Poly(ADP-ribose) polymerase inhibition with HYDAMTIQ reduces allergen-induced asthma-like reaction, bronchial hyper-reactivity and airway remodelling

Role of histamine H4 receptor in the anti-inflammatory pathway of glucocorticoid-induced leucin zipper (GILZ) in a model of lung fibrosis

INTRODUCTION

This study investigates the interactions between histaminergic system and glucocorticoid-induced leucin zipper (GILZ) in the inflammatory process and glucocorticoid modulation in lung fibrosis.

METHODS

Wild-type (WT) and GILZ Knock-Out (KO) mice were treated with bleomycin (0.05 IU) or saline, delivered by intra-tracheal injection. After surgery, mice received a continuous infusion of JNJ7777120 (JNJ, 2 mg/kg b.wt.) or vehicle for 21 days. Lung function was studied by measuring airway resistance to air insufflation through the analysis of pressure at airway opening (PAO). Lung samples were collected to evaluate the expression of histamine H4R, Anx-A1, and p65-NF-kB, the activity of myeloperoxidase (MPO), and the production of pro-inflammatory cytokines.

RESULTS

Airway fibrosis and remodeling were assessed by measuring TGF-β production and α-SMA deposition. JNJ reduces PAO in WT but not in GILZ KO mice (from 22 ± 1 mm to 15 ± 0.5 and from 24 ± 1.5 to 19 ± 0.5 respectively), MPO activity (from 204 ± 3.13 pmol/mg to 73.88 ± 2.63 in WT and from 221 ± 4.46 pmol/mg to 107 ± 5.54 in GILZ KO), the inflammatory response, TGF-β production, and α-SMA deposition in comparison to WT and GILZ KO vehicle groups.

CONCLUSION

In conclusion, the role of H4R and GILZ in relation to glucocorticoids could pave the way for innovative therapies to counteract pulmonary fibrosis.

Peripheral Neuropathy Potentially Associated to Poly (ADP-Ribose) Polymerase Inhibitors: An Analysis of the Eudravigilance Database

Poly (ADP-Ribose) polymerase inhibitors (PARPi) have emerged as a targeted therapy in cancer treatment with promising results in various types of cancer. This work aims to investigate the profile of adverse drug reactions (ADRs) associated with PARPi through the reports provided by the Eudravigilance (EV) database. We also intend to analyze the potential association of peripheral neuropathy to PARPi. Data on individual case safety reports (ICSRs) were obtained by accessing the European spontaneous reporting system via the EV website. A total of 12,762 ICSRs were collected from the EV database. Serious cases of nervous system disorders were analyzed providing strong evidence that peripheral neuropathy was reported in a higher frequency in patients treated with niraparib. Most cases reported a not recovered/not resolved outcome and involved drug withdrawal. However, several studies suggest that PARPi attenuate chemotherapy-induced painful neuropathy. Unexpected ADRs such as peripheral neuropathy may also occur, mostly in patients taking niraparib. Further pharmacovigilance studies should be conducted in this area to clarify with more precision the toxicity profile of these drugs.

Promotion of a synthetic degradation of activated STAT6 by PARP-1 inhibition: roles of poly(ADP-ribosyl)ation, calpains and autophagy

Background

We reported that PARP-1 regulates genes whose products are crucial for asthma, in part, by controlling STAT6 integrity speculatively through a calpain-dependent mechanism. We wished to decipher the PARP-1/STAT6 relationship in the context of intracellular trafficking and promoter occupancy of the transcription factor on target genes, its integrity in the presence of calpains, and its connection to autophagy.

Methods

This study was conducted using primary splenocytes or fibroblasts derived from wild-type or PARP-1^−/− mice and Jurkat T cells to mimic Th2 inflammation.

