Signaling for contraction and relaxation in smooth muscle of the gut

Biomimetic Hydrogels as the Inductive Endochondral Ossification Template for Promoting Bone Regeneration

Repairing critical size bone defects (CSBD) is a major clinical challenge and requires effective intervention by biomaterial scaffolds. Inspired by the fact that the cartilaginous template-based endochondral ossification (ECO) process is crucial to bone healing and development, developing biomimetic biomaterials to promote ECO is recognized as a promising approach for repairing CSBD. With the unique highly hydrated 3D polymeric network, hydrogels can be designed to closely emulate the physiochemical properties of cartilage matrix to facilitate ECO. In this review, the various preparation methods of hydrogels possessing the specific physiochemical properties required for promoting ECO are introduced. The materiobiological impacts of the physicochemical properties of hydrogels, such as mechanical properties, topographical structures and chemical compositions on ECO, and the associated molecular mechanisms related to the BMP, Wnt, TGF-β, HIF-1α, FGF, and RhoA signaling pathways are further summarized. This review provides a detailed coverage on the materiobiological insights required for the design and preparation of hydrogel-based biomaterials to facilitate bone regeneration.

Retracted: PKC-delta and PKD activate MAPK signal pathway in mechano-transcription of colonic smooth muscle cells

Retraction: [PKC-delta and PKD activate MAPK signal pathway in mechano-transcription of colonic smooth muscle cells, Z. Yang, K. He, T. Wang, et al. Neurogastroenterology & Motility 2023; e14623 (https://onlinelibrary.wiley.com/doi/full/10.1111/nmo.14623)]. The above article, published online on June 6, 2023 in Wiley Online Library (wileyonlinelibrary.com), has been retracted by agreement between the authors, the Journal Editor in Chief, Maura Corsetti, and John Wiley & Sons Ltd. The retraction has been agreed due to unat[1]tributed overlap between this article and the abstract published in Gastroenterology: Li F, Sarna SK and Shi XP. Roles of PKCs and PKD in Mechanotranscription in Colonic Smooth Muscle Cells: Inhibition of Mechanotranscription as a Potential Treatment for Motility Dysfunction in Obstructive Disorders. In: 2012 Digestive Disease Week Abstract Supplement; May 19-22, San Diego, CA. Abstract 120 (https://www.gastrojournal.org/article/S0016-5085(12)60115-2/pdf).

Role of mechanoregulation in mast cell-mediated immune inflammation of the smooth muscle in the pathophysiology of esophageal motility disorders

Major esophageal disorders involve obstructive transport of bolus to the stomach, causing symptoms of dysphagia and impaired clearing of the refluxed gastric contents. These may occur due to mechanical constriction of the esophageal lumen or loss of relaxation associated with deglutitive inhibition, as in achalasia-like disorders. Recently, immune inflammation has been identified as an important cause of esophageal strictures and the loss of inhibitory neurotransmission. These disorders are also associated with smooth muscle hypertrophy and hypercontractility, whose cause is unknown. This review investigated immune inflammation in the causation of smooth muscle changes in obstructive esophageal bolus transport. Findings suggest that smooth muscle hypertrophy occurs above the obstruction and is due to mechanical stress on the smooth muscles. The mechanostressed smooth muscles release cytokines and other molecules that may recruit and microlocalize mast cells to smooth muscle bundles, so that their products may have a close bidirectional effect on each other. Acting in a paracrine fashion, the inflammatory cytokines induce genetic and epigenetic changes in the smooth muscles, leading to smooth muscle hypercontractility, hypertrophy, and impaired relaxation. These changes may worsen difficulty in the esophageal transport. Immune processes differ in the first phase of obstructive bolus transport, and the second phase of muscle hypertrophy and hypercontractility. Moreover, changes in the type of mechanical stress may change immune response and effect on smooth muscles. Understanding immune signaling in causes of obstructive bolus transport, type of mechanical stress, and associated smooth muscle changes may help pathophysiology-based prevention and targeted treatment of esophageal motility disorders.NEW & NOTEWORTHY Esophageal disorders such as esophageal stricture or achalasia, and diffuse esophageal spasm are associated with smooth muscle hypertrophy and hypercontractility, above the obstruction, yet the cause of such changes is unknown. This review suggests that smooth muscle obstructive disorders may cause mechanical stress on smooth muscle, which then secretes chemicals that recruit, microlocalize, and activate mast cells to initiate immune inflammation, producing functional and structural changes in smooth muscles. Understanding the immune signaling in these changes may help pathophysiology-based prevention and targeted treatment of esophageal motility disorders.

Pharmacological study on the enhancing effects of U46619 on guinea pig urinary bladder smooth muscle contraction induced by acetylcholine and α,β-methylene ATP and the possible involvement of protein kinase C

We examined whether U46619 (a prostanoid TP receptor agonist) could enhance the contractions of guinea pig urinary bladder smooth muscle (UBSM) in response to acetylcholine (ACh) and an ATP analog (α,β-methylene ATP (αβ-MeATP)) through stimulation of the UBSM TP receptor and whether protein kinase C (PKC) is involved. U46619 (10-7 M) markedly enhanced UBSM contractions induced by electrical field stimulation and ACh/αβ-MeATP (3 × 10-6 M each), the potentiation of which was completely suppressed by SQ 29,548 (a TP receptor antagonist, 6 × 10-7 M). PKC inhibitors did not attenuate the ACh-induced contractions enhanced by U46619 although they partly suppressed the U46619-enhanced, αβ-MeATP-induced contractions. While phorbol 12-myristate 13-acetate (PMA, a PKC activator, 10-6 M) did not enhance ACh-induced contractions, it enhanced αβ-MeATP-induced contractions, an effect that was completely suppressed by PKC inhibitors. αβ-MeATP-induced contractions, both with and without U46619 enhancement, were strongly inhibited by diltiazem. U46619/PMA enhanced 50 mM KCl-induced contractions, the potentiation of which was partly/completely attenuated by PKC inhibitors. These findings suggest that U46619 potentiates parasympathetic nerve-associated UBSM contractions by stimulating UBSM TP receptors. PKC-increased Ca2+ influx through voltage-dependent Ca2+ channels may partially play a role in purinergic receptor-mediated UBSM contractions enhanced by TP receptor stimulation.

Multi-disciplinary Insights from the First European Forum on Visceral Myopathy 2022 Meeting

Visceral myopathy is a rare, life-threatening disease linked to identified genetic mutations in 60% of cases. Mostly due to the dearth of knowledge regarding its pathogenesis, effective treatments are lacking. The disease is most commonly diagnosed in children with recurrent or persistent disabling episodes of functional intestinal obstruction, which can be life threatening, often requiring long-term parenteral or specialized enteral nutritional support. Although these interventions are undisputedly life-saving as they allow affected individuals to avoid malnutrition and related complications, they also seriously compromise their quality of life and can carry the risk of sepsis and thrombosis. Animal models for visceral myopathy, which could be crucial for advancing the scientific knowledge of this condition, are scarce. Clearly, a collaborative network is needed to develop research plans to clarify genotype-phenotype correlations and unravel molecular mechanisms to provide targeted therapeutic strategies. This paper represents a summary report of the first 'European Forum on Visceral Myopathy'. This forum was attended by an international interdisciplinary working group that met to better understand visceral myopathy and foster interaction among scientists actively involved in the field and clinicians who specialize in care of people with visceral myopathy.

Naringenin modulates Cobalt activities on gut motility through mechanosensors and serotonin signalling

IntroductionCobalt chloride-(CoCl₂) exerts beneficial and toxic activities depending on dose however Naringenin-(Nar) a flavonoid, chelates heavy metals. Absorption of ingested heavy metals, or chelates are dependent on gut motility (gastric emptying and intestinal transit time) and mechanosensor regulation. Literature is vague on CoCl₂ activities on gut motility and mechanosensor nor probable chelating actions with naringenin which was investigated in this study.MethodOne hundred male Wistar rats were grouped viz; A to D (25, 62, 150 and 300 mg/kg CoCl₂), E to H doses of CoCl₂+Nar (50 mg/kg), I-Narigenin and J-Control. Gastric emptying and intestinal transit time were evaluated by day eight, intestinal tissue assayed for biochemical, histological and immunohistochemistry reactivity.ResultCoCl₂ significantly increased Gastric emptying (150 and 300 mg/kg) and Intestinal transit time unlike Naringenin. CoCl₂ (150 mg/kg) significantly increased Catalase and Nitric oxide but ameliorated by Naringenin. ATPase activities significantly increased in 150 mg/kg-CoCl₂ but ameliorated by Naringenin. Carbonyl levels increased in all CoCl₂+Nar groups. High Enterochromaffin-cell count in 25 and 62 mg/kg-CoCl₂ were ameliorated by Naringenin. Serotonin immunoreactivity increased in CoCl₂ (25, 62, 300 mg/kg) but reduced in CoCl₂+Nar groups.ConclusionCobalt chloride enhanced gastric motility via increased mechanosensor activities and serotonin expression at low doses. Naringenin ameliorated toxicity of high cobalt chloride via metal-flavonoid chelates.

