Differential sensitivity of naïve and subsets of memory CD4+ and CD8+ T cells to hydrogen peroxide-induced apoptosis

IL-4-Induced Gene 1: A Potential Player in Myocardial Infarction

Myocardial infarction (MI), a severe outcome of cardiovascular disease, poses a serious threat to human health. Uncontrolled inflammation and excessive cardiomyocyte death, following an infarction event, significantly contribute to both the mortality rate and complications associated with MI. The protein IL-4-induced gene 1 (IL4I1 or FIG1) serves as a natural inhibitor of innate and adaptive immunity, playing a crucial role in CD4+ T cell differentiation, macrophage polarization, and ferroptosis inhibition. Previous studies have linked IL4I1 to acute MI. This review summarizes evidence from both basic and clinical research, highlighting IL4I1 as a critical immunoregulatory enzyme that not only regulates inflammatory responses, but also potentially mitigates MI-induced damage.

GGT5: a potential immunotherapy response inhibitor in gastric cancer by modulating GSH metabolism and sustaining memory CD8+ T cell infiltration

PURPOSE

The variable responses to immunotherapy observed in gastric cancer (GC) patients can be attributed to the intricate nature of the tumor microenvironment. Glutathione (GSH) metabolism significantly influences the initiation and progression of gastric cancer. Consequently, targeting GSH metabolism holds promise for improving the effectiveness of Immune checkpoints inhibitors (ICIs).

METHODS

We investigated 16 genes related to GSH metabolism, sourced from the MSigDB database, using pan-cancer datasets from TCGA. The most representative prognosis-related gene was identified for further analysis. ScRNA-sequencing analysis was used to explore the tumor heterogeneity of GC, and the results were confirmed by  Multiplex immunohistochemistry (mIHC).

RESULTS

Through DEGs, LASSO, univariate and multivariate Cox regression analyses, and survival analysis, we identified GGT5 as the hub gene in GSH metabolism with the potential to promote GC. Combining CIBERSORT, ssGSEA, and scRNA analysis, we constructed the immune architecture of GC. The subpopulations of T cells were isolated, revealing a strong association between GGT5 and memory CD8+ T cells. Furthermore, specimens from 10 GC patients receiving immunotherapy were collected. mIHC was used to assess the expression levels of GGT5 and memory CD8+ T cell markers. Our results established a positive correlation between GGT5 expression, the enrichment of memory CD8+ T cells, and a suboptimal response to immunotherapy.

CONCLUSIONS

Our study identifies GGT5, a hub gene in GSH metabolism, as a potential therapeutic target for inhibiting the response to immunotherapy in GC patients. These findings offer new insights into strategies for optimizing immunotherapy of GC.

Regulation of c-SMAC formation and AKT-mTOR signaling by the TSG101-IFT20 axis in CD4+ T cells

CD4⁺ T cells play major roles in the adaptive immune system, which requires antigen recognition, costimulation, and cytokines for its elaborate orchestration. Recent studies have provided new insight into the importance of the supramolecular activation cluster (SMAC), which comprises concentric circles and is involved in the amplification of CD4⁺ T cell activation. However, the underlying mechanism of SMAC formation remains poorly understood. Here, we performed single-cell RNA sequencing of CD4⁺ T cells left unstimulated and stimulated with anti-CD3 and anti-CD28 antibodies to identify novel proteins involved in their regulation. We found that intraflagellar transport 20 (IFT20), previously known as cilia-forming protein, was upregulated in antibody-stimulated CD4⁺ T cells compared to unstimulated CD4⁺ T cells. We also found that IFT20 interacted with tumor susceptibility gene 101 (TSG101), a protein that endocytoses ubiquitinated T-cell receptors. The interaction between IFT20 and TSG101 promoted SMAC formation, which led to amplification of AKT-mTOR signaling. However, IFT20-deficient CD4⁺ T cells showed SMAC malformation, resulting in reduced CD4⁺ T cell proliferation, aerobic glycolysis, and cellular respiration. Finally, mice with T-cell-specific IFT20 deficiency exhibited reduced allergen-induced airway inflammation. Thus, our data suggest that the IFT20-TSG101 axis regulates AKT-mTOR signaling via SMAC formation.