Results

We show that the role for PARP-1 in expression of IL-4-induced genes (e.g. gata-3) in splenocytes did not involve effects on STAT6 phosphorylation or its subcellular trafficking, rather, it influenced its occupancy of gata-3 proximal and distal promoters in the early stages of IL-4 stimulation. At later stages, PARP-1 was crucial for STAT6 integrity as its inhibition, pharmacologically or by gene knockout, compromised the fate of the transcription factor. Calpain-1 appeared to preferentially degrade JAK-phosphorylated-STAT6, which was blocked by calpastatin-mediated inhibition or by genetic knockout in mouse fibroblasts. The STAT6/PARP-1 relationship entailed physical interaction and modification by poly(ADP-ribosyl)ation independently of double-strand-DNA breaks. Poly(ADP-ribosyl)ation protected phosphorylated-STAT6 against calpain-1-mediated degradation. Additionally, our results show that STAT6 is a bonafide substrate for chaperone-mediated autophagy in a selective and calpain-dependent manner in the human Jurkat cell-line. The effects were partially blocked by IL-4 treatment and PARP-1 inhibition.

Conclusions

The results demonstrate that poly(ADP-ribosyl)ation plays a critical role in protecting activated STAT6 during Th2 inflammation, which may be synthetically targeted for degradation by inhibiting PARP-1.

Adenosine A3 Receptor (A3AR) Agonist for the Treatment of Bleomycin-Induced Lung Fibrosis in Mice

Adenosine receptors (ARs) are involved in the suppression and development of inflammatory and fibrotic conditions. Specifically, AR activation promotes differentiation of lung fibroblasts into myofibroblasts, typical of a fibrotic event. Pulmonary fibrosis is a severe disease characterized by inflammation and fibrosis of unknown etiology and lacking an effective treatment. The present investigation explored the action of MRS5980, a new, highly potent and selective A₃AR agonist, in an established murine model of lung fibrosis. The effects of either vehicle or MRS5980 were studied in mice following intratracheal bleomycin administration. We evaluated the role of the A₃AR agonist on lung stiffness, studying the airway resistance to inflation, oxidative stress (8-OHdG and MDA), inflammation, pro- and anti-inflammatory marker levels (IL-1β, IL-6, TNF-α, IL-10 and IL-17A) and fibrosis establishment, evaluating transforming growth factor (TGF)-β expression and α-smooth muscle actin (α-SMA) deposition in lungs. Bleomycin administration increased lung stiffness, TGF-β levels, α-SMA deposition, and inflammatory and oxidative stress markers. The treatment with MRS5980 attenuated all the analyzed functional, biochemical and histopathological markers in a dose-dependent manner. Our findings support the therapeutic potential of A₃AR agonists in lung fibrosis by demonstrating reduced disease progression, as indicated by decreased inflammation, TGF-β expression and fibrotic remodeling.

MiR-21 modulates proliferation and apoptosis of human airway smooth muscle cells by regulating autophagy via PARP-1/AMPK/mTOR signalling pathway

Superfluous human airway smooth muscle (HASM) cell proliferation is an important pathological feature of airway remodelling in asthma. This study aimed to determine whether miR-21 is involved in the regulation of HASM cell survival. Overexpressed miR-21 inhibited HASM cell apoptosis and autophagy and promoted proliferation, whereas a miR-21 inhibitor exerted the opposite effects (P < 0.05). Overexpressed poly (ADP-ribose) polymerase-1 (PARP-1) promoted apoptosis and inhibited proliferation of HASM cells (P < 0.05). Dual-luciferase assays confirmed that miR-21 directly targeted poly (ADP-ribose) polymerase-1 (PARP-1) mRNA (P < 0.05). Silencing PARP-1 based on miR-21 downregulation mimicked the role of 3-methyladenine (3-MA), an autophagy inhibitor (P < 0.05). Overexpressed PARP-1 reversed the effects of miR-21 on HASM cells, somewhat dependently on PARP-1-induced enhanced autophagy, which we elucidated by 3-MA block (P < 0.05). MicroRNA-21 mimics reduced AMPK and increased mTOR signalling by downregulating PARP-1, and a miR-21 inhibitor exerted the opposite effects (P < 0.05). Collectively, miR-21 inhibitor could upregulate PARP-1 in HASM cells to promote autophagy and thus inhibit proliferation and promote apoptosis that might be mediated by the AMPK/mTOR signalling pathway.

