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Aslamkhan AG, Michna L, Podtelezhnikov A, Vlasakova K, Suemizu H, Ohnishi Y, Liu L, Lane P, Xu Q, Kuhls MC, Wang Z, Pacchione S, Erdos Z, Tracy RW, Koeplinger K, Muniappa N, Valentine J, Galijatovic-Idrizbegovic A, Glaab WE, Sistare FD, Lebron J. A mechanistic biomarker investigation of fialuridine hepatotoxicity using the chimeric TK-NOG Hu-liver mouse model and in vitro micropatterned hepatocyte cocultures. Toxicol Res (Camb) 2024; 13:tfad120. [PMID: 38223529 PMCID: PMC10784659 DOI: 10.1093/toxres/tfad120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2023] [Revised: 10/20/2023] [Accepted: 12/01/2023] [Indexed: 01/16/2024] Open
Abstract
Fialuridine (FIAU) is a nucleoside-based drug that caused liver failure and deaths in a human clinical trial that were not predicted by nonclinical safety studies. A recent report concluded that a TK-NOG humanized liver (hu-liver) mouse model detected human-specific FIAU liver toxicity, and broader use of that model could improve drug safety testing. We further evaluated this model at similar dose levels to assess FIAU sensitivity and potential mechanistic biomarkers. Although we were unable to reproduce the marked acute liver toxicity with two separate studies (including one with a "sensitized" donor), we identified molecular biomarkers reflecting the early stages of FIAU mitochondrial toxicity, which were not seen with its stereoisomer (FIRU). Dose dependent FIAU-induced changes in hu-liver mice included more pronounced reductions in mitochondrial to nuclear DNA (mtDNA/nucDNA) ratios in human hepatocytes compared to mouse hepatocytes and kidneys of the same animals. FIAU treatment also triggered a p53 transcriptional response and opposing changes in transcripts of nuclear- and mitochondrial-encoded mitochondrial proteins. The time dependent accumulation of FIAU into mtDNA is consistent with the ≥9-week latency of liver toxicity observed for FIAU in the clinic. Similar changes were observed in an in vitro micro-patterned hepatocyte coculture system. In addition, FIAU-dependent mtDNA/nucDNA ratio and transcriptional alterations, especially reductions in mitochondrially encoded transcripts, were seen in livers of non-engrafted TK-NOG and CD-1 mice dosed for a shorter period. Conclusion: These mechanistic biomarker findings can be leveraged in an in vitro model and in a more routine preclinical model (CD-1 mice) to identify nucleosides with such a FIAU-like mitochondrial toxicity mechanistic liability potential. Further optimization of the TK-NOG hu-liver mouse model is necessary before broader adoption for drug safety testing.
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Affiliation(s)
- Amy G Aslamkhan
- Nonclinical Drug Safety, Merck & Co., Inc., 770 Sumneytown Pike, West Point, PA 19486, United States
| | - Laura Michna
- Nonclinical Drug Safety, Merck & Co., Inc., 770 Sumneytown Pike, West Point, PA 19486, United States
| | - Alexei Podtelezhnikov
- Nonclinical Drug Safety, Merck & Co., Inc., 770 Sumneytown Pike, West Point, PA 19486, United States
| | - Katerina Vlasakova
- Nonclinical Drug Safety, Merck & Co., Inc., 770 Sumneytown Pike, West Point, PA 19486, United States
| | - Hiroshi Suemizu
- Laboratory Animal Research, Central Institute for Experimental Animals, 210-0821 Kawasaki-ku, Kawasaki 3-25-12 Tonomachi, Japan
| | - Yasuyuki Ohnishi
- Laboratory Animal Research, Central Institute for Experimental Animals, 210-0821 Kawasaki-ku, Kawasaki 3-25-12 Tonomachi, Japan
| | - Liping Liu
