Journal of Smooth Muscle Research最新文献

Smooth muscle relaxation after contraction is thought to reflect "latch-like" slow cycling bridge formation and deformation. However, how actin-myosin interaction contributes to the transfer from fast-cycling cross bridges to slow-cycling bridges is still unclear. The thiadiazinone compound EMD57033 is known to bind to an allosteric pocket in the myosin motor domain and to increase basal and actin-activated myosin ATPase activity and contractile force in striated muscles. Therefore, we investigated whether EMD57033 affected the relaxation process after Ca²⁺ removal by affecting slow cycling bridge formation and/or deformation in β-escin skinned (cell membrane-permeabilized) carotid artery and taenia cecum from guinea pigs. EMD57033 at ≥30 µM decreased the force decay during relaxation in both the skinned carotid artery and taenia cecum, irrespective of the presence of ATP. A kinetic analysis in the present study indicated that EMD57033 significantly prolonged τslow-detach, a time constant of detachment of the slow cycling bridge, in both the skinned carotid artery and taenia cecum, irrespective of the presence of nucleoside triphosphates (ATP or ITP). Further studies are necessary to elucidate how EMD57033 modulates the smooth muscle myosin (SMM) structure, SMM activity, and thick filament organization, affecting slow cycling bridge formation and deformation, although EMD57033 might change slow cycling bridge formation, resulting in both cycling rate modulation and an increase in the affinity of SMM to actin.

Distal gastrectomy is the most frequently performed procedure for gastric cancer. Gastric emptying after distal gastrectomy is generally considered to be accelerated due to resection of the antrum, pylorus, and duodenal bulb. Food residue, however, is frequently observed in the gastric remnant in patients after distal gastrectomy at the time of endoscopy after routine overnight fasting. This observation suggests delayed gastric emptying and conflicts with the general understanding of accelerated gastric emptying after distal gastrectomy. We searched for reports that evaluated the separate gastric emptying of liquids and solids with scintigraphy after distal gastrectomy in humans and also addressed the physiologic changes in gastric emptying after distal gastrectomy. Most all reports showed that gastric emptying of liquids after distal gastrectomy was accelerated compared to healthy controls, especially immediately after feeding. In contrast, some gastric emptying of solids was accelerated early after the meal ingestion, but thereafter emptying of solids remaining in the stomach was delayed beginning about 60 min after the meal in patients after distal gastrectomy. This delayed solid gastric emptying after distal gastrectomy was considered associated with food residue in the remnant stomach. We conclude that gastric emptying after distal gastrectomy was accelerated for liquids and solids soon after the meal ingestion but delayed for solids later than 60 min after the meal ingestion.

A number of factors have been recently associated with the development of disorders of gut-brain interaction (DGBI), including genetic predisposition, early-life environment, intestinal microbiota, infection, microinflammation, and increased mucosal permeability. In addition, impaired gastrointestinal motility is important not only as a cause of DGBI but also as a consequent final phenotype. Gastrointestinal motor measurements are the predominant method for the assessment of and therapeutic intervention into motor abnormalities. As such, these measurements should be considered for DGBI patients who do not respond to first-line approaches such as behavioral therapy, dietary modifications, and pharmacotherapy. This comprehensive review focuses on the functional changes in the upper gastrointestinal tract caused by DGBI and describes ongoing attempts to develop imaging modalities to assess these dysfunctions in the esophageal and gastric regions. Recent advances in imaging techniques could help elucidate the pathophysiology of DGBI, with exciting potential for research and clinical practice.

