Antiproliferative responses to two human colon cancer cell lines to vitamin D3 are differently modified by 9-cis-retinoic acid.

1 alpha,25-Dihydroxyvitamin D3 [1,25(OH)2D3] exerts antiproliferative actions in colorectal cancer, but their underlying molecular mechanisms have not been determined. 1,25(OH)2D3 regulates target gene transcription via a specific nuclear vitamin D receptor (VDR), which mediates hormone action preferentially as a heterodimer with 9-cis-retinoic acid receptors (RXRs). We investigated the actions of 1,25(OH)2D3 and 9-cis-retinoic acid (RA) in two human colon cancer cell lines, HT-29 and Caco-2. Both expressed mRNAs encoding VDR, RXR alpha, and RXR gamma, and VDR was regulated posttranscriptionally in Caco-2 cells. There was an antiproliferative response of both cell lines to 1,25(OH)2D3. 9-cis-RA exerted antiproliferative effects on Caco-2 cells but blocked 1,25(OH)2D3 actions in HT-29 cells. The 1,25(OH)2D3-responsive gene 25-hydroxyvitamin D3 24-hydroxylase was induced in both cell lines b 1,25(OH)2D3 but in only HT-29 cells by 9-cis-RA. 1,25(OH)2D3 and 9-cis-RA cotreatment enhanced 24-hydroxylase expression in HT-29 cells only. The 24-hydroxylase enzyme is known to result in catabolism of 1,25(OH)2D3 and attenuation of its actions. Increased 24-hydroxylase activity in HT-29 cells, but not in Caco-2 cells, in response to 9-cis-RA may account for some of the complex cell-specific responses demonstrated in these studies.

Systemic hypertension and glaucoma: mechanisms in common and co-occurrence.

AIMS: To determine whether systemic hypertension and glaucoma might coexist more often than expected, with possible implications for treatment. METHODS: Case-control study using general practitioner database of patients with glaucoma matched with controls for age and sex. RESULTS: Hypertension was significantly more common in the 27,080 patients with glaucoma (odds ratio 1.29, 95% confidence intervals 1.23 to 1.36, p<0.001) than in controls. Treatment by oral beta blockade appeared to protect from risk (odds ratio 0.77, 95% CI 0.73 to 0.83, p<0.0001), but oral calcium channel antagonists or angiotensin converting enzyme (ACE) inhibitors did not (odds ratios 1.34, 1.24 to 1.44 and 1.16 1.09-1.24, respectively, p<0.0001 in each case). Oral corticosteroid treatment was associated with enhanced risk (odds ratio 1.78, 1.61 to 1.96). CONCLUSION: Common pathogenetic mechanisms in ciliary and renal tubular epithelia may explain coincidence of glaucoma and systemic hypertension. The choice of cardiovascular treatment, could substantially influence glaucoma incidence, with beta blockade protecting and ACE inhibitors or calcium channel blockers not affecting underlying risk.

Loss of estrogen inactivation in colonic cancer.

Age and sex differences in the incidence of colonic cancer, together with epidemiological data on patients taking hormone replacement therapy, suggest the involvement of estrogens. Analogous to the role of aromatase in breast cancer, we postulated that steroid metabolism within the colon itself may be a crucial mechanism in regulating tissue exposure to estrogens. We have characterized expression of aromatase (responsible for converting C19 androgens to C18 estrogens) and 17beta-hydroxysteroid dehydrogenase (17beta-HSD) [responsible for interconversion of active estradiol (E2) to less potent estrone (E1)] in normal and neoplastic human colon from 24 patients undergoing tumor resection. Aromatase activity was similar in homogenates from normal mucosa, tissue adjacent to tumors, and the tumors themselves. Analysis of 17beta-HSD activity indicated that the predominant activity was oxidative (E2 to E1), and this conversion was significantly lower in colonic tumors [444 (90-1735); median (95% confidence interval) pmol/mg protein x h], compared with normal mucosa [1709 (415-13828), P < 0.001]. Northern blot analyses indicated expression of messenger RNAs (mRNAs) for the type 2 and 4 isozymes of 17beta-HSD in normal colon; messenger RNA for 17beta-HSD 4 was significantly lower in tumor tissue [0.75 +/- 0.22 (mean +/- SD) arbitrary U vs. 0.43 +/- 0.17, P < 0.01]. Studies in vitro, using three colonic cancer cell lines, indicated that there was an inverse correlation between 17beta-HSD oxidative activity and the rate of cell proliferation. In addition, E1, but not E2, was shown to significantly decrease proliferation when added exogenously to the colonic epithelial cell line, SW620 cells. Colonic mucosa can regulate estrogen hormone action in an intracrine fashion. The loss of estrogen inactivation may be an important mechanism in the pathogenesis of colonic cancer.

