Transmembrane TNF-α promotes activation-induced cell death by forward and reverse signaling

TNF-α protects from exacerbated myocarditis and cardiac death by suppressing expansion of activated heart-reactive CD4+ T cells

AIMS

Tumour necrosis factor α (TNF-α) represents a classical pro-inflammatory cytokine, and its increased levels positively correlate with the severity of many cardiovascular diseases. Surprisingly, some heart failure patients receiving high doses of anti-TNF-α antibodies showed serious health worsening. This work aimed to examine the role of TNF-α signalling on the development and progression of myocarditis and heart-specific autoimmunity.

METHODS AND RESULTS

Mice with genetic deletion of TNF-α (Tnf+/- and Tnf-/-) and littermate controls (Tnf+/+) were used to study myocarditis in the inducible and the transgenic T cell receptor (TCRM) models. Tnf+/- and Tnf-/- mice immunized with α-myosin heavy chain peptide (αMyHC) showed reduced myocarditis incidence, but the susceptible animals developed extensive inflammation in the heart. In the TCRM model, defective TNF-α production was associated with increased mortality at a young age due to cardiomyopathy and cardiac fibrosis. We could confirm that TNF-α as well as the secretome of antigen-activated heart-reactive effector CD4+ T (Teff) cells effectively activated the adhesive properties of cardiac microvascular endothelial cells (cMVECs). Our data suggested that TNF-α produced by endothelial in addition to Teff cells promoted leucocyte adhesion to activated cMVECs. Analysis of CD4+ T lymphocytes from both models of myocarditis showed a strongly increased fraction of Teff cells in hearts, spleens, and in the blood of Tnf+/- and Tnf-/- mice. Indeed, antigen-activated Tnf-/- Teff cells showed prolonged long-term survival and TNF-α cytokine-induced cell death of heart-reactive Teff.

CONCLUSION

TNF-α signalling promotes myocarditis development by activating cardiac endothelial cells. However, in the case of established disease, TNF-α protects from exacerbating cardiac inflammation by inducing activation-induced cell death of heart-reactive Teff. These data might explain the lack of success of standard anti-TNF-α therapy in heart failure patients and open perspectives for T cell-targeted approaches.

Role of TNF-α-induced m6A RNA methylation in diseases: a comprehensive review

Tumor Necrosis Factor-alpha (TNF-α) is ubiquitous in the human body and plays a significant role in various physiological and pathological processes. However, TNF-α-induced diseases remain poorly understood with limited efficacy due to the intricate nature of their mechanisms. N6-methyladenosine (m6A) methylation, a prevalent type of epigenetic modification of mRNA, primarily occurs at the post-transcriptional level and is involved in intranuclear and extranuclear mRNA metabolism. Evidence suggests that m6A methylation participates in TNF-α-induced diseases and signaling pathways associated with TNF-α. This review summarizes the involvement of TNF-α and m6A methylation regulators in various diseases, investigates the impact of m6A methylation on TNF-α-induced diseases, and puts forth potential therapeutic targets for treating TNF-α-induced diseases.

The capsaicinoid nonivamide suppresses the inflammatory response and attenuates the progression of steatosis in a NAFLD-rat model

Nonalcoholic fatty liver disease (NAFLD) is relatively associated with comorbidities in obesity and metabolic inflammation. Low-grade inflammation following the high-fat diet (HFD)-induced NAFLD can promote the development of nonalcoholic steatohepatitis (NASH) through particularly liver-resident immune cell recruitment and hepatic nuclear factor kappa B (NF-κB) pathway. Therefore, inflammatory intervention may contribute to NASH reduction. Pelargonic acid vanillylamide (PAVA) or nonivamide is one of the pungent capsaicinoids of Capsicum species and has been found in chili peppers. Our previous study demonstrated that PAVA improved hepatic function, decreased oxidative stress and reduced apoptotic cell death but the insight role of PAVA on NAFLD is still unclear. Thus, this study aimed to investigate the underlying anti-inflammatory mechanism of PAVA in an NAFLD-rat model. Male Sprague Dawley rats were fed with normal diet or HFD for 16 weeks. Then high-fat rats were given vehicle or PAVA (1 mg/kg/day) for another 4 weeks. We found that PAVA alleviated hepatic inflammation associated with the reducing toll-like receptor 4/NF-κB pathway, showing significantly lower recruitment of cluster of differentiation 44. PAVA also maintained activity of insulin signaling pathway, and attenuated NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3) inflammasome formation. NAFLD progresses to NASH through transforming growth factor (TGF-β1), and also recovery to simple stage followed by PAVA suppresses pro-inflammatory cytokines such as tumor necrosis factor-α, interleukin-1β, interleukin-6, and Janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) pathway. Therefore, our findings suggest that PAVA provides a novel therapeutic approach for NAFLD and slows the progression to NASH.

