Bucillamine induces glutathione biosynthesis via activation of the transcription factor Nrf2

The properties of bucillamine, a synthetic antioxidant, have been attributed mainly to the donation of thiol groups to glutathione (GSH). We recently demonstrated that glutamate-cysteine ligase catalytic subunit (GCLC), the rate-limiting enzyme of GSH biosynthesis, and the multidrug-resistance-associated protein 2 (Mrp2/MRP2) are coordinately induced in response to xenobiotic through the activation of the antioxidant-response element (ARE) by nuclear factor-erythroid 2 p45-related factor (Nrf2). We tested the hypothesis that bucillamine and its oxidized metabolite SA 981 also activate the Nrf2 pathway, thereby increasing glutathione biosynthesis in human HepG2 and murine Hepa 1-6 hepatoma cell lines, through the induction of the GCLC enzyme as well as the Mrp2/MRP2 transporter, which mediates the excretion of glutathione and its conjugates from hepatocytes. Both bucillamine and SA 981 produced a significant dose-dependent increase in the mRNA levels of Mrp2/MRP2 and GCLC after 24 h. The levels of the transcription factor Nrf2 in the nuclei were maximal at 3 h, remained elevated at 6 h, and decreased to control values at 24 h in both cell lines. Moreover, both bucillamine and SA 981 significantly increased the expressions of Mrp2/MRP2 and GCLC proteins in both cell lines. Finally, in both cell lines, bucillamine and SA 981 increased the GSH content two- to three-fold. These results demonstrate that bucillamine and SA 981 activate the ARE-ARE pathway increasing the expression of ARE-driven genes such as those of GCLC and Mrp2/MRP2. The role of bucillamine as a chemopreventive agent against cancer remains to be elucidated.

Role of Nrf2 in the regulation of the Mrp2 (ABCC2) gene

The Nrf2 (nuclear factor-erythroid 2 p45-related factor 2) transcription factor regulates gene expression of the GCLC (glutamate-cysteine ligase catalytic subunit), which is a key enzyme in glutathione synthesis, and GSTs (glutathione S-transferases) via the ARE (antioxidant-response element). The Mrp2 (multidrug-resistance protein 2) pump mediates the excretion of GSH and GSSG excretion as well as endo- and xeno-biotics that are conjugated with GSH, glucuronate or sulphate. Considering that Mrp2 acts synergistically with these enzymes, we hypothesized that the regulation of Mrp2 gene expression is also dependent on Nrf2. Using BHA (butylated hydroxyanisole), which is a classical activator of the ARE-Nrf2 pathway, we observed an increase in the transcriptional activity of Mrp2, GCLC and Gsta1/Gsta2 genes in the mouse liver. A similar pattern of co-induction of Mrp2 and GCLC genes was also observed in mouse (Hepa 1-6) and human (HepG2) hepatoma cells treated with BHA, beta-NF (beta-naphthoflavone), 2,4,5-T (trichlorophenoxyacetic acid) or 2AAF (2-acetylaminofluorene), suggesting that these genes share common mechanism(s) of transcriptional activation in response to exposure to xenobiotics. To define the mechanism of Mrp2 gene induction, the 5'-flanking region of the mouse Mrp2 gene (2.0 kb) was isolated, and two ARE-like sequences were found: ARE-2 (-1391 to -1381) and ARE-1 (-95 to -85). Deletion analyses demonstrated that the proximal region (-185 to +99) contains the elements for the basal expression and xenobiotic-mediated induction of the Mrp2 gene. Gel-shift and supershift assays indicated that Nrf2-protein complexes bind ARE sequences of the Mrp2 promoter, preferentially to the ARE-1 sequence. Overexpression of Nrf2 increased ARE-1-mediated CAT (chloramphenicol acetyltransferase) gene activity, while overexpression of mutant Nrf2 protein repressed the activity. Thus Nrf2 appears to regulate Mrp2 gene expression via an ARE element located at the proximal region of its promoter in response to exposure to xenobiotics.

Differential expression of canalicular membrane Ca2+/Mg(2+)-ecto-ATPase in estrogen-induced and obstructive cholestasis in the rat

