Targeting the Na(+)/K(+)-ATPase alpha1 subunit of hepatoma HepG2 cell line to induce apoptosis and cell cycle arresting

Pathophysiological role of ion channels and transporters in hepatocellular carcinoma

The incidence of hepatocellular carcinoma (HCC) has continued to increase annually worldwide, and HCC has become a common cause of cancer-related death. Despite great progress in understanding the molecular mechanisms underlying HCC development, the treatment of HCC remains a considerable challenge. Thus, the survival and prognosis of HCC patients remain extremely poor. In recent years, the role of ion channels in the pathogenesis of diseases has become a hot topic. In normal liver tissue, ion channels and transporters maintain water and electrolyte balance and acid‒base homeostasis. However, dysfunction of these ion channels and transporters can lead to the development and progression of HCC, and thus these ion channels and transporters are expected to become new therapeutic targets. In this review, ion channels and transporters associated with HCC are reviewed, and potential targets for new and effective therapies are proposed.

Bufalin CaCO3 Nanoparticles Triggered Pyroptosis through Calcium Overload via Na+/Ca2+ Exchanger Reverse for Cancer Immunotherapy

Bufalin is a promising active ingredient in traditional Chinese medicine but has shown limited anticancer applications due to its toxicity. Here, we report BCNPs@gel, a bufalin-containing CaCO3 nanoparticle hydrogel, for enhancing cancer treatment through inducing cellular pyroptosis. Under the tumor microenvironment's low pH conditions, bufalin and Ca2+ are released from the delivery system. Bufalin serves as a direct anticancer drug and a Na+/K+-ATPase inhibitor by forcing the Na+/Ca2+ exchanger to reverse its function, which transfers Ca2+ into cytoplasm and ultimately causes Ca2+ overload-triggered pyroptosis. Meanwhile, we found that bufalin can upregulate PD-L1 in tumor cells. In combination with the PD-1 antibody, the delivery system showed a greater performance during the cancer treatment. BCNPs@gel enhances antitumor efficiency, reduces systemic side effects, extends antitumor mechanism of bufalin, and provides new strategies for inducing pyroptosis and calcium overload in cancer immunotherapy via Na+/K+-ATPase inhibitor. This work provides an application model for numerous other traditional Chinese medicine ingredients.

Occupational second-hand smoke exposure: A comparative shotgun proteomics study on nasal epithelia from healthy restaurant workers

Non-smokers exposed to second-hand smoke (SHS) present risk of developing tobacco smoke-associated pathologies. To investigate the airway molecular response to SHS exposure that could be used in health risk assessment, comparative shotgun proteomics was performed on nasal epithelium from a group of healthy restaurant workers, non-smokers (never and former) exposed and not exposed to SHS in the workplace. HIF1α-glycolytic targets (GAPDH, TPI) and proteins related to xenobiotic metabolism, cell proliferation and differentiation leading to cancer (ADH1C, TUBB4B, EEF2) showed significant modulation in non-smokers exposed. In never smokers exposed, enrichment of glutathione metabolism pathway and EEF2-regulating protein synthesis in genotoxic response were increased, while in former smokers exposed, proteins (LYZ, ATP1A1, SERPINB3) associated with tissue damage/regeneration, apoptosis inhibition and inflammation that may lead to asthma, COPD or cancer, were upregulated. The identified proteins are potential response and susceptibility/risk biomarkers for SHS exposure.

Cytostatic and cytotoxic effects of a hot water and methanol extract of Acokanthera oppositifolia in HepG2 hepatocarcinoma cells

ETHNOPHARMACOLOGICAL RELEVANCE

Herb-induced liver injury is poorly described for African herbal remedies, such as Acokanthera oppositifolia. Although a commonly used treatment for pain, snake bites and anthrax, it is also a well-known arrow poison, thus toxicity is to be expected.

AIM OF THE STUDY

The cytotoxicity and preliminary mechanisms of toxicity in HepG2 hepatocarcinoma cells were assessed.

MATERIALS AND METHODS

The effect of hot water and methanol extracts were on cell density, oxidative status, mitochondrial membrane potential, fatty acids, caspase-3/7 activity, adenosine triphosphate levels, cell cycling and viability was assessed. Phytochemicals were tentatively identified using ultra-performance liquid chromatography.

RESULTS

The hot water extract displayed an IC₅₀ of 24.26 μg/mL, and reduced proliferation (S- and G2/M-phase arrest) and viability (by 30.71%) as early as 24 h after incubation. The methanol extract had a comparable IC₅₀ of 26.16 μg/mL, and arrested cells in the G2/M-phase (by 18.87%) and induced necrosis (by 13.21%). The hot water and methanol extracts depolarised the mitochondrial membrane (up to 0.84- and 0.74-fold), though did not generate reactive oxygen species. The hot water and methanol extracts decreased glutathione (0.42- and 0.62-fold) and adenosine triphosphate (0.08- and 0.26-fold) levels, while fatty acids (2.00- and 4.61-fold) and caspase-3/7 activity (1.98- and 5.82-fold) were increased.

CONCLUSION

Extracts were both cytostatic and cytotoxic in HepG2 cells. Mitochondrial toxicity was evident and contributed to reducing adenosine triphosphate production and fatty acid accumulation. Altered redox status perturbed proliferation and promoted necrosis. Extracts of A. oppositifolia may thus promote necrotic cell death, which poses a risk for inflammatory hepatotoxicity with associated steatosis.

The Alpha-1 Subunit of the Na+/K+-ATPase (ATP1A1) Is a Host Factor Involved in the Attachment of Porcine Epidemic Diarrhea Virus

Porcine epidemic diarrhea (PED) is an acute and severe atrophic enteritis caused by porcine epidemic diarrhea virus (PEDV) that infects pigs and makes huge economic losses to the global swine industry. Previously, researchers have believed that porcine aminopeptidase-N (pAPN) was the primary receptor for PEDV, but it has been found that PEDV can infect pAPN knockout pigs. Currently, the functional receptor for PEDV remains unspecified. In the present study, we performed virus overlay protein binding assay (VOPBA), found that ATP1A1 was the highest scoring protein in the mass spectrometry results, and confirmed that the CT structural domain of ATP1A1 interacts with PEDV S1. First, we investigated the effect of ATP1A1 on PEDV replication. Inhibition of hosts ATP1A1 protein expression using small interfering RNA (siRNAs) significantly reduced the cells susceptibility to PEDV. The ATP1A1-specific inhibitors Ouabain (a cardiac steroid) and PST2238 (a digitalis toxin derivative), which specifically bind ATP1A1, could block the ATP1A1 protein internalization and degradation, and consequently reduce the infection rate of host cells by PEDV significantly. Additionally, as expected, overexpression of ATP1A1 notably enhanced PEDV infection. Next, we observed that PEDV infection of target cells resulted in upregulation of ATP1A1 at the mRNA and protein levels. Furthermore, we found that the host protein ATP1A1 was involved in PEDV attachment and co-localized with PEDV S1 protein in the early stage of infection. In addition, pretreatment of IPEC-J2 and Vero-E6 cells with ATP1A1 mAb significantly reduced PEDV attachment. Our observations provided a perspective on identifying key factors in PEDV infection, and may provide valuable targets for PEDV infection, PEDV functional receptor, related pathogenesis, and the development of new antiviral drugs.