Ulcer complications and nonsteroidal anti-inflammatory drugs.

Rates of ulcer perforation, hospital admission, and death are usually regarded as the best available measures of the frequency of severe peptic ulcer disease. Overall admission rates have tended to decline, which almost certainly reflects the widespread adoption of effective outpatient therapy. The overall incidence of ulcer perforation and death may also have fallen. However, at least in Europe, and in the United Kingdom in particular, there may be differences between the young and the elderly; rates of perforation and death in the young appear to be declining, whereas they are rising or static in the elderly. Although there are various interpretations for these changing patterns, data for the United Kingdom suggest that during the last 15 to 20 years some unidentified factor or factors began to influence the rates of severe peptic ulcer disease among the elderly. At least part of this change may reflect increasingly frequent prescribing of nonsteroidal anti-inflammatory drugs (NSAIDs). In the United Kingdom, most adverse drug reactions attributable to NSAIDs are gastrointestinal and are usually serious. Bleeding and perforation are common, may occur in the absence of warning symptoms, and are associated with a high mortality rate. In some countries, other factors, including smoking and diet, may be equally important. It is difficult to determine the relative contribution of each factor, though the widespread perception that the gastrointestinal tolerance of NSAIDs is poor, particularly in the elderly, may be well founded. About half the prescriptions for non-aspirin NSAIDs in the United Kingdom are for patients over 60 years of age. About one quarter of all cases of upper gastrointestinal bleeding in the elderly are likely caused by NSAIDs and are associated with a death rate of 10 percent or possibly higher. Although the absolute risk of a serious gastrointestinal complication may be low, perhaps one in several thousand NSAID prescriptions, the total burden of disease is high because of the multimillion NSAID prescriptions issued yearly.

Analgesic intake and the risk of acute upper gastrointestinal bleeding.

A comparison of aspirin and acetaminophen consumption in 346 matched pairs of patients with hematemesis and melena and general population control subjects has shown associations between intake of both drugs and bleeding. The association for acetaminophen was weaker and was not detectable for habitual intake, whereas the association for aspirin was detectable for recent and habitual intake. Taken overall, the results suggest, by reference to acetaminophen, that patients frequently take analgesic drugs because of the symptoms of bleeding, and such intake is not causal of bleeding. Investigators who fail to employ appropriate control subjects to take account of this point exaggerate the possible risks of aspirin consumption.

Oestrogen-induced apoptosis in colonocytes expressing oestrogen receptor beta.

Epidemiological studies of postmenopausal hormone replacement therapy show a reduction in the risk of developing colon cancer, and animal studies using 17beta-oestradiol (E(2)) demonstrate a decreased incidence of chemically-induced colon cancer. Using the colon cancer cell line, COLO205, we found that E(2) induced a dose-dependent increase in DNA fragmentation and nuclear condensation, significant effects being seen at 10(-12 )mol/l. BSA-conjugated E(2), which cannot enter cells, was ineffective at inducing apoptosis in COLO205 cells, indicating that E(2) was not acting through a cell-membrane receptor. E(2) did not induce the morphological changes characteristic of differentiation. Using RT-PCR we found that the oestrogen receptor alpha (ERalpha) isoform was absent in the COLO205 cell line in contrast to CACO-2, LoVo and SW620 cells, but mRNAs for ERbeta1, -beta2, -beta5 and -beta6 isoforms were detected. Western immunoblotting results showed full-length ERbeta protein but no detectable ERalpha in COLO205 cells. In normal human colon tissue samples immunoreactive ERbeta was found but ERalpha was barely detectable. Expression of ERbeta was lost in some colon cancer specimens and reduced in others. We conclude that E(2), through ERbeta, at concentrations found during replacement therapy, may inhibit the development of colon cancer by inducing apoptosis.

Antisecretory drugs. Safe and effective?

