s-PRGF promotes proliferation and migration and influences limbal stemness, adhesion and fibrosis during corneal healing.

No abstract

High catecolamine plasma levels because of sympathetic nervous system over-activity contribute to cirrhosis progression. The aim of this study was to investigate whether chromaffin cells of the adrenal gland might potentiate the deleterious effect exerted by this over-activity. Electrophysiological patch-clamp and amperometric experiments with carbon-fibre electrodes were conducted in single chromaffin cells of control and CCl 4induced cirrhotic rats. The spontaneous action potential firing frequency was increased in chromaffin cells of cirrhotic rats with respect to control rats. The exocytosis evoked by that firing was also increased. However, exocytosis elicited by ACh did not vary between control and cirrhotic rats. Exocytosis triggered by depolarizing pulses was also unchanged. Amperometric recordings confirmed the lack of increased catecholamine charge released in cirrhosis after ACh or depolarization stimuli. However, the amperometric spikes exhibited faster kinetics of release. The overall Ca 2+ entry through voltage-dependent Ca 2+ channels (VDCC), or in particular through Cav1 channels, did not vary between chromaffin cells of control and cirrhotic rats. The inhibition of VDCC by methionine-enkephaline or ATP was not either altered, but it was increased by adrenaline in cells of cirrhotic rats. When a cocktail composed by the three neurotransmitters was tested in order to approach a situation closer to the physiological condition, the inhibition of VDCC was similar between both types of cells. In summary, chromaffin cells of the adrenal gland might contribute to exacerbate the sympathetic nervous system over-activity in cirrhosis because of an increased exocytosis elicited by an enhanced spontaneous electrical activity.

No abstract

The physical interaction and functional cross talk among the different subtypes of neuronal nicotinic acetylcholine receptors (nAChRs) expressed in the various tissues is unknown. Here, we have investigated this issue between the only two nAChRs subtypes expressed, the a7 and a3b4 subtypes, in a human native neuroendocrine cell (the chromaffin cell) using electrophysiological patch-clamp, fluorescence, and Förster resonance energy transfer (FRET) techniques. Our data show that a7 and a3b4 receptor subtypes require their mutual and maximal efficacy of activation to increase their expression, to avoid their desensitization, and therefore, to increase their activity. In this way, after repetitive stimulation with acetylcholine (ACh), a7 and a3b4 receptor subtypes do not desensitize, but they do with choline. The nicotinic current increase associated with the a3b4 subtype is dependent on Ca 21 . In addition, both receptor subtypes physically interact. Interaction and expression of both subtypes are reversibly reduced by tyrosine and serine/threonine phosphatases inhibition, not by Ca 21 . In addition, expression is greater in human chromaffin cells from men compared to women, but FRET efficiency is not affected. Together, our findings indicate that human a7 and a3b4 subtypes mutually modulate their expression and activity, providing a promising line of research to pharmacologically regulate their activity.

Background and Purpose: Cardiovascular side effects from varenicline, and a case report of a hypertensive crisis event in a patient with pheochromocytoma being treated with varenicline, have been reported. The goal of the present study was to determine if such side effects might derive, in part, from increased exocytosis of secretory vesicles and subsequent catecholamine release triggered by varenicline in chromaffin cells of the adrenal gland. Experimental Approach: We performed electrophysiological plasma membrane capacitance (Cm) and carbon fiber amperometry experiments to evaluate the effect of varenicline on exocytosis and catecholamine release, respectively, at concentrations reached during varenicline therapy (100 nM). Experiments were conducted in the absence or presence of nicotine, at plasma concentrations achieved right after smoking (250 nM) or steady-state concentrations (110 nM), in chromaffin cells of the adrenal gland obtained from human organ donors or rats. Key Results: Varenicline increased the exocytosis of secretory vesicles and the release of catecholamines from human chromaffin cells in the presence of nicotine. Comparable results were found using rat chromaffin cells; varenicline alone or in the presence of acute or steady-state concentrations of nicotine found in human plasma increased exocytosis. These effects were not due to an increase of Cm or currents triggered by the nicotinic agonists alone. Conclusion and Implications: Therapeutic concentrations of varenicline in the presence of nicotine increased exocytosis and catecholamine release from human chromaffin cells. These results should be taken into account in nicotine addiction therapies when varenicline is used.

Abstractα7 nicotinic receptors have been involved in numerous pathologies. A hallmark of these receptors is their extremely fast desensitization, a process not fully understood yet. Here we show that human native α7 and α3β4 nicotinic receptors physically interact in human chromaffin cells of adrenal glands. The full activation of this α7-α3β4 receptor complex avoids subtypes receptor desensitization, leading to gradual increase of currents with successive acetylcholine pulses. Instead, full and partial activation with choline of α7 and α3β4 subtypes, respectively, of this linked receptor leads to α7 receptor desensitization. Therefore choline, a product of the acetylcholine hydrolysis, acts as a brake by limiting the increase of currents by acetylcholine. Very importantly, the efficiency of the α7-α3β4 interaction diminishes in subjets older than 50 years, accordingly increasing receptor desensitization and decreasing nicotinic currents. These results open a new line of research to achieve improved therapeutic treatments for nicotinic receptors related diseases.