Centrally administered butyrate improves gut barrier function, visceral sensation and septic lethality in rats.

Short chain fatty acids readily crosses the gut-blood and blood-brain barrier and acts centrally to influence neuronal signaling. We hypothesized that butyrate, a short-chain fatty acid produced by bacterial fermentation, in the central nervous system may play a role in the regulation of intestinal functions. Colonic permeability and visceral sensation was evaluated in rats. Septic lethality was evaluated in a sepsis model induced by subcutaneous administration of both lipopolysaccharide and colchicine. Intracisternal butyrate dose-dependently improved colonic hyperpermeability and visceral nociception. In contrast, subcutaneous injection of butyrate failed to change it. Intracisternal orexin 1 receptor antagonist or surgical vagotomy blocked the central butyrate-induced improvement of colonic hyperpermeability. The improvement of intestinal hyperpermeability by central butyrate or intracisternal orexin-A was blocked by cannabinoid 1 or 2 receptor antagonist. Intracisternal butyrate significantly improved survival period in septic rats. These results suggest that butyrate acts in the central nervous system to improve gut permeability and visceral nociception through cannabinoid signaling. Endogenous orexin in the brain may mediate the reduction of intestinal hyperpermeability by central butyrate through the vagus nerve. We would suggest that improvement of leaky gut by central butyrate may induce visceral antinociception and protection from septic lethality.

Prostaglandin I2 suppresses the development of diet-induced nonalcoholic steatohepatitis in mice.

Nonalcoholic steatohepatitis (NASH) is a hepatic manifestation of metabolic syndrome. Although the prostaglandin (PG)I2 receptor IP is expressed broadly in the liver, the role of PGI2-IP signaling in the development of NASH remains to be determined. Here, we investigated the role of the PGI2-IP system in the development of steatohepatitis using mice lacking the PGI2 receptor IP [IP-knockout (IP-KO) mice] and beraprost (BPS), a specific IP agonist. IP-KO and wild-type (WT) mice were fed a methionine- and choline-deficient diet (MCDD) for 2, 5, or 10 wk. BPS was administered orally to mice every day during the experimental periods. The effect of BPS on the expression of chemokine and inflammatory cytokines was examined also in cultured Kupffer cells. WT mice fed MCDD developed steatohepatitis at 10 wk. IP-KO mice developed steatohepatitis at 5 wk with augmented histologic derangements accompanied by increased hepatic monocyte chemoattractant protein-1 (MCP-1) and TNF-α concentrations. After 10 wk of MCDD, IP-KO mice had greater hepatic iron deposition with prominent oxidative stress, resulting in hepatocyte damage. In WT mice, BPS improved histologic and biochemical parameters of steatohepatitis, accompanied by reduced hepatic concentration of MCP-1 and TNF-α. Accordingly, BPS suppressed the LPS-stimulated Mcp-1 and Tnf-α mRNA expression in cultured Kupffer cells prepared from WT mice. PGI2-IP signaling plays a crucial role in the development and progression of steatohepatitis by modulating the inflammatory response, leading to augmented oxidative stress. We suggest that the PGI2-IP system is an attractive therapeutic target for treating patients with NASH.-Kumei, S., Yuhki, K.-I., Kojima, F., Kashiwagi, H., Imamichi, Y., Okumura, T., Narumiya, S., Ushikubi, F. Prostaglandin I2 suppresses the development of diet-induced nonalcoholic steatohepatitis in mice.

Metformin inhibits visceral allodynia and increased gut permeability induced by stress in rats.

