Anti-inflammatory effects of PJ34, a poly(ADP-ribose) polymerase inhibitor, in transient focal cerebral ischemia in mice

Formononetin alleviates cerebral ischemia-reperfusion injury in rats by targeting the PARP-1/PARG/Iduna signaling pathway

Formononetin has been demonstrated to protect against cerebral ischemia-reperfusion injury, however its mechanism has to be further researched. This study examined the effect of formononetin on cerebral ischemia-reperfusion injury in rats using the PARP-1/PARG/Iduna signaling pathway. In male SD rats, a model of cerebral ischemia-reperfusion injury was developed. Animals were randomly assigned to one of eight groups: Sham operation, Sham operation + formononetin, MCAO, MCAO + formononetin, PARP inhibitor (PJ34) + MCAO, formononetin + PJ34 + MCAO, PARG inhibitor (Ethacridine lactate) + MCAO, and ethacridine lactate + formononetin. The neurological deficit test, TTC staining, HE staining, Nissl staining, TUNEL staining, and western blotting were utilized to assess formononetin's protective effects in MCAO rats. The data show that formononetin can effectively alleviate neurological dysfunction and pathological changes in brain tissue in rats with cerebral ischemia-reperfusion injury, reduce the area of cerebral infarction and neuronal apoptosis, decrease the protein levels of PARP-1, PARG, Caspase-3, P53, and AIF in brain tissue, and increase the protein levels of Iduna and p-AKT. As a result, we concluded that formononetin improves brain ischemia-reperfusion injury in rats by modulating the PARP-1/PARG/Iduna signaling pathway.

Involvement of Calpain in Neurovascular Unit Damage through Up-regulating PARP-NF-κB Signaling during Experimental Ischemic Stroke

Calpain and PARP-NF-κB signaling are reported to participate in the ischemic brain injury. In this study, it was investigated whether calpain was contributed to the neurovascular unit (NVU) damage through up-regulating PARP-NF-κB signaling during experimental ischemic stroke. Male Sprague-Dawley rats were suffered from 90 min of middle cerebral artery occlusion, followed by reperfusion. The NVU damage was evaluated by the permeability of blood-brain barrier (BBB), the degradation of proteins in extracellular matrix and tight junctions, and ultrastructural changes. The inflammatory response was determined by the expression of inflammatory genes driven by PARP-NF-κB signaling and the activities of myeloperoxidase (MPO). Treatment with MDL 28,170, a calpain inhibitor, improved neurological functions, reduced TUNEL staining index, lessened brain swelling, and decreased infarct volume in ischemic rats. Moreover, it reduced the BBB permeability, enhanced the levels of laminin, collagen IV and occludin, and attenuated the ultrastructural damage of NVU in penumbra and core after induction of ischemia. Meanwhile, it enhanced the levels of cytosolic IκBα, lessened the levels of nuclear PARP and NF-κB p65, reduced the levels of ICAM-1, TNF-α, IL-1β, MMP-9, and MMP-2,and suppressed the activities of MPO in penumbra and core. These data showed that calpain inhibition suppressed PARP-NF-κB signaling-mediated inflammatory response, reduced NVU damage, and protected brain against ischemic stroke, suggesting the involvement of calpain in the NVU damage through up-regulating PARP-NF-κB signaling during brain ischemia.

DNA Double Strand Break and Response Fluorescent Assays: Choices and Interpretation

Accurately characterizing DNA double-stranded breaks (DSBs) and understanding the DNA damage response (DDR) is crucial for assessing cellular genotoxicity, maintaining genomic integrity, and advancing gene editing technologies. Immunofluorescence-based techniques have proven to be invaluable for quantifying and visualizing DSB repair, providing valuable insights into cellular repair processes. However, the selection of appropriate markers for analysis can be challenging due to the intricate nature of DSB repair mechanisms, often leading to ambiguous interpretations. This comprehensively summarizes the significance of immunofluorescence-based techniques, with their capacity for spatiotemporal visualization, in elucidating complex DDR processes. By evaluating the strengths and limitations of different markers, we identify where they are most relevant chronologically from DSB detection to repair, better contextualizing what each assay represents at a molecular level. This is valuable for identifying biases associated with each assay and facilitates accurate data interpretation. This review aims to improve the precision of DSB quantification, deepen the understanding of DDR processes, assay biases, and pathway choices, and provide practical guidance on marker selection. Each assay offers a unique perspective of the underlying processes, underscoring the need to select markers that are best suited to specific research objectives.

An auto-photoacoustic melanin-based drug delivery nano-platform for self-monitoring of acute kidney injury therapy via a triple-collaborative strategy

Rhabdomyolysis-induced acute kidney injury (AKI) is closely related to toxic reactive oxygen species (ROS), apoptosis, and inflammation. Excessive activation of poly (ADP-ribose) polymerase-l (PARP-1) by ROS can cause mitochondrial dysfunction and release of the proapoptotic protein AIF, which triggers an intrinsic PARP-1-dependent cell death program. Considering these characteristics of rhabdomyolysis-induced AKI, we developed a targeting nanodrug delivery platform by loading PJ34 and coupling anti-GPR97 with melanin nanoparticles (GMP nanoparticles) that could realize photoacoustic self-monitoring and triple-collaborative treatment (antioxidant, antiapoptotic, and anti-inflammatory). The nanoparticles exhibited good dispersibility, solubility, and broad-spectrum ROS scavenging ability. In vitro experiments revealed high biocompatibility of the GMP nanoparticles and strong ability of scavenging multiple toxic ROS, antiapoptotic activity, and anti-inflammatory activity. Because melanin nanoparticles possess inherent photoacoustic (PA) imaging capability, they can not only serve as a drug carrier but also perform self-monitoring for real-time tracking of GMP biodistribution and renal uptake in a murine AKI model through PA imaging. In vivo experiments showed that the GMP nanoparticles could effectively reduce oxidative stress, apoptosis, and inflammatory response in mice with rhabdomyolysis-induced AKI, and the mechanism of alleviation was verified through western blot experiments. These results indicated that the nanoplatform could realize the targeted delivery and curative effect monitoring under the guidance of PA imaging, which is of great significance for the prevention and treatment of AKI. STATEMENT OF SIGNIFICANCE: : A targeting nanodrug delivery platform was developed by loading PJ34 and coupling anti-GPR97 with melanin nanoparticles (GMP nanoparticles) for photoacoustic self-monitoring and triple-collaborative treatment (antioxidant, antiapoptotic, and anti-inflammatory) of acute kidney injury (AKI). Further studies indicated that the Keap-1/Nrf2/HO-1 and PARP-1/AIF signaling pathways are involved in the therapeutic mechanisms to alleviate AKI. Immunohistochemical staining and routine blood test confirmed the anti-inflammatory performance of GMP nanoparticles. Compared to exogenous nanomaterials, we used endogenous melanin with broad ROS scavenging capacity as the nanocarrier and antioxidant, which not only overcomes the defects of high specificity, potential toxicity, low loading capacity, and high cost but also shows good biosafety and photoacoustic imaging performance in vivo.

Poly (ADP-ribose) polymerase: An Overview of Mechanistic Approaches and Therapeutic Opportunities in the Management of Stroke

Stroke is one of the leading causes of morbidity and mortality accompanied by blood supply loss to a particular brain area. Several mechanistic approaches such as inhibition of poly (ADP-ribose) polymerase, therapies against tissue thrombosis, and neutrophils lead to stroke's therapeutic intervention. Evidence obtained with the poly (ADP-ribose) polymerase (PARP) inhibition and animals having a deficiency of PARP enzymes; represented the role of PARP in cerebral stroke, ischemia/reperfusion, and neurotrauma. PARP is a nuclear enzyme superfamily with various isoforms, each with different structural domains and functions, and out of all, PARP-1 is the best-characterized member. It has been shown to perform multiple physiological as well as pathological processes, including its role in inflammation, oxidative stress, apoptosis, and mitochondrial dysfunction. The enzyme interacts with NF-κB, p53, and other transcriptional factors to regulate survival and cell death and modulates multiple downstream signaling pathways. Clinical trials have also been conducted using PARP inhibitors for numerous disorders and have shown positive results. However, additional information is yet to be established for the therapeutic intervention of PARP inhibitors in stroke. These agents' utilization appears to be challenging due to their unknown potential long-term side effects. PARP activity increased during ischemia, but its inhibition provided significant neuroprotection. Despite the increased interest in PARP as a pharmacological modulator for novel therapeutic therapies, the current review focused on stroke and poly ADP-ribosylation.

