Tumor necrosis factor receptor-2 (TNFR2): an overview of an emerging drug target

TNFR2 expression is a hallmark of human memory B cells with suppressive function

Tumor Necrosis Factor Receptor 2 (TNFR2) expression is increasingly being linked to tolerogenic immune reactions and cells with suppressor function including a subset of T-regulatory cells. B-regulatory cells play an important role in control of T-cell responses and inflammation. Recently, we described TNFR2 as a marker for IL-10-producing B cells, a hallmark of this cell subset. Here, we demonstrate that proliferation of T cells is reduced in the presence of TNFR2 positive human memory B cells generated with TLR9 ligand, while TNFR2- and TNFR2+CD27- B cells display costimulatory activity. Our data further reveal that IL-10 secretion is characteristic of IgM+ naïve and memory B cells but suppressive activity is not restricted to IL-10: (i) the inhibitory effect of TNFR2+ switched memory B cells was comparable to that exerted by TNFR2+ IgM+ memory B cells although IL-10 secretion levels in the cocultures were lower; (ii) supernatants from TNFR2+ memory B cells failed to suppress T-cell proliferation. Based on our findings, we propose that formation of Breg is a specific characteristic of human memory B cells undergoing terminal differentiation. Our data further corroborate that TNFR2 represents a viable marker for identification of memory B cells with regulatory function.

Effects of selective TNFR1 inhibition or TNFR2 stimulation, compared to non-selective TNF inhibition, on (neuro)inflammation and behavior after myocardial infarction in male mice

BACKGROUND

Myocardial infarction (MI) coinciding with depression worsens prognosis. Although Tumor Necrosis Factor alpha (TNF) is recognized to play a role in both conditions, the therapeutic potential of TNF inhibition is disappointing. TNF activates two receptors, TNFR1 and TNFR2, associated with opposite effects. Therefore, anti-inflammatory treatment with specific TNF receptor interference was compared to non-specific TNF inhibition regarding effects on heart, (neuro)inflammation, brain and behavior in mice with MI.

METHODS

Male C57BL/6 mice were subjected to MI or sham surgery. One hour later, MI mice were randomized to either non-specific TNF inhibition by Enbrel, specific TNFR1 antagonist-, or specific TNFR2 agonist treatment until the end of the protocol. Control sham and MI mice received saline. Behavioral evaluation was obtained day 10-14 after surgery. Eighteen days post-surgery, cardiac function was measured and mice were sacrificed. Blood and tissue samples were collected for analyses of (neuro)inflammation.

RESULTS

MI mice displayed left ventricular dysfunction, without heart failure, (neuro) inflammation or depressive-like behavior. Both receptor-specific interventions, but not Enbrel, doubled early post-MI mortality. TNFR2 agonist treatment improved left ventricular function and caused hyper-ramification of microglia, with no effect on depressive-like behavior. In contrast, TNFR1 antagonist treatment was associated with enhanced (neuro)inflammation: more plasma eosinophils and monocytes; increased plasma Lcn2 and hippocampal microglia and astrocyte activation. Moreover, increased baseline heart rate, with reduced beta-adrenergic responsiveness indicated sympathetic activation, and coincided with reduced exploratory behavior in the open field. Enbrel did not affect neuroinflammation nor behavior.

CONCLUSION

Early receptor interventions, but not non-specific TNF inhibition, increased mortality. Apart from this undesired effect, the general beneficial profile after TNFR2 stimulation, rather than the unfavourable effects of TNFR1 inhibition, would render TNFR2 stimulation preferable over non-specific TNF inhibition in MI with comorbid depression. However, follow-up studies regarding optimal timing and dosing are needed.