Mechanism of Oxytocin-Induced Contraction in Rat Gastric Circular Smooth Muscle

Oxytocin produces an excitatory effect on gastric muscle through the activation of receptors present on stomach smooth muscle cells. However, the intracellular mechanisms that mediate oxytocin excitatory effects are still largely unknown. Therefore, we aimed to investigate the signaling pathways involved in oxytocin-induced contractions in gastric smooth muscle, shedding light on phospholipase C (PLC)-β1 signaling and its downstream molecules, including inositol 1,4,5- trisphosphate (IP₃) and myosin light chain kinase (MLCK). The contractions of gastric smooth muscle from male rats were measured in an organ bath set up in response to exogenous oxytocin 10^-7 M, in the presence and absence of inhibitors of the indicated signaling molecules. Oxytocin (10^-9-10^-5 M) induced dose-dependent stomach smooth muscle contraction. Pre-incubation with atosiban, an oxytocin receptor inhibitor, abolished the oxytocin-induced contraction. Moreover, PLC β1 inhibitor (U73122) and IP₃ inhibitor Xestospongin C inhibited oxytocin-induced muscle contraction to various degrees. Verapamil, a calcium channel blocker, inhibited oxytocin-induced contraction, and pre-incubation of the strips, with both verapamil and Xestospongin C, further inhibited the excitatory effect of oxytocin. Chelation of intracellular calcium with BAPT-AM (1,2-bis-(o-aminophenoxy) ethane-N,N,N',N'-tetraacetic acid) significantly inhibited the effect of oxytocin on muscle contraction. Finally, pre-incubation of the strips with the Ca²⁺/calmodulin-dependent protein kinase selective inhibitor STO-609 significantly inhibited the contraction induced by oxytocin. These results suggest that oxytocin directly stimulates its cell surface receptor to activate PLC β1, which in turn liberates IP₃, which eventually elevates intracellular calcium, the prerequisite for smooth muscle contraction.

Identification of lysophosphatidic acid in serum as a factor that promotes epithelial apical junctional complex organization

The apical junctional complex (AJC) consists of adherens junctions (AJs) and tight junctions and regulates epithelial integrity and remodeling. However, it is unclear how AJC organization is regulated based on environmental cues. We found here using cultured EpH4 mouse mammary epithelial cells that fetal bovine serum (FBS) in a culture medium showed an activity to promote AJC organization and that FBS showed an activity to promote tight junction formation even in the absence of AJ proteins, such as E-cadherin, αE-catenin, and afadin. Furthermore, we purified the individual factor responsible for these functions from FBS and identified this molecule as lysophosphatidic acid (LPA). In validation experiments, purified LPA elicited the same activity as FBS. In addition, we found that the AJC organization–promoting activity of LPA was mediated through the LPA receptor 1/5 via diacylglycerol–novel PKC and Rho–ROCK pathway activation in a mutually independent, but complementary, manner. We demonstrated that the Rho–ROCK pathway activation–mediated AJC organization was independent of myosin II-induced actomyosin contraction, although this signaling pathway was previously shown to induce myosin II activation. These findings are in contrast to the literature, as previous results suggested an AJC organization–disrupting activity of LPA. The present results indicate that LPA in serum has an AJC organization–promoting activity in a manner dependent on or independent of AJ proteins.

MYPT1 reduction is a pathogenic factor of erectile dysfunction

Erectile dysfunction (ED) is closely associated with smooth muscle dysfunction, but its underlying mechanisms remains incompletely understood. We here reported that the reduced expression of myosin phosphatase target subunit 1 (MYPT1), the main regulatory unit of myosin light chain phosphatase, was critical for the development of vasculogenic ED. Male MYPT1 knockout mice had reduced fertility and the penises displayed impaired erections as evidenced by reduced intracavernous pressure (ICP). The penile smooth muscles of the knockout mice displayed enhanced response to G-Protein Couple Receptor agonism and depolarization contractility and resistant relaxation. We further identified a natural compound lotusine that increased the MYPT1 expression by inhibiting SIAH1/2 E3 ligases-mediated protein degradation. This compound sufficiently restored the ICP and improved histological characters of the penile artery of Mypt1 haploinsufficiency mice. In diabetic ED mice (db/db), the decreased expression of MYPT1 was measured, and ICP was improved by lotusine treatment. We conclude that the reduction of MYPT1 is the major pathogenic factor of vasculogenic ED. The restoration of MYPT1 by lotusine improved the function of injured penile smooth muscles, and could be a novel strategy for ED therapy.

Erectile Dysfunction: Key Role of Cavernous Smooth Muscle Cells

Erectile dysfunction is increasingly affecting men, from the elderly to young adults, being a sexual disorder related to the inability to generate or maintain a penile erection. This disorder is related to psychosocial factors such as anxiety, depression, and low self-esteem, to organic factors such as the presence of preexisting conditions like hypertension, diabetes and dyslipidemia. The pathophysiology of the disease is related to changes in the neurotransmission of the autonomic or the non-cholinergic non-adrenergic nervous system, as well as the release of local mediators, such as thromboxane A₂ and endothelin, and hormonal action. These changes lead to impaired relaxation of cavernous smooth muscle, which reduces local blood flow and impairs penile erection. Currently, therapy is based on oral vasodilation, such as sildenafil, tadalafil, vardenafil and iodenafil, or by direct administration of these agents into the corpus cavernosum or by intraurethral route, such as alprostadil and papaverine. Despite this, studies that consolidate the understanding of its pathophysiological process contribute to the discovery of new more efficient drugs for the treatment of erectile dysfunction. In this sense, in the present work an extensive survey was carried out of the mechanisms already consolidated and the most recent ones related to the development of erectile dysfunction.

Effect of phosphodiesterase-4 inhibitor rolipram on colonic hypermotility in water avoidance stress rat model

BACKGROUND

Phosphodiesterase (PDE) inhibition has been reported to play a role in regulating gut motility, but the evidence is insufficient, and the mechanism remains unknown. The aim of this study was to investigate the possible role of phosphodiesterase-4 (PDE4) inhibitor rolipram in water avoidance stress-induced colonic hypermotility.

METHODS

A rat model of irritable bowel syndrome (IBS) with diarrhea (IBS-D) was established by water avoidance stress (WAS). Intestinal motility was assessed by fecal pellets expulsion per hour. The cyclic adenosine monophosphate (cAMP) and nitric oxide (NO) level in colon tissue were detected using ELISA assay and the Griess test, respectively. Western blotting was performed to assess the protein level of PDE, PKA/p-CREB, and neuronal nitric oxide synthase (nNOS) in the colon. To determine the role of rolipram in gut motility, the rats of the WAS + Rolipram and Rolipram group were injected with rolipram intraperitoneally. The colonic contractile activity was recorded with a RM6240 multichannel physiological signal system.

KEY RESULTS

WAS-induced gastrointestinal hypermotility and increased defecation in rats. After repeated stress, protein levels of PDE4 in the colon were promoted while PKA/p-CREB and nNOS were highly decreased. cAMP content in colon tissue did not change significantly. However, NO content decreased after WAS, and rolipram partly enhanced NO in WAS-exposed rats. In addition, intraperitoneal injection of rolipram partly inhibited the colonic motility in vivo. Meanwhile, we observed rolipram inhibited the contraction of colonic smooth muscle strips, and this inhibitory effect was abolished by Nω-Nitro-L-arginine (L-NNA), a nitric oxide synthase (NOS) inhibitor, tetrodotoxin (TTX), a blocker of neuronal voltage-dependent Na⁺ channels, Rp-Adenosine 3',5'-cyclic monophosphorothioate triethylammonium salt hydrate (Rp-cAMPS), an antagonist of cAMP.

CONCLUSIONS AND INFERENCES

Rolipram could relieve stress-induced gastrointestinal hypermotility. This effect may be partly through the cAMP-PKA-p-CREB pathway and NO pathway.

Research on the Mechanism and Prevention of Hypertension Caused by Apatinib Through the RhoA/ROCK Signaling Pathway in a Mouse Model of Gastric Cancer

Hypertension is one of the main adverse effects of antiangiogenic tumor drugs and thus limits their application. The mechanism of hypertension caused by tyrosine kinase inhibitors (TKIs) targeting vascular endothelial growth factors is mainly related to inhibition of the nitric oxide (NO) pathway and activation of the endothelin pathway, as well as vascular rarefaction and increased salt sensitivity; consequently, prevention and treatment differ for this type of hypertension compared with primary hypertension. Apatinib is a highly selective TKI approved in China for the treatment of advanced or metastatic gastric cancer. The RhoA/ROCK pathway is involved in the pathogenesis of hypertension and mediates smooth muscle contraction, eNOS inhibition, endothelial dysfunction and vascular remodeling. In this study, in vivo experiments were performed to explore whether the RhoA/ROCK signaling pathway is part of a possible mechanism of apatinib in the treatment of gastric cancer-induced hypertension and the impairment of vascular remodeling and left ventricular function. Y27632, a selective small inhibitor of both ROCK1 and ROCK2, was combined with apatinib, and its efficacy was evaluated, wherein it can reduce hypertension induced by apatinib treatment in gastric cancer mice and weaken the activation of the RhoA/ROCK pathway by apatinib and a high-salt diet (HSD). Furthermore, Y-27632 improved aortic remodeling, fibrosis, endothelial dysfunction, superior mesenteric artery endothelial injury, left ventricular dysfunction and cardiac fibrosis in mice by weakening the activation of the RhoA/ROCK pathway. The expression of RhoA/ROCK pathway-related proteins and relative mRNA levels in mice after apatinib intervention were analyzed by various methods, and blood pressure and cardiac function indexes were compared. Endothelial and cardiac function and collagen levels in the aorta were also measured to assess vascular and cardiac fibrosis and to provide a basis for the prevention and treatment of this type of hypertension.

