Lipid metabolism enzyme 5-LOX and its metabolite LTB4 are capable of activating transcription factor NF-κB in hepatoma cells
Department of Biochemistry, College of Life Sciences, State Key Laboratory of Medicinal Chemical Biology, Nankai University, Tianjin 300071, China.Biochemical and Biophysical Research Communications (Impact Factor: 2.3). 02/2012; 418(4):647-51. DOI: 10.1016/j.bbrc.2012.01.068
The issue that lipid metabolism enzyme and its metabolites regulate transcription factors in cancer cell is not fully understood. In this study, we first report that the lipid metabolism enzyme 5-Lipoxygenase (5-LOX) and its metabolite leukotriene B4 (LTB4) are capable of activating nuclear factor-κB (NF-κB) in hepatoma cells. We found that the treatment of MK886 (an inhibitor of 5-LOX) or knockdown of 5-LOX was able to downregulate the expression of NF-κB p65 at the mRNA level and decreased the phosphorylation level of inhibitor κBα (IκBα) in the cytoplasm of hepatoma HepG2 or H7402 cells, which resulted in the decrease of the level of nuclear NF-κB p65. These were confirmed by immunofluorescence staining in HepG2 cell. Moreover, the above treatments were able to decrease the transcriptional activity of NF-κB in the cells. The LTB4, one of metabolites of 5-LOX, is responsible for 5-LOX-activated NF-κB in a dose-dependent manner. Thus, we conclude that the lipid metabolism enzyme 5-LOX and its metabolite LTB4 are capable of activating transcription factor NF-κB in hepatoma cells. Our finding provides new insight into the significance of lipid metabolism in activation of transcription factors in cancer.
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ABSTRACT: Purpose: We assessed whether tetramethylpyrazine (TMP), an active ingredient of Ligusticum wallichii Franchat, attenuates atherosclerosis (AS) development in rabbits and protects endothelial cells injured by ox-LDL. Methods: In vivo, rabbits subjected to atherosclerosis were treated with TMP (75 and 150 mg/kg) by oral gavage for 12 weeks. In vitro, rat aortic endothelial cells (RAECs) were stimulated by ox-LDL. Results: TMP treatment with 75 and 150 mg/kg significantly reduced the relative atherosclerosis area ratio in the aorta (0.41 ± 0.042, 0.27 ± 0.047 vs. 0.66 ± 0.058 in AS), the ratio of intimal/medial thickness (0.54 ± 0.09, 0.39 ± 0.07 vs. 1.1 ± 0.3 in AS) and the number of monocytes in intimal (10.1 ± 2.8, 8.2 ± 2.0 vs. 14.1 ± 4.9 counts/mm(2) in AS). TMP also decreased levels of TC (15 ± 4.2 to 6.1 ± 1.2 mmol/L), TG (1.8 ± 0.3 to 1.08 ± 0.24 mmol/L), LDL-C (20.1 ± 4.3 to 10.2 ± 1.6 mmol/L) and increased HDL-C levels (0.40 ± 0.08 to 0.85 ± 0.17 mmol/L) in atherosclerosis rabbit plasma. TMP decreased the MCP-1 (187.3 ± 38.4 to 86.1 ± 17.2 pg/ml) and ICAM-1 (350.6 ± 43.7 to 260.6 ± 46.1 pg/ml) levels in plasma and inhibited LOX-1 expression in the rabbit aortas. Moreover, our in vitro study revealed that TMP suppressed monocyte adhesion to RAECs, inhibited RAEC migration, and down-regulated MCP-1 and ICAM-1 expression in ox-LDL-injured RAECs. Likewise, TMP inhibited LOX-1 and 5-LOX expression, and prevented nuclear accumulation of RelA/p65 and IκB degradation in ox-LDL-injured RAECs. Furthermore, TMP suppressed ox-LDL-induced activations of p-ERK, p-p38, and p-JNK MAPK. Conclusion: TMP produces a tangible protection in atherosclerosis and endothelial cells. TMP might be a potential protective agent for atherosclerosis.
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ABSTRACT: Kaposi's sarcoma-associated herpes virus (KSHV) is etiologically associated with Kaposi's sarcoma (KS) and primary effusion lymphoma (PEL). KS lesions are characterized by endothelial cells with multiple copies of latent KSHV episomal genome, lytic replication in a low percentage of infiltrating monocytes, inflammatory cytokines plus growth factors. We demonstrated that KSHV utilizes inflammatory COX-2/PGE2 to establish and maintain latency (Sharma-Walia, N., A. G. Paul, V. Bottero, S. Sadagopan, M. V. Veettil, N. Kerur, and B. Chandran. 2010. PLoS Pathog 6:e1000777). Here, we evaluated the role of 5-lipoxygenase (5LO) and its chemotactic metabolite leukotriene B4 (LTB4) in KSHV biology. Abundant staining of 5LO was detected in human KS tissue sections. We observed elevated levels of 5LO and high secretion of LTB4 during primary KSHV infection of endothelial cells and in PEL B cells (BCBL-1 and BC-3). Blocking the 5LO/LTB4 cascade inhibited viral latent ORF73, immunemodulatory K5, vMIP1, and vMIP2 gene expression, without much effect on lytic switch ORF50, immediate early lytic K8 and vIRF2 gene expression. 5LO inhibition significantly downregulated latent v-Cyclin and LANA-2 levels in PEL cells. 5LO/LTB4 inhibition downregulated TH2 and elevated TH1 related cytokine secretion, and reduced human monocyte recruitment, adhesion and transendothelial migration. 5LO/LTB4 inhibition reduced fatty acid synthase (FASN) promoter activity and its expression. Since FASN, a key enzyme required in lipogenesis, is important in KSHV latency, collectively, these findings suggest that the 5LO/LTB4 play important role in KSHV biology, and that effective inhibition of the 5LO/LTB4 pathway could potentially be used in treatment to control KS/PEL.
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ABSTRACT: Emerging evidence has shown that cancer stem cells (CSCs) are the cellular determinants to promote cancer invasion and metastasis. However, the mechanism underlying CSC invasion remains unknown. MicroRNAs are evolutionally conserved small noncoding RNAs that are critical for the regulation of gene expression, and their expressions are often dysregulated in cancers. In the present study, we demonstrated that two functionally related microRNAs, miR-20a and -106a (miR-20a/106a), were capable of enhancing the invasiveness of CD133(+) glioma stem cells (GSCs) isolated from both glioblastoma cell line U87 and primary human glioma specimens. We found that the level of miR-20a/106a in GSCs was significantly higher than that in the committed CD133(-) glioma cells, and correlated with the invasive capability of GSCs. By bioinformatic analysis, we identified tissue inhibitor of metalloproteinases-2 (TIMP-2) as one of the miR-20a/106a-targeted genes. TIMP-2 level correlated inversely with miR-20/106 expression. Directly targeting by miR-20a/106a on 3'-untranslation region (3'-UTR) of TIMP-2 mRNA was confirmed by 3'-UTR dual-luciferase reporter assay. Knockdown of miR-20a/106a in GSCs increased endogenous TIMP-2 protein abundance, thereby inhibiting GSC invasion. We also found that Nordy, a synthetic lipoxygenase inhibitor, inhibited GSC invasiveness by elevating the expression of TIMP-2 via downregulation of miR-20a/106a. Our results indicate that miR-20a/106a has a key role in GSC invasion and may serve as targets for treatment of glioblastoma.Oncogene advance online publication, 7 April 2014; doi:10.1038/onc.2014.75.
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