A novel piperine analogue exerts in vivo antitumor effect by inducing oxidative, antiangiogenic and immunomodulatory actions

Structural diversity characterizes natural products as prototypes for design of lead compounds. The aim of this study was to synthetize, and to evaluate the toxicity and antitumor action of a new piperine analogue, the butyl 4-(4-nitrobenzoate)-piperinoate (DE-07). Toxicity was evaluated against zebrafish, and in mice (acute and micronucleus assays). To evaluate the DE-07 antitumor activity Ehrlich ascites carcinoma model was used in mice. Angiogenesis, Reactive Oxygen Species (ROS) production and cytokines levels were investigated. Ninety-six hours exposure to DE-07 did not cause morphological or developmental changes in zebrafish embryos and larvae, with estimated LC₅₀ (lethal concentration 50%) higher than 100 μg/mL. On the acute toxicity assay in mice, LD₅₀ (lethal dose 50%) was estimated at around 1000 mg/kg, intraperitoneally (i.p.). DE-07 (300 mg/kg, i.p.) did not induce increase in the number of micronucleated erythrocytes in mice, suggesting no genotoxicity. On Ehrlich tumor model, DE-07 (12.5, 25 or 50 mg/kg, i.p.) induced a significant decrease on cell viability. In addition, there was an increase on ROS production and a decrease in peritumoral microvessels density. Moreover, DE-07 induced an increase of cytokines levels involved in oxidative stress and antiangiogenic effect (IL-1β, TNF-α and IL-4). No significant clinical toxicological effects were recorded in Ehrlich tumor transplanted animals. These data provide evidence that DE-07 presents low toxicity, and antitumor effect via oxidative and antiangiogenic actions by inducing modulation of inflammatory response in the tumor microenvironment.

The malignancy of liver cancer cells is increased by IL-4/ERK/AKT signaling axis activity triggered by irradiated endothelial cells

The malignant traits involved in tumor relapse, metastasis and the expansion of cancer stem-like cells are acquired via the epithelial-mesenchymal transition (EMT) process in the tumor microenvironment. In addition, the tumor microenvironment strongly supports the survival and growth of malignant tumor cells and further contributes to the reduced efficacy of anticancer therapy. Ionizing radiation can influence the tumor microenvironment, because it alters the biological functions of endothelial cells composing tumor vascular systems. However, to date, studies on the pivotal role of these endothelial cells in mediating the malignancy of cancer cells in the irradiated tumor microenvironment are rare. We previously evaluated the effects of irradiated endothelial cells on the malignant traits of human liver cancer cells and reported that endothelial cells irradiated with 2 Gy reinforce the malignant properties of these cancer cells. In this study, we investigated the signaling mechanisms underlying these events. We revealed that the increased expression level of IL-4 in endothelial cells irradiated with 2 Gy eventually led to enhanced migration and invasion of cancer cells and further expansion of cancer stem-like cells. In addition, this increased level of IL-4 activated the ERK and AKT signaling pathways to reinforce these events in cancer cells. Taken together, our data indicate that ionizing radiation may indirectly modulate malignancy by affecting endothelial cells in the tumor microenvironment. Importantly, these indirect effects on malignancy are thought to offer valuable clues or targets for overcoming the tumor recurrence after radiotherapy.

Hypoxia enhances CD8+ TC2 cell-dependent airway hyperresponsiveness and inflammation through hypoxia-inducible factor 1α

BACKGROUND

CD8+ type 2 cytotoxic T (TC2) cells undergo transcriptional reprogramming to IL-13 production in the presence of IL-4 to become potent, steroid-insensitive, pathogenic effector cells in asthmatic patients and in mice in a model of experimental asthma. However, no studies have described the effects of hypoxia exposure on TC2 cell differentiation.

OBJECTIVE

We determined the effects of hypoxia exposure on IL-13-producing CD8+ TC2 cells.

METHODS

CD8+ transgenic OT-1 cells differentiated with IL-2 and IL-4 (TC2 cells) were exposed to normoxia (21% oxygen) or hypoxia (3% oxygen), and IL-13 production in vitro was monitored. After differentiation under these conditions, cells were adoptively transferred into CD8-deficient mice, and lung allergic responses, including airway hyperresponsiveness to inhaled methacholine, were assessed. The effects of pharmacologic inhibitors of hypoxia-inducible factor (HIF) 1α and HIF-2α were determined, as were responses in HIF-1α-deficient OT-1 cells.

