piggyBac transposon plus insulators overcome epigenetic silencing to provide for stable signaling pathway reporter cell lines

Terpenes from Cannabis sativa induce antinociception in a mouse model of chronic neuropathic pain via activation of adenosine A2A receptors

ABSTRACT

Terpenes are small hydrocarbon compounds that impart aroma and taste to many plants, including Cannabis sativa. A number of studies have shown that terpenes can produce pain relief in various pain states in both humans and animals. However, these studies were methodologically limited and few established mechanisms of action. In our previous work, we showed that the terpenes geraniol, linalool, β-pinene, α-humulene, and β-caryophyllene produced cannabimimetic behavioral effects via multiple receptor targets. We thus expanded this work to explore the potential antinociception and mechanism of these Cannabis terpenes in a mouse model of chronic pain. We first tested for antinociception by injecting terpenes (200 mg/kg, IP) into male and female CD-1 mice with mouse models of chemotherapy-induced peripheral neuropathy (CIPN) or lipopolysaccharide-induced inflammatory pain, finding that the terpenes produced roughly equal antinociception to 10 mg/kg morphine or 3.2 mg/kg WIN55,212. We further found that none of the terpenes produced reward as measured by conditioned place preference, while low doses of terpene (100 mg/kg) combined with morphine (3.2 mg/kg) produced enhanced antinociception vs either alone. We then used the adenosine A2A receptor (A2AR) selective antagonist istradefylline (3.2 mg/kg, IP) and spinal cord-specific CRISPR knockdown of the A2AR to identify this receptor as the mechanism for terpene antinociception in CIPN. In vitro cAMP and binding studies and in silico modeling studies further suggested that the terpenes act as A2AR agonists. Together these studies identify Cannabis terpenes as potential therapeutics for chronic neuropathic pain and identify a receptor mechanism for this activity.

Microglia Signaling Pathway Reporters Unveiled Manganese Activation of the Interferon/STAT1 Pathway and Its Mitigation by Flavonoids

Neuroinflammatory responses to neurotoxic manganese (Mn) in CNS have been associated with the Mn-induced Parkinson-like syndromes. However, the framework of molecular mechanisms contributing to manganism is still unclear. Using an in vitro neuroinflammation model based on the insulated signaling pathway reporter transposon constructs stably transfected into a murine BV-2 microglia line, we tested effects of manganese (II) together with a set of 12 metal salts on the transcriptional activities of the NF-κB, activator protein-1 (AP-1), signal transducer and activator of transcription 1 (STAT1), STAT1/STAT2, STAT3, Nrf2, and metal-responsive transcription factor-1 (MTF-1) via luciferase assay, while concatenated destabilized green fluorescent protein expression provided for simultaneous evaluation of cellular viability. This experiment revealed specific and strong responses to manganese (II) in reporters of the type I and type II interferon-induced signaling pathways, while weaker activation of the NF-κB in the microglia was detected upon treatment of cells with Mn(II) and Ba(II). There was a similarity between Mn(II) and interferon-γ in the temporal STAT1 activation profile and in their antagonism to bacterial LPS. Sixty-four natural and synthetic flavonoids differentially affected both cytotoxicity and the pro-inflammatory activity of Mn (II) in the microglia. Whereas flavan-3-ols, flavanones, flavones, and flavonols were cytoprotective, isoflavones enhanced the cytotoxicity of Mn(II). Furthermore, about half of the tested flavonoids at 10-50 μM could attenuate both basal and 100-200 μM Mn(II)-induced activity at the gamma-interferon activated DNA sequence (GAS) in the cells, suggesting no critical roles for the metal chelation or antioxidant activity in the protective potential of flavonoids against manganese in microglia. In summary, results of the study identified Mn as a specific elicitor of the interferon-dependent pathways that can be mitigated by dietary polyphenols.

Terpenes from Cannabis sativa Induce Antinociception in Mouse Chronic Neuropathic Pain via Activation of Spinal Cord Adenosine A2A Receptors

Terpenes are small hydrocarbon compounds that impart aroma and taste to many plants, including Cannabis sativa. A number of studies have shown that terpenes can produce pain relief in various pain states in both humans and animals. However, these studies were methodologically limited and few established mechanisms of action. In our previous work, we showed that the terpenes geraniol, linalool, β-pinene, α-humulene, and β-caryophyllene produced cannabimimetic behavioral effects via multiple receptor targets. We thus expanded this work to explore the efficacy and mechanism of these Cannabis terpenes in relieving chronic pain. We first tested for antinociceptive efficacy by injecting terpenes (200 mg/kg, IP) into male and female CD-1 mice with chemotherapy-induced peripheral neuropathy (CIPN) or lipopolysaccharide-induced inflammatory pain, finding that the terpenes produced roughly equal efficacy to 10 mg/kg morphine or 3.2 mg/kg WIN55,212. We further found that none of the terpenes produced reward as measured by conditioned place preference, while low doses of terpene (100 mg/kg) combined with morphine (3.2 mg/kg) produced enhanced antinociception vs. either alone. We then used the adenosine A2A receptor (A2AR) selective antagonist istradefylline (3.2 mg/kg, IP) and spinal cord-specific CRISPR knockdown of the A2AR to identify this receptor as the mechanism for terpene antinociception in CIPN. In vitro cAMP and binding studies and in silico modeling studies further suggested that the terpenes act as A2AR agonists. Together these studies identify Cannabis terpenes as potential therapeutics for chronic neuropathic pain, and identify a receptor mechanism in the spinal cord for this activity.