Pleiotropic role of PARP1: an overview

Poly (ADP-ribose) polymerase 1 (PARP1) protein is encoded by the PARP1 gene located on chromosome 1 (1q42.12) in human cells. It plays a crucial role in post-translational modification by adding poly (ADP-ribose) (PAR) groups to various proteins and PARP1 itself by utilizing nicotinamide adenine dinucleotide (NAD +) as a substrate. Since the discovery of PARP1, its role in DNA repair and cell death has been its identity. This is evident from an overwhelmingly high number of scientific reports in this regard. However, PARP1 also plays critical roles in inflammation, metabolism, tumor development and progression, chromatin modification and transcription, mRNA stability, and alternative splicing. In the present study, we attempted to compile all the scattered scientific information about this molecule, including the structure and multifunctional role of PARP1 in cancer and non-cancer diseases, along with PARP1 inhibitors (PARPis). Furthermore, for the first time, we have classified PARP1-mediated cell death for ease of understanding its role in cell death pathways.

Radiation-induced neuroinflammation: a potential protective role for poly(ADP-ribose) polymerase inhibitors?

Radiotherapy (RT) plays a fundamental role in the treatment of glioblastoma (GBM). GBM are notoriously invasive and harbor a subpopulation of cells with stem-like features which exhibit upregulation of the DNA damage response (DDR) and are radioresistant. High radiation doses are therefore delivered to large brain volumes and are known to extend survival but also cause delayed toxicity with 50%-90% of patients developing neurocognitive dysfunction. Emerging evidence identifies neuroinflammation as a critical mediator of the adverse effects of RT on cognitive function. In addition to its well-established role in promoting repair of radiation-induced DNA damage, activation of poly(ADP-ribose) polymerase (PARP) can exacerbate neuroinflammation by promoting secretion of inflammatory mediators. Therefore, PARP represents an intriguing mechanistic link between radiation-induced activation of the DDR and subsequent neuroinflammation. PARP inhibitors (PARPi) have emerged as promising new agents for GBM when given in combination with RT, with multiple preclinical studies demonstrating radiosensitizing effects and at least 3 compounds being evaluated in clinical trials. We propose that concomitant use of PARPi could reduce radiation-induced neuroinflammation and reduce the severity of radiation-induced cognitive dysfunction while at the same time improving tumor control by enhancing radiosensitivity.

Neuroprotective Action of Multitarget 7-Aminophenanthridin-6(5H)-one Derivatives against Metal-Induced Cell Death and Oxidative Stress in SN56 Cells

Neurodegenerative diseases have been associated with brain metal accumulation, which produces oxidative stress (OS), matrix metalloproteinases (MMPs) induction, and neuronal cell death. Several metals have been reported to downregulate both the nuclear factor erythroid 2-related factor 2 (Nrf2) pathway and the antioxidant enzymes regulated by it, mediating OS induction and neurodegeneration. Among a recently discovered family of multitarget 7-amino-phenanthridin-6-one derivatives (APH) the most promising compounds were tested against metal-induced cell death and OS in SN56 cells. These compounds, designed to have chelating activity, are known to inhibit some MMPs and to present antioxidant and neuroprotective effects against hydrogen peroxide treatment to SN56 neuronal cells. However, the mechanisms that mediate this protective effect are not fully understood. The obtained results show that compounds APH1, APH2, APH3, APH4, and APH5 were only able to chelate iron and copper ions among all metals studied and that APH3, APH4, and APH5 were also able to chelate mercury ion. However, none of them was able to chelate zinc, cadmium, and aluminum, thus exhibiting selective chelating activity that can be partly responsible for their neuroprotective action. Otherwise, our results indicate that their antioxidant effect is mediated through induction of the Nrf2 pathway that leads to overexpression of antioxidant enzymes. Finally, these compounds exhibited neuroprotective effects, reversing partially or completely the cytotoxic effects induced by the metals studied depending on the compound used. APH4 was the most effective and safe compound.

Galectin-3 Mediated Inflammatory Response Contributes to Neurological Recovery by QiShenYiQi in Subacute Stroke Model

Effective therapies for stroke are still limited due to its complex pathological manifestations. QiShenYiQi (QSYQ), a component-based Chinese medicine capable of reducing organ injury caused by ischemia/reperfusion, may offer an alternative option for stroke treatment and post-stroke recovery. Recently, we reported a beneficial effect of QSYQ for acute stroke via modulation of the neuroinflammatory response. However, if QSYQ plays a role in subacute stroke remains unknown. The pharmacological action of QSYQ was investigated in experimental stroke rats which underwent 90 min ischemia and 8 days reperfusion in this study. Neurological and locomotive deficits, cerebral infarction, brain edema, and BBB integrity were assessed. TMT-based quantitative proteomics were performed to identify differentially expressed proteins following QSYQ treatment. Immunohistochemistry, western blot analysis, RT-qPCR, and ELISA were used to validate the proteomics data and to reveal the action mechanisms. Therapeutically, treatment with QSYQ (600 mg/kg) for 7 days significantly improved neurological recovery, attenuated infarct volume and brain edema, and alleviated BBB breakdown in the stroke rats. Bioinformatics analysis indicated that protein galectin-3 and its mediated inflammatory response was closely related to the beneficial effect of QSYQ. Specially, QSYQ (600 mg/kg) markedly downregulated the mRNA and protein expression levels of galectin-3, TNF-α, and IL-6 in CI/RI brain as well as serum levels of TNF-α and IL-6. Overall, our findings showed that the effective action of QSYQ against the subacute phase of CI/RI occurs partly via regulating galectin-3 mediated inflammatory reaction.

Nutraceutical induction and mimicry of heme oxygenase activity as a strategy for controlling excitotoxicity in brain trauma and ischemic stroke: focus on oxidative stress

Introduction: Ischemic stroke and traumatic brain injury are leading causes of acute mortality, and in the longer run, major causes of significant mental and physical impairment. Most of the brain neuronal cell death in the minutes and hours following an ischemic stroke or brain trauma is mediated by the process of excitotoxicity, in which sustained elevations of extracellular glutamate, reflecting a failure of ATP-dependent mechanism which sequester glutamate in neurons and astrocytes, drive excessive activation of NMDA receptors. Areas covered: A literature search was undertaken to clarify the molecular mechanisms whereby excessive NMDA activation leads to excitotoxic neuronal death, and to determine what safe nutraceutical agents might have practical potential for rescuing at-risk neurons by intervening in these mechanisms. Expert opinion: Activation of both NADPH oxidase and neuronal nitric oxide synthase in the microenvironment of activated NMDA receptors drives production of superoxide and highly toxic peroxynitrite. This leads to excessive activation of PARP and p38 MAP kinase, mitochondrial dysfunction, and subsequent neuronal death. Heme oxygenase-1 (HO-1) induction offers protection via inhibition of NADPH oxidase and promotion of cGMP generation. Phase 2-inductive nutraceuticals can induce HO-1, and other nutraceuticals can mimic the effects of its products biliverdin and carbon monoxide.

Breviscapine Alleviates Cognitive Impairments Induced by Transient Cerebral Ischemia/Reperfusion through Its Anti-Inflammatory and Anti-Oxidant Properties in a Rat Model

Cerebral ischemia/reperfusion (I/R)-induced injury is a common phenomenon of stroke, and the effective treatment for I/R-induced brain tissue damage is limited. Breviscapine has been widely used in China as herbal medicine to treat cardiovascular diseases for hundreds of years and has been demonstrated to possess potent cardiovascular pharmacological effects. This study aims to investigate the neuroprotective effect of breviscapine on cerebral I/R-induced injury. The rat model of middle cerebral artery occlusion (MCAO) was applied in our study. The cerebral I/R rats received multiple injections of breviscapine. All rats were subject to neurological behavior tests by open field test and Morris water maze test. The pro-inflammatory cytokines and oxidative stress marker levels were determined by ELISA and colorimetric analysis, respectively. We demonstrated that administration of breviscapine dose-dependently ameliorated cerebral I/R-induced injury and improved the neurological performance of cerebral I/R rats. Further studies illustrated that breviscapine treatment effectively attenuated inflammatory cytokine expression, reduced oxidative stress, and pro-apoptosis protein expression and inhibited the activation of NF-κB signaling and microglia in the I/R injury tissues. Breviscapine may serve as a single drug or a promising adjuvant that can be used in conjunction with other medicine for the treatment of cerebral I/R-induced injury.

