mTOR Modulates Lymphocyte Differentiation through T-bet and Eomesodermin in Response to Invasive Pulmonary Aspergillosis in Rats

Impact of mTOR signaling pathway on CD8+ T cell immunity through Eomesodermin in response to invasive candidiasis

BACKGROUND

We investigated the effect of the mammalian target of rapamycin (mTOR) pathway on CD8+ T cell immunity through Eomesodermin (Eomes) in intensive care unit (ICU) patients with invasive candidiasis (IC) and in a mouse model.

METHODS

We evaluated quantitative changes in parameters of the mTOR/phosphorylated ribosomal S6 kinase (pS6K) pathway and immune system at the onset of infection in ICU patients. The study was registered on 28 February 2017 at chictr.org.cn (ChiCTR-ROC-17010750). We also used a mouse model of Candida infection and constructed T-cell-specific mTOR and T-cell-specific tuberous sclerosis complex (TSC) 1 conditional knockout mice to elucidate the molecular mechanisms.

RESULTS

We enrolled 88 patients, including 8 with IC. The IC group had lower CD8+ T cell counts, higher serum levels of mTOR, pS6K, Eomes and interleukin (IL)-6. The mouse model with IC showed results consistent in the clinical study. The CD8+ T cell immune response to IC seemed to be weakened in TSC1 knockout mice compared with wild-type IC mice, demonstrating that mTOR activation resulted in the impaired CD8+ T cell immunity in IC.

CONCLUSIONS

In IC, the mTOR activation may play a vital role in impaired CD8+ T cell immunity through enhancing expression of Eomes. The study was registered on 28 February 2017 at chictr.org.cn (identifier ChiCTR-ROC-17010750).

T-Bet Expression Mediated by the mTOR Pathway Influences CD4+ T Cell Count in Mice With Lethal Candida Sepsis

The sustained high morbidity and mortality of Candida sepsis are mainly caused by compromise of host immunity. Clinically, it is often manifested as a significant decrease in CD4+ T cell count, although the mechanism is unclear. We established a lethal mice Candida sepsis model and used Murine Sepsis Score to group mice with different disease severity to establish the influence of T-bet expression on CD4+ T cell count in Candida sepsis. We found that CD4+ T cell count decreased in Candida-infected compared to uninfected mice, and the degree of decrease increased with aggravation of sepsis. Expression of T-bet similarly decreased with worsening of sepsis, but it was significantly enhanced in candidiasis in comparison of naïve state. To clarify its possible mechanism, we measured the activity of mammalian target of rapamycin (mTOR), which is a key regulator of T-bet expression. The mTOR pathway was activated after infection and its activity increased with progression of sepsis. We used mice with T-cell-specific knockout of mTOR or tuberous sclerosis complex (TSC)1 to further inhibit or strengthen the mTOR signaling pathway. We found that mTOR deletion mice had a higher CD4+ T cell count by regulating T-bet expression, and the result in TSC1 deletion mice was reversed. These results demonstrate that T-bet expression mediated by the mTOR pathway influences the CD4+ T cell count in mice with Candida sepsis.

T-cell-specific mTOR deletion in mice ameliorated CD4+ T-cell survival in lethal sepsis induced by severe invasive candidiasis

The mammalian target of rapamycin (mTOR) pathway can mediate T-cell survival; however, the role of this pathway in T-cell survival during fungal sepsis is unclear. Here, we investigated the role of the mTOR pathway in CD4+ T-cell survival in a mouse model of rapidly progressive lethal sepsis induced by severe invasive candidiasis and explored the possible mechanism. The decrease in CD4+ T-cell survival following fungal sepsis was ameliorated in mice with a T-cell-specific mTOR deletion, whereas it was exacerbated in mice with a T-cell-specific tuberous sclerosis complex (TSC)1 deletion. To explore the mechanism further, we measured expression of autophagy proteins light chain 3B and p62/sequestosome 1 in CD4+ T cells. Both proteins were increased in T-cell-specific mTOR knockout mice but lower in T-cell-specific TSC1 knockout mice. Transmission electron microscopy revealed that T-cell-specific mTOR knockout mice had more autophagosomes than wild-type mice following fungal sepsis. CD4+ T-cell mTOR knockout decreased CD4+ T-cell apoptosis in fungal sepsis. Most notably, the T-cell-specific mTOR deletion mice had an increased survival rate after fungal sepsis. These results suggest that the mTOR pathway plays a vital role in CD4+ T-cell survival during fungal sepsis, partly through the autophagy-apoptosis pathway.

