in a time-dependent manner following tumor cell injection. In vitro production of TGF-β by splenocytes recovered from prenatally exposed, tumor-bearing mice was also altered. Neither prenatal CS exposure nor subsequent administration of EL4 cells exerted any marked effects on lymphoid organ weights, cellularity, or histologic profiles. Given that Treg cells and TGF-β suppress effector T-cell activities, these findings suggest possible immune mechanisms by which early exposure to CS reduces CTL tumoricidal activity during tumor cell development. Data suggest that children of smoking mothers may be less able to mount an appropriate adaptive immune response to tumors, thus increasing their risk for some cancers later in life.

N-acetylcysteine reduces disease activity by blocking mammalian target of rapamycin in T cells from systemic lupus erythematosus patients: a randomized, double-blind, placebo-controlled trial

OBJECTIVE

Systemic lupus erythematosus (SLE) patients exhibit T cell dysfunction, which can be regulated through mitochondrial transmembrane potential (Δψm) and mammalian target of rapamycin (mTOR) by glutathione (GSH). This randomized, double-blind, placebo-controlled study was undertaken to examine the safety, tolerance, and efficacy of the GSH precursor N-acetylcysteine (NAC).

METHODS

A total of 36 SLE patients received either daily placebo or 1.2 gm, 2.4 gm, or 4.8 gm of NAC. Disease activity was evaluated monthly by the British Isles Lupus Assessment Group (BILAG) index, the SLE Disease Activity Index (SLEDAI), and the Fatigue Assessment Scale (FAS) before, during, and after a 3-month treatment period. Mitochondrial transmembrane potential and mTOR were assessed by flow cytometry. Forty-two healthy subjects matched to patients for age, sex, and ethnicity were studied as controls.

RESULTS

NAC up to 2.4 gm/day was tolerated by all patients, while 33% of those receiving 4.8 gm/day had reversible nausea. Placebo or NAC 1.2 gm/day did not influence disease activity. Considered together, 2.4 gm and 4.8 gm NAC reduced the SLEDAI score after 1 month (P = 0.0007), 2 months (P = 0.0009), 3 months (P = 0.0030), and 4 months (P = 0.0046); the BILAG score after 1 month (P = 0.029) and 3 months (P = 0.009); and the FAS score after 2 months (P = 0.0006) and 3 months (P = 0.005). NAC increased Δψm (P = 0.0001) in all T cells, profoundly reduced mTOR activity (P = 0.0009), enhanced apoptosis (P = 0.0004), reversed expansion of CD4-CD8- T cells (mean ± SEM 1.35 ± 0.12-fold change; P = 0.008), stimulated FoxP3 expression in CD4+CD25+ T cells (P = 0.045), and reduced anti-DNA production (P = 0.049).

CONCLUSION

This pilot study suggests that NAC safely improves lupus disease activity by blocking mTOR in T lymphocytes.

Expansion of CD3+/CD4+/CD25+/Foxp3+ T cells in rapamycin-treated lupus patients (143.52)

Activation and death pathway selection of T cells are regulated via the mitochondrial transmembrane potential (Δψm). Systemic lupus erythematosus (SLE) patients’ T cells exhibit persistent Δψm elevation or mitochondrial hyperpolarization (MHP) and ATP depletion which predispose them to pro-inflammatory death via necrosis. Here, we examined the role of the mammalian target of rapamycin (mTOR), which serves as a sensor of MHP, in T cell activation in 34 female SLE patients and 30 female controls matched for age and ethnicity. MHP and mitochondrial mass was most robustly (1.6-2.0-fold; p= 0.0027) increased in CD3+/CD4-/CD8- cells. The prevalence of Foxp3+ cells within the CD4+/CD25+ compartment was reduced in SLE patients (37.05 ± 3.0 %) relative to controls (48.37 ± 2.5 %; p = 0.0014). mTOR activity, as measured by the accumulation of pS6 protein, was increased &gt; 1.5-fold in CD3+ T cells (p=0.012) and CD19+ B cells (p=0.006). Relative to healthy controls (3.18 ± 0.39%), the frequency of Foxp3+/CD4+/CD25+ cells was reduced in 6 lupus patients (1.70 ± 0.42%; p=0.021) prior to rapamycin treatment. In vivo treatment with rapamycin increased the frequency of Tregs from 1.50 ± 0.45% to 2.8 ± 0.59% (p=0.040) while the SLEDAI scores were reduced in 5 SLE patients from 22.4 ± 5.7 to 16.7 ± 2.8 (p=0.017).These data identify the in vivo expansion of Tregs as a potential mechanism of action that may contribute to the therapeutic efficacy of rapamycin in SLE.

