Depletion of BIS sensitizes A549 cells to treatment with cisplatin

Advanced pathophysiology mimicking lung models for accelerated drug discovery

BACKGROUND

Respiratory diseases are the 2nd leading cause of death globally. The current treatments for chronic lung diseases are only supportive. Very few new classes of therapeutics have been introduced for lung diseases in the last 40 years, due to the lack of reliable lung models that enable rapid, cost-effective, and high-throughput testing. To accelerate the development of new therapeutics for lung diseases, we established two classes of lung-mimicking models: (i) healthy, and (ii) diseased lungs - COPD.

METHODS

To establish models that mimic the lung complexity to different extents, we used five design components: (i) cell type, (ii) membrane structure/constitution, (iii) environmental conditions, (iv) cellular arrangement, (v) substrate, matrix structure and composition. To determine whether the lung models are reproducible and reliable, we developed a quality control (QC) strategy, which integrated the real-time and end-point quantitative and qualitative measurements of cellular barrier function, permeability, tight junctions, tissue structure, tissue composition, and cytokine secretion.

RESULTS

The healthy model is characterised by (i) continuous tight junctions, (ii) physiological cellular barrier function, (iii) a full thickness epithelium composed of multiple cell layers, and (iv) the presence of ciliated cells and goblet cells. Meanwhile, the disease model emulates human COPD disease: (i) dysfunctional cellular barrier function, (ii) depletion of ciliated cells, and (ii) overproduction of goblet cells. The models developed here have multiple competitive advantages when compared with existing in vitro lung models: (i) the macroscale enables multimodal and correlative characterisation of the same model system, (ii) the use of cells derived from patients that enables the creation of individual models for each patient for personalised medicine, (iii) the use of an extracellular matrix proteins interface, which promotes physiological cell adhesion and differentiation, (iv) media microcirculation that mimics the dynamic conditions in human lungs.

CONCLUSION

Our model can be utilised to test safety, efficacy, and superiority of new therapeutics as well as to test toxicity and injury induced by inhaled pollution or pathogens. It is envisaged that these models can also be used to test the protective function of new therapeutics for high-risk patients or workers exposed to occupational hazards.

Lung development, repair and cancer: A study on the role of MMP20 gene in adenocarcinoma

Multiple matrix metalloproteinases have significant roles in tissue organization during lung development, and repair. Imbalance of proteinases may lead to chronic inflammation, changes in tissue structure, and are also highly associated to cancer development. The role of MMP20 is not well studied in lung organogenesis, however, it was previously shown to be present at high level in lung adenocarcinoma. The current study aimed to identify the functional properties of MMP20 on cell proliferation and motility in a lung adenocarcinoma in vitro cell model, and relate the interaction of MMP20 with other molecular signalling pathways in the lung cells after gaining tumoral properties. In this study, two different single guide RNA (sgRNAs) that specifically targeted on MMP20 sites were transfected into human lung adenocarcinoma A549 cells by using CRISPR-Cas method. Following that, the changes of PI3-K, survivin, and MAP-K mRNA gene expression were determined by Real-Time Polymerase Chain Reaction (RT-PCR). The occurrence of cell death was also examined by Acridine Orange/Propidium Iodide double staining. Meanwhile, the motility of the transfected cells was evaluated by wound healing assay. All the data were compared with non-transfected cells as a control group. Our results demonstrated that the transfection of the individual sgRNAs significantly disrupted the proliferation of the A549 cell line through suppression in the gene expression of PI3-K, survivin, and MAP-K. When compared to non-transfected cells, both experimental cell groups showed reduction in the migration rate, as reflected by the wider gaps in the wound healing assay. The current study provided preliminary evidence that MMP20 could have regulatory role on stemness and proliferative genes in the lung tissues and affect the cell motility. It also supports the notion that targeting MMP20 could be a potential treatment mode for halting cancer progression.

SRSF3 Is a Critical Requirement for Inclusion of Exon 3 of BIS Pre-mRNA

BCL-2 interacting cell death suppressor (BIS), also known as BAG3, is a multifunctional protein. Aberrant expression and mutation of BIS have been implicated in cancers and myopathy. However, there have only been a few studies on the splicing of BIS pre-mRNA. In the present study, through RT-PCR and sequencing in various cell lines and mouse tissues, we identified for the first time the presence of BIS mRNA isomers in which exon 3 or exons 2–3 are skipped. We also demonstrated that the depletion of SRSF3 promoted the skipping of exon 3 of BIS pre-mRNA in endogenous BIS and the GFP-BIS minigene. SRSF3 specifically interacts with the putative binding sites in exon 3, in which deletion promoted the skipping of exon 3 in the GFP-BIS minigene, which was comparable to the effect of SRSF knockdown. Even though acceleration of exon 3 skipping was not observed in response to various stimuli, SRSF3 depletion, accompanied by the production of a truncated BIS protein, inhibited the nuclear translocation of HSF1, which was restored by the wild-type BIS, not by exon 3-depleted BIS. Therefore, our results suggested that the maintenance of SRSF3 levels and subsequent preservation of the intact BIS protein is an important factor in modulating HSF1 localization upon cellular stress.

