Triggering the Resolution of Immune Mediated Inflammatory Diseases: Can Targeting Leukocyte Migration Be the Answer?

Targeting Pathways and Integrated Approaches to Treat Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a chronic symmetrical systemic disorder that not only affects joints but also other organs such as heart, lungs, kidney, and liver. Approximately there is 0.5%-1% of the total population affected by RA. RA pathogenesis still remains unclear due to which its appropriate treatment is a challenge. Further, multitudes of factors have been reported to affect its progression i.e. genetic factor, environmental factor, immune factor, and oxidative factor. Therapeutic approaches available for the treatment of RA include NSAIDs, DMARDs, enzymatic, hormonal, and gene therapies. But most of them provide the symptomatic relief without treating the core of the disease. This makes it obligatory to explore and reach the molecular targets for cure and long-term relief from RA. Herein, we attempt to provide extensive overlay of the new targets for RA treatment such as signaling pathways, proteins, and receptors affecting the progression of the disease and its severity. Precise modification in these targets such as suppressing the notch signaling pathway, SIRT 3 protein, Sphingosine-1-phosphate receptor and stimulating the neuronal signals particularly efferent vagus nerve and SIRT 1 protein may offer long term relief and potentially diminish the chronicity. To target or alter the novel molecules and signaling pathway a specific delivery system is required such as liposome, nanoparticles and micelles and many more. Present review paper discusses in detail about novel targets and delivery systems for treating RA.

Therapeutic Plasma Exchange and Multiple Sclerosis Dysregulations: Focus on the Removal of Pathogenic Circulatory Factors and Altering Nerve Growth Factor and Sphingosine-1-Phosphate Plasma Levels

Multiple sclerosis (MS) is predominantly an immune-mediated disease of the central nervous system (CNS) of unknown etiology with a possible genetic predisposition and effect of certain environmental factors. It is generally accepted that the disease begins with an autoimmune inflammatory reaction targeting oligodendrocytes followed by a rapid depletion of their regenerative capacity with subsequent permanent neurodegenerative changes and disability. Recent research highlights the central role of B lymphocytes and the corresponding IgG and IgM autoantibodies in newly forming MS lesions. Thus, their removal along with the modulation of certain bioactive molecules to improve neuroprotection using therapeutic plasma exchange (TPE) becomes of utmost importance. Recently, it has been proposed to determine the levels and precise effects of both beneficial and harmful components in the serum of MS patients undergoing TPE to serve as markers for appropriate TPE protocols. In this review we discuss some relevant examples, focusing on the removal of pathogenic circulating factors and altering the plasma levels of nerve growth factor and sphingosine-1-phosphate by TPE. Altered plasma levels of the reviewed molecular compounds in response to TPE reflect a successful reduction of the pro-inflammatory burden at the expense of an increase in anti-inflammatory potential in the circulatory and CNS compartments.

In vivo anti-inflammatory activities of Plantago major extract and fractions and analysis of their phytochemical components using a high-resolution mass spectrometry

Background and purpose

Plantago major has been applied as a herbal remedy for centuries. However, studies on anti-inflammatory activities and their chemical ingredients are limited. The objective of this study was to investigate the anti-inflammatory properties of P. major in three animal models and its phytochemical contents.

Experimental approach

Dichloromethane extract (DCM) of P. major was fractionated with n-hexane to yield the soluble (SHF) and insoluble (IHF) fractions. The anti-inflammatory activities of DCM, SHF, and IHF were evaluated using rat's paw edema induced by carrageenan, thioglycolate-induced leukocyte emigration in the mice, and rheumatoid arthritis (RA) induced by complete Freund's adjuvants in rats. The chemical constituents were analyzed using a high-resolution mass spectrometer (HRMS).

Findings / Results

The DCM, SHF, and IHF inhibited paw edema in the rats and reduced the leukocyte migration in the mice. At dose 560 mg/kg, the percentage of inhibitory was 47.33%, 55.51%, and 46.61% for the DCM, IHF, and SHF, respectively. In the RA animal model, IHF at 280 and 560 mg/kg reduced osteoclast formation and COX-2 expression compared to diclofenac. Some compounds namely oleic acid, linoleic acid, palmitic acid, and oleamide identified in the DCM, IHF, and SHF may be responsible for these activities.