MicroRNA-21 promotes epithelial-mesenchymal transition and migration of human bronchial epithelial cells by targeting poly (ADP-ribose) polymerase-1 and activating PI3K/AKT signaling

Epithelial-mesenchymal transition (EMT) is known to be involved in airway remodeling and fibrosis of bronchial asthma. However, the molecular mechanisms leading to EMT have yet to be fully clarified. The current study was designed to reveal the potential mechanism of microRNA-21 (miR-21) and poly (ADP-ribose) polymerase-1 (PARP-1) affecting EMT through the PI3K/AKT signaling pathway. Human bronchial epithelial cells (16HBE cells) were transfected with miR-21 mimics/inhibitors and PARP-1 plasmid/small interfering RNA (siRNA). A dual luciferase reporter assay and biotin-labeled RNA pull-down experiments were conducted to verify the targeting relationship between miR-21 mimics and PARP-1. The migration ability of 16HBE cells was evaluated by Transwell assay. Quantitative real-time polymerase chain reaction and Western blotting experiments were applied to determine the expression of Snail, ZEB1, E-cadherin, N-cadherin, Vimentin, and PARP-1. The effects of the PI3K inhibitor LY294002 on the migration of 16HBE cells and EMT were investigated. Overexpression of miR-21 mimics induced migration and EMT of 16HBE cells, which was significantly inhibited by overexpression of PARP-1. Our findings showed that PARP-1 was a direct target of miR-21, and that miR-21 targeted PARP-1 to promote migration and EMT of 16HBE cells through the PI3K/AKT signaling pathway. Using LY294002 to block PI3K/AKT signaling pathway resulted in a significant reduction in the migration and EMT of 16HBE cells. These results suggest that miR-21 promotes EMT and migration of HBE cells by targeting PARP-1. Additionally, the PI3K/AKT signaling pathway might be involved in this mechanism, which could indicate its usefulness as a therapeutic target for asthma.

Risk of pneumonitis in cancer patients treated with PARP inhibitors: A meta-analysis of randomized controlled trials and a pharmacovigilance study of the FAERS database

OBJECTIVE/BACKGROUND

We aimed to evaluate the risk of PARP inhibitors (PARPis) causing pneumonitis in randomized controlled trials (RCTs) and in the real-world practice.

METHODS

First, a systematic review based on meta-analysis was conducted. RCTs with available data reporting pneumonitis events for PARPis were eligible for analysis. Second, we conducted a disproportionality analysis based on data from the FDA Adverse Event Reporting System (FAERS) database to characterize the main features of PARPi-related pneumonitis.

RESULTS

16 trials with 5771 patients were included in our meta-analysis. Compared with control arms, PARPis showed a significant increase in the risk of pneumonitis events (Peto OR 2.68 [95% CI 1.31-5.47], p = 0.007) with no heterogeneity (I² = 0%, χ²p = 0.70). The incidence of pneumonitis across treatment arms was 0.79% (28/3551). In the FAERS database, we identified 84 cases of PARPi-pneumonitis with a fatality rate of 16% (13/79). The median time to event onset was 81 (interquartile range [IQR] 27-131) days and 87% of the adverse events occurred within 6 months.

CONCLUSION

PARPis increased the risk of pneumonitis that can result in serious outcomes and tend to occur early. Early recognition and management of PARPi-pneumonitis is of vital importance in clinical practice. The mechanisms and risk factors should be studied further to improve clinical understanding and innovative treatment strategies for these diseases.