A systematic review of translation and experimental studies on internal anal sphincter for fecal incontinence

The complexity in the molecular mechanism of the internal anal sphincter (IAS) limits preclinical or clinical outcomes of fecal incontinence (FI) treatment. So far, there are no systematic reviews of IAS translation and experimental studies that have been reported. This systematic review aims to provide a comprehensive understanding of IAS critical role in FI. Previous studies revealed the key pathway for basal tone and relaxation of IAS in different properties as follows; calcium, Rho-associated, coiled-coil containing serine/threonine kinase, aging-associated IAS dysfunction, oxidative stress, renin-angiotensin-aldosterone, cyclooxygenase, and inhibitory neurotransmitters. Previous studies have reported improved functional outcomes of cellular treatment for regeneration of dysfunctional IAS, using various stem cells, but did not demonstrate the interrelationship between those results and basal tone or relaxation-related molecular pathway of IAS. Furthermore, these results have lower specificity for IAS-incontinence due to the included external anal sphincter or nerve injury regardless of the cell type. An acellular approach using bioengineered IAS showed a physiologic response of basal tone and relaxation response similar to human IAS. However, in both cellular and acellular approaches, the lack of human IAS data still hampers clinical application. Therefore, the IAS regeneration presents more challenges and warrants more advances.

Biological responses of Eisenia fetida towards the exposure and metabolism of tris (2-butoxyethyl) phosphate

The toxicity of various organophosphorus flame retardants (OPFRs) is of increasing concern. However, there is still a lack of research on the toxicity of OPFRs to terrestrial invertebrates and its metabolism in vivo. Herein, earthworms (Eisenia fetida) were exposed to soil spiked with 0, 0.05, 0.5, and 5 mg/kg tris(2-butoxyethyl) phosphate (TBOEP, a typical alkyl OPFRs) for 28 d to study the biological responses to the exposure and metabolism of TBOEP. TBOEP exposure inhibited the activity of acetyl-cholinesterase (64.4-68.6% of that in the control group), increased the energy consumption level, and affected calcium-dependent pathways of E. fetida, which caused a 3.6-12.4% reduction in the weight gain rate (developmental toxicity), a 10.6-69.4% reduction in the number of juveniles (reproduction toxicity), and neurotoxicity to E. fetida. The 5 mg/kg TBOEP exposure caused a significant accumulation of malondialdehyde (1.68 times higher than that in the control group) in E. fetida, which indicated that the balance of oxidation and anti-oxidation of E. fetida was broken. Meanwhile, E. fetida maintained the absorption and metabolic abilities to TBOEP under the environmental condition. The removal rate of soil TBOEP was increased by 25.1-35.5% by the presence of E. fetida. Importantly, TBOEP could accumulate in E. fetida (0.09-76.0 μg/kg) and the activation of cytochrome P450 and glutathione detoxification pathway promoted the metabolism of TBOEP in E. fetida. These findings link the biological responses and metabolic behavior of earthworms under pollution stress and provide fundamental data for the environmental risk assessment and pollution removal of OPFRs in soil.

Nebulization of risedronate alleviates airway obstruction and inflammation of chronic obstructive pulmonary diseases via suppressing prenylation-dependent RAS/ERK/NF-κB and RhoA/ROCK1/MLCP signaling

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is a progressive disorder that causes airway obstruction and lung inflammation. The first-line treatment of COPD is the bronchodilators of β2-agonists and antimuscarinic drugs, which can help control the airway obstruction, but the long-term use might render the drug tolerance. Bisphosphonates are widely used in osteoclast-mediated bone diseases treatment for decades. For drug repurposing, can delivery of a third generation of nitrogen-containing bisphosphonate, risedronate (RIS) ameliorate the progression of COPD?

METHODS

COPD rats or mice models have been established through cigarette-smoking and elastase injection, and then the animals are received RIS treatment via nebulization. Lung deposition of RIS was primarily assessed by high-performance liquid chromatography (HPLC). The respiratory parameters of airway obstruction in COPD rats and mice were documented using plethysmography method and resistance-compliance system.

RESULTS

High lung deposition and bioavailability of RIS was monitored with 88.8% of RIS input dose. We found that RIS could rescue the lung function decline of airspace enlargement and mean linear intercept in the COPD lung. RIS could curb the airway obstruction by suppressing 60% of the respiratory resistance and elevating the airway's dynamic compliance, tidal volume and mid-expiratory flow. As an inhibitor of farnesyl diphosphate synthase (FDPS), RIS suppresses FDPS-mediated RAS and RhoA prenylation to obstruct its membrane localization in airway smooth muscle cells (ASMCs), leading to the inhibition of downstream ERK-MLCK and ROCK1-MLCP pathway to cause ASMCs relaxation. Additionally, RIS nebulization impeded pro-inflammatory cell accumulation, particularly macrophages infiltration in alveolar parenchyma. The NF-κB, tumor necrosis factor-alpha, IL-1β, IL-8, and IL-6 declined in microphages following RIS nebulization. Surprisingly, nebulization of RIS could overcome the tolerance of β2-agonists in COPD-rats by increasing the expression of β2 receptors.

CONCLUSIONS

Nebulization of RIS could alleviate airway obstruction and lung inflammation in COPD, providing a novel strategy for treating COPD patients, even those with β2-agonists tolerance.

Targeting Mechano-Transcription Process as Therapeutic Intervention in Gastrointestinal Disorders

Mechano-transcription is a process whereby mechanical stress alters gene expression. The gastrointestinal (GI) tract is composed of a series of hollow organs, often encountered by transient or persistent mechanical stress. Recent studies have revealed that persistent mechanical stress is present in obstructive, functional, and inflammatory disorders and alters gene transcription in these conditions. Mechano-transcription of inflammatory molecules, pain mediators, pro-fibrotic and growth factors has been shown to play a key role in the development of motility dysfunction, visceral hypersensitivity, inflammation, and fibrosis in the gut. In particular, mechanical stress-induced cyclooxygenase-2 (COX-2) and certain pro-inflammatory mediators in gut smooth muscle cells are responsible for motility dysfunction and inflammatory process. Mechano-transcription of pain mediators such as nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) may lead to visceral hypersensitivity. Emerging evidence suggests that mechanical stress in the gut also leads to up-regulation of certain proliferative and pro-fibrotic mediators such as connective tissue growth factor (CTGF) and osteopontin (OPN), which may contribute to fibrostenotic Crohn's disease. In this review, we will discuss the pathophysiological significance of mechanical stress-induced expression of pro-inflammatory molecules, pain mediators, pro-fibrotic and growth factors in obstructive, inflammatory, and functional bowel disorders. We will also evaluate potential therapeutic targets of mechano-transcription process for the management of these disorders.

A Note of Caution: Gramicidin Affects Signaling Pathways Independently of Its Effects on Plasma Membrane Conductance

Gramicidin is a thoroughly studied cation ionophore widely used to experimentally manipulate the plasma membrane potential (PMP). In addition, it has been established that the drug, due to its hydrophobic nature, is capable of affecting the organization of membrane lipids. We have previously shown that modifications in the plasma membrane potential of epithelial cells in culture determine reorganizations of the cytoskeleton. To elucidate the molecular mechanisms involved, we explored the effects of PMP depolarization on some putative signaling intermediates. In the course of these studies, we came across some results that could not be interpreted in terms of the properties of gramicidin as an ionic channel. The purpose of the present work is to communicate these results and, in general, to draw attention to the fact that gramicidin effects can be misleadingly attributed to its ionic or electrical properties. In addition, this work also contributes with some novel findings of the modifications provoked on the signaling intermediates by PMP depolarization and hyperpolarization.

Antispasmodic Effect of Asperidine B, a Pyrrolidine Derivative, through Inhibition of L-Type Ca2+ Channel in Rat Ileal Smooth Muscle

Antispasmodic agents are used for modulating gastrointestinal motility. Several compounds isolated from terrestrial plants have antispasmodic properties. This study aimed to explore the inhibitory effect of the pyrrolidine derivative, asperidine B, isolated from the soil-derived fungus Aspergillus sclerotiorum PSU-RSPG178, on spasmodic activity. Isolated rat ileum was set up in an organ bath. The contractile responses of asperidine B (0.3 to 30 µM) on potassium chloride and acetylcholine-induced contractions were recorded. To investigate its antispasmodic mechanism, CaCl2, acetylcholine, Nω-nitro-l-arginine methyl ester (l-NAME), nifedipine, methylene blue and tetraethylammonium chloride (TEA) were tested in the absence or in the presence of asperidine B. Cumulative concentrations of asperidine B reduced the ileal contraction by ~37%. The calcium chloride and acetylcholine-induced ileal contraction was suppressed by asperidine B. The effects of asperidine B combined with nifedipine, atropine or TEA were similar to those treated with nifedipine, atropine or TEA, respectively. In contrast, in the presence of l-NAME and methylene blue, the antispasmodic effect of asperidine B was unaltered. These results suggest that the antispasmodic property of asperidine B is probably due to the blockage of the L-type Ca2+ channel and is associated with K+ channels and muscarinic receptor, possibly by affecting non-selective cation channels and/or releasing intracellular calcium.