Neuroprotective Effects of Activated Protein C Involve the PARP/AIF Pathway against Oxygen-Glucose Deprivation in SH-SY5Y Cells

Protein C, a member of the zymogen family of serine proteases in plasma, is one of the several vitamin K dependent glycoproteins known to induce anti-apoptotic activity. However, the target molecule involved in the mechanism needs to be investigated. We sought to investigate the pathways involved in the anti-apoptotic role of activated protein C (APC) on oxygen-glucose deprivation (OGD) induced ischemic conditions in in-vitro SH-SY5Y cells. SH-SY5Y cells were exposed to OGD in an airtight chamber containing 95% N₂ and 5% CO₂ and media deprived of glucose for 4 h following 24 h of reoxygenation. The cell toxicity, viability, expression of receptors such as endothelial cell protein C receptor (EPCR), protease-activated receptor (PAR)1, PAR3, and apoptosis-related proteins B-cell lymphoma 2 (BCL-2), BCL-2-like protein 4 (Bax), Poly [ADP-ribose] polymerase-1 (PARP-1) were assessed. Administration of APC decreased the cellular injury when compared to the OGD exposed group in a dose-dependent manner and displayed increased expression of PAR-1, PAR-3, and EPCR. The APC treatment leads to a reduction in PARP-1 expression and cleavage and apoptosis-inducing factor (AIF) expression. The reduction of caspase-3 activity and PARP-1 and AIF expression following APC administration results in restoring mitochondrial function with decreased cellular injury and apoptosis. Our results suggested that APC has potent protective effects against in-vitro ischemia in SH-SY5Y cells by modulating mitochondrial function.

Protection against acute cerebral ischemia/reperfusion injury by QiShenYiQi via neuroinflammatory network mobilization

Cerebral ischemia/reperfusion injury (CI/RI) is a common feature of ischemic stroke, involving a period of impaired blood supply to the brain, followed by the restoration of cerebral perfusion through medical intervention. Although ischemia and reperfusion brain damage is a complex pathological process with an unclear physiological mechanism, more attention is currently focused on the neuroinflammatory response of an ischemia/reperfusion origin, and anti-inflammatory appears to be a potential therapeutic strategy following ischemic stroke. QiShenYiQi (QSYQ), a component-based Chinese medicine with Qi-tonifying and blood-activating property, has pharmacological actions of anti-inflammatory, antioxidant, mitochondrial protectant, anti-apoptosis, and antiplatelet aggregation. We have previously reported that the cardioprotective effect of QSYQ against ischemia/reperfusion injury is via improvement of mitochondrial functional integrity. In this research work, we aimed to investigate the possible mechanism involved in the neuroprotection of QSYQ in mice model of cerebral ischemia/reperfusion injury based on the inflammatory pathway. The cerebral protection was evaluated in the stroke mice after 24 h reperfusion by assessing the neurological deficit, cerebral infarction, brain edema, BBB functionality, and via histopathological assessment. TCM-based network pharmacology method was performed to establish and analyze compound-target-disease & function-pathway network so as to find the possible mechanism linking to the role of QSYQ in CI/RI. In addition, RT-qPCR was used to verify the accuracy of predicted signaling gene expression. As a result, improvement of neurological outcome, reduction of infarct volume and brain edema, a decrease in BBB disruption, and amelioration of histopathological alteration were observed in mice pretreated with QSYQ after experimental stroke surgery. Network pharmacology analysis revealed neuroinflammatory response was associated with the action of QSYQ in CI/RI. RT-qPCR data showed that the mice pretreated with QSYQ could significantly decrease IFNG-γ, IL-6, TNF-α, NF-κB p65, and TLR-4 mRNA levels and increase TGF-β1 mRNA level in the brain compared to the untreated mice after CI/RI (p < 0.05). In conclusion, our study indicated the cerebral protective effect of pretreatment with QSYQ against CI/RI, which may be partly related to its potential to the reduction of neuroinflammatory response in a stroke subject.

Additional functions of selected proteins involved in DNA repair

Protein moonlighting is a phenomenon in which a single polypeptide chain can perform a number of different unrelated functions. Here we present our analysis of moonlighting in the case of selected DNA repair proteins which include G:T mismatch-specific thymine DNA glycosylase (TDG), methyl-CpG-binding domain protein 4 (MBD4), apurinic/apyrimidinic endonuclease 1 (APE1), AlkB homologs, poly (ADP-ribose) polymerase 1 (PARP-1) and single-strand selective monofunctional uracil DNA glycosylase 1 (SMUG1). Most of their additional functions are not accidental and clear patterns are emerging. Participation in RNA metabolism is not surprising as bases occurring in RNA are the same or very similar to those in DNA. Other common additional function involves regulation of transcription. This is not unexpected as these proteins bind to specific DNA regions for DNA repair, hence they can also be recruited to regulate transcription. Participation in demethylation and replication of DNA appears logical as well. Some of the multifunctional DNA repair proteins play major roles in many diseases, including cancer. However, their moonlighting might prove a major difficulty in the development of new therapies because it will not be trivial to target a single protein function without affecting its other functions that are not related to the disease.

PARP Inhibitor Protects Against Chronic Hypoxia/Reoxygenation-Induced Retinal Injury by Regulation of MAPKs, HIF1α, Nrf2, and NFκB

Purpose

In the eye, chronic hypoxia/reoxygenation (H/R) contributes to the development of a number of ocular disorders. H/R induces the production of reactive oxygen species (ROS), leading to poly(ADP-ribose) polymerase-1 (PARP1) activation that promotes inflammation, cell death, and disease progression. Here, we analyzed the protective effects of the PARP1 inhibitor olaparib in H/R-induced retina injury and investigated the signaling mechanisms involved.

Methods

A rat retinal H/R model was used to detect histologic and biochemical changes in the retina.

Results

H/R induced reductions in the thickness of most retinal layers, which were prevented by olaparib. Furthermore, H/R caused increased levels of Akt and glycogen synthase kinase-3β phosphorylation, which were further increased by olaparib, contributing to retina protection. By contrast, H/R-induced c-Jun N-terminal kinase and p38 mitogen-activated protein kinases (MAPK) phosphorylation and activation were reduced by olaparib, via mitogen-activated protein kinase phosphatase 1 (MKP-1) expression. In addition, H/R-induced hypoxia-inducible factor 1α (HIF1α) levels were decreased by olaparib, which possibly contributed to reduced VEGF expression. Nuclear factor (erythroid-derived 2)-like 2 (Nrf2) expression was slightly increased by H/R and was further activated by olaparib. Nuclear factor-κB (NFκB) was also activated by H/R through phosphorylation (Ser536) and acetylation (Lys310) of the p65 subunit, although this was significantly reduced by olaparib.

Conclusions

Olaparib reduced H/R-induced degenerative changes in retinal morphology. The protective mechanisms of olaparib most probably involved Nrf2 activation and ROS reduction, as well as normalization of HIF1α and related VEGF expression. In addition, olaparib reduced inflammation by NFκB dephosphorylation/inactivation, possibly via the PARP1 inhibition-MKP-1 activation-p38 MAPK inhibition pathway. PARP inhibitors represent potential therapeutics in H/R-induced retinal disease.

Novel insights into PARPs in gene expression: regulation of RNA metabolism

Poly(ADP-ribosyl)ation (PARylation) is an important post-translational modification in which an ADP-ribose group is transferred to the target protein by poly(ADP-riboses) polymerases (PARPs). Since the discovery of poly-ADP-ribose (PAR) 50 years ago, its roles in cellular processes have been extensively explored. Although research initially focused on the functions of PAR and PARPs in DNA damage detection and repair, our understanding of the roles of PARPs in various nuclear and cytoplasmic processes, particularly in gene expression, has increased significantly. In this review, we discuss the current advances in understanding the roles of PARylation with a particular emphasis in gene expression through RNA biogenesis and processing. In addition to updating PARP's significance in transcriptional regulation, we specifically focus on how PARPs and PARylation affect gene expression, especially inflammation-related genes, at the post-transcriptional levels by modulating RNA processing and degrading. Increasing evidence suggests that PARP inhibition is a promising treatment for inflammation-related diseases besides conventional chemotherapy for cancer.

