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カフェインはA2Aアデノシン受容体とヒトの血小板におけるその機能を変化させます
K Varani1, F Portaluppi, S Merighi
1Department of Clinical and Experimental Medicine, University of Ferrara, San Raffaele Science Park, Milan, Italy.
Circulation
|May 20, 1999
まとめ
カフェインの繰り返し摂取は,ヒトの血小板A2Aアデノシン受容体を調節する. これは,A2A受容体刺激の後,cAMP蓄積や結合の減少など,血小板反応の感受性の増加につながります.
科学分野:
- 薬理学 薬理学とは
- 分子生物学は分子生物学である.
- 心血管研究 循環器科の研究
背景:
- カフェインは主にアデノシン受容体 (A1,A2A,A2B,A3のサブタイプを含む) を阻害することで作用します.
- アデノシン受容体は,血小板機能を含む様々な生理学的プロセスにおいて重要な役割を果たします.
研究 の 目的:
- 慢性的なカフェイン摂取がヒト血小板のA2Aアデノシン受容体を上調するかどうかを調査する.
- このアップレギュレーションが,A2A受容体刺激に対する血小板の感受性の向上と関連しているかどうかを判断する.
主な方法:
- ヒトのボランティアは,1週間,毎日750mgのカフェインを摂取した.
- 血小板の採取は,ベースライン (禁断) とカフェイン離脱後12時間および60時間で行われました.
- A2A受容体密度は,ラジオリガンド結合 ([3H]SCH 58261) を用いて測定されました.
- cAMPの蓄積と集積を含む血小板応答は,A2A受容体アゴニスト (HE-NECA) による刺激後に評価されました.
主要な成果:
- 慢性的なカフェイン摂取は,ヒトの血小板内のA2A受容体の密度 (Bmax) を著しく増加させた.
- カフェインを摂取しなくなったボランティアの血小板は,A2A受容体アゴニストHE-NECAに対する感受性の上昇を示した.
- この過敏化は,HE-NECAがcAMPの蓄積を増やし (EC50の減少),血小板の集積を抑制するために必要なより低い濃度 (IC50の減少) によって証明されました.
結論:
- 慢性的なカフェイン摂取は,ヒト血小板のA2Aアデノシン受容体のアップレギュレーションにつながります.
- このアップレギュレーションには,A2A受容体アゴニスト刺激に対する血小板の反応性が向上し,機能的感受性を示す.
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