Acidic Exo-Polysaccharide Obtained from Bacillus sp. NRC5 Attenuates Testosterone-DMBA-Induced Prostate Cancer in Rats via Inhibition of 5 α-Reductase and Na+/K+ ATPase Activity Mechanisms

Bacillus sp. NRC5 is a new strain that grows in Egyptian beaches. This strain produces acidic exo-polysaccharide that have excellent antioxidant, anti-inflammatory and anti-tumor properties. The current study aimed to introduce a new natural product feasible for prostate cancer therapies. The anti-prostate cancer of acidic exo-polysaccharide produced from marine Bacillus sp. NRC5 (EBPS) was determined using 7,12-dimethylbenz-(a)-anthracene; DMBA-induced prostate cancer in male Sprague Dawley rats. Rats were subcutaneously injected with testosterone (3 mg/kg/day for 3 months) and a single dose of DMBA (65 mg/kg) for induction of prostate cancer. EBPS was administrated orally at dose 200 mg/kg/day for 3 months. To study protective effect of EBPS, animals received EBPS before cancer induction, meanwhile in therapeutic effect animals received EBPS after cancer induction. EBPS debug oxidative stress and inflammatory conditions associated with prostate cancer. EBPS either protective or therapeutic material considerably reduced cancer growth rate-limiting enzyme-i.e., 5-α-reductase (46.89 ± 1.72 and 44.86 ± 2.56 µg Eq/mL) and Na⁺/K⁺ ATPase (0.44 ± 0.03 and 0.42 ± 0.02 µg Eq/mL), compared to cancer control (69.68 ± 3.46 µg Eq/mL). In addition, both cancer biomarkers-i.e., prostate-specific antigen and carcinoembryonic antigen were significantly lowered as evidence of the ability of EBPS to protect and treat prostate cancer in chemically induced rats. EBPS showed protective and therapeutic efficacy on testosterone-DMBA-induced prostate cancer rats with a good safety margin. This study may go to clinical trials after a repeated study on another type of small experimental animal, their offspring, and one big experimental animal.

The expression of the alpha1 subunit of Na+/K+-ATPase is related to tumor development and clinical outcomes in gastric cancer

BACKGROUND

The Na⁺/K⁺-ATPase alpha1 subunit (ATP1A1) is a critical component of Na⁺/K⁺-ATPase (NKA), a membrane pump that maintains a low intracellular Na⁺/K⁺ ratio and retains cellular volume and osmolarity. ATP1A1 was recently implicated in tumor behavior. Therefore, the present study investigated the role of ATP1A1 in patients with gastric cancer (GC).

METHODS

Knockdown experiments were conducted on human GC cell lines using ATP1A1 siRNA, and its effects on proliferation, the cell cycle, apoptosis, and cellular movement were examined. Gene expression profiling was performed by a microarray analysis. Primary tumor samples from 192 GC patients who underwent gastrectomy were subjected to an immunohistochemical analysis.

RESULTS

High ATP1A1 expression levels were observed in NUGC4 and MKN74 cells. Cell proliferation was suppressed and apoptosis was induced by the siRNA-induced knockdown of ATP1A1. The microarray analysis showed that knockdown of ATP1A1 leads to the up-regulated expression of genes involved in the interferon (IFN) signaling pathway, such as STAT1, STAT2, IRF1, and IRF9. Furthermore, the depletion of ATP1A1 altered the phosphorylation of the MAPK pathway. The immunohistochemical analysis revealed that the expression of ATP1A1 was associated with the histological type, venous invasion, and the pathological T stage. Furthermore, the prognostic analysis showed a relationship between high ATP1A1 expression levels and poor postoperative survival.

CONCLUSIONS

ATP1A1 appears to regulate tumor progression by altering IFN signaling, and high ATP1A1 expression levels were associated with poor postoperative survival in GC patients. The present results provide novel insights into the function of ATP1A1 as a mediator and/or biomarker of GC.

Downregulation of ATP1A1 Expression by Panax notoginseng (Burk.) F.H. Chen Saponins: A Potential Mechanism of Antitumor Effects in HepG2 Cells and In Vivo

The Na⁺/K⁺-ATPase α1 subunit (ATP1A1) is a potential target for hepatic carcinoma (HCC) treatment, which plays a key role in Na⁺/K⁺ exchange, metabolism, signal transduction, etc. In vivo, we found that Panax notoginseng saponins (PNS) could inhibit tumor growth and significantly downregulate the expression and phosphorylation of ATP1A1/AKT/ERK in tumor-bearing mice. Our study aims to explore the potential effects of PNS on the regulation of ATP1A1 and the possible mechanisms of antitumor activity. The effects of PNS on HepG2 cell viability, migration, and apoptosis were examined in vitro. Fluorescence, Western blot, and RT-PCR analyses were used to examine the protein and gene expression. Further analysis was assessed with a Na⁺/K⁺-ATPase inhibitor (digitonin) and sorafenib in vitro. We found that the ATP1A1 expression was markedly higher in HepG2 cells than in L02 cells and PNS exhibited a dose-dependent effect on the expression of ATP1A and the regulation of AKT/ERK signaling pathways. Digitonin did not affect the expression of ATP1A1 but attenuated the effects of PNS on the regulation of ATP1A1/AKT/ERK signaling pathways and enhanced the antitumor effect of PNS by promoting nuclear fragmentation. Taken together, PNS inhibited the proliferation of HepG2 cells via downregulation of ATP1A1 and signal transduction. Our findings will aid a data basis for the clinical use of PNS.

Sodium Pump Na + /K + ATPase Subunit α1-Targeted Positron Emission Tomography Imaging of Hepatocellular Carcinoma in Mouse Models

PURPOSE

Positron emission tomography (PET) imaging was not efficiently used in the early diagnosis of hepatocellular carcinoma (HCC) due to the lack of appropriate tracers. Sodium pump Na + /K + ATPase subunit α1 (NKAα1) emerges to be a potential diagnostic biomarker of HCC. Here, we investigated the feasibility of ¹⁸F-ALF-NOTA-S3, a PET tracer based on an NKAα1 peptide, to detect small HCC.

PROCEDURES

GEPIA database was searched to obtain the expression characteristics of NKAα1 in HCC and its relationship with the prognosis. PET/CT was performed in orthotopic, diethylnitrosamine (DEN)-induced and genetically engineered HCC mouse models to evaluate the use of ¹⁸F-ALF-NOTA-S3 to detect HCC lesions.

RESULTS

NKAα1 is overexpressed in early HCC with a high positive rate and may correlate with poor survival. In orthotopic, DEN-induced and genetically engineered HCC mouse models, PET/CT imaging showed a high accumulation of ¹⁸F-ALF-NOTA-S3 in the tumor. The tumor-to-liver ratios are 2.56 ± 1.02, 4.41 ± 1.09, and 4.59 ± 0.65, respectively. Upregulated NKAα1 expression in tumors were verified by immunohistochemistry. Furthermore, ¹⁸F-ALF-NOTA-S3 has the ability to detect small HCC lesions with diameters of 2-5 mm.

CONCLUSIONS

NKAα1 may serve as a suitable diagnostic biomarker for HCC. ¹⁸F-ALF-NOTA-S3 shows great potential for PET imaging of HCC.

Pericardial Adipose Tissue-Derived Leptin Promotes Myocardial Apoptosis in High-Fat Diet-Induced Obese Rats Through Janus Kinase 2/Reactive Oxygen Species/Na+/K+-ATPase Signaling Pathway

Background

Pathophysiologic mechanisms underlying cardiac structural and functional changes in obesity are complex and linked to adipocytokines released from pericardial adipose tissue (PAT) and cardiomyocyte apoptosis. Although leptin is involved in various pathological conditions, its role in paracrine action of pericardial adipose tissue on myocardial apoptosis remains unknown. This study was designed to investigate the role of PAT‐derived leptin on myocardial apoptosis in high‐fat diet–induced obese rats.

Methods and Results

Hearts were isolated from lean or high‐fat diet–induced obese Wistar rats for myocardial remodeling studies. Obese rats had abnormal myocardial structure, diastolic dysfunction, greatly elevated cardiac apoptosis, enhanced cardiac fibrosis, and increased oxidative stress level. ELISA detected significantly higher than circulating leptin level in PAT of obese, but not lean, rats. Western blot and immunohistochemical analyses demonstrated increased leptin receptor density in obese hearts. H9c2 cardiomyoblasts, after being exposed to PAT‐conditioned medium of obese rats, exhibited pronounced reactive oxygen species–mediated apoptosis, which was partially reversed by leptin antagonist. Moreover, leptin derived from PAT of obese rats inhibited Na⁺/K⁺‐ATPase activity of H9c2 cells through stimulating reactive oxygen species, thereby activating calcium‐dependent apoptosis. Pretreatment with specific inhibitors revealed that Janus kinase 2/signal transducer and activator of transcription 3 and phosphoinositide 3‐kinase/protein kinase B signaling pathways were involved in leptin‐induced myocardial apoptosis.

