Chaperoning of the A1-adenosine receptor by endogenous adenosine - an extension of the retaliatory metabolite concept.

Cell-permeable orthosteric ligands can assist folding of G protein-coupled receptors in the endoplasmic reticulum (ER); this pharmacochaperoning translates into increased cell surface levels of receptors. Here we used a folding-defective mutant of human A1-adenosine receptor as a sensor to explore whether endogenously produced adenosine can exert a chaperoning effect. This A1-receptor-Y(288)A was retained in the ER of stably transfected human embryonic kidney 293 cells but rapidly reached the plasma membrane in cells incubated with an A1 antagonist. This was phenocopied by raising intracellular adenosine levels with a combination of inhibitors of adenosine kinase, adenosine deaminase, and the equilibrative nucleoside transporter: mature receptors with complex glycosylation accumulated at the cell surface and bound to an A1-selective antagonist with an affinity indistinguishable from the wild-type A1 receptor. The effect of the inhibitor combination was specific, because it did not result in enhanced surface levels of two folding-defective human V2-vasopressin receptor mutants, which were susceptible to pharmacochaperoning by their cognate antagonist. Raising cellular adenosine levels by subjecting cells to hypoxia (5% O2) reproduced chaperoning by the inhibitor combination and enhanced surface expression of A1-receptor-Y(288)A within 1 hour. These findings were recapitulated for the wild-type A1 receptor. Taken together, our observations document that endogenously formed adenosine can chaperone its cognate A1 receptor. This results in a positive feedback loop that has implications for the retaliatory metabolite concept of adenosine action: if chaperoning by intracellular adenosine results in elevated cell surface levels of A1 receptors, these cells will be more susceptible to extracellular adenosine and thus more likely to cope with metabolic distress.

Polyphenol metabolism provides a screening tool for beneficial effects of Onobrychis viciifolia (sainfoin).

Onobrychis viciifolia (sainfoin) is a traditional fodder legume showing multiple benefits for the environment, animal health and productivity but weaker agronomic performance in comparison to other legumes. Benefits can be mainly ascribed to the presence of polyphenols. The polyphenol metabolism in O. viciifolia was studied at the level of gene expression, enzyme activity, polyphenol accumulation and antioxidant activity. A screening of 37 accessions regarding each of these characters showed a huge variability between individual samples. Principal component analysis revealed that flavonols and flavan 3-ols are the most relevant variables for discrimination of the accessions. The determination of the activities of dihydroflavonol 4-reductase and flavonol synthase provides a suitable screening tool for the estimation of the ratio of flavonols to flavan 3-ols and can be used for the selection of samples from those varieties that have a specific optimal ratio of these compounds for further breeding.

[The influence of interleukin-6 and tumor necrosis factor alpha gene polymorphisms on bone mineral density in postmenopausal women]. / Wplyw polimorfizmu genu interleukiny-6 i czynnika martwicy nowotworu alpha na gestosc mineralna kosci kobiet po menopauzie.

UNLABELLED: Proinflammatory cytokines, interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-alpha), involved into osteoclastogenesis and responsible for bone resorption process, participate in the pathogenesis of the osteoporosis. In vitro studies have shown that single nucleotide polymorphisms of IL-6 and TNF-alpha genes could influence the transcription process of the genes and the cytokines level. AIM: Assessment of the influence of IL-6 and TNF-alpha gene polymorphisms on bone mineral density (BMD) and evaluation of their connection with osteoporosis prevalence in women from Wielkopolska region. MATERIAL AND METHODS: In the group of 267 postmenopausal women (average age 58.5+/-5.9 years, average age of last period 49.8+/-3.9 years) bone mineral density in lumbar spine (L2-L4) was performed using dual energy X-ray absorptiometry (DXA). Genotypes frequencies were determined by polymerase chain reaction with restriction fragment length polymorphism (PCR/RFLP) using restriction enzymes Lwe I and Faq I, respectively. The connection between the polymorphisms of investigated genes and body mass index, age of menarche and menopause and length of reproductive age had been analyzed as well. RESULTS: No statistically significant association was found between examined genetic factors and the value of bone mineral density in the investigated group of postmenopausal women. The frequencies of investigated genotypes were in compliance with Hardy-Weinberg equilibrium. The correspondence between evaluated clinical parameters and IL-6 i TNF-alpha genotypes frequencies has not been proven. CONCLUSIONS: The -174G/C polymorphism in the IL-6 and -308G/A polymorphism in TNF-alpha genes have no influence on bone mineral density value (BMD) in the investigated population of women from Wielkopolska region.