MHC class II-associated variation in the production of tumor necrosis factor in mice and humans: relevance to the pathogenesis of autoimmune diseases

Improved monovalent TNF receptor 1-selective inhibitor with novel heterodimerizing Fc

The development of alternative therapeutic strategies to tumor necrosis factor (TNF)-blocking antibodies for the treatment of inflammatory diseases has generated increasing interest. In particular, selective inhibition of TNF receptor 1 (TNFR1) promises a more precise intervention, tackling only the pro-inflammatory responses mediated by TNF while leaving regenerative and pro-survival signals transduced by TNFR2 untouched. We recently generated a monovalent anti-TNFR1 antibody fragment (Fab 13.7) as an efficient inhibitor of TNFR1. To improve the pharmacokinetic properties of Fab 13.7, the variable domains of the heavy and light chains were fused to the N-termini of newly generated heterodimerizing Fc chains. This novel Fc heterodimerization technology, designated "Fc-one/kappa" (Fc1κ) is based on interspersed constant Ig domains substituting the CH3 domains of a γ1 Fc. The interspersed immunoglobulin (Ig) domains originate from the per se heterodimerizing constant CH1 and CLκ domains and contain sequence stretches of an IgG1 CH3 domain, destined to enable interaction with the neonatal Fc receptor, and thus promote extended serum half-life. The resulting monovalent Fv-Fc1κ fusion protein (Atrosimab) retained strong binding to TNFR1 as determined by enzyme-linked immunosorbent assay and quartz crystal microbalance, and potently inhibited TNF-induced activation of TNFR1. Atrosimab lacks agonistic activity for TNFR1 on its own and in the presence of anti-human IgG antibodies and displays clearly improved pharmacokinetic properties.

Evaluation of the pro-inflammatory cytokine tumor necrosis factor-α in adolescents with polycystic ovary syndrome

BACKGROUND

Patients with polycystic ovary syndrome (PCOS) often suffer from comorbidities associated with chronic inflammation characterized by elevations in pro-inflammatory cytokines. There is limited data on markers of chronic inflammation, in particular Tumor Necrosis Factor-alpha (TNF-α), in adolescents with PCOS.

OBJECTIVES

To compare serum levels of TNF-α in overweight or obese adolescents with PCOS and obese controls. In the PCOS group, to correlate serum TNF-α levels with body mass index (BMI) z-score, severity of hyperandrogenism, degree of insulin resistance, and ovarian ultrasonographic characteristics.

METHODS

We performed a cross-sectional retrospective analysis of clinical and biochemical findings in 23 overweight or obese adolescent females with PCOS (mean BMI z-score 2, mean age 15.2 yrs) and 12 obese age- and sex-matched controls (mean BMI z-score 2, mean age 14.1 y). All subjects were post-menarchal. Serum TNF-α levels were compared between groups. In the PCOS group, cytokine levels were correlated with BMI z-score, androgen levels, fasting insulin and glucose levels as well as ovarian ultrasonographic features.

RESULTS

Both groups were comparable in age, BMI z-score, fasting glucose, and fasting insulin. Mean free testosterone was 9.76 ± 5.13 pg/mL in the PCOS group versus 5 ± 2.02 pg/mL in the control group (P = .0092). Serum TNF-α was 7.4 ± 4 pg/mL in the PCOS group versus 4.8 ± 3.16 pg/mL in the control group (P = .0468). There was no significant correlation between serum TNF-α and BMI z-score, free testosterone, fasting insulin, or fasting glucose. No correlation existed between serum TNF-α and ovarian follicle number, distribution, or volume.

CONCLUSIONS

Serum TNF-α is elevated in overweight/obese adolescents with PCOS. Chronic inflammation in adolescents with PCOS render them at a potential increased risk for the development of atherosclerosis, type 2 diabetes, cancer, infertility, and other comorbidities. Every effort should be made to identify adolescents with PCOS early and initiate aggressive therapy to prevent future complications.

