Effect of Helicobacter pylori infection and acid blockade by lansoprazole on clarithromycin bioavailability

The effect of proton pump inhibitors and Helicobacter pylori infection on the bioavailability of antibiotics is poorly understood. We determined the effects of 5-day oral administration of 60 mg lansoprazole on the bioavailability of clarithromycin in individuals with and without H. pylori infection. Thirteen H. pylori-infected and 10 non-infected healthy volunteers were enrolled in a study with an open-randomized two-period crossover design and a 21-day washout period between phases. Plasma concentrations of clarithromycin in subjects with and without lansoprazole pre-treatment were measured by liquid chromatography coupled to a tandem mass spectrometer. Clarithromycin Cmax and AUC0-10 h were significantly reduced after lansoprazole administration. In addition, lansoprazole treatment of the H. pylori-positive group resulted in a statistically significant greater reduction in Cmax (40 vs 15%) and AUC0-10 h (30 vs 10%) compared to lansoprazole-treated H. pylori-negative subjects. Thus, treatment with lansoprazole for 5 days reduced bioavailability of clarithromycin, irrespective of H. pylori status. This reduction, however, was even more pronounced in H. pylori-infected individuals.

Analysis of DNA damage induced by aflatoxin B1 in Dunkin–Hartley guinea pigs

Aflatoxin B1 (AFB1) is among the most potent naturally occurring carcinogens and classified as a group I carcinogen. Since the ingestion of aflatoxin-contaminated food is associated with several liver diseases, the aim of the present study was to evaluate the effect of 2, 20, and 200 ppb of AFB1 on DNA damage in peripheral blood lymphocytes and liver cells in Dunkin-Hartley guinea pigs. The animals were divided into four groups according to the given diet. After the treatment the lymphocytes and liver cells were isolated and DNA damage determined by Comet assay. The levels of DNA damage in lymphocytes were higher animals treated with 200 ppb of AFB1-enriched diet (P = 0.02). In the liver cells there were a relationship between the levels of DNA damage and the consumption of AFB1 in all studied groups. These results suggest that Comet assay performed on lymphocytes is a valuable genotoxic marker for high levels of exposure to AFB1 in guinea pig. Additionally our results indicate that the exposure to this toxin increases significantly and increases the level of DNA damage in liver cells, which is a key step on liver cancer development. We also suggest that the Comet assay is an useful tool for monitoring the genotoxicity of AFB1 in liver.

17-β-Estradiol upregulates COX-2 in the rat oviduct

We investigated the regulation of cyclooxygenase-2 (COX-2) by 17-beta-estradiol (E2) in the rat oviduct. We observed that COX-2 is expressed mainly in proestrous and estrous stages, periods under estrogenic influence. While exogenous administration of E2 (1 microg/rat) significantly increased COX-2 protein levels, progesterone did not modify it. COX-2 was mainly localized on oviductal epithelial cells from estrogenized rat. Induction of COX-2 expression by E2 was partially reverted by tamoxifen (1 mg/rat), an E2 receptor antagonist. Estradiol treatment also increased prostaglandins (PGs) synthesis: 6-keto-PGF(1alpha) (40%), a stable metabolite of prostacyclin (PGI2), PGF(2alpha) (40%) and PGE2 (50%). Tamoxifen completely suppressed this enhancement. In order to discriminate which isoform of COX was implicated in the stimulatory effect of E2 on PGs synthesis, oviducts were preincubated with meloxicam (Melo: 10(-9)M) or NS-398 (10(-7)M), two selective COX-2 inhibitors. Both Melo and NS-398 abolished the increase of PGs synthesis stimulated by E2. All together, these data indicate that E2 could upregulate COX-2 expression and activity in the rat oviduct and that the stimulatory effect of E2 may be receptor-mediated.