Identification and Validation of a PPP1R12A-Related Five-Gene Signature Associated With Metabolism to Predict the Prognosis of Patients With Prostate Cancer

Background

Prostate cancer (PCa) is the most common malignant male neoplasm in the American male population. Our prior studies have demonstrated that protein phosphatase 1 regulatory subunit 12A (PPP1R12A) could be an efficient prognostic factor in patients with PCa, promoting further investigation. The present study attempted to construct a gene signature based on PPP1R12A and metabolism-related genes to predict the prognosis of PCa patients.

Methods

The mRNA expression profiles of 499 tumor and 52 normal tissues were extracted from The Cancer Genome Atlas (TCGA) database. We selected differentially expressed PPP1R12A-related genes among these mRNAs. Tandem affinity purification-mass spectrometry was used to identify the proteins that directly interact with PPP1R12A. Gene set enrichment analysis (GSEA) was used to extract metabolism-related genes. Univariate Cox regression analysis and a random survival forest algorithm were used to confirm optimal genes to build a prognostic risk model.

Results

We identified a five-gene signature (PPP1R12A, PTGS2, GGCT, AOX1, and NT5E) that was associated with PPP1R12A and metabolism in PCa, which effectively predicted disease-free survival (DFS) and biochemical relapse-free survival (BRFS). Moreover, the signature was validated by two internal datasets from TCGA and one external dataset from the Gene Expression Omnibus (GEO).

Conclusion

The five-gene signature is an effective potential factor to predict the prognosis of PCa, classifying PCa patients into high- and low-risk groups, which might provide potential novel treatment strategies for these patients.

Portal hypertension in cirrhosis: Pathophysiological mechanisms and therapy

Portal hypertension, defined as increased pressure in the portal vein, develops as a consequence of increased intrahepatic vascular resistance due to the dysregulation of liver sinusoidal endothelial cells (LSECs) and hepatic stellate cells (HSCs), frequently arising from chronic liver diseases. Extrahepatic haemodynamic changes contribute to the aggravation of portal hypertension. The pathogenic complexity of portal hypertension and the unsuccessful translation of preclinical studies have impeded the development of effective therapeutics for patients with cirrhosis, while counteracting hepatic and extrahepatic mechanisms also pose a major obstacle to effective treatment. In this review article, we will discuss the following topics: i) cellular and molecular mechanisms of portal hypertension, focusing on dysregulation of LSECs, HSCs and hepatic microvascular thrombosis, as well as changes in the extrahepatic vasculature, since these are the major contributors to portal hypertension; ii) translational/clinical advances in our knowledge of portal hypertension; and iii) future directions.

Characterization of Contractile Machinery of Vascular Smooth Muscles in Hypertension

Hypertension is a key risk factor for cardiovascular disease and it is a growing public health problem worldwide. The pathophysiological mechanisms of vascular smooth muscle (VSM) contraction contribute to the development of hypertension. Calcium (Ca²⁺)-dependent and -independent signaling mechanisms regulate the balance of the myosin light chain kinase and myosin light chain phosphatase to induce myosin phosphorylation, which activates VSM contraction to control blood pressure (BP). Here, we discuss the mechanism of the contractile machinery in VSM, especially RhoA/Rho kinase and PKC/CPI-17 of Ca²⁺ sensitization pathway in hypertension. The two signaling pathways affect BP in physiological and pathophysiological conditions and are highlighted in pulmonary, pregnancy, and salt-sensitive hypertension.

BDNF rescues aging-associated internal anal sphincter dysfunction

Aging can lead to rectoanal incontinence due to internal anal sphincter (IAS) dysfunction, which is characterized by a decrease in IAS tone and contractility and an increase in nonadrenergic noncholinergic (NANC) relaxation. We aimed to determine whether brain-derived neurotropic factor (BDNF) rescues this aging-associated IAS dysfunction (AAID). To do so, we studied the effects of BDNF on the basal and G protein-coupled receptors (GPCR)-stimulated IAS smooth muscle tone and on NANC relaxation in Fischer 344 rats representing different age groups [26-mo-old (aging) vs. 6-mo-old (young)], before and after tyrosine kinase receptor B (TrkB) antagonist K252a. We also used isolated smooth muscle cells (SMCs) to determine the effects of BDNF before and after different agonists. For some studies, we monitored NO release using smooth muscle perfusates. BDNF reversed AAID by rescuing the basal IAS tone and agonists [thromboxane A₂ analog (U46619) and angiotensin II (ANG II)]-induced contractility, and NANC relaxation. These rescue effects of BDNF were selective as K252a attenuated the changes in the IAS without modifying the effects of K⁺depolarization. Because of the direct association between the basal and GPCR-stimulated IAS tone and RhoA/ROCK activation, we speculate that this pathway in the rescue effects of BDNF. Conversely, our data suggest that aging-associated increased NANC relaxation is reversed by decreased release of NO and decrease in the sensitivity of the released inhibitory neurotransmitter. In summary, BDNF rescue of AAID involves RhoA/ROCK and inhibitory neurotransmission. These data have direct implications for the role of BDNF in the pathophysiology and therapeutic targeting of aging-associated rectoanal motility disorders.NEW & NOTEWORTHY These studies demonstrate that brain-derived neurotropic factor (BDNF) rescues the aging-associated internal anal sphincter (IAS) dysfunction, characterized by a decrease in IAS tone, and increase in non-adrenergic noncholinergic relaxation. We determined the effects of BDNF on the basal and GPCR (TXA₂ and ANG II)-stimulated IAS tone, and on NANC relaxation, before and after TrkB inhibitor K252a. BDNF may have an important role in the pathophysiology and therapeutic targeting of certain rectoanal motility disorders.

Blockage of Cholinergic Signaling via Muscarinic Acetylcholine Receptor 3 Inhibits Tumor Growth in Human Colorectal Adenocarcinoma

Cholinergic signaling via the muscarinic M3 acetylcholine receptor (M3R) is involved in the development and progression of colorectal cancer (CRC). The present study aimed to analyze the blocking of M3R signaling in CRC using darifenacin, a selective M3R antagonist. Darifenacin effects were studied on HT-29 and SW480 CRC cells using MTT and BrdU assays, Western blotting and real time RT-PCR. In vivo, blocking of M3R was assessed in an orthotopic CRC xenograft BALB/c^nu/nu mouse model. M3R expression in clinical tumor specimens was studied by immunohistochemistry on a tissue microarray of 585 CRC patients. In vitro, darifenacin decreased tumor cell survival and proliferation in a dose-dependent manner. Acetylcholine-induced p38, ERK1/2 and Akt signaling, and MMP-1 mRNA expression were decreased by darifenacin, as well as matrigel invasion of tumor cells. In mice, darifenacin reduced primary tumor volume and weight (p < 0.05), as well as liver metastases, compared to controls. High expression scores of M3R were found on 89.2% of clinical CRC samples and correlated with infiltrative tumor border and non-mucinous histology (p < 0.05). In conclusion, darifenacin inhibited components of tumor growth and progression in vitro and reduced tumor growth in vivo. Its target, M3R, was expressed on the majority of CRC. Thus, repurposing darifenacin may be an attractive addition to systemic tumor therapy in CRC patients expressing M3R.

Characterization of Cecal Smooth Muscle Contraction in Laying Hens

The ceca play an important role in the physiology of the gastrointestinal tract in chickens. Nevertheless, there is a gap of knowledge regarding the functionality of the ceca in poultry, especially with respect to physiological cecal smooth muscle contraction. The aim of the current study is the ex vivo characterization of cecal smooth muscle contraction in laying hens. Muscle strips of circular cecal smooth muscle from eleven hens are prepared to investigate their contraction ex vivo. Contraction is detected using an isometric force transducer, determining its frequency, height and intensity. Spontaneous contraction of the chicken cecal smooth muscle and the influence of buffers (calcium-free buffer and potassium-enriched buffer) and drugs (carbachol, nitroprusside, isoprenaline and Verapamil) affecting smooth muscle contraction at different levels are characterized. A decrease in smooth muscle contraction is observed when a calcium-free buffer is used. Carbachol causes an increase in smooth muscle contraction, whereas atropine inhibits contraction. Nitroprusside, isoprenaline and Verapamil result in a depression of smooth muscle contraction. In conclusion, the present results confirm a similar contraction behavior of cecal smooth muscles in laying hens as shown previously in other species.

