Differential effects of curcumin on vasoactive factors in the diabetic rat heart.
BACKGROUND
Increased oxidative stress has been associated with the pathogenesis of chronic diabetic complications, including cardiomyopathy. Recent studies indicate that curcumin, a potent antioxidant, may be beneficial in preventing diabetes-induced oxidative stress and subsequent secondary complications. We have investigated the effects of curcumin on the nitric oxide (NO) pathway in cardiac tissues and cultured cells.


METHODS
Streptozotocin-induced diabetic rats were treated with curcumin for a period of one month. Heart tissues were then analyzed for endothelial NO synthase (eNOS) and inducible NO synthase (iNOS) mRNA expression. Oxidative protein and DNA damage were assessed by immunohistochemical analysis of nitrotyrosine and 8-hydroxy-2'-deoxyguanosine (8-OHdG). Heart tissues were further subjected to endothelin-1 (ET-1) mRNA expression. In order to further characterize the effects of curcumin, we assayed microvascular endothelial cells (MVECs). Cultured MVECs, exposed either to glucose or glucose and varying concentrations of curcumin, were assessed for alterations of NOS expression and activation of nuclear factor-kappaB (NF-kappaB) and activating protein-1 (AP-1). Oxidative stress and ET-1 expression levels were also assayed.


RESULTS
Our results indicate that one month of diabetes causes an upregulation of both eNOS and iNOS mRNA levels, and nitrotyrosine and 8-OHdG immunoreactivity in the heart. Treatment of diabetic rats with curcumin reduced eNOS and iNOS levels in association with reduced oxidative DNA and protein damage. Interestingly, curcumin further increased vasoconstrictor ET-1 in the heart. Exposure of MVECs to high glucose increased both eNOS and iNOS levels and oxidative stress. Curcumin prevented NOS alteration and oxidative stress in a dose-dependent manner which was mediated by nuclear factor-kappaB and activating protein-1. Exposure to curcumin also increased ET-1 levels in the MVECs.


CONCLUSIONS
Our studies indicate the differential effects of curcumin in vasoactive factor expression in the heart and indicate the importance of tissue microenvironment in the treatment of diabetic complications.
Farhangkhoee
Hana
H
Department of Pathology, The University of Western Ontario, London, Ontario N6A 5C1, Canada. hfarhang@uwo.ca
Khan
Zia A
ZA
Chen
Shali
S
Chakrabarti
Subrata
S