PARP‑1 may be involved in hydroquinone‑induced apoptosis by poly ADP‑ribosylation of ZO‑2

Synthetic Lethality by Co-Inhibition of Androgen Receptor and Polyadenosine Diphosphate-Ribose in Metastatic Prostate Cancer

Androgen receptor pathway inhibitors (ARPI) and polyadenosine diphosphate-ribose inhibitors (PARPi) are part of the standard of care in patients with metastatic castration-resistant prostate cancer (mCRPC). There is biological evidence that the association of ARPI and PARPi could have a synergistic effect; therefore, several ongoing clinical trials are investigating the efficacy of this combination with preliminary results that are not perfectly concordant in identifying patients who can obtain the most benefit from this therapeutic option. The purpose of this review is to describe the PARPi mechanisms of action and to analyze the biological mechanisms behind the interplay between the androgen receptor and the PARPi system to better understand the rationale of the ARPI + PARPi combinations. Furthermore, we will summarize the preliminary results of the ongoing studies on these combinations, trying to understand in which patients to apply. Finally, we will discuss the clinical implications of this combination and its possible future perspectives.

Cytosine-phosphate-guanine oligodeoxynucleotides alleviate radiation-induced kidney injury in cervical cancer by inhibiting DNA damage and oxidative stress through blockade of PARP1/XRCC1 axis

BACKGROUND

Radiotherapy can cause kidney injury in patients with cervical cancer. This study aims to investigate the possible molecular mechanisms by which CpG-ODNs (Cytosine phosphate guanine-oligodeoxynucleotides) regulate the PARP1 (poly (ADP-ribose) polymerase 1)/XRCC1 (X-ray repair cross-complementing 1) signaling axis and its impact on radiation kidney injury (RKI) in cervical cancer radiotherapy.

METHODS

The GSE90627 dataset related to cervical cancer RKI was obtained from the Gene Expression Omnibus (GEO) database. Bioinformatics databases and R software packages were used to analyze the target genes regulated by CpG-ODNs. A mouse model of RKI was established by subjecting C57BL/6JNifdc mice to X-ray irradiation. Serum blood urea nitrogen (BUN) and creatinine levels were measured using an automated biochemical analyzer. Renal tissue morphology was observed through HE staining, while TUNEL staining was performed to detect apoptosis in renal tubular cells. ELISA was conducted to measure levels of oxidative stress-related factors in mouse serum and cell supernatant. An in vitro cell model of RKI was established using X-ray irradiation on HK-2 cells for mechanism validation. RT-qPCR was performed to determine the relative expression of PARP1 mRNA. Cell proliferation activity was assessed using the CCK-8 assay, and Caspase 3 activity was measured in HK-2 cells. Immunofluorescence was used to determine γH2AX expression.

RESULTS

Bioinformatics analysis revealed that the downstream targets regulated by CpG-ODNs in cervical cancer RKI were primarily PARP1 and XRCC1. CpG-ODNs may alleviate RKI by inhibiting DNA damage and oxidative stress levels. This resulted in significantly decreased levels of BUN and creatinine in RKI mice, as well as reduced renal tubular and glomerular damage, lower apoptosis rate, decreased DNA damage index (8-OHdG), and increased levels of antioxidant factors associated with oxidative stress (SOD, CAT, GSH, GPx). Among the CpG-ODNs, CpG-ODN2006 had a more pronounced effect. CpG-ODNs mediated the inhibition of PARP1, thereby suppressing DNA damage and oxidative stress response in vitro in HK-2 cells. Additionally, PARP1 promoted the formation of the PARP1 and XRCC1 complex by recruiting XRCC1, which in turn facilitated DNA damage and oxidative stress response in renal tubular cells. Overexpression of either PARP1 or XRCC1 reversed the inhibitory effects of CpG-ODN2006 on DNA damage and oxidative stress in the HK-2 cell model and RKI mouse model.

CONCLUSION

CpG-ODNs may mitigate cervical cancer RKI by blocking the activation of the PARP1/XRCC1 signaling axis, inhibiting DNA damage and oxidative stress response in renal tubule epithelial cells.