Airway Redox Homeostasis and Inflammation Gone Awry: From Molecular Pathogenesis to Emerging Therapeutics in Respiratory Pathology

As aerobic organisms, we are continuously and throughout our lifetime subjected to an oxidizing atmosphere and, most often, to environmental threats. The lung is the internal organ most highly exposed to this milieu. Therefore, it has evolved to confront both oxidative stress induced by reactive oxygen species (ROS) and a variety of pollutants, pathogens, and allergens that promote inflammation and can harm the airways to different degrees. Indeed, an excess of ROS, generated intrinsically or from external sources, can imprint direct damage to key structural cell components (nucleic acids, sugars, lipids, and proteins) and indirectly perturb ROS-mediated signaling in lung epithelia, impairing its homeostasis. These early events complemented with efficient recognition of pathogen- or damage-associated recognition patterns by the airway resident cells alert the immune system, which mounts an inflammatory response to remove the hazards, including collateral dead cells and cellular debris, in an attempt to return to homeostatic conditions. Thus, any major or chronic dysregulation of the redox balance, the air-liquid interface, or defects in epithelial proteins impairing mucociliary clearance or other defense systems may lead to airway damage. Here, we review our understanding of the key role of oxidative stress and inflammation in respiratory pathology, and extensively report current and future trends in antioxidant and anti-inflammatory treatments focusing on the following major acute and chronic lung diseases: acute lung injury/respiratory distress syndrome, asthma, chronic obstructive pulmonary disease, pulmonary fibrosis, and cystic fibrosis.

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.

Effects of PARP-1 Deficiency and Histamine H4 Receptor Inhibition in an Inflammatory Model of Lung Fibrosis in Mice

Pulmonary fibrosis is the most frequent form of interstitial lung disease. Effective therapies are not yet available; novel therapeutic approaches are needed for counteracting fibrosis. Poly(ADP-ribose) polymerases are enzymes, involved in DNA repair and cell apoptosis. PARP-1 deficient mice exhibited reduced lung fibrosis in response to bleomycin treatment compared to wild-type controls. Histamine H₄ receptors (H₄Rs) have been recognized as a new target for inflammatory and immune diseases, and H₄R ligands reduced inflammation and oxidative stress in lung tissue. The aim of the study was to evaluate the cross-talk between PARP-1 and H₄R in a model of bleomycin-induced lung fibrosis in PARP-1^−/− and WT mice. Animals were treated with bleomycin or saline by intra-tracheal injection. JNJ7777120, an H₄R antagonist, or VUF8430, an H₄R agonist, were administered i.p for 21 days. Airway resistance to inflation was evaluated, and lung tissues were processed for PARylated protein content, oxidative stress evaluation, and histology of small bronchi. The levels of pro-inflammatory (IL-1β and TNF-α), regulatory (IL-10), and pro-fibrotic (TGF-β) cytokines were evaluated. The deposition of αSMA was determined by immunofluorescence analysis. The results indicate that JNJ7777120 reduces PARylated protein production, decreases oxidative stress damage, and MPO, a marker for leukocyte tissue infiltration, in PARP-1^−/− mice. A significant decrease in the production of both IL-1β and TNF-α and a significant increase in IL-10 levels are observed in mice treated with H₄R antagonist, suggesting a crucial anti-inflammatory activity of JNJ7777120. The smooth muscle layer thickness, the goblet cell relative number, and collagen deposition decreased following JNJ7777120 administration. The H₄R antagonist treatment also reduces TGF-β production and αSMA deposition, suggesting an important role of JNJ7777120 in airway remodeling. Our results show that PARylation is essential for the pathogenesis of pulmonary fibrosis and propose that PARP-1 and H₄Rs are both involved in inflammatory and fibrotic responses. JNJ7777120 treatment, in a condition of PARP-1 inhibition, exerts anti-inflammatory and anti-fibrotic effects, reducing airway remodeling and bronchoconstriction. Therefore, selective inhibition of H₄Rs together with non-toxic doses of selective PARP-1 inhibitors could have clinical relevance for the treatment of idiopathic pulmonary fibrosis.

