Increased systemic and brain cytokine production and neuroinflammation by endotoxin following ethanol treatment.
BACKGROUND
Cytokines and alcohol share a common modulation of inflammation and hormones as well as being implicated in multiple diseases, but the mechanisms are poorly understood. The purpose of this study was to investigate the interaction of liver, serum and brain cytokines as well as whether ethanol would potentiate endotoxin (Lipopolysaccharide, LPS) responses once ethanol had cleared.


METHODS
Male C57BL/6J mice were treated intragastrically with water (control) or ethanol (5 g/kg, i.g., 25% ethanol, w/v), with volumes matched, for 1 day or daily for 10 days. Mice were then injected intraperitoneally with saline (control) or LPS (3 mg/kg, i.p.) in saline 24 hrs after the last dose of ethanol. Gene expression and protein synthesis of proinflammatory cytokines and anti-inflammatory cytokine, oxidative enzymes, microglial activation and inhibition of neurogenesis were examined using real-time PCR, ELISA, and immunohistochemistry.


RESULTS
LPS increased proinflammatory cytokines (TNFalpha, MCP-1, IL-1beta) several fold in liver, brain and serum at 1 hr. Ethanol is known to increase liver cytokines and alter the risk of multiple chronic diseases. Ten daily doses of ethanol increased brain and liver TNFalpha, and pretreatment with ethanol potentiated LPS-induced increases in TNFalpha, MCP-1, IL-1beta in liver, serum and brain. Proinflammatory cytokine levels in liver and serum returned to basal levels within a day, whereas brain proinflammatory cytokines remained elevated for long periods. IL-10, an anti-inflammatory cytokine, is reduced in brain by ethanol and LPS, while brain proinflammatory cytokines remain increased, whereas liver IL-10 is increased when proinflammatory cytokines have returned to control levels. Activation of brain microglia indicated by morphological changes, reduced neurogenesis and increased brain expression of COX-2 and gp91phox NADPH oxidase subunit mRNA were found in the 10 daily doses of ethanol-pretreated LPS group.


CONCLUSIONS
Acute increases in serum cytokines induce long lasting increases in brain proinflammatory cytokines. Ten daily doses of ethanol exposure results in persistent alterations of cytokines and significantly increases the magnitude and duration of central and peripheral proinflammatory cytokines and microglial activation. Ethanol induced differential anti-inflammatory cytokine IL-10 responses in liver and brain could cause long lasting disruption of cytokine cascades that could contribute to protection or increased risk of multiple chronic diseases.
Qin
Liya
L
Bowles Center for Alcohol Studies, School of Medicine, CB#7178 UNC-CH, Chapel Hill, NC 27599, USA. liya_qin@med.unc.edu
He
Jun
J
Hanes
Richard N
RN
Pluzarev
Olivera
O
Hong
Jau-Shyong
JS
Crews
Fulton T
FT
D000818:Animals; D001921:Brain / Q000378:metabolism*; D002492:Central Nervous System Depressants / Q000633:toxicity*; D018932:Chemokine CCL2 / Q000097:blood / Q000378:metabolism; D051546:Cyclooxygenase 2 / Q000097:blood / Q000378:metabolism; D016207:Cytokines / Q000097:blood / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004660:Encephalitis / Q000097:blood / Q000139:chemically induced* / Q000378:metabolism*; D004731:Endotoxins / Q000009:adverse effects*; D000431:Ethanol / Q000633:toxicity*; D016753:Interleukin-10 / Q000097:blood / Q000378:metabolism; D053583:Interleukin-1beta / Q000097:blood / Q000378:metabolism; D008070:Lipopolysaccharides / Q000009:adverse effects; D008099:Liver / Q000378:metabolism*; D008297:Male; D008562:Membrane Glycoproteins / Q000097:blood / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases / Q000097:blood / Q000378:metabolism; D011897:Random Allocation; D014409:Tumor Necrosis Factor-alpha / Q000097:blood / Q000378:metabolism
C491768:Ccl2 protein, mouse; D002492:Central Nervous System Depressants; D018932:Chemokine CCL2; D016207:Cytokines; D004731:Endotoxins; D053583:Interleukin-1beta; D008070:Lipopolysaccharides; D008562:Membrane Glycoproteins; D014409:Tumor Necrosis Factor-alpha; D016753:Interleukin-10; D000431:Ethanol; D051546:Cyclooxygenase 2; C488842:Cybb protein, mouse; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases