Search

Endogenous biomarkers remain at the forefront of early disease detection efforts, but many lack the sensitivities and specificities necessary to influence disease management. Here, we describe a cell-based in vivo sensor for highly sensitive early cancer detection. We engineer macrophages to produce a synthetic reporter on adopting an M2 tumor-associated metabolic profile by coupling luciferase expression to activation of the arginase-1 promoter. After adoptive transfer in colorectal and breast mouse tumor models, the engineered macrophages migrated to the tumors and activated arginase-1 so that they could be detected by bioluminescence imaging and luciferase measured in the blood. The macrophage sensor detected tumors as small as 25-50 mm 3 by blood luciferase measurements, even in the presence of concomitant inflammation, and was more sensitive than clinically used protein and nucleic acid cancer biomarkers. Macrophage sensors also effectively tracked the immunological response in muscle and lung models of inflammation, suggesting the potential utility of this approach in disease states other than cancer.

In vivo bioluminescence imaging (BLI) has become a standard, non-invasive imaging modality for following gene expression or the fate of proteins and cells in living animals. Currently, bioluminescent reporters used in laboratories are mostly derivatives of two major luciferase families: ATP-dependent insect luciferases and ATP-independent marine luciferases. Inconsistent results of experiments using different bioluminescent reporters, such as Akaluc and Antareas2, have been reported. Herein, we re-examined the inconsistency in several experimental settings and identified the factors, such as ATP dependency, stability in serum, and molecular sizes of luciferases, that contributed to the observed differences. We expect this study will make the research community aware of these factors and facilitate more accurate interpretation of BLI data by considering the nature of each bioluminescent reporter.

We developed a tissue suction-mediated transfection method (suction method) as a relatively reliable and less invasive technique for in vivo transfection. In this study, we determined hepatic transgene expression characteristics in the mouse liver, using a suction device, collecting information relevant to gene therapy and gene functional analysis by the liver suction method. To achieve high transgene expression levels, we developed a suction device with four holes (multiple hole device) and applied it to the larger portion of the left lateral lobe of the mouse liver. Hepatic transfection with physical stimuli was potentially controlled by activator protein-1 (AP-1) and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB). We examined the spatial distribution of transgene expression in the suctioned lobe by 2-dimensional imaging with histochemical staining and 3-dimensional multicolor deep imaging with tissue clearing methods. Through monitoring spatial distribution of transgene expression, the liver suction method was used to efficiently transfect extravascular hepatocytes in the suction-deformable upper lobe of the liver. Moreover, long-term transgene expression, at least 14 d, was achieved with the liver suction method when cytosine-phosphate-guanine (CpG)-free plasmid DNA was applied.

Systemic mastocytosis are rare neoplasms characterized by accumulation of mast cells in at least one internal organ. The majority of systemic mastocytosis patients carry KIT D816V mutation, which activates constitutively the KIT receptor. Patient with advanced forms of systemic mastocytosis, such as aggressive systemic mastocytosis or mast cell leukemia, are poorly treated to date. Unfortunately, the lack of in vivo models reflecting KIT D816V+ advanced disease hampers pathophysiological studies and preclinical development of new therapies for such patients. Here, we describe a new in vivo model of KIT D816V+ advanced systemic mastocytosis developed by transplantation of the human ROSAKIT D816V-Gluc mast cell line in NOD-SCID IL-2R γ-/- mice, using Gaussia princeps luciferase as a reporter. Intravenous injection of ROSAKIT D816V-Gluc cells led, in 4 weeks, to engraftment in all injected primary recipient mice. Engrafted cells were found at high levels in bone marrow, and at lower levels in spleen, liver and peripheral blood. Disease progression was easily monitored by repeated quantification of Gaussia princeps luciferase activity in peripheral blood. This quantification evidenced a linear relationship between the number of cells injected and the neoplastic mast cell burden in mice. Interestingly, the secondary transplantation of ROSAKIT D816V-Gluc cells increased their engraftment capability. To conclude, this new in vivo model mimics at the best the features of human KIT D816V+ advanced systemic mastocytosis. In addition, it is a unique and convenient tool to study the kinetics of the disease and the potential in vivo activity of new drugs targeting neoplastic mast cells.

