A(2A) adenosine receptor ligands and proinflammatory cytokines induce PC 12 cell death through apoptosis

Inflammatory Signaling in Hypertension: Regulation of Adrenal Catecholamine Biosynthesis

The immune system is increasingly recognized for its role in the genesis and progression of hypertension. The adrenal gland is a major site that coordinates the stress response via the hypothalamic-pituitary-adrenal axis and the sympathetic-adrenal system. Catecholamines released from the adrenal medulla function in the neuro-hormonal regulation of blood pressure and have a well-established link to hypertension. The immune system has an active role in the progression of hypertension and cytokines are powerful modulators of adrenal cell function. Adrenal medullary cells integrate neural, hormonal, and immune signals. Changes in adrenal cytokines during the progression of hypertension may promote blood pressure elevation by influencing catecholamine biosynthesis. This review highlights the potential interactions of cytokine signaling networks with those of catecholamine biosynthesis within the adrenal, and discusses the role of cytokines in the coordination of blood pressure regulation and the stress response.

Prognostic impact of CD73 and A2A adenosine receptor expression in non-small-cell lung cancer

In immune cells, CD73 dephosphorylates and converts extracellular AMP into adenosine, which binds the A2A adenosine receptor (A2AR). Blockade of this interaction, which induces an immunosuppressed niche in the tumor microenvironment, represents a potential novel treatment strategy. The clinical significance of CD73 and A2AR expression in non-small-cell lung cancer (NSCLC), however, has yet to be thoroughly investigated. Here we evaluated CD73 and A2AR protein expression levels using immunohistochemistry in tissue microarrays containing 642 resected NSCLC specimens. Furthermore, we compared the expression profiles of 133 paired primary tumors and lymph node metastases. CD73 and A2AR expression levels were significantly higher in females than in males, in never smokers than in ever smokers, and in adenocarcinomas than in squamous cell carcinomas. Among adenocarcinomas, significantly higher CD73 and A2AR expression was observed in TTF-1-positive and mutant EGFR-positive tumors than in their counterparts. Compared with CD73, A2AR expression was more inconsistent between primary tumors and lymph node metastases. Among NSCLC patients, high CD73 expression was an independent indicator of poor prognosis in multivariate Cox regression analyses for overall survival [hazard ratio (HR), 2.18; 95% confidence interval (CI), 1.38–3.46] and recurrence-free survival (HR, 2.05; 95% CI, 1.42–2.95). In contrast, high A2AR expression was an independent predictor of favorable prognosis for overall survival (HR, 0.70; 95% CI, 0.50–0.98) and recurrence-free survival (HR, 0.74; 95% CI, 0.56–0.97). Together, these findings indicate that CD73 and A2AR have opposing prognostic effects, although cases involving CD73 or A2AR expression share some clinicopathological features.

Research advances on apoptosis caused by quantum dots

Recently, quantum dots (QDs) have been widely applied in biological and biomedical fields such as cell labeling, living tissue imaging, and photodynamic therapy because of their superior optical properties. Meanwhile, the potential biological negative effects and/or toxic effects of QDs have become increasingly important, especially the cytotoxicity caused by QDs. One of the common cytotoxicity when living organisms are treated with QD is apoptosis, where many attempts have been made to explain the mechanisms of apoptosis caused by QDs' use. One of the mechanisms is the production of cadmium ion (Cd(2+)) and reactive oxygen species (ROS). Excess generation of ROS will result in oxidative stress that would mediate apoptosis. Furthermore, the activation of cell death receptors and mitochondria-dependent such as B cell lymphoma 2 (Bcl-2) family and the caspase family could onset apoptosis. Signal transduction such as some classical signal pathways of PI3K-AKT, NF-E2-related factor 2 (Nrf2)-antioxidant response element (ARE), mitogen-activated protein kinases (MAPKs), and nuclear factor kappa B (NF-κB) also plays an important role in the regulation of apoptosis. Several ways to reduce the apoptotic rate have been introduced, such as surface modification, controlling, the dose, size, and exposure time of QDs as well as using antioxidants or inhibitors. In this review, we attempted to review the most recent findings associated with apoptosis caused by QDs so as to provide some guidelines for a safer QD application in the future.