Identification of stage-specific gene modulation during early thymocyte development by whole-genome profiling analysis after aryl hydrocarbon receptor activation

The aryl hydrocarbon receptor (AHR) is a basic helix-loop-helix transcription factor, implicated as an important modulator of the immune system and of early thymocyte development. We have shown previously that AHR activation by the environmental contaminant and potent AHR agonist 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) leads to a significant decline in the percentage of S-phase cells in the CD3(-)CD4(-)CD8(-) triple-negative stage (TN) 3 and TN4 T-cell committed thymocytes 9 to 12 h after exposure. In the more immature TN1- or TN2-stage cells, no effect on cell cycle was observed. To identify early molecular targets, which could provide insight into how the AHR acts as a modulator of thymocyte development and cell cycle regulation, we performed gene-profiling experiments using RNA isolated from four intrathymic progenitor populations in which the AHR was activated for 6 or 12 h. This microarray analysis of AHR activation identified 108 distinct gene probes that were significantly modulated in the TN1-4 thymocyte progenitor stages. Although most of the genes identified have specific AHR recognition sequences, only seven genes were altered exclusively in the two T-cell committed stages of early thymocyte development (TN3 and TN4) in which the decline of S-phase cells is seen. Moreover, all seven of these genes were reduced in expression, and five of the seven are associated with cell cycle regulatory processes. These seven genes are novel targets for modulation by the TCDD-activated AHR and may be involved in the observed cell-cycle arrest and suppression of early thymocyte development.

Effects of Prenatal Exposure to Cigarette Smoke on Offspring Tumor Susceptibility and Associated Immune Mechanisms

Epidemiologic evidence suggests that prenatal exposure to intact (unfractionated) cigarette smoke (CS) increases the incidence of cancer in the offspring. A toxicology study was carried out to examine the effects and underlying mechanisms of prenatal exposure to mainstream cigarette smoke (MCS) on offspring resistance to tumor challenge and surveillance mechanisms critical for the recognition and destruction of tumors. Pregnant B6C3F1 mice were exposed by inhalation to MCS for 5 days/week (4 h/day from gestational day 4 to parturition). Smoke-induced effects on offspring-host resistance to transplanted tumor cells; natural killer (NK) cell and cytotoxic T-lymphocyte (CTL) activity; cytokine levels; lymphoid organ immune cell subpopulations; and histology-were examined in 5-, 10- and 20-week-old male and female offspring. At a concentration of smoke roughly equivalent to smoking <1 pack of cigarettes/day, prenatally exposed male offspring challenged at 5 week of age with EL4 lymphoma cells demonstrated a greater than two-fold increase in tumor incidence (relative to age-/gender-matched air-exposed offspring); tumors in prenatally smoke-exposed pups also grew significantly faster. Cytotoxic T-lymphocyte activity in the smoke-exposed 5- and 10-week-old male pups was significantly less than that of the age- and gender-matched controls. No effects of prenatal CS exposure were observed on offspring NK activity, cytokine levels, lymphoid organ histology, or immune cell subpopulations. Results demonstrated that exposure of pregnant mice to a relevant dose of MCS decreased offspring resistance against transplanted tumor cells and persistently reduced CTL activity in prenatally exposed pups. This study provides biological plausibility for the epidemiologic data indicating that children of mothers who smoke during pregnancy have a greater risk of developing cancer in later life.

