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

Transcriptional regulation mechanism of PARP1 and its application in disease treatment

Poly (ADP-ribose) polymerase 1 (PARP1) is a multifunctional nuclear enzyme that catalyzes poly-ADP ribosylation in eukaryotic cells. In addition to maintaining genomic integrity, this nuclear enzyme is also involved in transcriptional regulation. PARP1 can trigger and maintain changes in the chromatin structure and directly recruit transcription factors. PARP1 also prevents DNA methylation. However, most previous reviews on PARP1 have focused on its involvement in maintaining genome integrity, with less focus on its transcriptional regulatory function. This article comprehensively reviews the transcriptional regulatory function of PARP1 and its application in disease treatment, providing new ideas for targeting PARP1 for the treatment of diseases other than cancer.

miR-21-5p Modulates Airway Inflammation and Epithelial-Mesenchymal Transition Processes in a Mouse Model of Combined Allergic Rhinitis and Asthma Syndrome

INTRODUCTION

Combined allergic rhinitis and asthma syndrome (CARAS) is a concurrent allergic symptom of diseases of allergic rhinitis and asthma. However, the mechanism of CARAS remains unclear. The study aimed to investigate the impact of microRNA-21 (miR-21) on CARAS via targeting poly (ADP-ribose) polymerase-1 (PARP-1) and phosphoinositide 3-kinase (PI3K)/AKT pathways.

METHODS

The levels of miR-21-5p and PARP-1 in CARAS patients were detected by quantitative reverse transcription polymerase chain reaction and enzyme-linked immunosorbent assay (ELISA). An ovalbumin-sensitized mouse model of CARAS was established. And knock down of miR-21-5p was constructed by intranasally administering with miR-21-5p shRNA-encoding adeno-associated virus vector. Airway resistance and airway inflammatory response were detected. ELISA was used to evaluate IL-4/IL-5/IL-13 levels in bronchoalveolar lavage fluid (BALF). Expression levels of E-cadherin, fibronectin, and α-SMA were determined using Western blotting. The levels of PARP-1 and the activation of PI3K/AKT were assayed.

RESULTS

Downregulation of miR-21-5p relieved pathophysiological symptoms of asthma including airway hyperreactivity and inflammatory cell infiltration. Downregulation of miR-21-5p significantly reduced the levels of IL4, IL-5, and IL-13 in BALF. Additionally, downregulation of miR-21-5p inhibited the epithelial-mesenchymal transition (EMT) process in CARAS mice. Furthermore, miR-21-5p regulated PARP-1 and was involved in PI3K/AKT activation in CARAS mice.

CONCLUSION

Downregulation of miR-21-5p ameliorated CARAS-associated lung injury by alleviating airway inflammation, inhibiting the EMT process, and regulating PARP-1/PI3K/AKT in a mouse model of CARAS.

Poly-(ADP-ribose) polymerases inhibition by olaparib attenuates activities of the NLRP3 inflammasome and of NF-κB in THP-1 monocytes

Poly-(ADP-ribose) polymerases (PARPs) are a protein family that make ADP-ribose modifications on target genes and proteins. PARP family members contribute to the pathogenesis of chronic inflammatory diseases, including atherosclerosis, in which monocytes/macrophages play important roles. PARP inhibition is protective against atherosclerosis. However, the mechanisms by which PARP inhibition exerts this beneficial effect are not well understood. Here we show that in THP-1 monocytes, inhibition of PARP by olaparib attenuated oxidized low-density lipoprotein (oxLDL)-induced protein expressions of nucleotide-binding oligomerization domain, leucine-rich repeat and pyrin domain-containing-3 (NLRP3) inflammasome components: NLRP3, apoptosis-associated speck-like protein containing a caspase activation and recruitment domain (ASC), and caspase-1. Consistent with this effect, olaparib decreased oxLDL-enhanced interleukin (IL)-1β and IL-18 protein expression. Olaparib also decreased the oxLDL-mediated increase in mitochondrial reactive oxygen species. Similar to the effects of the NLRP3 inhibitor, MCC950, olaparib attenuated oxLDL-induced adhesion of monocytes to cultured human umbilical vein endothelial cells and reduced foam cell formation. Furthermore, olaparib attenuated the oxLDL-mediated activation of nuclear factor (NF)-κB through the oxLDL-mediated increase in IκBα phosphorylation and assembly of NF-κB subunits, demonstrated by co-immunoprecipitation of IκBα with RelA/p50 and RelB/p52 subunits. Moreover, PARP inhibition decreased oxLDL-mediated protein expression of a NF-κB target gene, VCAM1, encoding vascular cell adhesion molecule-1. This finding indicates an important role for NF-κB activity in PARP-mediated activation of the NLRP3 inflammasome. Thus, PARP inhibition by olaparib attenuates NF-κB and NLRP3 inflammasome activities, lessening monocyte cell adhesion and macrophage foam cell formation. These inhibitory effects of olaparib on NLRP3 activity potentially protect against atherosclerosis.

