Plasma levels of 5-HT and 5-HIAA increased after intestinal ischemia/reperfusion in rats

Research progress in biological activities of succinimide derivatives

Succinimides are well recognized heterocyclic compounds in drug discovery which produce diverse therapeutically related applications in pharmacological practices. Researches in medicinal chemistry field have isolated and synthesized succinimide derivatives with multiple medicinal properties including anticonvulsant, anti-inflammatory, antitumor and antimicrobial agents, 5-HT receptor ligands and enzyme inhibitors. Simultaneously, SAR (Structure-Activity Relationship) analysis has been gradually possessed, along with a great deal of derivatives have been derived for potential targets. In this article, we comprehensively summarize the biological activities and SAR for succinimide derivatives, along with the featuring bioactive molecules reported in patents, wishing to provide an overall retrospect and prospect on the succinimide analogues.

Involvement of 5-HT1B/1D receptors in the inflammatory response and oxidative stress in intestinal ischemia/reperfusion in rats

Acute mesenteric ischemia (AMI) is caused by an abrupt cessation of blood flow to the small intestine. Reperfusion is the return of blood flow to the ischemic bowel. Intestinal ischemia/reperfusion (I/R) leads to the formation of reactive oxygen species, local inflammatory response, and may lead to the patient's death. Pre-treatment of the intestinal may reduce the high mortality associated with AMI. 5-Hydroxytryptamine 1B (5-HT1B) and 5-HT1D receptors have anti-inflammatory and neuroprotective effects in different experimental studies. We aimed to investigate the potential involvement of these receptors in intestinal I/R injury. Firstly, we assessed the expression and localization of 5-HT1B and 5-HT1D receptors in the enteric nervous system using an immunofluorescence-based method. Intestinal I/R in rats was induced by 30 min occlusion of superior mesenteric artery and reperfusion for 2 h. Rats were randomly divided in different control and I/R groups (n = 6) receiving either vehicle, sumatriptan (5-HT1B/1D receptors agonist; 0.1 mg/kg), GR127,935 (5-HT1B/1D receptors antagonist; 0.1 mg/kg) and combination of sumatriptan (0.1 mg/kg) + GR127,935 (0.1 mg/kg) before determination of biochemical and histological parameters. In the enteric nervous system, 5-HT1B and 5-HT1D receptors were expressed 17% and 11.5%, respectively. Pre-treatment with sumatriptan decreased 5-hydroxytryptamine (5HT) level by 53%, and significantly decreased calcitonin gene-related peptide (CGRP) levels, lipid pereoxidation, neutrophil infiltration, and level of pro-inflammatory markers in the serum. Histopathologic studies also showed a remarkable decrease in intestinal tissue injury. These findings suggest that sumatriptan may inhibit intestinal injury induced by I/R through modulating the inflammatory response by activation of 5-HT1B/1D receptors.

The association of intraoperative end-tidal carbon dioxide with the risk of postoperative nausea and vomiting

PURPOSE

Patients undergoing gynecological surgery are considered to be a high-risk cohort for postoperative nausea and vomiting (PONV). The purpose of this study was to assess the association of intraoperative end-tidal carbon dioxide (EtCO₂) with risk of PONV in patients underwent gynecological open surgery.

METHODS

In this single-center retrospective observational study, we included patients aged 20-60 years who underwent elective gynecological open surgery. We obtained data for the incidence of PONV within 24 h after operation. We collected EtCO₂ every minute during the operation, and determined the lowest value of EtCO₂. We compared the lowest EtCO₂ between patients with and without PONV. Multivariate logistic regression analysis was performed to assess the independent association of EtCO₂ with the risk of PONV.

RESULTS

A total of 146 patients were included in the current study. There were 81 patients with PONV within 24 h after the operation. The median lowest value of EtCO₂ in patients with PONV was significantly lower than that in patients without PONV (31 vs 33 mmHg, p = 0.02). In the multivariate logistic regression model, we found that lowest EtCO₂ ≤ 31 mmHg was independently associated with increase in the risk of PONV (adjusted odds ratio = 3.37, p = 0.02).

CONCLUSION

In this retrospective observational study, low intraoperative EtCO₂ was shown to be independently associated with increased risk of PONV. However, this result may be skewed by uncollected information including previous PONV, motion sickness or other unknown bias, so future studies should be conducted to refute or confirm our findings.

