A trimeric structural fusion of an antagonistic tumor necrosis factor-α mutant enhances molecular stability and enables facile modification

CRISPR/Cas9-mediated knockout of tnf-α1 in zebrafish reduces disease resistance after Edwardsiella piscicida bacterial infection

Tumor necrosis factor (TNF) is an important cytokine involved in immune responses to bacterial infections in vertebrates, including fish. Although Tnf-α is a well-studied cytokine, there are contradictory findings about Tnf-α function following bacterial infection. In this study, we analyzed the expression and function of the Tnf-α-type I isoform (Tnf-α1) in zebrafish by knockout experiments using the CRISPR/Cas9 gene-editing tool. The open reading frame of tnf-α1 encodes a 25.82 kDa protein with 234 amino acids (aa). The expression of tnf-α1 in the early stages of zebrafish was observed from the 2-cell stage. Adult zebrafish spleens showed the highest expression of tnf-α1. To evaluate the function of Tnf-α1, an 8 bp deletion in the target region, resulting in a short truncated protein of 55 aa, was used to create the tnf-α1 knockout mutant. The pattern of downstream gene expression in 7-day larvae in wild-type (WT) and tnf-α1 knockout fish was examined. We also verified the fish mortality rate after Edwardsiella piscicida challenge and found that it was much higher in tnf-α1 knockout fish than in WT fish. Additionally, downstream gene expression analyses after E. piscicida exposure revealed a distinct expression pattern in tnf-α1 knockout fish compared to that in WT fish. Overall, our study using tnf-α1 deletion in zebrafish confirmed that Tnf-α1 is critical for immune regulation during bacterial infection.

Bivalent structure of a TNFR2-selective and agonistic TNF-α mutein Fc-fusion protein enhances the expansion activity of regulatory T cells

Recently, TNF receptor type 2 (TNFR2) signaling was found to be involved in the proliferation and activation of regulatory T cells (Tregs), a subpopulation of lymphocytes that suppress immune responses. Tregs mediate peripheral immune tolerance, and the disruption of their functions causes autoimmune diseases or allergy. Therefore, cell expanders or regulators of Tregs that control immunosuppressive activity can be used to treat these diseases. We focused on TNFR2, which is preferentially expressed on Tregs, and created tumor necrosis factor-α (TNF-α) muteins that selectively activate TNFR2 signaling in mice and humans, termed R2agoTNF and R2-7, respectively. In this study, we attempted to optimize the structure of muteins to enhance their TNFR2 agonistic activity and stability in vivo by IgG-Fc fusion following single-chain homo-trimerization. The fusion protein, scR2agoTNF-Fc, enhanced the expansion of CD4+CD25+ Tregs and CD4+Foxp3+ Tregs and contributed to their immunosuppressive activity ex vivo and in vivo in mice. The prophylactic administration of scR2agoTNF-Fc suppressed inflammation in contact hypersensitivity and arthritis mouse models. Furthermore, scR2-7-Fc preferentially expanded Tregs in human peripheral blood mononuclear cells via TNFR2. These TNFR2 agonist-Fc fusion proteins, which have bivalent structures, are novel Treg expanders.

The Dysregulation of Inflammatory Pathways Triggered by Copper Exposure

Copper (Cu) is an essential micronutrient for both human and animals. However, excessive intake of copper will cause damage to organs and cells. Inflammation is a biological response that can be induced by various factors such as pathogens, damaged cells, and toxic compounds. Dysregulation of inflammatory responses are closely related to many chronic diseases. Recently, Cu toxicological and inflammatory effects have been investigated in various animal models and cells. In this review, we summarized the known effect of Cu on inflammatory responses and sum up the molecular mechanism of Cu-regulated inflammation. Excessive Cu exposure can modulate a huge number of cytokines in both directions, increase and/or decrease through a variety of molecular and cellular signaling pathways including nuclear factor kappa-B (NF-κB) pathway, mitogen-activated protein kinase (MAPKs) pathway, JAK-STAT (Janus Kinase- signal transducer and activator of transcription) pathway, and NOD-like receptor protein 3 (NLRP3) inflammasome. Underlying the molecular mechanism of Cu-regulated inflammation could help further understanding copper toxicology and copper-associated diseases.

The role of TNF-α in the fate regulation and functional reprogramming of mesenchymal stem cells in an inflammatory microenvironment

Mesenchymal stem cells (MSCs) are pluripotent stem cells with multidirectional differentiation potential and strong immunomodulatory capacity. MSCs have been widely used in the treatment of injured, inflammatory, and immune-related diseases. Resting MSCs lack differentiation and immunomodulatory ability. Instead, they rely on microenvironmental factors to: 1) stimulate and regulate their expression of specific cell growth factors, chemokines, immunomodulatory factors, or receptors; or 2) direct their differentiation into specific tissue cells, which ultimately perform tissue regeneration and repair and immunomodulatory functions. Tumor necrosis factor (TNF)-α is central to the creation of an inflammatory microenvironment. TNF-α regulates the fate and functional reprogramming of MSCs, either alone or in combination with a variety of other inflammatory factors. TNF-α can exert opposing effects on MSCs, from inducing MSC apoptosis to enhancing their anti-tumor capacity. In addition, the immunomodulation and osteogenic differentiation capacities of MSCs, as well as their exosome or microvesicle components vary significantly with TNF-α stimulating concentration, time of administration, or its use in combination with or without other factors. Therefore, this review discusses the impact of TNF-α on the fate and functional reprogramming of MSCs in the inflammatory microenvironment, to provide new directions for improving the immunomodulatory and tissue repair functions of MSCs and enhance their therapeutic potential.

The Screening of Therapeutic Peptides for Anti-Inflammation through Phage Display Technology

For the treatment of inflammatory illnesses such as rheumatoid arthritis and carditis, as well as cancer, several anti-inflammatory medications have been created over the years to lower the concentrations of inflammatory mediators in the body. Peptides are a class of medication with the advantages of weak immunogenicity and strong activity, and the phage display technique is an effective method for screening various therapeutic peptides, with a high affinity and selectivity, including anti-inflammation peptides. It enables the selection of high-affinity target-binding peptides from a complex pool of billions of peptides displayed on phages in a combinatorial library. In this review, we will discuss the regular process of using phage display technology to screen therapeutic peptides, and the peptides screened for anti-inflammation properties in recent years according to the target. We will describe how these peptides were screened and how they worked in vitro and in vivo. We will also discuss the current challenges and future outlook of using phage display to obtain anti-inflammatory therapeutic peptides.

Immunosuppressant Therapies in COVID-19: Is the TNF Axis an Alternative?

The study of cytokine storm in COVID-19 has been having different edges in accordance with the knowledge of the disease. Various cytokines have been the focus, especially to define specific treatments; however, there are no conclusive results that fully support any of the options proposed for emergency treatment. One of the cytokines that requires a more exhaustive review is the tumor necrosis factor (TNF) and its receptors (TNFRs) as increased values of soluble formats for both TNFR1 and TNFR2 have been identified. TNF is a versatile cytokine with different impacts at the cellular level depending on the action form (transmembrane or soluble) and the receptor to which it is associated. In that sense, the triggered mechanisms can be diversified. Furthermore, there is the possibility of the joint action provided by synergism between one or more cytokines with TNF, where the detonation of combined cellular processes has been suggested. This review aims to discuss some roles of TNF and its receptors in the pro-inflammatory stage of COVID-19, understand its ways of action, and let to reposition this cytokine or some of its receptors as therapeutic targets.

The unique structure of the zebrafish TNF-α homotrimer

In the current study, zebrafish TNF-α1 (zTNF-α1) was crystallized, and the structure was analyzed. The zTNF-α1 trimer is composed of three monomers whose height and width are 50 Å and 60 Å, respectively. Compared with human TNF-α, zTNF-α1 shows only ~30% amino acid identity, the EF loop of each monomer lacks three amino acids, the CD loop is increased by four amino acids, and the AA'' loop is increased by one amino acid. In addition, an A″-β-chain is added to the zTNF-α1 monomer, forming two β-sheet layers with 6:5 β-chains. The top of the trimer is missing three amino acids and the inner coil because the EF loop seals the central hole at the top, forming a unique structure. In conclusion, the results elucidated the structure of the zTNF-α1 trimer, providing immunological knowledge for studying TNF-α function in the zebrafish animal model and structural information for exploring TNF-α family evolution.

