Alon Y. Hershko

CD300f associates with IL-4 receptor α and amplifies IL-4–induced immune cell responses

Significance IL-4 receptor (R) α is a critical component in IL-4– and IL-13–mediated signaling and subsequent effector functions such as those observed in allergy. Thus, it is a primary therapeutic target in diseases such as atopic dermatitis and asthma. Despite extensive studies, it is unknown whether an additional receptor system exists that may act to amplify IL-4Rα signaling and subsequent IL-4/IL-13–induced responses. We now report that CD300f is physically associated with IL-4Rα and potently amplifies IL-4Rα–induced responses in vitro and in vivo. Our results establish CD300f as a previously unidentified IL-4Rα coreceptor. To the best of our knowledge, this is the first report of an additional receptor that serves to amplify the IL-4 signaling pathway. IL-4 receptor (R) α, the common receptor chain for IL-4 and IL-13, is a critical component in IL-4– and IL-13–mediated signaling and subsequent effector functions such as those observed in type 2 inflammatory responses. Nonetheless, the existence of intrinsic pathways capable of amplifying IL-4Rα–induced responses remains unknown. In this study, we identified the myeloid-associated Ig receptor CD300f as an IL-4–induced molecule in macrophages. Subsequent analyses demonstrated that CD300f was colocalized and physically associated with IL-4Rα. Using Cd300f−/− cells and receptor cross-linking experiments, we established that CD300f amplified IL-4Rα–induced responses by augmenting IL-4/IL-13–induced signaling, mediator release, and priming. Consistently, IL-4– and aeroallergen-treated Cd300f−/− mice displayed decreased IgE production, chemokine expression, and inflammatory cell recruitment. Impaired responses in Cd300f−/− mice were not due to the inability to generate a proper Th2 response, because IL-4/IL-13 levels were markedly increased in allergen-challenged Cd300f−/− mice, a finding that is consistent with decreased cytokine consumption. Finally, CD300f expression was increased in monocytes and eosinophils obtained from allergic rhinitis patients. Collectively, our data highlight a previously unidentified role for CD300f in IL-4Rα–induced immune cell responses. These data provide new insights into the molecular mechanisms governing IL-4Rα–induced responses, and may provide new therapeutic tools to target IL-4 in allergy and asthma.

T Cell-Mediated Modulation of Mast Cell Function: Heterotypic Adhesion-Induced Stimulatory or Inhibitory Effects

Close physical proximity between mast cells and T cells has been demonstrated in several T cell mediated inflammatory processes such as rheumatoid arthritis and sarcoidosis. However, the way by which mast cells are activated in these T cell-mediated immune responses has not been fully elucidated. We have identified and characterized a novel mast cell activation pathway initiated by physical contact with activated T cells, and showed that this pathway is associated with degranulation and cytokine release. The signaling events associated with this pathway of mast cell activation have also been elucidated confirming the activation of the Ras mitogen-activated protein kinase systems. More recently, we hypothesized and demonstrated that mast cells may also be activated by microparticles released from activated T cells that are considered as miniature version of a cell. By extension, microparticles might affect the activity of mast cells, which are usually not in direct contact with T cells at the inflammatory site. Recent works have also focused on the effects of regulatory T cells (Treg) on mast cells. These reports highlighted the importance of the cytokines IL-2 and IL-9, produced by mast cells and T cells, respectively, in obtaining optimal immune suppression. Finally, physical contact, associated by OX40–OX40L engagement has been found to underlie the down-regulatory effects exerted by Treg on mast cell function.

Herpes simplex virus infection in a hyper-IgE patient: appearance of unusual mass lesions.

A 7-year-old girl presented with large soft masses rising from the nostril and from behind the ear. She had previously been diagnosed as suffering from hyper-IgE syndrome. The presence of herpes simplex virus infection within these lesions was confirmed by biopsy and immunohistochemical studies. The mass lesions did not respond to antibacterial therapy with cefazolin, but improved promptly under antiviral therapy with acyclovir. Immunological studies revealed a mild decrease in the CD4 cell population. Based on our results and on the relevant literature we propose an immunological mechanism for this unique manifestation of herpes simplex virus infection in hyper-IgE syndrome.

Mast cells as sources and targets of membrane vesicles.

