Autophagic flux blockage in alveolar epithelial cells is essential in silica nanoparticle-induced pulmonary fibrosis

New Insights into Pathomechanisms and Treatment Possibilities for Lung Silicosis

Inhalation of silica particles is an environmental and occupational cause of silicosis, a type of pneumoconiosis. Development of the lung silicosis is a unique process in which the vicious cycle of ingestion of inhaled silica particles by alveolar macrophages and their release triggers inflammation, generation of nodular lesions, and irreversible fibrosis. The pathophysiology of silicosis is complex, and interactions between the pathomechanisms have not been completely understood. However, elucidation of silica-induced inflammation cascades and inflammation-fibrosis relations has uncovered several novel possibilities of therapeutic targeting. This article reviews new information on the pathophysiology of silicosis and points out several promising treatment approaches targeting silicosis-related pathways.

Cigarette smoke-inactivated SIRT1 promotes autophagy-dependent senescence of alveolar epithelial type 2 cells to induce pulmonary fibrosis

The senescence of alveolar epithelial type 2 (AT2) cells is implicated in the pathogenesis of idiopathic pulmonary fibrosis (IPF). Cigarette smoke (CS) is a strong risk factor for IPF and it is also a pro-senescent factor. Here we aimed to investigate whether and how CS induces AT2 cells senescence via a SIRT1/autophagy dependent pathway. Our results showed that CS extract (CSE) reduced autophagy and mitophagy and increased mitochondrial reactive oxygen species (mitoROS) in MLE-12 cells, an AT2 cell line. The autophagy inducer rapamycin (RAPA) and the mitochondria-targeted antioxidant mitoquinone (mitoQ) inhibited CSE-related senescence and decreased mitoROS. Next, we found that CSE promoted DNA damage, downregulated the nicotinamide adenine dinucleotide (NAD⁺)/nicotinamide adenine dinucleotide (NADH) ratio and suppressed SIRT1 activity. Activating SIRT1 with its activator SRT1720 attenuated senescence through an autophagy-dependent pathway. The NAD⁺ precursor nicotinamide mononucleotide and the poly ADP-ribose polymerase (PARP1) inhibitor olaparib also exerted anti-senescent effects by activating SIRT1. Moreover, the results showed that mitoQ and RAPA, in turn, elevated SIRT1 activity by inhibiting DNA damage. Consistent with these results, SRT1720 and mitoQ mitigated CS-induced AT2 cells senescence and lung fibrosis in vivo. Moreover, autophagy in AT2 cells was rescued by SRT1720. Taken together, our results suggested that CS-induced senescence of AT2 cells was due to decreased autophagy mediated by SIRT1 inactivation, which was attributed to competitive consumption of NAD⁺ caused by DNA damage-induced PARP1 activation. The reduction in autophagy, in turn, decreased SIRT1 activity by promoting mitochondrial oxidative stress-related DNA damage, thereby establishing a positive feedback loop between SIRT1 and autophagy in CS-induced AT2 cells senescence. Consequently, CS-inactivated SIRT1 promoted autophagy-dependent senescence of AT2 cells to induce pulmonary fibrosis.

Adverse effects of amorphous silica nanoparticles: Focus on human cardiovascular health

Amorphous silica nanoparticle (SiNPs) has tremendous potential for a host of applications, while its mass production, broad application and environmental release inevitably increase the risk of human exposure. SiNPs could enter into the human body through different routes such as inhalation, ingestion, skin contact and even injection for medical applications. The cardiovascular system is gradually recognized as one of the primary sites for engineered NPs exerting adverse effects. Accumulating epidemiological or experimental evidence support the association between SiNPs exposure and adverse cardiovascular effects. However, this topic is still in its infancy, and the literature shows high inter-study variability and even contradictory results. New challenges still present in the safety evaluation of SiNPs, and its toxicological mechanisms are poorly understood. Here, scientific papers related to cardiovascular studies of SiNPs in vivo and in vitro were selected, and the updated particle-caused cardiovascular toxicity and potential mechanisms were summarized. Moreover, the understanding of how factors primarily including exposure dose, route of administration, particle size and surface properties, influence the interaction between SiNPs and cardiovascular system was discussed. In particular, the adverse outcome pathway (AOP) framework by which SiNPs cause deleterious effects in the cardiovascular system was described, aiming to provide useful information necessary for the regulatory decision and to guide a safer application of nanotechnology.

