Marie-Agnès Pélissier

Protection against dextran sodium sulfate-induced colitis by dehydroepiandrosterone and 7α-hydroxy-dehydroepiandrosterone in the rat

In this study the anti-oxidant effect of DHEA and 7alpha-hydroxy-DHEA against oxidative stress induced by colitis was investigated in vivo in rats. The two steroids were intraperitoneally injected once daily (50 mg/kg body weight) for 7 days before the induction of colitis that was effected by a daily treatment of 5% (w/v) dextran sodium sulfate (DSS) in drinking water for 7 days. This was quantified by the evidence of weight loss, rectal bleeding, increased wall thickness, and colon length. The inflammatory response was assessed by neutrophil infiltration after a histological examination and myeloperoxidase (MPO) activity measurement. Two markers of oxidative damage were measured in colon homogenates after the onset of DSS treatment: protein carbonyls and thiobarbituric acid-reacting substances. The colonic metabolism of corticosterone by 11beta-hydroxysteroid dehydrogenases types 1 and 2 (11beta-HSD) was investigated in control and treated animals. Results indicated that colitis caused a decrease in body weight and colon length. Severe lesions were observed in the colon with a reduced number of goblet cells which contained less mucins. The lesions were associated with increased MPO activity and oxidative damage. Colonic inflammation down and up regulated the 11beta-HSD2 and 11beta-HSD1, respectively. Treatments by DHEA and 7alpha-hydroxy-DHEA attenuated the inflammatory response when MPO activity decreased; but this did not increase the colonic oxidation of corticosterone into 11-dehydrocorticosterone. Both DHEA and 7alpha-hydroxy-DHEA exerted a significant anti-oxidant effect against oxidative stress induced by colitis through reducing the oxidative damage to proteins and lipids. This resulted in a moderate increase in the amount of colonic mucus. Both DHEA and 7alpha-hydroxy-DHEA may prove useful in the prevention or treatment of colitis.

Anti-inflammatory effects and changes in prostaglandin patterns induced by 7β-hydroxy-epiandrosterone in rats with colitis

High dose levels of dehydroepiandrosterone and its 7-hydroxylated derivatives have been shown to reduce oxidative stress and inflammatory responses in dextran sodium sulfate (DSS)-induced colitis in rats. Another endogenous steroid, 7beta-hydroxy-epiandrosterone (7beta-hydroxy-EpiA) has been shown to exert neuroprotective effects at much smaller doses. Our aims were to evaluate whether 7beta-hydroxy-EpiA pre-treatment prevents DSS-induced colitis and to determine whether the effects involve changes in anti-inflammatory prostaglandin (PG) D(2) and 15-deoxy-Delta(12,14)-PGJ(2) (15d-PGJ(2)) levels. Rats were administered 0.01, 0.1 and 1mg/kg 7beta-hydroxy-EpiA i.p. once a day for 7 days. Thereafter, colitis was induced by administration of 5% DSS in drinking water for 7 days. Levels of the PGs and the expression of cyclooxygenase (COX-2) and PG synthases were assessed during the course of the experiment. Administration of 7beta-hydroxy-EpiA caused a transient increase in COX-2 and PGE synthase expression within 6-15h and augmented colonic tissue levels of 15d-PGJ(2) levels starting at day 2. Treatment with DSS resulted in shortened colon length, depleted mucus in goblet cells and induced oxidative stress. COX-2 and mPGES-1 synthase expression were enhanced and accompanied by increased PGE(2), D(2) and 15d-PGJ(2) production. Although all dose levels of 7beta-hydroxy-EpiA reduced PGE(2) production, only the lowest dose (0.01mg/kg) of the steroid completely prevented colitis damage and tissue inflammation. 7beta-Hydroxy-EpiA pre-treatment prevents the occurrence of DSS-induced colitis through a shift from PGE(2) to PGD(2) production, associated with an early but transient increase in COX-2 expression and a sustained increase in the production of the anti-inflammatory prostaglandin 15d-PGJ(2).