Purinergic signalling and cancer

Receptors for extracellular nucleotides are widely expressed by mammalian cells. They mediate a large array of responses ranging from growth stimulation to apoptosis, from chemotaxis to cell differentiation and from nociception to cytokine release, as well as neurotransmission. Pharma industry is involved in the development and clinical testing of drugs selectively targeting the different P1 nucleoside and P2 nucleotide receptor subtypes. As described in detail in the present review, P2 receptors are expressed by all tumours, in some cases to a very high level. Activation or inhibition of selected P2 receptor subtypes brings about cancer cell death or growth inhibition. The field has been largely neglected by current research in oncology, yet the evidence presented in this review, most of which is based on in vitro studies, although with a limited amount from in vivo experiments and human studies, warrants further efforts to explore the therapeutic potential of purinoceptor targeting in cancer.

High mechanical strain of primary intervertebral disc cells promotes secretion of inflammatory factors associated with disc degeneration and pain

Introduction

Excessive mechanical loading of intervertebral discs (IVDs) is thought to alter matrix properties and influence disc cell metabolism, contributing to degenerative disc disease and development of discogenic pain. However, little is known about how mechanical strain induces these changes. This study investigated the cellular and molecular changes as well as which inflammatory receptors and cytokines were upregulated in human intervertebral disc cells exposed to high mechanical strain (HMS) at low frequency. The impact of these metabolic changes on neuronal differentiation was also explored to determine a role in the development of disc degeneration and discogenic pain.

Methods

Isolated human annulus fibrosus (AF) and nucleus pulposus (NP) cells were exposed to HMS (20% cyclical stretch at 0.001 Hz) on high-extension silicone rubber dishes coupled to a mechanical stretching apparatus and compared to static control cultures. Gene expression of Toll-like receptors (TLRs), neuronal growth factor (NGF) and tumour necrosis factor α (TNFα) was assessed. Collected conditioned media were analysed for cytokine content and applied to rat pheocromocytoma PC12 cells for neuronal differentiation assessment.

Results

HMS caused upregulation of TLR2, TLR4, NGF and TNFα gene expression in IVD cells. Medium from HMS cultures contained elevated levels of growth-related oncogene, interleukin 6 (IL-6), IL-8, IL-15, monocyte chemoattractant protein 1 (MCP-1), MCP-3, monokine induced by γ interferon, transforming growth factor β1, TNFα and NGF. Exposure of PC12 cells to HMS-conditioned media resulted in both increased neurite sprouting and cell death.

Conclusions

HMS culture of IVD cells in vitro drives cytokine and inflammatory responses associated with degenerative disc disease and low-back pain. This study provides evidence for a direct link between cellular strain, secretory factors, neoinnervation and potential degeneration and discogenic pain in vivo.

Quantum dots trigger immunomodulation of the NFκB pathway in human skin cells

The immunological effects of quantum dots are dependent on a variety of factors including, but not limited to, exposure time and dosing concentrations. In this study, we investigated the influence of 15 nm CdSe/ZnS-COOH quantum dot nanocrystals (QDs) on cell density, viability, and morphology in human epidermal keratinocytes (HEK) and human dermal fibroblasts (HDF). Furthermore, inflammatory and non-inflammatory immune responses were measured using protein and real time PCR array analysis from HDF cells exposed to predetermined sub-lethal concentrations of QDs. CdSe/ZnS-COOH QDs caused concentration-dependent (1-120 nM exposure concentrations) and time-dependent (8 h or 48 h) cell death, as evidenced by metabolic activity and morphological changes. QD exposure induced upregulation of apoptotic, inflammatory and immunoregulatory proteins such as TNF-α, IL-1B and IL-10. HMOX1, an indicator of stress due to reactive oxygen intermediates (ROIs) and/or metals, was upregulated at the later time point as well. QDs also caused modulation of genes known to be associated with inflammatory (IL1-β, CCL2, IRAK-2), immune (IL-1, IL-6, PGLYRP1, SERPINA1, IL-10), stress due to ROIs and/or heavy metals (HMOX1), and apoptotic (CASP1, ADORA2A) responses. Cellular effects from QD exposure were found to primarily follow the NFκB pathway. In addition, QDs induced a differential cytotoxicity in keratinocytes and fibroblasts at different exposure concentrations and time points, even at physiologically relevant dosing concentrations, thus emphasizing the need to investigate potential mechanisms of action among different cell types within the same target organ.