Depressive disorder and gastrointestinal dysfunction after myocardial infarct are associated with abnormal tryptophan-5-hydroxytryptamine metabolism in rats

In this study, we investigated the relationship between tryptophan-5-hydroxytryptamine metabolism, depressive disorder, and gastrointestinal dysfunction in rats after myocardial infarction. Our goal was to elucidate the physiopathologic bases of somatic/psychiatric depression symptoms after myocardial infarction. A myocardial infarction model was established by permanent occlusion of the left anterior descending coronary artery. Depression-like behavior was evaluated using the sucrose preference test, open field test, and forced swim test. Gastric retention and intestinal transit were detected using the carbon powder labeling method. Immunohistochemical staining was used to detect indoleamine 2,3-dioxygenase expression in the hippocampus and ileum. High-performance liquid chromatography with fluorescence and ultraviolet detection determined the levels of 5-hydroxytryptamine, its precursor tryptophan, and its metabolite 5-hydroxyindoleacetic acid in the hippocampus, distal ileum, and peripheral blood. All data were analyzed using one-way analyses of variance. Three weeks after arterial occlusion, rats in the model group began to exhibit depression-like symptoms. For example, the rate of sucrose consumption was reduced, the total and central distance traveled in the open field test were reduced, and immobility time was increased, while swimming, struggling and latency to immobility were decreased in the forced swim test. Moreover, the gastric retention rate and gastrointestinal transit rate were increased in the model group. Expression of indoleamine 2,3-dioxygenase was increased in the hippocampus and ileum, whereas 5-hydroxytryptamine metabolism was decreased, resulting in lower 5-hydroxytryptamine and 5-hydroxyindoleacetic acid levels in the hippocampus and higher levels in the ileum. Depressive disorder and gastrointestinal dysfunction after myocardial infarction involve abnormal tryptophan-5-hydroxytryptamine metabolism, which may explain the somatic, cognitive, and psychiatric symptoms of depression commonly observed after myocardial infarction. Peripheral 5-hydroxytryptamine is an important substance in the gut-brain axis, and its abnormal metabolism is a critical finding after myocardial infarct.

Dual Role of Endogenous Serotonin in 2,4,6-Trinitrobenzene Sulfonic Acid-Induced Colitis

BACKGROUND AND AIMS

Changes in gut serotonin (5-HT) content have been described in Inflammatory Bowel Disease (IBD) and in different experimental models of colitis: the critical role of this monoamine in the pathogenesis of chronic gastrointestinal inflammation is gradually emerging. Aim of the present study was to evaluate the contribution of endogenous 5-HT through the activation of its specific receptor subtypes to the local and systemic inflammatory responses in an experimental model of IBD.

MATERIALS AND METHODS

Colitis was induced by intrarectal 2,4,6-TriNitroBenzene Sulfonic acid in mice subacutely treated with selective antagonists of 5-HT1A (WAY100135), 5-HT2A (Ketanserin), 5-HT3 (Ondansetron), 5-HT4 (GR125487), 5-HT7 (SB269970) receptors and with 5-HT1A agonist 8-Hydroxy-2-(di-n-propylamino)tetralin.

RESULTS

Blockade of 5-HT1A receptors worsened TNBS-induced local and systemic neutrophil recruitment while 5-HT1A agonist delayed and mitigated the severity of colitis, counteracting the increase in colonic 5-HT content. On the contrary, blockade of 5-HT2A receptors improved global health conditions, reduced colonic morphological alterations, down-regulated neutrophil recruitment, inflammatory cytokines levels and colonic apoptosis. Antagonism of 5-HT3, 5-HT4, and 5-HT7 receptor sites did not remarkably affect the progression and outcome of the pathology or only slightly improved it.

CONCLUSION

The prevailing deleterious contribution given by endogenous 5-HT to inflammation in TNBS-induced colitis is seemingly mediated by 5-HT2A and, to a lesser extent, by 5-HT4 receptors and coexists with the weak beneficial effect elicited by 5-HT1A stimulation. These findings suggest how only a selective interference with 5-HT pro-inflammatory actions may represent an additional potential therapeutic option for intestinal inflammatory disorders.

