Ikarashi N, Baba K, Ushiki T, Kon R, Mimura A, Toda T, Ishii M, Ochiai W, Sugiyama K. The laxative effect of bisacodyl is attributable to decreased aquaporin-3 expression in the colon induced by increased PGE 2 secretion from macrophages. Am J Physiol Gastrointest Liver Physiol 301: G887-G895, 2011. First published August 25, 2011; doi:10.1152/ajpgi.00286.2011.-The purpose of this study was to investigate the role of aquaporin3 (AQP3) in the colon in the laxative effect of bisacodyl. After oral administration of bisacodyl to rats, AQP3, macrophages, cyclooxygenase 2 (COX2), and prostaglandin E 2 (PGE2) were examined in the colon. The mechanism by which bisacodyl decreases the expression of AQP3 was examined using HT-29 and Raw264.7 cells. When diarrhea occurred, a significant increase in the expression of PGE 2 and a decrease in AQP3 expression were observed. Immunostaining showed COX2 expression only in macrophages. The PGE 2 concentration increased significantly 30 min after the addition of bisacodyl to Raw264.7 cells. Thirty minutes after PGE 2 addition to HT-29 cells, the AQP3 expression level decreased to 40% of the control. When pretreated with indomethacin, bisacodyl did not induce an increase in the colon PGE 2 level, a decrease in the AQP3 expression level, or diarrhea. The results suggest that bisacodyl may decrease the expression of AQP3 in the colon, which inhibits water transfer from the luminal to the vascular side and leads to a laxative effect. This study also showed that direct activation of colon macrophages by bisacodyl increases the secretion of PGE 2, which acts as a paracrine factor and decreases AQP3 expression in colon mucosal epithelial cells. aquaporin-3; prostaglandin E 2; bisacodyl; cyclooxygenase IN RECENT YEARS, IT HAS BECOME increasingly clear that aquaporins (AQPs), water channels, are involved in water transport in the intestinal tract (20). There are currently 13 known types of AQPs in humans, AQP0 through AQP12, which are expressed in a variety of tissues (15). Several AQPs are expressed in the intestinal tract, and at least the following eight types are known to exist there: AQP1, AQP2, AQP3, AQP4, AQP7, AQP8, AQP9, and AQP10 (5, 7, 17, 23). The main AQPs expressed in the colon are AQP1, AQP2, AQP3, AQP4, and AQP8 (5,16,23). Of these, extensive research has been conducted on AQP3, which is considered to play an important role in the colon, especially regarding water transfer (13, 34). We have found that the administration of the osmotic laxative magnesium sulfate (MgSO 4 ) to rats increases the expression of AQP3 in the colon, and an increase in the expression of AQP3 plays an essential role in the laxative effect of MgSO 4 (11,12).Bisacodyl is classified as a stimulant laxative and is widely used to treat constipation. Bisacodyl increases the production of prostaglandin E 2 (PGE 2 ) in intestinal epithelial cells and inhibits the activity of Na ϩ -K ϩ -ATPase, and, as a result, the osmotic pressure in the intestinal tract increases. It is believed that this increase in osmoti...

In human, aquaporins (AQPs) are expressed in a variety of tissues, and there are currently 13 known types of AQPs: AQP0 through AQP12.1) Several members of the AQP family are expressed in the intestinal tract, and at least 8 types are known to exist there: AQP1, AQP2, AQP3, AQP4, AQP7, AQP8, AQP9, and AQP10. 2-4)The main types expressed in mucosal epithelial cells in the colon are AQP3, AQP4 and AQP8.5) It has been reported that vasoactive intestinal polypeptide (VIP), a gastrointestinal hormone, is the causative agent in Verner-Morrison syndrome, a disease associated with diarrhoea 6) ; that intravenous administration of VIP in healthy adults causes diarrhoea 7) ; that serum VIP concentrations are elevated in rats with colitis 8) ; and that VIP increases mRNA and protein expression levels of AQP3 in HT-29 cells, which are human colonic epithelial cells.9) It has also been reported that following resection of the small bowel in rats, there is an increase in the mRNA expression of AQP3 in the colon as diarrhoea occurs.9) Based on these findings, AQP3 appears to play a particularly important role in water transport in the colon. Despite suggestions of an apparent relationship between the occurrence of diarrhoea and AQP3 expression levels, the manner in which variations in AQP3 expression are related to the mechanism of action of laxatives has yet to be elucidated.It is believed that commonly used osmotic laxatives, such as magnesium sulphate (MgSO 4 ) and magnesium oxide (MgO), induce diarrhoea by causing an increase in the osmotic pressure in the intestinal tract, 10) but no details are known about the relationship between these osmotic laxatives and water transport. In the present study, we investigated the role of AQP3 in the colon on the laxative effect of MgSO 4 , a widely used osmotic laxative. First, rats were administered MgSO 4 , and faecal water content was measured over time as an indicator of diarrhoea. Then, by analyzing the expression level of genes that sharply increase as a result of increased osmotic pressure, we investigated the relationship between diarrhoea and osmotic pressure. Next, protein expression levels of AQP3, AQP4, and AQP8 in the rat colon were analyzed by immunostaining in order to investigate the distribution and intensity of AQP expression. By analyzing the expression of AQP3 in the colons of rats administered MgSO 4 , the relationship between the expression level and the laxative effects of MgSO 4 was then investigated. MATERIALS AND METHODS AnimalsMale Wistar rats (10 weeks old) were purchased from Sankyo Labo Service Corp., Inc. (Tokyo, Japan). Each rat was caged separately and kept at room temperature (24Ϯ1°C) and 55Ϯ5% humidity with 12 h of light (artificial illumination; 08:00-20:00). The present study was conducted in accordance with the Guiding Principles for the Care and Use of Laboratory Animals, as adopted by the Committee on Animal Research at Hoshi University.Treatment Rats were fasted for 18 h before MgSO 4 administration (water provided ad libitum). An aqueous solut...