The Great Escape: The Power of Cancer Stem Cells to Evade Programmed Cell Death

Cancer is one of the primary causes of death worldwide. Tumour malignancy is related to tumor heterogeneity, which has been suggested to be due to a small subpopulation of tumor cells named cancer stem cells (CSCs). CSCs exert a key role in metastasis development, tumor recurrence, and also epithelial-mesenchymal transition, apoptotic resistance, self-renewal, tumorigenesis, differentiation, and drug resistance. Several current therapies fail to eradicate tumors due to the ability of CSCs to escape different programmed cell deaths. Thus, developing CSC-selective and programmed death-inducing therapeutic approaches appears to be of primary importance. In this review, we discuss the main programmed cell death occurring in cancer and the promising CSC-targeting agents developed in recent years. Even if the reported studies are encouraging, further investigations are necessary to establish a combination of agents able to eradicate CSCs or inhibit their growth and proliferation.

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.

Stable human regulatory T cells switch to glycolysis following TNF receptor 2 costimulation

Following activation, conventional T (T_conv) cells undergo an mTOR-driven glycolytic switch. Regulatory T (T_reg) cells reportedly repress the mTOR pathway and avoid glycolysis. However, here we demonstrate that human thymus-derived T_reg (tT_reg) cells can become glycolytic in response to tumour necrosis factor receptor 2 (TNFR2) costimulation. This costimulus increases proliferation and induces a glycolytic switch in CD3-activated tT_reg cells, but not in T_conv cells. Glycolysis in CD3-TNFR2-activated tT_reg cells is driven by PI3-kinase-mTOR signalling and supports tT_reg cell identity and suppressive function. In contrast to glycolytic T_conv cells, glycolytic tT_reg cells do not show net lactate secretion and shuttle glucose-derived carbon into the tricarboxylic acid cycle. Ex vivo characterization of blood-derived TNFR2^hiCD4⁺CD25^hiCD127^lo effector T cells, which were FOXP3⁺IKZF2⁺, revealed an increase in glucose consumption and intracellular lactate levels, thus identifying them as glycolytic tT_reg cells. Our study links TNFR2 costimulation in human tT_reg cells to metabolic remodelling, providing an additional avenue for drug targeting.

Death Receptors and Their Ligands in Inflammatory Disease and Cancer

On binding to their cognate ligands, death receptors can initiate a cascade of events that can result in two distinct outcomes: gene expression and cell death. The study of three different death receptor-ligand systems, the tumor necrosis factor (TNF)-TNF receptor 1 (TNFR1), the CD95L-CD95, and the TNF-related apoptosis-inducing ligand (TRAIL)-TRAIL-R1/2 system, has drawn the attention of generations of scientists over the past 50 years. This scientific journey, as often happens in science, has been anything but a straight line to success and discoveries in this field were often made by serendipity, catching the scientists by surprise. However, as Louis Pasteur pointed out, luck prefers the prepared mind. It is therefore not surprising that the most impactful discovery of the field to date, the fact that TNF inhibition serves as an effective treatment for several inflammatory and autoimmune diseases, has been like this. Luckily, the scientists who made this discovery were prepared and, most importantly, determined to harness their discovery for therapeutic benefit. Today's research on these death receptor-ligand systems has led to the discovery of a causal link between cell death induced by a variety of these systems and inflammation. In this review, we explain why we predict that therapeutic exploitation of this discovery may profoundly impact the future treatment of inflammatory disease and cancer.

Cacalol Acetate, a Sesquiterpene from Psacalium decompositum, Exerts an Anti-inflammatory Effect through LPS/NF-KB Signaling in Raw 264.7 Macrophages

Inflammatory diseases remain critical health problems worldwide. The search for anti-inflammatory drugs is a primary activity in the pharmaceutical industry. Cacalol is a sesquiterpene with anti-inflammatory potential that is isolated from Psacalium decompositum, a medicinal plant with several scientific reports supporting its anti-inflammatory activity. Cacalol acetate (CA) is the most stable form. Nevertheless, the participation of CA in the main signaling pathway associated with inflammation is unknown. Our aim was to study the anti-inflammatory effect of CA and to determine its participation in NF-κB signaling. In TPA-induced edema in mice, CA produced 70.3% inhibition. To elucidate the influence of CA on the NF-κB pathway, RAW 264.7 macrophages were pretreated with CA and then stimulated with LPS, evaluating NF-ΚB activation, IKK phosphorylation, IΚB-α, p65, cytokine expression, and COX-2 release and activity. CA inhibited NF-κB activation and its upstream signaling, decreasing phosphorylation IKB-α and p65 levels. CA also reduced expression and secretion of TNF-α, IL-1β, and IL-6. Additionally, it decreased the activity and expression of COX-2 mRNA. These data support that CA regulates the NF-κB signaling pathway, which might explain, at least in part, its anti-inflammatory effect. CA is a bioactive molecule useful for the development of anti-inflammatory agents with innovative mechanisms of action.

