Ca(2+) signaling in porcine duodenal glands by muscarinic receptor activation

Reduced acetylcholine and elevated muscarinic receptor 2 in duodenal mucosa contribute to the impairment of mucus secretion in 6-hydroxydopamine-induced Parkinson's disease rats

Patients with Parkinson's disease (PD) have a higher incidence rate of duodenal ulcers. The mucus barrier provides the first line of defense for duodenal mucosal protection. However, it is unknown whether duodenal mucus secretion is affected in PD. In the present study, we used the rats microinjected 6-hydroxydopamine (6-OHDA) into the bilateral substantia nigra to investigate duodenal mucus secretion and potential therapeutic targets in duodenal ulcer in PD. Alcian blue-periodic acid-Schiff, transmission electron microscopy, immunofluorescence, duodenal mucosal incubation, and enzyme-linked immunosorbent assays were used. The 6-OHDA rats exhibited mucin accumulation and retention in duodenal goblet cells. Mucin granules were unable to fuse with the apical membranes of goblet cells, and the exocytosis ratio of goblet cells was significantly reduced. Moreover, decreased acetylcholine and increased muscarinic receptor 2 (M₂R) levels were detected in the duodenal mucosa of 6-OHDA rats. Bilateral vagotomy rats were also characterized by defective duodenal mucus secretion and decreased acetylcholine with increased M₂R levels in the duodenal mucosa. Application of the cholinomimetic drug carbachol or blocking M₂R with methoctramine significantly promoted mucus secretion by goblet cells and increased MUC2 content in duodenal mucosa-incubated solutions from 6-OHDA and vagotomy rats. We conclude that the reduced acetylcholine and increased M₂R contribute to the impaired duodenal mucus secretion of 6-OHDA rats. The study provides new insights into the mechanism of duodenal mucus secretion and potential therapeutic targets for the treatment of duodenal ulcers in PD patients.

Potassium currents regulating secretion from Brunner's glands in guinea pig duodenum

This study examined the role of outward K(+) currents in the acinar cells underlying secretion from Brunner's glands in guinea pig duodenum. Intracellular recordings were made from single acinar cells in intact acini in in vitro submucosal preparations, and videomicroscopy was employed in the same preparation to correlate these measures with secretion. Mean resting membrane potential was -74 mV and was depolarized by high external K(+) (20 mM) and the K(+) channel blockers 4-aminopyridine (4-AP), quinine, and clotrimazole. The cholinergic agonist carbachol (60-2,000 nM; EC(50) = 200 nM) caused a concentration-dependent initial hyperpolarization of the membrane and an associated decrease in input resistance. This hyperpolarization was significantly decreased by 20 mM external K(+) or membrane hyperpolarization and increased by 1 mM external K(+) or membrane depolarization. It was blocked by the K(+) channel blockers tetraethylammonium (TEA), 4-AP, quinine, and clotrimazole but not iberiotoxin. When videomicroscopy was employed to measure dilation of acinar lumen in the same preparation, carbachol-evoked dilations were altered in a parallel fashion when external K(+) was altered. The dilations were also blocked by the K(+) channel blockers TEA, 4-AP, quinine, and clotrimazole but not iberiotoxin. These findings suggest that activation of outward K(+) currents is fundamental to the initiation of secretion from these glands, consistent with the model of K(+) efflux from the basolateral membrane providing the driving force for secretion. The pharmacological profile suggests that these K(+) channels belong to the intermediate conductance group.

Decreased apoptosis of β2‐ integrin‐deficient bovine neutrophils

Stimulant-induced viability of neutrophils, nuclear-fragmentation, increase in intracellular calcium ([Ca2+]i), expression of annexin V on neutrophils and proteolysis of a fluorogenic peptide substrate Ac-DEVD-MCA (acetyl Asp-Glu-Val-Asp alpha-[4-methyl-coumaryl-7-amide]) by neutrophil lysates from five normal calves and three calves with leucocyte adhesion deficiency were determined to evaluate the apoptosis of normal and CD18-deficient neutrophils. Viability was markedly decreased in control neutrophils stimulated with opsonized zymosan (OPZ), compared to CD18-deficient neutrophils at 37 degrees C after incubation periods of 6 and 24 hours. The rate of apoptosis of control neutrophils stimulated with OPZ increased significantly depending on the incubation time, whereas no apparent increase in apoptosis was found in CD18-deficient neutrophils under the same conditions. Aggregated bovine (Agg) IgG-induced apoptosis of control neutrophils was not significantly different from that of CD18-deficient neutrophils. The expression of annexin V on OPZ-stimulated control neutrophils was greater than that of unstimulated ones 6 h after stimulation. No apparent increase in annexin V expression on CD18-deficient neutrophils was found with OPZ stimulation. A delay in apoptosis was demonstrated in CD18-deficient bovine neutrophils and this appeared to be closely associated with lowered signalling via [Ca2+]i, diminished annexin V expression on the cell surface, and decreased caspase 3 activity in lysates.

Establishment of an efficient method to quantify embryo attachment to endometrial epithelial cell monolayers

During implantation, complex embryo-endometrium interactions result in blastocyst adhesion. To study the mechanisms of implantation, an effective assay for monitoring adhesiveness between embryos and endometrial epithelium is essential. In this study, we describe a simple and reliable method to quantify embryo-endometrium adhesion in vitro. Murine blastocysts or BeWo trophoblast spheroids were cocultured with monolayers of RL95-2 endometrial epithelial cells (EEC) grown in 96-well plates. At the end of coculture, the wells were filled with medium, and the plate was sealed with an adhesive film, inverted, and centrifuged at 25 x g for 5 min. After centrifugation, the plate was kept inverted and directly examined microscopically to determine whether the blastocysts or spheroids were attached to EEC monolayers. Our assay demonstrated that blastocysts recovered at 1200-1400 h on d 4 were more adherent to EEC than those recovered earlier, consistent with the timing of intrauterine embryo activation. Serum also enhanced blastocyst-EEC adhesion. Spheroid-EEC adhesion was inhibited by blocking Ca(2+) influx with extracellular Ca(2+) chelators (ethylenediaminetetraacetic acid or ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid) or a Ca(2+) channel blocker (verapamil) but not by interfering with Ca(2+) release from intracellular stores using chelating (1,2-bis(2-aminophenoxy)-ethane-N,N,N',N'-tetraacetic acid tetrakis(acetoxymethyl ester) or depleting (thapsigargin) agents. Using 96-well plates for coculture, centrifugation, and examination to minimize transfer procedures, our assay system is readily applicable to investigate implantation mechanisms.