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Antisecretory Factor Suppresses Intestinal Inflammation And 642 Gut 1997; 41: 642–645 Antisecretory factor suppresses intestinal inflammation and hypersecretion Gut: first published as 10.1136/gut.41.5.642 on 1 November 1997. Downloaded from E Johansson, E Jennische, S Lange, I Lönnroth Abstract Diarrhoeal shellfish poisoning appears in Background—Antisecretory factor (AF) man after consumption of shellfish which have is a recently identified regulatory protein been contaminated with marine phytoplank- which inhibits the intestinal fluid secre- ton. The causative agent, okadaic acid, is tion induced by cholera toxin. produced by the plankton and induces diar- Aims—To test the eVect of AF on: (a) rhoea, nausea, and vomiting without any inflammation and hypersecretion induced inflammatory reaction.10 11 In the rat the toxin by toxin A from Clostridium diYcile; and induces rapid fluid secretion12 and a concomi- (b) morphological changes and hyperse- tant shedding of epithelial cells in the intestinal cretion induced by okadaic acid (the blue mucosa without inflammation or any apparent mussel toxin) in rat intestinal mucosa. disruption of the epithelial barrier.13 The cellu- Methods—Morphological changes and lar action of okadaic acid is to inhibit cellular fluid accumulation were observed in in- phosphatases types 1 and 2A, an action which testinal loops challenged with 1 µg of toxin has been demonstrated in epithelial cells, nerve A or 3 µg of okadaic acid administered cells and neutrophils.14 15 before or after injection of 0.1 µg of The mucosal barrier protects against the recombinant AF (rAF). action of bacterial toxins by means of both Results—The cytotoxic and inflammatory physiological and immunological defence reaction caused by toxin A was abolished mechanisms. We have previously shown that after treatment with rAF given either antisecretory factor (AF), a protein produced intraveneously or intraluminally prior to in the pituitary gland and in the intestinal the toxin or one hour after the toxin. The mucosa, reverses intestinal hypersecretion in- intestinal fluid response induced by toxin duced by bacterial enterotoxins. Thus, a small A and okadaic acid was reduced 55–80% by amount of porcine AF was able to inhibit the rAF. However, the characteristic increase action of a variety of enterotoxins in the pig16 17 18 in goblet cells at the tips of villi in the oka- and in the rat, including the heat labile http://gut.bmj.com/ daic acid treated mucosa was not inhib- enterotoxins from Vibrio cholerae and Es- ited by rAF. cherichia coli and toxin A. With the help of anti- Conclusion—Results suggest that AF bodies raised against AF purified from porcine might be involved in protection against blood we were able to clone complementary inflammation and in counteracting dehy- DNA (cDNA) and express the human AF in E dration caused by enterotoxins. Both coli.19 Less than one picomole of homogeneous human recombinant AF (rAF) was shown to eVects are probably mediated via the on September 25, 2021 by guest. Protected copyright. enteric nervous system. inhibit cholera toxin induced fluid secretion in (Gut 1997; 41: 642–645) rat intestinal loops. In the present paper we describe the action of rAF on fluid secretion Keywords: okadaic acid; Clostridium diYcile toxin A; induced by toxin A and okadaic acid in rat Department of diarrhoea; neuropeptide; S5a; rat small intestine. The eVect of rAF on toxin A Medical Microbiology and Immunology, induced cytotoxicity and inflammation in rat University of intestinal mucosa is also described. Gothenburg, Bacterial enterotoxins induce fluid secretion Guldhedsgatan 10, 413 and inflammation in the intestine. A fatal form Methods 46 Gothenburg, of intestinal toxinosis is caused by toxin A from RECOMBINANT ANTISECRETORY FACTOR Sweden Clostridium diYcile, a bacterium which fre- Human rAF was expressed in E coli and E Johansson quently colonises the gut after treatment with purified as previously described.19 In brief, the I Lönnroth 1 antibiotics. Toxin A causes fluid secretion, full length cDNA was subcloned into the inflammation, and mucosal damage in the glutathione S-transferase (GST) expression Department of Clinical 23 Bacteriology small intestine of hamsters, rabbits, and rats vector pGEX-1ëT (Pharmacia, Uppsala, Swe- S Lange and is probably the main cause of pseudomem- den), and the expressed fusion protein was branous colitis in man.1 After an initial attach- purified on a glutathione-Sepharose column Department of ment to oligosaccharide receptors,45 the toxin (Pharmacia) and cleaved with thrombin to Anatomy and Cell seems to penetrate into the mucosal epithelium Biology, University of elute pure rAF protein. The purity of the pro- Gothenburg and acting as an enzyme it transfers glucose tein was evaluated by sodium dodecyl sulphate E Jennische residues to the G-protein rho causing rear- (SDS) polyacrylamide gel electrophoresis rangement of the cytoskeleton.67 The initial using Coomassie brilliant blue staining.19 Correspondence to: cytophatic eVect of toxin A