Signaling In A549 Cells Research Articles

Interference with Histone Deacetylase 4 Regulates c-Jun N-terminal Kinase/Activating Protein-1 Signaling to Ameliorate Sepsis-induced Alveolar Epithelial Cell Injury.

Sepsis is a syndrome of systemic inflammatory response resulting from infection, which can lead to severe lung injury. Histone deacetylase 4 (HDAC4) is a key protein known to regulate a wide range of cellular processes. This study was designed to investigate the role of HDAC4 in lipopolysaccharide (LPS)-induced alveolar epithelial cell injury as well as to disclose its potential molecular mechanisms. The alveolar epithelial cell injury model was established by inducing A549 cells with LPS. A549 cell viability was detected by cell counting kit-8 assay and the transfection efficiency of small interfering RNA targeting HDAC4 was appraised utilizing Western blot. The levels of inflammatory cytokines and oxidative stress markers were detected using corresponding assay kits. Dichloro-dihydro-fluorescein diacetate assay was used for the measurement of reactive oxygen species (ROS) content. Flow cytometry, 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethyl-benzimidazolyl-carbocyanine iodide-1 staining, adenosine triphosphate (ATP) assay kits, and MitoSOX Red assay kits were employed to estimate cell apoptosis, mitochondrial membrane potential, ATP level, and mitochondrial ROS level, respectively. The oxygen consumption rate of A549 cells was evaluated with XF96 extracellular flux analyzer. Western blot was applied for the evaluation of HDAC4, apoptosis- and c-Jun N-terminal kinase (JNK)/activating protein-1 (AP-1) signaling pathway-related proteins. HDAC4 expression was found to be increased in LPS-induced A549 cells and HDAC4 silence inhibited inflammatory damage, repressed oxidative stress, alleviated cell apoptosis, improved mitochondrial function, and blocked JNK/AP-1 signaling in A549 cells stimulated by LPS, which were all reversed by JNK activator anisomycin. Collectively, the interference with HDAC4 could ameliorate LPS-induced alveolar epithelial cell injury, and such protective effect may be potentially mediated through the JNK/AP-1 signaling pathway.

Ganoderma microsporum immunomodulatory protein combined with KRASG12C inhibitor impedes intracellular AKT/ERK network to suppress lung cancer cells with KRAS mutation

KRAS mutations are tightly associated with lung cancer progression. Despite the unprecedented clinical success of KRASG12C inhibitors, recurrent mechanisms of resistance and other KRAS mutations require further therapeutic approaches. GMI, a protein from the medicinal mushroom Ganoderma microsporum, possesses antitumor activity; whereas, the biological function of GMI on regulating KRAS mutant lung cancer cells remains unknown. Herein, RNA-sequencing and bioinformatics showed that GMI may regulate KRAS-modulated MAPK and PI3K-AKT pathways in A549 (KRASG12S) cells. Further experiments demonstrated that GMI inhibited KRAS activation and suppressed ERK1/2 and AKT signaling in A549 cells. Intriguingly, GMI inhibited AKT signaling but increased phosphorylation of ERK in H358 (KRASG12C) cells. GMI significantly suppressed tumor growth in LLC1 cells-allograft and H358 cells-xenograft mice. GMI showed a synergistic effect with KRASG12C inhibitors in inhibiting cell growth, KRAS activation and KRAS-mediated downstream signaling, leading to apoptosis in H358 cells. Combination of GMI and KRASG12C inhibitor, AMG 510, resulted in more durable inhibition of tumor growth and KRAS activity in H358 cells-xenograft mice. This study highlights the potential of GMI, a dietary fungal protein, as a viable therapeutic avenue for KRAS-mutant lung cancer in combination with KRASG12C inhibitors.

Human metapneumovirus M2-2 protein inhibits RIG-I signaling by preventing TRIM25-mediated RIG-I ubiquitination.