The synthesized novel fluorinated compound (LJJ-10) induces death receptor- and mitochondria-dependent apoptotic cell death in the human osteogenic sarcoma U-2 OS cells

We designed the 6-fluoro-2-(3-fluorophenyl)-4-substituted anilinoquinazoline derivatives as less toxic anti-cancer candidates. Our result demonstrated that LJJ-10 has greater cytotoxicity than that of the other compounds in human osteogenic sarcoma U-2 OS cells. LJJ-10-induced apoptosis was associated with enhancing ROS generation, DNA damage, and an increase of the protein levels of Fas, FasL, FADD, caspase-8, cytochrome c, Apaf-1, AIF, Endo G, caspase-9 and caspase-3 in U-2 OS cells. LJJ-10-triggered growth inhibition was significantly attenuated by N-acetylcysteine, cyclosporine A, anti-FasL monoclonal antibody, and caspase-8, -9 and -3 specific inhibitors in U-2 OS cells. We suggest that LJJ-10-induced apoptotic cell death in U-2 OS cells through death receptor- and mitochondria-dependent apoptotic signaling pathways.

Adenosine A2A receptor is a unique angiogenic target of HIF-2alpha in pulmonary endothelial cells

Hypoxia, through the hypoxia-inducible transcription factors HIF-1alpha and HIF-2alpha (HIFs), induces angiogenesis by up-regulating a common set of angiogenic cytokines. Unlike HIF-1alpha, which regulates a unique set of genes, most genes regulated by HIF-2alpha overlap with those induced by HIF-1alpha. Thus, the unique contribution of HIF-2alpha remains largely obscure. By using adenoviral mutant HIF-1alpha and adenoviral mutant HIF-2alpha constructs, where the HIFs are transcriptionally active under normoxic conditions, we show that HIF-2alpha but not HIF-1alpha regulates adenosine A(2A) receptor in primary cultures of human lung endothelial cells. Further, siRNA knockdown of HIF-2alpha completely inhibits hypoxic induction of A(2A) receptor. Promoter studies show a 2.5-fold induction of luciferase activity with HIF-2alpha cotransfection. Analysis of the A(2A) receptor gene promoter revealed a hypoxia-responsive element in the region between -704 and -595 upstream of the transcription start site. By using a ChIP assay, we demonstrate that HIF-2alpha binding to this region is specific. In addition, we demonstrate that A(2A) receptor has angiogenic potential, as assessed by increases in cell proliferation, cell migration, and tube formation. Additional data show increased expression of A(2A) receptor in human lung tumor cancer samples relative to adjacent normal lung tissue. These data also demonstrate that A(2A) receptor is regulated by hypoxia and HIF-2alpha in human lung endothelial cells but not in mouse-derived endothelial cells.