The expression pattern of membranous TNF-α is distinct from its intracellular form in the breast cancer draining lymph nodes

Tumor necrosis factor-alpha (TNF-α) is mostly known as a soluble cytokine. However, this study focused on its membranous form whose significance is rarely investigated in antitumor immunity. Herein, we assessed the expression of both membranous and intracellular forms of TNF-α (m/icTNF-α) in the lymphocytes derived from breast cancer-draining lymph nodes. CD4⁺T cells were the main subset expressing mTNF-α with the highest intensity, whereas icTNF-α expression was most intense in CD8⁺T cells. An inverse correlation was seen between the frequency of mTNF-α and the expression intensity of this cytokine in B cells. In the clinical context, the higher intensity of mTNF-α expression in CD19⁺ cells correlated with poor prognosticators, while the frequency of mTNF-α⁺CD19⁺ cells showed a reverse correlation with the number of involved lymph nodes. The two forms of TNF-α did not show similar associations with cancer parameters, which highlights the complex role of this cytokine in breast cancer immunity.

Meprin and ADAM proteases as triggers of systemic inflammation in sepsis

Systemic inflammatory disorders (SIDs) comprise a broad range of diseases characterized by dysregulated excessive innate immune responses. Severe forms of SIDs can lead to organ failure and death, and their increasing incidence represents a major issue for the healthcare system. Protease-mediated ectodomain shedding of cytokines and their receptors represents a central mechanism in the regulation of inflammatory responses. The metalloprotease A disintegrin and metalloproteinase (ADAM) 17 is the best-characterized ectodomain sheddase capable of releasing TNF-α and soluble IL-6 receptor, which are decisive factors of systemic inflammation. Recently, meprin metalloproteases were also identified as IL-6 receptor sheddases and activators of the pro-inflammatory cytokines IL-1β and IL-18. In different mouse models of SID, particularly those mimicking a sepsis-like phenotype, ADAM17 and meprins have been found to promote disease progression. In this review, we summarize the role of ADAM10, ADAM17, and meprins in the onset and progression of sepsis and discuss their potential as therapeutic targets.

Cytoplasmic and Nuclear Functions of cIAP1

Cellular inhibitor of apoptosis 1 (cIAP1) is a cell signaling regulator of the IAP family. Through its E3-ubiquitine ligase activity, it has the ability to activate intracellular signaling pathways, modify signal transduction pathways by changing protein-protein interaction networks, and stop signal transduction by promoting the degradation of critical components of signaling pathways. Thus, cIAP1 appears to be a potent determinant of the response of cells, enabling their rapid adaptation to changing environmental conditions or intra- or extracellular stresses. It is expressed in almost all tissues, found in the cytoplasm, membrane and/or nucleus of cells. cIAP1 regulates innate immunity by controlling signaling pathways mediated by tumor necrosis factor receptor superfamily (TNFRs), some cytokine receptors and pattern recognition-receptors (PRRs). Although less documented, cIAP1 has also been involved in the regulation of cell migration and in the control of transcriptional programs.

Engineered Liposomes Protect Immortalized Immune Cells from Cytolysins Secreted by Group A and Group G Streptococci

The increasing antibiotic resistance of bacterial pathogens fosters the development of alternative, non-antibiotic treatments. Antivirulence therapy, which is neither bacteriostatic nor bactericidal, acts by depriving bacterial pathogens of their virulence factors. To establish a successful infection, many bacterial pathogens secrete exotoxins/cytolysins that perforate the host cell plasma membrane. Recently developed liposomal nanotraps, mimicking the outer layer of the targeted cell membranes, serve as decoys for exotoxins, thus diverting them from attacking host cells. In this study, we develop a liposomal nanotrap formulation that is capable of protecting immortalized immune cells from the whole palette of cytolysins secreted by Streptococcus pyogenes and Streptococcus dysgalactiae subsp. equisimilis—important human pathogens that can cause life-threatening bacteremia. We show that the mixture of cholesterol-containing liposomes with liposomes composed exclusively of phospholipids is protective against the combined action of all streptococcal exotoxins. Our findings pave the way for further development of liposomal antivirulence therapy in order to provide more efficient treatment of bacterial infections, including those caused by antibiotic resistant pathogens.