Macrophage autophagy protects mice from cerium oxide nanoparticle-induced lung fibrosis

BACKGROUND

Cerium (Ce) is a rare earth element, rapidly oxidizing to form CeO2, and currently used in numerous commercial applications, especially as nanoparticles (NP). The potential health effects of Ce remain uncertain, but literature indicates the development of rare earth pneumoconiosis accompanied with granuloma formation, interstitial fibrosis and inflammation. The exact underlying mechanisms are not yet completely understood, and we propose that autophagy could be an interesting target to study, particularly in macrophages. Therefore, the objective of our study was to investigate the role of macrophagic autophagy after pulmonary exposure to CeO2 NP in mice. Mice lacking the early autophagy gene Atg5 in their myeloid lineage and their wildtype counterparts were exposed to CeO2 NP by single oropharyngeal administration and sacrificed up to 1 month after. At that time, lung remodeling was thoroughly characterized (inflammatory cells infiltration, expression of fibrotic markers such as αSMA, TGFβ1, total and type I and III collagen deposition), as well as macrophage infiltration (quantification and M1/M2 phenotype).

RESULTS

Such pulmonary exposure to CeO2 NP induces a progressive and dose-dependent lung fibrosis in the bronchiolar and alveolar walls, together with the activation of autophagy. Blockage of macrophagic autophagy protects from alveolar but not bronchiolar fibrosis, via the modulation of macrophage polarization towards M2 phenotype.

CONCLUSION

In conclusion, our findings bring novel insight on the role of macrophagic autophagy in lung fibrogenesis, and add to the current awareness of pulmonary macrophages as important players in the disease.

Gas6 or Mer deficiency ameliorates silica-induced autophagosomes accumulation in mice lung

Published evidences have shown that autophagy plays an important role in silica-induced lung inflammation and collagen deposition. Our previous study found that the level of growth arrest-specific protein 6 (Gas6) in bronchoalveolar lavage fluid was increased after silica exposure. However, it is unclear whether Gas6 is involved in the regulation of silica-induced autophagy dysfunction. In this study, we observed an autophagosomes accumulation in wild-type C57BL/6 (WT) mice lung after silica intratracheal instillation and then investigated whether genetic loss of Gas6 (Gas6^-/-) could ameliorate it. Our data showed that Gas6^-/- mice exhibited a limited autophagosomes accumulation from days 7-84 after silica exposure, revealed by reduced induction and increased degradation of autophagosomes in mice lung tissue. Interestingly, silica particles could elevate the expression of Mer receptor, which was significantly decreased in Gas6^-/- mice (P < 0.05). Furthermore, we found that Mer deficiency (Mer^-/-) could also reduce the formation of autophagosomes and restore the function of impaired lysosomes in silica-treated mice. Taken together, our results indicate that genetic loss of Gas6 attenuates silica-induced autophagosomes accumulation partly through down-regulating the expression of Mer receptor. Targeting Gas6/Mer-mediated autophagy pathway may provide a novel insight into the prevention and therapy of silica-induced pulmonary fibrosis.

Pyrogenic and Precipitated Amorphous Silica Nanoparticles Differentially Affect Cell Responses to LPS in Human Macrophages

Previous work has demonstrated that precipitated (NM-200) and pyrogenic (NM-203) Amorphous Silica Nanoparticles (ASNPs) elicit the inflammatory activation of murine macrophages, with more pronounced effects observed with NM-203. Here, we compare the effects of low doses of NM-200 and NM-203 on human macrophage-like THP-1 cells, assessing how the pre-exposure to these nanomaterials affects the cell response to lipopolysaccharide (LPS). Cell viability was affected by NM-203, but not by NM-200, and only in the presence of LPS. While NM-203 stimulated mTORC1, neither ASNPs activated NFκB or the transcription of its target genes PTGS2 and IL1B. NM-200 and NM-203 caused a block of the autophagic flux and inhibited the LPS-dependent increase of Glutamine Synthetase (GS) expression. Both ASNPs suppressed the activation of caspase-1, delaying the LPS-dependent secretion of IL-1β. Thus, ASNPs modulate several important pathways in human macrophages, altering their response to LPS. NM-203 had larger effects on autophagy, mTORC1 activity and GS expression than NM-200, confirming the higher biological activity of pyrogenic ASNPs when compared with precipitated ASNPs.

