Suppressive effect of PARP-1 inhibitor on JC virus replication in vitro

An Elusive Target: Inhibitors of JC Polyomavirus Infection and Their Development as Therapeutics for the Treatment of Progressive Multifocal Leukoencephalopathy

Progressive multifocal leukoencephalopathy (PML) is a rare demyelinating disease caused by infection with JC Polyomavirus (JCPyV). Despite the identification of the disease and isolation of the causative pathogen over fifty years ago, no antiviral treatments or prophylactic vaccines exist. Disease onset is usually associated with immunosuppression, and current treatment guidelines are limited to restoring immune function. This review summarizes the drugs and small molecules that have been shown to inhibit JCPyV infection and spread. Paying attention to historical developments in the field, we discuss key steps of the virus lifecycle and antivirals known to inhibit each event. We review current obstacles in PML drug discovery, including the difficulties associated with compound penetrance into the central nervous system. We also summarize recent findings in our laboratory regarding the potent anti-JCPyV activity of a novel compound that antagonizes the virus-induced signaling events necessary to establish a productive infection. Understanding the current panel of antiviral compounds will help center the field for future drug discovery efforts.

Lactate drives cellular DNA repair capacity: Role of lactate and related short-chain fatty acids in cervical cancer chemoresistance and viral infection

The characteristic feature of a cancer microenvironment is the presence of a highly elevated concentration of L-lactate in the tumor niche. The lactate-rich environment is also maintained by commensal mucosal microbiota, which has immense potential for affecting cancer cells through its receptoric and epigenetic modes of action. Some of these lactate activities might be associated with the failure of anticancer therapy as a consequence of the drug resistance acquired by cancer cells. Upregulation of cellular DNA repair capacity and enhanced drug efflux are the most important cellular mechanisms that account for ineffective radiotherapy and drug-based therapies. Here, we present the recent scientific knowledge on the role of the HCA1 receptor for lactate and lactate intrinsic activity as an HDAC inhibitor in the development of an anticancer therapy-resistant tumor phenotype, with special focus on cervical cancer cells. In addition, a recent study highlighted the viable role of interactions between mammalian cells and microorganisms in the female reproductive tract and demonstrated an interesting mechanism regulating the efficacy of retroviral transduction through lactate-driven modulation of DNA-PKcs cellular localization. To date, very few studies have focused on the mechanisms of lactate-driven enhancement of DNA repair and upregulation of particular multidrug-resistance proteins in cancer cells with respect to their intracellular regulatory mechanisms triggered by lactate. This review presents the main achievements in the field of lactate impact on cell biology that may promote undesirable alterations in cancer physiology and mitigate retroviral infections.

The oncogenic roles of JC polyomavirus in cancer

JC polyomavirus (JCPyV) belongs to the human polyomavirus family. Based on alternative splicing, the early region encodes the large and small T antigens, while the late region encodes the capsid structural proteins (VP1, VP2, and VP3) and the agnoprotein. The regulatory transcription factors for JCPyV include Sp1, TCF-4, DDX1, YB-1, LCP-1, Purα, GF-1, and NF-1. JCPyV enters tonsillar tissue through the intake of raw sewage, inhalation of air droplets, or parent-to-child transmission. It persists quiescently in lymphoid and renal tissues during latency. Both TGF-β1 and TNF-α stimulates JCPyV multiplication, while interferon-γ suppresses the process. The distinct distribution of caspid receptors (α-2, 6-linked sialic acid, non-sialylated glycosaminoglycans, and serotonin) determines the infection capabilities of JCPyV virions, and JCPyV entry is mediated by clathrin-mediated endocytosis. In permissive cells, JCPyV undergoes lytic proliferation and causes progressive multifocal leukoencephalopathy, while its DNA is inserted into genomic DNA and leads to carcinogenesis in non-permissive cells. T antigen targets p53, β-catenin, IRS, Rb, TGF-β1, PI3K/Akt and AMPK signal pathways in cancer cells. Intracranial injection of T antigen into animals results in neural tumors, and transgenic mice develop neural tumors, lens tumor, breast cancer, gastric, Vater’s, colorectal and pancreatic cancers, insulinoma, and hepatocellular carcinoma. Additionally, JCPyV DNA and its encoded products can be detected in the brain tissues of PML patients and brain, oral, esophageal, gastric, colorectal, breast, cervical, pancreatic, and hepatocellular cancer tissues. Therefore, JCPyV might represent an etiological risk factor for carcinogenesis and should be evaluated for early prevention, diagnosis, and treatment of cancers.