Immunoregulatory role of TNFalpha in inflammatory kidney diseases

Tumor necrosis factor alpha (TNFalpha), a pleiotropic cytokine, plays important inflammatory roles in renal diseases such as lupus nephritis, anti-neutrophil cytoplasmic antibody (ANCA)-associated glomerulonephritis and renal allograft rejection. However, TNFalpha also plays critical immunoregulatory roles that are required to maintain immune homeostasis. These complex biological functions of TNFalpha are orchestrated by its two receptors, TNFR1 and TNFR2. For example, TNFR2 promotes leukocyte infiltration and tissue injury in an animal model of immune complex-mediated glomerulonephritis. On the other hand, TNFR1 plays an immunoregulatory function in a murine lupus model with a deficiency in this receptor that leads to more severe autoimmune symptoms. In humans, proinflammatory and immunoregulatory roles for TNFalpha are strikingly illustrated in patients on anti-TNFalpha medications: These treatments are greatly beneficial in certain inflammatory diseases such as rheumatoid arthritis but, on the other hand, are also associated with the induction of autoimmune lupus-like syndromes and enhanced autoimmunity in multiple sclerosis patients. The indication for anti-TNFalpha treatments in renal inflammatory diseases is still under discussion. Ongoing clinical trials may help to clarify the potential benefit of such treatments in lupus nephritis and ANCA-associated glomerulonephritis. Overall, the complex biology of TNFalpha is not fully understood. A greater understanding of the function of its receptors may provide a framework to understand its contrasting proinflammatory and immunoregulatory functions. This may lead the development of new, more specific anti-inflammatory drugs.

Short communication: impairment of membrane markers on peripheral blood mononuclear cells and imbalance of cytokine secretion in the pathogenesis of multiple sclerosis active phases

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS). In active disease, a transmigration of autoreactive T cells to myelin antigens recruited from the peripheral blood (PBMC) to the CNS occurs, and there these cells prolong their survival and contribute to the perpetuation of the inflammation. In the active local lesions of MS patients, these cells display activation and apoptosis surface markers and secrete a range of cytokines. The aim of this research is to study on PBMCs and in the serum of stable and active MS subjects (1) the behavior of the CD40/CD40L system and the consequent balance of Th1 and Th2 cytokines and (2) the apoptosis marker system CD95/CD95L and tumor necrosis factor (TNF)- binding receptors, TNFRI and TNFRII. A possible excess of activation marker expression affecting and driving Th1 cytokine production or a parallel impairment of apoptosis may contribute to MS relapses. Our results may indicate that a dysregulation of early activation and apoptosis receptor systems and a profound and complex imbalance of cytokine production occurred in the peripheral blood of MS patients. This impairment could account for active phases of the disease.

The death domain kinase RIP protects thymocytes from tumor necrosis factor receptor type 2-induced cell death

Fas and the tumor necrosis factor receptor (TNFR)1 regulate the programmed cell death of lymphocytes. The death domain kinase, receptor interacting protein (rip), is recruited to the TNFR1 upon receptor activation. In vitro, rip-/- fibroblasts are sensitive to TNF-induced cell death due to an impaired nuclear factor kappaB response. Because rip-/- mice die at birth, we were unable to examine the effects of a targeted rip mutation on lymphocyte survival. To address the contribution of RIP to immune homeostasis, we examined lethally irradiated mice reconstituted with rip-/- hematopoietic precursors. We observed a decrease in rip-/- thymocytes and T cells in both wild-type C57BL/6 and recombination activating gene 1-/- irradiated hosts. In contrast, the B cell and myeloid lineages are unaffected by the absence of rip. Thus, the death domain kinase rip is required for T cell development. Unlike Fas-associated death domain, rip does not regulate T cell proliferation, as rip-/- T cells respond to polyclonal activators. However, rip-deficient mice contain few viable CD4+ and CD8+ thymocytes, and rip-/- thymocytes are sensitive to TNF-induced cell death. Surprisingly, the rip-associated thymocyte apoptosis was not rescued by the absence of TNFR1, but appears to be rescued by an absence of TNFR2. Taken together, this study implicates RIP and TNFR2 in thymocyte survival.

