A branched DNA signal amplification assay to quantitate messenger RNA of human uncoupling proteins 1, 2, and 3

Challenges and opportunities in bioanalytical support for gene therapy medicinal product development

Gene and nucleic acid therapies have demonstrated patient benefits to address unmet medical needs. Beside considerations regarding the biological nature of the gene therapy, the quality of bioanalytical methods plays an important role in ensuring the success of these novel therapies. Inconsistent approaches among bioanalytical labs during preclinical and clinical phases have been observed. There are many underlying reasons for this inconsistency. Various platforms and reagents used in quantitative methods, lacking of detailed regulatory guidance on method validation and uncertainty of immunogenicity strategy in supporting gene therapy may all be influential. This review summarizes recent practices and considerations in bioanalytical support of pharmacokinetics/pharmacodynamics and immunogenicity evaluations in gene therapy development with insight into method design, development and validations.

Soluble thrombomodulin reduces inflammation and prevents microalbuminuria induced by chronic endothelial activation in transgenic mice

Chronic kidney disease pathogenesis involves both tubular and vascular injuries. Despite abundant investigations to identify the risk factors, the involvement of chronic endothelial dysfunction in developing nephropathies is insufficiently explored. Previously, soluble thrombomodulin (sTM), a cofactor in the activation of protein C, has been shown to protect endothelial function in models of acute kidney injury. In this study, the role for sTM in treating chronic kidney disease was explored by employing a mouse model of chronic vascular activation using endothelial-specific TNF-α-expressing (tie2-TNF) mice. Analysis of kidneys from these mice after 3 mo showed no apparent phenotype, whereas 6-mo-old mice demonstrated infiltration of CD45-positive leukocytes accompanied by upregulated gene expression of inflammatory chemokines, markers of kidney injury, and albuminuria. Intervention with murine sTM with biweekly subcutaneous injections during this window of disease development between months 3 and 6 prevented the development of kidney pathology. To better understand the mechanisms of these findings, we determined whether sTM could also prevent chronic endothelial cell activation in vitro. Indeed, treatment with sTM normalized increased chemokines, adhesion molecule expression, and reduced transmigration of monocytes in continuously activated TNF-expressing endothelial cells. Our results suggest that vascular inflammation associated with vulnerable endothelium can contribute to loss in renal function as suggested by the tie2-TNF mice, a unique model for studying the role of vascular activation and inflammation in chronic kidney disease. Furthermore, the ability to restore the endothelial balance by exogenous administration of sTM via downregulation of specific adhesion molecules and chemokines suggests a potential for therapeutic intervention in kidney disease associated with chronic inflammation.

The Role of Trace Metals in Cytochrome P4501 Regulation

Trace metals and polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental co-contaminants and the trace metals could influence the carcinogenicity of the PAHs by altering their extent of induction of cytochromes P4501A1, 1A2, and 1B1 (CYP). Studies in cell lines from humans, rodents, chickens, and fish, and in cell culture generally indicate that trace metals diminish the inductive potency of PAHs for these CYPs. The extent of the effect is species-, metal-, PAH-, and metal dose-dependent. Both transcriptional and post-translational mechanisms are involved in the trace metal-mediated down regulation of the CYP1 forms. The latter mechanism incorporates induction of heme oxygenase-1 by the metals, with resultant heme catabolism. Thus, trace metals could diminish the carcinogenicity of PAHs.

Effect of bupropion on CYP2B6 and CYP3A4 catalytic activity, immunoreactive protein and mRNA levels in primary human hepatocytes: comparison with rifampicin