We previously showed that high and sustained transgene expression of antigenic proteins induced transgene-specific immune responses. In the present study, a detailed relationship between the level of transgene expression per cell and immune response after hydrodynamic gene transfer was investigated. Cypridina luciferase (cLuc), a secretory antigenic reporter protein, was selected as a model antigen, and pROSA-cLuc, a plasmid expressing cLuc, was constructed. A fixed dose (30 μg) of pROSA-cLuc was delivered to mice by a single hydrodynamic injection or three injections at 24-h intervals because the number of cells transfected with plasmids is dependent on the number of hydrodynamic injections. Serum cLuc activity, an indicator of the total amount of cLuc transgene expression, was almost equal between these two groups. In contrast, the high-dose single injection induced higher levels of cLuc-specific humoral and cellular immune responses than the three low-dose injections. Moreover, the serum cLuc activity of the high-dose single injection group began to decline ~10 days after injection, whereas the activity remained constant in the three low-dose injection group. These results indicate that it is preferable to reduce the level of transgene expression per cell to avoid induction of the transgene-specific immune response after hydrodynamic gene transfer.

Background & Aims: Liver inflammatory diseases associated with cancer promoting somatic oncogene mutations are increasing in frequency. Preclinical cancer models that allow for the study of early tumor progression are often protracted, which limits the experimental study parameters due to time and expense. Here we report a robust inexpensive approach using Sleeping Beauty transposition (SBT) delivery of oncogenes along with Gaussia Luciferase expression vector GLuc, to assess de novo liver tumor progression, as well as the detection of innate immune responses or responses induced by therapeutic intervention., Methods: Tracking de novo liver tumor progression with GLuc was demonstrated in models of hepatocellular carcinoma (HCC) or adenoma (HCA) initiated by hydrodynamic delivery of SBT oncogenes., Results: Rising serum luciferase levels correlated directly with increasing liver tumor burden and eventual morbidity. Early detection of hepatocyte apoptosis from mice with MET+CAT transfected hepatocytes was associated with a transient delay in HCC growth mediated by a CD8(+) T-cell response against transformed hepatocytes. Furthermore, mice that lack B cells or macrophages had an increase in TUNEL(+) hepatocytes following liver MET transfection demonstrating that these cells provide protection from MET-induced hepatocyte apoptosis. Treatment with IL-18+IL-12 of mice displaying established HCC decreased tumor burden which was associated with decreased levels of serum luciferase., Conclusions: Hydrodynamic delivery of the SBT vector GLuc to hepatocytes serves as a simple blood-based approach for real-time tracking of pathologically distinct types of liver cancer. This revealed tumor-induced immunologic responses and was beneficial in monitoring the efficacy of therapeutic interventions., (Published by Elsevier B.V.)

Measurement of bacterial burden in animal infection models is a key component for both bacterial pathogenesis studies and therapeutic agent research. The traditional quantification means for in vivo bacterial burden requires frequent animal sacrifice and enumerating colony forming units (CFU) recovered from infection loci. To address these issues, researchers have developed a variety of luciferase-expressing bacterial reporter strains to enable bacterial detection in living animals. To date, all such luciferase-based bacterial reporters are in cell-associated form. Production of luciferase-secreting recombinant bacteria could provide the advantage of reporting CFU from both infection loci themselves and remote sampling (eg. body fluid and plasma). Toward this end, we have genetically manipulated a pathogenic Escherichia coli (E. coli) strain, ATCC25922, to secrete the marine copepod Gaussia princeps luciferase (Gluc), and assessed the use of Gluc as both an in situ and ex situ reporter for bacterial burden in mouse tissue cage infections. The E. coli expressing Gluc demonstrates in vivo imaging of bacteria in a tissue cage model of infection. Furthermore, secreted Gluc activity and bacterial CFUs recovered from tissue cage fluid (TCF) are correlated along 18 days of infection. Importantly, secreted Gluc can also be detected in plasma samples and serve as an ex situ indicator for the established tissue cage infection, once high bacterial burdens are achieved. We have demonstrated that Gluc from marine eukaryotes can be stably expressed and secreted by pathogenic E. coli in vivo to enable a facile tool for longitudinal evaluation of persistent bacterial infection.

