[show abstract][hide abstract] ABSTRACT: Muscle-specific tyrosine kinase (MuSK) is essential for clustering of acetylcholine receptors (AChRs) at embryogenesis and likely also important for maintaining synaptic structure in adult muscle. In 5 to 7% of myasthenia gravis (MG) cases, the patients' blood contains antibodies to MuSK. To investigate the effect of MuSK-MG antibody on synapse regeneration, notexin was used to induce damage to the flexor digitorum brevis muscle. We administered aliquots of MuSK-MG patients' plasma to the flexor digitorum brevis twice daily for a period up to 21 days, and muscles were investigated ex vivo in contraction experiments. AChR levels were measured with (125)I-alpha-bungarotoxin, and endplates were studied with quantitative immunohistochemistry. In normal muscles and in 14-day regenerated muscles, MuSK plasma caused impairment of nerve stimulus-induced contraction in the presence of 0.35 and 0.5 mmol/L Ca(2+) with or without 100 to 400 nmol/L tubocurarine. Endplate size was decreased in regenerated muscles relative to controls; however, we did not observe such differences in muscle not treated with notexin. MuSK plasma had no effect on the amount and turnover rate of AChRs. Our results suggest that anti-MuSK antibodies influence the activity of MuSK molecules without reducing their number, thereby diminishing the size of the endplate and affecting the functioning of AChRs.
American Journal Of Pathology 10/2009; 175(4):1536-44. · 4.52 Impact Factor
[show abstract][hide abstract] ABSTRACT: Besides regulation of upper gastrointestinal motility, motilin seems to play a role in the inflammatory response. Motilin receptor expression in human intestine has not been studied thoroughly. This study aimed to describe the intestinal distribution of motilin receptors in inflammatory bowel disease (IBD) and control patients.
Quantitative autoradiography, immunohistochemistry, and reverse-transcriptase polymerase chain reaction (RT-PCR) were used to detect motilin receptors in tissue of 25 IBD patients (13 Crohn's disease [CD], 12 ulcerative colitis [UC]) and 19 patients with a neoplasm (controls).
Median muscular motilin binding was 3 and 8 fmol/g tissue in colon and ileum, respectively. In the gastroduodenal region the median was higher (93 fmol/g). In UC colonic muscular motilin binding was significantly increased compared to controls (7 vs. 3 fmol/g, P < or = 0.05). Expression in CD was similar to controls. Besides the binding found in the muscular compartment, motilin binding was also found in the mucosa, which was even higher than in the muscle (3 versus 11 and 8 versus 27 fmol/g for colon and ileum (P < or = 0.06), respectively). RT-PCR and immunohistochemistry confirmed the mucosal motilin receptor expression. The mucosal motilin receptors were located in the epithelial cells. In the muscular compartment receptors were strongly present in the myenteric plexus and weakly in the smooth muscle cells. In IBD tissue the expression pattern was not different.
The motilin receptor is expressed in human colonic and ileal smooth muscle. Further, motilin receptor expression was also shown in the mucosa. Muscular binding in UC patients is increased but no different expression pattern was found.
[show abstract][hide abstract] ABSTRACT: Inflammatory bowel disease (IBD) is characterized by chronic intestinal inflammation accompanied by changes in motility. It is known that regulatory peptides like substance P (SP) are important pro-inflammatory peptides which are also involved in neuronal conduction. To get clues for new diagnostic and therapeutic approaches we describe the SP receptor (NK-1) distribution in IBD compared to control intestinal tissue, on mRNA and protein level by three complementary techniques. Autoradiography showed differences within the intestinal wall of control patients; mucosal binding was 17 fmol/g and muscular binding was significantly (p=0.01) higher (98 fmol/g). In inflamed specimens of patients with IBD mucosal SP binding was increased compared to controls (55+/-10 vs 18+/-4 fmol/g mucosa, p=0.002). However RT-PCR showed that the mRNA content of the NK-1 receptor in these samples was not increased. In non-inflamed samples of patients with Crohn's disease (CD) and ulcerative colitis (UC) SP binding was similar as in controls, while mRNA was significantly decreased in CD patients (0.7+/-0.02 vs 4.4+/-0.7, p=0.01) but not in UC patients (4.4+/-0.7 vs 4.1+/-1.4). Immunohistochemistry identified a broad spectrum of NK-1 receptor locations in control intestine. No aberrant expression in IBD was found. This study showed that although there was no difference in location of the SP receptors in IBD patients versus controls, the quantity of SP binding was significantly increased in the inflamed mucosa of IBD patients, while the mRNA level was not increased. Further a difference in mRNA level between non-inflamed tissue of CD and UC patients was shown, with mRNA in CD being lower. These changes in SP receptor expression during chronic inflammation suggest that SP receptors are a potential target for therapeutic regulation of the inflammatory response.
[show abstract][hide abstract] ABSTRACT: Gastrin releasing peptide (GRP) and neuromedin B are bombesin (BN)-like peptides involved in regulating motility and inflammation in the gastrointestinal tract, which may be useful in treating inflammatory bowel disease (IBD). Three bombesin-like peptide receptors have been reported, but no studies have investigated their localisation in normal and inflamed human intestine.
To localise and characterise BN receptors in normal intestine and to see whether this is modified in IBD.
Full thickness intestinal tissue samples were collected from 13 patients with Crohn's disease (CD), 11 with ulcerative colitis (UC), and 19 controls. BN receptor expression was characterised and quantified with storage phosphor autoradiography using BN, GRP, neuromedin B, and the synthetic analogue BN(6-14) as ligands.
Only BN receptor type 2 (high affinity for GRP) was present in intestinal tissue. Minimal BN binding was detected in the mucosa. In normal colonic smooth muscle, mean BN binding was 336 fmol/g tissue in longitudinal muscle, including the myenteric plexus, and 71 fmol/g in circular muscle. In CD, colonic smooth muscle BN binding was significantly decreased (longitudinal muscle, 106; circular muscle, 19 fmol/g), in contrast to UC (377 and 62 fmol/g, respectively). In CD, a small (not significant) decrease was seen in ileal muscle compared with controls (111 v 169 and 18 v 32 fmol/g tissue for longitudinal and circular muscle, respectively).
Only the GRP receptor is expressed in human intestine; expression is highest in longitudinal muscle and myenteric plexus of the colon. Expression is decreased in inflamed and non-inflamed colon of CD, but not in UC.
Journal of Clinical Pathology 11/2004; 57(10):1047-51. · 2.44 Impact Factor