Apocynin, an NADPH oxidase inhibitor, suppresses progression of prostate cancer via Rac1 dephosphorylation

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.

Apocynin-loaded PLGA nanomedicine tailored with galactosylated chitosan intrigue asialoglycoprotein receptor in hepatic carcinoma: Prospective targeted therapy

Nature serves as a priceless source for phytomedicines to treat different types of cancer, including hepatocellular carcinoma (HCC). Apocynin (APO), an anti-cancer phytomedicine, is a particular nicotinamide adenine dinucleotide phosphate-oxidase (NADPH-oxidase) inhibitor, which has recently dawned for its multilateral pharmacological activities. As far as we are aware, no investigation has been carried out yet to develop a targeted-nanostructured delivery system of APO to HCC. Consequently, chitosan derivative with galactose groups namely; galactosylated chitosan (GC), particularly recognized by the asialoglycoprotein receptor (ASGR), was synthesized and its chemical structure was thoroughly characterized by substantial techniques. Afterwards, GC-coated nanoplatform for hepatocyte attachment "APO-loaded galactosylated chitosan-coated poly(d,l-lactide-co-glycolide) nanoparticles (APO-loaded GC-coated PLGA NPs)" was developed. The prosperous APO-loaded GC-coated PLGA NPs would be comprehensively appraised through extensive investigations. Their solid state characterization using Fourier transform-infrared spectroscopy, powder X-ray diffraction, and differential scanning calorimetry proved APO's encapsulation in the polymeric matrix. Transmission electron microscopy imaging of the investigated NPs highlighted their spherical architecture with a nanosized range and a characteristic halo-like appearance traceable to the GC coating of the NPs' surface. Saliently, the results of in vitro cytotoxicity screening revealed the spectacular anti-cancer efficacy of APO-loaded GC-coated PLGA NPs formula against the HepG2 cell line. Moreover, the fluorescence microscope disclosed the distinguished cellular uptake of such formula via ASGPR mediated endocytosis. Inclusively, a multifunctional nano-phytomedicine delivery system with a promising active hepatocyte-targeting, effective uptake into HepG2 cells, and sustained drug release pattern was successfully developed.

Protective effects of apocynin against ionizing radiation-induced hepatotoxicity in rats

Radiation hepatotoxicity is thought to be due to free oxygen radicals. We investigated the protective effects of apocynin (APO) against ionizing radiation induced oxidative stress in liver tissue following whole body ionizing radiation. We divided rats into four groups. The control group was injected intraperitoneally (i.p.) with saline for five consecutive days. A second group was injected i.p. with saline for 5 days and after 24 h, a single-dose of radiation (800 cGy) was administered to the whole abdomen. A third group was injected i.p. with 20 mg/kg APO for 5 days. A fourth group was injected i.p. with APO for 5 days and after 24 h, the rats were exposed to radiation. Ionizing radiation induced hepatotoxicity was demonstrated biochemically by significant changes in oxidative and antioxidant parameters. Our findings suggest that APO treatment may be protective against radiation induced hepatic injury by decreasing oxidative stress and increasing antioxidant activity.

Anti-Inflammatory Effect of Auranofin on Palmitic Acid and LPS-Induced Inflammatory Response by Modulating TLR4 and NOX4-Mediated NF-κB Signaling Pathway in RAW264.7 Macrophages

Chronic inflammation, which is promoted by the production and secretion of inflammatory mediators and cytokines in activated macrophages, is responsible for the development of many diseases. Auranofin is a Food and Drug Administration-approved gold-based compound for the treatment of rheumatoid arthritis, and evidence suggests that auranofin could be a potential therapeutic agent for inflammation. In this study, to demonstrate the inhibitory effect of auranofin on chronic inflammation, a saturated fatty acid, palmitic acid (PA), and a low concentration of lipopolysaccharide (LPS) were used to activate RAW264.7 macrophages. The results show that PA amplified LPS signals to produce nitric oxide (NO) and various cytokines. However, auranofin significantly inhibited the levels of NO, monocyte chemoattractant protein-1, and pro-inflammatory cytokines, such as interleukin (IL)-1β, tumor necrosis factor-α, and IL-6, which had been increased by co-treatment with PA and LPS. Moreover, the expression of inducible NO synthase, IL-1β, and IL-6 mRNA and protein levels increased by PA and LPS were reduced by auranofin. In particular, the upregulation of NADPH oxidase (NOX) 4 and the translocation of the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) induced by PA and LPS were suppressed by auranofin. The binding between the toll-like receptor (TLR) 4 and auranofin was also predicted, and the release of NO and cytokines was reduced more by simultaneous treatment with auranofin and TLR4 inhibitor than by auranofin alone. In conclusion, all these findings suggested that auranofin had anti-inflammatory effects in PA and LPS-induced macrophages by interacting with TLR4 and downregulating the NOX4-mediated NF-κB signaling pathway.