Lessons from the NZM2410 model and related strains

SLE susceptibility requires the interplay of an unknown number of genes and equally unidentified triggering events. The past few years have seen significant advances in our understanding of SLE susceptibility through the genetic analysis of murine models. The NZM2410 strain, which is derived from the NZB/WF1 model has played a significant role in these advances. The main advantages presented by this strain over other models are the genetic homozygozity at all loci and an highly penetrant early onset lupus nephritis in both males and females, indicating that the strongest BWF1 susceptibility loci were retained in NZM2410. After identification of NZM2410 susceptibility loci via linkage analyses, congenic strains have been derived in order to convert a polygenic system into a series of monogenic traits. These congenic strains have been analyzed in an integrated process which has provided simultaneously 1) novel functional characterization of the Sle susceptibility loci, 2) high resolution genetic maps that will lead to the identification of the corresponding susceptibility genes by either candidate locus or positional cloning, and 3) insights into the mechanisms by which these loci interact to produce systemic autoimmunity with fatal end-organ damage.

Involvement of nuclear factor-kappaB in a murine model for the acute form of autoimmune-like toxic oil syndrome

The toxic oil syndrome (TOS) represents an exogenously induced autoimmune disease with acute or chronic symptoms similar to systemic lupus erythematosus or scleroderma. When genetically different mouse strains were exposed to oleic acid anilide (OAA), it was possible to mimic the different syndrome manifestations. The aim of the present study was to examine the role of NF-kappaB/Rel transcription factors in the development of the severe acute wasting disease observed in A/J mice. Within a week of OAA exposure, the A/J, but not B10.S strain, displayed weight loss, cachexia, apathy, reduced activity, and breathing difficulties. In affected A/J mice we observed a marked increase in NF-kappaB activation (p50/p65 dimers) both in splenic T cells and peritoneal macrophages as well as in tissue from aorta and gut. Incubation of splenocytes with OAA in vitro induced a dose-dependent removal of IkappaB-alpha, accompanied by NF-kappaB activation, whereas Sp-1 binding was not affected. Furthermore, we demonstrated the increased expression of the two NF-kappaB target genes IL-6 and IL-1beta in OAA-exposed mice and a transient OAA-induced accumulation of TNFalpha in vitro. This is the first report which implicates NF-kappaB/Rel in acute forms of chemically induced autoimmune-like disease and may serve as a paradigm for the involvement of this transcriptional system in acute processes associated with autoimmunity, suggesting possible avenues of therapeutic intervention.

The TNF-ligand and receptor superfamilies: controllers of immunity and the Trojan horses of autoimmune disease?

This review is concerned with the tumour necrosis factor receptor and ligand superfamilies, with particular reference to their roles in the immunopathogenesis of Systemic Lupus Erythematosus (SLE). The tumour necrosis factor receptor and ligand superfamilies are well characterized as the molecular controllers of the immune system, acting as 'judges', 'juries', and, where necessary, 'executioners' to determine the fate of immune cells during development, proliferation and differentiation. However, these molecules exert extreme immunopathological effects when unregulated, or dysfunctional. The importance of these molecules in the pathogenesis of autoimmunity is now apparent, and has been considered in detail. Finally, specific consideration has been given to their clinical significance and potential diagnostic and therapeutic applications.

