Alcohol and inflammation : a study of effects of ethanol on endothelial and epithelial cell functions

Abstract

Although short–term alcohol drinking causes euphoric and stress relieving effects, alcohol abuse is a major risk factor for neurobehavioural, liver and muscle injury as well as reduced host defence with enhanced susceptibility to bacterial infections. Although such reductions also suggest potential use as an anti-inflammatory drug, well known side effects of ethanol limits its clinical use. Instead, an ethanol derivate, ethyl pyruvate (EtP), might serve as an alternative; it is not associated with cerebral intoxica-tion, prolongs survival in a septic shock model and acts rapidly.

Endothelial and epithelial cells, the former at the interface between blood and tissues and the latter facing various bodily surfaces, are among the first cells to become ex-posed to ethanol following ingestion. In this thesis I explored their reactions to ethanol and EtP in the setting of an acute inflammatory reaction, e.g. after challenge with LPS, IL-1, TNFalpha or LTB4 mimicking, for instance, sepsis.

In paper I, we observed that ethanol attenuated LPS triggered human umbilical vein endothelial cells (HUVEC) to release chemokines and myeloid growth factors such as IL-8, G-CSF, GM-CSF and SCF. Furthermore, exposure to ethanol reduced the adhe-siveness of HUVEC for neutrophils, effects that were possibly linked to the reduced activation of the transcription factor NF-kappaB.

In paper II, we report that ethanol impaired G-CSF and IL-8 release from lung epithelial cells (EpC, A549) elicited by IL-1beta or TNFalpha. Moreover, we found that ethanol interfered with translocation from cytosol to nucleus as well as gene activation of the p65 components of NF-kappaB, important for activation of many genes controlling pro-inflammatory systems.

In paper III, we compared effects of ethanol and EtP on LPS, IL-1beta or TNFalpha stimu-lated reactions in and between neutrophils, HUVEC and EpC. EtP was several folds more potent than ethanol in decreasing cytokine release, surface expression of adhesion molecules and adhesion of neutrophils. Ethanol and EtP hampered IRAK-1, IkappaBalpha and p65 equally, whereas impaired translocation of p50 was dependant on stimulus use.

In paper IV, we report that LPS, IL-1beta and TNFalpha, as well as LTB4 itself induced the upregulation of expression of surface receptors for LTB4, BLT, on HUVEC. In addi-tion, treatment of HUVEC with LTB4 caused increased release of both nitric oxide and MCP-1. Our data indicate that BLT receptors might have functional consequences during the early vascular responses to inflammation.

In paper V, we noted that ethanol and EtP abrogated stimulatory effects on HUVEC for neutrophil adhesion, calcium transients and nitric oxide generation when elicited by LTB4. We also found that ethanol and EtP reduced BLT mRNA and protein expression.

Our results provide clues to understanding how ethanol and EtP affects pro-inflam-matory responses of EC and EpC. Inhibition of chemokines and growth factors that promote myeloid cell development and maturation, may likewise contribute to the in-creased susceptibility to bacterial infections that is associated with alcohol abuse. Thus, these dual roles of ethanol and EtP might be used to modulate vascular responses to inflammation.