Conclusions

PAT‐derived leptin induces myocardial apoptosis in high‐fat diet–induced obese rats via activating Janus kinase 2/signal transducer and activator of transcription 3/reactive oxygen species signaling pathway and inhibiting its downstream Na⁺/K⁺‐ATPase activity.

Inducible ATP1B1 Upregulates Antiviral Innate Immune Responses by the Ubiquitination of TRAF3 and TRAF6

The antiviral innate immune responses are crucial steps during host defense and must be strictly regulated, but the molecular mechanisms of control remain unclear. In this study, we report increased expression of human ATPase Na⁺/K⁺ transporting subunit β 1(ATP1B1) after DNA and RNA virus infections. We found that the expression of ATP1B1 can inhibit viral replication and increase the levels of IFNs, IFN-stimulated genes, and inflammatory cytokines. Knockdown of ATP1B1 by specific short hairpin RNA had the opposite effects. Upon viral infection, ATP1B1 was induced, interacted with TRAF3 and TRAF6, and potentiated the ubiquitination of these proteins, leading to increased phosphorylation of downstream molecules, including TGF-β-activated kinase 1 (TAK1) and TANK-binding kinase 1 (TBK1). These results reveal a previously unrecognized role of ATP1B1 in antiviral innate immunity and suggest a novel mechanism for the induction of IFNs and proinflammatory cytokines during viral infection.

Molecular mechanisms of bufadienolides and their novel strategies for cancer treatment

Bufadienolides are cardioactive C24 steroids with an α-pyrone ring at position C17. In the last ten years, accumulating studies have revealed the anticancer activities of bufadienolides and their underlying mechanisms, such as induction of autophagy and apoptosis, cell cycle disruption, inhibition of angiogenesis, epithelial-mesenchymal transition (EMT) and stemness, and multidrug resistance reversal. As Na⁺/K⁺-ATPase inhibitors, bufadienolides have inevitable cardiotoxicity. Short half-lives, poor stability, low plasma concentration and oral bioavailability in vivo are obstacles for their applications as drugs. To improve the drug potency of bufadienolides and reduce their side effects, prodrug strategies and drug delivery systems such as liposomes and nanoparticles have been applied. Therefore, systematic and recapitulated information about the antitumor activity of bufadienolides, with special emphasis on the molecular or cellular mechanisms, prodrug strategies and drug delivery systems, is of high interest. Here, we systematically review the anticancer effects of bufadienolides and the molecular or cellular mechanisms of action. Research advancements regarding bufadienolide prodrugs and their tumor-targeting delivery strategies are critically summarized. This work highlights recent scientific advances regarding bufadienolides as effective anticancer agents from 2011 to 2019, which will help researchers to understand the molecular pathways involving bufadienolides, resulting in a selective and safe new lead compound or therapeutic strategy with improved therapeutic applications of bufadienolides for cancer therapy.

Three organophosphate flame retardants (OPFRs) reduce sperm quality in Chinese rare minnows (Gobiocypris rarus)

Organophosphate flame retardants (OPFRs) are widespread in the aquatic environment, but the effects of these chemicals on reproductive toxicity are far from clear. In this study, sperm quality in adult male Chinese rare minnows after exposure to tris-(2-butoxyethyl) phosphate (TBOEP), tris-(1,3-dichloro-2-propyl) phosphate (TDCIPP), and triphenyl phosphate (TPHP) was investigated. No obvious change in sperm concentration and vitality was observed after treatments, whereas significant changes in sperm velocity and morphology were found following all treatments (P < 0.05). Moreover, OPFR exposure significantly increased the apoptosis ratios in testis cells. Analysis of the transcriptomic data revealed that Na⁺/K⁺ ATPase (NKA) related genes were significantly downregulated, and the NKA enzyme activities after all treatments were significantly inhibited (P < 0.05). However, no obvious change in hormone levels in the groups exposed to TBOEP and TDCIPP was observed. These findings indicate that the OPFR-induced reduction of sperm quality might be due to the effects of OPFRs on NKA enzyme instead of changes in hormone levels.

Digitoxin inhibits proliferation of multidrug-resistant HepG2 cells through G2/M cell cycle arrest and apoptosis

Hepatocellular carcinoma (HCC) remains a challenge in the medical field due to its high malignancy and mortality rates particularly for HCC, which has developed multidrug resistance. Therefore, the identification of efficient chemotherapeutic drugs for multidrug resistant HCC has become an urgent issue. Natural products have always been of significance in drug discovery. In the present study, a cell-based method was used to screen a natural compound library, which consisted of 78 compounds, and the doxorubicin-resistant cancer cell line, HepG2/ADM, as screening tools. The findings of the present study led to the shortlisting of one of the compounds, digitoxin, which displayed an inhibitory effect on HepG2/ADM cells, with 50% inhibitory concentration values of 132.65±3.83, 52.29±6.26, and 9.13±3.67 nM for 24, 48, and 72 h, respectively. Immunofluorescence, western blotting and cell cycle analyses revealed that digitoxin induced G₂/M cell cycle arrest via the serine/threonine-protein kinase ATR (ATR)-serine/threonine-protein kinase Chk2 (CHK2)-M-phase inducer phosphatase 3 (CDC25C) signaling pathway in HepG2/ADM cells, which may have resulted from a DNA double-stranded break. Digitoxin also induced mitochondrial apoptosis, which was characterized by changes in the interaction between Bcl-2 and Bax, the release of cytochrome c, as well as the activation of the caspase-3 and −9. To the best of our knowledge, the present study is the first report that digitoxin displays an anti-HCC effect on HepG2/ADM cells through G₂/M cell cycle arrest, which was mediated by the ATR-CHK2-CDC25C signaling pathway and mitochondrial apoptosis. Therefore, digitoxin could be a promising chemotherapeutic agent for the treatment of patients with HCC.

Inhibitors of Na+/K+ ATPase exhibit antitumor effects on multicellular tumor spheroids of hepatocellular carcinoma

Hepatocellular carcinoma (HCC), one of the most common malignant cancers worldwide, is associated with substantial mortality. Because HCCs have strong resistance to conventional chemotherapeutic agents, novel therapeutic strategies are needed to improve survival in patients with HCC. The multicellular tumor spheroid (MCTS) model is a powerful method for anticancer research because of its ability to mimic the complexity and heterogeneity of tumor tissue, the three-dimensional cellular context of tumor tissue, and the pathophysiological gradients of in vivo tumors. However, it is difficult to obtain meaningful results from the MCTS model without considering the conditions of clinical tumors. We, therefore, provided a proof of concept to determine whether spheroid models simulate in vivo tumor microenvironments. Through a high-throughput screening for HCC therapy using the MCTS model, we selected inhibitors of Na⁺/K⁺-ATPase (ouabain and digoxin) that could suppress cell growth and migration via inhibition of the epithelial-mesenchymal transition of HCC in vivo and in vitro. The results showed that this model provides a new paradigm for high-throughput drug screening and will significantly improve the efficiency of identifying new drugs for HCC treatment. Through utilization of MCTS models, here we found that inhibitors of Na⁺/K⁺-ATPase may be feasible as a novel target to sensitize HCC cells.

Acidic Exopolysaccharide Produced from Marine Bacillus amyloliquefaciens 3MS 2017 for the Protection and Treatment of Breast Cancer

PURPOSE

This study was planned to investigate the anti-breast-cancer property of acidic exopolysaccharide produced from marine Bacillus amyloliquefaciens 3MS 2017 (BAEPS) in an animal model, which previously showed in-vitro anti-breast-cancer activity, by studying its potential participation in various targeted mechanisms.

METHODS

Mammary carcinoma in female Sprague-Dawley rats, both in prophylactic and in curative designs, was chemically induced using 7,12-dimethylebenz-(a)-anthracene (DMBA). B. amyloliquefaciens 3MS 2017 anti-breast-cancer property was evaluated by studying its effects on cancer-growth-rate-limiting enzymes (aromatase and Na+/K+ ATPase), sexual hormones (estrogen and progesterone), antioxidant and inflammatory biomarkers (cyclooxygenase-1; COX-1 and cyclooxygenase-2; COX-2). The incidence of breast cancer by DMBA was dependent on the level of carcinoembryonic antigen (CEA) and aromatase.

