MHY884, a newly synthesized tyrosinase inhibitor,suppresses UVB-induced activation of NF-κB signaling pathway through the downregulation of oxidative stress

The skin is the primary target of prolonged and repeated ultraviolet (UVB) irradiation which induces cutaneous inflammation and pigmentation. Nuclear factor κB (NF-κB) is the major factor mediating UVB-induced inflammatory responses through the expression of various proinflammatory proteins such as inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). We have previously reported that the synthetic novel compound 4-(5-chloro-2,3-dihydrobenzo[d]thiazol-2-yl)-2,6-dimethoxyphenol (MHY884) strongly suppressed tyrosinase activity and melanin synthesis in B16F10 melanoma cells. In the present study, we investigated the effect of MHY884 on the inhibition of UVB-induced NF-κB activation and its proinflammatory downstream proteins through the suppression of oxidative stress in an in vivo model of photoaging. Generation of reactive oxygen species (ROS) and peroxynitrite was measured in vitro and in B16F10 melanoma cells to verify the scavenging activity of MHY884. MHY884 suppressed oxidative stress both in vitro and in the melanoma cells in a dose-dependent manner. Next, melanin-possessing hairless mice were pre-treated with MHY884 and then irradiated with UVB repeatedly. Topical application of MHY884 attenuated UVB-induced oxidative stress, resulting in reduced NF-κB activity. Pre-treatment with MHY884 inhibited Akt and IκB kinase α/β signaling pathways, leading to decreased translocation and phosphorylation of p65, a subunit of NF-κB. This result correlated with the expression levels of iNOS and COX-2 in the skin of MHY884-treated mice. Thus, the novel tyrosinase inhibitor MHY884 suppressed NF-κB activation signaling pathway by scavenging UVB-induced oxidative stress. The discovery of MHY884, a novel tyrosinase inhibitor that targets NF-κB signaling, is significant, because this compound is a promising protective agent against UVB-induced skin damage.     

内皮细胞和平滑肌细胞氧化应激时Nrf2/ARE信号通路对抗氧化基因表达的调控:与动脉粥样硬化和先兆子痫的关系

动脉粥样硬化、糖尿病、慢性肾功能衰竭和先兆子痫等血管疾病时活性氧(reactive oxygen species,ROS)生成增加,容易导致内皮依赖性血管舒张功能的损害和血管损伤,而细胞可以诱导多种编码Ⅱ相解毒酶和抗氧化蛋白的基因表达,从而减轻ROS和亲电子物质介导的细胞损伤。一个被称为抗氧化反应元件(antioxidant response element,ARE)或亲电子反应元件(electrophile response element,EpRE)的顺式转录调控元件,可以介导诸如亚铁血红素加氧酶1、γ-谷氨酰半胱氨酸合成酶、硫氧还蛋白还原酶、谷胱甘肽-S转移酶和NAD(P)H:苯醌氧化还原酶等基因的转录。其他抗氧化酶,如超氧化物歧化酶、过氧化氢酶和非酶清除剂(如谷胱甘肽)等也参与ROS的清除。转录因子NF-E2相关因子2(nuclear factor-erythroid 2-related factor 2, Nrf2)是属于Cap‘n’Collar家族的转录因子,具有碱性亮氨酸拉链(basic region-leucine zipper,bZIP),它在ARE介导的抗氧化基因表达中起重要的作用。在正常情况下,Kelch样环氧氯丙烷相关蛋白-1(Kelch-like ECH-associated protein-1,Keapl)与Nrf2耦联,并与肌动蛋白细胞骨架结合被锚定于胞浆,但是在半胱氨酸残基发生氧化的情况下,Nrf2和Keapl解耦联,进入细胞核并与ARE结合,从而激活多种抗氧化基因和Ⅱ相解毒酶基因的转录。蛋白激酶C、丝裂原活化蛋白激酶和磷脂酰肌醇-3激酶参与Nrf2／ARE信号转导的调控。本文综述了有关Nrf2／ARE信号转导通路在血管稳态和动脉硬化、先兆子痫等疾病情况下内皮及平滑肌细胞对抗持续性氧化应激中起的作用。     

C-Phycocyanin inhibits 2-acetylaminofluorene-induced expression of MDR1 in mouse macrophage cells: ROS mediated pathway determined via combination of experimental and In silico analysis

We studied the effects of C-Phycocyanin (C-PC), a biliprotein from Spirulina platensis on the 2-acetylaminofluorene (2-AAF)-induced expression of MDR1, encoded by the multidrug resistance (MDR1) gene, in mouse macrophage cell line (RAW 264.7). Our experimental and In silico studies revealed a significant inhibition of 2-AAF-induced expression of MDR1 protein in C-PC treated mouse macrophage cell line. MDR1 induction by 2-AAF was dependent on ROS (reactive oxygen species)-Akt (protein kinase B)-NF-κB (Nuclear factor kappa B) signaling pathway. Generation of ROS, phosphorylation of Akt and corresponding nuclear translocation of NF-κB, the events that play a major role in the induction of MDR1 expression, were decreased significantly in C-PC treated cells. NADPH oxidase inhibitor, DPI (Diphenyl iodide), and pharmacological inhibitor of Akt, Akt inhibitor IV, also showed a reduction in MDR1 expression, although not to the same extent as C-PC mediated inhibition of MDR1 expression. To further understand the mechanism, we created a computational model of the detailed ROS-Akt-NF-κB pathway. C-PC was modeled purely as a ROS scavenger and this representation matched the experimental trends accurately. Also the ROS levels determined through In silico investigation showed that C-PC was more effective in reduction of MDR1 expression than inhibitors of NADPH oxidase and Akt. Our experimental and In silico studies collectively suggest that 2-AAF induces MDR1 by ROS dependent pathway and C-PC is a potential negative regulator of MDR1 expression. This down regulation of MDR1 expression, induced by xenobiotics such as 2-AAF, suggests C-PC’s usefulness in overcoming the drug resistance in cellular systems.