Brassinin Induces Apoptosis, Autophagy, and Paraptosis via MAPK Signaling Pathway Activation in Chronic Myelogenous Leukemia Cells

Brassinin (BSN), a potent phytoalexin found in cruciferous vegetables, has been found to exhibit diverse anti-neoplastic effects on different cancers. However, the impact of BSN on chronic myelogenous leukemia (CML) cells and the possible mode of its actions have not been described earlier. We investigated the anti-cytotoxic effects of BSN on the KBM5, KCL22, K562, and LAMA84 CML cells and its underlying mechanisms of action in inducing programmed cell death. We noted that BSN could induce apoptosis, autophagy, and paraptosis in CML cells. BSN induced PARP cleavage, subG1 peak increase, and early apoptosis. The potential action of BSN on autophagy activation was confirmed by an LC3 expression and acridine orange assay. In addition, BSN induced paraptosis through increasing the reactive oxygen species (ROS) production, mitochondria damage, and endoplasmic reticulum (ER) stress. Moreover, BSN promoted the activation of the MAPK signaling pathway, and pharmacological inhibitors of this signaling pathway could alleviate all three forms of cell death induced by BSN. Our data indicated that BSN could initiate the activation of apoptosis, autophagy, and paraptosis through modulating the MAPK signaling pathway.

SIRT1 regulated hexokinase-2 promoting glycolysis is involved in hydroquinone-enhanced malignant progression in human lymphoblastoid TK6 cells

Reprogramming of cellular metabolism is a vital event during tumorigenesis. The role of glycolysis in malignant progression promoted by hydroquinone (HQ), one of the metabolic products of benzene, remains to be understood. Recently, we reported the overexpression of sirtuin 1 (SIRT1) in HQ-enhanced malignant progression of TK6 cells and hypothesized that SIRT1 might contribute to glycolysis and favor tumorigenesis. Our data showed that acute exposure of TK6 cells to HQ for 48 h inhibited glycolysis, as indicated by reduction in glucose consumption, lactate production, hexokinase activity, and the expression of SIRT1 and glycolytic enzymes, including HIF-1α, hexokinase-2 (HK-2), ENO-1, glucose transporter 1 (Glut-1), and lactic dehydrogenase A (LDHA). Knockdown of SIRT1 or inhibition of glycolysis using the glycolytic inhibitor 2-deoxy-D-glucose (2-DG) downregulated the levels of SIRT1 and glycolytic enzymes and significantly enhanced HQ-induced cell apoptosis, although knockdown of SIRT1 or 2-DG alone had little effect on apoptosis. Furthermore, immunofluorescence and Co-IP assays demonstrated that SIRT1 regulated the expression of HK-2, and HQ treatment caused a decrease in SIRT1 and HK-2 binding to mitochondria. Importantly, we found that glycolysis was promoted with increasing HQ treatment weeks. Long-term HQ exposure increased the expression of SIRT1 and several glycolytic enzymes and promoted malignant cell progression. Moreover, compared with the PBS group, glucose consumption and lactate production increased after 10 weeks of HQ exposure, and the protein levels of SIRT1 and HK-2 were increased after 15 weeks of HQ exposure, while those of Glut-1, ENO-1, and LDHA were elevated. In addition, SIRT1 knockdown HQ 19 cells exhibited decreased lactate production, glucose consumption, glycolytic enzymes expression, cell growth, and tumor formation in nude mice. Our findings identify the high expression of SIRT1 as a strong oncogenic driver that positively regulates HK-2 and promotes glycolysis in HQ-accelerated malignant progression of TK6 cells.

Gamma-oryzanol protects human liver cell (L02) from hydrogen peroxide-induced oxidative damage through regulation of the MAPK/Nrf2 signaling pathways

