Effect of chronic, extrinsic denervation on functional NANC innervation with vasoactive intestinal polypeptide and substance P in longitudinal muscle of rat jejunum

Isobaric tags for relative and absolute quantification-based proteomic analysis that reveals the roles of progesterone receptor, inflammation, and fibrosis for slow-transit constipation

BACKGROUND AND AIM

Progesterone receptor, inflammation, neurotransmitter expression, and fibrosis are involved in slow-transit constipation. The aim of the present study was to examine whether patients with slow-transit constipation have an overexpression of progesterone receptor and serotonin, which may impair the fibrosis of muscularis propria in colorectal wall.

METHODS

High-resolution colon manometry was used to record the colorectal peristaltic contractions of the proximal ascending and sigmoid colon in patients. Protein samples prepared from frozen sigmoid colon tissue and the proximal margin of the ascending colon of four female patients were compared using isobaric tags for relative and absolute quantification labeling technique coupled to 2D liquid chromatography-tandem mass spectrometry analysis. Immunohistochemical staining of progesterone receptor, serotonin, and fibronectin was performed in paraffin-embedded sigmoid colon tissues and the proximal margin of the ascending colon or ileum from 43 patients with slow-transit constipation.

RESULTS

Among these differentially regulated proteins based on isobaric tags for relative and absolute quantification and liquid chromatography-tandem mass spectrometry analysis, 56 proteins involved in the response to progesterone, inflammation, matrix remodeling, fibrosis, and muscle metabolism. Immunohistochemical staining confirmed that there was significantly higher expression of progesterone receptor (t = 19.19, P = 0.000) and serotonin (t = 13.52, P = 0.004) in sigmoid colon than in the proximal margin of the ascending colon and ileum. Progesterone receptor and fibronectin expression in the outer layer of muscularis propria were higher than in the middle layer.

CONCLUSIONS

These results demonstrate that progesterone receptor, along with inflammation and fibrosis, may take part in slow-transit constipation development.

Changes in peptidergic neurotransmission during postoperative ileus in rat circular jejunal muscle

BACKGROUND

Our aim was to explore unknown changes in neurotransmission with vasoactive intestinal peptide (VIP) and Substance P (Sub P) during postoperative ileus (POI).

METHODS

Contractile activity of rat circular jejunal muscle strips was studied in five groups (n = 6/group): Naïve controls, sham controls 12 h and 3 days after laparotomy, and rats 12 h, 3 days after induction of POI. Dose-responses to VIP (10(-10) -10(-7) M), Sub P (3 × 10(-10) -3 × 10(-7) M), and electrical field stimulation (EFS, to study endogenous release of neurotransmitters) were studied with different antagonists. Intestinal transit, inflammatory cells and immunoreactivity for VIP and Sub P were investigated in the bowel wall and cellular Finkel osteo sarcoma expression was determined in vagal afferent and efferent nuclei of the brainstem.

KEY RESULTS

Postoperative ileus characterized by delayed intestinal transit and intramural inflammation was associated with an increased inhibitory effect of VIP on contractile activity. A biphasic impact was observed for Sub P with a decrease in its excitatory potential on contractility at 12 h, followed by a later increase 3 days postoperatively. Inhibitory response to EFS was increased, whereas the excitatory response decreased in ileus animals. VIP expression was increased in all postoperative animals while only animals 3 days after ileus induction showed increased Sub P expression in the myenteric plexus. These changes were associated with an activation of afferent but not efferent vagal nuclei in the brain stem.

CONCLUSIONS & INFERENCES

Specific, time-dependent changes in peptidergic neurotransmission with VIP and Sub P occur during POI that are associated with vagal afferent activation, but are independent of the activation of efferent vagal pathways.

Role of hydrogen sulfide as a gasotransmitter in modulating contractile activity of circular muscle of rat jejunum

AIM

Our aim was to determine mechanisms of action of the gasotransmitter hydrogen sulfide (H(2)S) on contractile activity in circular muscle of rat jejunum.

METHODS

Jejunal circular muscle strips were prepared to measure isometric contractions. Effects of sodium hydrosulfide (NaHS), a H(2)S donor, were evaluated on spontaneous contractile activity and after pre-contraction with bethanechol. L-cysteine was evaluated as an endogenous H(2)S donor. We evaluated extrinsic nerves, enteric nervous system, visceral afferent nerves, nitric oxide, K(ATP)+ and K(Ca)+ channels, and myosin light chain phosphatase on action of H(2)S using non-adrenergic/non-cholinergic conditions, tetrodotoxin, capsaicin, L-N(G)-nitro arginine (L-NNA), glibenclamide, apamin, and calyculin A, respectively, and electrical field stimulation (EFS).