Conclusion and implications

This study showed that P. major has several in-vivo anti-inflammatory activities.

T cell interaction with activated endothelial cells primes for tissue-residency

Tissue-resident memory T cells (TRM) are suspected drivers of chronic inflammation, but their induction remains unclear. Since endothelial cells (EC) are obligate interaction partners for T cells trafficking into inflamed tissues, they may play a role in TRM development. Here, we used an in vitro co-culture system of human cytokine-activated EC and FACS-sorted T cells to study the effect of EC on T(RM) cell differentiation. T cell phenotypes were assessed by flow cytometry, including proliferation measured by CellTrace Violet dilution assay. Soluble mediators were analyzed by multiplex immunoassay. Co-culture of T cells with cytokine-activated, but not resting EC induced CD69 expression without activation (CD25, Ki67) or proliferation. The dynamic of CD69 expression induced by EC was distinct from that induced by TCR triggering, with rapid induction and stable expression over 7 days. CD69 induction by activated EC was higher in memory than naive T cells, and most pronounced in CD8+ effector memory T cells. Early CD69 induction was mostly mediated by IL-15, whereas later effects were also mediated by interactions with ICAM-1 and/or VCAM-1. CD69+ T cells displayed a phenotype associated with tissue-residency, with increased CD49a, CD103, CXCR6, PD-1 and CD57 expression, and decreased CD62L and S1PR1. EC-induced CD69+ T cells were poised for high production of pro-inflammatory cytokines and showed increased expression of T-helper 1 transcription factor T-bet. Our findings demonstrate that activated EC can induce functional specialization in T cells with sustained CD69 expression, increased cytokine response and a phenotypic profile reminiscent of TRM. Interaction with activated EC during transmigration into (inflamed) tissues thus contributes to TRM-residency priming.

Tinker, tailor, soldier, cell: the role of C-type lectins in the defense and promotion of disease

C-type lectins (CTLs) represent a large family of soluble and membrane-bound proteins which bind calcium dependently via carbohydrate recognition domains (CRDs) to glycan residues presented on the surface of a variety of pathogens. The deconvolution of a cell's glycan code by CTLs underpins several important physiological processes in mammals such as pathogen neutralization and opsonization, leukocyte trafficking, and the inflammatory response. However, as our knowledge of CTLs has developed it has become apparent that the role of this innate immune family of proteins can be double-edged, where some pathogens have developed approaches to subvert and exploit CTL interactions to promote infection and sustain the pathological state. Equally, CTL interactions with host glycoproteins can contribute to inflammatory diseases such as arthritis and cancer whereby, in certain contexts, they exacerbate inflammation and drive malignant progression. This review discusses the 'dual agent' roles of some of the major mammalian CTLs in both resolving and promoting infection, inflammation and inflammatory disease and highlights opportunities and emerging approaches for their therapeutic modulation.

Endothelial Cell Adhesion Molecules- (un)Attainable Targets for Nanomedicines

Endothelial cell adhesion molecules have long been proposed as promising targets in many pathologies. Despite promising preclinical data, several efforts to develop small molecule inhibitors or monoclonal antibodies (mAbs) against cell adhesion molecules (CAMs) ended in clinical-stage failure. In parallel, many well-validated approaches for targeting CAMs with nanomedicine (NM) were reported over the years. A wide range of potential applications has been demonstrated in various preclinical studies, from drug delivery to the tumor vasculature, imaging of the inflamed endothelium, or blocking immune cells infiltration. However, no NM drug candidate emerged further into clinical development. In this review, we will summarize the most advanced examples of CAM-targeted NMs and juxtapose them with known traditional drugs against CAMs, in an attempt to identify important translational hurdles. Most importantly, we will summarize the proposed strategies to enhance endothelial CAM targeting by NMs, in an attempt to offer a catalog of tools for further development.

TNF Decoy Receptors Encoded by Poxviruses

Tumour necrosis factor (TNF) is an inflammatory cytokine produced in response to viral infections that promotes the recruitment and activation of leukocytes to sites of infection. This TNF-based host response is essential to limit virus spreading, thus poxviruses have evolutionarily adopted diverse molecular mechanisms to counteract TNF antiviral action. These include the expression of poxvirus-encoded soluble receptors or proteins able to bind and neutralize TNF and other members of the TNF ligand superfamily, acting as decoy receptors. This article reviews in detail the various TNF decoy receptors identified to date in the genomes from different poxvirus species, with a special focus on their impact on poxvirus pathogenesis and their potential use as therapeutic molecules.