Extracellular adenosine triphosphate (ATP) may regulate hepatocyte and cholangiocyte functions, and under some conditions it may have deleterious effects on bile secretion and cause cholestasis. The canalicular membrane enzyme Ca2+/Mg2+-ecto-ATPase (ecto-ATPase) hydrolyzes ATP/adenosine diphosphate (ATP/ADP) and regulates hepatic extracellular ATP concentration. Changes in liver ecto-ATPase in estrogen-induced cholestasis were examined in male rats receiving 17alpha-ethinylestradiol (E groups) for 1, 3, or 5 days (5 mg/kg/day, sc) and compared with changes in rats subjected to obstructive cholestasis (O groups) for 1, 3, or 8 days. Activity of ecto-ATPase, protein mass in canalicular membranes and bile (estimated by Western blotting), steady state mRNA levels (by Northern blotting), and cellular and acinar distributions of the enzyme (histochemistry and immunocytochemistry) were assessed in these groups. Activity of ecto-ATPase, protein mass in isolated canalicular membranes, and enzyme mRNA levels were significantly increased in E group rats as compared with controls. In contrast, these parameters were markedly decreased in O group rats, and the enzyme protein was undetectable in bile. The ecto-ATPase histochemical reaction was markedly increased in the canalicular membrane of E group rats, extending from acinar zone 2 to zone 1, whereas it decreased in the O group. The ecto-ATPase immunocytochemical reaction was present in the canalicular membrane and pericanalicular vesicles in control and E group hepatocytes, but it decreased in obstructive cholestasis and was localized only to the canalicular membrane. Thus, significant changes in liver ecto-ATPase were apparent in 17alpha-ethinylestradiol-induced cholestasis that were opposite to those observed in obstructive cholestasis. Assuming that the alterations observed in obstructive cholestasis are the result of the cholestatic phenomenon, we conclude that changes in ecto-ATPase in 17alpha-ethinylestradiol-treated rats might be either primary events or part of an adaptive response in 17alpha-ethinylestradiol-induced cholestasis.

Induction of the multispecific organic anion transporter (cMoat/mrp2) gene and biliary glutathione secretion by the herbicide 2,4,5-trichlorophenoxyacetic acid in the mouse liver

The canalicular multispecific organic anion transporter, cMoat, is an ATP-binding-cassette protein expressed in the canalicular domain of hepatocytes. In addition to the transport of endo- and xenobiotics, cMoat has also been proposed to transport GSH into bile, the major driving force of bile-acid-independent bile flow. We have shown previously that the herbicide 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), a peroxisome-proliferator agent, significantly increases bile-acid-independent bile flow in mice. On this basis, the effect of the herbicide on cMoat gene expression was studied. A 3.6-fold increase in cMoat mRNA levels and a 2.5-fold increase in cMoat protein content were observed in the liver of mice fed on a diet supplemented with 0.125% 2,4,5-T. These effects were due to an increased rate of gene transcription (3.9-fold) and were not associated with peroxisome proliferation. Significant increases in bile flow (2.23+/-0.39 versus 1.13+/-0.15 microl/min per g of liver; P<0.05) and biliary GSH output (7.40+/-3.30 versus 2.65+/-0.34 nmol/min per g of liver; P<0.05) were observed in treated animals. The hepatocellular concentration of total glutathione also increased in hepatocytes of treated mice (10.95+/-0.84 versus 5.12+/-0.47 mM; P<0.05), because of the induction (2.4-fold) of the heavy subunit of the gamma-glutamylcysteine synthetase (GCS-HS) gene. This is the first model of co-induction of cMoat and GCS-HS genes in vivo in the mouse liver, associated with increased glutathione synthesis and biliary glutathione output. Our observations are consistent with the hypothesis that the cMoat transporter plays a crucial role in the secretion of biliary GSH.

Enhanced differentiation of HL-60 leukemia cells to macrophages induced by ciprofibrate

Ciprofibrate, an hypolipidaemic peroxisome proliferator, induced differentiation of HL-60 cells. The effect was greatly potentiated by phorbol 12-myristate 13-acetate at a concentration where neither phorbol ester nor ciprofibrate alone had any effect on these cells. As occurs for HL-60 cell differentiation induced by high phorbol ester concentration, the ciprofibrate-induced phorbol ester-dependent differentiation of HL-60 cells proceeded through the monocytic/macrophage pathway and induced the phosphorylation of proteins with similar molecular weights suggesting that increased protein kinase C activity may be involved in the effect. The peroxisome proliferator-activated receptor (PPARalpha) transcription factor is expressed in HL-60 cells, but no changes were observed in its expression upon HL-60 cell differentiation.

Genetic polymorphisms of CYP2D6, CYP1A1 and CYP2E1 in the South-Amerindian population of Chile

