Inhibition of protein kinase Cbeta prevents foam cell formation by reducing scavenger receptor A expression in human macrophages.
BACKGROUND
Low-density lipoprotein (LDL) uptake by monocyte-derived macrophages is a crucial step in foam cell formation and early atherosclerotic lesion. Increasing evidence supports the theory that activation of protein kinase Cbeta (PKCbeta) is involved in many mechanisms promoting atherosclerosis. Thus, we investigated whether inhibition of PKCbeta prevents foam cell formation.


RESULTS
The differentiation of human primary monocytes or the monocytic THP-1 cell line into monocyte-derived macrophages was induced by phorbol 12-myristate 13-acetate (PMA; 0.1 mmol/L), a potent activator of PKC. Incubation of monocyte-derived macrophages with DiI-modified LDL (acetylated LDL and oxidized LDL, 10 mug/mL) led to lipoprotein uptake. Interestingly enough, the nonselective inhibitor of PKCbeta(1) and PKCbeta(2), LY379196 (5x10(-7) to 10(-5) mol/L), blunted LDL uptake in monocyte-derived macrophages as shown by flow cytometry. Specific siRNA-mediated knockdown of PKCbeta exerted a similar effect. Furthermore, PMA alone and in the presence of modified LDL induced scavenger receptor A mRNA and protein expression, which was abolished by LY379196. CGP53353, a selective inhibitor of PKCbeta(2), did not affect LDL uptake, nor did it prevent scavenger receptor A upregulation. Incubation of monocyte-derived macrophages with PMA/LDL increased PKCbeta(1) phosphorylation at the Thr-642 residue, which was blunted by LY379196. However, the expression of CD68, a marker of activated macrophages, was not affected by LY379196. Moreover, LY379196 did not affect lipopolysaccharide-induced CD14 degradation, tumor necrosis factor-alpha release, or superoxide anion production, ruling out any effect of PKCbeta inhibition on innate immunity.


CONCLUSIONS
Nonspecific inhibition of PKCbeta prevents LDL uptake in macrophages. These findings suggest that PKCbeta inhibitors may represent a novel class of antiatherosclerotic drugs.
Osto
Elena
E
Department of Cardiology, University Hospital and Cardiovascular Research, Institute of Physiology, University of Zurich, Zurich, Switzerland.
Kouroedov
Alexei
A
Mocharla
Pavani
P
Akhmedov
Alexander
A
Besler
Christian
C
Rohrer
Lucia
L
von Eckardstein
Arnold
A
Iliceto
Sabino
S
Volpe
Massimo
M
Lüscher
Thomas F
TF
Cosentino
Francesco
F
D015703:Antigens, CD / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D015214:Antigens, Differentiation, Myelomonocytic / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D050197:Atherosclerosis / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism; D002273:Carcinogens / Q000494:pharmacology; D002460:Cell Line; D005487:Foam Cells / Q000378:metabolism* / Q000473:pathology; D005786:Gene Expression Regulation / Q000187:drug effects*; D006801:Humans; D007113:Immunity, Innate / Q000187:drug effects / Q000235:genetics; D018950:Lipopolysaccharide Receptors / Q000235:genetics / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D008077:Lipoproteins, LDL / Q000235:genetics / Q000378:metabolism; D008262:Macrophage Activation / Q000187:drug effects / Q000235:genetics; D008698:Mesylates / Q000494:pharmacology* / Q000627:therapeutic use; D010766:Phosphorylation / Q000187:drug effects / Q000235:genetics; D011493:Protein Kinase C / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D064546:Protein Kinase C beta; D047428:Protein Kinase Inhibitors / Q000494:pharmacology* / Q000627:therapeutic use; D011758:Pyrroles / Q000494:pharmacology* / Q000627:therapeutic use; D034741:RNA, Small Interfering / Q000235:genetics; D051117:Scavenger Receptors, Class A / Q000096:biosynthesis* / Q000235:genetics; D013481:Superoxides / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis / Q000235:genetics; D000097382:CD68 Molecule
D015703:Antigens, CD; D015214:Antigens, Differentiation, Myelomonocytic; D002273:Carcinogens; D018950:Lipopolysaccharide Receptors; D008070:Lipopolysaccharides; D008077:Lipoproteins, LDL; D008698:Mesylates; D011493:Protein Kinase C; D064546:Protein Kinase C beta; D047428:Protein Kinase Inhibitors; D011758:Pyrroles; D034741:RNA, Small Interfering; D051117:Scavenger Receptors, Class A; D013481:Superoxides; D013755:Tetradecanoylphorbol Acetate; D014409:Tumor Necrosis Factor-alpha; C434605:5,21 - 12,17-dimetheneo-18H-dibenzo(i,o)pyrrolo(3,4-1)(1,8)diazacyclohexandecine-18,10(19H)dione,8((dimethylamino)methyl)-6,7,8,9,10,11-hexahydro,monomethanesulfonate; C067980:CD68 antigen, human; D000097382:CD68 Molecule