Palmitate-induced apoptosis of microvascular endothelial cells and pericytes.
BACKGROUND
Recent observations in the EURODIAB Complications Study demonstrated that markers of insulin resistance are strong risk factors for retinopathy incidence in patients with diabetes. However, the molecular mechanism underlying this remains to be elucidated. In this study, we investigated the influence of palmitate, a major saturated free fatty acid in plasma, on the apoptotic cell death of cultured microvascular endothelial cells (EC) and retinal pericytes.


METHODS
The intracellular formation of reactive oxygen species (ROS) was detected using the fluorescent probe CM-H(2)DCFDA. DNA synthesis was determined by measuring [(3) H]-thymidine incorporation into cells. DNA fragmentations of EC were quantitatively analyzed in an enzyme-linked immunosorbent assay, and DNA laddering was evaluated on agarose gel electrophoresis.


RESULTS
Palmitate increased ROS generation in microvascular EC. Furthermore, palmitate significantly inhibited DNA synthesis and induced apoptotic cell death in EC, which were completely prevented by an antioxidant, N-acetylcysteine. Palmitate up-regulated pericyte mRNA levels of a receptor for advanced glycation end products (AGE), and thereby potentiated the apoptotic effects of AGE on pericytes.


CONCLUSIONS
The results suggest that palmitate could induce apoptotic cell death in microvascular EC and pericytes through the overgeneration of intracellular ROS, and thus be involved in the development of diabetic retinopathy.
Yamagishi
Sho-Ichi
S
Division of Endocrinology and Metabolism, Department of Medicine, Kurume University School of Medicine, Kurume, Japan. shoichi@med.kurume-u.ac.jp
Okamoto
Tamami
T
Amano
Shinjiro
S
Inagaki
Yosuke
Y
Koga
Kohachiro
K
Koga
Mari
M
Choei
Hiroshi
H
Sasaki
Nobuyuki
N
Kikuchi
Seiji
S
Takeuchi
Masayoshi
M
Makita
Zenji
Z
D017209:Apoptosis; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000166:cytology* / Q000187:drug effects / Q000502:physiology; D005456:Fluorescent Dyes / Q000378:metabolism; D005786:Gene Expression Regulation; D017127:Glycation End Products, Advanced / Q000378:metabolism; D006801:Humans; D010168:Palmitates / Q000494:pharmacology*; D020286:Pericytes / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D012333:RNA, Messenger / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D000067759:Receptor for Advanced Glycation End Products; D011971:Receptors, Immunologic / Q000235:genetics / Q000378:metabolism; D012160:Retina / Q000166:cytology; D013936:Thymidine / Q000378:metabolism
D005456:Fluorescent Dyes; D017127:Glycation End Products, Advanced; D010168:Palmitates; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D000067759:Receptor for Advanced Glycation End Products; D011971:Receptors, Immunologic; D013936:Thymidine