Repeated radon exposure induced ATM kinase-mediated DNA damage response and protective autophagy in mice and human bronchial epithelial cells.

OBJECTIVE: Radon ( 222 Rn) is a naturally occurring radioactive gas that has been closely linked with the development of lung cancer. In this study, we investigated the radon-induced DNA strand breaks, a critical event in lung carcinogenesis, and the corresponding DNA damage response (DDR) in mice and human bronchial epithelial (BEAS-2B) cells. METHODS: Biomarkers of DNA double-strand breaks (DSBs), DNA repair response to DSBs, ataxia-telangiectasia mutated (ATM) kinase, autophagy, and a cell apoptosis signaling pathway as well as cell-cycle arrest and the rate of apoptosis were determined in mouse lung and BEAS-2B cells after radon exposure. RESULTS: Repeated radon exposure induced DSBs indicated by the increasing expressions of γ-Histone 2AX (H2AX) protein and H2AX gene in a time and dose-dependent manner. Additionally, a panel of ATM-dependent repair cascades [i.e. non-homologous DNA end joining (NHEJ), cell-cycle arrest and the p38 mitogen activated protein kinase (p38MAPK)/Bax apoptosis signaling pathway] as well as the autophagy process were activated. Inhibition of autophagy by 3-methyladenine pre-treatment partially reversed the expression of NHEJ-related genes induced by radon exposure in BEAS-2B cells. CONCLUSIONS: The findings demonstrated that long-term exposure to radon gas induced DNA lesions in the form of DSBs and a series of ATM-dependent DDR pathways. Activation of the ATM-mediated autophagy may provide a protective and pro-survival effect on radon-induced DSBs.

Hepatotoxicity induced in rats by chronic exposure to F-53B, an emerging replacement of perfluorooctane sulfonate (PFOS).

A plethora of studies have shown the prominent hepatotoxicity caused by perfluorooctane sulfonate (PFOS), yet the research on the causality of F-53 B (an alternative for PFOS) exposure and liver toxicity, especially in mammals, is largely limited. To investigate the effects that chronic exposure to F-53 B exert on livers, in the present study, male SD rats were administrated with F-53 B in a certain dose range (0, 1, 10, 100, 1000 µg/L, eight rats per group) for 6 months via drinking water and the hepatotoxicity resulted in was explored. We reported that chronic exposure to 100 and 1000 µg/L F-53 B induced remarkable histopathological changes in liver tissues such as distinct swollen cells and portal vein congestion. In addition, the increase of cytokines IL-6, IL-2, and IL-8 upon long-term administration of F-53 B demonstrated the high level of inflammation. Moreover, F-53 B exposure was revealed to disrupt the lipid metabolism in the rat livers, mainly manifesting as the upregulation of some proteins involved in lipid synthesis and degradation, including ACC, FASN, SREBP-1c as well as ACOX1. These findings provided new evidence for the adverse effects caused by chronic exposure to F-53 B in rodents. It is crucial for industries, regulatory agencies as well as the public to remain vigilant about the adverse health effects associated with the emerging PFOS substitutes such as F-53 B. Implementation of regular monitoring and risk assessments is of great importance to alleviate environmental concerns towards PFOS alternatives exposure, and furthermore, to minimize the latent health risks to the public health.

Repeated radon exposure induced epithelial-mesenchymal transition-like transformation via disruption of p53-dependent mitochondrial function.

