METABOLIC KINETICS OF BRAIN MUSCARINIC CHOLINERGIC RECEPTORS IN NORMAL AND HYPOTHYROID MICE

A technique for studying in vivo the production rate and turnover rate constant of mouse brain M-receptors was established. A single injection of 25 mg / kg of Benzilylcholine Mustard to living mice resulted in 90 % irreversible block of brain M-receptors. The time course of the receptor density was then monitored by 3H-QNB binding assay and the production rate and turnover rate constant were calculated from the time course curve with a computer program. It was found that in normal mice the turnover rate constant was about 0.035 h-1 (half-life was about 20 h) and the production rate was 30-42 fmol / (h ·mg protein). Parallel experiments revealed a significant slow down of the turnover of brain M-receptors in hypothyroid mice (turnover rate constant was 0.0257±0.0012 h-1 in hypothyroid vs. 0.0356±0.0021 h-1 in normal) while the production rate was not changed significantly. The results suggest that thyroid hormones have a regulatory action on the turnover of brain M-receptors and the elevation of brain M-receptor density together with slow down of the turnover of brain M- receptors is probably one of the important mechanisms relevant to the brain dysfunction in hypothyroidism.

Nicotinic cholinergic receptors in esophagus:Early alteration during carcinogenesis and prognostic value

AIM: To compare expression of nicotinic cholinergic receptors(CHRNs) in healthy and squamous cell carcinoma-affected esophagus and determine the prognostic value.METHODS: We performed RT-q PCR to measure the expression of CHRNs in 44 esophageal samples from healthy individuals and in matched normal surrounding mucosa, and in tumors from 28 patientsdiagnosed with esophageal squamous cell carcinoma(ESCC). Next, we performed correlation analysis for the detected expression of these receptors with the habits and clinico-pathological characteristics of all study participants. In order to investigate the possible correlations between the expression of the different CHRN subunits in both healthy esophagus and tissues from ESCC patients, correlation matrices were generated. Subsequently, we evaluated whether the detected alterations in expression of the various CHRNs could precede histopathological modifications during the esophageal carcinogenic processes by using receiver operating characteristic curve analysis. Finally, we evaluated the impact of CHRNA5 and CHRNA7 expression on overall survival by using multivariate analysis.RESULTS: CHRNA3, CHRNA5, CHRNA7 and CHRNB4, but not CHRNA1, CHRNA4, CHRNA9 or CHRNA10, were found to be expressed in normal(healthy) esophageal mucosa. In ESCC, CHRNA5 and CHRNA7 were overexpressed as compared with patient-matched surrounding non-tumor mucosa(ESCC-adjacent mucosa; P < 0.0001 and P = 0.0091, respectively). Positive correlations were observed between CHRNA3 and CHRNB4 expression in all samples analyzed. Additionally, CHRNB4 was found to be differentially expressed in the healthy esophagus and the normalappearing ESCC-adjacent mucosa, allowing for distinguishment between these tissues with a sensitivity of 75.86% and a specificity of 78.95%(P = 0.0002). Finally, CHRNA5 expression was identified as an independent prognostic factor in ESCC; patients with high CHRNA5 expression showed an increased overall survival, in comparison with those with low expression. The corresponding age- and tumor stage-adjusted hazard ratio was 0.2684(95%CI: 0.075-0.97, P = 0.0448).CONCLUSION: Expression of CHRNs is homogeneous along healthy esophagus and deregulated in ESCC, suggesting a pathogenic role for these receptors in ESCC development and progression.

Involvement of M3 Cholinergic Receptor Signal Transduction Pathway in Regulation of the Expression of Chemokine MOB-1, MCP-1 Genes in Pancreatic Acinar Cells