BACKGROUND AND AIM: Metformin has been shown to have anti-cytokine property. Lipopolysaccharide (LPS)-induced or repeated water avoidance stress (WAS)-induced visceral allodynia and increased gut permeability were pro-inflammatory cytokine-dependent responses, which were considered to be animal models of irritable bowel syndrome (IBS). We hypothesized that metformin improves symptoms in the patients with IBS by attenuating these visceral changes and tested the hypothesis in rats. METHODS: The threshold of the visceromotor response induced by colonic balloon distention was measured. Colonic permeability was determined in vivo by quantifying the absorbed Evans blue for 15 min spectrophotometrically. RESULTS: Subcutaneously injected LPS (1 mg/kg) reduced the threshold of visceromotor response, and metformin (5-50 mg/kg for 3 days) intraperitoneally attenuated this response in a dose-dependent manner. Repeated WAS (1 h daily for 3 days) induced visceral allodynia, which was also blocked by metformin. The antinociceptive effect of metformin on the LPS-induced allodynia was reversed by compound C, an adenosine monophosphate-activated protein kinase inhibitor or NG -nitro-L-arginine methyl ester, a nitric oxide synthesis inhibitor but not modified by naloxone. Additionally, it was blocked by sulpiride, a dopamine D2 receptor antagonist, but domperidone, a peripheral dopamine D2 receptor antagonist, did not alter it. Metformin also blocked the LPS-induced or repeated WAS-induced increased colonic permeability. CONCLUSIONS: Metformin attenuated the visceral allodynia and increased gut permeability in animal IBS models. These actions may be evoked via activation of adenosine monophosphate-activated protein kinase, nitric oxide, and central dopamine D2 pathways. These results indicate the possibility that metformin can be useful for treating IBS.

Role of the cannabinoid signaling in the brain orexin- and ghrelin-induced visceral antinociception in conscious rats.

We hypothesized that the cannabinoid (CB) system may mediate the brain orexin- or ghrelin-induced visceral antinociception. Intraperitoneal injection of either CB1/2 agonist, WIN 55212 or O-Arachidonoyl ethanolamine increased the threshold volume of colonic distension-induced abdominal withdrawal reflex in rats, suggesting CB could induce visceral antinociception. Pretreatment with either the CB1 or CB2 antagonist potently blocked the centrally injected orexin-A-induced antinociceptive action against colonic distension while CB2 but not CB1 antagonist blocked the brain ghrelin-induced visceral antinociception. These results suggest that the cannabinoid signaling may be involved in the central orexin- or ghrelin-induced antinociceptive action in a different mechanistic manner.

Glucagon-like peptide-1 analog, liraglutide, improves visceral sensation and gut permeability in rats.

BACKGROUND AND AIM: A glucagon-like peptide-1 analog, liraglutide, has been reported to block inflammatory somatic pain. We hypothesized that liraglutide attenuates lipopolysaccharide (LPS)-induced and repeated water avoidance stress (WAS)-induced visceral hypersensitivity and tested the hypothesis in rats. METHODS: The threshold of the visceromotor response induced by colonic balloon distention was measured to assess visceral sensation. Colonic permeability was determined in vivo by quantifying the absorbed Evans blue spectrophotometrically, which was instilled in the proximal colon for 15 min. The interleukin-6 level in colonic mucosa was also quantified using ELISA. RESULTS: Subcutaneously injected LPS (1 mg/kg) reduced the visceromotor response threshold after 3 h. Liraglutide (300 µg/kg subcutaneously) at 15 h and 30 min before injecting LPS eliminated LPS-induced allodynia. It also blocked the allodynia induced by repeated water avoidance stress for 1 h for three consecutive days. Neither vagotomy nor naloxone altered the antinociceptive effect of liraglutide, but NG -nitro-L-arginine methyl ester, a nitric oxide synthesis inhibitor, blocked it. LPS increased colonic permeability and the interleukin-6 level, and the analog significantly inhibited these responses. CONCLUSIONS: This study suggests that liraglutide blocked LPS-induced visceral allodynia, which may be a nitric oxide-dependent response, and was probably mediated by inhibiting pro-inflammatory cytokine production and attenuating the increased gut permeability. Because the LPS-cytokine system is considered to contribute to altered visceral sensation in irritable bowel syndrome, these results indicate the possibility that liraglutide can be useful for treating this disease.

Levodopa acts centrally to induce an antinociceptive action against colonic distension through activation of D2 dopamine receptors and the orexinergic system in the brain in conscious rats.

Levodopa possesses antinociceptive actions against several somatic pain conditions. However, we do not know at this moment whether levodopa is also effective to visceral pain. The present study was therefore performed to clarify whether levodopa is effective to visceral pain and its mechanisms. Visceral sensation was evaluated by colonic distension-induced abdominal withdrawal reflex (AWR) in conscious rats. Subcutaneously (80 mg/rat) or intracisternally (2.5 µg/rat) administered levodopa significantly increased the threshold of colonic distension-induced AWR in conscious rats. The dose difference to induce the antinociceptive action suggests levodopa acts centrally to exert its antinociceptive action against colonic distension. While neither sulpiride, a D2 dopamine receptor antagonist, nor SCH23390, a D1 dopamine receptor antagonist by itself changed the threshold of colonic distension-induced AWR, the intracisternally injected levodopa-induced antinociceptive action was significantly blocked by pretreatment with subcutaneously administered sulpiride but not SCH23390. Treatment with intracisternal SB334867, an orexin 1 receptor antagonist, significantly blocked the subcutaneously administered levodopa-induced antinociceptive action. These results suggest that levodopa acts centrally to induce an antinociceptive action against colonic distension through activation of D2 dopamine receptors and the orexinergic system in the brain.

