AKT/mTOR and c-Jun N-terminal kinase signaling pathways are required for chrysotile asbestos-induced autophagy

Small Molecules Targeting Programmed Cell Death in Breast Cancer Cells

Targeted chemotherapy has become the forefront for cancer treatment in recent years. The selective and specific features allow more effective treatment with reduced side effects. Most targeted therapies, which include small molecules, act on specific molecular targets that are altered in tumour cells, mainly in cancers such as breast, lung, colorectal, lymphoma and leukaemia. With the recent exponential progress in drug development, programmed cell death, which includes apoptosis and autophagy, has become a promising therapeutic target. The research in identifying effective small molecules that target compensatory mechanisms in tumour cells alleviates the emergence of drug resistance. Due to the heterogenous nature of breast cancer, various attempts were made to overcome chemoresistance. Amongst breast cancers, triple negative breast cancer (TNBC) is of particular interest due to its heterogeneous nature in response to chemotherapy. TNBC represents approximately 15% of all breast tumours, however, and still has a poor prognosis. Unlike other breast tumours, signature targets lack for TNBCs, causing high morbidity and mortality. This review highlights several small molecules with promising preclinical data that target autophagy and apoptosis to induce cell death in TNBC cells.

Capsaicin protects cardiomyocytes against lipopolysaccharide-induced damage via 14-3-3γ-mediated autophagy augmentation

Background: The myocardium is susceptible to lipopolysaccharide (LPS)-induced damage in sepsis, and cardiac dysfunction is a leading cause of mortality in patients with sepsis. The changes in cardiomyocyte autophagy in sepsis and the effects and mechanism of action of capsaicin (Cap) remain unclear.

Methods and Results: The potential pathway of 14-3-3γ-dependent autophagy and the effects and mechanisms of Cap were studied in LPS-induced injury to primary cultured neonatal rat cardiomyocytes. The results showed that cardiomyocyte viability decreased, lactate dehydrogenase and creatine kinase activities increased, 14-3-3γ expression was downregulated, and autophagy was inhibited after LPS challenge. Cap pretreatment augmented autophagy by upregulating 14-3-3γ expression and activating AMP-activated protein kinase (AMPK) and unc-51 like autophagy-activating kinase 1 (ULK1), suppressing mammalian target of rapamycin (mTOR), alleviating cardiac dysfunction and improving the inflammation response, whereas pAD/14-3-3γ-shRNA nullified the above effects. Cap pretreatment also decreased the levels of IL-1β, TNF-α, IL-6, and IL-10; suppressed intracellular oxidative stress; reduced the intracellular/mitochondrial reactive oxygen species (ROS); balanced GSH/GSSG; increased GSH-Px, catalase, and SOD activities; and decreased MDA contents. It also increased ATP content, activated complex Ⅰ and complex Ⅲ, stabilized the mitochondrial membrane potential, and decreased the mitochondrial permeability transition pore opening, thereby improving mitochondrial function.

Conclusion: Pretreatment with Cap can regulate autophagy by upregulating 14-3-3γ expression, inhibiting oxidative stress and inflammation, maintaining mitochondrial function, and protecting cardiomyocytes against LPS-induced injury.

Long-term instillation to four natural representative chrysotile of China induce the inactivation of P53 and P16 and the activation of C-JUN and C-FOS in the lung tissues of Wistar rats

Chrysotile is the only type of asbestos still widely exploited, and all kinds of asbestos including chrysotile was classified as a group I carcinogen by the IARC. There is a wealth of evidence that chrysotile can cause a range of cancers, including cancer of the lung, larynx, ovary, and mesothelioma. As the second largest chrysotile producer, China is at great risk of occupational exposure. Moreover, our previous experiment and some other studies have shown that the toxicity of mineral fibre from various mining areas may be different. To explore the oncogenic potential of chrysotile from different mining areas of China, Wistar rats were administered 0.5 mL chrysotile asbestos suspension of 2.0 mg/mL (from Akesai, Gansu; Mangnai, Qinghai; XinKang, Sichuan; and Shannan, Shaanxi) dissolved in saline by intratracheal instillation once-monthly and were sacrificed at 1 mo, 6 mo, and 12 mo. Our results found that chrysotile caused lung inflammation and lung tissue damage. Moreover, prolonged exposure of chrysotile can induce inactivation of the tumor suppressor gene P53 and P16 and activation of the protooncogene C-JUN and C-FOS both in the messenger RNA and protein level. In addition, chrysotile from Shannan and XinKang has a stronger effect which may link to cancer than that from Akesai and Mangnai.