Polymorphisms of cytochrome P450 genes show pronounced interethnic variation and have not been previously studied in the South-Amerindian population, which probably has an Asian origin. Therefore, a similar distribution of allelic and haplotype frequencies of cytochrome P450 genes to Asian populations might be expected in South-Amerindians. We analysed the allelic frequencies and haplotype distribution for CYP2D6, CYP1A1 and CYP2E1 genes in the South-Amerindian population of Chile (Mapuche, n = 84) by Southern blot or polymerase chain reaction-restriction fragment length polymorphism. Similar allelic frequencies and haplotype distribution for the CYP2E1 gene between Mapuches and Asian populations were observed. Frequencies of the two major functional CYP2D6*1 and CYP2D6*2 alleles and the CYP2D6*5 null allele were similar to most populations world-wide. The alleles CYP2D6*3 and *9, absent in Asians, were not found in Mapuches. The CYP2D6*4 allelic group, uncommon in Asian populations, had a low frequency in Mapuches (0.036). However, the CYP2D6*10 allele (Ch1, Ch2 and J), highly frequent in Asians (0.33-0.50), had a very low frequency (0.018) in our study population. In addition, the presence of the common Chinese 44 kb XbaI fragment of CYP2D6 (0.19-0.31 in Asians) was not detected in South-Amerindians. Interestingly, high frequencies for the rare m2 and Val alleles of the CYP1A1 gene were found in Mapuches (0.821 and 0.91, respectively), and the rare Val/m2 haplotype was significantly higher in Mapuches (0.748) than in Asians (0.24) (P < 0.01). The frequency of this haplotype in Mapuches is the highest frequency reported to date. The population studied was in Hardy-Weinberg equilibrium for these polymorphisms. The major differences between Mapuches and Asians were for CYP2D6*10 and CYP1A1 allelic frequencies, as well as the absence of the common Chinese 44 kb XbaI fragment of CYP2D6. These differences might be interpreted as a consequence of genetic drifts caused by a founder effect in the settlement of South-Amerindians, or genetic selection caused by dietary or environmental factors.

[Intrasphincteric injection of botulinum toxin in patients with esophageal achalasia]

BACKGROUND

Intrasphincteric injection of botulinum toxin (BoTx) has demonstrated to be effective in the short-term treatment of achalasia.

AIM

To assess the efficacy, safety and long-term outcome of BoTx injection into the lower esophageal sphincter (LES) of patients with achalasia.

PATIENTS AND METHODS

Eight patients received 80 units of BoTx. Assessment of response was based on changes in the symptom scores (0-9) and esophageal manometric studies.

RESULTS

Six out of 8 patients (75%) had sustained clinical improvement after therapy. This effect was maintained for a mean time of 17.8 months. The symptom score decreased from a mean of 6.7 to 0.5 (p < 0.01) and after treatment, LES pressure decreased from 63 to 25.5 mm Hg (p = 0.07). There were no serious adverse effects. Five of the six responders have relapsed. Two of these patients received a second BoTx injection with satisfactory results, two went to surgery and one refused other type of therapy and died of pneumonia.

CONCLUSIONS

Intrasphincteric BoTx injection is a simple, safe and effective method of treatment in patients with achalasia, with a duration of response averaging 1.5 years. Its use may be suggested in some patients with high surgical risk and those who refuse a more invasive therapy. It is also useful in malnourished patients to attain an adequate nutritional status before surgery.

Overexpression of mdr2 gene by peroxisome proliferators in the mouse liver

BACKGROUND

In mice, fibrates induce mdr2 gene expression, and its encoded P-glycoprotein in the canalicular domain of hepatocytes, as well as increasing biliary phospholipid output. It is not known whether this effect is restricted to fibrates or is a common property of peroxisome proliferators.

AIMS

To test the effect of structurally unrelated peroxisome proliferators on mdr2 gene expression and biliary phospholipid output, and to explore the molecular mechanism(s) of mdr2 gene induction.

METHODS

Male CFI mice were fed on a diet supplemented with several peroxisome proliferators: phenoxyacetic acid herbicides, plasticizers, acetylsalicylic acid and partially hydrogenated fish oil.

RESULTS

Increased levels of mdr2 mRNAs, assessed by Northern blot analysis, were observed in the liver of mice treated with phenoxyacetic acid herbicides: 2,4,5-trichlorophenoxyacetic acid 570+/-133%, 2,4-dichlorophenoxyacetic acid 233+/-54% (p<0.005); plasticizers: di-(2-ethylhexyl)phthalate 282+/-78%, di-(isoheptyl)phthalate 163+/-40%, phthalic acid dinonyl ester 225+/-48% (p<0.01); and partially hydrogenated fish oil 372+/-138% (p<0.005). P-glycoprotein traffic ATPase content increased in the canalicular domain of hepatocyte of mice treated with the herbicide 2,4,5-trichlorophenoxyacetic acid and with partially hydrogenated fish oil (108% and 87%, respectively, p<0.05) as well as biliary phospholipid output (106% and 74%, respectively, p<0.05). In 2,4,5-trichlorophenoxyacetic acid-fed mice we found five-fold increase on mdr2 transcription rate, assessed by nuclear run-off assay.

CONCLUSIONS

Peroxisome proliferators induce mdr2 gene, its encoded P-gp in the canalicular domain of hepatocytes and increase biliary phospholipid output. The modulation of mdr2 gene might be part of the pleiotrophic response of peroxisome proliferation in mice liver and seems to be regulated mainly at a transcriptional level.