RESULTS

NaHS dose-dependently and reversibly inhibited spontaneous and bethanechol-stimulated contractile activity (p < 0.05). L-cysteine had a dose-dependent inhibitory effect. Non-adrenergic/non-cholinergic conditions, tetrodotoxin, capsaicin, L-NNA, or apamin had no effect on contractile inhibition by NaHS; in contrast, low-dose glibenclamide and calyculin A prevented NaHS-induced inhibition. We could not demonstrate H(2)S release by EFS.

CONCLUSIONS

H(2)S inhibits contractile activity of jejunal circular muscle dose-dependently, in part by K(ATP)+ channels and via myosin light chain phosphatase, but not via pathways mediated by the extrinsic or enteric nervous system, visceral afferent nerves, nitric oxide, or K(Ca)+ channels.

Mechanisms of action of the gasotransmitter hydrogen sulfide in modulating contractile activity of longitudinal muscle of rat ileum

AIM

This study aims to determine mechanisms of action of the gasotransmitter hydrogen sulfide (H(2)S) on contractile activity in longitudinal muscle of rat ileum.

METHODS

Ileal longitudinal muscle strips were prepared to measure isometric contractions. Effects of sodium hydrosulfide (NaHS), a donor of H(2)S, were evaluated on spontaneous contractile activity and after enhanced contractile activity with bethanechol. L-cysteine was evaluated as a potential endogenous donor of H(2)S. We evaluated involvement of extrinsic nerves, enteric nervous system, visceral afferent nerves, nitric oxide, and K(ATP)(+) channel and K(Ca)(+) channel activity on the action of H(2)S using non-adrenergic/non-cholinergic conditions, tetrodotoxin, capsaicin, L-N(G)-nitro arginine (L-NNA), glibenclamide, and apamin, respectively, as well as electrical field stimulation.

RESULT

NaHS dose-dependently and reversibly inhibited spontaneous and bethanechol-stimulated contractile activity (p < 0.05). L-cysteine had no inhibitory effect. Non-adrenergic/non-cholinergic conditions, tetrodotoxin, capsaicin, L-NNA, glibenclamide, or apamin had no major effect on total contractile activity by NaHS, although both tetrodotoxin and apamin decreased the frequency of bethanechol-enhanced contractile activity (p < 0.05). We could not demonstrate H(2)S release by electrical field stimulation but did show that inhibition of cystathionine β synthase, an endogenous source of H(2)S, augmented the inhibitory effect of low-frequency electrical field stimulation.

CONCLUSION

H(2)S inhibits contractile activity of ileal longitudinal muscle dose-dependently but not through pathways mediated by the extrinsic or enteric nervous system, visceral afferent nerves, nitric oxide, K(ATP)(+) channels, or K(Ca)(+) channels.

Age-related changes in functional NANC innervation with VIP and substance P in the jejunum of Lewis rats

Age-related changes in non-adrenergic, non-cholinergic (NANC) neurotransmission might contribute to differences in gastrointestinal motility. Our aim was to determine age-related changes in functional innervation with vasoactive intestinal polypeptide (VIP) and substance P (Sub P) in rat jejunum. We hypothesized that maturation causes changes in neurotransmission with these two neuropeptides. Longitudinal and circular jejunal muscle strips from young (3 months) and middle-aged (15 months) rats (total: 24 rats) were studied; the response to exogenous VIP and Sub P and the effect of their endogenous release from the enteric nervous system during electrical field stimulation (EFS) were evaluated. In longitudinal muscle, response to exogenous VIP and endogenously released VIP during EFS were increased in middle-aged rats, while the effect of endogenously released Sub P was decreased. In the circular muscle, the response to endogenously released VIP was increased in middle-aged rats, while the effects of exogenous VIP and endogenously released Sub P were unchanged. Response to exogenous Sub P was unaffected by maturation in both muscle layers. Spontaneous contractile activity was increased in the longitudinal and circular muscle of the older rats. In the jejunum of middle-aged rats, participation of VIP in functional NANC innervation was increased, while functional innervation with Sub P was decreased. These changes in the balance of inhibitory and excitatory neurotransmission occur during the year of maturation in rats and demonstrate an age-dependant plasticity of neuromuscular bowel function.