Inflammation-induced DNA damage, mutations and cancer

The relationships between inflammation and cancer are varied and complex. An important connection linking inflammation to cancer development is DNA damage. During inflammation reactive oxygen and nitrogen species (RONS) are created to combat pathogens and to stimulate tissue repair and regeneration, but these chemicals can also damage DNA, which in turn can promote mutations that initiate and promote cancer. DNA repair pathways are essential for preventing DNA damage from causing mutations and cytotoxicity, but RONS can interfere with repair mechanisms, reducing their efficacy. Further, cellular responses to DNA damage, such as damage signaling and cytotoxicity, can promote inflammation, creating a positive feedback loop. Despite coordination of DNA repair and oxidative stress responses, there are nevertheless examples whereby inflammation has been shown to promote mutagenesis, tissue damage, and ultimately carcinogenesis. Here, we discuss the DNA damage-mediated associations between inflammation, mutagenesis and cancer.

PARP Inhibitors in Ovarian Cancer: The Route to "Ithaca"

Poly (ADP-ribose) polymerase (PARP) inhibitors are a novel class of therapeutic agents that target tumors with deficiencies in the homologous recombination DNA repair pathway. Genomic instability characterizes high-grade serous ovarian cancer (HGSOC), with one half of all tumors displaying defects in the important DNA repair pathway of homologous recombination. Early studies have shown significant efficacy for PARP inhibitors in patients with germline breast related cancer antigens 1 and 2 (BRCA1/2) mutations. It has also become evident that BRCA wild-type patients with other defects in the homologous recombination repair pathway benefit from this treatment. Companion homologous recombination deficiency (HRD) scores are being developed to guide the selection of patients that are most likely to benefit from PARP inhibition. The choice of which PARP inhibitor is mainly based upon the number of prior therapies and the presence of a BRCA mutation or HRD. The identification of patients most likely to benefit from PARP inhibitor therapy in view of HRD and other biomarker assessments is still challenging. The aim of this review is to describe the current evidence for PARP inhibitors in ovarian cancer, their mechanism of action, and the outstanding issues, including the rate of long-term toxicities and the evolution of resistance.

Role of immune responses for extracellular matrix remodeling in the ischemic brain

Neuroinflammation is one of the key components contributing to the devastating outcome of ischemic stroke. Starting with stroke onset, inflammatory processes contribute both to cell damage and tissue remodeling. The early release of alarmins triggers the upregulation of multiple proinflammatory cytokines, resulting in the compromised integrity of the blood–brain barrier. From this moment on, the infiltration of peripheral immune cells, reactive gliosis and extracellular matrix (ECM) alterations become intricately intertwined and act as one unit during the tissue remodeling. While the mechanisms of leukocyte and glia activation are amply reviewed, the field of ECM modification remains as yet under explored. In this review, we focus on the interplay between neuroinflammatory cascades and ECM in the ischemic brain. By summarizing the currently available evidence obtained by in vitro research, animal experimentation and human studies, we aim to propose a new direction for the future investigation of stroke recovery.

Combining PARP inhibition, radiation, and immunotherapy: A possible strategy to improve the treatment of cancer?

Immunotherapy has revolutionized the practice of oncology, improving survival in certain groups of patients with cancer. Immunotherapy can synergize with radiation therapy, increase locoregional control, and have abscopal effects. Combining it with other treatments, such as targeted therapies, is a promising means of improving the efficacy of immunotherapy. Because the value of immunotherapy is amplified with the expression of tumor antigens, coupling poly(ADP-ribose) polymerase (PARP) inhibitors and immunotherapy might be a promising treatment for cancer. Further, PARP inhibitors (PARPis) are being combined with radiation therapy to inhibit DNA repair functions, thus enhancing the effects of radiation; this association might interact with the antitumor immune response. Cytotoxic T lymphocytes are central to the antitumor immune response. PARP inhibitors and ionizing radiation can enhance the infiltration of cytotoxic T lymphocytes into the tumor bed, but they can also enhance PD-1/PDL-1 expression. Thus, the addition of immune checkpoint inhibitors with PARP inhibitors and/or ionizing radiation could counterbalance such immunosuppressive effects. With the present review article, we proposed to evaluate some of these associated therapies, and we explored the biological mechanisms and medical benefits of the potential combination of radiation therapy, immunotherapy, and PARP inhibitors.

FAF1 mediates necrosis through JNK1-mediated mitochondrial dysfunction leading to retinal degeneration in the ganglion cell layer upon ischemic insult

BACKGROUND

Aberrant cell death induced by ischemic stress is implicated in the pathogenesis of ischemic diseases. Fas-associated factor 1 (FAF1) has been identified as a death-promoting protein. This study demonstrates that FAF1 functions in death signaling triggered by ischemic insult.

METHODS

The expression changes of FAF1 and phophorylated JNK1 were detected by Western blotting. Immunoprecipitation was employed to investigate protein-protein interaction. We determined the cell death using flow cytometry and lactate dehydrogenase release measurement. To validate the death-promoting role of FAF1 in the retina, we generated conditional retinal FAF1 knockout mice. We used hematoxylin and eosin staining to detect retinal cell death in retinal ganglion cell layer.

RESULTS

FAF1 was found to function upstream of c-Jun N-terminal kinase 1 (JNK1), followed by mitochondrial dysregulation and necrotic cell death processes upon ischemic insult. We investigated whether FAF1 is involved in the pathogenesis of ischemic diseases using a retinal ischemia model. Indeed, FAF1 potentiated necrosis through JNK1 activation upon ischemic stress in retinal cells demonstrating retinal ganglion-like character. Conditional FAF1 depletion attenuated JNK1 activation in the retinas of Dkk3-Cre;Faf1flox/flox mice and ameliorated death of retinal cells due to elevated intraocular pressure (IOP).

CONCLUSIONS

Our results show that FAF1 plays a key role in ischemic retinal damage and may be implicated in the pathogenesis of retinal ischemic disease.

Role of Peroxynitrite-Induced Activation of Poly(ADP-Ribose) Polymerase (PARP) in Circulatory Shock and Related Pathological Conditions

Peroxynitrite is a powerful oxidant, formed from the reaction of nitric oxide and superoxide. It is known to interact and modify different biological molecules such as DNA, lipids and proteins leading to alterations in their structure and functions. These events elicit various cellular responses, including cell signaling, causing oxidative damage and committing cells to apoptosis or necrosis. This review discusses nitrosative stress-induced modification in the DNA molecule that results in the formation of 8-nitroguanine and 8-oxoguanine, and its role in disease conditions. Different approaches of cell death, such as necrosis and apoptosis, are modulated by cellular high-energy species, such as ATP and NAD⁺. High concentrations of peroxynitrite are known to cause necrosis, whereas low concentrations lead to apoptosis. Any damage to DNA activates cellular DNA repair machinery, like poly(ADP-ribose) polymerase (PARP). PARP-1, an isoform of PARP, is a DNA nick-sensing enzyme that becomes activated upon sensing DNA breakage and triggers the cleavage of NAD⁺ into nicotinamide and ADP-ribose and polymerizes the latter on nuclear acceptor proteins. Peroxynitrite-induced hyperactivation of PARP causes depletion of NAD⁺ and ATP culminating cell dysfunction, necrosis or apoptosis. This mechanistic pathway is implicated in the pathogenesis of a variety of diseases, including circulatory shock (which is characterized by cellular hypoxia triggered by systemic altered perfusion and tissue oxygen utilization leading end-organ dysfunction), sepsis and inflammation, injuries of the lung and the intestine. The cytotoxic effects of peroxynitrite centering on the participation of PARP-1 and ADP-ribose in previously stated diseases have also been discussed in this review.

Regulatory T cells increase after treatment with poly (ADP-ribose) polymerase-1 inhibitor in ischemic stroke patients

BACKGROUND

Regulatory T cells (Tregs) are thought to play a modulatory role in immune responses and to improve outcomes after ischemic stroke. Thus, various strategies for increasing Tregs in animal models of ischemic stroke have yielded successful results. The aim of this study was to examine the potential effect of poly (ADP-ribose) polymerase-1 (PARP-1) inhibitor on Treg proportion in stroke patients.

METHODS

Peripheral blood samples were collected from 12 ischemic stroke patients (within 72 h of stroke onset) and 5 healthy control subjects. Flow cytometry analyses and quantitative reverse transcription polymerase chain reactions (qRT-PCR) were performed on peripheral blood mononuclear cells (PBMCs) before and after treating them with PARP-1 inhibitor (3-AB; JPI-289 1 μm, JPI-289 10 μm) for 24 h.

