Decoding and overcoming T cell exhaustion: Epigenetic and transcriptional dynamics in CAR-T cells against solid tumors.

T cell exhaustion, which is observed in various chronic infections and malignancies, is characterized by elevated expression of multiple inhibitory receptors, impaired effector functions, decreased proliferation, and reduced cytokine production. Notably, while adoptive T cell therapies, such as chimeric antigen receptor (CAR)-T therapy, have shown promise in treating cancer and other diseases, the efficacy of these therapies is often compromised by T cell exhaustion. It is imperative, therefore, to understand the mechanisms underlying this exhaustion to promote advances in T cell-related therapies. Here, we divided exhausted T cells into three distinct subsets according to their developmental and functional profiles: stem-like progenitor cells, intermediately exhausted cells, and terminally exhausted cells. These subsets are carefully regulated by synergistic mechanisms that involve transcriptional and epigenetic modulators. Key transcription factors, such as TCF1, BACH2, and TOX, are crucial for defining and sustaining exhaustion phenotypes. Concurrently, epigenetic regulators, such as TET2 and DNMT3A, shape the chromatin dynamics that direct T cell fate. The interplay of these molecular drivers has recently been highlighted in CAR-T research, revealing promising therapeutic directions. Thus, a profound understanding of exhausted T cell hierarchies and their molecular complexities may reveal innovative and improved tumor treatment strategies.

PSGL-1 attenuates early TCR signaling to suppress CD8+ T cell progenitor differentiation and elicit terminal CD8+ T cell exhaustion.

PSGL-1 (P-selectin glycoprotein-1) is a T cell-intrinsic checkpoint regulator of exhaustion with an unknown mechanism of action. Here, we show that PSGL-1 acts upstream of PD-1 and requires co-ligation with the T cell receptor (TCR) to attenuate activation of mouse and human CD8+ T cells and drive terminal T cell exhaustion. PSGL-1 directly restrains TCR signaling via Zap70 and maintains expression of the Zap70 inhibitor Sts-1. PSGL-1 deficiency empowers CD8+ T cells to respond to low-affinity TCR ligands and inhibit growth of PD-1-blockade-resistant melanoma by enabling tumor-infiltrating T cells to sustain an elevated metabolic gene signature supportive of increased glycolysis and glucose uptake to promote effector function. This outcome is coupled to an increased abundance of CD8+ T cell stem cell-like progenitors that maintain effector functions. Additionally, pharmacologic blockade of PSGL-1 curtails T cell exhaustion, indicating that PSGL-1 represents an immunotherapeutic target for PD-1-blockade-resistant tumors.

Induction of the activating transcription factor-4 in the intratumoral CD8+ T cells sustains their viability and anti-tumor activities.

Immune suppressive factors of the tumor microenvironment (TME) undermine viability and exhaust the activities of the intratumoral cytotoxic CD8 + T lymphocytes (CTL) thereby evading anti-tumor immunity and decreasing the benefits of immune therapies. To counteract this suppression and improve the efficacy of therapeutic regimens, it is important to identify and understand the critical regulators within CD8 + T cells that respond to TME stress and tumor-derived factors. Here we investigated the regulation and importance of activating transcription factor-4 (ATF4) in CTL using a novel Atf4ΔCD8 mouse model lacking ATF4 specifically in CD8 + cells. Induction of ATF4 in CD8 + T cells occurred in response to antigenic stimulation and was further increased by exposure to tumor-derived factors and TME conditions. Under these conditions, ATF4 played a critical role in the maintenance of survival and activities of CD8 + T cells. Conversely, selective ablation of ATF4 in CD8 + T cells in mice rendered these Atf4ΔCD8 hosts prone to accelerated growth of implanted tumors. Intratumoral ATF4-deficient CD8 + T cells were under-represented compared to wild-type counterparts and exhibited impaired activation and increased apoptosis. These findings identify ATF4 as an important regulator of viability and activity of CD8 + T cells in the TME and argue for caution in using agents that could undermine these functions of ATF4 for anti-cancer therapies.

