Multiple facets of poly(ADP-ribose) polymerase-1 in neurological diseases

The highly conserved abundant nuclear protein poly （ADP-ribose） polymerase-1 （PARP-1） is activated by DNA damage. PARP-1 activation is associated in DNA repair, cell death and inflammation. Since oxidative stress induced robust DNA damage and wide spread inflamma- tory responses are common pathologies of various CNS diseases, the attention towards PARP-1 as a therapeutic target has been amplifying. This review highlights the multiple roles of PARP- 1 in neurological diseases and po- tential of PARP- 1 inhibitors to enter clinical translation.

Poly(ADP-ribose) polymerase-1 gene polymorphism in various Chinese nationalities

Poly （ADP-ribose） polymerase-1 （PARP-1） can exacerbate ischemic brain injury and lessen ischemic neuronal death, which may be associated with PARP-1 polymorphisms. The present study investigated human PARP-1 gene polymorphisms in various Chinese nationalities, the results of which could potentially help in the treatment and prevention of neurologic diseases. Genetic polymorphisms of seven exons in the PARP-1 gene, in 898 Chinese Han, Buyi, Shui, Miao, and Zhuang subjects, were investigated by PCR-single-strand conformation polymorphism. A single-strand conformation polymorphism variant in exons 12, 13, 16, and 17 of the PARP-1 gene was identified in 148 people, with two stationary bands showing three degenerative single strands. Results showed that the PARP-1 gene polymorphisms exist in various nationalities, and may act as a biomarker for susceptibility to disease.

Inhibition of poly(ADP-Ribose)polymerase:A promising strategy targeting pancreatic cancer with BRCAness phenotype

The use of chemotherapeutic regimens for the treatment of pancreatic cancer is still limited because pancreatic cancer is usually diagnosed at an advanced stage as a refractory disease in which symptoms are difficult to recognize in the early stages.Furthermore,at advanced stages,there are important challenges to achieve clinical benefit and symptom resolution,even with the use of an expanded spectrum of anticancer drugs.Recently,a point of reduced susceptibility to conventional chemotherapies by breast cancer susceptibility gene(BRCA)mutations led to a new perspective for overcoming the resistance of pancreatic cancer within the framework of increased genome instability.Poly(ADP-Ribose)polymerase(PARP)-1 is an enzyme that can regulate intrinsic functions,such as response to DNA damage.Therefore,in an environment where germline mutations in BRCAs(BRCAness)inhibit homologous recombination in DNA damage,resulting in a lack of DNA damage response,a key role of PARP-1 for the adaptation of the genome instability could be further emphasized.Here,we summarized the key functional role of PARP-1 in genomic instability of pancreatic cancer with the BRCAness phenotype and listed clinical applications and outcomes of PARP-1 inhibitors to highlight the importance of targeting PARP-1 activity.

Synergistic Suppressive Effect of PARP-1 Inhibitor PJ34 and HDAC Inhibitor SAHA on Proliferation of Liver Cancer Cells

Summary： Poly （ADP-ribose） polymerase-1 （PARP-1） inhibitors and histone deacetylase （HDAC） in- hibitors have recently emerged as promising anticancer drugs. The aim of this study was to investigate the effect of combination treatment with the PARP inhibitor P J34 and HDAC inhibitor SAHA on the proliferation of liver cancer cells. Cell proliferation and apoptosis were assessed in three human liver cancer cell lines （HepG2, Hep3B and HCC-LM3） treated with PJ34 （8 μmol/L） and SAHA （1 panol/L）, alone or combined, by Cell Counting Kit-8 assay and flow cytometry, respectively. The nude mice bear- ing subcutaneous HepG2 tumors were administered different groups of drugs （10 mg/kg PJ34, 25 mg/kg SAHA, 10 mg/kg PJ34＋25 mg/kg SAHA）, and the inhibition rates of tumor growth were compared between groups. The results showed that combined use of P J34 and SAHA could synergistically inhibit the proliferation of liver cancer cell lines HepG2, Hep3B and HCC-LM3. The apoptosis rate of HepG2 cells treated with PJ34＋SAHA was significantly higher than that of HepG2 cells treated with PJ34 or SAHA alone （P〈0.05）. In vivo, the tumor inhibition rates were 53.5%, 61.4% and 82.6% in PJ34, SAHA and PJ34＋SAHA groups, respectively. The combined use of PJ34 and SAHA could significantly inhibit the xenograft tumor growth when compared with use of P J34 or SAHA alone （P〈0.05）. It was led to conclude that P J34 and SAHA can synergistically suppress the proliferation of liver cancer cells.