Backgrouds: As a human carcinogen, radon and its progeny are the second most important risk factor for lung cancer after smoking. The tumor suppressor gene, p53, is reported to play an important role in the maintenance of mitochondrial function. In this work, we investigated the association between p53 and p53-responsive signaling pathways and radon-induced carcinogenesis. Methods: After repeated radon exposure, the malignant characteristics, cell cycle arrest, cell apoptotic rate, adenosine triphosphate (ATP) content, reactive oxygen species (ROS) level, mitochondrial DNA (mtDNA) copy number as well as indicative biomarkers involved in mitochondrial energy metabolism were evaluated in BEAS-2B cells or BALB-c mouse lung tissue. Results: Radon exposure induced epithelial-mesenchymal transition (EMT)-like transformation in BEAS-2B cells, as indicated by increased cell proliferation and migration. Additional mitochondrial alterations, including decreased ATP content, increased ROS levels, mtDNA copy numbers, cell apoptosis, and G2/M cell cycle arrest were observed. Radon exposure caused an energy generation shift from aerobic respiration to glycolysis as reflected by increased expression of TIGAR and p53R2 proteins and decreased expression of SCO2 protein in BEAS-2B cells, and increased expression of p53, SCO2 and TIGAR proteins in mouse lung tissue, respectively. The effects of p53 deficiency on the prevention of mitochondrial dysfunction suggested a protective role of p53 in radon-induced malignant-like features in BEAS-2B cells. Conclusions: Repeated radon exposure induced EMT-like transformation in BEAS-2B cells via disruption of mitochondrial function. Activation of p53 and p53-responsive signaling pathways in BEAS-2B cells and BALB-c mice may confer a protective mechanism for radon-induced lung injury.

Silver Nanoparticles Induce a Size-dependent Neurotoxicity to SH-SY5Y Neuroblastoma Cells via Ferritinophagy-mediated Oxidative Stress.

Silver nanoparticles (AgNPs) are widely used in a variety of consumer products because of their antibacterial and antifungal characteristics, but little is known about their toxicity to the brain. In this study, we investigated AgNP-induced neurotoxicity using the human neuroblastoma cancer (SH-SY5Y) cell line. After a 24 h treatment of AgNPs with two primary sizes (5 and 50 nm labeled as Ag-5 and Ag-50, respectively), a series of toxicological endpoints including cell viability, expression of proteins and genes in amyloid precursor protein (APP) amyloid hydrolysis process and ferritinophagy signaling pathways, oxidative stress, intracellular iron levels, and molecular regulators of iron metabolism were evaluated. Our results showed that both Ag-5 and Ag-50 induced notable neurotoxic effects on SH-SY5Y cells indicated by cell proliferation inhibition, increased BACE1 protein expression, and decreased APP and ADAM10 gene expression. Activation of nuclear receptor coactivator 4-mediated ferritinophagy and blockade of autophagic flux were induced by AgNPs, accompanied by intracellular iron accumulation and overexpression of divalent metal-ion transporter-1 and ferroportin1 in SH-SY5Y cells. In addition, AgNPs significantly decreased glutathione peroxidase 4 protein expression but increased malondialdehyde concentration, suggesting that AgNP-induced iron accumulation may trigger oxidative stress by disruption of the intracellular oxidant and antioxidant systems. In addition, compared with Ag-50, Ag-5 with higher cellular uptake efficiency caused more detrimental effects on SH-SY5Y cells. In conclusion, our findings demonstrated a size-dependent neurotoxicity in SH-SY5Y cells by AgNPs via ferritinophagy-mediated oxidative stress.

Melatonin protects against nonylphenol caused pancreatic ß-cells damage through MDM2-P53-P21 axis.

Nonylphenol (NP) is an endocrine disrupting chemical, which widely exists in environment and can result in multiple system dysfunction. Pancreas as one of the most important organs is sensitive to NP, while the detail toxic effect is still less studied. Previously, we unveiled nonylphenol causes pancreatic damage in rats, herein, we further explore the potential mechanism and seek protection strategy in vitro. Insulinoma (INS-1) cells exposed to NP were observed to suffer oxidative stress and mitochondrial dysfunction, as reflected by the abnormal levels of reactive oxygen species, malonic dialdehyde, superoxide dismutase, Ca2+, and mitochondrial membrane potential. Melatonin (MT) was found to alleviate NP-induced mitochondrial dysfunction and oxidative stress, further inhibit apoptosis and restore pancreas function. Mechanically, MT induced the MDM2-P53-P21 signaling, which upregulated the Nrf2 signaling pathway. In summary, our study clarified NP-induced INS-1 cells mitochondrial dysfunction and oxidative stress, which could be ameliorated by MT through MDM2-P53-P21 axis.

