Jingxin Li

Oxytocin hyperpolarizes cultured duodenum myenteric intrinsic primary afferent neurons by opening BKCa channels through IP3 pathway

J. Neurochem. (2012) 121, 516–525.

H2S modulates duodenal motility in male rats via activating TRPV1 and KATP channels

H2S induces vasodilatation by opening KATP channels but it may also affect other ion channels. The aim of this study was to investigate the effect of H2S on intestinal motility in rats and its underlying mechanism.

Oxytocin-induced membrane hyperpolarization in pain-sensitive dorsal root ganglia neurons mediated by Ca2+/nNOS/NO/KATP pathway

Oxytocin (OT) plays an important role in pain modulation and antinociception in the central nervous system. However, little is known about its peripheral effects. This study was conducted to investigate the effect of OT on the electrical properties of neurons in the dorsal root ganglia (DRG) and the underlying mechanisms. DRG neurons from adult rats were acutely dissociated and cultured. Intracellular Ca(2+) was determined by fluorescent microscopy using an indicator dye. The electrical properties of DRG neurons were tested by patch-clamp recording. The oxytocin receptor (OTR) and neuronal nitric oxide synthase (nNOS) on DRG neurons were assessed with immunofluorescence assays. OTR co-localized with nNOS in most of Isolectin B4 (IB4)-binding cultured DRG neurons in rats. OT decreased the excitability, increased the outward current, and evoked the membrane hyperpolarization in cultured DRG neurons. Sodium nitroprusside (SNP), the donor of nitric oxide (NO), exerted similar effects as OT on the membrane potential of cultured DRG neurons. OT increased the production of NO in DRGs and cultured DRG neurons. Pre-treatment of the OTR antagonist atosiban or the selective nNOS inhibitor N-Propyl-l-arginine (NPLA) significantly attenuated the hyperpolarization effect evoked by OT. OT produced a concentration-dependent increase in intracellular Ca(2+) in DRG neurons that responds to capsaicin, which can be attenuated by atosiban, but not by NPLA. OT-evoked membrane hyperpolarization and increase of outward current were distinctly attenuated by glibenclamide, a blocker of ATP-sensitive K(+) (KATP) channel. OT might be an endogenous antinociceptive agent and the peripheral antinociceptive effects of OT are mediated by activation of the Ca(2+)/nNOS/NO/KATP pathway in DRG neurons.

H2S Relaxes Vas Deferens Smooth Muscle by Modulating the Large Conductance Ca2+‐Activated K+ (BKCa) Channels via a Redox Mechanism

INTRODUCTIONnHydrogen sulfide (H(2) S) is generated in mammalian cells mainly by one of the two pyridoxal-5-phosphate-dependent enzymes, cystathione-γ-lyase (CSE), and cystathione-β-synthase (CBS) using L-cysteine as the main substrate. In previous studies, we found that CBS and CSE were functionally expressed in vas deferens (VD) and H(2) S-mediated VD smooth muscle relaxation. However, the detail mechanisms that H(2) S-relaxed VD smooth muscle were unknown so far.nnnAIMnThe aim of this study is to explore the molecular target sites of H(2) S in VD smooth muscle.nnnMETHODSnIsolated rat VD smooth muscle strips were used for tension recording in vitro. Double immunofluorescence staining was used to identify the localization of large conductance Ca(2+) -activated K(+) (BK(Ca)) channels.nnnMAIN OUTCOME MEASURESnChanges in tonic contraction of isolated rat VD smooth muscle strip were measured after the treatment of drugs. The expression of BKca channels in rat VD smooth muscle cells was also assessed.nnnRESULTSnThe results showed that L-NG-nitroarginine methyl ester (a nitric oxide synthase inhibitor) did not affect the response of VD to sodium hydrosulphide (NaHS), suggesting that nitric oxide pathway was not involved. Further studies revealed that transient receptor potential (TRP) channels did not contribute to the NaHS-induced relaxant effect. Glibenclamide, an ATP-sensitive K channel blocker, did the same thing, whereas BK(Ca) channel blockers iberiotoxin or tetraethylammonium largely reversed the relaxant effect, suggesting that H(2) S may target BK(Ca) channels. We also confirmed that BK(Ca) channels were localized in VD smooth muscle cells. Then, studies revealed that NaHS-induced VD smooth muscle relaxation was abolished by N-ethylmaleimide, which was widely used as a sulfhydryl alkylation compound protecting thiols from oxidation, whereas DL-Dithiothreitol, a strong reducing agent, did not affect the response of VD to NaHS.nnnCONCLUSIONSnWe concluded that H(2) S relaxed the VD smooth muscle by targeting BK(Ca) channels via redox-mediated mechanism.

A local GABAergic system is functionally expressed in human fallopian tube.

