Apocynin, an NADPH oxidase inhibitor, suppresses rat prostate carcinogenesis

Therapeutic Potential of Clusterin Inhibition in Human Cancer

Clusterin (CLU) protein is involved in various pathophysiological processes including carcinogenesis and tumor progression. In recent years, the role of the secretory isoform has been demonstrated in tumor cells, where it inhibits apoptosis and favors the acquisition of resistance to conventional treatments used to treat cancer. To determine the possible therapeutic potential of inhibiting this protein, numerous studies have been carried out in this field. In this article, we present the existing knowledge to date on the inhibition of this protein in different types of cancer and analyze the importance it could have in the development of new therapies targeted against this disease.

Targeting benign prostate hyperplasia treatments: AR/TGF-β/NOX4 inhibition by apocynin suppresses inflammation and proliferation

INTRODUCTION

Apocynin (Apo), an NADPH oxidase (NOX) inhibitor, has been widely used to treat various inflammatory diseases. However, the therapeutic effects of Apo on benign prostatic hyperplasia (BPH), a multifactorial disease associated with chronic inflammation and hormone imbalance, remain unknown.

OBJECTIVES

The link between androgen signaling, reactive oxygen species (ROS), and prostate cell proliferation may contribute to the pathogenesis of BPH; therefore, the aim of this study was to identify the specific signaling pathway involved and to demonstrate whether the anti-oxidant Apo plays a role in the prevention and treatment of BPH.

METHODS

Ingenuity pathway analysis and si-RNA transfection were conducted to demonstrate the androgen receptor (AR) and NOX4 linkage in BPH. Pathological markers of BPH were measured by H&E staining, immunoblotting, ELISA, qRT-PCR, and immunofluorescence to examine the effect of Apo. Rats stimulated with testosterone and BPH-1 cells were used as BPH models.

RESULTS

AR and NOX4 network-mediated oxidative stress was upregulated in the BPH model. Next, we examined the effects of Apo on oxidative stress and chronic prostatic inflammation in BPH mouse models. In a testosterone-induced BPH rat model, Apo alleviated pathological prostate enlargement and suppressed androgen/AR signaling. Apo suppressed the upregulation of proinflammatory markers and promoted the expression of anti-oxidant factors. Furthermore, Apo regulated the TGF-β/Glut9/activin pathway and macrophage programming. In BPH-1 cells, Apo suppressed AR-mediated proliferation and upregulation of TGFB and NOX4 expression by alleviating oxidative stress. Apo activated anti-oxidant and anti-inflammatory systems and regulated macrophage polarization in BPH-1 cells. AR knockdown partially abolished the beneficial effects of Apo in prostate cells, indicating AR-dependent effects of Apo.

CONCLUSION

In contrast with existing BPH therapies, Apo may provide a new application for prostatic disease treatment, especially for BPH, by targeting the AR/TGF-β/NOX4 signaling pathway.

Evaluation of the Mechanisms Involved in the Development of Bladder Toxicity following Exposure to Occupational Bladder Cancer Causative Chemicals Using DNA Adductome Analysis

Occupational exposure to aromatic amines (AAs) is an important risk factor for urinary bladder cancer. This study aimed to evaluate the toxicity of AAs and analyze the carcinogenic mechanisms in rat bladder by comprehensive analysis of DNA adducts (DNA adductome). DNA was extracted from the bladder epithelia of rats treated with AAs, including acetoacet-o-toluidine (AAOT) and o-toluidine (OTD), and adductome analysis was performed. Principal component analysis-discriminant analysis revealed that OTD and AAOT observed in urinary bladder hyperplasia could be clearly separated from the controls and other AAs. After confirming the intensity of each adduct, four adducts were screened as having characteristics of the OTD/AAOT treatment. Comparing with the in-house DNA adduct database, three of four candidates were identified as oxidative DNA adducts, including 8-OH-dG, based on mass fragmentation together with high-resolution accurate mass (HRAM) spectrometry data. Therefore, findings suggested that oxidative stress may be involved in the toxicity of rat bladder epithelium exposed to AAs. Consequently, the administration of apocynin, an inhibitor of nicotinamide adenine dinucleotide phosphate oxidase, in six-week-old rats fed with 0.6% OTD in their diet resulted in simple hyperplastic lesions in the bladder that were suppressed by apocynin. The labeling indices of Ki67, γ-H2AX, and 8-OHdG were significantly decreased in an apocynin concentration-dependent manner. These findings indicate that oxidative stress may have contributed to the development of urinary cancer induced by OTD.

