Calcium-dependent ultrasound stimulation of secretory events from pancreatic beta cells

Abstract

BackgroundOur previous studies have indicated that ultrasound can stimulate the release of insulin from pancreatic beta cells, providing a potential novel treatment for type 2 diabetes. The purpose of this study was to explore the temporal dynamics and Ca2+-dependency of ultrasound-stimulated secretory events from dopamine-loaded pancreatic beta cells in an in vitro setup.MethodsCarbon fiber amperometry was used to detect secretion from INS-1832/13 beta cells in real time. The levels of released insulin were also measured in response to ultrasound treatment using insulin-specific ELISA kit. Beta cells were exposed to continuous wave 800 kHz ultrasound at intensities of 0.1 W/cm2, 0.5 W/cm2 and 1 W/cm2 for several seconds. Cell viability tests were done with trypan blue dye exclusion test and MTT analysis.ResultsCarbon fiber amperometry experiments showed that application of 800 kHz ultrasound at intensities of 0.5 and 1 W/cm2 was capable of stimulating secretory events for durations lasting as long as the duration of the stimulus. Furthermore, the amplitude of the detected peaks was reduced by 64% (p < 0.01) when extracellular Ca2+ was chelated with 10 mM EGTA in cells exposed to ultrasound intensity of 0.5 W/cm2. Measurements of released insulin in response to ultrasound stimulation showed complete inhibition of insulin secretion by chelating extracellular Ca2+ with 10 mM EGTA (p < 0.01). Viability studies showed that 800 kHz, 0.5 W/cm2 ultrasound did not cause any significant effects on viability and metabolic activity in cells exposed to ultrasound as compared to sham-treated cells.ConclusionsOur results demonstrated that application of ultrasound was capable of stimulating the release of insulin from pancreatic beta cells in a safe, controlled and Ca2+-dependent manner.

Focused ultrasound excites neurons via mechanosensitive calcium accumulation and ion channel amplification

“…In addition to neurons, it would also be interesting in future studies to examine the biophysical and molecular bases of ultrasonic stimulation in other cell types. For example, recent studies have demonstrated ultrasound-enhanced cholinergic signaling in the spleen (Gigliotti et al, 2013;Zachs et al, 2019), insulin release from pancreatic beta cells (Suarez Castellanos et al, 2017) and bone fracture healing (Zhang et al, 2012). Furthermore, overexpression of the mechanoreceptors and amplifier channels identified in this study could sensitize cells that do not have intrinsic ultrasound responses.…”

Piezo1 channel agonist mimics high glucose as a stimulator of insulin release

“…Interestingly, Piezo1 can be activated by ultrasound [35]. Though the significance of Piezo1 in physiological insulin secretion is not evident from our study, using mechanosensitive Piezo1 induction as a strategy to induce insulin secretion has clear clinical potential and warrants further investigation [34]. It is an attractive approach particularly in neonatal diabetes where the disease is caused by gain-of-mutations in KATP channels [36].…”

“…However the current secretagogue pharmaceuticals are not favoured due to their adverse cardiovascular reactions and reported induction of b-cell apoptosis [32]. The search for non-pharmacological approaches led to the identification of ultrasound as a Ca 2+ dependent insulin secretion inducer [33], [34]. Stimulation of stretch activated channels was proposed as the underlying mechanism.…”

Investigation of Ultrasound-Mediated Intracellular Ca2+ Oscillations in HIT-T15 Pancreatic β-Cell Line

“…We are not the first to investigate how β-cells respond to ultrasound stimulation. Castellanos et al [14,37] reported insulin releases from INS-1 832/13 rat insulinoma cell line in response to 800 kHz of ultrasound stimulation (continuous ultrasound, I SATA = 1 W/cm 2 ). In another sequential paper, the authors monitored ultrasound-induced secretary events by carbon fiber amperometry and detected sustained amperometric peaks, which prolong the duration of ultrasound stimulation [14].…”

“…However, the level of intracellular Ca 2+ plays a fundamental role in all suggested pathways. Recently, Castellanos et al [14] reported the Ca 2+ -dependent insulin release from rat INS 832/13 β-cells upon ultrasound stimulation, suggesting a possible therapeutic intervention of the diabetic condition using mechanical energy-based modality.…”