Induction of ornithine decarboxylase and histidine decarboxylase activities in rat colon mucosa after application of 12-o-tetradecanoylphorbol-13-acetate (TPA), sodium deoxycholate and indole

Histaminergic control of mucosal repair in the small intestine

The aim of the present paper was to summarize histamine-mediated repair of rat intestinal mucosa. To evaluate intestinal repair, we examined lipid transport (an index of intestinal mucosal function) after 15 minutes occlusion of the superior mesenteric artery. Rats were pretreated with alpha-fluoromethylhistidine (a suicide inhibitor of histidine decarboxylase, a synthesizing enzyme of histamine), H1-receptor antagonist (chlorpheniramine maleate), H2-antagonist (cimetidine), or H3-antagonist (thioperamide) before ischemia-reperfusion (I/R). Lipid transport to rat mesenteric lymph decreased significantly 24 hours after I/R in all groups tested compared to sham-treated rats. Lipid transport was restored 48 hours after I/R in the vehicle-pretreated control group. Lipid transport was not restored to the control level 48 hours after I/R in rats pretreated with H1-antagonist and a suicide inhibitor of histidine decarboxylase. In contrast, intestinal function was restored to the control level 48 hours after I/R in rats pretreated with H2- and H3-antagonists. These results support our previous findings that newly formed histamine after I/R plays an important role in mucosal recovery through H1-receptors.

Newly synthesized histamine accelerates ornithine decarboxylase activity in rat intestinal mucosa after ischemia-reperfusion

We previously demonstrated that both histamine synthesis (histidine decarboxylase activity) and polyamine synthesis (ornithine decarboxylase activity) increased in the rat intestinal mucosa after ischemia-reperfusion, whereas the relationship between these two factors remains unclear. To elucidate this relationship, we performed the present study. The superior mesenteric artery was occluded for 15 min followed by reperfusion. After ischemia-reperfusion, histidine decarboxylase activity and ornithine decarboxylase activity in the rat jejunal mucosa were measured in a time-dependent manner. Histidine decarboxylase activity increased 1 hr after ischemia-reperfusion, although ornithine decarboxylase activity did not; however, its activity did increase 6 hr after. The increase of ornithine decarboxylase activity was attenuated when the increase of histamine synthesis was suppressed by the inhibition of histidine decarboxylase activity caused by pretreatment with alpha-fluoromethylhistidine, a suicide inhibitor of histidine decarboxylase. Pretreatment with H1-receptor antagonist attenuated the increase of ornithine decarboxylase activity after ischemia-reperfusion. These results indicate that the newly synthesized histamine, as indicated by an increase of histidine decarboxylase activity, increases ornithine decarboxylase activity after ischemia-reperfusion of the rat intestinal mucosa.

Role of histamine receptors in intestinal repair after ischemia-reperfusion in rats

BACKGROUND/AIMS

Previously, we showed that an elevated production of histamine promotes the healing of injured intestinal mucosa after ischemia-reperfusion. The aim of the present study was to determine whether histamine-mediated repair of the intestinal mucosa after ischemia-reperfusion involves the engagement of H1 or H2 receptors.

METHODS

The superior mesenteric artery was occluded for 15 minutes followed by reperfusion, and H1- or H2-receptor antagonists were infused intraduodenally. After ischemia-reperfusion, ornithine decarboxylase activity in the jejunal mucosa and lipid transport to mesenteric lymph were examined.

RESULTS

In jejunal mucosa, ornithine decarboxylase activity markedly increased at 6 hours after reperfusion and remained elevated at 48 hours. The ischemia-reperfusion-induced increase in ornithine decarboxylase activity was attenuated (in a dose-dependent manner) by an H1-receptor antagonist (chlorpheniramine maleate) but not by an H2 antagonist (cimetidine). Intraperitoneal injection of an H3 antagonist (thioperamide) increased histamine output in mesenteric lymph and stimulated intestinal ornithine decarboxylase activity. Transport of dietary lipid into mesenteric lymph was depressed 24 hours after an ischemic insult, yet it returned to the normal level 48 hours after ischemia-reperfusion. The recovery of the lipid transport normally observed at 48 hours after ischemia-reperfusion was attenuated by the H1 antagonist.

CONCLUSIONS

The beneficial effects of histamine on the repair of intestinal mucosa after ischemia-reperfusion results from the engagement and activation of the H1 receptor.