TNFR2 depletion reduces psoriatic inflammation in mice via downregulating specific dendritic cell populations in lymph nodes and inhibiting IL-23/IL-17 pathways

TNF-α, a proinflammatory cytokine, is a crucial mediator of psoriasis pathogenesis. TNF-α functions by activating TNFR1 and TNFR2. Anti-TNF drugs that neutralize TNF-α, thus blocking the activation of TNFR1 and TNFR2, have been proven highly therapeutic in psoriatic diseases. TNF-α also plays an important role in host defense; thus, anti-TNF therapy can cause potentially serious adverse effects, including opportunistic infections and latent tuberculosis reactivation. These adverse effects are attributed to TNFR1 inactivation. Therefore, understanding the relative contributions of TNFR1 and TNFR2 has clinical implications in mitigating psoriasis versus global TNF-α blockade. We found a significant reduction in psoriasis lesions as measured by epidermal hyperplasia, characteristic gross skin lesion, and IL-23 or IL-17A levels in Tnfr2-knockout but not in Tnfr1-knockout mice in the imiquimod psoriasis model. Furthermore, imiquimod-mediated increase in the myeloid dendritic cells, TNF/inducible nitric oxide synthase‒producing dendritic cells, and IL-23 expression in the draining lymph nodes were dependent on TNFR2 but not on TNFR1. Together, our results support that psoriatic inflammation is not dependent on TNFR1 activity but is driven by a TNFR2-dependent IL-23/IL-17 pathway activation. Thus, targeting the TNFR2 pathway may emerge as a potential next-generation therapeutic approach for psoriatic diseases.

Differential impacts of TNFα inhibitors on the transcriptome of Th cells

BACKGROUND

Targeting TNFα is beneficial in many autoimmune and inflammatory diseases, including rheumatoid arthritis. However, the response to each of the existing TNFα inhibitors (TNFis) can be patient- and/or disease-dependent. In addition, TNFis can induce the production of type 1 interferons (IFNs), which contribute to their non-infection side effects, such as pustular psoriasis. Thus far, the molecular mechanisms mediating the drug-specific effects of TNFis and their induction of type 1 IFNs are not fully understood.

METHODS

Peripheral blood mononuclear cells (PBMCs) were collected from healthy donors and stimulated in vitro with anti-CD3 and anti-CD28 in the absence or presence of adalimumab, etanercept, or certolizumab. Th cells were isolated from the stimulated PBMCs, and their RNA was subjected to RNA-seq and quantitative polymerase chain reaction.

RESULTS

Adalimumab and etanercept, which contain Fc, but not certolizumab, which does not contain Fc, inhibited the expression of several effector cytokines by Th cells within anti-CD3/anti-CD28-stimulated PBMCs. Transcriptomic analyses further showed that adalimumab, but not certolizumab, reciprocally induced type 1 IFN signals and the expression of CD96 and SIRPG in Th cells. The unique effects of adalimumab were not due to preferential neutralization of soluble TNFα but instead were mediated by several distinct mechanisms independent or dependent of Fc-facilitated physical interaction between Th cells and CD14+ monocytes.

CONCLUSIONS

TNFis can have drug-specific effects on the transcriptional profile of Th cells.

Transmembrane TNF and Its Receptors TNFR1 and TNFR2 in Mycobacterial Infections

Tumor necrosis factor (TNF) is one of the main cytokines regulating a pro-inflammatory environment. It has been related to several cell functions, for instance, phagocytosis, apoptosis, proliferation, mitochondrial dynamic. Moreover, during mycobacterial infections, TNF plays an essential role to maintain granuloma formation. Several effector mechanisms have been implicated according to the interactions of the two active forms, soluble TNF (solTNF) and transmembrane TNF (tmTNF), with their receptors TNFR1 and TNFR2. We review the impact of these interactions in the context of mycobacterial infections. TNF is tightly regulated by binding to receptors, however, during mycobacterial infections, upstream activation signalling pathways may be influenced by key regulatory factors either at the membrane or cytosol level. Detailing the structure and activation pathways used by TNF and its receptors, such as its interaction with solTNF/TNFRs versus tmTNF/TNFRs, may bring a better understanding of the molecular mechanisms involved in activation pathways which can be helpful for the development of new therapies aimed at being more efficient against mycobacterial infections.