PARP inhibition by olaparib alleviates chronic asthma-associated remodeling features via modulating inflammasome signaling in mice

Despite the reported role of poly(ADP-ribose) polymerase (PARP) in asthma inflammation, its contribution during remodeling is not clearly known. The main aim of the current investigation was to examine the potential of olaparib, a pharmacological inhibitor of PARP against airway remodeling using an ovalbumin (OVA)-based murine model of chronic asthma. The results demonstrated that post-challenge olaparib treatment (5 mg/kg i.p., 30 min after OVA exposure) for six weeks (3 days/week) attenuates inflammation, mucus production, and collagen deposition in lungs. Additionally, olaparib blunted the protein expression of STAT-6 and GATA-3 considerably along with a modest reduction in p65-NF-κB phosphorylation. Furthermore, olaparib normalized the OVA-induced redox imbalance as reflected by data on reactive oxygen species, malondialdehyde, protein carbonyls, and reduced glutathione/oxidized glutathione ratio. Interestingly, the protection offered by olaparib was further linked with the altered level of NLRP3 inflammasome-mediated IL-1β release and consequent expression of its downstream targets matrix metalloproteinase-9 and transforming growth factor beta. Suppressed collagen deposition in the lungs correlates well with the reduced expression of vimentin upon olaparib treatment. Finally, olaparib restored the expression of histone deacetylase 2, a steroid-responsive element in asthma. Overall, results suggest that olaparib prevents OVA-induced airway inflammation as well as remodeling via modulating inflammasome signaling in mice. © 2019 IUBMB Life, 1-11, 2019.

Exploring and comparing adverse events between PARP inhibitors

Ovarian cancer remains one of the most challenging malignancies to treat. Targeted therapies such as poly (ADP-ribose) polymerase (PARP) inhibitors have emerged as one of the most exciting new treatments for ovarian cancer, particularly in women with BRCA1 or BRCA2 mutations or those without a functional homologous recombination repair pathway. Perhaps the most advantageous characteristic of PARP inhibitors is their mechanism of action, which targets cancer cells on the basis of their inherent deficiencies while seemingly avoiding normally functioning cells. Although health-care providers might assume a low toxicity profile because of their specific mechanism of action, PARP inhibitors are not completely benign and overall show a class effect adverse-event profile. Further complicating this situation, three different PARP inhibitors have been approved by the US Food and Drug Administration since 2014, each with their own specific indications and individual toxicity profiles. The diversity of adverse events seen both within and across this class of drug underscores the importance of having a comprehensive reference to help guide clinical decision making when treating patients. This Review characterises and compares all toxicities associated with each PARP inhibitor, both in monotherapy and in novel combinations with other drugs, with a particular focus on potential management strategies to help mitigate toxic effects. Although the excitement surrounding PARP inhibitors might certainly be warranted, a thorough understanding of all associated toxicities is imperative to ensure that patients can achieve maximal clinical benefit.

Asthma and poly(ADP-ribose) polymerase inhibition: a new therapeutic approach

Asthma is a chronic lung disease affecting people of all ages worldwide, and it frequently begins in childhood. Because of its chronic nature, it is characterized by pathological manifestations, including airway inflammation, remodeling, and goblet cell hyperplasia. Current therapies for asthma, including corticosteroids and beta-2 adrenergic agonists, are directed toward relieving the symptoms of the asthmatic response, with poor effectiveness against the underlying causes of the disease. Asthma initiation and progression depends on the T helper (Th) 2 type immune response carried out by a complex interplay of cytokines, such as interleukin (IL) 4, IL5, and IL13, and the signal transducer and activator of transcription 6. Much of the data resulting from different laboratories support the role of poly(ADP-ribose) polymerase (PARP) 1 and PARP14 activation in asthma. Indeed, PARP enzymes play key roles in the regulation and progression of the inflammatory asthma process because they affect the expression of genes and chemokines involved in the immune response. Consistently, PARP inhibition achievable either upon genetic ablation or by using pharmacological agents has shown a range of therapeutic effects against the disease. Indeed, in the last two decades, several preclinical studies highlighted the protective effects of PARP inhibition in various animal models of asthma. PARP inhibitors showed the ability to reduce the overall lung inflammation acting with a specific effect on immune cell recruitment and through the modulation of asthma-associated cytokines production. PARP inhibition has been shown to affect the Th1–Th2 balance and, at least in some aspects, the airway remodeling. In this review, we summarize and discuss the steps that led PARP inhibition to become a possible future therapeutic strategy against allergic asthma.