The novel prostaglandin I2 mimetic ONO-1301 escapes desensitization in an antiplatelet effect due to its inhibitory action on thromboxane A2 synthesis in mice.

ONO-1301 [(E)-[5-[2-[1-phenyl-1-(3-pyridyl)methylidene-aminooxy]ethyl]-7,8-dihydronaphthalene-1-yloxy]acetic acid] is a novel prostaglandin (PG) I2 mimetic with inhibitory activity on the thromboxane (TX) A2 synthase. Interestingly, ONO-1301 retains its inhibitory effect on platelet aggregation after repeated administration, while beraprost, a representative agonist for the PGI2 receptor (IP), loses its inhibitory effect after repeated administration. In the present study, we intended to clarify the mechanism by which ONO-1301 escapes desensitization of an antiplatelet effect. In platelets prepared from wild-type mice, ONO-1301 inhibited collagen-induced aggregation and stimulated cAMP production in an IP-dependent manner. In addition, ONO-1301 inhibited arachidonic acid-induced TXA2 production in platelets lacking IP. Despite the decrease in stimulatory action on cAMP production, the antiplatelet effect of ONO-1301 hardly changed after repeated administration for 10 days in wild-type mice. Noteworthy, beraprost could retain its antiplatelet effect after repeated administration in combination with a low dose of ozagrel, a TXA2 synthase inhibitor. Therefore, we hypothesized that chronic IP stimulation by beraprost induces an increase in TXA2 production, leading to reduction in the antiplatelet effect. As expected, repeated administration of beraprost increased the plasma and urinary levels of a TXA2 metabolite, while ONO-1301 did not increase them significantly. In addition, beraprost could retain the ability to inhibit platelet aggregation after repeated administration in mice lacking the TXA2 receptor (TP). These results indicate that TP-mediated signaling participates in platelet desensitization against IP agonists and that simultaneous inhibition of TXA2 production confers resistance against desensitization on IP agonists.

Prostaglandin I2 suppresses the development of gut-brain axis disorder in irritable bowel syndrome in rats.

In this study, we attempted to clarify a role of prostaglandin (PG) I2 and its specific receptor, IP in the pathogenesis of irritable bowel syndrome (IBS) using a maternal separation (MS)-induced IBS model. Administration of beraprost (BPS), a specific IP agonist, improved visceral hypersensitivity and depressive state with decreased serum CRF level in the IBS rats. To clarify the mechanism of the effect of BPS, we performed serum metabolome analysis and 1-methylnicotinamide (1-MNA) was identified as a possible candidate for a clue metabolite of pathogenesis of IBS. The serum 1-MNA levels revealed inverse correlation to the level of visceral sensitivity, and positive correlation to a depression marker, immobilizing time. Administration of 1-MNA induced visceral hypersensitivity and depression with increased levels of serum CRF. Since fecal 1-MNA is known for a marker of dysbiosis, we examined the composition of fecal microbiota by T-RFLP analysis. The proportion of clostridium cluster XI, XIVa and XVIII was significantly changed in MS-induced IBS rats treated with BPS. Fecal microbiota transplant of BPS-treated rats improved visceral hypersensitivity and depression in IBS rats. These results suggest for the first time that PGI2-IP signaling plays an important role in IBS phenotypes such as visceral hypersensitivity and depressive state. BPS modified microbiota, thereby inhibition of 1-MNA-CRF pathway, followed by improvement of MS-induced IBS phenotype. These results suggest that the PGI2-IP signaling could be considered to be a therapeutic option for IBS.

IL-1 receptor antagonist blocks the lipopolysaccharide-induced inhibition of gastric motility in freely moving conscious rats.