Animals treated with multiple doses of bupropion have had increased bupropion clearance or increased liver weight, suggesting induction of drug-metabolizing activity. The possibility of cytochrome p450 (CYP) induction by bupropion (10 microM) was evaluated in-vitro by comparing catalytic activity, immunoreactive protein and CYP mRNA levels from human hepatocytes in primary culture versus cells treated with vehicle (0.5% methanol) and with rifampicin (rifampin) as a positive control. mRNA levels were analysed using a branched DNA luminescent assay. CYP2B6 activity, protein and mRNA levels were increased by 2.5, 1.5 and 2.1 fold, respectively, by 20 microM rifampicin. However, 10 microM bupropion minimally altered CYP2B6 (1.4, 1.1, 0.8 fold). Although CYP3A4 activity, protein, and mRNA levels were increased by 4.0, 2.3, and 14.0 fold, respectively, by 20 microM rifampicin, 10 microM bupropion minimally altered CYP3A4 (1.4, 1.0, 0.8 fold). Rifampicin (20 microM) increased CYP2E1 protein by 2.1 fold, while 10 microM bupropion minimally altered CYP2E1 protein (1.2 fold). Overall, results of this study suggest that multiple doses of bupropion are not likely to induce CYP2B6, 3A4 or 2E1 in-vivo in man.

Antisense and sense RNA probe hybridization to immobilized crude cellular lysates: a tool to screen growth hormone antagonists

The growth-promoting effect of growth hormone (GH) is primarily mediated by insulin-like growth factor-1 (IGF-1). The liver is the main source of circulating IGF-I. The authors have used rodent primary hepatocytes for studies on pharmacological intervention of IGF-I mRNA expression. A 96-well nonradioactive IGF-1 mRNA quantification assay was developed, based on the hybridization of sense and antisense RNA probes, to replicate membranes with crude hepatocyte lysates. The sense hybridization was used as an internal standard. The antagonistic properties of a set of GH-receptor binding compounds were evaluated. Two compounds were found to down-regulate IGF-I mRNA. Effects due to metabolic inhibition or toxicity were excluded using a cell proliferation assay. To investigate potential unspecific transcriptional effects, the mRNA levels of the housekeeping genes, beta-actin and glyceraldehyde-3-phosphate dehydrogenase (GAPDH), were determined. Two other GH-regulated genes, cytochrome P450 2C12 (CYP2C12) and a rat homologue to the human alpha1B-glycoprotein (A1BG), were quantified by RNase protection assays and found to be down-regulated, confirming the antagonistic property of 1 compound. In conclusion, a direct filter hybridization assay of hepatocyte lysates using nonradioactive sense and antisense probes can be used for quantitative mRNA measurements and could constitute a valuable tool in screening for pharmacologically active compounds.

Quantitation of CYP1A1 and 1B1 mRNA in polycyclic aromatic hydrocarbon-treated human T-47D and HepG2 cells by a modified bDNA assay using fluorescence detection

The quantitation of mRNA, essential for assessing mechanisms of enzyme regulation, is normally carried out using reverse transcriptase-polymerase chain reaction (RT-PCR). An alternative method uses a signal-amplification nucleic acid probe assay, which measures RNA directly by the QuantiGene Expression Kit and incorporates branched DNA technology from Bayer and luminometer-based readings of a chemilumigenic alkaline phosphatase substrate. To broaden the utility of this assay, we investigated substitution of a fluorescent substrate, 2'-(2-benzothiazol)-6'-hydroxybenzothiazole phosphate and a fluorometer, and applied the method to quantitation of CYP1A1 and 1B1 mRNA in human T-47D and HepG2 cells following induction by benzo[a]pyrene (B[a]P) and dibenzo[a,h]anthracene (DB[a,h]A). The fluorescence response increased linearly for 200 min without photobleaching and increased linearly (r2=0.997) up to at least 0.2 microg total RNA. The data revealed that at 0.5 and 1.0 microM inducing agent, the induction of CYP1A1 mRNA in HepG2 cells by DB[a,h]A exceeded that by B[a]P by 18- and 6-fold, respectively. In T-47D cells B[a]P induced CYP1A1 mRNA by 23-fold and CYP1B1 mRNA by 3.9-fold. A B[a]P cocontaminant in the environment, arsenite, did not affect B[a]P-induced levels of CYP1A1 or 1B1 mRNA in these cells. The modified analytical system provides a rapid-throughput, reproducible, and less labor-intensive method than RT-PCR for quantifying cellular mRNA levels.

