Activation of poly(ADP-Ribose) polymerase-1 is a central mechanism of lipopolysaccharide-induced acute lung inflammation

Type III secretion system effector YfiD inhibits the activation of host poly(ADP-ribose) polymerase-1 to promote bacterial infection

Modulation of cell death is a powerful strategy employed by pathogenic bacteria to evade host immune clearance and occupy profitable replication niches during infection. Intracellular pathogens employ the type III secretion system (T3SS) to deliver effectors, which interfere with regulated cell death pathways to evade immune defenses. Here, we reveal that poly(ADP-ribose) polymerase-1 (PARP1)-dependent cell death restrains Edwardsiella piscicida's proliferation in mouse monocyte macrophages J774A.1, of which PARP1 activation results in the accumulation of poly(ADP-ribose) (PAR) and enhanced inflammatory response. Moreover, E. piscicida, an important intracellular pathogen, leverages a T3SS effector YfiD to impair PARP1's activity and inhibit PAR accumulation. Once translocated into the host nucleus, YfiD binds to the ADP-ribosyl transferase (ART) domain of PARP1 to suppress its PARylation ability as the pharmacological inhibitor of PARP1 behaves. Furthermore, the interaction between YfiD and ART mainly relies on the complete unfolding of the helical domain, which releases the inhibitory effect on ART. In addition, YfiD impairs the inflammatory response and cell death in macrophages and promotes in vivo colonization and virulence of E. piscicida. Collectively, our results establish the functional mechanism of YfiD as a potential PARP1 inhibitor and provide more insights into host defense against bacterial infection.

Inhibition of host PARP1 contributes to the anti-inflammatory and antitubercular activity of pyrazinamide

The antibiotic pyrazinamide (PZA) is a cornerstone of tuberculosis (TB) therapy that shortens treatment durations by several months despite being only weakly bactericidal. Intriguingly, PZA is also an anti-inflammatory molecule shown to specifically reduce inflammatory cytokine signaling and lesion activity in TB patients. However, the target and clinical importance of PZA's host-directed activity during TB therapy remain unclear. Here, we identify the host enzyme Poly(ADP-ribose) Polymerase 1 (PARP1), a pro-inflammatory master regulator strongly activated in TB, as a functionally relevant host target of PZA. We show that PZA inhibits PARP1 enzymatic activity in macrophages and in mice where it reverses TB-induced PARP1 activity in lungs to uninfected levels. Utilizing a PZA-resistant mutant, we demonstrate that PZA's immune-modulatory effects are PARP1-dependent but independent of its bactericidal activity. Importantly, PZA's bactericidal efficacy is impaired in PARP1-deficient mice, suggesting that immune modulation may be an integral component of PZA's antitubercular activity. In addition, adjunctive PARP1 inhibition dramatically reduces inflammation and lesion size in mice and may be a means to reduce lung damage and shorten TB treatment duration. Together, these findings provide insight into PZA's mechanism of action and the therapeutic potential of PARP1 inhibition in the treatment of TB.

Mycobacterium tuberculosis: Pathogenesis and therapeutic targets

Tuberculosis (TB) remains a significant public health concern in the 21st century, especially due to drug resistance, coinfection with diseases like immunodeficiency syndrome (AIDS) and coronavirus disease 2019, and the lengthy and costly treatment protocols. In this review, we summarize the pathogenesis of TB infection, therapeutic targets, and corresponding modulators, including first-line medications, current clinical trial drugs and molecules in preclinical assessment. Understanding the mechanisms of Mycobacterium tuberculosis (Mtb) infection and important biological targets can lead to innovative treatments. While most antitubercular agents target pathogen-related processes, host-directed therapy (HDT) modalities addressing immune defense, survival mechanisms, and immunopathology also hold promise. Mtb's adaptation to the human host involves manipulating host cellular mechanisms, and HDT aims to disrupt this manipulation to enhance treatment effectiveness. Our review provides valuable insights for future anti-TB drug development efforts.

Human umbilical cord mesenchymal stromal cell small extracellular vesicle transfer of microRNA-223-3p to lung epithelial cells attenuates inflammation in acute lung injury in mice

BACKGROUND

Acute lung injury (ALI), manifested as strong pulmonary inflammation and alveolar epithelial damage, is a life-threatening disease with high morbidity and mortality. Small extracellular vesicles (sEVs), secreted by multiple types of cells, are critical cellular communication mediators and can inhibit inflammation by transferring bioactive molecules, such as microRNAs (miRNAs). Thus, we hypothesized that sEVs derived from mesenchymal stromal cells (MSC sEVs) could transfer miRNAs to attenuate inflammation of lung epithelial cells during ALI.

METHODS

C57BL/6 male mice were intratracheally administered LPS (10 mg/kg). Six hours later, the mice were randomly administered with MSC sEVs (40 µg per mouse in 150 µl of saline), which were collected by ultracentrifugation. Control group received saline administration. After 48 h, the mice were sacrificed to evaluate pulmonary microvascular permeability and inflammatory responses. In vitro, A549 cells and primary human small airway epithelial cells (SAECs) were stimulated with LPS with or without MSC sEVs treatment.

RESULTS

In vitro, MSC sEVs could also inhibit the inflammation induced by LPS in A549 cells and SAECs (reducing TNF-α, IL-1β, IL-6 and MCP-1). Moreover, MSC sEV treatment improved the survival rate, alleviated pulmonary microvascular permeability, and inhibited proinflammatory responses (reducing TNF-α, IL-1β, IL-6 and JE-1) in ALI mice. Notably, miR-223-3p was found to be served as a critical mediator in MSC sEV-induced regulatory effects through inhibition of poly (adenosine diphosphate-ribose) polymerase-1 (PARP-1) in lung epithelial cells.

CONCLUSIONS

Overall, these findings suggest that MSC sEVs may offer a novel promising strategy for ALI.

Foxm1 haploinsufficiency drives clonal hematopoiesis and promotes a stress-related transition to hematologic malignancy in mice

Clonal hematopoiesis plays a critical role in the initiation and development of hematologic malignancies. In patients with del(5q) myelodysplastic syndrome (MDS), the transcription factor FOXM1 is frequently downregulated in CD34+ cells. In this study, we demonstrated that Foxm1 haploinsufficiency disturbed normal hematopoiesis and conferred a competitive repopulation advantage for a short period. However, it impaired the long-term self-renewal capacity of hematopoietic stem cells, recapitulating the phenotypes of abnormal hematopoietic stem cells observed in patients with MDS. Moreover, heterozygous inactivation of Foxm1 led to an increase in DNA damage in hematopoietic stem/progenitor cells (HSPCs). Foxm1 haploinsufficiency induced hematopoietic dysplasia in a mouse model with LPS-induced chronic inflammation and accelerated AML-ETO9a-mediated leukemogenesis. We have also identified Parp1, an important enzyme that responds to various types of DNA damage, as a target of Foxm1. Foxm1 haploinsufficiency decreased the ability of HSPCs to efficiently repair DNA damage by downregulating Parp1 expression. Our findings suggest that the downregulation of the Foxm1-Parp1 molecular axis may promote clonal hematopoiesis and reduce genome stability, contributing to del(5q) MDS pathogenesis.

Efficacy of Clinically Used PARP Inhibitors in a Murine Model of Acute Lung Injury

Poly(ADP-ribose) polymerase 1 (PARP1), as a potential target for the experimental therapy of acute lung injury (ALI), was identified over 20 years ago. However, clinical translation of this concept was not possible due to the lack of clinically useful PARP inhibitors. With the clinical introduction of several novel, ultrapotent PARP inhibitors, the concept of PARP inhibitor repurposing has re-emerged. Here, we evaluated the effect of 5 clinical-stage PARP inhibitors in oxidatively stressed cultured human epithelial cells and monocytes in vitro and demonstrated that all inhibitors (1-30 µM) provide a comparable degree of cytoprotection. Subsequent in vivo studies using a murine model of ALI compared the efficacy of olaparib and rucaparib. Both inhibitors (1-10 mg/kg) provided beneficial effects against lung extravasation and pro-inflammatory mediator production-both in pre- and post-treatment paradigms. The underlying mechanisms include protection against cell dysfunction/necrosis, inhibition of NF-kB and caspase 3 activation, suppression of the NLRP3 inflammasome, and the modulation of pro-inflammatory mediators. Importantly, the efficacy of PARP inhibitors was demonstrated without any potentiation of DNA damage, at least as assessed by the TUNEL method. These results support the concept that clinically approved PARP inhibitors may be repurposable for the experimental therapy of ALI.

Acteoside attenuates acute lung injury following administration of cobra venom factor to mice

Background

Acteoside, a water-soluble active constituent of diverse valuable medicinal vegetation, has shown strong anti-inflammatory property. However, studies on the anti-inflammatory property of acteoside in complement-induced acute lung injury (ALI) are limited. Therefore, this study aims to evaluate the anti-inflammatory activity of acteoside in cobra venom factor (CVF)-stimulated human microvascular endothelial cells (HMEC) and in ALI mice model.