The role and function of CLU in cancer biology and therapy

Clusterin (CLU) is a highly evolutionary conserved glycoprotein with multiple isoform-specific functions and is widely distributed in different species. Accumulated evidence has shown the prominent role of CLU in regulating several essential physiological processes, including programmed cell death, metastasis, invasion, proliferation and cell growth via regulating diverse signaling pathways to mediate cancer progression in various cancers, such as prostate, breast, lung, liver, colon, bladder and pancreatic cancer. Several studies have revealed the potential benefit of inhibiting CLU in CLU inhibition-based targeted cancer therapies in vitro, in vivo or in human, suggesting CLU is a promising therapeutic target. This review discusses the multiple functions and mechanisms of CLU in regulating tumor progression of various cancers and summarizes the inhibitors of CLU used in CLU inhibition-based targeted cancer therapies.

Prostate cancer addiction to oxidative stress defines sensitivity to anti-tumor neutrophils

Bone metastatic prostate cancer (BM-PCa) remains one of the most difficult cancers to treat due to the complex interactions of cancer and stromal cells. We previously showed that bone marrow neutrophils elicit an anti-tumor immune response against BM-PCa. Further, we demonstrated that BM-PCa induces neutrophil oxidative burst, which has previously been identified to promote primary tumor growth of other cancers, and a goal of this study was to define the importance of neutrophil oxidative burst in BM-PCa. To do this, we first examined the impact of depletion of reactive oxygen species (ROS), via systemic deletion of the main source of ROS in phagocytes, NADPH oxidase (Nox)2, which we found to suppress prostate tumor growth in bone. Further, using pharmacologic ROS inhibitors and Nox2-null neutrophils, we found that ROS depletion specifically suppresses growth of androgen-insensitive prostate cancer cells. Upon closer examination using bulk RNA sequencing analysis, we identified that metastatic prostate cancer induces neutrophil transcriptomic changes that activates pathways associated with response to oxidative stress. In tandem, prostate cancer cells resist neutrophil anti-tumor response via extracellular (i.e., regulation of neutrophils) and intracellular alterations of glutathione synthesis, the most potent cellular antioxidant. These findings demonstrate that BM-PCa thrive under oxidative stress conditions and such that regulation of ROS and glutathione programming could be leveraged for targeting of BM-PCa progression.

Recruitment of miR-8080 by luteolin inhibits androgen receptor splice variant 7 expression in castration-resistant prostate cancer

A need exists for seeking effective treatments for castration-resistant prostate cancer (CRPC) in response to its emergence following androgen deprivation therapy as a major clinical problem. In the present study, we investigated the chemopreventive and chemotherapeutic potential of luteolin, a flavonoid with antioxidative properties, on prostate cancer, including CRPC. Luteolin inhibited the progression of rat prostate carcinogenesis by induction of apoptosis in a transgenic rat for adenocarcinoma of prostate (TRAP) model. Luteolin decreased cell proliferation in a dose-dependent manner and induced apoptosis with the activation of caspases 3 and 7 in both rat (PCai1, established from a TRAP prostate tumor) and human (22Rv1) CRPC cells. Dietary luteolin also suppressed tumor growth via an increase in apoptosis and inhibition of angiogenesis in PCai1 and 22Rv1 xenografts implanted in castrated nude mice. We also focused on androgen receptor splice variant 7 (AR-V7), which contributes to cell proliferation and therapeutic resistance in CRPC. Luteolin dramatically suppressed AR-V7 protein expression in 22Rv1 cells in vitro and ex vivo. Microarray analysis identified MiR-8080, which contains a possible target sequence for AR-V7 3′-UTR, as a gene upregulated by luteolin. MiR-8080 transfection decreased the AR-V7 expression level and the induction of apoptosis in 22Rv1 cells. Furthermore, miR-8080 knockdown canceled luteolin decreasing AR-V7 and the cell growth of 22Rv1. MiR-8080 induced by luteolin intake enhanced the therapeutic effect of enzalutamide on 22Rv1 xenografts under castration conditions. These results indicate luteolin inhibits CRPC by AR-V7 suppression through miR-8080, highlighting luteolin and miR-8080 as promising therapeutic agents for this disease.