- Nonclinical Drug Safety, Merck & Co., Inc., 770 Sumneytown Pike, West Point, PA 19486, United States
| | - Pamela Lane
- Nonclinical Drug Safety, Merck & Co., Inc., 770 Sumneytown Pike, West Point, PA 19486, United States
| | - Qiuwei Xu
- Nonclinical Drug Safety, Merck & Co., Inc., 770 Sumneytown Pike, West Point, PA 19486, United States
| | - Matthew C Kuhls
- Nonclinical Drug Safety, Merck & Co., Inc., 770 Sumneytown Pike, West Point, PA 19486, United States
| | - Zhibin Wang
- Nonclinical Drug Safety, Merck & Co., Inc., 770 Sumneytown Pike, West Point, PA 19486, United States
| | - Stephen Pacchione
- Nonclinical Drug Safety, Merck & Co., Inc., 770 Sumneytown Pike, West Point, PA 19486, United States
| | - Zoltan Erdos
- Nonclinical Drug Safety, Merck & Co., Inc., 770 Sumneytown Pike, West Point, PA 19486, United States
| | - Rodger William Tracy
- Pharmacokinetics, Dynamics, Metabolism and Bioanalytics, Merck & Co., Inc., 770 Sumneytown Pike, West Point, PA, United States
| | - Kenneth Koeplinger
- Pharmacokinetics, Dynamics, Metabolism and Bioanalytics, Merck & Co., Inc., 770 Sumneytown Pike, West Point, PA, United States
| | - Nagaraja Muniappa
- Nonclinical Drug Safety, Merck & Co., Inc., 770 Sumneytown Pike, West Point, PA 19486, United States
| | - John Valentine
- Pharmacokinetics, Dynamics, Metabolism and Bioanalytics, Merck & Co., Inc., 770 Sumneytown Pike, West Point, PA, United States
| | | | - Warren E Glaab
- Nonclinical Drug Safety, Merck & Co., Inc., 770 Sumneytown Pike, West Point, PA 19486, United States
| | - Frank D Sistare
- Nonclinical Drug Safety, Merck & Co., Inc., 770 Sumneytown Pike, West Point, PA 19486, United States
| | - Jose Lebron
- Nonclinical Drug Safety, Merck & Co., Inc., 770 Sumneytown Pike, West Point, PA 19486, United States
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Gu YZ, Vlasakova K, Miller G, Gatto NT, Ciaccio PJ, Kuruvilla S, Besteman EG, Smith R, Reynolds SJ, Amin RP, Glaab WE, Wollenberg G, Lebron J, Sistare FD. Early-Onset albuminuria and Associated Renal Pathology in Leucine-Rich Repeat Kinase 2 Knockout Rats. Toxicol Pathol 2023; 51:15-26. [PMID: 37078689 DOI: 10.1177/01926233231162809] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/21/2023]
Abstract
Activating mutations of the leucine-rich repeat kinase 2 (LRRK2) gene are associated with Parkinson disease (PD), prompting development of LRRK2 inhibitors as potential treatment for PD. However, kidney safety concerns have surfaced from LRRK2 knockout (KO) mice and rats and from repeat-dose studies in rodents administered LRRK2 inhibitors. To support drug development of this therapeutic target, we conducted a study of 26 weeks' duration in 2-month-old wild-type and LRRK2 KO Long-Evans Hooded rats to systematically examine the performance of urinary safety biomarkers and to characterize the nature of the morphological changes in the kidneys by light microscopy and by ultrastructural evaluation. Our data reveal the time course of early-onset albuminuria at 3 and 4 months in LRRK2 KO female and male rats, respectively. The increases in urine albumin were not accompanied by concurrent increases in serum creatinine, blood urea nitrogen, or renal safety biomarkers such as kidney injury molecule 1 or clusterin, although morphological alterations in both glomerular and tubular structure were identified by light and transmission electron microscopy at 8 months of age. Diet optimization with controlled food intake attenuated the progression of albuminuria and associated renal changes.
