Entamoeba histolytica Causes Intestinal Secretion: Role of Serotonin

Abstract

Lysates of the protozoan parasite Entamoeba histolytica altered active electrolyte transport when present on the serosal surface of rabbit ileum and rat colon. The lysate-induced effects on electrolyte transport were similar to those caused by serotonin, and were blocked by bufotenine, an analog known to inhibit the action of serotonin. The transport effects were partially inhibited by antibody to serotonin. The amebic lysates were shown to contain serotonin by radioimmunoassay, high-performance liquid chromatography, and thin-layer chromatography. These results suggest that the serotonin present in Entamoeba histolytica may be important in the diarrhea seen in amebiasis.

Neurohumoral alterations and their role in amoebiasis

“…The altered active electrolyte transport and diarrhea of rabbit ileum and rat colon induced by E. histotytica lysate was found similar to those caused by serotonin (19). Thus, the enhanced circulatory 5-HT level as seen in these patients may be both due to the stress of the disease (20) and E. histolytica infection, and responsible for the diarrhea seen in amoebiasis (19).Furthermore, the administration of 5-HT or its precursor L-tryptophan in infected animals is reported to significantly enhance the pathogenicity of various strains of E.histolytica (21).…”

“…The Nears caecal score of non-pathogenic strain NIH-200 were also found increased significantly in the presence of histamine (20 pg/ml) stepwise up to second culture and became stabilized at third generation with histamine (18). The enhanced level of histamine may be due to its release from the mast cells in response to increased serum IgE levels caused by the E.histolytica infestation (19).The increased level of histaminase the degrading enzyme of histamine may be due to body's natural response to degrade the excessive histamine.…”

“…Thus, the enhanced circulatory 5-HT level as seen in these patients may be both due to the stress of the disease (20) and E. histolytica infection, and responsible for the diarrhea seen in amoebiasis (19).Furthermore, the administration of 5-HT or its precursor L-tryptophan in infected animals is reported to significantly enhance the pathogenicity of various strains of E.histolytica (21). It is well recognized fact that the enzymes involved in metabolism of various neurohumors play an important role in the actual neurohumoral activity.…”

Entamoeba histolytica: Host parasite interactions at the colonic epithelium

“…Anion transport, particularly chloride, has been shown to drive diarrheal disease through serotonin that is produced by Eh. 49 Characteristic of a neuronal peptide, this effect was specific to the serosal side of the tissue. In addition to detection of serotonin in Eh lysates, neutralization of Eh serotonin by antibodies or desensitization by pre-treatment of bufotenine abolished the effects on ion transport and short circuit current.…”

Immunobiology of Human Infection by <i>Entamoeba histolytica</i>

“…Soluble E. histolytica pro tein fractions have enterotoxic activity in indomethacin (0.1 mg/pg)-treated rats or rabbits; enterotoxigenic activity is inhibited by fetuin or high concentrations of indo methacin [76], A recently partially purified toxin was found to be heat labile, inhibited by sialoglycoproteins (fetuin and mucin) and by p-chloromercuribenzoate, and to have a molecular weight on SDS-PAGE of 30,000 [77]. Lysates of E. histolytica applied to the serosal side of rabbit ileum in a Ussing chamber induce a transient increase in shortcircuit current, a finding suggestive of a se cretory effect [78]. This effect can be inhib ited with the calcium channel blocker vera pamil; amebic lysates contain serotonin (at 4.0 ng/mg) which appears to be partly re sponsible for the gut secretory effect ob served [79].…”