Contractile effects and intracellular Ca²⁺ signalling induced by motilin and erythromycin in the circular smooth muscle of human colon

Abstract

Motilin has excitatory effects on the colon of the rabbit and the dog, but little is known of its effect on the human colon. The aim of this study was to investigate the effects induced by motilin and erythromycin A (EMA) on muscle strips and on single cells from primary cultures from human colon. Isotonic contraction was recorded in circular muscle strips from macroscopically normal resection specimens of patients operated on for colonic neoplasm. Agonist-induced intracellular Ca2+ ([Ca2+]i) signalling was studied in primary cultures of colonic smooth-muscle cells using the ratiometric Ca2+ indicator Indo 1, on a laser-scanning confocal epifluorescence microscope. In circular muscle strips, norleucine13-porcine motilin ([Nle13]-pm)and EMA induced tonic contractions with an EC50 of 92 +/- 21 nmol L(-1) and 31 +/- 16 micromol L(-1), respectively. The maximal contraction was 21 +/- 4% (motilin) and 33 +/- 12% (EMA) of the response to 10(-4) mol L(-1) acetylcholine (ACh). The motilin antagonist OHM-11526 (10(-5.5) mol L(-1)) abolished the effects of both [Nle13]-pm and EMA. Neither tetrodotoxin (10(-5.5) mol L(-1)), L-nitro-D-arginine methyl ester (L-NAME) (10(-3.5) mol L(-1)) nor guanethidine (10(-5) mol L(-1)) interfered with the effects of [Nle13]-pm or EMA. [Nle13]-pm (10(-11)-10(-6) mol L(-1)) induced rises of [Ca2+]i in cultured colonic myocytes. At 10(-6) mol L-1, 94% of the cells responded, and half of the cells responded at 1.4 nmol L(-1) [Nle13]-pm. 81% (35/43) and 95% (75/79) responded to EMA (10(-6) mol L(-1)) and acetylcholine (ACh, 10(-4) mol L(-1)), respectively. The motilin antagonist GM-109 inhibited motilin- and EMA-induced [Ca2+]i rises. In the absence of extracellular Ca2+, only 13% (7/52) of the cells responded to [Nle13]-pm (10(-6) mol L(-1)) vs. 90% (47/52) to ACh (10(-4) mol L(-1)). Motilin and EMA have direct excitatory effects on circular smooth muscle from the human colon and these effects are mediated via a smooth-muscle motilin receptor. These findings suggest that motilin may regulate colonic motility and that motilides may have therapeutic potential for the treatment of colonic hypomotility.

Signaling pathways mediating gastrointestinal smooth muscle contraction and MLC20 phosphorylation by motilin receptors

“…Motilin-induced PI hydrolysis was concentration dependent and paralleled motilin-induced contraction (2). In cultured, human colonic smooth muscle cells loaded with indomethacin-1, motilin caused an increase in cytosolic free Ca 2ϩ { [Ca 2ϩ ] i }, consistent with inositol 1,4,5-trisphosphate (IP 3 )-dependent Ca 2ϩ release (35). Motilin-induced increase in [Ca 2ϩ ] i in the human medulloblastoma cell line TE671, which express motilin receptors, was retained in Ca 2ϩ -free medium or the presence of the Ca 2ϩ channel blocker nifedipine (32).…”

“…A number of previous studies have shown that motilin receptors are present in smooth muscle cells derived from various regions of the gut (stomach, small intestine, colon, gallbladder) in different species (human, dog, rat, and guinea pig) (2,5,7,15,30,35 (24), and LPA 3 (39) receptors, all of which stimulate PI hydrolysis by activating PLC-␤1 via G␣ q .…”

“…Motilin activates L-type Ca 2ϩ channels in dispersed human and canine intestinal muscle cells (5,16) and enhances carbachol-induced cationic current in dispersed duodenal muscle cells (38). Motilin and related motilides such as erythromycin induce contraction of guinea pig, rat, and human gastric muscle cells, canine jejunal muscle cells, and rabbit colonic muscle cells and stimulate Ca 2ϩ mobilization in cultured human colonic muscle cells (8,15,17,31,35,39).…”

Motilin receptor expression in smooth muscle, myenteric plexus, and mucosa of human inflamed and noninflamed intestine

“…The highest frequency was found in nerve fractions of antrum, but also binding sites in duodenum and colon were detected, while there were no receptors demonstrated in ileum and jejunum. [15][16][17] Due to the species differences it is important that more studies are performed on motilin receptor expression in human intestine. A few years ago an orphan human G-protein receptor (GPR38-A) was identified as a motilin receptor 18 and more techniques became available to detect this motilin receptor.…”

Alteração das pressões anais na gravidez

“…De todo modo, o efeito procinético da motilina está bem estabelecido, embora não esteja definida sua atividade no cólon 17,18,19,20,21,22,23 . Constituímos quatro grupos de 15 pacientes: a) controle: nuligestas; b) primigestas no 1º trimestre; c) 2º trimestre; d) 3º trimestre.…”