Adenosine protects against suicidal erythrocyte death

Suicidal death of erythrocytes or eryptosis is characterized by cell shrinkage and cell membrane scrambling leading to phosphatidylserine exposure at the erythrocyte surface. The cell membrane scrambling is triggered by an increase in cytosolic Ca(2+) activity and activation of protein kinase C (PKC). Phosphatidylserine exposure fosters adherence of affected erythrocytes to the vascular wall. Thus, microcirculation in ischemic tissues may be impaired by the appearance of eryptotic erythrocytes. Ischemia leads to release of adenosine, which in most tissues leads to vasodilation and protects against cell injury. The present experiments explored whether adenosine influences mechanisms underlying eryptosis. Erythrocyte phosphatidylserine exposure was estimated from annexin V binding, cell volume from forward scatter and cytosolic Ca(2+) activity from Fluo3 fluorescence. Glucose depletion (for 24 or 48 h) significantly increased annexin binding and decreased forward scatter, effects partially reversed by adenosine. The protective effect of adenosine reached statistical significance (s.d.) at > =30 microM. Low Cl(-) solution (Cl(-) exchanged by gluconate for 24 h) similarly increased annexin binding and decreased forward scatter, effects again reversed by adenosine (s.d. at > or =10 and 30 microM, respectively). Similarly, phosphatase inhibitor okadaic acid (OA, 1 microM) and PKC activator phorbol 12-myristate-13-acetate (PMA, 3 microM) significantly enhanced annexin binding and decreased forward scatter. Adenosine significantly blunted the effects of OA and PMA on annexin V binding (s.d. at > or =30 and 10 microM, respectively) and the effect of OA on forward scatter (s.d. at > or =10 microM). In conclusion, adenosine inhibits eryptosis by a mechanism presumably effective downstream of PKC. The effect may participate in the maintenance of microcirculation in ischemic tissue.

Growth inhibitory effect and apoptosis induced by extracellular ATP and adenosine on human gastric carcinoma cells: involvement of intracellular uptake of adenosine

AIM

To study the growth inhibitory and apoptotic effects of adenosine triphosphate (ATP) and adenosine (ADO) on human gastric carcinoma (HGC)-27 cells in vitro and the mechanisms related to the actions of ATP and ADO.

METHODS

MTT assay was used to determine the reduction of cell viability. The morphological changes of HGC-27 cells induced by ATP or ADO were observed under fluorescence light microscope by acridine orange/ethidium bromide double-stained cells. The internucleosomal fragmentation of genomic DNA was detected by agarose gel electrophoresis. The apoptotic rate and cell-cycle analysis after treatment with ATP or ADO was determined by flow cytometry.

RESULTS

ATP, ADO and the intermediate metabolites, ADP and AMP, and the agonist of purinergic receptors, reduced cell viability of HGC-27 cells at doses of 0.3 and 1.0 mmol/L. The distribution of cell cycle phase and proliferation index (PI) value of HGC-27 cells changed when exposed to ATP or ADO at the concentrations of 0.1, 0.3 and 1 mmol/L for 48 h. ATP and ADO both altered the distribution of cell cycle phase via G0/G1- phase arrest and significantly decreased PI value. Under light microscope, the tumor cells exposed to 0.3 mmol/L ATP or ADO displayed morphological changes of apoptosis; a ladder-like pattern of DNA fragmentation obtained from HGC-27 cells treated with 0.1-1 mmol/L ATP or ADO appeared in agarose gel electrophoresis; ATP and ADO induced the apoptosis of HGC-27 cells in a dose-dependent manner at concentrations between 0.03-1 mmol/L. The maximum apoptotic rate of HGC-27 cells exposed to ATP or ADO for 48 h was 13.53% or 15.9%, respectively. HGC-27 cell death induced by ATP or ADO was significantly inhibited by dipyridamole (10 mmol/L), an inhibitor of adenosine transporter, but was not affected by aminophylline, a broad inhibitor of P1 receptors and pyridoxal-phosphate-6-azophenyl-2, 4-disulphonic acid tetrasodium salt (30 micromol/L), a non-selective antagonist of P2 receptors.

CONCLUSION

Extracellular ATP and ADO reduced the cell viability, arrested cell cycle and induced apoptosis in HGC-27 cell line by intracellular uptake of ADO. One of the main routes of ATP-induced apoptosis in HGC-27 cells is through the breakdown to adenosine.