Chromatographic Detection of 8-Hydroxy-2'-Deoxyguanosine in Leukocytes of Asbestos Exposed Workers for Assessing Past and Recent Carcinogen Exposures

Asbestos fibers include a group of silicate minerals that occur in the environment and are widely employed in occupational settings. Asbestos exposure has been associated to various chronic diseases; such as pulmonary fibrosis; mesothelioma; and lung cancer; often characterized by a long period of latency. Underlying mechanisms that are behind the carcinogenic effect of asbestos have not been fully clarified. Therefore; we have conducted an epidemiological study to evaluate the relationship between 8-hydroxy-2'-deoxyguanosine (8-oxodG), one of the most reliable biomarkers of oxidative stress and oxidative DNA damage; and asbestos exposure in the peripheral blood of residents in Tuscany and Liguria regions; Italy; stratified by occupational exposure to this carcinogen. Levels of 8-oxodG were expressed such as relative adduct labeling (RAL); the frequency of 8-oxodG per 105 deoxyguanosine was significantly higher among exposed workers with respect to the controls; i.e., 3.0 ± 0.2 Standard Error (SE) in asbestos workers versus a value of 1.3 ± 0.1 (SE) in unexposed controls (p < 0.001). When the relationship with occupational history was investigated; significant higher levels of 8-oxodG were measured in current and former asbestos workers vs. healthy controls; 3.1 ± 0.3 (SE) and 2.9 ± 0.2 (SE), respectively. After stratification for occupational history; a significant 194% excess of adducts was found in workers with 10 or more years of past asbestos exposure (p < 0.001). 8-oxodG can be used for medical surveillance programs of cohorts of workers with past and recent exposures to carcinogens for the identification of subjects requiring a more intense clinical surveillance.

Antitumor effects of rafoxanide in diffuse large B cell lymphoma via the PTEN/PI3K/Akt and JNK/c-Jun pathways

AIMS

Diffuse large B-cell lymphoma (DLBCL) is one of the most aggressive lymphoid malignancies, which remains incurable, thus warranting the development of new therapies. Our previous study determined that rafoxanide is very effective in treating multiple myeloma (MM). In the present study, we tried to evaluate the effects of rafoxanide on DLBCL, as well as the potential underlying molecular mechanisms.

MAIN METHODS

We used CCK-8 assay and flow cytometry to assess cell viability and apoptosis. The proteins and pathways associated with apoptosis and proliferation were evaluated through western blot, and xenograft mice were used as the experimental animal model. We also used the TUNEL assay and immunofluorescence for further analyses.

KEY FINDINGS

Treatment with different doses of rafoxanide significantly inhibited cell viability and apoptosis. Additionally, the compound induced cell cycle arrest, reduced mitochondrial membrane potential (Δψm), and stimulated reactive oxygen species (ROS) generation without the influence of normal peripheral blood monocytes (PBMCs). As expected, rafoxanide played a role in regulating these proteins and the PTEN/PI3K/AKT and JNK/c-Jun pathways. Furthermore, immunofluorescence and western blot results showed that rafoxanide upregulated H2AX phosphorylation and then inhibited DNA repair in DLBCL. In the xenograft mouse model, tumor volumes were reduced after intraperitoneal injection with rafoxanide. We also observed that TUNEL positive cells were remarkably increased in rafoxanide-treated tumor tissues.

SIGNIFICANCE

These results collectively provide a novel choice to regular treatment for DLBCL patients with poor prognosis.

Conditioned medium from asbestos-exposed fibroblasts affects proliferation and invasion of lung cancer cell lines

The importance of the role of fibroblasts in cancer microenvironment is well-recognized. However, the relationship between fibroblasts and asbestos-induced lung cancer remains underexplored. To investigate the effect of the asbestos-related microenvironment on lung cancer progression, lung cancer cells (NCI-H358, Calu-3, and A549) were cultured in media derived from IMR-90 lung fibroblasts exposed to 50 mg/L asbestos (chrysotile, amosite, and crocidolite) for 24 h. The kinetics and migration of lung cancer cells in the presence of asbestos-exposed lung fibroblast media were monitored using a real-time cell analysis system. Proliferation and migration of A549 cells increased in the presence of media derived from asbestos-exposed lung fibroblasts than in the presence of media derived from normal lung fibroblasts. We observed no increase in proliferation and migration in lung cancer cells cultured in asbestos-exposed lung cancer cell medium. In contrast, increased proliferation and migration in lung cancer cells exposed to media from asbestos-exposed lung fibroblasts was observed for all types of asbestos. Media derived from lung fibroblasts exposed to other stressors, such as hydrogen peroxide and UV radiation didn't show as similar effect as asbestos exposure. An enzyme-linked immunosorbent assay (ELISA)-based cytokine array identified interleukin (IL)-6 and IL-8, which show pleiotropic regulatory effects on lung cancer cells, to be specifically produced in higher amounts by the three types of asbestos-exposed lung fibroblasts than normal lung fibroblasts. Thus, the present study demonstrated that interaction of lung fibroblasts with asbestos may support the growth and metastasis of lung cancer cells and that chrysotile exposure can lead to lung cancer similar to that caused by amphibole asbestos (amosite and crocidolite).

