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Vascular wall-produced prostaglandin E2 exacerbates arterial thrombosis and atherothrombosis through platelet EP3 receptors.

Gross S, Tilly P, Hentsch D, Vonesch JL, Fabre JE - J. Exp. Med. (2007)

Bottom Line: Next, we detected PGE2 in mouse atherosclerotic plaques.We demonstrate that this plaque-produced PGE2 is not altered and is still able to activate EP3.In conclusion, PGE2 facilitates the initiation of arterial thrombosis and, hence, contributes to atherothrombosis.

View Article: PubMed Central - PubMed

Affiliation: Institut de Génétique et de Biologie Moléculaire et Cellulaire, Institut National de la Santé et de la Recherche Médicale U596, Centre National de la Recherche Scientifique UMR7104, Université Louis Pasteur, 67400 Illkirch, France.

ABSTRACT
Prostanoids, bioactive lipids derived from arachidonic acid (AA), are important for vascular homeostasis. Among them, prostaglandin E2 (PGE2) enhances aggregation of platelets submaximally stimulated in vitro. This results from activation of EP3, one of the four PGE2 receptors, which decreases the threshold at which agonists activate platelets to aggregate. Although PGE2 altered venous thrombosis induced by administration of AA, its role in pathophysiopathological conditions has remained speculative. We report that arterial walls subjected to inflammatory stimuli produce PGE2. In several models, we show that PGE2 produced by the arterial wall facilitates arterial thrombosis. Next, we detected PGE2 in mouse atherosclerotic plaques. We demonstrate that this plaque-produced PGE2 is not altered and is still able to activate EP3. In addition, we present evidence that PGE2 can leave the plaque and activate EP3 on blood platelets. Consistent with these findings, we observed that atherothrombosis induced in vivo by mechanical rupture of the plaque was drastically decreased when platelets lacked EP3. In conclusion, PGE2 facilitates the initiation of arterial thrombosis and, hence, contributes to atherothrombosis. Inhibition of the platelet EP3 receptor should improve prevention of atherothrombosis.

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PGE2 found in mouse atherosclerotic plaques can act on blood platelets. (A) Model depicting the in vivo set-up used for endoluminal delivery of AA at low concentrations to the plaque. (B) Images from videos recorded under fluorescence, showing a segment of carotid with a plaque in yellow (autofluorescence) and thrombi in green. (top) An example of the absence of response to 2 μg/ml AA in healthy carotid. Conversely, thrombosis developed on plaques after the same amount of AA was delivered in carotids of double-mutant (ApoE−/− × Ep3−/−) mice injected with WT (middle) or Ep3−/− (bottom) platelets. (C) Quantitative analysis of experiments depicted in A. The chosen dose of AA never induced thrombosis in the absence of plaque (control, platelets Ep3+/+), whereas thrombosis observed on plaques in double mutants injected with WT platelets (ApoE−/− × Ep3−/−, platelets Ep3+/+) was significantly decreased when platelets lacked EP3 (ApoE−/− × Ep3−/−, platelets Ep3−/−). ***, P < 0.001; *, P < 0.05. Horizontal lines indicate the mean value for each group. DKO, double knockout.
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fig5: PGE2 found in mouse atherosclerotic plaques can act on blood platelets. (A) Model depicting the in vivo set-up used for endoluminal delivery of AA at low concentrations to the plaque. (B) Images from videos recorded under fluorescence, showing a segment of carotid with a plaque in yellow (autofluorescence) and thrombi in green. (top) An example of the absence of response to 2 μg/ml AA in healthy carotid. Conversely, thrombosis developed on plaques after the same amount of AA was delivered in carotids of double-mutant (ApoE−/− × Ep3−/−) mice injected with WT (middle) or Ep3−/− (bottom) platelets. (C) Quantitative analysis of experiments depicted in A. The chosen dose of AA never induced thrombosis in the absence of plaque (control, platelets Ep3+/+), whereas thrombosis observed on plaques in double mutants injected with WT platelets (ApoE−/− × Ep3−/−, platelets Ep3+/+) was significantly decreased when platelets lacked EP3 (ApoE−/− × Ep3−/−, platelets Ep3−/−). ***, P < 0.001; *, P < 0.05. Horizontal lines indicate the mean value for each group. DKO, double knockout.