The Inhibitory Effects of HYDAMTIQ, a Novel PARP Inhibitor, on Growth in Human Tumor Cell Lines With Defective DNA Damage Response Pathways

The poly(ADP-ribose) polymerase (PARP) enzymes play a key role in the regulation of cellular processes (e.g., DNA damage repair, genomic stability). It has been shown that PARP inhibitors (PARPIs) are selectively cytotoxic against cells having dysfunctions in genes involved in DNA repair mechanisms (synthetic lethality). Drug-induced PARP inhibition potentiates the activity of anticancer drugs such as 5-fluorouracil in enhancing DNA damage, whose repair involves PARP-1 activity. The aim of this study was to evaluate the inhibitory effects of a novel PARPI, HYDAMTIQ, on growth in human tumor cell lines characterized by different features with regard to DNA damage response pathways (BRCA mutational status, microsatellite status, and ATM expression level) and degree of sensitivity/resistance to 5-fluorouracil. HYDAMTIQ showed a more potent inhibitory effect on cell growth in a BRCA2 mutant cell line (CAPAN-1) compared with wild-type cells (C2-6, C2-12, and C2-14 CAPAN-1 clones, and MCF-7). No statistically significant difference was observed after HYDAMTIQ exposure between cells having a different MS status or a different MRE11 mutational status. HYDAMTIQ induced greater antiproliferative effects in SW620 cells expressing a low level of ATM than in H630 cells expressing a high level of ATM. Finally, the combination of HYDAMTIQ and 5-fluorouracil exerted a synergistic effect on the inhibition of SW620 cell growth and an antagonistic effect on that of H630 cell growth. Our results show that the novel PARP inhibitor HYDAMTIQ potently inhibits the growth of human tumor cells with defective DNA damage response pathways and exerts synergistic cytotoxicity in combination with 5-fluorouracil. These data provide relevant examples of synthetic lethality and evidence for further development of this novel PARPI.

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.

Advance of antioxidants in asthma treatment

Asthma is an allergic disease, characterized as a recurrent airflow limitation, airway hyperreactivity, and chronic inflammation, involving a variety of cells and cytokines. Reactive oxygen species have been proven to play an important role in asthma. The pathogenesis of oxidative stress in asthma involves an imbalance between oxidant and antioxidant systems that is caused by environment pollutants or endogenous reactive oxygen species from inflammation cells. There is growing evidence that antioxidant treatments that include vitamins and food supplements have been shown to ameliorate this oxidative stress while improving the symptoms and decreasing the severity of asthma. In this review, we summarize recent studies that are related to the mechanisms and biomarkers of oxidative stress, antioxidant treatments in asthma.

Airway remodeling in asthma: what really matters

Airway remodeling is generally quite broadly defined as any change in composition, distribution, thickness, mass or volume and/or number of structural components observed in the airway wall of patients relative to healthy individuals. However, two types of airway remodeling should be distinguished more clearly: (1) physiological airway remodeling, which encompasses structural changes that occur regularly during normal lung development and growth leading to a normal mature airway wall or as an acute and transient response to injury and/or inflammation, which ultimately results in restoration of a normal airway structures; and (2) pathological airway remodeling, which comprises those structural alterations that occur as a result of either disturbed lung development or as a response to chronic injury and/or inflammation leading to persistently altered airway wall structures and function. This review will address a few major aspects: (1) what are reliable quantitative approaches to assess airway remodeling? (2) Are there any indications supporting the notion that airway remodeling can occur as a primary event, i.e., before any inflammatory process was initiated? (3) What is known about airway remodeling being a secondary event to inflammation? And (4), what can we learn from the different animal models ranging from invertebrate to primate models in the study of airway remodeling? Future studies are required addressing particularly pheno-/endotype-specific aspects of airway remodeling using both endotype-specific animal models and “endotyped” human asthmatics. Hopefully, novel in vivo imaging techniques will be further advanced to allow monitoring development, growth and inflammation of the airways already at a very early stage in life.