MicroRNA-142-3p inhibits IFN-γ production via targeting of RICTOR in Aspergillus fumigatus activated CD4+ T cells

Background

Aspergillus fumigatus (AFE) is a well-adapted, opportunistic fungus that causes a severe and commonly fatal disease, wherein IFN-γ is one of the most important protective cytokines. The aim of this study was to investigate the microRNA expression profile and explore the underlying mechanism during infection with AFE.

Methods

CD4⁺ T cells were activated by co-culturing with dendritic cells (DCs), which were pre-treated with AFE. Next, we performed microRNA microarray expression profiles of activated and control T cells, following which, miRNA-142-3P was selected. To explore the effect of miR-142-3P on T cell activation, miRNA-142-3P expression was disrupted by transient transfection with miR-142-3P mimic or inhibitor. Then, levels of RICTOR, phosphorylated AKT and IFN-γ were detected via Western blotting and qPCR respectively. We further used siRNA to decrease RICTOR expression and determined the role played by RICTOR in miR-142-3P mediated-IFN-γ expression by qPCR following AFE-mediated T cell activation.

Results

The heat-map of miRNA expression profiles showed that 54 microRNAs (miRNAs) were filtered, the levels of which, were significantly different between CD4⁺ T cells activated by AFE and control T cells, in which microRNA-142-3 was involved. Forced expression of miRNA-142-3P dramatically suppressed RICTOR levels, phosphorylated AKT and IFN-γ in AFE activated T cells. Conversely, loss of miRNA-142-3P elevated RICTOR levels, phosphorylated AKT and IFN-γ. Notably, RICTOR deficiency decreased AKT phosphorylation levels and IFN-γ secretion.

Conclusions

Observations indicated that down-regulation of microRNA-142-3p enhanced IFN-γ expression, and did so by promoting RICTOR expression in CD4⁺ T cells activated by AFE.

Variant of EOMES Associated with Increasing Risk in Chinese Patients with Relapsing-remitting Multiple Sclerosis

Background:

Multiple sclerosis (MS) is a common central nervous system autoimmune disorder. Increasing number of genome-wide association study (GWAS) analyses hint that MS is strongly associated with genetics. Unfortunately, almost all the GWAS analyses were Caucasian population based. Numbers of risk loci might not be replicated in Chinese MS patients. Hence, we performed a MassArray Assay to genotype the previously reported variants located in the transcription regulation genes in order to elucidate their role in the Chinese MS patients.

Methods:

One hundred and forty-two relapsing-remitting MS (RRMS) patients and 301 healthy controls were consecutively collected from September 2, 2008, to June 7, 2013, as stage 1 subjects. Eight reported transcription regulation-related single-nucleotide polymorphisms (SNPs) were genotyped using the Sequenom MassArray system. In stage 2, another 44 RRMS patients and 200 healthy controls were consecutively collected and Sanger sequenced from April 7, 2015, to June 29, 2017, for the validation of positive results in stage 1. Differences in allele and genotype frequencies between patients and healthy controls, odds ratios, and 95% confidence intervals were calculated with the Chi-square test or Fisher's exact test. Hardy-Weinberg equilibrium was tested also using the Chi-square test.

Results:

In stage 1 analysis, we confirmed only one previously reported risk variant, rs11129295 in EOMES gene. We found that the frequency of T/T genotype was much higher in MS group (χ² = 10.251, P = 0.005) and the T allele of rs11129295 increased the risk of MS (χ² = 10.022, P = 0.002). In stage 2 and combined analyses, the T allele of rs11129295 still increased the risk of MS (χ² = 4.586, P = 0.030 and χ² = 16.378, P = 5.19 × 10⁻⁵, respectively).

Conclusions:

This study enhances the knowledge that the variant of EOMES is associated with increasing risk in Chinese RRMS patients and provides a potential therapeutic target in RRMS.

