Mechanism of bombesin-induced tonic contraction of the porcine lower esophageal sphincter

Abstract

Gastroesophageal reflux disease (GERD) is a disorder that is related to an incompetent lower esophageal sphincter (LES). Previous studies showed that bombesin could increase LES pressure in humans and opossums. The aim of the present study was to characterize the effects of bombesin on porcine LES contraction. We used the selective agonists, neuromedin B (NMB), gastrin-releasing peptide (GRP), and [D-Tyr6,Apa-4Cl11,Phe13,Nle14]bombesin-(6-14) (DTACPN-BN), as well as receptor antagonists of bombesin receptor subtype 2 (BB2), and 3 (BB3) for ex vivo contraction studies. Atropine, nifedipine, tetrodotoxin, and ω-conotoxin GVIA were used to explore the agonist-induced LES contraction mechanism. Reverse transcription polymerase chain reaction and immunohistochemistry were applied to detect bombesin receptor expression. Our results indicate that GRP and DTACPN-BN, but not NMB, induced tonic contractions of the porcine LES in a dose-dependent manner, and the contractions were inhibited with selective BB2 and BB3 antagonists. The GRP-induced contraction is mainly caused by L-type Ca2+ channel-mediated Ca2+ influx. However, DTACPN-BN-induced contractions are associated with neuronal conduction. RT-PCR and immunohistochemistry revealed that BB2 and BB3 were expressed in the porcine LES. Bombesin-induced tonic contraction of the LES is mediated through BB2 and BB3. Bombesin, BB2, and BB3 agonists might have the potential to treat GERD.

Long-Chain Fatty Acid Receptors Mediate Relaxation of the Porcine Lower Esophageal Sphincter

“…The porcine LES, which has similar structure to the human LES, was divided into clasp with LC and sling with GC muscle strips according to previously published procedures with minor modifications (Farré et al, 2007; Tsai et al, 2015, 2018). The porcine LES is often used as an animal model system to study esophageal motility and GERD in humans (Korn et al, 1997; Schopf et al, 1997).…”

“…Immunostaining with anti-FFA1 (polyclonal, GeneTex, CA, United States) and anti-FFA4 (polyclonal, GeneTex, CA, United States) antibodies were executed on the fully automated Bond-Max system (Leica Microsystems, Nussloch, Germany) according to previously described procedures with minor modifications (Tsai et al, 2015, 2018). Slides carrying tissue sections of porcine sling and clasp muscles, cut from paraffin-embedded, formalin-fixed sections, were dried for 30 min at 60°C.…”

Effects of neuromedin B on steroidogenesis, cell proliferation and apoptosis in porcine Leydig cells

“…NMB exerts several biological functions by binding NMBR, such as stimulating smooth muscle, mediating stress and fear reactions, regulating feeding, regulating temperature, energy balance, regulating endocrine and/ or exocrine secretions and promoting cell growth (Ohki-Hamazaki 2000, Jensen et al 2008). In addition, NMB can stimulate the hypothalamic-pituitary-gonadal (HPG) axis in male rats, which indicates that NMB can also regulate reproduction (Boughton et al 2013); however, little is known about the physiological functions of NMB in pigs, except that it can contract the porcine lower esophageal sphincter (Tsai et al 2015). We had previously found that NMB and NMBR mRNAs are expressed in pig testes and that they exhibit developmental changes in the gonadal axis of boars (Ma et al 2016); therefore, we speculated that the NMB/NMBR system might have an impact on the reproductive function of boars.…”

Pharmacological Effects of Two Novel Bombesin-Like Peptides from the Skin Secretions of Chinese Piebald Odorous Frog (Odorrana schmackeri) and European Edible Frog (Pelophylax kl. esculentus) on Smooth Muscle

“…As explained previously, bombesin mediates its functions through specific receptors. Additionally, bombesin and their receptors are widely distributed in the periphery and CNS, and are associated with various functions like food intake, pain, stress, and fear responses [ 23 ]. Henceforth, it will be meaningful for scientists to study the physiological and pathological aspects of bombesin relationships with receptors in amphibians.…”