RESULTS

7,12-Dimethylebenz-(a)-anthracene female rats were characterized by a significant increase in cancer-related biomarkers with an increase of oxidative stress biomarkers, in comparison with the negative control. Potent BAEPS anticancer activity on DMBA rats was exhibited either as a prophylactic or as a curative agent, which appeared via restoring the aromatase and Na+/K+ ATPase subunits levels and CEA close to the normal level. Besides, BAEPS modulated a sexual hormone, in comparison with the cancer control group (P ⩽ .05). B. amyloliquefaciens 3MS 2017 selectively inhibited COX-2 in parallel with promising antioxidant properties. The curative characters of BAEPS were more promising than the prophylactic.

CONCLUSION

The anti-breast-cancer characters accompanied with a good safety margin may be attributed to its inhibitory effect on cancer-growth-rate-limiting enzymes, estrogen production, COX-2 level and lipid peroxidation, concurrent with enhancing COX-1 level, progesterone production, and antioxidant status.

Ouabain potentiates the antimicrobial activity of aminoglycosides against Staphylococcus aureus

Background

Staphylococcus aureus is a notorious pathogen which often causes nosocomial and community attained infections. These infections steadily increased after evolving the resistance due to indecorous practice of antibiotics and now become a serious health issue. Ouabain is a Na⁺/K⁺-ATPase inhibitor that leads to increase the heart contraction in patients with congestive heart failure.

Methods

In the present study, in vitro antimicrobial effect of ouabain together with aminoglycosides was determined against clinical and non-clinical S. aureus strains. Using checkerboard, Gentamycin uptake and biofilm assays, we analysed he interactions of ouabain with aminoglycosides.

Results

Ouabain induced the staphylocidal potency of aminoglycosides by remarkably reducing the MIC of gentamycin (GEN) by 16 (0.25 μg/mL), 8 folds (0.5 μg/mL) amikacin (AMK); and 16 folds (1.0 μg/mL) with kanamycin (KAN), compared to their individual doses. OBN severely reduced cell viability within 60 min with GEN (1 μg/mL), KAN (2 μg/mL) and 90 min with AMK (1 μg/mL). This bactericidal effect was enhanced due to GEN uptake potentiated by 66% which led to increase the cell permeability as revealed by leakage of bacterial ATP and nitrocefin assay. The biofilm adherence disrupted by 80 and 50% at 5 mg/mL and 1.5 mg/mL OBN and 50 and 90% biofilm formation was inhibited at 5 mg/mL (MBIC₅₀) and 10 mg/mL (MBIC₉₀), respectively. Moreover, OBN with GEN further induced biofilm inhibition by 67 ± 5% at pH 7.0.

Conclusions

Taken together, we established that OBN synergizes the antimicrobial activity of aminoglycosides that induces cell killing due to intracellular accumulation of GEN by disturbing cell homeostasis. It may be proven an effective approach for the treatment of staphylococcal infections.

Cardenolides: Insights from chemical structure and pharmacological utility

Cardiac glycosides (CGs) are a class of naturally occurring steroid-like compounds, and members of this class have been in clinical use for more than 1500 years. They have been used in folk medicine as arrow poisons, abortifacients, heart tonics, emetics, and diuretics as well as in other applications. The major use of CGs today is based on their ability to inhibit the membrane-bound Na+/K+-ATPase enzyme, and they are regarded as an effective treatment for congestive heart failure (CHF), cardiac arrhythmia and atrial fibrillation. Furthermore, increasing evidence has indicated the potential cytotoxic effects of CGs against various types of cancer. In this review, we highlight some of the structural features of this class of natural products that are crucial for their efficacy, some methods of isolating these compounds from natural resources, and the structural elucidation tools that have been used. We also describe their physicochemical properties and several modern biotechnological approaches for preparing CGs that do not require plant sources.

The isoform A of reticulon-4 (Nogo-A) in cerebrospinal fluid of primary brain tumor patients: influencing factors

Background

The influence of isoform A of reticulon-4 (Nogo-A), also known as neurite outgrowth inhibitor, on primary brain tumor development was reported. Therefore the aim was the evaluation of Nogo-A concentrations in cerebrospinal fluid (CSF) and serum of brain tumor patients compared with non-tumoral individuals.

Results

All serum results, except for two cases, obtained both in brain tumors and non-tumoral individuals, were below the lower limit of ELISA detection. Cerebrospinal fluid Nogo-A concentrations were significantly lower in primary brain tumor patients compared to non-tumoral individuals. The univariate linear regression analysis found that if white blood cell count increases by 1 × 10³/μL, the mean cerebrospinal fluid Nogo-A concentration value decreases 1.12 times. In the model of multiple linear regression analysis predictor variables influencing cerebrospinal fluid Nogo-A concentrations included: diagnosis, sex, and sodium level. The mean cerebrospinal fluid Nogo-A concentration value was 1.9 times higher for women in comparison to men. In the astrocytic brain tumor group higher sodium level occurs with lower cerebrospinal fluid Nogo-A concentrations. We found the opposite situation in non-tumoral individuals.

Conclusions

Univariate linear regression analysis revealed, that cerebrospinal fluid Nogo-A concentrations change in relation to white blood cell count. In the created model of multiple linear regression analysis we found, that within predictor variables influencing CSF Nogo-A concentrations were diagnosis, sex, and sodium level. Results may be relevant to the search for cerebrospinal fluid biomarkers and potential therapeutic targets in primary brain tumor patients.

Materials and methods

Nogo-A concentrations were tested by means of enzyme-linked immunosorbent assay (ELISA).

Identification of a sodium pump Na+/K+ ATPase α1-targeted peptide for PET imaging of breast cancer

The sodium pump Na⁺/K⁺ ATPase a1 subunit(NKA a1), an attractive cancer-related biomarker and therapeutic target, is closely related to the development and progression of several cancers including breast cancer. Currently, a NKA a1 inhibitor, UNBS1450, has already evidenced its great therapeutic potential in personalized cancer treatment. The ability of non-invasive imaging of NKA a1 expression would be useful for selecting cancer patients who may benefit from this drug. Here, we identified an S3 peptide that is specifically homed to breast cancer by phage display. All data of in vitro and in vivo experiments suggested the excellent targeting character of the S3 peptide. As the binding activity of the S3 phage was positively correlated to the level of NKA α1 expression in various breast cancer cells, NKA α1 was validated as the primary target of the S3 peptide. Based on immunohistochemistry staining result of 107 breast cancer patients, NKA α1 was verified to be a novel tracking marker and a prognostic predictor for breast cancer. Importantly, we proposed and validated an S3 peptide-based radiotracer ¹⁸F-ALF-NOTA-S3 for PET (Positron Emission Tomography) imaging of breast cancer and other NKA α1-overexpressing cancers, including hepatocellular carcinoma and non-small cell lung cancer, in mouse models. Our findings demonstrated the potential application of ¹⁸F-ALF-NOTA-S3 for visualization of NKA α1-positive lesions, which provide a new approach to character tumor phenotypic imaging.

Expression of the β3 subunit of Na+/K+-ATPase is increased in gastric cancer and regulates gastric cancer cell progression and prognosis via the PI3/AKT pathway

ATP1B3 encodes the β3 subunit of Na⁺/K⁺-ATPase and is located in the q22-23 region of chromosome 3. Na⁺/K⁺-ATPase participates in normal cellular activities but also plays a crucial role in carcinogenesis. In the present study, we found that expression of the β3 subunit of Na⁺/K⁺-ATPase was increased in human gastric cancer tissues compared with that in normal matched tissues and that this increased expression predicted a poor outcome. ATP1B3 expression was elevated at both the mRNA and protein levels in gastric cancer cell lines relative to those in a normal gastric epithelial cell line. Interestingly, ATP1B3 knockdown significantly inhibited cell proliferation, colony-formation ability, migration, and invasion and increased apoptosis in human gastric carcinoma cell lines. Additionally, knockdown induced cell cycle arrest at the G2/M phase. Furthermore, we demonstrated that ATP1B3 silencing decreased the expression of phosphatidylinositol 3-kinase (PI3K), protein kinase B (AKT) and phosphorylated AKT (p-AKT), indicating that ATP1B3 regulates gastric cancer cell progression via the PI3K/AKT signalling pathway. Hence, the β3 subunit of Na⁺/K⁺-ATPase plays an essential role in the tumourigenesis of gastric cancer and may be a potential prognostic and therapeutic target for the treatment of gastric cancer.