Screening a small hydrazide-hydrazone combinatorial library for targeting the STAT3 in monocyte-macrophages with insulated reporter transposons

The Signal Transducer and Activator of Transcription 3 (STAT3) pharmacological targeting is regarded as a prospective approach to treat cancer, autoimmune disorders, or inflammatory diseases. We have developed a series of reporters of the STAT3, NF-κB, Nrf2, metal-responsive transcription factor-1 (MTF-1), and hypoxia-inducible factor 1α (HIF-1α) transcriptional activation in human monocyte-macrophage line THP-1. The reporter lines were employed to test a set of hydrazide-hydrazones as potential STAT3 inhibitors. A hydrazide-hydrazone library composed of 70 binary combinations of 7 carbonyl and 10 hydrazide components, including a STAT3 inhibitor clinical drug nifuroxazide, has been assembled and screened by the reporters. For the library as a whole, significant correlations between responses of the STAT3 and NF-κB or the STAT3 and HIF-1α reporters in THP-1 monocytes were found. For selected inhibitory combinations, respective hydrazide-hydrazones have been prepared and tested individually. The most potent 2-acetylpyridine 4-chlorobenzoylhydrazone exhibited the STAT3 inhibitory potential significantly exceeding that of nifuroxazide (ED50 2 vs 50 μM respectively) in THP-1 cells. We conclude that insulated reporter transposons could be a useful tool for drug discovery applications.

Graphical Abstract

Structural and Functional Studies of S-(2-Carboxyethyl)-L-Cysteine and S-(2-Carboxyethyl)-l-Cysteine Sulfoxide

Insecticidal non-proteinogenic amino acid S-(2-carboxyethyl)-L-cysteine (β-CEC) and its assumed metabolite, S-(2-carboxyethyl)-l-cysteine sulfoxide (β-CECO), are present abundantly in a number of plants of the legume family. In humans, these amino acids may occur as a result of exposure to environmental acrylonitrile or acrylamide, and due to consumption of the legumes. The β-CEC molecule is a homolog of S-carboxymethyl-l-cysteine (carbocisteine, CMC), a clinically employed antioxidant and mucolytic drug. We report here detailed structural data for β-CEC and β-CECO, as well as results of in vitro studies evaluating cytotoxicity and the protective potential of the amino acids in renal tubular epithelial cells (RTECs) equipped with reporters for activity of seven stress-responsive transcription factors. In RTECs, β-CEC and the sulfoxide were not acutely cytotoxic, but activated the antioxidant Nrf2 pathway. β-CEC, but not the sulfoxide, induced the amino acid stress signaling, which could be moderated by cysteine, methionine, histidine, and tryptophan. β-CEC enhanced the cytotoxic effects of arsenic, cadmium, lead, and mercury, but inhibited the cytotoxic stress induced by cisplatin, oxaliplatin, and CuO nanoparticles and acted as an antioxidant in a copper-dependent oxidative DNA degradation assay. In these experiments, the structure and activities of β-CEC closely resembled those of CMC. Our data suggest that β-CEC may act as a mild activator of the cytoprotective pathways and as a protector from platinum drugs and environmental copper cytotoxicity.

LuminoCell: a versatile and affordable platform for real-time monitoring of luciferase-based reporters

Luciferase reporter assays represent a simple and sensitive experimental system in cell and molecular biology to study multiple biological processes. However, the application of these assays is often limited by the costs of conventional luminometer instruments and the versatility of their use in different experimental conditions. Therefore, we aimed to develop a small, affordable luminometer allowing continuous measurement of luciferase activity, designed for inclusion into various kinds of tissue culture incubators. Here, we introduce LuminoCell-an open-source platform for the construction of an affordable, sensitive, and portable luminometer capable of real-time monitoring in-cell luciferase activity. The LuminoCell costs $40, requires less than 1 h to assemble, and it is capable of performing real-time sensitive detection of both magnitude and duration of the activity of major signalling pathways in cell cultures, including receptor tyrosine kinases (EGF and FGF), WNT/β-catenin, and NF-κB. In addition, we show that the LuminoCell is suitable to be used in cytotoxicity assays as well as for monitoring periodic circadian gene expression.

Bidirectional Responses of Eight Neuroinflammation-Related Transcriptional Factors to 64 Flavonoids in Astrocytes with Transposable Insulated Signaling Pathway Reporters

