Oxidized-LDL Enhances Coronary Vasoconstriction by Increasing the Activity of Protein Kinase C Isoforms α and ε

摘要: Oxidized low-density lipoprotein (ox-LDL) plays a critical role in the development of atherosclerotic coronary vasospasm; however, cellular mechanisms involved are not fully understood. We tested hypothesis that ox-LDL enhances vasoconstriction by increasing activity specific protein kinase C (PKC) isoforms smooth muscle. Active stress was measured de-endothelialized porcine artery strips; cell contraction and [Ca 2+ ] i were monitored single muscle cells loaded with fura-2; cytosolic particulate fractions examined for PKC reactivity isoform-specific anti-PKC antibodies Western blots. Ox-LDL (100 μg/mL) caused slow but significant increases active to 1.3±0.4×10 3 N/m 2 (10%) completely inhibited GF109203X (10 −6 mol/L), an inhibitor Ca -dependent -independent isoforms, no change . 5-Hydroxytryptamine (5-HT; 10 −7 mol/L) KCl (24 mmol/L) channel blocker verapamil mol/L). enhanced 5-HT additional Direct activation phorbol 12-myristate13-acetate (PMA; similar magnitude time course ox-LDL–induced 5-HT– KCl-induced The enhancement Go6976 isoforms. Both PMA increase fraction, decrease particulate/cytosolic ratio. blots revealed PKC-α PKC-δ, -e, -ζ In unstimulated tissues, PKC-α- -e mainly cytosolic, PKC-δ PKC-ζ equally distributed fractions. alone or translocation PKC-e from whereas distribution pattern PKC-α, -δ, remained unchanged. did activity. tissues pretreated PMA, Native LDL significantly affect contraction, , These results suggest causes via -increasing agonists activating PKC-α. Activation may represent possible mechanism which could enhance vasospasm.