Na/K Pump and Beyond: Na/K-ATPase as a Modulator of Apoptosis and Autophagy

Lung cancer is a leading cause of global cancer deaths. Na/K-ATPase has been studied as a target for cancer treatment. Cardiotonic steroids (CS) trigger intracellular signalling upon binding to Na/K-ATPase. Normal lung and tumour cells frequently express different pump isoforms. Thus, Na/K-ATPase is a powerful target for lung cancer treatment. Drugs targeting Na/K-ATPase may induce apoptosis and autophagy in transformed cells. We argue that Na/K-ATPase has a role as a potential target in chemotherapy in lung cancer treatment. We discuss the effects of Na/K-ATPase ligands and molecular pathways inducing deleterious effects on lung cancer cells, especially those leading to apoptosis and autophagy.

Overexpression of ATP1B1 predicts an adverse prognosis in cytogenetically normal acute myeloid leukemia

ATP1B1 encodes the Na,K-ATPase β subunit, a key regulator of the Na⁺ and K⁺ electrochemical gradients across the plasma membrane and an essential regulator of cellular activity. We used several microarray datasets to test the prognostic efficacy of ATP1B1 expression in cytogenetically normal acute myeloid leukemia (CN-AML). Within the primary cohort (n = 157), high ATP1B1 expression (ATP1B1^high) was associated with shorter overall survival (OS) and event-free survival (EFS) (P = 0.0068, P = 0.0039, respectively). Similar results were also obtained in the European Leukemia Net (ELN) Intermediate-I genetic category (OS: P = 0.0035, EFS: P = 0.0007). Multivariable analyses confirmed ATP1B1^high is an independent predictor of shorter OS (P = 0.042) and EFS (P = 0.035). Analysis of another CN-AML cohort confirmed that ATP1B1^high is associated with shorter OS (P = 0.0046, n = 162). In addition, up-regulation of oncogenes/onco-microRNAs such as MYCN, CCND2, CDK6, KIT and miR-155, among others, was associated with ATP1B1^high, which may be indicative of ATP1B1's leukemogenicity. Our results may improve risk stratification and indicate new therapeutic targets for CN-AML.

Effect of bafilomycin and NAADP on membrane-associated ATPases and respiration of isolated mitochondria of the murine Nemeth-Kellner lymphoma

The goal of the study was to estimate the effect of a selective V-type H⁺ -ATPase inhibitor bafilomycin A1 and nicotinic acid adenine dinucleotide phosphate (NAADP) on energetic processes in NK/Ly cell by directly measuring the respiration of isolated mitochondria and ATPase activities. NAADP (7 μM) increased the activity of Na⁺ /K⁺ -ATPase in the postmitochondrial fraction of NK/Ly cells, but lower concentration of NAADP decreased it (0.1 and 1 μM). The increase the activity of plasma membrane Ca²⁺ ATPase (PMCA) under NAADP application (1 and 7 μM) was observed. However, NAADP (1 μM) decreased activities of sarcoendoplasmic reticulum Ca²⁺ -ATPase (SERCA) and basal Mg²⁺ -ATPase. Bafilomycin A1 (1 μM) increased the activity of Na⁺ /K⁺ -ATPase and potentiated the effect of NAADP (1 μM) on this pump. At the same time, bafilomycin A1 (1 μM) completely prevented all effects of NAADP (1 μM) on activities of PMCA, SERCA, and basal Mg²⁺ -ATPase, confirming that these effects are dependent on acidic stores. Bafilomycin A1 or NAADP decreased respiratory and oxidative phosphorylation rates in NK/Ly mitochondria when α-ketoglutarate was used as substrate in contrast to succinate. Thus, α-ketoglutarate oxidation is more sensitive to bafilomycin A1 and NAADP influences compared with succinate oxidation. However, bafilomycin A1 + NAADP and any of these compounds separately lead to full uncoupling of mitochondria after ADP addition irrespectively to substrate used. Bafilomycin A1 affects isolated tumor mitochondria more effectively in combination with NAADP. Bafilomycin and NAADP alter some membrane-associated ATPases and inhibit respiration in mitochondria of the Nemeth-Kellner lymphoma.

SIGNIFICANCE OF RESEARCH PARAGRAPH

Bafilomycin A1 potentiates the effect of NAADP by inhibiting the mitochondrial energetic process in lymphoma cells and activity of Na⁺ /K⁺ -ATPase. The obtained data show promising possibility to use bafilomycin A1 and NAADP as chemotherapeutic agents for lymphoma cells treatment. This is important because lymphomas are seventh most common form of cancer. Today the lymphoma mortality is 15% to 30%, whereas the effectiveness of malignant neoplasms treatment is less than 50%.

Arenobufagin intercalates with DNA leading to G2 cell cycle arrest via ATM/ATR pathway

Arenobufagin, a representative bufadienolide, is the major active component in the traditional Chinese medicine Chan'su. It possesses significant antineoplastic activity in vitro. Although bufadienolide has been found to disrupt the cell cycle, the underlying mechanisms of this disruption are not defined. Here, we reported that arenobufagin blocked the transition from G2 to M phase of cell cycle through inhibiting the activation of CDK1-Cyclin B1 complex; The tumor suppressor p53 contributed to sustaining arrest at the G2 phase of the cell cycle in hepatocellular carcinoma (HCC) cells. Moreover, arenobufagin caused double-strand DNA breaks (DSBs) and triggered the DNA damage response (DDR), partly via the ATM/ATR-Chk1/Chk2-Cdc25C signaling pathway. Importantly, we used a synthetic biotinylated arenobufagin-conjugated chemical probe in live cells to show that arenobufagin accumulated mainly in the nucleus. The microscopic thermodynamic parameters measured using isothermal titration calorimetry (ITC) also demonstrated that arenobufagin directly bound to DNA in vitro. The hypochromicity in the UV-visible absorption spectrum, the significant changes in the circular dichroism (CD) spectrum of DNA, and the distinct quenching in the fluorescence intensity of the ethidium bromide (EB)-DNA system before and after arenobufagin treatment indicated that arenobufagin bound to DNA in vitro by intercalation. Molecular modeling suggested arenobufagin intercalated with DNA via hydrogen bonds between arenobufagin and GT base pairs. Collectively, these data provide novel insights into arenobufagin-induced cell cycle disruption that are valuable for the further discussion and investigation of the use of arenobufagin in clinical anticancer chemotherapy.

Knockdown of Apolipoprotein E Enhanced Sensitivity of Hep3B Cells to Cardiac Steroids via Regulating Na+/K+-ATPase Signalosome

This study compared the sensitivity of human hepatoma Hep3B, SK-HEP-1, SMMC-7721, and BEL-7402 cells to cardiac steroids, including bufalin (BF), a bufalin derivative (BF211), ouabain (OUA), and digitoxin (DIG). Hep3B cells exhibited relatively low sensitivity to cardiac steroids. Expression levels of subunits of Na⁺/K⁺-ATPase were high in Hep3B cells. However, colocalization of Na⁺/K⁺-ATPase and caveolin was nearly undetectable in Hep3B cells. By using RNA-Seq technology, we found a total of 36 genes to be differentially expressed between Hep3B cells and SK-HEP-1 cells, which are highly sensitive to cardiac steroids. Our bioinformatics analysis determined that these genes were mostly comprised of extracellular space, protein binding, and extracellular region. Among these 36 genes, apolipoprotein E (APOE) played a critical role, as knockdown APOE expression induced colocalization of Na⁺/K⁺-ATPase and caveolin and increased sensitivity of Hep3B cells to both proliferation-inhibiting and cytotoxic effects of BF or BF211. Also, the effects of BF on PI3K/AKT/GSK3β and apoptosis signal cascades were enhanced in APOE knockdown cells. The results of our study confirmed the role of Na⁺/K⁺-ATPase signalosome in cytotoxicity of cardiac steroids and suggested that APOE regulated the sensitivity of cells to cardiac steroids by affecting formation and function of Na⁺/K⁺-ATPase signalosome. In addition, intercellular interaction with high level of Na⁺/K⁺-ATPase β1 subunit may be also a factor in the low sensitivity of Hep3B cells to cardiac steroids. Mol Cancer Ther; 15(12); 2955-65. ©2016 AACR.