Retinoic acid-inducible gene I (RIG-I) is a receptor that senses viral RNA and interacts with mitochondrial antiviral signaling (MAVS) protein, leading to the production of type I interferons and inflammatory cytokines to establish an antiviral state. This signaling axis is initiated by the K63-linked RIG-I ubiquitination, mediated by E3 ubiquitin ligases such as TRIM25. However, many viruses, including several members of the family Paramyxoviridae and human respiratory syncytial virus (HRSV), a member of the family Pneumoviridae, escape the immune system by targeting RIG-I/TRIM25 signaling. In this study, we screened human metapneumovirus (HMPV) open reading frames (ORFs) for their ability to block RIG-I signaling reconstituted in HEK293T cells by transfection with TRIM25 and RIG-I CARD (an N-terminal CARD domain that is constitutively active in RIG-I signaling). HMPV M2-2 was the most potent inhibitor of RIG-I/TRIM25-mediated interferon (IFN)-β activation. M2-2 silencing induced the activation of transcription factors (IRF and NF-kB) downstream of RIG-I signaling in A549 cells. Moreover, M2-2 inhibited RIG-I ubiquitination and CARD-dependent interactions with MAVS. Immunoprecipitation revealed that M2-2 forms a stable complex with RIG-I CARD/TRIM25 via direct interaction with the SPRY domain of TRIM25. Similarly, HRSV NS1 also formed a stable complex with RIG-I CARD/TRIM25 and inhibited RIG-I ubiquitination. Notably, the inhibitory actions of HMPV M2-2 and HRSV NS1 are similar to those of V proteins of several members of the Paramyxoviridae family. In this study, we have identified a novel mechanism of immune escape by HMPV, similar to that of Pneumoviridae and Paramyxoviridae family members.

Glycitin exerts anticancer effect on human lung cancer cells through induction of apoptosis, cell cycle arrest, and inhibition of PI3K/AKT signal pathway

Purpose: To determine the effect of glycitin on PI3K/AKT signaling, migration, invasion, apoptosis, and cell cycle in A549 lung cancer cells.Methods: 3-[4,5-Dimethylthiazole-2-yl]-2,5-diphenyltetrazolium bromide (MTT) and clonogenic assays were used to determine the proliferation and colony generation potency of A549 cells, respectively, after treatment with glycitin (0 - 120 μM). Apoptosis in A549 cells was measured using DAPI and Annexin V/PI-FITC assays. Cell cycle arrest was assessed byflow cytometry, while the effect of glycitin on migration and invasion of A549 cells was determined by Transwell assay. The effect of glycitin on expressions of proteins associated with PI3K/AKT signaling in A549 cells was measured using western blotting.Results: Glycitin significantly inhibited the proliferation and colony generation potential of A549 cells (p < 0.05). The antiproliferative effects of glycitin on A549 cells were mediated through stimulation of apoptosis and cell cycle arrest at G0/G1-phase. The compound also distorted normal cellular morphology by causing membrane damage and nuclear fragmentation. The proportion of cells in the G0/G1-phase increased after glycitin treatment, when compared to the other two phases, demonstrating cell cycle arrest (p < 0.05). Glycitin suppressed the migration and invasion of A549 cells. However, Western blotting results showed that glycitin down-regulated the expressions of PI3K/AKT signaling proteins in A549 cells (p < 0.05).Conclusion: Glycitin produced significant anticancer effect on A549 cells via enhanced apoptosis, induction of cell cycle arrest, and inhibition of PI3K/AKT signalling. Moreover, it suppressed the migration and invasion of A549 cells. Therefore, glycitin is a potential lead molecule for the development of a therapeutic agent for invasive lung cancer.

Artesunate Suppresses the Growth of Lung Cancer Cells by Downregulating the AKT/Survivin Signaling Pathway.