Neuroinflammation is implicated in a variety of pathologies and is mechanistically linked to hyperactivation of glial cells in the central nervous system (CNS), predominantly in response to external stimuli. Multiple dietary factors were reported to alter neuroinflammation, but their actions on the relevant transcription factors in glia are not sufficiently understood. Here, an in vitro protocol employing cultured astroglial cells, which carry reporters of multiple signaling pathways associated with inflammation, was developed for screening environmental factors and synthetic drugs. Immortalized rat astrocyte line DI TNC1 was stably transfected with piggyBac transposon vectors containing a series of insulated reporters for the transcriptional activity of NF-κB, AP-1, signal transducer and activator of transcription 1 (STAT1), signal transducer and activator of transcription 3 (STAT3), aromatic hydrocarbon receptor (AhR), Nrf2, peroxisome proliferator-activated receptor γ (PPARγ), and HIF-1α, which is quantified via luciferase assay. Concatenated green fluorescent protein (GFP) expression was employed for simultaneous evaluation of cellular viability. Responses to a set of 64 natural and synthetic monomeric flavonoids representing six main structural classes (flavan-3-ols, flavanones, flavones, flavonols, isoflavones, and anthocyan(id)ins) were obtained at 10 and 50 μM concentrations. Except for HIF-1α, the activity of NF-κB and other transcription factors (TFs) in astrocytes was predominantly inhibited by flavan-3-ols and anthocyan(id)ins, while flavones and isoflavones generally activated these TFs. In addition, we obtained dose-response profiles for 11 flavonoids (apigenin, baicalein, catechin, cyanidin, epigallocatechin gallate, genistein, hesperetin, kaempferol, luteolin, naringenin, and quercetin) within the 1-100 μM range and in the presence of immune-stimulants and immune-suppressors. The flavonoid concentration profiles for TF-activation reveal biphasic response curves from the astrocytes. Apart from epigallocatechin gallate (EGCG), flavonoids failed to inhibit the NF-κB activation by proinflammatory agents [lipopolysaccharide (LPS), cytokines], but most of the tested polyphenols synergized with STAT3 inhibitors (stattic, ruxolitinib) against the activation of this TF in the astrocytes. We conclude that transposable insulated reporters of transcriptional activation represent a convenient neurochemistry tool in screening for activators/inhibitors of signaling pathways.

An RNA aptamer restores defective bone growth in FGFR3-related skeletal dysplasia in mice

Achondroplasia is the most prevalent genetic form of dwarfism in humans and is caused by activating mutations in FGFR3 tyrosine kinase. The clinical need for a safe and effective inhibitor of FGFR3 is unmet, leaving achondroplasia currently incurable. Here, we evaluated RBM-007, an RNA aptamer previously developed to neutralize the FGFR3 ligand FGF2, for its activity against FGFR3. In cultured rat chondrocytes or mouse embryonal tibia organ culture, RBM-007 rescued the proliferation arrest, degradation of cartilaginous extracellular matrix, premature senescence, and impaired hypertrophic differentiation induced by FGFR3 signaling. In cartilage xenografts derived from induced pluripotent stem cells from individuals with achondroplasia, RBM-007 rescued impaired chondrocyte differentiation and maturation. When delivered by subcutaneous injection, RBM-007 restored defective skeletal growth in a mouse model of achondroplasia. We thus demonstrate a ligand-trap concept of targeting the cartilage FGFR3 and delineate a potential therapeutic approach for achondroplasia and other FGFR3-related skeletal dysplasias.

Structure, Antioxidant and Anti-inflammatory Activities of the (4R)- and (4S)-epimers of S-Carboxymethyl-L-cysteine Sulfoxide

S-Carboxymethyl-L-cysteine (CMC) is an antioxidant and mucolytic commonly prescribed to patients with chronic obstructive pulmonary disease. In humans, CMC is rapidly metabolized to S-carboxymethyl-L-cysteine sulfoxide (CMCO). In this study, we assessed structural and functional similarities between CMC and CMCO. X-Ray diffraction analysis provided detailed structural information about CMCO, which exists as a 1:1 mixture of epimers, due to the emergence of a new chiral center at the sulfur atom. Both CMC and CMCO epimers protected model DNA from copper-mediated hydroxyl free radical damage. Using an insulated transposable construct for reporting activity of the cellular stress-responsive transcription factors Nrf2, p53, NF-κB, and AP-1, we demonstrate that CMCO, especially its (4R)-epimer, is comparable to CMC in their ability to mitigate the effects of oxidative stress and pro-inflammatory stimuli in human alveolar (A549) and bronchial epithelial (BEAS-2B) cells. The results of these in vitro studies suggest that CMCO retains, at least partially, the antioxidant potential of CMC and may inform pharmacodynamics considerations of CMC use in clinics.

Characterization of the cHS4 insulator in mouse embryonic stem cells

Synthetic biology circuits are often constructed with multiple gene expression units assembled in close proximity, and they can be used to perform complex functions in embryonic stem cells (ESCs). However, mutual interference between transcriptional units has not been well studied in mouse ESCs. To assess the efficiency of insulators at suppressing promoter interference in mouse ESCs, we used an evaluation scheme in which a tunable tetracycline response element promoter is connected to a constant Nanog promoter. The chicken hypersensitive site 4 (cHS4) insulator, widely used both for enhancer blocking and for barrier insulation in vitro and in vivo, was positioned between the two expression units for assessment. By inserting the cassette into various loci of the mouse ESC genome with PiggyBac transposon, we were able to quantitatively examine the protective effect of cHS4 by gradually increasing the transcriptional activity of the tetracycline response element promoter with doxycycline and then measuring the transcriptional activity of the Nanog promoter. Our results indicate that the cHS4 insulator has minimal insulating effects on promoter interference in mouse ESCs. Further studies show that the cHS4 insulation effect may be promoter specific and related to interaction with CCCTC‐binding factor‐mediated loop formation. In addition, we also compared DNA transposition and transgene expression with or without the cHS4 insulator using well‐established ESC reporters. The results indicate that cHS4 has no apparent effects on DNA transposition and transgene expression levels, but exerts modest protective effects on long‐term transgene silencing.