Nitric oxide (NO) inhibits prostaglandin E2 9-ketoreductase (9-KPR) activity in human fetal membranes

Nitric oxide (NO) synthesized by fetal membranes may act either directly inhibiting myometrium contractility or indirectly interacting with tocolytic agents as prostaglandins (PGs). Here we examined if NO could modulate prostaglandin E(2) 9-ketoreductase (9-KPR) activity in human fetal membranes (HFM). 9-KPR is the enzyme that converts PGE(2) into PGF(2alpha), the main PGs known to induce uterine contractility at term. Chorioamnion explants obtained from elective caesareans were incubated with aminoguanidine (AG), an iNOS inhibitor, or NOC-18, a NO donor. NOC-18 (2mM) increased PGE(2) production and diminished PGF(2alpha) synthesis in HFM. AG presented the opposite effect. When we evaluated the activity of 9-KPR by the conversion of [(3)H]-PGE(2) into [(3)H]-PGF(2alpha) and 13,14-dihidro-15-keto prostaglandin F(2alpha) (the PGF(2alpha) metabolite), we found that NOC-18 inhibited 9-KPR activity. Interestingly, AG did not elicit any effect on 9-KPR but l-NAME, a non-selective NOS inhibitor, significantly increased its activity. Our data suggests that exogenous NO inhibits 9-KPR activity in HFM, thus modulating the synthesis of important labor mediators as PGF(2alpha).

Effect of in vivo administration of epidermal growth factor on prostaglandin production and NOS activity in term rat placentae. Possible participation of placental EGF receptors

Many authors hypothesize that the epidermal growth factor (EGF) is involved in the onset of labor. Previous reports from our laboratory showed that intrauterine administration of EGF delays the beginning of labor. The aims of this study were: 1) to analyze the effect of intrauterine administration of 500 ng EGF on placental prostaglandins and nitric oxide, and 2) to characterize the expression of EGF receptors (EGF-R) in pregnant rat placentae. Saline solution (sham group) and 500 ng EGF (EGF-treated group) were administered via intrauterine injection on day 21 of gestation, and both groups of animals were sacrificed on day 22 (sham rats delivered on day 22). Results showed that EGF treatment: 1) inhibited the production of prostaglandin E (p<0.001) and F(2alpha) (p<0.01), 2) increased the synthesis of nitric oxide (p<0.001), and 3) reduced the expression of cyclooxygenase-II, the enzyme responsible for PG synthesis. Placentae were found to express EGF-R and its activated form, and the expressions of both forms were higher at mid and term pregnancy. Hence, EGF is a very interesting molecule for studying the regulation of placental prostaglandin and nitric oxide production related to the parturition process.

Epidermal growth factor prevents prepartum luteolysis in the rat

We have previously reported that intrauterine (i/u) administration of epidermal growth factor (EGF 500 ng) on day (d) 21 of pregnancy delayed 19.0 +/- 0.6 h the onset of labor. Progesterone (P) is secreted by ovarian corpora lutea (CL) throughout gestation in the rat. Prepartum CL regression due to increased uterine cyclooxygenase I and prostaglandin F(2alpha) results in P withdrawal followed by labor. The aims of the present work were (i) to study whether EGF delayed-onset of labor was mediated by a mechanism that prevented CL regression; (ii) to determine amniotic fluid (AF) EGF in pregnant rats. Rats on d21 of pregnancy received i/u EGF (500 ng) and were killed 0, 4, 8, 12, 24, and 48 h later. Control AF from rats on d13 and 18-22 of pregnancy was obtained. EGF decreased uterine prostaglandin F(2alpha) synthesis 8 h after treatment. Twelve hours after EGF injection, P reached its highest serum level and uterine cyclooxygenase I expression was undetectable. CL from rats killed 8 and 12 h after EGF were similar to those from rats on d13 of pregnancy, when serum P is maximum. EGF in AF increased throughout gestation, reached a maximum on d21, and decreased before the onset of labor. We suggest that the effect of EGF on the onset of labor was mediated by an early effect on the uterus that prevented prepartum CL regression.

