Microparticles of healthy origins improve endothelial progenitor cell dysfunction via microRNA transfer in an atherosclerotic hamster model.

AIM: In this study, we aimed: (i) to obtain and functionally characterize the cultures of late endothelial progenitor cells (EPCs) from the animal blood; (ii) to investigate the potential beneficial effects of circulating microparticles (MPs) of healthy origins on EPC dysfunctionality in atherosclerosis as well as involved mechanisms. METHODS: Late EPCs were obtained and expanded in culture from peripheral blood isolated from two animal groups: hypertensive-hyperlipidaemic (HH) and control (C) hamsters. In parallel experiments, late EPC cultures from HH were incubated with MPs from C group. RESULTS: The results showed that late EPCs display endothelial cell phenotype: (i) have ability to uptake 1,1-dioctadecyl-3,3,3,3 tetramethylindocarbocyanine-labelled acetylated low-density lipoprotein and Ulex europaeus agglutinin lectin-1; (ii) express CD34, CD133, KDR, CD144, vWF, Tie-2. Late EPCs from HH exhibited different morphological and functional characteristics compared to control: (i) are smaller and irregular in shape; (ii) present decreased endothelial surface marker expression; (iii) display reduced proliferation, migration and adhesion; (iv) lose ability to organize themselves into tubular structures and integrate into vascular network; (v) have diminished function of inward rectifier potassium channels. The incubation of late EPCs with MPs improved EPC functionality by miR-10a, miR-21, miR-126, miR-146a, miR-223 transfer and IGF-1 expression activation; the kinetic study of MP incorporation into EPCs demonstrated MP uptake by EPCs followed by the miRNA transfer. CONCLUSION: The data reveal that late EPCs from atherosclerotic model exhibit distinctive features and are dysfunctional, and their function recovery can be supported by MP ability to transfer miRNAs. These findings bring a new light on the vascular repair in atherosclerosis.

Chemokine (C-X-C motif) ligand 1 (CXCL1) and chemokine (C-X-C motif) ligand 2 (CXCL2) modulate the activity of TRPV1+/IB4+ cultured rat dorsal root ganglia neurons upon short-term and acute application.

CXCL1 and CXCL2 are two chemokines with 78% homology of their sequence. CXCL1 was associated with atopic dermatitis, a highly pruritic skin disease, but it is not clear what is its mechanism of action, while for CXCL2 there are no data about an association with itch sensitivity. CXCL1 and CXCL2 can modulate TRPV1 receptors, which are one of the most important downstream effectors for itch sensitivity, upon short-term (4 h) or long-term (24 h) incubation, but the data are incomplete. Therefore, the aims of this study were to better characterize the short-term effects of CXCL1 and CXCL2 on TRPV1+/IB4+ dorsal root ganglia neurons known to include nociceptor and itch-sensitive neurons, and to obtain new data about the acute application (12 min) of the two chemokines on the same population of neurons. The results showed that 4 nM CXCL1 and 3.6 nM CXCL2 significantly reduce TRPV1 desensitization in TRPV1+/IB4+ DRG +neurons after short-term incubation, but when acutely applied CXCL1 activated a sub-population of itch-sensitive TRPV1+/IB4+ cells in a slow, low amplitude manner, while CXCL2 had a similar effect but on non-itch TRPV1+/IB4+ DRG neurons. These data contribute to a better understanding of CXCL1 and CXCL2 mechanism of action for both pain and itch inducing effects.

Catecholamines reduce transient receptor potential vanilloid type 1 desensitization in cultured dorsal root ganglia neurons.

Sympathetic nervous system and adrenergic receptors are involved in the modulation of dorsal root ganglia neuronal activity, with TRPV1 receptor as an important downstream effector. It is already known that adrenergic sensitization of TRPV1 receptors or catecholamine-induced TRPV1 upregulation are involved in increased excitability and pain via mainly α1 adrenergic receptors, but it is not known if reduced TRPV1 desensitization is involved in this process, as well. Therefore, the aims of this study were to evaluate the effects of epinephrine and norepinephrine on TRPV1 desensitization induced by repeated applications of capsaicin and to assess what would be the involvement of the major α1, α2 and ß adrenergic receptor subtypes. Using calcium microfluorimetry, the effects were evaluated by exposure to 1 µM epinephrine or 10 µM norepinephrine, alone or in the presence of adrenergic receptor inhibitors (phentolamine, prazosin and propranolol) before a 4th capsaicin application in a series of 5 consecutive capsaicin applications. The results showed that both catecholamines produced significant reduction of TRPV1 desensitization, which was mediated by α1, α2 and ß2 receptors. This study completes the general information about TRPV1 sensitization via adrenergic stimulation and may open perspectives for novel pharmacological approaches in skin inflammatory disorders and pain therapy.

Slowed inactivation at positive potentials in a rat axonal K+ channel is not due to preferential closed-state inactivation.

We have investigated slow inactivation in a rat axonal K+ channel, the I channel. Using voltage steps to potentials between -70 mV and +80 mV, from a holding potential of -100 mV, we observed a marked slowing of inactivation at positive potentials: the time constant was 4.5+/-0.4 s at -40 mV (mean +/- S.E.M.), increasing to 14.7+/-2.0 s at +40 mV. Slowed inactivation at positive potentials is not consistent with published descriptions of C-type inactivation, but can be explained by models in which inactivation is preferentially from closed states (which have been developed for Kv2.1 and some Ca2+ channels). We tested two predictions of preferential closed-state models: inactivation should be more rapid during a train of brief pulses than during a long pulse to the same potential, and the cumulative inactivation measured with paired pulses should be greater than the inactivation at the same time during a continuous pulse. The I channel does not behave according to these predictions, indicating that preferential closed-state inactivation does not explain the slowing of inactivation we observe at positive potentials. Inactivation of the I channel therefore differs both from C-type inactivation, as presently understood, and from the inactivation of Kv2.1.