MicroRNA-139 Expression Is Dispensable for the Generation of Influenza-Specific CD8+ T Cell Responses.

MicroRNAs (miRNAs/miRs) are small, endogenous noncoding RNAs that are important post-transcriptional regulators with clear roles in the development of the immune system and immune responses. Using miRNA microarray profiling, we characterized the expression profile of naive and in vivo generated murine effector antiviral CD8+ T cells. We observed that out of 362 measurable mature miRNAs, 120 were differentially expressed by at least 2-fold in influenza-specific effector CD8+ CTLs compared with naive CD8+ T cells. One miRNA found to be highly downregulated on both strands in effector CTLs was miR-139. Because previous studies have indicated a role for miR-139-mediated regulation of CTL effector responses, we hypothesized that deletion of miR-139 would enhance antiviral CTL responses during influenza virus infection. We generated miR-139-/- mice or overexpressed miR-139 in T cells to assess the functional contribution of miR-139 expression in CD8+ T cell responses. Our study demonstrates that the development of naive T cells and generation or differentiation of effector or memory CD8+ T cell responses to influenza virus infection are not impacted by miR-139 deficiency or overexpression; yet, miR-139-/- CD8+ T cells are outcompeted by wild-type CD8+ T cells in a competition setting and demonstrate reduced responses to Listeria monocytogenes Using an in vitro model of T cell exhaustion, we confirmed that miR-139 expression similarly does not impact the development of T cell exhaustion. We conclude that despite significant downregulation of miR-139 following in vivo and in vitro activation, miR-139 expression is dispensable for influenza-specific CTL responses.

GITR Agonism Triggers Antitumor Immune Responses through IL21-Expressing Follicular Helper T Cells.

Although treatment with the glucocorticoid-induced tumor necrosis factor receptor-related protein (GITR) agonistic antibody (DTA-1) has shown antitumor activity in various tumor models, the underlying mechanism is not fully understood. Here, we demonstrate that interleukin (IL)-21-producing follicular helper T (Tfh) cells play a crucial role in DTA-1-induced tumor inhibition. The administration of DTA-1 increased IL21 expression by Tfh cells in an antigen-specific manner, and this activation led to enhanced antitumor cytotoxic T lymphocyte (CTL) activity. Mice treated with an antibody that neutralizes the IL21 receptor exhibited decreased antitumor activity when treated with DTA-1. Tumor growth inhibition by DTA-1 was abrogated in Bcl6 fl/fl Cd4 Cre mice, which are genetically deficient in Tfh cells. IL4 was required for optimal induction of IL21-expressing Tfh cells by GITR costimulation, and c-Maf mediated this pathway. Thus, our findings identify GITR costimulation as an inducer of IL21-expressing Tfh cells and provide a mechanism for the antitumor activity of GITR agonism.

Differentiation of c-Kit+ CD24+ natural killer cells into myeloid cells in a GATA-2-dependent manner.

Myeloid progenitor cells have generally been considered the predominant source of myeloid cells under steady-state conditions. Here we show that NK cells contributed to a myeloid cell lineage pool in naïve and tumor-bearing mice. Using fate tracing of NKp46+ cells, we found that myeloid cells could be derived from NK cells. Notably, among mature CD11b+ CD27+ NK cells, c-Kit+ CD24+ NK cells were capable of differentiating into a range of myeloid lineages in vitro and produced neutrophils and monocytes in vivo. The differentiation was completely inhibited by NK-stimulating cytokines. In addition to the potential for differentiation into myeloid cells, c-Kit+ CD24+ NK cells retained NK cell phenotypes and effector functions. Mechanistically, GATA-2 was necessary for the differentiation of c-Kit+ CD24+ NK cells. Therefore, we discovered that GATA-2-dependent differentiation of c-Kit+ CD24+ NK cells contributes to myeloid cell development and identified a novel pathway for myeloid lineage commitment under physiological conditions.