VIP induces PKA-mediated rapid and sustained phosphorylation of HSP20

The small molecular weight heat shock protein HSP20 has been proposed to regulate smooth muscle relaxation in a manner dependent on its phosphorylated state. We present the first evidence of HSP20 phosphorylation in response to a naturally occurring neurotransmitter. HSP20 was rapidly phosphorylated in colonic circular smooth muscle cells exposed to the physiologically relevant relaxant neuropeptide, Vasoactive Intestinal Peptide (VIP). HSP20 phosphorylation was significantly and substantially increased by 30s following VIP treatment and remained elevated for 30 min. VIP-induced HSP20 phosphorylation was dose dependent. Both basal and VIP-induced HSP20 phosphorylations were solely mediated by Protein Kinase A. Maximal phosphorylation of HSP20 was induced by the same VIP concentration range which induces maximal relaxation. Increased phosphorylation of HSP20 occurred in both cytosolic and particulate cell fractions. Our findings represent evidence for neurogenic modulation of the cyclic molecular regulation of relaxation required for peristalsis via a VIP-PKA-HSP20 pathway.

Effects of extrinsic denervation on innervation with VIP and substance P in circular muscle of rat jejunum

Extrinsic denervation contributes to enteric motor dysfunction after small bowel transplantation (SBT). Our aim was to determine changes in nonadrenergic, noncholinergic innervation with vasoactive intestinal polypeptide (VIP) and substance P (Sub P) in rat jejunal circular muscle after SBT. Muscle strips were studied in tissue chambers from six groups of rats (n > or = 6 per group): naïve controls (NC), animals 1 week after anaesthesia/sham celiotomy (SC-1), and 1 and 8 weeks after jejunal and ileal transection/reanastomosis (TA-1, TA-8) and after syngeneic, orthotopic SBT (SBT-1, SBT-8). Response to exogenous VIP and Sub P and their endogenous release during electrical field stimulation (EFS) were studied. Exogenous VIP and Sub P caused a dose-dependent inhibition and stimulation of mechanical activity in all groups respectively (P < 0.05). The responses to VIP and Sub P were decreased (compared to NC) in all groups at 1 and 8 weeks postoperatively. The VIP antagonist ([D-p-Cl-Phe(6),Leu(17)]-VIP) did not prevent the inhibition by exogenous VIP in any group, while the Sub P antagonist ([D-Pro(2),D-Trp(7,9)]-Sub P) prevented the effect of exogenous Sub P in NC, TA-8 and SBT-8 (P < 0.05). Responses to exogenous VIP were unaffected by the nitric oxide synthase inhibitor l-N(G)-nitro arginine and precontraction of muscle strips with Sub P. Endogenous release of VIP and Sub P during EFS was preserved after SBT. In circular muscle of rat jejunum, changes in neuromuscular transmission with VIP and Sub P during the first 8 weeks after SBT are not mediated by extrinsic denervation.

Long-term effects of extrinsic denervation on VIP and substance P innervation in circular muscle of rat jejunum

Intestinal denervation contributes to enteric motor dysfunction after small bowel transplantation (SBT). Our aim was to determine long-term effects of extrinsic denervation on function of nonadrenergic, noncholinergic innervation with substance P and vasoactive intestinal polypeptide (VIP). Contractile activity of jejunal circular muscle strips from six age-matched, naive control rats (NC) and eight rats 1 year after syngeneic SBT was studied in tissue chambers. Spontaneous contractile activity did not differ between groups. Exogenous VIP inhibited contractile activity dose-dependently to a comparable degree in both groups. The VIP antagonist ([D-p-Cl-Phe(6),Leu(17)]-VIP) and the nitric oxide synthase inhibitor L-NG-nitro-arginine did not affect VIP-induced inhibition but increased contractile activity during electrical field stimulation (EFS) in both groups. Exogenous substance P increased contractile activity dose-dependently, greater in NC than SBT. The substance P antagonist ([D-Pro(2),D-Trp(7,9)]-substance P) inhibited effects of exogenous substance P and decreased the excitatory EFS response. Immunohistofluorescence showed tyrosine hydroxylase staining after SBT indicating sympathetic reinnervation. In jejunal circular muscle after chronic denervation, response to exogenous substance P, but not VIP, is decreased, whereas endogenous release of both neurotransmitters is preserved. Alterations in balance of excitatory and inhibitory pathways occur despite extrinsic reinnervation and might contribute to enteric motor dysfunction after SBT.