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Involvement of the gut chemosensory system in the regulation of colonic anion secretion.

Kuwahara A - Biomed Res Int (2015)

Bottom Line: However, study of the regulation of gut function by the gut chemosensory system has become increasingly important, as failure of this system causes dysfunctions in host homeostasis, as well as functional GI disorders.Furthermore, regulation of ion transport in the colon is critical for host defense and for electrolytes balance.This review discusses the role of the gut chemosensory system in epithelial transport, with a particular emphasis on the colon.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Physiology, School of Food and Nutritional Sciences/Graduate Division of Nutritional and Environmental Sciences, University of Shizuoka, Shizuoka, 422-8526, Japan.

ABSTRACT
The primary function of the gastrointestinal (GI) tract is the extraction of nutrients from the diet. Therefore, the GI tract must possess an efficient surveillance system that continuously monitors the luminal content for beneficial or harmful compounds. Recent studies have shown that specialized cells in the intestinal lining can sense changes in this content. These changes directly influence fundamental GI processes such as secretion, motility, and local blood flow via hormonal and/or neuronal pathways. Until recently, most studies examining the control of ion transport in the colon have focused on neural and hormonal regulation. However, study of the regulation of gut function by the gut chemosensory system has become increasingly important, as failure of this system causes dysfunctions in host homeostasis, as well as functional GI disorders. Furthermore, regulation of ion transport in the colon is critical for host defense and for electrolytes balance. This review discusses the role of the gut chemosensory system in epithelial transport, with a particular emphasis on the colon.

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Schematic diagram of Cl− secretion stimulated by an odor tastant (thymol) in colonic epithelial cells. Activation of OR1G1 by luminal thymol increases [Ca2+]i. The elevated [Ca2+]i may modulate Ca2+-activated basolateral K+ channels, providing a driving force for the exit of Cl−/HCO3−. Activation of OR1G1 may also activate TRPA1 although it is still unclear whether ORs are linked to TRPA1.
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fig3: Schematic diagram of Cl− secretion stimulated by an odor tastant (thymol) in colonic epithelial cells. Activation of OR1G1 by luminal thymol increases [Ca2+]i. The elevated [Ca2+]i may modulate Ca2+-activated basolateral K+ channels, providing a driving force for the exit of Cl−/HCO3−. Activation of OR1G1 may also activate TRPA1 although it is still unclear whether ORs are linked to TRPA1.

Mentions: Recently, we showed that mucosal addition of thymol (10−3 M) induces Cl− and HCO3− secretion in a concentration-dependent manner in both the human and rat colon [8]. Addition of TTX (10−6 M) or piroxicam (10−5 M) did not affect this response, suggesting that thymol-induced anion secretion is independent of the neural and PG synthesis pathways. This differs from stimulation of the bitter taste receptor; thus, there are distinct mechanisms for detecting tastants in the colonic mucosa. It has been reported that odorant stimulation leads to an increase in [Ca2+]i in olfactory neurons and in other OR-expressing cells, depending on extracellular Ca2+ [54, 62, 63]. Thymol-induced electrogenic anion secretion is also abolished under Ca2+-free conditions [8]. These results suggest that extracellular Ca2+ is required to elicit thymol-induced anion secretion in the large intestine (Figure 3).


Involvement of the gut chemosensory system in the regulation of colonic anion secretion.

Kuwahara A - Biomed Res Int (2015)

Schematic diagram of Cl− secretion stimulated by an odor tastant (thymol) in colonic epithelial cells. Activation of OR1G1 by luminal thymol increases [Ca2+]i. The elevated [Ca2+]i may modulate Ca2+-activated basolateral K+ channels, providing a driving force for the exit of Cl−/HCO3−. Activation of OR1G1 may also activate TRPA1 although it is still unclear whether ORs are linked to TRPA1.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4383346&req=5

fig3: Schematic diagram of Cl− secretion stimulated by an odor tastant (thymol) in colonic epithelial cells. Activation of OR1G1 by luminal thymol increases [Ca2+]i. The elevated [Ca2+]i may modulate Ca2+-activated basolateral K+ channels, providing a driving force for the exit of Cl−/HCO3−. Activation of OR1G1 may also activate TRPA1 although it is still unclear whether ORs are linked to TRPA1.
Mentions: Recently, we showed that mucosal addition of thymol (10−3 M) induces Cl− and HCO3− secretion in a concentration-dependent manner in both the human and rat colon [8]. Addition of TTX (10−6 M) or piroxicam (10−5 M) did not affect this response, suggesting that thymol-induced anion secretion is independent of the neural and PG synthesis pathways. This differs from stimulation of the bitter taste receptor; thus, there are distinct mechanisms for detecting tastants in the colonic mucosa. It has been reported that odorant stimulation leads to an increase in [Ca2+]i in olfactory neurons and in other OR-expressing cells, depending on extracellular Ca2+ [54, 62, 63]. Thymol-induced electrogenic anion secretion is also abolished under Ca2+-free conditions [8]. These results suggest that extracellular Ca2+ is required to elicit thymol-induced anion secretion in the large intestine (Figure 3).

Bottom Line: However, study of the regulation of gut function by the gut chemosensory system has become increasingly important, as failure of this system causes dysfunctions in host homeostasis, as well as functional GI disorders.Furthermore, regulation of ion transport in the colon is critical for host defense and for electrolytes balance.This review discusses the role of the gut chemosensory system in epithelial transport, with a particular emphasis on the colon.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Physiology, School of Food and Nutritional Sciences/Graduate Division of Nutritional and Environmental Sciences, University of Shizuoka, Shizuoka, 422-8526, Japan.

ABSTRACT
The primary function of the gastrointestinal (GI) tract is the extraction of nutrients from the diet. Therefore, the GI tract must possess an efficient surveillance system that continuously monitors the luminal content for beneficial or harmful compounds. Recent studies have shown that specialized cells in the intestinal lining can sense changes in this content. These changes directly influence fundamental GI processes such as secretion, motility, and local blood flow via hormonal and/or neuronal pathways. Until recently, most studies examining the control of ion transport in the colon have focused on neural and hormonal regulation. However, study of the regulation of gut function by the gut chemosensory system has become increasingly important, as failure of this system causes dysfunctions in host homeostasis, as well as functional GI disorders. Furthermore, regulation of ion transport in the colon is critical for host defense and for electrolytes balance. This review discusses the role of the gut chemosensory system in epithelial transport, with a particular emphasis on the colon.

Show MeSH
Related in: MedlinePlus