Self-eating: friend or foe? The emerging role of autophagy in fibrotic diseases

Fibrosis occurs in most human organs including the liver, lung, heart and kidney, and is crucial for the progression of most chronic diseases. As an indispensable catabolic process for intracellular quality control and homeostasis, autophagy occurs in most mammalian cells and is implicated in many biological processes including fibrogenesis. Although advances have been made in understanding autophagy process, the potential role of autophagy in fibrotic diseases remains controversial and has recently attracted a great deal of attention. In the current review, we summarize the commonalities of autophagy affecting different types of fibrosis in different organs, including the liver, lung, heart, and kidney as well as in cystic fibrosis, systematically outline the contradictory results and highlight the distinct role of autophagy during the various stages of fibrosis. In summary, the exact role autophagy plays in fibrogenesis depends on specific cell types and different stimuli, and identifying and evaluating the pathogenic contribution of autophagy in fibrogenesis will promote the discovery of novel therapeutic strategies for the clinical management of these fibrotic diseases.

Silica nanoparticles induce lung inflammation in mice via ROS/PARP/TRPM2 signaling-mediated lysosome impairment and autophagy dysfunction

Background

Wide applications of nanoparticles (NPs) have raised increasing concerns about safety to humans. Oxidative stress and inflammation are extensively investigated as mechanisms for NPs-induced toxicity. Autophagy and lysosomal dysfunction are emerging molecular mechanisms. Inhalation is one of the main pathways of exposing humans to NPs, which has been reported to induce severe pulmonary inflammation. However, the underlying mechanisms and, more specifically, the interplays of above-mentioned mechanisms in NPs-induced pulmonary inflammation are still largely obscure. Considered that NPs exposure in modern society is often unavoidable, it is highly desirable to develop effective strategies that could help to prevent nanomaterials-induced pulmonary inflammation.

Results

Pulmonary inflammation induced by intratracheal instillation of silica nanoparticles (SiNPs) in C57BL/6 mice was prevented by PJ34, a poly (ADP-ribose) polymerase (PARP) inhibitor. In human lung bronchial epithelial (BEAS-2B) cells, exposure to SiNPs reduced cell viability, and induced ROS generation, impairment in lysosome function and autophagic flux. Inhibition of ROS generation, PARP and TRPM2 channel suppressed SiNPs-induced lysosome impairment and autophagy dysfunction and consequent inflammatory responses. Consistently, SiNPs-induced pulmonary inflammation was prevented in TRPM2 deficient mice.

Conclusion

The ROS/PARP/TRPM2 signaling is critical in SiNPs-induced pulmonary inflammation, providing novel mechanistic insights into NPs-induced lung injury. Our study identifies TRPM2 channel as a new target for the development of preventive and therapeutic strategies to mitigate nanomaterials-induced lung inflammation.

Graphical abstract

An integrative multi-omics approach uncovers the regulatory role of CDK7 and CDK4 in autophagy activation induced by silica nanoparticles