The role of inflammatory factors and T-cell subsets in the diagnosis of recurrence in epithelial ovarian cancer patients and the effect of olaparin treatment on them

BACKGROUND

The aim of the study is to investigate the role of serum inflammatory factors and T-cell subsets in the diagnosis of recurrence in epithelial ovarian cancer patients and the effect of olaparib on inflammatory factor and T-lymphocyte subsets in patients with recurrent epithelial ovarian cancer.

METHODS

In this study, 100 patients diagnosed as recurrent epithelial ovarian cancer in our hospital and 100 patients without recurrent epithelial ovarian cancer in the same period were selected. According to the treatment plan, the recurrent patients were divided into conventional therapy group (Paclitaxel and Carboplatin) and combined therapy group (Paclitaxel, Carboplatin, and olaparib). The levels of serum inflammatory factors were evaluated by enzyme-linked immunosorbent assay. The peripheral blood T-lymphocyte subsets in each group were detected by flow cytometry.

RESULTS

Compared with nonrecurrent patients, recurrent patients have higher serum interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) levels (p < .05), and lower interferon-γ (IFN-γ) level and the CD4+/CD8+ ratio. After adjusting for confounding factors, the results showed that the serum IL-6, IFN-γ, and TNF-α levels were influencing factors of recurrence in epithelial ovarian cancer patients. The area under the receiver operating curve and the sensitivity of serum TNF-α in predicting ovarian cancer recurrence were higher than those of IL-6 and IFN-γ. After secondary chemotherapy and/or olaparib maintenance treatment, the IL-6 (p < .001) and TNF-α (p < .001) levels in combined therapy group were lower than those in the conventional therapy, whereas the IFN-γ level (p < .001), the CD4+ T-cell proportion (p = .0069) and the CD4+/CD8+ ratio (p = .0201) were higher than those in the conventional therapy.

CONCLUSION

The serum IL-6, TNF-α, and IFN-γ levels were closely related to the recurrence of ovarian cancer. Olaparib maintenance treatment can significantly decrease the IL-6 and TNF-α level, and increase IFN-γ level and the CD4+/CD8+ ratio in patients with recurrent ovarian cancer.

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.

A Double-Edged Sword: The Two Faces of PARylation

Poly ADP-ribosylation (PARylation) is a post-translational modification process. Following the discovery of PARP-1, numerous studies have demonstrated the role of PARylation in the DNA damage and repair responses for cellular stress and DNA damage. Originally, studies on PARylation were confined to PARP-1 activation in the DNA repair pathway. However, the interplay between PARylation and DNA repair suggests that PARylation is important for the efficiency and accuracy of DNA repair. PARylation has contradicting roles; however, recent evidence implicates its importance in inflammation, metabolism, and cell death. These differences might be dependent on specific cellular conditions or experimental models used, and suggest that PARylation may play two opposing roles in cellular homeostasis. Understanding the role of PARylation in cellular function is not only important for identifying novel therapeutic approaches; it is also essential for gaining insight into the mechanisms of unexplored diseases. In this review, we discuss recent reports on the role of PARylation in mediating diverse cellular functions and homeostasis, such as DNA repair, inflammation, metabolism, and cell death.