Methods

In this study, we investigated the effects of acteoside (20, 10, and 5 μg/mL) in vitro in CVF induced HMECs and the activity of acteoside (100, 50, and 20 mg/kg/day bodyweight) in vivo in CVF induced ALI mice. Each eight male mice were orally administered acteoside or the positive drug PDTC (100 mg/kg/day) for 7 days before CVF (35 μg/kg) injection. After injection for 1 h, the pharmacological effects of acteoside were investigated by spectrophotometry, pathological examination, enzyme-linked immunosorbent assay, and immunohistochemistry.

Results

In vitro, acteoside (20, 10, and 5 μg/mL) reduced the protein expression of adhesion molecules and pro-inflammatory cytokines and transcriptional activity of NF-κB (P < 0.01). In vivo studies showed that acteoside dose-dependently alleviated lung histopathologic lesion, inhibited the production of the protein content of BALF, leukocyte cell number, lung MPO activity, and expression levels of IL-6, TNF-α, and ICAM-1, and suppressed the C5b-9 deposition and NF-κB activation in CVF-induced acute lung inflammation in mice (P < 0.05, 0.01).

Conclusion

This study demonstrates that acteoside exerts strong anti-inflammatory activities in the CVF-induced acute lung inflammation model and suggests that acteoside is a potential therapeutic agent for complement-related inflammatory diseases.

Effects of the PARP Inhibitor Olaparib on the Response of Human Peripheral Blood Leukocytes to Bacterial Challenge or Oxidative Stress

Prior studies demonstrate the activation of poly-(ADP-ribose) polymerase 1 (PARP1) in various pathophysiological conditions, including sepsis. We have assessed the effect of olaparib, a clinically used PARP1 inhibitor, on the responses of human peripheral blood leukocytes (PBMCs) obtained from healthy volunteers in response to challenging with live bacteria, bacterial lipopolysaccharide (LPS), or oxidative stress (hydrogen peroxide, H₂O₂). The viability of PBMCs exposed to olaparib or to the earlier generation PARP inhibitor PJ-34 (0.1–1000 µM) was monitored using Annexin V and 7-aminoactinomycin D. To evaluate the effects of olaparib on the expression of PARP1 and its effects on protein PARylation, PBMCs were stimulated with Staphylococcus aureus with or without olaparib (1–10 μM). Changes in cellular levels of nicotinamide adenine dinucleotide (NAD⁺) and adenosine triphosphate (ATP), as well as changes in mitochondrial membrane potential (MMP), were measured in PBMCs exposed to H₂O₂. Bacterial killing was evaluated in PBMCs and polymorphonuclear leukocytes (PMNs) incubated with S. aureus. Cytokine production was measured in supernatants using a cytometric bead array. Reactive oxygen species (ROS), nitric oxide (NO) production, and phagocytic activity of monocytes and neutrophils were measured in whole blood. For ROS and NO production, samples were incubated with heat-killed S. aureus; phagocytic activity was assessed using killed Escherichia coli conjugated to FITC. Olaparib (0.1–100 µM) did not adversely affect lymphocyte viability. Olaparib also did not interfere with PARP1 expression but inhibits S. aureus-induced protein PARylation. In cells challenged with H₂O₂, olaparib prevented NAD⁺ and ATP depletion and attenuated mitochondrial membrane depolarization. LPS-induced production of TNF-α, MIP-1α, and IL-10 by PBMCs was also reduced by olaparib. Monocytes and neutrophils displayed significant increases in the production of ROS and NO after stimulation with S. aureus and phagocytic (E. coli) and microbicidal activity, and these responses were not suppressed by olaparib. We conclude that, at clinically relevant concentrations, olaparib exerts cytoprotective effects and modulates inflammatory cytokine production without exerting adverse effects on the cells’ ability to phagocytose or eradicate pathogens. The current data support the concept of repurposing olaparib as a potential experimental therapy for septic shock.

Hesperetin may alleviate the development of doxorubicin-induced pulmonary toxicity by decreasing oxidative stress and apoptosis in male rats

Doxorubicin (DOX) is one of the most widely used chemotherapeutic agents. However, it causes pulmonary toxicity which decreases its clinical use in human cancer therapy. The present study was undertaken to obtain an insight into the potential protective effect of hesperetin (HES) against doxorubicin-induced pulmonary toxicity in rats. The animals were divided into 4 groups with 7 rats per group. The experimental treatments were as follows: Control, DOX, DOX + HES, and HES groups. DOX was administered at the dosage of 15 mg/kg i.p for a single dose. HES was administered at the dosage of 50 mg/kg by oral gavage every other day. After 28 days, biochemical parameters, oxidative stress status, histopathological changes, apoptosis-related genes and apoptotic index (AI) were examined of lung tissue. Histopathological changes, Poly [ADP-ribose] polymerase 1 (PARP-1), Caspase-3 (Casp3), Cytochrome c (Cytc), apoptosis-related genes, and AI significantly increased in the DOX group relative to the control group. Malondialdehyde (MDA) significantly increased, while superoxide dismutase (SOD) and glutathione peroxidase (GPx) decreased in the DOX group relative to the control group. However, histopathological findings, MDA, AI, and PAPR1, Casp3 protein expression, mRNA expression of Cytc significantly decreased, while SOD, GPx increased in the DOX + HES group relative to the DOX group. These results attested HES might be a potential agent for the treatment of DOX-induced pulmonary toxicity.

PARP-1-Associated Pathological Processes: Inhibition by Natural Polyphenols

Poly (ADP-ribose) polymerase-1 (PARP-1) is a nuclear enzyme involved in processes of cell cycle regulation, DNA repair, transcription, and replication. Hyperactivity of PARP-1 induced by changes in cell homeostasis promotes development of chronic pathological processes leading to cell death during various metabolic disorders, cardiovascular and neurodegenerative diseases. In contrast, tumor growth is accompanied by a moderate activation of PARP-1 that supports survival of tumor cells due to enhancement of DNA lesion repair and resistance to therapy by DNA damaging agents. That is why PARP inhibitors (PARPi) are promising agents for the therapy of tumor and metabolic diseases. A PARPi family is rapidly growing partly due to natural polyphenols discovered among plant secondary metabolites. This review describes mechanisms of PARP-1 participation in the development of various pathologies, analyzes multiple PARP-dependent pathways of cell degeneration and death, and discusses representative plant polyphenols, which can inhibit PARP-1 directly or suppress unwanted PARP-dependent cellular processes.

PARP-1 inhibition attenuates the inflammatory response in the cartilage of a rat model of osteoarthritis

Aims

Poly (ADP-ribose) polymerase (PARP) inhibitor has been reported to attenuate inflammatory response in rat models of inflammation. This study was designed to investigate the effect of PARP signalling in osteoarthritis (OA) cartilage inflammatory response in an OA rat model.

Methods

The OA model was established by anterior cruciate ligament transection with medial meniscectomy in Wistar rats. The poly (ADP-ribose) polymerase 1 (PARP-1) shRNA (short hairpin (sh)-PARP-1) and negative control shRNA (sh-NC) were delivered using a lentiviral vector and were intra-articularly injected into rats after surgery. The weight-bearing distribution of the hind limbs and the knee joint width were measured every two weeks. The expression levels of PARP-1, inducible nitric oxide synthase (iNOS), and cyclooxygenase-2 (COX-2) in cartilage were determined using real-time quantitative reverse transcription polymerase chain reaction (RT-qPCR) and Western blot. The serum concentrations of inflammatory cytokines were detected using enzyme-linked immunosorbent assay (ELISA).

Results

PARP-1 expression level significantly increased in the cartilage of the established OA rat model. sh-PARP-1 treatment suppressed PARP-1 levels, decreased the Δ Force (the difference between the weight on ipsilateral limb and contralateral limb) and the knee joint width, inhibited cartilage matrix catabolic enzymes, and ameliorated OA cartilage degradation and attenuated inflammatory response.

Conclusion

PARP-1 inhibition attenuates OA cartilage inflammatory response in the OA rat model.

Cite this article: Bone Joint Res 2021;10(7):401–410.

Olaparib attenuates sepsis-induced acute multiple organ injury via ERK-mediated CD14 expression

Sepsis is characterized by persistent systemic inflammation, which can cause multi-organ dysfunction. The poly polymerase-1 inhibitor olaparib possesses anti-inflammatory properties. This study aimed to assess the effects of olaparib (pre- and post-treatments) on sepsis, and to investigate whether it could suppress CD14 expression via the ERK pathway in polymicrobial sepsis and peritoneal macrophages models. Sepsis was induced by cecal ligation and puncture in C57BL/6 male mice. Fifty mice were randomly divided into five groups: The sham group was treated with vehicle or olaparib, the cecal ligation and puncture group with vehicle or with olaparib (5 mg/kg i.p.) 1 h before or 2 h after surgery. Olaparib pretreatment significantly improved the survival of septic mice (P < 0.001). Pre- and post-treatment of mice with olaparib partly alleviated cecal ligation and puncture-induced organ injury by decreasing the amounts of the pro-inflammatory mediators TNF-α and IL-6 as well as bacterial burden in the serum, peritoneal lavage fluid, and organs (P < 0.05). The protective effect of olaparib was associated with CD14 suppression via inhibition of ERK activation. Olaparib facilitated negative regulation of ERK-mediated CD14 expression, which may contribute to multi-organ injury in sepsis.