Clonal expansion of large granular lymphocytes in patients with spondyloarthritis and psoriatic arthritis treated with TNFα inhibitors

To determine the prevalence of clonal T-large granular lymphocyte (T-LGL) cells in patients with spondyloarthritis (SpA) and psoriatic arthritis (PsA) and to define possible risk factors for this condition. We present a cross-sectional analysis with retrospective and prospective aspects. 115 SpA patients, 48 PsA patients and 51 controls were recruited between December 28, 2017 and January 23, 2019. Flow cytometry (FACS) was performed to screen for aberrant T-LGL cells. Molecular analysis was then employed to confirm the diagnosis in patients with suggestive FACS findings. Patients with clonal T-LGL populations were followed prospectively by FACS analysis. Electronic patient files were retrospectively analyzed to determine risk factors. Median age was 49 years for SpA, 55.5 years for PsA, and 54 years for controls. Median disease duration of SpA and PsA was 15 years and 11 years, respectively. 79.8% of patients had received biologics at some point, 75.5% had ever received tumor necrosis factor (TNF) inhibitors. 59.5% were treated with TNF inhibitors at the time of study inclusion. We identified clonal T-LGL expansions in 13 individuals equaling a prevalence of 6% (13/214). T-LGL patients were taking TNF inhibitors more frequently at the time of study inclusion (p = 0.022) and were more likely to have ever been treated with TNF inhibition (p = 0.046). Clonal T-LGL expansions can be detected in patients with SpA, PsA and also in healthy controls. Confirming earlier results, exposure to TNFα-blocking agents appears to increase the risk of developing clonal expansions of T-LGL cells.

Effect of Anti-TNF Therapy on Mucosal Apoptosis Genes Expression in Crohn's Disease

Crohn's disease (CD) is a chronic immune-mediated disorder for which there is not a fully effective treatment. Moreover, biological therapy with anti-tumor necrosis factor-α (anti-TNF-α) monoclonal antibodies leads to an effective response in only 60–70% of patients. Our previous data suggested that specific loci polymorphism of the TNFRSF1B, FCGR3A, IL1R, IL1B, and FAS genes could be a predictor of the primary non-response to anti-TNF therapy in CD patients. In this work, we propose to explain this hypothesis by functional analysis in colon biopsies and in a cell culture model. Using the RT-qPCR analysis, we estimated the FCGR3A, IL1R, TNFRSF1B, IL1B, FAS, and ADAM17 genes mRNA level in colon biopsies material from inflamed and non-inflamed tissue from 21 CD patients (14 responders and 7 non-responders to anti-TNF therapy) and 6 controls, as well as in vitro in a peripheral blood mononuclear cells (PBMCs) from 14 CD patients (seven responders and seven non-responders to anti-TNF therapy) and eight controls cultured for 72 h with 10 μg/ml of anti-TNF antibody. Our findings demonstrated a significant down-regulation of TNFRSF1B gene expression in non-responders both in inflamed and in non-inflamed colon tissue, while the expression of the FCGR3A and IL1B genes was significantly up-regulated in non-responders in the inflamed colon region. In vitro research results indicate that the anti-TNF drug induced a significant decrease in TNFRSF1B, FCGR3A, and FAS gene expression in non-responders. These results show that altered TNFRSF1B, FCGR3A, and IL1B genes expression can be a predictor of the primary non-response to anti-TNF therapy in CD patients.

Regulatory Roles of Tumor Necrosis Factor-α-Induced Protein 8 Like-Protein 2 in Inflammation, Immunity and Cancers: A Review

Tumor necrosis factor-alpha (TNF-α)-induced protein 8 (TNFAIP8/TIPE) family, including TNFAIP8 (TIPE), TNFAIP8 like-protein 1 (TNFAIP8L1/TIPE1), TNFAIP8 like-protein 2 (TNFAIP8L2/TIPE2), and TNFAIP8 like-protein 3 (TNFAIP8L3/TIPE3), plays a vital role in regulating inflammatory responses, immune homeostasis, and cancer development. Over the last decade, studies have shown that TIPE2 protein is differentially expressed in diverse cells and tissues. The dysregulation of TIPE2 protein can lead to dysregulation of inflammatory responses and immune homeostasis, and change the basic characteristics of cancers. In consideration of the immeasurable values of TIPE2 in diagnosis, treatment, and prognosis of various human diseases, this review will focus on the expression pattern, structure, and regulatory roles of TIPE2 in inflammation, immunity, and cancers.

