Review for 10.1186/1471-230X-12-156 (2012)

Reviewer's report
Title:Lubiprostone stimulates intestinal mucin release
Version: 2Date:2 September 2012
Reviewer: Yasutada Akiba
Reviewer's report:
The author examined the effect of lubiprostone on intestinal mucus secretion
using ex vivo perfusion and dot blot mucin analysis. Data is interesting, but
preliminary. Furthermore, Figs. 1 and 2 are substantially not novel.
1. It is surprising that the author did not cite the original technique for
dot-blot/PAS staining mucin analysis [1], by which dynamics of mucus secretion
can be measured through duodenal loop perfusion in rat in vivo, the method
adapted from the former technique [2]. This technique has been introduced to Dr.
Quinton’s lab (Erratum in J Clin Invest. 2009 Nov;119(11):3497). These original
works should be cited for the author’s modified method.
2. Intact mucin release should be combined with the concomitant HCO3-
secretion at the time of mucus exocytosis, regardless of the perfusate HCO3-
(ref. 3). Small intestinal HCO3- secretion requires intact CFTR function [3].
Lubiprostone increases duodenal HCO3- secretion via EP4 receptor and CFTR
activation [4]. Increased mucus accumulation by lubiprostone in the crypt of
CFTR knockout mouse intestine (ref. 2) may be explained by the stimulated
mucus secretion without the intact HCO3- secretion. These results suggest that
effect of lubiprostone on intestinal mucin release involves activated CFTR via
EP4 receptor activation as well as stimulated mucus exocytosis likely via
activation of EP4 (cAMP) or EP1 (Ca2+) receptor. EP3 receptor (Gi/o & Gq/11) is
involved in duodenal HCO3- secretion [5,6], while the effect of EP3 activation on
mucus secretion is questioned, because EP3 activation decreases cAMP and
increase Ca2+. The author should test the effect of CFTR inhibition, and EP
receptor inhibition or activation to determine which receptor/pathway is involved
in the effect of lubiprostone in mucin release.
3. Intestinal segment the author studied should be clearly specified throughout
the manuscript, especially in title, abstract, etc. Methods sound that the author
used ileum segment. ‘Small intestinal mucin release’ or ‘mucin release in ileum’
may be adequate, since colonic (large intestinal) mucin release may be distinctly
regulated.
References
1 Akiba Y, Guth PH, Engel E, Nastaskin I, Kaunitz JD. Dynamic regulation of
mucus gel thickness in rat duodenum. Am J Physiol Gastrointest Liver Physiol.
2000;279:G437-G447.
2 Goso Y, Hotta K. Dot blot analysis of rat gastric mucin using histochemical
staining methods. Anal Biochem. 1994;223:274-279.
3 Hogan DL, Crombie DL, Isenberg JI, Svendsen P, Schaffalitzky de Muckadell
OB, Ainsworth MA. Acid-stimulated duodenal bicarbonate secretion involves a
CFTR-mediated transport pathway in mice. Gastroenterology. 1997;113:533-541.
4 Mizumori M, Akiba Y, Kaunitz JD. Lubiprostone stimulates duodenal
bicarbonate secretion in rats. Dig Dis Sci. 2009;54:2063-2069.
5 Takeuchi K, Yagi K, Kato S, Ukawa H. Roles of prostaglandin E-receptor
subtypes in gastric and duodenal bicarbonate secretion in rats. Gastroenterology.
1997;113:1553-1559.
6 Takeuchi K, Ukawa H, Kato S, et al. Impaired duodenal bicarbonate secretion
and mucosal integrity in mice lacking prostaglandin E-receptor subtype EP3.
Gastroenterology. 1999;117:1128-1135.
Level of interest: An article of importance in its field
Quality of written English: Acceptable
Statistical review: No, the manuscript does not need to be seen by a
statistician.
Declaration of competing interests:
I declare that I have no competing interests.