A Novel Function of TLR2 and MyD88 in the Regulation of Leukocyte Cell Migration Behavior During Wounding in Zebrafish Larvae

Toll-like receptor (TLR) signaling via myeloid differentiation factor 88 protein (MyD88) has been indicated to be involved in the response to wounding. It remains unknown whether the putative role of MyD88 in wounding responses is due to a control of leukocyte cell migration. The aim of this study was to explore in vivo whether TLR2 and MyD88 are involved in modulating neutrophil and macrophage cell migration behavior upon zebrafish larval tail wounding. Live cell imaging of tail-wounded larvae was performed in tlr2 and myd88 mutants and their corresponding wild type siblings. In order to visualize cell migration following tissue damage, we constructed double transgenic lines with fluorescent markers for macrophages and neutrophils in all mutant and sibling zebrafish lines. Three days post fertilization (dpf), tail-wounded larvae were studied using confocal laser scanning microscopy (CLSM) to quantify the number of recruited cells at the wounding area. We found that in both tlr2^-/- and myd88^-/- groups the recruited neutrophil and macrophage numbers are decreased compared to their wild type sibling controls. Through analyses of neutrophil and macrophage migration patterns, we demonstrated that both tlr2 and myd88 control the migration direction of distant neutrophils upon wounding. Furthermore, in both the tlr2 and the myd88 mutants, macrophages migrated more slowly toward the wound edge. Taken together, our findings show that tlr2 and myd88 are involved in responses to tail wounding by regulating the behavior and speed of leukocyte migration in vivo.

Say no to drugs: Bioactive macromolecular therapeutics without conventional drugs

The vast majority of nanomedicines (NM) investigated today consists of a macromolecular carrier and a drug payload (conjugated or encapsulated), with a purpose of preferential delivery of the drug to the desired site of action, either through passive accumulation, or by active targeting via ligand-receptor interaction. Several drug delivery systems (DDS) have already been approved for clinical use. However, recent reports are corroborating the notion that NM do not necessarily need to include a drug payload, but can exert biological effects through specific binding/blocking of important target proteins at the site of action. The seminal work of Kopeček et al. on N-(2-hydroxypropyl)methacrylamide (HPMA) copolymers containing biorecognition motifs (peptides or oligonucleotides) for crosslinking cell surface non-internalizing receptors of malignant cells and inducing their apoptosis, without containing any low molecular weight drug, led to the definition of a special group of NM, termed Drug-Free Macromolecular Therapeutics (DFMT). Systems utilizing this approach are typically designed to employ pendant targeting-ligands on the same macromolecule to facilitate multivalent interactions with receptors. The lack of conventional small molecule drugs reduces toxicity and adverse effects at off-target sites. In this review, we describe different types of DFMT that possess biological activity without attached low molecular weight drugs. We classified the relevant research into several groups by their mechanisms of action, and compare the advantages and disadvantages of these different approaches. We show that identification of target sites, specificity of attached targeting ligands, binding affinity and the synthesis of carriers of defined size and ligand spacing are crucial aspects of DFMT development. We further discuss how knowledge in the field of NM accumulated in the past few decades can help in the design of a successful DFMT to speed up the translation into clinical practice.

Resolvin D1 protects against sepsis-induced cardiac injury in mice

Increased inflammation is the key mechanism that mediates sepsis induced cardiac injury. Resolvin D1 (RvD1), a bioactive lipid mediator synthesized from docosahexaenoic acid, can attenuate the severity of many inflammation-related diseases through anti-inflammatory and pro-resolving properties. However, the protective role of RvD1 in sepsis induced cardiac injury remains unclear. Mice were randomly divided into three groups: the control group, LPS group and RvD1 + LPS group. LPS (10 mg/kg, i.p.) was used to establish a sepsis-induced cardiac injury model. RvD1 (5 ug/kg, i.p.) was injected 30 min before LPS injection. RvD1 treatment significantly attenuated the deteriorated cardiac function and cardiac injury induced by LPS, as evidenced by the improved left ventricular ejection fraction, serum levels of cardiac injury markers and severity of cardiomyocyte apoptosis. In addition, RvD1 treatment significantly attenuated the infiltration of pro-inflammatory M1 macrophages and expression of inflammatory cytokines in the heart. Mechanistically, the attenuated activation of NK-κB and MAPK signaling mediated the anti-inflammatory and antiapoptotic effects of RvD1. In addition, LPS-induced infiltration of neutrophils and M1 macrophages in the spleen was significantly attenuated by the RvD1 treatment. Results of the present study suggest that RvD1 protects the heart against LPS-induced injuries by attenuating the local and systemic inflammatory response, highlighting the therapeutic effects of RvD1 in sepsis-induced cardiac injury.