[Semiquantitative histopathologic analysis of chronic gastritis: extension and grading score]

Three endoscopic systematic biopsies were obtained from 261 patients showing chronic gastritis. Histopathologic features of chronic gastritis were graded from 0 to 3 points according to the Sydney System. In addition, an extension and grading histopathologic score was applied. This score was obtained from the sum of qualified grades for each feature in all three samples. Inflammation, activity, atrophy, and intestinal metaplasia were predominantly grade 1 and H pylori density was predominantly grade 2. Only 2.6% of the sections without atrophy showed intestinal metaplasia, while 79.3% of the sections depicting grade 2-3 intestinal metaplasia showed moderate to severe atrophy. Inflammation was more severe in the antral lesser curvature and the more severe atrophy was present in the antrum than in the corpus mucosa. Sydney System and extension and grading histopathologic score showed more extensive activity in patients older than 45 years. A lower histopathologic score of H pylori was seen in these patients. The presence of H pylori was directly correlated with inflammation severity and inversely with atrophy. These results, in accordance with data shown in the literature, suggest that the Sydney System and the extension and grading histopathologic score can be applied to compare chronic gastritis features in different groups of patients.

Modulation of hepatic content and biliary excretion of P-glycoproteins in hepatocellular and obstructive cholestasis in the rat

BACKGROUND/AIMS

Release into bile of canalicular membrane enzymes, such as alkaline phosphatase and gamma-glutamyl transpeptidase, is significantly increased in rats subjected to experimental models of hepatocellular or obstructive cholestasis. This effect appears to be related to a greater susceptibility of these membrane intrinsic proteins to the solubilizing effects of secreted bile acids. It is not known whether canalicular membrane transport proteins, such as P-glycoprotein isoforms, involved in ATP-dependent xenobiotic biliary excretion and phospholipid secretion, are excreted into bile and whether this process is modified in cholestasis. The aims of this work have been to investigate in the rat: a) whether P-glycoproteins are normally excreted into bile, b) whether their excretion is modified in two experimental models of cholestasis, i.e., hepatocellular cholestasis induced by ethynylestradiol and obstructive cholestasis, and c) whether observed changes correlate with bile acid and phospholipid secretion and enzyme release into bile and with relative P-glycoprotein content in hepatic tissue and isolated and purified canalicular membranes.

METHODS

P-glycoproteins in bile and hepatic tissue were identified and quantitated by Western-blotting and immunohistochemistry using the C219 MAb. Changes in total mdr mRNA were analyzed by Northern-blotting.

RESULTS

Like canalicular membrane enzymes, P-glycoproteins are normally excreted into bile. Ethynylestradiol-induced cholestasis was associated with a 4.9-fold increase in P-glycoprotein excretion compared with controls while, in contrast, the excretion of the carrier decreased markedly in obstructive cholestasis to 2% of control values. P-glycoprotein excretion per nmol of secreted bile acids increased 4.4-fold in ethynylestradiol-induced cholestasis but decreased to 2% of control values in obstructive cholestasis. Total mdr mRNA levels in hepatic tissue were markedly increased (3.4-fold) in rats subjected to obstructive cholestasis and moderately increased (1.6-fold) in the ethynylestradiol group, compared with controls. P-glycoprotein content in isolated canalicular membranes was slightly decreased by 15% in ethynylestradiol-induced cholestasis, while it increased 4.7-fold in obstructive cholestasis. Immunohistochemistry of rat livers showed that P-glycoprotein reaction at the canalicular domain of hepatocytes at acinar zone 1 was decreased in ethynylestradiol-treated rats and markedly increased in obstructive cholestasis.

CONCLUSIONS

Ethynylestradiol-induced cholestasis is associated with increased P-glycoprotein biliary excretion and decreased hepatic content. In contrast, obstructive cholestasis results in decreased P-glycoprotein biliary excretion and increased hepatic content. These results suggest that biliary P-glycoprotein excretion might be a modulating factor in canalicular membrane P-glycoprotein content. Increased P-glycoprotein release into bile in ethynylestradiol-treated rats is apparently not a consequence of cholestasis, but it might be a primary event and play a pathogenetic role in ethynylestradiol-induced cholestasis.

[Frequency and histopathologic features of chronic gastritis in 300 patients without endoscopic lesions]

Three gastric mucosal biopsies were obtained from 300 patients showing a normal upper digestive tract endoscopy. Histologically, in 9% of the patients the biopsies were normal: in 87%, showed a common-type chronic gastritis, and in 4% showed a reactive (chemical or reflux-type) gastritis. Helicobacter pylori was present in 25.9% of the patients without gastritis, in 33.3% of the patients with reactive gastritis, and in 87.7% of those with common-type gastritis. In 19.9% of the patients with common-type chronic gastritis there was intestinal metaplasia, consisting of type I metaplasia in 14.1%, type II in 3.1% and type III metaplasia in 2.3%. The association of type III intestinal metaplasia with the other forms of metaplasia, its lower frequency and its tendency to be present in older patients supports the hypothesis that type III incomplete colonic metaplasia represents a more advanced stage than complete and incomplete small bowed metaplasia of the gastric mucosa.