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.

Small molecules regulating reactive oxygen species homeostasis for cancer therapy

Elevated intracellular reactive oxygen species (ROS) and antioxidant defense systems have been recognized as one of the hallmarks of cancer cells. Compared with normal cells, cancer cells exhibit increased ROS to maintain their malignant phenotypes and are more dependent on the "redox adaptation" mechanism. Thus, there are two apparently contradictory but virtually complementary therapeutic strategies for the regulation of ROS to prevent or treat cancer. The first strategy, that is, chemoprevention, is to prevent or reduce intracellular ROS either by suppressing ROS production pathways or by employing antioxidants to enhance ROS clearance, which protects normal cells from malignant transformation and inhibits the early stage of tumorigenesis. The second strategy is the ROS-mediated anticancer therapy, which stimulates intracellular ROS to a toxicity threshold to activate ROS-induced cell death pathways. Therefore, targeting the regulation of intracellular ROS-related pathways by small-molecule candidates is considered to be a promising treatment for tumors. We herein first briefly introduce the source and regulation of ROS, and then focus on small molecules that regulate ROS-related pathways and show efficacy in cancer therapy from the perspective of pharmacophores. Finally, we discuss several challenges in developing cancer therapeutic agents based on ROS regulation and propose the direction of future development.

Inhibiting the Activity of NADPH Oxidase in Cancer

Significance: The primary function of NADPH oxidases (NOX1-5 and dual oxidases DUOX1/2) is to produce reactive oxygen species (ROS). If inadequately regulated, NOX-associated ROS can promote oxidative stress, aberrant signaling, and genomic instability. Correspondingly, NOX isoforms are known to be overexpressed in multiple malignancies, thus constituting potential therapeutic targets in cancer. Recent Advances: Multiple genetic studies aimed at suppressing the expression of NOX proteins in cellular and animal models of cancer have provided support for the notion that NOXs play a pro-tumorigenic role. Further, large drug screens and rational design efforts have yielded inhibitor compounds, such as the diphenylene iodonium (DPI) analog series developed by our group, with increased selectivity and potency over "first generation" NOX inhibitors such as apocynin and DPI. Critical Issues: The precise role of NOX enzymes in tumor biology remains poorly defined. The tumorigenic properties of NOXs vary with cancer type, and precise tools, such as selective inhibitors, are needed to deconvolute NOX contribution to cancer development. Most NOX inhibitors developed to date are unspecific, and/or their mechanistic and pharmacological characteristics are not well defined. A lack of high-resolution crystal structures for NOX functional domains has hindered the development of potent and selective inhibitors. Future Directions: In-depth studies of NOX interactions with the tumor microenvironment (e.g., cytokines, cell-surface antigens) will help identify new approaches for NOX inhibition in cancer.

Targeting the Redox Landscape in Cancer Therapy

Reactive oxygen species (ROS) are produced predominantly by the mitochondrial electron transport chain and by NADPH oxidases in peroxisomes and in the endoplasmic reticulum. The antioxidative defense counters overproduction of ROS with detoxifying enzymes and molecular scavengers, for instance, superoxide dismutase and glutathione, in order to restore redox homeostasis. Mutations in the redox landscape can induce carcinogenesis, whereas increased ROS production can perpetuate cancer development. Moreover, cancer cells can increase production of antioxidants, leading to resistance against chemo- or radiotherapy. Research has been developing pharmaceuticals to target the redox landscape in cancer. For instance, inhibition of key players in the redox landscape aims to modulate ROS production in order to prevent tumor development or to sensitize cancer cells in radiotherapy. Besides the redox landscape of a single cell, alternative strategies take aim at the multi-cellular level. Extracellular vesicles, such as exosomes, are crucial for the development of the hypoxic tumor microenvironment, and hence are explored as target and as drug delivery systems in cancer therapy. This review summarizes the current pharmaceutical and experimental interventions of the cancer redox landscape.

Inhibition of NADPH oxidase alleviates germ cell apoptosis and ER stress during testicular ischemia reperfusion injury

Testicular torsion and detorsion (TTD) is a serious urological condition affecting young males that is underlined by an ischemia reperfusion injury (tIRI) to the testis as the pathophysiological mechanism. During tIRI, uncontrolled production of oxygen reactive species (ROS) causes DNA damage leading to germ cell apoptosis (GCA). The aim of the study is to explore whether inhibition of NADPH oxidase (NOX), a major source of intracellular ROS, will prevent tIRI-induced GCA and its association with endoplasmic reticulum (ER) stress. Sprague-Dawley rats (n = 36) were divided into three groups: sham, tIRI only and tIRI treated with apocynin (a NOX inhibitor). Rats undergoing tIRI endured an ischemic injury for 1 h followed by 4 h of reperfusion. Spermatogenic damage was evaluated histologically, while cellular damages were assessed using real time PCR, immunofluorescence staining, Western blot and biochemical assays. Disrupted spermatogenesis was associated with increased lipid and protein peroxidation and decreased antioxidant activity of the enzyme superoxide dismutase (SOD) as a result of tIRI. In addition, increased DNA double strand breaks and formation of 8-OHdG adducts associated with increased phosphorylation of the DNA damage response (DDR) protein H2AX. The ASK1/JNK apoptosis signaling pathway was also activated in response to tIRI. Finally, increased immuno-expression of the unfolded protein response (UPR) downstream targets: GRP78, eIF2-α1, CHOP and caspase 12 supported the presence of ER stress. Inhibition of NOX by apocynin protected against tIRI-induced GCA and ER stress. In conclusion, NOX inhibition minimized tIRI-induced intracellular oxidative damages leading to GCA and ER stress.

Apocynin prevents GM-CSF-induced-ERK1/2 activation and -neutrophil survival independently of its inhibitory effect on the phagocyte NADPH oxidase NOX2

Neutrophils are key cells in innate immunity and inflammation. Granulocyte-macrophage colony-stimulating factor (GM-CSF) is known to enhance many neutrophil functions such as reactive oxygen species (ROS) production, degranulation and cell survival via the activation of the ERK1/2 pathway. ERK1/2 pathway activation is redox sensitive and could be modulated by ROS. In order to investigate whether NADPH oxidase NOX2-derived ROS could contribute to GM-CSF-induced ERK1/2 phosphorylation, we tested the effect of two selective NOX2 inhibitors, diphenylene iodonium (DPI) and apocynin. Results showed that, while both DPI and apocynin strongly inhibited neutrophil ROS production, only apocynin, but not DPI, inhibited GM-CSF-induced ERK1/2 phosphorylation, suggesting that ROS are not involved in this process. Apocynin did not affect GM-CSF-induced p38MAPKinase phosphorylation, another redox sensitive kinase. Interestingly, apocynin inhibited GM-CSF-induced MEK1/2 and AKT phosphorylation without affecting fMLF-induced phosphorylation of these proteins. GM-CSF is known to inhibit neutrophils apoptosis and to promote cell survival via the AKT-ERK1/2 pathway. In this regard, we found that apocynin also inhibited GM-CSF-induced anti-apoptotic effect in neutrophils. These results suggest that NADPH oxidase NOX2-derived ROS are not involved in GM-CSF-induced ERK1/2 phosphorylation and that apocynin inhibits GM-CSF-induced ERK1/2 phosphorylation pathway independently of its inhibitory action on NADPH oxidase NOX2. Thus, apocynin can exert an anti-inflammatory effect not only by limiting neutrophil ROS production but also by decreasing neutrophil survival at inflammatory site.