Regulation of human monocyte functions by acute ethanol treatment: decreased tumor necrosis factor-alpha, interleukin-1 beta and elevated interleukin-10, and transforming growth factor-beta production

We and others have previously shown that even acute ethanol exposure has the capacity to modulate immune functions, particularly monocyte functions. Herein, we tested the hypothesis that acute ethanol treatment inhibits inflammatory, while increasing inhibitory cytokine production in human blood monocytes that, in turn, could contribute to the overall immune abnormalities seen after alcohol use. Our data show that in vitro treatment of blood monocytes with a physiologically relevant dose of alcohol (25 mM) results in significantly decreased induction of tumor necrosis factor-alpha (TNF alpha) and interleukin (IL)-1 beta by bacterial stimulation of either Gram-positive [staphylococcal enterotoxin B (SEB), 1 microgram/ml of SEB] or Gram-negative [lipopolysaccharide (LPS), 1 microgram/ml of LPS] origin both at the protein and mRNA levels. In contrast, acute ethanol treatment induces monocyte production of mediators with immunoinhibitory potential, including transforming growth factor-beta and IL-10. We further show that ethanol not only induces monocyte/macrophage (Mø) IL-10 and transforming growth factor-beta, but even augments bacterial (both LPS and SEB) stimulation-induced production of both of these cytokines. IL-10 is a potent inhibitor of Mø TNF alpha production. We found that ethanol-induced elevation in Mø IL-10 levels contributes to the decreased Mø TNF alpha production to bacterial challenge in ethanol-exposed Mø. However, mRNA levels for TNF alpha are downregulated as early as 1.5 hr after ethanol treatment, suggesting that ethanol likely has an IL-10 independent, direct effect on early signaling events of TNF alpha induction.

Cytokines, inflammation, and autoimmune diseases

The understanding of cytokines is in its infancy, but it appears that overproduction or deficiency of these intracellular mediators may contribute to inflammatory and autoimmune diseases such as insulin-dependent diabetes mellitus and rheumatoid arthritis. As the complexities of cytokine actions and interactions are unraveled, therapeutic blockade or upregulation may be possible.

Acute ethanol consumption synergizes with trauma to increase monocyte tumor necrosis factor alpha production late postinjury

The hypothesis that acute ethanol uptake plus trauma can synergize to increase immunosuppression was tested. We found that, unlike non-alcohol-exposed patients, patients with acute alcohol use prior to trauma have a transient decrease in monocyte tumor necrosis factor alpha (TNF alpha) production during the very early postinjury (0-3 days) period. However, TNF alpha production by these alcohol-exposed patients' monocytes (M0) became hyperelevated late postinjury (> 9 days). Consequently, these massively elevated M0 TNF alpha levels can contribute to posttrauma immunosuppression after acute alcohol use. We also demonstrate that normal monocyte activation with the superantigen, Staphylococcus enterotoxin B (SEB), results in a preferential induction of cell-associated M0 TNF alpha production, described as characteristic of immunosuppressed trauma patients. Acute in vitro ethanol treatment down-regulated the elevated TNF alpha production by trauma patients' M0 after either SEB, muramyl-dipeptide (MDP), interferon-gamma plus MDP, or lipopolysaccharide (LPS) stimulation. Both SEB- and LPS-induced TNF alpha mRNA induction was inhibited by acute alcohol treatment in normal M0, indicating that ethanol can regulate cytokine gene expression. An additional immunosuppressive effect of acute ethanol's stimulation was suggested by its induction of elevated transforming growth factor beta production in trauma patients' activated M0.

Studies on the role of tumor necrosis factor in murine and human autoimmunity

We have analyzed the roles of tumor necrosis factor alpha (TNF-alpha) in human systemic lupus erythematosus (SLE) and murine models of lupus as well as in type 1 diabetes in NOD mice. These studies suggest an important role for TNF-alpha in the pathogenesis of autoimmune disease. Rather than being involved mainly in the effector arm of the inflammatory process of autoimmune organ destruction, our data suggest a primary involvement in some of the basic mechanisms of the autoimmune process. Evidence has been presented that emphasizes the possibility of the involvement of this cytokine in the genetic predisposition to SLE. The data may imply that the effect of TNF on the immune system may be more relevant to the pathogenesis of the autoimmune disease than direct local effects at some target organs. Based on the data presented, one should be cautious in extrapolating the effects of this cytokine in various in vitro systems to the in vivo situation.