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Affiliation(s)
- Yi-Zhong Gu
- Merck & Co., Inc., West Point, Pennsylvania, USA
| | | | - Glen Miller
- Merck & Co., Inc., West Point, Pennsylvania, USA
| | | | | | | | | | - Roger Smith
- Merck & Co., Inc., West Point, Pennsylvania, USA
| | | | | | | | | | - Jose Lebron
- Merck & Co., Inc., West Point, Pennsylvania, USA
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3
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Kang W, Podtelezhnikov AA, Tanis KQ, Pacchione S, Su M, Bleicher KB, Wang Z, Laws GM, Griffiths TG, Kuhls MC, Chen Q, Knemeyer I, Marsh DJ, Mitra K, Lebron J, Sistare FD. Development and Application of a Transcriptomic Signature of Bioactivation in an Advanced In Vitro Liver Model to Reduce Drug-induced Liver Injury Risk Early in the Pharmaceutical Pipeline. Toxicol Sci 2021; 177:121-139. [PMID: 32559289 DOI: 10.1093/toxsci/kfaa094] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Early risk assessment of drug-induced liver injury (DILI) potential for drug candidates remains a major challenge for pharmaceutical development. We have previously developed a set of rat liver transcriptional biomarkers in short-term toxicity studies to inform the potential of drug candidates to generate a high burden of chemically reactive metabolites that presents higher risk for human DILI. Here, we describe translation of those NRF1-/NRF2-mediated liver tissue biomarkers to an in vitro assay using an advanced micropatterned coculture system (HEPATOPAC) with primary hepatocytes from male Wistar Han rats. A 9-day, resource-sparing and higher throughput approach designed to identify new chemical entities with lower reactive metabolite-forming potential was qualified for internal decision making using 93 DILI-positive and -negative drugs. This assay provides 81% sensitivity and 90% specificity in detecting hepatotoxicants when a positive test outcome is defined as the bioactivation signature score of a test drug exceeding the threshold value at an in vitro test concentration that falls within 3-fold of the estimated maximum drug concentration at the human liver inlet following highest recommended clinical dose administrations. Using paired examples of compounds from distinct chemical series and close structural analogs, we demonstrate that this assay can differentiate drugs with lower DILI risk. The utility of this in vitro transcriptomic approach was also examined using human HEPATOPAC from a single donor, yielding 68% sensitivity and 86% specificity when the aforementioned criteria are applied to the same 93-drug test set. Routine use of the rat model has been adopted with deployment of the human model as warranted on a case-by-case basis. This in vitro transcriptomic signature-based strategy can be used early in drug discovery to derisk DILI potential from chemically reactive metabolites by guiding structure-activity relationship hypotheses and candidate selection.
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Affiliation(s)
- Wen Kang
- Safety Assessment & Laboratory Animal Resources
| | | | | | | | - Ming Su
- Safety Assessment & Laboratory Animal Resources
| | | | - Zhibin Wang
- Safety Assessment & Laboratory Animal Resources
| | | | | | | | - Qing Chen
- Pharmacokinetics, Pharmacodynamics & Drug Metabolism, Merck & Co., Inc., West Point, Pennsylvania 19486
| | - Ian Knemeyer
- Pharmacokinetics, Pharmacodynamics & Drug Metabolism, Merck & Co., Inc., West Point, Pennsylvania 19486
| | | | | | - Jose Lebron
- Safety Assessment & Laboratory Animal Resources
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4
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Collinge M, Schneider P, Li D, Parish S, Dumont C, Freebern W, Ghanime J, Guimont-Derochers F, Langenkamp A, Lebron J, Li N, Marban C, Plitnick L, Wheeler J. Cross-company evaluation of the human lymphocyte activation assay. J Immunotoxicol 2021; 17:51-58. [PMID: 32124652 DOI: 10.1080/1547691x.2020.1725694] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022] Open
Abstract
Nonclinical immunotoxicity evaluation is an important component of safety assessment for pharmaceuticals. One in vitro assay that can be applied in a weight of evidence assessment is the human lymphocyte activation (HuLA) assay, an antigen recall assay, similar in many respects to the in vivo T-cell-dependent antibody response (TDAR) in that cooperation of multiple immune cell types are needed to produce responses. This assay uses human cells and is more amenable than the TDAR to compound ranking and mechanistic studies. The HuLA assay requires less time and drug than TDAR assays, uses a relevant antigen (influenza), reflects a human immune response, and applies principles of the 3Rs to non-clinical safety assessment. Peripheral blood mononuclear cells (PBMC) from flu-immunized donors are re-stimulated with flu-vaccine in the presence of test articles, and proliferation is measured. Published data demonstrate the applicability of the HuLA assay, but it has not been evaluated for reproducibility across testing sites. To evaluate assay reproducibility, scientists from a consortium of institutions conducted the assay in parallel, using a common pool of donor PBMC, influenza vaccine, and known immunosuppressant compounds (cyclosporine A and mycophenolic acid). The HuLA assay was highly reproducible in identification of inhibition of antigen-specific responses, and there was significant agreement across testing sites in the half maximal inhibitory concentration (IC50) values. Intra-site variability was the largest contributor to the variability observed within the assay. The HuLA assay was demonstrated to be ideally suited to comparing multiple compounds (i.e. compound ranking or benchmarking) within the same assay. Overall, the data reported herein support the HuLA assay as a useful tool in mechanistic evaluations of antigen-specific immune responses.