Mesenteric ischemia-reperfusion injury: specific impact on different cell populations within the jejunal wall in rats

The progress of jejunal damage and recovery in the course of mesenteric ischemia-reperfusion injury in rats at different time periods was investigated. Mesenteric ischemia lasting 1h followed by 1h of reperfusion caused a significant disintegration of the mucosa, reduction of the muscular layer and diminution of the wall thickness. The loss of epithelium included enterocytes, goblet cells and Paneth cells. Paradoxically, increasing numbers of serotonin-producing cells and the beginning of regenerative processes, expressed by significantly higher proliferation, were recorded in the epithelium during this period. Disintegration of connective tissue and massive degranulation of serotonin-positive cells were found in the lamina propria. After 24h of reperfusion, restitution of the mucosa was found, expressed by normal villous morphology and re-epithelialization. However, some parameters were still significantly affected even more than in the acute phase of reperfusion. In the epithelium, decreased numbers of Paneth cells and increased population of serotonin-producing cells were found. The greatest proliferation of connective tissue cells and intensified reduction of the muscular layer were also detected in this reperfusion period. After 30 days of reperfusion, moderate damage remained, but only the increased number of Paneth cells and decreased number of serotonin-producing cells in the lamina propria were significant.

Ischemic post-conditioning to counteract intestinal ischemia/reperfusion injury

Intestinal ischemia is a severe disorder with a variety of causes. Reperfusion is a common occurrence during treatment of acute intestinal ischemia but the injury resulting from ischemia/reperfusion (IR) may lead to even more serious complications from intestinal atrophy to multiple organ failure and death. The susceptibility of the intestine to IR-induced injury (IRI) appears from various experimental studies and clinical settings such as cardiac and major vascular surgery and organ transplantation. Whereas oxygen free radicals, activation of leukocytes, failure of microvascular perfusion, cellular acidosis and disturbance of intracellular homeostasis have been implicated as important factors in the pathogenesis of intestinal IRI, the mechanisms underlying this disorder are not well known. To date, increasing attention is being paid in animal studies to potential pre- and post-ischemia treatments that protect against intestinal IRI such as drug interference with IR-induced apoptosis and inflammation processes and ischemic pre-conditioning. However, better insight is needed into the molecular and cellular events associated with reperfusion-induced damage to develop effective clinical protection protocols to combat this disorder. In this respect, the use of ischemic post-conditioning in combination with experimentally prolonged acidosis blocking deleterious reperfusion actions may turn out to have particular clinical relevance.

Effect of bencyclane fumarate on intestinal ischaemia reperfusion injury

BACKGROUND

Post-ischaemic intestinal tissue damage appears to be due to the formation of oxygen radicals. Free radical-initiated lipid peroxidation following intestinal ischaemia/reperfusion (I/R) may disrupt mucosal integrity. Indirectly, the radicals trigger the accumulation of neutrophils within the affected tissue, initiating inflammatory processes that lead to severe mucosal lesions. We have investigated the protective effect of bencyclane fumarate, a vasodilating Ca(2+) channel blocker, which has been used for the treatment of peripheral arterial occlusive diseases, on intestinal ischaemia reperfusion (IR) injury in rats.

METHODS

Forty-eight Wistar albino rats were divided into three groups: a sham-operated group (no IR injury, n = 16), an ischaemic control group (IR, n = 16), and BF-treated group (pretreatment 5 mg/kg bencyclane fumarate + IR, n = 16). A marker for lipid peroxidation, namely malondialdehyde; free radical scavengers, glutathione peroxidase, catalase and superoxide dismutase levels; an index of polymorphonuclear neutrophils, myeloperoxidase activity and mucosal damage were investigated.

RESULTS

Malondialdehyde levels, myeloperoxidase activity and the severity of mucosal damage were decreased in the BF group. In addition, in the BF group, glutathione peroxidase, catalase and superoxide dismutase levels were higher compared with the IR group.

CONCLUSION

The pretreatment of rats with bencyclane fumarate before intestinal ischaemia attenuates the mucosal damage in intestinal IR injury, probably by altering lipid peroxidation, neutrophil accumulation and antioxidant activity.