Mechanisms of acquired resistance of BRCA1/2-driven tumors to platinum compounds and PARP inhibitors

Molecular pathogenesis of tumors arising in BRCA1/2 germ-line mutation carriers usually includes somatic inactivation of the remaining allele of the involved gene.Consequently,BRCA1/2-driven cancers are sensitive to platinum-based therapy and poly(ADP-ribose)polymerase inhibitors(PARPi).Long-term exposure to these drugs may result in the emergence of secondary BRCA1/2 mutations,which restore the open-reading frame of the affected allele.This platinum/PARPi crossresistance mechanism applies both for BRCA1 and BRCA2 genes and has been repeatedly validated in various laboratory models and multiple clinical studies.There are some other routes associated with the partial rescue of BRCA1/2 function or the development of BRCA1/2-independent pathways for genomic maintenance;however,their actual clinical relevance remains to be established.In addition,studies on the short-term neoadjuvant therapy for ovarian cancer revealed that even chemonaive BRCA1-driven tumors contain a small proportion of BRCA1-proficient cells.These pre-existing cells with retained BRCA1 heterozygosity rapidly repopulate the tumor mass during platinum exposure,but become outcompeted by BRCA1-deficient cells during therapy holidays.Understanding of the platinum/PARPi resistance pathways has led to the development of novel therapeutic approaches,which aim to improve the management of BRCA1/2-related cancers and are currently undergoing preclinical and clinical evaluation.

High mobility group box-1 release from H2O2-injured hepatocytes due to sirt1 functional inhibition

BACKGROUND High mobility group box-1 (HMGB1), recognized as a representative of damageassociated molecular patterns, is released during cell injury/death, triggering the inflammatory response and ultimately resulting in tissue damage. Dozens of studies have shown that HMGB1 is involved in certain diseases, but the details on how injured hepatocytes release HMGB1 need to be elicited. AIM To reveal HMGB1 release mechanism in hepatocytes undergoing oxidative stress. METHODS C57BL6/J male mice were fed a high-fat diet for 12 wk plus a single binge of ethanol to induce severe steatohepatitis. Hepatocytes treated with H2O2 were used to establish an in vitro model. Serum alanine aminotransferase, liver H2O2 content and catalase activity, lactate dehydrogenase and 8-hydroxy-2- deoxyguanosine content, nicotinamide adenine dinucleotide (NAD+) levels, and Sirtuin 1 (Sirt1) activity were detected by spectrophotometry. HMGB1 release was measured by enzyme linked immunosorbent assay. HMGB1 translocation was observed by immunohistochemistry/immunofluorescence or Western blot. Relative mRNA levels were assayed by qPCR and protein expression was detected by Western blot. Acetylated HMGB1 and poly(ADP-ribose)polymerase 1 (Parp1) were analyzed by Immunoprecipitation. RESULTS When hepatocytes were damaged, HMGB1 translocated from the nucleus to the cytoplasm because of its hyperacetylation and was passively released outside both in vivo and in vitro. After treatment with Sirt1-siRNA or Sirt1 inhibitor (EX527), the hyperacetylated HMGB1 in hepatocytes increased, and Sirt1 activity inhibited by H2O2 could be reversed by Parp1 inhibitor (DIQ). Parp1 and Sirt1 are two NAD+-dependent enzymes which play major roles in the decision of a cell to live or die in the context of stress . We showed that NAD+ depletion attributed to Parp1 activation after DNA damage was caused by oxidative stress in hepatocytes and resulted in Sirt1 activity inhibition. On the contrary, Sirt1 suppressed Parp1 by negatively regulating its gene expression and deacetylation. CONCLUSION The functional inhibition between Parp1 and Sirt1 leads to HMGB1 hyperacetylation, which leads to its translocation from the nucleus to the cytoplasm and finally outside the cell.