Functional bowel disorders (FBD) have a major potential to degrade the standards of public life. Juniperus oxycedrus L. (J. oxycedrus) (Cupressaceae) has been described as a plant used in traditional medicine as an antidiarrheal medication. The present study is the first to obtain information on the antispasmodic and antidiarrheic effects of J. oxycedrus aqueous extract through in vitro and in vivo studies. An aqueous extract of J. oxycedrus (AEJO) was extracted by decoctioning air-dried aerial sections of the plant. Antispasmodic activity was tested in an isolated jejunum segment of rats exposed to cumulative doses of drogue extract. The antidiarrheic activity was tested using diarrhea caused by castor oil, a transit study of the small intestine, and castor oil-induced enteropooling assays in mice. In the jejunum of rats, the AEJO (0.1, 0.3 and 1 mg/ml) diminished the maximum tone induced by low K⁺ (25 mM), while it exhibited a weak inhibitory effect on high K⁺ (75 mM) with an IC₅₀=0.49 ± 0.01 mg/ml and IC₅₀=2.65 ± 0.16 mg/ml, respectively. In the contractions induced by CCh (10^-6 M), AEJO diminished the maximum tone, similar to that induced by low K⁺ (25 mM). with an IC₅₀=0.45 ± 0.02 mg/ml. The inhibitory effect of AEJO on low K⁺ induced contractions was significantly diminished in the presence of glibenclamide (GB) (0.3 µM) and 4-aminopyrimidine (4-AP) (100 µM), with IC₅₀ values of 1.84 ± 0.09 mg/ml. and 1.63 ± 0.16 mg/ml, respectively). The demonstrated inhibitory effect was similar to that produced by a non-competitive antagonist acting on cholinergic receptors and calcium channels. In castor oil-induced diarrhea in mice, AEJO (100, 200, and 400 mg/kg) caused an extension of the latency time, a reduced defecation frequency, and a decrease in the amount of wet feces compared to the untreated group (distilled water). Moreover, it showed a significant anti-motility effect and reduced the amount of fluid accumulated in the intestinal lumen at all tested doses. These findings support the conventional use of Juniperus oxycedrus L. as a remedy for gastrointestinal diseases.

Detrusor underactivity, a condition in which the bladder muscle does not contract strongly or long enough to empty the bladder completely or within the normal time frame, is a common cause of lower urinary tract symptoms in older individuals of both sexes. Although aging is a known risk factor for detrusor underactivity, its pathophysiological mechanisms are not fully understood. Therefore, establishing animal models that closely mimic the pathophysiology of detrusor underactivity in humans is necessary to elucidate these mechanisms. Metabolic syndrome is a cluster of several risk factors, including obesity, hyperlipidemia, hyperglycemia, and hypertension, which are associated with the development of diabetes, cardiovascular disease, and lower urinary tract dysfunction in both sexes. Notably, bladder dysfunction resulting from detrusor underactivity is observed at an earlier age in animal models with diabetes mellitus than in those without. Recently, detrusor underactivity-like phenotypes have been observed at a relatively early age in animal models with metabolic syndrome, involving obesity, hyperlipidemia, and hypertension, compared with those without. Therefore, this review introduces the association of detrusor underactivity with aging and metabolic syndrome, as well as possible pathophysiological mechanisms for detrusor underactivity from reports of various animal models. Notably, metabolic syndrome may accelerate the onset of age-related detrusor underactivity, and further analysis of old animal models with metabolic syndrome may help elucidate the pathogenesis of detrusor underactivity in humans.

Although naloxone is an antagonist of the opioid µ receptor, its effect on the peripheral sympathetic nerve function in the blood vessels has not yet been definitively elucidated. Therefore, we examined the effects of naloxone on vasoconstriction of the vascular smooth muscle of rats. Isolated rat mesenteric vascular-intestinal loop preparations were treated with either endogenous or exogenous α₁ adrenoceptor agonists followed by prazosin, a selective antagonist of the α₁ adrenoceptor, or naloxone, and noradrenaline overflow was measured. Vasoconstriction caused by peri-arterial nerve stimulation (PNS) and phenylephrine, an exogenous agonist of the α₁ adrenoceptor, was abolished by prazosin. However, prazosin did not affect PNS-induced endogenous noradrenaline overflow. Naloxone did not affect either PNS-induced endogenous noradrenaline overflow or vasoconstriction. However, naloxone did inhibit phenylephrine-induced vasoconstriction. In addition, naloxone did not affect the angiotensin II-induced vasoconstriction. These results demonstrate that naloxone selectively inhibits vasoconstriction caused by phenylephrine, but not vasoconstriction caused by endogenous noradrenaline released from sympathetic nerve cells in the rat mesenteric vasculature.

