Lee Eung-Ryoung, Kang Yong-Jin, Kim Jung-Hyun, Lee Hoon Taek, Cho Ssang-Goo
Department of Animal Biotechnology, Bio/Molecular Informatics Center, Konkuk University, Seoul 143-701, South Korea.
J Biol Chem. 2005 Sep 9;280(36):31498-507. doi: 10.1074/jbc.M505537200. Epub 2005 Jul 13.
The exact molecular mechanisms underlying the cellular effects associated with various flavonoids have yet to be fully explained. In the present study, we have administered several flavonoids to human HaCaT keratinocytes and determined that 3,4'-dihydroxy flavone (3,4'-DHF) exerts a slight stimulatory effect on cell growth, although other flavonoids, including kaempferol, quercetin, and isorhamnetin, exhibited growth inhibitory properties. 3,4'-DHF was found to exert an anti-apoptotic effect on etoposide-induced cell death of HaCaT keratinocytes. We were also able to determine that sustained ERK activation was intimately associated with the etoposide-induced apoptosis of HaCaT cells, and treatment with 3,4'-DHF induced a significant suppression of etoposide-induced ERK activation, concomitant with the repression of poly(ADP-ribose) polymerase or the cleavage of pro-caspase 3. ERK overexpression significantly overrode the anti-apoptotic function of 3,4'-DHF, but this was not true of ERK-DN. Moreover, treatment with 3,4'-DHF resulted in the protection of cells from H2O2-induced cell death and exerted an apparent suppressive effect on the stress-induced generation of reactive oxygen species (ROS). Finally, we showed that 3,4'-DHF almost completely abolished kaempferol-induced apoptosis, coupled with a concomitant suppression of both intracellular ROS generation and the activation of ERK. Taken together, our data clearly indicate that a host of phytochemicals, including etoposide and a variety of flavonoids, differentially regulate the apoptosis of human HaCaT keratinocytes via the differential modulation of intracellular ROS production, coupled with the concomitant activation of the ERK signaling pathway. According to these results, we are able to conclude the distinct structure-activity relationship between several flavonoids.
与各种黄酮类化合物相关的细胞效应背后的确切分子机制尚未完全阐明。在本研究中，我们将几种黄酮类化合物施用于人HaCaT角质形成细胞，并确定3,4'-二羟基黄酮（3,4'-DHF）对细胞生长有轻微的刺激作用，而其他黄酮类化合物，包括山奈酚、槲皮素和异鼠李素，则表现出生长抑制特性。发现3,4'-DHF对依托泊苷诱导的HaCaT角质形成细胞死亡具有抗凋亡作用。我们还能够确定，持续的ERK激活与依托泊苷诱导的HaCaT细胞凋亡密切相关，用3,4'-DHF处理可显著抑制依托泊苷诱导的ERK激活，同时抑制聚（ADP-核糖）聚合酶或前半胱天冬酶3的裂解。ERK过表达显著抵消了3,4'-DHF的抗凋亡功能，但ERK-DN并非如此。此外，用3,4'-DHF处理可保护细胞免受H2O2诱导的细胞死亡，并对应激诱导的活性氧（ROS）生成产生明显的抑制作用。最后，我们表明3,4'-DHF几乎完全消除了山奈酚诱导的凋亡，同时抑制了细胞内ROS生成和ERK激活。综上所述，我们的数据清楚地表明，包括依托泊苷和多种黄酮类化合物在内的许多植物化学物质，通过差异调节细胞内ROS生成以及伴随的ERK信号通路激活，以不同方式调节人HaCaT角质形成细胞的凋亡。根据这些结果，我们能够得出几种黄酮类化合物之间独特的构效关系。
