Ethanol exposure impairs LPS-induced pulmonary LIX expression: alveolar epithelial cell dysfunction as a consequence of acute intoxication.
BACKGROUND
Alcohol intoxication impairs innate immune responses to bacterial pneumonia, including neutrophil influx. Lipopolysaccharide (LPS)-induced chemokine (LIX or CXCL5) is a recently described chemokine produced by type-II alveolar epithelial (AE2) cells which facilitates neutrophil recruitment. The effect of acute alcohol intoxication on AE2 cell expression of LIX is unknown.


METHODS
C57BL/6 mice were given an intraperitoneal (i.p.) injection of ethanol (4 g/kg) or saline 30 minutes prior to intratracheal (i.t.) injection with 10 mug Escherichia coli LPS. In vitro stimulation of primary AE2 cells or murine AE2 cell line MLE-12 was performed with LPS and tumor necrosis factor-alpha (TNF-alpha).


RESULTS
LIX protein is readily detectable in the lung but not in plasma following LPS administration, demonstrating "compartmentalization" of this chemokine during pulmonary challenge. In contrast to the CXC chemokines keratinocyte-derived chemokine and macrophage inflammatory protein-2, which are abundantly expressed in both lung tissue and alveolar macrophages, LIX expression is largely confined to the lung parenchyma. Compared to controls, intoxicated animals show a decrease in LIX and neutrophil number in bronchoalveolar lavage fluid following LPS challenge. Ethanol inhibits LIX at the transcriptional level. In vitro studies show that LPS and TNF-alpha are synergistic in inducing LIX by either primary AE2 or MLE-12 cells. Acute ethanol exposure potently and dose-dependently inhibits LIX expression by AE2 cells. Activation of nuclear factor-kappaB is critical to LIX expression in MLE-12 cells, and acute ethanol treatment interferes with early activation of this pathway as evidenced by impairing phosphorylation of p65 (RelA). Inhibition of p38 mitogen-activated protein kinase signaling, but not ERK1/2 activity, in MLE-12 cells by acute alcohol is likely an important cause of decreased LIX expression during challenge.


CONCLUSIONS
These data demonstrate direct suppression of AE2 cell innate immune function by ethanol and add to our understanding of the mechanisms by which acute intoxication impairs the lung's response to microbial challenge.
Walker
James E
JE
Section of Pulmonary and Critical Care Medicine, Department of Medicine, Louisiana State University Health Sciences Center, 1901 Perdido Street, New Orleans, LA 70112, USA.
Odden
Anthony R
AR
Jeyaseelan
Samithamby
S
Zhang
Ping
P
Bagby
Gregory J
GJ
Nelson
Steve
S
Happel
Kyle I
KI
D000435:Alcoholic Intoxication / Q000378:metabolism* / Q000473:pathology; D000818:Animals; D001992:Bronchoalveolar Lavage Fluid / Q000166:cytology; D002469:Cell Separation; D002478:Cells, Cultured; D002492:Central Nervous System Depressants / Q000008:administration & dosage / Q000097:blood / Q000633:toxicity*; D054365:Chemokine CXCL5 / Q000096:biosynthesis* / Q000235:genetics; D000431:Ethanol / Q000008:administration & dosage / Q000097:blood / Q000633:toxicity*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D007278:Injections, Spinal; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008168:Lung / Q000187:drug effects* / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009504:Neutrophils / Q000187:drug effects / Q000378:metabolism; D011650:Pulmonary Alveoli / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D051996:Transcription Factor RelA / Q000378:metabolism
D002492:Central Nervous System Depressants; D054365:Chemokine CXCL5; C094739:Cxcl5 protein, mouse; D008070:Lipopolysaccharides; D051996:Transcription Factor RelA; D000431:Ethanol; D048049:Extracellular Signal-Regulated MAP Kinases