BACKGROUND AND AIMS: Endotoxin/lipopolysaccharide (LPS) alters gastrointestinal functions. However, little is known as to whether LPS could change gastric antral contractility in freely moving conscious animals. We tried to clarify this problem and the associated mechanisms. METHODS: In this study, we recorded intraluminal gastric pressure waves in freely moving conscious rats by manometric catheter located in the antrum. Area under the manometric trace was evaluated as motor index (MI). RESULTS: Intraperitoneal injection of LPS at doses of 0.2 mg/kg or more significantly inhibited MI. The inhibition started immediately after the administration of LPS and lasted over 1 h. Intraperitoneal injection of IL-1ß potently decreased MI while neither IL-6 nor TNF-α inhibited gastric motility, suggesting IL-1ß specifically reduced gastric motility. Next, we examined the hypothesis that endogenous IL-1 mediates the LPS-induced inhibition of gastric motility. To address the speculation, an IL-1 receptor antagonist (IL-1Ra) was used to block IL-1 signaling. Pretreatment with IL-1Ra at a dose of 20 mg/kg significantly blocked the inhibition of gastric contractility by LPS at a dose of 0.2 mg/kg. CONCLUSIONS: These results suggest for the first time that LPS or IL-1ß is capable of inhibiting gastric motility in conscious rats and that endogenously released IL-1 may mediate the LPS-evoked inhibition of gastric antral motility. This evidence also led us to speculate that IL-1Ra may be a therapeutic tool for patients with disturbed gastrointestinal functions under septic conditions.

A patient with familial Mediterranean fever mimicking diarrhea-dominant irritable bowel syndrome who successfully responded to treatment with colchicine: a case report.

BACKGROUND: Irritable bowel syndrome is a functional gastrointestinal disease. Visceral hypersensitivity is the most important pathophysiology in irritable bowel syndrome. Currently, diagnosis of irritable bowel syndrome is based on symptoms and exclusion of other organic diseases. Although the diagnosis of irritable bowel syndrome can be made based on the Rome IV criteria, one may speculate that complete exclusion of other organic diseases is not so easy, especially in cases uncontrolled with standard therapies. CASE PRESENTATION: We present herein a case of familial Mediterranean fever in a young Japanese patient who had been suffering from an irritable bowel syndrome-like clinical course. A 25-year-old Japanese male had been diagnosed as having diarrhea-predominant irritable bowel syndrome 5 years earlier. Unfortunately, standard therapies failed to improve irritable bowel syndrome symptoms. After careful medical history-taking, we understood that he had also experienced periodic fever since 10 years ago. Although no mutation was identified in the Mediterranean fever gene, not only periodic fever but abdominal symptoms improved completely after colchicine administration. He was therefore diagnosed as having familial Mediterranean fever and that the abdominal symptoms may be related to the disease. CONCLUSIONS: Familial Mediterranean fever should be considered as a cause of irritable bowel syndrome-like symptoms.

Epipericardial Fat Necrosis: A Retrospective Analysis in Japan.

Objective Epipericardial fat necrosis (EFN) has been considered to be a rare cause of acute chest pain, and especially important for emergency physicians. Chest computed tomography (CT) is often used for the diagnosis of EFN after excluding life-threatening states, such as acute coronary syndrome and pulmonary embolism. While the proportion of EFN patients who underwent chest CT in emergency departments is being clarified, little is still known about other departments in Japan. To investigate the proportion of EFN patients who underwent chest CT for acute chest pain in various departments. Methods Chest CT performed from January 2015 to July 2020 in Asahikawa Medical University Hospital in Japan was retrospectively analyzed in this study. All images were reviewed by two radiologists. Results There were 373 outpatients identified by a search using the word 'chest pain' who underwent chest CT. Eight patients satisfying the imaging criteria were diagnosed with EFN. The proportions of patients diagnosed with EFN were 10.7%, 4.8%, 2.8%, 0.9% and 0% in the departments of general medicine, cardiovascular surgery, emergency medicine, cardiovascular internal medicine and respiratory medicine, respectively. Only 12.5% of the patients were correctly diagnosed with EFN, and the other patients were treated for musculoskeletal symptoms, acute pericarditis or hypochondriasis. Conclusion EFN is not rare and is often overlooked in various departments. All physicians as well as emergency physicians should consider the possibility of EFN as the cause of pleuritic chest pain.

Oxytocin acts centrally in the brain to improve leaky gut through the vagus nerve and a cannabinoid signaling in rats.