Phosphorylated‑myosin light chain mediates the destruction of small intestinal epithelial tight junctions in mice with acute liver failure

Tight junction dysregulation and epithelial damage contribute to intestinal barrier loss in patients with acute liver failure (ALF); however, the regulatory mechanisms of these processes remain poorly understood. The aim of the present study was to investigate the changes of intestinal tight junction and intestinal mucosa in mice with ALF and their mechanisms. In the present study, ALF was induced in mice through an intraperitoneal injection of D-galactosamine and lipopolysaccharide (D-GalN/LPS), and the morphological changes of the liver or small intestine were analyzed using hematoxylin and eosin staining, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The intestinal tissues and isolated serum were analyzed using western blotting, immunofluorescence staining and ELISA. D-GalN/LPS-induced mice exhibited signs of hepatocyte necrosis, alongside inflammatory cell infiltration into the liver tissue and partial microvilli detachment in the small intestinal mucosa. TEM demonstrated that the intestinal epithelial tight junctions were impaired, whereas SEM micrographs revealed the presence of abnormal microvilli in D-GalN/LPS-induced mice. In addition, the expression levels of phosphorylated (p)-myosin light chain (MLC), MLC kinase (MLCK) and Rho-associated kinase (ROCK) were significantly increased in the D-GalN/LPS-induced mice compared with those in the control mice, whereas the subsequent inhibition of MLCK or ROCK significantly reduced p-MLC expression levels. Conversely, the expression levels of occludin and zonula occludens-1 (ZO-1) were significantly decreased in the D-GalN/LPS-induced mice, and the inhibition of MLCK or ROCK significantly increased occludin and ZO-1 protein expression levels compared with those in the control group. Changes in the serum levels of tumor necrosis factor-α (TNF-α) and interleukin (IL)-6 were similar to the trend observed in p-MLC expression levels. In conclusion, the findings of the present study suggested that in a D-GalN/LPS-induced ALF model, TNF-α and IL-6 signaling may increase MLCK and ROCK expression levels, further mediate phosphorylation of MLC, which may result in tight junction dysregulation and intestinal barrier dysfunction.

Mechanism of α1-Adrenergic Receptor-Induced Increased Contraction of Rat Mesenteric Artery in Aging Hypertension Rats

INTRODUCTION

Vasoconstriction is triggered by an increase in intracellular-free calcium concentration. Growing evidence indicates that contraction is also regulated by calcium-independent mechanisms involving RhoA-Rho kinase (ROCK), protein kinase C (PKC), and so on. In this study, we studied the changes of vascular reactivity as well as the underlying signaling pathways in aging spontaneously hypertensive rats (SHRs).

METHODS

The artery tension induced by α1-adrenergic receptor activator (α1-AR) phenylephrine (PE) was measured in the absence or presence of myosin light chain kinase (MLCK), PKC, and ROCK inhibitors. The α1-AR, PKC, ROCK, phosphorylation of myosin light chain (MLC), and PKC-potentiated phosphatase inhibitors of 17 kDa (CPI-17) of rat mesenteric arteries were analyzed at the mRNA level or protein level.

RESULTS

The vascular tension measurements showed that there was a significant increase in the mesenteric artery contraction induced by PE in old SHR. MLCK inhibitor ML-7 can similarly inhibit PE-induced vasoconstriction. PKC inhibitor GF109203X has the weakest inhibitory effect on PE-induced contraction in old SHR. At the presence of ROCK inhibitor H1152, PE-induced contraction was significantly reduced in young Wistar-Kyoto (WKY) rats, but this phenomenon disappeared in other rats. Furthermore, in old SHR the protein expression of α1-AR decreased and phosphorylation of MLC and CPI-17 were upregulated and MLC phosphatase (MLCP) activity was significantly lower. The expressions of PKC were upregulated in SHR and old rats. In addition, the expression of ROCK-1 was decreased and ROCK-2 was significantly upregulated with age in SHR.

CONCLUSION

In aging hypertension, the expression/activity of PKC or ROCK-2/CPI-17 excessively increased, MLCP activity decreased and MLC phosphorylation enhanced, leading to increased α1-AR-induced vasoconstriction.

Effect of Evodiamine on Rat Colonic Hypermotility Induced by Water Avoidance Stress and the Underlying Mechanism

Background and Aim

EVO is a natural alkaloid that reportedly has potential value in regulating gastrointestinal motility, but this conclusion remains controversial, and the molecular mechanism is unclear. In this study, we aimed to explore the effect of short-chain fatty acids on rat colonic hypermotility induced by water avoidance stress and the underlying mechanism.

Methods

We constructed a hypermotile rat model by chronic water avoidance stress, and Western blot was used to detect the protein level of nNOS in colon tissue. The organ bath and multichannel physiological signal acquisition systems were used to examine the spontaneous contractions of smooth muscle strips. The whole-cell patch-clamp technique was used to investigate L-type voltage-dependent calcium and BK_Ca channel currents in colonic smooth muscle cells.

Results

EVO inhibited the spontaneous contractions of colonic smooth muscle strips in a dose-dependent manner. Moreover, EVO decreased the fecal output induced by chronic water avoidance stress. TTX did not block the inhibitory effect of EVO on spontaneous colon contractions, while L-NNA, a selective nNOS synthase inhibitor, did partially abolish this inhibitory effect. The protein expression of nNOS in the colon tissues of rats administered EVO was significantly increased compared to that in control rats. EVO reversibly inhibited the L-type calcium channel current without changing the steady-state activation or inactivation in colonic smooth muscle cells. EVO significantly inhibited the BK_Ca current but did not change the shape of the I-V curves.

Conclusion

EVO inhibits gastrointestinal motility by inhibiting L-type calcium and BK_Ca channels in colonic smooth muscle cells and indirectly interacting with nNOS.

Effects of shRNA-mediated silencing of PDE5A3 on intracellular cGMP and free Ca2+ levels and human prostate smooth muscle cell proliferation from benign prostatic hyperplasia

Benign prostatic hyperplasia (BPH) with lower urinary tract symptoms (LUTS) is a common disease among elderly men, for which safe and effective treatment strategies remain limited. The aim of the present study was to explore the potential effects of phosphodiesterase 5A3 (PDE5A3) silencing on human prostate smooth muscle cells (HPSMCs). HPSMCs were initially obtained from patients with BPH/LUTS. Short hairpin RNA (shRNA) targeting the PDE5A3 gene was subsequently transfected into cultured HPSMCs. The expression of PDE5A3 was measured using reverse transcription-quantitative PCR and western blotting. cGMP levels were then measured using western blotting and immunocytochemical staining and intracellular Ca²⁺ concentration was measured using rhod2-AM in HPSMCs after transfection. HPSMC proliferation was also observed within 4 days. Cells transfected with PDE5A3-shRNA2 exhibited the most notable decline in PDE5A3 expression compared with that in the Control or NC groups. cGMP levels in HPSMCs transfected with PDE5A3-shRNA2 was significantly increased compared with those in the Control or NC groups, whereas intracellular Ca²⁺ concentrations in cells in the PDE5A3-shRNA2 group were decreased compared with that in the Control or NC groups. The proliferation of HPSMCs in the PDE5A3-shRNA2 group was also inhibited compared with that in the Control or NC groups after 72 h of culture. In conclusion, shRNA-mediated silencing of PDE5A3 was able to increase the levels of cGMP whilst reducing the concentration of Ca²⁺ in HPSMCs, in turn suppressing their proliferation. These findings may potentially provide a novel therapeutic target for treating BPH/LUTS.

Decreased smooth muscle function, peristaltic activity, and gastrointestinal transit in dystrophic (mdx) mice

BACKGROUND

Duchenne muscular dystrophy (DMD) is characterized by the lack of dystrophin in skeletal, cardiac, and smooth muscle. Slow colonic transit and constipation are common in DMD patients and animal models of DMD. However, the cause of this hypocontractility and the expression of contractile proteins in smooth muscle are unknown. The aim of the study was to investigate the expression of contractile proteins in the colonic smooth muscle and the function of the colon in control and mdx mice.

METHODS

Muscle contraction was measured in muscle strips and isolated muscle cells. Peristaltic activity was measured in ex vivo preparations by spatiotemporal mapping, and gastrointestinal (GI) transit in vivo was measured by the distribution of fluorescent marker along the intestine and colon. mRNA expression of contractile proteins smoothelin, caldesmon, calponin, and tropomyosin was measured by qRT-PCR.

RESULTS

Expression of mRNA for contractile proteins was decreased in colonic smooth muscle of mdx mice compared with control. Contraction in response to acetylcholine and KCl was decreased in colonic muscle strips and in isolated muscle cells of mdx mice. Distension of ex vivo colons with Krebs buffer induced peristalsis in both control and mdx mice; however, significantly fewer full peristaltic waves were recorded in the colons of mdx mice. GI transit was also inhibited in mdx mice.

CONCLUSION AND INFERENCES

The data indicate that the lack of dystrophin causes decrease in colonic smooth muscle contractility, peristalsis, and GI transit and provides the basis for analysis of mechanisms involved in smooth muscle dysfunction in DMD.