Cell proliferation of rat bladder urothelium induced by nicotine is suppressed by the NADPH oxidase inhibitor, apocynin

Tobacco smoking is a major risk factor for human cancers including urinary bladder carcinoma. In a previous study, nicotine enhanced rat urinary bladder carcinogenesis in a two-stage carcinogenesis model. Nicotine also induced cytotoxicity in the bladder urothelium in a short-term study. In the present study, male rats were treated with nicotine (40 ppm) in drinking water co-administered with the NADPH oxidase inhibitor, apocynin (0, 250 or 750 mg/kg) in diet for 4 weeks. The apocynin treatment induced no clinical toxic effects. Reduction of reactive oxygen species (ROS) by apocynin was confirmed by immunohistochemistry of 8-OHdG in the bladder urothelium. Incidences of simple hyperplasia, cell proliferation and apoptosis were reduced by apocynin treatment in the bladder urothelium. However, despite reduction of cell proliferation (labeling index), apocynin did not affect the incidence of simple hyperplasia, apoptosis, or ROS generation in the kidney pelvis urothelium, in addition to 8-OHdG positivity induced by nicotine being lower. In vitro, apocynin (500 μM) reduced ROS generation, but induced cell proliferation in bladder cancer cell lines (T24 and UMUC3 cells). These data suggest that oxidative stress may play a role in the cell proliferation of the bladder urothelium induced by nicotine.

Depigmentation and Anti-aging Treatment by Natural Molecules

Natural molecules are becoming more accepted choices as cosmetic agents, many products in the market today claim to include natural components. Plants include many substances that could be of a value in the whitening of the skin and working as anti-aging agents. A wide range of articles related to natural skin whitening and anti-aging agents have been reviewed. Many plant-derived and natural molecules have shown to affect melanin synthesis by different mechanisms, examples include Arbutin, Ramulus mori extract, Licorice extract, Glabridin, Liquiritin, Kojic acid, Methyl gentisate, Aloesin, Azelaic acid, Vitamin C, Thioctic acid, Soya bean extracts, Niacinamide, α and β-hydroxy acids, Lactic acid, Chamomile extract, and Ellagic acid. Some of the widely used natural anti-aging products as natural antioxidants, collagen, hyaluronic acid, and coenzyme Q can counteract the effects of reactive oxygen species in skin cells and have anti-aging properties on the skin. It was concluded that many natural products including antioxidants can prevent UV-induced skin damage and have whitening and anti-aging effects. It is very important to develop and stabilize appropriate methods for the evaluation of the whitening and anti-aging capacity of natural products and their exact mechanism of action to ensure real efficacy based on evidence-based studies. The attention should be oriented on the formulations and the development of an appropriate vehicle to ensure suitable absorption of these natural products in addition to evaluating the suitable concentration of these molecules required having the desired effects without causing harmful side effects.

