Department of Biochemistry and Molecular Pharmacology
Biochemistry | Enzymes and Coenzymes | Musculoskeletal Diseases | Rheumatology
BACKGROUND: The relationship between lung and joint inflammation in rheumatoid arthritis is poorly understood. Lung inflammation with resultant protein citrullination may trigger anti-citrullinated protein antibodies, inflammation, and arthritis. Alternatively, lung and joint inflammation may be two manifestations of a single underlying pathology. The lung has increased citrullination and TNF-alpha levels are high in rheumatoid arthritis; however, it is unknown if TNF-alpha can induce lung protein citrullination. The citrullinating enzyme peptidylarginine deiminase 4 (PAD4) exacerbates TNF-alpha-induced arthritis, but a role for PAD4 in lung citrullination and TNF-alpha-induced lung inflammation has not been explored. Our aim was to use TNF-alpha-overexpressing mice to clarify the intersection of TNF-alpha, citrullination, PAD4, arthritis, and lung inflammation.
METHODS: Lung protein citrullination in wild-type mice, mice that overexpress TNF-alpha systemically (TNF(+)), TNF(+)PAD4(+/+), and TNF(+)PAD4(-/-) mice was quantified by both gel electrophoresis using a citrulline probe and western blot. Hematoxylin and eosin (HandE)-stained lung sections from TNF(+)PAD4(+/+) and TNF(+)PAD4(-/-) mice were scored for lung inflammation. HandE-stained ankle joint sections from mice that overexpress TNF-alpha only in the lungs were assessed for arthritis.
RESULTS: TNF(+) mice have increased lung protein citrullination. TNF(+)PAD4(-/-) mice do not have significantly reduced lung protein citrullination, but do have decreased lung inflammation compared to TNF(+)PAD4(+/+) mice. Mice that overexpress TNF-alpha only in the lungs do not develop arthritis.
CONCLUSIONS: PAD4 exacerbates lung inflammation downstream of TNF-alpha without having a major role in generalized protein citrullination in inflamed lungs. Also, TNF-alpha-induced lung inflammation is not sufficient to drive murine arthritis.
Citrullination, Experimental arthritis, Lung, Peptidylarginine deiminase 4, Rheumatoid arthritis, TNF-α
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Copyright © The Author(s). 2016. Open Access.
DOI of Published Version
Arthritis Res Ther. 2016 Jul 22;18(1):173. doi: 10.1186/s13075-016-1068-0. Link to article on publisher's site
Arthritis research and therapy
Bawadekar M, Gendron-Fitzpatrick A, Rebernick R, Shim D, Warner TF, Nicholas AP, Lundblad LK, Thompson PR, Shelef MA. (2016). Tumor necrosis factor alpha, citrullination, and peptidylarginine deiminase 4 in lung and joint inflammation. Open Access Articles. https://doi.org/10.1186/s13075-016-1068-0. Retrieved from https://escholarship.umassmed.edu/oapubs/2785
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