Kim K. Creus

Role of cytokines and chemokines in idiopathic inflammatory myopathies.

Purpose of reviewCytokines and chemokines are essential players in the initiation and progression of the idiopathic inflammatory myopathies (IIMs). This review focuses on the most recent data and the new insight they provide for the disease mechanisms of dermatomyositis, polymyositis and sporadic inclusion body myositis. Recent findingsInterferon-α and β are implicated in the innate immune responses underlying dermatomyositis, whereas interferon-γ stands forward as a more general regulator of the IIMs, reflected by the induction of many interferon-γ-inducible genes in patients. Interleukin-1β and interleukin-18 are localized to the inflammatory cells present in IIM muscle, where they may focally induce further recruitment of immune cells. Lymphotoxins are implicated in the cytotoxic activities toward polymyositis and inclusion body myositis muscle fibers, and in the organization and antibody production by B-cells in dermatomyositis. The α-chemokines CXCL9, CXCL10 and the β-chemokines CCL2, CCL3, CCL4, CCL19 and CCL21 are expressed in IIM muscle. The B-cell activator CXCL13 is particularly prominent in the larger perimysial infiltrates of dermatomyositis. SummaryThe cytokine–chemokine patterns described in recent studies provide further evidence for predominance of Th1-mediated reactions in the different IIMs, inflammation-induced degenerative phenomena in inclusion body myositis, and a possible role for lymphoneogenesis in the sustained inflammatory response in dermatomyositis.

Chemokine profile of different inflammatory myopathies reflects humoral versus cytotoxic immune responses

Abstract:  The idiopathic inflammatory myopathies (IM) are subdivided into dermatomyositis (DM), polymyositis (PM), and sporadic inclusion body myositis (IBM). These autoimmune muscle diseases represent different immunopathological entities. DM is a humoral endotheliopathy initiated by complement deposition in intramuscular blood vessels, and characterized by perimysial inflammation and muscle fiber atrophy in perifascicular regions. In PM and IBM, nonnecrotic muscle fibers are actively invaded by autoaggressive macrophages and cytotoxic T cells. Chemokines are key mediators of inflammatory disease as they regulate leukocyte recruitment to tissue target sites. We studied a large selection of α/β‐chemokines and receptors in normal controls and in the IM using immunohistochemistry, immunofluorescence, in situ hybridization, and Western blotting. We showed that the chemokine array of normal myocytes was limited, while the blood vessels in normal skeletal muscle tissue displayed a broad chemokine profile. The IM were characterized by a general increase of specific chemokines and chemokine receptors, while chemokine distribution reflected the two different immune responses represented within these muscle diseases. In DM, endothelial expression of CCL2 and CXCL12β was highly increased. In PM and IBM, macrophages and cytotoxic T cells actively invading nonnecrotic muscle fibers expressed highest levels of CXCL10 and CCL2. Some chemokines were selectively expressed by different IM infiltrates: CCL4 was present only in the perimysial inflammatory foci of a subset of DM biopsies, while CXCL1, CXCL2, CXCL3, and CCL7‐positive cells were exclusively detected in endomysial infiltrates of a number of PM and IBM samples. The chemokine receptor profile of the IM indicated the predominance of Th1‐mediated immune responses in all three IM. Our studies identified three ligand‐receptor pairs, namely CXCL10/CXCR3, CXCL12/CXCR4, and CCL2/CCR2, as potential targets for chemokine‐based therapy in IM.

The Tumor Necrosis Factor Superfamily of Cytokines in the Inflammatory Myopathies: Potential Targets for Therapy

The idiopathic inflammatory myopathies (IM) represent a heterogeneous group of autoimmune diseases, of which dermatomyositis (DM), polymyositis (PM), and sporadic inclusion body myositis (IBM) are the most common. The crucial role played by tumor necrosis factor alpha (TNFα) in the IM has long been recognized. However, so far, 18 other members of the TNF superfamily have been characterized, and many of these have not yet received the attention they deserve. In this paper, we summarize current findings for all TNF cytokines in IM, pinpointing what we know already and where current knowledge fails. For each TNF family member, possibilities for treating inflammatory diseases in general and the IM in particular are explored.

Idiopathic inflammatory myopathies and the classical NF-κB complex: Current insights and implications for therapy

The idiopathic inflammatory myopathies (IIM) comprise a heterogeneous group of muscle diseases. The three best-studied subgroups are dermatomyositis (DM), polymyositis (PM) and sporadic inclusion body myositis (IBM). The latter represents a steroid-refractory condition. PM and IBM are characterized by a cell-mediated immune response directed against non-necrotic fibers expressing Major Histocompatibility Complex class I (MHC class I). IBM presents with additional degenerative features, including rimmed vacuoles and depositions of aberrant proteins. DM is a complement-mediated endotheliopathy often accompanied by characteristic skin manifestations. The ubiquitously expressed transcription factor NF-kappaB is considered essential for the development of auto-immunity. This review describes data gathered so far concerning the distribution of the classical heterodimer p65/p50 and its inhibitor I-kappaBalpha in IIM skeletal muscle. Data suggest that the NF-kappaB complex plays a role in the endotheliopathy characterizing DM and might be involved in myofiber regeneration, and appoint CD4+ and CD68+ mononuclear cells with a more prominent role than previously assumed. Fragmentary knowledge of the immunopathogenesis of IIM hampers the development of therapeutic strategies suited to all patient groups. Unravelling the precise involvement of NF-kappaB subunits in IIM immunopathogenesis can shed new light onto the etiology of these diseases and may offer a novel therapeutic target.