Mentions: We wondered whether PGE2 can exit from the plaque to act efficiently on blood platelets. To address the question, we enforced the plaque production of PGE2 by exposing its endoluminal side to low concentrations of AA (2 mg/ml; Fig. 5 A). We observed thrombi forming spontaneously when blood flow returned after the plaque has been incubated with AA (Fig. 5 B, middle). Importantly, thrombosis was detected only at the contact of the plaque, indicating that the plaque produced a platelet agonist that triggered local aggregation. Conversely, healthy the arterial wall was left unchanged by AA incubation, showing that the chosen dose of AA was too low to induce thrombosis at its contact (Fig. 5 B, top). We examined whether the plaque-produced PGE2 could modulate the local thrombosis elicited by the plaque, using Ep3−/− mice crossed with ApoE−/− mice. In these >55-wk-old double-mutant mice (ApoE−/− × Ep3−/−), the lack of EP3 did not alter the extent of atherosclerosis, because their plaques covered 49.3 ± 4.1% (n = 10) of the total aortic surface versus 49.8 ± 5.1% (n = 9; P = 0.94) in ApoE−/− × Ep3+/+ controls. The extent of thrombosis induced by intraluminal AA delivery reached 5.3 ± 1.5 × 106 pixels/min (n = 10) in the presence of WT platelets but was drastically reduced to 0.9 ± 0.2 × 106 pixels/min (n = 10; P < 0.05) when injected fluorescent platelets lacked EP3 (Fig. 5 C and Video S2, available at http://www.jem.org/cgi/content/full/jem.20061617/DC1). This experiment shows that AA-induced atherothrombosis in these mice was modulated by PGE2, which indicates that the plaque-produced PGE2 was able to act on blood platelets through EP3.


Vascular wall-produced prostaglandin E2 exacerbates arterial thrombosis and atherothrombosis through platelet EP3 receptors.

Gross S, Tilly P, Hentsch D, Vonesch JL, Fabre JE - J. Exp. Med. (2007)

PGE2 found in mouse atherosclerotic plaques can act on blood platelets. (A) Model depicting the in vivo set-up used for endoluminal delivery of AA at low concentrations to the plaque. (B) Images from videos recorded under fluorescence, showing a segment of carotid with a plaque in yellow (autofluorescence) and thrombi in green. (top) An example of the absence of response to 2 μg/ml AA in healthy carotid. Conversely, thrombosis developed on plaques after the same amount of AA was delivered in carotids of double-mutant (ApoE−/− × Ep3−/−) mice injected with WT (middle) or Ep3−/− (bottom) platelets. (C) Quantitative analysis of experiments depicted in A. The chosen dose of AA never induced thrombosis in the absence of plaque (control, platelets Ep3+/+), whereas thrombosis observed on plaques in double mutants injected with WT platelets (ApoE−/− × Ep3−/−, platelets Ep3+/+) was significantly decreased when platelets lacked EP3 (ApoE−/− × Ep3−/−, platelets Ep3−/−). ***, P < 0.001; *, P < 0.05. Horizontal lines indicate the mean value for each group. DKO, double knockout.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2118736&req=5