Hexane Insoluble Fraction from Purple Rice Extract Retards Carcinogenesis and Castration-Resistant Cancer Growth of Prostate Through Suppression of Androgen Receptor Mediated Cell Proliferation and Metabolism

Prostate cancer and castration-resistant prostate cancer (CRPC) remain major health challenges in men. In this study, the inhibitory effects of a hexane insoluble fraction from a purple rice ethanolic extract (PRE-HIF) on prostate carcinogenesis and CRPC were investigated both in vivo and in vitro. In the Transgenic Rat for Adenocarcinoma of Prostate (TRAP) model, 1% PRE-HIF mixed diet-fed rats showed a significantly higher percentage of low-grade prostatic intraepithelial neoplasia and obvious reduction in the incidence of adenocarcinoma in the lateral lobes of the prostate. Additionally, 1% PRE-HIF supplied diet significantly suppressed the tumor growth in a rat CRPC xenograft model of PCai1 cells. In LNCaP and PCai1 cells, PRE-HIF treatment suppressed cell proliferation and induced G0/G1 cell-cycle arrest. Furthermore, androgen receptor (AR), cyclin D1, cdk4, and fatty acid synthase expression were down-regulated while attenuation of p38 mitogen-activated protein kinase, and AMP-activated protein kinase α activation occurred in PRE-HIF treated prostate cancer cells, rat prostate tissues, and CRPC tumors. Due to consistent results with PRE-HIF in PCai1 cells, cyanidin-3-glucoside was characterized as the active compound. Altogether, we surmise that PRE-HIF blocks the development of prostate cancer and CRPC through the inhibition of cell proliferation and metabolic pathways.

Dimethylarsinic acid may promote prostate carcinogenesis in rats

Arsenic is a known human carcinogen, inducing tumors of the lung, urinary bladder, skin, liver and prostate. However, there are no reports of prostate tumors induced by arsenicals in in vivo animal models. In a previous study, we found that HMGB2 expression was a predictive marker for prostate carcinogens in the rat 4-week repeated dose test. In this study, six-week-old male F344 rats were orally treated with a total of six chemicals (2-acetylaminofluorene (2-AAF), p-cresidine, dimethylarsinic acid (DMA), glycidol, N-nitrosodiethylamine and acrylamide) for four weeks. Animals were sacrificed at the end of the study, and HMGB2 and Ki-67 immunohistochemistry was performed. The numbers of HMGB2- and Ki-67- positive cells in all prostate lobes were significantly increased by DMA, one of the arsenicals, compared with the controls. Meanwhile, the number of Ki-67-positive cells in lateral and dorsal prostate lobes was significantly decreased by 2-AAF with the reduction of body weight, but HMGB2 expression was not. The other chemicals did not change HMGB2 and Ki-67 expression. These data indicate that DMA may have an ability to enhance prostate carcinogenesis.

The Role of Acrolein and NADPH Oxidase in the Granulocyte-Mediated Growth-Inhibition of Tumor Cells

Although granulocytes are the most abundant leukocytes in human blood, their involvement in the immune response against cancer is not well understood. While granulocytes are known for their “oxidative burst” when challenged with tumor cells, it is less known that oxygen-dependent killing of tumor cells by granulocytes includes peroxidation of lipids in tumor cell membranes, yielding formation of reactive aldehydes like 4-hydroxynonenal (4-HNE) and acrolein. In the present work, we investigate the role of reactive aldehydes on cellular redox homeostasis and surface toll-like receptor 4 (TLR4) expression. We have further study the granulocyte-tumor cell intercellular redox signaling pathways. The data obtained show that granulocytes in the presence of 4-HNE and acrolein induce excessive ROS formation in tumor cells. Acrolein was also shown to induce granulocyte TLR4 expression. Furthermore, granulocyte-mediated antitumor effects were shown to be mediated via HOCl intracellular pathway by the action of NADPH oxidase. However, further studies are needed to understand interaction between TLR4 and granulocyte-tumor cell intercellular signaling pathways.

17-DMAG regulates p21 expression to induce chondrogenesis in vitro and in vivo

Cartilage degeneration after injury affects a significant percentage of the population, including those that will go on to develop osteoarthritis (OA). Like humans, most mammals, including mice, are incapable of regenerating injured cartilage. Interestingly, it has previously been shown that p21 (Cdkn1a) knockout (p21^-/-) mice demonstrate auricular (ear) cartilage regeneration. However, the loss of p21 expression is highly correlated with the development of numerous types of cancer and autoimmune diseases, limiting the therapeutic translation of these findings. Therefore, in this study, we employed a screening approach to identify an inhibitor (17-DMAG) that negatively regulates the expression of p21. We also validated that this compound can induce chondrogenesis in vitro (in adult mesenchymal stem cells) and in vivo (auricular cartilage injury model). Furthermore, our results suggest that 17-DMAG can induce the proliferation of terminally differentiated chondrocytes (in vitro and in vivo), while maintaining their chondrogenic phenotype. This study provides new insights into the regulation of chondrogenesis that might ultimately lead to new therapies for cartilage injury and/or OA.