NF-κB/mTOR-mediated autophagy can regulate diquat-induced apoptosis

Autophagy and apoptosis are the major types of cell death in pesticide-induced neurotoxicity, and autophagy is known to play a role in cell protection by inhibiting apoptosis. In this study, we characterized the relationship between autophagy and apoptosis in diquat (DQ)-induced cell death and explored a novel pharmacotherapeutic approach involving autophagy regulation to prevent DQ neurotoxicity. DQ was cytotoxic to PC12 cells in a concentration-dependent manner, as shown by decreased cell viability and decreased dopamine (DA) levels. DQ-induced apoptosis was found in PC12 cells, as demonstrated by activation of caspase-3 and -9 and by nuclear condensation. By monitoring expression of microtubule-associated protein 1A/1B light chain 3B (LC3-II) and p62, DQ was found to induce autophagy. Exposure of PC12 cells to DQ led to the production of reactive oxygen species (ROS), and N-acetyl-cysteine (NAC) antioxidant effectively blocked both apoptosis and autophagy. Interestingly, DQ in PC12 cells showed increased p53 and NF-κB in a time-dependent manner; furthermore, pifithrin-α (PFT-α), a p53 inhibitor, downregulates the cytotoxicity of DQ, as shown by decreased LC3-II and cleaved caspase-3. SN50, an NF-κB inhibitor, results in diminished LC3-II, cleaved caspase-3, and p53. DQ induces mitogen-activated protein kinase (MAPK) signaling including ERK, JNK, and p38, which inhibit regulated apoptosis and autophagic cell death by controlling mTOR signaling. In addition, modulation of DQ-induced apoptosis in response to autophagy regulation was investigated. Pretreatment with rapamycin, an autophagy inducer, significantly enhanced the viability of DQ-exposed cells by alleviating DQ-induced apoptosis. Conversely, cell pretreatment with 3-methyladenine (3MA), an autophagy inhibitor increased DQ toxicity. Our results suggest that DQ-induced cytotoxicity is modified by autophagy regulation. Pharmacologic induction of autophagy may be a useful treatment strategy in neurodegenerative disorders.

The Regulation of JNK Signaling Pathways in Cell Death through the Interplay with Mitochondrial SAB and Upstream Post-Translational Effects

c-Jun-N-terminal kinase (JNK) activity plays a critical role in modulating cell death, which depends on the level and duration of JNK activation. The kinase cascade from MAPkinase kinase kinase (MAP3K) to MAPkinase kinase (MAP2K) to MAPKinase (MAPK) can be regulated by a number of direct and indirect post-transcriptional modifications, including acetylation, ubiquitination, phosphorylation, and their reversals. Recently, a JNK-mitochondrial SH3-domain binding protein 5 (SH3BP5/SAB)-ROS activation loop has been elucidated, which is required to sustain JNK activity. Importantly, the level of SAB expression in the outer membrane of mitochondria is a major determinant of the set-point for sustained JNK activation. SAB is a docking protein and substrate for JNK, leading to an intramitochondrial signal transduction pathway, which impairs electron transport and promotes reactive oxygen species (ROS) release to sustain the MAPK cascade.

Ambiguous Effects of Autophagy Activation Following Hypoperfusion/Ischemia

Autophagy primarily works to counteract nutrient deprivation that is strongly engaged during starvation and hypoxia, which happens in hypoperfusion. Nonetheless, autophagy is slightly active even in baseline conditions, when it is useful to remove aged proteins and organelles. This is critical when the mitochondria and/or proteins are damaged by toxic stimuli. In the present review, we discuss to that extent the recruitment of autophagy is beneficial in counteracting brain hypoperfusion or, vice-versa, its overactivity may per se be detrimental for cell survival. While analyzing these opposite effects, it turns out that the autophagy activity is likely not to be simply good or bad for cell survival, but its role varies depending on the timing and amount of autophagy activation. This calls for the need for an appropriate autophagy tuning to guarantee a beneficial effect on cell survival. Therefore, the present article draws a theoretical pattern of autophagy activation, which is hypothesized to define the appropriate timing and intensity, which should mirrors the duration and severity of brain hypoperfusion. The need for a fine tuning of the autophagy activation may explain why confounding outcomes occur when autophagy is studied using a rather simplistic approach.