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Affiliation(s)
| | | | | | - Stanley Parish
- Health and Environmental Sciences Institute, Washington, DC, USA
| | | | | | | | | | - Anja Langenkamp
- Roche Pharmaceutical Research and Development, Basel, Switzerland
| | | | | | - Celine Marban
- Roche Pharmaceutical Research and Development, Basel, Switzerland
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5
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Gu YZ, Chu X, Houle R, Vlasakova K, Koeplinger KA, Bourgeois I, Palyada K, Anderson KD, Brynczka C, Bhatt B, Chen F, Smith R, Amin R, Glaab WE, Lebron J, Cox K, Sistare FD. Polyethlyene Glycol 200 can Protect Rats against Drug-Induced Kidney Toxicity through Inhibition of the Renal Organic Anion Transporter 3. Toxicol Sci 2019; 172:155-166. [PMID: 31406999 DOI: 10.1093/toxsci/kfz186] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2019] [Revised: 07/18/2019] [Accepted: 07/19/2019] [Indexed: 01/15/2023] Open
Abstract
MK-7680, a cyclic nucleotide prodrug, caused significant kidney tubule injury in female rats when administered orally at 1000 mg/kg/day for 2 weeks using 10% Polysorbate 80 as vehicle. However, kidney injury was absent when MK-7680 was administered at the same dose regimen using 100% Polyethylene Glycol 200 (PEG 200) as the vehicle. Subsequent investigations revealed that MK-7680 triphosphate concentrations in kidney were much lower in rats treated with MK-7680 using PEG 200 compared to 10% Polysorbate 80 vehicle while plasma exposures of MK-7680 prodrug were similar. In vitro studies demonstrated that PEG 200 is an inhibitor of human renal uptake transporter organic anion transporter 3 (OAT3), of which MK-7680 is a substrate. Furthermore, PEG 200 and PEG 400 were found to interfere in vitro with human renal transporters OAT3, organic cation transporter (OCT) 2, multidrug resistance-associated protein (MRP) 2 and 4, and multidrug and toxin extrusion protein (MATE) 1 and 2K, but not OAT1. These results support a conclusion that PEG 200 may prevent MK-7680-induced kidney injury by inhibiting its active uptake into proximal tubular cells by OAT3. Caution should be exercised therefore when using PEGs as vehicles for toxicity assessment for compounds that are substrates of renal transporters.
