Natriuretic peptide receptor A signaling regulates stem cell recruitment and angiogenesis: a model to study linkage between inflammation and tumorigenesis

New retinoblastoma (RB) drug delivery approaches: anti-tumor effect of atrial natriuretic peptide (ANP)-conjugated hyaluronic-acid-coated gold nanoparticles for intraocular treatment of chemoresistant RB

Intraocular drug delivery is a promising approach for treatment of ocular diseases. Chemotherapeutic drugs used in retinoblastoma (RB) treatment often lead to side effects and drug resistances. Therefore, new adjuvant therapies are needed to treat chemoresistant RBs. Biocompatible gold nanoparticles (GNPs) have unique antiangiogenic properties and can inhibit cancer progression. The combination of gold and low-molecular-weight hyaluronan (HA) enhances the stability of GNPs and promotes the distribution across ocular barriers. Attached to HA-GNPs, the atrial natriuretic peptide (ANP), which diminishes neovascularization in the eye, is a promising new therapeutic agent for RB treatment. In the study presented, we established ANP-coupled HA-GNPs and investigated their effect on the tumor formation potential of chemoresistant RB cells in an in ovo chicken chorioallantoic membrane model and an orthotopic in vivo RB rat eye model. Treatment of etoposide-resistant RB cells with ANP-HA-GNPs in ovo resulted in significantly reduced tumor growth and angiogenesis compared with controls. The antitumorigenic effect could be verified in the rat eye model, including a noninvasive application form via eye drops. Our data suggest that ANP-HA-GNPs represent a new minimally invasive, adjuvant treatment option for RB.

Therapeutic antibody targeting natriuretic peptide receptor 1 inhibits gastric cancer growth via BCL-2-mediated intrinsic apoptosis

Despite recent advances in the development of therapeutic antibodies, the prognosis of unresectable or metastatic gastric cancer (GC) remains poor. Here, we searched for genes involved in the malignant phenotype of GC and investigated the potential of one candidate gene to serve as a novel therapeutic target. Analysis of transcriptome datasets of GC identified natriuretic peptide receptor 1 (NPR1), a plasma membrane protein, as a potential target. We employed a panel of human GC cell lines and gene-specific small interfering RNA-mediated NPR1 silencing to investigate the roles of NPR1 in malignancy-associated functions and intracellular signaling pathways. We generated an anti-NPR1 polyclonal antibody and examined its efficacy in a mouse xenograft model of GC peritoneal dissemination. Associations between NPR1 expression in GC tissue and clinicopathological factors were also evaluated. NPR1 mRNA was significantly upregulated in several GC cell lines compared with normal epithelial cells. NPR1 silencing attenuated GC cell proliferation, invasion, and migration, and additionally induced the intrinsic apoptosis pathway associated with mitochondrial dysfunction and caspase activation via downregulation of BCL-2. Administration of anti-NPR1 antibody significantly reduced the number and volume of GC peritoneal tumors in xenografted mice. High expression of NPR1 mRNA in clinical GC specimens was associated with a significantly higher rate of postoperative recurrence and poorer prognosis. NPR1 regulates the intrinsic apoptosis pathway and plays an important role in promoting the GC malignant phenotype. Inhibition of NPR1 with antibodies may have potential as a novel therapeutic modality for unresectable or metastatic GC.

MSC-NPRA loop drives fatty acid oxidation to promote stemness and chemoresistance of gastric cancer

Cisplatin (CDDP)-based chemotherapy is the preferred treatment strategy for advanced stage gastric cancer (GC) patients. Despite the efficacy of chemotherapy, the development of chemoresistance negatively affects the prognosis of GC and the underlying mechanism remains poorly understood. Accumulated evidence suggests that mesenchymal stem cells (MSCs) play important roles in drug resistance. The chemoresistance and stemness of GC cells were observed by colony formation, CCK-8, sphere formation and flow cytometry assays. Cell lines and animal models were utilized to investigate related functions. Western blot, quantitative real-time PCR (qRT-PCR) and co-immunoprecipitation were used to explore related pathways. The results showed that MSCs improved the stemness and chemoresistance of GC cells and accounted for the poor prognosis of GC. Natriuretic peptide receptor A (NPRA) was upregulated in GC cells cocultured with MSCs and knockdown of NPRA reversed the MSC-induced stemness and chemoresistance. At the same time, MSCs could be recruited to GC by NPRA, which formed a loop. In addition, NPRA facilitated stemness and chemoresistance through fatty acid oxidation (FAO). Mechanistically, NPRA protected Mfn2 against protein degradation and promoted its mitochondrial localization, which consequently improved FAO. Furthermore, inhibition of FAO with etomoxir (ETX) attenuated MSC-induced CDDP resistance in vivo. In conclusion, MSC-induced NPRA promoted stemness and chemoresistance by upregulating Mfn2 and improving FAO. These findings help us understand the role of NPRA in the prognosis and chemotherapy of GC. NPRA may be a promising target to overcome chemoresistance.