Inhibition of PARP1 Increases IRF-dependent Gene Transcription in Jurkat Cells

Poly(ADP-ribose) polymerase 1 (PARP1) plays important roles in the regulation of transcription factors. Mounting evidence has shown that inhibition of PARP1 influences the expression of genes associated with inflammatory response. Interferon regulatory factor 1 (IRF1) is a critical transcription factor for the development of both the innate and adaptive immune responses against infections. However, the molecular mechanism through which PARP1 mediates the effects has not been clearly demonstrated. Jurkat cells were exposed to dexamethasone (Dex) or PARP1 inhibitor PJ34. The expression levels of IL-12, LMP2, OAS1 and PKR were detected using real-time RT-PCR. The interactions between PARP1 and IRF1 were examined by coimmunoprecipitation (co-IP) assays. We further explored the mechanism of PARP1 suppressing IRF1 by assessing the activities of interferon stimulated response element (ISRE). The mRNA expression of IL-12, LMP2, OAS1 and PKR was obviously suppressed by Dex in Jurkat cells, which could be rescued by PJ34 treatment. Luciferase study revealed that poly(ADP-ribosyl)- ation suppressed IRF1-mediated transcription through preventing the binding of IRF1 to ISREs. PARP1 inhibited IRF1-mediated transcription in Jurkat cells by preventing IRF1 binding to ISREs in the promoters of target genes. It is suggested that PARP1 is a crucial regulator of IRF1-mediated immune response. This study provides experimental evidence for the possible application of PARP1 inhibitors in the treatment of IRF1-related immune anergy.

Poly adenosine diphosphate-ribosylation, a promising target for colorectal cancer treatment

The development of colorectal cancer(CRC)can result from changes in a variety of cellular systems within the tumor microenvironment.Particularly,it is primarily associated with genomic instability that is the gradual accumulation of genetic and epigenetic changes consisting of a characteristic set of mutations crucial for pathways in CRC progression.Based on this background,the potential to focus on poly[adenosine diphosphate(ADP)-ribose]polymerase(PARP)-1 and poly-ADP ribosylation(PARylation)as the main causes of malignant formation of CRC may be considered.One of the important functions of PARP-1 and PARylation is its deoxyribonucleic acid(DNA)repair function,which plays a pivotal role in the DNA damage response and prevention of DNA damage maintaining the redox homeostasis involved in the regulation of oxidation and superoxide.PARP-1 and PARylation can also alter epigenetic markers and chromatin structure involved in transcriptional regulation for the oncogenes or tumor suppressor genes by remodeling histone and chromatin enzymes.Given the high importance of these processes in CRC,it can be considered that PARP-1 and PARylation are at the forefront of the pathological changes required for CRC progression.Therefore,this review addresses the current molecular biological features for understanding the multifactorial function of PARP-1 and PARylation in CRC related to the aforementioned roles;furthermore,it presents a summary of recent approaches with PARP-1 inhibition in non-clinical and clinical studies targeting CRC.This understanding could help embrace the importance of targeting PARP-1 and PARylation in the treatment of CRC,which may present the potential to identify various research topics that can be challenged both nonclinically and clinically.

Correlation of LSD1 and PARP1 with cell proliferation and epithelial-mesenchymal transition in ovarian cancer tissue from ultrasound-guided puncture

Objective: To study the correlation of LSD1 and PARP1 with cell proliferation and epithelial-mesenchymal transition in ovarian cancer tissue from ultrasound-guided puncture. Methods:The ovarian cancer and ovarian benign lesion tissue from ultrasound-guided puncture in Pangang Group General Hospital in Panzhihua between May 2014 and March 2017 were collected to detect the mRNA expression of LSD1 and PARP1 as well as the protein levels of cell proliferation molecules and epithelial-mesenchymal transition molecules in them. Results: LSD1 and PARP1 mRNA expression in ovarian cancer tissue were significantly higher than those in benign ovarian tissue;P21, P27 and E-cadherin protein levels in ovarian cancer tissue were significantly lower than those in benign ovarian tissue while CyclinD1, E2F, Twist1, Snail, Slug and N-cadherin protein levels were significantly higher those in benign ovarian tissue;P21 and P27 protein levels in the ovarian cancer tissue with high LSD1 expression were significantly lower than those in the ovarian cancer tissue with low LSD1 expression while CyclinD1 and E2F protein levels were significantly higher than those in the ovarian cancer tissue with low LSD1 expression;Twist1, Snail, Slug and N-cadherin protein levels in the ovarian cancer tissue with high PARP1 expression were significantly higher than those in the ovarian cancer tissue with low PARP1 expression while E-cadherin protein level was significantly lower than that in the ovarian cancer tissue with low PARP1 expression. Conclusion: The LSD1 and PARP1 highly expressed in ovarian cancer tissue can promote the proliferation and epithelial-mesenchymal transition of cancer cells.