Role of the MAPK/cJun NH2-terminal kinase signaling pathway in starvation-induced autophagy

Autophagy is required for cellular homeostasis and can determine cell viability in response to stress. It is established that MTOR is a master regulator of starvation-induced macroautophagy/autophagy, but recent studies have also implicated an essential role for the MAPK8/cJun NH₂-terminal kinase 1 signal transduction pathway. We found that MAPK8/JNK1 and MAPK9/JNK2 were not required for autophagy caused by starvation or MTOR inhibition in murine fibroblasts and epithelial cells. These data demonstrate that MAPK8/9 has no required role in starvation-induced autophagy. We conclude that the role of MAPK8/9 in autophagy may be context-dependent and more complex than previously considered.

Abbreviations: AKT: thymoma viral proto-oncogene;ALB: albumin; ATG4: autophagy related 4; BCL2: B cell leukemia/lymphoma 2; BECN1: beclin 1, autophagy related; BNIP3: BCL2/adenovirus E1B interacting protein 3; CQ: chloroquine diphosphate; DMEM: Dulbecco’s modified Eagle’s medium; EDTA: ethylenediaminetetraacetic acid; EBSS: Earle’s balanced salt solution; FBS: fetal bovine serum; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; GFP: green fluorescent protein; HRAS: Harvey rat sarcoma virus oncogene; IgG: Immunoglobulin G; MAPK3/ERK1: mitogen-activated protein kinase 3; MAPK8/JNK1: mitogen-activated protein kinase 8; MAPK9/JNK2: mitogen-activated protein kinase 9; MAPK10/JNK3: mitogen-activated protein kinase 10; MAP1LC3B/LC3B: microtubule-associated protein 1 light chain 3 beta; MEFs: mouse embryonic fibroblasts; MTOR: mechanistic target of rapamycin kinase; RPS6KB1/p70: ribosomal protein S6 kinase, polypeptide 1; PPARA: peroxisome proliferator activated receptor alpha; SEM: standard error of the mean; SQSTM1/p62: sequestosome 1; TORC1: target of rapamycin complex 1; TORC2: target of rapamycin complex 2; TRP53: transforming related protein 53; TUBA: tubulin alpha; UV: ultraviolet; WT: wild-type

Natural Cyclopeptide RA-XII, a New Autophagy Inhibitor, Suppresses Protective Autophagy for Enhancing Apoptosis through AMPK/mTOR/P70S6K Pathways in HepG2 Cells

Liver cancer is a progressive, irreversible and aggressive malignant disease, which has no effective chemotherapeutic drugs. RA-XII, a natural cyclopeptide isolated from the traditional Chinese medicine Rubia yunnanensis, exerts anti-cancer and anti-inflammatory activities. This work aimed to investigate the effects of RA-XII on a hepatic tumor and its underlying mechanisms in human hepatoma HepG2 cells. The results showed that RA-XII effectively inhibited the proliferation of HepG2 cells. Consistently, RA-XII significantly induced apoptosis in HepG2 cells by decreasing the expression of caspase 3, 8, 9, and promoting the Cleavage of PARP. Moreover, RA-XII-induced apoptosis was attenuated in the presence of apoptosis inhibitor N-Benzyloxycarbonyl-Val-Ala-Asp (O-Me) fluoromethyl keton, suggesting that RA-XII induced apoptosis-cell-death in HepG2 cells. Furthermore, autophagy-related proteins and mRNA levels were dramatically reduced after RA-XII treatment. Meanwhile, we observed that autophagy inhibitor chloroquine could enhance apoptosis in RA-XII-treated HepG2 cells, indicating that autophagy played a protective role in HepG2 cells and RA-XII might inhibit protective autophagy. Further analysis showed that RA-XII inhibited AMPK phosphorylation and led to the mTOR/P70S6K pathway activation, suggesting that RA-XII inhibited autophagy through AMPK/mTOR/P70S6K pathways. This study demonstrated that RA-XII promoted apoptosis and inhibited protective autophagy through AMPK/mTOR/P70S6K pathways in HepG2 cells. In conclusion, these findings suggest that RA-XII might potentially be a candidate as an autophagy inhibitor agent for further therapy of liver cancer.