Dynamic alterations of immunosenescence-related genes in older women with breast cancer receiving chemotherapy: A prospective study

BACKGROUND

The exact impact of chemotherapy on the immune system of older patients with breast cancer is not well known. A longitudinal study was performed investigating the evolution of the blood immune profile during and after chemotherapy in this population.

PATIENTS AND METHODS

The study included 39 patients receiving adjuvant chemotherapy (chemotherapy group, CTG) and 32 patients receiving only hormone therapy (control group, CG). A 10-gene panel associated with immunosenescence was measured in peripheral blood mononuclear cells (PBMC) before (T1), at 3 months (T2) and at 12 months (T3) after initiation of adjuvant therapy. Nutrition status was assessed by using a mini nutritional assessment scale. Linear mixed model analyses were performed for trajectory evolution, with or without adjusting for age, tumor stage, breast cancer phenotype, and/or corresponding baseline gene levels.

RESULTS

Six genes relating to T cell activation (CD28, CD27, CD86, LCK, GRAP, LRRN3), and two genes relating to oxidative stress (PRDX6, HMOX1) exhibited a significant group-by-time effect, even after adjusting covariates(p≤ 0.01). In CTG, the T cell activation genes substantially declined from T1 to T2 and bounced back to a level higher than baseline at T3 (p<0.03), which was not observed in CG (p>0.26). Patients with malnutrition detected at T1 experienced more pronounced perturbation regarding CD27, LCK, CD69, VAMP5, and LRRN3 (p<0.05).

CONCLUSION

Chemotherapy leads to transient perturbation of immune-related gene expression and potentially stimulates immunity in the long term. Well-nourished patients experience less impact of chemotherapy on immune-related gene expression profiles.

Regulated cell death (RCD) in cancer: key pathways and targeted therapies

Regulated cell death (RCD), also well-known as programmed cell death (PCD), refers to the form of cell death that can be regulated by a variety of biomacromolecules, which is distinctive from accidental cell death (ACD). Accumulating evidence has revealed that RCD subroutines are the key features of tumorigenesis, which may ultimately lead to the establishment of different potential therapeutic strategies. Hitherto, targeting the subroutines of RCD with pharmacological small-molecule compounds has been emerging as a promising therapeutic avenue, which has rapidly progressed in many types of human cancers. Thus, in this review, we focus on summarizing not only the key apoptotic and autophagy-dependent cell death signaling pathways, but the crucial pathways of other RCD subroutines, including necroptosis, pyroptosis, ferroptosis, parthanatos, entosis, NETosis and lysosome-dependent cell death (LCD) in cancer. Moreover, we further discuss the current situation of several small-molecule compounds targeting the different RCD subroutines to improve cancer treatment, such as single-target, dual or multiple-target small-molecule compounds, drug combinations, and some new emerging therapeutic strategies that would together shed new light on future directions to attack cancer cell vulnerabilities with small-molecule drugs targeting RCD for therapeutic purposes.

Distinct pro-inflammatory properties of myeloid cell-derived apolipoprotein E2 and E4 in atherosclerosis promotion

Polymorphisms in the apolipoprotein E (apoE) gene are risk factors for chronic inflammatory diseases including atherosclerosis. The gene product apoE is synthesized in many cell types and has both lipid transport–dependent and lipid transport–independent functions. Previous studies have shown that apoE expression in myeloid cells protects against atherogenesis in hypercholesterolemic ApoE^−/− mice. However, the mechanism of this protection is still unclear. Using human APOE gene replacement mice as models, this study showed that apoE2 and apoE4 expressed endogenously in myeloid cells enhanced the inflammatory response via mechanisms independent of plasma lipoprotein transport. The data revealed that apoE2-expressing myeloid cells contained higher intracellular cholesterol levels because of impaired efflux, causing increasing inflammasome activation and myelopoiesis. In contrast, intracellular cholesterol levels were not elevated in apoE4-expressing myeloid cells, and its proinflammatory property was found to be independent of inflammasome signaling and related to enhanced oxidative stress. When ApoE^−/− mice were reconstituted with bone marrow from various human APOE gene replacement mice, effective reduction of atherosclerosis was observed with marrow cells obtained from APOE3 but not APOE2 and APOE4 gene replacement mice. Taken together, these results documented that apoE2 and apoE4 expression in myeloid cells promotes inflammation via distinct mechanisms and promotes atherosclerosis in a plasma lipoprotein transport–independent manner.