Testing the role of SOX15 in human primordial germ cell fate

Background: Potentially novel regulators of early human germline development have been identified recently, including SOX15 and SOX17, both of which show specific expression in human primordial germ cells. SOX17 is now known to be a critical specifier of human germ cell identity. There have been suggestions, as yet without evidence, that SOX15 might also play a prominent role. The early human germline is inaccessible for direct study, but an in vitro model of human primordial germ cell-like cell (hPGCLC) specification from human embryonic stem cells (hESCs) has been developed. This enables mechanistic study of human germ cell specification using genetic tools to manipulate the levels of SOX15 and SOX17 proteins to explore their roles in hPGCLC specification. Methods: SOX15 and SOX17 proteins were depleted during hPGCLC specification from hESCs using the auxin-inducible degron system, combined with a fluorescent reporter for tracking protein levels. Additionally, SOX15 protein was overexpressed using the ProteoTuner system. Protein-level expression changes were confirmed by immunofluorescence. The impact on hPGCLC specification efficiency was determined by flow cytometry at various time points. qPCR experiments were performed to determine some transcriptional effects of SOX15 perturbations. Results: We observed specific SOX15 expression in hPGCLCs by using immunofluorescence and flow cytometry analysis. Depletion of SOX15 had no significant effect on hPGCLC specification efficiency on day 4 after induction, but there was a significant and progressive decrease in hPGCLCs on days 6 and 8. By contrast, depletion of SOX17 completely abrogated hPGCLC specification. Furthermore, SOX15 overexpression resulted in a significant increase in hPGCLC fraction on day 8. qPCR analysis revealed a possible role for the germ cell and pluripotency regulator PRDM14 in compensating for changes to SOX15 protein levels. Conclusions: SOX17 is essential for hPGCLC specification, yet SOX15 is dispensable. However, SOX15 may have a role in maintaining germ cell identity.

Testing the role of SOX15 in human primordial germ cell fate

Background: Potentially novel regulators of early human germline development have been identified recently, including SOX15 and SOX17, both of which show specific expression in human primordial germ cells. SOX17 is now known to be a critical specifier of human germ cell identity. There have been suggestions, as yet without evidence, that SOX15 might also play a prominent role. The early human germline is inaccessible for direct study, but an in vitro model of human primordial germ cell-like cell (hPGCLC) specification from human embryonic stem cells (hESCs) has been developed. This enables mechanistic study of human germ cell specification using genetic tools to manipulate the levels of SOX15 and SOX17 proteins to explore their roles in hPGCLC specification. Methods: SOX15 and SOX17 proteins were depleted during hPGCLC specification from hESCs using the auxin-inducible degron system, combined with a fluorescent reporter for tracking protein levels. Additionally, SOX15 protein was overexpressed using the ProteoTuner system. Protein-level expression changes were confirmed by immunofluorescence. The impact on hPGCLC specification efficiency was determined by flow cytometry at various time points. qPCR experiments were performed to determine some transcriptional effects of SOX15 perturbations. Results: We observed specific SOX15 expression in hPGCLCs by using immunofluorescence and flow cytometry analysis. Depletion of SOX15 had no significant effect on hPGCLC specification efficiency on day 4 after induction, but there was a significant and progressive decrease in hPGCLCs on days 6 and 8. By contrast, depletion of SOX17 completely abrogated hPGCLC specification. Furthermore, SOX15 overexpression resulted in a significant increase in hPGCLC fraction on day 8. qPCR analysis revealed a possible role for the germ cell and pluripotency regulator PRDM14 in compensating for changes to SOX15 protein levels. Conclusions: SOX17 is essential for hPGCLC specification, yet SOX15 is dispensable. However, SOX15 may have a role in maintaining germ cell identity.

Intravenous Delivery of piggyBac Transposons as a Useful Tool for Liver-Specific Gene-Switching

Hydrodynamics-based gene delivery (HGD) is an efficient method for transfecting plasmid DNA into hepatocytes in vivo. However, the resulting gene expression is transient, and occurs in a non-tissue specific manner. The piggyBac (PB) transposon system allows chromosomal integration of a transgene in vitro. This study aimed to achieve long-term in vivo expression of a transgene by performing hepatocyte-specific chromosomal integration of the transgene using PB and HGD. Using this approach, we generated a novel mouse model for a hepatic disorder. A distinct signal from the reporter plasmid DNA was discernible in the murine liver approximately two months after the administration of PB transposons carrying a reporter gene. Then, to induce the hepatic disorder, we first administered mice with a PB transposon carrying a CETD unit (loxP-flanked stop cassette, diphtheria toxin-A chain gene, and poly(A) sites), and then with a plasmid expressing the Cre recombinase under the control of a liver-specific promoter. We showed that this system can be used for in situ manipulation and analysis of hepatocyte function in vivo in non-transgenic (Tg) animals.

Interaction of Bacterial Phenazines with Colistimethate in Bronchial Epithelial Cells

