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Efficient inhibition of collagen-induced platelet activation and adhesion by LAIR-2, a soluble Ig-like receptor family member.

Lenting PJ, Westerlaken GH, Denis CV, Akkerman JW, Meyaard L - PLoS ONE (2010)

Bottom Line: LAIR-2/Fc but not LAIR-1/Fc inhibited collagen-induced platelet aggregation.Additional experiments revealed that LAIR-2/Fc leaves interactions between collagen and alpha2beta1 unaffected, but efficiently prevents binding of collagen to Glycoprotein VI and von Willebrand factor.Thus, LAIR-2/Fc has the capacity to interfere with platelet-collagen interactions mediated by Glycoprotein VI and the VWF/Glycoprotein Ib axis.

View Article: PubMed Central - PubMed

Affiliation: Institut National de la Santé et de la Recherche Médicale (INSERM) U770 & Univ Paris-Sud, Le Kremlin-Bicêtre, France.

ABSTRACT
LAIR-1 (Leukocyte Associated Ig-like Receptor -1) is a collagen receptor that functions as an inhibitory receptor on immune cells. It has a soluble family member, LAIR-2, that also binds collagen and can interfere with LAIR-1/collagen interactions. Collagen is a main initiator for platelet adhesion and aggregation. Here, we explored the potential of soluble LAIR proteins to inhibit thrombus formation in vitro. LAIR-2/Fc but not LAIR-1/Fc inhibited collagen-induced platelet aggregation. In addition, LAIR-2/Fc also interfered with platelet adhesion to collagen at low shear rate (300 s(-1); IC(50) = 18 microg/ml) and high shear rate (1500 s(-1); IC(50) = 30 microg/ml). Additional experiments revealed that LAIR-2/Fc leaves interactions between collagen and alpha2beta1 unaffected, but efficiently prevents binding of collagen to Glycoprotein VI and von Willebrand factor. Thus, LAIR-2/Fc has the capacity to interfere with platelet-collagen interactions mediated by Glycoprotein VI and the VWF/Glycoprotein Ib axis.

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LAIR-2/Fc inhibits adhesion of platelets to collagen under flow conditions.Panel A: Collagen type III-coated coverslips were perfused with whole blood in the absence or presence of 100 µg/ml soluble LAIR-1/Fc, LAIR-2/Fc or SIRL-1/Fc. Representative pictures are shown. Perfusion was performed at a shear rate of 300 s−1 (upper panels) or 1500 s−1 (lower panels). Percentages below figures indicate percentage surface-coverage for each individual photo. Panels B & C: Quantitative representation of surface coverage of collagen type III-coated coverslips that were perfused in the absence or presence of 100 µg/ml soluble LAIR-1/Fc, LAIR-2/Fc or SIRL-1/Fc at 300 s−1 (panel B) or 1500 s−1 (panel C). Data represent mean±SD of three independent perfusions. Panel D: Dose dependent inhibition of surface platelet coverage in the presence of LAIR-2/Fc at shear rates of 300 s−1 (open symbols) or 1500 s−1 (closed symbols). *: p<0.005.
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pone-0012174-g003: LAIR-2/Fc inhibits adhesion of platelets to collagen under flow conditions.Panel A: Collagen type III-coated coverslips were perfused with whole blood in the absence or presence of 100 µg/ml soluble LAIR-1/Fc, LAIR-2/Fc or SIRL-1/Fc. Representative pictures are shown. Perfusion was performed at a shear rate of 300 s−1 (upper panels) or 1500 s−1 (lower panels). Percentages below figures indicate percentage surface-coverage for each individual photo. Panels B & C: Quantitative representation of surface coverage of collagen type III-coated coverslips that were perfused in the absence or presence of 100 µg/ml soluble LAIR-1/Fc, LAIR-2/Fc or SIRL-1/Fc at 300 s−1 (panel B) or 1500 s−1 (panel C). Data represent mean±SD of three independent perfusions. Panel D: Dose dependent inhibition of surface platelet coverage in the presence of LAIR-2/Fc at shear rates of 300 s−1 (open symbols) or 1500 s−1 (closed symbols). *: p<0.005.