Background: Induction of the immune response to transgene products is a serious concern in gene therapy, and is generally known to be influenced by the transgene expression profile, as well as the types of cells that express the transgene. However, the exact nature of the association between the transgene expression profile and immune induction following gene transfer is unclear., Methods: In the present study, plasmids, pCpG-fLuc or pCMV-fLuc, used for driving long- or short-term expression of firefly luciferase, respectively, were injected into mice by hydrodynamic injections along with a reporter plasmid expressing Gaussia luciferase (pROSA-gLuc) to evaluate the transgene expression profile in the liver. Single pROSA-gLuc administration resulted in stable gLuc activity in serum for more than 1 year; thus, gLuc activity was used for monitoring immune responses to the liver cells expressing both gLuc and fLuc after co-injection., Results: A significant reduction in gLuc activity was observed 2 weeks after co-injection of pROSA-gLuc with pCpG-fLuc, whereas stable gLuc activity was observed when pROSA-gLuc was co-injected with pCMV-fLuc. A high level of fLuc-specific immunoglobulin G was detectable in pCpG-fLuc-injected mice; furthermore, histological analysis of the liver sections of these mice indicated CD8(+) cell infiltration, implying that the transgene-expressing hepatocytes were removed by the infiltrating cells., Conclusions: Our results demonstrate that sustained transgene expression in hepatocytes triggers antigen-specific immune responses, although short-term expression of the same transgene product elicits little, if any, immune response., (Copyright © 2014 John Wiley & Sons, Ltd.)

Only a few techniques are currently available for quantifying systemic metastases in preclinical models. Cancer cell expression of naturally secreted Gaussia luciferase (Gluc) provides a useful circulating biomarker that enables the monitoring of metastatic tumor burden and of treatment response from minimal drops of blood. This blood-based Gluc assay exhibits several distinct advantages: (1) It is highly sensitive in quantifying metastatic tumor growth, particularly when compared to whole-body bioluminescence imaging (BLI) alone; (2) It is quantitative by nature and reflects viable tumor burden in a minimally invasive manner; (3) Through longitudinal collection of blood samples, treatment response can be monitored in real-time; and (4) Gluc bioluminescence provides a means to localize and assess metastatic colonization using BLI. By elucidating the progression of systemic metastases and therapeutic response in animal models, the blood-based Gluc assay is emerging as a valuable quantitative tool for novel drug development.

Reporters secreted into the conditioned medium of cells in culture or into blood in vivo have shown to be useful tools for simple and noninvasive monitoring of biological processes in real-time. Here, we characterize the naturally secreted Vargula luciferase as a secreted blood reporter and show that this reporter can be multiplexed with the secreted Gaussia luciferase and alkaline phosphatase for simultaneous monitoring of three different cellular processes in the same biological system. We applied this system to monitor the response of three different subsets of glioma cells to a clinically relevant chemotherapeutic agent in the same well in culture or animal in vivo. This system could be extended to any field to detect multiple processes in the same biological system and is amenable for high-throughput screening to find drugs that affect multiple cellular populations/phenomena simultaneously.

Background: Better understanding of the molecular mechanisms of remodeling has become a major objective of heart failure (HF) research to stop or reverse its progression. Left ventricular assist devices (LVADs) are being used in patients with HF, leading to partial reverse remodeling. In the present study, proteomics identified significant changes in α-1-antichymotrypsin (ACT) levels during LVAD support. Moreover, the potential role of ACT in reverse remodeling was studied in detail., Methods and Results: Expression of ACT mRNA (quantitative-polymerase chain reaction) decreased significantly in post-LVAD myocardial tissue compared with pre-LVAD tissue (n=15; P<0.01). Immunohistochemistry revealed that ACT expression and localization changed during LVAD support. Circulating ACT levels were elevated in HF patients (n=18) as compared with healthy controls (n=6; P=0.001) and normalized by 6 months of LVAD support. Because increasing evidence implicates that microRNAs (miRs) are involved in myocardial disease processes, we also investigated whether ACT is post-transcriptionally regulated by miRs. Bioinformatics analysis pointed miR-137 as a potential regulator of ACT. The miR-137 expression is inversely correlated with ACT mRNA in myocardial tissue. Luciferase activity assays confirmed ACT as a direct target for miR-137, and in situ hybridization indicated that ACT and miR-137 were mainly localized in cardiomyocytes and stromal cells., Conclusions: High ACT plasma levels in HF normalized during LVAD support, which coincides with decreased ACT mRNA in heart tissue, whereas miR-137 levels increased. MiR-137 directly targeted ACT, thereby indicating that ACT and miR-137 play a role in the pathophysiology of HF and reverse remodeling during mechanical support.

To establish an orthotopic transplant mouse model of hepatocellular carcinoma (HCC) labeled with secretary luciferase and to study its response to anti-tumor treatment with interferon-beta gene therapy. We labeled the murine hepatoma Hepal-6 cells with secretary Gaussia princeps luciferase (Gluc), and then injected Gluc labeled Hepal-6 cells intrasplenically in C57BL/6 mice. We monitored blood Glue to evaluate the tumor development and anti-tumor effects of hydrodynamic injection with interferon-beta expressing plasmid. We successfully established the orthotopic mouse model of HCC by intrasplenic injection of Glue labeled Hepal-6 cells. The Glue blood assay could reflect the amount of cancer cells in vivo, tumor progression, as well as anti-tumor effect of interferon-beta gene therapy. In conclusion, Gluc labeled orthotopic transplant mouse model of HCC can ex vivo real-time monitor the tumor development and tumor response to treatments.

Secreted Gaussia luciferase (Gluc) has been shown to be a useful tool for ex vivo monitoring of in vivo biological processes. The Gluc level in the blood was used to detect tumor growth, metastasis and response to therapy, gene transfer, and circulating cells viability, as well as transcription factors activation, complementing in vivo bioluminescence imaging. The sensitivity of the Gluc blood assay is limited due to the absorption of blue light by pigmented molecules such as hemoglobin, resulting in quenching of the signal and therefore lower sensitivity. To overcome this problem, we designed an alternative microtiter well-based binding assay in which Gluc is captured first from blood using a specific antibody followed by the addition of coelenterazine and signal acquisition using a luminometer. This assay showed to be over 1 order of magnitude more sensitive in detecting Gluc in the blood as compared to the direct Gluc blood assay enhancing ex vivo monitoring of biological processes.

PhiC31 integrase has the potential to achieve long-term transgene expression because of site-specific and unidirectional recombination. In this study, plasmid DNA (pDNA) encoding Gaussia luciferase (Gluc) cDNA was constructed and the optimal condition for long-term gene expression using phiC31 integrase in mouse liver after hydrodynamic injection was investigated. Gluc is secreted and thus allows quantification of its expression level in blood and easy determination of the expression time-course. Mice were co-transfected with 25 µg donor pDNA (pORF-Gluc/attB) and different amounts of helper pDNA (pCMV-int; from 1 to 50 µg). Serum Gluc expression was evaluated during 120 d. The most highly sustained gene expression was obtained when 10 µg of helper pDNA was co-transfected in ICR and C57BL/6 mice. However, the Gluc expression in C57BL/6 mice was slightly lower and less durable than that in ICR mice. Little hepatic damage caused by phiC31 integrase was observed during 120 d in ICR and C57BL/6 mice.

The cationic lipid GL67A is one of the more efficient non-viral gene transfer agents (GTAs) for the lungs, and is currently being evaluated in an extensive clinical trial programme for cystic fibrosis gene therapy. Despite conferring significant expression of vector-specific mRNA following transfection of differentiated human airway cells cultured on air liquid interfaces (ALI) cultures and nebulisation into sheep lung in vivo we were unable to detect robust levels of the standard reporter gene Firefly luciferase (FLuc). Recently a novel secreted luciferase isolated from Gaussia princeps (GLuc) has been described. Here, we show that (1) GLuc is a more sensitive reporter gene and offers significant advantages over the traditionally used FLuc in pre-clinical models for lung gene transfer that are difficult to transfect, (2) GL67A-mediated gene transfection leads to significant production of recombinant protein in these models, (3) promoter activity in ALI cultures mimics published in vivo data and these cultures may, therefore, be suitable to characterise promoter activity in a human ex vivo airway model and (4) detection of GLuc in large animal broncho-alveolar lavage fluid and serum facilitates assessment of duration of gene expression after gene transfer to the lungs. In summary, we have shown here that GLuc is a sensitive reporter gene and is particularly useful for monitoring gene transfer in difficult to transfect models of the airway and lung. This has allowed us to validate that GL67A, which is currently in clinical use, can generate significant amounts of recombinant protein in fully differentiated human air liquid interface cultures and the ovine lung in vivo., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