Correlation of serum sLAG-3, PARP-1 and CA50 levels with oncogene expression in surgically removed lesions in patients with gastric cancer

Objective:To study the correlation of serum sLAG-3, PARP-1 and CA50 levels with oncogene expression in surgically removed lesions in patients with gastric cancer.Methods: A total of 98 patients who were diagnosed with gastric cancer in Zhouzhi County People's Hospital between June 2015 and March 2017 were selected as the gastric cancer group of the research, and 60 healthy volunteers who received physical examination during the same period were selected as control group of the research. The serum was collected from the two groups to determine sLAG-3, PARP-1 and CA50 levels;gastric cancer lesions and adjacent lesions were collected from gastric cancer group to determine the protein expression of PDCD4, RASSF1A, p16ink4a, Kiss-1, Eaf-2, CDC4, UHRF1, OCT4, Zeb-1 and c-jun.Results:Serum sLAG-3, PARP-1 and CA50 levels of gastric cancer group were significantly higher than those of control group, and the higher the TNM stage, the higher the serum sLAG-3, PARP-1 and CA50 levels;PDCD4, RASSF1A, p16ink4a, Kiss-1, Eaf-2 and CDC4 protein levels in gastric cancer lesions were significantly lower than those in adjacent lesions and negatively correlated with serum sLAG-3, PARP-1 and CA50 levels, while UHRF1, OCT4, Zeb-1 and c-jun protein levels in gastric cancer lesions were significantly higher than those in adjacent lesions and positively correlated with serum sLAG-3, PARP-1 and CA50 levels.Conclusions:The increase in serum sLAG-3, PARP-1 and CA50 levels in patients with gastric cancer is closely related to the pathological process of gastric cancer, deletion of tumor suppressor gene expression and increase of proto-oncogene expression.

Combining PD1 inhibitor,PARP inhibitor and antiangiogenic medication for lung squamous cell carcinoma with liver metastasis:a case report

A 68-year-old man with left chest pain accompanied by chest tightness was reported.The computed tomography revealed a massive liver mass.Genetic and pathological tests confirmed advanced squamous cell lung carcinoma with the mutation of breast cancer susceptibility gene 1 and liver metastasis.The primary lung lesions and local liver metastases were well controlled through combined immunotherapy,antiangiogenic medications and Poly ADP-ribose polymerase inhibitors.Considering the high tumor load and the generally poor condition of the patient,transarterial chemoembolization,in place of the conventional chemotherapy treatment mode was chosed for liver metastasis in the current case.We discussed selecting a tailored program and outlined the patient’s diagnosis and treatment process.Additionally mentioned multiple drug combination strategies for squamous lung cancer.

Poly （ADP-ribose） polymerase inhibitor reduces heart ischaemia/ reperfusion injury via inflammation and Akt signalling in rats

Background Poly （ADP-ribose） polymerase （PARP） has been proposed to play an important role in the pathogenesis of heart ischaemia/reperfusion （I/R） injury. 3,4-dihydro-5-[4-（1-piperidinyl）butoxy]-l（2H）-isoquinolinone （DPQ）, a potent PARP inhibitor, has cardiac protective effects. Because the underlying mechanisms are not understood, we investigated the effect of DPQ on heart I/R injury and its mechanisms. Methods Studies were performed with I/R rats＇ hearts. DPQ was used to inhibit the activation of PARP. Cardiac function and cellular apoptosis were assessed. The activation of PARP, transcription factor nuclear factor-kappaB （NF-KB）, intercellular adhesion molecule-1 （ICAM-1）, cyclooxygenase-2 （COX-2） and matrix metalloproteinase-9 （MMP-9） were evaluated. We also evaluated expression of Akt and two of its downstream targets, glycogen synthase kinase-313 （GSK- 3β） and forkhead transcription factor FOXO3a. Results Administration of DPQ significantly decreased the activation of PARP and cellular apoptosis from （35±5）% to （20±4）% and simultaneously improved the cardiac function. DPQ reduced the expressions of NF-KB, ICAM-1, COX-2 and MMP-9 in rat heart and facilitated the activations of phosphor-Akt, phosphor-GSK-3β and phosphor-FOXO3a. Conclusion The protective effects of DPQ were associated with the suppression of inflammation and the activation of the Akt signalling pathways suggesting that the inhibition of poly （ADP-ribose） polymerase reduced heart I/R injury in rats.

Systemic treatment strategies for triple-negative breast cancer

Triple-negative breast cancer(TNBC) is defined by the lack of immunohistochemical expression of the estrogen and progesterone receptors and human epidermal growth factor receptor 2(EGFR2). Most TNBC has a basal-like molecular phenotype by gene expression profiling and shares clinical and pathological features with hereditary BRCA1 related breast cancers. This review evaluates the activity of available chemotherapy and targeted agents in TNBC. A systematic review of PubM ed and conference databases was carried out to identify randomised clinical trials reporting outcomes in women with TNBC treated with chemotherapy and targeted agents. Our review identified TNBC studies of chemotherapy and targeted agents with different mechanisms of action, including induction of synthetic lethality and inhibition of angiogenesis, growth and survival pathways. TNBC is sensitive to taxanes and anthracyclins. Platinum agents are effective in TNBC patients with BRCA1 mutation, either alone or in combination with poly adenosine diphosphate polymerase 1 inhibitors. Combinations of ixabepilone and capecitabine have added to progression-free survival(PFS) without survival benefit in metastatic TNBC. Antiangiogenic agents, tyrosine kinase inhibitors and EGFR inhibitorsin combination with chemotherapy produced only modest gains in PFS and had little impact on survival. TNBC subgroups respond differentially to specific targeted agents. In future, the treatment needs to be tailored for a specific patient, depending on the molecular characteristics of their malignancy. TNBC being a chemosensitive entity, combination with targeted agents have not produced substantial improvements in outcomes. Appropriate patient selection with rationale combinations of targeted agents is needed for success.

Effect of minocycline on cerebral ischemia-reperfusion injury

Minocylcine, a tetracycline derivate, has been shown to cross the blood-brain barrier and enter the central nervous system. In this study, cerebral ischemia-reperfusion injury models were established using the suture method, and minocycline was immediately injected intraperitoneally after cerebral ischemia-repeffusion （22.5 mg/kg, initially 45 mg/kg） at a 12-hour interval. Results showed that after minocycline treatment, the volume of cerebral infarction was significantly reduced, the number of surviving cell in the hippocampal CA1 region increased, the number of apoptotic cells decreased, the expression of caspase-3 and poly（adenosine diphosphate-ribose） polymerase-1 protein was down-regulated, and the escape latency in the water maze test was significantly shortened compared with the ischemia-reperfusion group. Our experimental findings indicate that minocycline can protect against neuronal injury induced by focal ischemia-reperfusion, which may be mediated by the inhibition of caspase-3 and poly（adenosine diphosphate-ribose） polymerase-1 protein expression.

核因子蛋白90敲减对肝癌细胞增殖影响及机制的研究

目的探究核因子蛋白90(NF90)敲减对肝癌细胞增殖影响并探讨其可能机制。方法将靶向NF90的寡核苷酸链克隆至PLKO质粒后,包装出靶向敲减NF90的慢病毒shRNA(带有绿色荧光标签及G418抗性)。将肝癌细胞QGY-7703、SMMC-7721分为对照组及干扰组,分别感染包含随机序列shRNA和靶向NF90 shRNA的病毒液。48 h后流式分选出带有绿色荧光的阳性细胞,G418筛选阳性单克隆细胞株,Western blotting鉴定NF90的蛋白表达水平,最终在对照组中选取一株细胞命名shRNA-ns,在干扰组中选取NF90敲减效果良好且稳定的两株细胞命名为shRNA-1、shRNA-2。采用CCK-8法检测各株细胞的增殖情况,克隆形成试验分析各株细胞的克隆形成能力。质谱分析预测NF90的相关结合蛋白,内、外源免疫共沉淀确定NF90与多聚ADP核糖合成酶(PARP1)的关系,荧光定位分析NF90与PARP1在细胞内的定位情况。结果 shRNA-1、shRNA-2细胞中的NF90表达水平显著低于shRNA-ns细胞,表明包装的慢病毒敲减NF90效果良好。与shRNA-ns细胞比较,shRNA-1、shRNA-2细胞的生长缓慢,克隆形成数减少,差异均有统计学意义(P<0.01)。NF90与PARP1在细胞内相互结合并且共定位于细胞核。结论敲减NF90可抑制肝癌细胞增殖,其机制可能与PARP1相互作用有关。

