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

4'-O-methylbavachalcone alleviates ischemic stroke injury by inhibiting parthanatos and promoting SIRT3

Cerebral ischemia-reperfusion injury (CIRI) can induce massive death of ischemic penumbra neurons via oxygen burst, exacerbating brain damage. Parthanatos is a form of caspase-independent cell death involving excessive activation of PARP-1, closely associated with intense oxidative stress following CIRI. 4'-O-methylbavachalcone (MeBavaC), an isoprenylated chalcone component in Fructus Psoraleae, has potential neuroprotective effects. This study primarily investigates whether MeBavaC can act on SIRT3 to alleviate parthanatos of ischemic penumbra neurons induced by CIRI. MeBavaC was oral gavaged to the middle cerebral artery occlusion-reperfusion (MCAO/R) rats after occlusion. The effects of MeBavaC on cerebral injury were detected by the neurological deficit score and cerebral infarct volume. In vitro, PC-12 cells were subjected to oxygen and glucose deprivation/reoxygenation (OGD/R), and assessed cell viability and cell injury. Also, the levels of ROS, mitochondrial membrane potential (MMP), and intracellular Ca2+ levels were detected to reflect mitochondrial function. We conducted western blotting analyses of proteins involved in parthanatos and related signaling pathways. Finally, the exact mechanism between the neuroprotection of MeBavaC and parthanatos was explored. Our results indicate that MeBavaC reduces the cerebral infarct volume and neurological deficit scores in MCAO/R rats, and inhibits the decreased viability of PC-12 cells induced by OGD/R. MeBavaC also downregulates the expression of parthanatos-related death proteins PARP-1, PAR, and AIF. However, this inhibitory effect is weakened after the use of a SIRT3 inhibitor. In conclusion, the protective effect of MeBavaC against CIRI may be achieved by inhibiting parthanatos of ischemic penumbra neurons through the SIRT3-PARP-1 axis.

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.

Inhibition of GSDMD Activates Poly(ADP-ribosyl)ation and Promotes Myocardial Ischemia-Reperfusion Injury

The precise control of cardiomyocyte viability is imperative to combat myocardial ischemia-reperfusion injury (I/R), in which apoptosis and pyroptosis putatively contribute to the process. Recent researches indicated that GSDMD is involved in I/R as an executive protein of pyroptosis. However, its effect on other forms of cell death is unclear. We identified that GSDMD and GSDMD-N levels were significantly upregulated in the I/R myocardium of mice. Knockout of GSDMD conferred the resistance of the hearts to reperfusion injury in the acute phase of I/R but aggravated reperfusion injury in the chronic phase of I/R. Mechanistically, GSDMD deficiency induced the activation of PARylation and the consumption of NAD+ and ATP, leading to cardiomyocyte apoptosis. Moreover, PJ34, a putative PARP-1 inhibitor, reduced the myocardial injury caused by GSDMD deficiency. Our results reveal a novel action modality of GSDMD in the regulation of cardiomyocyte death; inhibition of GSDMD activates PARylation, suggesting the multidirectional role of GSDMD in I/R and providing a new theory for clinical treatment.

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.

Poly(ADP-ribose) Polymerase (PARP) is Critically Involved in Liver Ischemia/reperfusion-injury

BACKGROUND

Poly(ADP-ribose) polymerase (PARP) is a DNA-repairing enzyme activated by extreme genomic stress, and therefore is potently activated in the remnant liver suffering from ischemia after surgical resection. However, the impact of PARP on post-ischemic liver injury has not been elucidated yet.

MATERIALS AND METHODS

We investigated the impact of PARP on murine hepatocyte/liver injury induced by hypoxia/ischemia, respectively.