Noncytotoxic functions of killer cell granzymes in viral infections

Cytotoxic lymphocytes produce granules armed with a set of 5 serine proteases (granzymes (Gzms)), which, together with the pore-forming protein (perforin), serve as a major defense against viral infections in humans. This granule-exocytosis pathway subsumes a well-established mechanism in which target cell death is induced upon perforin-mediated entry of Gzms and subsequent activation of various (apoptosis) pathways. In the past decade, however, a growing body of evidence demonstrated that Gzms also inhibit viral replication and potential reactivation in cell death–independent manners. For example, Gzms can induce proteolysis of viral or host cell proteins necessary for the viral entry, release, or intracellular trafficking, as well as augment pro-inflammatory antiviral cytokine response. In this review, we summarize current evidence for the noncytotoxic mechanisms and roles by which killer cells can use Gzms to combat viral infections, and we discuss the potential thereof for the development of novel therapies.

NAD+ Degrading Enzymes, Evidence for Roles During Infection

Declines in cellular nicotinamide adenine dinucleotide (NAD) contribute to metabolic dysfunction, increase susceptibility to disease, and occur as a result of pathogenic infection. The enzymatic cleavage of NAD⁺ transfers ADP-ribose (ADPr) to substrate proteins generating mono-ADP-ribose (MAR), poly-ADP-ribose (PAR) or O-acetyl-ADP-ribose (OAADPr). These important post-translational modifications have roles in both immune response activation and the advancement of infection. In particular, emergent data show viral infection stimulates activation of poly (ADP-ribose) polymerase (PARP) mediated NAD⁺ depletion and stimulates hydrolysis of existing ADP-ribosylation modifications. These studies are important for us to better understand the value of NAD⁺ maintenance upon the biology of infection. This review focuses specifically upon the NAD⁺ utilising enzymes, discusses existing knowledge surrounding their roles in infection, their NAD⁺ depletion capability and their influence within pathogenic infection.

Elucidating the tunability of binding behavior for the MERS-CoV macro domain with NAD metabolites

The macro domain is an ADP-ribose (ADPR) binding module, which is considered to act as a sensor to recognize nicotinamide adenine dinucleotide (NAD) metabolites, including poly ADPR (PAR) and other small molecules. The recognition of macro domains with various ligands is important for a variety of biological functions involved in NAD metabolism, including DNA repair, chromatin remodeling, maintenance of genomic stability, and response to viral infection. Nevertheless, how the macro domain binds to moieties with such structural obstacles using a simple cleft remains a puzzle. We systematically investigated the Middle East respiratory syndrome-coronavirus (MERS-CoV) macro domain for its ligand selectivity and binding properties by structural and biophysical approaches. Of interest, NAD, which is considered not to interact with macro domains, was co-crystallized with the MERS-CoV macro domain. Further studies at physiological temperature revealed that NAD has similar binding ability with ADPR because of the accommodation of the thermal-tunable binding pocket. This study provides the biochemical and structural bases of the detailed ligand-binding mode of the MERS-CoV macro domain. In addition, our observation of enhanced binding affinity of the MERS-CoV macro domain to NAD at physiological temperature highlights the need for further study to reveal the biological functions.

Meng-Hsuan Lin et al. investigate MERS-CoV macro domain binding selectivity with NAD and NAD metabolites under various conditions. At physiological temperature, NAD is observed to have enhanced binding affinity to the MERS-CoV macro domain, shedding light on a new possible role of the MERS-CoV macro domain in viral replication.