Novel bio-genetic predictors of response to biologic treatment in inflammatory bowel diseases

Despite the evolving therapeutic armamentarium, the treatment of IBD patients remains challenging and many patients fail to respond to biologic agents. With the limited yield of clinical factors to predict the outcome of biologic treatments, studies have focused on identifying genetic alterations and circulating or tissue biomarkers to identify patients who are likely to respond to therapy. In this review, we examine the current knowledge and status of genetic, expression biomarkers, and microbiome predictors. The search for genetic predictors has yielded many genetic loci variants, but few were reproducible. Expression studies of putative biomarkers show promising results, especially with TREM1, oncostatin M and TNF biomarkers, but confirmatory studies are warranted. Finally, the microbiome is emerging as an important player with specific taxa and functional pathways differentially abundant and enriched in responders versus non-responders to certain biologics. Integrating different factors into a robust predictive model, which is both reproducible, accurate and affordable, remains the main challenge before these individualized strategies can reach clinical use.

Tumor Necrosis Factor Receptors: Pleiotropic Signaling Complexes and Their Differential Effects

Since its discovery in 1975, TNFα has been a subject of intense study as it plays significant roles in both immunity and cancer. Such attention is well deserved as TNFα is unique in its engagement of pleiotropic signaling via its two receptors: TNFR1 and TNFR2. Extensive research has yielded mechanistic insights into how a single cytokine can provoke a disparate range of cellular responses, from proliferation and survival to apoptosis and necrosis. Understanding the intracellular signaling pathways induced by this single cytokine via its two receptors is key to further revelation of its exact functions in the many disease states and immune responses in which it plays a role. In this review, we describe the signaling complexes formed by TNFR1 and TNFR2 that lead to each potential cellular response, namely, canonical and non-canonical NF-κB activation, apoptosis and necrosis. This is followed by a discussion of data from in vivo mouse and human studies to examine the differential impacts of TNFR1 versus TNFR2 signaling.

Complexity of TNF-α Signaling in Heart Disease

Heart disease is a leading cause of death with unmet clinical needs for targeted treatment options. Tumor necrosis factor alpha (TNF-α) represents a master pro-inflammatory cytokine that plays an important role in many immunopathogenic processes. Anti-TNF-α therapy is widely used in treating autoimmune inflammatory disorders, but in case of patients with heart disease, this treatment was unsuccessful or even harmful. The underlying reasons remain elusive until today. This review summarizes the effects of anti-TNF-α treatment in patients with and without heart disease and describes the involvement of TNF-α signaling in a number of animal models of cardiovascular diseases. We specifically focused on the role of TNF-α in specific cardiovascular conditions and in defined cardiac cell types. Although some mechanisms, mainly in disease development, are quite well known, a comprehensive understanding of TNF-α signaling in the failing heart is still incomplete. Published data identify pathogenic and cardioprotective mechanisms of TNF-α in the affected heart and highlight the differential role of two TNF-α receptors pointing to the complexity of the TNF-α signaling. In the light of these findings, it seems that targeting the TNF-α pathway in heart disease may show therapeutic benefits, but this approach must be more specific and selectively block pathogenic mechanisms. To this aim, more research is needed to better understand the molecular mechanisms of TNF-α signaling in the failing heart.

Unfolding transmembrane TNFα dynamics in cancer therapeutics

Cytokines are a group of glycoprotein signaling mediators, which play essential roles in maintaining several complex physiological functions of our body. TNFα is such a pleiotropic cytokine, which involves maintaining a plethora of immune responses. Initially, TNFα is synthesized as a 26 kDa full-length transmembrane form, which is enzymatically cleaved to produce the soluble circulating 17 kDa TNFα. Although the anti-cancer potential of soluble TNFα was discovered more than a century back, its dual ability to promote tumor, posed a major hindrance in finding its acceptance as a proper anti-cancer molecule. In contrast, the membrane-tethered tmTNFα holds the potential of tumor regression without initiating cell proliferation. The membrane-tethered form of TNFα is the physiological precursor of soluble TNFα that remains biologically active and is capable of initiating signaling cascades after binding with the TNFα receptors- TNFR I and TNFR II. In this review, we emphasize on the basic biology and molecular aspects of tmTNFα for its anti-cancer potential.