Dysfunction of macroautophagy/autophagy has been postulated as a major cellular toxicological response to nanomaterials. It has been reported that excessive autophagy activation, induced by silica nanoparticles (SiNPs), contributes to autophagy dysfunction, whereas little is known how SiNPs trigger autophagy activation. Here, we treated normal rat kidney (NRK) cells using 3 different sizes of SiNPs (16, 29, and 51 nm) and observed that 16-nm SiNPs, with a final concentration of 60 μg/mL, dramatically induce autophagy activation without reducing cell viability. We further conducted a transcriptomic, proteomic, and phosphoproteomic profiling, and detected 23 autophagy-related (Atg) genes and 35 autophagy regulators regulated on at least one omic layer. To identify key regulators from the multi-omics data, we developed a new algorithm of computational prediction of master autophagy-regulating kinases (cMAK) to detect 21 candidates and revealed the CDK7-CDK4 cascade to be functional. The silence or inhibition of Cdk7 or Cdk4 significantly attenuated autophagic activation but not influenced autophagic flux blockage induced by 16-nm SiNPs. Further computational modeling indicated that the CDK7-CDK4 signaling axis potentially triggers autophagy activation by phosphorylating RB1 (RB transcriptional corepressor 1), activating two critical transcription factors, E2F1 (E2F transcription factor 1) and FOXO3 (forkhead box O3), and enhancing the transcriptional levels of at least 8 Atg genes and autophagy regulators in response to SiNPs. Our studies not only established a powerful method for predicting regulatory kinases from the multi-omics data but also revealed a potential mechanism of SiNP-triggered autophagy activation through modulating the CDK7-CDK4 cascade.Abbreviations: 3-MA: 3-methyladenine; Atg: autophagy-related; BECN1: beclin 1; CCK-8: cell counting kit-8; CDK4: cyclin dependent kinase 4; CDK7: cyclin dependent kinase 7; cMAK: computational prediction of master autophagy-regulating kinases; CQ: chloroquine; DMEM: Dulbecco's modified Eagle's medium; DMSO: dimethyl sulfoxide; E-ratio: enrichment ratio; E2F1: E2F transcription factor 1; EBSS: Earle's balanced salt solution; ER: endoplasmic reticulum; FOXO3: forkhead box O3; FPKM: fragments per kilobase of exon per million fragments mapped; GO: gene ontology; H₂O₂: hydrogen peroxide; iGPS: in vivo GPS; KEGG: Kyoto Encyclopedia of Genes and Genomes; LC-MS/MS: liquid chromatography-tandem mass spectrometry; LDH: lactate dehydrogenase; MAP1LC3B/LC3: microtubule associated protein 1 light chain 3 beta; NRK: normal rat kidney; p-site: phosphorylation site; PBS: phosphate-buffered saline; PDI: polydispersity index; PTM: post-translational modification; QKS: quantitative kinase state; RB1: RB transcriptional corepressor 1; RBHs: reciprocal best hits; RNA-Seq: RNA sequencing; ROS: reactive oxygen species; rSiNPs: SiNPs fluorescently labeled with rhodamine B; SEM: scanning electronic microscopy; SiNPs: silica nanoparticles; siRNA: small interfering RNA; SQSTM1/p62: sequestosome 1; ssKSR: site-specific kinase-substrate relation; TEM: transmission electron microscopy; tfLC3: mRFP-GFP tandem fluorescent-tagged LC3.

p62/SQSTM1 accumulation due to degradation inhibition and transcriptional activation plays a critical role in silica nanoparticle-induced airway inflammation via NF-κB activation

BACKGROUND

Most nanoparticles (NPs) reportedly block autophagic flux, thereby upregulating p62/SQSTM1 through degradation inhibition. p62 also acts as a multifunctional scaffold protein with multiple domains, and is involved in various cellular processes. However, the autophagy substrate-independent role of p62 and its regulation at the transcriptional level upon NPs exposure remain unclear.

RESULTS

In this work, we exposed BEAS-2b cells and mice to silica nanoparticles (SiNPs), and found that SiNPs increased p62 protein levels in vivo and vitro. Then, we further explored the role and mechanism of SiNPs-stimulated p62 in vitro, and found that p62 degradation was inhibited due to autophagic flux blockade. Mechanistically, SiNPs blocked autophagic flux through impairment of lysosomal capacity rather than defective autophagosome fusion with lysosomes. Moreover, SiNPs stimulated translocation of NF-E2-related factor 2 (Nrf2) to the nucleus from the cytoplasm, which upregulated p62 transcriptional activation through direct binding of Nrf2 to the p62 promoter. Nrf2 siRNA dramatically reduced both the mRNA and protein levels of p62. These two mechanisms led to p62 protein accumulation, thus increasing interleukin (IL)-1 and IL-6 expression. SiNPs activated nuclear factor kappa B (NF-κB), and this effect could be alleviated by p62 knockdown.