Abstract. Histologic and immunohistochemical studies were carried out on four young cattle with diabetes mellitus associated with persistent bovine viral diarrhea (BVD) virus infection. Clinical findings included persistent hyperglycemia, decreased glucose tolerance, glycosuria, polydipsia, and severe emaciation. Macroscopically, multiple erosions and ulcers in the mucosa of upper and lower alimentary tracts and swollen lymph nodes were commonly observed. Erosions and ulcers in the mucosa of tongue, esophagus, and forestomach were represented histologically by necrosis of squamous epithelium with neutrophilic infiltration. In the small and large intestines, villous atrophy and suppurative cryptitis were often observed, along with diffuse infiltration of lymphocytes and macrophages and fibroplasia in the lamina propna. In the pancreas of all cattle, there was a reduction in the number of islet cells, and most of the residual islet cells had hydropic degeneration and a decreased number of secretory granules. Immunohistochemical examination confirmed that these cells were severely degranulated P-cells. In addition, many islets containing necrotic islet cells were observed. These islet cells had increased eosinophilia and shrinkage of cytoplasm, as well as pyknotic nuclei. Inflammation of the islets with mild infiltration of lymphocytes was observed in all pancreatic lobes. In addition, bovine IgGimmunoreactive cells were identified immunohistochemically in the affected pancreatic islets. The BVD virus antigen was not identified in the cytoplasm of the islet cells by immunohistochemical study, although it was identified in the epithelial cells of the small intestine. The histologic and immunohistochemical studies demonstrated that the pancreatic lesions in these animals were similar to those caused by acute insulin-dependent diabetes mellitus (IDDM) in human beings. These findings suggest that IDDM in Japanese Black cattle is an autoimmune disease induced through persistent infection by BVD virus.

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The pharmacokinetics of drugs can change in diabetes mellitus and even among diabetics. They may differ between type I diabetes (T1DM) and type 2 diabetes (T2DM). As triazolam was administered orally to Tsumura, Suzuki, obese, diabetes (TSOD) mice and streptozotocin (STZ) mice, clearance per body (CL/F) in TSOD mice did not differ compared with Tsumura, Suzuki, non-obesity (TSNO) mice. In STZ mice, CL/F was greater than in control mice. Small intestinal cytochrome P450 (Cyp) 3a expression in TSOD mice was significantly lower than in TSNO mice. No significant difference existed in small intestinal Cyp3a expression between STZ mice and control mice. In insulin-treated mice, small intestinal Cyp3a expression was significantly lower than in control mice. These results suggested that the differences in changes in small intestinal Cyp3a expression between T1DM and T2DM may be due to differences in plasma insulin concentrations. This may be a factor in the difference in the drug pharmacokinetics between T2DM and T1DM patients.