Downregulation of BIS sensitizes A549 cells for digoxin-mediated inhibition of invasion and migration by the STAT3-dependent pathway

Digoxin, a compound of the cardiac glycoside family, was originally prescribed for heart failure but has recently been rediscovered for its potent antitumor activity. However, it has a narrow therapeutic margin due to its cardiotoxicity, limiting its safe use as an antitumor agent in clinical practice. To widen its therapeutic margin, we investigated whether the antitumor effect of digoxin is potentiated by the depletion of BCL-2-interacting cell death suppressor (BIS) in A549 lung cancer cells. BIS is a multifunctional protein that is frequently overexpressed in most human cancers including lung cancer. Our results demonstrated that the inhibitory potential of digoxin on the migratory behavior of A549 cells is significantly enhanced by BIS depletion as assessed by transwell assay and collagen-incorporated 3D spheroid culture. Western blotting revealed that combination treatment significantly reduces p-STAT3 expression. In addition, a STAT3 inhibitor substantially suppressed the aggressive phenotypes of A549 cells. Thus, our results suggest that loss of STAT3 activity is a possible molecular mechanism for the synergistic effect of digoxin and BIS depletion. Our findings suggest the sensitizing role of BIS silencing to reduce the dose of digoxin for treatment of lung cancer with a high metastatic potential.

Human pluripotent stem cell-derived alveolar epithelial cells are alternatives for in vitro pulmotoxicity assessment

Human pluripotent stem cell (hPSC)-derived alveolar epithelial cells (AECs) provide new opportunities for understanding lung development and the treatment of pulmonary diseases. However, toxicity assessments using hPSC-AECs have not been undertaken. In this study, we generated functional AECs from hPSCs and evaluated their inflammatory and apoptotic responses to cadmium (Cd) exposure (1, 5, and 10 μM) for 24 h compared with the human bronchial epithelial cell line (BEAS-2B) and primary AECs as controls. Our data showed that Cd (10 μM) treatment induced substantial inflammatory responses and apoptosis in BEAS-2B cells, but not in both hPSC-AECs and primary AECs. Interestingly, conditioned medium from AEC cultures significantly alleviated apoptotic and inflammatory responses to Cd exposure in BEAS-2B cells. Using cytokine arrays, several potential factors secreted from hPSC-AECs and primary AECs were detected and may be involved in reducing Cd-induced cytotoxicity. We also observed higher expression of surfactant proteins B and C in both hPSC-AECs and primary AECs, which may contribute to protection against Cd-induced cytotoxicity. These results suggested that hPSC-AECs phenotypically and functionally resemble primary AECs and could be more biologically relevant alternatives for evaluating the pathological contribution of confirmed or potential pulmotoxic materials included in smoking and microdust.

Effect of BIS depletion on HSF1-dependent transcriptional activation in A549 non-small cell lung cancer cells

The expression of BCL-2 interacting cell death suppressor (BIS), an anti-stress or anti-apoptotic protein, has been shown to be regulated at the transcriptional level by heat shock factor 1 (HSF1) upon various stresses. Recently, HSF1 was also shown to bind to BIS, but the significance of these protein-protein interactions on HSF1 activity has not been fully defined. In the present study, we observed that complete depletion of BIS using a CRISPR/Cas9 system in A549 non-small cell lung cancer did not affect the induction of heat shock protein (HSP) 70 and HSP27 mRNAs under various stress conditions such as heat shock, proteotoxic stress, and oxidative stress. The lack of a functional association of BIS with HSF1 activity was also demonstrated by transient downregulation of BIS by siRNA in A549 and U87 glioblastoma cells. Endogenous BIS mRNA levels were significantly suppressed in BIS knockout (KO) A549 cells compared to BIS wild type (WT) A549 cells at the constitutive and inducible levels. The promoter activities of BIS and HSP70 as well as the degradation rate of BIS mRNA were not influenced by depletion of BIS. In addition, the expression levels of the mutant BIS construct, in which 14 bp were deleted as in BIS-KO A549 cells, were not different from those of the WT BIS construct, indicating that mRNA stability was not the mechanism for autoregulation of BIS. Our results suggested that BIS was not required for HSF1 activity, but was required for its own expression, which involved an HSF1-independent pathway.