CONCLUSION

SiNPs caused accumulation of p62 through both pre- and post-translational mechanisms, resulting in airway inflammation. These findings improve our understanding of SiNP-induced pulmonary damage and the molecular targets available to mitigate it.

Iron Oxide Nanoparticle-Induced Autophagic Flux Is Regulated by Interplay between p53-mTOR Axis and Bcl-2 Signaling in Hepatic Cells

Iron oxide-based nanoparticles have been repeatedly shown to affect lysosomal-mediated signaling. Recently, nanoparticles have demonstrated an ability to modulate autophagic flux via lysosome-dependent signaling. However, the precise underlying mechanisms of such modulation as well as the impact of cellular genetic background remain enigmatic. In this study, we investigated how lysosomal-mediated signaling is affected by iron oxide nanoparticle uptake in three distinct hepatic cell lines. We found that nanoparticle-induced lysosomal dysfunction alters sub-cellular localization of pmTOR and p53 proteins. Our data indicate that alterations in the sub-cellular localization of p53 protein induced by nanoparticle greatly affect the autophagic flux. We found that cells with high levels of Bcl-2 are insensitive to autophagy initiated by nanoparticles. Altogether, our data identify lysosomes as a central hub that control nanoparticle-mediated responses in hepatic cells. Our results provide an important fundamental background for the future development of targeted nanoparticle-based therapies.

Silibinin Attenuates Silica Dioxide Nanoparticles-Induced Inflammation by Suppressing TXNIP/MAPKs/AP-1 Signaling

Silica dioxide nanoparticles (SiONPs) have been applied to several fields, such as drug delivery and gene therapy. However, SiONPs are a constituent of fine dust and can induce excessive inflammatory responses in the lungs via the airways. Silibinin, a major component of silymarin, has been known for its anti-oxidant and anti-inflammatory effects. In the present study, we explored the protective effects of silibinin against SiONPs-induced airway inflammation and explored its underlying mechanism of action, focusing on thioredoxin-interacting protein (TXNIP)/mitogen-activated protein kinases (MAPKs) in vitro and in vivo. In SiONPs-stimulated NCI-H292 airway epithelial cells, silibinin treatment effectively suppressed the elevation of the mRNA expression of tumor necrosis factor-α (TNF-α), interleukin (IL)-6, and IL-1β, which was accompanied by the reduction in the expression of TXNIP, MAPKs, and activator protein-1 (AP-1). In SiONPs-treated mice, silibinin administration inhibited the increase in inflammatory cell counts and proinflammatory mediators, and it alleviated airway inflammation by SiONPs exposure. In addition, silibinin administration effectively suppressed the elevation of TXNIP/MAPKs/AP-1 signaling by SiONPs exposure. Taken together, silibinin effectively inhibited SiONPs-induced inflammatory responses, and this effect was closely related to the inhibition of TXNIP/MAPK/AP-1 signaling. These results suggested that silibinin might be useful for reducing pulmonary inflammation induced by SiONPs.

DROSHA-Dependent miRNA and AIM2 Inflammasome Activation in Idiopathic Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive interstitial lung disease. Chronic lung inflammation is linked to the pathogenesis of IPF. DROSHA, a class 2 ribonuclease III enzyme, has an important role in the biogenesis of microRNA (miRNA). The function of miRNAs has been identified in the regulation of the target gene or protein related to inflammatory responses via degradation of mRNA or inhibition of translation. The absent-in-melanoma-2 (AIM2) inflammasome is critical for inflammatory responses against cytosolic double stranded DNA (dsDNA) from pathogen-associated molecular patterns (PAMPs) and self-DNA from danger-associated molecular patterns (DAMPs). The AIM2 inflammasome senses double strand DNA (dsDNA) and interacts with the adaptor apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC), which recruits pro-caspase-1 and regulates the maturation and secretion of interleukin (IL)-1β and IL-18. A recent study showed that inflammasome activation contributes to lung inflammation and fibrogenesis during IPF. In the current review, we discuss recent advances in our understanding of the DROSHA-miRNA-AIM2 inflammasome axis in the pathogenesis of IPF.