Surveillance of takers of the antisecretory drug cimetidine has failed to reveal any disturbing trends. This pattern is reassuring but the difficulties of detecting drug-induced disease mimicking ordinary community complaints deserve emphasis. Experience since the surveillance study began has not revealed any disturbing trends. Observed mortality rates have fallen to match population expectation, both for ordinary disease and for cancer. The pattern is generally reassuring and suggests that significant drug-induced disease is not being missed. Nevertheless the ability of this or any other surveillance study to detect drug-induced illness mimicking ordinary disease is likely to be low.

Carbenoxolone sodium: its role in ulcer healing.

In summary, carbenoxolone is a useful drug in accelerating short-term ulcer healing during ambulatory treatments. Provided treatment is responsibly controlled the adverse effects should not present frequent or severe problems; however, there is a clear need for an analogue which is substantially side-effect free.

Antacids and ulcer healing. A review of the evidence.

There have been a number of controlled trials of antacids in the treatment of patients with peptic ulcer disease. As a general rule the size of studies has been small and there have been difficulties ensuring adequate binding, because of the formulation and taste of the antacids. Despite these difficulties, antacids appear to be effective ulcer healing agents with efficacies resembling those of other antiulcer drugs. Definite dose relationships are unclear but high doses of buffering capacity over 200 mmol/day appear unnecessary and are associated with increasingly frequent adverse effects. Low dose maintenance treatment is effective at limiting duodenal ulcer relapse.

Omeprazole.

Omeprazole is a potent and effective antisecretory drug. Benefits in gastric and duodenal ulceration nevertheless seem marginal because standard treatments are very effective. More obvious advantages are discernible in oesophageal reflux disease where more profound acid inhibition may be needed to obtain symptom relief. Fears of important adverse effects either through inducing ECL cell hyperplasia or outright carcinogenesis, do not seem firmly founded, nor is there convincing evidence of significant interactions with other xenobiotics. Nevertheless, continued caution seems justified.

Ulcer and ulcer complications from non-steroidal anti-inflammatory drugs: what is the risk?

Gastroenterologists believe that non-steroidal anti-inflammatory drugs (NSAIDs) cause dyspepsia, may cause ulcers to develop de novo and cause ulcer bleeding and perforation. Regulatory authorities are aware that NSAID-associated adverse events are reported more often than for any other drug class, and that gastrointestinal events are most common and often serious. A case-control study in the UK indicates that those who use NSAIDs may be between two and four times as liable to gastrointestinal bleeding and probably perforation as non-users, particularly if elderly. It has further been suggested that the chances of dying of ulcer complications are very high in NSAID users. By contrast, studies in the USA conducted prospectively and post-marketing surveillance in the UK have appeared to show little risk. Differences may be partially, if not completely, explained by the variable methodologies employed. Dispute also exists about the rank order and significance of toxic effects among the various agents.

Discrepancies between population-based data and adverse reaction reports in assessing drugs as causes of acute pancreatitis.

BACKGROUND: Many drugs are believed, clinically, to cause acute pancreatitis. We used information held on the UK General Practitioner Research Database to compare risks for drugs for which reports of pancreatitis were common or uncommon. METHODS: Drug prescriptions were examined in 3673 patients with acute pancreatitis and in matched controls. Odds ratios were calculated for recent (1-90 days before the episode), past (91-360 days before the episode) or continuing (prescription in both periods) use. RESULTS: Odds ratios were markedly increased for recent antisecretory use in non-ulcer patients only [all H2-antagonists, 12.4 (9.5-16.4); all proton pump antagonists, 9.3 (6.6-13.0)], with smaller increases for past [3.1 (2.5-3.7) and 3.5 (2.6-4.6), respectively] and continuing [2.6 (2.2-3.1) and 3.7 (2.9-4.7), respectively] use in patients without ulcer. Recent users of mesalazine showed a markedly increased risk [9.0 (1.8-44.6)], with smaller increases in past and continuing users [4.5 (1.3-16.0) and 2.5 (1.2-5.0), respectively]. Odds ratios for other drugs, suspect or not, were modestly increased, irrespective of whether the use was recent, past or continuing. The presence of gall-stones was not associated with a modified risk. CONCLUSIONS: Mesalazine, azathioprine and antisecretory drugs in non-ulcer subjects may increase the risk of pancreatitis, but warnings of drug-induced pancreatitis are generally not accompanied by increased population risks.

Effect of ranitidine and indomethacin on nocturnal gastric acidity in normal subjects.