Activation of intestinal olfactory receptor stimulates glucagon-like peptide-1 secretion in enteroendocrine cells and attenuates hyperglycemia in type 2 diabetic mice

Odorants are non-nutrients. However, they exist abundantly in foods, wines, and teas, and thus can be ingested along with the other nutrients during a meal. Here, we have focused on the chemical-recognition ability of these ORs and hypothesized that the odorants ingested during a meal may play a physiological role by activating the gut-expressed ORs. Using a human-derived enteroendocrine L cell line, we discovered the geraniol- and citronellal-mediated stimulation of glucagon-like peptide-1 (GLP-1) secretion and elucidated the corresponding cellular downstream signaling pathways. The geraniol-stimulated GLP-1 secretion event in the enteroendocrine cell line was mediated by the olfactory-type G protein, the activation of adenylyl cyclase, increased intracellular cAMP levels, and extracellular calcium influx. TaqMan qPCR demonstrated that two ORs corresponding to geraniol and citronellal were expressed in the human enteroendocrine cell line and in mouse intestinal specimen. In a type 2 diabetes mellitus mouse model (db/db), oral administration of geraniol improved glucose homeostasis by increasing plasma GLP-1 and insulin levels. This insulinotropic action of geraniol was GLP-1 receptor-mediated, and also was glucose-dependent. This study demonstrates that odor compounds can be recognized by gut-expressed ORs during meal ingestion and therefore, participate in the glucose homeostasis by inducing the secretion of gut-peptides.

KRIBB11 accelerates Mcl-1 degradation through an HSF1-independent, Mule-dependent pathway in A549 non-small cell lung cancer cells

The Bcl-2 family protein, Mcl-1 is known to have anti-apoptotic functions, and depletion of Mcl-1 by cellular stresses favors the apoptotic process. Moreover, Mcl-1 levels are frequently increased in various cancer cells, including non-small cell lung cancer (NSCLC), and is implicated in resistance to conventional chemotherapy and in cancer metastasis. In this study, we demonstrated that KRIBB11 accelerates the proteasomal degradation of Mcl-1 in the NSCLC cell line, A549. While KRIBB11 is an inhibitor of HSF1, we found that KRIBB11 induced Mcl-1 degradation in an HSF1-independent manner. Furthermore, this process was triggered via increase ubiquitination by the E3 ligase, Mule, rather than via de-ubiquitination by USP9X. Additionally, we found that Mcl-1 levels were only transiently reduced by KRIBB11: Mcl-1 levels were gradually restored as KRIBB11 activity diminished. However, we found that this effect was blocked in BIS (Bcl-2 interacting cell death suppressor, also called BAG3)-depleted cells, and that BIS prevents Mcl-1 from undergoing HSP70-driven proteasomal degradation, through an interaction with HSP70. Taken together, our results suggest that targeting Mcl-1 with KRIBB11 treatment, while simultaneously downregulating BIS, could be a therapeutic strategy in NSCLC.

Heat Shock Factor 1 Depletion Sensitizes A172 Glioblastoma Cells to Temozolomide via Suppression of Cancer Stem Cell-Like Properties

Heat shock factor 1 (HSF1), a transcription factor activated by various stressors, regulates proliferation and apoptosis by inducing expression of target genes, such as heat shock proteins and Bcl-2 (B-cell lymphoma 2) interacting cell death suppressor (BIS). HSF1 also directly interacts with BIS, although it is still unclear whether this interaction is critical in the regulation of glioblastoma stem cells (GSCs). In this study, we examined whether small interfering RNA-mediated BIS knockdown decreased protein levels of HSF1 and subsequent nuclear localization under GSC-like sphere (SP)-forming conditions. Consistent with BIS depletion, HSF1 knockdown also reduced sex determining region Y (SRY)-box 2 (SOX2) expression, a marker of stemness, accompanying the decrease in SP-forming ability and matrix metalloprotease 2 (MMP2) activity. When HSF1 or BIS knockdown was combined with temozolomide (TMZ) treatment, a standard drug used in glioblastoma therapy, apoptosis increased, as measured by an increase in poly (ADP-ribose) polymerase (PARP) cleavage, whereas cancer stem-like properties, such as colony-forming activity and SOX2 protein expression, decreased. Taken together, our findings suggest that targeting BIS or HSF1 could be a viable therapeutic strategy for GSCs resistant to conventional TMZ treatment.