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Affiliation(s)
- Yi-Zhong Gu
- Safety Assessment and Laboratory Animal Resources, Riom, France
| | - Xiaoyan Chu
- Pharmacokinetics, Pharmacodynamics and Metabolism, Riom, France
| | - Robert Houle
- Pharmacokinetics, Pharmacodynamics and Metabolism, Riom, France
| | | | | | - Isabelle Bourgeois
- Safety Assessment and Laboratory Animal Resources, Riom, France.,Merck & Co., Inc., West Point, PA 19486, USA; MSD, Riom, France
| | - Kiran Palyada
- Safety Assessment and Laboratory Animal Resources, Riom, France
| | | | | | - Bhavana Bhatt
- Safety Assessment and Laboratory Animal Resources, Riom, France
| | - Feifei Chen
- Safety Assessment and Laboratory Animal Resources, Riom, France
| | - Roger Smith
- Safety Assessment and Laboratory Animal Resources, Riom, France
| | - Rupesh Amin
- Safety Assessment and Laboratory Animal Resources, Riom, France
| | - Warren E Glaab
- Safety Assessment and Laboratory Animal Resources, Riom, France
| | - Jose Lebron
- Safety Assessment and Laboratory Animal Resources, Riom, France
| | - Kathleen Cox
- Pharmacokinetics, Pharmacodynamics and Metabolism, Riom, France
| | - Frank D Sistare
- Safety Assessment and Laboratory Animal Resources, Riom, France
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6
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Xu Q, Liu L, Vu H, Kuhls M, Aslamkhan AG, Liaw A, Yu Y, Kaczor A, Ruth M, Wei C, Imredy J, Lebron J, Pearson K, Gonzalez R, Mitra K, Sistare FD. Can Galactose Be Converted to Glucose in HepG2 Cells? Improving the in Vitro Mitochondrial Toxicity Assay for the Assessment of Drug Induced Liver Injury. Chem Res Toxicol 2019; 32:1528-1544. [PMID: 31271030 DOI: 10.1021/acs.chemrestox.9b00033] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Human hepatocellular carcinoma cells, HepG2, are often used for drug mediated mitochondrial toxicity assessments. Glucose in HepG2 culture media is replaced by galactose to reveal drug-induced mitochondrial toxicity as a marked shift of drug IC50 values for the reduction of cellular ATP. It has been postulated that galactose sensitizes HepG2 mitochondria by the additional ATP consumption demand in the Leloir pathway. However, our NMR metabolomics analysis of HepG2 cells and culture media showed very limited galactose metabolism. To clarify the role of galactose in HepG2 cellular metabolism, U-13C6-galactose or U-13C6-glucose was added to HepG2 culture media to help specifically track the metabolism of those two sugars. Conversion to U-13C3-lactate was hardly detected when HepG2 cells were incubated with U-13C6-galactose, while an abundance of U-13C3-lactate was produced when HepG2 cells were incubated with U-13C6-glucose. In the absence of glucose, HepG2 cells increased glutamine consumption as a bioenergetics source. The requirement of additional glutamine almost matched the amount of glucose needed to maintain a similar level of cellular ATP in HepG2 cells. This improved understanding of galactose and glutamine metabolism in HepG2 cells helped optimize the ATP-based mitochondrial toxicity assay. The modified assay showed 96% sensitivity and 97% specificity in correctly discriminating compounds known to cause mitochondrial toxicity from those with prior evidence of not being mitochondrial toxicants. The greatest significance of the modified assay was its improved sensitivity in detecting the inhibition of mitochondrial fatty acid β-oxidation (FAO) when glutamine was withheld. Use of this improved assay for an empirical prediction of the likely contribution of mitochondrial toxicity to human DILI (drug induced liver injury) was attempted. According to testing of 65 DILI positive compounds representing numerous mechanisms of DILI together with 55 DILI negative compounds, the overall prediction of mitochondrial mechanism-related DILI showed 25% sensitivity and 95% specificity.