Poly(ADP-Ribose) Polymerase Inhibition in Acute Lung Injury. A Reemerging Concept

PARP1, the major isoform of a family of ADP-ribosylating enzymes, has been implicated in the regulation of various biological processes including DNA repair, gene transcription, and cell death. The concept that PARP1 becomes activated in acute lung injury (ALI) and that pharmacological inhibition or genetic deletion of this enzyme can provide therapeutic benefits emerged over 20 years ago. The current article provides an overview of the cellular mechanisms involved in the pathogenetic roles of PARP1 in ALI and provides an overview of the preclinical data supporting the efficacy of PARP (poly[ADP-ribose] polymerase) inhibitors. In recent years, several ultrapotent PARP inhibitors have been approved for clinical use (for the therapy of various oncological diseases): these newly-approved PARP inhibitors were recently reported to show efficacy in animal models of ALI. These observations offer the possibility of therapeutic repurposing of these inhibitors for patients with ALI. The current article lays out a potential roadmap for such repurposing efforts. In addition, the article also overviews the scientific basis of potentially applying PARP inhibitors for the experimental therapy of viral ALI, such as coronavirus disease (COVID-19)-associated ALI.

The impact of PARPs and ADP-ribosylation on inflammation and host-pathogen interactions

Poly-adenosine diphosphate-ribose polymerases (PARPs) promote ADP-ribosylation, a highly conserved, fundamental posttranslational modification (PTM). PARP catalytic domains transfer the ADP-ribose moiety from NAD⁺ to amino acid residues of target proteins, leading to mono- or poly-ADP-ribosylation (MARylation or PARylation). This PTM regulates various key biological and pathological processes. In this review, we focus on the roles of the PARP family members in inflammation and host-pathogen interactions. Here we give an overview the current understanding of the mechanisms by which PARPs promote or suppress proinflammatory activation of macrophages, and various roles PARPs play in virus infections. We also demonstrate how innovative technologies, such as proteomics and systems biology, help to advance this research field and describe unanswered questions.

PARP-1 deregulation in multiple sclerosis

Background

Poly (ADP-ribose) polymerase 1 (PARP-1) plays pivotal roles in immune and inflammatory responses. Accumulating evidence suggests PARP-1 as a promising target for immunomodulation in multiple sclerosis and natalizumab-associated progressive multifocal leukoencephalopathy.

Objective

This study explores expression of PARP-1 and downstream effectors in multiple sclerosis and during natalizumab treatment.

Methods

Transcriptional expressions were studied by real-time reverse transcriptase polymerase chain reaction on CD4⁺T/CD8⁺T/CD14⁺/B cells and peripheral blood mononuclear cells from healthy volunteers, untreated and natalizumab-treated non-progressive multifocal leukoencephalopathy and progressive multifocal leukoencephalopathy multiple sclerosis patients.

Results

PARP-1 expression was higher in CD4⁺T, CD8⁺T and B cells from untreated patients compared to healthy volunteers. Natalizumab treatment restored deregulated PARP-1 expression in T cells but not in B cells. Sustained upregulation of PARP-1 was associated with decreased expression of downstream PARP-1 factors such as TGFBR1/TGFBR2/BCL6 in B cells. Notably, a higher expression of PARP-1 was detected in progressive multifocal leukoencephalopathy patients.

Conclusions

Given the importance of PARP-1 in inflammatory processes, its upregulation in multiple sclerosis lymphocyte populations suggests a potential role in the immune pathogenesis of multiple sclerosis. Strikingly higher PARP-1 expression in progressive multifocal leukoencephalopathy cases suggests its involvement in progressive multifocal leukoencephalopathy disease pathomechanisms. These results further support the value of PARP-1 inhibitors as a potential novel therapeutic strategy for multiple sclerosis and natalizumab-associated progressive multifocal leukoencephalopathy.

Diagnosis and Treatment of Progressive Multifocal Leukoencephalopathy Associated with Multiple Sclerosis Therapies