Whether M3 cholinergic receptor signal transduction pathway is involved in regulation of the activation of NF-κB and the expression of chemokine MOB-1, MCP-1genes in pancreatic acinar cells was investigated. Rat pancreatic acinar cells were isolated, cultured and treated with carbachol, atropine and PDTC in vitro. The MOB-1 and MCP-1 mRNA expression was detected by using RT-PCR. The activation of NF-κB was monitored by using electrophoretic mobility shift assay. The results showed that as compared with control group, M3 cholinergic receptor agonist (10 -3 mol/L, 10 -4 mol/L carbachol) could induce a concentration-dependent and time-dependent increase in the expression of MOB-1, MCP-1 mRNA in pancreatic acinar cells. After treatment with 10 -3 mol/L carbachol for 2 h, the expression of MOB-1, MCP-1 mRNA was strongest. The activity of NF-κB in pancreatic acinar cells was significantly increased (P<0.01) after treated with M3 cholinergic receptor agonist (10 -3 mol/L carbachol) in vitro for 30 min. Either M3 cholinergic receptor antagonist (10 -5 mol/L atropine) or NF-κB inhibitor (10 -2 mol/L PDTC) could obviously inhibit the activation of NF-κB and the chemokine MOB-1, MCP-1 mRNA expression induced by carbachol (P<0.05). This inhibitory effect was significantly increased by atropine plus PDTC (P<0.01). The results of these studies indicated that M3 cholinergic receptor signal transduction pathway was likely involved in regulation of the expression of chemokine MOB-1 and MCP-1genes in pancreatic acinar cells in vitro through the activation of NF-κB.

THE EFFECT OF ACUPUNCTURE ON PREVENTION AND TREATMENT OF ISCHEMIC ARRHYTHMIA AND THE RELATION BETWEEN EFFECT OF ACUPUNCTURE AND CHOLINERGIC MUSCARINE-LIKE RECEPTORS

For investigating the effect of acupuncture on ischemic arrhythmia and its mech-anism, adult albino rats with ligated anterior descending branch of coronary artery as experimentalmodel were treated with or without acupuncture, and others with imitative operation but without bothcoronary artery ligation and acupuncture treatment were used as control. It was found in acupuncturegroup that the fibrillation-liability of ischemic myocardium was efficiently decreased, the affinity ofAch-M receptors on membranes of ischemic myocardium was markedly increased, and the tolerance ofischemic myocardium to atropine was elevated in the experiment of atropine inducing fibrillation.These results indicate that acupuncture may play a therapeutic role on ischemic arrhythmia throughactivating the activity of muscarine-like receptors of cholinergic nervous system.

Role of Cholinergic Receptors in Colorectal Cancer: Potential Therapeutic Implications of Vagus Nerve Stimulation?

Inflammatory Bowel Disease (IBD) patients, such as Crohn’s disease or ulcerative colitis suffer from chronic and relapsing intestinal inflammation that favours the development of colitis associated cancer (CAC). This inflammation is initiated by aberrant activations of the innate immune responses associated to intestinal barrier defects. The conventional medical therapies consist to decrease the inflammatory response, which also decrease the risk of colon carcinoma but lead to severe side-effects. Recently, a number of animal studies have demonstrated that innate immune responses are attenuated by stimulation of the efferent arm of vagus nerve (VN) through its neurotransmitter acetylcholine (ACh), that acts on resident macrophages α7 nicotinic receptor (α7 nAChR). ACh also acts as a signalling molecule in epithetlial cells through cholinergic receptors such as nAChR or muscarinic (mAChR) receptors. In the current study, we aimed to extend these findings to CAC prevention by treating human adenocarcinoma cell lines through targeting cholinergic receptors with nicotine (which binds nAChR) and ACh (which binds both cholinergic receptors). Using HT-29 and Caco-2 cell lines, we demonstrated that ACh-induced activation of mAChR results in cell dissociation together with changes in expression and localization of intestinal tight and adherens junction proteins. ACh-induced modulation of cell adhesion proprieties correlates with the acquisition of invasive potential. By contrast, nicotine-mediated activation of nAChR maintains epithelial cell organisation. ACh-released by VN stimulation (VNS) could effectively preserve epithelium integrity thus limiting inflammatory response and tumor development. However, attention should be paid on the nature of the cholinergic receptor solicited. Indeed, regarding to the protective effects of nAChR signalling on epithelial cells, activation of mAChR would worsen the disease and led to increase inflammation. These data have important repercussions on the therapeutic potential of VNS in IBD and CAC, which may represent “the yin and yang” of the intestinal homeostasis.

Cholinergic receptor, nicotinic, alpha 7 as a target molecule of Arctic mutant amyloid β

Alzheimer’s disease（AD）is a progressive cognitive disorder that develops predominantly in elderly patients and is characterized by cognitive impairments affecting memory,learning,and attention（Selkoe,2002）.