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Affiliation(s)
- Qiuwei Xu
- Merck & Co. Inc. , Kenilworth , New Jersey 07033 , United States
| | - Liping Liu
- Merck & Co. Inc. , Kenilworth , New Jersey 07033 , United States
| | - Heather Vu
- Merck & Co. Inc. , Kenilworth , New Jersey 07033 , United States
| | - Matthew Kuhls
- Merck & Co. Inc. , Kenilworth , New Jersey 07033 , United States
| | - Amy G Aslamkhan
- Merck & Co. Inc. , Kenilworth , New Jersey 07033 , United States
| | - Andy Liaw
- Merck & Co. Inc. , Kenilworth , New Jersey 07033 , United States
| | - Yan Yu
- Merck & Co. Inc. , Kenilworth , New Jersey 07033 , United States
| | - Allen Kaczor
- Merck & Co. Inc. , Kenilworth , New Jersey 07033 , United States
| | - Michael Ruth
- Merck & Co. Inc. , Kenilworth , New Jersey 07033 , United States
| | - Christina Wei
- Merck & Co. Inc. , Kenilworth , New Jersey 07033 , United States
| | - John Imredy
- Merck & Co. Inc. , Kenilworth , New Jersey 07033 , United States
| | - Jose Lebron
- Merck & Co. Inc. , Kenilworth , New Jersey 07033 , United States
| | - Kara Pearson
- Merck & Co. Inc. , Kenilworth , New Jersey 07033 , United States
| | - Raymond Gonzalez
- Merck & Co. Inc. , Kenilworth , New Jersey 07033 , United States
| | - Kaushik Mitra
- Merck & Co. Inc. , Kenilworth , New Jersey 07033 , United States
| | - Frank D Sistare
- Merck & Co. Inc. , Kenilworth , New Jersey 07033 , United States
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Oropallo MA, Shang J, Ke Z, Gonzalez RJ, Sistare FD, Lebron J, Monroe JJ. Developing a T cell:Dendritic cell co-culture system to predict idiosyncratic drug induced hypersensitivity reactions. The Journal of Immunology 2016. [DOI: 10.4049/jimmunol.196.supp.194.10] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Abstract
Idiosyncratic drug induced hypersensitivy reactions (IDHR)s pose a significant safety risk to patients. Indeed, IDHRs have been associated with severe, life-threatening conditions such as Stevens Johnson syndrome, Toxic epidermal necrolysis, and hepatotoxicity. Though drug-induced immune system activation is often implicated in IDHRs, the mechanisms by which this occurs are poorly understood and likely involve formation of drug metabolites or haptens. Furthermore, pre-clinical models often fail to detect the potential of drugs to cause these reactions. Thus, there is a need to create models that can 1) examine how drugs or drug byproducts activate the immune system and 2) predict the potential of drugs to induce IDHRs before they are evaluated in clinical trials. To that end, we have examined the in vitro activation of T cells by autologous monocyte derived dendritic cells (DC)s in the presence of drugs that are associated with IDHR. In concert with previous findings, IDHR associated drugs induce T cell proliferation. Additionally, T cells stimulated by IDHR associated drugs upregulate cell surface markers of activation including CD71, CD69, CD45RO, CD25, and MHC-II. Importantly, we have begun to explore how drug metabolites formed either during T cell:DC co-culture or during culture with hepatocytes influence DC presentation and T cell activation.
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8
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Lebron J. [Jesus Lebron: an interview with the man who threw water at Reverend Ruben Diaz]. Sidahora 1995:37-40. [PMID: 11363217] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 04/16/2023]
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Semrau JD, Chistoserdov A, Lebron J, Costello A, Davagnino J, Kenna E, Holmes AJ, Finch R, Murrell JC, Lidstrom ME. Particulate methane monooxygenase genes in methanotrophs. J Bacteriol 1995; 177:3071-9. [PMID: 7768803 PMCID: PMC176995 DOI: 10.1128/jb.177.11.3071-3079.1995] [Citation(s) in RCA: 151] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
A 45-kDa membrane polypeptide that is associated with activity of the particulate methane monooxygenase (pMMO) has been purified from three methanotrophic bacteria, and the N-terminal amino acid sequence was found to be identical in 17 of 20 positions for all three polypeptides and identical in 14 of 20 positions for the N terminus of AmoB, the 43-kDa subunit of ammonia monooxygenase. DNA from a variety of methanotrophs was screened with two probes, an oligonucleotide designed from the N-terminal sequence of the 45-kDa polypeptide from Methylococcus capsulatus Bath and an internal fragment of amoA, which encodes the 27-kDa subunit of ammonia monooxygenase. In most cases, two hybridizing fragments were identified with each probe. Three overlapping DNA fragments containing one of the copies of the gene encoding the 45-kDa pMMO polypeptide (pmoB) were cloned from Methylococcus capsulatus Bath. A 2.1-kb region was sequenced and found to contain both pmoB and a second gene, pmoA. The predicted amino acid sequences of these genes revealed high identity with those of the gene products of amoB and amoA, respectively. Further hybridization experiments with DNA from Methylococcus capsulatus Bath and Methylobacter albus BG8 confirmed the presence of two copies of pmoB in both strains. These results suggest that the 45- and 27-kDa pMMO-associated polypeptides of methanotrophs are subunits of the pMMO and are present in duplicate gene copies in methanotrophs.
