Na⁺/Ca²⁺ exchanger 1 is a key mechanosensitive molecule of the esophageal myenteric neurons

Abstract

Aim: Our earlier studies showed that mechanical stretch activates inhibitory motor neurons of the oesophagus; however, the underlying molecular mechanisms are unclear. Here, we sought to examine if Na + /Ca 2+ exchanger 1 (NCX1) is responsible for the mechanosensitivity in the esophageal myenteric neurons (EMN) of rats and humans. Methods: The function of NCX1 in primary culture of neurons was determined using calcium imaging, and mechanosensitivity was tested using osmotic stretch and direct mechanical stretch. Axial stretch-induced relaxation of the lower esophageal sphincter (LES) was also studied in vivo in rats. Results: The expression and co-localization of NCX1 with nNOS were identified in the EMN from both rats and humans. The extracellular Ca 2+ entry caused by ATP through purinergic signalling in the rat EMN was significantly inhibited by selective NCX blockers. Removal of extracellular Na + to activate the Ca 2+ entry mode of NCX1 induced an increase in the cytoplasmic calcium ([Ca 2+ ] cyt ), which was attenuated by NCX blockers. Osmotic stretch and mechanical stretch-induced [Ca 2+ ] cyt signalling in the rat and human EMN were attenuated by NCX blockers as well as specific NCX1 knockdown. Osmotic stretch and mechanical stretch also induced [Ca 2+ ] cyt signalling in the Chinese hamster ovary (CHO) cells with NCX1 over-expression, which was attenuated by NCX blockers. Finally, NCX blockade inhibited axial stretch-activated LES relaxation in vivo experiments in the rats. Conclusions:We demonstrate a novel NCX1/Ca 2+ pathway in the mechanosensitive neurons of rat and human oesophagus, which may provide a potential therapeutic target for the treatment of oesophageal motility disorders. K E Y W O R D Sesophageal myenteric neurons, lower esophageal sphincter relaxation, mechanosensitive neurons, Na +/ Ca 2+ exchanger 1

Google maps for tissues: Multiscale imaging of biological systems and disease

“…A striking example from human integrative muscle physiology revealed that a reduction in activation level reduces residual force depression in tibialis anterior muscle. 11 In another report Ca 2+ imaging was employed to investigate morphologically distinct paraneurones of the urethra -a class of specialized cells that express serotonin-and their potential role in peripheral sensory information processing. 6 Trevino et al used US to probe muscle cross-sectional area and muscle tissue composition (contractile vs non-contractile tissue), thereby revealing details of sex-related differences in trapezoid muscles.…”

“…10 A recent study took advantage of mechanical stretch-induced real time Ca 2+ imaging in isolated esophageal myenteric neurones (EMN) to demonstrate that the Na + /Ca 2+ exchanger 1 plays an important role for the mechanosensitivity in the EMN of rats and humans. 11 In another report Ca 2+ imaging was employed to investigate morphologically distinct paraneurones of the urethra -a class of specialized cells that express serotonin-and their potential role in peripheral sensory information processing. 12 On the nanoscopic scale, development and application of next generation optical microscopy encompasses single molecule analyses and super-resolution microscopy in signalling research.…”