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Kiy RT, Khoo SH, Chadwick AE. Assessing the mitochondrial safety profile of the molnupiravir active metabolite, β-d-N4-hydroxycytidine (NHC), in the physiologically relevant HepaRG model. Toxicol Res (Camb) 2024; 13:tfae012. [PMID: 38328743 PMCID: PMC10848230 DOI: 10.1093/toxres/tfae012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2023] [Revised: 01/10/2024] [Accepted: 01/16/2024] [Indexed: 02/09/2024] Open
Abstract
Background β-d-N4-Hydroxycytidine (NHC) is the active metabolite of molnupiravir, a broad-spectrum antiviral approved by the MHRA for COVID-19 treatment. NHC induces lethal mutagenesis of the SARS-CoV-2 virus, undergoing incorporation into the viral genome and arresting viral replication. It has previously been reported that several nucleoside analogues elicit off-target inhibition of mitochondrial DNA (mtDNA) or RNA replication. Although NHC does not exert these effects in HepG2 cells, HepaRG are proven to be advantageous over HepG2 for modelling nucleoside analogue-induced mitochondrial dysfunction. Therefore, the objective of this work was to assess the mitotoxic potential of NHC in HepaRG cells, a model more closely resembling physiological human liver. Methods Differentiated HepaRG cells were exposed to 1-60 μM NHC for 3-14 days to investigate effects of sub-, supra-, and clinically-relevant exposures (in the UK, molnupiravir for COVID-19 is indicated for 5 days and reported Cmax is 16 μM). Following drug incubation, cell viability, mtDNA copy number, mitochondrial protein expression, and mitochondrial respiration were assessed. Results NHC induced minor decreases in cell viability at clinically relevant exposures, but did not decrease mitochondrial protein expression. The effects on mtDNA were variable, but typically copy number was increased. At supra-clinical concentrations (60 μM), NHC reduced mitochondrial respiration, but did not appear to induce direct electron transport chain dysfunction. Conclusions Overall, NHC does not cause direct mitochondrial toxicity in HepaRG cells at clinically relevant concentrations, but may induce minor cellular perturbations. As HepaRG cells have increased physiological relevance, these findings provide additional assurance of the mitochondrial safety profile of NHC.
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Affiliation(s)
- Robyn T Kiy
- Department of Pharmacology and Therapeutics, University of Liverpool, Sherrington Building, Ashton Street, Liverpool, L69 3GE, United Kingdom
| | - Saye H Khoo
- Department of Pharmacology and Therapeutics, University of Liverpool, Sherrington Building, Ashton Street, Liverpool, L69 3GE, United Kingdom
- Tropical Infectious Diseases Unit, Royal Liverpool University Hospital, Prescot Street, Liverpool, L7 8XP, United Kingdom
| | - Amy E Chadwick
- Department of Pharmacology and Therapeutics, University of Liverpool, Sherrington Building, Ashton Street, Liverpool, L69 3GE, United Kingdom
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Yu HJ, Xiao GL, Zhao YY, Wang XX, Lan R. Targeting Mitochondrial Metabolism and RNA Polymerase POLRMT to Overcome Multidrug Resistance in Cancer. Front Chem 2022; 9:775226. [PMID: 34976949 PMCID: PMC8716502 DOI: 10.3389/fchem.2021.775226] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2021] [Accepted: 12/06/2021] [Indexed: 11/13/2022] Open
Abstract
Clinically, the prognosis of tumor therapy is fundamentally affected by multidrug resistance (MDR), which is primarily a result of enhanced drug efflux mediated by channels in the membrane that reduce drug accumulation in tumor cells. How to restore the sensitivity of tumor cells to chemotherapy is an ongoing and pressing clinical issue. There is a prevailing view that tumor cells turn to glycolysis for energy supply due to hypoxia. However, studies have shown that mitochondria also play crucial roles, such as providing intermediates for biosynthesis through the tricarboxylic acid (TCA) cycle and a plenty of ATP to fuel cells through the complete breakdown of organic matter by oxidative phosphorylation (OXPHOS). High OXPHOS have been found in some tumors, particularly in cancer stem cells (CSCs), which possess increased mitochondria mass and may be depends on OXPHOS for energy supply. Therefore, they are sensitive to inhibitors of mitochondrial metabolism. In view of this, we should consider mitochondrial metabolism when developing drugs to overcome MDR, where mitochondrial RNA polymerase (POLRMT) would be the focus, as it is responsible for mitochondrial gene expression. Inhibition of POLRMT could disrupt mitochondrial metabolism at its source, causing an energy crisis and ultimately eradicating tumor cells. In addition, it may restore the energy supply of MDR cells to glycolysis and re-sensitize them to conventional chemotherapy. Furthermore, we discuss the rationale and strategies for designing new therapeutic molecules for MDR cancers by targeting POLRMT.