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.

Characterization of a TNFR2-Selective Agonistic TNF-α Mutant and Its Derivatives as an Optimal Regulatory T Cell Expander

Regulatory T cells (Tregs) are a subpopulation of lymphocytes that play a role in suppressing and regulating immune responses. Recently, it was suggested that controlling the functions and activities of Tregs might be applicable to the treatment of human diseases such as autoimmune diseases, organ transplant rejection, and graft-versus-host disease. TNF receptor type 2 (TNFR2) is a target molecule that modulates Treg functions. In this study, we investigated the role of TNFR2 signaling in the differentiation and activation of mouse Tregs. We previously reported the generation of a TNFR2-selective agonist TNF mutant, termed R2agoTNF, by using our unique cytokine modification method based on phage display. R2agoTNF activates cell signaling via mouse TNFR2. In this study, we evaluated the efficacy of R2agoTNF for the proliferation and activation of Tregs in mice. R2agoTNF expanded and activated mouse CD4⁺CD25⁺ Tregs ex vivo. The structural optimization of R2agoTNF by internal cross-linking or IgG-Fc fusion selectively and effectively enhanced Treg expansion in vivo. Furthermore, the IgG-Fc fusion protein suppressed skin-contact hypersensitivity reactions in mice. TNFR2 agonists are expected to be new Treg expanders.

Selective Targeting of TNF Receptors as a Novel Therapeutic Approach

Tumor necrosis factor (TNF) is a central regulator of immunity. Due to its dominant pro-inflammatory effects, drugs that neutralize TNF were developed and are clinically used to treat inflammatory and autoimmune diseases, such as rheumatoid arthritis, inflammatory bowel disease and psoriasis. However, despite their clinical success the use of anti-TNF drugs is limited, in part due to unwanted, severe side effects and in some diseases its use even is contraindicative. With gaining knowledge about the signaling mechanisms of TNF and the differential role of the two TNF receptors (TNFR), alternative therapeutic concepts based on receptor selective intervention have led to the development of novel protein therapeutics targeting TNFR1 with antagonists and TNFR2 with agonists. These antibodies and bio-engineered ligands are currently in preclinical and early clinical stages of development. Preclinical data obtained in different disease models show that selective targeting of TNFRs has therapeutic potential and may be superior to global TNF blockade in several disease indications.

Structural optimization of a TNFR1-selective antagonistic TNFα mutant to create new-modality TNF-regulating biologics

Excessive activation of the proinflammatory cytokine tumor necrosis factor-α (TNFα) is a major cause of autoimmune diseases, including rheumatoid arthritis. TNFα induces immune responses via TNF receptor 1 (TNFR1) and TNFR2. Signaling via TNFR1 induces proinflammatory responses, whereas TNFR2 signaling is suggested to suppress the pathophysiology of inflammatory diseases. Therefore, selective inhibition of TNFR1 signaling and preservation of TNFR2 signaling activities may be beneficial for managing autoimmune diseases. To this end, we developed a TNFR1-selective, antagonistic TNFα mutant (R1antTNF). Here, we developed an R1antTNF derivative, scR1antTNF-Fc, which represents a single-chain form of trimeric R1antTNF with a human IgG-Fc domain. scR1antTNF-Fc had properties similar to those of R1antTNF, including TNFR1-selective binding avidity, TNFR1 antagonistic activity, and thermal stability, and had a significantly extended plasma t _1/2 in vivo In a murine rheumatoid arthritis model, scR1antTNF-Fc and 40-kDa PEG-scR1antTNF (a previously reported PEGylated form) delayed the onset of collagen-induced arthritis, suppressed arthritis progression in mice, and required a reduced frequency of administration. Interestingly, with these biologic treatments, we observed an increased ratio of regulatory T cells to conventional T cells in lymph nodes compared with etanercept, a commonly used TNF inhibitor. Therefore, scR1antTNF-Fc and 40-kDa PEG-scR1antTNF indirectly induced immunosuppression. These results suggest that selective TNFR1 inhibition benefits the management of autoimmune diseases and that R1antTNF derivatives hold promise as new-modality TNF-regulating biologics.