RESULTS

PJ34, a specific inhibitor of PARP, markedly protected against hypoxia/reoxygenation (H/R)-induced cell death, though z-VAD-fmk, a pan-caspase inhibitor similarly showed the protective effect. PJ34 did not affect H/R-induced caspase activity or caspase-mediated cell death. z-VAD-fmk also did not affect the production of PAR (i.e., PARP activity). Therefore, PARP- and caspase-mediated cell death occurred in a mechanism independent of each other in H/R. H/R immediately induced activation of PARP and cell death afterwards, both of which were suppressed by PJ34 or Trolox, an antioxidant. This suggests that H/R-induced cell death occurred redox-dependently through PARP activation. H/R and OS induced nuclear translocation of apoptosis inducing factor (AIF, a marker of parthanatos) and RIP1-RIP3 interaction (a marker of necroptosis), both of which were suppressed by PJ34. H/R induced PARP-mediated parthanatos and necroptosis redox-dependently. In mouse experiments, PJ34 significantly reduced serum levels of AST, ALT & LDH and areas of hepatic necrosis after liver ischemia/reperfusion, similar to z-VAD-fmk or Trolox.

CONCLUSION

PARP, activated by ischemic damage and/or oxidative stress, may play a critical role in post-ischemic liver injury by inducing programmed necrosis (parthanatos and necroptosis). PARP inhibition may be one of the promising strategies against post-ischemic liver injury.

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

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

Therapeutic Strategies and Biomarkers to Modulate PARP Activity for Targeted Cancer Therapy

Poly-(ADP-ribose) polymerase 1 (PARP1) is commonly known for its vital role in DNA damage response and repair. However, its enzymatic activity has been linked to a plethora of physiological and pathophysiological transactions ranging from cellular proliferation, survival and death. For instance, malignancies with BRCA1/2 mutations heavily rely on PARP activity for survival. Thus, the use of PARP inhibitors is a well-established intervention in these types of tumors. However, recent studies indicate that the therapeutic potential of attenuating PARP1 activity in recalcitrant tumors, especially where PARP1 is aberrantly overexpressed and hyperactivated, may extend its therapeutic utility in wider cancer types beyond BRCA-deficiency. Here, we discuss treatment strategies to expand the tumor-selective therapeutic application of PARP inhibitors and novel approaches with predictive biomarkers to perturb NAD⁺ levels and hyperPARylation that inactivate PARP in recalcitrant tumors. We also provide an overview of genetic alterations that transform non-BRCA mutant cancers to a state of "BRCAness" as potential biomarkers for synthetic lethality with PARP inhibitors. Finally, we discuss a paradigm shift for the use of novel PARP inhibitors outside of cancer treatment, where it has the potential to rescue normal cells from severe oxidative damage during ischemia-reperfusion injury induced by surgery and radiotherapy.

Targeting intestinal epithelial cell-programmed necrosis alleviates tissue injury after intestinal ischemia/reperfusion in rats

BACKGROUND

Intestinal dysfunction, especially acute pathologies linked to intestinal ischemia/reperfusion (I/R) injury, is profoundly affected by inflammation and improper execution of cell death. Few studies have examined the efficacy of combined strategies in regulated intestinal epithelial necrosis after intestinal I/R. Here, we evaluated the functional interaction between poly (adenosine diphosphate-ribose) polymerase 1 (PARP-1)-induced parthanatos and receptor-interacting protein 1/3 (RIP1/3) kinase-induced necroptosis in the pathophysiological course of acute ischemic intestinal injury.

METHODS

Anesthetized adult male Sprague-Dawley rats were subjected to superior mesenteric artery occlusion consisting of 1.5 h of ischemia and 6 h of reperfusion. The PARP-1-specific inhibitor PJ34 (10 mg/kg) and the RIP1-specific inhibitor Necrostatin-1 (1 mg/kg) were intraperitoneally administered 30 min before the induction of ischemia.

RESULTS

Intestinal I/R was found to result in PARP-1 activation and RIP1/3-mediated necrosome formation. PJ34 or Necrostatin-1 treatment significantly improved the mucosal injury, while the combined inhibition of PARP-1 and RIP1/3 conferred optimal protection of the intestine. Meanwhile, results from terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick end labeling assay showed a decrease in intestinal epithelial cell death. Interestingly, we further showed that PARP-1 might act as a downstream signaling molecule of RIP1 in the process of I/R-induced intestinal injury and that the RIP1/PARP-1-dependent cell death signaling pathway functioned independently of caspase 3 inhibition.

