<i>Aim:</i> We compared the ulcerogenic effects of aspirin (ASA) and indomethacin in the rat gastric mucosa depending on the route of administration, together with the expression of COX-2. <i>Methods:</i> Animals fasted for 18 h were given ASA or indomethacin, either p.o. or s.c., and the stomach was examined 4 h later. <i>Results:</i> Indomethacin decreased mucosal PGE<sub>2 </sub>level, increased gastric motility, and caused gastric lesions with the up-regulation of COX-2 expression, irrespective of the route of administration. ASA induced both damage and COX-2 expression in the stomach when given p.o. but not s.c., despite decreasing the PGE<sub>2</sub> level similarly via either route of administration. Gastric motility was temporarily increased and gastric potential difference (PD) was markedly decreased by ASA given p.o. PGE<sub>2</sub> and atropine, although preventing ASA-induced gastric lesions as well as hypermotility, affected neither the COX-2 expression nor PD reduction induced by p.o. ASA. By contrast, the COX-2 expression induced by indomethacin was prevented by both PGE<sub>2</sub> and atropine. <i>Conclusion:</i> ASA given p.o. caused damage in the stomach, together with the up-regulation of COX-2 expression, and this expression may be due to the topical irritative action, rather than being a result of PG deficiency. The expression of COX-2 after indomethacin is associated with gastric hypermotility due to PG deficiency.
AbstractNostocionone (Nost), a compound isolated from Nostoc commune, and its synthesized derivatives (NostDs) were evaluated for in vitro cytotoxicity against human T-cell leukemia Jurkat cells. NostD3 [(1E,4E)-1-(3,4-dihydroxyphenyl)-5-(2,6,6-trimethylcyclohex-1-enyl)penta-1,4-dien-3-one] inhibited cell growth more potently than Nost. To elucidate the mechanisms of NostD3-induced cell death, we examined changes in cell morphology, the loss of mitochondrial membrane potential (MMT), and DNA fragmentation. From these results, the cytotoxic effects of NostD3 were found to be mainly due to Type I programmed cell death (PCDI; i.e., apoptosis). Using caspase inhibitors, we further found that NostD-3-induced PCDI occurred through a caspase-independent pathway. Moreover, NostD3 decreased MMT and modulated multiple signaling molecules (MAPKs, Akt, Bcl-2, Bax, and c-Myc) in Jurkat cells, thereby inducing the release of endonuclease G (Endo-G) from mitochondria. The level of intracellular reactive oxygen species (ROS) in cells treated with NostD3 was elevated up to 1 h after the treatment. However, suppression of ROS by N-acetyl-l-cysteine restored Jurkat cell growth. Taken together, our data suggested that ROS production acted as a trigger in NostD3-induced PCDI in Jurkat cells through release of Endo-G from the mitochondria.
Indomethacin in small doses is known to inhibit prostaglandin (PG) production, yet it does not damage the gastrointestinal mucosa. We examined whether a cyclooxygenase (COX)-2 inhibitor induces gastrointestinal damage in the presence of a low dose of indomethacin and investigated the ulcerogenic mechanism in relation to COX-2 expression. Rats with or without 18-h fasting were administered rofecoxib (a selective COX-2 inhibitor; 10 or 30 mg/kg p.o.) in the absence or presence of indomethacin (3 mg/kg p.o.), and the gastric or intestinal mucosa was examined 8 and 24 h later, respectively. Neither indomethacin nor rofecoxib alone caused damage in the stomach or small intestine. However, indomethacin damaged the small intestine in the presence of rofecoxib, yet the same treatment did not damage the stomach. Indomethacin reduced the mucosal PGE2 content in both tissues, whereas rofecoxib did not. The COX-2 mRNA was up-regulated in the intestine but not the stomach after indomethacin treatment, and the reduced PGE2 content was significantly recovered later only in the small intestine, in a rofecoxib-inhibitable manner. Indomethacin produced hypermotility in the small intestine but not the stomach, whereas rofecoxib had no effect. These results suggest that the PG deficiency caused by a low dose of indomethacin produces hypermotility and COX-2 expression in the small intestine but not the stomach, resulting in damage when COX-2 is inhibited. It is assumed that the hypermotility response is a key event in the expression of COX-2 and thereby important in the development of mucosal damage in the gastrointestinal tract.
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