Vorapaxar: A novel agent to be considered in the secondary prevention of myocardial infarction

Protease-Activated Receptor Antagonist for Reducing Cardiovascular Events - A Review on Vorapaxar

Acute Coronary Syndrome (ACS) is a term that describes pathologies related to myocardial ischemia, and is comprised of unstable angina, non-ST elevation myocardial infarction, and ST elevation myocardial infarction. Urgent management of ACS is typically necessary to prevent future morbidity and mortality. Current medical recommendations of ACS management involve use of dual antiplatelet therapy, typically with aspirin and clopidogrel. However, newer therapies are being designed and researched to improve outcomes for patients with ACS. Vorapaxar is a novel antiplatelet therapy that inhibits thrombin-mediated platelet aggregation to prevent recurrence of ischemic events. It has been Food and Drug Administration approved for reduction of thrombotic cardiovascular events in patients with a history of MI or peripheral arterial disease with concomitant use of clopidogrel and/or aspirin, based upon the findings of the TRA 2°P-TIMI 50 trial. However, Vorapaxar was also found to have a significantly increased risk of bleeding, which must be considered when administering this drug. Based upon further subgroup analysis of both the TRA 2°P-TIMI 50 trial and TRACER trial, Vorapaxar was found to be potentially beneficial in patients with peripheral artery disease, coronary artery bypass grafting, and ischemic stroke. There are current trials in progress that are further evaluating the use of Vorapaxar in those conditions, and future research and trials are necessary to fully determine the utility of this drug.

Activation of calcium signaling in human gingival fibroblasts by recombinant Porphyromonas gingivalis RgpB protein

Arginine-specific cysteine proteinases, such as Arg-gingipain B (RgpB), mediate inflammation by activating protease-activated receptors (PARs). Arg-gingipain B is produced by Porphyromonas gingivalis, and is implicated in the causation of periodontal disease. The purpose of the present study was to observe the influence of recombinant RgpB protein (rRgpB) on PAR activation by monitoring intracellular Ca2+ ion concentration ([Ca2+]i) and inositol-1,4,5-triphosphate (IP3) levels in human gingival fibroblasts (HGFs). Our findings showed that rRgpB could cause a transient increase in [Ca2+]i. This increase in [Ca2+]i was completely suppressed by vorapaxar, a PAR-1 antagonist. Recombinant Arg-gingipain B increased the concentration of IP3, reaching a maximum at 60 s after treatment; this was completely inhibited by vorapaxar. We therefore conclude that rRgpB-induced calcium signaling in HGFs is mainly caused by PAR-1 activation. This suggests that PAR-1 activation plays a significant role in chronic inflammatory periodontal disease induced by P. gingivalis RgpB.

The Thrombin Receptor Restricts Subventricular Zone Neural Stem Cell Expansion and Differentiation

Thrombin is frequently increased in the CNS after injury yet little is known regarding its effects on neural stem cells. Here we show that the subventricular zone (SVZ) of adult mice lacking the high affinity receptor for thrombin, proteinase activated receptor 1 (PAR1), show increased numbers of Sox2+ and Ki-67+ self-renewing neural stem cells (NSCs) and Olig2+ oligodendrocyte progenitors. SVZ NSCs derived from PAR1-knockout mice, or treated with a PAR1 small molecule inhibitor (SCH79797), exhibited enhanced capacity for self-renewal in vitro, including increases in neurosphere formation and BrdU incorporation. PAR1-knockout SVZ monolayer cultures contained more Nestin, NG2+ and Olig2+ cells indicative of enhancements in expansion and differentiation towards the oligodendrocyte lineage. Cultures of NSCs lacking PAR1 also expressed higher levels of myelin basic protein, proteolipid protein and glial fibrillary acidic protein upon differentiation. Complementing these findings, the corpus callosum and anterior commissure of adult PAR1-knockout mice contained greater numbers of Olig2+ progenitors and CC1+ mature oligodendrocytes. Together these findings highlight PAR1 inhibition as a means to expand adult SVZ NSCs and to promote an increased number of mature myelinating oligodendrocytes in vivo that may be of particular benefit in the context of neural injury where PAR1 agonists such as thrombin are deregulated.