Quantitative single-molecule imaging of TNFR1 reveals zafirlukast as antagonist of TNFR1 clustering and TNFα-induced NF-ĸB signaling

TNFR1 is a crucial regulator of NF-ĸB-mediated proinflammatory cell survival responses and programmed cell death (PCD). Deregulation of TNFα- and TNFR1-controlled NF-ĸB signaling underlies major diseases, like cancer, inflammation, and autoimmune diseases. Therefore, although being routinely used, antagonists of TNFα might also affect TNFR2-mediated processes, so that alternative approaches to directly antagonize TNFR1 are beneficial. Here, we apply quantitative single-molecule localization microscopy (SMLM) of TNFR1 in physiologic cellular settings to validate and characterize TNFR1 inhibitory substances, exemplified by the recently described TNFR1 antagonist zafirlukast. Treatment of TNFR1-mEos2 reconstituted TNFR1/2 knockout mouse embryonic fibroblasts (MEFs) with zafirlukast inhibited both ligand-independent preligand assembly domain (PLAD)-mediated TNFR1 dimerization as well as TNFα-induced TNFR1 oligomerization. In addition, zafirlukast-mediated inhibition of TNFR1 clustering was accompanied by deregulation of acute and prolonged NF-ĸB signaling in reconstituted TNFR1-mEos2 MEFs and human cervical carcinoma cells. These findings reveal the necessity of PLAD-mediated, ligand-independent TNFR1 dimerization for NF-ĸB activation, highlight the PLAD as central regulator of TNFα-induced TNFR1 oligomerization, and demonstrate that TNFR1-mEos2 MEFs can be used to investigate TNFR1-antagonizing compounds employing single-molecule quantification and functional NF-ĸB assays at physiologic conditions.

The Effects of Vitamin D Supplementation on Lipid and Inflammatory Profile of Healthy Adolescent Boys: A Randomized Controlled Trial

Background: Deficiency of vitamin D, an anti-inflammatory micronutrient with some favorable effects on lipid profiles, has been found to be highly prevalent in adolescents. We aimed to investigate the effect of a school-based vitamin D supplementation regimen on the correction of vitamin D deficiency as well as lipid and inflammatory profiles of healthy adolescent boys. Methods: In this randomized single-blind placebo-controlled trial, seventy-one healthy adolescent boys (age 17 years old) were recruited from one high school in Tehran, Iran, and randomly assigned to two groups. The supplement group received vitamin D pearls at a dose of 50,000 IU monthly for 6 months, this dose is indeed defined by the Ministry of Health in Iran for a potential national school-based vitamin D supplementation program. The other group was given placebo pearls for the same duration. Before and after the treatment, the serum levels of 25-hydroxy vitamin D (25(OH) D), parathyroid hormone (PTH), retinol, lead (Pb), the lipid profile and the inflammatory biomarkers were measured and compared. Results: Between-groups statistical analysis showed that a dose (50,000 IU/month) vitamin D significantly increased the serum levels of 25-hydroxyvitamin D (25 (OH) D) (p < 0.001) and decreased serum levels of PTH (p = 0.003). No significant change was observed in serum levels of retinol and Pb. Between-group analysis revealed that the serum levels of TG (P = 0.001) decreased while an increase in serum levels of HDL (p = 0.021) was observed (p < 0.05). Both the within- and between-group analysis showed that serum tumor necrosis factor receptor 2 (TNFR2) concentration declined while serum interleukin-10 (IL-10) increased in response to vitamin D supplementation (p < 0.05). Conclusion: A supplementation regimen of (50,000 IU/month) vitamin D in a context with high rates of vitamin deficiency has shown positive impacts on the serum vitamin D, lipid profile and inflammatory biomarkers in healthy adolescent boys.

