OnabotulinumtoxinA (onabotA) has shown efficacy in chronic migraine (CM). Its mechanism of action, however, remains obscure. We have analysed whether treatment with onabotA is able to induce changes in interictal plasma calcitonin gene-related peptide (CGRP) concentrations, which have been shown to be increased in patients with CM. Calcitonin gene-related peptide levels were determined in samples obtained from the right antecubital vein using ELISA, outside a migraine attack and having taken no symptomatic medication in the previous 24 hours, in 83 patients with CM (average age 44 years; 94% females) before and 1 month after treatment with 155 to 195 U of onabotA. CGRP levels after onabotA treatment (median, 51.89 pg/mL; range, 199.4-10.2) were significantly lower as compared with CGRP levels obtained before onabotA treatment (median, 74.09 pg/mL; range, 241.0-11.4; P = 0.001). Pretreatment CGRP levels in responders (76.85 pg/mL) were significantly higher than those seen in nonresponders (50.45 pg/mL; P = 0.001). One month after treatment, the CGRP levels did not change in nonresponders (51.89 pg/mL; P not significant), but significantly decreased in responders (52.48 pg/mL; P = 0.003). A number of demographic factors, clinical features, and comorbidities were not different in responders as compared with those of nonresponders. These results confirm that interictal CGRP levels can be of help in predicting the response to onabotA and suggest that the mechanism of action of onabotA in CM is the reversal of sensitization as a result of the inhibition of CGRP release.

Background.-Onabotulinumtoxin type A (onabotA) has shown efficacy in chronic migraine (CM). Its precise mechanism of action, however, is unknown.Objective.-To analyze a potential relationship between calcitonin gene-related peptide (CGRP) and vasoactive intestinal peptide (VIP) levels and response to onabotA in CM.Methods.-Adult patients with CM were recruited. Matched healthy subjects with no headache history served as controls. CGRP and VIP levels were determined in samples obtained from the right antecubital vein by ELISA outside of a migraine attack and having taken no symptomatic medication prior to treatment with onabotA. OnabotA was administered according to the PREEMPT protocol every 12 weeks for at least two treatment cycles. A patient was considered as a moderate responder when both: (1) moderate-severe headache episodes were reduced by between 33 and 66%; (2) subjective benefit in a visual scale of 0-100 was recorded by the patient of between 33-66%. Patients were considered as excellent responders when both items improved >66%. Those without improvement of at least one-third in the two items were considered as nonresponders.Results.-We assessed plasma samples from 81 patients with CM and 33 healthy controls. CGRP and VIP levels were significantly increased in CM population vs controls. CGRP and, to a lesser degree, VIP levels were significantly increased in responders vs nonresponders. For CGRP, a threshold of 72 pg/mL positively correlated with 95% of nonresponders. The probability of being a responder to onabotA was 28 times higher in patients with a CGRP level above the threshold of 72 pg/mL. Even though the sensitivity for the calculated threshold for VIP was poor, the probability that CM patients with low CGRP levels will respond to onabotA was significantly higher in those patients with high VIP levels.Conclusions.-Interictal CGRP and, to a lesser degree, VIP levels measured in peripheral blood are of great help in predicting response to onabotA.

Extracellular vesicles (EV) are small membrane structures released by cells that act as potent mediators of intercellular communication. The study of EV biology is important, not only to strengthen our knowledge of their physiological roles, but also to better understand their involvement in several diseases. In the field of biomedicine they have been studied as a novel source of biomarkers and drug delivery vehicles. The most commonly used method for EV enrichment in crude pellet involves serial centrifugation and ultracentrifugation. Recently, different protocols and techniques have been developed to isolate EV that imply less time and greater purification. Here we carry out a comparative analysis of three methods to enrich EV from plasma of healthy controls: ultracentrifugation, ExoQuickTM precipitation solution (System Biosciences), and Total Exosome Isolation kit (Invitrogen). Our results show that commercial precipitation reagents are more efficient and enable higher EV enrichment factors compared with traditional ultracentrifugation, although subsequent imaging analysis is not possible with some of them. We hope that this work will contribute to the current research on isolation techniques to assist the progress of clinical applications with diagnostic or therapeutic objectives.

BackgroundCell-derived microparticles are secreted in response to cell damage or dysfunction. Endothelial and platelet dysfunction are thought to contribute to the development of multiple sclerosis (MS). Our aim here is, first, to compare the presence of microparticles of endothelial and platelet origin in plasma from patients with different clinical forms of MS and with clinically isolated syndrome. Second, to investigate the effect of microparticles on endothelial barrier function.ResultsPlatelet-poor plasma from 95 patients (12 with clinically isolated syndrome, 51 relapsing-remitting, 23 secondary progressive, 9 primary progressive) and 49 healthy controls were analyzed for the presence of platelet-derived and endothelium-derived microparticles by flow cytometry. The plasma concentration of platelet-derived and endothelium-derived microparticles increased in all clinical forms of MS and in clinically isolated syndrome versus controls. The response of endothelial barriers to purified microparticles was measured by electric cell-substrate impedance sensing. Microparticles from relapsing-remitting MS patients induced, at equivalent concentrations, a stronger disruption of endothelial barriers than those from healthy donors or from patients with clinically isolated syndrome. MS microparticles acted synergistically with the inflammatory mediator thrombin to disrupt the endothelial barrier function.ConclusionsPlasma microparticles should be considered not only as markers of early stages of MS, but also as pathological factors with the potential to increase endothelial permeability and leukocyte infiltration.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2202-15-110) contains supplementary material, which is available to authorized users.

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