Effects of a single dose of 2,3,7,8-tetrachlorodibenzo-p-dioxin, given at post-puberty, in senescent mice

2,3,7,8-Tetrachlorodibenzo-p-dioxin is a well-known immunosuppressive environmental pollutant. TCDD interferes with physiological signaling of the arylhydrocarbon receptor, leading to cell-specific changes in gene transcription and cell differentiation. With respect to the immune system, the T-cell lineage and B-cell lineages are particularly affected. Although a single dose given to mice is excreted within weeks, these changes in differentiation may have long-term consequences for immune competence. We studied the effects of a single dose of TCDD given to young mice on some parameters of their immune system after they had aged almost to the end of their lifespan. Groups of 15 mice were given either 2.5 microg TCDD/kg b.w. or 25 microg TCDD/kg b.w. at the age of 8-12 weeks, and were analyzed between 16 and 21 months of age. Survival was equal in all groups. Blood glucose levels did not differ, and glucose tolerance after oral challenge was normal in old control mice and TCDD-exposed mice. No differences in the frequencies of B-cells, T-cells, or NK-cells were detectable. TCDD-exposed mice at both doses had a significantly higher titer of IgM compared to controls. Histological examination of pancreas, liver, kidney, spleen, and lungs yielded no differences, except for the lungs, where a significantly higher number of animals displayed activated BALT. In conclusion, our data suggest that a single dose of TCDD in young mice is correlated to activated secondary lymphoid tissues and high IgM titers. Both findings are congruent with a weakened immune system.

Bcl2-Independent Chromatin Cleavage is a Very Early Event during Induction of Apoptosis in Mouse Thymocytes after Treatment with Either Dexamethasone or Ionizing Radiation

We have quantified the emergence of early chromatin breaks during the signal transduction phase of apoptosis in mouse thymocytes after treatment with either ionizing radiation or dexamethasone. Dexamethasone at 1 microM can induce significant levels of DNA breaks (equivalent to the amount induced directly by 7.5 Gy ionizing radiation) within 0.5 h of treatment. The execution phase of apoptosis was not observed until 4-6 h after the same treatment. The presence of the Bcl2 transgene under the control of the p56lck promoter almost completely inhibited apoptosis up to 24 h after treatment, but it had virtually no effect on the early chromatin cleavage occurring in the first 6 h. Ionizing radiation induced chromatin cleavage both directly by damaging DNA and indirectly with kinetics similar to the induction of chromatin cleavage by dexamethasone. The presence of the Bcl2 transgene had no effect on the direct or indirect radiation-induced cleavage in the first 6 h, but after the first 6 h, the Bcl2 gene inhibited further radiation-induced chromatin cleavage. These results suggest that endonucleases are activated within minutes of treatment with either dexamethasone or ionizing radiation as part of the very early signal transduction phase of apoptosis, and prior to the irreversible commitment to cell death.

2,3,7,8-tetrachlorodibenzo-p-dioxin causes alterations in lymphocyte development and thymic atrophy in hemopoietic chimeras generated from mice deficient in ARNT2

It is well established that dioxins cause a variety of toxic effects and syndromes including alterations of lymphocyte development. Exposure to the prototypical dioxin, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) leads to severe thymic atrophy in all species studied. It has been shown that most of this toxicity is due to TCDD binding to and activating the aryl hydrocarbon receptor (AHR). Upon activation, the AHR enters the nucleus, dimerizes with the AHR nuclear translocator (ARNT), and this heterodimer modulates a number of genes that mediate toxicity. The AHR and ARNT are members of the basic-helix-loop-helix-Per, ARNT, and Sim homology (bHLH-PAS) family of transcription factors. In this study, we wanted to determine if another bHLH-PAS transcription factor, ARNT2, which has high amino acid sequence identity to ARNT and has been shown to dimerize with the TCDD-activated AHR, is involved in mediating TCDD's effect on lymphocyte development. We determined by RT-PCR that ARNT2 is expressed at a low level in whole thymus, thymocytes, and bone marrow lymphocytes. We created hemopoietic chimeras by lethally irradiating C57BL/6 mice and reconstituting them with fetal liver stem cells that either have or are deficient in a portion of chromosome 7 that contains ARNT2. Regardless of whether chimeras possessed or lacked this chromosome fragment, equal sensitivity to TCDD-induced thymic atrophy was observed despite expression of ARNT2 in the thymus. Furthermore, the absence of ARNT2 (or any other genes found on this portion of chromosome 7) did not confer any protection against TCDD-induced alterations in bone marrow B-cell subsets. These data indicate that in this model system the effects of TCDD-induced thymic atrophy and alterations in B-cell maturation are not dependent on an AHR-ARNT2 heterodimer.