COVID-19 and pulmonary fibrosis: therapeutics in clinical trials, repurposing, and potential development

In 2019, an unprecedented disease named coronavirus disease 2019 (COVID-19) emerged and spread across the globe. Although the rapid transmission of COVID-19 has resulted in thousands of deaths and severe lung damage, conclusive treatment is not available. However, three COVID-19 vaccines have been authorized, and two more will be approved soon, according to a World Health Organization report on December 12, 2020. Many COVID-19 patients show symptoms of acute lung injury that eventually leads to pulmonary fibrosis. Our aim in this article is to present the relationship between pulmonary fibrosis and COVID-19, with a focus on angiotensin converting enzyme-2. We also evaluate the radiological imaging methods computed tomography (CT) and chest X-ray (CXR) for visualization of patient lung condition. Moreover, we review possible therapeutics for COVID-19 using four categories: treatments related and unrelated to lung disease and treatments that have and have not entered clinical trials. Although many treatments have started clinical trials, they have some drawbacks, such as short-term and small-group testing, that need to be addressed as soon as possible.

The PARP Enzyme Family and the Hallmarks of Cancer Part 2: Hallmarks Related to Cancer Host Interactions

Poly (ADP-ribose) polymerases (PARPs) modify target proteins with a single ADP-ribose unit or with a poly (ADP-ribose) (PAR) polymer. PARP inhibitors (PARPis) recently became clinically available for the treatment of BRCA1/2 deficient tumors via the synthetic lethality paradigm. This personalized treatment primarily targets DNA damage-responsive PARPs (PARP1-3). However, the biological roles of PARP family member enzymes are broad; therefore, the effects of PARPis should be viewed in a much wider context, which includes complex effects on all known hallmarks of cancer. In the companion paper (part 1) to this review, we presented the fundamental roles of PARPs in intrinsic cancer cell hallmarks, such as uncontrolled proliferation, evasion of growth suppressors, cell death resistance, genome instability, replicative immortality, and reprogrammed metabolism. In the second part of this review, we present evidence linking PARPs to cancer-associated inflammation, anti-cancer immune response, invasion, and metastasis. A comprehensive overview of the roles of PARPs can facilitate the identification of novel cancer treatment opportunities and barriers limiting the efficacy of PARPi compounds.

Host-Directed Therapies: Modulating Inflammation to Treat Tuberculosis

Following infection with Mycobacterium tuberculosis, the causative agent of tuberculosis (TB), most human hosts are able to contain the infection and avoid progression to active TB disease through expression of a balanced, homeostatic immune response. Proinflammatory mechanisms aiming to kill, slow and sequester the pathogen are key to a successful host response. However, an excessive or inappropriate pro-inflammatory response may lead to granuloma enlargement and tissue damage, which may prolong the TB treatment duration and permanently diminish the lung function of TB survivors. The host also expresses certain anti-inflammatory mediators which may play either beneficial or detrimental roles depending on the timing of their deployment. The balance between the timing and expression levels of pro- and anti-inflammatory responses plays an important role in the fate of infection. Interestingly, M. tuberculosis appears to manipulate both sides of the human immune response to remodel the host environment for its own benefit. Consequently, therapies which modulate either end of this spectrum of immune responses at the appropriate time may have the potential to improve the treatment of TB or to reduce the formation of permanent lung damage after microbiological cure. Here, we highlight host-directed TB therapies targeting pro- or anti-inflammatory processes that have been evaluated in pre-clinical models. The repurposing of already available drugs known to modulate these responses may improve the future of TB therapy.

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.

PolyADP-Ribosylation of NFATc3 and NF-κB Transcription Factors Modulate Macrophage Inflammatory Gene Expression in LPS-Induced Acute Lung Injury

Pulmonary macrophages play a critical role in the recognition of pathogens, initiation of host defense via inflammation, clearance of pathogens from the airways, and resolution of inflammation. Recently, we have shown a pivotal role for the nuclear factor of activated T-cell cytoplasmic member 3 (NFATc3) transcription factor in modulating pulmonary macrophage function in LPS-induced acute lung injury (ALI) pathogenesis. Although the NFATc proteins are activated primarily by calcineurin-dependent dephosphorylation, here we show that LPS induces posttranslational modification of NFATc3 by polyADP-ribose polymerase 1 (PARP-1)-mediated polyADP-ribosylation. ADP-ribosylated NFATc3 showed increased binding to iNOS and TNFα promoter DNA, thereby increasing downstream gene expression. Inhibitors of PARP-1 decreased LPS-induced NFATc3 ribosylation, target gene promoter binding, and gene expression. LPS increased NFAT luciferase reporter activity in lung macrophages and lung tissue that was inhibited by pretreatment with PARP-1 inhibitors. More importantly, pretreatment of mice with the PARP-1 inhibitor olaparib markedly decreased LPS-induced cytokines, protein extravasation in bronchoalveolar fluid, lung wet-to-dry ratios, and myeloperoxidase activity. Furthermore, PARP-1 inhibitors decreased NF-кB luciferase reporter activity and LPS-induced ALI in NF-кB reporter mice. Thus, our study demonstrates that inhibiting NFATc3 and NF-кB polyADP-ribosylation with PARP-1 inhibitors prevented LPS-induced ALI pathogenesis.

Poly(ADP-ribose) polymerase inhibition: past, present and future

The process of poly(ADP-ribosyl)ation and the major enzyme that catalyses this reaction, poly(ADP-ribose) polymerase 1 (PARP1), were discovered more than 50 years ago. Since then, advances in our understanding of the roles of PARP1 in cellular processes such as DNA repair, gene transcription and cell death have allowed the investigation of therapeutic PARP inhibition for a variety of diseases - particularly cancers in which defects in DNA repair pathways make tumour cells highly sensitive to the inhibition of PARP activity. Efforts to identify and evaluate potent PARP inhibitors have so far led to the regulatory approval of four PARP inhibitors for the treatment of several types of cancer, and PARP inhibitors have also shown therapeutic potential in treating non-oncological diseases. This Review provides a timeline of PARP biology and medicinal chemistry, summarizes the pathophysiological processes in which PARP plays a role and highlights key opportunities and challenges in the field, such as counteracting PARP inhibitor resistance during cancer therapy and repurposing PARP inhibitors for the treatment of non-oncological diseases.

Pharmacological inhibition of poly (ADP-ribose) polymerase by olaparib ameliorates influenza-virus-induced pneumonia in mice

Treatments against influenza A viruses (IAV) have to be updated regularly due to antigenic drift and drug resistance. Poly (ADP-ribose) polymerases (PARPs) are considered effective therapeutic targets of acute lung inflammatory injury. This study aimed to explore the effects of PARP-1 inhibitor olaparib on IAV-induced lung injury and the underlying mechanisms. Male wild-type C57BL/6 mice were intranasally infected with IAV strain H1N1 to mimic pneumonia experimentally. Olaparib at different doses was intraperitoneally injected 2 days before and 5 consecutive days after virus stimulation. On day 6 post-infection, lung tissues as well as bronchoalveolar lavage fluid (BALF) were sampled for histological and biochemical analyses. Olaparib increased the survival rate of IAV mice dose-dependently. Olaparib remarkably reduced IAV mRNA expression, myeloperoxidase (MPO) level, and inflammatory cell infiltration in IAV lungs. Moreover, olaparib significantly reduced the level of interleukin (IL)-1β, tumor necrosis factor (TNF)-α, interferon (IFN)-γ, IL-6, and IL-4 and increased IL-10 in IAV lungs. Also, olaparib efficiently reduced IL-6, monocyte chemotactic protein (MCP)-1, granulocyte colony-stimulating factor (G-CSF), TNF-α, chemokine (C–X–C motif) ligand (CXCL)1, CXCL10, chemokine (C–C motif) ligand (CCL)3, and regulated on activation, normal T cell expressed and secreted (RANTES) release in IAV BALF. Olaparib decreased PARylated protein content and p65, IκBα phosphorylation in IAV lung tissues. This study successfully constructed the pneumonia murine model using IAV. Olaparib decreased IAV-induced mortality in mice, lung injury, and cytokine production possibly via modulation of PARP-1/NF-κB axis.

Repositioning PARP inhibitors for SARS-CoV-2 infection(COVID-19); a new multi-pronged therapy for acute respiratory distress syndrome?

Clinically approved PARP inhibitors (PARPi) have a mild adverse effect profile and are well tolerated as continuous daily oral therapy. We review the evidence that justifies the repurposing of PARPi to block the proliferation of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and combat the life-threatening sequelae of coronavirus disease 2019 (COVID-19) by several mechanisms. PARPi can effectively decrease IL-6, IL-1 and TNF-α levels (key interleukins in SARS-CoV-2-induced cytokine storm) and can alleviate subsequent lung fibrosis, as demonstrated in murine experiments and clinical trials. PARPi can tune macrophages towards a tolerogenic phenotype. PARPi may also counteract SARS-CoV-2-induced and inflammation-induced cell death and support cell survival. PARPi is effective in animal models of acute respiratory distress syndrome (ARDS), asthma and ventilator-induced lung injury. PARPi may potentiate the effectiveness of tocilizumab, anakinra, sarilumab, adalimumab, canakinumab or siltuximab therapy. The evidence suggests that PARPi would benefit COVID-19 patients and trials should be undertaken.