Progressive multifocal leukoencephalopathy (PML) is a rare, but serious, complication encountered in patients treated with a select number of disease-modifying therapies (DMTs) utilized in treating multiple sclerosis (MS). PML results from a viral infection in the brain for which the only demonstrated effective therapy is restoring the perturbed immune system-typically achieved in the patient with MS by removing the offending therapeutic agent or, in the case of HIV-associated PML, treatment with highly active antiretroviral therapies. Other therapies for PML remain either ineffective or experimental. Significant work to understand the virus and host interaction has been undertaken, but lack of an animal model for the disorder has significantly hindered progress, especially with respect to development of treatments. Strategies to limit risk of PML with natalizumab, a drug that carries a uniquely high risk for the development of the disorder, have been developed. Identifying factors such as positive JC virus antibody status that increase PML risk, at least in theory, should decrease the incidence rate of the disease. Whether other risk factors for PML can be identified and validated or unique strategies should be employed in association with other DMTs that predispose to PML and whether this has a salutary effect on outcome remains to be demonstrated. Identifying PML early, then promptly eliminating drug in the case of natalizumab-associated PML has demonstrated better outcomes, but the complication of PML continues to carry significant morbidity and mortality. While the scientific community has yet to identify targeted therapy with proven efficacy against JCV or PML there are several candidates being studied.

Suppressive effect of topoisomerase inhibitors on JC polyomavirus propagation in human neuroblastoma cells

JC polyomavirus (JCPyV) causes progressive multifocal leukoencephalopathy (PML), a fatal demyelinating disease of the central nervous system, in immunocompromised patients. Because no drugs have been approved for treating PML, many antiviral agents are currently being investigated for this purpose. The inhibitory effects of the topoisomerase I inhibitors topotecan and β-lapachone were assessed by investigating viral replication, propagation and viral protein 1 (VP1) production in cultured cells. JCPyV replication was assayed using the human neuroblastoma cell line IMR-32 transfected with the JCPyV plasmid and RT- PCR combined with Dpn I treatment. Dpn I digests the input plasmid DNA containing methylated adenosine, but not newly replicated JCPyV DNA, in IMR-32 cells. It was found that JCPyV replicates less in IMR-32 cells treated with topotecan or β-lapachone than in untreated cells. Moreover, drug treatment of JCI cells, which are IMR-32 cells persistently infected with JCPyV, led to a reduction in the amount of JCPyV DNA and population of VP1-positive cells. These results demonstrate that topotecan and β-lapachone affects JCPyV propagation in human neuroblastoma cell lines, suggesting that topotecan and β-lapachone could potentially be used to treat PML.

Progressive multifocal leukoencephalopathy: current treatment options and future perspectives

Progressive multifocal leukoencephalopathy (PML) is a rare but debilitating and frequently fatal viral disease of the central nervous system, primarily affecting individuals with chronically and severely suppressed immune systems. The disease was relatively obscure until the outbreak of HIV/AIDS, when it presented as one of the more frequent opportunistic infections in this immune deficiency syndrome. It attracted additional attention from the medical and scientific community following the discovery of significant PML risk associated with natalizumab, a monoclonal antibody used for treatment of relapsing-remitting multiple sclerosis. This was followed by association of PML with other immunosuppressive or immunomodulating drugs. PML is currently untreatable disease with poor outcomes, so it is a significant concern when developing new immunotherapies. Current prophylaxis and treatment of PML are focused on immune reconstitution, restoration of immune responses to JC virus infection, and eventual suppression of immune reconstitution inflammatory syndrome. This approach was successful in reducing the incidence of PML and improved survival of PML patients with HIV infection. However, the outcome for the majority of PML patients, regardless of their medical history, is still relatively poor. There is a high unmet need for both prophylaxis and treatment of PML. The aim of this review is to discuss potential drug candidates for prophylaxis and treatment of PML with a critical review of previously conducted and completed PML treatment studies as well as to provide perspectives for future therapies.

Oligomerization of neutral peptides derived from the JC virus agnoprotein through a cysteine residue

The JC virus is the causative agent of progressive multifocal leukoencephalopathy. The viral genome encodes a multifunctional protein known as agnoprotein which is essential for viral proliferation and reported to possess the oligomerization sequence. However, the structural relationship with the oligomerization is unclear. We synthesized 23 amino acid residue neutral peptides derived from the JC virus agnoprotein, Lys22 to Asp44. The secondary structures of these peptides were β-sheet in aqueous buffer that converted to a helical structure in a hydrophobic environment. These peptides interestingly formed dimers and oligomers under oxidizing conditions. The oligomerization was facilitated by addition of bismaleimides and the derivative without thiol group did not form such oligomers. These results suggest that Agno(22-44) could be transmembrane and one disulfide bond between Cys40 triggers the oligomerization.