Olaparib, a PARP-1 inhibitor, protects retinal cells from ocular hypertension-associated oxidative damage

Glaucoma is the most common cause of irreversible blindness worldwide. Elevated intraocular pressure (IOP) and relative hypoxia in the retina stimulate the production of reactive oxygen species (ROS), which, in turn, puts the retina and optic nerve under chronic oxidative stress. Emerging evidence has shown that oxidative stress can trigger PARP-1 overactivation, mitochondrial-associated endoplasmic reticulum membrane (MAM) dysregulation, and NLRP3 activation. Oxidative damage can trigger inflammasome activation, and NLRP3 is the only inflammasome associated with MAM dysregulation. In addition, multiple transcription factors are located on the MAM. This study aimed to investigate the protective effects and underlying mechanisms of a PARP-1 inhibitor (olaparib) against chronic ocular hypertension-associated retinal cell damage. We also mimicked hypoxic stimulation of a retinal precursor cell line by exposing the cells to 0.2% O₂in vitro. We discovered that chronic ocular hypertension (COH) induces oxidative damage and MAM dysregulation in the retinal ganglion cells (RGCs). The protein levels of cleaved-PARP and NLRP3 were upregulated in the retinas of the COH rats. Olaparib, a PARP-1 inhibitor, alleviated COH-induced RGC loss, retinal morphological alterations, and photopic negative response amplitude reduction. Olaparib also relieved hypoxic stimulation-induced loss of cell viability and MAM dysregulation. Additionally, some indicators of mitochondrial performance, such as reactive oxygen species accumulation, mitochondrial Ca²⁺ influx, and mitochondrial membrane potential collapse, decreased after olaparib treatment. Olaparib attenuated the hypoxia-induced upregulation of NLRP3 protein levels as well as the phosphorylation of ERK1/2 and histone H2A.X. These results suggest that olaparib protects RGCs from chronic intraocular pressure elevation in vivo and alleviates the abnormal MAM dysregulation and mitochondrial dysfunction caused by hypoxia in vitro. This protection may be achieved by inhibiting PARP-1 overactivation, NLRP3 upregulation, and phosphorylation of ERK1/2.

A Real-World Disproportionality Analysis of Olaparib: Data Mining of the Public Version of FDA Adverse Event Reporting System

Background

Olaparib, the world’s first poly ADP-ribose polymerase (PARP) inhibitor (PARPi), has been approved for treatment of ovarian cancer, breast cancer, pancreatic cancer and prostate cancer by FDA. The current study was to assess olaparib-related adverse events (AEs) of real-world through data mining of the US Food and Drug Administration Adverse Event Reporting System (FAERS).

Methods

Disproportionality analyses, including the reporting odds ratio (ROR), the proportional reporting ratio (PRR), the Bayesian confidence propagation neural network (BCPNN) and the multi-item gamma Poisson shrinker (MGPS) algorithms were employed to quantify the signals of olaparib-associated AEs.

Results

Out of 8,450,009 reports collected from the FAERS database, 6402 reports of olaparib-associated AEs were identified. A total of 118 significant disproportionality preferred terms (PTs) conforming to the four algorithms simultaneously were retained. The most common AEs included anemia, thrombocytopenia, nausea, decreased appetite, blood creatinine increased and dermatomyositis, which were corresponding to those reported in the specification and clinical trials. Unexpected significant AEs as interstitial lung disease, Pneumocystis jirovecii pneumonia, folate deficiency, renal impairment and intestinal obstruction might also occur. The median onset time of olaparib-related AEs was 61 days (interquartile range [IQR] 14–182 days), and most of the cases occurred within the first 1 month after olaparib initiation.

Conclusion

Results of our study were consistent with clinical observations, and we also found potential new and unexpected AEs signals for olaparib, suggesting prospective clinical studies were needed to confirm these results and illustrate their relationship. Our results could provide valuable evidence for further safety studies of olaparib.

PARP-1 regulates inflammasome activity by poly-ADP-ribosylation of NLRP3 and interaction with TXNIP in primary macrophages

Poly(ADP-ribose) polymerase-1 (PARP-1) plays an essential role in DNA repair by catalyzing the polymerization of ADP-ribose unit to target proteins. Several studies have shown that PARP-1 can regulate inflammatory responses in various disease models. The intracellular Nod-like receptor NLRP3 has emerged as the most crucial innate immune receptor because of its broad specificity in mediating immune response to pathogen invasion and danger signals associated with cellular damage. In our study, we found NLRP3 stimuli-induced caspase-1 maturation and IL-1β production were impaired by PARP-1 knockout or PARP-1 inhibition in bone marrow-derived macrophages (BMDM). The step 1 signal of NLRP3 inflammasome activation was not affected by PARP-1 deficiency. Moreover, ATP-induced cytosolic ROS production was lower in Parp-1-/- BMDM, resulting in the decreased inflammasome complex assembly. PARP-1 can translocate to cytosol upon ATP stimulation and trigger the PARylation modification on NLRP3, leading to NLRP3 inflammasome assembly. PARP-1 was also a bridge between NLRP3 and thioredoxin-interacting protein (TXNIP) and participated in NLRP3/TXNIP complex formation for inflammasome activation. Overall, PARP-1 positively regulates NLRP3 inflammasome activation via increasing ROS production and interaction with TXNIP and NLRP3, leading to PARylation of NLRP3. Our data demonstrate a novel regulatory mechanism for NLRP3 inflammasome activation by PARP-1. Therefore, PARP-1 can serve as a potential target in the treatment of IL-1β associated inflammatory diseases.

