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The Effects of vanilloid-like agents on platelet aggregation

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Almaghrabi, SY (2012) The Effects of vanilloid-like agents on platelet aggregation. Research Master thesis, University of Tasmania.

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Abstract

Capsaicin, the ‘hot’ principle found in chilli, and other vanilloids exert their effects
on neuronal cells through activation of transient receptor potential vanilloid 1
(TRPV1). TRPV1 is widely distributed in neuronal and non-neuronal cells. It has
been proposed that consumption of vanilloid-like agents, including capsaicinoids,
inhibits platelet aggregation and may protect against the development of
cardiovascular disease. The aim of this study was to investigate the effects of a range
of vanilloid-like agents on in vitro platelet aggregation.
Venous blood was collected from healthy subjects who avoided antiplatelet
medications and dietary chilli for at least 10 and 2 days, respectively. Collagen (4
and 8 μg/mL), ADP (10 and 5 μM) and arachidonic acid (AA) (300 and 400 mg/mL)
-induced platelet aggregation was determined using platelet rich plasma (PRP;
250x10 9/L) in the absence and presence of the capsaicinoids [capsaicin and
dihydrocapsaicin (DHC)] and the endocannabinoid/endovanilloid agents [Noleoyldopamine
(OLDA) and N-arachidonoyl-dopamine e (NADA)]. %Maximum
aggregation (%Max), % area under curve (%AUC) and slope of platelet aggregation
were determined. Platelet lactate dehydrogenase (LDH), which is released rapidly
after cell membrane damage, was investigated to determine the direct toxic effects of
these agents on platelets. Platelet factor 4 (PF4) and β-thromboglobulin (β-TG)
release were examined to determine the effects of vanilloids on alpha granule
release. Finally, the effects of TRPV1 antagonist (SB-452533) on capsaicin- and
OLDA-mediated inhibition of ADP-induced platelet aggregation were investigated. ADP-induced (5 μM) platelet aggregation was inhibited in a concentration-dependent
manner by capsaicin (%Max, mean +/-SEM; 0 vs 100 μM, 83.8=/-0.9% vs 45.2+/-2.4%,
n=6, p0.001); OLDA (0 vs 100 μM, 71.68.2% vs 9.41.4%, n=4, p0.001); and
NADA (0 vs 100 μM, 71.5+/-5.9% vs 38.2+/-1.4%, n=4, p0.008). Similar results were
observed using 10 μM ADP. OLDA and NADA, but not capsaicin and DHC,
inhibited platelet aggregation induced by 4μg/mL collagen: OLDA (Max%, 0 vs 100
μM, 89.3+/-1.4% vs 45.5+/-12.5%, p<0.001); and NADA (0 vs 100 μM, 87.7+/-0.8% vs
28.5+/-8.2%, p<0.001). AA-induced (300 mg/mL) aggregation was inhibited in a
concentration-dependent manner by capsaicin (Max%, 0 vs 100 μM, 89.6=/-0.9% vs
11+/-0.8%, p<0.001); DHC (0 vs 100 μM, 88.3+/-2.1% vs 18.7+/-6.9%, p<0.001); and
NADA (0 vs 100 μM, 84+/-1.8% vs 21.9+-4.7%, p<0.001). Similar results were
observed using 400mg/mL AA. The inhibition of platelet aggregation by all agents
was not due to direct toxic effects as LDH release from platelets was unaffected by
any of the vanilloids. SB-452533 did not inhibit the effects of OLDA (SB-45253;
Max 0 vs 10μM, 55.9+/-2.1% vs 58.4+/-1.37%) and capsaicin (SB-45253; Max 0 vs
10μM, 65.15+/-0.44% vs 65.55+/-1%) on platelet aggregation, suggesting that
inhibition of ADP-induced aggregation is not TRPV1 mediated. ADP-stimulated PF4
release from platelets was impaired by capsaicin, DHC and OLDA whereas NADA
enhanced ADP-stimulated PF4 release. Furthermore, OLDA and capsaicin impaired
the release of β-TG from ADP-stimulated platelets.
The present study using human platelet shows that capsaicin, DHC, OLDA and
NADA inhibit in vitro aggregation. The inhibitory effects of vanilloids are not
TRPV1 mediated and not due to a direct toxic effect on platelets. Vanilloids may inhibit platelet aggregation by interfering with granule release, although further
investigation of this possibility is warranted.

Item Type: Thesis (Research Master)
Keywords: platelet aggregration, capsaicin, vanilloids, cardiovascular disease
Copyright Information:

Copyright 2012 the Author - The University is continuing to endeavour to trace the copyright
owner(s) and in the meantime this item has been reproduced here in good faith. We
would be pleased to hear from the copyright owner(s).

Date Deposited: 11 Jan 2013 05:29
Last Modified: 11 May 2016 22:53
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