RESULTS

Under hypoxic conditioning, CD8+ TC2 cell differentiation was significantly enhanced, with increased numbers of IL-13+ T cells and increased production of IL-13 in vitro. Adoptive transfer of TC2 cells differentiated under hypoxic conditioning restored lung allergic responses in sensitized and challenged CD8-deficient recipients to a greater degree than seen in recipients of TC2 cells differentiated under normoxic conditioning. Pharmacologic inhibition of HIF-1α or genetic manipulation to reduce HIF-1α expression reduced the hypoxia-enhanced differentiation of TC2 cells, IL-13 production, and the capacity of transferred cells to restore lung allergic responses in vivo. IL-4-dependent, hypoxia-mediated increases in HIF-1α and TC2 cell differentiation were shown to be mediated through activation of Janus kinase 1/3 and GATA-3.

CONCLUSIONS

Hypoxia enhances CD8+ TC2 cell-dependent airway hyperresponsiveness and inflammation through HIF-1α activation. These findings coupled with the known insensitivity of CD8+ T cells to corticosteroids suggests that activation of the IL-4-HIF-1α-IL-13 axis might play a role in the development of steroid-refractory asthma.

Tumor growth suppressive effect of IL-4 through p21-mediated activation of STAT6 in IL-4Rα overexpressed melanoma models

To evaluate the significance of interleukin 4 (IL-4) in tumor development, we compared B16F10 melanoma growth in IL-4-overespressing transgenic mice (IL-4 mice) and non-transgenic mice. In IL-4 mice, reduced tumor volume and weight were observed when compared with those of non-transgenic mice. Significant activation of DNA binding activity of STAT6, phosphorylation of STAT6 as well as IL-4, IL-4Rα and p21 expression were found in the tumor tissues of IL-4 mice compared to non-transgenic mice. Higher expression of IL-4, STAT6 and p21 in human melanoma tissue compared to normal human skin tissue was also found. Higher expression of apoptotic protein such as cleaved caspase-3, cleaved caspase-8, cleaved caspase-9, Bax, p53 and p21, but lower expression levels of survival protein such as Bcl-2 were found in the tumor of IL-4 mice. In vitro study, we found that overexpression of IL-4 significantly inhibited SK-MEL-28 human melanoma cell and B16F10 murine melanoma cell growth via p21-mediated activation of STAT6 pathway as well as increased expression of apoptotic cell death proteins. Moreover, p21 knockdown with siRNA abolished IL-4 induced activation of STAT6 and expression of p53 and p21 accompanied with reduced IL-4 expression as well as melanoma cell growth inhibition. Therefore, these results showed that IL-4 overexpression suppressed tumor development through p21-mediated activation of STAT6 pathways in melanoma models.

Redox-signals and macrophage biology

Macrophages are known for their versatile role in biology. They sense and clear structures that contain exogenous or endogenous pathogen-associated molecular patterns. This process is tightly linked to the production of a mixture of potentially harmful oxidants and cytokines. Their inherent destructive behavior is directed against foreign material or structures of 'altered self', which explains the role of macrophages during innate immune reactions and inflammation. However, there is also another side of macrophages when they turn into a tissue regenerative, pro-resolving, and healing phenotype. Phenotype changes of macrophages are termed macrophage polarization, representing a continuum between classical and alternative activation. Macrophages as the dominating producers of superoxide/hydrogen peroxide and nitric oxide are not only prone to oxidative modifications but also to more subtle signaling properties of redox-active molecules conveying redox regulation. We review basic concepts of the enzymatic nitric oxide and superoxide production within macrophages, refer to their unique chemical reactions and outline biological consequences not only for macrophage biology but also for their communication with cells in the microenvironment. These considerations link hypoxia to the NO system, addressing feedforward as well as feedback circuits. Moreover, we summarize the role of redox-signaling affecting epigenetics and reflect the central role of mitochondrial-derived oxygen species in inflammation. To better understand the diverse functions of macrophages during initiation as well as resolution of inflammation and to decode their versatile roles during innate and adaptive immunity with the entire spectrum of cell protective towards cell destructive activities we need to appreciate the signaling properties of redox-active species. Herein we discuss macrophage responses in terms of nitric oxide and superoxide formation with the modulating impact of hypoxia.