Purpose: We previously showed that E2F1 overexpression radiosensitizes prostate cancer cells in vitro. Here, we demonstrate the radiosensitization efficacy of adenovirus (Ad)-E2F1 infection in growing (orthotopic) LNCaP and (subcutaneous) PC3 nude mice xenograft tumors., Methods and Materials: Ad-E2F1 was injected intratumorally in LNCaP (3 × 10(8) plaque-forming units [PFU]) and PC3 (5 × 10(8) PFU) tumors treated with or without radiation. LNCaP tumor volumes (TV) were measured by magnetic resonance imaging, caliper were used to measure PC3 tumors, and serum prostate-specific antigen (PSA) levels were determined by enzyme-linked immunosorbent assay. Apoptosis was measured by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling, and key proteins involved in cell death signaling were analyzed by Western blotting., Results: Intracellular overexpression of Ad-E2F1 had a significant effect on the regression of TV and reduction of PSA levels relative to that of adenoviral luciferase (Ad-Luc)-infected control. The in vivo regressing effect of Ad-E2F1 on LNCaP tumor growth was significant (PSA, 34 ng/ml; TV, 142 mm(3)) compared to that of Ad-Luc control (PSA, 59 ng/ml; TV, 218 mm(3); p <0.05). This effect was significantly enhanced by radiation therapy (compare: Ad-E2F1+RT/PSA, 16 ng/ml, and TV, 55 mm(3) to Ad-Luc+RT/PSA, 42 ng/ml, and TV, 174 mm(3), respectively; p <0.05). For PC3 tumors, the greatest effect was observed with Ad-E2F1 infection alone; there was little or no effect when radiotherapy (RT) was combined. However, addition of RT enhanced the level of in situ apoptosis in PC3 tumors. Molecularly, addition of Ad-E2F1 in a combination treatment abrogated radiation-induced BCL-2 protein expression and was associated with an increase in activated BAX, and together they caused a potent radiosensitizing effect, irrespective of p53 and androgen receptor functional status., Conclusions: We show here for the first time that ectopic overexpression of E2F1 in vivo, using an adenoviral vector, significantly inhibits orthotopic p53 wild-type LNCaP tumors and subcutaneous p53-null PC3 tumors in nude mice. Furthermore, we demonstrate that E2F1 strongly sensitizes LNCaP tumors to RT. These findings suggest that E2F1 overexpression can sensitize prostate tumor cells in vivo, independent of p53 or androgen receptor status., (Copyright © 2011 Elsevier Inc. All rights reserved.)

Background: Currently, only few techniques are available for quantifying systemic metastases in preclinical model. Thus techniques that can sensitively detect metastatic colonization and assess treatment response in real-time are urgently needed. To this end, we engineered tumor cells to express a naturally secreted Gaussia luciferase (Gluc), and investigated its use as a circulating biomarker for monitoring viable metastatic or primary tumor growth and their treatment responses., Methodology/principal Findings: We first developed orthotopic primary and metastatic breast tumors with derivative of MDA-MB-231 cells expressing Gluc. We then correlated tumor burden with Gluc activity in the blood and urine along with bioluminescent imaging (BLI). Second, we utilized blood Gluc assay to monitor treatment response to lapatinib in an experimental model of systemic metastasis. We observed good correlation between the primary tumor volume and Gluc concentration in blood (R(2) = 0.84) and urine (R(2) = 0.55) in the breast tumor model. The correlation deviated as a primary tumor grew due to a reduction in viable tumor fraction. This was also supported by our mathematical models for tumor growth to compare the total and viable tumor burden in our model. In the experimental metastasis model, we found numerous brain metastases as well as systemic metastases including bone and lungs. Importantly, blood Gluc assay revealed early growth of metastatic tumors before BLI could visualize their presence. Using secreted Gluc, we localized systemic metastases by BLI and quantitatively monitored the total viable metastatic tumor burden by blood Gluc assay during the course of treatment with lapatinib, a dual tyrosine kinase inhibitor of EGFR and HER2., Conclusion/significance: We demonstrated secreted Gluc assay accurately reflects the amount of viable cancer cells in primary and metastatic tumors. Blood Gluc activity not only tracks metastatic tumor progression but also serves as a longitudinal biomarker for tumor response to treatments.