Brain oxytocin plays a role in gastrointestinal functions. Among them, oxytocin acts centrally to modulate gastrointestinal motility and visceral sensation. Intestinal barrier function, one of important gut functions, is also regulated by the central nervous system. Little is, however, known about a role of central oxytocin in the regulation of intestinal barrier function. The present study was performed to clarify whether brain oxytocin is also involved in regulation of intestinal barrier function and its mechanism. Colonic permeability was estimated in vivo by quantifying the absorbed Evans blue in colonic tissue in rats. Intracisternal injection of oxytocin dose-dependently abolished increased colonic permeability in response to lipopolysaccharide while intraperitoneal injection of oxytocin at the same dose failed to block it. Either atropine or surgical vagotomy blocked the central oxytocin-induced improvement of colonic hyperpermeability. Cannabinoid 1 receptor antagonist but not adenosine or opioid receptor antagonist prevented the central oxytocin-induced blockade of colonic hyperpermeability. In addition, intracisternal injection of oxytocin receptor antagonist blocked the ghrelin- or orexin-induced improvement of intestinal barrier function. These results suggest that oxytocin acts centrally in the brain to reduce colonic hyperpermeability. The vagal cholinergic pathway or cannabinoid 1 receptor signaling plays a vital role in the process. The oxytocin-induced improvement of colonic hyperpermeability mediates the central ghrelin- or orexin-induced improvement of intestinal barrier function. We would therefore suggest that activation of central oxytocin signaling may be useful for leaky gut-related diseases such as irritable bowel syndrome and autism.

Activation of central adenosine A2B receptors mediate brain ghrelin-induced improvement of intestinal barrier function through the vagus nerve in rats.

Leaky gut that is a condition reflecting intestinal barrier dysfunction has been attracting attention for its relations with many diseases such as irritable bowel syndrome or Alzheimer dementia. We have recently demonstrated that ghrelin acts in the brain to improve leaky gut via the vagus nerve. In the present study, we tried to clarify the precise central mechanisms by which ghrelin improves intestinal barrier function through the vagus nerve. Colonic permeability was estimated in vivo by quantifying the absorbed Evans blue in colonic tissue in rats. Adenosine receptor antagonist, 1,3-dipropyl-8-cyclopentylxanthine (DPCPX), blocked the intracisternal ghrelin-induced improvement of intestinal hyperpermeability while dopamine, cannabinoid or opioid receptor antagonist failed to prevent it. Since DPCPX can block adenosine A1 and adenosine A2B receptors, we examined which subtype is involved in the mechanism. Intracisternal injection of adenosine A2B agonist but not adenosine A1 agonist improved colonic hyperpermeability, while peripheral injection of adenosine A2B agonist failed to improve it. Intracisternal adenosine A2B agonist-induced improvement of colonic hyperpermeability was blocked by vagotomy. Adenosine A2B specific antagonist, alloxazine blocked the ghrelin- or central vagal stimulation by 2-deoxy-d-glucose-induced improvement of intestinal hyperpermeability. These results suggest that activation of adenosine A2B receptors in the central nervous system is capable of improving intestinal barrier function through the vagal pathway, and the adenosine A2B receptors may mediate the ghrelin-induced improvement of leaky gut in a vagal dependent fashion. These findings may help us understand the pathophysiology in not only gastrointestinal diseases but also non-gastrointestinal diseases associated with the altered intestinal permeability.

Adenosine A1 receptor agonist induces visceral antinociception via 5-HT1A, 5-HT2A, dopamine D1 or cannabinoid CB1 receptors, and the opioid system in the central nervous system.

We have recently demonstrated that N(6)-cyclopentyladenosine (CPA), an adenosine A1 receptor agonist, acts centrally to induce a visceral antinociception. Since serotonin (5-HT), cannabinoid (CB), dopamine or opioid signaling in the central nervous system is involved in the regulation of visceral sensation, we made a hypothesis that the signaling may play a role in the CPA-induced visceral antinociception. Visceral sensation was evaluated by colonic distension-induced abdominal withdrawal reflex (AWR) in conscious rats. Subcutaneously administered CPA significantly increased the threshold of colonic distension-induced AWR. Intracisternal injection of either 5-HT1A or 5-HT2A receptor antagonist blocked the CPA-induced visceral antinociception while 5-HT1B antagonist did not block the CPA-induced visceral antinociception. Subcutaneous injection of dopamine D1 receptor antagonist, CB1 receptor antagonist or naloxone significantly blocked the CPA-induced visceral antinociception while neither subcutaneous injection of dopamine D2 receptor antagonist nor CB2 receptor antagonist blocked the CPA-induced anti-pain action. These results suggest that 5-HT1A, 5-HT2A, dopamine D1, CB1 receptors and the opioid system in the CNS may specifically mediate the CPA-induced visceral antinociception. These findings may help in understanding the physiological relevance of central adenosine with special reference to the pathophysiology of altered visceral sensation especially in irritable bowel syndrome.