Monocyte-Derived Dendritic Cells Dictate the Memory Differentiation of CD8+ T Cells During Acute Infection.

Monocyte-derived dendritic cells (moDCs) have been shown to robustly expand during infection; however, their roles in anti-infectious immunity remain unclear. Here, we found that moDCs were dramatically increased in the secondary lymphoid organs during acute LCMV infection in an interferon-γ (IFN-γ)-dependent manner. We also found that priming by moDCs enhanced the differentiation of memory CD8+ T cells compared to differentiation primed by conventional dendritic cells (cDCs) through upregulation of Eomesodermin (Eomes) and T cell factor-1 (TCF-1) expression in CD8+ T cells. Consequently, impaired memory formation of CD8+ T cells in mice that had reduced numbers of moDCs led to defective clearance of pathogens upon rechallenge. Mechanistically, attenuated interleukin-2 (IL-2) signaling in CD8+ T cells primed by moDCs was responsible for the enhanced memory programming of CD8+ T cells. Therefore, our findings unveil a specialization of the antigen-presenting cell subsets in the fate determination of CD8+ T cells during infection and pave the way for the development of a novel therapeutic intervention on infection.

Striking a Balance-Cellular and Molecular Drivers of Memory T Cell Development and Responses to Chronic Stimulation.

Effective adaptive immune responses are characterized by stages of development and maturation of T and B cell populations that respond to disturbances in the host homeostasis in cases of both infections and cancer. For the T cell compartment, this begins with recognition of specific peptides by naïve, antigen-inexperienced T cells that results in their activation, proliferation, and differentiation, which generates an effector population that clears the antigen. Loss of stimulation eventually returns the host to a homeostatic state, with a heterogeneous memory T cell population that persists in the absence of antigen and is primed for rapid responses to a repeat antigen exposure. However, in chronic infections and cancers, continued antigen persistence impedes a successful adaptive immune response and the formation of a stereotypical memory population of T cells is compromised. With repeated antigen stimulation, responding T cells proceed down an altered path of differentiation that allows for antigen persistence, but much less is known regarding the heterogeneity of these cells and the extent to which they can become "memory-like," with a capacity for self-renewal and recall responses that are characteristic of bona fide memory cells. This review focuses on the differentiation of CD4+ and CD8+ T cells in the context of chronic antigen stimulation, highlighting the central observations in both human and mouse studies regarding the differentiation of memory or "memory-like" T cells. The importance of both the cellular and molecular drivers of memory T cell development are emphasized to better understand the consequences of persisting antigen on T cell fates. Integrating what is known and is common across model systems and patients can instruct future studies aimed at further understanding T cell differentiation and development, with the goal of developing novel methods to direct T cells toward the generation of effective memory populations.

Roles of NKT cells in cancer immunotherapy.

Cancer immunotherapy has emerged as an effective therapeutic strategy to treat cancer. Among diverse immune populations, invariant natural killer T (iNKT) cells have shown potent antitumor activity by linking innate and adaptive immune systems. Upon activation by lipid antigens on CD1d molecules, iNKT cells rapidly produce various cytokines and trigger antitumor immunity directly or indirectly by activating other antitumor immune cells. Administration of a representative iNKT cell ligand alpha-galactosylceramide (α-GalCer) or α-GalCer-pulsed APCs effectively stimulates iNKT cells and thereby induces antitumor effects. In this review, we will introduce the biology and importance of NKT cells in antitumor immunity. Previous studies have demonstrated that iNKT cells not only activate various immune cells but also reinvigorate exhausted immune cells in the tumor microenvironment. Furthermore, we will summarize the major clinical trials utilizing iNKT-based immunotherapies.

GM-CSF Promotes Antitumor Immunity by Inducing Th9 Cell Responses.