Dimethyl fumarate induced lymphopenia in multiple sclerosis: A review of the literature

Dimethyl fumarate (DMF) is a first line medication for multiple sclerosis. It has a favourable safety profile, however, there is concern regarding the occurrence of moderate-severe and sustained lymphopenia and the associated risk of progressive multifocal leukoencephalopathy. We carried out an extensive literature review to understand the molecular mechanisms underlying this adverse reaction. Dynamic changes in certain components of the immune system are likely to be important for the therapeutic effects of DMF, including depletion of memory T cells and decrease in activated T cells together with expansion of naïve T cells. Similar modifications were reported for the B cell components. CD8⁺ T cells are particularly susceptible to DMF-induced cell death, with marked reductions observed in lymphopenic subjects. The reasons underlying such increased sensitivity are not known, nor it is known how expansion of other lymphocyte subsets occurs. Understanding the molecular mechanisms underlying DMF action is challenging: in vivo DMF is rapidly metabolized to monomethyl fumarate (MMF), a less potent immunomodulator in vitro. Pharmacokinetics indicate that MMF is the main active species in vivo. However, the relative importance of DMF and MMF in toxicity remains unclear, with evidence presented in favour of either of the compounds as toxic species. Pharmacogenetic studies to identify genetic predictors of DMF-induced lymphopenia are limited, with inconclusive results. A role of the gut microbiome in the pharmacological effects of DMF is emerging. It is clear that further investigations are necessary to understand the mechanisms of DMF-induced lymphopenia and devise preventive strategies. Periodic monitoring of absolute lymphocyte counts, currently performed in clinical practise, allows for the early detection of lymphopenia as a risk-minimization strategy.

Cell death mechanisms in eukaryotes

Like the organism they constitute, the cells also die in different ways. The death can be predetermined, programmed, and cleanly executed, as in the case of apoptosis, or it can be traumatic, inflammatory, and sudden as many types of necrosis exemplify. Nevertheless, there are a number of cell deaths-some of them bearing a resemblance to apoptosis and/or necrosis, and many, distinct from each-that serve a multitude of roles in either supporting or disrupting the homoeostasis. Apoptosis is coordinated by death ligands, caspases, b-cell lymphoma-2 (Bcl-2) family proteins, and their downstream effectors. Events that can lead to apoptosis include mitotic catastrophe and anoikis. Necrosis, although it has been considered an abrupt and uncoordinated cell death, has many molecular events associated with it. There are cell death mechanisms that share some standard features with necrosis. These include methuosis, necroptosis, NETosis, pyronecrosis, and pyroptosis. Autophagy, generally a catabolic pathway that operates to ensure cell survival, can also kill the cell through mechanisms such as autosis. Other cell-death mechanisms include entosis, ferroptosis, lysosome-dependent cell death, and parthanatos.

Aerobic endurance training status affects lymphocyte apoptosis sensitivity by induction of molecular genetic adaptations

Apoptosis is a genetically regulated form of programmed cell death which promotes the elimination of potentially detrimental immune cells. However, exercise-associated apoptosis is thought to induce a temporarily decline of the adaptive immune competence in the early post-exercise period. The purpose of the present study was to investigate if the aerobic endurance training status affects the sensitivity of human peripheral blood lymphocytes towards different types of apoptosis inducers and secondly, if this is mediated by the modulation of apoptosis-associated proteins and microRNAs. Collected at resting conditions, isolated lymphocytes of endurance trained athletes (ET) and healthy untrained subjects were either exposed to phytohemagglutinin-L (PHA-L), hydrogen peroxide (H₂O₂), or dexamethasone (DEX) as apoptosis inducer. Results revealed no significant differences between ET and UT in terms of lymphocyte apoptosis immediately following isolation as determined by flow cytometry using annexin V staining. After 24 h of ex vivo cultivation, lymphocytes of ET showed a reduced sensitivity to PHA-L-induced lymphocyte apoptosis which was accompanied by a noticeably up-regulation of the prominent apoptosis inhibitor genes X-linked inhibitor of apoptosis (XIAP) and Cyclin dependent kinase inhibitor 1B (CDKN1B) as analyzed by quantitative real-time PCR. Moreover, a trend was observed for the suppression of the corresponding pro-apoptotic miR-221. Lymphocyte apoptosis in control, H₂O₂ and DEX treated cells was not affected by aerobic endurance training status. However, distinct molecular signatures could be identified in un-treated control samples characterized by a counterbalanced modulation of pro- and anti-apoptotic mediators in ET. The results of the current study suggest that lymphocytes adapt to repetitive endurance exercise training by promoting lymphocyte homeostasis and increasing their resistance to apoptosis. This could be based on an up-regulation of anti-apoptotic proteins and a reduction in pro-apoptotic microRNAs which together tightly regulate the genetically defined apoptotic pathways governed by the type of apoptosis stimuli. Thus, the lymphocytes of endurance-trained athletes may be primed to counteract the transient immune suppression post-exercise.