Vegetal diamine oxidase alleviates histamine-induced contraction of colonic muscles

Excess of histamine in gut lumen generates a pronounced gastrointestinal discomfort, which may include diarrhea and peristalsis dysfunctions. Deleterious effects of histamine can be alleviated with antihistamine drugs targeting histamine receptors. However, many antihistamine agents come with various undesirable side effects. Vegetal diamine oxidase (vDAO) might be a relevant alternative owing to its histaminase activity. Mammalian intestinal mucosa contains an endogenous DAO, yet possessing lower activity compared to that of vDAO preparation. Moreover, in several pathological conditions such as inflammatory bowel disease and irritable bowel syndrome, this endogenous DAO enzyme can be lost or inactivated. Here, we tested the therapeutic potential of vDAO by focusing on the well-known effect of histamine on gut motility. Using ex vivo and in vitro assays, we found that vDAO is more potent than commercial anti-histamine drugs at inhibiting histamine-induced contraction of murine distal colon muscles. We also identified pyridoxal 5′-phosphate (the biologically active form of vitamin B6) as an effective enhancer of vDAO antispasmodic activity. Furthermore, we discovered that rectally administered vDAO can be retained on gut mucosa and remain active. These observations make administration of vDAO in the gut lumen a valid alternative treatment for histamine-induced intestinal dysfunctions.

Alternative pathways control actomyosin contractility in epitheliomuscle cells during morphogenesis and body contraction

In adult Hydra, epitheliomuscle cells form the monolayered ecto- and endodermal epithelia. Their basal myonemes function as a longitudinal and circular muscle, respectively. Based on the observation that a Rho/Rock pathway, controlling the cell shape changes during detachment of Hydra buds, is not involved in body movement, at least two actomyosin compartments must exist in these cells: a basal one for body movement and a cortical one for cell shape changes. We therefore analyzed the regional and subcellular localization of the Ser19-phosphorylated myosin regulatory light chain (pMLC20). Along the body column, pMLC20 was detected strongly in the basal myonemes and weakly in the apical cell compartments of ectodermal epitheliomuscle cells. In cells of the bud base undergoing morphogenesis, pMLC20 was localized to intracellular stress fibers as well as to the apical and additionally to the lateral cortical compartment. Pharmacological inhibition revealed that pMLC20 is induced in these compartments by at least two independent pathways. In myonemes, MLC is phosphorylated mainly by myosin light chain kinase (MLCK). In contrast, the cortical apical and lateral MLC phosphorylation in constricting ectodermal cells of the bud base is stimulated via the Rho/ROCK pathway.

Improving Small Intestinal Motility in Experimental Acute Necrotising Pancreatitis by Modulating the CPI-17/MLCP Pathway Using Chaiqin Chengqi Decoction

Protein kinase C-potentiated inhibitor protein of 17 kDa (CPI-17), a specific inhibitor of myosin light-chain phosphatase (MLCP) regulated by proinflammatory cytokines, is central for calcium sensitisation. We investigated the effects of chaiqin chengqi decoction (CQCQD) on the CPI-17/MLCP pathway in the small intestinal smooth muscle cells (SMCs) and strips (SMS) in an AP model. Necrotising AP was induced in rats by intraperitoneal injections (IPI) of L-ornithine (3.0 g/kg, pH 7.0; hourly × 2) at 1 hour apart; controls received saline. In treatment groups, carbachol (CCh; 60 μg/kg, IPI) or CQCQD (20 g/kg; 2-hourly × 3, intragastric) was administered. The necrotising AP model was associated with systemic inflammation (serum IL-1β and TNF-α) and worsened jejunum histopathology and motility (serum vasoactive intestinal peptide and intestinal fatty acid-binding protein) as the disease progressed. There was decreased intracellular calcium concentration ([Ca²⁺]_i) SMCs. Contractile function of isolated SMCs was reduced and associated with down-regulated expression of key mRNAs and proteins of the CPI-17/MLCP pathway as well as increased IL-1β and TNF-α. CQCQD and CCh significantly reversed these changes and the disease severity. These data suggest that CQCQD can improve intestinal motility by modulating the CPI-17/MLCP pathway in small intestinal smooth muscle during AP.

ITRAQ-Based Proteomics Analysis Reveals the Effect of Neoliensinine on KCl-Induced Vascular Smooth Muscle Contraction by Inhibiting Regulatory Light Chain Phosphorylation

Smooth muscle (SM) contraction is one of the important physiological functions of the human body, and SM abnormal contraction will induce many diseases. The phosphorylated regulatory light chains (p-RLC) play a decisive role in SM contraction, and dephosphorylation of p-RLC is an effective way to relax SM. Our previous study showed that the novel benzylisoquinoline alkaloid, neoliensinine (Neo), could relax microvascular SM contracted by KCl hyperpolarization. In this study, mesenteric capillaries isolated from 45 mice were divided into normal tension group (Control), 124 mM KCl induced contraction model group (Model), and KCl and Neo-treatment group (Drug). The dephosphorylation levels of RLC in the three groups were measured. Compared with the model group, the phosphorylation of RLC in the drug group was decreased dramatically as expected, suggesting that the relaxation effect of Neo was caused by downregulating p-RLC of microvessel SM. In order to fully understand its fundamental mechanism, our research focused on the identification of target proteins in mice with KCl-induced contractile mesenteric capillary. Isobaric tags for relative and absolute quantification (ITRAQ) tagging was carried out by nanospray liquid chromatography-tandem mass spectrometry. The results allowed the upregulation of 164 differential abundance proteins (DAPs) among the 3,474 protein abundance disturbances identified from the model/control samples. Further comparison showed that there were 16 DAP convergences associated with vascular SM contraction between the drug/model and the drug/control samples. Among them, two proteins with known function, PLCβ and RhoGEF12, were selected as target proteins of the relaxation effect of Neo. The two selective target DAPs were verified by Western blot at protein level. The results suggested that changes of the two proteins were consistent with that of the iTRAQ results. Our present work reveals that Neo relaxes vascular smooth muscle via inhibition of RLC phosphorylation, and PLCβ and RhoGEF12 may be potential biomarkers for evaluating the effects mediated by Neo.

Closer to Nature Through Dynamic Culture Systems

Mechanics in the human body are required for normal cell function at a molecular level. It is now clear that mechanical stimulations play significant roles in cell growth, differentiation, and migration in normal and diseased cells. Recent studies have led to the discovery that normal and cancer cells have different mechanosensing properties. Here, we discuss the application and the physiological and pathological meaning of mechanical stimulations. To reveal the optimal conditions for mimicking an in vivo microenvironment, we must, therefore, discern the mechanotransduction occurring in cells.

TIMAP inhibits endothelial myosin light chain phosphatase by competing with MYPT1 for the catalytic protein phosphatase 1 subunit PP1cβ

Transforming growth factor-β membrane associated protein (TIMAP) is an endothelial cell (EC)-predominant PP1 regulatory subunit and a member of the myosin phosphatase target (MYPT) protein family. The MYPTs preferentially bind the catalytic protein phosphatase 1 subunit PP1cβ, forming myosin phosphatase holoenzymes. We investigated whether TIMAP/PP1cβ could also function as a myosin phosphatase. Endogenous PP1cβ, myosin light chain 2 (MLC2), and myosin IIA heavy chain coimmunoprecipitated from EC lysates with endogenous TIMAP, and endogenous MLC2 colocalized with TIMAP in EC projections. Purified recombinant GST-TIMAP interacted directly with purified recombinant His-MLC2. However, TIMAP overexpression in EC enhanced MLC2 phosphorylation, an effect not observed with a TIMAP mutant that does not bind PP1cβ. Conversely, MLC2 phosphorylation was reduced in lung lysates from TIMAP-deficient mice and upon silencing of endogenous TIMAP expression in ECs. Ectopically expressed TIMAP slowed the rate of MLC2 dephosphorylation, an effect requiring TIMAP-PP1cβ interaction. The association of MYPT1 with PP1cβ was profoundly reduced in the presence of excess TIMAP, leading to proteasomal MYPT1 degradation. In the absence of TIMAP, MYPT1-associated PP1cβ readily bound immobilized microcystin-LR, an active-site inhibitor of PP1c. By contrast, TIMAP-associated PP1cβ did not interact with microcystin-LR, indicating that the active site of PP1cβ is blocked when it is bound to TIMAP. Thus, TIMAP inhibits myosin phosphatase activity in ECs by competing with MYPT1 for PP1cβ and blocking the PP1cβ active site.

Flavonoids in a crude extract of Catha edulis inhibit rat intestinal contraction via blocking Ca2+ channels

BACKGROUND

Animal studies show that Catha edulis inhibits gastrointestinal tract motility. However, there is little or no information on its effect on colon motility and the mechanism of action and active constituents responsible for this effect. This study therefore attempted to discern the effect, suggest the mechanism, and identify the active compounds from the crude extract.

METHODS

A crude extract of Catha edulis was fractionated and subfractionated using column chromatography and HPLC. The activity of all fractions and subfractions was evaluated on rat colon longitudinal muscle. Nuclear magnetic resonance (NMR) spectroscopic data elucidations were used to identify the active compounds. An ileal segment preparation was used to investigate the possible mechanism of action.