Upregulation of chemokines and their receptors in duchenne muscular dystrophy: potential for attenuation of myofiber necrosis

Introduction: In Duchenne muscular dystrophy (DMD), the infiltration of skeletal muscle by immune cells aggravates disease, yet the precise mechanisms behind these inflammatory responses remain poorly understood. Chemotactic cytokines, or chemokines, are considered essential recruiters of inflammatory cells to the tissues. Methods: We assayed chemokine and chemokine receptor expression in DMD muscle biopsies (n = 9, average age 7 years) using immunohistochemistry, immunofluorescence, and in situ hybridization. Results: CXCL1, CXCL2, CXCL3, CXCL8, and CXCL11, absent from normal muscle fibers, were induced in DMD myofibers. CXCL11, CXCL12, and the ligand–receptor couple CCL2–CCR2 were upregulated on the blood vessel endothelium of DMD patients. CD68+ macrophages expressed high levels of CXCL8, CCL2, and CCL5. Conclusions: Our data suggest a possible beneficial role for CXCR1/2/4 ligands in managing muscle fiber damage control and tissue regeneration. Upregulation of endothelial chemokine receptors and CXCL8, CCL2, and CCL5 expression by cytotoxic macrophages may regulate myofiber necrosis. Muscle Nerve, 2012

Provision of an explanation for the inefficacy of immunotherapy in sporadic inclusion body myositis: quantitative assessment of inflammation and β-amyloid in the muscle.

OBJECTIVE In sporadic inclusion body myositis (IBM), inflammation and accumulation of β-amyloid-associated molecules cause muscle fiber damage. We undertook this study to determine why intravenous immunoglobulin (IVIG) and prednisone are not effective in sporadic IBM despite their effectiveness in other inflammatory myopathies. METHODS Relevant inflammatory and degeneration- associated markers were assessed by quantitative polymerase chain reaction and immunohistochemistry in repeated muscle biopsy specimens from patients with sporadic IBM treated in a controlled study with IVIG and prednisone (n = 5) or with prednisone alone (n = 5). Functional effects were assessed in a muscle cell culture model. RESULTS In muscle biopsy specimens, messenger RNA (mRNA) expression of the proinflammatory chemokines CXCL9, CCL3, and CCL4 and of the cytokines interferon-γ (IFNγ), transforming growth factor β, interleukin-10 (IL-10), and IL-1β was significantly reduced after treatment in both groups. No consistent changes were observed for tumor necrosis factor α, IL-6, inducible costimulator (ICOS), its ligand ICOSL, and perforin. Messenger RNA expression of the degeneration-associated molecule ubiquitin and the heat-shock protein αB-crystallin was also reduced, but no changes were noted for amyloid precursor protein (APP) or desmin. By immunohistochemistry, a significant down-modulation of chemokines was observed, but not of inducible nitric oxide (NO) synthase, nitrotyrosine, IL-1β, APP, and ubiquitin; β-amyloid was reduced in 6 of 10 patients. Pronounced staining of IgG was observed in the muscle after treatment with IVIG, indicating penetration of infused IgG into the muscle and a possible local effect. In muscle cells exposed to IFNγ plus IL-1β, IgG and/or prednisone down-regulated mRNA expression of IL-1β 2.5-fold. Accumulation of β-amyloid, overexpression of αB-crystallin, and cell death were prevented. In contrast, NO-associated cell stress remained unchanged. CONCLUSION IVIG and prednisone reduce some inflammatory and degenerative molecules in muscle of patients with sporadic IBM and in vitro, but do not sufficiently suppress myotoxic and cell stress mediators such as NO. The data provide an explanation for the resistance of sporadic IBM to immunotherapy and identify markers that may help to design novel treatment strategies.

