心血管疾病，如動脈粥狀硬化以及主動脈瘤，發生在腹主動脈的機率高於在胸主動脈。血管的老化是心血管疾病發生的一個決定性的危險因子，通常以血管細胞的老化來呈現，且伴隨發炎反應以及活性氧分子(ROS)的產生。在過去的研究中發現，介白素-1β (IL-1β)，一種促發炎的細胞素，會促使多種細胞ROS的產生並導致去氧核醣核酸(DNA)損傷。我們假設IL-1β會誘導血管平滑肌細胞老化，並探討IL-1β的作用在大鼠胸主動脈所衍生的平滑肌細胞(RTA-VSMCs)以及腹主動脈衍生的平滑肌細胞(RAA-VSMCs)之間是否有差異。我們藉由細胞週期抑制蛋白p16和p21的表現以及老化相關的β-半乳糖苷酶(SA-β-Gal)的活性來評估細胞的老化。在IL-1β處理24小時後，在RTA-VSMCs及RAA-VSMCs均可偵測到p16和p21的表現量增加，但IL-1β所需的濃度在RTA-VSMCs為100-1000 pg/mL，而在RAA-VSMCs則是1-10 pg/mL。當給予RTA-VSMCs與RAA-VSMCs其各自最大效應濃度的IL-1β處理24、48和72小時後，其SA-β-Gal的活性都顯著地增加，且比例相似。以1和10 pg/mL的IL-1β處理24小時之後，RAA-VSMCs中ROS的量以及DNA損傷的指標，γH2AX，皆顯著上升，但對RTA-VSMCs中的ROS增加及γH2AX的量並無影響。此外，以1和10 pg/mL的IL-1β處理24小時，也會增加RAA-VSMCs粒線體中ROS的生成。我們接著觀察IL-1β在RAA-VSMCs中誘發ROS產生、DNA損傷和老化指標蛋白表現發生的時序。在IL-1β處理後，RAA-VSMCs的ROS量在45分鐘時顯著地上升，並持續至少2小時；DNA損傷的指標γH2AX在1小時後顯著地增加；而p21和p16的表現量則分別在6小時及24小時後上升。我們使用兩種抗氧化劑，N-乙酰基-L-半胱氨酸(NAC)以及具細胞膜通透性的過氧化氫酶(catalase-PEG)，進一步確認ROS在IL-1β所引起的RAA-VSMCs細胞老化所扮演的角色。結果顯示，在RAA-VSMCs中，NAC或catalase-PEG的共同處理都能有效地抑制IL-1β所刺激的ROS產生，同時抑制了IL-1β所誘發的γH2AX量以及p16和p21的表現。本研究結果顯示，RAA-VSMCs較RTA-VSMCs更容易被IL-1β誘導而引起細胞老化。在RAA-VSMCs，IL-1β藉由產生氧化壓力，進而誘發DNA損傷以及細胞老化。

Cardiovascular diseases including atherosclerosis and aortic aneurysms occur more often in the abdominal aorta (AA) than in the thoracic aorta (TA). Vascular aging, a dominant risk factor for cardiovascular diseases, is manifested with vascular cell senescence and increases in inflammation and reactive oxygen species (ROS) production. The pro-inflammatory cytokine, interleukin-1β (IL-1β), was reported to induce ROS production and trigger DNA damage in various cell types. We hypothesized that IL-1β induces cellular senescence of vascular smooth muscle cells (VSMCs) and examined whether IL-1β differentially induced cellular senescence of VSMCs derived from rat TA (TA-VSMCs) and AA (AA-VSMCs). Cellular senescence was assessed with the expression of two cell cycle inhibitors, p16 and p21, and senescence-associated β-galactosidase (SA-β-Gal) activity. IL-1β treatment for 24 hours (24 h) up-regulated the expression of p16 and p21, which was most pronounced between 100 and 1000 pg/mL in rat TA-VSMCs but peaked between 1 and 10 pg/mL in rat AA-VSMCs. When treated with their respective, maximally effective doses of IL-1β for 24 h, 48 h, and 72 h, SA-β-Gal activities were stimulated to similar degrees in these VSMCs. Treatment with IL-1β at 1 & 10 pg/mL for 24 h markedly increased ROS production and DNA damage marker γH2AX levels in rat AA-VSMCs without significant effects on rat TA-VSMCs. Furthermore, IL-1β stimulated mitochondrial ROS production detected with MitoSOXTM in rat AA-VSMCs. We next examined time courses of IL-1β-induced ROS production, DNA damage, and senescence marker expression in AA-VSMCs. Following IL-1β treatment, ROS production markedly increased at 45 min and sustained to 2 h, DNA damage marker γH2AX levels increased markedly at 1 h and stayed elevated up to 24 h, whereas the expression of p21 and p16 was upregulated at 6 h and 24 h, respectively. ROS scavengers, N-acetyl-L-cysteine and a membrane-permeable catalase, reduced IL-1β-induced ROS production at 24 h with concomitant inhibition on DNA damage marker γH2AX levels and the expression of p21 and p16 in AA-VSMCs. These results suggested that AA-derived VSMCs are more susceptible to IL-1β-induced cellular senescence than their counterparts from TA. Furthermore, ROS production is required for IL-1β-induced DNA damage and cellular senescence of rat AA-VSMCs.

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