Dioxin-induced adseverin expression in the mouse thymus is strictly regulated and dependent on the aryl hydrocarbon receptor

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD), a ligand for the ubiquitous, intracellular aryl hydrocarbon receptor (AhR), up-regulates the actin-modulating protein adseverin in mouse lymphoid tissues, a response that may be correlated to the immunotoxicity of TCDD. Here, by using chimeric mice with TCDD-responsive (AhR(+/+)) hematopoietic cells and TCDD-unresponsive (AhR(minus sign/minus sign)) thymic stroma, or the reverse, we show that TCDD-induced expression of adseverin in thymus is dependent on AhR expression in hematopoietic cells but not in stroma. The use of fetal thymic organ cultures also indicates that TCDD-induced expression of adseverin is confined to the thymocytes. The thymic stroma showed no induction of adseverin expression after TCDD exposure, although TCDD clearly activated the AhR in these cells, as indicated by the induction of CYP1A1. Adseverin was not induced in the thymus of normal adult C57BL/6 mice exposed to beta-estradiol or dexamethasone, two other agents, which also cause thymic atrophy. This further supports that adseverin induction is a specific gene regulatory effect by TCDD on thymocytes.

Differential effects of diethylstilbestrol and 2,3,7,8-tetrachlorodibenzo-p-dioxin on thymocyte differentiation, proliferation, and apoptosis in bcl-2 transgenic mouse fetal thymus organ culture

Both the estrogenic drug diethylstilbestrol (DES) and the pervasive environmental contaminant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) inhibit thymocyte development. The mechanisms by which either agent induces thymic atrophy are still undetermined. We previously found that TCDD and DES inhibited C57BL/6 murine fetal thymocyte organ cultures (FTOC) at different stages of development. Now, using bcl-2 transgenic (TG) mice, we have further investigated their effects on FTOC proliferation, differentiation, maturation, and apoptosis. As with C57BL/6 mice, thymocyte development in C3H/bcl-2 FTOCs was inhibited by either TCDD (10 nM) or DES (20 microM) in both bcl-2 TG- and TG+ littermates. However, the percentage reduction of cell number induced by DES in bcl-2 TG+ FTOCs was significantly less than the level of inhibition in TG- FTOCs. There was no difference in the level of reduction from TCDD-exposed TG+ or TG- FTOC. Whereas TCDD increased production of mature CD8 cells in either strain, DES mainly yielded cells in the CD4(-)CD8(-)(DN) stage in TG- mice. The anti-apoptotic bcl-2 transgene overcame some DES blocking of DN thymocyte development, allowing more cells to differentiate into CD4 single-positive cells. Analysis of cell cycle showed that TCDD inhibited entry into S phase, whereas DES blocked cell cycling in the G2/M phase. TCDD did not induce detectable apoptosis in FTOC. However, unlike the effects of 17 beta-estradiol (E2) in vivo, DES induced apoptosis in the TG- FTOC, and these apoptotic cells were mainly in the DN subpopulation. This apoptosis could be prevented by the overexpression of bcl-2 in the TG+ mice. Our results demonstrate that, in addition to inhibition of fetal thymocytes at different stages of development by TCDD and DES, DES also induces thymic atrophy by both bcl-2-inhibitable apoptosis and by inducing cell cycle arrest in G2/M in the latest stage in the stem cell compartment. TCDD, on the other hand, does not induce apoptosis, but inhibits entry into cell cycle in the earliest stage in the stem cell compartment.

2,3,7,8-Tetrachlorodibenzo-p-dioxin and diethylstilbestrol affect thymocytes at different stages of development in fetal thymus organ culture

