Resistin-like molecule-beta is an allergen-induced cytokine with inflammatory and remodeling activity in the murine lung.

Resistin-like molecule (RELM)-beta is a cysteine-rich cytokine implicated in insulin resistance and asthmatic responses, but its function remains an enigma. We now report that RELM-beta has a role in promoting airway inflammation and lung remodeling in the mouse lung. RELM-beta is strongly induced by diverse allergens and T helper type 2 (Th2) cytokines by an IL-13- and STAT6-dependent mechanism. To understand the in vivo role of RELM-beta, we delivered recombinant murine RELM-beta intratracheally to naïve mice. RELM-beta induced dose-dependent leukocyte accumulation (most prominently involving macrophages) and goblet cell hyperplasia. The most prominent effect induced by RELM-beta was increased perivascular and peribronchial collagen deposition. Mice genetically deficient in RELM-beta had reduced accumulation of collagen and goblet cell hyperplasia in an experimental model of allergic airway inflammation. In vitro experiments demonstrated that RELM-beta had fibroblast motogenic activity. These results identify RELM-beta as a Th2-associated cytokine with potent inflammatory and remodeling activity.

Critical role for adaptive T cell immunity in experimental eosinophilic esophagitis in mice.

We have previously developed a murine model of allergen-induced eosinophilic esophagitis (EE), characterized by intraepithelial eosinophils, extracellular granule deposition, and epithelial cell hyperplasia, features that mimic the pathophysiological changes observed in individuals with various forms of EE. We now test the hypothesis that adaptive T cell immunity is critical in initiating experimental EE. We first demonstrate that EE induction is associated with an increase in lymphocyte subpopulations (B+, CD4+, and CD8+ cells) in the esophagus. We induced experimental EE in wild-type and various lymphocyte subpopulation-deficient mice by intranasal allergen sensitization. Eosinophil levels and epithelial cell proliferation were determined by performing antimajor basic protein and antiproliferation cell nuclear antigen immunohistochemical analysis. Eosinophil accumulation in the esophagus was ablated completely in RAG1 gene-deficient mice, but no role for B cells or antigen-specific antibodies was found, as B cell-deficient (IgH6) mice developed unabated, experimental EE. In addition, T cell-deficient (forkhead box N1-/-) mice were protected from the induction of experimental EE. CD8alpha-deficient mice developed unaltered, experimental EE, and CD4-deficient mice were only protected moderately from disease induction. Taken together, these studies indicate a role for CD4+ and CD4- cell populations in EE pathogenesis and demonstrate that experimental allergen-induced EE is dependent on adaptive T cell immunity.

Infantile dilated X-linked cardiomyopathy, G4.5 mutations, altered lipids, and ultrastructural malformations of mitochondria in heart, liver, and skeletal muscle.

Mutations in the Xq28 gene G4.5 lead to dilated cardiomyopathy (DCM). Differential splicing of G4.5 results in a family of proteins called "tafazzins" with homology to acyltransferases. These enzymes assemble fatty acids into membrane lipids. We sequenced G4.5 in two kindreds with X-linked DCM and in two unrelated men, one with idiopathic DCM and the other with DCM of arrhythmogenic right ventricular dysplasia. We examined the ultrastructure of heart, liver, and muscle biopsy specimens in these three DCM types; we used gas chromatography to compare fatty acid composition in heart, liver, and muscle autopsy specimens of two patients of kindred 1 with that of controls. In X-linked DCM, G4.5 had a stop codon (E188X), a nonsense mutation, in kindred 1 and an amino acid substitution (G240R), a missense mutation, in kindred 2. In the two men with isolated DCM, G4.5 was not mutated. Ultrastructural mitochondrial malformations were present in the biopsy tissues of the patients with DCM. Cardiac biopsy specimens of both kindreds with X-linked DCM exhibited greatly enlarged mitochondria with large bundles of stacked, compacted, disarrayed cristae that differed from those of the two types of isolated DCM. Autopsy tissue of patients with X-linked DCM had decreased unsaturated and increased saturated fatty acid concentrations. Seven of 13 published G4.5 missense mutations, including the one presented here, occur in acyltransferase motifs. Impaired acyltransferase function could result in increased fatty acid saturation that would decrease membrane fluidity. Mitochondrial membrane proliferation may be an attempt to compensate for impaired function of acyltransferase. Cardiac ultrastructure separates X-linked DCM with G4.5 mutations from the two types of isolated DCM without G4.5 mutations. Electron microscopy of promptly fixed myocardial biopsy specimens has a role in defining the differential diagnosis of DCM. Mutational analysis of the G4.5 gene also serves this purpose.