Hyperoxia-mediated LC3B activation contributes to the impaired transdifferentiation of type II alveolar epithelial cells (AECIIs) to type I cells (AECIs)

Life-saving mechanical ventilation can also cause lung injury through the overproduction of reactive oxygen species (ROS), leading to bronchopulmonary dysplasia (BPD)-like symptoms in preterm infants. It is reported that the autophagic protein microtubule-associated protein-1 light chain (LC)-3B can confer protection against hyperoxia-induced DNA damage in lung alveolar epithelium. However, its role in the transdifferentiation of type II alveolar epithelial cells (AECIIs) to type I cells (AECIs) is unclear and requires further investigation. In this study, newborn Sprague-Dawley rats were exposed to 90% oxygen for up to 14 days to mimic BPD in human infants, with neonatal pups exposed to room air (21% oxygen) as controls. Primary rat AECIIs were cultured under hyperoxic conditions for up to 24 hours to further investigate the underlying mechanisms. This study found that hyperoxia promoted a significant and time-dependent increase of AECII marker surfactant protein (SP)-C in the lung. The increase of AECI marker T1α was repressed by hyperoxia during lung development. These results indicated an impaired AECII transdifferentiation. Pulmonary ROS concentration and expression of autophagic protein LC-3B were increased gradually in response to hyperoxia exposure. Furthermore, AECIIs produced more ROS when cultured under hyperoxic conditions in vitro. Both the LC3B expression and the conversion from LC3BI to LC3BII were enhanced in hyperoxic AECs. Interestingly, inhibition of LC3B either by ROS inhibitor N-acetyl-l-cysteine (NAC) or adenovirus-mediated LC3B shRNA could partly restore AECII transdifferentiation under hyperoxia condition. In summary, the current study reveals a novel role of activated LC3B induced by hyperoxia in AECII transdifferentiation.

Bisindolylmaleimide alkaloid BMA-155Cl induces autophagy and apoptosis in human hepatocarcinoma HepG-2 cells through the NF-κB p65 pathway

Bisindolylmaleimides, a series of derivatives of a PKC inhibitor staurosporine, exhibit potential as anti-cancer drugs and have received considerable attention in clinical trials. This study aims to investigate the effects of a bisindolylmaleimide alkaloid 155Cl (BMA-155Cl) with a novel structure on autophagy and apoptosis in human hepatocarcinoma HepG-2 cells in vitro and in vivo. The cell poliferation was assessed with a MTT assay. Autophagy was evaluated by MDC staining and TEM analysis. Apoptosis was investigated using Annexin V-FITC/PI and DAPI staining. The antitumor effects were further evaluated in nude mice bearing HepG-2 xenografts, which received BMA-155Cl (10, 20 mg/kg, ip) for 18 days. Autophagy- and apoptosis-associated proteins and their mRNA levels were examined with Western blotting, immunohistochemistry, and RT-PCR. BMA-155Cl (2.5-20 μmol/L) inhibited the growth of HepG-2 cells with IC₅₀ values of 16.62±1.34, 12.21±0.83, and 8.44±1.82 μmol/L at 24, 48, and 72 h, respectively. Furthermore, BMA-155Cl (5-20 μmol/L) dose-dependently induced autophagy and apoptosis in HepG-2 cells. The formation of autophagic vacuoles was induced by BMA-155Cl (10 μmol/L) at approximately 6 h and peaked at approximately 15 h. Pretreatment with 3-MA potentiated BMA-155Cl-mediated apoptotic cell death. This compound dose-dependently increased the mRNA and protein levels of Beclin-1, NF-κB p65, p53, and Bax, but decreased the expression of IκB and Bcl-2. Pretreatment with BAY 11-7082, a specific inhibitor of NF-κB p65, blocked BMA-155Cl-induced expression of autophagy- and apoptosis-associated proteins. BMA-155Cl administration effectively suppressed the growth of HepG-2 xenografts in vivo, and increased the protein expression levels of LC3B, Beclin-1, NF-κB p65, and Bax in vivo. We conclude that the NF-κB p65 pathway is involved in BMA-155Cl-triggered autophagy, followed by apoptosis in HepG-2 cells in vitro and in vivo. Hence, BMA-155Cl could be a promising pro-apoptotic candidate for developing as a novel anti-cancer drug.