Macrophage NOS2 in Tumor Leukocytes

SIGNIFICANCE

Leukocytes and especially macrophages are a major cellular constituent of the tumor mass. The tumor microenvironment not only determines their activity but in turn these cells also contribute to tumor initiation and progression. Recent Advances: Proinflammatory stimulated macrophages upregulate inducible nitric oxide synthase (NOS2) and produce high steady-state NO concentrations. NO provokes tumor cell death by initiating apoptosis and/or necrosis. Mechanisms may comprise p53 accumulation, immunestimulatory activities, and an increased efficacy of chemo- and/or radiotherapy. However, the potential cytotoxic activity of macrophages often is compromised in the tumor microenvironment and instead a protumor activity of macrophages dominates. Contributing factors are signals generated by viable and dying tumor cells, attraction and activation of myeloid-derived suppressor cells, and hypoxia. Limited oxygen availability not only attenuates NOS2 activity but also causes accumulation of hypoxia-inducible factors 1 and 2 (HIF-1/HIF-2). Activation of the HIF system is tightly linked to NO formation and affects the expression of macrophage phenotype markers that in turn add to tumor progression.

CRITICAL ISSUES

To make use of the cytotoxic arsenal of activated macrophages directed against tumor cells, it will be critical to understand how, when, and where these innate immune responses are blocked and whether it will be possible to reinstall their full capacity to kill tumor cells.

FUTURE DIRECTIONS

Low-dose irradiation or proinflammatory activation of macrophages in the tumor microenvironment may open options to boost NOS2 expression and activity and to initiate immunestimulatory features of NO that may help to restrict tumor growth. Antioxid. Redox Signal. 26, 1023-1043.

Hypoxic inhibition of JMJD3 reduces H3K27me3 demethylation and induction of the STAT6 target gene CCL18

Hypoxia, by activating transcription factors induces transcription of some genes but it also reduces mRNA synthesis by mechanisms that are poorly defined. Activation of human macrophages with interleukin (IL)-4 showed that up-regulation of some IL-4 target genes was reduced when macrophages were incubated at 1% oxygen. Hypoxia impaired induction of chemokine (C-C motif) ligand 18 (CCL18), although IL-4-induced DNA binding of the transcription factor STAT6 remained intact. In contrast, induction of serine peptidase inhibitor, Kunitz type (SPINT)2, another IL-4/STAT6 target gene, was not affected by hypoxia. The repressive histone mark histone 3 lysine 27 trimethylation (H3K27me3), known to prevent chromatin remodelling and transcription, was removed from the SPINT2 but not the CCL18 gene locus under hypoxia or dimethyloxalylglycine-treatment. The H3K27me3 demethylase JMJD3 was required for CCL18 gene induction but dispensable for induction of SPINT2. Our data indicate that hypoxic inhibition of JMJD3 activity reduces demethylation of H3K27me3, nucleosome removal, and hence induction of the STAT6 target gene CCL18, while induction of other STAT6-inducible genes such as SPINT2 remained unaffected by JMJD3. In contrast to mouse MΦ in human cells JMJD3 is not recruited by transcription factors like IRF4, KL4, or PPARγ to convey specificity in gene induction.

Hypoxia Potentiates Palmitate-induced Pro-inflammatory Activation of Primary Human Macrophages

