title: Microsatellite instability and suppressed DNA repair enzyme expression in rheumatoid arthritis.
abstract: Reactive oxygen and nitrogen are produced by rheumatoid arthritis (RA) synovial tissue and can potentially induce mutations in key genes. Normally, this process is prevented by a DNA mismatch repair (MMR) system that maintains sequence fidelity during DNA replication. Key members of the MMR system include MutSalpha (hMSH2 and hMSH6) and MutSbeta (hMSH2 and hMSH3). To provide evidence of DNA damage in inflamed synovium, we analyzed synovial tissues for microsatellite instability (MSI). MSI was examined by PCR on genomic DNA of paired synovial tissue and peripheral blood cells of RA patients using specific primer sequences for five key microsatellites. Surprisingly, abundant MSI was observed in RA synovium compared with osteoarthritis tissue. Western blot analysis for the expression of MMR proteins demonstrated decreased hMSH6 and increased hMSH3 in RA synovium. To evaluate potential mechanisms of MMR regulation in arthritis, fibroblast-like synoviocytes (FLS) were isolated from synovial tissues and incubated with the NO donor S-nitroso-N-acetylpenicillamine. Western blot analysis demonstrated constitutive expression of hMSH2, 3, and 6 in RA and osteoarthritis FLS. When FLS were cultured with S-nitroso-N-acetylpenicillamine, the pattern of MMR expression in RA synovium was reproduced (high hMSH3, low hMSH6). Therefore, oxidative stress can relax the DNA MMR system in RA by suppressing hMSH6. Decreased hMSH6 can subsequently interfere with repair of single base mutations, which is the type observed in RA. We propose that oxidative stress not only creates DNA adducts that are potentially mutagenic, but also suppresses the mechanisms that limit the DNA damage.
authors.affiliation: Division of Rheumatology, Allergy, and Immunology, Division of Gastroenterology, School of Medicine, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA.
authors.forename: Sang-Heon
authors.initials: SH
authors.lastname: Lee
authors.forename: Dong Kyung
authors.initials: DK
authors.lastname: Chang
authors.forename: Ajay
authors.initials: A
authors.lastname: Goel
authors.forename: C Richard
authors.initials: CR
authors.lastname: Boland
authors.forename: William
authors.initials: W
authors.lastname: Bugbee
authors.forename: David L
authors.initials: DL
authors.lastname: Boyle
authors.forename: Gary S
authors.initials: GS
authors.lastname: Firestein
mesh_terms: D000251:Adenosine Triphosphatases / Q000096:biosynthesis; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001172:Arthritis, Rheumatoid / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D001426:Bacterial Proteins; D020137:Base Pair Mismatch / Q000276:immunology; D002478:Cells, Cultured; D011088:DNA Ligases / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D004260:DNA Repair / Q000276:immunology*; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D004306:Dose-Response Relationship, Immunologic; D004794:Enzyme Repression / Q000276:immunology; D029968:Escherichia coli Proteins / Q000096:biosynthesis; D005260:Female; D005347:Fibroblasts / Q000201:enzymology / Q000473:pathology; D006801:Humans; D018895:Microsatellite Repeats / Q000276:immunology*; D008875:Middle Aged; D051719:MutS DNA Mismatch-Binding Protein; D051718:MutS Homolog 2 Protein; D000074081:MutS Homolog 3 Protein; D010003:Osteoarthritis / Q000201:enzymology / Q000235:genetics / Q000473:pathology; D018384:Oxidative Stress / Q000235:genetics / Q000276:immunology; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D026361:Reactive Nitrogen Species / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000494:pharmacology; D013583:Synovial Membrane / Q000201:enzymology / Q000378:metabolism / Q000473:pathology
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C094443:G-T mismatch-binding protein; C078444:MSH3 protein, human; D000074081:MutS Homolog 3 Protein; D011518:Proto-Oncogene Proteins; D026361:Reactive Nitrogen Species; D017382:Reactive Oxygen Species; D000251:Adenosine Triphosphatases; C497172:MSH2 protein, human; D051719:MutS DNA Mismatch-Binding Protein; D051718:MutS Homolog 2 Protein; C497175:MutS protein, E coli; D011088:DNA Ligases