Mentions: In another series of experiments, we tested the potential of LAIR-1/Fc and LAIR-2/Fc to interfere with the adhesion of platelets to collagen surfaces under conditions of flow. Glass coverslips coated with collagen type III were perfused with citrated whole blood in the absence or presence of LAIR-1/Fc, LAIR-2/Fc or control protein SIRL-1/Fc (100 µg/ml; Fig. 3A). Quantitative analysis revealed that a surface coverage of 21.3±3.6% (mean±SD) was obtained in the absence of these proteins when blood was perfused at low shear rate (300 s−1; Fig. 3B). A similar surface coverage was found when LAIR-1/Fc or SIRL-1/Fc were added (18.2±8.1% and 17.5±6.4%, respectively). In contrast, surface coverage was reduced to 2.8±3.8% (p<0.005) in the presence of LAIR-2/Fc (Fig. 3B). At high shear rate (1500 s−1), surface coverage increased to 50.7±2.1% when performed in the absence of the Fc-fusion proteins (Fig. 3C). Again, addition of control protein SIRL-1/Fc resulted in a similar coverage (47.0±2.8%). Surface coverage was slightly but not significantly reduced in the presence of LAIR-1/Fc (34.3±11.2%; p = 0.067), and strongly reduced to 7.0±9.9% (p<0.005) in the presence of LAIR-2/Fc (Fig. 3C). The inhibitory potential of LAIR-2/Fc was then assessed in more detail in additional flow adhesion experiments. As depicted in Fig. 3D, half-maximal inhibition was obtained at 18 µg/ml and 30 µg/ml LAIR-2/Fc at 300 s−1 and 1500 s−1, respectively. Apparently, LAIR-2/Fc not only efficiently interferes with collagen-induced platelet aggregation, but also inhibits platelet-collagen interactions at both low and high shear rates.


Efficient inhibition of collagen-induced platelet activation and adhesion by LAIR-2, a soluble Ig-like receptor family member.

Lenting PJ, Westerlaken GH, Denis CV, Akkerman JW, Meyaard L - PLoS ONE (2010)

LAIR-2/Fc inhibits adhesion of platelets to collagen under flow conditions.Panel A: Collagen type III-coated coverslips were perfused with whole blood in the absence or presence of 100 µg/ml soluble LAIR-1/Fc, LAIR-2/Fc or SIRL-1/Fc. Representative pictures are shown. Perfusion was performed at a shear rate of 300 s−1 (upper panels) or 1500 s−1 (lower panels). Percentages below figures indicate percentage surface-coverage for each individual photo. Panels B & C: Quantitative representation of surface coverage of collagen type III-coated coverslips that were perfused in the absence or presence of 100 µg/ml soluble LAIR-1/Fc, LAIR-2/Fc or SIRL-1/Fc at 300 s−1 (panel B) or 1500 s−1 (panel C). Data represent mean±SD of three independent perfusions. Panel D: Dose dependent inhibition of surface platelet coverage in the presence of LAIR-2/Fc at shear rates of 300 s−1 (open symbols) or 1500 s−1 (closed symbols). *: p<0.005.
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Related In: Results  -  Collection

