Cell Biology Program, Research Institute, Hospital for Sick Children, 555 University Avenue, Toronto, Ontario, Canada M5G 1X8.
J Mol Cell Cardiol. 2011 May;50(5):826-40. doi: 10.1016/j.yjmcc.2011.02.011. Epub 2011 Feb 23.
The coxsackie-adenovirus receptor (CAR) is a viral receptor for Group B coxsackieviruses (CVBs) and adenoviruses. CAR has been linked with the innate immune response to CVB myocarditis, and with activation of inflammatory cells in vitro. We hypothesized that CAR activates signals that promote inflammation in the myocardium independent of viral infection. To test this we conditionally overexpressed murine CAR in cardiomyocytes of adult binary transgenic mice under the control of a tetracycline-responsive (tet-off) α-myosin heavy chain (αMtTA) promoter (mCAR(+)/αMtTA(+) mice). An inflammatory cardiomyopathy developed in both lines generated (6-mCAR(+)/αMtTA(+) and 12-mCAR(+)/αMtTA(+)) following withdrawal of doxycycline. Cardiac CAR was upregulated at 4weeks of age in 6-mCAR(+)/αMtTA(+) mice and induced a mild inflammatory infiltrate (score 1.3 of 4.0±0.3) at 6weeks, with 95% of mice surviving to that time. In the second line, 12-mCAR(+)/αMtTA(+) mice, CAR was upregulated in the majority of mice by 3weeks of age, and by 5weeks of age more severe cardiac inflammation (score 2.8 of 4.0±0.4) developed with only 56% of mice surviving. The cardiac inflammatory infiltrate was primarily natural killer cells and macrophages in both mCAR(+)/αMtTA(+) lines. A proinflammatory cytokine response with increased cardiac interferon-γ, interleukin (IL)-12, IL-1β, tumor necrosis factor-α and IL-6 was detected by real-time RT-PCR. CAR has been linked to signaling via the inflammatory mitogen-activated protein kinase (MAPK) cascades; therefore, we evaluated the response of these pathways in hearts with upregulated CAR. Both stress-activated JNK and p38MAPK were activated in mCAR(+)/αMtTA(+) hearts prior to onset of inflammation and in isolated mCAR(+)/αMtTA(+) cardiomyocytes. In conclusion, we show for the first time that CAR upregulation in the adult mouse heart induces cardiac inflammation reminiscent of early viral myocarditis. CAR-induced stress-activated MAPK signaling may contribute to the development of cardiac inflammation unrelated to viral infection per se.
柯萨奇病毒-腺病毒受体 (CAR) 是 B 族柯萨奇病毒 (CVB) 和腺病毒的病毒受体。CAR 与 CVB 心肌炎的先天免疫反应以及体外炎症细胞的激活有关。我们假设 CAR 激活信号，促进心肌炎症的发生，而与病毒感染无关。为了验证这一点，我们在成年双转基因小鼠的心肌细胞中条件性过表达小鼠 CAR，受四环素反应 (tet-off) α-肌球蛋白重链 (αMtTA) 启动子的控制 (mCAR(+)/αMtTA(+) 小鼠)。在停用强力霉素后，两种系 (6-mCAR(+)/αMtTA(+) 和 12-mCAR(+)/αMtTA(+)) 均发展出炎症性心肌病。6-mCAR(+)/αMtTA(+) 小鼠在 4 周龄时心脏 CAR 上调，6 周时诱导轻度炎症浸润 (评分 4.0±0.3 中的 1.3)，95%的小鼠存活至此时。在第二条线中，12-mCAR(+)/αMtTA(+) 小鼠的 CAR 在大多数小鼠中在 3 周龄时上调，在 5 周龄时，更严重的心脏炎症 (评分 4.0±0.4 中的 2.8) 发展，只有 56%的小鼠存活。在两条 mCAR(+)/αMtTA(+) 线中，心脏炎症浸润主要是自然杀伤细胞和巨噬细胞。通过实时 RT-PCR 检测到心脏干扰素-γ、白细胞介素 (IL)-12、IL-1β、肿瘤坏死因子-α和 IL-6 的促炎细胞因子反应。CAR 已与通过炎症有丝分裂原激活的蛋白激酶 (MAPK) 级联的信号转导有关；因此，我们评估了上调 CAR 的心脏中这些途径的反应。在炎症发作前和分离的 mCAR(+)/αMtTA(+) 心肌细胞中，应激激活的 JNK 和 p38MAPK 均在 mCAR(+)/αMtTA(+) 心脏中被激活。总之，我们首次表明，成年小鼠心脏中 CAR 的上调诱导类似于早期病毒性心肌炎的心脏炎症。CAR 诱导的应激激活 MAPK 信号可能有助于与病毒感染本身无关的心脏炎症的发展。