Gamma-aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the mammalian central nervous system and exerts its actions via ionotropic (GABAA and GABAC) and metabotropic (GABAB) receptors. The GABAB receptor is a dimer composed of R1 and R2 components. In addition to their location on neurons, GABA and functional GABAB receptors also have been detected in some peripheral tissues. In the present study, we combined immunohistochemistry, immunoblot and tension recording to determine if the human fallopian tube express glutamic acid decarboxylase (GAD65/67), two isoforms for synthesis of GABA and functional GABAB receptors. Immunoblots showed that the human fallopian tube tissue contained GABABR1 protein which was localized in the epithelial cells and smooth muscle cells by immunohistochemistry. In addition, epithelial cells also expressed GAD65/67. Tension recording found that both GABA and baclofen, a GABAB receptor agonist increased the spontaneous activity of human fallopian tube. The expressions of GABABR and GAD65/67 were significantly upregulated in the ectopic pregnancy group than in the intrauterine pregnancy group. We conclude that the human fallopian tube is capable of synthesizing GABA and expresses functionally active GABAB receptors. An upregulation of GABA synthesis and corresponding GABAB receptors may involve in ectopic pregnancy.

Endogenous hydrogen sulfide as a mediator of vas deferens smooth muscle relaxation

Cystathionine-lyase and cystathionine-synthase, both H(2)S-synthesizing enzymes, were functionally expressed in the vas deferens of rat, mice, and human. Endogenous H(2)S mediated vas deferens smooth muscle relaxation.

Oxytocin down‐regulates mesenteric afferent sensitivity via the enteric OTR/nNOS/NO/KATP pathway in rat

Oxytocin plays an analgesic role in modulation of nociception and pain. Most work to date has focused on the central mechanisms of oxytocin analgesia, but little is known about whether peripheral mechanisms are also involved.

Nitric oxide in enteric nervous system mediated the inhibitory effect of vasopressin on the contraction of circular muscle strips from colon in male rats

Backgroundu2002 Arginine vasopressin (AVP) is widely used in the treatment of critical diseases with hypotension, but the reports about its effect on gastrointestinal motility are controversial. The purpose of this study was to characterize the role of AVP in the regulation of colonic motility and the underlying mechanism.

Nano-hydroxyapatite/polyamide 6 scaffold as potential tissue engineered bone substitutes

Abstract In this study, nano-hydroxyapatite/polyamide 6 composite scaffold was prepared by phase separation and particle leaching combined method (PS/PL), and the scaffold, cultured with and without mesenchymal stem cells (MSCs), was investigated in vitro and in vivo. The scanning electron microscope photographs show a three-dimensional interconnected macroporosity of the scaffold. The compressive strength of the scaffold is 3˙27±0˙60 MPa is 81˙72±0˙68%. The biological results show that the scaffolds act as a template for the adhesion, growth, differentiation and proliferation of cells and have no negative effects on the MSCs in vitro. In the animal experiments, n-HA/PA6 scaffolds and MSCs cocultured scaffolds were implanted into the critical sized calvarial defect of rats respectively, to study their biocompatibility and osteogenesis in vivo. Both pure scaffolds and MSCs hybridised scaffolds exhibited favourable biocompatibility and osteogenesis. In contrast with pure scaffolds, the hybrid scaffolds can accelerate the bone reconstruction. These results indicate that n-HA/PA6 composite porous materials are suitable materials for bone tissue engineering and have the feasibility to be widely used in orthopaedics for clinical application.

l‐Cysteine enhances nutrient absorption via a cystathionine‐β‐synthase‐derived H2S pathway in rodent jejunum

Hydrogen sulphide (H2S) is generated endogenously from l‐cysteine (l‐Cys) by the enzymes cystathionine‐β‐synthase (CBS) and cystathionine‐γ‐lyase (CSE). In addition, l‐Cys is commonly used as a precursor in the food and pharmaceutical industries. The aim of the present study is to determine whether l‐Cys regulates intestinal nutrient transport. To that end, the presence of CBS and CSE in the jejunum epithelium was assessed by immunohistochemistry, Western blotting and the methylene blue assay. In addition, in vivo l‐Cys (100 mg/kg, administered immediately after the glucose load) significantly increased blood glucose levels 30 min after the oral administration of glucose to mice. This effect of l‐Cys was completely blocked by amino‐oxyacetic acid (AOA; 50 mg/kg; administered at the same time as l‐Cys) an inhibitor of CBS. Measurements of the short‐circuit current (Isc) in the rat jejunum epithelium revealed that l‐Cys (1 mmol/L; 6 min before the administration of l‐alanine) enhances Na+‐coupled l‐alanine or glucose transport, and that this effect is inhibited by AOA (1 mmol/L;10 min before the administration of l‐Cys), but not d,l‐propargylglycine (PAG;1 mmol/L; 10 min before the administration of l‐Cys), a CSE inhibitor. Notably, l‐Cys‐evoked enhancement of nutrient transport was alleviated by glibenclamide (Gli;0.1 mmol/L; 10 min before the administration of l‐Cys), a K+ channel blocker. Together, the data indicate that l‐Cys enhances jejunal nutrient transport, suggesting a new approach to future treatment of nutrition‐related maladies, including a range of serious health consequences linked to undernutrition.