Treatment with 3-aminobenzamide during ex vivo lung perfusion of damaged rat lungs reduces graft injury and dysfunction after transplantation

Ex vivo lung perfusion (EVLP) with pharmacological reconditioning may increase donor lung utilization for transplantation (LTx). 3-Aminobenzamide (3-AB), an inhibitor of poly(ADP-ribose) polymerase (PARP), reduces ex vivo lung injury in rat lungs damaged by warm ischemia (WI). Here we determined the effects of 3-AB reconditioning on graft outcome after LTx. Three groups of donor lungs were studied: Control (Ctrl): 1 hour WI + 3 hours cold ischemia (CI) + LTx; EVLP: 1 hour WI + 3 hours EVLP + LTx; EVLP + 3-AB: 1 hour WI + 3 hours EVLP + 3-AB (1 mg^. mL^-1 ) + LTx. Two hours after LTx, we determined lung graft compliance, edema, histology, neutrophil counts in bronchoalveolar lavage (BAL), mRNA levels of adhesion molecules within the graft, as well as concentrations of interleukin-6 and 10 (IL-6, IL-10) in BAL and plasma. 3-AB reconditioning during EVLP improved compliance and reduced lung edema, neutrophil infiltration, and the expression of adhesion molecules within the transplanted lungs. 3-AB also attenuated the IL-6/IL-10 ratio in BAL and plasma, supporting an improved balance between pro- and anti-inflammatory mediators. Thus, 3-AB reconditioning during EVLP of rat lung grafts damaged by WI markedly reduces inflammation, edema, and physiological deterioration after LTx, supporting the use of PARP inhibitors for the rehabilitation of damaged lungs during EVLP.

Pharmacological inhibition of poly (ADP-ribose) polymerase by olaparib, prevents acute lung injury associated cognitive deficits potentially through suppression of inflammatory response

Acute lung injury (ALI) has been reported to be associated with high mortality rate. Moreover, ALI survivors, frequently present chronic cognitive deterioration. We have previously shown that 'two hit' (hydrochloric acid + lipopolysaccharide) induced ALI resulted in cognitive dysfunction through the induction of systemic inflammation. The present study was designed to explore the potential anti-inflammatory effects of olaparib (Poly ADP-ribose polymerase-1 inhibitor), on ALI mediated cognitive impairment. Olaparib was administered at dose of 5 mg/kg body weight (i.p.) 30 min before each hit. Data show that olaparib pre-treatment markedly reduced the neutrophil infiltration, alveolar capillary damage, inflammatory cytokines level (TNF-α/IL-1β/IL-6) and oxidative stress in the lungs at 24 h after ALI induction. Also, olaparib pre-treatment ameliorated the ALI associated cognitive impairment as assessed by Morris water maze test on weekly basis for 2 consecutive weeks. Further, restoration of cognitive function was associated with normalization of serum levels of TNF-α/IL-1β and improved the blood brain barrier (BBB) function, as reflected by data on expression of occludin/claudin-5 and extravasation of Evans-blue/FITC dextran in hippocampus at 1 week post injury. Finally, increased mRNA expression of VCAM-1, TNF-α and IL-1β and NF-κB activation in hippocampus indicate induction of neuro-inflammation, which was downregulated upon olaparib administration. Further, olaparib treatment 1 week after ALI induction blunted the systemic inflammation which was associated with improved BBB and cognitive function. Altogether, our results showed that olaparib protects against ALI and associated cognitive deficits in mice, and thus may offer a new treatment avenue in the area.

Toll-like Receptor Signaling Rewires Macrophage Metabolism and Promotes Histone Acetylation via ATP-Citrate Lyase

Toll-like receptor (TLR) activation induces inflammatory responses in macrophages by activating temporally defined transcriptional cascades. Whether concurrent changes in the cellular metabolism that occur upon TLR activation influence the quality of the transcriptional responses remains unknown. Here, we investigated how macrophages adopt their metabolism early after activation to regulate TLR-inducible gene induction. Shortly after TLR4 activation, macrophages increased glycolysis and tricarboxylic acid (TCA) cycle volume. Metabolic tracing studies revealed that TLR signaling redirected metabolic fluxes to generate acetyl-Coenzyme A (CoA) from glucose resulting in augmented histone acetylation. Signaling through the adaptor proteins MyD88 and TRIF resulted in activation of ATP-citrate lyase, which in turn facilitated the induction of distinct LPS-inducible gene sets. We postulate that metabolic licensing of histone acetylation provides another layer of control that serves to fine-tune transcriptional responses downstream of TLR activation. Our work highlights the potential of targeting the metabolic-epigenetic axis in inflammatory settings.

Magnesium sulfate attenuates lipopolysaccharides-induced acute lung injury in mice

Acute lung injury (ALI) is a common and severe respiratory disease with high morbidity and mortality. Although some progress has been made in the past years, the pathogenesis of ALI is still poorly understood and the therapeutic outcome has still not been significantly improved. It is well-recognized that magnesium sulfate (MgSO₄) possesses potent anti-inflammation capacity. The present study was designed to investigate the protective effects of MgSO₄ in lipopolysaccharides (LPSs)-induced ALI taken into account that excessive inflammatory response plays critical role in the development of ALI. In this study, Kunming mice were intravenously injected with LPS through tail vein to establish the ALI model and in parallel, A549 cells were used to establish cell model. The lung wet-to-dry weight ratio, malondialdehyde (MDA) levels in lung tissue, lung permeability index, hematoxylin and eosin staining, cytokines in the serum and bronchoalveolar lavage fluid (BALF), neutrophil counts in BALF, LPS-induced A549 cell apoptosis as well as apoptosis-inducing factor (AIF), and Poly(ADP-ribose) polymerase-1 (PARP-1) expression in both mice and A549 cells were detected. Our results demonstrated that MgSO₄ significantly attenuated the LPS-induced ALI, oxidative stress (decreased MDA levels), and lung inflammatory response. Moreover, MgSO₄ exerted protective effects by mitigating LPS-induced A549 cell apoptosis. Furthermore, MgSO₄ decreased the AIF and PARP-1 expression both in vivo and in vitro. Our results, taken together, demonstrated that MgSO₄ is a potential therapeutic agent for ALI taken into consideration that MgSO₄ is commonly used in clinical settings.

Diverse therapeutic efficacies and more diverse mechanisms of nicotinamide

BACKGROUND

Nicotinamide (NAM) is a form of vitamin B3 that, when administered at near-gram doses, has been shown or suggested to be therapeutically effective against many diseases and conditions. The target conditions are incredibly diverse ranging from skin disorders such as bullous pemphigoid to schizophrenia and depression and even AIDS. Similar diversity is expected for the underlying mechanisms. In a large portion of the conditions, NAM conversion to nicotinamide adenine dinucleotide (NAD⁺) may be a major factor in its efficacy. The augmentation of cellular NAD⁺ level not only modulates mitochondrial production of ATP and superoxide, but also activates many enzymes. Activated sirtuin proteins, a family of NAD⁺-dependent deacetylases, play important roles in many of NAM's effects such as an increase in mitochondrial quality and cell viability countering neuronal damages and metabolic diseases. Meanwhile, certain observed effects are mediated by NAM itself. However, our understanding on the mechanisms of NAM's effects is limited to those involving certain key proteins and may even be inaccurate in some proposed cases.

AIM OF REVIEW

This review details the conditions that NAM has been shown to or is expected to effectively treat in humans and animals and evaluates the proposed underlying molecular mechanisms, with the intention of promoting wider, safe therapeutic application of NAM.

KEY SCIENTIFIC CONCEPTS OF REVIEW

NAM, by itself or through altering metabolic balance of NAD⁺ and tryptophan, modulates mitochondrial function and activities of many molecules and thereby positively affects cell viability and metabolic functions. And, NAM administration appears to be quite safe with limited possibility of side effects which are related to NAM's metabolites.

Protective Effects of Myxobacterial Extracts on Hydrogen Peroxide-induced Toxicity on Human Primary Astrocytes

Astrocytes, the main non-neuronal cells in the brain, have significant roles in the maintenance and survival of neurons. Oxidative stress has been implicated in various neurodegenerative disorders such as Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS), and Parkinson's disease (PD). Myxobacteria produce a wide range of bioactive metabolites with notable structures and modes of action, which introduce them as potent natural product producers. In the present study, we evaluated the effects of myxobacterial extracts on hydrogen peroxide (H₂O₂)-mediated toxicity on primary human astrocytes. We showed that myxobacterial extracts could decrease the formation of reactive oxygen species (ROS), nitric oxide (NO) production, and cell death assessed by the release of lactate dehydrogenase (LDH). Myxobacterial extracts were also able to reduce the nitric oxide synthase (NOS) activity. The extracts reduced the oxidative effect of H₂O₂ on over-activation of poly (ADP-ribose) polymerase (PARP1), therefore preventing the cell death by restoring the NAD⁺ levels. In addition, myxobacterial extracts ameliorated the oxidative stress by increasing the glutathione level in cells. The overall results showed myxobacterial extracts, especially from the strains Archangium sp. UTMC 4070 and Cystobacter sp. UTMC 4073, were able to protect human primary astrocytes from oxidative stress.