Changes in the mitochondrial protein profile due to ROS eruption during ageing of elm (Ulmus pumila L.) seeds

Reactive oxygen species (ROS)-related mitochondrial dysfunction is considered to play a vital role in seed deterioration. However, the detailed mechanisms remain largely unknown. To address this, a comparison of mitochondrial proteomes was performed, and we identified several proteins that changed in abundance with accompanying ROS eruption and mitochondrial aggregation and diffusion. These are involved in mitochondrial metabolisms, stress resistance, maintenance of structure and intracellular transport during seed aging. Reduction of ROS content by the mitochondrial-specific scavenger MitoTEMPO suppressed these changes, whereas pre-treatment of seeds with methyl viologen (MV) had the opposite effect. Furthermore, voltage-dependent anion channels (VDAC) were found to increase both in abundance and carbonylation level, accompanied by increased cytochrome c (cyt c) release from mitochondria to cytosol, indicating the profound effect of ROS and VDAC on mitochondria-dependent cell death. Carbonylation detection revealed the specific target proteins of oxidative modification in mitochondria during ageing. Notably, membrane proteins accounted for a large proportion of these targets. An in vitro assay demonstrated that the oxidative modification was concomitant with a change of VDAC function and a loss of activity in malate dehydrogenase. Our data suggested that ROS eruption induced alteration and modification of specific mitochondrial proteins that may be involved in the process of mitochondrial deterioration, which eventually led to loss of seed viability.

Relationship between redox status and cell fate in immunity and autoimmunity

SIGNIFICANCE

The signaling function of redox molecules is essential for an efficient and proper execution of a large number of cellular processes, contributing to the maintenance of cell homeostasis. Excessive oxidative stress is considered as playing an important role in the pathogenesis of autoimmune diseases by enhancing inflammation and breaking down the immunological tolerance through protein structural modifications that induce the appearance of neo/cryptic epitopes.

RECENT ADVANCES

There is a complex reciprocal relationship between oxidative stress and both apoptosis and autophagy, which is essential to determine cell fate. This is especially relevant in the context of autoimmune disorders in which apoptosis and autophagy play a crucial pathogenic role.

CRITICAL ISSUES

In this review, we describe the latest developments with regard to the involvement of redox molecules in the initiation and progression of autoimmune disorders, focusing on their role in cell fate regulation. We also discuss new therapeutic approaches that target oxidative stress in the treatment of these disorders. The administration of antioxidants is scarcely studied in autoimmunity, and future analyses are needed to assess its beneficial effects in preventing or ameliorating these diseases.

FUTURE DIRECTIONS

Deciphering the intricate relationships between oxidative stress and both apoptosis and autophagy in the context of autoimmunity could be critical in elucidating key pathogenic mechanisms and could lead to novel interventions for the clinical management of autoimmune diseases.