RESULTS

Treg proportions were significantly higher in healthy controls (median 2.8%, IQR 2.6-5.0%) than ischemic stroke patients (median 1.6%, IQR 1.25-2.2%) (p < 0.001). In the latter, Treg proportions were positively correlated with age (r = 0.595, p = 0.041), but not with infarct volume (r = 0.367, p = 0.241). After PARP-1 inhibitor treatment, Treg proportions among PBMCs increased in response to high dose (10 μm) JPI-289 (median 2.3%, IQR 2.0-2.9%) as did Treg-associated transcription factors such as FoxP3 and CTLA-4 mRNA. PARP-1 inhibitor treatment also decreased pro-inflammatory cytokines (IFN-γ, TNF-α, and IL-17) and increased anti-inflammatory cytokines (IL-4, IL-10, and TGF-β1).

CONCLUSION

Treg proportions are reduced in ischemic stroke patients and increased by treatment with high-dose PARP-1 inhibitor JPI-289. The PARP-1 inhibitor also had a possible anti-inflammatory effect on cytokine levels, and may ameliorate the outcome of ischemic stroke by up-regulating Tregs.

Improved Reperfusion and Vasculoprotection by the Poly(ADP-Ribose)Polymerase Inhibitor PJ34 After Stroke and Thrombolysis in Mice

Benefits from thrombolysis with recombinant tissue plasminogen activator (rt-PA) after ischemic stroke remain limited due to a narrow therapeutic window, low reperfusion rates, and increased risk of hemorrhagic transformations (HT). Experimental data showed that rt-PA enhances the post-ischemic activation of poly(ADP-ribose)polymerase (PARP) which in turn contributes to blood-brain barrier injury. The aim of the present study was to evaluate whether PJ34, a potent PARP inhibitor, improves poor reperfusion induced by delayed rt-PA administration, exerts vasculoprotective effects, and finally increases the therapeutic window of rt-PA. Stroke was induced by thrombin injection (0.75 UI in 1 μl) in the left middle cerebral artery (MCA) of male Swiss mice. Administration of rt-PA (0.9 mg kg^-1) or saline was delayed for 4 h after ischemia onset. Saline or PJ34 (3 mg kg^-1) was given intraperitoneally twice, just after thrombin injection and 3 h later, or once, 3 h after ischemia onset. Reperfusion was evaluated by laser Doppler, vascular inflammation by immunohistochemistry of vascular cell adhesion molecule-1 (VCAM-1) expression, and vasospasm by morphometric measurement of the MCA. Edema, cortical lesion, and sensorimotor deficit were evaluated. Treatment with PJ34 improved rt-PA-induced reperfusion and promoted vascular protection including reduction in vascular inflammation (decrease in VCAM-1 expression), HT, and MCA vasospasm. Additionally, the combined treatment significantly reduced brain edema, cortical lesion, and sensorimotor deficit. In conclusion, the combination of the PARP inhibitor PJ34 with rt-PA after cerebral ischemia may be of particular interest in order to improve thrombolysis with an extended therapeutic window.

Effects of Veliparib on Microglial Activation and Functional Outcomes after Traumatic Brain Injury in the Rat and Pig

The inflammation response induced by brain trauma can impair recovery. This response requires several hours to develop fully and thus provides a clinically relevant therapeutic window of opportunity. Poly(ADP-ribose) polymerase inhibitors suppress inflammatory responses, including brain microglial activation. We evaluated delayed treatment with veliparib, a poly(ADP-ribose) polymerase inhibitor, currently in clinical trials as a cancer therapeutic, in rats and pigs subjected to controlled cortical impact (CCI). In rats, CCI induced a robust inflammatory response at the lesion margins, scattered cell death in the dentate gyrus, and a delayed, progressive loss of corpus callosum axons. Pre-determined measures of cognitive and motor function showed evidence of attentional deficits that resolved after three weeks and motor deficits that recovered only partially over eight weeks. Veliparib was administered beginning 2 or 24 h after CCI and continued for up to 12 days. Veliparib suppressed CCI-induced microglial activation at doses of 3 mg/kg or higher and reduced reactive astrocytosis and cell death in the dentate gyrus, but had no significant effect on delayed axonal loss or functional recovery. In pigs, CCI similarly induced a perilesional microglial activation that was attenuated by veliparib. CCI in the pig did not, however, induce detectable persisting cognitive or motor impairment. Our results showed veliparib suppression of CCI-induced microglial activation with a delay-to-treatment interval of at least 24 h in both rats and pigs, but with no associated functional improvement. The lack of improvement in long-term recovery underscores the complexities in translating anti-inflammatory effects to clinically relevant outcomes.

PARP1 in Carcinomas and PARP1 Inhibitors as Antineoplastic Drugs

Poly (ADP-ribose) polymerase 1 (PARP1), the best-studied isoform of the nuclear enzyme PARP family, plays a pivotal role in cellular biological processes, such as DNA repair, gene transcription, and so on. PARP1 has been found to be overexpressed in various carcinomas. These all indicate the clinical potential of PARP1 as a therapeutic target of human malignancies. Additionally, multiple preclinical research studies and clinical trials demonstrate that inhibition of PARP1 can repress tumor growth and metastasis. Up until now, PARP1 inhibitors are clinically used not only for monotherapy to suppress various tumors, but also for adjuvant therapy, to maintain or enhance therapeutic effects of mature antineoplastic drugs, as well as protect patients from chemotherapy and surgery-induced injury. To supply a framework for understanding recent research progress of PARP1 in carcinomas, we review the structure, expression, functions, and mechanisms of PARP1, and summarize the clinically mature PARP1-related anticancer agents, to provide some ideas for the development of other promising PARP1 inhibitors in antineoplastic therapy.

Protective Functions of PJ34, a Poly(ADP-ribose) Polymerase Inhibitor, Are Related to Down-Regulation of Calpain and Nuclear Factor-κB in a Mouse Model of Traumatic Brain Injury

OBJECTIVES

Poly(ADP-ribose) polymerase (PARP), calpain, and nuclear factor-κB (NF-κB) are reported to participate in inflammatory reactions in pathologic conditions and are involved in traumatic brain injury. The objective of this study was to investigate whether PARP participates in inflammation related to calpain and NF-κB in a mouse model of controlled cortical impact (CCI).

METHODS

PJ34 (10 mg/kg), a selective PARP inhibitor, was administered intraperitoneally 5 minutes and 8 hours after experimental CCI. We then performed a histopathologic analysis, and we measured calpain activity and protein levels in all animals. The cytosolic, mitochondria, and nuclear fractions were prepared and used to determine the levels of PARP, calpastatin, NF-κB p65, inhibitory-κB-α, tumor necrosis factor-α, interleukin-1β, intracellular adhesion molecule-1, inducible nitric oxide synthase, and cyclooxygenase-2. We then measured blood-brain barrier disruption using electron microscopy at 6 and 24 hours after CCI.

RESULTS

Treatment with PJ34 markedly reduced the extent of both cerebral contusion and edema, improved neurologic scores, and attenuated blood-brain barrier damage resulting from CCI. Our data showed that the cytosolic and nuclear fractions of calpain and NF-κB were up-regulated in the injured cortex and that these changes were reversed by PJ34. Moreover, PJ34 significantly enhanced the calpastatin and inhibitory-κB levels and decreased the levels of inflammatory mediators.

CONCLUSIONS

PARP inhibition by PJ34 suppresses the overactivation of calpain and the production of inflammatory factors that are caused by NF-κB activation and attenuates neuronal cell death in a mouse model of CCI.

Cerebral ischemic damage in diabetes: an inflammatory perspective

Stroke is one of the leading causes of death worldwide. A strong inflammatory response characterized by activation and release of cytokines, chemokines, adhesion molecules, and proteolytic enzymes contributes to brain damage following stroke. Stroke outcomes are worse among diabetics, resulting in increased mortality and disabilities. Diabetes involves chronic inflammation manifested by reactive oxygen species generation, expression of proinflammatory cytokines, and activation/expression of other inflammatory mediators. It appears that increased proinflammatory processes due to diabetes are further accelerated after cerebral ischemia, leading to increased ischemic damage. Hypoglycemia is an intrinsic side effect owing to glucose-lowering therapy in diabetics, and is known to induce proinflammatory changes as well as exacerbate cerebral damage in experimental stroke. Here, we present a review of available literature on the contribution of neuroinflammation to increased cerebral ischemic damage in diabetics. We also describe the role of hypoglycemia in neuroinflammation and cerebral ischemic damage in diabetics. Understanding the role of neuroinflammatory mechanisms in worsening stroke outcome in diabetics may help limit ischemic brain injury and improve clinical outcomes.