Ouabain Enhances ADPKD Cell Apoptosis via the Intrinsic Pathway

Progression of autosomal dominant polycystic kidney disease (ADPKD) is highly influenced by factors circulating in blood. We have shown that the hormone ouabain enhances several characteristics of the ADPKD cystic phenotype, including the rate of cell proliferation, fluid secretion and the capacity of the cells to form cysts. In this work, we found that physiological levels of ouabain (3 nM) also promote programmed cell death of renal epithelial cells obtained from kidney cysts of patients with ADPKD (ADPKD cells). This was determined by Alexa Fluor 488 labeled-Annexin-V staining and TUNEL assay, both biochemical markers of apoptosis. Ouabain-induced apoptosis also takes place when ADPKD cell growth is blocked; suggesting that the effect is not secondary to the stimulatory actions of ouabain on cell proliferation. Ouabain alters the expression of BCL family of proteins, reducing BCL-2 and increasing BAX expression levels, anti- and pro-apoptotic mediators respectively. In addition, ouabain caused the release of cytochrome c from mitochondria. Moreover, ouabain activates caspase-3, a key “executioner” caspase in the cell apoptotic pathway, but did not affect caspase-8. This suggests that ouabain triggers ADPKD cell apoptosis by stimulating the intrinsic, but not the extrinsic pathway of programmed cell death. The apoptotic effects of ouabain are specific for ADPKD cells and do not occur in normal human kidney cells (NHK cells). Taken together with our previous observations, these results show that ouabain causes an imbalance in cell growth/death, to favor growth of the cystic cells. This event, characteristic of ADPKD, further suggests the importance of ouabain as a circulating factor that promotes ADPKD progression.

Stigmasterol protects against Ang II-induced proliferation of the A7r5 aortic smooth muscle cell-line

Excessive proliferation of vascular smooth muscle cells is a crucial event in the pathogenesis of several cardiovascular diseases, including atherosclerosis and restenosis.

Cytotoxicity effect of degraded and undegraded kappa and iota carrageenan in human intestine and liver cell lines

Background

Carrageenan is a linear sulphated polysaccharide extracted from red seaweed of the Rhodophyceae family. It has broad spectrum of applications in biomedical and biopharmaceutical field. In this study, we determined the cytotoxicity of degraded and undegraded carrageenan in human intestine (Caco-2; cancer and FHs 74 Int; normal) and liver (HepG2; cancer and Fa2N-4; normal) cell lines.

Methods

Food grade k-carrageenan (FGKC), dried sheet k-carrageenan (DKC), commercial grade k-carrageenan (CGKC), food grade i-carrageenan (FGIC) and commercial grade i-carrageenan (CGIC) were dissolved in hydrochloric acid and water to prepare degraded and undegraded carrageenan, respectively. Carrageenan at the concentration range of 62.5 – 2000.0 μg mL⁻¹ was used in the study. MTT assay was used to determine the cell viability while the mode of cell death was determined by May-Grunwald Giemsa (MGG) staining, acridine orange-ethidium bromide (AO/EtBr) staining, agarose gel electrophoresis and gene expression analysis.

Results

Degraded FGKC, DKC and CGKC showed IC₅₀ in 24, 48 and 72 hours treated Caco-2, FHs 74 Int, HepG2 and Fa2N-4 cell lines as tested by MTT assay. Degraded FGIC and CGIC only showed its toxicity in Fa2N-4 cells. The characteristics of apoptosis were demonstrated in degraded k-carrageenan treated Caco-2, FHs 74 Int, HepG2 and Fa2N-4 cells after MGG staining. When Caco-2 and HepG2 cells were undergone AO/EtBr staining, chromatin condensation and nuclear fragmentation were clearly seen under the microscope. However, DNA ladder was only found in HepG2 cells after gel electrophoresis analysis. Degraded k-carrageenan also inactivated PCNA, Ki-67 and survivin gene in HepG2. On the other hand, undegraded FGKC, DKC, CGKC, FGIC and CGIC treated cells showed no cytotoxic effect after analyzed by the same analyses as in degraded carrageenan.

Conclusion

Degraded k-carrageenan inhibited cell proliferation in Caco-2, FHs 74 Int, HepG2 and Fa2N-4 cell lines and the anti-proliferative effect was related to apoptosis together with inactivation of cell proliferating genes as determined by morphological observation and molecular analysis. However, no cytotoxic effect was found in undegraded carrageenan towards normal and cancer intestine and liver cell lines.

Inhibition of Na+/K+-ATPase induces hybrid cell death and enhanced sensitivity to chemotherapy in human glioblastoma cells

Background

Glioblastoma multiforme (GBM) is very difficult to treat with conventional anti-cancer/anti-apoptotic drugs. We tested the hypothesis that inhibition of Na⁺/K⁺-ATPase causes a mixed or hybrid form of concurrent apoptosis and necrosis and therefore should enhance anti-cancer effects of chemotherapy on glioblastoma cells.

Methods

In human LN229 and drug-resistant T98G glioblastoma cell cultures, cell death and signal pathways were measured using immunocytochemistry and Western blotting. Fluorescent dyes were applied to measure intracellular Ca²⁺, Na⁺ and K⁺ changes.

Results

The specific Na⁺/K⁺-ATPase blocker ouabain (0.1 - 10 μM) induced cell death and disruption of K⁺ homeostasis in a time- and concentration-dependent manner. Annexin-V translocation and caspase-3 activation indicated an apoptotic component in ouabain cytoxicity, which was accompanied with reduced Bcl-2 expression and mitochondrial membrane potential. Ouabain-induced cell death was partially attenuated by the caspase inhibitor Z-VAD (100 μM). Consistently, the K⁺ ionophore valinomycin initiated apoptosis in LN229 cells in a K⁺ efflux-dependent manner. Ouabain caused an initial cell swell, which was followed by a sustained cell volume decrease. Electron microscopy revealed ultrastructural features of both apoptotic and necrotic alterations in the same cells. Finally, human T98G glioblastoma cells that are resistant to the chemotherapy drug temozolomide (TMZ) showed a unique high expression of the Na⁺/K⁺-ATPase α2 and α3 subunits compared to the TMZ-sensitive cell line LN229 and normal human astrocytes. At low concentrations, ouabain selectively killed T98G cells. Knocking down the α3 subunit sensitized T98G cells to TMZ and caused more cell death.

Conclusion

This study suggests that inhibition of Na⁺/K⁺-ATPase triggers hybrid cell death and serves as an underlying mechanism for an enhanced chemotherapy effect on glioblastoma cells.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2407-14-716) contains supplementary material, which is available to authorized users.

Usefulness of monitoring γ-H2AX and cell cycle arrest in HepG2 cells for estimating genotoxicity using a high-content analysis system

Formation of the phosphorylated protein γ-H2AX is a well-established marker of DNA strand breakage induced by DNA-damaging compounds. Many of these genotoxic compounds also inhibit cell division, leading to arrest at specific points in the cell cycle. Detection of γ-H2AX in combination with cell cycle arrest may therefore be useful for estimating the genotoxicity of experimental compounds. In this study, we examined γ-H2AX formation and cell cycle arrest using high-content screening (HCS) as a method for determining genotoxicity. HepG2 cells were treated with a panel of compounds and then stained with Hoechst 33342 and anti-γ-H2AX, anti-phospho-histone H3, and anti-tubulin antibodies. In total, 19 genotoxic and 7 nongenotoxic compounds were tested in this study. γ-H2AX production was observed within 1 h posttreatment for the majority of Ames-positive compounds, topoisomerase inhibitors, and DNA polymerase inhibitors. Cell cycle arrest in either the S or G2 phase was detected for all DNA-damaging compounds 24 h posttreatment, whereas tubulin-targeting compounds were shown to induce cell cycle arrest in the mitotic phase. Together, these results show that HCS is a simple, rapid, and effective tool for estimating the genotoxicity of compounds through detection of γ-H2AX production and cell cycle arrest.