NSCLC (non-small-cell lung cancer) is the deadliest cancer in the world. Artesunate is one of the most potent and rapidly acting antimalarial agents. Recently, emerging evidence has suggested the anticancer function of artesunate. In our work, we aimed to investigate the molecular mechanism of artesunate-induced growth inhibition in human lung adenocarcinoma cells and reported that the anticancer effects of artesunate is related to its ability in downregulating AKT/Survivin signaling in A549 cells. The effect of artesunate on the proliferation of A549 cells was determined by CCK-8 assay and colony formation assay; its effect on A549 cell apoptosis was evaluated by lactate dehydrogenase (LDH) release assay. The role of artesunate on the activation of AKT/Survivin signaling was analyzed by western blot and quantitative QPCR. Finally, we used two mouse tumor models to investigate the function of artesunate on the in vivo growth of lung cancer cells. Artesunate treatment caused significant growth inhibition and apoptosis in A549 cells. Mechanistically, artesunate downregulated the activation of AKT/Survivin signaling. In agreement, hyperactivation of AKT signaling restored artesunate-induced growth inhibition in A549 cells. In mouse lung cancer models, artesunate administration significantly reduced the growth of A549 cells and LLC cells in nude mice and immunocompetent mice, respectively. Our findings suggest that artesunate serves as a potential tumor suppressor in lung cancer and hopefully can provide new insight into the development of therapeutic strategies in the clinical lung cancer treatment.

13-Methyl-palmatrubine shows an anti-tumor role in non-small cell lung cancer via shifting M2 to M1 polarization of tumor macrophages

BackgroundPrevious studies have substantiated that M2-activated tumor-associated macrophages (M2-TAMs) are involved in multiple malignancies. Presently, we probe the impact and related mechanisms of 13-methyl-palmatrubine (13MP), the Corydalis yanhusuo extract, on M2-TAM-mediated non-small cell lung cancer (NSCLC) development. MethodsIL-4 and IL-13 were adopted to induce M2-TAMs. The polarization state of TAMs was evaluated by quantitative reverse transcription PCR (qRT-PCR), Western blot (WB) and cellular immunofluorescence. NSCLC cells (A549 and NCL-H1975) were co-cultured with the conditioned medium (CM) of M2-TAMs. Followed by 13MP treatment, cell viability, proliferation, invasion, epithelial-mesenchymal transition (EMT), and in-vivo growth of NSCLC cells were determined. Additionally, human umbilical vein endothelial cells (HUVECs) were co-cultured with the CM of M2-TAMs. The tube formation assay was made to test the tube formation capacity of HUVECs, and the expression of MMP3, MMP9, and VEGF was assessed by WB in the co-culture model. Mechanistically, WB was performed to validate the expression of the PI3K/AKT and JAK/STAT3 pathways in NSCLC cells (A549 and NCL-H1975) as well as in endothelial cell lines co-cultured with M2-TAMs. Results13MP inhibited the proliferation, invasion, EMT, growth and enhanced apoptosis of NSCLC cells. 13MP dose-dependently boosted the polarization of TAM from M2 to M1 state. M2-TAMs enhanced the malignant behaviors of NSCLC cells, whereas 13MP hindered M2-TAM-mediated NSCLC cell proliferation and invasion. Meanwhile, 13MP weakened the M2-TAM-mediated angiogenesis. Moreover, 13MP inactivated the PI3K/AKT and JAK/STAT3 signaling in A549 cells, NCL-H1975 cells and HUVECs. Conclusion13MP suppresses TAM-mediated NSCLC progression via transforming the polarization of TAM from M2 to M1.

Diallyl Disulfide Attenuates Ionizing Radiation-Induced Migration and Invasion by Suppressing Nrf2 Signaling in Non-small-Cell Lung Cancer.

Non–small-cell lung cancer (NSCLC) is the leading cause of cancer-associated deaths. Radiotherapy remains the primary treatment method for NSCLC. Despite great advances in radiotherapy techniques and modalities, recurrence and resistance still limit therapeutic success, even low-dose ionizing radiation (IR) can induce the migration and invasion. Diallyl disulfide (DADS), a bioactive component extracted from garlic, exhibits a wide spectrum of biological activities including antitumor effects. However, the effect of DADS on IR-induced migration and invasion remains unclear. The present study reported that IR significantly promoted the migration and invasion of A549 cells. Pretreatment with 40 μM DADS enhanced the radiosensitivity of A549 cells and attenuated IR-induced migration and invasion. In addition, 40 μM DADS inhibited migration-related protein matrix metalloproteinase-2 and 9 (MMP-2/9) expression and suppressed IR-aggravated EMT by the upregulation of the epithelial marker, E-cadherin, and downregulation of the mesenchymal marker, N-cadherin, in A549 cells. Furthermore, DADS was found to inhibit the activation of Nrf2 signaling. Based on our previous results that knockdown of Nrf2 by siRNA suppressed IR-induced migration and invasion in A549 cells, we speculated that DADS attenuated IR-induced migration and invasion by suppressing the activation of Nrf2 signaling in A549 cells.