Nucleocytoplasmic distribution of S6K1 depends on the density and motility of MCF-7 cells in vitro

Background: The ribosomal protein S6 kinase 1 (S6K1) is one of the main components of the mTOR/S6K signal transduction pathway, which controls cellular metabolism, autophagy, growth, and proliferation. Overexpression of S6K1 was detected in tumors of different origin including breast cancer, and correlated with the worse disease outcome. In addition, significant accumulation of S6K1 was found in the nuclei of breast carcinoma cells suggesting the implication of kinase nuclear substrates in tumor progression. However, this aspect of S6K1 functioning is still poorly understood. The main aim of the present work was to study the subcellular localization of S6K1 in breast cancer cells with the focus on cell migration. Methods: Multicellular spheroids of MCF-7 cells were generated using agarose-coated Petri dishes. Cell migration was induced by spheroids seeding onto adhesive growth surface and subsequent cultivation for 24 to 72 hours. The subcellular localization of S6K1 was studied in human normal breast and cancer tissue samples, 2D and 3D MCF-7 cell cultures using immunofluorescence analysis and confocal microscopy. Results: Analysis of histological sections of human breast tissue samples revealed predominantly nuclear localization of S6K1 in breast malignant cells and its mainly cytoplasmic localization in conditionally normal cells. In vitro studies of MCF-7 cells demonstrated that the subcellular localization of S6K1 depends on the cell density in the monolayer culture. S6K1 relocalization from the cytoplasm into the nucleus was detected in MCF-7 cells migrating from multicellular spheroids onto growth surface. Immunofluorescence analysis of S6K1 and immunocoprecipitation assay revealed the colocalization and interaction between S6K1 and transcription factor TBR2 (T-box brain protein 2) in MCF-7 cells. Conclusions: Subcellular localization of S6K1 depends on the density and locomotor activity of the MCF-7 cells.

Nucleocytoplasmic distribution of S6K1 depends on the density and motility of MCF-7 cells in vitro

Background: The ribosomal protein S6 kinase 1 (S6K1) is one of the main components of the mTOR/S6K signal transduction pathway, which controls cellular metabolism, autophagy, growth, and proliferation. Overexpression of S6K1 was detected in tumors of different origin including breast cancer, which was associated with a worse disease outcome. In addition, significant accumulation of S6K1 was found in the nuclei of breast carcinoma cells suggesting the implication of kinase nuclear substrates in tumor progression. However, this aspect of S6K1 functioning is poorly understood. The main aim of the present work was to study the subcellular localization of S6K1 in breast cancer cells with focus on cell migration. Methods: Multicellular spheroids of MCF-7 cells were generated using agarose-coated Petri dishes. Cell migration was initiated by spheroids seeding onto growth surface and subsequent cultivation for 24 and 72 hours. S6K1 subcellular localization was studied in human breast cancer and normal tissue, 2D and 3D MCF-7 cell culture using immunofluorescence analysis and confocal microscopy. Results: Analysis of histological sections of human breast cancer and normal tissue revealed predominantly nuclear localization of S6K1 in breast malignant cells and mainly cytoplasmic one in conditionally normal cells. In vitro studies of MCF-7 cells showed that the subcellular localization of S6K1 depends on the cell density in the monolayer culture. S6K1 relocalization from the cytoplasm into the nucleus was detected in MCF-7 cells migrating from multicellular spheroids onto growth surface. Immunofluorescence analysis of S6K1 and immunocoprecipitation assay revealed the colocalization and interaction between S6K1 and transcription factor TBR2 (T-box brain protein 2) in MCF-7 cells. Bioinformatical analysis revealed existence of several phosphorylation sites in TBR2 for S6K1 suggesting that TBR2 can be a target for phosphorylation and regulation by S6K1. Conclusions: Subcellular localization of S6K1 depends on the density and locomotor activity of the MCF-7 cells.

mTOR Modulates CD8+ T Cell Differentiation in Mice with Invasive Pulmonary Aspergillosis

CD8⁺ T cells are a vital component of the adaptive immune system and important for eliminating intracellular pathogens. Notably, mTOR activity is associated with CD8⁺ T effector memory (Tem) cell differentiation in fungal infections. This study investigates the molecular mechanisms of CD8⁺ Tem cell proliferation and differentiation mediated by the mTOR pathway in immunosuppressed mice with invasive pulmonary aspergillosis (IPA). We first established the immunosuppressed IPA mouse model, then mice were subjected to rapamycin treatment daily or interleukin (IL)-12 treatment every other day. Lung tissues and blood samples were obtained seven days later. Aspergillus fumigatus was cultured from the lung tissue of mice inoculated with A. fumigatus spores. After IL-12 treatment, the expression of mTOR and its downstream signaling molecule S6 kinase, number of CD8⁺ Tem cells and interferon-γ expression were significantly increased, while they were significantly decreased after treatment with rapamycin. Additionally, IL-12 treatment induced T-bet but inhibited Eomesodermin expression, while the opposite was seen when the mTOR pathway was blocked by rapamycin. In conclusion, we found that the mTOR pathway induced CD8⁺ T cell proliferation and differentiation by regulating T-bet and Eomesodermin expression, which significantly influenced immune regulation during IPA and enhanced the immune response against fungal infection.

