Microsatellite instability and suppressed DNA repair enzyme expression in rheumatoid arthritis
Microsatellite instability and suppressed DNA repair enzyme expression in rheumatoid arthritis
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DOI：
10.4049/jimmunol.170.4.2214
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发表时间：
2003-02-15
影响因子：
4.4
通讯作者：
Firestein, GS
中科院分区：
文献类型：
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作者：
Lee, SH;Chang, DK;Firestein, GS
活性氧和氮由类风湿关节炎（RA）滑膜组织产生，并可能诱导关键基因突变。通常情况下，这个过程是由DNA错配修复（MMR）系统，在DNA复制过程中保持序列保真度阻止。MMR系统的关键成员包括MutSalpha（hMSH 2和hMSH 6）和MutSbeta（hMSH 2和hMSH 3）。为了提供炎症滑膜中DNA损伤的证据，我们分析了滑膜组织的微卫星不稳定性（MSI）。用5个关键微卫星的特异性引物序列对RA患者配对滑膜组织和外周血细胞的基因组DNA进行PCR检测MS 1。令人惊讶的是，与骨关节炎组织相比，在RA滑膜中观察到丰富的MS 1。Western blot分析显示RA滑膜中MMR蛋白表达减少，hMSH 3表达增加。为了评估关节炎中MMR调节的潜在机制，从滑膜组织中分离成纤维细胞样滑膜细胞（FLS），并与NO供体S-亚硝基-N-乙酰青霉胺孵育。Western blot分析表明hMSH 2、3和6在RA和骨关节炎FLS中的组成性表达。当FLS与S-亚硝基-N-乙酰青霉胺培养时，RA滑膜中MMR表达的模式再现（高hMSH 3，低hMSH 6）。因此，氧化应激可以通过抑制hMSH 6来放松RA中的DNA MMR系统。减少hMSH 6随后可以干扰单碱基突变的修复，这是在RA中观察到的类型。我们认为，氧化应激不仅产生DNA加合物，是潜在的致突变性，但也抑制了限制DNA损伤的机制。
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). MS1 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 MS1 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.