In addition to being major effector cells in the elicitation of allergic responses, mast cells have been found to play a significant role in the establishment of innate and adaptive immune responses. This occurs, in part, by regulating the phenotype and function of immune cells such as T cells, B cells and dendritic cells, and by acting as antigen presenting cells. Indeed, mast cells have been found to be activated in various T cell-mediated inflammatory processes and to reside in close physical proximity to T cells. Such observations have led investigators to propose a functional relationship between these two cell populations. Mast cells can interact with other cells including T cells in several ways such as cell-cell interaction via membrane associated receptors, release of cytokines and chemokines or by heterotypic adhesion to activated T cells. In this review, we focus on a novel communication pathway between mast cells and other inflammatory cells that occurs by the release of or response to membrane vesicles. Membrane vesicles are circular fragments, released from the endosomal compartment as exosomes or shed from the cell plasma membrane as microparticles. Because their membrane orientation is the same as that of the donor cell, they can be considered to be miniature versions of a cell. Growing evidence indicates that microparticles play a pivotal role in cell to cell communication. The functional consequences of such membrane transfers include the induction, amplification and/or modulation of immune responses, as well as the acquisition of new functional properties by recipient cells.

Cyclosporin A impairs the secretion and activity of ADAMTS13 (a disintegrin and metalloprotease with thrombospondin type 1 repeat).

Background: Immunosuppressive drug cyclosporin A (CsA) is a potent inhibitor of cyclophilin B (CypB) function. Results: CsA treatment leading to reduction in CypB levels is associated with decreased secretion of ADAMTS13 (a disintegrin and metalloprotease with thrombospondin type 1 repeat). Conclusion: CypB function and levels affect the secretion of ADAMTS13. Significance: A novel mechanistic explanation for CsA-induced thrombotic thrombocytopenic purpura in transplant patients is suggested. The protease ADAMTS13 (a disintegrin and metalloprotease with thrombospondin type 1 repeat) cleaves multimers of von Willebrand factor, thus regulating platelet aggregation. ADAMTS13 deficiency leads to the fatal disorder thrombotic thrombocytopenic purpura (TTP). It has been observed that cyclosporin A (CsA) treatment, particularly in transplant patients, may sometimes be linked to the development of TTP. Until now, the reason for such a link was unclear. Here we provide evidence demonstrating that cyclophilin B (CypB) activity plays an important role in the secretion of active ADAMTS13. We found that CsA, an inhibitor of CypB, reduces the secretion of ADAMTS13 and leads to conformational changes in the protein resulting in diminished ADAMTS13 proteolytic activity. A direct, functional interaction between CypB (which possesses peptidyl-prolyl cis-trans isomerase (PPIase) and chaperone functions) and ADAMTS13 is demonstrated using immunoprecipitation and siRNA knockdown of CypB. Finally, CypB knock-out mice were found to have reduced ADAMTS13 levels. Taken together, our findings indicate that cyclophilin-mediated activity is an important factor affecting secretion and activity of ADAMTS13. The large number of proline residues in ADAMTS13 is consistent with the important role of cis-trans isomerization in the proper folding of this protein. These results altogether provide a novel mechanistic explanation for CsA-induced TTP in transplant patients.

IL‐33 and IgE stimulate mast cell production of IL‐2 and regulatory T cells expansion in allergic dermatitis

We have previously shown that mast cells (MCs) suppress chronic allergic dermatitis in mice. The underlying mechanism involves MC‐derived IL‐2, which supports regulatory T cell (Treg) response at the site of inflammation. However, it is not clear what are the factors that drive MCs to produce IL‐2.

MicroRNA-4443 regulates mast cell activation by T cell–derived microvesicles

Background: The mechanism by which mast cells (MCs) are activated in T cell–mediated inflammatory processes remains elusive. Recently, we have shown that microvesicles derived from activated T cells (mvT*s) can stimulate MCs to degranulate and release several cytokines. Objective: The aim of this study was to characterize the contribution of microRNAs (miRs) delivered by microvesicles to MC activation. Methods: miR profiling was performed with NanoString technology and validated by using real‐time PCR. The biological role of mvT* miR was verified by overexpression of miRs in MCs using mimic or inhibitory molecules and analyzing the effect on their predicted targets. Results: mvT*s were found to downregulate the expression of the tyrosine phosphatase protein tyrosine phosphatase receptor type J (PTPRJ), a known extracellular signal‐regulated kinase inhibitor. Bioinformatics analysis predicted that miR‐4443 regulates the PTPRJ gene expression. Indeed, miR‐4443, which was present in mvT*s, was also found to be overexpressed in human MCs stimulated with these MVs. &agr;‐Amanitin insensitivity confirmed that overexpression of miR‐4443 was not due to transcriptional activation. The luciferase reporter assay indicated that the 3′ untranslated region of PTPRJ was targeted by this miR. Transfection of MCs with mimic or inhibitor of miR‐4443 resulted in decreased or enhanced PTPRJ expression, respectively. Furthermore, miR‐4443 regulated extracellular signal‐regulated kinase phosphorylation and IL‐8 release in MCs activated by mvT*s. Conclusion: These results support a scenario by which T cell–derived microvesicles act as intercellular carriers of functional miR‐4443, which might exert heterotypic regulation of PTPRJ gene expression in MCs, leading to their activation in the context of T cell–mediated inflammatory processes.