MicroRNA Networks Modulate Oxidative Stress in Cancer

Imbalanced regulation of reactive oxygen species (ROS) and antioxidant factors in cells is known as "oxidative stress (OS)". OS regulates key cellular physiological responses through signal transduction, transcription factors and noncoding RNAs (ncRNAs). Increasing evidence indicates that continued OS can cause chronic inflammation, which in turn contributes to cardiovascular and neurological diseases and cancer development. MicroRNAs (miRNAs) are small ncRNAs that produce functional 18-25-nucleotide RNA molecules that play critical roles in the regulation of target gene expression by binding to complementary regions of the mRNA and regulating mRNA degradation or inhibiting translation. Furthermore, miRNAs function as either tumor suppressors or oncogenes in cancer. Dysregulated miRNAs reportedly modulate cancer hallmarks such as metastasis, angiogenesis, apoptosis and tumor growth. Notably, miRNAs are involved in ROS production or ROS-mediated function. Accordingly, investigating the interaction between ROS and miRNAs has become an important endeavor that is expected to aid in the development of effective treatment/prevention strategies for cancer. This review provides a summary of the essential properties and functional roles of known miRNAs associated with OS in cancers.

Synthesis and Evaluations of Novel Apocynin Derivatives as Anti-Glioma Agents

Apocynin (4-hydroxy-3-methoxyacetophenone) is a natural polyphenolic compound with multiple biological activities. In the present study, a series of apocynin derivatives were designed and synthesized. The in silico ADMET prediction, blood–brain barrier (BBB) penetration assay, anti-NADPH oxidase activity, reactive oxygen species (ROS) levels, and anti-glioma effects of these apocynin derivatives were evaluated. The anti-glioma mechanisms of candidate compounds were studied by flow cytometer and Western blot. The results showed that D31 exhibited higher BBB penetration, increased ROS generations and significant anti-glioma effects both in vitro and in vivo. Further studies showed that D31 inhibited the activations of NF-κB pathway. Overall, our data demonstrated that D31 inhibited growth and induced apoptosis of glioma, which might be caused by ROS-related NF-κB activation. The current study suggested that D31 could be further explored for its potential use in anti-glioma therapy.

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.

Inhibiting geranylgeranyl diphosphate synthesis reduces nuclear androgen receptor signaling and neuroendocrine differentiation in prostate cancer cell models

BACKGROUND

Following androgen deprivation for the treatment of advanced adenocarcinoma of the prostate, tumors can progress to neuroendocrine prostate cancer (NEPC). This transdifferentiation process is poorly understood, but trafficking of transcriptional factors and/or cytoskeletal rearrangements may be involved. We observed the role of geranylgeranylation in this process by treatment with digeranyl bisphosphonate (DGBP), a selective inhibitor of geranylgeranyl pyrophosphate synthase which blocks the prenylation of small GTPases such as Rho and Rab family proteins, including Cdc42 and Rac1.

METHODS

We examined the therapeutic potential of DGBP in LNCaP, C4-2B4, and 22Rv1 cell culture models. Cell morphology and protein expression were quantified to observe the development of the neuroendocrine phenotype in androgen-deprivation and abiraterone-treated LNCaP models of NEPC development. Luciferase reporter assays were utilized to examine AR activity, and immunofluorescence visualized the localization of AR within the cell.

RESULTS

Essential genes in the isoprenoid pathway, such as HMGCR, MVK, GGPS1, and GGT1, were highly expressed in a subset of castration resistant prostate cancers reported by Beltran et al. Under treatment with DGBP, nuclear localization of AR decreased in LNCaP, 22Rv1, and C4-2B4 cell lines, luciferase reporter activity was reduced in LNCaP and 22Rv1, and AR target gene transcription also decreased in LNCaP. Conversely, nuclear localization of AR was enhanced by the addition of GGOH. Finally, induction of the NEPC structural and molecular phenotype via androgen deprivation in LNCaP cells was inhibited by DGBP in a GGOH-dependent manner.

CONCLUSIONS

DGBP is a novel compound with the potential to reduce AR transcriptional activity and inhibit PCa progression to NEPC phenotype. These results suggest that DGBP may be used to block cell growth and metastasis in both hormone therapy sensitive and resistant paradigms.