Natural Antioxidants: Multiple Mechanisms to Protect Skin From Solar Radiation

Human skin exposed to solar ultraviolet radiation (UVR) results in a dramatic increase in the production of reactive oxygen species (ROS). The sudden increase in ROS shifts the natural balance toward a pro-oxidative state, resulting in oxidative stress. The detrimental effects of oxidative stress occur through multiple mechanisms that involve alterations to proteins and lipids, induction of inflammation, immunosuppression, DNA damage, and activation of signaling pathways that affect gene transcription, cell cycle, proliferation, and apoptosis. All of these alterations promote carcinogenesis and therefore, regulation of ROS levels is critical to the maintenance of normal skin homeostasis. Several botanical products have been found to exhibit potent antioxidant capacity and the ability to counteract UV-induced insults to the skin. These natural products exert their beneficial effects through multiple pathways, including some known to be negatively affected by solar UVR. Aging of the skin is also accelerated by UVR exposure, in particular UVA rays that penetrate deep into the epidermis and the dermis where it causes the degradation of collagen and elastin fibers via oxidative stress and activation of matrix metalloproteinases (MMPs). Because natural compounds are capable of attenuating some of the UV-induced aging effects in the skin, increased attention has been generated in the area of cosmetic sciences. The focus of this review is to cover the most prominent phytoproducts with potential to mitigate the deleterious effects of solar UVR and suitability for use in topical application.

Chemopreventive effects of angiotensin II receptor type 2 agonist on prostate carcinogenesis by the down-regulation of the androgen receptor

We recently reported that angiotensin II receptor blockers (ARBs) have chemopreventive and chemotherapeutic potential against prostate cancer via the reduction of androgen receptor (AR) expression. In this study, we investigated the effects of the angiotensin II receptor type 2 (AT2R) agonist Compound 21 (C21), which is expected to play similar roles to an ARB, on prostate carcinogenesis using the transgenic rat for adenocarcinoma of prostate (TRAP) model previously established in our laboratory. In vitro analyses of the cell growth, Western blotting and reporter gene assays were performed using LNCaP cells. TRAP rats at 6 weeks of age were randomly divided into 3 groups of 12 animals each and treated with C21 at 1 or 2 mg/kg/day in drinking water for 12 weeks. C21 reduced the proliferation activity of prostate cancer cells and down-regulated the PSA promoter activity and the AR protein expression. We discovered that C21 inhibited the progression of prostate carcinogenesis in TRAP rats and decreased the incidence of adenocarcinoma in the lateral prostate. A significant increase in the apoptotic index with activation of caspase 3 and 7 were observed by immunohistochemistry and Western blotting analyses. C21 also down-regulated the expression of AR significantly in TRAP rat prostate. C21 decreased the expression of AR and reduced the proliferation activity effectively in prostate cancer cells and TRAP rat prostate. These findings suggest that AT2R agonist may be a candidate novel chemopreventive agent against human prostate cancer.

The NADPH Oxidase Inhibitor Apocynin Suppresses Preneoplastic Liver Foci of Rats

Reactive oxygen species (ROS) have been revealed to be important factors for carcinogenesis and tumor progression. Therefore, we focused on an ROS-generating protein, nicotinamide adenine dinucleotide phosphate oxidase, and evaluated whether its inhibitor, apocynin, could suppress hepatocarcinogenesis in a medium-term rat liver bioassay. The number and size of glutathione S-transferase placental form (GST-P)-positive foci were significantly reduced by apocynin in a dose-dependent manner. The reduction of ROS generation by apocynin was confirmed by dihydroethidium staining. Apocynin treatment also significantly reduced Ki-67 positivity, downregulated cyclooxygenase 2, and suppressed the activation of the c-Myc pathway. Meanwhile, ROS generation was not different between GST-P-positive foci and surrounding GST-P-negative areas of the liver. In conclusion, the present data suggest that apocynin possesses a potential antihepatocarcinogenic property.