Multidrug-resistant bacterial infections are being increasingly treated in clinics with polymyxins, a class of antibiotics associated with adverse effects on the kidney, nervous system, or airways of a significant proportion of human and animal patients. Although many of the resistant pathogens display enhanced virulence, the hazard of cytotoxic interactions between polymyxin antibiotics and bacterial virulence factors (VFs) has not been assessed, to date. We report here the testing of paired combinations of four Pseudomonas aeruginosa VF phenazine toxins, pyocyanin (PYO), 1-hydroxyphenazine (1-HP), phenazine-1-carboxylic acid (PCA), and phenazine-1-carboxamide (PCN), and two commonly prescribed polymyxin drugs, colistin-colistimethate sodium (CMS) and polymyxin B, in three human airway cell lines, BEAS-2B, HBE-1, and CFT-1. Cytotoxicities of individual antibiotics, individual toxins, and their combinations were evaluated by the simultaneous measurement of mitochondrial metabolic, total transcriptional/translational, and Nrf2 stress response regulator activities in treated cells. Two phenazines, PYO and 1-HP, were cytotoxic at clinically relevant concentrations (100 to 150 μM) and prompted a significant increase in oxidative stress-induced transcriptional activity in surviving cells. The polymyxin antibiotics arrested cell proliferation at clinically achievable (<1 mM) concentrations as well, with CMS displaying surprisingly high cytotoxicity (50% effective dose [ED₅₀] = 180 μM) in BEAS-2B cells. The dose-response curves were probed by a median-effect analysis, which established a synergistically enhanced cytotoxicity of the PYO-CMS combination in all three airway cell lines; a particularly strong effect on BEAS-2B cells was observed, with a combination index (CI) of 0.27 at the ED₅₀. PCA, PCN, and 1-HP potentiated CMS cytotoxicity to a smaller extent. The cytotoxicity of CMS could be reduced with 10 mM N-acetyl-cysteine. Iron chelators, while ineffective against the polymyxins, could rescue all three bronchial epithelial cell lines treated with lethal PYO or CMS-PYO doses. These findings suggest that further evaluations of CMS safety are needed, along with a search for means to moderate potentially cytotoxic interactions.

Genetic screening and multipotency in rhesus monkey haploid neural progenitor cells

Haploid embryonic stem cells (haESCs) have been extensively applied in forward and reverse genetic screening. However, a mammalian haploid somatic cell line is difficult to achieve because of spontaneous diploidization in differentiation. As a non-human primate species, monkeys are widely used in basic and pre-clinical research in which haploid cells are restricted to ESCs. Here, we report that rhesus monkey haESCs in an optimized culture medium show naïve-state pluripotency and stable haploidy. This model facilitated the derivation of haploid neural progenitor cells (haNPCs), which maintained haploidy and differentiation potential into neurons and glia for a long period in vitro High-throughput trapping mutations can be efficiently introduced into haNPCs via piggyBac transposons. This system proves useful when identifying gene targets of neural toxicants via a proof-of-concept experiment. Using CRISPR/Cas9 editing, we confirmed that B4GALT6, from the candidate gene list, is a resistance gene of A803467 (a tetrodotoxin-like toxicant). This model is the first non-human primate haploid somatic cell line with proliferative ability, multipotency and an intact genome, thus providing a cellular resource for recessive genetic and potential drug screening.

High-fat, high-fructose, high-cholesterol feeding causes severe NASH and cecal microbiota dysbiosis in juvenile Ossabaw swine

Pediatric obesity and nonalcoholic steatohepatitis (NASH) are on the rise in industrialized countries, yet our ability to mechanistically examine this relationship is limited by the lack of a suitable higher animal models. Here, we examined the effects of high-fat, high-fructose corn syrup, high-cholesterol Western-style diet (WD)-induced obesity on NASH and cecal microbiota dysbiosis in juvenile Ossabaw swine. Juvenile female Ossabaw swine (5 wk old) were fed WD (43.0% fat; 17.8% high-fructose corn syrup; 2% cholesterol) or low-fat diet (CON/lean; 10.5% fat) for 16 wk ( n = 6 each) or 36 wk ( n = 4 each). WD-fed pigs developed obesity, dyslipidemia, and systemic insulin resistance compared with CON pigs. In addition, obese WD-fed pigs developed severe NASH, with hepatic steatosis, hepatocyte ballooning, inflammatory cell infiltration, and fibrosis after 16 wk, with further exacerbation of histological inflammation and fibrosis after 36 wk of WD feeding. WD feeding also resulted in robust cecal microbiota changes including increased relative abundances of families and genera in Proteobacteria ( P < 0.05) (i.e., Enterobacteriaceae, Succinivibrionaceae, and Succinivibrio) and LPS-containing Desulfovibrionaceae and Desulfovibrio and a greater ( P < 0.05) predicted microbial metabolic function for LPS biosynthesis, LPS biosynthesis proteins, and peptidoglycan synthesis compared with CON-fed pigs. Overall, juvenile Ossabaw swine fed a high-fat, high-fructose, high-cholesterol diet develop obesity and severe microbiota dysbiosis with a proinflammatory signature and a NASH phenotype directly relevant to the pediatric/adolescent and young adult population.

Preclinical and clinical advances in transposon-based gene therapy

Transposons derived from Sleeping Beauty (SB), piggyBac (PB), or Tol2 typically require cotransfection of transposon DNA with a transposase either as an expression plasmid or mRNA. Consequently, this results in genomic integration of the potentially therapeutic gene into chromosomes of the desired target cells, and thus conferring stable expression. Non-viral transfection methods are typically preferred to deliver the transposon components into the target cells. However, these methods do not match the efficacy typically attained with viral vectors and are sometimes associated with cellular toxicity evoked by the DNA itself. In recent years, the overall transposition efficacy has gradually increased by codon optimization of the transposase, generation of hyperactive transposases, and/or introduction of specific mutations in the transposon terminal repeats. Their versatility enabled the stable genetic engineering in many different primary cell types, including stem/progenitor cells and differentiated cell types. This prompted numerous preclinical proof-of-concept studies in disease models that demonstrated the potential of DNA transposons for ex vivo and in vivo gene therapy. One of the merits of transposon systems relates to their ability to deliver relatively large therapeutic transgenes that cannot readily be accommodated in viral vectors such as full-length dystrophin cDNA. These emerging insights paved the way toward the first transposon-based phase I/II clinical trials to treat hematologic cancer and other diseases. Though encouraging results were obtained, controlled pivotal clinical trials are needed to corroborate the efficacy and safety of transposon-based therapies.