Chloride channel blocker 4,4-diisothiocyanatostilbene-2,2'-disulfonic acid inhibits nitric oxide-induced apoptosis in cultured rat hippocampal neurons

Apoptosis in cultured rat hippocampal neurons was induced using the nitric oxide donor 3-morpholinosydnonimine, and cells were treated with the chloride channel blocker, 4,4- diisothiocyanatostilbene-2,2＇-disulfonic acid. Results showed that the survival rate of neurons was significantly increased after treatment with 4,4-diisothiocyanatostilbene-2,2＇-disulfonic acid, and the rate of apoptosis decreased. In addition, the expression of the apoptosis-related proteins poly（adenosine diphosphate-ribose）polymerase-1 and apoptosis-inducing factor were significantly reduced. Our experimental findings indicate that the chloride channel blocker 4,4- diisothiocyanatostilbene-2,2＇-disulfonic acid can antagonize apoptotic cell death of hippocampal neurons by inhibiting the expression of the apoptosis-related proteins poly（adenosine diphosphate-ribose）polymerase-1 and apoptosis-inducing factor.

PARP-1对卵巢癌血管生成的影响

目的观察上皮性卵巢癌中聚腺苷酸二磷酸核糖聚合酶-1(PARP-1)表达与血管内皮生长因子-A(VEGF-A)、微血管密度(MVD)的关系,探讨PARP-1对卵巢癌血管生成的影响。方法采用免疫组织化学SP法检测60例上皮性卵巢癌原发灶中PARP-1、VEGF-A、MVD的表达以及30例正常卵巢对照组织中PARP-1的表达,根据组化结果判定标准将卵巢癌组织分为PARP-1阳性组和PARP-1阴性组。RNA干扰沉默卵巢癌SKOV3细胞的PARP-1基因,将细胞分为转染阴性对照siRNA组(NC-siRNA组)、转染PARP-1 siRNA组(PARP1-siRNA组),观察对脐静脉内皮细胞(HUVEC)体外成管的影响,ELISA法检测转染后细胞VEGF-A的表达水平。结果卵巢癌组织中PARP-1阳性率为73.3%(44/60),正常卵巢对照组织中PARP-1阳性率为26.7%(8/30),差异有统计学意义(P<0.05)。PARP-1表达与肿块大小、病理分级和淋巴结转移具有相关性;PARP-1表达与VEGF-A表达呈正相关(P<0.05);PARP-1阳性组MVD值显著高于PARP-1阴性组(P<0.01);体外成管数目NC-siRNA组(14.67±1.21)高于PARP1-siRNA组(8.83±1.47),差异有统计学意义(P<0.01);PARP1-siRNA组细胞VEGF-A的表达显著低于NC-siRNA组(P<0.01)。结论 PARP-1通过调控VEGF-A的表达影响卵巢癌的血管生成。

Regulation of DNA double-strand break repair pathway choice:a new focus on 53BP1

Maintenance of cellular homeostasis and genome integrity is a critical responsibility of DNA double-strand break(DSB)signaling.P53-binding protein 1(53BP1)plays a critical role in coordinating the DSB repair pathway choice and promotes the non-homologous end-joining(NHEJ)-mediated DSB repair pathway that rejoins DSB ends.New insights have been gained into a basic molecular mechanism that is involved in 53BP1 recruitment to the DNA lesion and how 53BP1 then recruits the DNA break-responsive effectors that promote NHEJ-mediated DSB repair while inhibiting homologous recombination(HR)signaling.This review focuses on the up-and downstream pathways of 53BP1 and how 53BP1 promotes NHEJ-mediated DSB repair,which in turn promotes the sensitivity of poly(ADP-ribose)polymerase inhibitor(PARPi)in BRCA1-deficient cancers and consequently provides an avenue for improving cancer therapy strategies.