Zhu W, Friedman H, Klein T W
Department of Medical Microbiology and Immunology, University of South Florida, College of Medicine, Tampa, Florida 33162, USA.
J Pharmacol Exp Ther. 1998 Aug;286(2):1103-9.
Apoptosis is programed cell death characterized by certain cellular changes and regulated by various gene products including Bcl-2 and caspase-1. The marijuana cannabinoid, Delta9tetrahydrocannabinol (THC), has been reported to suppress in culture the proliferation of splenocytes and increase the release of IL-1 from macrophages; however, the mechanisms of these effects remain unclear. Because cannabinoids have also been reported to induce apoptosis and because the release of IL-1 and suppression of lymphoproliferation are related to apoptosis, we tested for the induction of apoptosis by THC in murine immune cell cultures. Splenocytes cultured with Con A for up to 24 hr showed evidence of DNA fragmentation determined by gel electrophoresis, terminal deoxynucleotide transferase-mediated dUTP-fluorescein nick end labeling and 3H-thymidine labeling and THC (15-30 microM) treatment increased fragmentation under these conditions. Resident peritoneal macrophages cultured with lipopolysaccharides showed no obvious fragmentation unless they were also treated with THC. Time course studies examining DNA fragmentation and cell membrane integrity (assessed by dye exclusion) showed that fragmentation preceded membrane damage indicating that THC induced apoptosis rather than cell necrosis. In addition, THC treatment of splenocytes resulted in a decrease of Bcl-2 mRNA and protein as measured by Northern and Western blotting, respectively, and the drug induced apoptosis was blocked by the caspase inhibitor, Ac-Tyr-Val-Ala-L-aspartic acid aldehyde. These data suggest that THC treatment of cultured immune cells induces apoptosis through the regulation of Bcl-2 and caspase activity.
细胞凋亡是一种程序性细胞死亡，其特征为特定的细胞变化，并受包括Bcl-2和半胱天冬酶-1在内的多种基因产物调控。据报道，大麻素Δ9-四氢大麻酚（THC）在培养过程中可抑制脾细胞增殖，并增加巨噬细胞释放白细胞介素-1；然而，这些作用的机制仍不清楚。由于也有报道称大麻素可诱导细胞凋亡，且白细胞介素-1的释放和淋巴细胞增殖的抑制与细胞凋亡有关，因此我们在小鼠免疫细胞培养中测试了THC对细胞凋亡的诱导作用。用刀豆蛋白A培养长达24小时的脾细胞，通过凝胶电泳、末端脱氧核苷酸转移酶介导的dUTP-荧光素缺口末端标记和3H-胸腺嘧啶核苷标记检测到DNA片段化的证据，在这些条件下，THC（15-30微摩尔）处理增加了片段化。用脂多糖培养的腹腔常驻巨噬细胞，除非也用THC处理，否则未显示明显的片段化。检查DNA片段化和细胞膜完整性（通过染料排除法评估）的时间进程研究表明，片段化先于膜损伤，这表明THC诱导的是细胞凋亡而非细胞坏死。此外，分别通过Northern印迹和Western印迹检测，THC处理脾细胞导致Bcl-2 mRNA和蛋白减少，并且半胱天冬酶抑制剂Ac-Tyr-Val-Ala-L-天冬氨酸醛可阻断该药物诱导的细胞凋亡。这些数据表明，THC处理培养的免疫细胞通过调节Bcl-2和半胱天冬酶活性诱导细胞凋亡。
