Limonene protects human skin keratinocytes against UVB-induced photodamage and photoaging by activating the Nrf2-dependent antioxidant defense system

Long term exposure to solar ultraviolet B (UVB) radiation is one of the primary factors of premature skin aging and is referred to as photoaging. Also, mammalian skin exposed to UVB triggers an increase in production of α-melanocyte-stimulating hormone (α-MSH), which is critically involved in the pathogenesis of hyperpigmentary skin diseases. This study investigated the protective effect of limonene on UVB-induced photodamage and photoaging in immortalized human skin keratinocytes (HaCaT) in vitro. Initially, we determined cell viability and levels of reactive oxygen species (ROS) in UVB-irradiated HaCaT cells. Pretreatment with limonene increased cell viability followed by inhibition of intracellular ROS generation in UVB-irradiated HaCaT cells. Interestingly, the antioxidative activity of limonene was directly correlated with an increase in expression of endogenous antioxidants, including heme oxygenase 1 (HO-1), NAD(P)H:quinone oxidoreductase 1 (NQO-1), and γ-glutamylcysteine synthetase (γ-GCLC), which was associated with enhanced nuclear translocation and activation of NF-E2-related factor-2 (Nrf2). Indeed, Nrf2 knockdown reduced limonene's protective effects. Additionally, we observed that limonene treatment inhibited UVB-induced α-MSH secretion followed by inhibition of proopiomelanocortin (POMC) via suppression of p53 transcriptional activation. Moreover, limonene prevented UVB-mediated depletion of tight junction regulatory proteins, including occludin and zonula occludens-1. On the other hand, limonene treatment significantly decreased matrix metalloproteinase-2 levels in UVB-irradiated HaCaT cells. Based on these results, limonene may have a dermato-protective effect in skin cells by activating the Nrf2-dependent cellular antioxidant defense system.

Antcins from Antrodia cinnamomea and Antrodia salmonea Inhibit Angiotensin-Converting Enzyme 2 (ACE2) in Epithelial Cells: Can Be Potential Candidates for the Development of SARS-CoV-2 Prophylactic Agents

Antcins are newly identified steroid-like compounds from Taiwan's endemic medicinal mushrooms Antrodia cinnamomea and Antrodia salmonea. Scientific studies of the past two decades confirmed that antcins have various pharmacological activities, including potent anti-oxidant and anti-inflammatory effects. The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) caused the coronavirus disease-2019 (COVID-19) pandemic and is characterized as a significant threat to global public health. It was recently identified that SARS-CoV-2 required angiotensin converting enzyme 2 (ACE2), a receptor which supports host cell entry and disease onset. Here, we report a novel function of antcins, in which antcins exhibit inhibitory effects on ACE2. Compared to the untreated control group, treatment with various antcins (antcin-A, antcin-B, antcin-C, antcin-H, antcin-I, and antcin-M) significantly inhibited ACE2 activity in cultured human epithelial cells. Indeed, among the investigated antcins, antcin-A, antcin-B, antcin-C, and antcin-I showed a pronounceable inhibition against ACE2. These findings suggest that antcins could be novel anti-ACE2 agents to prevent SARS-CoV-2 host cell entry and the following disease onset.

Geranium and Lemon Essential Oils and Their Active Compounds Downregulate Angiotensin-Converting Enzyme 2 (ACE2), a SARS-CoV-2 Spike Receptor-Binding Domain, in Epithelial Cells

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), also known as coronavirus disease-2019 (COVID-19), is a pandemic disease that has been declared as modern history’s gravest health emergency worldwide. Until now, no precise treatment modality has been developed. The angiotensin-converting enzyme 2 (ACE2) receptor, a host cell receptor, has been found to play a crucial role in virus cell entry; therefore, ACE2 blockers can be a potential target for anti-viral intervention. In this study, we evaluated the ACE2 inhibitory effects of 10 essential oils. Among them, geranium and lemon oils displayed significant ACE2 inhibitory effects in epithelial cells. In addition, immunoblotting and qPCR analysis also confirmed that geranium and lemon oils possess potent ACE2 inhibitory effects. Furthermore, the gas chromatography-mass spectrometry (GC–MS) analysis displayed 22 compounds in geranium oil and 9 compounds in lemon oil. Citronellol, geraniol, and neryl acetate were the major compounds of geranium oil and limonene that represented major compound of lemon oil. Next, we found that treatment with citronellol and limonene significantly downregulated ACE2 expression in epithelial cells. The results suggest that geranium and lemon essential oils and their derivative compounds are valuable natural anti-viral agents that may contribute to the prevention of the invasion of SARS-CoV-2/COVID-19 into the human body.

MicroRNA-708 activation by glucocorticoid receptor agonists regulate breast cancer tumorigenesis and metastasis via downregulation of NF-κB signaling

Therapeutic administration of glucocorticoids (GCs) is frequently used as add-on chemotherapy for palliative purposes during breast cancer treatment. Recent studies have shown that GC treatment induces microRNA-708 in ovarian cancer cells, resulting in impaired tumor cell proliferation and metastasis. However, the regulatory functions of GCs on miR-708 and its downstream target genes in human breast cancer cells (BCCs) are poorly understood. In this study, we found that treatment with either the synthetic GC dexamethasone (DEX) or the natural GC mimic, antcin A (ATA) significantly increased miR-708 expression by transactivation of glucocorticoid receptor alpha (GRα) in MCF-7 and MDA-MB-231 human BCCs. Induction of miR-708 by GR agonists resulted in inhibition of cell proliferation, cell-cycle progression, cancer stem cell (CSC)-like phenotype and metastasis of BCCs. In addition, GR agonist treatment or miR-708 mimic transfection remarkably inhibited IKKβ expression and suppressed nuclear factor-kappaB (NF-κB) activity and its downstream target genes, including COX-2, cMYC, cyclin D1, Matrix metalloproteinase (MMP)-2, MMP-9, CD24, CD44 and increased p21CIP1 and p27KIP1 that are known to be involved in proliferation, cell-cycle progression, metastasis and CSC marker protein. BCCs xenograft models indicate that treatment with GR agonists significantly reduced tumor growth, weight and volume. Overall, our data strongly suggest that GR agonists induced miR-708 and downstream suppression of NF-κB signaling, which may be applicable as a novel therapeutic intervention in breast cancer treatment.

Antcin-A Modulates Epithelial-to-Mesenchymal Transition and Inhibits Migratory and Invasive Potentials of Human Breast Cancer Cells via p53-Mediated miR-200c Activation

Antcin-A (ATA) is a steroid-like phytochemical isolated from the fruiting bodies of a precious edible mushroom Antrodia cinnamomea. We previously showed that ATA has strong anti-inflammatory and anti-tumor effects; however, other possible bioactivities of this unique compound remain unexplored. In the present study, we aimed to investigate the modulation of epithelial-to-mesenchymal transition (EMT), anti-migration, and anti-invasive potential of ATA against human breast cancer cells in vitro. Human breast cancer cell lines, MCF-7 and MDA-MB-231, were incubated with ATA for 24 h. Wound healing, trans-well invasion, western blot, q-PCR, F-actin staining, and immunofluorescence assays were performed. We found that treatment with ATA significantly blocked EMT processes, as evidenced by upregulation of epithelial markers (E-cadherin and occludin) and downregulation of mesenchymal markers (N-cadherin and vimentin) via suppression of their transcriptional repressor ZEB1. Next, we found that ATA could induce miR-200c, which is a known player of ZEB1 repression. Further investigations revealed that ATA-mediated induction of miR-200c is associated with transcriptional activation of p53, as confirmed by the fact that ATA failed to induce miR-200c or suppress ZEB1 activity in p53 inhibited cells. Further in vitro wound healing and trans-well invasion assays support that ATA could inhibit migratory and invasive potentials of breast cancer cells, and the effect was likely associated with induced phenotypic modulation. Taken together, the present study suggests that antcin-A could be a lead phyto-agent for the development of anti-metastatic drug for breast cancer treatment.

Antrodin C inhibits epithelial-to-mesenchymal transition and metastasis of breast cancer cells via suppression of Smad2/3 and β-catenin signaling pathways

Epithelial-to-mesenchymal transition (EMT) is a crucial event involved metastasis of certain tumors. Thus, identifying chemical agents that can block EMT is highly warranted for the development of anti-cancer chemoprevention/chemotherapies. In this study, we found that Antrodin C (ADC), a maleimide derivative isolated from Antrodia cinnamomea health food product inhibits TGF-β1-induced EMT and breast cancer cell metastasis in vitro. Pretreatment of MCF-7 cells with ADC significantly blocked TGF-β1-induced phenotypic changes and actin cytoskeleton remodeling. In addition, ADC was able to up-regulate epithelial markers such as E-cadherin and occludin, whereas mesenchymal markers including N-cadherin and vimentin were significantly inhibited, possibly through the modulation of transcriptional regulators Smad/Smad3. ADC blocked TGF-β1-induced migration and invasion of MCF-7 cells through the down-regulation of matrix-metalloproteinases (MMP-2, -9) and urokinase plasminogen activator (uPA). The inhibition of MMPs and uPA activity by ADC was reasoned by suppression of its corresponding transcription factor β-catenin. Taken together, our data suggested that ADC attenuates the TGF-β1-induced EMT, migration and invasion of human breast carcinoma through the suppression of Smad2/3 and β-catenin signaling pathways.