Pro-inflammatory cytokines secreted by adipose tissue macrophages (ATMs) contribute to chronic low-grade inflammation and obesity-induced insulin resistance. Recent studies have shown that adipose tissue hypoxia promotes an inflammatory phenotype in ATMs. However, our understanding of how hypoxia modulates the response of ATMs to free fatty acids within obese adipose tissue is limited. We examined the effects of hypoxia (1% O2) on the pro-inflammatory responses of human monocyte-derived macrophages to the saturated fatty acid palmitate. Compared with normoxia, hypoxia significantly increased palmitate-induced mRNA expression and protein secretion of IL-6 and IL-1β. Although palmitate-induced endoplasmic reticulum stress and nuclear factor κB pathway activation were not enhanced by hypoxia, hypoxia increased the activation of JNK and p38 mitogen-activated protein kinase signaling in palmitate-treated cells. Inhibition of JNK blocked the hypoxic induction of pro-inflammatory cytokine expression, whereas knockdown of hypoxia-induced transcription factors HIF-1α and HIF-2α alone or in combination failed to reduce IL-6 and only modestly reduced IL-1β gene expression in palmitate-treated hypoxic macrophages. Enhanced pro-inflammatory cytokine production and JNK activity under hypoxia were prevented by inhibiting reactive oxygen species generation. In addition, silencing of dual-specificity phosphatase 16 increased normoxic levels of IL-6 and IL-1β and reduced the hypoxic potentiation in palmitate-treated macrophages. The secretome of hypoxic palmitate-treated macrophages promoted IL-6 and macrophage chemoattractant protein 1 expression in primary human adipocytes, which was sensitive to macrophage JNK inhibition. Our results reveal that the coexistence of hypoxia along with free fatty acids exacerbates macrophage-mediated inflammation.

Hypoxia induces calpain activity and degrades SMAD2 to attenuate TGFβ signaling in macrophages

Background

Under inflammatory conditions or during tumor progression macrophages acquire distinct phenotypes, with factors of the microenvironment such as hypoxia and transforming growth factor β (TGFβ) shaping their functional plasticity. TGFβ is among the factors causing alternative macrophage activation, which contributes to tissue regeneration and thus, resolution of inflammation but may also provoke tumor progression. However, the signal crosstalk between TGFβ and hypoxia is ill defined.

Results

Exposing human primary macrophages to TGFβ elicited a rapid SMAD2/SMAD3 phosphorylation. This early TGFβ-signaling remained unaffected by hypoxia. However, with prolonged exposure periods to TGFβ/hypoxia the expression of SMAD2 declined because of decreased protein stability. In parallel, hypoxia increased mRNA and protein amount of the calpain regulatory subunit, with the further notion that TGFβ/hypoxia elicited calpain activation. The dual specific proteasome/calpain inhibitor MG132 and the specific calpain inhibitor 1 rescued SMAD2 degradation, substantiating the ability of calpain to degrade SMAD2. Decreased SMAD2 expression reduced TGFβ transcriptional activity of its target genes thrombospondin 1, dystonin, and matrix metalloproteinase 2.

Conclusions

Hypoxia interferes with TGFβ signaling in macrophages by calpain-mediated proteolysis of the central signaling component SMAD2.

Electronic supplementary material

The online version of this article (doi:10.1186/s13578-015-0026-x) contains supplementary material, which is available to authorized users.

Hypoxia induces macrophage polarization and re-education toward an M2 phenotype in U87 and U251 glioblastoma models

Hypoxia is a common feature of solid tumors, particularly in glioblastoma (GBM), and known to be a poor prognosis factor in GBM patients. The growth of GBM is also associated with a marked inflammation partially characterized by an accumulation of macrophage (MΦ) of the M2 phenotype. However, the transition between M1 MΦ (antitumoral) and M2 MΦ (protumoral) phenotypes is a dynamic process. We made the assumption that oxygen (O2) availability could be a major regulator of this transition and that the intratumoral O2 gradient is of importance. We evaluated, in vivo, the impact of hypoxia on MΦ tropism and polarization in two models of human GBM, well differentiated by their degree of hypoxia. MΦ migration in the tumor was more pronounced in the more hypoxic tumor of the two GBM models. In the more hypoxic of the models, we have shown that MΦ migrated at the tumor site only when hypoxia takes place. We also demonstrated that the acquisition of the M2 phenotype was clearly an evolving phenomenon with hypoxia as the major trigger for this transition. In support of these in vivo finding, M0 but also M1 MΦ cultured in moderate or severe hypoxia displayed a phenotype close to that of M2 MΦ whose phenotype was further reinforced by severe hypoxia. These results highlight the role of hypoxia in the aggressiveness of GBM, in part, by transforming MΦ such that a protumoral activity is expressed.

