copper-bis(3-5-diisopropylsalicylate) and phenidone

Our previous studies had suggested a link between bile salt stimulation of colonic epithelial proliferation and the release and oxygenation of arachidonate via the lipoxygenase pathway. In the present study, we examined the role of reactive oxygen versus end products of arachidonate metabolism via the cyclooxygenase and lipoxygenase pathways in bile salt stimulation of rat colonic epithelial proliferation. Intracolonic instillation of 5 mM deoxycholate increased mucosal ornithine decarboxylase activity and [3H]thymidine incorporation into DNA. Responses to deoxycholate were abolished by the superoxide dismutase mimetic CuII (3,5 diisopropylsalicylic acid)2 (CuDIPS), and by phenidone or esculetin, which inhibit both lipoxygenase and cyclooxygenase activities. By contrast, indomethacin potentiated the response. Phenidone and esculetin suppressed deoxycholate-induced increases in prostaglandin E2 (PGE2), leukotriene B4 (LTB4), and 5, 12, and 15-hydroxyeicosatetraenoic acid (HETE), whereas CuDIPS had no effect. Indomethacin suppressed only PGE2. Deoxycholate (0.5-5 mM) increased superoxide dismutase sensitive chemiluminescence 2-10-fold and stimulated superoxide production as measured by cytochrome c reduction in colonic mucosal scrapings or crypt epithelium. Bile salt-induced increases in chemiluminescence were abolished by CuDIPS, phenidone, and esculetin, but not by indomethacin. Intracolonic generation of reactive oxygen by xanthine-xanthine oxidase increased colonic mucosal ornithine decarboxylase activity and [3H]thymidine incorporation into DNA approximately twofold. These effects were abolished by superoxide dismutase. The findings support a key role for reactive oxygen, rather than more distal products of either the lipoxygenase or cyclooxygenase pathways, in the stimulation of colonic mucosal proliferation by bile salts.

Topics: Animals; Arachidonic Acid; Arachidonic Acids; Bile Acids and Salts; Cell Cycle; Deoxycholic Acid; DNA; Female; Free Radicals; Indomethacin; Intestinal Mucosa; Lipoxygenase; Luminescent Measurements; Ornithine Decarboxylase; Oxygen; Prostaglandin-Endoperoxide Synthases; Pyrazoles; Rats; Salicylates; Superoxide Dismutase; Superoxides; Umbelliferones; Xanthine Oxidase

Bile acids increase the proliferative activity of rat colonic epithelium. However, the mechanisms responsible are unknown. The present study examined the relationships between deoxycholate (DOC) induced surface cell sloughing, as measured by loss of DNA into the lumen and by light microscopy, and the subsequent increases in mucosal ornithine decarboxylase activity and [3H]thymidine (dThd) incorporation into mucosal DNA induced by deoxycholate. Intracolonic instillation of DOC (10 mumol; 5 mM) resulted in a progressive increase in luminal DNA content which was significant by 1 min and maximal by 1 h. No further increase in luminal DNA occurred between 1 and 4 h after DOC. Similarly, light microscopy demonstrated a progressive loss of surface epithelium between 10 min and 1 h after DOC instillation. By 4 h after DOC, the colonic mucosal surface was normal histologically. The rapid repair of the epithelial surface occurred without a detectable increase in [3H]dThd incorporation into DNA within 4 h. The latter finding thus suggested that upward migration of nondividing crypt epithelial cells rather than the rapid initiation of new DNA synthesis and new mitotic activity was responsible for surface repair. Enhanced proliferative activity of colonic mucosa, as measured by increased [3H]dThd incorporation into DNA, did occur subsequently (12 to 24 h) after instillation of DOC. The dose response of early surface cell loss and the subsequent proliferative response to DOC were identical, consistent with a link between these two DOC mediated events. However, two observations suggested that surface epithelial loss alone was not sufficient to trigger the proliferative response to DOC: intracolonic instillation of DOC followed by removal of the DOC solution at 1 h, at which time surface epithelial loss was maximal, did not result in an increase in ornithine decarboxylase activity or [3H]dThd incorporation into DNA when these parameters were assessed at 4 h or 12 to 48 h, respectively; phenidone, an antioxidant and radical scavenger, and bis[(3,5-diisopropyl-salicylato) (O,O) copper(II), a lipophilic agent with superoxide dismutase activity, abolished the DOC mediated proliferative response but did not prevent the early loss of surface cells. The results imply that events other than or in addition to surface cell loss are necessary for the expression of the action of DOC to stimulate the proliferative activity of colonic epithelium.

Topics: Animals; Cell Cycle; Colon; Deoxycholic Acid; DNA; Dose-Response Relationship, Drug; Epithelial Cells; Epithelium; Intestinal Mucosa; Ornithine Decarboxylase; Pyrazoles; Rats; Salicylates