TNF-α stimulates efficient JC virus replication in neuroblastoma cells

JC polyomavirus (JCV) causes progressive multifocal leukoencephalopathy (PML), a fatal demyelinating disease of the central nervous system (CNS) in immunocompromised patients, and particularly in the severe immunosuppression associated with acquired immunodeficiency syndrome (AIDS). HIV-1 can lead to the production of tumor necrosis factor-alpha (TNF-α) in the CNS. Our aim was to examine the effects of TNF-α on JCV gene expression and replication using a human neuroblastoma cell line, IMR-32, transfected with JCV DNA, M1-IMRb. Quantitative RT-PCR analysis of JCV large T antigen and VP1 mRNA, the viral DNA replication assay, and the DNase protection assay were carried out. TNF-α treatment of IMR-32 cells transfected with JCV DNA induced large T antigen mRNA and JCV DNA replication, while other effects on VP1 mRNA expression and virus production were marginal. In addition, ELISA analysis of the nuclear p65 subunit of nuclear factor κB (NF-κB), which is a hallmark of NF-κB pathway activation, of IMR-32 cells upon TNF-α treatment showed that TNF-α treatment activated the NF-κB pathway in IMR-32 cells. Taken together, our results suggest that TNF-α stimulation could induce JCV replication associated with the induction of JCV large T antigen mRNA through the NF-κB pathway in IMR-32 cells transfected with JCV DNA. Our findings may contribute to further understanding of the pathogenesis of AIDS-related PML.

Immune surveillance and response to JC virus infection and PML

The ubiquitous human polyomavirus JC virus (JCV) is the established etiological agent of the debilitating and often fatal demyelinating disease, progressive multifocal leukoencephalopathy (PML). Most healthy individuals have been infected with JCV and generate an immune response to the virus, yet remain persistently infected at subclinical levels. The onset of PML is rare in the general population, but has become an increasing concern in immunocompromised patients, where reactivation of JCV leads to uncontrolled replication in the CNS. Understanding viral persistence and the normal immune response to JCV provides insight into the circumstances which could lead to viral resurgence. Further, clues on the potential mechanisms of reactivation may be gleaned from the crosstalk among JCV and HIV-1, as well as the impact of monoclonal antibody therapies used for the treatment of autoimmune disorders, including multiple sclerosis, on the development of PML. In this review, we will discuss what is known about viral persistence and the immune response to JCV replication in immunocompromised individuals to elucidate the deficiencies in viral containment that permit viral reactivation and spread.

New approaches of PARP-1 inhibitors in human lung cancer cells and cancer stem-like cells by some selected anthraquinone-derived small molecules

Poly (ADP-ribose) polymerase-1 (PARP-1) and telomerase, as well as DNA damage response pathways are targets for anticancer drug development, and specific inhibitors are currently under clinical investigation. The purpose of this work is to evaluate anticancer activities of anthraquinone-derived tricyclic and tetracyclic small molecules and their structure-activity relationships with PARP-1 inhibition in non-small cell lung cancer (NSCLC) and NSCLC-overexpressing Oct4 and Nanog clone, which show high-expression of PARP-1 and more resistance to anticancer drug. We applied our library selected compounds to NCI's 60 human cancer cell-lines (NCI-60) in order to generate systematic profiling data. Based on our analysis, it is hypothesized that these drugs might be, directly and indirectly, target components to induce mitochondrial permeability transition and the release of pro-apoptotic factors as potential anti-NSCLC or PARP inhibitor candidates. Altogether, the most active NSC747854 showed its cytotoxicity and dose-dependent PARP inhibitory manner, thus it emerges as a promising structure for anti-cancer therapy with no significant negative influence on normal cells. Our studies present evidence that telomere maintenance should be taken into consideration in efforts not only to overcome drug resistance, but also to optimize the use of telomere-based therapeutics. These findings will be of great value to facilitate structure-based design of selective PARP inhibitors, in general, and telomerase inhibitors, in particular. Together, the data presented here expand our insight into the PARP inhibitors and support the resource-demanding lead optimization of structurally related small molecules for human cancer therapy.