5-HT2A receptors but not cannabinoid receptors in the central nervous system mediate levodopa-induced visceral antinociception in conscious rats.

We have recently demonstrated that levodopa acts centrally to induce antinociceptive action against colonic distension through dopamine D2 receptors in rats. Since serotonin (5-HT) and cannabinoid are involved in the regulation of visceral sensation, we hypothesized that they may contribute to levodopa-induced visceral antinociception. We evaluated visceral sensation by colonic distension-induced abdominal withdrawal reflex (AWR) in conscious rats. Subcutaneously administered levodopa increased the threshold of colonic distension-induced AWR; moreover, an intracisternal injection of methiothepin, an unspecific 5-HT receptor antagonist, blocked the levodopa-induced visceral antinociception. Subsequently, we examined the roles of three 5-HT receptor subtypes: 5-HT1A, 5-HT1B, and 5-HT2A, in levodopa-induced visceral antinociception. Ketanserin is a 5-HT2A receptor antagonist that was intracisternally injected and blocked the levodopa-induced antinociception, but neither WAY100635 (5-HT1A receptor antagonist) nor isomoltane (5-HT1B receptor antagonist) did so. Antagonists AM251 (cannabinoid 1 receptor antagonist) or AM630 (cannabinoid 2 receptor antagonist) did not change the levodopa-induced visceral antinociception, suggesting that cannabinoid signaling may not be implicated in levodopa-induced visceral antinociception. We also examined the relation between dopamine D2 and 5-HT2A receptor signaling in the control of visceral sensation. Ketanserin, but not WAY100635, potently blocked the visceral antinociception by quinpirole, which is a dopamine D2 agonist. These results suggest that 5-HT2A receptors in the central nervous system may play specific roles in levodopa-dopamine D2 receptor-induced antinociceptive action against colonic distension.

Ghrelin acts in the brain to block colonic hyperpermeability in response to lipopolysaccharide through the vagus nerve.

Brain ghrelin plays a role in gastrointestinal functions. Among them, ghrelin acts centrally to stimulate gastrointestinal motility and induce visceral antinociception. Intestinal barrier function, one of important gastrointestinal functions, is also controlled by the central nervous system. Little is, however, known about a role of central ghrelin in regulation of intestinal permeability. The present study was performed to clarify whether brain ghrelin is also involved in regulation of intestinal barrier function and its mechanism. Colonic permeability was estimated in vivo by quantifying the absorbed Evans blue in colonic tissue in rats. Intracisternal injection of ghrelin dose-dependently abolished increased colonic permeability in response to LPS while intraperitoneal injection of ghrelin at the same dose or intracisternal injection of des-acyl-ghrelin failed to block it. Carbachol potently attenuated LPS-induced intestinal hyperpermeability, and atropine or bilateral subdiaphragmatic vagotomy prevented the improvement of intestinal hyperpermeability by central ghrelin. Intracisternal (D-Lys3)-GHRP-6, a selective ghrelin receptor antagonist, significantly blocked improvement of intestinal barrier function by intravenously administered 2-deoxy-d-glucose, central vagal stimulant. Intracisternal injection of orexin 1 receptor antagonist, SB-334867 blocked intracisternal ghrelin-induced improvement of colonic hyperpermeability. These results suggest that exogenously administered or endogenously released ghrelin acts centrally to improve a disturbed intestinal barrier function through orexinergic signaling and the vagal cholinergic pathway. Central ghrelin may be involved in the pathophysiology and be a novel therapeutic option in not only gastrointestinal diseases such as irritable bowel syndrome but also non-gastrointestinal diseases associated with the altered intestinal permeability.

Brain orexin improves intestinal barrier function via the vagal cholinergic pathway.