Repeated radon exposure induced lung damage via oxidative stress-mediated mitophagy in human bronchial epithelial cells and mice.

This study aimed to investigate the potential molecular mechanism underlying radon-induced lung damage. Our results showed that long-term radon exposure induced mitochondrial damage and redox imbalance in BEAS-2B cells and a time-dependent lung pathological injury in mice. The activation of Nrf-2 and its down-stream antioxidants, and the gene expression of the indicated markers at different stages of autophagy were found to be induced with the increasing of radon exposure time. Changes in the gene expression of PINK-1, Parkin, and p62 induced by radon showed differences in mechanisms of mitophagy activation and profiles of autophagic flux between BEAS-2B cells and mice. Our findings not only demonstrated that long-term radon exposure induced damages to bronchial epithelial cells and the mice lung through increasing oxidative stress, decreasing mitochondrial function and activating mitophagy with different profiles of autophagic flux, but also revealed Nrf-2 as a central regulator of mitochondrial homeostasis and lung damage.

Effect of 1α,25(OH)2D3-Treated M1 and M2 Macrophages on Cell Proliferation and Migration Ability in Ovarian Cancer.

The biological active form of vitamin D3, 1α,25-dehydroxyvitamin D3 [1α,25(OH)2D3], exerts pleiotropic effects including bone mineralization, anti-tumor, as well as immunomodulator. This study aimed to explore the potential impact of 1α,25(OH)2D3 on tumor-associated macrophages (TAMs) infiltration in ovarian cancer. Firstly, human monocytic THP-1 cells were differentiated into macrophages (M0) in the presence of phorbol 12-myristate 13-acetate (PMA). In Vivo, 1α,25(OH)2D3 not only reversed the polarization of M2 macrophages, but also decreased the proliferation and migration abilities of ovarian cancer cells induced by M2 macrophages supernatant. Furthermore, 1α,25(OH)2D3 dramatically decreased the secretion of TGF-ß1 and MMP-9 in M2 macrophages. However, no significant effect was observed in 1α,25(OH)2D3 treated M1 macrophages. In Vivo, vitamin D3 had an inhibitive effect of 1α,25(OH)2D3-treated M2 macrophages on tumorigenesis. In addition, we conducted the association of TAMs with the poor prognosis of patients with ovarian cancer by meta-analysis, which suggested the higher proportion of M2 macrophages was related to the poorer prognosis in ovarian cancer. Collectively, these results identified distinct roles of 1α,25(OH)2D3 treated M1 and M2 macrophages on cell proliferation and migration abilities in ovarian cancer.

Coordination Polymer-Coated CaCO3 Reinforces Radiotherapy by Reprogramming the Immunosuppressive Metabolic Microenvironment.

Radiotherapy is widely exploited for the treatment of a large range of cancers in clinic, but its therapeutic effectiveness is seriously crippled by the tumor immunosuppression, mainly driven by the altered metabolism of cancer cells. Here, a pH-responsive nanomedicine is prepared by coating calcium carbonate (CaCO3 ) nanoparticles with 4-phenylimidazole (4PI), an inhibitor against indoleamine 2,3-dioxygenase 1 (IDO-1), together with zinc ions via the coordination reaction, aiming at reinforcing the treatment outcome of radiotherapy. The obtained pH-responsive nanomedicine, coined as acidity-IDO1-modulation nanoparticles (AIM NPs), is able to instantly neutralize protons, and release 4PI to suppress the IDO1-mediated production of kynurenine (Kyn) upon tumor accumulation. As a result, treatment with AIM NPs can remarkably enhance the therapeutic efficacy of radiotherapy against both murine CT26 and 4T1 tumors by eliciting potent antitumor immunity. Furthermore, it is shown that such combination treatment can effectively suppress the growth of untreated distant tumors via the abscopal effect, and result in immune memory responses to reject rechallenged tumors. This work highlights a novel strategy of simultaneous tumor acidity neutralization and IDO1 inhibition to potentiate radiotherapy, with great promises to suppress tumor metastasis and recurrence by eliciting robust antitumor immunity.