Ginkgolide A ameliorates non-alcoholic fatty liver diseases on high fat diet mice

Non-alcoholic fatty liver disease (NAFLD) is one of the most common diseases worldwide and has continuously increased. NAFLD refers to a spectrum of diseases ranging from fatty liver to steatohepatitis, cirrhosis, and even to hepatocyte carcinoma. Excessive fatty acid enters the cell and the mitochondria undergo stress and unremoved ROS can trigger a form of cell apoptosis known as 'lipoapoptosis'. NASH arises from damaged liver hepatocytes due to lipotoxicity. NASH not only involves lipid accumulation and apoptosis but also inflammation. Ginkgo biloba has been tested clinical trials as a traditional medicine for asthma, bronchitis and cardiovascular disease. The effects of Ginkgolide A (GA), derived from the ginkgo biloba leaf, are still unknown in NAFLD. To determine the protective effects of GA in NAFLD, we examined the fatty liver disease condition in the non-esterified fatty acid (NEFA)-induced HepG2 cell line and in a high fat diet mouse model. The findings of this study suggest that GA is non-toxic at high concentrations in hepatocytes. Moreover, GA was found to inhibit cellular lipogenesis and lipid accumulation by causing mitochondrial oxidative stress. GA showed hepatoprotective efficacy by inducing cellular lipoapoptosis and by inhibiting cellular inflammation. The results demonstrated that GA may be feasible as a therapeutic agent for NAFLD patients.

ERK-mediated phosphorylation of BIS regulates nuclear translocation of HSF1 under oxidative stress

B-cell lymphoma (BCL)-2-interacting cell death suppressor (BIS) has diverse cellular functions depending on its binding partners. However, little is known about the effects of biochemical modification of BIS on its various activities under oxidative stress conditions. In this study, we showed that H₂O₂ reduced BIS mobility on SDS–polyacrylamide gels in a time-dependent manner via the activation of extracellular signaling-regulated kinase (ERK). The combined results of mass spectroscopy and computational prediction identified Thr285 and Ser289 in BIS as candidate residues for phosphorylation by ERK under oxidative stress conditions. Deletion of these sites resulted in a partial reduction in the H₂O₂-induced mobility shift relative to that of the wild-type BIS protein; overexpression of the deletion mutant sensitized A172 cells to H₂O₂-induced cell death without increasing the level of intracellular reactive oxygen species. Expression of the BIS deletion mutant decreased the level of heat shock protein (HSP) 70 mRNA following H₂O₂ treatment, which was accompanied by impaired nuclear translocation of heat shock transcription factor (HSF) 1. Co-immunoprecipitation assays revealed that the binding of wild-type BIS to HSF1 was decreased by oxidative stress, while the binding of the BIS deletion mutant to HSF1 was not affected. These results indicate that ERK-dependent phosphorylation of BIS has a role in the regulation of nuclear translocation of HSF1 likely through modulation of its interaction affinity with HSF1, which affects HSP70 expression and sensitivity to oxidative stress.

Anti-lipoapoptotic effects of Alisma orientalis extract on non-esterified fatty acid-induced HepG2 cells

BACKGROUND

Liver steatosis was caused by lipid accumulation in the liver. Alisma orientale (AO) is recognized as a promising candidate with therapeutic efficacy for the treatment of nonalcoholic fatty liver disease (NAFLD). HepG2 hepatocyte cell line is commonly used for liver disease cell model.

METHOD

The HepG2 cells were cultured with the NEFAs mixture (oleic and palmitic acids, 2:1 ratio) for 24 h to induce hepatic steatosis. Then different doses of Alisma orientale extract (AOE) was treated to HepG2 for 24 h. Incubated cells were used for further experiments.

RESULTS

The AOE showed inhibitory effects on lipid accumulation in the Oil Red O staining and Nile red staining tests with no cytotoxicity at a concentration of 300 μg/mL. Fatty acid synthase (FASN) and acetyl-CoA carboxylase 1 (ACC1) mRNA and protein expression level were down-regulated after AOE treatment. Bcl-2 associated X protein (Bax) and c-Jun N-terminal kinase (JNK) mRNA expression level were decreased as well as p-JNK (activated form of JNK), Bax, cleaved caspase-9, caspase-3 protein expression level. Anti-apopototic B-cell lymphoma 2 (Bcl-2) protein level increased after AOE treatment. In addition, inflammatory protein expression including p-p65, p65, COX-2 and iNOS were inhibited by AOE treatment.

CONCLUSION

The results suggest that AOE has anti-steatosis effects that involve lipogenesis, anti-lipoapoptosis, and anti-inflammation in the NEFA-induced NAFLD pathological cell model.