New once-daily, highly effective rescue triple therapy after multiple Helicobacter pylori treatment failures: a pilot study

BACKGROUND

Helicobacter pylori treatment failure is a growing problem in daily practice.

AIM

To determine the efficacy of the combination of rabeprazole, levofloxacin and furazolidone as a rescue therapy.

METHODS

Duodenal ulcer patients previously submitted, without success, to at least two H. pylori treatment regimens were included. Gastroscopy (urease test, histological examination and culture) and (13)C-urea breath test were performed. All patients received a combination of rabeprazole 20 mg, levofloxacin 500 mg and furazolidone 200 mg (two tablets) administered in a single dose in the morning for 10 days. Clinical examination and a new (13)C-urea breath test were performed 90 days after therapy.

RESULTS

Twelve patients (eight females and four males), mean age 43 (30-58) years were included. Two patients failed to complete the treatment because of nausea and vomiting. Ten patients completed the study and took all the medications as advised. Culture was obtained in six patients: 100 and 83% of the samples were sensitive to furazolidone and levofloxacin, respectively. Per-protocol and intention-to-treat eradication rates were 100 and 83% (P = 0.019).

CONCLUSIONS

the combination of rabeprazole, levofloxacin and furazolidone in a single daily dose for 10 days constitutes a highly-effective and low-cost alternative as a third-line therapy in patients infected with H. pylori.

Plasma hydroxy-metronidazole/metronidazole ratio in hepatitis C virus-induced liver disease

It has been suggested that the measurement of metronidazole clearance is a sensitive method for evaluating liver function. The aim of this study was to evaluate the usefulness of plasma hydroxy-metronidazole/metronidazole ratios as indicators of dynamic liver function to detect changes resulting from the various forms of chronic hepatitis C virus (HCV) infection. A total of 139 individuals were studied: 14 healthy volunteers, 22 healthy, asymptomatic, consecutive anti-HCV-positive HCV-RNA negative subjects, 81 patients with chronic hepatitis C (49 with moderate/severe chronic hepatitis and 34 with mild hepatitis), and 20 patients with cirrhosis of the liver. HCV status was determined by the polymerase chain reaction. Plasma concentrations of metronidazole and its hydroxy-metabolite were measured by reverse-phase high-performance liquid chromatography with ultraviolet detection in a blood sample collected 10 min after the end of a metronidazole infusion. Anti-HCV-positive HCV-RNA-negative individuals demonstrated a significantly reduced capacity to metabolize intravenously infused metronidazole compared to healthy individuals (0.0478 +/- 0.0044 vs 0.0742 +/- 0.0232). Liver cirrhosis patients also had a reduced plasma hydroxy-metronidazole/metronidazole ratio when compared to the other groups of anti-HCV-positive individuals (0.0300 +/- 0.0032 vs 0.0438 +/- 0.0027 (moderate/severe chronic hepatitis) vs 0.0455 +/- 0.0026 (mild chronic hepatitis) and vs 0.0478 +/- 0.0044 (anti-HCV-positive, HCV-RNA-negative individuals)). These results suggest an impairment of the metronidazole metabolizing system induced by HCV infection that lasts after viral clearance. In those patients with chronic hepatitis C, this impairment is paralleled by progression of the disease to liver cirrhosis.

Different mechanisms lead to the angiogenic process induced by three adenocarcinoma cell lines