Effect of activated human polymorphonuclear leucocytes on T lymphocyte proliferation and viability

Human polymorphonuclear leucocytes (PMN) are thought to be immunosuppressive. The suppressive mechanism(s) used by PMN are, however, not well defined and in this study they were analysed using T-cell responses to CD3(+) CD28 monoclonal antibodies (mAb) as a readout. We demonstrate that in vitro activated PMN (PMN(act)) can, without any T-cell interaction, induce apparent T-cell suppression by inhibiting the stimulatory capacity of the CD3 mAb. However, a cell-directed suppression of T-cell proliferation was observed when PMN(act) were added to pre-activated T cells that are already committed to polyclonal proliferation. This suppression was partially reversed by catalase addition (P < 0·01) and largely reversed by addition of exogenous interleukin-2 (P < 0·001) but was not significantly reduced by nitric oxide synthase inhibition, myeloperoxidase inhibition or addition of excess arginine. Following removal of PMN(act) , suppressed T cells could respond normally to further stimulation. In addition to suppressing proliferation, co-culture with PMN(act) also induced a significant decrease in T-cell viability that was reversed by catalase addition (P < 0·05). The addition of the arginase inhibitor N-hydroxy-nor-l-arginine induced both a further significant, catalase-sensitive, loss in T-cell viability and increased nitrite release (P < 0·001). These data demonstrate that PMN, when activated, can both induce T-cell death and reversibly inhibit proliferation of activated T cells. The mechanisms underlying these distinct processes and the effects of arginase inhibitors on PMN induced cytotoxicity merit further investigation.

Dendritic cells and aging: consequences for autoimmunity

The immune system has evolved to mount immune responses against foreign pathogens and to remain silent against self-antigens. A balance between immunity and tolerance is required as any disturbance may result in chronic inflammation or autoimmunity. Dendritic cells (DCs) actively participate in maintaining this balance. Under steady-state conditions, DCs remain in an immature state and do not mount an immune response against circulating self-antigens in the periphery, which maintains a state of tolerance. By contrast, foreign antigens result in DC maturation and DC-induced T-cell activation. Inappropriate maturation of DCs due to infections or tissue injury may cause alterations in the balance between the tolerogenic and immunogenic functions of DCs and instigate the development of autoimmune diseases. This article provides an overview of the effects of advancing age on DC functions and their implications in autoimmunity.

MHC class I dimer formation by alteration of the cellular redox environment and induction of apoptosis

Many MHC class I molecules contain unpaired cysteine residues in their cytoplasmic tail domains, the function of which remains relatively uncharacterized. Recently, it has been shown that in the small secretory vesicles known as exosomes, fully folded MHC class I dimers can form through a disulphide bond between the cytoplasmic tail domain cysteines, induced by the low levels of glutathione in these extracellular vesicles. Here we address whether similar MHC class I dimers form in whole cells by alteration of the redox environment. Treatment of the HLA-B27-expressing Epstein-Barr virus-transformed B-cell line Jesthom, and the leukaemic T-cell line CEM transfected with HLA-B27 with the strong oxidant diamide, and the apoptosis-inducing and glutathione-depleting agents hydrogen peroxide and thimerosal, induced MHC class I dimers. Furthermore, induction of apoptosis by cross-linking FasR/CD95 on CEM cells with monoclonal antibody CH-11 also induced MHC class I dimers. As with exosomal MHC class I dimers, the formation of these structures on cells is controlled by the cysteine at position 325 in the cytoplasmic tail domain of HLA-B27. Therefore, the redox environment of cells intimately controls induction of MHC class I dimers, the formation of which may provide novel structures for recognition by the immune system.

HIV-1 induces DCIR expression in CD4+ T cells

The C-type lectin receptor DCIR, which has been shown very recently to act as an attachment factor for HIV-1 in dendritic cells, is expressed predominantly on antigen-presenting cells. However, this concept was recently challenged by the discovery that DCIR can also be detected in CD4⁺ T cells found in the synovial tissue from rheumatoid arthritis (RA) patients. Given that RA and HIV-1 infections share common features such as a chronic inflammatory condition and polyclonal immune hyperactivation status, we hypothesized that HIV-1 could promote DCIR expression in CD4⁺ T cells. We report here that HIV-1 drives DCIR expression in human primary CD4⁺ T cells isolated from patients (from both aviremic/treated and viremic/treatment naive persons) and cells acutely infected in vitro (seen in both virus-infected and uninfected cells). Soluble factors produced by virus-infected cells are responsible for the noticed DCIR up-regulation on uninfected cells. Infection studies with Vpr- or Nef-deleted viruses revealed that these two viral genes are not contributing to the mechanism of DCIR induction that is seen following acute infection of CD4⁺ T cells with HIV-1. Moreover, we report that DCIR is linked to caspase-dependent (induced by a mitochondria-mediated generation of free radicals) and -independent intrinsic apoptotic pathways (involving the death effector AIF). Finally, we demonstrate that the higher surface expression of DCIR in CD4⁺ T cells is accompanied by an enhancement of virus attachment/entry, replication and transfer. This study shows for the first time that HIV-1 induces DCIR membrane expression in CD4⁺ T cells, a process that might promote virus dissemination throughout the infected organism.