Antioxidant effects of dehydroepiandrosterone and 7α-hydroxy-dehydroepiandrosterone in the rat colon, intestine and liver

This study examined in healthy male Wistar rats the in vivo antioxidant effect of dehydroepiandrosterone (DHEA) and 7alpha-hydroxy-DHEA administered by intraperitoneal injections (50 mg/kg body weight) for 2 or 7 days. Markers of oxidative damage to lipids (thiobarbituric acid-reacting substances, TBARS) and to proteins (protein carbonyls) were assessed in colon, small intestine, and liver homogenates. DHEA and 7alpha-hydroxy-DHEA caused a decrease in body weight. DHEA treatment significantly increased liver, colon, and small intestine cell weights. After 7 days, DHEA exerted an antioxidant effect in all organs studied. In the colon, oxidative damage protection was accompanied by a goblet cell proliferation and increase in acidic mucus production. After 2 days, the antioxidant effect of 7alpha-hydroxy-DHEA was mainly observed in the liver. Nonprotein sulfhydryl groups (mostly glutathione levels) were altered by DHEA in the liver whereas they remained unchanged after 7alpha-hydroxy-DHEA treatment. The results indicate that in healthy animals, DHEA exerts a protective effect, particularly in the colon, by reducing the tissue susceptibility to oxidation of both lipids and proteins. This effect was not limited to a specific tissue, whereas the metabolite 7alpha-hydroxy-DHEA exerted its antioxidant effect towards the two markers of oxidative damage earlier than DHEA, and mainly in the liver.

Metronidazole effects on microbiota and mucus layer thickness in the rat gut

Both mucus and mucosa-associated bacteria form a specific environment in the gut; their disruption may play a crucial role in the development of intestinal bowel disease (IBD). Metronidazole, an antibiotic used in the treatment of IBD, alters gut microbiota and reduces basal oxidative stress to proteins in colonic tissue of healthy rats. The aim of this study was to evaluate the impact of the altered microbiota due to the metronidazole on the thickness of the mucus layer. This study was performed in healthy untreated rats (control group) or rats treated by metronidazole (metronidazole-treated rats, 1 mg mL(-1) in drinking water for 7 days). Both PCR-temporal temperature gradient gel electrophoresis and quantitative PCR (qPCR) revealed an altered microbiota with an increase in bifidobacteria and enterobacteria in metronidazole-treated rats compared with control rats. Moreover, a dominant bifidobacterial species, Bifidobacterium pseudolongum, was detected. Using qPCR and FISH, we showed that bifidobacteria were also increased in the microbiota-associated mucosa. At the same time, the mucus layer thickness was increased approximately twofold. These results could explain the benefits of metronidazole treatment and warrant further investigations to define the role of bifidobacteria in the colonic mucosa.

The DHEA metabolite 7β-hydroxy-epiandrosterone exerts anti-estrogenic effects on breast cancer cell lines

7β-Hydroxy-epiandrosterone (7β-OH-EpiA), an endogenous androgenic derivative of dehydroepiandrosterone, has previously been shown to exert anti-inflammatory action in vitro and in vivo via a shift from prostaglandin E2 (PGE2) to 15-deoxy-Δ(12,14)-PGJ2 production. This modulation in prostaglandin production was obtained with low concentrations of 7β-OH-EpiA (1-100nM) and suggested that it might act through a specific receptor. Inflammation and prostaglandin synthesis is important in the development and survival of estrogen-dependent mammary cancers. Estrogen induced PGE2 production and cell proliferation via its binding to estrogen receptors (ERs) in these tumors. Our objective was to test the effects of 7β-OH-EpiA on the proliferation (by counting with trypan blue exclusion), cell cycle and cell apoptosis (by flow cytometry) of breast cancer cell lines MCF-7 (ERα+, ERβ+, G-protein coupled receptor 30: GPR30+) and MDA-MB-231 (ERα-, ERβ+, GPR30+) and to identify a potential target of this steroid in these cell lineages (by transactivations) and in the nuclear ER-negative SKBr3 cells (GPR30+) (by proliferation assays). 7β-OH-EpiA exerted anti-estrogenic effects in MCF-7 and MDA-MB-231 cells associated with cell proliferation inhibition and cell cycle arrest. Moreover, transactivation and proliferation with ER agonists assays indicated that 7β-OH-EpiA interacted with ERβ. Data from proliferation assays on the MCF-7, MDA-MB-231 and SKBr3 cell lines suggested that 7β-OH-EpiA may also act through the membrane GPR30 receptor. These results support that this androgenic steroid acts as an anti-estrogenic compound. Moreover, this is the first evidence that low doses of androgenic steroid exert antiproliferative effects in these mammary cancer cells. Further investigations are needed to improve understanding of the observed actions of endogenous 7β-OH-EpiA.