RESULTS

The crude extract of Catha edulis (0.05-0.5 mg/mL) inhibited spontaneous contraction of rat colon and ileum (P < 0.05), and tetrodotoxin (TTX, 10 µmol/L) failed to block this effect. Similar to verapamil (0.01-0.1 μmol/L), the Catha edulis extract (0.05-0.5 mg/mL) inhibited high K⁺ (80 mmol/L)-induced sustained ileal contraction and decreased the response to Ca²⁺ . Analysis of the NMR data showed that quercetin, kaempferol, and myricetin were the active phytochemicals. All the identified compounds were flavonoids and significantly inhibited (P < 0.05) spontaneous contraction of the rat colon longitudinal muscle compared to controls.

CONCLUSIONS

The crude extract of Catha edulis has a spasmolytic effect on the rat ileum, which is mediated through blocking Ca²⁺ channels, and quercetin, kaempferol, and myricetin were found to be the causative compounds.

Downregulation of thromboxane A2 and angiotensin II type 1 receptors associated with aging-related decrease in internal anal sphincter tone

Aging-associated decrease in internal anal sphincter (IAS) tone (AADI) is a major contributor in the rectoanal incontinence (RI). To determine the pathogenesis of AADI, we investigated the effect of aging on GPCR activation and related downstream signaling. We particularly investigated two GPCRs that characterize IAS smooth muscle cells (SMCs): thromboxane A2 and angiotensin II type 1. Two groups of Fischer 344 rats (6-month-old [young group] and 26-month-old [old group]) were employed to determine the GPCR function by isometric contraction, the expressions of GPCRs, and their downstream regulatory signaling proteins (regulator of G-protein signaling 2, RGS2; GPCR Kinase 5, GRK5; and β-arrestin, Arrb2) using RT-PCR, qPCR, and western blot analyses. We used reversible biotinylation to monitor the GPCR trafficking using SMCs. Aging selectively attenuated thromboxane A2 and Ang II-induced IAS contraction. RT-PCR, qPCR, and WB data revealed a significant decrease in the expressions of the GPCRs and increase in the expression of RGS2, GRK5, and Arrb2. The increased GPCR internalization and decreased recycling under aging were validated by reversible biotinylation. We conclude that downregulation of GPCR, accompanied by upregulation of regulatory proteins, plays an important role in receptor desensitization and may be important underlying mechanisms of RI in certain aging patients.

Branched Short-Chain Fatty Acid Isovaleric Acid Causes Colonic Smooth Muscle Relaxation via cAMP/PKA Pathway

BACKGROUND

Isovaleric acid (IVA) is a 5-carbon branched-chain fatty acid present in fermented foods and produced in the colon by bacterial fermentation of leucine. We previously reported that the shorter, straight-chain fatty acids acetate, propionate and butyrate differentially affect colonic motility; however, the effect of branched-chain fatty acids on gut smooth muscle and motility is unknown.

AIMS

To determine the effect of IVA on contractility of colonic smooth muscle.

METHODS

Murine colonic segments were placed in a longitudinal orientation in organ baths in Krebs buffer and fastened to force transducers. Segments were contracted with acetylcholine (ACh), and the effects of IVA on ACh-induced contraction were measured in the absence and presence of tetrodotoxin (TTx) or inhibitors of nitric oxide synthase [L-N-nitroarginine (L-NNA)] or adenylate cyclase (SQ22536). The effect of IVA on ACh-induced contraction was also measured in isolated muscle cells in the presence or absence of SQ22536 or protein kinase A (PKA) inhibitor (H-89). Direct activation of PKA was measured in isolated muscle cells.

RESULTS

In colonic segments, ACh-induced contraction was inhibited by IVA in a concentration-dependent fashion; the IVA response was not affected by TTx or L-NNA but inhibited by SQ22536. Similarly, in isolated colonic muscle cells, ACh-induced contraction was inhibited by IVA in a concentration-dependent fashion and the effect blocked by SQ22536 and H-89. IVA also increased PKA activity in isolated smooth muscle cells.

CONCLUSIONS

The branched-chain fatty acid IVA acts directly on colonic smooth muscle and causes muscle relaxation via the PKA pathway.

Changes in Gastric Smooth Muscle Cell Contraction during Pregnancy: Effect of Estrogen

It is well known that pregnancy is associated with frequent gastrointestinal (GI) disorders and symptoms. Moreover, previous reports have shown that estrogen, which changes in levels during pregnancy, participates in the regulation of GI motility and is involved in the pathogenesis of various functional disorders in the stomach. The aim of the current study was to explore the changes in the expression of estrogen receptors (ERs) and examine the effect of estrogen on nitric oxide- (NO-) cyclic guanosine monophosphate (cGMP) pathway and thus relaxation in gastric smooth muscle cells (GSMC) during pregnancy. Single GSMC from early-pregnant and late-pregnant Sprague-Dawley rats were used. Protein and mRNA expression levels of ERs were measured via specifically designed enzyme-linked immunosorbent assay (ELISA) and polymerase chain reaction (PCR), respectively. NO and cGMP levels were measured via specifically designed ELISA kits. Effect of estrogen on acetylcholine- (ACh-) induced contraction of single GSMC was measured via scanning micrometry in the presence or absence of the NO synthase inhibitor, N-nitro-L-arginine (L-NNA), or guanylyl cyclase inhibitor, 1H-[1,2,4]oxadiazolo[4,3,-a]quinoxalin-1-one (ODQ). Estrogen increased both NO and cGMP levels and their levels were greater in early compared to late pregnancy. Expression of ERs was greater in early compared to late pregnancy. ACh induced greater contraction of GSMC in late pregnancy compared to early pregnancy. Estrogen inhibited ACh-induced contraction in both periods of pregnancy. Importantly, pretreatment of GSMC with either L-NNA or ODQ abolished estrogen inhibitory action on muscle contraction. In conclusion, GSMC contractile behavior undergoes drastic changes in response to estrogen during pregnancy and this might explain some of the pregnancy-associated gastric disorders.

Advances in the physiology of gastric emptying

There have been many recent advances in the understanding of various aspects of the physiology of gastric motility and gastric emptying. Earlier studies had discovered the remarkable ability of the stomach to regulate the timing and rate of emptying of ingested food constituents and the underlying motor activity. Recent studies have shown that two parallel neural circuits, the gastric inhibitory vagal motor circuit (GIVMC) and the gastric excitatory vagal motor circuit (GEVMC), mediate gastric inhibition and excitation and therefore the rate of gastric emptying. The GIVMC includes preganglionic cholinergic neurons in the DMV and the postganglionic inhibitory neurons in the myenteric plexus that act by releasing nitric oxide, ATP, and peptide VIP. The GEVMC includes distinct gastric excitatory preganglionic cholinergic neurons in the DMV and postganglionic excitatory cholinergic neurons in the myenteric plexus. Smooth muscle is the final target of these circuits. The role of the intramuscular interstitial cells of Cajal in neuromuscular transmission remains debatable. The two motor circuits are differentially regulated by different sets of neurons in the NTS and vagal afferents. In the digestive period, many hormones including cholecystokinin and GLP-1 inhibit gastric emptying via the GIVMC, and in the inter-digestive period, hormones ghrelin and motilin hasten gastric emptying by stimulating the GEVMC. The GIVMC and GEVMC are also connected to anorexigenic and orexigenic neural pathways, respectively. Identification of the control circuits of gastric emptying may provide better delineation of the pathophysiology of abnormal gastric emptying and its relationship to satiety signals and food intake.

TGFβ-activation by dendritic cells drives Th17 induction and intestinal contractility and augments the expulsion of the parasite Trichinella spiralis in mice

Helminths are highly prevalent metazoan parasites that infect over a billion of the world's population. Hosts have evolved numerous mechanisms to drive the expulsion of these parasites via Th2-driven immunity, but these responses must be tightly controlled to prevent equally devastating immunopathology. However, mechanisms that regulate this balance are still unclear. Here we show that the vigorous Th2 immune response driven by the small intestinal helminth Trichinella spiralis, is associated with increased TGFβ signalling responses in CD4+ T-cells. Mechanistically, enhanced TGFβ signalling in CD4+ T-cells is dependent on dendritic cell-mediated TGFβ activation which requires expression of the integrin αvβ8. Importantly, mice lacking integrin αvβ8 on DCs had a delayed ability to expel a T. spiralis infection, indicating an important functional role for integrin αvβ8-mediated TGFβ activation in promoting parasite expulsion. In addition to maintaining regulatory T-cell responses, the CD4+ T-cell signalling of this pleiotropic cytokine induces a Th17 response which is crucial in promoting the intestinal muscle hypercontractility that drives worm expulsion. Collectively, these results provide novel insights into intestinal helminth expulsion beyond that of classical Th2 driven immunity, and highlight the importance of IL-17 in intestinal contraction which may aid therapeutics to numerous diseases of the intestine.

