[60]Fullerene derivative modulates adenosine and metabotropic glutamate receptors gene expression: a possible protective effect against hypoxia

Resveratrol enhances A1 and hinders A2A adenosine receptors signaling in both HeLa and SH-SY5Y cells: Potential mechanism of its antitumoral action

Despite great efforts, effective treatment against cancer has not yet been found. However, natural compounds such as the polyphenol resveratrol have emerged as promising preventive agent in cancer therapy. The mode of action of resveratrol is still poorly understood, but it can modulate many signaling pathways related to the initiation and progression of cancer. Adenosinergic signaling may be involved in the antitumoral action of resveratrol since resveratrol binds to the orthosteric binding site of adenosine A_2A receptors and acts as a non-selective agonist for adenosine receptors. In the present study, we measured the impact of resveratrol treatment on different adenosinergic pathway components (i.e. adenosine receptors levels, 5'-nucleotidase, adenosine deaminase, and adenylyl cyclase activities, protein kinase A levels, intracellular adenosine and other related metabolites levels) and cell viability and proliferation in HeLa and SH-SY5Y cell lines. Results revealed changes leading to turning off cAMP signaling such as decreased levels of A_2A receptors and reduced adenylyl cyclase activation, increased levels of A₁ receptors and increased adenylyl cyclase inhibition, and lower levels of PKA. All these changes could contribute to the antitumoral action of resveratrol. Interestingly, these effects were almost identical in HeLa and SH-SY5Y cells suggesting that resveratrol enhances A₁ and hinders A_2A adenosine receptors signaling as part of a potential mechanism of antitumoral action.

Modulation of Adenosine Receptors by Hops and Xanthohumol in Cell Cultures

Adenosine receptors (ARs) have been involved in neurodegenerative diseases such as Alzheimer disease, where oxidative stress contributes to neurodegeneration and cell death. Therefore, there is increasing interest in developing antioxidative strategies to avoid or reduce neurodegeneration. We have previously described that different beer extracts modulate ARs and protect glioma and neuroblastoma cells from oxidative stress. The present work aimed to analyze the possible protective effect of hops (Humulus lupulus L.), a major component of beer, and xanthohumol on cell death elicited by oxidative stress and their modulation of ARs in rat C6 glioma and human SH-SY5Y neuroblastoma cells. Different extraction methods were employed in two hops varieties (Nugget and Columbus). Cell viability was determined by the XTT method in cells exposed to these hops extracts and xanthohumol. ARs were analyzed by radioligand binding and real-time PCR assays. Hops extract reverted the cell death observed under oxidative stress and modulated adenosine A₁ and A₂ receptors in both cell types. Xanthohumol was unable to revert the effect of oxidative stress in cell viability but it also modulated ARs similarly to hops. Therefore, healthy effects of beer described previously could be due, at least in part, to their content of hops and the modulation of ARs.

Neuroprotective Effects of Adenosine A1 Receptor Signaling on Cognitive Impairment Induced by Chronic Intermittent Hypoxia in Mice

Obstructive sleep apnea-hypopnea syndrome (OSAHS) is a breathing disorder associated with cognitive impairment. However, the mechanisms leading to cognitive deficits in OSAHS remain uncertain. In this study, a mouse model of chronic intermittent hypoxia (CIH) exposures were applied for simulating the deoxygenation-reoxygenation events occurring in OSAHS. The conventional adenosine A1 receptor gene (A1R) knockout mice and the A1R agonist CCPA- or antagonist DPCPX-administrated mice were utilized to determine the precise function of A1R signaling in the process of OSAHS-relevant cognitive impairment. We demonstrated that CIH induced morphological changes and apoptosis in hippocampal neurons. Further, CIH blunted hippocampal long-term potentiation (LTP) and resulted in learning/memory impairment. Disruption of adenosine A1R exacerbated morphological, cellular, and functional damage induced by CIH. In contrast, activation of adenosine A1R signaling reduced morphological changes and apoptosis of hippocampal neurons, promoted LTP, and enhanced learning and memory. A1Rs may up-regulate protein kinase C (PKC) and its subtype PKC-ζ through the activation of Gα(i) improve spatial learning and memory disorder induced by CIH in mice. Taken together, A1R signaling plays a neuroprotective role in CIH-induced cognitive dysfunction and pathological changes in the hippocampus.

Modulation of Adenosine Receptors and Antioxidative Effect of Beer Extracts in in Vitro Models

The fight against neurodegenerative diseases is promoting the searching of nutrients, preferably of wide consumption, with proven effects on health. Beer is widely consumed and has potential benefits on health. In this work, three different extracts from dark beer (DB), non-alcoholic beer (NAB), and lager beer (LB) were assayed at 30 min and 24 h in rat C6 glioma and human SH-SY5Y neuroblastoma cells in order to study their possible protective effects. Cell viability and adenosine A₁, A_2A, A_2B, and A₃ receptor gene expression and protein levels were measured in control cells and in cells challenged with hydrogen peroxide as an oxidant stressor. Among the three extracts analyzed, DB showed a greater protective effect against H₂O₂-induced oxidative stress and cell death. Moreover, a higher A₁ receptor level was also induced by this extract. Interestingly, A₁ receptor level was also increased by NAB and LB extracts, but to a lower extent, and the protective effect of these extracts against H₂O₂ was lower. This possible correlation between protection and A₁ receptor level was observed at 24 h in both C6 and SH-SY5Y cells. In summary, different beer extracts modulate, to a different degree, adenosine receptors expression and protect both glioma and neuroblastoma cells from oxidative stress.