ABSTRACT
The developing central nervous system is a primary target of ethanol toxicity. The teratogenic effect of ethanol may result from its action on prostaglandins. Prostaglandins are generated through the release of arachidonic acid (AA) by the action of cytosolic phospholipase A(2) (cPLA(2)) on membrane-bound phospholipids and the catalytic conversion of AA to prostaglandin E(2) (PGE(2)) by cyclo-oxygenase (COX). COX is expressed in two isoforms, constitutive COX1 and inducible COX2. Cultured astrocytes and neurons from immature cerebral cortex were used as in vitro models to investigate the effect of ethanol on PGE(2) synthesis. In both cell types, neither the activity nor the expression of cPLA(2) was affected by ethanol. PGE(2) was synthesized by astrocytes and neurons. Ethanol (200-400 mg/dL for 24 h) significantly increased PGE(2) production in both cell types and the ethanol-induced increase in PGE(2) accumulation in astrocytes was significantly greater than in neurons. These increases resulted from the effects of ethanol on COX. Overall COX activity was up-regulated by ethanol in astrocytes and neurons, and indomethacin, a nonselective blocker for COX, eliminated the ethanol-induced increases of COX activity in both cell types. Increased COX activity in astrocytes resulted from an increase in COX2 expression. NS-398, a selective COX2 blocker, completely inhibited ethanol-induced alterations in COX activity. In neurons, however, ethanol had a direct effect on COX activity in the absence of a change in COX expression. NS-398 only partially blocked ethanol-induced increases in neuronal COX activity. Thus, astrocytes are a primary target of ethanol and ethanol-induced increases in glial PGE(2) synthesis are mediated by COX, principally COX2. Ethanol toxicity may be mediated through PGE(2) in immature cortical cells.
Subject(s)
Astrocytes/enzymology , Cerebral Cortex/enzymology , Ethanol/pharmacology , Isoenzymes/metabolism , Neurons/enzymology , Prostaglandin-Endoperoxide Synthases/metabolism , Animals , Animals, Newborn , Arachidonic Acid/metabolism , Astrocytes/cytology , Cells, Cultured , Cyclooxygenase 1 , Cyclooxygenase 2 , Cyclooxygenase 2 Inhibitors , Cyclooxygenase Inhibitors/pharmacology , Dinoprostone/metabolism , Indomethacin/pharmacology , Kinetics , Membrane Proteins , Neurons/cytology , Nitrobenzenes/pharmacology , Phospholipases A/metabolism , Rats , Sulfonamides/pharmacologyABSTRACT
BACKGROUND: Colonic permeability was studied in vitro in patients subjected to colectomy because of ulcerative colitis and in control patients undergoing colonic resections for cancer. METHODS: The mucosal layer from fresh colonic segments was stripped and mounted in Ussing diffusion chambers containing modified Krebs buffer solution. The mucosa to serosa passage of the marker molecules 14C-mannitol and ovalbumin was measured for 120 min. RESULTS: Marker passage was significantly increased in colitis patients compared with control patients, irrespective of age, sex, duration of disease, and treatment. Marker passage was further increased in patients with acute colitis. The increased colonic permeability may be explained by inflammation and the resultant loss of mucosal integrity. The increased permeability to ovalbumin implies that permeability to luminal macromolecules, such as bacterial products and other antigenic substances, might be increased in colitis. CONCLUSIONS: The results suggest a derangement of the colonic barrier, as evidenced by an increased mucosal permeability in both chronic and acute colitis.