Pleiotropic Roles of Atrial Natriuretic Peptide in Anti-Inflammation and Anti-Cancer Activity

Simple Summary

The relationship between inflammation and carcinogenesis, as well as the response to anti-tumor therapy, is intimate. Atrial natriuretic peptides (ANPs) play a pivotal role in the homeostatic control of blood pressure, electrolytes, and water balance. In addition, ANPs exert immune-modulatory effects in the tissue microenvironment, thus exhibiting a fascinating ability to prevent inflammation-related tumorigenesis and cancer recurrence. In cancers, ANPs show anti-proliferative effects through several molecular pathways. Furthermore, ANPs attenuate the side effects of cancer therapy. Therefore, ANPs have potential therapeutic value in tumors. Here, we summarized the roles of ANPs in diverse aspects of the immune system and the molecular mechanisms underlying the anti-cancer effects of ANPs, contributing to the development of ANP-based anti-cancer agents.

Abstract

The atrial natriuretic peptide (ANP), a cardiovascular hormone, plays a pivotal role in the homeostatic control of blood pressure, electrolytes, and water balance and is approved to treat congestive heart failure. In addition, there is a growing realization that ANPs might be related to immune response and tumor growth. The anti-inflammatory and immune-modulatory effects of ANPs in the tissue microenvironment are mediated through autocrine or paracrine mechanisms, which further suppress tumorigenesis. In cancers, ANPs show anti-proliferative effects through several molecular pathways. Furthermore, ANPs attenuate the side effects of cancer therapy. Therefore, ANPs act on several hallmarks of cancer, such as inflammation, angiogenesis, sustained tumor growth, and metastasis. In this review, we summarized the contributions of ANPs in diverse aspects of the immune system and the molecular mechanisms underlying the anti-cancer effects of ANPs.

Atrial Natriuretic Peptide Orchestrates a Coordinated Physiological Response to Fuel Non-shivering Thermogenesis

Atrial natriuretic peptide (ANP) is a cardiac hormone controlling blood volume and pressure in mammals. It is still unclear whether ANP controls cold-induced thermogenesis in vivo. Here, we show that acute cold exposure induces cardiac ANP secretion in mice and humans. Genetic inactivation of ANP promotes cold intolerance and suppresses half of cold-induced brown adipose tissue (BAT) activation in mice. While white adipocytes are resistant to ANP-mediated lipolysis at thermoneutral temperature in mice, cold exposure renders white adipocytes fully responsive to ANP to activate lipolysis and a thermogenic program, a physiological response that is dramatically suppressed in ANP null mice. ANP deficiency also blunts liver triglycerides and glycogen metabolism, thus impairing fuel availability for BAT thermogenesis. ANP directly increases mitochondrial uncoupling and thermogenic gene expression in human white and brown adipocytes. Together, these results indicate that ANP is a major physiological trigger of BAT thermogenesis upon cold exposure in mammals.