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) and estrogen induce thymic atrophy and alter thymocyte development. In the present study we investigate whether TCDD and the synthetic estrogen diethylstilbestrol (DES) alter intrathymic development by the same or different mechanisms. We compared the effects of TCDD and DES on thymocyte development in fetal thymus organ culture (FTOC) and found that both compounds caused a reduction in cell yield. TCDD- and DES-treated FTOCs yielded fewer CD4 + CD8+ double-positive cells. However TCDD treatment also led to a greater percentage of cells in the CD8+ single-positive compartment. At lower dioxin concentrations, our results demonstrated an actual increase in CD8+ cells, whereas DES-treated fetal thymocytes were mainly enriched in CD4-CD8- double-negative cells. More alpha beta-TCR+ positive cells were seen in TCDD- but not in DES-exposed cultures. Furthermore, in this study we found that TCDD and DES also alter intrathymic development at different stages in the CD4-CD8- double-negative compartment. TCDD induced a relative increase in c-kit + CD44 + CD25-HSA-thymocytes, while DES induced an relative increase in c-kit-CD44-CD25 + HSA+ cells. RT-PCR revealed that TCDD reduced RAG-1, RAG-2, and TdT gene expression in the CD4-CD8- double-negative thymocytes. Co-treatment by TCDD and DES in FTOC yielded a mixture of effects induced by each agent. Taken together, our results demonstrate that TCDD and DES affect thymocytes at different stages of development, suggesting distinct mechanisms for induction of thymic atrophy.

Cytokine gene expression during ontogeny in murine thymus on activation of the aryl hydrocarbon receptor by 2,3,7,8-tetrachlorodibenzo-p-dioxin

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) binds and activates the aryl hydrocarbon receptor (Ah-R), an endogenous transcription factor that is expressed in the thymus. TCDD exposure leads, among other effects, to thymus atrophy and immunosuppression. We previously analyzed the interference of TCDD with differentiation processes in fetal thymus organ cultures and found that in the presence of TCDD, the proliferation rate of immature (CD4- CD8- and CD4- CD8+ HSA+) thymocytes is inhibited, whereas the maturation along the CD4/CD8 path is accelerated. Moreover, the differentiation of thymocytes is skewed by TCDD at < or = 40% (compared with approximately 15% without TCDD) of the CD8 single-positive subset of future cytotoxic T cells, and apparently more cells audition for and pass positive selection. The fetal murine thymus expresses functional Ah-R mRNA, as shown by reverse transcription-polymerase chain reaction and TCDD-inducible CYP1A1 and CYP1B1 expression. Because the differentiation of thymocytes is to a considerable extent controlled by cytokines and many cytokine genes are potential targets of the Ah-R due to Ah-R-binding elements (xenobiotic response elements) in their promoters, we analyzed the cytokine expression in fetal thymus organ culture exposed to TCDD. Fetal thymi were cultured from gestation day 15 for < or = 8 days, thus covering ex vivo the period after population of the thymus anlage until birth. We show with semiquantitative reverse transcription-polymerase chain reaction that more interleukin (IL)-1beta, IL-2, IL-6, tumor growth factor (TGF)-beta3, and tumor necrosis factor-alpha are produced in TCDD-exposed thymi, whereas other cytokines (e.g., TGF-beta1, PAI-2, or IL-4) are only slightly up- and down-modulated during the culture period or not modulated at all (e.g., IL-1beta, IL-7, interferon-gamma, and TGF-beta2).

Identification of dioxin-responsive elements (DREs) in the 5' regions of putative dioxin-inducible genes

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is an exogenous ligand for the cytosolic aryl hydrocarbon receptor (AhR), a ligand-inducible transcription factor whose exact physiological role remains elusive. TCDD has been shown to modulate the expression of a large array of genes, albeit often indirectly, by demonstration of protein or mRNA upregulation. Here, by computer analysis of available promoter sequences, we identify dioxin-responsive elements in the promoter regions of many putative AhR regulated and therefore dioxin-inducible genes.

Evidence for the promotion of positive selection of thymocytes by Ah receptor agonist 2,3,7,8-tetrachlorodibenzo-p-dioxin

2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is a ligand for the arylhydrocarbon receptor (Ah receptor), abundant in the murine thymus. In the thymus immunocompetent T cells develop. Upon exposure of murine fetal thymi in organ cultures to TCDD the distribution of mature and immature thymocytes is skewed towards apparently mature, prospective cytotoxic cells of the CD4-CD8+T cell receptor+ phenotype. The normally abundant CD4+ CD8+ cells are decreased. Proliferation of the most immature thymocyte subpopulations is inhibited and maturation of thymocytes appears accelerated by TCDD. Eventually the thymocyte number is significantly decreased. Selective treatment of stroma cells showed them to be the primary target cells of TCDD action. Thymus stroma plays a pivotal role in thymocyte maturation and is indispensable for the selection of thymocytes bearing T cell receptors specific for foreign antigen in the context of self. We tested whether the effects of TCDD on thymocyte differentiation and maturation has further consequences for the selection processes by analysing (a) the repertoire of V beta genes used as a measure for negative selection and (b) the expression of CD69 and bcl-2 by thymocytes as a parameter of positive selection. Our data indicate that TCDD does not cause gross disturbance of negative selection but provide evidence for more cells auditioning for positive selection by TCDD exposure.