FXYD6: a novel therapeutic target toward hepatocellular carcinoma

FXYD6, FXYD domain containing ion transport regulator 6, has been reported to affect the activity of Na(+)/K(+)-ATPase and be associated with mental diseases. Here, we demonstrate that FXYD6 is up-regulated in hepatocellular carcinoma (HCC) and enhances the migration and proliferation of HCC cells. Up-regulation of FXYD6 not only positively correlates with the increase of Na(+)/K(+)-ATPase but also coordinates with the activation of its downstream Src-ERK signaling pathway. More importantly, blocking FXYD6 by its functional antibody significantly inhibits the growth potential of the xenografted HCC tumors in mice, indicating that FXYD6 represents a potential therapeutic target toward HCC. Altogether, our results establish a critical role of FXYD6 in HCC progression and suggest that the therapy targeting FXYD6 can benefit the clinical treatment toward HCC patients.

Association of cord blood digitalis-like factor and necrotizing enterocolitis

OBJECTIVE

Endogenous digoxin-like factor (EDLF) has been linked to vasoconstriction, altered membrane transport, and apoptosis. Our objective was to determine whether increased EDLF in the cord sera of preterm infants was associated with an increased incidence of necrotizing enterocolitis (NEC).

STUDY DESIGN

Cord sera from pregnant women enrolled in a randomized trial of MgSO4 for fetal neuroprotection were analyzed for EDLF using a red cell Rb(+) uptake assay in which the inhibition of sodium pump-mediated Rb(+) transport was used as a functional assay of EDLF. Specimens were assayed blinded to neonatal outcome. Cases (NEC, n = 25) and controls (neonates not developing stage 2 or 3 NEC, n = 24) were matched by study center and gestational age. None of the women had preeclampsia. Cases and controls were compared using the Wilcoxon test for continuous and the Fisher exact test for categorical variables. A conditional logistic regression analysis was used to assess the odds of case vs control by EDLF level.

RESULTS

Cases and controls were not significantly different for gestational age, race, maternal steroid use, premature rupture of membranes, or MgSO4 treatment. In logistic models adjusted for treatment group, race, premature rupture of membranes, and gestational age, cord sera EDLF was significantly associated with development of NEC (P = .023).

CONCLUSION

These data demonstrated an association between cord sera EDLF and NEC.

Anticancer steroids: linking natural and semi-synthetic compounds

Steroids, a widespread class of natural organic compounds occurring in animals, plants and fungi, have shown great therapeutic value for a broad array of pathologies. The present overview is focused on the anticancer activity of steroids, which is very representative of a rich structural molecular diversity and ability to interact with various biological targets and pathways. This review encompasses the most relevant discoveries on steroid anticancer drugs and leads through the last decade and comprises 668 references.

The effect of ouabain on mitochondrial DNA damage in HepG2 cell lines

Our purpose in this study is to analyze mitochondrial DNA (mtDNA) lesion frequencies and mtDNA(4977) deletion in HepG2 cells to examine the effects of ouabain on mtDNA. HepG2 cells were treated with 0.75, 7.5, 75, and 750 nM of ouabain for 24 h in the presence and absence of 10 mM 2-deoxyglucose (2-DG). The frequency of mtDNA(4977) deletions and mitochondrial lesions were determined by real-time polymerase chain reaction. A ≥ 1.2-fold change or greater was considered significant. Ouabain doses of 750, 75, and 7.5 nM alone increased the frequency of mtDNA(4977) deletions 1.39, 1.92, and 1.44 times, respectively. The 750 and 75 nM ouabain doses combined with 2-DG increased the mtDNA(4977) deletion frequency 4.94 and 1.57 times, respectively. The 750 and 75 nM ouabain doses alone increased the mtDNA lesion frequency 2.5 and 1.5 times, respectively. The 750 nM ouabain dose combined with 2-DG increased the mtDNA lesion frequency 2.28 times. The 7.5 nM ouabain dose alone and combined with 2-DG decreased the mtDNA lesion frequency 0.67 and 0.45 times, respectively. Ouabain alone and when combined with 2-DG increases mtDNA lesion and mtDNA(4977) deletion frequencies. This supports the thesis that ouabain creates oxidative stress and induces DNA damage and apoptosis.

Ouabain targets the unfolded protein response for selective killing of HepG2 cells during glucose deprivation

Ouabain is a cardiotonic steroid and specific inhibitor of the Na(+)/K(+)-ATPase. The relationship between ouabain treatment and the unfolded protein response (UPR) in cells is not precisely understood. Therefore, we studied the possible effects of ouabain on proliferation, apoptosis, and the UPR. HepG2 cells were cultured overnight and then treated with various concentrations of ouabain (0.75 to 750 nM) in the absence or presence of 10 mM 2-deoxyglucose (2-DG) for 48 hours. We also used real-time polymerase chain reaction to obtain quantitative measurements of expression levels of Grp78, Grp94, CHOP, MTJ-1, HKII, MDR-1, MRP-1, HO-1, and Par-4. Cell number, viability, and proliferation of HepG2 cells were monitored with a real-time cell analyzer system (xCELLigence). We show that ouabain modulates the UPR transcription program and induces cell death in glucose-deprived tumor cells. Ouabain at all concentrations showed no cytotoxicity whereas all concentrations were very effective under 2-DG stress conditions. Our findings show that disruption of the UPR during glucose deprivation could be an attractive approach for selective cancer cell killing and could provide a chemical basis for developing UPR-targeting drugs against solid tumors. Ouabain use as an adjunct to conventional cancer therapy also warrants vigorous investigation.

Covalent binding of cisplatin impairs the function of Na(+)/K(+)-ATPase by binding to its cytoplasmic part

This study was aimed at verifying the hypothesis that acute kidney failure accompanying cisplatin administration in the cancer therapy could be due to cisplatin interaction with the cytoplasmic part of Na(+)/K(+)-ATPase. Our results demonstrated that cisplatin-binding caused inhibition of Na(+)/K(+)-ATPase, in contrast to other platinated chemotherapeutics such as carboplatin and oxaliplatin, which are known to be much less nephrotoxic. To acquire more detailed structural information, we performed a series of experiments with the isolated large cytoplasmic segment connecting transmembrane helices 4 and 5 (C45 loop) of Na(+)/K(+)-ATPase. Electrochemistry showed that cisplatin is bound to the cysteine residues of the C45 loop, mass spectrometry revealed a modification of the C45 peptide fragment GSHMASLEAVETLGSTSTICSDK, which contains the conserved phosphorylated residue Asp369. Hence, we hypothesize that binding of cisplatin to Cys367 can cause sterical obstruction during the phosphorylation or dephosphorylation step of the Na(+)/K(+)-ATPase catalytic cycle.

Effects of NaF on the expression of intracellular Ca2+ fluxes and apoptosis and the antagonism of taurine in murine neuron

Sodium fluoride (NaF) has been shown to be cytotoxic and produces inflammatory responses in humans. However, the cellular mechanisms underlying the neurotoxicity of fluoride are unclear. The present study aims to define a possible mechanism of NaF-induced neurotoxicity with respect to apoptosis and intracellular Ca(2+) fluxes. Meanwhile, the cytoprotective role of taurine in intervention, the toxic effects of NaF on neurons, is also investigated. The primary mouse hippocampal neurons were incubated with 5.0, 10.0, 15.0, 20.0, and 40.0 mg NaF/L in vitro and Kunming mice were exposed to 0.7, 2.8, and 11.2 mg NaF/kg and 7.5 and 15.0 mg taurine/kg in vivo. Intracellular Ca(2+) fluxes and apoptosis were assayed. Compared with the control, the significant differences of intracellular Ca(2+) concentration and apoptotic peaks were found in 5.0-40.0 mg NaF/L groups in vitro (p < 0.01) and in the groups of 0.7-11.2 mg NaF/kg in vivo (p < 0.01). Instantaneously, taurine can minimize F-induced neurotoxicity significantly at doses of 7.5 and 15.0 mg/kg (p < 0.01). The present study herein suggested that NaF could increase intercellular Ca(2+) concentration leading to apoptosis. Meanwhile, taurine could minimize neurotoxicity caused by fluoride through decreasing intercellular Ca(2+) concentration and cell apoptosis.