Microvesicles (MIVs) secreted from adipose-derived stem cells (ADSCs) contain multiple microRNAs and promote the migration and invasion of endothelial cells

Extracellular vesicles (EVs) such as microvesicles (MIVs) play an important role in intercellular communications. MIVs are small membrane vesicles sized 100–1000 nm in diameter that are released by many types of cells, such as mesenchymal stem cells (MSCs), tumor cells and adipose-derived stem cells (ADSC). As EVs can carry out autocrine and paracrine functions by controlling multiple cell processes, it is conceivable that EVs can be used as delivery vehicles for treating several clinical conditions, such as to improve cardiac angiogenesis after myocardial infarction (MI). Here, we seek to investigate whether ADSC-derived MIVs contain microRNAs that regulate angiogenesis and affect cell migration of endothelial cells. We first characterized the ADSC-derived MIVs and found that the MIVs had a size range of 100–300 nm, and expressed the MIV marker protein Alix. We then analyzed the microRNAs in ADSCs and ADSC-derived MIVs and demonstrated that ADSC-derived MIVs selectively released a panel of microRNAs, several of which were related to angiogenesis, including two members of the let-7 family. Furthermore, we demonstrated that ADSC-derived MIVs promoted the cell migration and invasion of the HUVEC endothelial cells. The PKH26-labeled ADSC-derived MIVs were effectively uptaken into the cytoplasm of HUVEC cells. Collectively, our results demonstrate that the ADSC-derived MIVs can promote migration and invasion abilities of endothelial cells, suggesting pro-angiogenetic potential. Future studies should focus on investigating the roles and mechanisms through which ADSC-derived MIVs regulate angiogenesis.

Atrial natriuretic peptide accelerates human endothelial progenitor cell-stimulated cutaneous wound healing and angiogenesis

Atrial natriuretic peptide (ANP) is a powerful vasodilating peptide secreted by cardiac muscle cells, and endothelial progenitor cells (EPCs) have been reported to stimulate cutaneous wound healing by mediating angiogenesis. To determine whether ANP can promote the EPC-mediated repair of injured tissues, we examined the effects of ANP on the angiogenic properties of EPCs and on cutaneous wound healing. In vitro, ANP treatment enhanced the migration, proliferation, and endothelial tube-forming abilities of EPCs. Furthermore, small interfering RNA-mediated silencing of natriuretic peptide receptor-1, which is a receptor for ANP, abrogated ANP-induced migration, tube formation, and proliferation of EPCs. In a murine cutaneous wound model, administration of either ANP or EPCs had no significant effect on cutaneous wound healing or angiogenesis in vivo, whereas the coadministration of ANP and EPCs synergistically potentiated wound healing and angiogenesis. In addition, ANP promoted the survival and incorporation of transplanted EPCs into newly formed blood vessels in wounds. These results suggest ANP accelerates EPC-mediated cutaneous wound healing by promoting the angiogenic properties and survival of transplanted EPCs.

Natriuretic Peptides: The Case of Prostate Cancer

Cardiac natriuretic peptides have long been known to act as main players in the homeostatic control of blood pressure, salt and water balance. However, in the last few decades, new properties have been ascribed to these hormones. A systematic review of English articles using MEDLINE Search terms included prostate cancer, inflammation, cardiac hormones, atrial natriuretic peptide, and brain natriuretic peptide. Most recent publications were selected. Natriuretic peptides are strongly connected to the immune system, whose two branches, innate and adaptive, are finely tuned and organized to kill invaders and repair injured tissues. These peptides control the immune response and act as anti-inflammatory and immune-modulatory agents. In addition, in cancers, natriuretic peptides have anti-proliferative effects by molecular mechanisms based on the inhibition/regulation of several pathways promoting cell proliferation and survival. Nowadays, it is accepted that chronic inflammation is a crucial player in prostate cancer development and progression. In this review, we summarize the current knowledge on the link between prostate cancer and inflammation and the potential use of natriuretic peptides as anti-inflammatory and anticancer agents.

Systemic inflammatory response syndrome following burns is mediated by brain natriuretic peptide/natriuretic peptide A receptor-induced shock factor 1 signaling pathway