Muscarinic m2 receptor-mediated actin polymerization via PI3 kinase γ and integrin-linked kinase in gastric smooth muscle

BACKGROUND

Actin polymerization plays an important role in smooth muscle contraction. Integrin-linked kinase (ILK) was shown to mediate actin polymerization in airway smooth muscle. The role of ILK in actin polymerization in response to m2 receptor activation was not in gastric smooth muscle.

METHODS

Phosphorylation of paxillin, neuronal Wiskott-Aldrich syndrome protein (N-WASp), and association of paxillin with GEF proteins (Cool2/αPix [Cool2/PAK-interacting exchange factor alpha], Cool1/βPix [Cool1/PAK-interacting exchange factor beta], and DOCK 180 [Dedicator of cytokinesis]) and N-WASp with Arp2/3 complex were measured by western blot. Activation of Cdc42 was determined using an antibody for activated Cdc42. Actin polymerization was measured as an increase in F-actin/G-actin ratio.

RESULTS

Phosphorylation of paxillin, an association of paxillin with GEF proteins, Cdc42 activity, and actin polymerization were increased in response to m2 receptor activation in gastric smooth muscle cells. The increases in paxillin phosphorylation, Cdc42 activity, and actin polymerization were inhibited by a PI3Kγ inhibitor (AS-605240), ILK siRNA, and ILK dominant negative mutant (ILK [R211]). Increase in actin polymerization was also inhibited by Cdc42 dominant negative mutant (Cdc42 [T17N]). Increases in the association of paxillin with GEF proteins, phosphorylation of N-WASp and its association with Arp2/3 complex were inhibited by ILK (R211).

CONCLUSION

In gastric smooth muscle cells, activation of PI3Kγ by muscarinic m2 receptors causes ILK-dependent phosphorylation of paxillin, an association of paxillin with Cdc42 GEF proteins and activation of Cdc42, which, in turn, causes phosphorylation of N-WASp and its association with Arp2/3 complex leading to actin polymerization.

Effects of exendin-4 on colonic motility in rats and its underlying mechanism

BACKGROUND

Glucagon-like peptide-1 (GLP-1) receptor (GLP-1R) agonists modulate gastrointestinal motility; however, the effects of GLP-1R agonists on colonic motility are still controversial, and the molecular mechanism is unclear. Exendin-4 shares 53% homology with GLP-1 and is a full agonist of GLP-1R. In this study, our aims were to explore the role and mechanism of exendin-4 in isolated rat colonic tissues and cells.

METHODS

An organ bath system was used to examine the spontaneous contractions of smooth muscle strips. The whole-cell patch-clamp technique was used to investigate the currents of L-type voltage-dependent calcium channels and large conductance Ca²⁺ -activated K⁺ (BK_Ca ) channels in smooth muscle cells.

KEY RESULTS

Exendin-4 decreased both the amplitude and frequency of spontaneous contractions of smooth muscle strips in a concentration-dependent manner. The inhibitory effect was completely blocked by exendin-4(9-39), a GLP-1R antagonist. Moreover, this effect was partially abolished by tetrodotoxin (TTX), a blocker of neuronal voltage-dependent Na⁺ channels, Nω-Nitro-l-arginine (L-NNA), a nitric oxide synthase (NOS) inhibitor, apamin, an inhibitor of small-conductance Ca²⁺ -activated K⁺ (SK) channels. Whole-cell patch-clamp recordings revealed that exendin-4 inhibited the peak current of L-type calcium channels in colonic smooth muscle cells, but did not change the shape of the current-voltage (I-V) curves. The steady-state activation and steady-state inactivation of L-type calcium channels were not affected. Likewise, BK_Ca currents were significantly inhibited by exendin-4.

CONCLUSIONS

Exendin-4 indirectly inhibits colonic muscle activity via a nitrergic and a purinergic neural pathway through NO and ATP release and inhibits L-type voltage-dependent calcium channels and BK_Ca channels in smooth muscle cells.

Effect of piperine on arecoline induced contraction of isolated small intestinal smooth muscle from rabbits

AIM

To investigate the effect of piperine on arecoline induced contraction of isolated small intestinal smooth muscle from rabbits and explore the possible mechanism involved.

METHODS

The method of ex vitro smooth muscle perfusion at a constant temperature was used to collect the rabbit small intestine in vitro. The effect of piperine solution at concentrations of 0.06 g/L, 0.6 g/L, and 6 g/L on the spontaneous contraction of isolated rabbit small intestinal smooth muscle was observed using the BL-420 bio-functional experiment system. Then, the effect of piperine and arecoline, alone or in combination, on spontaneous contraction of isolated small intestinal smooth muscle from rabbits was observed. To explore the mechanism by which piperine affected the contraction of isolated rabbit small intestinal smooth muscle, an inositol 1,4,5-trisphosphate (IP3) receptor antagonist (heparin, HP), a ryanodine receptor antagonist (ruthenium red, RR), and a nitric oxide synthase (NOS) inhibitor (nitro-L-arginine methyl ester, L-NAME) were used.

RESULTS

Piperine inhibited the spontaneous contraction of isolated small intestinal smooth muscle from rabbits. At a concentration of 6 g/L, piperine showed a significant inhibitory effect on the amplitude of spontaneous contractions (P < 0.01). On this basis, arecoline solution at 0.006 g/L significantly increased the amplitude of contraction of isolated rabbit small intestinal smooth muscle (P < 0.05), but the amplitude of small intestinal smooth muscle contraction was smaller than that treated with arecoline alone (P < 0.05). IP3 receptor antagonist heparin could strengthen the relaxation effect of piperine on intestinal smooth muscle (P < 0.05), but ryanodine receptor antagonist ruthenium red had no effect on the relaxation effect of piperine (P > 0.05). L-NAME inhibited the relaxation effect of piperine (P < 0.05).

CONCLUSION

Piperine can inhibit the amplitude of spontaneous and arecoline induced contraction of rabbit intestinal smooth muscle. The mechanism may be related to the increase of NO concentration in intestinal smooth muscle and the inhibition of intracellular Ca²⁺release via IP3 of sarcoplasmic reticulum.

Regulation of gastric smooth muscle contraction via Ca2+-dependent and Ca2+-independent actin polymerization

In gastrointestinal smooth muscle, acetylcholine induced muscle contraction is biphasic, initial peak followed by sustained contraction. Contraction is regulated by phosphorylation of 20 kDa myosin light chain (MLC) at Ser¹⁹, interaction of actin and myosin, and actin polymerization. The present study characterized the signaling mechanisms involved in actin polymerization during initial and sustained muscle contraction in response to muscarinic M3 receptor activation in gastric smooth muscle cells by targeting the effectors of initial (phospholipase C (PLC)-β/Ca²⁺ pathway) and sustained (RhoA/focal adhesion kinase (FAK)/Rho kinase pathway) contraction. The initial Ca²⁺ dependent contraction and actin polymerization is mediated by sequential activation of PLC-β1 via Gα_q, IP₃ formation, Ca²⁺ release and Ca²⁺ dependent phosphorylation of proline-rich-tyrosine kinase 2 (Pyk2) at Tyr⁴⁰². The sustained Ca²⁺ independent contraction and actin polymerization is mediated by activation of RhoA, and phosphorylation of FAK at Tyr³⁹⁷. Both phosphorylation of Pyk2 and FAK leads to phosphorylation of paxillin at Tyr¹¹⁸ and association of phosphorylated paxillin with the GEF proteins p21-activated kinase (PAK) interacting exchange factor α, β (α and β PIX) and DOCK 180. These GEF proteins stimulate Cdc42 leading to the activation of nucleation promoting factor N-WASP (neuronal Wiskott-Aldrich syndrome protein), which interacts with actin related protein complex 2/3 (Arp2/3) to induce actin polymerization and muscle contraction. Acetylcholine induced muscle contraction is inhibited by actin polymerization inhibitors. Thus, our results suggest that a novel mechanism for the regulation of smooth muscle contraction is mediated by actin polymerization in gastrointestinal smooth muscle which is independent of MLC₂₀ phosphorylation.

The Effect of Myosin Light Chain Kinase on the Occurrence and Development of Intracranial Aneurysm

Myosin light chain kinase is a key enzyme in smooth muscle cell contraction. However, whether myosin light chain kinase plays a role in the occurrence or development of intracranial aneurysms is not clear. The present study explored the function of myosin light chain kinase in human intracranial aneurysm tissues. Five aneurysm samples and five control samples were collected, and smooth muscle cells (SMCs) were dissociated and cultured. A label-free proteomic analysis was performed to screen the differentially expressed proteins between aneurysm and control samples. The expression and function of myosin light chain kinase in aneurysms were examined. We found that 180 proteins were differentially expressed between the aneurysm and control samples, among which 88 were increased and 92 (including myosin light chain kinase) were decreased in aneurysms compared to control tissues. In a model of the inflammatory environment, contractility was weakened and apoptosis was increased in aneurysm SMCs compared to human brain SMCs (p < 0.05). The knock down of myosin light chain kinase in human brain SMCs caused effects similar to those observed in aneurysm SMCs. These results indicated that myosin light chain kinase plays an important role in maintaining smooth muscle contractility, cell survival and inflammation tolerance.