Methyl lucidone inhibits airway inflammatory response by reducing TAK1 activity in human bronchial epithelial NCI-H292 cells.

Background: Methyl lucidone (ML), a methyl derivative of lucidone, has anti-inflammatory properties. However, the molecular mechanisms that reduce the inflammatory effect of ML in human lung epithelial cells remain unkown. This study aimed to elucidate the molecular mechanisms underlying the anti-inflammatory effect of ML. Methods: Four compounds (ML, methyl linderone, kanakugiol, and linderone) from Lindera erythrocarpa Makino were evaluated for their ability to reduce MUC5AC secretion levels in phorbol-12-myristate-13-acetate (PMA)-stimulated NCI-H292 cells using ELISA. The expression and secretion levels of inflammatory response-related proteins were analyzed using quantitative reverse transcription-PCR, ELISA, and western blotting. To determine whether ML directly regulates TGF-ß-activated kinase 1 (TAK1), we performed an in vitro kinase assay. Results: ML treatment effectively reduced the levels of inflammatory cytokines, including interleukin-1ß and TNF-α, increased by stimulation. Furthermore, ML downregulated the pathway cascade of both IκB kinase (IKK)/NF-κB and p38 mitogen-activated protein (MAP) kinase/CREB by inhibiting the upstream kinase TAK1. An in vitro kinase analysis confirmed that ML treatment significantly reduced the kinase activity of TAK1. Conclusion: ML pretreatment repressed the PMA-stimulated inflammation reaction by reducing the TAK1-mediated IKK/NF-κB and p38 MAP kinase/CREB signaling. These findings suggest that ML may improve respiratory health and can be used as a dietary supplement or functional food to prevent inflammatory lung diseases.

Lucidone inhibits autophagy and MDR1 via HMGB1/RAGE/PI3K/Akt signaling pathway in pancreatic cancer cells.

Gemcitabine (GEM) drug resistance remains a difficult challenge in pancreatic ductal adenocarcinoma (PDAC) treatment. Therefore, identifying a safe and effective treatment strategy for PDAC is urgent. Lucidone is a natural compound extracted from the fruits of Lindera erythrocarpa Makino. However, the role of lucidone in PDAC inhibition remains unclear. In addition, high-mobility group box 1 (HMGB1) and receptor for advanced glycation end products (RAGE) are involved in multidrug resistance protein 1 (MDR1) regulation and GEM resistance. Thus, this study aimed to explore the function of lucidone in tumor cytotoxicity and chemosensitivity through the suppression of RAGE-initiated signaling in PDAC cells. The data showed that lucidone significantly promoted apoptotic cell death and inhibited the expression of autophagic proteins (Atg5, Beclin-1, LC3-II, and Vps34) and MDR1 by inhibiting the HMGB1/RAGE/PI3K/Akt axis in both MIA Paca-2 cells and MIA Paca-2GEMR cells (GEM-resistant cells). Notably, convincing data were also obtained in experiments involving RAGE-specific siRNA transfection. In addition, remarkable cell proliferation was observed after treatment with lucidone combined with GEM, particularly in MIA Paca-2GEMR cells, indicating that lucidone treatment enhanced chemosensitivity. Collectively, this study provided the underlying mechanism by which lucidone treatment inhibited HMGB1/RAGE-initiated PI3K/Akt/MDR1 signaling and consequently enhanced chemosensitivity in PDAC.

Lucidone suppresses dengue viral replication through the induction of heme oxygenase-1.

Dengue virus (DENV) infection causes life-threatening diseases such as dengue hemorrhagic fever and dengue shock syndrome. Currently, there is no effective therapeutic agent or vaccine against DENV infection; hence, there is an urgent need to discover anti-DENV agents. The potential therapeutic efficacy of lucidone was first evaluated in vivo using a DENV-infected Institute of Cancer Research (ICR) suckling mouse model by monitoring body weight, clinical score, survival rate, and viral titer. We found that lucidone effectively protected mice from DENV infection by sustaining survival rate and reducing viral titers in DENV-infected ICR suckling mice. Then, the anti-DENV activity of lucidone was confirmed by western blotting and quantitative-reverse-transcription-polymerase chain reaction analysis, with an EC50 value of 25 ± 3 µM. Lucidone significantly induced heme oxygenase-1 (HO-1) production against DENV replication by inhibiting DENV NS2B/3 protease activity to induce the DENV-suppressed antiviral interferon response. The inhibitory effect of lucidone on DENV replication was attenuated by silencing of HO-1 gene expression or blocking HO-1 activity. In addition, lucidone-stimulated nuclear factor erythroid 2-related factor 2 (Nrf2), which is involved in transactivation of HO-1 expression for its anti-DENV activity. Taken together, the mechanistic investigations revealed that lucidone exhibits significant anti-DENV activity in in vivo and in vitro by inducing Nrf2-mediated HO-1 expression, leading to blockage of viral protease activity to induce the anti-viral interferon (IFN) response. These results suggest that lucidone is a promising candidate for drug development.