To assess the effect of indomethacin on gastric acidity and to identify a potential pharmacodynamic interaction between indomethacin and ranitidine, we measured nocturnal acidity on half-hourly aliquots of gastric contents from 10 volunteers on the seventh day of four dosing regimens given in a randomized double-blind manner. These were indomethacin (50 mg t.d.s.) and ranitidine (300 mg in the evening) together or alone with matching placebos. Median nocturnal acidity on placebo was 41.7 mmol/L (range 67.6-25.1 mmol/L) and was 39.8 mmol/L (63.1-24.0 mmol/L) on indomethacin (N.S.). During ranitidine dosing it was 0.4 mmol/L (21.3-0.0 mmol/L) without and 0.8 mmol/L (43.7-0.0 mmol/L) with concurrent indomethacin, representing 99 and 98% decreases in gastric acidity (P less than 0.01) compared with placebo. Indomethacin did not increase overnight gastric acidity and did not influence the suppression of acidity produced by ranitidine. It is unlikely that the ulcerogenic potential of indomethacin is explicable by an effect on gastric acidity.

Intragastric pH monitoring in acute upper gastrointestinal bleeding and the effect of intravenous cimetidine and ranitidine.

Intragastric pH was measured continuously from 1800 to 1200 hours the following day in 22 duodenal ulcer patients and in eight gastric ulcer patients, all of whom had been admitted as emergencies with acute upper gastrointestinal haemorrhage. The effects of intravenous cimetidine or ranitidine were compared with no treatment. In patients with duodenal ulcer, median intragastric pH was 1.8 (range 1.0-4.9) in the group receiving no treatment. In the cimetidine group (400 mg, 6-hourly, n = 8) median pH was 4.7 (range 1.5-7.7) and after ranitidine (50 mg, 6-hourly, n = 10) it was 3.8 (range 1.2-7.8). The pH remained above 4.0 for 67% of the recording time with cimetidine, 47% with ranitidine and for only 3% with placebo. Intragastric pH in gastric ulcer patients without treatment was higher (median 3.4, range 1.0-6.9) than in duodenal ulcer patients with treatment. Both H2 antagonists raised intragastric pH in patients with gastric ulcer and maintained a gastric pH of greater than 4.0 for at least 50% of the time. Presently recommended i.v. doses of cimetidine and ranitidine do not consistently maintain gastric pH above 4.0 for long periods in patients with peptic ulcer bleeding.

Review: post-marketing surveillance of the safety of cimetidine--the problems of data interpretation.

Experience obtained during post-marketing surveillance of the safety of cimetidine emphasizes the difficulties in interpretation posed by the high background frequency of disease of all types in drug takers. The multiple sources of confounding factors, and their high prevalence, make it impossible to detect adverse events which mimic ordinary disease, particularly when a consistent relationship between adverse event and drug exposure is not observed. The inclusion of controls emphasizes the difficulties but does not ease interpretation.

Sulphide-induced energy deficiency in colonic cells is prevented by glucose but not by butyrate.

BACKGROUND: In ulcerative colitis, hydrogen sulphide is postulated to impair colonocyte butyrate metabolism, leading to cellular energy deficiency and dysfunction. AIMS: To determine the effects of sulphide exposure on butyrate metabolism and adenosine triphosphate levels of HT29 colonic epithelial cancer cells, and to establish whether energy deficiency can be prevented by increased butyrate concentrations or the presence of glucose. METHODS: HT29 cells were maintained in medium containing 3 mM butyrate, 5 mM glucose, or both substrates. Oxidation rates were measured by 14CO2 release from 14C-labelled substrates. Cellular adenosine triphosphate was assayed using the luciferin/luciferase chemiluminescent method. The effects of sulphide (0-5 mM) on substrate oxidation and adenosine triphosphate levels and of increasing butyrate concentration (0-30 mM) with sulphide were observed. RESULTS: HT29 cells showed similar energy substrate usage to primary colonocyte cultures. Sulphide exposure inhibited butyrate oxidation and led to a reduction in cellular adenosine triphosphate. This fall was prevented by co-incubation with glucose, but not by increasing concentrations of butyrate. CONCLUSIONS: HT29 cells utilize butyrate as an energy substrate and represent a useful in vitro model of the effects of sulphide on colonocytes. Sulphide inhibits butyrate oxidation and leads to demonstrable energy deficiency, prevented by the presence of glucose but not by increased butyrate concentrations.

A comparison of roxatidine and ranitidine for the acute treatment of duodenal ulcer.