Methotrexate Enhances Apoptosis of Transmembrane TNF-Expressing Cells Treated With Anti-TNF Agents

Background

Concomitant use of methotrexate (MTX) improves the clinical efficacy of anti-TNF agents in the treatment of rheumatoid arthritis (RA). We aimed to clarify the cytotoxic effect of MTX on transmembrane TNF (tmTNF)-expressing cells treated with anti-TNF agents.

Methods

Jurkat T cells stably expressing tmTNF were used for the following experiments. Cytotoxicity induced by an anti-TNF agent (infliximab, adalimumab, or certolizumab pegol) with concomitant MTX were compared with that by MTX alone or by an anti-TNF agent alone using flow cytometry. Apoptosis-induction mediated by reverse signal through tmTNF, complement-dependent cytotoxicity (CDC), antibody-dependent cell-mediated cytotoxicity (ADCC), and antibody-dependent cellular phagocytosis (ADCP) were evaluated. Folic acid and Y-27632, a Rho kinase inhibitor, were used as inhibitors to study intracellular signaling pathway in apoptosis induced by MTX and anti-TNF agents.

Results

Apoptosis of tmTNF-expressing cells was significantly increased by the concomitant administration of MTX and an anti-TNF agent, compared with MTX alone or an anti-TNF agent alone. The apoptosis induction by concomitant MTX was most pronounced in infliximab-treatment. Reverse signal transduction, but not CDC or ADCC/ADCP, was responsible for the coordinate effect of MTX and an anti-TNF agent on tmTNF-expressing cells. Folic acid inhibited MTX-mediated apoptosis, while Y-27632 suppressed JNK activation and infliximab-induced apoptosis via revere signal through tmTNF.

Conclusion

The apoptotic effect was enhanced by combination of MTX and an anti-TNF agent in tmTNF-expressing cells. The intracellular pathways induced by MTX and anti-TNF agents seem to be independent. These findings might explain at least in part improved the clinical response upon co-therapy of MTX and an anti-TNF agent in RA.

Epicatechin Reduces Spatial Memory Deficit Caused by Amyloid-β25⁻35 Toxicity Modifying the Heat Shock Proteins in the CA1 Region in the Hippocampus of Rats

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by dementia and the aggregation of the amyloid beta peptide (Aβ). Aβ_25-35 is the most neurotoxic sequence, whose mechanism is associated with the neuronal death in the Cornu Ammonis 1 (CA1) region of the hippocampus (Hp) and cognitive damage. Likewise, there are mechanisms of neuronal survival regulated by heat shock proteins (HSPs). Studies indicate that pharmacological treatment with flavonoids reduces the prevalence of AD, particularly epicatechin (EC), which shows better antioxidant activity. The aim of this work was to evaluate the effect of EC on neurotoxicity that causes Aβ_25-35 at the level of spatial memory as well as the relationship with immunoreactivity of HSPs in the CA1 region of the Hp of rats. Our results show that EC treatment reduces the deterioration of spatial memory induced by the Aβ_25-35, in addition to reducing oxidative stress and inflammation in the Hp of the animals treated with EC + Aβ_25-35. Likewise, the immunoreactivity to HSP-60, -70, and -90 is lower in the EC + Aβ_25-35 group compared to the Aβ_25-35 group, which coincides with a decrease of dead neurons in the CA1 region of the Hp. Our results suggest that EC reduces the neurotoxicity induced by Aβ_25-35, as well as the HSP-60, -70, and -90 immunoreactivity and neuronal death in the CA1 region of the Hp of rats injected with Aβ_25-35, which favors an improvement in the function of spatial memory.