Research on Autoantibodies Against Myocardialβ_1-adrenergic and M_2 Cholinergic Receptors in Patients With Chronic Keshan Disease

Objectives To explore the relationship between serum autoantibodies against myocardial β1-adrenergic, M2-cholinergic receptors and chronic Keshan disease （CKD）. Methods The second extracellular loops of β1 and M2 receptors on human cardiomyocytes were used as the antigens. Enzyme linked immunosorbent assay （ELISA） was applied to determine serum autoantibodies against myocardial β1 and ME receptors in 32 CKD patients. 31 healthy subjects from endemic area were selected as the control. Results Positive rate of autoantibodies against myocardial β1 adrenergic （51.3%, 17/32） and M2 cholinergic （56.3% , 18/32） receptors were significantly higher than those in the control （9.7%, 3/ 31; 12.9%, 4/31） （both P〈 0.01）. Both positive rate and titers of above autoantibodies in NYHA Ⅱ - Ⅲ CKD patients were significantly higher than those in NYHA Ⅳ, demonstrating an apparently positive correlation between serum antibodies against myocardial β1 and M2 receptors （r=0.95）. Conclusions Autoantibodies against myocardial β1 and M2 receptors were found in sera of CKD patients; distribution of positive rate and titers of the autoantibodies in CKD patients in various NYHA are significantly different. classes of cardiac function

Expression Imbalance of Cholinergic M₂and M₃Receptors Contributes to the Motility Reduction of the Small Intestine in Spleen Qi Deficiency

Objective: To study roles of cholinergic M2 and M3 receptors in the motility reduction of small intestine (SI) in spleen qi deficiency. Methods: 16 male SD rats were randomly divided in the control group and spleen qi deficiency group (model group)—8 rats each group;spleen qi deficiency model of the improper diet and overfatigue was established;the SI propelling rate (SIPR) was used to evaluate the SI motility;ELISA was used to measure concentrations of acetylcholine (ACh), cyclic adenosine monophosphate (cAMP) and protein kinase A (PKA) in the SI tissue;immohistochemistry was employed to detect expressions of cholinergic M2 and M3 receptors. Results: Compared with those in the control group, SIPR was reduced;expression of M2 receptors was increased;and expression of M3 receptors and concentrations of cAMP and PKA were decreased, significantly, in the model group. Conclusions: Expression imbalance of cholinergic M2 and M3 receptors might contribute to the motility reduction of the SI in spleen qi deficiency.

The Regulatory Action of Radix Astragali on M-Cholinergic Receptor of the Brain of Senile Rats

The changes in density of M-cholinergic receptors in different areas of senile rats and the regulatory action of Huang Qi ([symbol: see text] Radix Astragali, a drug for warming yang and replenishing qi) were observed by autoradiography. The results showed that the gray scale displayed in brain sections was clear and mainly distributed in the cortex, hippocampus and striate body, while that due to nonspecific combination was negligible. The gray scale in the cortex, hippocampus and striate body of the experimental group was markedly lower than that in the young control rats, decreased respectively by 24.87%, 14.12% and 12.76% (all P

Neurotrophin receptors,gamma-secretase inhibitors,and neurodegeneration of basal forebrain cholinergic neurons

The amyloid hypothesis of Alzhemer’s disease(AD)postulates that the generation of amyloid-beta(Aβ)peptide from the amyloid precursor protein(APP)by the action of theγ-secretase complex is one of the principal causes of AD.This idea is supported by the identification of several hereditary mutations in the APP gene or in the PSEN1 and PSEN2 genes that encode Presenilin-1 and Presenilin-2.

Donepezil rescues the medial septum cholinergic neurons via nicotinic ACh receptor stimulation in olfactory bulbectomized mice