Monoclonal antibodies expression improvement in CHO cells by PiggyBac transposition regarding vectors ratios and design

Establishing stable Chinese Hamster Ovary (CHO) cells producing monoclonal antibodies (mAbs) usually pass through the random integration of vectors to the cell genome, which is sensitive to gene silencing. One approach to overcome this issue is to target a highly transcribed region in the genome. Transposons are useful devices to target active parts of genomes, and PiggyBac (PB) transposon can be considered as a good option. In the present study, three PB transposon donor vectors containing both heavy and light chains were constructed, one contained independent expression cassettes while the others utilized either an Internal Ribosome Entry Site (IRES) or 2A element to express mAb. Conventional cell pools were created by transferring donor vectors into the CHO cells, whereas transposon-based cells were generated by transfecting the cells with donor vectors with a companion of a transposase-encoding helper vector, with 1:2.5 helper/donor vectors ratio. To evaluate the influence of helper/donor vectors ratio on expression, the second transposon-based cell pools were generated with 1:5 helper/donor ratio. Expression levels in the transposon-based cells were two to five -folds more than those created by conventional method except for the IRES-mediated ones, in which the observed difference increased more than 100-fold. The results were dependent on both donor vector design and vectors ratios.

Dynamic silencing of somatic L1 retrotransposon insertions reflects the developmental and cellular contexts of their genomic integration

Background

The ongoing mobilization of mammalian transposable elements (TEs) contributes to natural genetic variation. To survey the epigenetic control and expression of reporter genes inserted by L1 retrotransposition in diverse cellular and genomic contexts, we engineered highly sensitive, real-time L1 retrotransposon reporter constructs.

Results

Here we describe different patterns of expression and epigenetic controls of newly inserted sequences retrotransposed by L1 in various somatic cells and tissues including cultured human cancer cells, mouse embryonic stem cells, and tissues of pseudofounder transgenic mice and their progeny. In cancer cell lines, the newly inserted sequences typically underwent rapid transcriptional gene silencing, but they lacked cytosine methylation even after many cell divisions. L1 reporter expression was reversible and oscillated frequently. Silenced or variegated reporter expression was strongly and uniformly reactivated by treatment with inhibitors of histone deacetylation, revealing the mechanism for their silencing. By contrast, de novo integrants retrotransposed by L1 in pluripotent mouse embryonic stem (ES) cells underwent rapid silencing by dense cytosine methylation. Similarly, de novo cytosine methylation also was identified at new integrants when studied in several distinct somatic tissues of adult founder mice. Pre-existing L1 elements in cultured human cancer cells were stably silenced by dense cytosine methylation, whereas their transcription modestly increased when cytosine methylation was experimentally reduced in cells lacking DNA methyltransferases DNMT1 and DNMT3b. As a control, reporter genes mobilized by piggyBac (PB), a DNA transposon, revealed relatively stable and robust expression without apparent silencing in both cultured cancer cells and ES cells.

Conclusions

We hypothesize that the de novo methylation marks at newly inserted sequences retrotransposed by L1 in early pre-implantation development are maintained or re-established in adult somatic tissues. By contrast, histone deacetylation reversibly silences L1 reporter insertions that had mobilized at later timepoints in somatic development and differentiation, e.g., in cancer cell lines. We conclude that the cellular contexts of L1 retrotransposition can determine expression or silencing of newly integrated sequences. We propose a model whereby reporter expression from somatic TE insertions reflects the timing, molecular mechanism, epigenetic controls and the genomic, cellular and developmental contexts of their integration.

Electronic supplementary material

The online version of this article (doi:10.1186/s13100-017-0091-2) contains supplementary material, which is available to authorized users.

The Functionality of Minimal PiggyBac Transposons in Mammalian Cells

Minimal piggyBac vectors are a modified single-plasmid version of the classical piggyBac delivery system that can be used for stable transgene integration. These vectors have a truncated terminal domain in the delivery cassette and thus, integrate significantly less flanking transposon DNA into host cell chromatin than classical piggyBac vectors. Herein, we test various characteristics of this modified transposon. The integration efficiency of minimal piggyBac vectors was inversely related to the size of both the transposon and the entire plasmid, but inserts as large as 15 kb were efficiently integrated. Open and super-coiled vectors demonstrated the same integration efficiency while DNA methylation decreased the integration efficiency and silenced the expression of previously integrated sequences in some cell types. Importantly, the incidence of plasmid backbone integration was not increased above that seen in nontransposon control vectors. In BALB/c mice, we demonstrated prolonged expression of two transgenes (intracellular mCherry and secretable Gaussia luciferase) when delivered by the minimal piggyBac that resulted in a more sustained antibody production against the immunogenic luciferase than when delivered by a transient (nontransposon) vector plasmid. We conclude that minimal piggyBac vectors are an effective alternative to other integrative systems for stable DNA delivery in vitro and in vivo.