Neoangiogenesis is essential for tumor and metastasis growth, but this complex process does not follow the same activation pathway, at least in tumor cell lines originated from different murine mammary adenocarcinomas. LMM3 cells were the most potent to stimulate new blood vessel formation. This response was significantly reduced by preincubating cells with indomethacin and NS-398, non-selective cyclooxygenase (COX) and COX-2 selective inhibitors, respectively. COX-1 and COX-2 isoenzymes were both highly expressed in LMM3 cells, and we observed that indomethacin was more effective than NS-398 to inhibit prostaglandin E2 (PGE2) synthesis. In addition, nitric oxide synthase (NOS) inhibitors, Nomega monomethyl L-arginine and aminoguanidine, also reduced LMM3-induced angiogenesis and nitric oxide (NO) synthesis as well. NOS2 > NOS3 proteins and arginase II isoform were detected in LMM3 cells by Western blot. The latter enzyme was also involved in the LMM3 neovascular response, since the arginase inhibitor, Nomega hydroxy L-arginine reduced the angiogenic cascade. On the other hand, parental LM3 cells were able to stimulate neovascularization via COX-1 and arginase products since only indomethacin and Nomega hydroxy L-arginine, which diminished PGE2 and urea synthesis, respectively, also reduced angiogenesis. In turn, LM2 cells angiogenic response could be due in fact to PGE2-induced VEGF liberation that stimulated neoangiogenesis at very low levels of NO.

Rarity of DNA sequence alterations in the promoter region of the human androgen receptor gene

The human androgen receptor (AR) gene promoter lies in a GC-rich region containing two principal sites of transcription initiation and a putative Sp1 protein-binding site, without typical "TATA" and "CAAT" boxes. It has been suggested that mutations within the 5'untranslated region (5'UTR) may contribute to the development of prostate cancer by changing the rates of gene transcription and/or translation. In order to investigate this question, the aim of the present study was to search for the presence of mutations or polymorphisms at the AR-5'UTR in 92 prostate cancer patients, where histological diagnosis of adenocarcinoma was established in specimens obtained from transurethral resection or after prostatectomy. The AR-5'UTR was amplified by PCR from genomic DNA samples of the patients and of 100 healthy male blood donors, included as controls. Conformation-sensitive gel electrophoresis was used for DNA sequence alteration screening. Only one band shift was detected in one individual from the blood donor group. Sequencing revealed a new single nucleotide deletion (T) in the most conserved portion of the promoter region at position +36 downstream from the transcription initiation site I. Although the effect of this specific mutation remains unknown, its rarity reveals the high degree of sequence conservation of the human androgen promoter region. Moreover, the absence of detectable variation within the critical 5'UTR in prostate cancer patients indicates a low probability of its involvement in prostate cancer etiology.

Biosynthesis and catabolism of prostaglandin F2alpha (PGF2alpha) are controlled by progesterone in the rat uterus during pregnancy

Myometrial quiescence is a key factor in all species to accomplish a successful gestation. PGs play a crucial role in mediating parturition events, and their synthesis and metabolism are regulated by cyclooxygenases (COXs) and NAD(+)-dependent 15-hydroxy-PG dehydrogenase (PGDH), respectively. Progesterone (P(4)) is the hormone responsible for maintaining uterine smooth muscle quiescence during pregnancy. In this work, we have studied the effect of P(4) on the activity of COXs and PGDH, the uterine enzymes involved in the biosynthesis and metabolism of prostanoids in the rat. We found that during pregnancy PGF(2alpha) production and also protein levels of COX-1 and COX-2 were decreased. The exogenous administration of P(4) significantly inhibited the uterine production of PGF(2alpha) and also the protein level of COX-2. PGF(2alpha), metabolism was assessed by PGDH activity, which resulted high during pregnancy and increased as a result of P(4) administration. These results indicate that PGs levels were negatively modulated by P(4), which could be exerting its effect by increasing PGs metabolism through stimulation on PGDH activity and an inhibition on COX and that is a major mechanism for maintain uterine quiescence in pregnancy.