Antcin C from Antrodia cinnamomea Protects Liver Cells Against Free Radical-Induced Oxidative Stress and Apoptosis In Vitro and In Vivo through Nrf2-Dependent Mechanism

In this study, we investigated the cytoprotective effects of antcin C, a steroid-like compound isolated from Antrodia cinnamaomea against AAPH-induced oxidative stress and apoptosis in human hepatic HepG2 cells. Pretreatment with antcin C significantly protects hepatic cells from AAPH-induced cell death through the inhibition of ROS generation. Furthermore, AAPH-induced lipid peroxidation, ALT/AST secretion and GSH depletion was significantly inhibited by antcin C. The antioxidant potential of antcin C was correlated with induction of antioxidant genes including, HO-1, NQO-1, γ -GCLC, and SOD via transcriptional activation of Nrf2. The Nrf2 activation by antcin C is mediated by JNK1/2 and PI3K activation, whereas pharmacologic inhibition of JNK1/2 and PI3K abolished antcin C-induced Nrf2 activity. In addition, AAPH-induced apoptosis was significantly inhibited by antcin C through the down-regulation of pro-apoptotic factors including, Bax, cytochrome c, capase 9, -4, -12, -3, and PARP. In vivo studies also show that antcin C significantly protected mice liver from AAPH-induced hepatic injury as evidenced by reduction in hepatic enzymes in circulation. Further, immunocytochemistry analyses showed that antcin C significantly increased HO-1 and Nrf2 expression in mice liver tissues. These results strongly suggest that antcin C could protect liver cells from oxidative stress and cell death via Nrf2/ARE activation.

In vitro and in vivo studies disclosed the depigmenting effects of gallic acid: a novel skin lightening agent for hyperpigmentary skin diseases

Gallic acid (GA) is a phenolic compound, which has been reported to suppress melanogenesis in melanoma cells. However, the molecular mechanism underlying this inhibitory effect was poorly understood. In this article, we revealed that GA down-regulated melanogenic regulatory genes including tyrosinase, tyrosinase related protein-1 (TRP-1), and dopachrome tatamerase (Dct) expression at transcriptional and translational level. In addition, GA effectively suppressed the microphthalmia-associated transcription factor (MITF) expression by down-regulating the cAMP-mediated PKA/CREB signaling cascades. To delineate the inhibition of MITF by GA, the activation of extracellular signal-regulated protein kinase (ERK) and AKT was investigated. GA caused significant increase of ERK and AKT phosphorylation, while ERK (PD98059) or AKT (LY294002) inhibitor prevents their phosphorylation and increased melanin biosynthesis. In addition, pre-treatment of MITF-siRNA significantly reduced melanin production from 100 to 40%, and even decreased into 10% by combination treatment with GA. Furthermore, UVB-induced hyperpigmentation in the mice skin was significantly rescued by topical application of GA for 4 weeks. Immunohistochemical analyses also confirmed that GA significantly inhibited melanin production followed by the down-regulation of MITF, tyrosinase and their regulatory proteins. In addition, when compared with control zebrafish, GA caused a remarkable inhibition on the endogenous pigmentation in the zebrafish. Results presented in this study strongly suggest that GA is an effective de-pigmenting or skin lightening cosmetics for topical application.

Hepatoprotective effect of lucidone against alcohol-induced oxidative stress in human hepatic HepG2 cells through the up-regulation of HO-1/Nrf-2 antioxidant genes

Lucidone was previously reported to exhibit anti-inflammatory activity in vitro and in vivo. In the present study, we characterized the mechanisms underlying the hepatoprotective effect of lucidone against alcohol-induced oxidative stress in vitro. Human hepatoma (HepG2) cells were pretreated with lucidone (1-10μg/mL) and then hepatotoxicity was stimulated by the addition ethanol (100mM). With response to ethanol-challenge, increased amount of alanine aminotransferase (ALT) and aspirate aminotransferase (AST) release were observed, whereas lucidone pretreatment significantly inhibited the leakage of AST and ALT in HepG2 cells without appreciable cytotoxic effects. We also found that lucidone pretreatment significantly decreased ethanol-induced nitric oxide (NO), tumor necrosis factor-α (TNF-α), malondialdehyde (MDA), reactive oxygen species (ROS) and glutathione (GSH) depletion in HepG2 cells. Furthermore, Western blot and quantitative-PCR analyses showed that ethanol-exposure apparently down-regulated endogenous anti-oxidant hemoxygenase-1 (HO-1) expression, whereas pretreatment with lucidone significantly up-regulates HO-1 expression followed by the transcriptional activation of NF-E2 related factor-2 (Nrf-2). Interestingly, the profound up-regulation of HO-1 and Nrf-2 were observed in only ethanol-challenged cells, which evidenced that lucidone-induced induction of HO-/Nrf-2 were specific with oxidative stress. Thus, we concluded that lucidone-mediated up-regulation of phase-II enzymes and HO-1 via Nrf-2 signaling pathway may provide a pivotal mechanism for its hepatoprotective action.