Role of Triggering Receptor Expressed on Myeloid Cell-1 Expression in Mammalian Target of Rapamycin Modulation of CD8+ T-cell Differentiation during the Immune Response to Invasive Pulmonary Aspergillosis

Background:

Triggering receptor expressed on myeloid cell-1 (TREM-1) may play a vital role in mammalian target of rapamycin (mTOR) modulation of CD8⁺ T-cell differentiation through the transcription factors T-box expressed in T-cells and eomesodermin during the immune response to invasive pulmonary aspergillosis (IPA). This study aimed to investigate whether the mTOR signaling pathway modulates the proliferation and differentiation of CD8⁺ T-cells during the immune response to IPA and the role TREM-1 plays in this process.

Methods:

Cyclophosphamide (CTX) was injected intraperitoneally, and Aspergillus fumigatus spore suspension was inoculated intranasally to establish the immunosuppressed IPA mouse model. After inoculation, rapamycin (2 mg·kg⁻¹·d⁻¹) or interleukin (IL)-12 (5 μg/kg every other day) was given for 7 days. The number of CD8⁺ effector memory T-cells (Tem), expression of interferon (IFN)-γ, mTOR, and ribosomal protein S6 kinase (S6K), and the levels of IL-6, IL-10, galactomannan (GM), and soluble TREM-1 (sTREM-1) were measured.

Results:

Viable A. fumigatus was cultured from the lung tissue of the inoculated mice. Histological examination indicated greater inflammation, hemorrhage, and lung tissue injury in both IPA and CTX + IPA mice groups. The expression of mTOR and S6K was significantly increased in the CTX + IPA + IL-12 group compared with the control, IPA (P = 0.01; P = 0.001), and CTX + IPA (P = 0.034; P = 0.032) groups, but significantly decreased in the CTX + IPA + RAPA group (P < 0.001). Compared with the CTX + IPA group, the proportion of Tem, expression of IFN-γ, and the level of sTREM-1 were significantly higher after IL-12 treatment (P = 0.024, P = 0.032, and P = 0.017, respectively), and the opposite results were observed when the mTOR pathway was blocked by rapamycin (P < 0.001). Compared with the CTX + IPA and CTX + IPA + RAPA groups, IL-12 treatment increased IL-6 and downregulated IL-10 as well as GM, which strengthened the immune response to the IPA infection.

Conclusions:

mTOR modulates CD8⁺ T-cell differentiation during the immune response to IPA. TREM-1 may play a vital role in signal transduction between mTOR and the downstream immune response.

IL-12 Influence mTOR to Modulate CD8+ T Cells Differentiation through T-bet and Eomesodermin in Response to Invasive Pulmonary Aspergillosis

Objective: To investigate whether mTOR signaling pathway regulate the proliferation and differentiation of CD8⁺ T cells by transcription factors T-bet and Eomes, and explore the role of IL-12 in this biological procedure. Methods: Aspergillus fumigatus spore suspension nasal inhalation was used to establish the invasive pulmonary aspergillosis (IPA) mouse model. After inoculation, rapamycin (2mg/kg) each day or IL-12 (5ug/kg) every other day was given for 7 days. The blood samples were obtained before the mice sacrificed and lung specimens were taken. Pathological sections were stained with hematoxylin and eosin (HE). The number of CD8⁺effective memory T cells (Tem) and the expression of IFN-γ, mTOR, ribosomal protein S6 kinase (S6K), T-bet and EOMES were measured by flow cytometry. The levels of IL-6, IL-10 and Galactomannan (GM) were determined by ELISA. Results: After IL-12 treatment, the number of CD8⁺ Tem and the expression of IFN-γ increased significantly; while quite the opposite results were observed when the mTOR pathway was blocked by rapamycin. The expression of mTOR and S6K as well as the level of IFN-γ of the IL-12 treatment group were significantly higher than those in IPA and IPA + rapamycin groups. In addition, IL-12 promoted increasing T-bet and down regulating Eomes to make the Tem transformation. The final immune effector was high level of inflammatory cytokines (IL-6) and low level of anti-inflammatory factors (IL-10) and this strengthened immune response to the Aspergillus infection. Conclusions: The biological effects of Tem could significantly affect IPA infection host immune regulation, which depended on the activation of mTOR signaling pathway by IL-12.