"The Lower Threshold" phenomenon in tumor cells toward endogenous digitalis-like compounds: Responsible for tumorigenesis?

Since their first discovery as potential anti-cancer drugs decades ago, there is increasing evidence that digitalis-like compounds (DLC) have anti-tumor effects. Less is known about endogenous DLC (EDLC) metabolism and regulation. As stress hormones synthesized in and secreted from the adrenal gland, they likely take part in the hypothalamo-pituitary-adrenal (HPA) axis. In a previous study, we revealed reduced EDLC concentrations in plasma and organs from immune-compromised animals and proposed that a similar situation of a deregulated HPA axis with "adrenal EDLF exhaustion" may contribute to tumorigenesis in chronic stress situations. Here, we put forward the hypothesis that a lowered EDLC response threshold of tumor cells as compared with normal cells increases the risk of tumorigenesis, especially in those individuals with reduced EDLC plasma concentrations after chronic stress exposure. We will evaluate this hypothesis by (a) summarizing the effects of different DLC concentrations on tumor as compared with normal cells and (b) reviewing some essential differences in the Na/K-ATPase of tumor as compared with normal cells (isoform pattern, pump activity, mutations of other signalosome receptors). We will conclude that (1) tumor cells, indeed, seem to have their individual "physiologic" EDLC response range that already starts at pmolar levels and (2) that individuals with markedly reduced (pmolar) EDLC plasma levels are predisposed to cancer because these EDLC concentrations will predominantly stimulate the proliferation of tumor cells. Finally, we will summarize preliminary results from our department supporting this hypothesis.

Dengue virus capsid protein binding to hepatic lipid droplets (LD) is potassium ion dependent and is mediated by LD surface proteins

Dengue virus (DENV) affects millions of people, causing more than 20,000 deaths annually. No effective treatment for the disease caused by DENV infection is currently available, partially due to the lack of knowledge on the basic aspects of the viral life cycle, including the molecular basis of the interaction between viral components and cellular compartments. Here, we characterized the properties of the interaction between the DENV capsid (C) protein and hepatic lipid droplets (LDs), which was recently shown to be essential for the virus replication cycle. Zeta potential analysis revealed a negative surface charge of LDs, with an average surface charge of -19 mV. The titration of LDs with C protein led to an increase of the surface charge, which reached a plateau at +13.7 mV, suggesting that the viral protein-LD interaction exposes the protein cationic surface to the aqueous environment. Atomic force microscopy (AFM)-based force spectroscopy measurements were performed by using C protein-functionalized AFM tips. The C protein-LD interaction was found to be strong, with a single (un)binding force of 33.6 pN. This binding was dependent on high intracellular concentrations of potassium ions but not sodium. The inhibition of Na(+)/K(+)-ATPase in DENV-infected cells resulted in the dissociation of C protein from LDs and a 50-fold inhibition of infectious virus production but not of RNA replication, indicating a biological relevance for the potassium-dependent interaction. Limited proteolysis of the LD surface impaired the C protein-LD interaction, and force measurements in the presence of specific antibodies indicated that perilipin 3 (TIP47) is the major DENV C protein ligand on the surface of LDs.

Long-term exposure to hypoxia inhibits tumor progression of lung cancer in rats and mice

Background

Hypoxia has been identified as a major negative factor for tumor progression in clinical observations and in animal studies. However, the precise role of hypoxia in tumor progression has not been fully explained. In this study, we extensively investigated the effect of long-term exposure to hypoxia on tumor progression in vivo.

Methods

Rats bearing transplanted tumors consisting of A549 human lung cancer cells (lung cancer tumor) were exposed to hypoxia for different durations and different levels of oxygen. The tumor growth and metastasis were evaluated. We also treated A549 lung cancer cells (A549 cells) with chronic hypoxia and then implanted the hypoxia-pretreated cancer cells into mice. The effect of exposure to hypoxia on metastasis of Lewis lung carcinoma in mice was also investigated.

Results

We found that long-term exposure to hypoxia a) significantly inhibited lung cancer tumor growth in xenograft and orthotopic models in rats, b) significantly reduced lymphatic metastasis of the lung cancer in rats and decreased lung metastasis of Lewis lung carcinoma in mice, c) reduced lung cancer cell proliferation and cell cycle progression in vitro, d) decreased growth of the tumors from hypoxia-pretreated A549 cells, e) decreased Na⁺-K⁺ ATPase α1 expression in hypoxic lung cancer tumors, and f) increased expression of hypoxia inducible factors (HIF1α and HIF2α) but decreased microvessel density in the lung cancer tumors. In contrast to lung cancer, the growth of tumor from HCT116 human colon cancer cells (colon cancer tumor) was a) significantly enhanced in the same hypoxia conditions, accompanied by b) no significant change in expression of Na⁺-K⁺ ATPase α1, c) increased HIF1α expression (no HIF2α was detected) and d) increased microvessel density in the tumor tissues.

Conclusions

This study demonstrated that long-term exposure to hypoxia repressed tumor progression of the lung cancer from A549 cells and that decreased expression of Na⁺-K⁺ ATPase was involved in hypoxic inhibition of tumor progression. The results from this study provide new insights into the role of hypoxia in tumor progression and therapeutic strategies for cancer treatment.

Cardiotonic steroids attenuate ERK phosphorylation and generate cell cycle arrest to block human hepatoma cell growth

Recent studies revealed the potential of Na(+)/K(+)-ATPase as a target for anticancer therapy and showed additional modes of action of cardiotonic steroids (CSs), a diverse family of naturally derived compounds, as inhibitors of Na(+)/K(+)-ATPase. The results from epidemiological studies showed significantly lower mortality rates in cancer patients receiving CSs, which sparked interest in the anticancer properties of these drugs. The present study was designed to investigate the anticancer effect of CSs (ouabain or cinobufagin) and to elucidate the molecular mechanisms of CS activity in hepatoma cell lines (HepG2 and SMMC-7721). Ouabain and cinobufagin significantly inhibited cell proliferation by attenuating the phosphorylation of extracellular regulated kinase (ERK) and down-regulating the expression of C-myc. These CSs also induced cell apoptosis by increasing the concentration of intracellular free calcium ([Ca(2+)](i)) and induced S phase cell cycle arrest by down-regulating the expression of Cyclin A, cyclin dependent kinase 2 (CDK2) and proliferating cell nuclear antigen (PCNA) as well as up-regulating the expression of cyclin dependent kinase inhibitor 1A (p21(CIP1)). Overexpression of ERK reversed the antiproliferation effect of ouabain or cinobufagin in HepG2 and SMMC-7721 cells. Currently, the first generation of CS-based anticancer drugs (UNBS1450 and Anvirzel) are in Phase I clinical trials. These data clearly support their potential use as cancer therapies.

Proteomic profiling of human hepatocellular carcinoma SMMC-7721 cells under endoplasmic reticulum stress induced with dithiothreitol

AIM: To explore new therapy targets for human hepatocellular carcinoma by proteomic profiling of human hepatocellular carcinoma SMMC-7721 cells under endoplasmic reticulum stress.

METHODS: Cultured SMMC-7721 cells were divided into two groups: experimental group and control group. The experimental group was treated with dithiothreitol (DTT, 2.5 mmol/L), while the control group was treated with equal volume of culture medium. After treatment, total cell proteins were prepared and resolved by two-dimensional electrophoresis (2-DE). The two-dimensional electrophoresis maps for the two groups of cells were analyzed using ImageMaster 2D Platinum software. Proteins that showed obvious expression alteration in the experimental group were identified by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS).

RESULTS: There were 844 ± 46 protein spots in the 2-DE map for the experimental group and 1 015 ± 63 protein spots for the control group. There were 593 ± 23 pairs of matched protein spots between the two groups, and the matching rate was about 71%. Most of the proteins have an isoelectric point at pH5.2-6.5 and a molecular weight of 15 000-80 000 Da. Three protein spots showed 2-fold or greater differential expression between the two groups and were identified by MALDI-TOF-MS. They were protein fem-1 homolog B, cyclin A1, and proliferation-inducing protein 44.

CONCLUSION: Three differentially expressed proteins in SMMC-7721 cells under endoplasmic reticulum stress were identified and may be useful molecular targets for the diagnosis and treatment of hepatocellular carcinoma.