Rapid exposure of macrophages to drugs resolves four classes of effects on the leading edge sensory pseudopod: Non-perturbing, adaptive, disruptive, and activating

Leukocyte migration is controlled by a membrane-based chemosensory pathway on the leading edge pseudopod that guides cell movement up attractant gradients during the innate immune and inflammatory responses. This study employed single cell and population imaging to investigate drug-induced perturbations of leading edge pseudopod morphology in cultured, polarized RAW macrophages. The drugs tested included representative therapeutics (acetylsalicylic acid, diclofenac, ibuprofen, acetaminophen) as well as control drugs (PDGF, Gö6976, wortmannin). Notably, slow addition of any of the four therapeutics to cultured macrophages, mimicking the slowly increasing plasma concentration reported for standard oral dosage in patients, yielded no detectable change in pseudopod morphology. This finding is consistent with the well established clinical safety of these drugs. However, rapid drug addition to cultured macrophages revealed four distinct classes of effects on the leading edge pseudopod: (i) non-perturbing drug exposures yielded no detectable change in pseudopod morphology (acetylsalicylic acid, diclofenac); (ii) adaptive exposures yielded temporary collapse of the extended pseudopod and its signature PI(3,4,5)P3 lipid signal followed by slow recovery of extended pseudopod morphology (ibuprofen, acetaminophen); (iii) disruptive exposures yielded long-term pseudopod collapse (Gö6976, wortmannin); and (iv) activating exposures yielded pseudopod expansion (PDGF). The novel observation of adaptive exposures leads us to hypothesize that rapid addition of an adaptive drug overwhelms an intrinsic or extrinsic adaptation system yielding temporary collapse followed by adaptive recovery, while slow addition enables gradual adaptation to counteract the drug perturbation in real time. Overall, the results illustrate an approach that may help identify therapeutic drugs that temporarily inhibit the leading edge pseudopod during extreme inflammation events, and toxic drugs that yield long term inhibition of the pseudopod with negative consequences for innate immunity. Future studies are needed to elucidate the mechanisms of drug-induced pseudopod collapse, as well as the mechanisms of adaptation and recovery following some inhibitory drug exposures.

Addition of a Viral Immunomodulatory Domain to Etanercept Generates a Bifunctional Chemokine and TNF Inhibitor

The inhibition of tumor necrosis factor (TNF) through the use of either antibodies or soluble receptors is a highly effective strategy for the clinical control of chronic inflammatory conditions such as rheumatoid arthritis. Different viruses have similarly exploited this concept by expressing a set of specifically tailored secreted TNF decoy receptors to block host inflammatory responses. Poxviruses have been shown to encode at least two distinct molecules, termed Cytokine response modifier D (CrmD) and CrmB, in which a TNF inhibitor is combined with a chemokine inhibitor on the same molecule. The ectromelia virus CrmD protein was found to be a critical determinant of virulence in vivo, being able to control local inflammation to allow further viral spread and the establishment of a lethal infection. Strikingly, both the TNF and the chemokine inhibitory domains are required for the full activity of CrmD, suggesting a model in which inhibition of TNF is supported by the concomitant blockade of a reduced set of chemokines. Inspired by this model, we reasoned that a similar strategy could be applied to modify the clinically used human TNF receptor (etanercept), producing a generation of novel, more effective therapeutic agents. Here we show the analysis of a set of fusion proteins derived from etanercept by addition of a viral chemokine-binding protein. A bifunctional inhibitor capable of binding to and blocking the activity of TNF as well as a set of chemokines is generated that is active in the prevention of arthritis in a murine disease model.