TNFα receptor genotype influences smoking-induced muscle-fibre-type shift and atrophy in mice

Systemic manifestations of chronic obstructive pulmonary disease (COPD) include muscle wasting, and tumour necrosis factor α (TNFα) could represent a major inducer of these processes. We studied skeletal muscle histology in a murine model of cigarette smoke (CS)-induced COPD, comparing mice with different TNFα receptor genotypes. Muscles from hind limbs of wild type (WT), TNFα receptor 1 knockout (TNFαR1KO) and TNFαR2KO mice were prepared and weighed. The lower body weight, which was observed in CS-exposed WT and TNFαR1KO mice, was paralleled by reduced weights of gastrocnemius and biceps femoris muscle. The gastrocnemius muscle was evaluated for muscle fibre apoptosis and atrophy, and fibre-type distribution. CS-induced apoptosis was observed in all genotypes, while a significant reduction of cross-sectional areas of myofibres was present only in TNFαR2KO mice. A CS-induced fibre-type shift from the IIa to the IIb phenotype was observed in WT mice, an increase of muscle-fibre-type IIx was noticed in CS-exposed TNFαR2KO mice. Our data suggest that the skeletal muscle manifestations associated with this murine COPD model are under complex regulation by both TNFα receptors, but that TNFαR2 may be the most important determinant for the outcome of CS-induced myofibre apoptosis.

Heat shock protein families 70 and 90 in Duchenne muscular dystrophy and inflammatory myopathy: Balancing muscle protection and destruction

Heat shock proteins are important factors in skeletal muscle physiology and stress response. We examined the effects of chronic inflammation on the distribution of heat shock protein families 70 and 90 using immunofluorescence and Western blotting, in muscle biopsies from 33 idiopathic inflammatory myopathy patients [aged 26-66 (dermatomyositis), 17-78 (polymyositis) and 57-80 (sporadic inclusion body myositis) years], and seven Duchenne muscular dystrophy patients (aged 3-19 years). Our results reveal the multifaceted role played by chaperones in inflammatory muscle tissue. On the one hand, regenerating, atrophic and vacuolated muscle fibers displayed upregulation of both protein families. Higher levels of chaperones in challenged fibers point to the myocytes attempt to restore and regenerate. On the other hand, heat shock proteins of the 90 family were strongly upregulated in macrophages and cytotoxic T-cells actively invading nonnecrotic muscle fibers of sporadic inclusion body myositis and polymyositis, probably conferring enhanced myocytotoxic capacity. Our data provide positive arguments for exploring heat shock protein 90-based therapy in inflammatory muscle disease.

Distribution of the NF‐κB Complex in the Inflammatory Exudates Characterizing the Idiopathic Inflammatory Myopathies

The transcription factor nuclear factor‐κB (NF‐κB) is a ubiquitously expressed protein family that is considered crucial in autoimmunity. We describe NF‐κB p50 and p65, and the inhibitor I‐κBα in the inflammatory exudates characteristic for the different idiopathic inflammatory myopathies (IIM), that is, endomysial CD8+ cytotoxic T cells invading non‐necrotic fibers in polymyositis (PM) and sporadic inclusion body myositis (sIBM), and the perimysial/perivascular CD20+ B cells and CD4+ T cells in dermatomyositis (DM). We also analyzed other inflammatory cells in the vicinity of active inflammation sites. Strikingly, actively invading CD4+ cells in PM and sIBM contained both p65 and p50, whereas I‐κBα was absent. This could point to a high activation state in which these cells are capable of expressing a variety of inflammatory mediators, contributing to the degradation of non‐necrotic fibers. Secondly, CD68+ macrophages in the infiltrates in all three IIM subtypes showed strong nuclear p50 and I‐κBα staining. This may point to a role for p50 in counteracting inflammation, a reaction that could be enhanced by an upregulation of I‐κBα as we observed with immunofluorescence. These results shed further light on the immunopathology of PM, sIBM and DM. CD4+ and CD68+ mononuclear cells may play a more prominent role than previously assumed.

A dual role for HSP90 and HSP70 in the inflammatory myopathies: from muscle fiber protection to active invasion by macrophages.

Chaperones assist the metamorphosis of polypeptides to fully functional proteins. The family of heat shock proteins 70 (HSP70) bind at an early stage, while the HSP90 bind to proteins near their active conformation. We studied HSP90 and HSP70 in muscle biopsies from controls and patients diagnosed with the three main idiopathic inflammatory myopathies (IIM), namely dermatomyositis (DM), sporadic inclusion body myositis (IBM), and polymyositis (PM). Human skeletal muscle displayed constitutive levels of protein, but in IIM both HSP90 and HSP70 were upregulated. Regenerating muscle fibers of IIM and muscular dystrophy patients showed increased expression of HSP90 and HSP70, as did atrophic perifascicular muscle fibers of DM and vacuolated fibers of IBM. The infiltrates of IIM displayed weak homogeneous HSP70 staining. HSP90 were specifically upregulated in the CD68+ cells, actively invading non‐necrotic muscle fibers of IBM/PM and co‐localized with inducible NO synthase. HSP90:HSP70 ratios were increased in IBM and PM tissues displaying high inflammation grade. Our results point to a multifaceted role for chaperones in muscle tissue: a general protective role for both HSP90 and HSP70 families in damaged muscle fibers, and a specific cytotoxic role for HSP90 in muscle fiber invasion typically associated with IBM and PM.