RESEARCH ARTICLE


Involvement of Signaling Molecules on Na+/H+ Exchanger-1 Activity in Human Monocytes



Maria Sarigianni 1, 2, Apostolos Tsapas 1, 3, Dimitri P Mikhailidis 2, Martha Kaloyianni 4, George Koliakos 5, Konstantinos Paletas *, 1
1 Metabolic Diseases Unit, Second Department of Internal Medicine, Medical School, Aristotle University of Thessaloniki, Greece
2 Department of Clinical Biochemistry (Vascular Disease Prevention Clinics), Royal Free Hospital campus, University College London Medical School, University College London (UCL), London NW3 2QG, UK
3 University of Oxford, The Tseu Medical Institute, Harris Manchester College, Oxford, United Kingdom
4 Laboratory of Animal Physiology, Department of Zoology, School of Biology, Aristotle University of Thessaloniki, Greece
5 Department of Biological Chemistry, Medical School, Aristotle University of Thessaloniki, Greece


© Sarigianni et al.; Licensee Bentham Open.

open-access license: This is an open access article licensed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted, non-commercial use, distribution and reproduction in any medium, provided the work is properly cited.

* Address correspondence to this author at the 15 Ag. Sofias str, 54623, Thessaloniki, Greece; Tel: 00302310892751 Fax: 00302310992937 E-mail: paletas@med.auth.gr
# The paper has not been presented orally in any professional meeting.This paper is part of the 03ED29 research project, implemented within the framework of the “Reinforcement Programme of Human Research Manpower” (PENED) and cofinanced by National and European Community Funds (25% from the Greek Ministry of Development - General Secretariat of Research and Technology and 75% from the EU - European Social Fund).


Abstract

Background:

Sodium/hydrogen exchanger-1 (NHE-1) contributes to maintaining intracellular pH (pHi). We assessed the effect of glucose, insulin, leptin and adrenaline on NHE-1 activity in human monocytes in vitro. These cells play a role in atherogenesis and disturbances in the hormones evaluated are associated with obesity and diabetes.

Methods and Results:

Monocytes were isolated from 16 healthy obese and 10 lean healthy subjects. NHE-1 activity was estimated by measuring pHi with a fluorescent dye. pHi was assessed pre- and post-incubation with glucose, insulin, leptin and adrenaline. Experiments were repeated after adding a NHE-1 inhibitor (cariporide) or an inhibitor of protein kinase C (PKC), nitric oxide synthase (NOS), nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, phosphoinositide 3-kinases (PI3K) or actin polymerization. Within the whole study population, glucose enhanced NHE-1 activity by a processes involving PKC, NOS, PI3K and actin polymerization (p = 0.0006 to 0.01). Insulin-mediated activation of NHE-1 (p = <0.0001 to 0.02) required the classical isoforms of PKC, NOS, NADPH oxidase and PI3K. Leptin increased NHE-1 activity (p = 0.0004 to 0.04) through the involvement of PKC and actin polymerization. Adrenaline activated NHE-1 (p = <0.0001 to 0.01) by a process involving the classical isoforms of PKC, NOS and actin polymerization. There were also some differences in responses when lean and obese subjects were compared. Incubation with cariporide attenuated the observed increase in NHE-1 activity.

Conclusions:

Selective inhibition of NHE-1 in monocytes could become a target for drug action in atherosclerotic vascular disease.

Keywords: Na+/H+ exchanger-1, obesity, monocytes, intracellular pH..