PPMS onset upon adalimumab treatment extends the spectrum of anti-TNF-α therapy-associated demyelinating disorders

Since their introduction in 1999, anti-tumour necrosis factor-α (anti-TNF-α) therapies have been suspected repeatedly to be associated with the occurrence of central nervous system (CNS) demyelinating disorders, including multiple sclerosis (MS). However, recent publications were restricted to descriptions of monophasic demyelinating events or cases of relapsing–remitting MS (RRMS). We here provide the first case report of primary progressive MS (PPMS) onset upon anti-TNF-α therapy as well as a literature review of previously published cases of anti-TNF-α therapy-associated MS onset. The 51-year old male patient was treated with adalimumab due to psoriasis arthritis. About 18 months after treatment initiation, he developed slowly progressing neurological deficits including gait impairment, paraesthesia of the lower limbs, strangury and visual impairment, which led to the discontinuation of adalimumab therapy. Magnetic resonance imaging of the brain and the spinal cord revealed multiple inflammatory lesions and cerebrospinal fluid examination showed slight pleocytosis and positive oligoclonal bands. Thus, PPMS was diagnosed according to the 2017 revision of the McDonald criteria. As PPMS often causes only subtle symptoms in the beginning and early treatment discontinuation of anti-TNF-α therapy seems essential to improve the patient’s outcome, we think that it is important to increase the awareness of slowly progressing neurological deficits as a potential adverse event of anti-TNF-α therapy among all clinicians involved in the initiation and monitoring of these drugs. In addition, the occurrence of both RRMS and progressive MS upon anti-TNF-α therapy might suggest a shared TNF-α-mediated pathophysiological mechanism in the evolution of all MS subtypes.

Antibody-mediated targeting of TNFR2 activates CD8+ T cells in mice and promotes antitumor immunity

Tumor necrosis factor receptor 2 (TNFR2) is the alternate receptor for TNF and can mediate both pro- and anti-inflammatory activities of T cells. Although TNFR2 has been linked to enhanced suppressive activity of regulatory T cells (Tregs) in autoimmune diseases, the viability of TNFR2 as a target for cancer immunotherapy has been underappreciated. Here, we show that new murine monoclonal anti-TNFR2 antibodies yield robust antitumor activity and durable protective memory in multiple mouse cancer cell line models. The antibodies mediate potent Fc-dependent T cell costimulation and do not result in significant depletion of Tregs. Corresponding human agonistic monoclonal anti-TNFR2 antibodies were identified and also had antitumor effects in humanized mouse models. Anti-TNFR2 antibodies could be developed as a novel treatment option for patients with cancer.

TNFR1 and TNFR2 in the Control of the Life and Death Balance of Macrophages

Macrophages stand in the first line of defense against a variety of pathogens but are also involved in the maintenance of tissue homeostasis. To fulfill their functions macrophages sense a broad range of pathogen- and damage-associated molecular patterns (PAMPs/DAMPs) by plasma membrane and intracellular pattern recognition receptors (PRRs). Intriguingly, the overwhelming majority of PPRs trigger the production of the pleiotropic cytokine tumor necrosis factor-alpha (TNF). TNF affects almost any type of cell including macrophages themselves. TNF promotes the inflammatory activity of macrophages but also controls macrophage survival and death. TNF exerts its activities by stimulation of two different types of receptors, TNF receptor-1 (TNFR1) and TNFR2, which are both expressed by macrophages. The two TNF receptor types trigger distinct and common signaling pathways that can work in an interconnected manner. Based on a brief general description of major TNF receptor-associated signaling pathways, we focus in this review on research of recent years that revealed insights into the molecular mechanisms how the TNFR1-TNFR2 signaling network controls the life and death balance of macrophages. In particular, we discuss how the TNFR1-TNFR2 signaling network is integrated into PRR signaling.