Molecular Toxicology Laboratories, Division of Pharmaceutical Sciences, Arnold & Marie Schwartz College of Pharmacy and Health Sciences, Long Island University, Brooklyn, NY 11201, USA.
Toxicol Appl Pharmacol. 2010 Jun 1;245(2):143-52. doi: 10.1016/j.taap.2010.02.002. Epub 2010 Feb 6.
The emergence of silymarin (SMN) as a natural remedy for liver diseases, coupled with its entry into NIH clinical trial, signifies its hepatoprotective potential. SMN is noted for its ability to interfere with apoptotic signaling while acting as an antioxidant. This in vivo study was designed to explore the hepatotoxic potential of Doxorubicin (Dox), the well-known cardiotoxin, and in particular whether pre-exposures to SMN can prevent hepatotoxicity by reducing Dox-induced free radical mediated oxidative stress, by modulating expression of apoptotic signaling proteins like Bcl-xL, and by minimizing liver cell death occurring by apoptosis or necrosis. Groups of male ICR mice included Control, Dox alone, SMN alone, and Dox with SMN pre/co-treatment. Control and Dox groups received saline i.p. for 14 days. SMN was administered p.o. for 14 days at 16 mg/kg/day. An approximate LD(50) dose of Dox, 60 mg/kg, was administered i.p. on day 12 to animals receiving saline or SMN. Animals were euthanized 48 h later. Dox alone induced frank liver injury (>50-fold increase in serum ALT) and oxidative stress (>20-fold increase in malondialdehyde [MDA]), as well as direct damage to DNA (>15-fold increase in DNA fragmentation). Coincident genomic damage and oxidative stress influenced genomic stability, reflected in increased PARP activity and p53 expression. Decreases in Bcl-xL protein coupled with enhanced accumulation of cytochrome c in the cytosol accompanied elevated indexes of apoptotic and necrotic cell death. Significantly, SMN exposure reduced Dox hepatotoxicity and associated apoptotic and necrotic cell death. The effects of SMN on Dox were broad, including the ability to modulate changes in both Bcl-xL and p53 expression. In animals treated with SMN, tissue Bcl-xL expression exceeded control values after Dox treatment. Taken together, these results demonstrated that SMN (i) reduced, delayed onset, or prevented toxic effects of Dox which are typically associated with hydroxyl radical production, (ii) performed as an antioxidant limiting oxidative stress, (iii) protected the integrity of the genome, and (iv) antagonized apoptotic and necrotic cell death while increasing antiapoptotic Bcl-xL protein levels and minimizing the leakage of proapoptotic cytochrome c from liver mitochondria. These observations demonstrate the protective actions of SMN in liver, and raise the possibility that such protection may extend to other organs during Dox treatment including the heart.
水飞蓟素 (SMN) 作为一种治疗肝脏疾病的天然药物出现，并且进入 NIH 临床试验，这表明它具有肝保护作用。SMN 以其干扰细胞凋亡信号的能力以及作为抗氧化剂的作用而闻名。本体内研究旨在探索阿霉素 (Dox) 的肝毒性，特别是观察预先给予 SMN 是否可以通过减少 Dox 诱导的自由基介导的氧化应激、调节细胞凋亡信号蛋白（如 Bcl-xL）的表达以及最大限度地减少通过细胞凋亡或坏死发生的肝细胞死亡来预防肝毒性。雄性 ICR 小鼠的实验组包括对照组、单独给予 Dox、单独给予 SMN 以及预先/同时给予 Dox 和 SMN。对照组和 Dox 组通过腹腔注射生理盐水 14 天。SMN 通过灌胃给药 14 天，剂量为 16mg/kg/天。腹腔注射接近 LD(50)剂量的 60mg/kg Dox，于第 12 天给予接受生理盐水或 SMN 的动物。48 小时后处死动物。单独给予 Dox 会导致明显的肝损伤（血清 ALT 增加超过 50 倍）和氧化应激（丙二醛 [MDA] 增加超过 20 倍），以及对 DNA 的直接损伤（DNA 片段化增加超过 15 倍）。同时发生的基因组损伤和氧化应激影响基因组稳定性，反映在 PARP 活性和 p53 表达增加。Bcl-xL 蛋白减少，同时细胞质中细胞色素 c 积累增加，伴随着凋亡和坏死细胞死亡指数的升高。显著的是，SMN 暴露降低了 Dox 的肝毒性和相关的凋亡和坏死细胞死亡。SMN 对 Dox 的影响很广泛，包括调节 Bcl-xL 和 p53 表达的变化的能力。在给予 SMN 的动物中，Dox 处理后组织 Bcl-xL 表达超过对照组。综上所述，这些结果表明，SMN (i) 减少、延迟或预防了通常与羟基自由基产生相关的 Dox 的毒性作用，(ii) 作为抗氧化剂发挥作用，限制氧化应激，(iii) 保护基因组的完整性，(iv) 拮抗凋亡和坏死细胞死亡，同时增加抗凋亡 Bcl-xL 蛋白水平并最大限度地减少来自肝线粒体的促凋亡细胞色素 c 的泄漏。这些观察结果表明 SMN 在肝脏中的保护作用，并提出了在包括心脏在内的其他器官在接受 Dox 治疗期间可能会延伸到其他器官的可能性。