Poly(ADP-ribosylated) proteins in β-amyloid peptide-stimulated microglial cells

Amyloid-treated microglia prime and sustain neuroinflammatory processes in the central nervous system activating different signalling pathways inside the cells. Since a key role for PARP-1 has been demonstrated in inflammation and in neurodegeneration, we investigated PARylated proteins in resting and in β-amyloid peptide treated BV2 microglial cells. A total of 1158 proteins were identified by mass spectrometry with 117 specifically modified in the amyloid-treated cells. Intervention of PARylation on the proteome of microglia showed to be widespread in different cellular districts and to affect various cellular pathways, highlighting the role of this dynamic post-translational modification in cellular regulation. Ubiquitination is one of the more enriched pathways, encompassing PARylated proteins like NEDD4, an E3 ubiquitine ligase and USP10, a de-ubiquitinase, both associated with intracellular responses induced by β-amyloid peptide challenge. PARylation of NEDD4 may be involved in the recruiting of this protein to the plasma membrane where it regulates the endocytosis of AMPA receptors, whereas USP10 may be responsible for the increase of p53 levels in amyloid stimulated microglia. Unfolded protein response and Endoplasmic Reticulum Stress pathways, strictly correlated with the Ubiquitination process, also showed enrichment in PARylated proteins. PARylation may thus represent one of the molecular switches responsible for the transition of microglia towards the inflammatory microglia phenotype, a pivotal player in brain diseases including neurodegenerative processes. The establishment of trials with PARP inhibitors to test their efficacy in the containment of neurodegenerative diseases may be envisaged.

PARP inhibition induces Akt-mediated cytoprotective effects through the formation of a mitochondria-targeted phospho-ATM-NEMO-Akt-mTOR signalosome

PURPOSE

The cytoprotective effect of poly(ADP-ribose) polymerase 1 (PARP1) inhibition is well documented in various cell types subjected to oxidative stress. Previously, we have demonstrated that PARP1 inhibition activates Akt, and showed that this response plays a critical role in the maintenance of mitochondrial integrity and in cell survival. However, it has not yet been defined how nuclear PARP1 signals to cytoplasmic Akt.

METHODS

WRL 68, HeLa and MCF7 cells were grown in culture. Oxidative stress was induced with hydrogen peroxide. PARP was inhibited with the PARP inhibitor PJ34. ATM, mTOR- and NEMO were silenced using specific siRNAs. Cell viability assays were based on the MTT assay. PARP-ATM pulldown experiments were conducted; each protein was visualized by Western blotting. Immunoprecipitation of ATM, phospho-ATM and NEMO was performed from cytoplasmic and mitochondrial cell fractions and proteins were detected by Western blotting. In some experiments, a continually active Akt construct was introduced. Nuclear to cytoplasmic and mitochondrial translocation of phospho-Akt was visualized by confocal microscopy.

RESULTS

Here we present evidence for a PARP1 mediated, PARylation-dependent interaction between ATM and NEMO, which is responsible for the cytoplasmic transport of phosphorylated (thus, activated) ATM kinase. In turn, the cytoplasmic p-ATM and NEMO forms complex with mTOR and Akt, yielding the phospho-ATM-NEMO-Akt-mTOR signalosome, which is responsible for the PARP-inhibition induced Akt activation. The phospho-ATM-NEMO-Akt-mTOR signalosome localizes to the mitochondria and is essential for the PARP-inhibition-mediated cytoprotective effects in oxidatively stressed cells. When the formation of the signalosome is prevented, the cytoprotective effects diminish, but cells can be rescued by constantly active Akt1, further confirming the critical role of Akt activation in cytoprotection.

CONCLUSIONS

Taken together, the data presented in the current paper are consistent with the hypothesis that PARP inhibition suppresses the PARylation of ATM, which, in turn, forms an ATM-NEMO complex, which exits the nucleus, and combines in the cytosol with mTOR and Act, resulting in Act phosphorylation (i.e. activation), which, in turn, produces the cytoprotective action via the induction of Akt-mediated survival pathways. This mechanism can be important in the protective effect of PARP inhibitor in various diseases associated with oxidative stress. Moreover, disruption of the formation or action of the phospho-ATM-NEMO-Akt-mTOR signalosome may offer potential future experimental therapeutic checkpoints.

Effects of indole alkaloids from leaf of Alstonia scholaris on post-infectious cough in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Leaf of Alstonia scholaris (L.) R. Br. (Apocynaceae), a wide used ethic-medicine in many Asia and Africa counties, has also been recorded as the common traditional Chinese medicine for treatment of illnesses in respiratory system by Dai people.

AIM OF THE STUDY

To provide experimental data of clinical adaption of total indole alkaloids (TA) from leaf of A. scholaris for treating post-infectious cough in phase II clinical trial.

MATERIALS AND METHODS

To model post-infectious cough, all animals except control group were instilled intra-tracheal with lipopolysaccharide (LPS) (80 μg/50 µL/mouse), followed by subsequent exposure to cigarette smoke (CS) for 30 min per day for a total of 30 days. Mice were orally given TA at dose of 10, 25, 50 mg/kg, and four main alkaloids (Sch: scholaricine, Epi: 19-epischolaricine, Val: vallesamine, Pic: picrinine) once daily. Cellular infiltration was assessed in the broncho-alveolar lavage fluid (BALF). Expression of interleukin-6 (IL-6) and C-reactive protein (CRP) in the serum was determined, the superoxide dismutase (SOD) activity as well as malondialdehyde (MDA) content in the serum and homogenate were examined. Finally, histopathological examination in the lungs was assessed by H. E. staining.

RESULTS

After administration of TA and four major alkaloids respectively, the symptoms of cough in mice were obviously attenuated. Total white blood cells (WBC) and neutrophils (NEU) amounts in BALF were reduced obviously and the pathological damage of lung was also attenuated. There was also significant reduction in IL-6, CRP, MDA and a marked improvement in SOD.

CONCLUSIONS

The efficacy of indole alkaloids against post-infectious cough (PIC) was shown in the down-regulation of inflammatory cells, cytokines, and the balance of antioxidants. What's more, the pharmacological effects of TA were better than single indole alkaloid, which might be related to the synergic effect of four major alkaloids.

Neutrophil transfer of miR-223 to lung epithelial cells dampens acute lung injury in mice

Intercellular transfer of microRNAs can mediate communication between critical effector cells. We hypothesized that transfer of neutrophil-derived microRNAs to pulmonary epithelial cells could alter mucosal gene expression during acute lung injury. Pulmonary-epithelial microRNA profiling during coculture of alveolar epithelial cells with polymorphonuclear neutrophils (PMNs) revealed a selective increase in lung epithelial cell expression of microRNA-223 (miR-223). Analysis of PMN-derived supernatants showed activation-dependent release of miR-223 and subsequent transfer to alveolar epithelial cells during coculture in vitro or after ventilator-induced acute lung injury in mice. Genetic studies indicated that miR-223 deficiency was associated with severe lung inflammation, whereas pulmonary overexpression of miR-223 in mice resulted in protection during acute lung injury induced by mechanical ventilation or by infection with Staphylococcus aureus Studies of putative miR-223 gene targets implicated repression of poly(adenosine diphosphate-ribose) polymerase-1 (PARP-1) in the miR-223-dependent attenuation of lung inflammation. Together, these findings suggest that intercellular transfer of miR-223 from neutrophils to pulmonary epithelial cells may dampen acute lung injury through repression of PARP-1.

Poly(adenosine diphosphate-ribose) polymerase as therapeutic target: lessons learned from its inhibitors

Poly(ADP-ribose) polymerases are a family of DNA-dependent nuclear enzymes catalyzing the transfer of ADP-ribose moieties from cellular nicotinamide-adenine-dinucleotide to a variety of target proteins. Although they have been considered as resident nuclear elements of the DNA repair machinery, recent works revealed a more intricate physiologic role of poly(ADP-ribose) polymerases with numerous extranuclear activities. Indeed, poly(ADP-ribose) polymerases participate in fundamental cellular processes like chromatin remodelling, transcription or regulation of the cell-cycle. These new insight into the physiologic roles of poly(ADP-ribose) polymerases widens the range of human pathologies in which pharmacologic inhibition of these enzymes might have a therapeutic potential. Here, we overview our current knowledge on extranuclear functions of poly(ADP-ribose) polymerases with a particular focus on the mitochondrial ones and discuss potential fields of future clinical applications.