Olfactory bulbectomy (OBX) causes cognitive dysfunction by degeneration of cholinergic neurons in the medial septum. Here, we define an involvement of nicotinic acetylcholine receptor (nAChR) in neuroprotective effect of donepezil in the septum neurons of OBX mice. Neuroprotective effects on the medial septal cholinergic neurons were assessed after chronic donepezil administration in OBX mice. We also measured Akt and ERK phosphorylation to define the neuroprotective mechanism of donepezil. We found that treatment with donepezil (1 - 3 mg/kg) for 15 consecutive days completely rescued cholinergic neurons in the OBX mice with concomitant improved memory. Reduction of both protein kinase B (Akt) and extracellular signal-regulated kinase (ERK) phosphorylation were restored by chronic donepezil administration (1 - 3 mg/kg) in OBX mouse medial septum. Both phosphorylated Akt and ERK immunoreactivities were localized in cell bodies of choline acetyltransferase (ChAT)-positive cholinergic cells in the medial septum. Enhancement of Akt and ERK phosphorylation seen following donepezil administration was totally blocked by pre-administration of mecamylamine (10 μM), a nicotinic acetylcholine receptor antagonist. Donepezil increases phosphorylation of Akt and ERK via nAChR stimulation in the medial septum cholinergic neurons. The Akt and ERK stimulation by donepezil is associated with its ability of neuroprotection in the medial septum and memory improvement.

Cognitive disorder and changes in cholinergic receptors, N-methyl-D aspartate receptors, neural cell adhesion molecule, and brain-derived neurotrophic factor following brain injury

BACKGROUND： Learning and memory damage is one of the most permanent and the severest symptoms of traumatic brain injury; it can seriously influence the normal life and work of patients. Some research has demonstrated that cognitive disorder is closely related to nicotine cholinergic receptors, N-methyl-D aspartate receptors, neural cell adhesion molecule, and brain-derived neurotrophic factor. OBJECTIVE： To summarize the cognitive disorder and changes in nicotine cholinergic receptors, N-methyl-D aspartate receptors, neural cell adhesion molecule, and brain-derived neurotrophic factor following brain injury. RETRIEVAL STRATEGY： A computer-based online search was conducted in PUBMED for English language publications containing the key words ＂brain injured, cognitive handicap, acetylcholine, N-methyl-D aspartate receptors, neural cell adhesion molecule, brain-derived neurotrophic factor＂ from January 2000 to December 2007. There were 44 papers in total. Inclusion criteria： ① articles about changes in nicotine cholinergic receptors, N-methyl-D aspartate receptors, neural cell adhesion molecule, and brain-derived neurotrophic factor following brain injury; ② articles in the same researching circle published in authoritative journals or recently published. Exclusion criteria： duplicated articles. LITERATURE EVALUATION： References were mainly derived from research on changes in these four factors following brain injury. The 20 included papers were clinical or basic experimental studies. DATA SYNTHESIS： After craniocerebral injury, changes in these four factors in brain were similar to those during recovery from cognitive disorder, to a certain degree. Some data have indicated that activation of nicotine cholinergic receptors, N-methyl-D aspartate receptors, neural cell adhesion molecule, and brain-derived neurotrophic factor could greatly improve cognitive disorder following brain injury. However, there are still a lot of questions remaining; for example, how do these factors change at different time points after brain injury, and what is the relationship between associated factors and cognitive disorder. CONCLUSION： It is necessary to comprehensively study some associated factors, to analyze their changes and their relationship with cognitive disorder following brain injury, and to investigate their effects at different time points after brain injury.

C-C motif chemokine ligand 2/C-C motif chemokine receptor 2 pathway as a therapeutic target and regulatory mechanism for spinal cord injury

Spinal cord injury involves non-reversible damage to the central nervous system that is characterized by limited regenerative capacity and secondary inflammatory damage.The expression of the C-C motif chemokine ligand 2/C-C motif chemokine receptor 2 axis exhibits significant differences before and after injury.Recent studies have revealed that the C-C motif chemokine ligand 2/C-C motif chemokine receptor 2 axis is closely associated with secondary inflammatory responses and the recruitment of immune cells following spinal cord injury,suggesting that this axis is a novel target and regulatory control point for treatment.This review comprehensively examines the therapeutic strategies targeting the C-C motif chemokine ligand 2/C-C motif chemokine receptor 2 axis,along with the regenerative and repair mechanisms linking the axis to spinal cord injury.Additionally,we summarize the upstream and downstream inflammatory signaling pathways associated with spinal cord injury and the C-C motif chemokine ligand 2/C-C motif chemokine receptor 2 axis.This review primarily elaborates on therapeutic strategies that target the C-C motif chemokine ligand 2/C-C motif chemokine receptor 2 axis and the latest progress of research on antagonistic drugs,along with the approaches used to exploit new therapeutic targets within the C-C motif chemokine ligand 2/C-C motif chemokine receptor 2 axis and the development of targeted drugs.Nevertheless,there are presently no clinical studies relating to spinal cord injury that are focusing on the C-C motif chemokine ligand 2/C-C motif chemokine receptor 2 axis.This review aims to provide new ideas and therapeutic strategies for the future treatment of spinal cord injury.

