Gloria Gómez

Intestinal mucosal oxidative damage and bacterial translocation in cirrhotic rats

Background Bacterial translocation plays an important role in the pathogenesis of spontaneous bacterial peritonitis mainly due to intestinal bacterial overgrowth. Alterations in the functional integrity of the intestinal barrier caused by an increased production of free radical metabolites as a consequence of portal hypertension could also facilitate bacterial translocation in cirrhotic rats. Objective The aim of the study was to determine intestinal mucosal lipid peroxidation and neutrophil infiltration and their relationship with portal hypertension and bacterial translocation in cirrhotic rats. Design Eighteen male Sprague–Dawley rats with cirrhosis induced by carbon tetrachloride, administered by gavage, and eight control rats were included in the study. Methods Samples of jejunum, ileum and caecum were obtained by laparotomy for the determination of malondialdehyde and myeloperoxidase as indexes of lipid peroxidation and neutrophil infiltration, respectively. Samples of ascitic and pleural fluids, mesenteric lymph nodes and ileal stools were obtained for the culture of microoganisms. Results The concentration of malondialdehyde was significantly higher in ileal and caecal, but not in jejunal mucosa, in cirrhotic rats, mainly in those with ascites (P < 0.01), as compared to control rats (P < 0.01), and in cirrhotic rats with bacterial translocation compared to those without bacterial translocation (P < 0.01). No differences between groups were observed in the concentrations of myeloperoxidase in jejunum, ileum or caecum. A direct correlation between ileal malondialdehyde and portal pressure was observed (P < 0.01). Conclusions Cirrhotic rats, particularly those with ascites and bacterial translocation, show increased malondialdehyde levels in ileal and caecal mucosa. These results suggest that mucosal oxidative damage in ileum and caecum could favour bacterial translocation in cirrhotic rats.

Cyclooxygenase and lipoxygenase arachidonic acid metabolism by monocytes from human immune deficiency virus-infected drug users

Prostaglandin E2, thromboxane B2 and leukotriene B4 monocyte production have been determined in human immune deficiency virus (HIV)-infected drug users (n = 36) and healthy subjects (n = 29). Eicosanoids were extracted from the incubates using C18 solid-phase cartridges and determined by radioimmunoassay. An enhanced production of prostaglandin E2 and thromboxane B2 was detected in monocytes from HIV-positive drug users whether or not they had been previously stimulated with zymosan. Concomitant leukotriene B4 increases were not observed. The results reported in this paper indicate that altered cyclooxygenase arachidonic acid metabolism in monocytes from HIV-infected drug users is associated with the severe cellular immunodysfunction characteristic of AIDS. In contrast, leukotriene B4 does not seem to play a role in AIDS-associated immunosuppression.

Influence of Nitric Oxide Synthase and Kinin Antagonists on Metabolic Parameters in Chronic Streptozotocin-Induced Diabetes Mellitus

In vivo administration of HOE 140 (a new bradykinin receptor antagonist) and L-NAME (nitric oxide synthase inhibitor) was performed in chronic streptozotocin-diabetic rats. Basal increases (in umol.g dw-1) in liver (45.0 +/- 3.4.1) and uterine (40.0 +/- 2.95) triglyceride levels in diabetic animals vs control (liver: 34.0 +/- 3.87; uterus: 30.2 +/- 4.01) were partially prevented by L-NAME (p < 0.01), HOE 140 (p < 0.01) and L-NAME + HOE 140 (p < 0.01). High glycogen levels (in mg.g dw-1) observed in diabetic uterine tissue (3.07 +/- 0.90), and decreased glycogen content detected in diabetic liver (11.64 +/- 1.50) vs. control (uterus: 1.59 +/- 0.15, liver: 17.25 +/- 0.87) were unaffected. Uterine 14CO2 production from 14C-U-Glucose (in uCi.mg dw), which is lower in diabetic (35.0 +/- 5.12) than in control (50.12 +/- 4.54) tissues, was improved by HOE 140 (p < 0.05) and L-NAME+HOE 140 (p < 0.05), while hepatic glucose oxidation was not increased by the drugs. Glycemia levels were decreased in diabetic rats injected with L-NAME and L-NAME plus HOE 140. Pancreatic 6-Keto-prostaglandin F1 alpha to Thromboxane B2 ratio was lower in diabetic animals than in controls, and L-NAME and/or HOE 140 treatment prevented the decrement. These findings suggest that vasoactive compounds might prevent streptozotocin-induced damage in pancreatic tissue from chronic diabetic rats.