Autophagy, an important therapeutic target for pulmonary fibrosis diseases

As an evolutionarily conserved intracellular degradation pathway, autophagy is essential to cellular homeostasis. Several studies have demonstrated that autophagy showed an important effect on some pulmonary fibrosis diseases, including idiopathic pulmonary fibrosis (IPF), cystic fibrosis lung disease, silicosis and smoking-induced pulmonary fibrosis. For example, autophagy mitigates the pathological progression of IPF by regulating the apoptosis of fibroblasts and the senescence of alveolar epithelial cells. In addition, autophagy ameliorates cystic fibrosis lung disease via rescuing transmembrane conductance regulators (CFTRs) to the plasma membrane. Furthermore, autophagy alleviates the silica-induced pulmonary fibrosis by decreasing apoptosis of alveolar epithelial cells in silicosis. However, excessive macrophage autophagy aggravates the pathogenesis of silicosis fibrosis by promoting the proliferation and migration of lung fibroblasts in silicosis. Autophagy is also involved in smoking-induced pulmonary fibrosis, coal workers' pneumoconiosis, ionizing radiation-mediated pulmonary fibrosis and heavy metal nanoparticle-mediated pulmonary fibrosis. In this review, the role and signalling mechanisms of autophagy in the progression of pulmonary fibrosis diseases have been systematically analysed. It has provided a new insight into the therapeutic potential associated with autophagy in pulmonary fibrosis diseases. In conclusion, the targeting of autophagy might prove to be a prospective avenue for the therapeutic intervention of pulmonary fibrosis diseases.

Microarray-assisted size-effect study of amorphous silica nanoparticles on human bronchial epithelial cells

Amorphous silica nanoparticles (SiNPs) are not only abundant in nature, but also the second largest engineering nanomaterials in terms of annual output. Respiratory exposure is the main route for SiNPs to enter the human body. A large number of studies have focused on the respiratory toxicity of SiNPs and demonstrated that SiNPs could induce pulmonary tissue damage, inflammation, fibrosis, and even the malignant transformation of bronchial epithelial cells, while the size-dependent toxicity of SiNPs and their underlying biological mechanisms remain unclear. In this regard, a transcriptomics study would be conductive to gaining a better understanding of the toxic mechanism. In the present study, microarray analysis was performed to investigate the genome-wide transcriptional alteration induced by different sizes of SiNPs in human primary bronchial epithelial cells (BEAS-2B). To determine the effect of the particle size on the toxicity, nanoparticles of two sizes (41 nm and 61 nm) and submicron particles of one size (206 nm) were introduced. The bioinformatics analysis results indicated that: (1) the number of differentially expressed genes in the three SiNP-treated groups increased with the particle size decreasing; (2) the genes involved in the immune and inflammatory response, gene expression, signal transduction, endoplasmic reticulum stress, oxidative stress, cell metabolism, and cell proliferation were gradually upregulated with the particle size decreasing, while the genes related to the morphological development of the respiratory system were gradually downregulated with the particle size decreasing; (3) the modes of action of the two nanoparticles overlapped with each other to some degree, and there existed many different modes compared to those from the submicron particles; (4) both the silica nanoparticles affected the pathways associated with the cell entry of silica nanoparticles, autophagy and lysosomal dysfunction, endoplasmic reticulum stress, inflammatory response, DNA damage, and gene expression, as well as apoptotic resistance and cancer. To the best of our knowledge, this is the first study that has reported the alteration trend of gene expression profiles with the change in silica particle size. Our study provides a great deal of information on the toxic mechanisms underlying the respiratory toxicity induced by SiNPs, and can also serve as an experimental basis for the toxicity and safety evaluation of silica nanoparticles.