Resveratrol inhibits MUC5AC expression by regulating SPDEF in lung cancer cells

BackgroundMUC5AC was recently identified to play important roles in the proliferation and metastasis of malignant mucinous lung tumor cells. Resveratrol (Res), a natural compound with anticancer effects in lung cancer cells, has been reported to inhibit mucin production in airway epithelial cells. This study aimed to investigate the inhibitory effect of Res on MUC5AC expression in lung mucinous adenocarcinoma cells and the potential mechanisms. MethodsMucus-producing A549 human lung carcinoma cells were used to test the effects of Res on SPDEF and MUC5AC expression. Gene and protein expression was assessed by real-time quantitative PCR (qPCR), immunofluorescence and western blotting assays. SPDEF lentivirus was used to upregulate SPDEF expression levels in mucus-producing A549 human lung carcinoma cells. Cell proliferation was assessed by Cell Counting Kit-8 (CCK-8) assay. ResultsRes decreased MUC5AC expression in an SPDEF-dependent manner in mucus-producing A549 human lung carcinoma cells, and this change was accompanied by decreased ERK expression and AKT pathway activation. Moreover, SPDEF was found to be overexpressed in lung adenocarcinoma (LUAD), especially in mucinous adenocarcinoma. In-vitro functional assays showed that overexpression of SPDEF reduced the chemosensitivity of A549 cells to cisplatin (DDP). In addition, Res treatment increased A549 cell chemosensitivity to DDP by inhibiting the SPDEF-MUC5AC axis. ConclusionOur results indicate that the SPDEF-MUC5AC axis is associated with DDP sensitivity, and that Res decreases SPDEF and MUC5AC expression by inhibiting ERK and AKT signaling in A549 cells, which provides a potential pharmacotherapy for the prevention and therapeutic management of mucinous adenocarcinoma.

Low Vitamin D Status Is Associated with Inflammation in Patients with Chronic Obstructive Pulmonary Disease.

Vitamin D deficiency is associated with increased risks of chronic obstructive pulmonary disease (COPD). Nevertheless, the mechanisms remain unknown. This study analyzed the correlations between vitamin D levels and inflammation in COPD patients. One hundred and one patients with COPD and 202 control subjects were enrolled. Serum 25(OH)D level and inflammatory cytokines were detected. Serum 25(OH)D was decreased and inflammatory cytokines were increased in COPD patients. According to forced expiratory volume in 1 s, COPD patients were divided into three grades. Furthermore, serum 25(OH)D was gradually decreased in COPD patients ranging from grade 1-2 to 4. Serum 25(OH)D was inversely associated with inflammatory cytokines in COPD patients. Further analysis found that NF-κB and AP-1 signaling were activated in COPD patients. Besides, inflammatory signaling was gradually increased in parallel with the severity of COPD. By contrast, pulmonary nuclear vitamin D receptor was decreased in COPD patients. In vitro experiments showed that 1,25(OH)2D3 inhibited LPS-activated inflammatory signaling in A549 cells (human lung adenocarcinoma cell). Mechanically, 1,25(OH)2D3 reinforced physical interactions between vitamin D receptor with NF-κB p65 and c-Jun. Our results indicate that vitamin D is inversely correlated with inflammatory signaling in COPD patients. Inflammation may be a vital mediator of COPD progress in patients with low vitamin D levels.

Micropillar-arrayed surfaces promote transforming growth factor beta 1 induced epithelial to mesenchymal transition by focal adhesion kinase-related signaling in A549 cells.