Pioglitazone, a Peroxisome Proliferator-Activated Receptor γ Agonist, Suppresses Rat Prostate Carcinogenesis

Pioglitazone (PGZ), a peroxisome proliferator-activated receptor γ agonist, which is known as a type 2 diabetes drug, inhibits cell proliferation in various cancer cell lines, including prostate carcinomas. This study focused on the effect of PGZ on prostate carcinogenesis using a transgenic rat for an adenocarcinoma of prostate (TRAP) model. Adenocarcinoma lesions as a percentage of overall lesions in the ventral prostate were significantly reduced by PGZ treatment in a dose-dependent manner. The number of adenocarcinomas per given area in the ventral prostate was also significantly reduced by PGZ treatment. The Ki67 labeling index in the ventral prostate was also significantly reduced by PGZ. Decreased cyclin D1 expression in addition to the inactivation of both p38 mitogen-activated protein kinase (MAPK) and nuclear factor (NF)κB were detected in PGZ-treated TRAP rat groups. In LNCaP, a human androgen-dependent prostate cancer cell line, PGZ also inhibited cyclin D1 expression and the activation of both p38 MAPK and NFκB. The suppression of cultured cell growth was mainly regulated by the NFκB pathway as detected using specific inhibitors in both LNCaP and PC3, a human androgen-independent prostate cancer cell line. These data suggest that PGZ possesses a chemopreventive potential for prostate cancer.

Preventive Effects of Fermented Brown Rice and Rice Bran against Prostate Carcinogenesis in TRAP Rats

Fermented brown rice and rice bran with Aspergillus oryzae (FBRA) is considered to have the potential to prevent chemically-induced carcinogenesis in multiple organs of rodents. In the present study, we evaluated the possible chemopreventive effects of FBRA against prostate tumorigenesis. Six-week-old male rats of the transgenic rat for adenocarcinoma of prostate (TRAP) strain were fed diets containing 5% or 10% FBRA for 15 weeks. Animals were sacrificed at 21 weeks of age, and the ventral and lateral prostate were removed for histopathological evaluation and immunoblot analyses. FBRA decreased the incidence of adenocarcinoma in the lateral prostate and suppressed the progression of prostate carcinogenesis. Treatment with FBRA induced apoptosis and inhibited cell proliferation in histologically high-grade prostatic intraepithelial neoplasias. Phospho-AMP-activated kinase α (Thr172) was up-regulated in the prostate of rats fed the diet supplemented with FBRA. These results indicate that FBRA controls tumor growth by activating pathways responsive to energy deprivation and suggest that FBRA has translational potential for the prevention of human prostate cancer.

Treatment of Rats with Apocynin Has Considerable Inhibitory Effects on Arylamine N-Acetyltransferase Activity in the Liver

The effect of apocynin on the activity of arylamine N-acetyltransferases (NATs) in excised liver samples was examined using eighteen Sprague-Dawley rats. Three groups of six animals each were fed a normal diet alone or a treatment of 50 or 100 mg/kg/day of apocynin via gavages for eight (8) weeks. Chronic in vivo administration of apocynin led to significant (p < 0.001) reduction of in vitro liver NAT activity up to 93% as compared with untreated rats (18.80 ± 2.10 μmols p-anisidine/min/μg liver protein). In vitro exposure of untreated liver homogenates to apocynin led to a dose-dependent inhibition of NAT activity with IC₅₀ = 0.69 ± 0.02 mM. In silico modelling of apocynin tautomers and radical species into human NAT crystal structures supported the hypothesis that thiol functionalities in NAT enzymes may be crucial in apocynin binding. The involvement of human NAT enzymes in different pathological conditions, such as cancer, has encouraged the research for selective NAT inhibitors in both humans and animal models with possible chemopreventive properties.