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Affiliation(s)
- Hui-Jing Yu
- School of Pharmaceutical Sciences, Shenzhen University Health Science Center, Shenzhen, China
| | - Guan-Li Xiao
- School of Pharmaceutical Sciences, Shenzhen University Health Science Center, Shenzhen, China
| | - Yu-Ying Zhao
- Department of Cell Biology and Medical Genetics, School of Basic Medical Sciences, Shenzhen University Health Science Center, Shenzhen, China
| | - Xin-Xin Wang
- Department of Cell Biology and Medical Genetics, School of Basic Medical Sciences, Shenzhen University Health Science Center, Shenzhen, China
| | - Rongfeng Lan
- Department of Cell Biology and Medical Genetics, School of Basic Medical Sciences, Shenzhen University Health Science Center, Shenzhen, China
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Wu J, Chen Z, Han X, Chen Q, Wang Y, Feng T. SARS-CoV-2 RNA-dependent RNA polymerase as a target for high-throughput drug screening. Future Virol 2022:10.2217/fvl-2021-0335. [PMID: 36794167 PMCID: PMC9910510 DOI: 10.2217/fvl-2021-0335] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2022] [Accepted: 01/06/2023] [Indexed: 02/05/2023]
Abstract
The ongoing COVID-19 pandemic caused by the SARS-CoV-2 has necessitated rapid development of drug screening tools. RNA-dependent RNA polymerase (RdRp) is a promising target due to its essential functions in replication and transcription of viral genome. To date, through minimal RNA synthesizing machinery established from cryo-electron microscopy structural data, there has been development of high-throughput screening assays for directly screening inhibitors that target the SARS-CoV-2 RdRp. Here, we analyze and present verified techniques that could be used to discover potential anti-RdRp agents or repurposing of approved drugs to target the SARS-CoV-2 RdRp. In addition, we highlight the characteristics and application value of cell-free or cell-based assays in drug discovery.
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Affiliation(s)
- Jiahui Wu
- 1Institute of Biology & Medical Sciences, Jiangsu Key Laboratory of Infection & Immunity, Soochow University, Suzhou, 215123, Jiangsu Province, China
| | - Zhiqiang Chen
- 1Institute of Biology & Medical Sciences, Jiangsu Key Laboratory of Infection & Immunity, Soochow University, Suzhou, 215123, Jiangsu Province, China,2Department of Nuclear Medicine, The First Affiliated Hospital of Soochow University, Suzhou, 215000, Jiangsu Province, China
| | - Xue Han
- 3Department of Clinical Laboratory, the Affiliated Hospital of Qingdao University, 59 Haier Road, Qingdao, 266000, Shandong Province, China
| | - Qiaoqiao Chen
- 1Institute of Biology & Medical Sciences, Jiangsu Key Laboratory of Infection & Immunity, Soochow University, Suzhou, 215123, Jiangsu Province, China
| | - Yintao Wang
- 1Institute of Biology & Medical Sciences, Jiangsu Key Laboratory of Infection & Immunity, Soochow University, Suzhou, 215123, Jiangsu Province, China
| | - Tingting Feng
- 1Institute of Biology & Medical Sciences, Jiangsu Key Laboratory of Infection & Immunity, Soochow University, Suzhou, 215123, Jiangsu Province, China,Author for correspondence: Tel.: +86 512 6588 2429;
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Lu G, Zhang X, Zheng W, Sun J, Hua L, Xu L, Chu XJ, Ding S, Xiong W. Development of a Simple In Vitro Assay To Identify and Evaluate Nucleotide Analogs against SARS-CoV-2 RNA-Dependent RNA Polymerase. Antimicrob Agents Chemother 2020; 65:e01508-20. [PMID: 33122171 PMCID: PMC7927875 DOI: 10.1128/aac.01508-20] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Accepted: 10/26/2020] [Indexed: 02/07/2023] Open
Abstract
Nucleotide analogs targeting viral RNA polymerase have been proved to be an effective strategy for antiviral treatment and are promising antiviral drugs to combat the current severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic. In this study, we developed a robust in vitro nonradioactive primer extension assay to quantitatively evaluate the efficiency of incorporation of nucleotide analogs by SARS-CoV-2 RNA-dependent RNA polymerase (RdRp). Our results show that many nucleotide analogs can be incorporated into RNA by SARS-CoV-2 RdRp and that the incorporation of some of them leads to chain termination. The discrimination values of nucleotide analogs over those of natural nucleotides were measured to evaluate the incorporation efficiency of nucleotide analog by SARS-CoV-2 RdRp. In agreement with the data published in the literature, we found that the incorporation efficiency of remdesivir-TP is higher than that of ATP and incorporation of remdesivir-TP caused delayed chain termination, which can be overcome by higher concentrations of the next nucleotide to be incorporated. Our data also showed that the delayed chain termination pattern caused by remdesivir-TP incorporation is different for different template sequences. Multiple incorporations of remdesivir-TP caused chain termination under our assay conditions. Incorporation of sofosbuvir-TP is very low, suggesting that sofosbuvir may not be very effective in treating SARS-CoV-2 infection. As a comparison, 2'-C-methyl-GTP can be incorporated into RNA efficiently, and the derivative of 2'-C-methyl-GTP may have therapeutic application in treating SARS-CoV-2 infection. This report provides a simple screening method that should be useful for evaluating nucleotide-based drugs targeting SARS-CoV-2 RdRp and for studying the mechanism of action of selected nucleotide analogs.