Fibrates induce mdr2 gene expression and biliary phospholipid secretion in the mouse

Disruption of the murine mdr2 gene leads to the complete absence of biliary phospholipids. We tested the hypothesis that the increase in biliary phospholipid output induced by fibrates is mediated via induction of the hepatic mdr2 gene and its encoded product, the P-glucoprotein canalicular flippase. Increased levels of mdr2 mRNA were observed in the liver of mice treated with different fibrates: ciprofibrate, 660+/-155% (as compared with control group); clofibrate, 611+/-77%; bezafibrate, 410+/-47%; fenofibrate, 310+/-52%; gemfibrozil, 190+/-25% (P <0.05 compared with control group). Induction of expression of the mdr gene family was specific to the mdr2 gene. Two- to three-fold increases in P-glycoprotein immunodetection were evident on the canalicular plasma-membrane domain of clofibrate- and ciprofibrate-treated mice. Biliary phospholipid output increased from 4.2+/-1.2 nmol/min per g of liver in the control group to 8.5+/-0.6, 7.1+/-2.9 and 5.8+/-2.5 in ciprofibrate-, clofibrate- and bezafibrate-treated mice respectively (P <0.05 compared with control group). Moreover, a significant correlation between biliary phospholipid output and the relative levels of mdr2 mRNA was found (r=0.86; P <0.05). In treated animals, bile flow as well as cholesterol and bile acid outputs remained unchanged. Our findings constitute the first evidence that pharmacological modulation of biliary lipid secretion mediated by fibrates can be related to the overexpression of a specific liver gene product, the mdr2 P-glycoprotein, and are consistent with the hypothesis that the mdr2 P-glycoprotein isoform plays a crucial role in the secretion of biliary phospholipid.

Differences between nuclear run-off and mRNA levels for multidrug resistance gene expression in the cephalocaudal axis of the mouse intestine

P-glycoprotein is a multidrug transporter encoded by the mdr3 gene in the mouse intestinal epithelium. The aims of this study were to characterize the mdr3 gene expression in the cephalocaudal axis of the intestine in adult animals and during perinatal development, and to define the molecular mechanism responsible for the heterogeneous expression of the gene along the cephalocaudal axis. RNA extracted from stomach, duodenum, jejunum, ileum, cecum and colon was hybridized by slot blot and Northern blot using a mdr3 cDNA probe. The regulation of gene expression was investigated examining the rate of transcription by nuclear run-off analysis. Transport studies of rhodamine 123, a substrate of P-glycoprotein, were performed in everted jejunum and ileum. The level of mdr3 mRNA and P-glycoprotein found in ileum was 6-fold higher than the level found in duodenum. The regional pattern of mdr3 gene expression is established in the intestine of 10-day-old animals. Similar mdr3 hybridization signal in nuclear run-off assay was found in nuclei of enterocytes isolated from jejunum and ileum, suggesting that the heterogeneous expression of the mdr3 gene in the cephalocaudal axis of the small bowel may be predominantly regulated at the post-transcriptional level. Transport rate of rhodamine 123 from the serosal to mucosal side in everted ileum was higher than the rate of transport found in jejunum. These results indicate that enterocytes of the ileum may be more actively involved in the P-glycoprotein-mediated transport of xenobiotics into the intestinal lumen.

Endoscopic intrasphincteric injection of botulinum toxin for the treatment of achalasia

Three patients with achalasia were treated with endoscopic injection of botulinum toxin (BoTx). BoTx (80 U) was injected via a sclerotherapy needle into the lower esophageal sphincter (LES). One patient complained of transient heartburn that resolved after omeprazole treatment. Two patients reported sustained symptomatic improvement. They were able to eat normally 48 h after treatment and have remained symptom free for 5 and 6.5 months, respectively. In these patients, esophageal manometry 4 months after treatment showed a marked reduction of resting LES pressure and the appearance of a previously absent LES relaxation after swallowing. The third patient had only a transient clinical improvement, with occasional dysphagia beginning 3 months after treatment. All patients showed unchanged aperistalsis of the esophageal body. Its less invasive nature compared with other therapeutic alternatives may give BoTX injection a role in the treatment of some patients with achalasia.

Effect of colchicine and heat shock on multidrug resistance gene and P-glycoprotein expression in rat liver

The multidrug resistance genes encode plasma membrane glycoproteins named P-glycoproteins, that act as an ATP-dependent drug efflux pump and decrease the cytosolic concentration of chemotherapeutic agents. It has been hypothesized that in rat liver, this protein may have a physiological role as a biliary transporter of xenobiotics and endobiotics. Some human tumor cell lines turn on the human multidrug resistance gene in response to high temperature and after exposure to toxic chemicals. Accordingly, it has been proposed that the human multidrug resistance gene is a heat shock gene. We have assessed whether two environmental stresses, heat shock or acute exposure to cytotoxic drugs (colchicine, vincristine, vinblastine and daunomycin), induce changes in the expression of multidrug resistance genes in the rat. Total cellular RNA extracted from rat liver was hybridized to a labeled human multidrug resistance gene cDNA probe. Temperature upshift did not increase the steady-state of mdr mRNA levels in the tissues studied, suggesting that the mdr genes are not activated as part of a heat shock response. The mdr mRNA levels increased in rat liver as early as 3 h after a single injection of colchicine, reached a peak (500%; p < 0.05) after around 24 h and returned to constitutive levels after 48 h. Changes in the relative content of mdr mRNA were not detected in kidney, adrenal gland and small bowel, suggesting that the in vivo induction of the mdr gene in the liver is a tissue-specific response. The other cytotoxic drugs that were tested did not increase the steady-state of mdr mRNA levels.(ABSTRACT TRUNCATED AT 250 WORDS)