Gamma-oryzanol (Orz), a mixture of the ferulic acid ester of triterpene alcohols and phytosterols, was found abundantly in rice bran and rice bran oil which could be available and served as an antioxidant. The present study was to explore the potential protective effects of Orz on oxidative stress and cell apoptosis in human hepatic cells (L02 cells) induced by hydrogen peroxide (H₂ O₂ ). Flow cytometry detection and Hoechst 33258 staining showed that Orz significantly restored cell cycle and ameliorated apoptosis in H₂ O₂ -challenged L02 cells. Orz pretreatment inhibited H₂ O₂ -induced cell apoptosis by increasing the scavenging of hydroxyl radicals (OH·), and efficiently decreasing the production of nitric oxide (NO). Moreover, a loss of total antioxidant capacity (T-AOC) and adenosine triphosphatase (ATPase) were enhanced in H₂ O₂ -mediated L02 cells pretreated with Orz. Furthermore, preincubation with Orz reduced H₂ O₂ -mediated the proapoptotic protein of Bak expression and the phosphorylation of ASK1, p38, JNK, and ERK, and increased the anti-apoptotic protein of Bcl-xl expression and anti-oxidative stress proteins of Nrf2 and HO-1 expression. The findings suggested that Orz exerts the cytoprotective effects in H₂ O₂ -induced L02 cells apoptosis by ameliorating oxidative stress via inhibiting MAPK signaling pathway and activating Nrf2 signaling pathway. PRACTICAL APPLICATIONS: Gamma-oryzanol (Orz), a mixture of the ferulic acid ester of triterpene alcohols and phytosterols, was found abundantly in rice bran and rice bran oil which could be availably served as an antioxidant. In this study, it was found that Orz exerts the cytoprotective effects in H₂ O₂ -induced L02 cell apoptosis by ameliorating oxidative stress via the inhibition of MAPK signaling pathway and the activation of Nrf2 signaling pathway, which provides a theoretical basis for dietary adding natural products to prevent or treat oxidative stress-related diseases.

The DNMT1-associated lncRNA UCA1 was upregulated in TK6 cells transformed by long-term exposure to hydroquinone and benzene-exposed workers via DNA hypomethylation

Exposure to benzene or its metabolite hydroquinone (HQ) is a risk factor for a series of myeloid malignancies, and long noncoding RNAs play an important role in the process of pathogenesis. Urothelial cancer-associated 1 (UCA1) functions as an oncogene in the development of acute myeloid leukemia. However, the association between DNMT1 and UCA1 with benzene or HQ exposure has not been explored. We characterized UCA1 expression in cells briefly exposed to HQ (HQ-ST cells) and HQ-induced malignantly transformed (TK6-HT cells) treated with 5-aza-2'-deoxycytidine (5-AzaC) or trichostatin A (TSA). Compared to that in control cells, UCA1 expression was increased, whereas DNMT1 was decreased in HQ-ST cells and TK6-HT cells treated with 5-AzaC or TSA. Moreover, UCA1 expression was also upregulated and positively correlated with benzene exposure time in benzene-exposed workers. Furthermore, the expression of UCA1 was negatively associated with the DNA methylation level of its promoter in benzene-exposed workers. DNMT1 rather than DNMT3b knockout in TK6-HT cells activated the expression of UCA1 by inducing its promoter hypomethylation. These results suggest that benzene or HQ exposure leads to UCA1 upregulation via DNA hypomethylation in the UCA1 promoter, which is mediated by DNMT1.

Hydroquinone Induces NLRP3-Independent IL-18 Release from ARPE-19 Cells

Age-related macular degeneration (AMD) is a retinal disease leading to impaired vision. Cigarette smoke increases the risk for developing AMD by causing increased reactive oxygen species (ROS) production and damage in the retinal pigment epithelium (RPE). We have previously shown that the cigarette tar component hydroquinone causes oxidative stress in human RPE cells. In the present study, we investigated the propensity of hydroquinone to induce the secretion of interleukin (IL)-1β and IL-18. The activation of these cytokines is usually regulated by the Nucleotide-binding domain, Leucine-rich repeat, and Pyrin domain 3 (NLRP3) inflammasome. ARPE-19 cells were exposed to hydroquinone, and cell viability was monitored using the lactate dehydrogenase (LDH) and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide salt (MTT) assays. Enzyme-linked immunosorbent assays (ELISAs) were used to measure the levels of proinflammatory cytokines IL-1β and IL-18 as well as NLRP3, caspase-1, and poly (ADP-ribose) polymerase (PARP). Hydroquinone did not change IL-1β release but significantly increased the secretion of IL-18. Cytoplasmic NLRP3 levels increased after the hydroquinone treatment of IL-1α-primed RPE cells, but IL-18 was equally released from primed and nonprimed cells. Hydroquinone reduced the intracellular levels of PARP, which were restored by treatment with the ROS scavenger N-acetyl-cysteine (NAC). NAC concurrently reduced the NLRP3 levels but had no effect on IL-18 release. In contrast, the NADPH oxidase inhibitor ammonium pyrrolidinedithiocarbamate (APDC) reduced the release of IL-18 but had no effect on the NLRP3 levels. Collectively, hydroquinone caused DNA damage seen as reduced intracellular PARP levels and induced NLRP3-independent IL-18 secretion in human RPE cells.