Autophagy Modulation in Human Thyroid Cancer Cells following Aloperine Treatment

Aloperine, an alkaloid isolated from Sophoraalopecuroides, exhibits multiple pharmacological activities including anti-inflammatory, antioxidant, antiallergic, antinociceptive, antipathogenic, and antitumor effects. Furthermore, it exerts protective effects against renal and neuronal injuries. Several studies have reported antitumor effects of aloperine against various human cancers, including multiple myeloma; colon, breast, and prostate cancers; and osteosarcoma. Cell cycle arrest, apoptosis induction, and tumorigenesis suppression have been demonstrated following aloperine treatment. In a previous study, we demonstrated antitumor effects of aloperine on human thyroid cancer cells through anti-tumorigenesis and caspase-dependent apoptosis induction via the Akt signaling pathway. In the present study, we demonstrated the modulation of the autophagy mechanism following the incubation of multidrug-resistant papillary and anaplastic human thyroid cancer cells with aloperine; we also illustrate the underlying mechanisms, including AMPK, Erk, JNK, p38, and Akt signaling pathways. Further investigation revealed the involvement of the Akt signaling pathway in aloperine-modulated autophagy in human thyroid cancer cells. These results indicate a previously unappreciated function of aloperine in autophagy modulation in human thyroid cancer cells.

CNOT2 Is Critically Involved in Atorvastatin Induced Apoptotic and Autophagic Cell Death in Non-Small Cell Lung Cancers

Though Atorvastatin has been used as a hypolipidemic agent, its anticancer mechanisms for repurposing are not fully understood so far. Thus, in the current study, its apoptotic and autophagic mechanisms were investigated in non-small cell lung cancers (NSCLCs). Atorvastatin increased cytotoxicity, sub G1 population, the number of apoptotic bodies, cleaved poly (ADP-ribose) polymerase (PARP) and caspase 3 and activated p53 in H1299, H596, and H460 cells. Notably, Atorvastatin inhibited the expression of c-Myc and induced ribosomal protein L5 and L11, but depletion of L5 reduced PARP cleavages induced by Atorvastatin rather than L11 in H1299 cells. Also, Atorvastatin increased autophagy microtubule-associated protein 1A/1B-light chain 3II (LC3 II) conversion, p62/sequestosome 1 (SQSTM1) accumulation with increased number of LC3II puncta in H1299 cells. However, late stage autophagy inhibitor chloroquine (CQ) increased cytotoxicity in Atorvastatin treated H1299 cells compared to early stage autophagy inhibitor 3-methyladenine (3-MA). Furthermore, autophagic flux assay using RFP-GFP-LC3 constructs and Lysotracker Red or acridine orange-staining demonstrated that autophagosome-lysosome fusion is blocked by Atorvastatin treatment in H1299 cells. Conversely, overexpression of CCR4-NOT transcription complex subunit 2(CNOT2) weakly reversed the ability of Atorvastatin to increase cytotoxicity, sub G1 population, cleavages of PARP and caspase 3, LC3II conversion and p62/SQSTM1 accumulation in H1299 cells. In contrast, CNOT2 depletion enhanced cleavages of PARP and caspase 3, LC3 conversion and p62/SQSTM1 accumulation in Atorvastatin treated H1299 cells. Overall, these findings suggest that CNOT2 signaling is critically involved in Atorvastatin induced apoptotic and autophagic cell death in NSCLCs.

Kaempferol Modulates Autophagy and Alleviates Silica-Induced Pulmonary Fibrosis

Silicosis is an occupational disease characterized as inflammatory cells infiltration and severe progressive pulmonary fibrosis. Kaempferol (Kae), a flavonoid that exists in many plants and fruits, has been proved to have anti-inflammatory and antifibrosis functions. However, the effects of Kae on silicosis remain unclear. In the present study, we analyzed the therapeutic effects of Kae in 1-, 7-, and 28-day silicosis models, respectively. In the 1-day model, Kae treatment did not vary the wet-to-dry weight ratios of the lung, apoptotic rate, autophagy, or the expression of inflammatory factors. In contrast, Kae significantly inhibited pulmonary inflammation in the 7-day silicosis models and inhibited silica-induced pulmonary fibrosis in the 28-day models. Besides, we found that Kae partially restored silica-induced LC3 lipidation without increasing the p62 levels. Blocking autophagy with chloroquine antagonized the inhibitory effects of Kae on inflammation, suggesting that autophagy might be required in the therapeutic effects of Kae on silicosis. These findings indicated that Kae inhibits the progression of silica-induced pulmonary fibrosis, which may provide experimental evidences for Kae in the treatment of silicosis.

Endosomal/lysosomal location of organically modified silica nanoparticles following caveolae-mediated endocytosis

Organically modified silica (ORMOSIL) nanoparticles (NPs) are widely used in biomedicine.