Silver nanoparticles: Correlating particle size and ionic Ag release with cytotoxicity, genotoxicity, and inflammatory responses in human cell lines.

The widespread use of silver nanoparticles (AgNPs), their many sources for human exposure, and the ability of AgNPs to enter organisms and induce general toxicological responses have raised concerns regarding their public health and environmental safety. To elucidate the differential toxic effects of polyvinylpyrrolidone-capped AgNPs with different primary particle sizes (i.e. 5, 50, and 75 nm), we performed a battery of cytotoxicity and genotoxicity assays and examined the inflammatory responses in two human cell lines (i.e. HepG2 and A549). Concentration-dependent decreases in cell proliferation and mitochondrial membrane potential and increases in cytokine (i.e. interleukin-6 and interleukin-8) excretion indicated disruption of mitochondrial function and inflammation as the main mediating factors of AgNPs-induced cytotoxicity. An incremental increase in genotoxicity with decreasing AgNPs diameter was noted in HepG2 cells, which was associated with S and G2/M accumulation and transcriptional activation of the GADD45α promoter as reflected by luciferase activity. Dose-related genetic damage, as indicated by Olive tail moment and micronucleus formation, was also observed in A549 cells, but these effects as well as the AgNPs-induced cytotoxicity were more associated with ionic Ag release from nanoparticles (NPs). In summary, the present study addressed different toxicity mechanisms of AgNPs, depending on the cell model, toxicological endpoint, particle size, and degree of Ag+ release from NPs. The results suggest that the GADD45α promoter-driven luciferase reporter cell system provided a rapid screening tool for the identification of genotoxic properties of NPs across a range of different sizes and concentrations.

Cellular effects of PM2.5 from Suzhou, China: relationship to chemical composition and endotoxin content.

Exposure to PM2.5 can cause adverse health outcomes. In this study, we analyzed PM2.5 samples collected from suburban and urban sites, including a traffic tunnel in Suzhou, China, for their physicochemical properties, endotoxin contents, and effects on HepG2 and A549 cells in vitro. The greatest cellular responses, including oxidative stress, cytotoxicity, genotoxicity, inflammatory, and transcriptional activation of stress-responsive genes (i.e., HSPA1A, GADD45α), were observed in cells treated with traffic tunnel PM2.5. Cytokine expression was also measured and closely correlated with endotoxin content, while other toxic effects were largely related to PM2.5-bound metals and polycyclic aromatic hydrocarbons (PAHs). These findings suggested that chemical and biological composition of PM2.5, including adsorbed trace metals, PAHs, and endotoxin, may contribute significantly to their toxicity. In addition to commonly used in vitro toxicity tests, HSPA1A and GADD45α promoter-driven luciferase reporter cells may provide a potential new tool for rapid screening and quantification of PM2.5 toxicity.

Protection of melatonin against long-term radon exposure-caused lung injury.

Radon is one of the major pathogenic factors worldwide. Recently, epidemiological studies have suggested that radon exposure plays an important role in lung injury, which could further cause cancer. However, the toxic effects and underlying mechanism on lung injury are still not clear. Here, we identified the detailed toxic effects of long-term radon exposure. Specifically, the manifestations were inflammatory response and cell apoptosis in dose- and time-dependent manners. In detail, it caused the mitochondrial dysfunction and oxidative stress as determined by the abnormal levels of mitochondrial DNA copy number, adenosine triphosphate, mitochondrial membrane potential, superoxide dismutase, and cycloxygenase-2. Furthermore, we found that melatonin treatment ameliorated mitochondrial dysfunction and attenuated the levels of oxidative stress caused by long-term radon exposure, which could further inhibit the lung tissue apoptosis as determined by the decreased levels of cleaved caspase 3. Our study would provide potential therapeutic application of melatonin on lung tissue injury caused by long-term radon exposure.