CONCLUSIONS

The results of our study provide a molecular basis for combination therapy that targets both pathways of regulated necrosis (parthanatos and necroptosis), to treat acute intestinal I/R-induced intestinal epithelial barrier disruption.

The protective effect of dexmedetomidine in a rat ex vivo lung model of ischemia-reperfusion injury

PURPOSE

To investigate the effect of dexmedetomidine (Dex) in a rat ex vivo lung model of ischemia-reperfusion injury.

METHODS

An IL-2 ex vivo lung perfusion system was used to establish a rat ex vivo lung model of ischemia-reperfusion injury. Drugs were added to the perfusion solution for reperfusion. Lung injury was assessed by histopathological changes, airway pressure (Res), lung compliance (Compl), perfusion flow (Flow), pulmonary venous oxygen partial pressure (PaO2), and lung wet/dry (W/D) weight ratio. The levels of superoxide dismutase (SOD), malondialdehyde (MDA), 78 kDa glucose-regulated protein (GRP78) and CCAAT/enhancer-binding protein homologous protein (CHOP) were measured, respectively.

RESULTS

The introduction of Dex attenuated the post-ischemia-reperfusion lung damage and MDA level, improved lung histology, W/D ratio, lung injury scores and SOD activity. Decreased mRNA and protein levels of GRP78 and CHOP compared with the IR group were observed after Dex treatment. The effect of Dex was dosage-dependence and a high dose of Dex (10 nM) was shown to confer the strongest protective effect against lung damage (P<0.05). Yohimbine, an α2 receptor antagonist, significantly reversed the protective effect of Dex in lung tissues (P<0.05).

CONCLUSION

Dex reduced ischemia-reperfusion injury in rat ex vivo lungs.

Topiramate Reduces Aortic Cross-Clamping-Induced Lung Injury in Male Rats

BACKGROUND

Topiramate (TPM) decreases cytokine release and generation of reactive oxygen species (ROS). Cytokine and endothelin-1 (ET-1) secretion and ROS formation play an important role in ischemia-reperfusion (I/R) injury. We aimed to evaluate whether TPM prevents damage occurring in lung tissue during I/R.

MATERIALS AND METHODS

A total of 27 Wistar albino rats were divided into three groups of nine. To the I/R group, two hours of ischemia via infrarenal abdominal aorta cross-ligation and then two hours of reperfusion process were applied. TPM (100 mg/kg/day) orally for seven days was administered in the TPM treatment group. After the last dose of TPM treatment, respectively, two hours of ischemia and two hours of reperfusion were applied in this group.

RESULTS

Tumor necrosis factor-alpha (TNF-α) (p < 0.05), malondialdehyde (MDA) (p < 0.05), myeloperoxidase (MPO) (p < 0.05) and ET-1 (p < 0.05) levels of TPM treatment group's lung tissue were significantly lower than for the I/R group. Caspase-3 and histopathological damage were rather lower than that of the I/R group.

CONCLUSIONS

During I/R, lung damage occurs due to excessive TNF-α and ET-1 release and ROS generation. TPM could well reduce development of lung damage by decreasing cytokine and ET-1 release and levels of ROS produced.

Mechanisms of lung ischemia-reperfusion injury

PURPOSE OF REVIEW

Lungs are extremely susceptible to injury, and despite advances in surgical management and immunosuppression, outcomes for lung transplantation are the worst of any solid organ transplant. The success of lung transplantation is limited by high rates of primary graft dysfunction because of ischemia-reperfusion injury characterized by robust inflammation, alveolar damage, and vascular permeability. This review will summarize major mechanisms of lung ischemia-reperfusion injury with a focus on the most recent findings in this area.