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 treatment in a nonconventional experimental mouse model of chronic asthma

Allergic asthma is an immunological disease that occurs as a consequence of aeroallergen exposure. Inhibition of poly(ADP-ribose) polymerases (PARPs) in conventional models of asthma-like reaction has emerged as an effective anti-inflammatory and airway remodeling intervention. In a house dust mite (HDM) exposure mouse model, we investigated the impact of PARP inhibition on allergic airway inflammation, sensitization, and remodeling. Mice were intranasally exposed to a HDM extract for 5 days per week for up to 5 weeks. Mice were administered, or not, by PARP inhibitors 3-aminobenzamide (3-ABA) or 5-aminoisoquinolinone (5-AIQ) during the last 2 weeks of HDM treatment. Mice treated with PARP inhibitors after HDM stimulation showed a significant decrease in the number of total cells and eosinophils detectable in the bronchoalveolar lavage fluid as compared with the HDM-stimulated ones. In vitro HDM-stimulated splenocyte culture produced considerable amounts of the Th2 cytokines that were not affected by treatment with PARP inhibitors. Immunoglobulin levels in the serum were also unchanged. In the lung tissue, collagen deposition was decreased, whereas α-smooth muscle actin thickening was not significantly affected. Moreover, in HDM-stimulated PARP inhibitor-treated groups, we found a downregulation in the activation of signal transducer and activator of trascription-6 (STAT-6) and a significant decrease in the mRNA levels of C-C motif chemokine 11 (CCL11). In this mouse model of chronic asthma PARP inhibition treatment, although it does not affect sensitization, it effectively reduces the allergic airway inflammation and affects the remodeling through a mechanism involving STAT6 and CCL11.

PARP is activated in human asthma and its inhibition by olaparib blocks house dust mite-induced disease in mice

The present study establishes poly(ADP-ribose)polymerase's (PARP's) role in chronic asthma, demonstrates that it is activated in human asthma, increases the clinical relevance of targeting PARP for blocking or preventing chronic asthma in humans and presents olaparib as a likely candidate drug.

Our laboratory established a role for poly(ADP-ribose)polymerase (PARP) in asthma. To increase the clinical significance of our studies, it is imperative to demonstrate that PARP is actually activated in human asthma, to examine whether a PARP inhibitor approved for human testing such as olaparib blocks already-established chronic asthma traits in response to house dust mite (HDM), a true human allergen, in mice and to examine whether the drug modulates human cluster of differentiation type 4 (CD4⁺) T-cell function. To conduct the study, human lung specimens and peripheral blood mononuclear cells (PBMCs) and a HDM-based mouse asthma model were used. Our results show that PARP is activated in PBMCs and lung tissues of asthmatics. PARP inhibition by olaparib or gene knockout blocked established asthma-like traits in mice chronically exposed to HDM including airway eosinophilia and hyper-responsiveness. These effects were linked to a marked reduction in T helper 2 (Th2) cytokine production without a prominent effect on interferon (IFN)-γ or interleukin (IL)-10. PARP inhibition prevented HDM-induced increase in overall cellularity, weight and CD4⁺ T-cell population in spleens of treated mice whereas it increased the T-regulatory cell population. In CD3/CD28-stimulated human CD4 ⁺T-cells, olaparib treatment reduced Th2 cytokine production potentially by modulating GATA binding protein-3 (gata-3)/IL-4 expression while moderately affecting T-cell proliferation. PARP inhibition inconsistently increased IL-17 in HDM-exposed mice and CD3/CD28-stimulated CD4⁺ T cells without a concomitant increase in factors that can be influenced by IL-17. In the present study, we provide evidence for the first time that PARP-1 is activated in human asthma and that its inhibition is effective in blocking established asthma in mice.