Diarrhea is the second leading cause of death in children under five years of age globally. Traditional medicinal practices often use plants to manage gastrointestinal issues. Ammodaucus leucotrichus is a medicinal plant that holds significant importance in Moroccan traditional medicine for treating gastrointestinal problems. This study aimed to validate the traditional use of A. leucotrichus by providing scientific evidence for its efficacy. We evaluated the effectiveness of the methanol fraction of A. leucotrichus in alleviating diarrhea and reducing smooth muscle contractions using comprehensive in vivo and in vitro models. In vitro experiments were performed using an isotonic transducer in the jejunum of rats and rabbits. In vivo antidiarrheal effects were evaluated in mice with castor oil-induced diarrhea. The methanol fraction of A. leucotrichus (MFAl) inhibited diarrhea in a dose-dependent manner. It also exhibited spasmolytic activity at doses ranging from 5.5 to 65 μg/ml, with IC₅₀ values of 43.43 ± 2.63 μg/ml for potassium chloride (KCl) and 28.91 ± 0.43 μg/ml for carbachol (CCh). The obtained spasmolytic activities were comparable to those of a non-competitive antagonist of calcium channels and muscarinic receptors by rightward and downward shifts in the concentration-response curves for calcium and carbachol. Our results demonstrate that, with the addition of nifedipine, the spasmolytic effect of MFAl decreased by 70.11%. This indicates that the spasmolytic effect of MFAl is possibly mediated by the inhibition of Ca²⁺ influx. In addition, the presence of hexamethonium significantly modified the relaxation effect of MFAl by 46.20%, indicating that MFAl also acts through nicotinic receptors. These findings support the traditional use of A. leucotrichus for gastrointestinal disorders and highlight the need for further research to develop new anti-diarrheal and anti-spasmodic treatments.

Varicose veins are common lower extremity venous disorders characterized by dilated veins and incompetent valves. Although maintaining the required vein wall tone for adaptive responses depends on a proper contractile function of the human saphenous smooth muscle, the contractile properties of varicose veins are mostly unknown. We investigated the relationship between contractile responses and the internal diameter of human saphenous varicose veins. The absolute contractile forces induced by potassium chloride (KCl, 60 mmol/l), serotonin (5-hydroxytryptamine [5-HT], 10 µmol/l), and noradrenaline (NAd, 10 µmol/l) were similar between normal saphenous veins (control) and varicose veins. When the contractile forces were normalized to the internal diameter in each preparation, the contractile responses to these stimuli were significantly lower in varicose veins than in the control veins. Furthermore, varicose veins were divided into three groups according to their internal diameter (group 1, 3-4.5 mm; group 2, 4.5-6 mm; group 3, >6 mm). The contractile responses induced by KCl, 5-HT, and NAd did not differ between groups 1 and 2 and the control group, while the contractile responses in group 3 were significantly lower than those in the control group. Moreover, the contractions induced by KCl and NAd in Group 3 were smaller than those in group 1 or group 2. This trend was also observed in 5-HT-induced contractions, although the results were not statistically significant. In conclusion, contractile responses in varicose veins may be altered by an increase in internal diameter, although adequate contractile responses are preserved in some diameters.

Understanding the molecular interactions within the neuromuscular apparatus in the stomach is crucial for understanding their role in maintaining interstitial cells, such as the interstitial cells of Cajal (ICC), smooth muscle, and enteric neurons, as well as their contribution to gastric motility in both healthy and diseased states. Disruptions of these systems can lead to various gastric motor disorders and diseases, making it essential to explore their functions in detail. We herein present a protocol for gene knockdown using small interfering RNA (siRNAs) in organotypic culture. This ex vivo approach allows the precise manipulation of the gene expression in a tissue environment that closely mimics in vivo conditions, providing valuable insights into the gene function and its effects on gastric physiology. The protocol includes detailed steps for tissue preparation to ensure the preservation of the gastric muscles and the associated neuromuscular apparatus. We then describe the process of siRNA-mediated gene knockdown, offering tips for optimizing transfection efficiency and gene silencing. Additionally, we outline methods for analyzing the effectiveness of knockdown, including both quantitative and qualitative methods for the evaluation of the target gene expression. This protocol is adaptable to various research needs, allowing researchers to focus on specific genes of interest within the neuromuscular system of the stomach. By applying this approach, investigators can deepen their understanding of the molecular mechanisms underlying gastric motility and contribute to the development of new therapeutic strategies for treating gastric motor disorders and diseases.