CD8 thymocytes derived from 3,3',4,4'-tetrachlorobiphenyl-exposed fetal thymi possess killing activity

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) and its congeners such as 3,3',4,4'-tetrachlorobiphenyl (TCB) cause immunosuppression in experimental animals and possibly in humans. In previous studies we found that exposure of murine fetal thymic organ cultures (FTOCs) to TCDD or TCB reduced the proliferative capacity of immature thymocytes. At the same time, the kinetics of thymocyte maturation was changed, and thymocyte differentiation was skewed toward CD4-CD8+ phenotypically mature cells. Here, we analyze the biological activities of thymocytes generated in TCB-exposed fetal thymus to determine whether these cells are also functionally mature. C57BL/6 fetal thymic lobes from Day 15 of gestation were explanted and grown for 8 days in FTOC in the presence or absence of 3.3 microM TCB. Then, the functions of total thymocytes or sorted subsets thereof were tested. We found that thymocytes from TCB-exposed lobes responded to stimulation by Con A or anti-CD3 and possessed cytotoxic activity upon cultivation in the presence of H-2 allogenic spleen cells. Further analysis showed that the overall cytotoxic activity of thymocytes was mainly due to the CD4-CD8+ cells. Our results suggest that the CD4-CD8+ cells, which are generated in substantially increased numbers in TCB-exposed fetal thymus, are functionally competent cells.

3,3',4,4'-Tetrachlorobiphenyl inhibits proliferation of immature thymocytes in fetal thymus organ culture

The environmental pollutant 3,3',4,4'-tetrachlorobiphenyl (TCB) leads to thymic atrophy and immunosuppression, the former possibly causing the latter. TCB binds to the cytosolic aryl-hydrocarbon receptor (AhR) and transforms it into a DNA-binding state. The development of fetal thymocytes is severely affected by TCB and other AhR-binding xenobiotics, leading to a skewed pattern of thymocyte maturation stages. Murine thymocyte proliferation after exposure to TCB was studied in fetal thymus organ culture (FTOC). C57BL/6 fetus thymic lobes from day 15 of gestation were explanted and grown for 2, 4, 6, and 8 days in organ culture in the presence or absence of 3.3 microM TCB. Subsets of thymocytes were defined by CD4 and CD8 surface markers, and their cell cycle was analysed by DNA staining with 7-amino-actinomycin D (7-AAD). Exposure of fetal thymi in vitro to 3.3 microM TCB significantly reduced the total number of thymocytes, and fewer thymocytes were in S/G2M phase. The inhibition of cell proliferation induced by TCB treatment affected mainly the CD4-CD8- (double-negative, DN) and CD4-CD8+ (single-positive, SP) subsets, and these inhibition appeared mainly in more immature thymocytes, i.e. DNCD3- and CD8+CD3- subpopulations, whereas no effect of TCB on CD4+CD8+ (double-positive, DP) cell proliferative activity was observed. Analysis of the relation of cell proliferation and development of subsets in differentiating fetal thymocytes suggests that TCB enhanced thymocyte differentiation into mature CD8+ cells.

Toxicological studies on the organophosphorous insecticide methyl-ISP

Methyl-ISP, a newly developed organophosphorous insecticide, is used in China to treat and protect plants from pest infestation. Our studies demonstrated that methyl-ISP is metabolized rapidly in rat and mouse. Its toxicity was low, no obvious accumulative toxicity, chronic toxicity, teratogenicity, mutagenicity, reproductive toxicity or delayed neurotoxicity could be observed. It is therefore concluded that methyl-ISP is relatively safe to animals and human subjects. methyl-ISP is now employed to replace the other commonly used insecticide hexachlorobenzene (666) in agriculture. A preliminary study was performed to elucidate the mechanism of intoxication at subcellular levels.