PARP-1 inhibition ameliorates elastase induced lung inflammation and emphysema in mice

COPD is associated with high morbidity and mortality and no effective treatment is available till date. We have previously reported that PARP-1 plays an important role in the establishment of airway inflammation associated with asthma and ALI. In the present work, we have evaluated the beneficial effects of PARP-1 inhibition on COPD pathogenesis utilizing elastase induced mouse model of the disease. Our data show that PARP-1 inhibition by olaparib significantly reduced the elastase-induced recruitment of inflammatory cells particularly neutrophils in the lungs of mice when administered at a dose of 5 mg/kg b.wt (i.p.). Reduction in the lung inflammation was associated with suppressed myeloperoxidase activity. Further, the drug restored the redox status in the lung tissues towards normal as reflected by the levels of ROS, GSH and MDA. Olaparib administration prior to elastase instillation blunted the phosphorylation of P65-NF-κB at Ser 536 without altering phosphorylation of its inhibitor IκBα in the lungs. Furthermore, olaparib down regulated the elastase-induced expression of NF-κB dependent pro-inflammatory cytokines (TNF-A, IL-6), chemokine (MIP-2) and growth factor (GCSF) severely both at the mRNA and protein levels. Additionally, PARP-1 heterozygosity suppressed the recruitment of inflammatory cells and production of TNF-A, IL-6, MIP-2 and GCSF in the BALF to the similar extent as exhibited by olaparib administration. Finally, PARP-1 inhibition by olaparib or gene deletion protected against elastase-induced emphysema markedly. Overall, our data strongly suggest that PARP-1 plays a critical role in elastase induced lung inflammation and emphysema, and thus may be a new drug target candidate in COPD.

Olaparib protects cardiomyocytes against oxidative stress and improves graft contractility during the early phase after heart transplantation in rats

BACKGROUND AND PURPOSE

Olaparib, rucaparib and niraparib, potent inhibitors of poly(ADP-ribose) polymerase (PARP) are approved as anti-cancer drugs in humans. Considering the previously demonstrated role of PARP in various forms of acute and chronic myocardial injury, we tested the effects of olaparib in in-vitro models of oxidative stress in cardiomyocytes, and in an in vivo model of cardiac transplantation.

EXPERIMENTAL APPROACH

H9c2-embryonic rat heart-derived myoblasts pretreated with vehicle or olaparib (10μM) were challenged with either hydrogen peroxide (H₂ O₂ ) or with glucose oxidase (GOx, which generates H₂ O₂ in the tissue culture medium). Cell viability assays (MTT, lactate dehydrogenase) and Western blotting for PARP and its product, PAR was performed. Heterotopic heart transplantation was performed in Lewis rats; recipients were treated either with vehicle or olaparib (10 mg kg^-1 ). Left ventricular function of transplanted hearts was monitored via a Millar catheter. Multiple gene expression in the graft was measured by qPCR.

KEY RESULTS

Olaparib blocked autoPARylation of PARP1 and attenuated the rapid onset of death in H9c2 cells, induced by H₂ O₂ , but did not affect cell death following chronic, prolonged oxidative stress induced by GOx. In rats, after transplantation, left ventricular systolic and diastolic function were improved by olaparib. In the transplanted hearts, olaparib also reduced gene expression for c-jun, caspase-12, catalase, and NADPH oxidase-2.

CONCLUSIONS AND IMPLICATIONS

Olaparib protected cardiomyocytes against oxidative stress and improved graft contractility in a rat model of heart transplantation. These findings raise the possibility of repurposing this clinically approved oncology drug, to be used in heart transplantation.

LINKED ARTICLES

This article is part of a themed section on Inventing New Therapies Without Reinventing the Wheel: The Power of Drug Repurposing. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.2/issuetoc.

Poly(ADP-Ribose)Polymerase-1 in Lung Inflammatory Disorders: A Review

Asthma, acute lung injury (ALI), and chronic obstructive pulmonary disease (COPD) are lung inflammatory disorders with a common outcome, that is, difficulty in breathing. Corticosteroids, a class of potent anti-inflammatory drugs, have shown less success in the treatment/management of these disorders, particularly ALI and COPD; thus, alternative therapies are needed. Poly(ADP-ribose)polymerases (PARPs) are the post-translational modifying enzymes with a primary role in DNA repair. During the last two decades, several studies have reported the critical role played by PARPs in a good of inflammatory disorders. In the current review, the studies that address the role of PARPs in asthma, ALI, and COPD have been discussed. Among the different members of the family, PARP-1 emerges as a key player in the orchestration of lung inflammation in asthma and ALI. In addition, PARP activation seems to be associated with the progression of COPD. Furthermore, PARP-14 seems to play a crucial role in asthma. STAT-6 and GATA-3 are reported to be central players in PARP-1-mediated eosinophilic inflammation in asthma. Interestingly, oxidative stress-PARP-1-NF-κB axis appears to be tightly linked with inflammatory response in all three-lung diseases despite their distinct pathophysiologies. The present review sheds light on PARP-1-regulated factors, which may be common or differential players in asthma/ALI/COPD and put forward our prospective for future studies.

Role of poly(ADP-ribose) polymerase activation in the pathogenesis of periodontitis in diabetes

AIM

The aetiology of progressive periodontitis in diabetes has not yet been elucidated. We previously demonstrated that nitrosative stress is increased in diabetic rats with periodontitis. Nitrosative stress induces poly(ADP-ribose) polymerase (PARP) activation. Here, we demonstrated the involvement of PARP activation in diabetic periodontitis and detailed the therapeutic effects of PARP inhibitor.

MATERIALS AND METHODS

Experimental periodontitis was induced by placing a nylon thread ligature. Half of the normal and diabetic rats received the PARP inhibitor, 1,5-isoquinolinediol, for 2 weeks. Gingival PARP activation was detected by immunostaining for poly(ADP-ribose). Periodontitis was evaluated by gingival inflammatory cell infiltration, inflammatory gene expressions and micro-CT analyses.

RESULTS

Although both periodontitis and the presence of diabetes increased PARP activation in the gingiva, diabetic rats with periodontitis had the highest activation of PARP. Diabetic rats with periodontitis also showed significant increases in monocyte/macrophage invasion into the gingiva, inflammatory gene expressions, nitrotyrosine-positive cells in the gingiva and alveolar bone loss, all of which were suppressed by treatment with the PARP inhibitor.

CONCLUSIONS

These results indicate the involvement of PARP activation in the pathogenesis and aggravation of periodontal disease in diabetes and suggest the therapeutic potential of PARP inhibition for treating periodontal disease, especially in patients with diabetes.

Targeting NAD+ degradation: The therapeutic potential of flavonoids for Alzheimer's disease and cognitive frailty

Flavonoids are efficacious candidates as pharmaceuticals or nutraceuticals in the treatment of Alzheimer's disease (AD), aging and other age-related chronic inflammatory diseases. Natural flavonoids reduce pathological hallmarks, extracellular amyloid deposits and neurofibrillary tangles by mediating amyloid precursor protein (APP) processing, Aβ accumulation and tau pathology. The antioxidant and anti-inflammatory actions as well as modulation of sirtuins and telomeres are also involved in the amelioration of aging, neurodegeneration and other age-related diseases. Recently, some flavonoids were shown to inhibit poly (ADP-ribose) polymerases (PARPs) and cyclic ADP-ribose (cADP) synthases (CD38 and CD157), elevate intracellular nicotinamide adenine dinucleotide⁺ (NAD⁺) levels and activate NAD⁺ dependent sirtuin -mediated signaling pathways. We summarized how flavonoids reduce the degradation of NAD⁺ with an emphasis on the mechanisms through which flavonoids affect the NAD⁺-sirtuin axis to protect against AD. Aging and age-related diseases as well as a decline in the physiological reserve are the risk factors for cognitive frailty. Flavonoids with multiple therapeutic targets may also be potential candidates for the prevention and treatment of cognitive frailty.

Chronic PARP-1 inhibition reduces carotid vessel remodeling and oxidative damage of the dorsal hippocampus in spontaneously hypertensive rats

Vascular remodeling during chronic hypertension may impair the supply of tissues with oxygen, glucose and other compounds, potentially unleashing deleterious effects. In this study, we used Spontaneously Hypertensive Rats and normotensive Wistar-Kyoto rats with or without pharmacological inhibition of poly(ADP-ribose)polymerase-1 by an experimental compound L-2286, to evaluate carotid artery remodeling and consequent damage of neuronal tissue during hypertension. We observed elevated oxidative stress and profound thickening of the vascular wall with fibrotic tissue accumulation induced by elevated blood pressure. 32 weeks of L-2286 treatment attenuated these processes by modulating mitogen activated protein kinase phosphatase-1 cellular levels in carotid arteries. In hypertensive animals, vascular inflammation and endothelial dysfunction was observed by NF-κB nuclear accumulation and impaired vasodilation to acetylcholine, respectively. Pharmacological poly(ADP-ribose)polymerase-1 inhibition interfered in these processes and mitigated Apoptosis Inducing Factor dependent cell death events, thus improved structural and functional alterations of carotid arteries, without affecting blood pressure. Chronic poly(ADP-ribose)polymerase-1 inhibition protected neuronal tissue against oxidative damage, assessed by nitrotyrosine, 4-hydroxinonenal and 8-oxoguanosine immunohistochemistry in the area of Cornu ammonis 1 of the dorsal hippocampus in hypertensive rats. In this area, extensive pyramidal cell loss was also attenuated by treatment with lowered poly(ADP-ribose)polymer formation. It also preserved the structure of fissural arteries and attenuated perivascular white matter lesions and reactive astrogliosis in hypertensive rats. These data support the premise in which chronic poly(ADP-ribose)polymerase-1 inhibition has beneficial effects on hypertension related tissue damage both in vascular tissue and in the hippocampus by altering signaling events, reducing oxidative/nitrosative stress and inflammatory status, without lowering blood pressure.