Micropillar-arrayed surfaces promote transforming growth factor beta 1 induced epithelial to mesenchymal transition by focal adhesion kinase-related signaling in A549 cells.

NLRP3 upregulation in A549 cells co-cultured with THP-1 macrophages under hypoxia via deregulated TGF-β signaling

NOD-like receptor family, pyrin domain-containing 3 (NLRP3) is one of the key components of the inflammasome. NLRP3 also participates in the regulation of fibrosis independent of the inflammasome. In this study, we analyzed the mechanism of upregulation of NLRP3 expression in A549 cells co-cultured with THP-1 macrophages under hypoxia. Upregulation of NLRP3 was suppressed after treatment with inhibitors of TGF-β receptor or p38, but not with inhibitors of the IL-1 receptor and SMAD3. The analysis of downstream molecules of TGF-β signaling in A549 cells co-cultured with THP-1 macrophages under hypoxia showed that TGFBR1 was upregulated and SMAD7 was downregulated.Taken together, these results suggest that the upregulation of NLRP3 in A549 cells is associated with deregulated TGF-β signaling and that the interaction between NLRP3 and TGF-β signaling plays a fundamental role in fibrogenesis.

Quercetin and chrysin inhibit nickel-induced invasion and migration by downregulation of TLR4/NF-κB signaling in A549 cells

Nickel exposure promotes the invasive potential of human lung cancer cells. Polyphenols such as quercetin, curcumin, chrysin, apigenin, and luteolin, present in many plant foods may suppress the development of cancers. However, whether these compounds inhibit the promoting effects of Nickel on cancer cell invasion and migration as well as the possible mechanisms are unclear. In the present study, we first showed that quercetin, curcumin, chrysin, apigenin, and luteolin at 5 μM, significantly suppressed the promoting effects of NiCl2 (Ni) on migration and invasion in H1975 and A549 human lung cancer cells. The five phytochemicals also significantly suppressed the secretion of cytokines, IL-1β, IL-6, TNF-α and IL-10, induced by Ni in A549 cells. The overall efficiency of quercetin was the best, followed by chrysin and the other compounds. Furthermore, we found that quercetin and chrysin suppressed the mRNA and protein expression of TLR4 and Myd88. Consistently, quercetin and chrysin also decreased the phosphorylation of IKKβ and IκB, the nuclear level of p65 (NF-κB) as well as the expression of MMP-9 in A549 cells exposed to Ni. In conclusion, these results suggest the potential preventive effects of the five phytochemicals on the promoting effect of Ni on human lung cancer cell invasion. In addition, the preventive effects are associated with downregulation of the TLR4/NF-κB signaling pathway, especially for quercetin and chrysin.

Rosiglitazone inhibits PM2.5-induced cytotoxicity in human lung epithelial A549 cells.

Exposure to fine particulate matter <2.5 µm in diameter (PM2.5) leads to global adverse health effects, including increases in morbidity and mortality of respiratory diseases. PM2.5 increases production of reactive oxygen species (ROS) in the lung, which further lead to oxidative stress, cell apoptosis and cell death. According to results of previous studies, oxidative stress and subsequent cell apoptosis can be reduced by peroxisome proliferator-activated receptor gamma (PPARγ) in various cell types, however, its role in oxidative stress-related cell apoptosis caused by PM2.5 in respiratory systems is unclear. Human lung alveolar epithelial A549 cells were exposed to PM2.5 with or without rosiglitazone (an agonist of PPARγ) treatment. Cellular apoptosis and intracellular oxidative stress were determined by flow cytometry based on FITC Annexin V and DCFH-DA fluorescence, respectively. Western blot was conducted to determine the expression of Bax, Bcl2, PPARγ, P-ERK1/2, ERK1/2, P-STAT3, and STAT3. PPARγ was downregulated in PM2.5-treated A549 cells, and application of rosiglitazone reduced PM2.5-mediated ROS generation and cell apoptosis. In addition, our results indicated that rosiglitazone treatment suppressed PM2.5-induced ERK1/2 and STAT3 activation. Collectively, these data suggested that rosiglitazone protects against PM2.5-induced ROS production and cell apoptosis and represses activation of ERK1/2 and STAT3 signaling in A549 cells. Our results indicated that rosiglitazone is a potential therapeutic agent for PM2.5-induced lung diseases.

