Effects of L-amino Acids on Human Peripheral Neutrophil Granulocyte Activation

Sándor Sipka,Tamás Keresztes,Ildikó Kovács,Margit Zeher,Geza Bruckner,Gyula Szegedi,Sándor Baráth

doi:10.2174/1874288201408010001

Abstract

Objective: The objective was to investigate the early (20 minutes) effects of 21 L-amino acids on the activation of human neutrophils and to determine in healthy individuals the effects of a meal on the 1) number and relative luminescence unit (RLU) of peripheral neutrophils, 2) serum glutamate and glucose levels and 3) mTOR signaling network. Methods: The RLU of neutrophils stimulated by Ca2+ ionophor (CaI) and phorbol myristate acetate (PMA) following amino acid supplementation (3 x 10-4 M) or after consuming a meal was determined. L-glutamate was measured by HPLC. Results: All amino acids resulted in significant inhibitions of neutrophil RLU, except for arginine, which stimulated neutrophils. The ratios of amino acid induced inhibition were significantly higher in the cells stimulated by PMA than by CaI. The consumption of a meal resulted in a significant serum glutamate elevation compared to baseline (2.3 versus 0.9 x10-4 M) 90 minutes after ingestion of the meal. It was independent of the body mass index and returned near fasting levels after 150 minutes. The number of neutrophils was significantly elevated 90 minutes after the meal but the PMA induced RLU was significantly decreased. Conclusion: Our ex vivoand in vivoresults suggest that the L-amino acids, independent of their metabolic significance, may continuosly and quickly modify the activity of human peripheral neutrophils, and also the outcome of various immunologic reactions. The activation of the mTORC1 complex likely involves a transient impairment in the function of mTORC2 complex in these processes.

Highlights

Plasma free amino acid concentrations have been measured for various purposes, such as to evaluate the individual’s protein nutritional status, to determine amino acid requirements and circadian variations and to gain an understaning of the various metabolic aspects of amino acids [1]
Thirty one healthy subjects were tested in vivo after a 12 hours fast and 90 minutes after eating breakfast for changes in serum glutamate and glucose concentrations
The increase in the serum glutamate levels was independent of the body mass indexes (BMI); whereas the glucose elevation was dependent on BMI

Summary

Introduction

Plasma free amino acid concentrations have been measured for various purposes, such as to evaluate the individual’s protein nutritional status, to determine amino acid requirements and circadian variations and to gain an understaning of the various metabolic aspects of amino acids [1]. Other than being components of proteins, some amino acids have individual biological or biochemical effects. The current study investigated the effects of 21 individual amino acids on neutrophil activation. The effects of eating a simple meal on serum glutamate and glucose concentrations in healthy subjects, along with parallel measurements of the number and RLU, namely, chemiluminescence (CL) of peripheral neutrophil granulocytes, were determined. We measured and compared the effects of 3x10-4 M of 21 amino acids, 20 minutes into the reaction, on the RLU of peripheral neutrophil granulocytes, stimulated and not stimulated by CaI and PMA ex vivo, in relation to the mTOR (mechanistic target of rapamycin) signaling network; thereby testing the dose dependent effect of rapamycin (R). Aminoacids have been shown to activate the mTOR1 complex but are required for activation by other stimuli [8]

Results

Discussion

Conclusion