Chemokine-receptor signaling plays an important role in the inflammatory response often associated with tumor growth and metastasis. The NF-kappaB pathway, essential for transcription of chemokines/chemokine receptors and other key inflammatory modulators, has emerged as a potential target for tumor therapy. Here we describe an efficient approach to monitor drugs that target the NF-kappaB signaling as related to tumor growth and metastasis in vivo. For bioluminescence imaging, the firefly luciferase (Fluc) reporter has the advantage of stable signaling, while Gaussia luciferase (Gluc) provides very sensitive signaling based on secretion of Gluc. We introduce the use of monitoring intratumoral Gluc, which rapidly diffuses into the blood circulation and urine. The peripheral Gluc assay may complement bioluminescence imaging and provide a kinetic, noninvasive, real-time read-out of NF-kappaB activity by directly determining Gluc reporter activity in blood or urine samples from tumor-bearing mice.

We report two improved assays for in vitro and in vivo screening of chemicals with potential anti-malarial activity against the blood stages of the rodent malaria parasite Plasmodiumberghei. These assays are based on the determination of luciferase activity (luminescence) in small blood samples containing transgenic blood stage parasites that express luciferase under the control of a promoter that is either schizont-specific (ama-1) or constitutive (eef1alphaa). Assay 1, the in vitro drug luminescence (ITDL) assay, measured the success of schizont maturation in the presence of candidate drugs quantifying luciferase activity in mature schizonts only (ama-1 promoter). The ITDL assay generated drug-inhibition curves and EC(50) values comparable to those obtained with standard in vitro drug-susceptibility assays. The second assay, the in vivo drug-luminescence (IVDL) assay, measured parasite growth in vivo in a standard 4-day suppressive drug test, monitored by measuring the constitutive luciferase activity of circulating parasites (eef1alphaa promoter). The IVDL assay generates growth-curves that are identical to those obtained by manual counting of parasites in Giemsa-stained smears. The reading of luminescence assays is rapid, requires a minimal number of handling steps and no experience with parasite morphology or handling fluorescence-activated cell sorters, produces no radioactive waste and test-plates can be stored for prolonged periods before processing. Both tests are suitable for use in larger-scale in vitro and in vivo screening of drugs. The standard methodology of anti-malarial drug screening and validation, which includes testing in rodent models of malaria, can be improved by the incorporation of such assays.

In this study, we developed a simple and sensitive assay in mice for a challenge experiment by using a recombinant vaccinia virus dual-expressing antigen (HIV Env gp160) and firefly luciferase. This assay can detect the vaccine effect at real-time in vivo by using a small amount of mouse serum. The luciferase activity in mouse serum was in agreement with the viral titer in the ovary. This assay would be applicable as a challenge model for infectious diseases.

Secreted alkaline phosphatase (SEAP) and Metridia luciferase (MLuc) are useful reporter molecules in vitro, but little is understood about their usefulness in vivo. In this study, we investigated in vivo activity of recombinant SEAP and MLuc in blood and urine. When SEAP-transfected cells or recombinant SEAP were injected into rats, substantial increase in the level of serum SEAP was observed. In contrast, activity of SEAP was not detected in urine of rats injected with either the SEAP-transfected cells or recombinant SEAP. SEAP activity was also undetectable in urine of SEAP-injected Nagase analbuminemic rats in which glomerular permeability to macromolecules is enhanced. When MLuc-transfected cells were implanted into rats, activity of MLuc was undetectable not only in urine but also in serum. Even immediately after intravenous injection of recombinant MLuc, activity of MLuc was not detected in serum. Subsequent experiments revealed that, in contrast to SEAP, MLuc was rapidly inactivated either by rat serum, fetal bovine serum, or human serum. Albumin was identified as the molecule responsible for the inhibition of MLuc activity. These data elucidated advantages and limitations of secreted reporter molecules SEAP and MLuc under in vivo situations.