A Decreased Expression and Functionality of Muscarinic Cholinergic Receptor in Acute Chagas Myocarditis

Background: Chagas disease is still a public health problem because of the remaining high prevalence, the expansion of the disease into developed countries and the re-emergences by oral transmission outbreaks. Chagas cardiomyopathy evolves as a consequence of an autonomic un-balance where the parasympathetic tone is undermined. Objective: To determine the functionality and expression of muscarinic cholinergic receptors in acute Chagas disease. Methodology: 62 male, 3-week-old Sprague Dawley rats were assayed;32 were infected with Trypanosoma cruzi trypo-mastigotes and 30 were healthy controls. Electrocardiographic studies were conducted in the absence or presence of direct muscarinic (oxotremorine and McN-A-343) or indirect agonists (phenylephrine) or antagonist (pirenzepine). Muscarinic M1 and M2 receptor expression was determined by radioligand [3H]-QNB binding assay and immunoblot. Results: Chagasic acute myocarditis was sustained by electrocardiographic signs and histopathological findings. Bradycardia induced by oxotremorine was significantly higher in healthy rats (HR) and the differences were enhanced by CsCl. In the absence of the agonist, CsCl induced a greater bradycardia in chagasic rats (ChR). In HR McN-A-343 induced tachycardia, however it induces bradycardia in the presence of a acetylcholinesterase inhibitor (neostigmine);no effects were observed in ChR. Pirenzepine induced a higher tachycardia in HR. Phenylephrine in the presence of pirenzepine induced a similar bradycardia in both groups, but recovery was faster in ChR. Muscarinic M1 and M2 receptor density was higher in HR. Conclusion: Muscarinic receptor expression and functionality are decreased in the acute Chagas disease that could impact the evolution and prognosis of the disease.

P2Y1 receptor in Alzheimer’s disease

Alzheimer’s disease is the most frequent form of dementia characterized by the deposition of amyloid-beta plaques and neurofibrillary tangles consisting of hyperphosphorylated tau.Targeting amyloid-beta plaques has been a primary direction for developing Alzheimer’s disease treatments in the last decades.However,existing drugs targeting amyloid-beta plaques have not fully yielded the expected results in the clinic,necessitating the exploration of alternative therapeutic strategies.Increasing evidence unravels that astrocyte morphology and function alter in the brain of Alzheimer’s disease patients,with dysregulated astrocytic purinergic receptors,particularly the P2Y1 receptor,all of which constitute the pathophysiology of Alzheimer’s disease.These receptors are not only crucial for maintaining normal astrocyte function but are also highly implicated in neuroinflammation in Alzheimer’s disease.This review delves into recent insights into the association between P2Y1 receptor and Alzheimer’s disease to underscore the potential neuroprotective role of P2Y1 receptor in Alzheimer’s disease by mitigating neuroinflammation,thus offering promising avenues for developing drugs for Alzheimer’s disease and potentially contributing to the development of more effective treatments.

Melanocortin 3,5 receptors immunohistochemical expression in colonic mucosa of inflammatory bowel disease patients:A matter of disease activity?

BACKGROUND Melanocortin 3 and 5 receptors(i.e.,MC3R and MC5R)belong to the melanocortin family.However,data regarding their role in inflammatory bowel diseases(IBD)are currently unavailable.AIM This study aims to ascertain their expression profiles in the colonic mucosa of Crohn’s disease(CD)and ulcerative colitis(UC),aligning them with IBD disease endoscopic and histologic activity.METHODS Colonic mucosal biopsies from CD/UC patients were sampled,and immunohisto-chemical analyses were conducted to evaluate the expression of MC3R and MC5R.Colonic sampling was performed on both traits with endoscopic scores(Mayo endoscopic score and CD endoscopic index of severity)consistent with inflamed mucosa and not consistent with disease activity(i.e.,normal appearing mucosa).RESULTS In both CD and UC inflamed mucosa,MC3R(CD:+7.7 fold vs normal mucosa,P<0.01;UC:+12 fold vs normal mucosa,P<0.01)and MC5R(CD:+5.5 fold vs normal mucosa,P<0.01;UC:+8.1 fold vs normal mucosa,P<0.01)were significantly more expressed compared to normal mucosa.CONCLUSION MC3R and MC5R are expressed in the colon of IBD patients.Furthermore,expression may differ according to disease endoscopic activity,with a higher degree of expression in the traits affected by disease activity in both CD and UC,suggesting a potential use of these receptors in IBD pharmacology.