Orexins are neuropeptides that are implicated in a number of functions. With regard to the gastrointestinal functions, orexin acts centrally to regulate gastric secretion, gastrointestinal motility and visceral sensation. Little is however known about a role of central orexin in the control of intestinal barrier function. The present study was performed to clarify whether brain orexin plays a role in the control of intestinal permeability. Colonic permeability was estimated in vivo by quantifying the absorbed Evans blue in colonic tissue in rats. Intracisternally administered orexin-A but not orexin-B dose-dependently blocked the increased intestinal permeability by lipopolysaccharide (LPS) or corticotropin-releasing factor while intraperitoneally injected orexin-A failed to block it. Atropine or vagotomy abolished the action by central orexin-A. Intravenous injection of 2-deoxy-D-glucose (2-DG), a central vagal stimulant, significantly blocked the LPS-induced increase in intestinal permeability and atropine prevented the action of 2-DG. Intracisternal injection of SB-334687, a selective orexin 1 receptor antagonist, significantly blocked the action of 2-DG-induced improvement of intestinal hyperpermeability. These results suggest that exogenously administered or endogenously released orexin acts centrally to improve the intestinal hyperpermeability by LPS via the vagal cholinergic pathway. The findings also suggest for the first time that the brain could control intestinal permeability. The neuronal rapid protective advantage to the host by improving the intestinal barrier function by the neuropeptide may help us understand the brain-gut interaction in stress sensitive gastrointestinal disorders like irritable bowel syndrome associated with the altered intestinal permeability.

Centrally administered orexin prevents lipopolysaccharide and colchicine induced lethality via the vagal cholinergic pathway in a sepsis model in rats.

Orexins are neuropeptides implicated in several physiological functions. Accumulating findings suggest a relationship between orexin and sepsis. A recent study demonstrated that orexin acts centrally to improve conditions in sepsis. The present study aims to clarify the precise mechanisms by which central orexin could induce a protective action against septic conditions. We established a new septic model by treating rats with lipopolysaccharide (LPS) and colchicine and used this to examine the effect of brain orexin on survival. Observation of survival was stopped three days after the chemicals injection or at death. We established a lethal model (rats died within 24 h) by injecting subcutaneously a combination of 1 mg/kg LPS and 1 mg/kg colchicine. A Toll-like receptor 4 (TLR4) inhibitor completely blocked lethality, suggesting a vital role of LPS-TLR4 signaling in the process. Intracisternal orexin-A dose-dependently reduced lethality in the sepsis model while neither intracisternal orexin-B nor intraperitoneal orexin-A changed the mortality rate. Vagal stimulation with carbachol or 2-deoxy-D-glucose improved survival and atropine potently blocked the protection by carbachol or 2-deoxy-D-glucose. The orexin-A-induced reduction of lethality was significantly blocked by atropine or surgical vagotomy. Intracisternal injection of an OX1 receptor antagonist blocked the improvement of survival by intracisternal injection of orexin-A, carbachol, or 2-deoxy-D-glucose. These results suggest that orexin acts centrally to reduce the lethality in our septic model treated (LPS and colchicine). Activation of the vagal cholinergic pathway may mediate the action of orexin, and the OX1 receptor in the brain might play a role in the process. Since the efferent vagus nerve mediates anti-inflammatory mechanisms, we speculate that the vagal cholinergic anti-inflammatory pathway is implicated in the mechanisms of septic lethality reduction by brain orexin.

Troglitazone increases expression of E-cadherin and claudin 4 in human pancreatic cancer cells.

We examined the effects of troglitazone on expression of E-cadherin and claudin 4 in human pancreatic cancer cells. Troglitazone dose-dependently increased expression of E-cadherin and claudin 4 mRNA and protein in PK-1 cells. Snail, Slug and ZEB1, mRNAs were not changed by troglitazone, indicating that these three transcriptional repressors would not play a role in the induction of E-cadherin by troglitazone. GW9662, a PPARgamma antagonist, failed to block the increased expression of E-cadherin or claudin 4 mRNA, suggesting a PPARgamma-independent pathway. A MEK inhibitor, U0126, increased E-cadherin or claudin 4 mRNA and protein expression, and potently inhibited cell invasion. Because troglitazone down-regulates MEK-ERK signaling and inhibit cell invasion in PK-1 as shown in our previous study, these results suggest that troglitazone increases expression of E-cadherin and claudin 4 possibly through inhibition of MEK-ERK signaling in pancreatic cancer cells, which might be involved in the troglitazone-induced inhibition of cell invasive activity.