The type II transmembrane protein DCIR belongs to the C-type lectin domain family receptor and is predominantly expressed in cells of the myeloid lineage. However recent evidence suggests that it can also be induced in CD4⁺ T cells placed under an inflammatory condition. We assessed the capacity of HIV-1 to promote DCIR expression in CD4⁺ T cells because the establishment of an inflammatory state is a hallmark of this retroviral infection in humans. We report here that a higher DCIR expression is detected not only in CD4⁺ T cells acutely infected with HIV-1 in vitro but also in clinical cell samples. Additional studies suggest a possible link between DCIR induction and apoptosis through both caspase-dependent and -independent intrinsic pathways. The greater expression of DCIR on the surface of CD4⁺ T cells results in more efficient virus attachment/entry, replication and transfer processes.

Viability of Saccharomyces cerevisiae cells following exposure to H2O2 and protective effect of minocycline depend on the presence of VDAC

Proteins involved in apoptosis are still a matter of debate. Therefore, we decided to check the effect of the presence of VDAC (voltage dependent anion selective channel) on viability of Saccharomyces cerevisiae cells following their exposure to H(2)O(2) that is known to induce apoptosis both in S. cerevisiae and in mammalian cells. Mitochondria of S. cerevisiae contain only one channel-forming VDAC isoform (VDAC1), which simplifies studies on the channel. Using S. cerevisiae mutant depleted of VDAC1 (termed here VDAC) and the isogenic wild type, we have shown that VDAC is important for protection of S. cerevisiae cells against H(2)O(2) treatment, particularly in exponential growth phase that is known to be more affected by H(2)O(2). The increased viability of H(2)O(2) pretreated exponentially growing cells containing VDAC was accompanied by clear changes of the cytosol redox state and was potentiated by minocycline, an antibiotic of the tetracycline family that displays cytoprotective potency. The protective effect of minocycline also coincided with distinct changes of cytosol redox state. Thus, we conclude that the ability to change the cytosol redox state following exposure to H(2)O(2) or/and minocycline appears to be an intrinsic feature of exponentially growing cells (young cells) containing VDAC. Moreover, the ability seems to be crucial for both cell viability and protective effect of minocycline.

Differential effect of human herpesvirus 6A on cell division and apoptosis among naive and central and effector memory CD4+ and CD8+ T-cell subsets

The immune responses of naive and different memory subsets of CD4(+) and CD8(+) T cells to human herpesvirus 6 (HHV-6) have not been previously investigated. We show that HHV-6A induces cell division, as measured by 5,6-carboxyfluorescein succinimidyl ester dye and flow cytometry, predominantly in two populations of effector memory CD4(+) and CD8(+) T cells (T(EM) and T(EMRA)); naïve (T(N)) and central memory (T(CM)) CD4(+) and CD8(+) T cells showed almost no cell division. In contrast, HHV-6A induced apoptosis primarily in T(N) and T(CM) CD4(+) and CD8(+) T cells, whereas T(EM) and T(EMRA) CD4(+) and CD8(+) T cells were resistant to HHV-6A-induced apoptosis. HHV-6A-induced apoptosis was associated with activation of caspase-8, caspase-9, and caspase-3, suggesting the involvement of death receptor and mitochondrial signaling pathways. In addition, HHV-6A induced secretion of interleukin-6 (IL-6), tumor necrosis factor alpha (TNF-alpha), IL-8, and gamma interferon by peripheral blood mononuclear cells; TNF-alpha secretion was observed exclusively from CCR7(+) (T(N) plus T(CM)) CD4(+) T cells. These data show that HHV-6 differentially influences the functions of naïve T cells and different subsets of memory CD4(+) and CD8(+) T cells, which in part may be due to differential susceptibility to HHV-6A-induced apoptosis.