1α,25(OH)2D3 Radiosensitizes Cancer Cells by Activating the NADPH/ROS Pathway.

The radioresistance of tumors affect the outcome of radiotherapy. Accumulating data suggest that 1α,25(OH)2D3 is a potential anti-oncogenic molecule in various cancers. In the present study, we investigated the radiosensitive effects and underlying mechanisms of 1α,25(OH)2D3 in vitro and in vivo. We found that 1α,25(OH)2D3 enhanced the radiosensitivity of lung cancer and ovarian cancer cells by promoting the NADPH oxidase-ROS-apoptosis axis. Compared to the group that only received radiation, the survival fraction and self-renewal capacity of cancer cells treated with a combination of 1α,25(OH)2D3 and radiation were decreased. Both apoptosis and ROS were significantly increased in the combination group compared with the radiation only group. Moreover, N-acetyl-L-cysteine, a scavenger of intracellular ROS, reversed the apoptosis and ROS induced by 1α,25(OH)2D3, indicating that 1α,25(OH)2D3 enhanced the radiosensitivity of cancer cells in vitro by promoting ROS-induced apoptosis. Moreover, our results demonstrated that 1α,25(OH)2D3 promoted the ROS level via activating NADPH oxidase complexes, NOX4, p22phox, and p47phox. In addition, knockdown of the vitamin D receptor (VDR) abolished the radiosensitization of 1α,25(OH)2D3, which confirmed that 1α,25(OH)2D3 radiosensitized tumor cells that depend on VDR. Similarly, our study also evidenced that vitamin D3 enhanced the radiosensitivity of cancer cells in vivo and extended the overall survival of mice with tumors. In summary, these results demonstrate that 1α,25(OH)2D3 enhances the radiosensitivity depending on VDR and activates the NADPH oxidase-ROS-apoptosis axis. Our findings suggest that 1α,25(OH)2D3 in combination with radiation enhances lung and ovarian cell radiosensitivity, potentially providing a novel combination therapeutic strategy.

A 3,2-Hydroxypyridinone-based Decorporation Agent that Removes Uranium from Bones In Vivo.

Searching for actinide decorporation agents with advantages of high decorporation efficiency, minimal biological toxicity, and high oral efficiency is crucial for nuclear safety and the sustainable development of nuclear energy. Removing actinides deposited in bones after intake is one of the most significant challenges remaining in this field because of the instantaneous formation of highly stable actinide phosphate complexes upon contact with hydroxyapatite. Here we report a hydroxypyridinone-based ligand (5LIO-1-Cm-3,2-HOPO) exhibiting stronger affinity for U(VI) compared with the reported tetradentate hydroxypyridinone ligands. This is further revealed by the first principles calculation analysis on bonding between the ligand and uranium. Both in vitro uranium removal assay and in vivo decorporation experiments with mice show that 5LIO-1-Cm-3,2-HOPO can remove uranium from kidneys and bones with high efficiencies, while the decorporation efficiency is nearly independent of the treatment time. Moreover, this ligand shows a high oral decorporation efficiency, making it attractive for practical applications.

3-Hydroxy-2-Pyrrolidinone as a Potential Bidentate Ligand for in Vivo Chelation of Uranyl with Low Cytotoxicity and Moderate Decorporation Efficacy: A Solution Thermodynamics, Structural Chemistry, and in Vivo Uranyl Removal Survey.