The clinically used PARP inhibitor olaparib improves organ function, suppresses inflammatory responses and accelerates wound healing in a murine model of third-degree burn injury

BACKGROUND AND PURPOSE

The PARP inhibitor olaparib has recently been approved for human use for the therapy of cancer. Considering the role of PARP in critical illness, we tested the effect of olaparib in a murine model of burn injury, in order to begin exploring the feasibility of repurposing olaparib for the therapy of burn patients.

EXPERIMENTAL APPROACH

Mice were subjected to scald burn injury and randomized into vehicle or olaparib (10 mg·kg^-1 ·day^-1 i.p.) groups. Outcome variables included indices of organ injury, clinical chemistry parameters, plasma levels of inflammatory mediators (at 24 h, 7 and 21 days) and burn wound size (at 21 days).

KEY RESULTS

Olaparib reduced myeloperoxidase levels in heart and lung homogenates and reduced malondialdehyde levels in all tissues 24 h post-burn. Olaparib also reduced circulating alkaline aminotransferase, amylase and blood urea nitrogen and creatinine levels, indicative of protection against hepatic, pancreatic and renal dysfunction. Pro-inflammatory mediator (TNF-α, IL-1β, IFN-γ, GCSF, GM-CSF, eotaxin, KC, MIP-1-α and IL-3, 6 and 12) levels as well as the levels of several mediators that are generally considered anti-inflammatory (IL-4, 10 and 13) were reduced by olaparib. Plasma troponin-I levels (an indicator of skeletal muscle damage) was also attenuated by olaparib. Finally, olaparib stimulated wound healing.

CONCLUSIONS AND IMPLICATIONS

The clinically approved PARP inhibitor olaparib improves organ function, suppresses inflammatory responses and accelerates wound healing in murine burn injury. The data raise the potential utility of olaparib for severe burn injury.

LINKED ARTICLES

This article is part of a themed section on Inventing New Therapies Without Reinventing the Wheel: The Power of Drug Repurposing. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.2/issuetoc.

HYDAMTIQ, a selective PARP-1 inhibitor, improves bleomycin-induced lung fibrosis by dampening the TGF-β/SMAD signalling pathway

Idiopathic pulmonary fibrosis is a severe disease characterized by excessive myofibroblast proliferation, extracellular matrix and fibrils deposition, remodelling of lung parenchyma and pulmonary insufficiency. Drugs able to reduce disease progression are available, but therapeutic results are unsatisfactory; new and safe treatments are urgently needed. Poly(ADP‐ribose) polymerases‐1 (PARP‐1) is an abundant nuclear enzyme involved in key biological processes: DNA repair, gene expression control, and cell survival or death. In liver and heart, PARP‐1 activity facilitates oxidative damage, collagen deposition and fibrosis development. In this study, we investigated the effects of HYDAMTIQ, a potent PARP‐1 inhibitor, in a murine model of lung fibrosis. We evaluated the role of PARP on transforming growth factor‐β (TGF‐β) expression and TGF‐β/SMAD signalling pathway in lungs. Mice were intratracheally injected with bleomycin and then treated with either vehicle or different doses of HYDAMTIQ for 21 days. Airway resistance to inflation and lung static compliance, markers of lung stiffness, were assayed. Histochemical and biochemical parameters to evaluate TGF‐β/SMAD signalling pathway with alpha‐smooth muscle actin (αSMA) deposition and the levels of a number of inflammatory markers (tumour necrosis factor‐α, interleukin‐1β, iNOS and COX‐2) were performed. Bleomycin administration increased lung stiffness. It also increased lung PARP activity, TGF‐β levels, pSMAD3 expression, αSMA deposition and content of inflammatory markers. HYDAMTIQ attenuated all the above‐mentioned physiological, biochemical and histopathological markers. Our findings support the proposal that PARP inhibitors could have a therapeutic potential in reducing the progression of signs and symptoms of the disease by decreasing TGF‐β expression and the TGF‐β/SMAD transduction pathway.

PARP inhibition and postinfarction myocardial remodeling

Coronary artery disease accounts for the greatest proportion of cardiovascular diseases therefore it is the major cause of death worldwide. Its therapeutic importance is indicated by still high mortality of myocardial infarction, which is one of the most severe forms of CVDs. Moreover, the risk of developing heart failure is very high among survivors. Heart failure is accompanied by high morbidity and mortality rate, therefore this topic is in the focus of researchers' interest. After a myocardial infarct, at first ventricular hypertrophy develops as a compensatory mechanism to decrease wall stress but finally leads to left ventricular dilation. This phenomenon is termed as myocardial remodeling. The main characteristics of underlying mechanisms involve cardiomyocyte growth, vessel changes and increased collagen production, in all of which several mechanical stress induced neurohumoral agents, oxidative stress and signal transduction pathways are involved. The long term activation of these processes ultimately leads to left ventricular dilation and heart failure with decreased systolic function. Oxidative stress causes DNA breaks producing the activation of nuclear poly(ADP-ribose) polymerase-1 (PARP-1) enzyme that leads to energy depletion and unfavorable modulation of different kinase cascades (Akt-1/GSK-3β, MAPKs, various PKC isoforms) and thus it promotes the development of heart failure. Therefore inhibition of PARP enzyme could offer a promising new therapeutical approach to prevent the onset of heart failure among postinfarction patients. The purpose of this review is to give a comprehensive summary about the most significant experimental results and mechanisms in postinfarction remodeling.

Regulation of necrotic cell death: p53, PARP1 and cyclophilin D-overlapping pathways of regulated necrosis?

In contrast to apoptosis and autophagy, necrotic cell death was considered to be a random, passive cell death without definable mediators. However, this dogma has been challenged by recent developments suggesting that necrotic cell death can also be a regulated process. Regulated necrosis includes multiple cell death modalities such as necroptosis, parthanatos, ferroptosis, pyroptosis, and mitochondrial permeability transition pore (MPTP)-mediated necrosis. Several distinctive executive molecules, particularly residing on the mitochondrial inner and outer membrane, amalgamating to form the MPTP have been defined. The c-subunit of the F1F0ATP synthase on the inner membrane and Bax/Bak on the outer membrane are considered to be the long sought components that form the MPTP. Opening of the MPTP results in loss of mitochondrial inner membrane potential, disruption of ATP production, increased ROS production, organelle swelling, mitochondrial dysfunction and consequent necrosis. Cyclophilin D, along with adenine nucleotide translocator and the phosphate carrier are considered to be important regulators involved in the opening of MPTP. Increased production of ROS can further trigger other necrotic pathways mediated through molecules such as PARP1, leading to irreversible cell damage. This review examines the roles of PARP1 and cyclophilin D in necrotic cell death. The hierarchical role of p53 in regulation and integration of key components of signaling pathway to elicit MPTP-mediated necrosis and ferroptosis is explored. In the context of recent insights, the indistinct role of necroptosis signaling in tubular necrosis after ischemic kidney injury is scrutinized. We conclude by discussing the participation of p53, PARP1 and cyclophilin D and their overlapping pathways to elicit MPTP-mediated necrosis and ferroptosis in acute kidney injury.

Effect of total alkaloids from Alstonia scholaris on airway inflammation in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Alstonia scholaris (Apocynaceae) have been traditionally used for treatment of respiratory diseases in "dai" ethnopharmacy for hundreds years, especially for cough, asthma, phlegm, chronic obstructive pulmonary disease and so on. The formulas including the leaf extract have also been prescribed in hospitals and sold over the retail pharmacies.

AIM OF THE STUDY

A. scholaris is used as a traditional herbal medicine for the treatment of respiratory tract inflammation. However, there is no scientific evidence to validate the use of total alkaloids of A. scholaris in the literature. Here, we investigated the protective activity of total alkaloids (TA), extracted from the leaves of Alstonia scholaris, against lipopolysaccharide (LPS)-induced airway inflammation (AI) in rats.

MATERIALS AND METHODS

200 μg/μL LPS was instilled intratracheally in each rat, and then the modeling animals were divided into six groups (n=10, each) randomly: sham group, LPS group, Dexamethasone [1.5mg/kg, intra-gastricly (i.g.)] group, and three different doses (7.5, 15, and 30 mg/kg, i.g.) of total alkaloids-treated groups. Corresponding drugs or vehicles were orally administered once per day for 7 days consecutively. The concentration of albumin (ALB), alkaline phosphatase (AKP), lactate dehydrogenase (LDH), and the number of inflammatory cells in bronchoalveolar lavage fluid (BALF) were determined by fully automatic biochemical analyzer and blood counting instrument. Nitric oxide (NO) level, malondialdehyde (MDA) content, and superoxide dismutase (SOD) activities were examined by multiskan spectrum, and histological change in the lungs was analyzed by H.E. staining. The levels of inflammatory cytokine tumor necrosis factor-α (TNF-α) and interleukin-8 (IL-8) were measured using ELISA.