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Affiliation(s)
- Gaofei Lu
- Global Health Drug Discovery Institute, Beijing, China
| | - Xi Zhang
- Global Health Drug Discovery Institute, Beijing, China
| | - Weinan Zheng
- Global Health Drug Discovery Institute, Beijing, China
| | - Jialei Sun
- Global Health Drug Discovery Institute, Beijing, China
| | - Lan Hua
- Global Health Drug Discovery Institute, Beijing, China
| | - Lan Xu
- Global Health Drug Discovery Institute, Beijing, China
| | - Xin-Jie Chu
- Global Health Drug Discovery Institute, Beijing, China
| | - Sheng Ding
- Global Health Drug Discovery Institute, Beijing, China
- School of Pharmaceutical Sciences, Tsinghua University, Beijing, China
| | - Wen Xiong
- Global Health Drug Discovery Institute, Beijing, China
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Toots M, Plemper RK. Next-generation direct-acting influenza therapeutics. Transl Res 2020; 220:33-42. [PMID: 32088166 PMCID: PMC7102518 DOI: 10.1016/j.trsl.2020.01.005] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/23/2019] [Revised: 01/22/2020] [Accepted: 01/28/2020] [Indexed: 12/16/2022]
Abstract
Influenza viruses are a major threat to human health globally. In addition to further improving vaccine prophylaxis, disease management through antiviral therapeutics constitutes an important component of the current intervention strategy to prevent advance to complicated disease and reduce case-fatality rates. Standard-of-care is treatment with neuraminidase inhibitors that prevent viral dissemination. In 2018, the first mechanistically new influenza drug class for the treatment of uncomplicated seasonal influenza in 2 decades was approved for human use. Targeting the PA endonuclease subunit of the viral polymerase complex, this class suppresses viral replication. However, the genetic barrier against viral resistance to both drug classes is low, pre-existing resistance is observed in circulating strains, and resistant viruses are pathogenic and transmit efficiently. Addressing the resistance problem has emerged as an important objective for the development of next-generation influenza virus therapeutics. This review will discuss the status of influenza therapeutics including the endonuclease inhibitor baloxavir marboxil after its first year of clinical use and evaluate a subset of direct-acting antiviral candidates in different stages of preclinical and clinical development.
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Affiliation(s)
- Mart Toots
- Institute for Biomedical Sciences, Georgia State University, Atlanta, Georgia
| | - Richard K Plemper
- Institute for Biomedical Sciences, Georgia State University, Atlanta, Georgia.
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Analysis of the Potential for N 4-Hydroxycytidine To Inhibit Mitochondrial Replication and Function. Antimicrob Agents Chemother 2020; 64:AAC.01719-19. [PMID: 31767721 PMCID: PMC6985706 DOI: 10.1128/aac.01719-19] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2019] [Accepted: 11/18/2019] [Indexed: 02/06/2023] Open
Abstract
N4-Hydroxycytidine (NHC) is an antiviral ribonucleoside analog that acts as a competitive alternative substrate for virally encoded RNA-dependent RNA polymerases. It exhibits measurable levels of cytotoxicity, with 50% cytotoxic concentration values ranging from 7.5 μM in CEM cells and up to >100 μM in other cell lines. N4-Hydroxycytidine (NHC) is an antiviral ribonucleoside analog that acts as a competitive alternative substrate for virally encoded RNA-dependent RNA polymerases. It exhibits measurable levels of cytotoxicity, with 50% cytotoxic concentration values ranging from 7.5 μM in CEM cells and up to >100 μM in other cell lines. The mitochondrial DNA-dependent RNA polymerase (POLRMT) has been shown to incorporate some nucleotide analogs into mitochondrial RNAs, resulting in substantial mitochondrial toxicity. NHC was tested in multiple assays intended to determine its potential to cause mitochondrial toxicity. NHC showed similar cytotoxicity in HepG2 cells incubated in a glucose-free and glucose-containing media, suggesting that NHC does not impair mitochondrial function in this cell line based on the Crabtree effect. We demonstrate that the 5′-triphosphate of NHC can be used by POLRMT for incorporation into nascent RNA chain but does not cause immediate chain termination. In PC-3 cells treated with NHC, the 50% inhibitory concentrations of mitochondrial protein expression inhibition were 2.7-fold lower than those for nuclear-encoded protein expression, but this effect did not result in selective mitochondrial toxicity. A 14-day incubation of HepG2 cells with NHC had no effect on mitochondrial DNA copy number or extracellular lactate levels. In CEM cells treated with NHC at 10 μM, a slight decrease (by ∼20%) in mitochondrial DNA copy number and a corresponding slight increase in extracellular lactate levels were detected, but these effects were not enhanced by an increase in NHC treatment concentration. In summary, the results indicate that mitochondrial impairment by NHC is not the main contributor to the compound’s observed cytotoxicity in these cell lines.
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