Endothelin-1 accentuates the proatherosclerotic effects associated with C-reactive protein

A, Normal vascular NO homeostasis. B, Chronic inflammation results in endothelial dysfunction and facilitates the interactions between modified lipoproteins, monocyte-derived macrophages, T cells, and the normal cellular elements of the arterial wall, resulting in decreased NO production leading to impaired endothelial function and vasoconstriction. These same factors also increase ET-1 production, further promoting vasoconstriction and vasomotor impairment. C, Our hypothesis that CRP alters PKC activity leading to NO impairment.

A, NO production in HSVECs following treatment. The presence of CRP and ET-1 significantly reduced NO production. Coincubation of CRP with ET-1 resulted in a greater decrease in NO release. Bosentan treatment prevented ET-1-induced impairment in NO release but did not prevent the effects of CRP. B, Quantitative Western blot analysis following 24-hour exposure demonstrated that CRP, ET-1, and CRP + ET-1 exposure downregulated eNOS protein expression compared with control. Treatment of HSVEC with bosentan abrogated ET-1 inhibition of eNOS protein expression while having no effect on CRP-induced dowregulation.

A, PKCδ translocation. Top, Western blot of PKCδ expression in the cytosolic fractions (C) and membrane fractions (M) following treatment. Bottom, Quantitative Western blot analysis of PKCδ translocation. No differences were seen after CRP treatment, although ET-1 exposure resulted in a significant PKCδ translocation to the membrane compared with control. Coincubation of CRP with ET-1 resulted in a further increase in PKCδ translocation. B, PKCε translocation. Top, Western blot of PKCε expression in the cytosolic fractions (C) and membrane fractions (M) following treatment. Bottom, Quantitative Western blot analysis of PKCε translocation. PKCε was significantly translocated to the membrane following both CRP and ET-1 treatment compared with control. Coincubation demonstrated PKCε translocation that was significantly greater than that of CRP alone but similar to ET-1 exposed cells. C, PKCλ translocation. Top, Western blot of PKCλ expression in the cytosolic fractions (C) and membrane fractions (M) following treatment. Bottom, Quantitative Western blot analysis of PKCλ translocation. Exposure of HSVECs to CRP and ET-1 caused a significant lowering of PKCλ M/C ratio. Coincubation of CRP with ET-1 led to further decrease in PKCλ M/C ratio.

HSVEC PKC activity. CRP and ET-1 caused a significant decrease in PKC activity compared with control with a further reduction seen following coincubation.

A, B, Human endothelial cell exposed to CRP or ET-1 results in decreased NO production by reducing PKCλ activity and translocation leading to eNOS downregulation. C, The concomitant exposure of ET-1 with CRP further reduces endothelial cell NO release by enhancing PKCλ inhibition and increased eNOS downregulation.