[Treatment of non-variceal upper digestive hemorrhage with endoscopic thermocoagulation]

Over a year period, 60 of 172 patients presenting with upper gastrointestinal bleeding were treated by endoscopic thermocoagulation. Entry criteria included active bleeding (pulsatile or oozing), a visible vessel, sentinel clot or the presence of a pigmented protuberance at the ulcer crater. Hemostatic therapy was performed using the heat probe. The physical status and risk of the patients was estimated according to the ASA classification. Hemostasis was obtained in 17 of 21 patients with pulsatile bleeding (81%), 30 of 30 patients with oozing (100%) and 18 of 18 patients with a visible vessel or a pigmented protuberance in the lesion (100%). Three patients, older than 70 years of age, died. All had pulsatile bleeding from a deep ulcer located at the posterior-inferior wall of the duodenal bulb. They were classified as ASA III (n = 1) or IV (n = 2) with significant concomitant illness. These results suggest that endoscopic thermocoagulation is an effective treatment of active upper gastrointestinal bleeding, especially useful in a group of high risk patients.

Multidrug resistance gene and P-glycoprotein expression in gastric adenocarcinoma and precursor lesions

Overexpression of the Multiple Drug Resistance gene (MDR1) has been proposed as a major mechanism related to both intrinsic and acquired resistance to chemotherapeutic agents. The gene product is a membrane protein (P-glycoprotein), that acts as an energy-dependent drug efflux pump decreasing drug accumulation in resistant tumor cells. We have characterized MDR1 and P-Glycoprotein expression in human gastric adenocarcinoma and in precursor lesions. MDR1 mRNAs, analyzed by dot-blot technique, were detected in 9 of 10 non-tumoral gastric mucosae and in 8 of 10 gastric adenocarcinomas. Immunohistochemical analysis, using the MRK16 monoclonal antibody, revealed heterogeneous expression of P-Glycoprotein in individual cells. The P-Glycoprotein was found on the surface of cells of gastric areas with intestinal metaplasia subtype III. This type of intestinal metaplasia, also called "colonic metaplasia", has been strongly associated with a high risk for the development of gastric cancer. The fact that the P-Glycoprotein was detected in this precursor lesion is consistent with the intestinal metaplasia-dysplasia and carcinoma sequence proposed in the histogenesis of this tumour. The finding that P-Glycoprotein was heterogeneously expressed in malignant cells of some gastric adenocarcinomas also suggests that this transporter system probably contributes to primary and secondary multidrug resistance in this neoplasm.

[Gallbladder cancer mortality in Chile and its relation to cholecystectomy rates. An analysis of the last decade]

Extrahepatic biliary tract cancer (mainly gallbladder cancer) mortality rates have increased from 7.84 x 100.000 to 9.6 x 100.000 in Chile during the last decade. The most significant risk factor for gallbladder cancer is gallstone disease. However, no apparent changes in the prevalence of gallstone disease has occurred during this period. In contrast, cholecystectomy rates have consistently decreased during the decade. The aim of this study was to correlate extrahepatic biliary tract cancer mortality and cholecystectomy rates of previous years during the last decade in our country. The best correlation coefficient between both variables was obtained when mortality was correlated with cholecystectomy rates two years prior to the mortality rate (r = -0.92). This finding is consistent with the hypothesis that changes in the number of cholecystectomies performed in a specific geographic area would reciprocally change gallbladder cancer mortality rate. It was estimated that increasing cholecystectomies by 12,500 per year would decrease at mortality rate from this cancer by approximately 1.0 x 100.000 two years in Chile.

[The impact of molecular biology in medicine]

Over 30 years ago the genetic material of most organisms was shown to be deoxyribonucleic acid. A considerable amount of information on the fine structure and function of cells has accumulated during this time and important methodological and conceptual advances have occurred. The molecular biology techniques, restricted for many years to basic biologic research, are now being introduced in several areas of clinical medicine. These new ideas are changing the way scientists and physicians think about normal cell function and disease. The DNA recombinant methods allow us to define the molecular mechanisms of several genetic diseases and consider new therapeutic approaches. The biotechnological industry is now producing hormones, peptides and several vaccines by manipulation of genes in bacteria and cell cultures. Our understanding of cell growth and cell differentiation is opening new ways in cancer research; the use of DNA probes in the diagnostic laboratory is exciting to the clinical microbiologist. Molecular biology will continue to advance in the next decades with increasing economic, social and ethical implications.