The aim of this study was to determine whether systemic inflammatory response syndrome (SIRS) in burn patients is mediated by the brain natriuretic peptide (BNP)/natriuretic peptide A receptor (NPRA)-induced heat shock factor 1 (HSF-1) signalling pathway. Mononuclear cells (MNCs) that were isolated from patients with burn injuries and SIRS mouse models and a RAW264.7 cell line were treated with normal serum or serum obtained from animals with burn injuries. In parallel, small hairpin RNAs (shRNAs) against BNP or NPRA were transfected in both cell types. Western blotting (WB) and enzyme-linked immunosorbent assay (ELISA) were used to detect protein expression and inflammatory factor levels, respectively. We found that interleukin (IL)-12, tumour necrosis factor (TNF)-α, C-reactive protein (CRP), and BNP levels were increased and IL-10 levels were decreased in the plasma and MNCs in vivo in the animal model of SIRS. Additionally, NPRA was upregulated, whereas HSF-1 was downregulated in monocytes in vivo. Treatment of RAW264.7 cells with burn serum or BNP induced IL-12, TNF-α, and CRP secretion as well as HSF-1 expression. Finally, silencing BNP with shRNA interrupted the effect of burn serum on RAW264.7 cells, and silencing NPRA blocked burn serum- and BNP-mediated changes in RAW264.7 cells. These results suggest that the interaction of NPRA with BNP secreted from circulatory MNCs as well as mononuclear macrophages leads to inflammation via HSF-1 during SIRS development following serious burn injury.

The multifaceted role of natriuretic peptides in metabolic syndrome

Due to globalization and sophisticated western and sedentary lifestyle, metabolic syndrome has emerged as a serious public health challenge. Obesity is significantly increasing worldwide because of increased high calorie food intake and decreased physical activity leading to hypertension, dyslipidemia, atherosclerosis, and insulin resistance. Thus, metabolic syndrome constitutes cardiovascular disease, type 2 diabetes, obesity, and nonalcoholic fatty liver disease (NAFLD) and recently some cancers are also considered to be associated with this syndrome. There is increasing evidence of the involvement of natriuretic peptides (NP) in the pathophysiology of metabolic diseases. The natriuretic peptides are cardiac hormones, which are produced in the cardiac atrium, ventricles of the heart and the endothelium. These peptides are involved in the homeostatic control of body water, sodium intake, potassium transport, lipolysis in adipocytes and regulates blood pressure. The three known natriuretic peptide hormones present in the natriuretic system are atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP) and c-type natriuretic peptide (CNP). These three peptides primarily function as endogenous ligands and mainly act via their membrane receptors such as natriuretic peptide receptor A (NPR-A), natriuretic peptide receptor B (NPR-B) and natriuretic peptide receptor C (NPR-C) and regulate various physiological and metabolic functions. This review will shed light on the structure and function of natriuretic peptides and their receptors and their role in the metabolic syndrome.

Natriuretic peptide receptor A is related to the expression of vascular endothelial growth factors A and C, and is associated with the invasion potential of tongue squamous cell carcinoma

Natriuretic peptide receptor A (NPRA) is one of the natriuretic peptide receptors. NPRA has been reported to play a role in the carcinogenesis of various tumours, as well as functional roles in renal, cardiovascular, endocrine, and skeletal homeostasis. The clinicopathological significance of NPRA in tongue squamous cell carcinoma (TSCC) was examined in this study. The overexpression of NPRA was more frequent in TSCC (21/58, 36.2%) than in the normal oral epithelium (0/10, 0%) (P<0.05). It was also more frequently observed in cancers with higher grades according to the pattern of invasion (grades 1-2 vs. grades 3-4, P<0.01). Additionally, there was a tendency towards an association between the N classification and NPRA expression (N0 vs. N1-2, P=0.06). Significant correlations were also observed between the expression of NPRA and that of VEGF-A (P<0.001) and VEGF-C (P<0.001). The high-NPRA expression group had a significantly poorer prognosis, with a 5-year disease-specific survival rate of 39.7%, compared to 97.0% in the low-expression group (P<0.001). Multivariate analysis suggested that the overexpression of NPRA may also be an independent prognostic factor (P<0.05). In conclusion, NPRA is associated with VEGF expression levels, invasion, and metastasis, and may be a prognostic factor in TSCC patients.

Respiratory Syncytial Virus-Infected Mesenchymal Stem Cells Regulate Immunity via Interferon Beta and Indoleamine-2,3-Dioxygenase