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Affiliation(s)
- J D Semrau
- California Institute of Technology, Pasadena 91125, USA
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10
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Abstract
We have previously reported that a beta-endorphin-like substance inhibits phagocytosis in Tetrahymena perhaps by a mu-like opioid receptor. We now report a further characterization of the elements involved in the signal transduction mechanism of this opioid. Affinity chromatography followed by immunoblots of both intracellular extracts and extracellular medium reveal the presence of two main proteins of 64 and 75 kDa. These molecular weights are much higher than that of any known opioid peptide or precursor protein and suggest that we may be dealing with either a novel opioid or with proteins that by chance cross-react with anti-beta-endorphin antibody. Nevertheless, when the biological activity of these proteins was tested it was found that they had an effect similar to that of mammalian beta-endorphin, namely inhibition of phagocytosis by a naloxone-reversible mechanism. We have probed a size-selected Tetrahymena library with a pro-opiomelanocortin probe and have obtained several positive clones; the sequencing of their inserts should establish whether we are dealing with a bona fide member of the opioid family. Another aspect we have been studying is the G-proteins which appear to be involved in the modulation of phagocytosis. We have found, by means of Western blotting (using an antibody against the conserved GTP-binding region of the alpha-subunit), two bands of 51 and 59 kDa; no alpha-subunit of 59 kDa had been reported previously and may represent a novel G-protein. In spite of these differences, the opioid signal transduction mechanism appears to remarkably resemble that present in more complex organisms.
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Affiliation(s)
- F L Renaud
- Biology Department, University of Puerto Rico, San Juan 00931-3360
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11
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Viniegra M, Marchetti M, Losso M, Navigante A, Litovska S, Senderowicz A, Borghi L, Lebron J, Pujato D, Marrero H. Cardiovascular autonomic function in anthracycline-treated breast cancer patients. Cancer Chemother Pharmacol 1990; 26:227-31. [PMID: 2357771 DOI: 10.1007/bf02897205] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Preclinical studies suggest that in addition to the well-known direct damage to the myocardium, anthracycline antineoplastic drugs exert toxic effects on the cardiovascular autonomic system as well. To investigate whether this phenomenon occurs in the clinic, we carried out noninvasive, widely used tests of cardiovascular autonomic physiology in 55 women with stage II or III breast cancer. In all, 31 were being treated with anthracycline-containing chemotherapy regimens, and 24 who were receiving CMF (cyclophosphamide, Methotrexate, and fluorouracil) served as controls. Of 279 tests conducted in anthracycline (A)-treated patients, 123 were abnormal, vs 54 of 216 tests carried out in 24 controls (44% vs 25%; P less than 0.005). Abnormal variations in heart rate on standing and in diastolic blood pressure during handgrip was found in 25 (81%) and 17 patients receiving A, vs 9 (37%; P less than 0.005) and 5 (21%; P less than 0.0001), respectively, in controls. The incidence of abnormal tests was significantly higher in A-treated patients greater than 60 years of age (41%) vs 67%; P less than 0.05). Radionuclide ventriculography was carried out in 19 patients who showed abnormal tests of cardiovascular autonomic function after greater than or equal to 6 courses of a-containing chemotherapy; only 1 of them had abnormal cardiac contractility (global hypokinesia), suggesting that abnormal tests of cardiovascular autonomic function may occur in the absence of a detectable deterioration in left ventricular ejection fraction. A large number of factors may alter cardiovascular autonomic function in cancer patients, including age, radiation therapy to the chest, and multidrug treatment. Even after correcting for the most obvious of these, chemotherapy with anthracyclines is associated with a significantly higher percentage of abnormal tests for cardiovascular autonomic function. Although indirect and semi-quantitative, our results are compatible with the idea of A-induced cardiac autonomic dysfunction.
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Affiliation(s)
- M Viniegra
- Division of Neumonologia, Hospital de Clinicas, Buenos Aires, Argentina
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12
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Arrighi LA, Nicholson R, Young E, Videla Rivero L, Lebron J. [Importance of the in vitro test as a complement to the study of sperm migration]. Obstet Ginecol Lat Am 1977; 35:353-63. [PMID: 615723] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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