Graviola inhibits hypoxia-induced NADPH oxidase activity in prostate cancer cells reducing their proliferation and clonogenicity

Prostate cancer (PCa) is the leading malignancy among men. Importantly, this disease is mostly diagnosed at early stages offering a unique chemoprevention opportunity. Therefore, there is an urgent need to identify and target signaling molecules with higher expression/activity in prostate tumors and play critical role in PCa growth and progression. Here we report that NADPH oxidase (NOX) expression is directly associated with PCa progression in TRAMP mice, suggesting NOX as a potential chemoprevention target in controlling PCa. Accordingly, we assessed whether NOX activity in PCa cells could be inhibited by Graviola pulp extract (GPE) that contains unique acetogenins with strong anti-cancer effects. GPE (1–5 μg/ml) treatment strongly inhibited the hypoxia-induced NOX activity in PCa cells (LNCaP, 22Rv1 and PC3) associated with a decrease in the expression of NOX catalytic and regulatory sub-units (NOX1, NOX2 and p47^phox). Furthermore, GPE-mediated NOX inhibition was associated with a strong decrease in nuclear HIF-1α levels as well as reduction in the proliferative and clonogenic potential of PCa cells. More importantly, GPE treatment neither inhibited NOX activity nor showed any cytotoxicity against non-neoplastic prostate epithelial PWR-1E cells. Overall, these results suggest that GPE could be useful in the prevention of PCa progression via inhibiting NOX activity.

Chemopreventive effect of resveratrol and apocynin on pancreatic carcinogenesis via modulation of nuclear phosphorylated GSK3β and ERK1/2

Despite progress in clinical cancer medicine in multiple fields, the prognosis of pancreatic cancer has remained dismal. Recently, chemopreventive strategies using phytochemicals have gained considerable attention as an alternative in the management of cancer. The present study aimed to evaluate the chemopreventive effects of resveratrol (RV) and apocynin (AC) in N-Nitrosobis(2-oxopropyl)amine-induced pancreatic carcinogenesis in hamster. RV- and AC-treated hamsters showed significant reduction in the incidence of pancreatic cancer with a decrease in Ki-67 labeling index in dysplastic lesions. RV and AC suppressed cell proliferation of human and hamster pancreatic cancer cells by inhibiting the G1 phase of the cell cycle with cyclin D1 downregulation and inactivation of AKT-GSK3β and ERK1/2 signaling. Further, decreased levels of GSK3β(Ser9) and ERK1/2 phosphorylation and cyclin D1 expression in the nuclear fraction were observed in cells treated with RV or AC. Nuclear expression of phosphorylated GSK3β(Ser9) was also decreased in dysplastic lesions and adenocarcinomas of hamsters treated with RV or AC in vivo. These results suggest that RV and AC reduce phosphorylated GSK3β(Ser9) and ERK1/2 in the nucleus, resulting in inhibition of the AKT-GSK3β and ERK1/2 signaling pathways and cell cycle arrest in vitro and in vivo. Taken together, the present study indicates that RV and AC have potential as chemopreventive agents for pancreatic cancer.

Apocynin and Diphenyleneiodonium Induce Oxidative Stress and Modulate PI3K/Akt and MAPK/Erk Activity in Mouse Embryonic Stem Cells

Reactive oxygen species (ROS) are important regulators of cellular functions. In embryonic stem cells, ROS are suggested to influence differentiation status. Regulated ROS formation is catalyzed primarily by NADPH-dependent oxidases (NOXs). Apocynin and diphenyleneiodonium are frequently used inhibitors of NOXs; however, both exhibit uncharacterized effects not related to NOXs inhibition. Interestingly, in our model of mouse embryonic stem cells we demonstrate low expression of NOXs. Therefore we aimed to clarify potential side effects of these drugs. Both apocynin and diphenyleneiodonium impaired proliferation of cells. Surprisingly, we observed prooxidant activity of these drugs determined by hydroethidine. Further, we revealed that apocynin inhibits PI3K/Akt pathway with its downstream transcriptional factor Nanog. Opposite to this, apocynin augmented activity of canonical Wnt signaling. On the contrary, diphenyleneiodonium activated both PI3K/Akt and Erk signaling pathways without affecting Wnt. Our data indicates limits and possible unexpected interactions of NOXs inhibitors with intracellular signaling pathways.