Abstract 4665: Induction of receptor tyrosine kinase signaling by sera from patients with lung adenocarcinoma

Abstract Background: The objective of this study was to evaluate disease stage-associated differences in receptor tyrosine kinase (RTK) signaling in A549 cells using pretreatment sera from cases of pathologically-confirmed lung adenocarcinoma or control cases derived from a lung cancer screening study. This was accomplished as a means to explore the hypothesis that circulating concentrations of decoy receptors and/or ligands, as well as disease-specific ligand degradation all regulate RTK signaling in vivo. Methods: Pretreatment peripheral blood were prepared from either from non-cancer control patients (n=30) or those with lung adenocarcinoma, consisting of stage I (T1-2N0M0, n=25); locoregionally progressed (T1-2N1-2M0, n=36) or disseminated, stage IV disease (n=43). All patients were enrolled with written informed consent to our IRB-approved, institutional biorepository. Confluent cultures of A549 cells were stimulated for 10 minutes with patient sera diluted 1:1 in RPMI-1640 followed by immediate whole cell lysate preparation. After protein determinations by BCA, 8.5 µg of each sample was interrogated using the Human RTK (phosphoprotein) kit from MilliporeSigma according to manufacturer’s instructions. After being normalized to the kit-supplied (stimulated) HeLa cell lysates, all resulting data were evaluated by one-way ANOVA (LSD and Tukey post-hoc) for categorical comparisons. Results: The most commonly observed differences in RTK signaling was noted upon comparing cohorts with locoregional (T1-2N1-2M0) progression and disseminated (stage IV) disease. Levels of in c-Met and insulin receptor (IR) signaling were higher in patients with stage IV disease relative to those with locoregional disease by 24% and 10%, respectively (both p&amp;lt;0.01); whereas induction of c-Kit, VEGFR3, and Tie-1 were reduced by 12.8%, 6.67%, and 17.3%, respectively (all p&amp;lt;0.05). Circulating levels of HGF were previously observed by our group to be 25% higher in stage IV patients relative to those with locoregional progression (p=0.005) - agreeing with our observation in direction of change, though not scale. This is in contrast to levels of VEGF-C and VEGF-D previously being observed elevated 51% and 452% (both p&amp;lt;0.001) in these same cohorts. Also of note was the 1.9 fold decrease in ability of sera from stage I patients to stimulate IGF-1R signaling relative to control patients (p=0.002). We have previously reported a 12% increase in IGF-1 levels between these groups (p=0.002), though we observed no changes in IGF binding proteins that could account for the observed differences in IGF-1R signaling. Conclusions: We observed an apparent discoupling of certain circulating ligands in patient sera to stimulate their respective RTKs in a disease stage-specific manner. We are currently evaluating levels of circulating ligands, potential disease stage-associated (partial) proteolytic degradation, and decoy receptors to help explain these observations. Citation Format: Gabriela C. Lobato, Jared D. Fialkoff, Imad Tarhoni, Nicholas Lund, Vineela Chukkapalli, Selina Sayidine, Cristina L. Fhied, Sanjib Basu, Wen-Rong Lie, Michael J. Liptay, Philip Bonomi, Jeffrey A. Borgia. Induction of receptor tyrosine kinase signaling by sera from patients with lung adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4665. doi:10.1158/1538-7445.AM2017-4665

Emodin Inhibits ATP-Induced Proliferation and Migration by Suppressing P2Y Receptors in Human Lung Adenocarcinoma Cells