Transient Proteotoxicity of Bacterial Virulence Factor Pyocyanin in Renal Tubular Epithelial Cells Induces ER-Related Vacuolation and Can Be Efficiently Modulated by Iron Chelators

Persistent infections of biofilm forming bacteria, such as Pseudomonas aeruginosa, are common among human populations, due to the bacterial resistance to antibiotics and other adaptation strategies, including release of cytotoxic virulent factors such as pigment pyocyanin (PCN). Urinary tract infections harbor P. aeruginosa strains characterized by the highest PCN-producing capacity, yet no information is available on PCN cytotoxicity mechanism in kidney. We report here that renal tubular epithelial cell (RTEC) line NRK-52E responds to PCN treatments with paraptosis-like activity features. Specifically, PCN-treated cells experienced dilation of endoplasmic reticulum (ER) and an extensive development of ER-derived vacuoles after about 8 h. This process was accompanied with hyper-activation of proteotoxic stress-inducible transcription factors Nrf2, ATF6, and HSF-1. The cells could be rescued by withdrawal of PCN from the culture media before the vacuoles burst and cells die of non-programmed necrosis after about 24–30 h. The paraptosis-like activity was abrogated by co-treatment of the cells with metal-chelating antioxidants. A microscopic examination of cells co-treated with PCN and agents aiming at a variety of the cellular stress mediators and pathways have identified iron as a single most significant co-factor of the PCN cytotoxicity in the RTECs. Among biologically relevant metal ions, low micromolar Fe²⁺specifically mediated anaerobic oxidation of glutathione by PCN, but catechol derivatives and other strong iron complexing agents could inhibit the reaction. Our data suggest that iron chelation could be considered as a supplementary treatment in the PCN-positive infections.

The piggyBac-Based Gene Delivery System Can Confer Successful Production of Cloned Porcine Blastocysts with Multigene Constructs

The introduction of multigene constructs into single cells is important for improving the performance of domestic animals, as well as understanding basic biological processes. In particular, multigene constructs allow the engineering and integration of multiple genes related to xenotransplantation into the porcine genome. The piggyBac (PB) transposon system allows multiple genes to be stably integrated into target genomes through a single transfection event. However, to our knowledge, no attempt to introduce multiple genes into a porcine genome has been made using this system. In this study, we simultaneously introduced seven transposons into a single porcine embryonic fibroblast (PEF). PEFs were transfected with seven transposons containing genes for five drug resistance proteins and two (red and green) fluorescent proteins, together with a PB transposase expression vector, pTrans (experimental group). The above seven transposons (without pTrans) were transfected concomitantly (control group). Selection of these transfected cells in the presence of multiple selection drugs resulted in the survival of several clones derived from the experimental group, but not from the control. PCR analysis demonstrated that approximately 90% (12/13 tested) of the surviving clones possessed all of the introduced transposons. Splinkerette PCR demonstrated that the transposons were inserted through the TTAA target sites of PB. Somatic cell nuclear transfer (SCNT) using a PEF clone with multigene constructs demonstrated successful production of cloned blastocysts expressing both red and green fluorescence. These results indicate the feasibility of this PB-mediated method for simultaneous transfer of multigene constructs into the porcine cell genome, which is useful for production of cloned transgenic pigs expressing multiple transgenes.

Phytochemicals and botanical extracts regulate NF-κB and Nrf2/ARE reporter activities in DI TNC1 astrocytes

The increase in oxidative stress and inflammatory responses associated with neurodegenerative diseases has drawn considerable attention towards understanding the transcriptional signaling pathways involving NF-κB (nuclear factor kappa-light-chain-enhancer of activated B cells) and Nrf2 (Nuclear Factor Erythroid 2-like 2). Our recent studies with immortalized murine microglial cells (BV-2) demonstrated effects of botanical polyphenols to inhibit lipopolysaccharide (LPS)-induced nitric oxide (NO) and enhance Nrf2-mediated antioxidant responses (Sun et al., 2015). In this study, an immortalized rat astrocyte (DI TNC1) cell line expressing a luciferase reporter driven by the NF-κB or the Nrf2/Antioxidant Response Element (ARE) promoter was used to assess regulation of these two pathways by phytochemicals such as quercetin, rutin, cyanidin, cyanidin-3-O-glucoside, as well as botanical extracts from Withania somnifera (Ashwagandha), Sutherlandia frutescens (Sutherlandia) and Euterpe oleracea (Açaí). Quercetin effectively inhibited LPS-induced NF-κB reporter activity and stimulated Nrf2/ARE reporter activity in DI TNC1 astrocytes. Cyanidin and the glycosides showed similar effects but only at much higher concentrations. All three botanical extracts effectively inhibited LPS-induced NF-κB reporter activity. These extracts were capable of enhancing ARE activity by themselves and further enhanced ARE activity in the presence of LPS. Quercetin and botanical extracts induced Nrf2 and HO-1 protein expression. Interestingly, Ashwagandha extract was more active in inducing Nrf2 and HO-1 expression in DI TNC1 astrocytes as compared to Sutherlandia and Açaí extracts. In summary, this study demonstrated NF-kB and Nrf2/ARE promoter activities in DI TNC1 astrocytes, and further showed differences in ability for specific botanical polyphenols and extracts to down-regulate LPS-induced NF-kB and up-regulate the NRF2/ARE activities in these cells.

Ashwagandha attenuates TNF-α- and LPS-induced NF-κB activation and CCL2 and CCL5 gene expression in NRK-52E cells

Background

The aging kidney is marked by a chronic inflammation, which may exacerbate the progression of renal dysfunction, as well as increase the susceptibility to acute injury. The identification of strategies to alleviate inflammation may have translational impact to attenuate kidney disease.