Poly(ADP-ribose) polymerase activity and inhibition in cancer

Genomic instability resultant from defective DNA repair mechanisms is a fundamental hallmark of cancer. The poly(ADP-ribose) polymerase (PARP) proteins 1, 2 and 3 catalyze the polymerization of poly(ADP-ribose) and covalent attachment to proteins in a phylogenetically ancient form of protein modification. PARPs play a role in base excision repair, homologous recombination, and non-homologous end joining. The discovery that loss of PARP activity had cytotoxic effects in cells deficient in homologous recombination has sparked a decade of translational research efforts that culminated in the FDA approval of an oral PARP inhibitor for clinical use in patients with ovarian cancer and defective homologous recombination. Five PARP inhibitors are now in late-stage development in clinical trials that are seeking to expand the understanding of targeted therapies and DNA repair defects in human cancer. This review examines the cell biology of PARP, the discovery of synthetic lethality with HR deficiency, the clinical development of PARP inhibitors, and the role of PARP inhibitors in ongoing clinical trials and clinical practice.

The prognostic and predictive significance of PARP-1 in locally advanced breast cancer of Egyptian patients receiving neoadjuvant chemotherapy

PURPOSE

PARP-1 is a chromatin-associated enzyme that has a role in DNA repair and cell death. PARP-1 inhibitors are suggested therapy specifically for BRCA deficient breast carcinoma; however, their efficacy in sporadic breast cancer is under investigations. This study aimed to evaluate the PARP-1 in locally advanced breast cancer (LABC) cases to determine its predictive significance for outcome and response to neoadjuvant chemotherapy (NCT).

MATERIALS AND METHODS

This retrospective study was conducted on 84 LABC cases. Immunohistochemical expression of nuclear PARP-1 (nPARP-1) and cytoplasmic PARP-1 (cPARP-1) was evaluated in pretreatment needle core biopsies (NCBs). Results were correlated with clinicopathologic features, overall survival (OS), disease-free survival (DFS), and response to NCT in postoperative specimens.

RESULTS

High nPARP-1expression was observed in 64/84 (76%) of cases and was significantly associated with a lower lymph node stage (P=0.04). High cPARP-1 was observed in 40/84 (48%) of cases and it was significantly associated with lower lymph node stage (P=0.022) and lower tumor grade (P=0.050). High nPARP-1 expression was significantly associated with high cPARP-1 expression (P=0.005). Low cPARP-1 expression was associated with no response to chemotherapy in tumor site (P=0.021). According to the univariate survival analysis, high nPARP-1 and high cPARP-1 were significantly associated to longer OS (P=0.017 and P=0.019, respectively). High nPARP-1 but not cPARP-1 showed trend toward improved OS in multivariate Cox-regression analysis (P=0.053).

CONCLUSION

PARP-1 immunohistochemical expression is a marker of good prognosis and is predictive of response to NCT in LABC.

PARP inhibition attenuates early brain injury through NF-κB/MMP-9 pathway in a rat model of subarachnoid hemorrhage

Poly (ADP-ribose) polymerases (PARPs) play an important role in a range of neurological disorders, however, the role of PARP in early brain injury after subarachnoid hemorrhage (SAH) remains unclear. This study was designed to explore the role and the potential mechanisms of PARP in early brain injury after SAH. Eighty-nine male SD rats were randomly divided into the Sham group, SAH+Vehicle group and SAH+PARP inhibitor (PJ34) group. An endovascular perforation model was used to induce SAH in rats. PJ34 (10mg/kg) or vehicle (0.9% NaCl) was intraperitoneally administered at 5min and 8h after SAH induction. Mortality, SAH grades, neurological function, evans blue extravasation, brain edema, immunofluorescence staining and western blotting were performed. PJ34 reduced BBB permeability and brain edema, improved neurological function and attenuated neuronal cell death in the rat model of SAH. Moreover, PJ34 inhibited the nuclear translocation of NF-κB, decreased the expression of the proinflammatory cytokines IL-1ß, IL-6 and TNF-α, reduced the expression of MMP-9, prevented the degradation of tight junction proteins, and decreased microglia activation. These data indicated that PARP inhibition through PJ34 might be an important therapeutic drug for SAH.

Protective effects of PARP inhibitor, PJ34, is related to down-regulation of calpain and NF-κB in a mouse model of TBI

BACKGROUND

Poly(ADP-ribose) polymerase (PARP), calpain and nuclear factor-κB (NF-κB) are reported to participate in inflammatory reactions in pathological conditions and are involved in traumatic brain injury. The objective of this study was to investigate whether PARP participated in inflammation related to calpain and NF-κB in a mouse model of controlled cortical impact (CCI).

MATERIALS AND METHODS

PJ34 (10 mg kg-1), a selective PARP inhibitor, was administered intraperitoneally 5 minutes and 8 hours after experimental CCI. A neurobehavioural evaluation and a histopathological analysis were then performed and the contusion volume, calpain activity and protein levels were measured in all animals.

RESULTS

Treatment with PJ34 markedly reduced neurological deficits, decreased contusion volume and attenuated necrotic and apoptotic neuronal cell death 24 hours after CCI. The data showed that the cytosolic and nuclear fractions of calpain and NF-κB were up-regulated in the injured cortex and that these changes were reversed by PJ34. Moreover, PJ34 significantly enhanced the calpastatin and IκB levels and decreased the levels of inflammatory mediators.

CONCLUSIONS

PARP inhibition by PJ34 suppresses the over-activation of calpain and the production of inflammatory factors that are caused by NF-κB activation and it improves neurological functioning, decreases the contusion volume and attenuates neuronal cell death in a mouse model of CCI.

Deletion of Nuclear Localizing Signal Attenuates Proinflammatory Activity of Prothymosin-Alpha and Enhances Its Neuroprotective Effect on Transient Ischemic Stroke

Post-ischemic inflammation plays an important role in the progression of ischemia/reperfusion injuries. Prothymosin-α (ProT) can protect cells from necrotic death following ischemia; however, its immunostimulatory actions may counteract the neuroprotective effect. We proposed that ProTΔNLS, synthesized by deleting its nuclear localizing signal (NLS) at the C-terminal of ProT, can attenuate the immunostimulatory activity and has more salient neuroprotective effect. In this study, we examined the therapeutic effects of ProT and ProTΔNLS in a transient middle cerebral artery occlusion (tMCAO) model of rats. Rats that had sustained 90 min of tMCAO were treated with GST-vehicle, ProT, or ProTΔNLS. Therapeutic outcomes were evaluated by infarction volume assay and behavioral assessment. Changes to inflammatory mediators, including tumor necrosis factor α (TNF-α), interleukin-10 (IL-10), and myeloperoxidase (MPO) were evaluated by enzyme-linked immunosorbent assay. Activated matrix metalloproteinases 2 (MMP-2) and 9 (MMP-9) levels were evaluated by gelatin zymography. Microglial activation was identified by double-immunostaining for Iba-1 and CD68. Our results showed that while both ProT and ProTΔNLS reduce infarction volume and improve functional outcome, ProTΔNLS provides the best therapeutic outcome. ProT increases TNF-α but decreases IL-10 secretion after ischemic injury, reflecting its pro-inflammatory activity. ProTΔNLS suppresses expression of TNF-α, MPO, and activity of MMPs in ischemic brain tissue. It also suppresses activation of microglia in penumbral cortex. These data demonstrate the immunesuppressive activities of ProTΔNLS. In conclusion, ProT has pro-inflammatory effect that may counteract its neuroprotective effect. Deletion of NLS from ProT may attenuate post-ischemic inflammation and enhance the neuroprotective effects of ProT.

NF-κB transcriptional activation by TNFα requires phospholipase C, extracellular signal-regulated kinase 2 and poly(ADP-ribose) polymerase-1

BACKGROUND

The nuclear enzyme poly(ADP-ribose) polymerase-1 (PARP-1) is required for pro-inflammatory effects of TNFα. Our previous studies demonstrated that PARP-1 mediates TNFα-induced NF-κB activation in glia. Here, we evaluated the mechanisms by which TNFα activates PARP-1 and PARP-1 mediates NF-κB activation.