The emerging quest for the optimal angiostatic combination therapy

Angiostatic therapies are now routinely embedded in the daily clinical management of cancer. Although these agents clearly benefit patient survival rates, the effect is only moderate with sometimes considerable side effects. A major cause of failure in this respect is the induction of resistance and tolerability against these drugs. Most angiostatic drugs are tyrosine kinase inhibitors that aim to inhibit or neutralize the activity of tumour-produced growth factors. Frustrating the tumour cells in this way results in genetic adaptations in the cells, turning them into mutants that are dependent on other growth mechanisms. It may therefore be necessary to shift to another class of drugs that directly target the tumour vasculature. It is evident that improvement of future angiogenesis inhibitors can only arise from two efforts. First, through the identification of better targets, preferably specifically expressed in the tumour vasculature. Secondly, through the development of combination therapies. The present review highlights the current efforts and challenges in trying to develop effective angiostatic combination therapies.

Genome-wide identification of hypoxia-inducible factor-1 and -2 binding sites in hypoxic human macrophages alternatively activated by IL-10

Macrophages (MΦ) often accumulate in hypoxic areas, where they significantly influence disease progression. Anti-inflammatory cytokines, such as IL-10, generate alternatively activated macrophages that support tumor growth. To understand how alternative activation affects the transcriptional profile of hypoxic macrophages, we globally mapped binding sites of hypoxia-inducible factor (HIF)-1α and HIF-2α in primary human monocyte-derived macrophages prestimulated with IL-10. 713 HIF-1 and 795 HIF-2 binding sites were identified under hypoxia. Pretreatment with IL-10 altered the binding pattern, with 120 new HIF-1 and 188 new HIF-2 binding sites emerging. HIF-1 binding was most prominent in promoters, while HIF-2 binding was more abundant in enhancer regions. Comparison of ChIP-seq data obtained in other cells revealed a highly cell type specific binding of HIF. In MΦ HIF binding occurred preferentially in already active enhancers or promoters. To assess the roles of HIF on gene expression, primary human macrophages were treated with siRNA against HIF-1α or HIF-2α, followed by genome-wide gene expression analysis. Comparing mRNA expression to the HIF binding profile revealed a significant enrichment of hypoxia-inducible genes previously identified by ChIP-seq. Analysis of gene expression under hypoxia alone and hypoxia/IL-10 showed the enhanced induction of a set of genes including PLOD2 and SLC2A3, while another group including KDM3A and ADM remained unaffected or was reduced by IL-10. Taken together IL-10 influences the DNA binding pattern of HIF and the level of gene induction.

Amelioration of hypoxia and LPS-induced intestinal epithelial barrier dysfunction by emodin through the suppression of the NF-κB and HIF-1α signaling pathways

Intestinal barrier dysfunction occurs in critical illnesses and involves the inflammatory and hypoxic injury of intestinal epithelial cells. Researchers are still defining the underlying mechanisms and evaluating therapeutic strategies for restoring intestinal barrier function. The anti-inflammatory drug, emodin, has been shown to exert a protective effect on intestinal barrier function; however, its mechanisms of action remain unknown. In this study, we investigated the protective effects of emodin on intestinal barrier function and the underlying mechanisms in intestinal epithelial cells challenged with lipopolysaccharide (LPS) and hypoxia/reoxygenation (HR). To induce barrier dysfunction, Caco-2 monolayers were subjected to HR with or without LPS treatment. Transepithelial electrical resistance and paracellular permeability were measured to evaluate barrier function. The expression of the tight junction (TJ) proteins, zonula occludens (ZO)-1, occludin, and claudin-1, as well as that of hypoxia-inducible factor (HIF)-1α, phosphor-IκB-α, phosphor-nuclear factor (NF)-κB p65 and cyclooxygenase (COX)-2 was determined by western blot analysis. The results revealed that emodin markedly attenuated the decrease in transepithelial electrical resistance and the increase in paracellular permeability in the Caco-2 monolayers treated with LPS and subjected to HR. Emodin also markedly alleviated the damage caused by LPS and HR (manifested by a decrease in the expression of the TJ protein, ZO-1), and inhibited the expression of HIF-1α, IκB-α, NF-κB and COX-2 in a dose-dependent manner. In conclusion, our data suggest that emodin attenuates LPS- and HR-induced intestinal epithelial barrier dysfunction by inhibiting the HIF-1α and NF-κB signaling pathways and preventing the damage caused to the TJ barrier (shown by the decrease in the expression of ZO-1).