Macrophage migration inhibitory factor is necessary for the Lipo-oligosaccharide-induced response by modulation of Toll-like receptor 4 in monocytes from GBS patients

Role of Toll-Like Receptors in Neuroimmune Diseases: Therapeutic Targets and Problems

Toll-like receptors (TLRs) are a class of proteins playing a key role in innate and adaptive immune responses. TLRs are involved in the development and progression of neuroimmune diseases via initiating inflammatory responses. Thus, targeting TLRs signaling pathway may be considered as a potential therapy for neuroimmune diseases. However, the role of TLRs is elusive and complex in neuroimmune diseases. In addition to the inadequate immune response of TLRs inhibitors in the experiments, the recent studies also demonstrated that partial activation of TLRs is conducive to the production of anti-inflammatory factors and nervous system repair. Exploring the mechanism of TLRs in neuroimmune diseases and combining with developing the emerging drug may conquer neuroimmune diseases in the future. Herein, we provide an overview of the role of TLRs in several neuroimmune diseases, including multiple sclerosis, neuromyelitis optica spectrum disorder, Guillain-Barré syndrome and myasthenia gravis. Emerging difficulties and potential solutions in clinical application of TLRs inhibitors will also be discussed.

Novel Immunological and Therapeutic Insights in Guillain-Barré Syndrome and CIDP

Inflammatory neuropathies are a heterogeneous group of rare diseases of the peripheral nervous system that include acute and chronic diseases, such as Guillain-Barré syndrome (GBS) and chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). The etiology and pathophysiological mechanisms of inflammatory neuropathies are only partly known, but are considered autoimmune disorders in which an aberrant immune response, including cellular and humoral components, is directed towards components of the peripheral nerve causing demyelination and axonal damage. Therapy of these disorders includes broad-spectrum immunomodulatory and immunosuppressive treatments, such as intravenous immunoglobulin, corticosteroids, or plasma exchange. However, a significant proportion of patients do not respond to any of these therapies, and treatment selection is not optimized according to disease pathophysiology. Therefore, research on disease pathophysiology aiming to reveal clinically and functionally relevant disease mechanisms and the development of new treatment approaches are needed to optimize disease outcomes in CIDP and GBS. This topical review describes immunological progress that may help guide therapeutic strategies in the future in these two disorders.

Inhibition of TLR4 signaling protects mice from sensory and motor dysfunction in an animal model of autoimmune peripheral neuropathy

BACKGROUND

While the etiology remains elusive, macrophages and T cells in peripheral nerves are considered as effector cells mediating autoimmune peripheral neuropathy (APN), such as Guillain-Barre syndrome. By recognizing both pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs) signals, TLRs play a central role in the initiation of both innate and adaptive immune responses. In this study, we aimed to understand the involvement of TLR4 in the pathogenesis of APN and explore the potential of TLR4 as a drug target for therapeutic use.

METHODS

APN was induced by a partial ligation on one of the sciatic nerves in B7.2 (L31) transgenic mice which possess a predisposed inflammatory background. APN pathology and neurological function were evaluated on the other non-injured sciatic nerve.

RESULTS

TLR4 and its endogenous ligand HMGB1 were highly expressed in L31 mice, in circulating immune cells and in peripheral nerves. Enhanced TLR4 signaling was blocked with TAK 242, a selective TLR4 inhibitor, before and after disease onset. Intraperitoneal administration of TAK 242 not only inhibited monocyte, macrophage and CD8⁺ T cell activation, but also reduced the release of pro-inflammatory cytokines. TAK 242 protected mice from severe myelin and axonal loss, resulting in a remarkable improvement in mouse motor and sensory functions. TAK 242 was effective in alleviating the disease in both preventive and reversal paradigms.

CONCLUSION

The study identified the critical contribution of TLR4-mediated macrophage activation in disease course and provided strong evidence to support TLR4 as a useful drug target for treating inflammatory autoimmune neuropathy.

Macrophage migration inhibitory factor modulates cytokine expression in the trophoblast cell line HTR-8/SVneo