The Interaction Between Pulmonary Fibrosis and COVID-19 and the Application of Related Anti-Fibrotic Drugs

COVID-19 is a highly contagious respiratory disease, which mainly affects the lungs. Critically ill patients are easily complicated by cytokine storms, acute respiratory distress syndrome (ARDS), and respiratory failure, which seriously threaten their lives. Pulmonary fibrosis (PF) is a common interstitial lung disease, and its pathogenesis may involve the participation of a variety of immune cells and inflammatory factors. Current studies have shown that patients with COVID-19 may be complicated by pulmonary fibrosis, and patients with pulmonary fibrosis may also be at higher risk of contracting COVID-19 than healthy people. Pulmonary fibrosis is an important risk factor leading to the aggravation of COVID-19 disease. COVID-19 complicated by cytokine storm and ARDS mechanism pathways are similar to the pathogenesis of pulmonary fibrosis. The potential interaction between pulmonary fibrosis and COVID-19 can cause acute exacerbation of the patient's condition, but the potential mechanism between the two has not been fully elucidated. Most of the drug treatment programs for COVID-19-related pulmonary fibrosis are currently formulated about the relevant guidelines for idiopathic pulmonary fibrosis (IPF), and there is no clear drug treatment program recommendation. This article aims to summarize the relevant mechanism pathways of COVID-19 and pulmonary fibrosis, explore the interrelationships and possible mechanisms, and discuss the value and risks of existing and potential COVID-19-related pulmonary fibrosis treatment drugs, to provide reference for anti-fibrosis treatment for patients.

The effects of BRL-50481 on ovalbumin-induced asthmatic lung inflammation exacerbated by co-exposure to Asian sand dust in the murine model

Asian sand dust (ASD), which mainly originates in China and Mongolia in the spring and blows into Korea, can exacerbate respiratory and immunological diseases. This study aims to observe effects of co-exposure to ASD on ovalbumin (OVA)-induced asthmatic lung inflammation and of treatment with a phosphodiesterase 7 (PDE7) inhibitor in a mouse model. The challenge with OVA increased airway hyperresponsiveness (AHR) and inflammatory cell infiltration into the lung tissue. Interleukin (IL)-13, tumor necrosis factor-alpha, monocyte-protein-1, mucin, and antigen-specific IgE and IgG1 production increased in mouse serum. The co-exposure of ASD significantly exacerbated these effects in this asthma model. Notably, the administration of a PDE7 inhibitor, BRL-50481 (BRL), significantly reduced AHR, infiltration of inflammatory cells into the lungs, and the levels of type 2 T helper cell-related cytokines, antigen-specific immunoglobulins, and mucin. Thus, the administration of BRL ameliorated OVA-induced allergic asthmatic responses exacerbated by co-exposure to ASD. This study suggests that PDE7 inhibition can be a therapeutic strategy for inflammatory lung diseases and asthma via the regulation of T lymphocytes and reduction of IL-13, and, consequently, mucin production.

IL-1β augments TGF-β inducing epithelial-mesenchymal transition of epithelial cells and associates with poor pulmonary function improvement in neutrophilic asthmatics

Background

Neutrophilic asthmatics (NA) have less response to inhaled corticosteroids. We aimed to find out the predictor of treatment response in NA.

Methods

Asthmatics (n = 115) and healthy controls (n = 28) underwent clinical assessment during 6-month follow-up with standardized therapy. Asthmatics were categorized by sputum differential cell count. The mRNA expressions were measured by RT-qPCR for sputum cytokines (IFN-γ, IL-1β, IL-27, FOXP3, IL-17A, and IL-5). The protein of IL-1β in sputum supernatant was detected by ELISA. Reticular basement membranes (RBM) were measured in the biopsy samples. The role and signaling pathways of IL-1β mediating the epithelial-mesenchymal transition (EMT) process were explored through A549 cells.