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pone-0012174-g003: LAIR-2/Fc inhibits adhesion of platelets to collagen under flow conditions.Panel A: Collagen type III-coated coverslips were perfused with whole blood in the absence or presence of 100 µg/ml soluble LAIR-1/Fc, LAIR-2/Fc or SIRL-1/Fc. Representative pictures are shown. Perfusion was performed at a shear rate of 300 s−1 (upper panels) or 1500 s−1 (lower panels). Percentages below figures indicate percentage surface-coverage for each individual photo. Panels B & C: Quantitative representation of surface coverage of collagen type III-coated coverslips that were perfused in the absence or presence of 100 µg/ml soluble LAIR-1/Fc, LAIR-2/Fc or SIRL-1/Fc at 300 s−1 (panel B) or 1500 s−1 (panel C). Data represent mean±SD of three independent perfusions. Panel D: Dose dependent inhibition of surface platelet coverage in the presence of LAIR-2/Fc at shear rates of 300 s−1 (open symbols) or 1500 s−1 (closed symbols). *: p<0.005.
Mentions: In another series of experiments, we tested the potential of LAIR-1/Fc and LAIR-2/Fc to interfere with the adhesion of platelets to collagen surfaces under conditions of flow. Glass coverslips coated with collagen type III were perfused with citrated whole blood in the absence or presence of LAIR-1/Fc, LAIR-2/Fc or control protein SIRL-1/Fc (100 µg/ml; Fig. 3A). Quantitative analysis revealed that a surface coverage of 21.3±3.6% (mean±SD) was obtained in the absence of these proteins when blood was perfused at low shear rate (300 s−1; Fig. 3B). A similar surface coverage was found when LAIR-1/Fc or SIRL-1/Fc were added (18.2±8.1% and 17.5±6.4%, respectively). In contrast, surface coverage was reduced to 2.8±3.8% (p<0.005) in the presence of LAIR-2/Fc (Fig. 3B). At high shear rate (1500 s−1), surface coverage increased to 50.7±2.1% when performed in the absence of the Fc-fusion proteins (Fig. 3C). Again, addition of control protein SIRL-1/Fc resulted in a similar coverage (47.0±2.8%). Surface coverage was slightly but not significantly reduced in the presence of LAIR-1/Fc (34.3±11.2%; p = 0.067), and strongly reduced to 7.0±9.9% (p<0.005) in the presence of LAIR-2/Fc (Fig. 3C). The inhibitory potential of LAIR-2/Fc was then assessed in more detail in additional flow adhesion experiments. As depicted in Fig. 3D, half-maximal inhibition was obtained at 18 µg/ml and 30 µg/ml LAIR-2/Fc at 300 s−1 and 1500 s−1, respectively. Apparently, LAIR-2/Fc not only efficiently interferes with collagen-induced platelet aggregation, but also inhibits platelet-collagen interactions at both low and high shear rates.

Bottom Line: LAIR-2/Fc but not LAIR-1/Fc inhibited collagen-induced platelet aggregation.Additional experiments revealed that LAIR-2/Fc leaves interactions between collagen and alpha2beta1 unaffected, but efficiently prevents binding of collagen to Glycoprotein VI and von Willebrand factor.Thus, LAIR-2/Fc has the capacity to interfere with platelet-collagen interactions mediated by Glycoprotein VI and the VWF/Glycoprotein Ib axis.

View Article: PubMed Central - PubMed

Affiliation: Institut National de la Santé et de la Recherche Médicale (INSERM) U770 & Univ Paris-Sud, Le Kremlin-Bicêtre, France.

ABSTRACT
LAIR-1 (Leukocyte Associated Ig-like Receptor -1) is a collagen receptor that functions as an inhibitory receptor on immune cells. It has a soluble family member, LAIR-2, that also binds collagen and can interfere with LAIR-1/collagen interactions. Collagen is a main initiator for platelet adhesion and aggregation. Here, we explored the potential of soluble LAIR proteins to inhibit thrombus formation in vitro. LAIR-2/Fc but not LAIR-1/Fc inhibited collagen-induced platelet aggregation. In addition, LAIR-2/Fc also interfered with platelet adhesion to collagen at low shear rate (300 s(-1); IC(50) = 18 microg/ml) and high shear rate (1500 s(-1); IC(50) = 30 microg/ml). Additional experiments revealed that LAIR-2/Fc leaves interactions between collagen and alpha2beta1 unaffected, but efficiently prevents binding of collagen to Glycoprotein VI and von Willebrand factor. Thus, LAIR-2/Fc has the capacity to interfere with platelet-collagen interactions mediated by Glycoprotein VI and the VWF/Glycoprotein Ib axis.

Show MeSH
Related in: MedlinePlus