RESULTS

Total alkaloids decreased the percentage of neutrophil, number of WBC, levels of ALB, AKP and LDH in the BALF, while increased the content of ALB in serum. It also improved SOD activity and increased NO level in the lungs, serum and BALF, and reduced the concentration of MDA in the lungs. Total alkaloids also inhibited the production of inflammatory cytokines TNF-α and IL-8 in the BALF and lung. Finally, histopathological examination indicated that total alkaloids attenuated tissue injury of the lungs in LPS-induced AI.

CONCLUSIONS

Total alkaloids have an inhibitory effect against LPS-induced airway inflammation in rats.

The intracerebroventricular injection of rimonabant inhibits systemic lipopolysaccharide-induced lung inflammation

We investigated the role of intracerebroventricular (ICV) injection of rimonabant (500ng), a CB1 antagonist, on lipopolysaccharide ((LPS) 5mg/kg)-induced pulmonary inflammation in rats in an isolated perfused lung model. There were decreases in pulmonary capillary pressure (Ppc) and increases in the ((Wet-Dry)/Dry lung weight)/(Ppc) ratio in the ICV-vehicle/LPS group at 4h. There were decreases in TLR4 pathway markers, such as interleukin receptor-associated kinase-1, IκBα, Raf1 and phospho-SFK (Tyr416) at 30min and at 4h increases in IL-6, vascular cell adhesion molecule-1 and myeloperoxidase in lung homogenate. Intracerebroventricular rimonabant attenuated these LPS-induced responses, indicating that ICV rimonabant modulates LPS-initiated pulmonary inflammation.

Nicotinamide exacerbates hypoxemia in ventilator-induced lung injury independent of neutrophil infiltration

Background

Ventilator-induced lung injury is a form of acute lung injury that develops in critically ill patients on mechanical ventilation and has a high degree of mortality. Nicotinamide phosphoribosyltransferase is an enzyme that is highly upregulated in ventilator-induced lung injury and exacerbates the injury when given exogenously. Nicotinamide (vitamin B3) directly inhibits downstream pathways activated by Nicotinamide phosphoribosyltransferase and is protective in other models of acute lung injury.

Methods

We administered nicotinamide i.p. to mice undergoing mechanical ventilation with high tidal volumes to study the effects of nicotinamide on ventilator-induced lung injury. Measures of injury included oxygen saturations and bronchoalveolar lavage neutrophil counts, protein, and cytokine levels. We also measured expression of nicotinamide phosophoribosyltransferase, and its downstream effectors Sirt1 and Cebpa, Cebpb, Cebpe. We assessed the effect of nicotinamide on the production of nitric oxide during ventilator-induced lung injury. We also studied the effects of ventilator-induced lung injury in mice deficient in C/EBPε.

Results

Nicotinamide treatment significantly inhibited neutrophil infiltration into the lungs during ventilator-induced lung injury, but did not affect protein leakage or cytokine production. Surprisingly, mice treated with nicotinamide developed significantly worse hypoxemia during mechanical ventilation. This effect was not linked to increases in nitric oxide production or alterations in expression of Nicotinamide phosphoribosyl transferase, Sirt1, or Cebpa and Cebpb. Cebpe mRNA levels were decreased with either nicotinamide treatment or mechanical ventilation, but mice lacking C/EBPε developed the same degree of hypoxemia and ventilator-induced lung injury as wild-type mice.

Conclusions

Nicotinamide treatment during VILI inhibits neutrophil infiltration of the lungs consistent with a strong anti-inflammatory effect, but paradoxically also leads to the development of significant hypoxemia. These findings suggest that pulmonary neutrophilia is not linked to hypoxemia in ventilator-induced lung injury, and that nicotinamide exacerbates hypoxemia during VILI.

Necroptosis and parthanatos are involved in remote lung injury after receiving ischemic renal allografts in rats

Early renal graft injury could result in remote pulmonary injury due to kidney-lung cross talk. Here we studied the possible role of regulated necrosis in remote lung injury in a rat allogeneic transplantation model. In vitro, human lung epithelial cell A549 was challenged with TNF-α and conditioned medium from human kidney proximal tubular cells (HK-2) after hypothermia-hypoxia insults. In vivo, the Brown-Norway rat renal grafts were extracted and stored in 4 °C Soltran preserving solution for up to 24 h and transplanted into Lewis rat recipients, and the lungs were harvested on day 1 and day 4 after grafting for further analysis. Ischemia-reperfusion injury in the renal allograft caused pulmonary injury following engraftment. PARP-1 (marker for parthanatos) and receptor interacting protein kinase 1 (Rip1) and Rip3 (markers for necroptosis) expression was significantly enhanced in the lung. TUNEL assays showed increased cell death of lung cells. This was significantly reduced after treatment with necrostatin-1 (nec-1) or/and 3-aminobenzamide (3-AB). Acute immune rejection exacerbated the remote lung injury and 3-AB or/and Nec-1 combined with cyclosporine A conferred optimal lung protection. Thus, renal graft injury triggered remote lung injury, likely through regulated necrosis. This study could provide the molecular basis for combination therapy targeting both pathways of regulated necrosis to treat such complications after renal transplantation.

The poly(adenosine diphosphate-ribose) polymerase inhibitor PJ34 reduces pulmonary ischemia-reperfusion injury in rats

Supplemental digital content is available in the text.

Background

Ischemia-reperfusion (I/R) injury after lung transplantation causes alveolar damage, lung edema, and acute rejection. Poly(adenosine diphosphate-ribose) polymerase (PARP) is a single-stranded DNA repair enzyme that induces apoptosis and necrosis after DNA damage caused by reactive oxygen species. We evaluated tissue protective effects of the PARP inhibitor (PARP-i) PJ34 against pulmonary I/R injury.

Methods

Rats (total n=45) underwent a thoracotomy with left hilar isolation and saline administration (sham group) or thoracotomy with hilar clamping and saline administration (I/R group) or PJ34 administration (PARP-i group). Parameters were measured for 7 days after reperfusion.

Results

Pathologic analysis revealed that reperfusion injury was drastically suppressed in the PARP-i group 2 days after reperfusion. Terminal deoxynucleotide transferase-mediated deoxyuridine triphosphate nick-end labeling–positive cells were significantly decreased in the PARP-i group compared to the I/R group (P<0.05). Accordingly, the wet-to-dry lung ratio in the I/R group was significantly higher compared with the PARP-i group (P=0.025). Four hours after reperfusion, serum tissue necrosis factor-α and interleukin-6 were significantly suppressed in the PARP-i group compared with the I/R group (P<0.05). Serum derivatives of reactive oxygen metabolites increased quickly and remained high in the I/R and PARP-i groups from 4 hr until 7 days after reperfusion. Interestingly, the serum biologic antioxidant potential in the PARP-i group was significantly higher than that in the I/R group from day 2 until day 7.

Conclusion

The PARP-i decreased inflammation and tissue damage caused by pulmonary I/R injury. These beneficial effects of the PARP-i may be correlated with its antioxidative efficacy.

Poly(ADP-ribose) polymerase 1 activation links ischemic acute kidney injury to interstitial fibrosis

Inactivation of poly(ADP-ribose) polymerase 1 (PARP1) has been found to be protective in several disease models; however, the role of PARP1 in acute kidney injury-induced interstitial fibrosis has not been studied. Herein, we tested whether PARP1 inactivation by treatment with PJ34 (a PARP1 inactivator; 10 mg/kg body weight/day, intraperitoneal implantation of a miniosmotic pump at 2 days after the onset) contributed to the decrease in interstitial fibrosis induced by ischemia-reperfusion injury (IRI) in mouse kidneys. IRI increased PARP1 activation represented by poly(ADP-ribose) expression from 4 to 16 days postinjury, whereas treatment with PJ34 at 2 days after the onset efficaciously abolished the increase in PARP1 activation at 4, 8 and 16 days after IRI. Pharmacological inactivation of PARP1 significantly reduced interstitial fibrosis as represented by the collagen deposition and transforming growth factor-β1 level at 8 and 16 days after IRI. Consistent with collagen deposition, myofibroblast activation represented by α-smooth muscle actin expression was also reduced by PARP1 inactivation at 8 and 16 days after IRI. Furthermore, IRI enhanced macrophage influx, but PARP1 inactivaton remarkably reduced macrophage influx for 4 through 16 days after the injury. Among the chemoattractants for monocytes/macrophages and neutrophils, monocyte chemotactic protein-1 (MCP-1) production in IRI kidneys was significantly reduced by PARP1 inactivation from 4 to 16 days postinjury. These data demonstrate that PARP1 activation contributes to IRI-induced MCP-1 production and in turn to macrophage influx, resulting in the promotion of interstitial fibrosis.