GM-CSF as an adjuvant has been shown to promote antitumor immunity in mice and humans; however, the underlying mechanism of GM-CSF-induced antitumor immunity remains incompletely understood. In this study, we demonstrate that GM-CSF potentiates the efficacy of cancer vaccines through IL9-producing Th (Th9) cells. GM-CSF selectively enhanced Th9 cell differentiation by regulating the COX2-PGE2 pathway while inhibiting the differentiation of induced regulatory T (iTreg) cells in vitro and in vivo GM-CSF-activated monocyte-derived dendritic cells converted tumor-specific naïve Th cells into Th9 cells, and delayed tumor growth by inducing antitumor CTLs in an IL9-dependent manner. Our findings reveal a mechanism for the adjuvanticity of GM-CSF and provide a rationale for the use of GM-CSF in cancer vaccines.

Activation of NKT Cells in an Anti-PD-1-Resistant Tumor Model Enhances Antitumor Immunity by Reinvigorating Exhausted CD8 T Cells.

PD-1-based cancer immunotherapy is a successful example of immune checkpoint blockade that provides long-term durable therapeutic effects in patients with cancer across a wide spectrum of cancer types. Accumulating evidence suggests that anti-PD-1 therapy enhances antitumor immunity by reversing the function of exhausted T cells in the tumor environment. However, the responsiveness rate of patients with cancer to anti-PD-1 therapy remains low, providing an urgent need for optimization and improvement. In this study, we designed an anti-PD-1-resistant mouse tumor model and showed that unresponsiveness to anti-PD-1 is associated with a gradual increase in CD8 T-cell exhaustion. We also found that invariant natural killer T cell stimulation by the synthetic ligand α-galactosylceramide (αGC) can enhance the antitumor effect in anti-PD-1-resistant tumors by restoring the effector function of tumor antigen-specific exhausted CD8 T cells. IL2 and IL12 were among the cytokines produced by αGC stimulation critical for reinvigorating exhausted CD8 T cells in tumor-bearing mice and patients with cancer. Furthermore, we observed a synergistic increase in the antitumor effect between αGC-loaded antigen-presenting cells and PD-1 blockade in a therapeutic murine tumor model. Our study suggests NKT cell stimulation as a promising therapeutic strategy for the treatment of patients with anti-PD-1-resistant cancer.Significance: These findings provide mechanistic insights into the application of NKT cell stimulation as a potent adjuvant for immunotherapy against advanced cancer. Cancer Res; 78(18); 5315-26. ©2018 AACR.

IL21 Therapy Combined with PD-1 and Tim-3 Blockade Provides Enhanced NK Cell Antitumor Activity against MHC Class I-Deficient Tumors.

Increased expression of coinhibitory molecules such as PD-1 and Tim-3 on NK cells has been demonstrated in advanced cancer patients who harbor MHC class I-deficient tumors. However, even in preclinical models, the antitumor effects of checkpoint blockade on NK cells have not been clearly elucidated. Here, we show that anti-PD-1/anti-Tim-3 treatment suppressed tumor progression in mice bearing MHC class I-deficient tumors, and the suppression was further enhanced by recombinant IL21 (rIL21) treatments through an NK-cell-dependent mechanism. We also show that the intratumoral delivery of rIL21 attracted NK cells to the tumor site in a CXCR3-dependent fashion. A combination of IL21 and checkpoint blockade facilitated the effector function of exhausted NK cells in cancer patients. Given the effects of the checkpoint blockade and rIL21 combination on NK cells infiltrating into MHC class I-deficient tumors, we suggest that the efficacy of checkpoint blockade can be enhanced through the administration of IL21 for advanced cancer patients with MHC class I-low/deficient tumors. Cancer Immunol Res; 6(6); 685-95. ©2018 AACR.

IL-21-mediated reversal of NK cell exhaustion facilitates anti-tumour immunity in MHC class I-deficient tumours.