METHODS

Primary cultures of mouse cortical astrocytes and microglia were treated with TNFα and suitable signaling pathway modulators (pharmacological and molecular). Outcome measures included calcium imaging, PARP-1 activation status, NF-κB transcriptional activity, DNA damage assesment and cytokine relesease profiling.

RESULTS

TNFα induces PARP-1 activation in the absence of detectable DNA strand breaks, as measured by the PANT assay. TNFα-induced transcriptional activation of NF-κB requires PARP-1 enzymatic activity. Enzymatic activation of PARP-1 by TNFα was blocked in Ca(2+)-free medium, by Ca(2+) chelation with BAPTA-AM, and by D609, an inhibitor of phoshatidyl choline-specific phospholipase C (PC-PLC), but not by thapsigargin or by U73112, an inhibitor of phosphatidyl inisitol-specific PLC (PI -PLC). A TNFR1 blocking antibody reduced Ca(2+) influx and PARP-1 activation. TNFα-induced PARP-1 activation was also blocked by siRNA downregulation of ERK2 and by PD98059, an inhibitor of the MEK / ERK protein kinase cascade. Moreover, TNFα-induced NF-κB (p65) transcriptional activation was absent in cells expressing PARP-1 that lacked ERK2 phosphorylation sites, while basal NF-κB transcriptional activation increased in cells expressing PARP-1 with a phosphomimetic substitution at an ERK2 phophorylation site.

CONCLUSIONS

These results suggest that TNFα induces PARP-1 activation through a signaling pathway involving TNFR1, Ca(2+) influx, activation of PC-PLC, and activation of the MEK1 / ERK2 protein kinase cascade. TNFα-induced PARP-1 activation is not associated with DNA damage, but ERK2 mediated phosphorylation of PARP-1.

Synergistic inhibition of PARP-1 and NF-κB signaling downregulates immune response against recombinant AAV2 vectors during hepatic gene therapy

Host immune response remains a key obstacle to widespread application of adeno-associated virus (AAV) based gene therapy. Thus, targeted inhibition of the signaling pathways that trigger such immune responses will be beneficial. Previous studies have reported that DNA damage response proteins such as poly(ADP-ribose) polymerase-1 (PARP-1) negatively affect the integration of AAV in the host genome. However, the role of PARP-1 in regulating AAV transduction and the immune response against these vectors has not been elucidated. In this study, we demonstrate that repression of PARP-1 improves the transduction of single-stranded AAV vectors both in vitro (∼174%) and in vivo (two- to 3.4-fold). Inhibition of PARP-1, also significantly downregulated the expression of several proinflammatory and cytokine markers such as TLRs, ILs, NF-κB subunit proteins associated with the host innate response against self-complementary AAV2 vectors. The suppression of the inflammatory response targeted against these vectors was more effective upon combined inhibition of PARP-1 and NF-κB signaling. This strategy also effectively attenuated the AAV capsid-specific cytotoxic T-cell response, with minimal effect on vector transduction, as demonstrated in normal C57BL/6 and hemophilia B mice. These data suggest that targeting specific host cellular proteins could be useful to attenuate the immune barriers to AAV-mediated gene therapy.

PJ-34 inhibits PARP-1 expression and ERK phosphorylation in glioma-conditioned brain microvascular endothelial cells

Inhibitors of PARP-1(Poly(ADP-ribose) polymerase-1) act by competing with NAD(+), the enzyme physiological substrate, which play a protective role in many pathological conditions characterized by PARP-1 overactivation. It has been shown that PARP-1 also promotes tumor growth and progression through its DNA repair activity. Since angiogenesis is an essential requirement for these activities, we sought to determine whether PARP inhibition might affect rat brain microvascular endothelial cells (GP8.3) migration, stimulated by C6-glioma conditioned medium (CM). Through wound-healing experiments and MTT analysis, we demonstrated that PARP-1 inhibitor PJ-34 [N-(6-Oxo-5,6-dihydrophenanthridin-2-yl)-N,N-dimethylacetamide] abolishes the migratory response of GP8.3 cells and reduces their viability. PARP-1 also acts in a DNA independent way within the Extracellular-Regulated-Kinase (ERK) signaling cascade, which regulates cell proliferation and differentiation. By western analysis and confocal laser scanning microscopy (LSM), we analyzed the effects of PJ-34 on PARP-1 expression, phospho-ERK and phospho-Elk-1 activation. The effect of MEK (mitogen-activated-protein-kinase-kinase) inhibitor PD98059 (2-(2-Amino-3-methoxyphenyl)-4 H-1-benzopyran-4-one) on PARP-1 expression in unstimulated and in CM-stimulated GP8.3 cells was analyzed by RT-PCR. PARP-1 expression and phospho-ERK activation were significantly reduced by treatment of GP8.3 cells with PJ-34 or PD98059. By LSM, we further demonstrated that PARP-1 and phospho-ERK are coexpressed and share the same subcellular localization in GP8.3 cells, in the cytoplasm as well as in nucleoplasm. Based on these data, we propose that PARP-1 and phospho-ERK interact in the cytosol and then translocate to the nucleus, where they trigger a proliferative response. We also propose that PARP-1 inhibition blocks CM-induced endothelial migration by interfering with ERK signal-transduction pathway.

Protective actions of PJ34, a poly(ADP-ribose)polymerase inhibitor, on the blood-brain barrier after traumatic brain injury in mice

Poly(ADP-ribose) polymerase (PARP) is activated by oxidative stress and plays an important role in traumatic brain injury (TBI). The objective of this study was to investigate whether PARP activation participated in the blood-brain barrier (BBB) disruption and edema formation in a mouse model of controlled cortical impact (CCI). N-(6-oxo-5,6-dihydrophenanthridin-2-yl)-N,N-dimethylacetamide (PJ34) (10 mg/kg), a selective PARP inhibitor, was administered intraperitoneally at 5 min and 8 h after experimental CCI. After 6 h and 24 h of CCI, the permeability of the cortical BBB was determined after Evans Blue administration. The water content of the brain was also measured. Treatment with PJ34 markedly attenuated the permeability of the BBB and decreased the brain edema at 6 h and 24 h after CCI. Our data showed the up-regulation of nuclear factor-κB in cytosolic fractions and nuclear fractions in the injured cortex, and these changes were reversed by PJ34. Moreover, PJ34 significantly lessened the activities of myeloperoxidase and the levels of matrix metalloproteinase-9, enhanced the levels of occludin, laminin, collagen IV and integrin β1, reduced neurological deficits, decreased the contusion volume, and attenuated the necrotic and apoptotic neuronal cell death. These data suggest the protective effects of PJ34 on BBB integrity and cell death during acute TBI.

Poly(ADP-ribose) polymerase-1 inhibition in brain endothelium protects the blood-brain barrier under physiologic and neuroinflammatory conditions

Blood-brain barrier (BBB) dysfunction seen in neuroinflammation contributes to mortality and morbidity in multiple sclerosis, encephalitis, traumatic brain injury, and stroke. Identification of molecular targets maintaining barrier function is of clinical relevance. We used a novel in vivo model of localized aseptic meningitis where tumor necrosis factor alpha (TNFα) was introduced intracerebrally and surveyed cerebral vascular changes and leukocyte-endothelium interactions by intravital videomicroscopy. Poly(ADP-ribose) polymerase-1 (PARP) inhibition significantly reduced leukocyte adhesion to and migration across brain endothelium in cortical microvessels. PARP inactivation diminished BBB permeability in an in vivo model of systemic inflammation. PARP suppression in primary human brain microvascular endothelial cells (BMVEC), an in vitro model of BBB, enhanced barrier integrity and augmented expression of tight junction proteins. PARP inhibition in BMVEC diminished human monocyte adhesion to TNFα-activated BMVEC (up to 65%) and migration (80-100%) across BBB models. PARP suppression decreased expression of adhesion molecules and decreased activity of GTPases (controlling BBB integrity and monocyte migration across the BBB). PARP inhibitors down-regulated expression of inflammatory genes and dampened secretion of pro-inflammatory factors increased by TNFα in BMVEC. These results point to PARP suppression as a novel approach to BBB protection in the setting of endothelial dysfunction caused by inflammation.

Another "string to the bow" of PJ34, a potent poly(ADP-Ribose)polymerase inhibitor: an antiplatelet effect through P2Y12 antagonism?