5-HT activates vagal afferent cell bodies in vivo: Role of 5-HT2 and 5-HT3 receptors

Occipital artery (OA) injections of 5-HT elicit pronounced reductions in heart rate and mean arterial blood pressure (MAP) in urethane-anesthetized rats by activation of vagal afferent cell bodies in the ipsilateral nodose ganglion. In contrast, internal carotid artery (ICA) and i.v. injections elicit similar cardiovascular responses by activation of peripheral vagal afferent terminals. The aim of this study was to examine the roles of 5-HT3 and 5-HT2 receptors in the 5-HT-induced activation of vagal afferent cell bodies and peripheral afferent terminals in urethane-anesthetized rats. OA, ICA and i.v. injections of 5-HT elicited dose-dependent reductions in heart rate and MAP that were virtually abolished after i.v. administration of the 5-HT3 receptor antagonists, MDL 7222 or ICS 205-930. The responses elicited by the OA injections of 5-HT were markedly diminished after i.v. injection of the 5-HT2 receptor antagonists, xylamidine or ketanserin, whereas the responses elicited by i.v. or ICA injections of 5-HT were not affected. The present findings suggest that (1) 5-HT3 and 5-HT2 receptor antagonists gain ready access to nodose ganglion cells upon i.v. administration, and (2) functional 5-HT3 and 5-HT2 receptors exist on the cell bodies of vagal afferent neurons mediating the cardiovascular responses elicited by OA injections of 5-HT. These findings also support a wealth of evidence that 5-HT3 receptors exist on the peripheral terminals of vagal afferents, and although they do not discount the possibility that 5-HT2 receptors exist on peripheral vagal afferent terminals, it appears that activation of these receptors does not have pronounced effects on 5-HT3 receptor activity on terminals that mediate the hemodynamic responses to 5-HT.

Occipital artery injections of 5-HT may directly activate the cell bodies of vagal and glossopharyngeal afferent cell bodies in the rat

The primary objective of this study was to determine whether circulating factors gain direct access to and affect the activity of vagal afferent cell bodies in the nodose ganglia and glossopharyngeal afferents cell bodies in the petrosal ganglia, of the rat. We found that the occipital and internal carotid arteries provided the sole blood supply to the nodose ganglia, and that i.v. injections of the tracer, Basic Blue 9, elicited strong cytoplasmic staining in vagal and glossopharyngeal afferent cell bodies that was prevented by prior ligation of the occipital but not the internal carotid arteries. We also found that occipital artery injections of 5-HT elicited pronounced dose-dependent reductions in heart rate and diastolic arterial blood pressure that were (1) virtually abolished after application of the local anesthetic, procaine, to the ipsilateral nodose and petrosal ganglia, (2) markedly attenuated after transection of the ipsilateral vagus between the nodose ganglion and brain and virtually abolished after subsequent transection of the ipsilateral glossopharyngeal nerve between the petrosal ganglion and the brain, (3) augmented after ipsilateral transection of the aortic depressor and carotid sinus nerves, and (4) augmented after transection of all ipsilateral glossopharyngeal and vagal afferent nerves except for vagal cardiopulmonary afferents. These findings suggest that blood-borne 5-HT in the occipital artery gains direct access to and activates the cell bodies of vagal cardiopulmonary afferents of the rat and glossopharyngeal afferents of undetermined modalities.

Pathophysiology of mesenteric ischemia/reperfusion: a review

During ischemia, the cell structures are progressively damaged, but restoration of the blood flow, paradoxically, intensifies the lesions caused by the ischemia. The mechanisms of ischemia injury and reperfusion (I/R) have not been completely defined and many studies have been realized in an attempt to find an ideal therapy for mesenteric I/R. The occlusion and reperfusion of the splanchnic arteries provokes local and systemic alterations principally derived from the release of cytotoxic substances and the interaction between neutrophils and endothelial cells. Substances involved in the process are discussed in the present review, like oxygen-derived free radicals, nitric oxide, transcription factors, complement system, serotonin and pancreatic proteases. The mechanisms of apoptosis, alterations in other organs, therapeutic and evaluation methods are also discussed.