3-(2-deoxy-β-d-erythro-pentafuranosyl)pyrimido[1,2-α]purin-10(3H)-one deoxyguanosine adducts of workers exposed to asbestos fibers

Asbestos is the commercial name for a group of silicate minerals naturally occurring in the environment and widely used in the industry. Asbestos exposure has been associated with pulmonary fibrosis, mesothelioma, and malignancies, which may appear after a period of latency of 20-40 years. Mechanisms involved in the carcinogenic effects of asbestos are still not fully elucidated, although the oxidative stress theory suggests that phagocytic cells produce large amounts of reactive oxygen species, due to their inability to digest asbestos fiber. We have conducted a mechanistic study to evaluate the association between 3-(2-deoxy-β-d-erythro-pentafuranosyl)pyrimido[1,2-α]purin-10(3H)-one deoxyguanosine (M₁dG) adducts, a biomarker of oxidative stress and lipid peroxidation, and asbestos exposure in the peripheral blood of 327 subjects living in Tuscany and Liguria, Italy, stratified by occupational exposure to asbestos. Adduct frequency was significantly greater into exposed subjects with respect to the controls. M₁dG per 10⁸ normal nucleotides were 4.0±0.5 (SE) in 156 asbestos workers, employed in mechanic, naval, petrochemical, building industries, and in pottery and ceramic plants, versus a value of 2.3±0.1 (SE) in 171 controls (p<0.001). After stratification for occupational history, the effects persisted in 54 current asbestos workers, mainly employed in building renovation industry (2.9±0.3 (SE)), and in 102 former asbestos workers (4.5±0.7 (SE)), with p-values of 0.033, and <0.001, respectively. A significant effect of smoking on heavy smokers was found (p=0.005). Our study gives additional support to the oxidative stress theory, where M₁dG may reflect an additional potential mechanism of asbestos-induced toxicity.

Cinnamaldehyde ameliorates LPS-induced cardiac dysfunction via TLR4-NOX4 pathway: The regulation of autophagy and ROS production

Cinnamaldehyde (CA), a major bioactive compound extracted from the essential oil of Cortex Cinnamomi, exhibits anti-inflammatory activity on endotoxemia. Accumulating evidence indicates reactive oxygen species (ROS) and autophagy play a vital role in the cardiac dysfunction during endotoxemia. The aim of this study was to unveil the mechanism of CA on ROS production and autophagy during endotoxemia. Male Sprague-Dawley rats were stimulated by LPS (20mg/kg i.v.) with or without treatment of CA. Cardiac function and histopathological staining were preformed 4h after LPS stimulation. The levels of TNF-α, IL-1β and IL-6 were detected by ELISA. The expression of p-JNK, p-ERK, p-p38, TLR4, NOX4, NOX2, ATG5 and LC3 proteins were determined by Western blot. The results showed that CA inhibited cardiac dysfunction, inflammatory infiltration and the levels of TNF-α, IL-1β and IL-6 in LPS stimulated rats by blocking the TLR4, NOX4, MAPK and autophagy signalings. In order to obtain further confirmation of the mechanism of CA on endotoxemia in vitro, a limited time-course study was firstly performed by Western blot. TLR4, NOX4 and LC3 were significantly increased after 4h LPS stimulation. CA reversed the intracellular ROS production and MAPK signaling activation induced by LPS. Electron microscopy, mRFP-GFP-LC3 transfection and western blot results revealed autophagic flux were attenuated after CA treatment. The siRNA and molecular docking results suggest that CA can suppress both TLR4 and NOX4 during endotoxemia. Our data revealed that CA ameliorated LPS-induced cardiac dysfunction by inhibiting ROS production and autophagy through TLR4-NOX4 pathway.

JNK1 Inhibition Attenuates Hypoxia-Induced Autophagy and Sensitizes to Chemotherapy

Inhibition of hypoxia-induced stress signaling through JNK potentiates the effects of oxaliplatin. The JNK pathway plays a role in both autophagy and apoptosis; therefore, it was determined how much of the effect of JNK inhibition on oxaliplatin sensitivity is dependent on its effect on autophagy. We studied the impact of JNK isoform downregulation in the HT29 colon adenocarcinoma cell line on hypoxia- and oxaliplatin-induced responses. Electron microscopic analyses demonstrated that both oxaliplatin- and hypoxia-induced formations of autophagosomes were reduced significantly in HT29 cells treated with the JNK inhibitor SP600125. The role of specific JNK isoforms was defined using HT29-derived cell lines stably expressing dominant-negative constructs for JNK1 and JNK2 (HTJ1.3 and HTJ2.2, respectively). These cell lines demonstrated that functional JNK1 is required for hypoxia-induced autophagy and that JNK2 does not substitute for it. Inhibition of autophagy in HTJ1.3 cells also coincided with enhancement of intrinsic apoptosis. Analysis of Bcl2-family proteins revealed hyperphosphorylation of Bcl-XL in the HTJ1.3 cell line, but this did not lead to the expected dissociation from Beclin 1. Consistent with this, knockdown of Bcl-XL in HT29 cells did not significantly affect the induction of autophagy, but abrogated hypoxic resistance to oxaliplatin due to the faster and more robust activation of apoptosis.