Eicosanoid production by placental and amnion tissues from control and non-insulin-dependent diabetic rats. Influence of oxytocin in the incubating medium

Eicosanoid production by intrauterine tissues from control and neonatal-streptozotocin induced diabetic rats during late pregnancy was evaluated. In diabetic placenta the release of 6-keto-PGF1alpha was found diminished when compared to controls. In addition, LTB4 generation was increased in diabetic placenta. No alterations in the production of TXA2, PGE2, PGE1 and PGF2alpha was found when diabetic and control placenta were compared. In amnion tissue a decreased generation of 6-keto-PGF1alpha was observed in the diabetic group, but no alteration in any other eicosanoid evaluated was found. Oxytocin (5 mU/ml, in vitro), which increases prostaglandin synthesis in rabbit and human amnion tissues, did not modify eicosanoid generation in control rat amnion. In contrast, in diabetic amnion the presence of oxytocin further decreased the release of 6-keto-PGF1alpha and diminished PGE1 generation. The present results suggest that this mildly diabetic state induces alterations in eicosanoid production in intrauterine tissues, abnormalities probably enhanced during parturition, when endogenous concentrations of oxytocin are elevated.

Eicosanoid production and phospholipase A2 activity in uterine tissue from castrated rats with non-insulin dependent diabetes mellitus

In uterine tissue obtained from castrated control and non-insulin dependent diabetic (NIDDM) rats, eicosanoid production and its regulation by glucose levels and by the activity of phospholipase A2 (PLA2) was assessed. Basal outputs of prostaglandins (PGs) PGE2, PGE1, PGF2 alpha, 6-keto-PGF1 alpha (indicating the production of prostacyclin), thromboxane B2 (TXB2) (indicating the generation of TXA2) and leukotriene B4 (LTB4) were similar in control and NIDDM uterine preparations as assessed by RIA. When uterine conversion of labelled arachidonate into different prostanoids was evaluated, generation of 6-keto-PGF1 alpha, PGE2 and PGF2 alpha was similar in control and NIDDM uterine tissue, while TXB2 production was higher in the diabetic group. Moreover, when control tissue was incubated in the presence of elevated concentrations of glucose (22 mM) and compared to control tissue incubated in concentrations of glucose 11 mM, similar generation of 6-keto-PGF1 alpha, PGE2 and PGF2 alpha was observed, and higher concentrations of TXB2 were found, similar to those observed in diabetic uterine tissue. When NIDDM uterine tissue was incubated in the presence of glucose 22 mM, no difference in any prostanoid evaluated was observed when compared to values obtained in the presence of glucose 11 mM. In this work we have observed in NIDDM uterine tissue a normal TXA2 production when evaluated by RIA from endogenous arachidonic acid (AA) and a higher TXA2 generation from exogenous labelled AA. In addition PLA2 activity was found diminished in the NIDDM uteri in comparison to control uteri. A role of the diminished PLA2 as a protective mechanism that avoids TXA2 overproduction in uterine tissue from NIDDM rats is discussed.

Solid-phase extraction of prostanoids using an automatic sample preparation system

A commercial automated solid-phase extraction system for cyclooxygenase arachidonic acid metabolites in urine samples has been evaluated. Comparison of manual and automatic batch (36 samples) extraction procedures for tritium labelled prostanoids added as tracers to urine samples has shown equivalent results with recoveries greater than 90% for prostaglandins E2, F2alpha and 6-keto prostaglandin F1alpha as well as thromboxane B2. Analyte stability is not affected by the automated procedure, which uses less solvents and has a faster overall processing time than the manual method. The automated system has been applied to the extraction of prostanoids in urine samples from workers exposed to dichloroethane.