On the Impairment of Stress-Induced Changes in Triglyceride Levels via a Sub-Toxic Dose of Unmethylated Cytidine Phosphate Guanosine Oligodinucleotide (a Toll-Like Receptor 9 Ligand)

Changes in lipid metabolism have been implicated in protection against infectious diseases. In the first experiment of this study, we measured clinical lipid parameters in a murine model where the unmethylated cytidine phosphate guanosine (CpG) oligodinucleotide (ODN1826), a Toll-like receptor 9 (TLR9) agonist was administered in combination with D-galactosamine (GalN) that caused relatively liver-specific inflammation and toxicity. In the control mice group injected with phosphate-buffered saline (PBS) (acute psychological stress model associated with blood sampling), the serum triglyceride (TG) levels showed a rapid decrease followed by a rebound at 24 h as we have recently reported. However, such a TG rebound was impaired in the CpG/GalN- and solely CpG-treated groups of mice despite an absence of liver injury based on serum alanine aminotransferase levels in the latter group. Thus, the stress-associated serum TG rebound was abrogated by the injection of a sub-hepatotoxic CpG dose. In the second experiment, we simply measured the hepatic CD36 and SACRB1 (the gene for scavenger receptor B1 (SR-B1)) transcripts after the i.p. administration of PBS, CpG or CpG/GalN. There was a remarkable elevation of hepatic CD36 transcript expression in both the CpG- and CpG/GalN-treated mice at 8 h post-CpG injection whereas the increase in the PBS-treated mice was slower than the former two groups, suggesting that hepatic CD36 transcript expression is more pronounced in the combined stress models than under psychological stress alone. The individual mice data showed that the increase in CD36 expression was accompanied by a reduction in SCARB1 mRNA, showing reciprocal regulation between these two genes. Together with our previously reported findings, these data suggest that, in a murine model combining psychological stress with TLR-triggered hepatic inflammation, the psychological stress facilitates liver uptake of plasma TG (and its components fatty acids), but the subsequent re-esterification and/or release of TG-rich lipoproteins from the liver is impaired due to the concomitant TLR-signaling. We hypothesize that lipid metabolism during acute stress shifts toward an elevated hepatic uptake of lipids due to concomitant TLR signaling, facilitating the clearance of bacterial lipids by the liver.

Serotonin receptor 2B induces visceral hyperalgesia in rat model and patients with diarrhea-predominant irritable bowel syndrome