Respiratory syncytial virus (RSV) has been reported to infect human mesenchymal stem cells (MSCs) but the consequences are poorly understood. MSCs are present in nearly every organ including the nasal mucosa and the lung and play a role in regulating immune responses and mediating tissue repair. We sought to determine whether RSV infection of MSCs enhances their immune regulatory functions and contributes to RSV-associated lung disease. RSV was shown to replicate in human MSCs by fluorescence microscopy, plaque assay, and expression of RSV transcripts. RSV-infected MSCs showed differentially altered expression of cytokines and chemokines such as IL-1β, IL6, IL-8 and SDF-1 compared to epithelial cells. Notably, RSV-infected MSCs exhibited significantly increased expression of IFN-β (~100-fold) and indoleamine-2,3-dioxygenase (IDO) (~70-fold) than in mock-infected MSCs. IDO was identified in cytosolic protein of infected cells by Western blots and enzymatic activity was detected by tryptophan catabolism assay. Treatment of PBMCs with culture supernatants from RSV-infected MSCs reduced their proliferation in a dose dependent manner. This effect on PBMC activation was reversed by treatment of MSCs with the IDO inhibitors 1-methyltryptophan and vitamin K3 during RSV infection, a result we confirmed by CRISPR/Cas9-mediated knockout of IDO in MSCs. Neutralizing IFN-β prevented IDO expression and activity. Treatment of MSCs with an endosomal TLR inhibitor, as well as a specific inhibitor of the TLR3/dsRNA complex, prevented IFN-β and IDO expression. Together, these results suggest that RSV infection of MSCs alters their immune regulatory function by upregulating IFN-β and IDO, affecting immune cell proliferation, which may account for the lack of protective RSV immunity and for chronicity of RSV-associated lung diseases such as asthma and COPD.

Klf10 deficiency in mice exacerbates pulmonary inflammation by increasing expression of the proinflammatory molecule NPRA

KLF10 is a transforming growth factor (TGF)-β/Smad downstream regulated gene. KLF10 binds to the promoter of target genes and mimics the effects of TGF-β as a transcriptional factor. In our laboratory, we noted that Klf10 deficiency in mice is associated with significant inflammation of the lungs. However, the precise mechanism of this association remains unknown. We previously identified NPRA as a target gene potentially regulated by KLF10 through direct binding; NPRA knockout have known that prevented lung inflammation in a mouse model of allergic asthma. Here, we further explored the regulatory association between KLF10 and NPRA on the basis of the aforementioned findings. Our results demonstrated that KLF10 acts as a transcriptional repressor of NPRA and that KLF10 binding reduces NPRA expression in vitro. Compared with wild-type mice, Klf10-deficient mice were more sensitive to lipopolysaccharide or ovalbumin challenge and showed more severe inflammatory histological changes in the lungs. Moreover, Klf10-deficient mice showed pulmonary neutrophil accumulation. These findings collectively reveal the precise site where KLF10 signaling affects pulmonary inflammation by attenuating NPRA expression. They also verify the importance of KLF10 and atrial natriuretic peptide/NPRA in exerting influences on chronic pulmonary disease pathogenesis.

Glipizide, an antidiabetic drug, suppresses tumor growth and metastasis by inhibiting angiogenesis

Angiogenesis is involved in the development, progression and metastasis of various human cancers. Herein, we report the discovery of glipizide, a widely used drug for type 2 diabetes mellitus, as a promising anticancer agent through the inhibition of tumor angiogenesis. By high-throughput screening (HTS) of an FDA approved drug library utilizing our in vivo chick embryo chorioallantoic membrane (CAM) and yolk sac membrane (YSM) models, glipizide has been identified to significantly inhibit blood vessel formation and development. Moreover, glipizide was found to suppress tumor angiogenesis, tumor growth and metastasis using xenograft tumor and MMTV-PyMT transgenic mouse models. We further revealed that the anticancer capability of glipizide is not attributed to its antiproliferative effects, which are not significant against various human cancer cell lines. To investigate whether its anticancer efficacy is associated with the glucose level alteration induced by glipizide application, glimepiride, another medium to long-acting sulfonylurea antidiabetic drug in the same class, was employed for the comparison studies in the same fashion. Interestingly, glimepiride has demonstrated no significant impact on the tumor growth and metastasis, indicating that the anticancer effects of glipizide is not ascribed to its antidiabetic properties. Furthermore, glipizide suppresses endothelial cell migration and the formation of tubular structures, thereby inhibiting angiogenesis by up-regulating the expression of natriuretic peptide receptor A. These findings uncover a novel mechanism of glipizide as a potential cancer therapy, and also for the first time, provide direct evidence to support that treatment with glipizide may reduce the cancer risk for diabetic patients.