Solid-Phase synthesis and investigation of benzofurans as selective estrogen receptor modulators

A library of benzofurans was prepared by solid-phase synthesis methods, and several analogues were identified as potent ligands for the estrogen receptors ER-alpha and ER-beta, with some compounds having selectivity for ER-alpha. Analogues designed to more closely mimic Raloxifene were less effective. Certain benzofurans were effective in a bone pit assay, but were characterized as agonists in a MCF-7 breast tumor cell proliferation assay.

Development of a novel influenza A antiviral assay

Traditional methods used to monitor influenza infection typically require 2-5 days to perform, prompting a need for more rapid and quantitative methods for monitoring viral infection in 96-well formats. Such assays would find application in high-throughput screening for novel antiviral agents. A new method, based on branched DNA (bDNA) technology, is described for the specific detection of negative strand RNA of influenza A strains using a set of oligonucleotides designed for the A/PR/8/34 nucleoprotein (NP) transcript. By detecting the genomic strand, this signal amplification assay is appropriate for monitoring the kinetics of viral replication. Assay performance was monitored following infection of MDCK cells. The assay exhibited high reproducibility, good sensitivity over a range of multiplicity of infection and has a lower limit of detection of approximately 5 x 10 (5) RNA copies. Designed to quantitate the H1N1 strain A/PR/8/34, the assay also detects other influenza A subtypes, but not the evolutionarily more distant strain B/Yamagata/16/88. Validation as an antiviral assay was demonstrated with two influenza antivirals, zanamivir and rimantadine. The EC(50) values calculated following bDNA detection for zanamivir (265 nM) and rimantadine (9.4 microg/ml) in A/PR/8/34 infection correlate closely to data previously reported from visual CPE determinations, neutral red dye uptake and plaque assays, respectively. The advantages over the more time-consuming traditional assays suggest that the influenza bDNA assay is applicable to rapid screening of compound collections for antiviral activity.

Induction of the progesterone receptor gene in estrogen target cells monitored by branched DNA signal amplification

Estrogens have multiple effects on the growth and development of cells in their target tissues, including the uterus, ovary, breast, bone marrow and brain. The hormone regulates the transcription of diverse genes in these tissues via the estrogen receptor, a nuclear transcription factor. Naturally occurring estrogens and estrogen analogs including selective estrogen receptor modulators (SERMs), constitute important therapies for breast cancer and osteoporosis, and are major components of oral contraceptives. The in vitro biologic activities of pharmaceutical estrogen agonists and antagonists have frequently been monitored by cotransfection assay, where exogenous estrogen receptor and reporter genes are transiently inserted into a heterologous, non receptor-containing cell line, such as those derived from kidney cells. Here we describe an alternative to this method, where induction of an endogenous estrogen-responsive gene, the progesterone receptor gene, is monitored by branched DNA signal amplification. Assays are performed with cultured cells derived from estrogen-responsive tissues; namely, breast, uterine endothelium and bone. Hormonal induction occurs via the endogenous estrogen receptor of these cells. Our data show that SERMs, which are estrogen agonists on bone in vivo, antagonize estrogen-dependent target gene induction in conditionally immortalized osteoblast-like cells.

Single-copy gene detection using branched DNA (bDNA) in situ hybridization

We have developed a branched DNA in situ hybridization (bDNA ISH) method for detection of human papillomavirus (HPV) DNA in whole cells. Using human cervical cancer cell lines with known copies of HPV DNA, we show that the bDNA ISH method is highly sensitive, detecting as few as one or two copies of HPV DNA per cell. By modifying sample pretreatment, viral mRNA or DNA sequences can be detected using the same set of oligonucleotide probes. In experiments performed on mixed populations of cells, the bDNA ISH method is highly specific and can distinguish cells with HPV-16 from cells with HPV-18 DNA. Furthermore, we demonstrate that the bDNA ISH method provides precise localization, yielding positive signals retained within the subcellular compartments in which the target nucleic acid sequences are localized. As an effective and convenient means for nucleic acid detection, the bDNA ISH method is applicable to the detection of cancers and infectious agents. (J Histochem Cytochem 49:603-611, 2001)