BACKGROUND Serotonin receptor 2B(5-HT2B receptor)plays a critical role in many chronic pain conditions.The possible involvement of the 5-HT2B receptor in the altered gut sensation of irritable bowel syndrome with diarrhea(IBS-D)was investigated in the present study.AIM To investigate the possible involvement of 5-HT2B receptor in the altered gut sensation in rat model and patients with IBS-D.METHODS Rectosigmoid biopsies were collected from 18 patients with IBS-D and 10 patients with irritable bowel syndrome with constipation who fulfilled the Rome IV criteria and 15 healthy controls.The expression level of the 5-HT2B receptor in colon tissue was measured using an enzyme-linked immunosorbent assay and correlated with abdominal pain scores.The IBS-D rat model was induced by intracolonic instillation of acetic acid and wrap restraint.Alterations in visceral sensitivity and 5-HT2B receptor and transient receptor potential vanilloid type 1(TRPV1)expression were examined following 5-HT2B receptor antagonist adminis-tration.Changes in visceral sensitivity after administration of the TRPV1 antago-INTRODUCTION Irritable bowel syndrome(IBS)is a chronic functional bowel disorder characterized by recurrent abdominal pain with altered bowel habits that affects approximately 15%of the population worldwide[1].IBS significantly impacts the quality of life of patients.Although the pathogenesis of IBS is not completely understood,the role of abnormal visceral sensitivity in IBS has recently emerged[2,3].5-Hydroxytryptamine(5-HT)is known to play a key role in the physiological states of the gastrointestinal tract.Plasma 5-HT levels in IBS with diarrhea(IBS-D)patients were greater than those in healthy controls[4],suggesting a possible role of 5-HT in the pathogenesis of IBS-D.The serotonin receptor 2(5-HT2 receptor)family comprises three subtypes:5-HT2A,5-HT2B,and 5-HT2c.All 5-HT2 receptors exhibit 46%-50%overall sequence identity,and all of these receptors preferentially bind to Gq/11 to increase inositol phosphates and intracellular calcium mobilization[5].5-HT2B receptors are widely expressed throughout the gut,and experimental evidence suggests that the primary function of 5-HT2B receptors is to mediate contractile responses to 5-HT through its action on smooth muscle[6].The 5-HT2B receptor is localized to both neurons of the myenteric nerve plexus and smooth muscle in the human colon.The 5-HT2B receptor mediates 5-HT-evoked contraction of longitudinal smooth muscle[6].These findings suggest that the 5-HT2B receptor could play an important role in modulating colonic motility,which could affect sensory signaling in the gut.Other laboratories have shown that the 5-HT2B receptor participates in the development of mechanical and formalin-induced hyperalgesia[7,8].A 5-HT2B receptor antagonist reduced 2,4,6-trinitrobenzene sulfonic acid(TNBS)and stress-induced visceral hyperalgesia in rats[9,10].However,the role of the 5-HT2B receptor in IBS-D patients and in acetic acid-and wrap restraint-induced IBS-D rat models was not investigated.

Axonal growth inhibitors and their receptors in spinal cord injury:from biology to clinical translation

Axonal growth inhibitors are released during traumatic injuries to the adult mammalian central nervous system, including after spinal cord injury. These molecules accumulate at the injury site and form a highly inhibitory environment for axonal regeneration. Among these inhibitory molecules, myelinassociated inhibitors, including neurite outgrowth inhibitor A, oligodendrocyte myelin glycoprotein, myelin-associated glycoprotein, chondroitin sulfate proteoglycans and repulsive guidance molecule A are of particular importance. Due to their inhibitory nature, they represent exciting molecular targets to study axonal inhibition and regeneration after central injuries. These molecules are mainly produced by neurons, oligodendrocytes, and astrocytes within the scar and in its immediate vicinity. They exert their effects by binding to specific receptors, localized in the membranes of neurons. Receptors for these inhibitory cues include Nogo receptor 1, leucine-rich repeat, and Ig domain containing 1 and p75 neurotrophin receptor/tumor necrosis factor receptor superfamily member 19(that form a receptor complex that binds all myelin-associated inhibitors), and also paired immunoglobulin-like receptor B. Chondroitin sulfate proteoglycans and repulsive guidance molecule A bind to Nogo receptor 1, Nogo receptor 3, receptor protein tyrosine phosphatase σ and leucocyte common antigen related phosphatase, and neogenin, respectively. Once activated, these receptors initiate downstream signaling pathways, the most common amongst them being the Rho A/ROCK signaling pathway. These signaling cascades result in actin depolymerization, neurite outgrowth inhibition, and failure to regenerate after spinal cord injury. Currently, there are no approved pharmacological treatments to overcome spinal cord injuries other than physical rehabilitation and management of the array of symptoms brought on by spinal cord injuries. However, several novel therapies aiming to modulate these inhibitory proteins and/or their receptors are under investigation in ongoing clinical trials. Investigation has also been demonstrating that combinatorial therapies of growth inhibitors with other therapies, such as growth factors or stem-cell therapies, produce stronger results and their potential application in the clinics opens new venues in spinal cord injury treatment.

Practical guide:Glucagon-like peptide-1 and dual glucosedependent insulinotropic polypeptide and glucagon-like peptide-1 receptor agonists in diabetes mellitus

Practical guide:Glucagon-like peptide-1 and dual glucosedependent insulinotropic polypeptide and glucagon-like peptide-1 receptor agonists in diabetes mellitus common second-line choice after metformin for treating T2DM.Various considerations can make selecting and switching between different GLP-1 RAs challenging.Our study aims to provide a comprehensive guide for the usage of GLP-1 RAs and dual GIP and GLP-1 RAs for the management of T2DM.