Bacterial lipopolysaccharide protects gastric mucosa against acute injury in rats by activation of genes for cyclooxygenases and endogenous prostaglandins.
Lipopolysaccharides (LPS) derived from gram-negative bacteria were reported to impair gastrointestinal mucosal integrity, but the results obtained are controversial. This study was undertaken to determine the effects of short-term administration of LPS on gastric secretion and gastric damage induced by 100% ethanol and to assess the role of the gene expression of two isoforms of cyclooxygenase (COX), constitutive (COX-1) and inducible (COX-2), and endogenous prostaglandins (PG) on these effects of LPS. Fasted rats received vehicle (control) or LPS (0.1-40 mg/kg i.g. or i.p.) without or with pretreatment with nonselective inhibitors of COX activity, indomethacin (5 mg/kg i.p.) and meloxicam (2 mg/kg i.g.), or the selective COX-2 inhibitor NS-398 (10 mg/kg i.g.), followed by intragastric application of 100% ethanol. The area of gastric lesions was determined by planimetry, gastric blood flow (GBF) was measured by the H2-gas clearance technique, mucosal PGE2 generation was measured by radioimmunoassay, and expression of COX-1 and COX-1 mRNA was determined by reverse transcription polymerase chain reaction (RT-PCR), quantitative RT-PCR with [32P]dCTP and immunohistochemistry. LPS applied intraperitoneally in various doses (0.1-10 mg/kg), dose dependently inhibited gastric acid and pepsin secretion and significantly reduced the area of gastric lesions induced by ethanol, and this was accompanied by an attenuation of the ethanol-induced fall in GBF and increased mucosal generation of PGE2. LPS applied in higher doses, such as 20 or 40 mg/kg, that caused systemic hypotension failed to protect the mucosa against 100% ethanol. Suppression of mucosal PGE2 generation by indomethacin or meloxicam, significantly reduced the inhibitory action of LPS on gastric secretion and abolished LPS-induced gastroprotection and elevation of GBF. NS-398 did not influence PGE2 generation, but significantly attenuated the protection and hyperemia induced by LPS suggesting that COX-2-derived products play an important role in gastroprotection. The expression of COX-1 mRNA, as determined by RT-PCR, quantitative RT-PCR and immunohistochemistry was found in intact gastric mucosa and after LPS administration. In contrast, the expression of COX-2 mRNA was undetectable in intact gastric mucosa but appeared in this mucosa 2, 4 and 8 h after LPS administration. COX-2 mRNA was not detected in rats treated with ethanol but, when LPS was applied before ethanol, the enhanced expression of COX-2 was detected without affecting COX-1 mRNA expression. We conclude that acute parenteral LPS affords gastroprotection against ethanol-damage through an increase in gastric microcirculation and overexpression of COX-2 and enhanced endogenous PG release.
Konturek
P C
PC
Department of Medicine I, Friedrich Alexander University, Erlangen-Nuremberg, Germany.
Brzozowski
T
T
Konturek
S J
SJ
Taut
A
A
Kwiecien
S
S
Pajdo
R
R
Sliwowski
Z
Z
Hahn
E G
EG
D000818:Animals; D001783:Blood Flow Velocity / Q000187:drug effects; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; D052246:Cyclooxygenase 2 Inhibitors; D016861:Cyclooxygenase Inhibitors / Q000633:toxicity; D015232:Dinoprostone / Q000096:biosynthesis / Q000235:genetics*; D004305:Dose-Response Relationship, Drug; D004333:Drug Administration Routes; D004926:Escherichia coli; D000431:Ethanol / Q000633:toxicity; D005753:Gastric Mucosa / Q000098:blood supply / Q000187:drug effects* / Q000378:metabolism; D015870:Gene Expression / Q000187:drug effects; D007150:Immunohistochemistry; D007213:Indomethacin / Q000633:toxicity; D007527:Isoenzymes / Q000096:biosynthesis / Q000187:drug effects / Q000235:genetics*; D008070:Lipopolysaccharides / Q000008:administration & dosage*; D008297:Male; D000077239:Meloxicam; D008565:Membrane Proteins; D009578:Nitrobenzenes / Q000633:toxicity; D016133:Polymerase Chain Reaction; D011451:Prostaglandin-Endoperoxide Synthases / Q000096:biosynthesis / Q000187:drug effects / Q000235:genetics*; D012333:RNA, Messenger / Q000096:biosynthesis* / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D012997:Solvents / Q000633:toxicity; D013449:Sulfonamides / Q000633:toxicity; D013843:Thiazines / Q000633:toxicity; D013844:Thiazoles / Q000633:toxicity
D052246:Cyclooxygenase 2 Inhibitors; D016861:Cyclooxygenase Inhibitors; D007527:Isoenzymes; D008070:Lipopolysaccharides; D008565:Membrane Proteins; D009578:Nitrobenzenes; D012333:RNA, Messenger; D012997:Solvents; D013449:Sulfonamides; D013843:Thiazines; D013844:Thiazoles; C080955:N-(2-cyclohexyloxy-4-nitrophenyl)methanesulfonamide; D000431:Ethanol; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; D011451:Prostaglandin-Endoperoxide Synthases; C496513:Ptgs1 protein, rat; D015232:Dinoprostone; D000077239:Meloxicam; D007213:Indomethacin