Differences in PARP Inhibitors for the Treatment of Ovarian Cancer: Mechanisms of Action, Pharmacology, Safety, and Efficacy

Poly(ADP-ribose) polymerases (PARP) are proteins responsible for DNA damage detection and signal transduction. PARP inhibitors (PARPi) are able to interact with the binding site for PARP cofactor (NAD+) and trapping PARP on the DNA. In this way, they inhibit single-strand DNA damage repair. These drugs have been approved in recent years for the treatment of ovarian cancer. Although they share some similarities, from the point of view of the chemical structure and pharmacodynamic, pharmacokinetic properties, these drugs also have some substantial differences. These differences may underlie the different safety profiles and activity of PARPi.

Hydroquinone exposure alters the morphology of lymphoid organs in vaccinated C57Bl/6 mice

The influenza is a common viral infection that can be fatal, especially in high-risk groups such as children, pregnant women, elderly, and immune-deficient individuals. Vaccination is the most efficient approach to prevent the spreading of viral infection and promote individual and public health. In contrast, exposure to environmental pollutants such as cigarette smoke reduces the efficacy of vaccination. We investigated whether chronic exposure to hydroquinone (HQ), the most abundant compound of the tobacco particulate phase, could impair the adaptive immune responses elicited by influenza vaccination. For this, adult male C57BL/6 mice were daily exposed to either nebulized HQ or PBS for 1 h for a total of eight weeks. At weeks 6 and 8, the mice were primed and boosted with the trivalent influenza vaccine via IM respectively. Although the HQ exposure did not alter the body weight of the mice and the biochemical and hematological parameters, the pollutant increased the oxidative stress in splenocytes of immunized animals, modified the morphology of spleen follicles, and augmented the size of their lymph nodes. The lymphoid organs of HQ-exposed mice presented a similar number of vaccine-specific IgG-secreting cells, titers of vaccine-specific total IgG, and respective subclasses. Transcriptome studies with HQ, benzene, or cigarette smoke exposure were also analyzed. The genes up-regulated upon pollutant exposure were associated with neutrophil migration and were shown to be co-expressed with antibody-secreting cell genes. Therefore, these findings suggest that HQ exposure may trigger an immune-compensatory mechanism that enhances the humoral responses induced by influenza vaccination.

RMP/URI inhibits both intrinsic and extrinsic apoptosis through different signaling pathways

The evading apoptosis of tumor cells may result in chemotherapy resistance. Therefore, investigating what molecular events contribute to drug-induced apoptosis, and how tumors evade apoptotic death, provides a paradigm to explain the relationship between cancer genetics and treatment sensitivity. In this study, we focused on the role of RMP/URI both in cisplatin-induced endogenous apoptosis and in TRAIL-induced exogenous apoptosis in HCC cells. Although flow cytometric analysis indicated that RMP overexpression reduced the apoptosis rate of HCC cells treated with both cisplatin and TRAIL, there was a difference in mechanism between the two treatments. Western blot showed that in intrinsic apoptosis induced by cisplatin, the overexpression of RMP promoted the Bcl-xl expression both in vitro and in vivo. Besides, RMP activated NF-κB/p65(rel) through the phosphorylation of ATM. However, in TRAIL-induced extrinsic apoptosis, RMP significantly suppressed the transcription and expression of P53. Moreover, the forced expression of P53 could offset this inhibitory effect. In conclusion, we presumed that RMP inhibited both intrinsic and extrinsic apoptosis through different signaling pathways. NF-κB was distinctively involved in the RMP circumvention of intrinsic apoptosis, but not in the extrinsic apoptosis of HCC cells. RMP might play an important role in defects of apoptosis, hence the chemotherapeutic resistance in hepatocellular carcinoma. These studies are promising to shed light on a more rational approach to clinical anticancer drug design and therapy.