During cancer immunoediting, loss of major histocompatibility complex class I (MHC-I) in neoplasm contributes to the evasion of tumours from host immune system. Recent studies have demonstrated that most natural killer (NK) cells that are found in advanced cancers are defective, releasing the malignant MHC-I-deficient tumours from NK-cell-dependent immune control. Here, we show that a natural killer T (NKT)-cell-ligand-loaded tumour-antigen expressing antigen-presenting cell (APC)-based vaccine effectively eradicates these advanced tumours. During this process, we find that the co-expression of Tim-3 and PD-1 marks functionally exhausted NK cells in advanced tumours and that MHC-I downregulation in tumours is closely associated with the induction of NK-cell exhaustion in both tumour-bearing mice and cancer patients. Furthermore, the recovery of NK-cell function by IL-21 is critical for the anti-tumour effects of the vaccine against advanced tumours. These results reveal the process involved in the induction of NK-cell dysfunction in advanced cancers and provide a guidance for the development of strategies for cancer immunotherapy.

Characterization of age-associated exhausted CD8⁺ T cells defined by increased expression of Tim-3 and PD-1.

Aging is accompanied by altered T-cell responses that result in susceptibility to various diseases. Previous findings on the increased expression of inhibitory receptors, such as programmed cell death protein 1 (PD-1), in the T cells of aged mice emphasize the importance of investigations into the relationship between T-cell exhaustion and aging-associated immune dysfunction. In this study, we demonstrate that T-cell immunoglobulin mucin domain-3 (Tim-3), another exhaustion marker, is up-regulated on aged T cells, especially CD8(+) T cells. Tim-3-expressing cells also produced PD-1, but Tim-3(+) PD-1(+) CD8(+) T cells had a distinct phenotype that included the expression of CD44 and CD62L, from Tim-3(-) PD-1(+) cells. Tim-3(+) PD-1(+) CD8(+) T cells showed more evident properties associated with exhaustion than Tim-3(-) PD-1(+) CD8(+) T cells: an exhaustion-related marker expression profile, proliferative defects following homeostatic or TCR stimulation, and altered production of cytokines. Interestingly, these cells produced a high level of IL-10 and induced normal CD8(+) T cells to produce IL-10, which might contribute to immune dysregulation in aged mice. The generation of Tim-3-expressing CD8(+) T cells in aged mice seems to be mediated by encounters with antigens but not by specific infection, based on their high expression of CD49d and their unbiased TCR Vß usage. In conclusion, we found that a CD8(+) T-cell population with age-associated exhaustion was distinguishable by its expression of Tim-3. These results provide clues for understanding the alterations that occur in T-cell populations with age and for improving dysfunctions related to the aging of the immune system.

Glucocorticoid-induced tumor necrosis factor receptor-related protein co-stimulation facilitates tumor regression by inducing IL-9-producing helper T cells.

T cell stimulation via glucocorticoid-induced tumor necrosis factor receptor (TNFR)-related protein (GITR) elicits antitumor activity in various tumor models; however, the underlying mechanism of action remains unclear. Here we demonstrate a crucial role for interleukin (IL)-9 in antitumor immunity generated by the GITR agonistic antibody DTA-1. IL-4 receptor knockout (Il4ra(-/-)) mice, which have reduced expression of IL-9, were resistant to tumor growth inhibition by DTA-1. Notably, neutralization of IL-9 considerably impaired tumor rejection induced by DTA-1. In particular, DTA-1-induced IL-9 promoted tumor-specific cytotoxic T lymphocyte (CTL) responses by enhancing the function of dendritic cells in vivo. Furthermore, GITR signaling enhanced the differentiation of IL-9-producing CD4(+) T-helper (TH9) cells in a TNFR-associated factor 6 (TRAF6)- and NF-κB-dependent manner and inhibited the generation of induced regulatory T cells in vitro. Our findings demonstrate that GITR co-stimulation mediates antitumor immunity by promoting TH9 cell differentiation and enhancing CTL responses and thus provide a mechanism of action for GITR agonist-mediated cancer immunotherapies.