Histamine synthesis and content in benign and malignant breast tumours. Its effects on other host tissues

We studied 100 patients: 40 with breast cancer, 41 with benign breast tumours and 19 non-cancer-bearing cholecystectomy patients, in order to measure the histidine decarboxylase activity and histamine content in benign and malignant breast tumours, and to determine whether the histamine metabolism affected skin and muscle tissue distant from the tumour. The HDC-activity of cancerous tissue was significantly higher (P < 0.01) than that registered in the healthy mammary gland tissue of the same patient, being even more pronounced in benign tumour tissue (P < 0.001). However, the histamine content was found to be significantly lower (P < 0.01) in malignant tumours, but higher in benign tumoural tissue as compared with the healthy tissue of the same patient. We also found that the histamine content in muscle tissue was significantly higher in cancer patients than in non-cancer patients. These findings highlight the fact that intracellular histamine metabolism varies in benign and malignant tumours, and that high histamine synthesis of malignant tumours affects other host tissue.

Alterations in protein kinase C system of colonic epithelium during fasting-refeeding. Evidence for protein kinase C independent pathway of enhanced proliferative activity

In the present study, we compared (1) incorporation of [3H]dThd into DNA, (2) total protein kinase C (PKC) activity, (3) the subcellular distribution of PKC, and (4) PKC isozyme (alpha, beta and gamma) mass in colonic mucosal scrapings and isolated superficial and proliferative colonic epithelial cells from 48-hr fasted, 48-hr fasted-refed, and ad libitum-fed rats. Total colonic mucosal PKC activity and PKC alpha mass were higher and the in vivo rate of [3H]dThd incorporation into mucosal DNA was markedly depressed in 48-hr fasted rats compared to ad libitum-fed or fasted-refed rats. These alterations were localized predominantly to the proliferative pool of colonic epithelial cells. Despite an 11-fold increase in mucosal DNA synthesis, no alterations in total mucosal PKC activity were detected in fasted-refed rats compared to rats fed ad libitum. Moreover, no differences in the subcellular distribution of PKC were noted among any of the dietary groups. Intrarectal instillation of deoxycholate activated PKC and increased DNA synthesis 1.5- to 2-fold. Deoxycholate-induced increases in DNA synthesis, but not those induced by refeeding, were inhibited by treatment of rats with the PKC inhibitors H-7, sphingosine, or staurospaurine. The results do not support a role for PKC in the mediation of increased proliferative activity of colonic mucosa induced by refeeding.

Histamine and histidine decarboxylase are correlated with mucosal repair in rat small intestine after ischemia-reperfusion

The aim of this experiment was to demonstrate whether histamine and histidine decarboxylase (HDC) contribute to mucosal repair in small intestine subjected to ischemia-reperfusion (I/R). The superior mesenteric artery was occluded for 15 min followed by reperfusion. In jejunal mucosa, histamine content and HDC activity increased after I/R. Histamine output in mesenteric lymph was also elevated after I/R. These increases in HDC activity, and mucosal and lymph histamine levels were suppressed by pretreatment of alpha-fluoromethylhistidine (alpha-FMH), a suicide inhibitor of HDC. alpha-FMH also attenuated the increase of ornithine decarboxylase (ODC) activity normally observed after I/R. Transport of dietary lipid into lymph markedly decreased at 24 h after I/R, yet it was restored to normal at 48 h after I/R. alpha-FMH inhibitor led to a sustained deficit in lipid transport at 48 h after I/R. This sustained functional impairment in alpha-FMH treated animals was associated with blunted responses of HDC activity and histamine content to I/R. Our results suggest that histamine and HDC contribute to the restoration in mucosal function observed at 48 h after I/R. This response may be related, at least in part, to stimulation of ODC activity by histamine.

Free radicals, antioxidant enzymes, and carcinogenesis

Free radicals are found to be involved in both initiation and promotion of multistage carcinogenesis. These highly reactive compounds can act as initiators and/or promoters, cause DNA damage, activate procarcinogens, and alter the cellular antioxidant defense system. Antioxidants, the free radical scavengers, however, are shown to be anticarcinogens. They function as the inhibitors at both initiation and promotion/transformation stage of carcinogenesis and protect cells against oxidative damage. Altered antioxidant enzymes were observed during carcinogenesis or in tumors. When compared to their appropriate normal cell counterparts, tumor cells are always low in manganese superoxide dismutase activity, usually low in copper and zinc superoxide dismutase activity and almost always low in catalase activity. Glutathione peroxidase and glutathione reductase activities are highly variable. In contrast, glutathione S-transferase 7-7 is increased in many tumor cells and in chemically induced preneoplastic rat hepatocyte nodules. Increased glucose-6-phosphate dehydrogenase activity is also found in many tumors. Comprehensive data on free radicals, antioxidant enzymes, and carcinogenesis are reviewed. The role of antioxidant enzymes in carcinogenesis is discussed.