Protective effects of sarpogrelate, a 5-HT2A antagonist, against postischemic myocardial dysfunction in guinea-pig hearts

The protective effects of sarpogrelate (SG), a 5-HT2A antagonist, were investigated in perfused guinea-pig Langendorff hearts subjected to ischemia and reperfusion. Changes in cellular levels of high phosphorous energy, NO and Ca2+ in the heart together with simultaneous recordings of left ventricular developed pressure (LVDP) were monitored using an nitric oxide (NO) electrode, fluorometry and 31P-NMR. The recovery of LVDP from ischemia by reperfusion was 30.1% in the control, while the treatment with SG (5 x 10(-7) M) in pre- and post-ischemia hearts produced a gradual increase to 73.1 and 53.6%, respectively. At the final stage of ischemia, the intracellular concentration of Ca2+ ([Ca2+]i) and release of NO increased with no twitching and remained at a high steady level. The addition of SG increased the transient NO signal (TNO) level at the end of ischemia compared with the control, but [Ca2+]i during ischemia decreased. Meanwhile, mitochondrial Ca2+ uptake on acidification or Ca2+ content changes of the perfusate was suppressed by pre-treatment with SG or the KATP channel opener diazoxide, but not the KATP channel blocker 5-HD. The myocardial NO elevated with 5-HT in normal Langendorff hearts was suppressed by the treatment with SG. Therefore, the existence of the 5HT2A receptor in a Langendorff heart was anticipated. By in vitro EPR, SG was found to directly quench the hydroxy radical. Thus, these findings suggested that the 5-HT2A receptor induced in ischemia-reperfusion plays an important role in the mitochondrial KATP channel of hearts in close relation with NO and active oxygen radicals.

Long-term serotonin administration induces heart valve disease in rats

BACKGROUND

The purpose of this study was to investigate whether rats dosed with serotonin develop changes similar to those seen in human carcinoid heart disease.

METHODS AND RESULTS

Ten Sprague-Dawley rats were given serotonin injections subcutaneously once daily for 3 months; controls were given saline. A long-lasting hyperserotoninemia with a >10-fold increase in both platelet-poor plasma and dialysate from the femoral muscles appeared. The animals developed clinical signs such as flushing and loose stools. After 3 months, 6 of 10 rats given serotonin had pathological echocardiographs. Two animals had a combination of aortic and pulmonary valve insufficiency, 1 had isolated aortic valve insufficiency, and 3 had isolated pulmonary valve insufficiency. Histopathological examination revealed shortened and thickened aortic cusps and carcinoidlike plaques characterized by a collection of myofibroblasts within an extracellular matrix of collagen ground substance. Immunostaining for Ki-67 demonstrated an increased number of proliferating subendocardial cells. In the control group, no pathological changes were seen. With the use of reverse-transcription polymerase chain reaction, normal rat aortic cusps were shown to express mRNA for serotonin receptors 5-HT1A, 5-HT2A, and 5-HT2B and the serotonin transporter 5-HTT.

CONCLUSIONS

For the first time, long-term serotonin administration was performed in rats. Morphological and echocardiographic changes similar to those seen in human carcinoid heart disease developed. This study demonstrates that serotonin most likely is involved in the pathogenesis of carcinoid heart disease.

Serotonin induces the expression of tissue factor and plasminogen activator inhibitor-1 in cultured rat aortic endothelial cells

Serotonin (5-hydroxytryptamine, or 5-HT), released from activated platelets, not only accelerates aggregation of platelets but also is known to promote mitosis, migration, and contraction of vascular smooth muscle cells (VSMCs). These effects are considered to contribute to thrombus formation and atherosclerosis. The aim of this study was to investigate the effects of 5-HT on the expressions of coagulative and fibrinolytic factors in rat aortic endothelial cells. Endothelial cells were stimulated with various concentrations of 5-HT (0.1 approximately 10 microM), and the expressions of tissue factor (TF), tissue factor pathway inhibitor (TFPI), plasminogen activator inhibitor-1 (PAI-1), and tissue-type plasminogen activator (TPA) messenger RNAs (mRNAs) were evaluated by Northern blot analysis. The activities of TF and PAI-1 were also measured. TF and PAI-1 mRNA were increased significantly in a concentration- and time-dependent manner. However, TFPI and TPA mRNA expression did not change. The inductions of TF and PAI-1 mRNAs were inhibited by a 5-HT1/5-HT2 receptor antagonist (methiothepin) and a selective 5-HT2A receptor antagonist (MCI-9042). These results indicate that 5-HT increases procoagulant activity and reduces fibrinolytic activities of endothelial cells through the 5-HT2A receptor. It was concluded that the modulation of procoagulant and hypofibrinolytic activities of endothelial cells by 5-HT synergistically promotes thrombus formation at the site of vessel injury with the platelet aggregation, VSMC contraction, and VSMC proliferation.