The goal of this study was to identify the most important variables affecting bioluminescent ATP, ADP and AMP measurements in plasma and to develop an assay that takes these variables into account. Blood samples were drawn from conscious dogs. A 'stop solution' containing EDTA was prepared, which greatly retarded plasma ATP degradation by chelating Mg(+2) and Ca(+2) that are co-factors for many ATPases. Stop solution and blood were mixed using a two-syringe withdrawal system. Samples were centrifuged twice in order to remove red blood cells, and ATP was measured in the supernatant using the firefly luciferase assay. Sample pH was adjusted to the optimal range (7.75-7.95) and Mg(2+) (necessary for the luciferase reaction) was added back to the sample within the luminometer 2 s prior to luciferase addition. Four assay tubes were prepared for each plasma sample, containing standard additions of 0-15 pmol added ATP, in order to quantify native plasma ATP content. In separate plasma/stop solution samples ADP + ATP was measured after converting ADP to ATP via the pyruvate kinase reaction, and AMP + ADP + ATP was measured after addition of both myokinase and pyruvate kinase. Addition of forskolin and isobutylmethylxanthine (IBMX) to the stop solution to inhibit platelets resulted in lower ATP concentrations. Measurement of ATP and haemoglobin from lysed erythrocytes revealed that haemolysis exerts a strong influence on plasma ATP concentration that must be taken into account., (Copyright 2003 John Wiley & Sons, Ltd.)

Objective: To validate a luciferase bioassay, which is based on a recombinant mouse hepatoma cell line, for the detection of exposure to petroleum in mustelid species., Animals: 122 American mink (Mustela vison) and 15 sea otters (Enhydra lutris)., Procedures: Mink were exposed to Bunker C fuel oil or Alaska North Slope crude oil externally as a single exposure or internally via low dose concentrations in their ration for 6 months. Serum samples were analyzed for cytochrome P450 1A1 induction by quantification of luciferase activity in the bioassay. Mink liver specimens were also evaluated for cytochrome P450 1A1 induction by quantification of ethoxyresorufin-o-deethylase activity. Serum collected from exposed and unexposed sea otters was also analyzed using the luciferase bioassay., Results: Serum samples from mink externally exposed to petroleum had significantly increased luciferase activities at 1 week after exposure. Serum samples taken at later time points or from mink exposed to either product in the ration did not cause significant luciferase induction. Samples from otters exposed to petroleum had significantly higher luciferase induction as compared with samples from otters not exposed to petroleum at 2 and 8 years after the spill. Cytochrome P450 1A1 activity in liver specimens collected from mink that were internally exposed through diet was significantly increased at the conclusion of our study., Conclusion and Clinical Relevance: The luciferase bioassay is a sensitive and specific method for determining recent exposure to petroleum in mink. The lack of luciferase activity in serum samples collected from mink greater than 1 week after experimental exposure was likely attributable to lower overall petroleum exposure in our trial, compared with natural exposures.