Roxatidine acetate is a new histamine H2-antagonist of about twice the potency of ranitidine on a weight-for-weight basis. Two hundred and thirty-two patients participated in a double-blind randomized trial of duodenal ulcer healing comparing 300 mg ranitidine nocte with 150 mg roxatidine nocte. Endoscopy was repeated fortnightly to 4 weeks in each of four participating centres. Usual exclusion criteria applied but NSAID users were allowed. There were no important demographic differences between treatment recipients. Three analyses were used: protocol (dropouts and violators not included), intention-to-treat I (dropouts considered failures), and intention-to-treat II (dropouts considered failures, but violators outcome included). Healing rates differed markedly (but not significantly) with each analysis. After 2 weeks of treatment ulcers had healed in 51% versus 45% using the intention to treat I analysis with roxatidine and ranitidine, respectively; by the protocol analysis the healing proportions were 60% and 55%. These differences between treatments were not significant. After 4 weeks of treatment healing rates ranged from 71% to 83% on roxatidine and between 69% and 84% on ranitidine depending on the analysis. Differential healing proportions of smokers and non-smokers were non-significant (83% vs. 79%). Both drugs were well tolerated and adverse events were similar with each agent. Roxatidine should prove as effective as ranitidine for acute duodenal ulcer treatment.

Twenty-four-hour intragastric acidity and clinical trial of bedtime enprostil 70 micrograms compared with ranitidine 300 mg in duodenal ulcer.

The effects of bedtime 70 micrograms and twice daily 35 micrograms doses of enprostil on 24-hour intragastric acidity were investigated in nine duodenal ulcer patients in remission. Median nocturnal acidity decreased significantly by 30% with 35 micrograms twice daily, and by 48% with 70 micrograms at bedtime. In a clinical trial using bedtime dosing, 102 duodenal ulcer patients randomly received either ranitidine 300 mg or enprostil 70 micrograms. More ulcers healed after 4 and 8 weeks treatment with ranitidine than with enprostil (76% ranitidine vs 52% enprostil, at 4 weeks p = 0.0065 and 94% vs 68%, respectively at 8 weeks, P = 0.0007). However, 6 months after cessation of treatment there was no material difference in overall outcome. Despite combining mucosal protection with acid inhibition enprostil treatment conferred no advantage over simple acid inhibition.

Effects of low cobalamin diet and chronic cyanide toxicity in baboons.

The effects of a low cobalamin (Cbl) diet, together with chronic cyanide or thiocyanate administration in some animals have been investigated in baboons over a period of 42 months. All animals remained healthy throughout the study and gained weight at a similar rate. None became anaemic or showed major haematological changes and there were no major neurological changes. Plasma total Cbl in the animals on the low Cbl diet fell within 9 months to values below the lower limit in man and were lowest at 24 months in baboons not receiving cyanide or thiocyanate. A striking feature in all animals, however, was an apparently seasonal increase in the plasma total Cbl each autumn with a corresponding decrease the following spring. This fluctuation was detected by radioisotopic assay but not by Euglena. Methylmalonic (MMA) excretion after oral valine ranged from 0.1--8.4 mg/24 h and was greatest in animals on the low Cbl diet and not receiving cyanide or thiocyanate. The results suggested an inverse relationship between MMA excretion and plasma total Cbl. Plasma thiocyanate was consistently higher in animals receiving cyanide or thiocyanate and at the end of the study plasma cyanide was highest in animals on the low Cbl diet receiving cyanide. The results support the suggestions that cyanide affects bodily handling of Cbl and that hydroxo-cobalamin plays a part in detoxication of cyanide.

Differential growth response to oestrogen of premalignant and malignant colonic cell lines.

Epidemiological and experimental evidence support a role for sex steroid hormones in colorectal cancer. The aims of this study were to determine expression of oestrogen receptor in adenoma derived and carcinoma derived colonic epithelial cell lines, and to determine the in vitro effect of beta oestradiol on growth. Between 0.5-1.5 fmol/mg protein of oestrogen receptor was expressed in the colonic cell lines studied. mRNA for oestrogen receptor was also expressed. An adenoma derived cell line, AA/C1, demonstrated an increase in growth rate in response to beta oestradiol. The effect was density dependent. The cell line AA/C1/SB10, a chemically transformed derivative of AA/C1, did not respond to beta oestradiol. Adenoma derived and carcinoma derived colonic cell lines express oestrogen receptor. Oestrogen may have a trophic action in vivo on premalignant colonic epithelium.