Vasoactive intestinal peptide receptor subtypes and signalling pathways involved in relaxation of human stomach.

Vasoactive intestinal peptide (VIP) relaxes smooth muscle by interacting with receptors coupled to cAMP- or cGMP-signalling pathways. Their relative contribution to human gastric relaxation is unknown. This study aimed at investigating, in terms of biological activity, receptor expression and related signalling pathways, the action of VIP separately on the human fundus and the antrum. VIP caused greater relaxation of smooth muscle cells (SMC) and strips of the antrum presenting on the former a higher efficacy and potency (ED(50): 0.53 +/- 0.17 nmol L(-1)) than on the fundus (ED(50): 3.4 +/- 1.4 nmol L(-1)). On both fundus and antrum strips, its effect was tetrodotoxin insentitive. Reverse transcriptase-polymerase chain reaction analysis showed the sole expression of VPAC2 and natriuretic peptide clearance receptors, with VPAC2 being more abundant in the antrum. Functional regional differences in receptor-related signalling pathways were found. Activation of the cAMP-pathway by forskolin or its inhibition by adenylate cyclase (2'5'-dideoxyadenosine) or kinase (Rp-cAMPs) inhibitors had more pronounced effects on antrum SMC. Activation of the cGMP-pathway by sodium nitroprusside or its inhibition by guanylate cyclase (LY83583) or kinase (KT5823) inhibitors had more effects on fundus SMC, on which a higher expression of endothelial nitric oxide synthase was found. In conclusion, regional differences in VIP action on human stomach are related to distinct myogenic properties of SMC of the antrum and the fundus.

Somatostatin receptor subtypes mediate contractility on human colonic smooth muscle cells.

This study demonstrates the expression of functional somatostatin receptor (sstr) subtypes in human circular and longitudinal colonic smooth muscle cells (SMC). Native somatostatin (SS) and sstr subtype-specific analogues were used to characterize the sstr subtypes present in both cell types by contraction/relaxation studies. Qualitative and quantitative mRNA analysis and immunohistochemistry of sstr subtypes were also carried out. sstr subtype 2 mRNA was expressed in circular SMC, and various levels of subtypes 1, 2 and 3 mRNA were expressed in longitudinal colonic SMC. Native SS and each subtype-specific analogue exerted a modest, but significant, contraction, although inhibition of carbachol-induced contraction (relaxation) was the main effect on SMC from both layers. CH-288, a sstr subtype 1-specific analogue, and octreotide, a sstr subtype 2-specific analogue, were the most effective relaxant analogues on longitudinal and circular SMC, respectively. sstr subtypes display a distinct expression pattern on human colonic SMC; on circular SMC, subtype 2 is the only sstr, whereas sstr subtypes 1, 2 and 3 are expressed on human SMC isolated from the longitudinal layer. The contractile effects of SS are mediated through sstr subtype 2 and sstr subtype 1 on circular and longitudinal human colonic SMC, respectively.

Optimisation of isolation of richly pure and homogeneous primary human colonic smooth muscle cells.

BACKGROUND: Inherent properties of gastrointestinal smooth muscle can be assessed using isolated cell suspensions. Currently available isolation techniques, based on short 2-h enzymatic digestion, however, present the disadvantage of low cellular yield with brief viability. These features are an important limiting factor especially in studies in humans in which tissue may not be available daily and mixing of samples is not recommended. AIMS: To optimise the isolation procedure of cells from human colon to obtain a richly pure primary smooth muscle cell preparation. METHODS: Slices of circular muscle layer, obtained from surgical specimens of human colon, were incubated overnight in Dulbecco's modified eagle's medium supplemented with antibiotics, foetal bovine serum, an ATP-regenerating system and collagenase. On the following day, digested muscle strips were suspended in HEPES buffer, and spontaneously dissociated smooth muscle cells were harvested and used either immediately or maintained in suspension for up to 72 h. Cell yield, purity, viability, contractile responses, associated intracellular calcium signals and RNA and protein extraction were evaluated and compared to cell suspensions obtained with the current short digestion protocol. RESULTS AND CONCLUSION: The overnight isolation protocol offers the advantage of obtaining a pure, homogeneous, long-life viable cell suspension that maintains a fully differentiated smooth muscle phenotype unchanged for at least 72 h and that allows multiple functional/biochemical studies and efficient RNA extraction from a single human specimen.

Nod-like proteins in inflammation and disease.

The field of innate immunity has undergone an enormous upheaval during the last decade. The discovery of different groups of proteins, called pattern recognition molecules (PRMs), which detect microbial components, so-called pathogen-associated molecular patterns (PAMPs) and trigger protective responses, had a huge impact on the understanding of innate immune responses. Among the PRMs, the intracellular Nod-like receptors (NLRs) have recently been identified as key mediators of inflammatory and immune responses. The NLR family is divided into subfamilies on the basis of their different signal transduction domains, and recent studies have highlighted the role of certain NLRs, including Nod1, Nod2, Nalp3, Ipaf and Naip5, in the detection of intracellular microbes and possibly 'danger signals'. In this review, we summarize the current knowledge on the function of these proteins in immunity and inflammation, with a focus on their participation in different disease pathologies.