Firefly luciferase and Escherichia coli beta-galactosidase chemiluminescent reporter gene assays are rapid and sensitive means of detecting reporter enzyme activities in cell lysates of both eukaryotic and prokaryotic systems. In these assays, expression vectors containing the luciferase or beta-galactosidase genes are transferred to cells in culture or animal tissues in vivo. Crude cell or organ lysates are then prepared and submitted to enzyme assays. The level of enzyme activity is proportional to the efficiency of gene delivery and expression. When used with modified substrates that emit light when cleaved by the appropriate enzyme, luciferase and beta-galactosidase activity can be detected luminometrically. Attempts to apply these assays to cell lysates contaminated with blood, as from any whole organ lysate, have had questionable results thus far because of light absorption by hemoglobin in the ranges of light emission by both of these assays. We have made several adjustments to standard chemiluminescent reporter gene assay protocols to minimize errors in quantitation contributed by hemoglobin. To this end, we have developed a method for quantitating the protein due to blood and due to the organ itself in a blood-contaminated organ lysate. We have also found that the use of a colorimetric protein assay that is unaffected by hemoglobin absorbance is preferred for protein quantitation. In conclusion, luciferase and beta-galactosidase assays can be applied to blood-contaminated organ lysates; however, the luciferase assay proved to be superior due to minimal endogenous activity and lower absorption by hemoglobin of light emitted by the enzyme product., (Copyright 2000 Academic Press.)

Human serum paraoxonase (PON1) is an esterase that has been shown to decrease the susceptibility of lipoproteins to lipid peroxidation. We found a polymorphism of cytosine/thymidine (-108C/T, the number is from the ATG codon) in the upstream region of the PON1 gene. The luciferase activity was lower in the -108T allele than in the -108C allele. The serum PON1 concentrations in 132 normal subjects were as follows: -108CC>-108CT and>-108TT genotypes. The polymorphism upstream from the PON1 gene is associated with transcription of the PON1 gene and the serum PON1 concentration.

The expression of naked plasmid DNA coding for firefly luciferase (pRSVluc) or a secreted protein, human-alpha-1-antitrypsin (pRcCMVhAAT) in mouse skeletal muscle was characterized following administration by an improved intramuscular injection technique. Injection guided by intense illumination along the longitudinal axis of the mouse quadriceps muscle and parallel to the myofibers yielded 200-fold higher levels of luciferase expression than perpendicular injection. Luciferase expression was inhibited by an excess of non-coding DNA or dextran sulfate suggesting that muscle DNA uptake mechanism(s) can be saturated. Injected plasmid DNA was rapidly eliminated from the muscle as evidenced by tissue distribution studies of radiolabeled hAAT plasmid and Southern analysis. However, PCR analysis demonstrated that hAAT cDNA persisted in the muscle for at least 1 month after injection. Immunohistochemistry techniques indicated that the hAAT gene was expressed by the muscle fibers. ELISA analysis of serum samples collected from intramuscularly injected mice demonstrated that secreted hAAT protein concentration peaked in serum by day 7, started to decline by day 14 and was barely detectable 21 days post-injection. RT-PCR analysis demonstrated that hAAT transcript persisted at the site of injection for at least 1 month indicating that the decline of serum hAAT concentration 21 days post-injection was not due to the absence of hAAT transcript. However, the decline of hAAT protein concentration in the serum was inversely correlated with accumulation of murine anti-hAAT antibodies in circulation.

The firefly luciferase assay of adenosine-5'-triphosphate (ATP) is used in a simple procedure for the determination of adenine nucleotides in whole blood and red blood cells. Cells are lysed with cold trichloroacetic acid and nucleotides are determined in the lysate after dilution with buffer. In a comparative study with the spectrophotometric assay of ATP, extracts were prepared by centrifugation of the lysate to remove interfering turbidity. This step resulted in a significant loss of ATP in the clear supernatant. This loss could be avoided by determination of ATP by the firefly luciferase assay in diluted uncentrifuged lysates. The yields of ATP, ATP + ADP and ATP + ADP + AMP were compared in a red blood cell preparation after lysis with trichloroacetic acid and another lytic method based on the detergent triton X-100. The precision was better with acid whereas yields were essentially the same with both methods. The method of standardization, external or internal, was of little practical importance regarding yields and precision, but internal calibration is recommended to ensure that there is no interaction of the luciferase reaction with lytic reagent or sample.

Properties of a coupled system "LDH-bacterial luciferase" were studied. The light-generating enzymatic system from luminescent bacteria Photobacterium fisheri was used as an indicator of the dehydrogenase activity. Kinetic parameters of the coupled system were studied using commercially available preparation of LDH and the enzyme from human blood plasma. The luminescent activity of bacterial preparation was shown to correlate with the activity of LDH and its isoenzymes within wide range of blood plasma concentrations.