The Involvement of Protein Kinase D in T Cell-Induced Mast Cell Activation

Background: It has recently been reported that mast cells (MC) can be activated to degranulate and release certain cytokines in response to direct physical contact with activated but not resting T cells or their membranes. The MAPK family members ERK and p38 were found to participate. In this work, we further characterize the signaling events involved in this novel pathway of activation. Methods: Human MC were stimulated by activated T cell membranes (T*m). Phosphorylation of kinases was assessed by Western blotting. Protein kinase D (PKD) translocation was visualized by confocal microscopy. Degranulation was assessed by β-hexosaminidase release and cytokine production by ELISA. Results: Stimulation of human MC by activated T*m resulted in the activation of PKD. PKD inhibition by the specific pharmacological inhibitor Gö6976 resulted in a reduction in the phosphorylation of p38 but not ERK. Gö6976 also inhibited degranulation and cytokine release. Conclusions: MC stimulation by physical contact with T cells results in PKD activation, leading to the phosphorylation of p38, degranulation and release of cytokines. Understanding the molecular events associated with T cell-induced MC activation might lead to therapeutic approaches for controlling T cell-mediated inflammatory processes in which MC participate.

Colchicine–clarithromycin-induced rhabdomyolysis in Familial Mediterranean Fever patients under treatment for Helicobacter pylori

Abstract Chronic administration of colchicine remains a mainstay of therapy for patients with Familial Mediterranean Fever (FMF). As this medication is a strong CYP3A4 inhibitor, it has the potential to interact with many routinely used medications. One such medication is clarithromycin, itself a strong inhibitor of the same enzyme, and a typical choice for triple therapy eradication of H. pylori. Various sequelae of colchicine–clarithromycin interaction have been documented and can be expected by prescribing physicians, with rhabdomyolysis, though rare, being among the most serious. Review of cases from a tertiary academic medical center and full PubMed/MEDLINE literature review. Despite the prevalence of diseases treated with clarithromycin and the expected drug interaction with colchicine, only two cases in the literature document clinical rhabdomyolysis due to colchicine–clarithromycin interaction. In neither case, however, were patients undergoing treatment for FMF. Herein, we describe the first two cases in the literature of clinical rhabdomyolysis in FMF patients under colchicine therapy after administration of clarithromycin as part of therapy treating H. pylori infection.

Impaired renal function is associated with adverse outcomes in patients with chest pain discharged from internal medicine wards

BACKGROUND Assessment of chest pain is one of the most common reasons for hospital admissions in internal medicine wards. However, little is known regarding predictors for poor prognosis in patients discharged from internal medicine wards after acute coronary syndrome (ACS) rule-out. OBJECTIVE To assess the association of kidney function with mortality and hospital admissions due to ACS in patients with chest pain who were discharged from internal medicine wards following ACS rule-out. METHODS Included were patients admitted to an internal medicine ward who were subsequently discharged following an ACSrule-out during 2010-2016. The primary endpoint was the composite of all-cause mortality and hospital admission due to ACS at 30-days following hospital discharge. RESULTS Included in the study were12,337 patients who were divided into 3 groups according to renal function. Considering patients with an eGFR ≥ 60 ml/min/1.73m2 as the reference group yielded adjusted hazard ratios for the composite of 30-day all-cause mortality and hospital admission for ACS that increased with reduced eGFR (HR = 2, 95%CI = 1.3-3.3, HR = 4.8, 95%CI = 3-7.6, for patients with eGFR of 45 to 59.9 or <45 ml/min/1.73m2, respectively, p < 0.001). Similarly, reduced renal function was associated with increased 1-year all-cause mortality (HR = 1.6, 95%CI = 1.2-2.2, HR = 4.5, 95%CI = 3.4-5.9, for patients with eGFR of 45-59.9 or <45 ml/min/1.73m2, respectively, p < 0.001). CONCLUSION We found an independent graded association between lower eGFR and the risk of death and ACS among patients with chest pain who were discharged from internal medicine wards following an ACS rule-out. The eGFR may be combined in the risk stratification of patients with chest pain.