Cyclohexanone curcumin analogs inhibit the progression of castration-resistant prostate cancer in vitro and in vivo

Many prostate cancer patients develop resistance to treatment called castration‐resistant prostate cancer (CRPC) which is the major cause of recurrence and death. In the present study, four cyclohexanone curcumin analogs were synthesized. Additionally, their anticancer progression activity on CRPC cell lines, PC3 and PLS10 cells, was examined. We first determined their anti‐metastasis properties and found that 2,6‐bis‐(4‐hydroxy‐3‐methoxy‐benzylidene)‐cyclohexanone (2A) and 2,6‐bis‐(3,4‐dihydroxy‐benzylidene)‐cyclohexanone (2F) showed higher anti‐invasion properties against CRPC cells than curcumin. Analog 2A inhibited both MMP‐2 and MMP‐9 secretions and activities, whereas analog 2F reduced only MMP activities. These findings suggest that the compounds may inhibit CRPC cell metastasis by decreased extracellular matrix degradation. Analog 2A, the most potent analog, was then subjected to an in vivo study. Similar to curcumin, analog 2A was detectable in the serum of mice at 30 and 60 minutes after i.p. injections. Analog 2A and curcumin (30 mg/kg bodyweight) showed a similar ability to reduce tumor area in lungs of mice that were i.v. injected with PLS10 cells. Additionally, analog 2A showed superior growth inhibitory effect on PLS10 cells than that of curcumin both in vitro and in vivo. The compound inhibited PLS10 cells growth by induction of G1 phase arrest and apoptosis in vitro. Interestingly, analog 2A significantly decreased tumor growth with downregulation of cell proliferation and angiogenesis in PLS10‐bearing mice. Taken together, we could summarize that analog 2A showed promising activities in inhibiting CRPC progression both in vitro and in vivo.

Targeting protein geranylgeranylation slows tumor development in a murine model of prostate cancer metastasis

The isoprenoid biosynthetic pathway (IBP) plays a critical role in providing substrates and enzymes necessary for the post-translational modification and thus activation of a number of proteins involved in prostate cancer metastasis. Previous work by our lab found novel compound disodium [(6Z,11E,15E)-9-[bis(sodiooxy)phosphoryl]-17-hydroxy-2,6,12,16-tetramethyheptadeca-2,6,11,15-tetraen-9-yl]phosphonate (GGOHBP), which inhibits the IBP enzyme geranylgeranyl diphosphate synthase (GGDPS), reduced protein geranylgeranylation without altering protein farnesylation. This activity significantly reduced adrenal gland tumor burden in a murine model of human prostate cancer metastasis which relied on treatment of established disease. The present study determined the ability of GGDPS inhibition to slow the development of prostate cancer metastasis in a preventative murine model. Using tail vein injection of human derived PC-3 prostate cancer cells 4 d after initiating daily GGOHBP or vehicle treatments, we found GGOHBP significantly reduced whole body tumor burden, significantly slowed the development of tumors, and prolonged overall survival as compared to vehicle treated animals. The observed reduction in soft tissue tumor burden corresponded to a biochemical reduction in Rap1A geranylgeranylation, which for prostate cancer is important in its own merit and which serves as a surrogate marker for Rho family, i.e. Rac, protein modification. This effect was present in all treated mice pointing to strong target engagement, which was not observed in non-tumor burdened tissues or control mice. Our findings reiterate a role for protein geranylgeranylation in the development of prostate cancer metastasis in vivo.

Maltotriose Conjugation to a Chlorin Derivative Enhances the Antitumor Effects of Photodynamic Therapy in Peritoneal Dissemination of Pancreatic Cancer