Background/Aims: Extracellular ATP performs multiple important functions via activation of P2 receptors on the cell surface. P2Y receptors play critical roles in ATP evoked response in human lung adenocarcinoma cells (A549 cells). Emodin is an anthraquinone derivative originally isolated from Chinese rhubarb, possesses anticancer properties. In this study we examined the inhibiting effects of emodin on proliferation, migration and epithelial-mesenchymal transition (EMT) by suppressing P2Y receptors-dependent Ca²⁺ increase and nuclear factor-κB (NF-KB) signaling in A549 cells. Methods: A549 cells were pretreated with emodin before stimulation with ATP for the indicated time. Then, intracellular Ca²⁺ concentration ([Ca²⁺]_i) was measured by Fluo-8/AM staining. Cell proliferation and cell cycle progression were tested by CCK8 assay and flow cytometry In addition, wound healing and western blot were performed to determine cell migration and related protein levels (Bcl-2, Bax, claudin-1, NF-κB). Results: Emodin blunted ATP/UTP-induced increase of [Ca²⁺]_i and cell proliferation concentration-dependently Meanwhile, it decreased ATP-induced cells accumulation in the S phase. Furthermore, emodin altered protein abundance of Bcl-2, Bax and claudin-1 and attenuated EMT caused by ATP. Such ATP-induced cellular reactions were also inhibited by a nonselective P2Y receptors antagonist, suramin, in a similar way to emodin. Besides, emodin could inhibit activation of NF-κB, thus suppressed ATP-induced proliferation, migration and EMT. Conclusion: Our results demonstrated that emodin inhibits ATP-induced proliferation, migration, EMT by suppressing P2Y receptors-mediated [Ca²⁺]_i increase and NF-κB signaling in A549 cells.

Death-associated protein kinase 3 controls the tumor progression of A549 cells through ERK MAPK/c-Myc signaling

Death-associated protein kinases (DAPKs) are members of the serine/threonine protein kinase family, which regulate cell death. Although DAPK3 has been implicated as a tumor suppressor, a recent study revealed an oncogenic role of DAPK3. However, the role of DAPK3 in non-small cell lung cancer (NSCLC) remains unclear. Therefore, we examined whether DAPK3 controls the progression of NSCLC using the NSCLC cell line, A549. We generated A549 cells stably expressing small hairpin RNA (shRNA) targeting DAPK3. In the A549 cells, the protein level of DAPK3 was decreased and the cell proliferation was inhibited. DAPK3 knockdown caused G1/G0 cell cycle arrest as assessed by flow cytometric assay and reduced cyclinD1 expression in A549 cells. Phosphorylation of ERK and c-Myc, but not Akt and JNK, was inhibited by DAPK3 knockdown. Cell migration and invasion were also inhibited by DAPK3 knockdown as determined by a Boyden chamber assay and an invasion assay, respectively. Moreover, DAPK3 knockdown inhibited anchorage-independent cell growth as determined by soft-agar colony formation assay. In a mouse xenograft model, tumors derived from DAPK3-knockdown cells exhibited reduced tumor growth. The present results demonstrated for the first time that DAPK3 controls proliferation, migration, invasion, soft‑agar colony formation and tumor growth through activation of ERK/c-Myc signaling in A549 cells. These findings indicate that DAPK3 may be a novel target for the treatment of NSCLC.

Protocatechuic acid methyl ester ameliorates fluoride toxicity in A549 cells

The present study is aimed to determine the potential benefits of protocatechuic acid methyl ester (PCAME) against fluoride (F−) induced lung toxicity using A549 cells. The cells were treated with sodium fluoride (NaF) alone and in combination with PCAME for different time points (0–24 h) and evaluated for intracellular reactive oxygen species (ROS) production, F− content, oxidative stress markers, apoptosis and mRNA expression of redox signaling and inflammatory genes. The results shown that PCAME alleviates the toxic effects of F−via modulating its bioavailability, intracellular calcium level, mitochondrial membrane integrity and redox signaling in A549 cells. F− induced changes in ROS generation, oxidative stress markers, TUNEL positive cells and mRNA levels of inflammatory genes were further normalized by PCAME. Taken together, these findings revealed that PCAME effectively attenuated the F− induced changes in oxidative stress, inflammation and apoptosis markers by reducing its cellular content, ROS generation and biochemical and molecular changes. Thus PCAME can be used as a nutraceutical agent for F− toxicity.