A multimeric carcinoembryonic antigen signal inhibits the activation of human T cells by a SHP-independent mechanism: a potential mechanism for tumor-mediated suppression of T-cell immunity.

Carcinoembryonic antigen (CEA) is a well-known tumor antigen that is found in the serum of patients with various cancers and is correlated with an increased risk of cancer recurrence and metastasis. To understand the tumor environment and to develop antitumor therapies, CEA has been studied as an antigen to activate/tolerate specific T cells. In this study, we show that CEA can function as a coinhibitory molecule and can inhibit the activation of human peripheral blood mononucleated cell-derived T cells. The addition of CEA-overexpressing tumor cells or immobilized CEA dampened both cell proliferation and the expression of IL-2 and CD69 expression in T cells after TCR stimulation. The phosphorylation of ERK and translocation of NFAT were hampered in these cells, whereas the phosphorylation of proximal TCR signaling molecules such as ZAP70 and phospholipase Cγ was not affected by immobilized CEA. To determine the relevance of carcinoembryonic antigen-related cell adhesion molecule-1 and Src homology region 2 domain-containing phosphatase (SHP) molecules to CEA-mediated suppression, we tested the effect of the SHP inhibitor, NSC-87877, on CEA-mediated suppression of T cells; however, it did not reverse the effect of CEA. Collectively, these results indicate that CEA can function as a modulator of T-cell responses suggesting a novel mechanism of tumor evasion.

Inhibition of Helicobacter pylori adhesion to Kato III cells by intact and low molecular weight acharan sulfate.

We investigated the inhibitory activity of glycosaminoglycans (GAGs) in terms of growth, adhesion, and VacA vacuolation of Helicobacter pylori. Intact acharan sulfate (AS, MW:114 kDa) potently inhibited H. pylori adhesion to Kato III cells with IC(50) value of 1.4 mg/mL, while other GAGs did not show any inhibitory activity except for heparin which is a well-known inhibitor of H. pylori adhesion. To investigate whether low molecular weight acharan sulfate (LMWAS) can inhibit H. pylori adhesion, we performed chemical depolymerization of AS by radical reactions to obtain LMWAS. Its physicochemical properties were characterized by high-performance size exclusion chromatography (HPSEC), agarose gel electrophoresis, disaccharide compositional analysis after digestion with heparinase II, and (1)H-NMR spectroscopy. The most potent molecular size of LMWAS was 3 kDa with IC(50) value of 32 µg/mL, which is 44-fold more potent than intact AS. These results suggest that AS as well as other GAGs can be chemically depolymerized by free radicals and LMWAS compared to intact AS can be applied as a pharmaceutical candidate in order to inhibit H. pylori adhesion to Kato III cells.

Anti-allergic effects of fermented Ixeris sonchifolia and its constituent in mice.

To evaluate the antiallergic effect of fermented Ixeris sonchifolia (IS, family Compositae), we prepared IS Kimchi, isolated Lactic acid bacteria (LAB) from it, fermented IS with these LAB, and investigated their antiallergic effects. IS Kimchi more potently inhibited the passive cutaneous anaphylaxis (PCA) reaction induced by an IgE-antigen complex as well as the scratching behavior induced by compound 48/80 or histamine than IS. When IS was fermented with LAB isolated from IS Kimchi, its antiallergic effects was also increased. Of LAB used for fermentation, Lactobacillus brevis more potently increased the antiallergic effects. Its main constituents, chlorogenic acid and luteolin potently inhibited PCA reaction induced by IgE-antigen complex as well as pruritus induced by compound 48/80 or histamine. These constituents inhibited the expression of proinflammatory and allergic cytokines, TNF-alpha and IL-4, and transcription factor, NF-kappaB, activation induced by IgE-antigen complex in RBL-2H3 cells, as well as the degranulation of RBL-2H3 cells induced by an IgE-antigen complex. Luteolin more potently inhibited these allergic reactions than chlorogenic acid. These findings suggest that antiallergic effect of IS can be increased by LAB fermentation and fermented IS might improve allergic reactions, such as pruritus, anaphylaxis, and inflammation.

