The human AP-endonuclease (APE1/Ref-1), an essential multifunctional protein, plays a central role in the repair of oxidative base damage via the DNA base excision repair (BER) pathway. The mammalian AP-endonuclease (APE1) overexpression is often observed in tumor cells, and confers resistance to various anticancer drugs; its downregulation sensitizes tumor cells to those agents via induction of apoptosis. Here we show that wild type (WT) but not mutant p53 negatively regulates APE1 expression. Time-dependent decrease was observed in APE1 mRNA and protein levels in the human colorectal cancer line HCT116 p53(+/+), but not in the isogenic p53 null mutant after treatment with camptothecin, a DNA topoisomerase I inhibitor. Furthermore, ectopic expression of WTp53 in the p53 null cells significantly reduced both endogenous APE1 and APE1 promoter-dependent luciferase expression in a dose-dependent fashion. Chromatin immunoprecipitation assays revealed that endogenous p53 is bound to the APE1 promoter region that includes a Sp1 site. We show here that WTp53 interferes with Sp1 binding to the APE1 promoter, which provides a mechanism for the downregulation of APE1. Taken together, our results demonstrate that WTp53 is a negative regulator of APE1 expression, so that repression of APE1 by p53 could provide an additional pathway for p53-dependent induction of apoptosis in response to DNA damage.

BackgroundChronic administration of Aluminum is proposed as an environmental factor that may affect several enzymes and other biomolecules related to neurotoxicity and Alzheimer's disease (AD). APE1 a multifunctional protein, functions in DNA repair and plays a key role in cell survival versus cell death upon stimulation with cytotoxic agent, making it an attractive emerging therapeutic target. The promising protective effect of resveratrol (resv), which is known to exert potent anti-inflammatory effects on neurotoxicity induced by aluminum chloride (AlCl3), may be derived from its own antioxidant properties. In the present work we investigated the modulation of APE1 expression during AlCl3-induced neuroinflammation (25 mg/Kg body weight by oral gavages) in experimental rats. We tested the hypothesis that a reactive oxygen species (ROS)-scavenger, resveratrol at 0.5 mg/kg bodyweight, which is known to exert potent anti-inflammatory effects, would attenuate central inflammation and modulate APE1 expression in AlCl3-fed rats. Neuroinflammation-induced genes including β-secretase (BACE), amyloid-β precursor protein (APP), presenilin 2 (PSEN-2) and sirt-2 were determined by RT-PCR. APE1 is determined at mRNA and protein levels and confirmed by immunohistochemistry. The expression of pro-inflammatory cytokines (TNF-α, IL6) and iNOS by the rat brain extract were measured by RT-PCR.ResultOur results indicate that resveratrol may attenuate AlCl3-induced direct neuroinflammation in rats, and its mechanisms are, at least partly, due to maintaining high APE1 level. Resveratrol co-administration with aluminum chloride exerted more protective effect than pre-administration or treatment of induced rats. A significant elevation of APE1 at both mRNA and protein levels was observed in addition to a marked reduction in β-secretase and amyloid-β. We found that AlCl3 stimulated the expression of TNF-α, IL-6, and iNOS in rat brain in which NF-κB was involved. Resveratrol inhibited AlCl3-induced expression and release of TNF-α, IL-6, and iNOS in rat brain.ConclusionsThese findings establish a role for APE1 as a master regulator of AlCl3 dependent inflammatory responses in rat brain. In addition, there was an ameliorative change with resveratrol against AlCl3-induced neurotoxicity. These results suggest that rat brain cells produce pro-inflammatory cytokines in response to AlCl3 in a similar pattern, and further suggest that resveratrol exerts anti-inflammatory effects in rat brain, at least partly, by inhibiting different pro-inflammatory cytokines and key signaling molecules. It might be a potential agent for treatment of neuroinflammation-related diseases, such as AD.

Herein, both strategies of synergistic drug combination together with dual active tumor targeting were combined for effective therapy of hepatocellular carcinoma (HCC). Therefore, based on the tumor sensitizing action, the herbal quercetin (QRC) was co-delivered with the targeted therapeutic drug sorafenib (SFB), preformulated as phospholipid complex, via protein shell-oily core nanocapsules (NCs). Inspired by the targeting action of lactoferrin (LF) via binding to LF receptors overexpressed by HCC cells, LF shell was electrostatically deposited onto the drug-loaded oily core to elaborate LF shell-oily core NCs. For dual tumor targeting, lactobionic acid (LA) or glycyrrhetinic acid (GA) was individually coupled to LF shell for binding to asialoglycoprotein and GA receptors on liver cancer cells, respectively. Compared to LF and GA/LF NCs, the dual-targeted LA/LF-NCs showed higher internalization into HepG2 cells with 2-fold reduction in half-maximal inhibitory concentration compared to free combination therapy after 48 h. Moreover, dual-targeted LF-NCs showed powerful in vivo antitumor efficacy. It was revealed as significant downregulation of the mRNA expression levels of nuclear factor-kappa B and tumor necrosis factor α as well as suppression of Ki-67 protein expression level in diethylnitrosamine (DEN)-induced HCC mice (P < 0.05). Furthermore, dual-targeted LF-NCs attenuated the liver toxicity induced by DEN in animal models. Overall, this study proposes dual-targeted LF-NCs for combined delivery of SFB and QRC as a potential therapeutic HCC strategy.