Exclusive expression of transmembrane TNF aggravates acute glomerulonephritis despite reduced leukocyte infiltration and inflammation

Tumor necrosis factor-α (TNF) is a cytokine mediating inflammatory kidney diseases such as immune complex glomerulonephritis. Its two receptors, TNFR1 and TNFR2, play distinct roles in this process, with TNFR2 strongly required for induction of disease. In contrast to soluble TNF (sTNF), transmembrane TNF robustly activates TNFR2. Thus, we examined the functional role of transmembrane TNF by inducing heterologous nephrotoxic serum nephritis in wild-type and transgenic TNFΔ1-9,K11E knock-in mice expressing transmembrane TNF but no sTNF (memTNF mice). Compared to wild-type, nephritis was exacerbated in memTNF mice on day 5, indicated by increased albuminuria, higher serum urea levels, and more pronounced glomerular deposits, together with higher numbers of dying and proliferating glomerular cells. This was associated with greater loss of glomerular endothelial cells, increased podocyte stress, and signs of augmented necroptosis in memTNF kidneys. Aggravation of nephritis was dependent on transmembrane TNF expression in parenchymal cells, but not leukocytes. Surprisingly, increased kidney injury was associated with reduced renal leukocyte infiltration in memTNF mice, which correlated with decreased renal mRNA expression of pro-inflammatory mediators. This effect was also present in isolated memTNF glomeruli stimulated with interleukin-1β in vitro. Thus, uncleaved transmembrane TNF is an important mediator of renal tissue damage characterized by increased renal cell death and loss of glomerular endothelial cells in murine glomerulonephritis. In contrast, sTNF predominantly mediates renal leukocyte recruitment and inflammation. These findings highlight the importance of transmembrane TNF in inflammatory kidney disease as a possible therapeutic target.

Antagonist of cIAP1/2 and XIAP enhances anti-tumor immunity when combined with radiation and PD-1 blockade in a syngeneic model of head and neck cancer

Head and neck squamous cell carcinomas (HNSCCs) frequently harbor genomic mutations in cell death pathways. Nearly 30% of HNSCCs overexpress Fas-Associated Death Domain (FADD), with or without BIRC2/3 genes encoding cellular Inhibitor of Apoptosis Proteins 1/2 (cIAP1/2), critical components of the Tumor Necrosis Factor (TNF) Receptor signaling pathways. ASTX660 is a novel non-peptidomimetic antagonist of cIAP1/2 and XIAP under evaluation in a clinical trial for advanced solid tumors and lymphomas. Herein, we show that ASTX660, at nanomolar concentrations, sensitized Murine Oral Cancer (MOC1) cells to TNFα. Using syngeneic mouse models, ASTX660 showed additive anti-tumor activity with radiation therapy (XRT), cisplatin chemotherapy, and PD-1 blockade to significantly delay or eradicate MOC1 tumors. These combinations significantly increased CD8 + T cells and dendritic cells, as well as T cell activity. ASTX660 stimulated cytotoxic T lymphocyte (CTL) killing of MOC1 cells expressing ovalbumin. Early stages of CTL killing were predominantly mediated by perforin/granzyme B, whereas later stages were mediated by death ligands TNFα, TRAIL, and FasL. Correspondingly, depletion of CD8 + T cells and NK cells in vivo revealed both types of immune cells to be important components of the complete anti-tumor response enhanced by ASTX660+XRT. These findings serve to inform future studies of IAP inhibitors and support the potential for future clinical trials investigating ASTX660 with XRT and immunotherapies like PD-1/PD-L1 blockade in HNSCC.

Life and Death of Activated T Cells: How Are They Different from Naïve T Cells?

T cells are pivotal in immunity and immunopathology. After activation, T cells undergo a clonal expansion and differentiation followed by a contraction phase, once the pathogen has been cleared. Cell survival and cell death are critical for controlling the numbers of naïve T cells, effector, and memory T cells. While naïve T cell survival has been studied for a long time, more effort has gone into understanding the survival and death of activated T cells. Despite this effort, there is still much to be learnt about T cell survival, as T cells transition from naïve to effector to memory. One key advance is the development of inhibitors that may allow the temporal study of survival mechanisms operating in these distinct cell states. Naïve T cells were highly reliant on BCL-2 and sensitive to BCL-2 inhibition. Activated T cells are remarkably different in their regulation of apoptosis by pro- and antiapoptotic members of the BCL-2 family, rendering them differentially sensitive to antagonists blocking the function of one or more members of this family. Recent progress in understanding other programmed cell death mechanisms, especially necroptosis, suggests a unique role for alternative pathways in regulating death of activated T cells. Furthermore, we highlight a mechanism of epigenetic regulation of cell survival unique to activated T cells. Together, we present an update of our current understanding of the survival requirement of activated T cells.