title: Intracellular IL-1 receptor antagonist is elevated in human dermal fibroblasts that overexpress intracellular precursor IL-1 alpha.
abstract: Cultured dermal fibroblasts from systemic sclerosis patients express higher levels of intracellular IL-1 alpha than fibroblasts from healthy controls. In this study, we found that systemic sclerosis dermal fibroblasts also express higher levels of the intracellular isoform of IL-1 receptor antagonist (icIL-1Ra) than normal fibroblasts after stimulation with IL-1 beta or TNF-alpha. A possible relationship between elevated precursor IL-1 alpha (preIL-1 alpha) and elevated icIL-1Ra was investigated by transducing normal dermal fibroblasts to overexpress preIL-1 alpha, preIL-1 beta, or icIL-1Ra. Fibroblasts that overexpressed icIL-1Ra did not have elevated levels of IL-1 alpha. On the other hand, fibroblasts that overexpressed preIL-1 alpha had at least 4-fold higher basal levels of icIL-1Ra than control fibroblasts and 4-fold higher levels of icIL-1Ra after induction with IL-1 beta or TNF-alpha. Fibroblasts overexpressing preIL-1 beta did not exhibit elevated icIL-1Ra. The differences in icIL-1Ra protein levels were reflected in differences in mRNA. In contrast, IL-1-stimulated levels of MCP-1 and IL-6 were not different in control and preIL-1 alpha-transduced fibroblasts. Addition of neutralizing anti-IL-1 alpha Abs to fibroblast cultures did not diminish basal or stimulated levels of icIL-1Ra in the preIL-1 alpha-transduced cells, supporting an intracellular site of action of preIL-1 alpha. This is the first report of an association between intracellular levels of these IL-1 family members. We hypothesize that intracellular preIL-1 alpha participates in the regulation of icIL-1Ra.
authors.affiliation: Department of Pediatrics, Division of Clinical Immunology, Crippled Children's Foundation Research Center at LeBonheur Children's Medical Center, Memphis, TN 38103, USA. higginsg@pediatrics.ohiostate.edu
authors.forename: G C
authors.initials: GC
authors.lastname: Higgins
authors.forename: Y
authors.initials: Y
authors.lastname: Wu
authors.forename: A E
authors.initials: AE
authors.lastname: Postlethwaite
mesh_terms: D000328:Adult; D000368:Aged; D002478:Cells, Cultured; D016207:Cytokines / Q000096:biosynthesis; D005260:Female; D005347:Fibroblasts / Q000276:immunology / Q000378:metabolism* / Q000473:pathology; D005822:Genetic Vectors / Q000276:immunology / Q000378:metabolism; D006801:Humans; D007106:Immune Sera / Q000494:pharmacology; D053590:Interleukin 1 Receptor Antagonist Protein; D007375:Interleukin-1 / Q000037:antagonists & inhibitors* / Q000096:biosynthesis* / Q000235:genetics / Q000276:immunology; D007424:Intracellular Fluid / Q000276:immunology / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D011498:Protein Precursors / Q000037:antagonists & inhibitors* / Q000096:biosynthesis* / Q000235:genetics / Q000276:immunology; D012333:RNA, Messenger / Q000096:biosynthesis / Q000378:metabolism; D017472:Receptors, Interleukin-1 / Q000037:antagonists & inhibitors*; D012190:Retroviridae / Q000235:genetics; D012595:Scleroderma, Systemic / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D012795:Sialoglycoproteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D012867:Skin / Q000166:cytology* / Q000276:immunology / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
chemical_list: D016207:Cytokines; C507763:IL1RN protein, human; D007106:Immune Sera; D053590:Interleukin 1 Receptor Antagonist Protein; D007375:Interleukin-1; D011498:Protein Precursors; D012333:RNA, Messenger; D017472:Receptors, Interleukin-1; D012795:Sialoglycoproteins; D014409:Tumor Necrosis Factor-alpha; C043830:interleukin 1 precursor