Effects of in vivo administration of epidermal growth factor (EGF) on uterine contractility, prostaglandin production and timing of parturition in rats

Prostaglandins synthesized by cyclooxygenases elicit uterine contractions during labour. Nitric oxide synthases (NOS) produce nitric oxide (NO), which maintains uterine quiescence during pregnancy. Epidermal growth factor (EGF) interacts with prostaglandins and NO in many biological systems. The aim of this work was to study the effect of the in vivo administration of EGF on uterine contractility, prostaglandin production and timing of parturition in rats. EGF was injected into the uterine lumen of pregnant rats on day 20, 21 or 22 of gestation. Intra-uterine administration of 500 ng EGF on day 21 of gestation delayed parturition for 18 h compared with control rats. Administration of EGF was able to: (i) reduce cyclooxygenase expression in the uterus (determined by western blot analysis) and production of prostaglandins by the uterus (evaluated by conversion of [(14)C]arachidonate to labelled prostaglandins); (ii) decrease prostaglandin concentrations in amniotic fluid (radioimmunoassay); (iii) increase NO production (evaluated by conversion of [(14)C]arginine into [(14)C]citrulline); (iv) increase serum progesterone concentrations to more than control concentrations (P<0.05; radioimmunoassay); and (v) reduce the amplitude of the uterine contractions. The overall effect was a delay in the onset of delivery. This in vivo effect raises the question of whether exogenous EGF plays a role in the initiation of parturition.

IL-10 inhibits nitric oxide synthesis in murine uterus

OBJECTIVES

Recent reports point to a role for the nitric oxide/nitric oxide synthase (NO/NOS) system in implantation. It has been suggested that inducible NOS expressed at peri-implantation would lead to enhanced NO production, which could promote the attachment of the blastocyst. Short-term administration of NO donors during the pre-implantation period reduced the pregnancy rate in a dose-dependent manner. Thus, it is thought that optimal levels of NO are critical for embryo implantation, so regulation of NOS must be crucial. Taking this into consideration, interleukin-10 (IL-10), synthesized and secreted by the embryo, could be modulating NOS during implantation. In this study we have investigated the in vitro effect of IL-10 on NOS in the uterus.

METHODS

To determine the effect of IL-10, slices of uterus from estrogenized mice were pre-incubated for 60 min with different concentrations of IL-10 and NOS activity was measured.

RESULTS

IL-10 (50 and 100 ng/ml in vitro) diminished NOS activity. The in vivo administration of lipopolysaccharide (LPS; 8 mg/kg) significantly increased the conversion of arginine into citrulline. This effect was abolished after 60 min of preincubation with IL-10 (100 ng/ml). The stimulatory effect of LPS and estrogen on NOS activity is exerted on the Ca-independent isoform and IL-10 in vitro abolished this increase. We observed that the uterus of pregnant mice on day 5 of gestation synthesized NO. This production was significantly inhibited by preincubation with IL-10 (100 ng/ml).

CONCLUSIONS

This report demonstrates that IL-10 is capable of inhibiting NO synthesis in estrogenized, LPS-treated and pregnant rat uterus.

Epidermal growth factor modulation of prostaglandins and nitrite biosynthesis in rat fetal membranes

The production of prostaglandins (PGs) and nitric oxide (NO) by amnion tissue may play a significant role in parturition. It is thought that epidermal growth factor (EGF) may be one of the fetal signals that governs the initiation of labor. The aim of the present study was to investigate the effect of EGF in vivo on the PGs and nitrite production of rat fetal membranes. We have evaluated the regulation of PGs and nitrite production in rat fetal membranes ex vivo. The intra-uterine administration of EGF 500 ng in day 21 of pregnancy induced increases in PGE(2) (P<0.001) and PGF(2alpha) (P<0.01) compared to the control fetal membranes from pregnant rats on day 22. Also, this dose of EGF diminished nitrate production significantly (P<0.01). We found that fetal membranes at term (days 18-22 of gestation) expressed EGF-R. The NO donor, nitroprussiate 300 and 600 microM, elicited an inhibitory effect on the PGE(2) and PGF(2alpha) stimulated synthesis. On the other hand, indomethacin 10(-6) and 10(-7)M, a non-selective cyclooxygenase inhibitor, reverted the inhibitory effect exerted by EGF. Hence, rat fetal membranes were found to express epidermal growth factor receptors and, under the effect of EGF, PGs and nitrites production pathways interact probably to prevent a toxic effect caused by an exacerbated synthesis of these mediators.