IMPLICATIONS

These data suggest that balance between autophagy and apoptosis is shifted toward apoptosis by downregulation of JNK1, contributing to oxaliplatin sensitization. These findings further support the investigation of JNK inhibition in colorectal cancer treatment. Mol Cancer Res; 14(8); 753-63. ©2016 AACR.

Reactive oxygen species a double-edged sword for mesothelioma

It is well known that oxidative stress can lead to chronic inflammation which, in turn, could mediate most chronic diseases including cancer. Oxidants have been implicated in the activity of crocidolite and amosite, the most powerful types of asbestos associated to the occurrence of mesothelioma. Currently rates of mesothelioma are rising and estimates indicate that the incidence of mesothelioma will peak within the next 10-15 years in the western world, while in Japan the peak is predicted not to occur until 40 years from now. Although the use of asbestos has been banned in many countries around the world, production of and the potentially hazardous exposure to asbestos is still present with locally high incidences of mesothelioma. Today a new man-made material, carbon nanotubes, has arisen as a concern; carbon nanotubes may display 'asbestos-like' pathogenicity with mesothelioma induction potential. Carbon nanotubes resulted in the greatest reactive oxygen species generation. How oxidative stress activates inflammatory pathways leading to the transformation of a normal cell to a tumor cell, to tumor cell survival, proliferation, invasion, angiogenesis, chemoresistance, and radioresistance, is the aim of this review.

Genome-wide analysis of abdominal and pleural malignant mesothelioma with DNA arrays reveals both common and distinct regions of copy number alteration

Malignant mesothelioma (MM) is an aggressive tumor arising from mesothelial linings of the serosal cavities. Pleural space is the most common site, accounting for about 80% of cases, while peritoneum makes up the majority of the remaining 20%. While histologically similar, tumors from these sites are epidemiologically and clinically distinct and their attribution to asbestos exposure differs. We compared DNA array-based findings from 48 epithelioid peritoneal MMs and 41 epithelioid pleural MMs to identify similarities and differences in copy number alterations (CNAs). Losses in 3p (BAP1 gene), 9p (CDKN2A) and 22q (NF2) were seen in tumors from both tumor sites, although CDKN2A and NF2 losses were seen at a higher rate in pleural disease (p<0.01). Overall, regions of copy number gain were more common in peritoneal MM, whereas losses were more common in pleural MM, with regions of loss containing known tumor suppressor genes and regions of gain encompassing genes encoding receptor tyrosine kinase pathway members. Cases with known asbestos causation (n = 32 ) were compared with those linked to radiation exposure (n = 9 ). Deletions in 6q, 14q, 17p and 22q, and gain of 17q were seen in asbestos-associated but not radiation-related cases. As reported in post-radiation sarcoma, gains outnumbered losses in radiation-associated MM. The patterns of genomic imbalances suggest overlapping and distinct molecular pathways in MM of the pleura and peritoneum, and that differences in causation (i.e., asbestos vs. radiation) may account for some of these site-dependent differences.

The c-Jun N-terminal kinase signaling pathway mediates chrysotile asbestos-induced alveolar epithelial cell apoptosis

Exposure to chrysotile asbestos exposure is associated with an increased risk of mortality in combination with pulmonary diseases including lung cancer, mesothelioma and asbestosis. Multiple mechanisms by which chrysotile asbestos fibers induce pulmonary disease have been identified, however the role of apoptosis in human lung alveolar epithelial cells (AEC) has not yet been fully explored. Accumulating evidence implicates AEC apoptosis as a crucial event in the development of both idiopathic pulmonary fibrosis and asbestosis. The aim of the present study was to determine whether chrysotile asbestos induces mitochondria‑regulated (intrinsic) AEC apoptosis and, if so, whether this induction occurs via the activation of mitogen‑activated protein kinases (MAPK). Human A549 bronchoalveolar carcinoma‑derived cells with alveolar epithelial type II‑like features were used. The present study showed that chrysotile asbestos induced a dose‑ and time‑dependent decrease in A549 cell viability, which was accompanied by the activation of the MAPK c‑Jun N‑terminal kinases (JNK), but not the MAPKs extracellular signal‑regulated kinase 1/2 and p38. Chrysotile asbestos was also shown to induce intrinsic AEC apoptosis, as evidenced by the upregulation of the pro‑apoptotic genes Bax and Bak, alongside the activation of caspase‑9, poly (ADP‑ribose) polymerase (PARP), and the release of cytochrome c. Furthermore, the specific JNK inhibitor SP600125 blocked chrysotile asbestos‑induced JNK activation and subsequent apoptosis, as assessed by both caspase‑9 cleavage and PARP activation. The results of the present study demonstrated that chrysotile asbestos induces intrinsic AEC apoptosis by a JNK‑dependent mechanism, and suggests a potential novel target for the modulation of chrysotile asbestos‑associated lung diseases.