Peritoneal dissemination is a major clinical issue associated with dismal prognosis and poor quality of life for patients with pancreatic cancer; however, no effective treatment strategies have been established. Herein, we evaluated the effects of photodynamic therapy (PDT) with maltotriose-conjugated chlorin (Mal₃-chlorin) in culture and in a peritoneal disseminated mice model of pancreatic cancer. The Mal₃-chlorin was prepared as a water-soluble chlorin derivative conjugated with four Mal₃ molecules to improve cancer selectivity. In vitro, Mal₃-chlorin showed superior uptake into pancreatic cancer cells compared with talaporfin, which is clinically used. Moreover, the strong cytotoxic effects of PDT with Mal₃-chlorin occurred via apoptosis and reactive oxygen species generation, whereas Mal₃-chlorin alone did not cause any cytotoxicity in pancreatic cancer cells. Notably, using a peritoneal disseminated mice model, we demonstrated that Mal₃-chlorin accumulated in xenograft tumors and suppressed both tumor growth and ascites formation with PDT. Furthermore, PDT with Mal₃-chlorin induced robust apoptosis in peritoneal disseminated tumors, as indicated by immunohistochemistry. Taken together, these findings implicate Mal₃-chlorin as a potential next-generation photosensitizer for PDT and the basis of a new strategy for managing peritoneal dissemination of pancreatic cancer. Mol Cancer Ther; 16(6); 1124-32. ©2017 AACR.

Tiam1/Vav2-Rac1 axis: A tug-of-war between islet function and dysfunction

Glucose-stimulated insulin secretion [GSIS] from the islet β-cell involves a well-orchestrated interplay between metabolic and cationic events. It is well established that intracellular generation of adenine and guanine nucleotide triphosphates [e.g., ATP and GTP] represents one of the requisite signaling steps in GSIS. The small molecular mass GTP-binding proteins [G-proteins; e.g., Rac1 and Cdc42] have been shown to regulate islet β-cell function including actin cytoskeletal remodeling and fusion of insulin granules with the plasma membrane for GSIS to occur. In this context, several regulatory factors for these G-proteins have been identified in the pancreatic β-cell; these include guanine nucleotide exchange factors [GEFs] and guanine nucleotide dissociation inhibitors [GDI]. Recent pharmacological and molecular biological evidence identified Tiam1 and Vav2 as GEFs for Rac1 in promoting physiological insulin secretion. Paradoxically, emerging evidence in multiple cell types, including the islet β-cell, suggests key roles for Rac1 in the onset of cellular dysfunction under conditions of metabolic stress and diabetes. Furthermore, functional inactivation of either Tiam1 or Vav2 appears to attenuate sustained activation of Rac1 and its downstream signaling events [activation of stress kinases] under conditions of metabolic stress. Together, these findings suggest both "friendly" and "non-friendly" roles for Tiam1/Vav2-Rac1 signaling axis in islet β-cell in health and diabetes. Our current understanding of the field and the knowledge gaps that exist in this area of islet biology are heighted herein. Furthermore, potential caveats in the specificity and selectivity of pharmacological inhibitors that are available currently are discussed in this Commentary.

Dual oxidase 2 and pancreatic adenocarcinoma: IFN-γ-mediated dual oxidase 2 overexpression results in H2O2-induced, ERK-associated up-regulation of HIF-1α and VEGF-A

Several NADPH oxidase family members, including dual oxidase 2 [DUOX2], are expressed in human tumors, particularly gastrointestinal cancers associated with long-standing chronic inflammation. We found previously that exposure of pancreatic ductal adenocarcinoma cells to the pro-inflammatory cytokine IFN-γ increased DUOX2 expression (but not other NADPH oxidases) leading to long-lived H2O2 production. To elucidate the pathophysiology of DUOX2-mediated H2O2 formation in the pancreas further, we demonstrate here that IFN-γ-treated BxPC-3 and CFPAC-1 pancreatic cancer cells (known to increase DUOX2 expression) produce significant levels of intracellular oxidants and extracellular H2O2 which correlate with concomitant up-regulation of VEGF-A and HIF-1α transcription. These changes are not observed in the PANC-1 line that does not increase DUOX2 expression following IFN-γ treatment. DUOX2 knockdown with short interfering RNA significantly decreased IFN-γ-induced VEGF-A or HIF-1α up-regulation, as did treatment of pancreatic cancer cells with the NADPH oxidase inhibitor diphenylene iodonium, the multifunctional reduced thiol N-acetylcysteine, and the polyethylene glycol-modified form of the hydrogen peroxide detoxifying enzyme catalase. Increased DUOX2-related VEGF-A expression appears to result from reactive oxygen-mediated activation of ERK signaling that is responsible for AP-1-related transcriptional effects on the VEGF-A promoter. To clarify the relevance of these observations in vivo, we demonstrate that many human pre-malignant pancreatic intraepithelial neoplasms and frank pancreatic cancers express substantial levels of DUOX protein compared to histologically normal pancreatic tissues, and that expression of both DUOX2 and VEGF-A mRNAs is significantly increased in surgically-resected pancreatic cancers compared to the adjacent normal pancreas.

