Lymphocyte 5'-ectonucleotidase: an indicator of oxidative stress in humans?

Purinergic signaling in the modulation of redox biology

Purinergic signaling is a cell communication pathway mediated by extracellular nucleotides and nucleosides. Tri- and diphosphonucleotides are released in physiological and pathological circumstances activating purinergic type 2 receptors (P2 receptors): P2X ion channels and P2Y G protein-coupled receptors. The activation of these receptors triggers the production of reactive oxygen and nitrogen species and alters antioxidant defenses, modulating the redox biology of cells. The activation of P2 receptors is controlled by ecto-enzymes named ectonucleotidases, E-NTPDase1/CD39 and ecto-5'-nucleotidase/CD73) being the most relevant. The first enzyme hydrolyzes adenosine triphosphate (ATP) and adenosine diphosphate (ADP) into adenosine monophosphate (AMP), and the second catalyzes the hydrolysis of AMP to adenosine. The activity of these enzymes is diminished by oxidative stress. Adenosine actives P1 G-coupled receptors that, in general, promote the maintenance of redox hemostasis by decreasing reactive oxygen species (ROS) production and increase antioxidant enzymes. Intracellular purine metabolism can also contribute to ROS generation via xanthine oxidase activity, which converts hypoxanthine into xanthine, and finally, uric acid. In this review, we describe the mechanisms of redox biology modulated by purinergic signaling and how this signaling may be affected by disturbances in the redox homeostasis of cells.

Effects of vitamin supplementation on inflammatory markers and psychological wellbeing among distressed women: a randomized controlled trial

BACKGROUND

Multivitamins are a popular supplement taken to promote physical and mental health. During periods of stress, they may have a protective role for health and wellbeing, although the current evidence of their efficacy is mixed.

OBJECTIVE

To determine whether multivitamin supplementation impacts psychological and inflammatory markers of women who are experiencing psychological distress.

DESIGN, SETTING, PARTICIPANTS AND INTERVENTIONS

An 8-week randomized controlled trial was conducted to assess changes in both psychological state and pro-inflammatory markers of patients receiving multivitamins or placebo. The sample comprised women who reported elevated psychological distress in the previous 4 weeks.

MAIN OUTCOME MEASURES

Psychological state was assessed using Spielberger's State-Trait Personality Inventory to assess anxiety, curiosity, depression and anger. Pro-inflammatory markers comprised interleukin (IL)-1β, IL-5, IL-6, tumour necrosis factor (TNF)-α and TNF-β.

RESULTS

Improvements across time were observed for all psychological measures and cytokines, except IL-5, but were independent of the active intervention. Only TNF-β demonstrated a significant differential change between groups over the course of the intervention, in favour of multivitamin supplementation (active group mean rank decreased from 11.1 to 7.1; placebo group mean rank decreased from 8.9 to 7.8).

CONCLUSION

The results suggest that administration of multivitamins was not effective in improving psychological state. However, some evidence supported the positive impact of multivitamin supplementation on pro-inflammatory cytokine profiles of women currently experiencing stress.

Lymphocyte ecto-5'-nucleotidase in obese type 2 diabetic patients treated with gliclazide

OBJECTIVE

Lymphocyte 5'-nucleotidase is sensitive to superoxide anion, and is an indicator of oxidative stress in humans. The aim of this study was to assess the effect of the sulfonylurea drugs gliclazide and glibenclamide on lymphocyte ecto-5'-nucleotidase of type 2 diabetic patients.

METHODS

Thirty obese type 2 diabetic patients were treated for three months after randomisation either with gliclazide or glibenclamide. Basic laboratory parameters (glycaemia, fructosamine, C-peptide), plasma malondialdehyde levels (MDA) as well as lymphocyte 5'-nucleotidase activity were determined, for all patients and 16 healthy controls, before and after the treatment.

RESULTS

5'-nucleotidase activity in diabetic patients before treatment with gliclazide was 1.61 +/- 0.16 nmol/min/10(6) lymphocytes, and was significantly (P < 0.01) increased compared with the level in healthy controls. After three months of gliclazide treatment, ecto-5'-nucleotidase activity fell significantly by 47.39% and 36% in unstimulated Con A- and PMA-stimulated lymphocytes, respectively. Glibenclamide treatment had no effect on ecto-5'-nucleo-tidase of type 2 diabetic patients. Glycoregulation was improved, as plasma fructosamine decreased from 53.4 to 42.1 and from 50.5 to 43.4 U/g proteins after gliclazide and glibenclamide treatment, respectively. Plasma MDA levels markedly decreased after gliclazide but not glibenclamide treatment.

CONCLUSION

These results show that gliclazide treatment inhibits the activity of lymphocyte ecto-5'-nucleotidase and presumably de-creases the concentration of adenosine at the cell surface. A decrease in 5'-nucleotidase activity and attenuation of adenosine production may be a factor in the protection of tissue injury in type 2 diabetic patients.

Ecto-5'-nucleotidase in B-cell chronic lymphocytic leukemia

Literature on the behaviour of ecto-5'-nucleotidase in the course of B-cell chronic lymphocytic leukemia is briefly reviewed and aims for further researches are highlighted.