PARP inhibition by olaparib or gene knockout blocks asthma-like manifestation in mice by modulating CD4(+) T cell function

Background

An important portion of asthmatics do not respond to current therapies. Thus, the need for new therapeutic drugs is urgent. We have demonstrated a critical role for PARP in experimental asthma. Olaparib, a PARP inhibitor, was recently introduced in clinical trials against cancer. The objective of the present study was to examine the efficacy of olaparib in blocking established allergic airway inflammation and hyperresponsiveness similar to those observed in human asthma in animal models of the disease.

Methods

We used ovalbumin (OVA)-based mouse models of asthma and primary CD4⁺ T cells. C57BL/6J WT or PARP-1^−/− mice were subjected to OVA sensitization followed by a single or multiple challenges to aerosolized OVA or left unchallenged. WT mice were administered, i.p., 1 mg/kg, 5 or 10 mg/kg of olaparib or saline 30 min after each OVA challenge.

Results

Administration of olaparib in mice 30 min post-challenge promoted a robust reduction in airway eosinophilia, mucus production and hyperresponsiveness even after repeated challenges with ovalbumin. The protective effects of olaparib were linked to a suppression of Th2 cytokines eotaxin, IL-4, IL-5, IL-6, IL-13, and M-CSF, and ovalbumin-specific IgE with an increase in the Th1 cytokine IFN-γ. These traits were associated with a decrease in splenic CD4⁺ T cells and concomitant increase in T-regulatory cells. The aforementioned traits conferred by olaparib administration were consistent with those observed in OVA-challenged PARP-1^−/− mice. Adoptive transfer of Th2-skewed OT-II-WT CD4⁺ T cells reversed the Th2 cytokines IL-4, IL-5, and IL-10, the chemokine GM-CSF, the Th1 cytokines IL-2 and IFN-γ, and ovalbumin-specific IgE production in ovalbumin-challenged PARP-1^−/−mice suggesting a role for PARP-1 in CD4⁺ T but not B cells. In ex vivo studies, PARP inhibition by olaparib or PARP-1 gene knockout markedly reduced CD3/CD28-stimulated gata-3 and il4 expression in Th2-skewed CD4⁺ T cells while causing a moderate elevation in t-bet and ifn-γ expression in Th1-skewed CD4⁺ T cells.

Conclusions

Our findings show the potential of PARP inhibition as a viable therapeutic strategy and olaparib as a likely candidate to be tested in human asthma clinical trials.

Investigating the allosteric reverse signalling of PARP inhibitors with microsecond molecular dynamic simulations and fluorescence anisotropy

The inhibition of the poly(ADP-ribose) polymerase (PARP) family members is a strategy pursued for the development of novel therapeutic agents in a range of diseases, including stroke, cardiac ischemia, cancer, inflammation and diabetes. Even though some PARP-1 inhibitors have advanced to clinical setting for cancer therapy, a great deal of attention is being devoted to understand the polypharmacology of current PARP inhibitors. Besides blocking the catalytic activity, recent works have shown that some PARP inhibitors exhibit a poisoning activity, by trapping the enzyme at damaged sites of DNA and forming cytotoxic complexes. In this study we have used microsecond molecular dynamics to study the allosteric reverse signalling that is at the basis of such an effect. We show that Olaparib, but not Veliparib and HYDAMTIQ, is able to induce a specific conformational drift of the WGR domain of PARP-1, which stabilizes PARP-1/DNA complex through the locking of several salt bridge interactions. Fluorescence anisotropy assays support such a mechanism, providing the first experimental evidence that HYDAMTIQ, a potent PARP inhibitor with neuroprotective properties, is less potent than Olaparib to trap PARP-1/DNA complex.