Lucidone Promotes the Cutaneous Wound Healing Process via Activation of the PI3K/AKT, Wnt/ß-catenin and NF-κB Signaling Pathways.

Lucidone, which comprises a naturally occurring cyclopentenedione, has been investigated for its in vitro and in vivo wound healing properties, and the underlying molecular signaling cascades in the wound healing mechanism have been elucidated. We demonstrated the cell-/dose-specific responses of lucidone (0.5-8µM) on proliferation and migration/invasion of keratinocyte HaCaT and fibroblast Hs68 cells. In keratinocytes, lucidone-induced nuclear translocation of ß-catenin was accompanied by increased transcriptional target genes, including c-Myc and cyclin-D1, through GSK3ß-dependent pathway. Correspondingly, lucidone promoted the cell-cycle by increasing PCNA/CDK4 and decreasing p21/p27 expressions. Lucidone induced EMT through the downregulation of epithelial (E-cadherin/occludin) and upregulation of mesenchymal (vimentin/Twist/Snail) marker proteins. Activated MMP-9/-2 and uPA/uPAR as well as suppressed TIMP-1/-2 and PAI-1 expressions by lucidone may promote the migration/invasion of keratinocytes. Notably, lucidone activated NF-κB signaling via IKK-mediated-IκB degradation, and its inhibition abolished MMP-9 activation and keratinocyte migration. Inhibition of PI3K/AKT signaling impaired the lucidone-induced proliferation/migration with corresponding suppression of ß-catenin/c-Myc/cyclin-D1 and NF-κB/MMP-9 expressions. Results indicate that lucidone-induced PI3K/AKT signaling anchored the ß-catenin/NF-κB-mediated healing mechanism. ß-catenin knockdown substantially diminished lucidone-induced keratinocyte migration. Furthermore, lucidone increased endothelial cell proliferation/migration and triggered angiogenesis (MMP-9/uPA/ICAM-1). In macrophages, lucidone-activated NF-κB-mediated inflammation (COX-2/iNOS/NO) and VEGF, which may contribute to the growth of keratinocytes/fibroblasts and endothelial cells. Punched wounds on mice were rapidly healed with the topical application of lucidone (5mM) compared with control ointment-treated mice. Taken together, lucidone accelerates wound healing through the cooperation of keratinocyte/fibroblast/endothelial cell growth and migration and macrophage inflammation via PI3K/AKT, Wnt/ß-catenin and NF-κB signaling cascade activation.

Lucidone protects human skin keratinocytes against free radical-induced oxidative damage and inflammation through the up-regulation of HO-1/Nrf2 antioxidant genes and down-regulation of NF-κB signaling pathway.

We investigated the protective effects of lucidone, a naturally occurring cyclopentenedione isolated from the fruits of Lindera erythrocarpa Makino, against free-radical and inflammation stimulator 2,2'-azobis (2-amidinopropane) dihydrochloride (AAPH)-induced oxidative stress in human keratinocyte (HaCaT) cells, with the aim of revealing the possible mechanisms underlying the protective efficacy. Lucidone pretreatment (0.5-10 µg/mL) markedly increased HaCaT cell viability and suppressed AAPH-induced reactive oxygen species (ROS) generation, lipid peroxidation, and DNA damage. Notably, the antioxidant potential of lucidone was directly correlated with the increased expression of an antioxidant gene, heme oxygenase 1 (HO-1), which was followed by the augmentation of the nuclear translocation and transcriptional activation of NF-E2-related factor-2 (Nrf2), with or without AAPH. Nrf2 knockdown diminished the protective effects of lucidone. We also observed that lucidone pretreatment inhibited AAPH-induced inflammatory chemokine prostaglandin E2 (PGE2) production and the expression of cyclooxygenase-2 (COX-2) in HaCaT cells. Lucidone treatment also significantly inhibited AAPH-induced nuclear factor-κB (NF-κB) activation and suppressing the degradation of inhibitor-κB (I-κB). Furthermore, lucidone significantly diminished AAPH-induced COX-2 expression through the down-regulation of the extracellular signal-regulated kinase (ERK) and p38 MAPK signaling pathways. Therefore, lucidone may possess antioxidant and anti-inflammatory properties and may be useful for the prevention of free radical-induced skin damage.