Uranium poses a threat for severe renal and bone damage in vivo. With the rapid development of nuclear industry, it is more urgent than ever to search for potential in vivo uranium chelators. In this work, 3-hydroxy-2-pyrrolidinone (HPD) is investigated as a new potential uranium decorporation ligand. The potentiometric titration measurements were carried out, and the stability constants were determined to be log ß110 = 10.5(7), log ß120 = 20.7(9), and log ß130 = 28.2(4). The species distribution diagram shows that nearly all uranyl is complexed by HPD at pH 7.4 under the defined condition. A single crystal of uranyl and HPD complexes, [(UO2)3O(H2O)3(C4H6NO2)3]·NO3·12H2O (uranyl-HPD), was obtained via an evaporation method. The overall structure of uranyl-HPD is a trimer that consists of three uranyl units and three HPD ligands. The uranyl unit is equatorially coordinated by three oxygen atoms from two HPD agents, one coordinated water molecule, and one µ3-O atom that is shared by three uranyl units. The results of the cytotoxicity assay indicate that the ligand is less toxic than the chelators used clinically (i.e., DTPA-ZnNa3 and 3-hydroxy-1,2-dimethyl-4(1 H)-pyridone (DFP)). The results of the uranium removal assay using the NRK-52E cell show that it could reduce as much as 58% of the uranium content at the cellular level. Furthermore, the in vivo uranium decorporation assays demonstrate that HPD can remove 52% of uranium deposited in the kidney but shows poor uranium removal efficacy in the bone.

3,2-Hydroxypyridinone-Grafted Chitosan Oligosaccharide Nanoparticles as Efficient Decorporation Agents for Simultaneous Removal of Uranium and Radiation-Induced Reactive Oxygen Species in Vivo.

Most of the key radionuclides in the nuclear fuel cycle, such as actinides, possess a combination of heavy metal chemotoxicity and radiotoxicity and therefore represent a severe threat to the ecological environment and public safety. The radiotoxicity originates from direct radiation-induced organ damage and indirect damage, mostly through radiation-induced reactive oxygen species (ROS). Although effective chelating agents that can accelerate the excretion of actinides, such as uranium, have been developed in the past several decades, very few of them can reduce radiation-induced damage from internal contamination. In fact, the strategy of simultaneous removal of actinides and their induced-ROS in vivo has scarcely been considered. Here, we report a 3,2-hydroxypyridinone-grafted chitosan oligosaccharide nanoparticle (COS-HOPO) as a new type of decorporation agent that is effective for the removal of both uranium and ROS in vivo. The cytotoxicity and decorporation assays indicate that the marriage of chitosan oligosaccharide (COS) and hydroxypyridinone (HOPO) gives rise to a remarkable decrease in toxicity and promotion of the uranium removal capability from both kidneys and femurs. The decorporation efficacy can reach up to 43% in rat proximal tubular epithelial cells (NRK-52E), 44% in kidneys, and 32% in femurs. Moreover, the ROS levels of the cells treated with COS-HOPO are significantly lower than those of the control group, implying a promising radiation protection effect. The detoxification mechanism of COS-HOPO is closely related to both chelating U(VI)- and scavenging U(VI)-induced intracellular ROS.

Structural and thermodynamic stability of uranyl-deferiprone complexes and the removal efficacy of U(vi) at the cellular level.

Deferiprone (3-hydroxy-1,2-dimethyl-4(1H)-pyridone, DFP), which is a drug clinically used for removing heavy metals in vivo, was explored for its removal efficiency towards uranium. The reaction of uranyl nitrate hexahydrate with DFP at room temperature yielded the compound [(UO2)(H2O)(C7NO2H8)2]·4H2O (1), which crystallizes from a mixed solution of methanol and water (pH = 7.0). X-ray diffraction shows that the stable complexation of uranyl occurs from the coordination of two bidentate DFP ligands perpendicular to the O[double bond, length as m-dash]U[double bond, length as m-dash]O unit with a fifth coordinating oxygen atom coming from one water molecule, resulting in a pentagonal bipyramidal geometry. The formation constants of uranyl and DFP complexes were measured and the species distribution diagram illustrates that UO2L2 (94.6%) is the dominant uranyl-DFP complex in 0.1 M KCl solution at physiological pH = 7.4. The results from both crystallographic and potentiometric studies imply that the metal : ligand ratio is 1 : 2. The effectiveness of using DFP to remove uranium was examined at the cellular level, and the results suggest that it can significantly reduce the cellular uptake and increase the cellular release of U(vi) in renal proximal tubular epithelial cells (NRK-52E).