Differential Effects of Bifidobacterium pseudolongum Strain Patronus and Metronidazole in the Rat Gut

ABSTRACT In the luminal contents of metronidazole-treated rats, there was a dominant Bifidobacterium species. A strain has been isolated, its 16S rRNA gene has been sequenced, and the strain has been named Bifidobacterium pseudolongum strain Patronus. In this study, using an experimental model of healthy rats, the effects of metronidazole treatment and B. pseudolongum strain Patronus administration on the luminal and mucosa-associated microbiota and on gut oxidation processes were investigated. Metronidazole treatment and the daily gavage of rats with B. pseudolongum strain Patronus increased the numbers of bifidobacteria in cecal contents and in cecal mucosa-associated microbiota compared with those in control rats. Metronidazole reduced the colonic oxidative damage to proteins. This is the first evidence that B. pseudolongum strain Patronus exerts an effect on a biomarker of oxidative damage by reducing the susceptibility to oxidation of proteins in the colon and the small bowel. Antioxidant effects of metronidazole could be linked to the bifidobacterial increase but also to other bacterial modifications.

Homocysteine prevents total parenteral nutrition (TPN)-induced cholestasis without changes in hepatic oxidative stress in the rat.

Background The role of oxidative stress in total parenteral nutrition (TPN)–associated cholestasis with liver glutathione depletion was recently shown. The aims of this study were to test the appearance of cholestasis and oxidative stress during TPN, and the hypothesis that reducing oxidative stress with a precursor of glutathione (GSH), homocysteine, would restore bile flow. Methods Three groups of rats (weight, 179–278 g) were studied: 1) D/aa group received dextrose and amino acids (3.4 g/d); 2) D/aa/L group received the same amount of amino acids, and lipids were added on an equicaloric basis (50 kcal/d) with a lowered amount of dextrose; and 3) a control group, which received dextrose perfusion and had free access to chow. A subgroup of D/aa/L rats (n = 6) received a TPN solution containing homocysteine. After 5 days of TPN, bile was collected during 2 hours. In liver homogenates, GSH, thiobarbituric acid reactive substances (TBARS), and carbonyl content of proteins (Prot-CO) were measured to test the level of oxidative stress and hepatic lipid and protein oxidation. Results After TPN, bile flow was significantly lower in the D/aa group than in the control group. Addition of lipids further decreased bile flow. Addition of homocysteine to TPN with lipids significantly increased bile flow. Aspartate aminotransferase increased significantly in both TPN groups compared with the control group. &ggr;-Glutamyl transpeptidase was not different among TPN groups. An increased hepatic lipid oxidation was demonstrated by TBARS level in both TPN groups when compared with the control group. However, the liver GSH contents were not different. Protein oxidation was also significantly increased by TPN. The addition of homocysteine to TPN solution increased bile flow without liver injury or changes of lipid and protein oxidation. Discussion This study shows that TPN administered to rats induces a decrease of bile flow and an oxidative stress but that the two changes are not directly correlated. Addition of lipids further impairs bile flow but does not increase the occurrence of liver injury. Consequently, it seems more likely that TPN primarily induces a cholestatic effect that in turn induces an oxidative stress rather than inducing an oxidative stress that leads to cholestasis. However, an association of both mechanisms is not totally excluded.

Zinc and intestinal anaphylaxis to cow's milk proteins in malnourished guinea pigs.