Results

NA had increased baseline sputum cell IL-1β expression compared to eosinophilic asthmatics (EA). After follow-up, NA had less improvement in FEV₁ compared to EA. For all asthmatics, sputum IL-1β mRNA was positively correlated with protein expression. Sputum IL-1β mRNA and protein levels were negatively correlated to FEV₁ improvement. After subgrouping, the correlation between IL-1β mRNA and FEV₁ improvement was significant in NA but not in EA. Thickness of RBM in asthmatics was greater than that of healthy controls and positively correlated with neutrophil percentage in bronchoalveolar lavage fluid. In vitro experiments, the process of IL-1β augmenting TGF-β1-induced EMT cannot be abrogated by glucocorticoid or montelukast sodium, but can be reversed by MAPK inhibitors.

Conclusions

IL-1β level in baseline sputum predicts the poor lung function improvement in NA. The potential mechanism may be related to IL-1β augmenting TGF-β1-induced steroid-resistant EMT through MAPK signaling pathways.

Trial registration: This study was approved by the Ethics Committee of Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology (IRB ID: 20150406).

Supplementary Information

The online version contains supplementary material available at 10.1186/s12931-021-01808-7.

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.

Modulation of Inflammasome and Pyroptosis by Olaparib, a PARP-1 Inhibitor, in the R6/2 Mouse Model of Huntington's Disease

Pyroptosis is a type of cell death that is caspase-1 (Casp-1) dependent, which leads to a rapid cell lysis, and it is linked to the inflammasome. We recently showed that pyroptotic cell death occurs in Huntington’s disease (HD). Moreover, we previously described the beneficial effects of a PARP-1 inhibitor in HD. In this study, we investigated the neuroprotective effect of Olaparib, an inhibitor of PARP-1, in the mouse model of Huntington’s disease. R6/2 mice were administered Olaparib or vehicle from pre-symptomatic to late stages. Behavioral studies were performed to investigate clinical effects of the compound. Immunohistochemical and Western blotting studies were performed to evaluate neuroprotection and the impact of the compound on the pathway of neuronal death in the HD mice. Our results indicate that Olaparib administration starting from the pre-symptomatic stage of the neurodegenerative disease increased survival, ameliorated the neurological deficits, and improved clinical outcomes in neurobehavioral tests mainly by modulating the inflammasome activation. These results suggest that Olaparib, a commercially available drug already in use as an anti-neoplastic compound, exerts a neuroprotective effect and could be a useful pharmaceutical agent for Huntington’s disease therapy.

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.

Role of CD38/cADPR signaling in obstructive pulmonary diseases

The worldwide socioeconomical burden associated with chronic respiratory diseases is substantial. Enzymes involved in the metabolism of nicotinamide adenine dinucleotide (NAD) are increasingly being implicated in chronic airway diseases. One such enzyme, CD38, utilizes NAD to produce several metabolites, including cyclic ADP ribose (cADPR), which is involved in calcium signaling in airway smooth muscle (ASM). Upregulation of CD38 in ASM caused by exposure to cytokines or allergens leads to enhanced calcium mobilization by agonists and the development of airway hyperresponsiveness (AHR) to contractile agonists. Glucocorticoids and microRNAs can suppress CD38 expression in ASM, whereas cADPR antagonists such as 8Br-cADPR can directly antagonize intracellular calcium mobilization. Bronchodilators act via CD38-independent mechanisms. CD38-dependent mechanisms could be developed for chronic airway diseases therapy.

Multifaceted Role of PARP-1 in DNA Repair and Inflammation: Pathological and Therapeutic Implications in Cancer and Non-Cancer Diseases

PARP-1 (poly(ADP-ribose)-polymerase 1), mainly known for its protective role in DNA repair, also regulates inflammatory processes. Notably, defects in DNA repair and chronic inflammation may both predispose to cancer development. On the other hand, inhibition of DNA repair and inflammatory responses can be beneficial in cancer therapy and PARP inhibitors are currently used for their lethal effects on tumor cells. Furthermore, excess of PARP-1 activity has been associated with many tumors and inflammation-related clinical conditions, including asthma, sepsis, arthritis, atherosclerosis, and neurodegenerative diseases, to name a few. Activation and inhibition of PARP represent, therefore, a double-edged sword that can be exploited for therapeutic purposes. In our review, we will discuss recent findings highlighting the composite multifaceted role of PARP-1 in cancer and inflammation-related diseases.