on the intestinal Dr I Lönnroth. mucosa is followed by an inflammatory re- ENTEROTOXINS Accepted for publication sponse, probably via a nerve mediated eVect on CdiYcile toxin A was produced and purified 29 May 1997 intestinal mast cells and neutrophils.89 as previously described20 and checked for Antisecretory factor suppresses intestinal inflammation and hypersecretion 643 homogeneity by SDS polyacrylamide gel elec- ting the ligated loop longitudinally, 0.5–1.0 cm trophoresis. Okadaic acid was a gift from Pro- long sections were prepared from each of the fessor Lars Edebo, Gothenburg, Sweden. intestinal specimens. The specimens were fixed Gut: first published as 10.1136/gut.41.5.642 on 1 November 1997. Downloaded from by immersion for 24 hours in 4% paraformal- RAT INTESTINAL LOOP TEST dehyde diluted in PBS, after which they were The study design was approved by the Ethics immersed in 7.5% sucrose solution. After at Committee of the University of Gothenburg. least 24 hours’ incubation in the sucrose solu- Male Sprague-Dawley rats (300±10 g), housed tion, the specimens were frozen on dry ice, and in a controlled environment, were fasted for 20 5 µm thick cryostat sections were prepared; at hours before experimentation but given free least 5–10 sections were taken from each of two access to water. Intestinal secretion was diVerent parts of the specimen—that is, a investigated with the “ligated loop” method as minimum of 10 and a maximum of 20 sections described previously.21 Under ether anaesthesia from each specimen. The sections were then one loop, about 10 cm in length, was ligated in stained with periodic acid SchiV reagents the jejunum. The loop was challenged with (PAS) according to routine histological proce- 1.5 ml of phosphate buVered saline (PBS; dures. Finally, the sections were rinsed in water 0.15 M NaCl, 0.05 M sodium phosphate, pH and mounted in glycerol-gelatine. 7.5) in the control group, and in the test groups with 3 µg of okadaic acid or 0.5 µg of CdiYcile STATISTICAL ANALYSES toxin A, dissolved in the same volume of PBS. Student’s t test for non-paired data was used Two millilitres of 0.1 µg rAF (experimental for statistical analysis of the data. groups) or PBS (controls) were administrated intravenously via the dorsal vein of the penis. Results The animals were then allowed to wake up. QUANTITATIVE ASSESSMENT OF SECRETION IN The duration of challenge was five hours for LIGATED JEJUNAL LOOPS toxin A and 90 minutes for okadaic acid, inter- Five hours after challenge with CdiYcile toxin vals based on findings in earlier kinetic studies A in a ligated loop, there was pronounced fluid of fluid accumulation induced by the respective accumulation in the loop in the absence of rAF toxins. At the end of the observation period, the (controls), whereas in the presence of rAF (test rats were sacrificed by cervical spine disloca- animals) this response was significantly re- tion, the abdomen was opened and the loops duced (table 1). Intravenous and intraluminal dissected out. The net fluid secretion (mg/cm) administration of rAF yielded a similar inhibi- was estimated by subtracting the weight of a tion of response to toxin A (about 60% inhibi- control loop from that of the experimental tion); administration of rAF just before or one loop. Specimens for histological examination hour after toxin challenge resulted in the same (see later) were taken from each loop. magnitude of inhibition (60–70%). The fluid response to okadaic acid challenge was rapid http://gut.bmj.com/ ANIMAL GROUPS and transient, the most pronounced secretion Six groups of rats (I–VI) were studied, each already being observed after 90 minutes. As group containing at least five animals. Rats shown in table 1, this fluid response was also serving as controls were subjected to 1.5 ml of inhibited significantly by rAF (55%). intraluminal PBS challenge in combination with intravenous (n=6) or intraluminal (n=5) MORPHOLOGY OF THE LIGATED LOOP PBS injection. Groups I and V received 2 ml The ligated loops in all experimental groups PBS by intravenous injection some 10–20 sec- (table 1) were subjected to morphological on September 25, 2021 by guest. Protected copyright. onds before toxin challenge into the loop, while investigation after the challenge period. Con- groups II and VI were injected with rAF in the trol loops were obtained from rats treated sys- same volume and by the same route. Group III temically and intraluminally with PBS. Figure was injected with rAF 60 minutes after 1A shows the distinct and unchanged morphol- challenge with toxin A, while group IV was ogy in the controls. Severely damaged intestinal injected with rAF intraluminally just before morphology is seen in fig 1B, showing results challenge with toxin A. obtained five hours after challenge with CdiY- toxin A: 50–70% of the apical portion of the HISTOLOGICAL EXAMINATION cile A histological investigation of the gut wall was villi is completely destroyed, and the intestinal undertaken in all experimental groups (groups lumen is full of cellular debris.
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