Zinc supplementation could favor recovery from diarrhea in malnourished children. As the recent experimental evidence suggests that oxidative stress and intestinal anaphylaxis may contribute to the intestinal dysfunction associated with malnutrition, we postulated that zinc could act through antioxidant or antianaphylactic properties. Control (C), malnourished (M), and malnourished zinc-treated (MZ) guinea pigs were, respectively, fed a normal 30% protein diet, a low 4% protein diet, and a low 4% protein diet plus 1800 ppm of zinc. Milk proteins were included in the diets to trigger intestinal anaphylaxis. Milk sensitization was assessed by passive cutaneous anaphylaxis(PCA) against β-lactoglobulin and by intestinal anaphylaxis measured in Ussing chambers by the increase in short circuitcurrent after addition ofβ-lactoglobulin (ΔIscβLg). Oxidative stress was assessed by intestinal lipid peroxidation. The intestinal secretion was assessed by ΔIsc induced by inflammatory mediators. Malnutrition increased the level of anti-βLg reaginic antibodies [PCA = 1.19 ± 0.79 and 0.69 ± 0.67 log(1/titer) in M versus C guinea pigs, p = 0.07] and enhanced intestinal anaphylaxis(ΔIscβLg = 16.4 ± 9.9 and 9.1 ± 5.8μA/cm2 in M versus C guinea pigs, p = 0.07), without inducing intestinal lipid peroxidation. Moreover, malnutrition enhanced significantly the intestinal secretory response to histamine and 5-hydroxytryptamine. Administration of pharmacologic doses of zinc during malnutrition inhibited the increase in milk sensitization induced by malnutrition, both at the systemic [PCA = 0.35 ± 0.55 log(1/titer) in MZ guinea pigs, p = 0.03 versus M] and intestinal(ΔIscβLg = 2.8 ± 2.5 μA/cm2 in MZ guinea pigs; p = 0.001 versus M) level, and prevented the hypersecretion in response to histamine and 5-hydroxytryptamine. These data suggest that zinc has antianaphylactic and antisecretory properties that may contribute to its capacity to prevent intestinal dysfunction during malnutrition.

Serum osteocalcin concentrations in protein and/or energy restricted rats

Abstract The effects of protein and/or energy deficiency on serum osteocalcin concentrations were studied in growing rats. Animals were fed a high or a low protein diet (respectively 22 and 6% casein) either ad libitum or restricted (60%). After four weeks, serum osteocalcin concentrations were significantly decreased by imposed energy restriction. However, they were not affected by protein deficiency, although growth was similarly reduced in both cases. By comparison, serum transthyretin concentrations were decreased by protein and/or energy deficiency, and they were significantly correlated with serum osteocalcin concentrations. These results suggest that serum osteocalcin concentrations are not a reflection of bone growth in protein and energy restricted rats, but are related to energy availability.

Palm Versus Soybean Oil on Intestinal Recovery from Malnutrition in Guinea Pigs

Recent recommendations on feeding malnourished children do not provide indication on the nature of dietary lipids. Our aim was to compare the effect of palm oil (mainly saturated and monounsaturated fatty acids) and soybean oil (mainly polyunsaturated fatty acids) on the recovery from malnutrition in guinea pigs. In a first experiment, guinea pigs received a balanced (control group) or a maize (malnourished group) diet for 7, 12, and 21 d. In a second experiment, after 12 d of malnutrition, guinea pigs received a rehabilitation diet containing palm or soybean oil. Both rehabilitation diets allowed a partial recovery from the severe weight loss induced by malnutrition. Thiobarbituric acid reactive substances content, measured in intestinal homogenates, increased in malnourished guinea pigs compared with control animals (40%, p < 0.05) and returned to near control values after rehabilitation with palm (10%) but not soybean (43%) oil diet. Intestinal short-circuit current, assessed in jejunal segments mounted in Ussing chambers, increased progressively during malnutrition (p < 0.001) and returned to near control values with both rehabilitation diets. Compared with control animals, the cell turnover (Ki-67 index assessed by immunohistochemistry detection of the Ki-67 antigen) decreased after soybean (−60%, p < 0.01) but not after palm oil. These results confirm that experimental polydeficient malnutrition induces oxidative stress and dysfunction in the intestine. They show a differential effect of palm and soybean oil on these intestinal measurements, suggesting that the composition of dietary lipids may be important in the treatment of malnutrition.