Extravillous trophoblasts are specific placental cells that invade the uterine stroma and spiral arteries modifying and adjusting them to pregnancy. Many pregnancy pathologies are associated with impairment of this process, including preeclampsia and intrauterine growth restriction, among others. Macrophage migration inhibitory factor (MIF) is a pleiotropic cytokine that is abundant at the fetomaternal interface. Previous results from our group showed that MIF participates in trophoblast invasion and modulates the expression of molecules known to mediate stromal and endovascular trophoblast invasion. In this study we investigated the possibility that MIF could act as a regulator of cytokines known to modulate trophoblast invasion using the normal extravillous trophoblast-derived cell line HTR-8/SVneo. Expression of trophoblast MIF was attenuated by MIF mRNA-specific small interfering RNAs. Cytokine expression was assessed at the mRNA and protein levels using real-time quantitative polymerase chain reaction and flow cytometry respectively. Knockdown of MIF led to a significant decrease in mRNA for IL-1β (IL1B) and IL-8 (CXCL8) and interleukin (IL)-8 protein. The addition of recombinant human MIF to cell culture medium increased IL-6 after 24h treatment and IL-6 and IL-8 after 72h treatment. Cell viability was not affected by MIF silencing or rhMIF treatment. The results of this study imply that at least some of the effects of MIF on trophoblast invasion could be mediated through autocrine or paracrine modulation of trophoblast cytokine production.

Role of MIF and D-DT in immune-inflammatory, autoimmune, and chronic respiratory diseases: from pathogenic factors to therapeutic targets

Macrophage migration inhibitory factor (MIF) is a protein that acts as a cytokine-, enzyme-, endocrine- and chaperon-like molecule. It binds to the cell-surface receptor CD74 in association with CD44, which activates the downstream signal transduction pathway. In addition, MIF acts also as a noncognate ligand for C-X-C chemokine receptor type 2 (CXCR2), type 4 (CXCR4), and type 7 (CXCR7). Recently, D-dopachrome tautomerase (D-DT), a second member of the MIF superfamily, was identified. From a pharmacological and clinical point of view, the nonredundant biological properties of MIF and D-DT anticipate potential synergisms from their simultaneous inhibition. Here, we focus on the role of MIF and D-DT in human immune-inflammatory, autoimmune, and chronic respiratory diseases, providing an update on the progress made in the identification of specific small-molecule inhibitors of these proteins.

Monocyte Response to Different Campylobacter jejuni Lysates Involves Endoplasmic Reticulum Stress and the Lysosomal⁻Mitochondrial Axis: When Cell Death Is Better Than Cell Survival

Campylobacter jejuni is a Gram-negative spiral-shaped bacterium, commonly associated with gastroenteritis in humans. It explicates its virulence also by the cytolethal distending toxin (CDT), able to cause irreversible cell cycle arrest. Infection by C. jejuni may result in the development of the Guillain⁻Barré Syndrome, an acute peripheral neuropathy. Symptoms of this disease could be caused by CDT-induced cell death and a subsequent inflammatory response. We tested C. jejuni lysates from different strains on donor monocytes: in fact, monocytes are potent producers of both pro- and anti-inflammatory cytokines, playing a major role in innate immunity and in non-specific host responses. We found, by cytometric and confocal analyses, that mitochondria and lysosomes were differently targeted: The C. jejuni strain that induced the most relevant mitochondrial alterations was the ATCC 33291, confirming an intrinsic apoptotic pathway, whereas the C. jejuni ISS 1 wild-type strain mostly induced lysosomal alterations. Lysates from all strains induced endoplasmic reticulum (ER) stress in monocytes, suggesting that ER stress was not associated with CDT but to other C. jejuni virulence factors. The ER data were consistent with an increase in cytosolic Ca2+ content induced by the lysates. On the contrary, the changes in lysosomal acidic compartments and p53 expression (occurring together from time 0, T0, to 24 h) were mainly due to CDT. The loss of p53 may prevent or impede cell death and it was not observable with the mutant strain. CDT not only was responsible for specific death effects but also seemed to promote an apoptotic stimuli-resisting pathway.

Roles of macrophage migration inhibitory factor in Guillain-Barré syndrome and experimental autoimmune neuritis: beneficial or harmful?

INTRODUCTION

Macrophage migration inhibitory factor (MIF) plays an important role in the pathogenesis of Guillain-Barré syndrome (GBS) and its animal model experimental autoimmune neuritis (EAN), which may offer an opportunity for the development of the novel therapeutic strategies for GBS. Areas covered: 'macrophage migration inhibitory factor' and 'Guillain-Barré syndrome' were used as keywords to search for related publications on Pub-Med, National Center for Biotechnology Information (NCBI), USA. MIF is involved in the etiology of various inflammatory and autoimmune disorders. However, the roles of MIF in GBS and EAN have not been summarized in the publications we identified. Therefore, in this review, we described and analyzed the major roles of MIF in GBS/EAN. Primarily, this molecule aggravates the inflammatory responses in this disorder. However, multiple studies indicated a protective role of MIF in GBS. The potential of MIF as a therapeutic target in GBS has been recently demonstrated in experimental and clinical studies, although clinical trials have been unavailable to date. Expert opinion: MIF plays a critical role in the initiation and progression of GBS and EAN, and it may represent a potential therapeutic target for GBS.