Demonstration by in situ hybridization of the zonal modulation of rat liver cytochrome P-450b and P-450e gene expression after phenobarbital

The various physiological processes that constitute liver function are compartmentalized within the hepatic acinus. The molecular mechanisms modulating the development and maintenance of this hepatocyte heterogeneity have not been defined. The objective of this study was to determine whether transcriptional or posttranscriptional zonal modulation of cytochromes P-450b,e gene expression was responsible for the heterogeneous induction of the P-450 proteins, which is observed after phenobarbital (PB) administration. The exact localization in liver tissue of hepatocytes responding to PB with induction of either P-450b,e mRNA or proteins was established by in situ hybridization and by immunofluorescence, respectively. As demonstrated by quantitative assessment of autoradiographs of approximately 20 hepatocytes located between a terminal portal venule and a hepatic venule, PB induced the P-450b,e mRNA up to sixfold in the 12-15 hepatocytes located closer to the hepatic venules (zones 2 and 3). In contrast, there was only a twofold induction in the 4-6 hepatocytes surrounding the terminal portal venules (zone 1). Quantitative immunofluorescence using an MAb showed that the acinar distribution of PB-induced P-450b,e proteins was similar to that of the mRNA. This combined approach indicated that, most likely, an increased rate of transcription of cytochromes P-450b,e genes in hepatocytes of zones 2 and 3 concomitantly, with a relative lack of activation, or repression, of these genes in hepatocytes of zone 1, were responsible for the heterogeneous phenotype observed after PB administration. Therefore, modulation of gene expression among hepatocytes of the liver acinus is one mechanism by which the functional heterogeneity of hepatocytes is attained. Experiments in which the induction of cytochromes P-450b,e genes was studied after administration of either PB or para-hydroxyphenobarbital, a main hepatic metabolite of PB, suggested that the species involved in the inductive process is the parent PB molecule rather than para-hydroxyphenobarbital.

Expression of cytochrome P450b and P450e genes in small intestinal mucosa of rats following treatment with phenobarbital, polyhalogenated biphenyls, and organochlorine pesticides

The expression of cytochromes P450b and P450e genes was studied in the small intestinal mucosa of rats using a cDNA which recognizes the mRNAs of both cytochromes as well as oligonucleotide probes which are able to differentiate between the two gene products. Animals were treated with oral and intraperitoneal doses of phenobarbital, gamma-chlordane, trans-non-achlor, and polychlorinated and polybrominated biphenyls. RNA was extracted from small intestinal mucosa and liver. After treatment with each of the compounds, P450b mRNA was markedly induced in small intestinal mucosa and in liver. The greatest degree of induction was found in mucosa of the proximal small intestine where P450b mRNA levels were 4-6-fold higher than levels found in the distal small intestine. This distribution of P450b mRNA was not dependent on the route of administration of inducers. In contrast, although P450e mRNA was induced in the liver after treatment, P450e mRNA in the small intestine did not increase in response to any of the administered inducers. The location of the P450b mRNA within the intestinal mucosa following treatment with inducers was studied by in situ hybridization; the message was induced predominantly in enterocytes located in intestinal villi. These data indicate that the P450b gene is induced in the small intestine following treatment with various xenobiotics and that this induction may be secondary to either transcriptional activation of the gene or to mRNA stabilization in enterocytes located in the villi of the intestinal mucosa. The differential induction of P450b versus P450e genes in the small intestine and liver indicates that the regulation of these closely linked genes is tissue-specific. Furthermore, the marked induction of P450b mRNA in response to the administered xenobiotics indicates that this isoenzyme may have an important biological role in the small intestinal metabolism of environmental toxicants and drugs.

Phenobarbital induction of cytochrome P-450 b,e genes is dependent on protein synthesis

Phenobarbital induces liver cytochrome P-450 b,e proteins mainly by increasing the rate of transcription of these genes. The mechanism responsible for the phenobarbital increment in the rate of transcription of cytochrome P-450 b,e genes is unknown. The objective of this study was to assess whether active protein synthesis was needed for phenobarbital to induce the liver cytochrome P-450 b,e genes. Cycloheximide (2 mg per kg, i.p.) was administered 90 min prior to a single inductive dose of phenobarbital (80 mg per kg, i.p.) and mRNAS measured at 3, 6 and 12 hr by dot-blot hybridization. While phenobarbital increased cytochrome P-450 b,e mRNAs about 12-fold at 3 hr, this induction was abolished by cycloheximide. To define whether the absence of protein synthesis in hepatocytes inhibited the phenobarbital induction of cytochrome P-450 at the transcriptional level, in vitro transcription rates using isolated nuclei were measured. After phenobarbital administration, there was about a 20-fold increment in transcriptional rate of cytochrome P-450 b,e genes. This increment was abolished by prior injection of cycloheximide. It is proposed that either preexisting regulatory proteins or transacting factors dependent on active protein synthesis participate in the regulation of liver cytochrome P-450 b,e gene transcription after phenobarbital.