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Background: The extracellular matrix is associated with diabetic complications; however, chondroitin sulfate (CS) role remains unclear. Herein, genetically engineered mice lacking the rate-limiting CS-synthesizing enzyme, CS N-acetylgalactosaminyltransferase-1 (T1), were used to clarify CS effects on diabetic neuropathy. Diabetes was induced by streptozotocin injection in 6-week-old male T1 knockout (T1KO) and wild-type (WT) mice. Results: Previously reported preliminary data at the former ADA meeting revealed that thermal nociception and the number of plantar peripheral nerve fibers were disrupted in diabetic WT mice, whereas in diabetic T1KO were preserved. Moreover, conduction velocity in the sciatic nerve was significantly declined in diabetic WT than in T1KO mice. [A1] Immunohistochemical data revealed loss of calcitonin gene-related peptide-positive neurons in the dorsal root ganglia (DRG) in diabetic WT mice, whereas those neurons were protected in diabetic T1KO mice. Moreover, DRG gene expression analysis showed that caspase-3 and -9 were reduced in T1KO compared with WT mice. To investigate the mechanisms underlying these events, the role of pericytes, which are important CS-expressing components of the blood-nerve barrier (BNB), was explored. Assessment of the retinal vessels, which represent a good model to evaluate pericyte functions and easier to access than peripheral nerves, revealed a higher proportion of pericyte-deficient retina blood vessels in diabetic WT than in T1KO mice upon administration of a platelet-derived growth factor receptor (PDGFR) β antibody. Therefore, pericytes in T1KO mice were more resistant against PDGFRβ antibody than those of WT mice. Thus, it is possible that the BNB in T1KO mice may be more resistant against external stress, including diabetes. Conclusions: Reduced CS production may induce beneficial effects to prevent diabetic neuropathy by improving pericyte function. Disclosure H. Ishiguro: None. T. Ushiki: None. A. Honda: None. T. Mikami: None. H. Kitagawa: None. K. Sango: None. M. Masuko: None. M. Igarashi: None. H. Sone: Research Support; Self; Astellas Pharma Inc., Eisai Co., Ltd., Kyowa Kirin Co., Ltd., Novo Nordisk, Ono Pharmaceutical Co., Ltd., Taisho Pharmaceutical Co., Ltd., Takeda Pharmaceutical Co.

Background: The extracellular matrix is associated with the pathophysiology of diabetic complications; however, the role of chondroitin sulfate (CS) remains unclear. To clarify the effects of CS on diabetic neuropathy (DN), we assessed the effect of genetically reducing CS in mice through disruption of a gene encoding the rate-limiting CS-synthesizing enzyme, i.e., CS N-acetylgalactosaminyltransferase-1 (T1). Methods: T1 knockout (T1KO) mice were generated from the C57BL/6N strain and C57BL/6N were prepared as wild type (WT). Diabetes was induced through streptozotocin injection in 6-week-old male mice. All data were obtained 3 weeks after streptozotocin injection. Results: In the heat radiant test, while thermal nociception in nondiabetic WT and T1KO mice were normal and significantly disrupted in diabetic WT mice, that in diabetic T1KO mice was preserved. The number of plantar peripheral nerve fibers was also significantly decreased in diabetic WT mice; however, that in diabetic T1KO mice were relatively normal. Furthermore, immunohistochemistry revealed loss of calcitonin gene-related peptide-positive neurons in the dorsal root ganglia (DRG) in diabetic WT mice, which contains a cluster of sensory neuron bodies. In contrast, those neurons were protected in diabetic T1KO mice. Hence, nociception and thermoception are preserved in diabetic T1KO mice. To investigate the mechanisms underlying these events, we analyzed gene expression in DRG through real-time polymerase chain reaction and confirmed the suppression of caspase-3 and caspase-9 in diabetic T1KO mice, compared to those in diabetic WT mice. However, levels of Bcl2, TNF-α, MMP9, and reactive oxygen species-related enzymes (HO-1, NOX) did not differ significantly between WT and T1KO diabetic mice. Conclusions: Reduced CS production is suggested to have potentially beneficial effects on preventing DN by suppressing apoptotic signaling and could be a cutting-edge target of clinical application. Disclosure H. Ishiguro: Research Support; Self; MSD K.K., Sanofi K.K., Eli Lilly and Company. T. Ushiki: None. A. Kawasaki: None. K. Cho: None. M. Masuko: None. K. Sango: None. M. Igarashi: None. H. Sone: Research Support; Self; Novo Nordisk Inc., Eli Lilly and Company, MSD K.K., Chugai Pharmaceutical Co., Ltd., Taisho Pharmaceutical Co., Ltd., Takeda Development Center Asia, Pte. Ltd., Daiichi Sankyo Company, Limited, Ono Pharmaceutical Co., Ltd., Kyowa Hakko Kirin Co., Ltd., Sanofi, Kowa Pharmaceuticals America, Inc., Eisai Inc..