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In vitro evidence that rabbit distal colonic muscularis mucosae has a Clostridium difficile toxin A receptor
W H Percy1, R Burakoff, K Rose
1Department of Physiology and Pharmacology, School of Medicine, University of South Dakota, Vermillion, South Dakota 57069, USA.
Abstract:
In the rabbit ileum Clostridium difficile toxin A causes inflammation and mucosal damage via a specific glycoprotein receptor that contains alpha-D-galactose. In rabbit colon toxin A also causes inflammation, and this is associated with increased myoelectric activity and eicosanoid production. The present in vitro study was undertaken to determine if a toxin A receptor on one or more layers of colonic smooth muscle could mediate the motor effects of this agent. Toxin A (20-100 microg/ml) was without effect on longitudinal and circular muscle but had two different effects on the muscularis mucosae. Initial exposure to the toxin caused increased numbers of spontaneous contractions and a small, atropine-, tetrodotoxin-, and indomethacin-resistant increase in resting tone. More importantly, however, 30-min exposure to toxin A resulted in attenuated muscularis mucosae responses to acetylcholine and K+. Both the small excitatory and the larger inhibitory effects of toxin A were abolished by pretreatment with the lectin BS-1, which binds to toxin A receptors, but not by the nonreceptor-binding lectin DBA. These data strongly suggest that toxin A causes significant motor effects on the distal colonic muscularis mucosae via a receptor-mediated mechanism. These mechanical data were supported by the presence of histologically demonstrable toxin A and BS-1 binding sites on the muscularis mucosae but not on either the longitudinal or circular muscle layers, both of which were unresponsive to the toxin. By depressing muscularis mucosae function and, ultimately, mucosal movement as a result of toxin A production, C. difficile may promote its own proliferation, thus further contributing to the development of antibiotic-associated colitis.
Insights
Clostridium difficile toxin A affects the colonic muscularis mucosae via a receptor-mediated mechanism, causing motor dysfunction. This interaction may promote bacterial proliferation and antibiotic-associated colitis.
Area of Science:
- Gastroenterology
- Microbiology
- Cell Biology
Background:
- Clostridium difficile toxin A induces inflammation and mucosal damage in the rabbit ileum through a specific alpha-D-galactose glycoprotein receptor.
- Toxin A in the rabbit colon causes inflammation, increased myoelectric activity, and eicosanoid production.
Purpose of the Study:
- To investigate whether a toxin A receptor on colonic smooth muscle layers mediates the motor effects of the toxin.
- To elucidate the specific muscle layers affected by toxin A and the mechanism of action.
Main Methods:
- In vitro study using rabbit colonic smooth muscle.
- Exposure of longitudinal, circular, and muscularis mucosae muscle layers to toxin A.
- Assessment of muscle contractions and tone.
- Use of receptor-binding lectin BS-1 and non-receptor-binding lectin DBA to block toxin effects.
- Histological analysis to identify toxin A and BS-1 binding sites.
Main Results:
- Toxin A did not affect longitudinal or circular muscle layers.
- Toxin A induced initial spontaneous contractions and increased resting tone in the muscularis mucosae.
- Prolonged exposure to toxin A attenuated muscularis mucosae responses to acetylcholine and K+.
- Both excitatory and inhibitory effects of toxin A on the muscularis mucosae were blocked by BS-1, but not DBA.
- Histology confirmed toxin A and BS-1 binding sites on the muscularis mucosae, but not other muscle layers.
Conclusions:
- Toxin A exerts significant motor effects on the distal colonic muscularis mucosae through a receptor-mediated mechanism.
- The toxin's action on the muscularis mucosae may impair mucosal movement, potentially facilitating Clostridium difficile proliferation.
- These findings suggest a role for toxin A-induced muscularis mucosae dysfunction in the pathogenesis of antibiotic-associated colitis.