De-novo NAD+ synthesis regulates SIRT1-FOXO1 apoptotic pathway in response to NQO1 substrates in lung cancer cells.

Tryptophan metabolism is essential in diverse kinds of tumors via regulating tumor immunology. However, the direct role of tryptophan metabolism and its signaling pathway in cancer cells remain largely elusive. Here, we establish a mechanistic link from L-type amino acid transporter 1 (LAT1) mediated transport of tryptophan and the subsequent de-novo NAD+ synthesis to SIRT1-FOXO1 regulated apoptotic signaling in A549 cells in response to NQO1 activation. In response to NQO1 activation, SIRT1 is repressed leading to the increased cellular accumulation of acetylated FOXO1 that transcriptionally activates apoptotic signaling. Decreased uptake of tryptophan due to the downregulation of LAT1 coordinates with PARP-1 hyperactivation to induce rapid depletion of NAD+ pool. Particularly, the LAT1-NAD+-SIRT1 signaling is activated in tumor tissues of patients with non-small cell lung cancer. Because NQO1 activation is characterized with oxidative challenge induced DNA damage, these results suggest that LAT1 and de-novo NAD+ synthesis in NSCLC cells may play essential roles in sensing excessive oxidative stress.

Resveratrol-loaded Nanoparticles Induce Antioxidant Activity against Oxidative Stress.

Resveratrol acts as a free radical scavenger and a potent antioxidant in the inhibition of numerous reactive oxygen species (ROS). The function of resveratrol and resveratrol-loaded nanoparticles in protecting human lung cancer cells (A549) against hydrogen peroxide was investigated in this study. The 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid (ABTS) assay was performed to evaluate the antioxidant properties. Resveratrol had substantially high antioxidant capacity (trolox equivalent antioxidant capacity value) compared to trolox and vitamin E since the concentration of resveratrol was more than 50 μM. Nanoparticles prepared from β-lactoglobulin (β-lg) were successfully developed. The β-lg nanoparticle showed 60 to 146 nm diameter in size with negatively charged surface. Non-cytotoxicity was observed in Caco-2 cells treated with β-lg nanoparticles. Fluorescein isothiocynate-conjugated β-lg nanoparticles were identified into the cell membrane of Caco-2 cells, indicating that nanoparticles can be used as a delivery system. Hydrogen peroxide caused accumulation of ROS in a dose- and time-dependent manner. Resveratrol-loaded nanoparticles restored H2O2-induced ROS levels by induction of cellular uptake of resveratrol in A549 cells. Furthermore, resveratrol activated nuclear factor erythroid 2-related factor 2-Kelch ECH associating protein 1 (Nrf2-Keap1) signaling in A549 cells, thereby accumulation of Nrf2 abundance, as demonstrated by western blotting approach. Overall, these results may have implications for improvement of oxidative stress in treatment with nanoparticles as a biodegradable and non-toxic delivery carrier of bioactive compounds.

MicroRNA-381 Negatively Regulates TLR4 Signaling in A549 Cells in Response to LPS Stimulation.

It is widely reported that miR-381 is dysregulated in various tumors. However, the specific role of miR-381 in respiratory infections has not been reported. To probe this role, A549 cells were pretreated with 1 μg/mL LPS for 24 h. The level of miR-381 was detected using RT-qPCR. The expression of proinflammatory cytokines was determined using an ELISA kit and western blotting. Bioinformatics analysis was used to predict the target genes of miR-381, and a luciferase reporter assay was used to validate the expression of the target genes. miR-381 expression was increased in A549 cells treated with LPS, which is a ligand of TLRs. Further study revealed that the overexpression of miR-381 increased the activity of NF-κB signaling, thereby increasing the expression of IL-6, TNFα, and COX-2. Further study revealed that IκBα was a target gene of miR-381. The upregulation of miR-381 under LPS stimulation contributes to respiratory infections mainly by targeting IκBα.