Cytochrome P-450 gene expression in the functional units of the fetal liver

Hepatocytes of the right and left lobes of the fetal liver are surrounded by different microenvironments. The right and left lobes of the fetal liver are perfused by vascular systems carrying different concentrations of oxygen and constitute distinct functional units. The aim of this study was to assess the expression of the phenobarbital-inducible cytochrome P-450 b,e genes in hepatocytes of the right and left fetal liver lobes in mice. Northern-blot analysis using [32P]cDNAs and quantitative dot-blot hybridization were performed to assess the size and levels of these mRNAs in the right and left fetal liver lobes. In fetal mice, the levels of cytochrome P-450, b,e mRNAs were higher in the left than in the right fetal liver lobe. During the last days of gestation and in the immediate postnatal period, the levels of liver cytochrome P-450 b,e mRNAs increased predominantly in the left liver lobe. In contrast, the levels of albumin and alpha-fetoprotein mRNAs (genes studied to assess the specificity of these findings) were similar in each of functional units of the fetal liver. Phenobarbital induction of cytochromes P-450 b,e mRNAs was not observed in either of the fetal liver lobes. Postnatally, phenobarbital induced these cytochromes similarly in the right and left liver lobes. Therefore, the microenvironment surrounding fetal hepatocytes seems to influence the expression of the cytochrome P-450 b,e genes. This lobar heterogeneity of expression disappears as the pattern of adult liver circulation is attained.

Heterogeneous expression of phenobarbital-inducible cytochrome P-450 genes within the hepatic acinus in the rat

Within the hepatic acinus, the functional unit of liver parenchyma, the induction of cytochrome P-450 protein by phenobarbital is manifested primarily in hepatocytes located closer to the hepatic venule, i.e., distal hepatocytes. The objective of this study was to determine the levels of cytochromes P-450b and P-450e mRNAs in populations of hepatocytes originating in the proximal or distal half of the liver acinus in the rat, as an approach to the elucidation of the mechanisms responsible for the heterogeneous zonal expression of cytochrome P-450 protein. The development of a new method to isolate hepatocytes originating from the proximal or distal half of the liver acinus enabled the measurement of total cytochrome P-450 content and of cytochromes P-450b and P-450e mRNAs in these hepatocytes. Levels of cytochromes P-450b and P-450e mRNAs were assessed in proximal and distal hepatocytes by Northern blot hybridization of poly(A+)RNA with a cDNA recognizing sequences of these two cytochromes. The kinetics of induction were defined by measuring these parameters after a single phenobarbital injection. Cytochrome P-450 mRNA levels reached maximum induction at 16 hr, returning to basal values by 48 hr. In contrast, total cytochrome P-450 microsomal protein content reached maximum induction after 33 hr. Hepatocytes of the distal half of the hepatic acinus responded to phenobarbital with higher levels of cytochromes P-450b and P-450e mRNAs than proximal hepatocytes. These results indicated that there is modulation of the expression of the cytochromes P-450b and P-450e genes within the hepatic acinus.

The isolation of functionally heterogeneous hepatocytes of the proximal and distal half of the liver acinus in the rat

The objective of this study was to isolate hepatocytes of the proximal half (Zones 1 and 2) or distal half (Zones 2 and 3) of the liver acinus. The zonal origin of the isolated hepatocytes was recognized by: the presence in hepatocytes of a fluorescent marker, acridine orange, selectively delivered to either the proximal or the distal half of the acinus by in situ perfusion prior to cell isolation and the measurement of the induction of cytochrome P-450 by phenobarbital, an induction known to occur predominantly in the distal half of the acinus. Following the selective labeling of the acinus with acridine orange, livers were perfused with collagenase in either the portal to hepatic vein direction (anterograde) or in the retrograde direction. Hepatocytes isolated by either an anterograde or a retrograde perfusion were separated by centrifugation in a Percoll density gradient. This procedure isolated populations of proximal or distal hepatocytes, respectively, which were intact and 90% fluorescent. In an effort of assessing the heterogeneity of the separated proximal and distal hepatocytes, each population was further fractionated by centrifugal elutriation. This resulted in the arbitrary separation of proximal or distal hepatocytes into five fractions. Total cytochrome P-450 was determined spectrophotometrically in each of the fractions isolated from controls and after 3 days of the in vivo administration of phenobarbital. On the basis of the pattern of fluorescence in isolated hepatocytes and on the cytochrome P-450 inductive response to phenobarbital administration, it is proposed that: the anterograde or retrograde perfusion of the liver with collagenase separated hepatocytes predominantly of the proximal or distal half of the liver acinus, respectively and that hepatocytes of the distal half of the liver acinus responded to phenobarbital administration with the highest level of cytochrome P-450 induction, indicating that the isolated hepatocytes conserved the functional heterogeneity observed in vivo.