A stability-indicating high performance liquid chromatography method to determine apocynin in nanoparticles

In this study, we developed and validated a fast, specific, sensitive, precise and stability-indicating high performance liquid chromatography (HPLC) method to determine the drug apocynin in bovine serum albumin (BSA) nanoparticles. Chromatographic analyses were performed on an RP C₁₈ column and using a photodiode array detector at a wavelength of 276 nm. Mobile phase consisted of a mixture of acetonitrile and 1% acetic acid (60:40, v/v), and it was eluted isocratically at a flow rate of 0.8 mL/min. The retention time of apocynin chromatographic peak was 1.65 min. The method was linear, precise, accurate and specific in the range of 5–100 μg/mL. The intra- and inter-day precisions presented relative standard deviation (RSD) values lower than 2%. The method was robust regarding changes in mobile phase proportion, but not for flow rate. Limits of detection and quantitation were 78 ng/mL and 238 ng/mL, respectively. Apocynin was exposed to acid and alkali hydrolysis, oxidation and visible light. The drug suffered mild degradation under acid and oxidation conditions and great degradation under alkali conditions. Light exposure did not degrade the drug. The method was successfully applied to determine the encapsulation efficiency of apocynin in BSA nanoparticles.

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.

The protective effects of apocynin on ionizing radiation-induced intestinal damage in rats

BACKGROUND AND AIMS

Radiation colitis typically emerges during radiotherapy of intra-abdominal malignancies. While the underlying mechanism remains unclear, it is considered that free oxygen radicals act like cellular mediators to cause colonic damage. Apocynin (APO) prevents oxidative stress and apoptotic cell death by inhibiting NADPH oxidase, and preventing the formation of free oxygen radicals. The aim of the present study was to investigate the protective effect of APO, a strong antioxidant and antiinflammatory agent, on radiation induced colonic oxidative damage in rats.

MATERIALS AND METHODS

Rats were randomly divided into four groups (n = 8/group). Group I (control group); Group II (Group RAD) received a single dose of 800 cGy ionizing radiation to the whole abdomen with a linear accelerator (LINAC); Group III (Group APO) received a single dose of 20 mg/kg of APO intraperitoneally for five days; Group IV (Group APO+RAD) received APO for five days before radiation exposure (similar to Group III), (similar to Group II).

RESULTS

APO treatment prior to radiation led to protection in the biochemical and histopathological parameters.

CONCLUSIONS

Our study shows that APO treatment before radiation improves radiation induced colonic injury in rats, by decreasing oxidative stress and apoptosis.

Establishment of a syngeneic orthotopic model of prostate cancer in immunocompetent rats

We previously established 3 cell lines (PLS10, PLS20 and PLS30) from a chemically-induced prostate carcinoma in F344 rats, and demonstrated high potential for metastasis in nude mice. In the present study, we investigated the feasibility of establishing an orthotopic model using the 3 rat prostate cancer cell lines in immunocompetent rats with the aim of resolving species-mismatch problems and defects of immune systems. The PLS10, PLS20 and PLS30 cell lines were injected into the ventral prostates of 6-week-old rats, which were then sacrificed at experimental weeks 4 and 8. Tumor mass formation was found in rats with PLS10, but not in those with PLS20 or PLS30. Additionally, metastatic carcinomas could be detected in lymph nodes and lungs of PLS10-inoculated rats. Genetic analysis demonstrated K-ras gene mutations in PLS10 and PLS20, but not in PLS30 cells. There were no mutations in p53 and KLF6. In conclusion, we established a syngeneic orthotopic model for prostate cancer in immunocompetent rats simulating human castration-resistant prostate cancer (CRPC), which should prove useful for development and validation of therapeutic agents, especially with immunotherapy.

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.