Dextran sulfate sodium and 2,4,6-trinitrobenzene sulfonic acid induce lipid peroxidation by the proliferation of intestinal gram-negative bacteria in mice.

UNLABELLED: ABSTRECT: BACKGROUND: To understand whether TLR-4-linked NF-kB activation negatively correlates with lipid peroxidation in colitic animal models, we caused colitis by the treatment with dextran sulfate sodium (DSS) or 2,4,6-trinitrobenzenesulfonic acid (TNBS) to C3H/HeJ (TLR-4-defective) and C3H/HeN (wild type) mice, investigated inflammatory markers, lipid peroxidation, proinflammatory cytokines and TLR-4-linked NF-kappaB activation, in colon and intestinal bacterial composition in vivo. METHODS: Orally administered DSS and intrarectally injected TNBS all caused severe inflammation, manifested by shortened colons in both mice. These agents increased intestinal myeloperoxidase activity and the expression of the proinflammatory cytokines, IL-1beta, TNF-alpha and IL-6, in the colon. RESULTS: DSS and TNBS induced the protein expression of TLR-4 and activated transcription factor NF-kappaB. However, these colitic agents did not express TLR-4 in C3H/HeJ mice. Of proinflammatory cytokines, IL-1beta was most potently expressed in C3H/HeN mice. IL-1beta potently induced NF-kappaB activation in CaCo-2 cells, but did not induce TLR-4 expression. DSS and TNBS increased lipid peroxide (malondialdehyde) and 4-hydroxy-2-nonenal content in the colon, but reduced glutathione content and superoxide dismutase and catalase activities. These colitic inducers increased the number of Enterobacteriaceae grown in DHL agar plates in both mice, although the number of anaerobes and bifidobacteria grown in GAM and BL agar plates was reduced. E. coli, K. pneumoniae and Proteus mirabilis isolated in DHL agar plates increased lipid peroxidation in liposomes prepared by L-alpha-phosphatidylcholine, but B. animalis and B. cholerium isolated from BL agar plates inhibited it. DISCUSSION: These findings suggest that DSS and TNBS may cause colitis by inducing lipid peroxidation and enterobacterial proliferation, which may deteriorate the colitis by regulating proinflammatory cytokines via TLR-4-linked NF-kappaB activation pathway.

Bifidobacterium longum HY8004 attenuates TNBS-induced colitis by inhibiting lipid peroxidation in mice.

OBJECTIVE: To investigate the mechanisms of the preventive activity of lactic acid bacteria in colitis, the inhibitory effect of Bifidobacterium longum HY8004, which potently inhibited lipid peroxidation in vitro, was examined in 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitic mice. METHODS: We measured the ability of lactic acid bacteria (LAB) to inhibit lipid peroxidation in vitro and to inhibit colitis outcomes, colon shortening, and myeloperoxidase activity in TNBS-induced colitis in C3H/HeN and C3H/HeJ mice. We also measured levels of the inflammatory markers interleukin (IL)-1 beta and tumor necrosis factor (TNF)-alpha and their transcription factor, NF-kappaB, in the colon by enzyme-linked immunosorbent assay and immunoblot analysis. RESULTS: Among the LAB tested, B. logum HY8004 most potently inhibited lipid peroxidation in vitro but did not inhibit TLR-4-linked NF-kappaB activation in HEK cells. Oral administration of HY8004 inhibited TNBS-induced colon shortening and myeloperoxidase activity in the colon of C3H/HeN and C3H/HeJ mice as well as IL-1 beta and TNF-alpha expression. B. longum HY8004 also inhibited TNBS-induced lipid peroxidation, TLR-4 expression, and NF-kappaB activation in the colon of C3H/HeN and C3H/HeJ mice. CONCLUSION: B. longum HY8004 can improve colitis via the inhibition of lipid peroxidation as well as NF-kappaB activation.