fig5: PGE2 found in mouse atherosclerotic plaques can act on blood platelets. (A) Model depicting the in vivo set-up used for endoluminal delivery of AA at low concentrations to the plaque. (B) Images from videos recorded under fluorescence, showing a segment of carotid with a plaque in yellow (autofluorescence) and thrombi in green. (top) An example of the absence of response to 2 μg/ml AA in healthy carotid. Conversely, thrombosis developed on plaques after the same amount of AA was delivered in carotids of double-mutant (ApoE−/− × Ep3−/−) mice injected with WT (middle) or Ep3−/− (bottom) platelets. (C) Quantitative analysis of experiments depicted in A. The chosen dose of AA never induced thrombosis in the absence of plaque (control, platelets Ep3+/+), whereas thrombosis observed on plaques in double mutants injected with WT platelets (ApoE−/− × Ep3−/−, platelets Ep3+/+) was significantly decreased when platelets lacked EP3 (ApoE−/− × Ep3−/−, platelets Ep3−/−). ***, P < 0.001; *, P < 0.05. Horizontal lines indicate the mean value for each group. DKO, double knockout.
Mentions: We wondered whether PGE2 can exit from the plaque to act efficiently on blood platelets. To address the question, we enforced the plaque production of PGE2 by exposing its endoluminal side to low concentrations of AA (2 mg/ml; Fig. 5 A). We observed thrombi forming spontaneously when blood flow returned after the plaque has been incubated with AA (Fig. 5 B, middle). Importantly, thrombosis was detected only at the contact of the plaque, indicating that the plaque produced a platelet agonist that triggered local aggregation. Conversely, healthy the arterial wall was left unchanged by AA incubation, showing that the chosen dose of AA was too low to induce thrombosis at its contact (Fig. 5 B, top). We examined whether the plaque-produced PGE2 could modulate the local thrombosis elicited by the plaque, using Ep3−/− mice crossed with ApoE−/− mice. In these >55-wk-old double-mutant mice (ApoE−/− × Ep3−/−), the lack of EP3 did not alter the extent of atherosclerosis, because their plaques covered 49.3 ± 4.1% (n = 10) of the total aortic surface versus 49.8 ± 5.1% (n = 9; P = 0.94) in ApoE−/− × Ep3+/+ controls. The extent of thrombosis induced by intraluminal AA delivery reached 5.3 ± 1.5 × 106 pixels/min (n = 10) in the presence of WT platelets but was drastically reduced to 0.9 ± 0.2 × 106 pixels/min (n = 10; P < 0.05) when injected fluorescent platelets lacked EP3 (Fig. 5 C and Video S2, available at http://www.jem.org/cgi/content/full/jem.20061617/DC1). This experiment shows that AA-induced atherothrombosis in these mice was modulated by PGE2, which indicates that the plaque-produced PGE2 was able to act on blood platelets through EP3.

Bottom Line: Next, we detected PGE2 in mouse atherosclerotic plaques.We demonstrate that this plaque-produced PGE2 is not altered and is still able to activate EP3.In conclusion, PGE2 facilitates the initiation of arterial thrombosis and, hence, contributes to atherothrombosis.

View Article: PubMed Central - PubMed

Affiliation: Institut de Génétique et de Biologie Moléculaire et Cellulaire, Institut National de la Santé et de la Recherche Médicale U596, Centre National de la Recherche Scientifique UMR7104, Université Louis Pasteur, 67400 Illkirch, France.

ABSTRACT
Prostanoids, bioactive lipids derived from arachidonic acid (AA), are important for vascular homeostasis. Among them, prostaglandin E2 (PGE2) enhances aggregation of platelets submaximally stimulated in vitro. This results from activation of EP3, one of the four PGE2 receptors, which decreases the threshold at which agonists activate platelets to aggregate. Although PGE2 altered venous thrombosis induced by administration of AA, its role in pathophysiopathological conditions has remained speculative. We report that arterial walls subjected to inflammatory stimuli produce PGE2. In several models, we show that PGE2 produced by the arterial wall facilitates arterial thrombosis. Next, we detected PGE2 in mouse atherosclerotic plaques. We demonstrate that this plaque-produced PGE2 is not altered and is still able to activate EP3. In addition, we present evidence that PGE2 can leave the plaque and activate EP3 on blood platelets. Consistent with these findings, we observed that atherothrombosis induced in vivo by mechanical rupture of the plaque was drastically decreased when platelets lacked EP3. In conclusion, PGE2 facilitates the initiation of arterial thrombosis and, hence, contributes to atherothrombosis. Inhibition of the platelet EP3 receptor should improve prevention of atherothrombosis.

Show MeSH
Related in: MedlinePlus