Dual Mechanisms for Ethanol-Induced Inhibition of Monocyte Chemotactic Protein-3 mRNA Expression in Activated Glial Cells

Abstract

The differential display of mRNA technique was used to screen the expressed genes in control and 50 mM chronic ethanoltreated rat C6 glial cells, with and without activation by lipopolysaccharide (LPS) combined with phorbol 12-myristate 13-acetate (PMA). One differentially expressed transcript was identified as that corresponding to the chemokine monocyte chemotactic protein (MCP)-3. MCP-3 is a broadly active chemokine that functions in chemoattraction and activation of monocytes, T lymphocytes, eosinophils, basophils, natural killer cells, and dendritic cells. Steady-state MCP-3 mRNA levels were elevated 6-fold after 24-h stimulation of control cells but less than 3-fold after stimulation of 9-day chronic ethanol-exposed cells. One-and 5-day exposures to 50 mM ethanol were not effective at reducing steady-state MCP-3 mRNA levels in stimulated cells, whereas 1-day exposure to Ͼ150 mM ethanol was effective. Stimulation with tumor necrosis factor-␣ elevated MCP-3 mRNA in C6 glial cells to a lesser extent than with LPS plus PMA, but the effects of ethanol were consistent. To gain insight into possible mechanisms for ethanol-induced reductions in steady-state MCP-3 mRNA, additional studies examined nuclear MCP-3 RNA levels and MCP-3 mRNA degradation. MCP-3 RNA content was greatly reduced in isolated nuclei from acute and chronic ethanol-exposed cells, suggesting transcriptional inhibition. On the other hand, acute ethanol exposure enhanced degradation of preexisting MCP-3 mRNA, indicating message destabilization. Thus, the results are consistent with a dual mechanism for ethanol-induced reductions in steady-state MCP-3 mRNA levels.

Suppression of Innate Immunity by Acute Ethanol Administration: A Global Perspective and a New Mechanism Beginning with Inhibition of Signaling through TLR3

“…The generalized decrease in chemokines noted in the present study is consistent with a previous report of suppression of MIP-2 and cytokine-induced neutrophil chemoattractant in vivo by EtOH and consequent decreases in host resistance and inflammation in rats (3). EtOH-induced suppression of MCP-3 (CCL7) production by glial cells has also been reported (51). The present study is the first indication of suppression of CCL12 or CXCL9 expression by EtOH.…”

Brain Damage and Alcohol Dependence: How One May Influence the Other

“…In vitro studies found numerous interactions between alcohol and neuroinflammatory responses, including changes in production of different inflammatory proteins and enzymes. (Davis & Syapin, 2004a, 2004bRen & Syapin, 2002;Ren, Garrett, Syapin, & Syapin, 2000;Sanchez, Davis, & Syapin, 2007;Syapin, Militante, Garrett, & Ren, 2001). Alcohol exposure also has been reported to cause oxidative stress in cells that form the blood-brain-barrier (Haorah, Knipe, Leibhart, Ghorpade, & Persidsky, 2005), which could mean drinking alcohol also allows unwanted molecules that promote inflammation, known as proinflammatory cytokines, to enter the brain from the blood.…”

Alcohol Brain Damage and Neuroinflammation: Is There a Connection?

“…Not only does the fibronectin gene respond to inflammatory stimulation, it appears to play a role in the process of phagocytosis (Saba, 1989;Jun et al, 1995) but astrocytic fibronectin influences axonal regeneration and A␤-peptide expression (Moreno-Flores et al, 2001;Tom et al, 2004). The effect of ethanol on the MCP-3 was studied in greater detail and was found to reveal a dual mechanism for ethanol inhibition of inducible gene expression (Ren and Syapin, 2002). The inhibition by ethanol was not dependent on the immunologic stimuli used to enhance MCP-3 gene expression, and similar to the iNOS response, the cells became sensitized to the inhibitory effect of ethanol on MCP-3 mRNA levels with longer exposure times.…”