RECENT FINDINGS

Over the past 18 months, numerous studies have described strategies to limit lung ischemia-reperfusion injury in experimental settings, which often reveal mechanistic insight. Many of these strategies involved the use of various antioxidants, anti-inflammatory agents, mesenchymal stem cells, and ventilation with gaseous molecules. Further advancements have been achieved in understanding mechanisms of innate immune cell activation, neutrophil infiltration, endothelial barrier dysfunction, and oxidative stress responses.

SUMMARY

Methods for prevention of primary graft dysfunction after lung transplant are urgently needed, and understanding mechanisms of ischemia-reperfusion injury is critical for the development of novel and effective therapeutic approaches. In doing so, both acute and chronic outcomes of lung transplant recipients will be significantly improved.

Immersing lungs in hydrogen-rich saline attenuates lung ischaemia-reperfusion injury

Objectives

Anti-oxidant effects of hydrogen have been reported in studies examining ischaemia-reperfusion injury (IRI). In this study, we evaluated the therapeutic efficacy of immersing lungs in hydrogen-rich saline on lung IRI.

Methods

Lewis rats were divided into three groups: (i) sham, (ii) normal saline and (iii) hydrogen-rich saline. In the first experiment, the left thoracic cavity was filled with either normal saline or hydrogen-rich saline for 1 h. Then, we measured the hydrogen concentration in the left lung using a sensor gas chromatograph ( N = 3 per group). In the second experiment, lung IRI was induced by occlusion of the left pulmonary hilum for 1 h, followed by reperfusion for 3 h. During the ischaemic period, the left thoracic cavity was filled with either normal saline or hydrogen-rich saline. After reperfusion, we assessed lung function, histological changes and cytokine production ( N = 5-7 per group).

Results

Immersing lungs in hydrogen-rich saline resulted in an elevated hydrogen concentration in the lung (6.9 ± 2.9 μmol/1 g lung). After IRI, pulmonary function (pulmonary compliance and oxygenation levels) was significantly higher in the hydrogen-rich saline group than in the normal saline group ( P  < 0.05). Similarly, pro-inflammatory cytokine levels (interleukin-1β and interleukin-6) in the left lung were significantly lower in the hydrogen-rich saline group than in the normal saline group ( P  < 0.05).

Conclusions

Immersing lungs in hydrogen-rich saline delivered hydrogen into the lung and consequently attenuated lung IRI. Hydrogen-rich solution appears to be a promising approach to managing lung IRI.

PARP-1 promotes tumor recurrence after warm ischemic liver graft transplantation via neutrophil recruitment and polarization

Poly (ADP-ribose) polymerase 1 (PARP-1) is a crucial contributor to exacerbate ischemia and reperfusion (IR) injury and cancer process. However, there is little research into whether PARP-1 affects the hepatocellular carcinoma (HCC) recurrence after liver transplantation. In this study, we investigated the influence of PARP-1 on hepatic neutrophil mobilizing and phenotype shifting which may lead to HCC recurrence after liver transplantation. We found that rats received the grafts with warm ischemic injury had higher risk of HCC recurrence, which was markedly prevented by pharmacological inhibition of PARP-1 after liver transplantation. In mouse models, the up-regulation of PARP-1 was closely related to the greater tumor burden and increased hepatic susceptibility to recurrence after IR injury. The reason was that high hepatic PARP-1 led to increased liver CXCL1 levels, which in turn promoted recruitment of neutrophils. Both blocking CXCL1/CXCR2 signaling pathway and depleting neutrophils decreased tumor burden. Moreover, these infiltrating neutrophils were programmed to a proangiogenic phenotype under the influence of PARP-1 in vivo after hepatic IR injury. In conclusion, IR-induced PARP-1 up-regulation increased the hepatic recruitment of neutrophils through regulation of CXCL1/CXCR2 signaling and polarized hepatic neutrophils to proangiogenic phenotype, which further promoted HCC recurrence after transplantation.

Oxymatrine on Hsp90a expression and apoptosis in a model of lung ischemia-reperfusion injury

The protective effects of oxymatrine (OMT) on apoptosis and heat shock protein 90a (Hsp90a) expression in a rabbit model of lung ischemia-reperfusion injury (LIRI) were investigated. The model of LIRI was established in rabbits and they were randomly divided into two groups: The control group (group C, n=10), and experimental group (further divided into groups E1, n=10; and group E2, n=10), to measure the levels of malondialdehyde (MDA) and superoxide dismutase (SOD) activity in lung tissue homogenates at several time points (T₀, 0 min; T₁, 60 min; T₂, 120 min; T₃, 180 min; and T₄, 240 min), and to measures changes in lung tissue wet/dry weight ratio (W/D), apoptosis index (AI), and Hsp90a expression and organization at T₂, T₃ and T₄. Comparing group C with groups E1 and E2, the levels of SOD activity and MDA were not significantly different at T₀ and T₁ (P>0.05); W/D ratio and AI were significantly higher than in groups E1 and E2 (P<0.05, P<0.01); 120 min after LIR, MDA, W/D ratio, and AI were lower than in groups E1 and E2 (P<0.05, P<0.01). MDA, W/D ratio and AI were lower in E2 than in E1 (P<0.05), and SOD and Hsp90a expression increased (P<0.05). The ultrastructure in group E showed less injury compared with group C. In conclusion, by scavenging oxygen free radicals, OMT can inhibit apoptosis, increase Hsp90a expression, and reduce the injury caused by lung ischemia reperfusion.

Associations between autophagy, the ubiquitin-proteasome system and endoplasmic reticulum stress in hypoxia-deoxygenation or ischemia-reperfusion

The activation of autophagy has been demonstrated to exert protective roles during hypoxia-reoxygenation (H/R)-induced brain injuries. This study aimed to investigate whether and how preconditioning with a proteasome inhibitor (MG-132), a proteasome promoter (Adriamycin, ADM), an autophagy inhibitor (3-methyladenine, 3-MA) and an autophagy promoter (Rapamycin, Rap) affected endoplasmic reticulum stress (ERS), the ubiquitin-proteasome system (UPS), autophagy, inflammation and apoptosis. Ubiquitin protein and 26S proteasome activity levels were decreased by MG-132 pretreatment but increased by ADM pretreatment at 2h, 4h and 6h following H/R treatment. MG-132 pretreatment led to the increased expression of autophagy-related genes, ER stress-associated genes and IκB but decreased the expression levels of NF-κB and caspase-3. ADM pretreatment led to the decreased expression of autophagy-related genes, ERS-associated genes and IκB but increased the expression of NF-κB and caspase-3. Pretreatment with 3-MA reduced the expression of autophagy-related genes, autophagy and UPS co-related genes, as well as apoptosis-related although the latter was increased by Rap pretreatment at 2h, 4h and 6h following H/R treatment. In vivo, pretreatment of rats with ADM, MG-132, 3-MA or Rap followed by ischemia-reperfusion (I/R) treatment resulted in similar changes. Proteasome inhibition preconditioning strengthened autophagy and ER stress but decreased apoptosis and inflammation. Autophagy promotion preconditioning exhibited similar changes. The combination of a proteasome inhibitor and an autophagy promoter might represent a new possible therapy to treat H/R or I/R injury-related diseases.

Concepts and Molecular Aspects in the Polypharmacology of PARP-1 Inhibitors

Recent years have witnessed a renewed interest in PARP-1 inhibitors as promising anticancer agents with multifaceted functions. Particularly exciting developments include the approval of olaparib (Lynparza) for the treatment of refractory ovarian cancer in patients with BRCA1/2 mutations, and the increasing understanding of the polypharmacology of PARP-1 inhibitors. The aim of this review article is to provide the reader with a comprehensive overview of the distinct levels of the polypharmacology of PARP-1 inhibitors, including 1) inter-family polypharmacology, 2) intra-family polypharmacology, and 3) multi-signaling polypharmacology. Progress made in gaining insight into the molecular basis of these multiple target-independent and target-dependent activities of PARP-1 inhibitors are discussed, with an outlook on the potential impact that a better understanding of polypharmacology may have in aiding the explanation as to why some drug candidates work better than others in clinical settings, albeit acting on the same target with similar inhibitory potency.