ZO-2 Is a Master Regulator of Gene Expression, Cell Proliferation, Cytoarchitecture, and Cell Size

ZO-2 is a cytoplasmic protein of tight junctions (TJs). Here, we describe ZO-2 involvement in the formation of the apical junctional complex during early development and in TJ biogenesis in epithelial cultured cells. ZO-2 acts as a scaffold for the polymerization of claudins at TJs and plays a unique role in the blood–testis barrier, as well as at TJs of the human liver and the inner ear. ZO-2 movement between the cytoplasm and nucleus is regulated by nuclear localization and exportation signals and post-translation modifications, while ZO-2 arrival at the cell border is triggered by activation of calcium sensing receptors and corresponding downstream signaling. Depending on its location, ZO-2 associates with junctional proteins and the actomyosin cytoskeleton or a variety of nuclear proteins, playing a role as a transcriptional repressor that leads to inhibition of cell proliferation and transformation. ZO-2 regulates cell architecture through modulation of Rho proteins and its absence induces hypertrophy due to inactivation of the Hippo pathway and activation of mTOR and S6K. The interaction of ZO-2 with viral oncoproteins and kinases and its silencing in diverse carcinomas reinforce the view of ZO-2 as a tumor regulator protein.

Striatin is a novel modulator of cell adhesion

The adherens junctions (AJs) and tight junctions (TJs) provide critical adhesive contacts between neighboring epithelial cells and are crucial for epithelial adhesion, integrity, and barrier functions in a wide variety of tissues and organisms. The striatin protein family, which are part of the striatin interaction phosphatases and kinases complex, are multidomain scaffolding proteins that play important biologic roles. We have previously shown that striatin colocalizes with the tumor suppressor protein adenomatous polyposis coli in the TJs of epithelial cells. Here we show that striatin affects junction integrity and cell migration, probably through a mechanism that involves the adhesion molecule E-cadherin. Cells engaged in cell-cell adhesion expressed a high MW-modified form of striatin that forms stable associations with detergent-insoluble, membrane-bound cellular fractions. In addition, striatin has recently been suggested to be a target of the poly (ADP-ribose) polymerases Tankyrase 1, and we have found that striatin interacts with Tankyrase 1 and is subsequently poly-ADP-ribosylated. Taken together, our results suggest that striatin is a novel cell-cell junctional protein that functions to maintain correct cell adhesion and may have a role in establishing the relationship between AJs and TJs that is fundamental for epithelial cell-cell adhesion.-Lahav-Ariel, L., Caspi, M., Nadar-Ponniah, P. T., Zelikson, N., Hofmann, I., Hanson, K. K., Franke, W. W., Sklan, E. H., Avraham, K. B., Rosin-Arbesfeld, R. Striatin is a novel modulator of cell adhesion.

Protective Effects of Aqueous Extracts of Flos lonicerae Japonicae against Hydroquinone-Induced Toxicity in Hepatic L02 Cells

Hydroquinone (HQ) is widely used in food stuffs and is an occupational and environmental pollutant. Although the hepatotoxicity of HQ has been demonstrated both in vitro and in vivo, the prevention of HQ-induced hepatotoxicity has yet to be elucidated. In this study, we focused on the intervention effect of aqueous extracts of Flos lonicerae Japonicae (FLJ) on HQ-induced cytotoxicity. We demonstrated that HQ reduced cell viability in a concentration-dependent manner by administering 160 μmol/L HQ for 12 h as the positive control of cytotoxicity. The aqueous FLJ extracts significantly increased cell viability and decreased LDH release, ALT, and AST in a concentration-dependent manner compared with the corresponding HQ-treated groups in hepatic L02 cells. This result indicated that aqueous FLJ extracts could protect the cytotoxicity induced by HQ. HQ increased intracellular MDA and LPO and decreased the activities of GSH, GSH-Px, and SOD in hepatic L02 cells. In addition, aqueous FLJ extracts significantly suppressed HQ-stimulated oxidative damage. Moreover, HQ promoted DNA double-strand breaks (DSBs) and the level of 8-hydroxy-2'-deoxyguanosine and apoptosis. However, aqueous FLJ extracts reversed HQ-induced DNA damage and apoptosis in a concentration-dependent manner. Overall, our results demonstrated that the toxicity of HQ was mediated by intracellular oxidative stress, which activated DNA damage and apoptosis. The findings also proved that aqueous FLJ extracts exerted protective effects against HQ-induced cytotoxicity in hepatic L02 cells.