Particulate matter 2.5 induces autophagy via inhibition of the phosphatidylinositol 3-kinase/Akt/mammalian target of rapamycin kinase signaling pathway in human bronchial epithelial cells

Particulate matter 2.5 (PM2.5) is a significant risk factor for asthma. A recent study revealed that autophagy was associated with asthma pathogenesis. However, the specific mechanisms underlying PM2.5-induced autophagy in asthma have remained elusive. In the present study, PM2.5-induced autophagy was evaluated in Beas-2B human bronchial epithelial cells and the potential molecular mechanisms were investigated. Using electron microscopy, immunofluorescence staining and immunoblot studies, it was confirmed that PM2.5 induced autophagy in Beas-2B cells as a result of PM2.5-mediated inhibition of the phosphatidylinositol 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) pathway in Beas-2B cells. LY294002, a PI3K inhibitor, reduced the accumulation of microtubule-associated protein 1 light chain 3 II and attenuated the effect of PM2.5. Phosphorylated (p-)p38, p-extracellular signal-regulated kinase and p-c-Jun N-terminal kinase were dephosphorylated following exposure to PM2.5. The roles of p53, reactive oxygen species scavenger tetramethylthiourea and autophagy inhibitor 3-methyladenine in PM2.5-induced autophagy in Beas-2B cells were also investigated. The results suggested that the PI3K/Akt/mTOR signaling pathway may be a key contributor to PM2.5-induced autophagy in Beas-2B cells. The results of the present study therefore provided an a insight into potential future clinical applications targeting these signaling pathways, for the prevention and/or treatment of PM2.5-induced lung diseases.

AMPK is required for PM2.5-induced autophagy in human lung epithelial A549 cells

The aim is to investigate the molecular mechanisms underlying the PM2.5-induced autophagy in human lung cancer epithelial cells (A549). The effects of the PM2.5 on morphological and biochemical markers of autophagy in A549 were analyzed by electron microscopy, GFP-LC3 puncta was observed by confocal fluorescence microscope. The effects of phosphorylation of AMPK, mTOR, AKT, ERK, JNK, and p53 on LC3II in A549 were observed following PM2.5 exposure; the role of autophagy in PM2.5-induced apoptosis was examined using 3-methyladenine and rapamycin. PM2.5 induced morphological and biochemical markers of autophagy in A549. Phosphorylation of AMPK and dephosphorylation of mTOR were observed following PM2.5 treatment, and AMPK inhibitor blocked LC3B-II expression. In addition, we demonstrated that PM2.5-induced autophagy confers a pro-survival role in host defense.

Key autophagic targets and relevant small-molecule compounds in cancer therapy

Autophagy is a highly conserved lysosomal degradation process which can recycle unnecessary or dysfunctional cell organelles and proteins, thereby playing a crucial regulatory role in cell survival and maintenance. It has been widely accepted that autophagy regulates various pathological processes, among which cancer attracts much attention. Autophagy may either promote cancer cell survival by providing energy during unfavourable metabolic circumstance or can induce individual cancer cell death by preventing necrosis and increasing genetic instability. Thus, dual roles of autophagy may determine the destiny of cancer cells and make it an attractive target for small-molecule drug discovery. Collectively, key autophagy-related elements as potential targets, oncogenes mTORC1, class I PI3K and AKT, as well as tumour suppressor class III PI3K, Beclin-1 and p53, have been discussed. In addition, some small molecule drugs, such as rapamycin and its derivatives, rottlerin, PP242 and AZD8055 (targeting PI3K/AKT/mTORC1), spautin-1, and tamoxifen, as well as oridonin and metformin (targeting p53), can modulate autophagic pathways in different types of cancer. All these data will shed new light on targeting the autophagic process for cancer therapy, using small-molecule compounds, to fight cancer in the near future.