Long Noncoding RNA CRYBG3 Blocks Cytokinesis by Directly Binding G-Actin.

The dynamic interchange between monomeric globular actin (G-actin) and polymeric filamentous actin filaments (F-actin) is fundamental and essential to many cellular processes, including cytokinesis and maintenance of genomic stability. Here, we report that the long noncoding RNA LNC CRYBG3 directly binds G-actin to inhibit its polymerization and formation of contractile rings, resulting in M-phase cell arrest. Knockdown of LNC CRYBG3 in tumor cells enhanced their malignant phenotypes. Nucleotide sequence 228-237 of the full-length LNC CRYBG3 and the ser14 domain of ß-actin is essential for their interaction, and mutation of either of these sites abrogated binding of LNC CRYBG3 to G-actin. Binding of LNC CRYBG3 to G-actin blocked nuclear localization of MAL, which consequently kept serum response factor (SRF) away from the promoter region of several immediate early genes, including JUNB and Arp3, which are necessary for cellular proliferation, tumor growth, adhesion, movement, and metastasis. These findings reveal a novel lncRNA-actin-MAL-SRF pathway and highlight LNC CRYBG3 as a means to block cytokinesis and to treat cancer by targeting the actin cytoskeleton.Significance: Identification of the long noncoding RNA LNC CRYBG3 as a mediator of microfilament disorganization marks it as a novel therapeutic antitumor strategy. Cancer Res; 78(16); 4563-72. ©2018 AACR.

Dietary methionine source and level affect hepatic sulfur amino acid metabolism of broiler breeder hens.

A study was carried out to investigate the effects of dietary methionine source and level on plasma free amino acids patterns and the expression of genes involved in hepatic methionine metabolism in broiler breeders. A total of 2184 broiler breeders were assigned to 13 dietary treatments, with eight replicates per treatment. The 13 treatments included one control group and 12 additional treatments employing two sources and six levels (0.05, 0.10, 0.15, 0.20, 0.25 and 1.00%). Higher plasma methionine concentration was measured for DL-methionine (DLM) treated hens. Plasma alanine concentration was linearly increased as DLM or 2-hydroxy-4-(methylthio) butanoic acid (HMTBA) supplementation level increased. There was a linear increase in concentrations of tyrosine, valine, glycine and serine as dietary DLM supplementation level increased. Hens treated with DLM had higher relative expression of ADA than those fed HMTBA. The expression of MS, ADA, SAHH and MAT2A changed quadratically as HMTBA supplementation level increased, while the expression of GNMT and SAHH changed quadratically as DLM supplementation level increased. In conclusion, the effects of HMTBA on plasma free amino acid patterns and the expression of hepatic genes involved with methionine are different from DLM.

Tamoxifen promotes apoptosis and inhibits invasion in estrogen­positive breast cancer MCF­7 cells.

Tamoxifen (TAM) is the earliest non-steroidal antiestrogen drug, which has been widely used in endocrine therapy targeting breast cancer. The aim of the present study was to investigate the effect of TAM on the proliferation, apoptosis, migration and invasion of the estrogen­positive (ER+) breast cancer cell line MCF­7 in vitro, and elucidate its mechanisms. It was demonstrated that TAM suppressed proliferation, migration and invasion, and induced apoptosis in MCF­7 cells. Further investigation revealed that the mitochondrial membrane potential and the amount of ATP were significantly decreased following the treatment of MCF­7 cells with TAM. Mitochondria are an important source of reactive oxygen species (ROS) and they are also the target of ROS as well. In the present study, TAM promoted the formation of ROS in MCF­7 cells. In conclusion, these results reveal the underlying mechanism by which TAM induces ER+ breast cancer cell apoptosis and inhibits invasion, thereby supporting the use of TAM in breast cancer treatment.