Suppressive effects of the NADPH oxidase inhibitor apocynin on intestinal tumorigenesis in obese KK-A(y) and Apc mutant Min mice

Obesity is a risk factor for colorectal cancer. The accumulation of abdominal fat tissue causes abundant reactive oxygen species production through the activation of NADPH oxidase due to excessive insulin stimulation. The enzyme NADPH oxidase catalyzes the production of reactive oxygen species and evokes the initiation and progression of tumorigenesis. Apocynin is an NADPH oxidase inhibitor that blocks the formation of the NADPH oxidase complex (active form). In this study, we investigated the effects of apocynin on the development of azoxymethane‐induced colonic aberrant crypt foci in obese KK‐A^y mice and on the development of intestinal polyps in Apc mutant Min mice. Six‐week‐old KK‐A^y mice were injected with azoxymethane (200 μg/mouse once per week for 3 weeks) and given 250 mg/L apocynin or 500 mg/L apocynin in their drinking water for 7 weeks. Six‐week‐old Min mice were also treated with 500 mg/L apocynin for 6 weeks. Treatment with apocynin reduced the number of colorectal aberrant crypt foci in KK‐A^y mice by 21% and the number of intestinal polyps in Min mice by 40% compared with untreated mice. Both groups of mice tended to show improved oxidation of serum low‐density lipoprotein and 8‐oxo‐2′‐deoxyguanosine adducts in their adipose tissues. In addition, the inducible nitric oxide synthase mRNA levels in polyp tissues decreased. Moreover, apocynin was shown to suppress nuclear factor‐κB transcriptional activity in vitro. These results suggest that apocynin and other NADPH oxidase inhibitors may be effective colorectal cancer chemopreventive agents.

Reduced NADPH oxidase type 2 activity mediates sleep fragmentation-induced effects on TC1 tumors in mice

The molecular mechanisms underlying how sleep fragmentation (SF) influences cancer growth and progression remain largely elusive. Here, we present evidence that SF reduced ROS production by downregulating gp91^phox expression and activity in TC1 cell tumor associated macrophages (TAMs), while genetic ablation of phagocytic Nox2 activity increased tumor cell proliferation, motility, invasion, and extravasation in vitro. Importantly, the in vivo studies using immunocompetent syngeneic murine tumor models suggested that Nox2 deficiency mimics SF-induced TAMs infiltration and subsequent tumor growth and invasion. Taken together, these studies reveal that perturbed sleep could adversely affect innate immunity within the tumor by altering Nox2 expression and activity, and indicate that selective potentiation of Nox2 activity may present a novel therapeutic strategy in the treatment of cancer.

Apocynin, an NADPH oxidase inhibitor, suppresses rat prostate carcinogenesis

Recent evidence suggests that oxidative stress contributes to the pathogenesis of prostate cancer. The present study focused on the effect of apocynin, an inhibitor of NADPH oxidase, on prostate carcinogenesis using the transgenic rat for adenocarcinoma of prostate (TRAP) model. There were no toxic effects with apocynin treatment. The percentages and numbers of carcinomas in both the ventral and lateral prostate were significantly reduced by apocynin treatment, with dose dependence. Reduction of reactive oxygen species by apocynin was confirmed by immunohistochemistry of 8-OHdG and dihydroethidium staining. Positivity of Ki67 was significantly reduced by apocynin treatment, and downregulation of clusterin expression, as well as inactivation of the MEK-ERK1/2 pathway, was a feature of the apocynin treated groups. In human prostate cancer cell line LNCaP, apocynin also inhibited reactive oxygen species production and blocked cell growth by inducing G0/G1 arrest with downregulation of clusterin and cyclin D1. These data suggest that apocynin possesses chemopreventive potential against prostate cancer.