A low concentration of ethanol reduces the chemiluminescence of human granulocytes and monocytes but not the tumor necrosis factor alpha production by monocytes after endotoxin stimulation

Abstract

The ability of polymorphonuclear neutrophils (PMNs) and monocytes (Mphi) to produce reactive oxygen species (ROS) has been related closely to their potential in the killing of microorganisms. Ethanol has been shown to impair the generation of ROS in these phagocytes after stimulation with some immunogens and to increase the susceptibility of alcohol abusers to infectious diseases. As endotoxemia is common in alcohol abusers, we investigated the effect of ethanol (21.7 mmol/liter) on the luminol-amplified chemiluminescence of PMNs and Mphi after endotoxin stimulation and the release of tumor necrosis factor alpha (TNF-alpha) from Mphi. Further, the efficiency of ethanol to inactivate chemically generated ROS was tested. Significant stimulation of ROS release occurred at endotoxin concentrations of 1 ng/ml or higher in both PMNs and Mphi. Ethanol significantly suppressed the formation of ROS in both cell types, the decrease being more pronounced in Mphi (-73. 8%) than in PMNs (-45.7%). The correlations between endotoxin concentration and the amount of released ROS showed a dose-dependent, sigmoidal course. Concentrations of endotoxin necessary for half-maximum stimulation were nearly identical (6 to 8 ng/ml) in both PMNs and Mphi, independent of the presence of ethanol. In contrast to ROS formation, ethanol had no effect on the amount of TNF-alpha produced by endotoxin-stimulated Mphi. Ethanol was shown to be unable to decrease the levels of chemically generated ROS under physiological conditions. Therefore, ethanol cannot be assumed to be an "antioxidative" compound but rather seems to modify processes of endotoxin recognition, intracellular signal transduction, or metabolism.

FIG. 1

Time course of chemiluminescence (expressed as mean RLU ± standard error of the mean) of granulocytes with (solid lines) or without (dashed lines) 10 ng of endotoxin (E. coli O111:B4) per ml in the presence (▪, □) or absence (•, ○) of ethanol (21.7 mmol/liter). The AUC for comparative statistics was calculated from the function given in equation 1.

FIG. 2

Correlation between endotoxin concentration and release of ROS from PMNs in the presence (solid line) or absence (dashed line) of 21.7 mmol of ethanol per liter. ROS release was calculated as the AUC (mean ± SD) from the function given in equation 1. The course of AUC dependence on endotoxin concentration was approximated by equation 2 for calculation of the LPS concentration necessary for half-maximum stimulation (point of inflection, as given in the text). ∗, P < 0.05.

FIG. 3

Correlation between endotoxin concentration and release of ROS from PBMCs in the presence (solid line) or absence (dashed line) of 21.7 mmol of ethanol per liter. ROS release (AUC [mean ± SD]) and the point of inflection were calculated as described for PMNs. ∗, P < 0.05; ∗∗, P < 0.01.