Methods

We tested the potential of ashwaganda, sutherlandia and elderberry on tumor necrosis factor-α (TNF-α) and lipopolysaccharide (LPS) induced chemokine (CCL2 and CCL5) expression in vitro.

Results

Elderberry water-soluble extract (WSE) was pro-inflammatory, while sutherlandia WSE only partially attenuated the TNF-α-induced changes in CCL5. However, ashwaganda WSE completely prevented TNF-α-induced increases in CCL5, while attenuating the increase in CCL2 expression and NF-κB activation. The same pattern of ashwagandha protection was seen using LPS as the pro-inflammatory stimuli.

Conclusions

Taken together, these results demonstrate the ashwaganda WSE as a valid candidate for evaluation of therapeutic potential for the treatment of chronic renal dysfunction.

Unveiling the anti-inflammatory activity of Sutherlandia frutescens using murine macrophages

Sutherlandia frutescens is a botanical widely used in southern Africa for treatment of inflammatory and other conditions. Previously, an ethanolic extract of S. frutescens (SFE) has been shown to inhibit the production of reactive oxygen species (ROS) and nitric oxide (NO) by murine neurons and a microglia cell line (BV-2 cells). In this study we sought to confirm the anti-inflammatory activities of SFE on a widely used murine macrophage cell line (i.e., RAW 264.7 cells) and primary mouse macrophages. Furthermore, experiments were conducted to investigate the anti-inflammatory activity of the flavonol and cycloartanol glycosides found in high quantities in S. frutescens. While the SFE exhibited anti-inflammatory activities upon murine macrophages similar to that reported with the microglia cell line, this effect does not appear to be mediated by sutherlandiosides or sutherlandins. In contrast, chlorophyll in our extracts appeared to be partly responsible for some of the activity observed in our macrophage-dependent screening assay.

Immuno-stimulatory activity of a polysaccharide-enriched fraction of Sutherlandia frutescens occurs by the toll-like receptor-4 signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Sutherlandia frutescens (L.) R. Br. is an indigenous plant of southern Africa that has been traditionally used for various cancers, infections, and inflammatory conditions.

AIM OF THE STUDY

Our aim was to investigate the potential immuno-stimulatory activity of a polysaccharide-enriched fraction (SFPS) from a decoction of S. frutescens.

MATERIALS AND METHODS

RAW 264.7 cells (a murine macrophage cell line) were used to determine the activities of SFPS on macrophage function. The production of reactive oxygen species (ROS), nitric oxide (NO), and inflammatory cytokines were evaluated in the cells treated with or without SFPS. CLI-095, a toll-like receptor (TLR) 4-specific inhibitor, was used to identify whether or not SFPS exerts its effects through TLR4. An antagonist of endotoxin, polymyxin B, was used to evaluate whether endotoxin present in SFPS contributed to its immune-stimulatory activity.

RESULTS

SFPS exhibited potent immune-stimulatory activity by macrophages. The production of ROS, NO, and tumor necrosis factor (TNF-α) were increased upon exposure to SFPS in a dose-dependent manner. All of these activities were completely blocked by co-treatment with CLI-095, but only partially diminished by polymyxin B.

CONCLUSION

We demonstrate for the first time potent immune-stimulatory activity in a decoction prepared from S. frutescens. We believe that this immune stimulatory activity is due, in part, to the action of polysaccharides present in the decoction that acts by way of TLR4 receptors and the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) signaling pathway. These findings provide a plausible mechanism through which we can understand some of the medicinal properties of S. frutescens.

PiggyBac mediated multiplex gene transfer in mouse embryonic stem cell

PiggyBac system has been shown to have a high efficiency to mediate gene transfer. However, there are no reports on its efficiency to mediate multiplex transgenes in mouse embryonic stem cells. Here we first established an immortalized feeder cell line by introducing four antibiotic resistance genes simultaneously into the original SNL 76/7 feeder cell line utilizing the PiggyBac system. This is the feeder cell line with the most diverse types of antibiotic resistance genes reported so far, which will enable researchers to perform simultaneous multiplex gene transfer or gene targeting experiments in ES cells. With such feeder cell line, we were able to quantitatively characterize the transposition efficiency of PiggyBac system in mouse ES cells using five transposons carrying different inducible fluorescence proteins and antibiotic resistance genes, and the efficiency ranged from about 2% for one transposon to 0.5% for five transposons. The highly efficient multiplex gene transfer mediated by PiggyBac will no doubt provide researchers with more choices in biomedical research and development.

Live visualization and quantification of pathway signaling with dual fluorescent and bioluminescent reporters

Despite their fundamental importance, the dynamics of signaling pathways in living cells remain challenging to study, due to a lack of non-invasive tools for temporal assessment of signal transduction in desired cell models. Here we report a dual-reporter strategy that enables researchers to monitor signal transduction in mammalian cells in real-time, both temporally and quantitatively. This is achieved by co-expressing green fluorescent protein and firefly luciferase in response to signaling stimuli. To display the versatility of this approach, we constructed and assessed eight unique signaling pathway reporters. We further validated the system by establishing stable NF-κB pathway reporter cell lines. Using these stable cell lines, we monitored the activity of NF-κB-mediated inflammatory pathway in real-time, both visually and quantitatively. Live visualization has the power to reveal individual cell responses and is compatible with single cell analysis, In addition, we provide evidence that this system is readily amenable to a high-throughput format. Together, our findings demonstrate the potential of the dual reporter system, which significantly improves the capacity to study signal transduction pathways in mammalian cells.