Background

Neuro- and vasoprotective effects of poly(ADP-ribose)polymerase (PARP) inhibition have been largely documented in models of cerebral ischemia, particularly with the potent PARP inhibitor PJ34. Furthermore, after ischemic stroke, physicians are faced with incomplete tissue reperfusion and reocclusion, in which platelet activation/aggregation plays a key role. Data suggest that certain PARP inhibitors could act as antiplatelet agents. In that context, the present in vitro study investigated on human blood the potential antiplatelet effect of PJ34 and two structurally different PARP inhibitors, DPQ and INO-1001.

Methods and results

ADP concentrations were chosen to induce a biphasic aggregation curve resulting from the successive activation of both its receptors P2Y₁ and P2Y₁₂. In these experimental conditions, PJ34 inhibited the second phase of aggregation; this effect was reduced by incremental ADP concentrations. In addition, in line with a P2Y₁₂ pathway inhibitory effect, PJ34 inhibited the dephosphorylation of the vasodilator stimulated phosphoprotein (VASP) in a concentration-dependent manner. Besides, PJ34 had no effect on platelet aggregation induced by collagen or PAR1 activating peptide, used at concentrations inducing a strong activation independent on secreted ADP. By contrast, DPQ and INO-1001 were devoid of any effect whatever the platelet agonist used.

Conclusions

We showed that, in addition to its already demonstrated beneficial effects in in vivo models of cerebral ischemia, the potent PARP inhibitor PJ34 exerts in vitro an antiplatelet effect. Moreover, this is the first study to report that PJ34 could act via a competitive P2Y₁₂ antagonism. Thus, this antiplatelet effect could improve post-stroke reperfusion and/or prevent reocclusion, which reinforces the interest of this drug for stroke treatment.

Neuroprotection by the PARP inhibitor PJ34 modulates cerebral and circulating RAGE levels in rats exposed to focal brain ischemia

The receptor for advanced glycation end products (RAGE) has a potential role as a damage-sensing molecule; however, to date, its involvement in the pathophysiology of stroke and its modulation following neuroprotective treatment are not completely understood. We have previously demonstrated that expression of distinct RAGE isoforms, recognized by different antibodies, is differentially modulated in the brain of rats subjected to focal cerebral ischemia. Here, we focus on the full-length membrane-bound RAGE isoform, showing that its expression is significantly elevated in the striatum, whereas it is reduced in the cortex of rats subjected to transient middle cerebral artery occlusion (MCAo). Notably, the reduction of cortical levels of full-length RAGE detected 24 h after reperfusion is abolished by systemic administration of a neuroprotective dose of the poly(ADP-ribose) polymerase (PARP) inhibitor, N-(6-oxo-5,6-dihydrophenanthridin-2-yl)-N,N-dimethylacetamide (PJ34). More interestingly, a significant reduction of plasma soluble RAGE (sRAGE) occurs 24 h after reperfusion and this effect is reverted by a neuroprotective dose of PJ34. Soluble forms of RAGE, generated either by alternative splicing or by proteolysis of the full-length form, effectively bind advanced glycation end products, thereby competing with the cell surface full-length RAGE, thus providing a 'decoy' function that may counteract the adverse effects of receptor signaling in neurons and may possibly exert cytoprotective effects. Thus, our data confirm the important role of RAGE in ischemic cerebral damage and, more interestingly, suggest the potential use of sRAGE as a blood biomarker of stroke severity and of neuroprotective treatment efficacy.

Targeting poly(ADP-ribose)polymerase1 in neurological diseases: A promising trove for new pharmacological interventions to enter clinical translation

The highly conserved abundant nuclear protein poly(ADP-ribose)polymerase1 (PARP1) functions at the center of cellular stress response and is mainly implied in DNA damage repair mechanism. Apart from its involvement in DNA damage repair, it does sway multiple vital cellular processes such as cell death pathways, cell aging, insulator function, chromatin modification, transcription and mitotic apparatus function. Since brain is the principal organ vulnerable to oxidative stress and inflammatory responses, upon stress encounters robust DNA damage can occur and intense PARP1 activation may result that will lead to various CNS diseases. In the context of soaring interest towards PARP1 as a therapeutic target for newer pharmacological interventions, here in the present review, we are attempting to give a silhouette of the role of PARP1 in the neurological diseases and the potential of its inhibitors to enter clinical translation, along with its structural and functional aspects.

Therapeutic applications of PARP inhibitors: anticancer therapy and beyond

The aim of this article is to describe the current and potential clinical translation of pharmacological inhibitors of poly(ADP-ribose) polymerase (PARP) for the therapy of various diseases. The first section of the present review summarizes the available preclinical and clinical data with PARP inhibitors in various forms of cancer. In this context, the role of PARP in single-strand DNA break repair is relevant, leading to replication-associated lesions that cannot be repaired if homologous recombination repair (HRR) is defective, and the synthetic lethality of PARP inhibitors in HRR-defective cancer. HRR defects are classically associated with BRCA1 and 2 mutations associated with familial breast and ovarian cancer, but there may be many other causes of HRR defects. Thus, PARP inhibitors may be the drugs of choice for BRCA mutant breast and ovarian cancers, and extend beyond these tumors if appropriate biomarkers can be developed to identify HRR defects. Multiple lines of preclinical data demonstrate that PARP inhibition increases cytotoxicity and tumor growth delay in combination with temozolomide, topoisomerase inhibitors and ionizing radiation. Both single agent and combination clinical trials are underway. The final part of the first section of the present review summarizes the current status of the various PARP inhibitors that are in various stages of clinical development. The second section of the present review summarizes the role of PARP in selected non-oncologic indications. In a number of severe, acute diseases (such as stroke, neurotrauma, circulatory shock and acute myocardial infarction) the clinical translatability of PARP inhibition is supported by multiple lines of preclinical data, as well as observational data demonstrating PARP activation in human tissue samples. In these disease indications, PARP overactivation due to oxidative and nitrative stress drives cell necrosis and pro-inflammatory gene expression, which contributes to disease pathology. Accordingly, multiple lines of preclinical data indicate the efficacy of PARP inhibitors to preserve viable tissue and to down-regulate inflammatory responses. As the clinical trials with PARP inhibitors in various forms of cancer progress, it is hoped that a second line of clinical investigations, aimed at testing of PARP inhibitors for various non-oncologic indications, will be initiated, as well.

Beyond DNA Repair: Additional Functions of PARP-1 in Cancer

Poly(ADP-ribose) polymerases (PARPs) are DNA-dependent nuclear enzymes that transfer negatively charged ADP-ribose moieties from cellular nicotinamide-adenine-dinucleotide (NAD(+)) to a variety of protein substrates, altering protein-protein and protein-DNA interactions. The most studied of these enzymes is poly(ADP-ribose) polymerase-1 (PARP-1), which is an excellent therapeutic target in cancer due to its pivotal role in the DNA damage response. Clinical studies have shown susceptibility to PARP inhibitors in DNA repair defective cancers with only mild adverse side effects. Interestingly, additional studies are emerging which demonstrate a role for this therapy in DNA repair proficient tumors through a variety of mechanisms. In this review, we will discuss additional functions of PARP-1 - including regulation of inflammatory mediators, cellular energetics and death pathways, gene transcription, sex hormone- and ERK-mediated signaling, and mitosis - and the role these PARP-1-mediated processes play in oncogenesis, cancer progression, and the development of therapeutic resistance. As PARP-1 can act in both a pro- and anti-tumor manner depending on the context, it is important to consider the global effects of this protein in determining when, and how, to best use PARP inhibitors in anticancer therapy.

Neuroprotective Mechanisms of Taurine against Ischemic Stroke

Ischemic stroke exhibits a multiplicity of pathophysiological mechanisms. To address the diverse pathophysiological mechanisms observed in ischemic stroke investigators seek to find therapeutic strategies that are multifaceted in their action by either investigating multipotential compounds or by using a combination of compounds. Taurine, an endogenous amino acid, exhibits a plethora of physiological functions. It exhibits antioxidative properties, stabilizes membrane, functions as an osmoregulator, modulates ionic movements, reduces the level of pro-inflammators, regulates intracellular calcium concentration; all of which contributes to its neuroprotective effect. Data are accumulating that show the neuroprotective mechanisms of taurine against stroke pathophysiology. In this review, we describe the neuroprotective mechanisms employed by taurine against ischemic stroke and its use in clinical trial for ischemic stroke.