Glipizide suppresses embryonic vasculogenesis and angiogenesis through targeting natriuretic peptide receptor A

Glipizide, a second-generation sulfonylurea, has been widely used for the treatment of type 2 diabetes. However, it is controversial whether or not glipizide would affect angiogenesis or vasculogenesis. In the present study, we used early chick embryo model to investigate the effect of glipizide on angiogenesis and vasculogenesis, which are the two major processes for embryonic vasculature formation as well as tumor neovascularization. We found that Glipizide suppressed both angiogenesis in yolk-sac membrane (YSM) and blood island formation during developmental vasculogenesis. Glipizide did not affect either the process of epithelial to mesenchymal transition (EMT) or mesoderm cell migration. In addition, it did not interfere with separation of smooth muscle cell progenitors from hemangioblasts. Moreover, natriuretic peptide receptor A (NPRA) has been identified as the putative target for glipizide׳s inhibitory effect on vasculogenesis. When NPRA was overexpressed or activated, blood island formation was reduced. NPRA signaling may play a crucial role in the effect of glipizide on vasculogenesis during early embryonic development.

Atrial natriuretic peptide: an old hormone or a new cytokine?

Atrial natriuretic peptide (ANP) a cardiovascular hormone mainly secreted by heart atria in response to stretching forces induces potent diuretic, natriuretic and vasorelaxant effects and plays a major role in the homeostasis of blood pressure as well as of water and salt balance. The hormone can also act as autocrine/paracrine factor and modulate several immune functions as well as cytoprotective effects. ANP contributes to innate immunity being able to: (i) stimulate the host defense against extracellular microbes by phagocytosis and Reactive Oxygen Species (ROS) release; (ii) inhibit the synthesis and release of proinflammatory markers such as TNF-α, IL-1, MCP-1, nitric oxide (NO), cyclooxygenase-2 (COX-2); (iii) inhibit the expression of adhesion molecules such as ICAM-1 and E-selectin. ANP can also affect the adaptive immunity being able to: (i) reduce the number of CD4(+) CD8(+) lymphocytes as well as to increase the CD4(-) CD8(-) cells; (ii) stimulate the differentiation of naïve CD4(+) cells toward the Th2 and/or Th17 phenotype. The hormone shows protective effects during: (i) ventricular hypertrophy and myocardial injury; (ii) atherosclerosis and hypertension by the induction of antiproliferative effects; (iii) oxidative stress counteracting the dangerous effects of ROS; (iv) growth of tumors cells by the induction of apoptosis or necrosis. Since not much is known about of the role of ANP locally produced and released by non-cardiac cells, this review outlines the contribution of ANP in different aspect of innate as well as adaptive immunity also with respect to the excessive cell growth in physiological and/or pathological conditions.

A 3D fibrous scaffold inducing tumoroids: a platform for anticancer drug development

The development of a suitable three dimensional (3D) culture system for anticancer drug development remains an unmet need. Despite progress, a simple, rapid, scalable and inexpensive 3D-tumor model that recapitulates in vivo tumorigenesis is lacking. Herein, we report on the development and characterization of a 3D nanofibrous scaffold produced by electrospinning a mixture of poly(lactic-co-glycolic acid) (PLGA) and a block copolymer of polylactic acid (PLA) and mono-methoxypolyethylene glycol (mPEG) designated as 3P. Cancer cells cultured on the 3P scaffold formed tight irregular aggregates similar to in vivo tumors, referred to as tumoroids that depended on the topography and net charge of the scaffold. 3P scaffolds induced tumor cells to undergo the epithelial-to-mesenchymal transition (EMT) as demonstrated by up-regulation of vimentin and loss of E-cadherin expression. 3P tumoroids showed higher resistance to anticancer drugs than the same tumor cells grown as monolayers. Inhibition of ERK and PI3K signal pathways prevented EMT and reduced tumoroid formation, diameter and number. Fine needle aspirates, collected from tumor cells implanted in mice when cultured on 3P scaffolds formed tumoroids, but showed decreased sensitivity to anticancer drugs, compared to tumoroids formed by direct seeding. These results show that 3P scaffolds provide an excellent platform for producing tumoroids from tumor cell lines and from biopsies and that the platform can be used to culture patient biopsies, test for anticancer compounds and tailor a personalized cancer treatment.