R_U_SQ_XU_Adiponectin

Original Article Adiponectin Suppression of High-Glucose–Induced Reactive Oxygen Species in Vascular Endothelial Cells Evidence for Involvement of a cAMP Signaling Pathway Raogo Ouedraogo, 1 Xiangdong Wu, 1 Shi-Qiong Xu, 1 Lauren Fuchsel, 1 Hiroyuki Motoshima, 1 Kalyankar Mahadev, 1 Kelly Hough, 1 Rosario Scalia, 2 and Barry J. Goldstein 1 Adiponectin is an abundant adipocyte-derived plasma protein with antiatherosclerotic effects. Vascular signal trans- duc tion by adi pon ectin is poo rly und erstood and may invol ve 5 -AMP –act ivated prot ein kinas e (AMP K), cAMP signaling, and other pathways. Hyperglycemia sharply increases the production of reactive oxygen species (ROS), which play a key role in endothelial dysfunction in diabetes. Because the rec ombi nant globular domain of huma n adip onec tin (gAd ) reduces the gene ration of endo thel ial ROS ind uce d by oxi diz ed LDL, we sought to deter mine whether adiponectin could also suppress ROS production induced by high glucose in cultured human umbilical vein endothel ial cells. Incubat ion in 25 mmol/l glucose for 16 h incr ease d ROS produ ction 3.8-fold ( P < 0.0 5), usi ng a luminol ass ay. Treatment wit h gAd for 16 h sup pre sse d gluc ose- induc ed ROS in a dose -dep ende nt manner up to 81% at 300 nmol/l ( P < 0.05). The AMPK activator 5-ami- noimidazole-4-carboxamide-1- -D-ribofuranoside (AICAR; 1 mmol /l, 16 h) only parti ally dec reas ed gluc ose- induc ed ROS by 22% ( P < 0.05 ). Cell pretreatment with AMPK inhibitors , howe ver, failed to bloc k the eff ect of gAd to suppress glucose-induced ROS, suggesting that the action of gAd was independent of AMPK. Interestingly, activation of cAMP signaling by treatment with forskolin (2 mol/l) or dibut yryl- cAMP (0.5 mmol /l) reduced gluc ose- induc ed ROS genera tion by 43 and 67%, respe ctiv ely (both P < 0.05). Incubation with the cAMP-dependent protein kinase (PKA) inhibitor H-89 (1 mol/l) fully abrogated the effect of gAd, but not that of AICAR, on ROS induced by glucose. gAd also increased cellula r cAMP conte nt by 70% in an AMPK-independent manner. Full-length adiponectin puri- fied from a eukaryotic expression system also suppressed ROS induced by high glucose or by treatment of endothelial cells wit h oxi diz ed LDL. Thus, adi pon ect in sup pre sse s excess ROS production under high-glucose conditions via a cAMP/PKA-dependent pathway, an effect that has implica- tions for vas cul ar protec tio n in dia bet es. Diabetes 55: 1840–1846, 2006 A dipo nectin is an abundant adipocyte- der ived circulating plasma protein with insulin-sensitiz- ing metabol ic ef fects and vascul ar protec tive pr operti es (1–4). Low adi pone ctin levels are associated with endothelial dysfunction (5–7) and a pre- disposition to vascular injury (8–11). In cultured endothelial cells, adiponectin has been shown to exhibit various anti-inflammatory effects, in particular those that counter the adverse cel lul ar influ ences of increa sed oxi dati ve stress or stimulation with cytokines such as tumor necrosis factor- (TNF-) (2). Adiponectin binds to the walls of cathete r-inju red vessels (12,13) and inhibits the expres - sion of several adhesion molecules, including vascular cell adhesion molecul e-1, E-sel ectin, and intrac ellular adhesion mole cul e-1 induced by the cyt okin e TNF- , and it reverses the adhesion of human monocytic THP-1 cells to cultured endothelial cells (14) and enhances nitric oxide (NO) production by endothelial cells (15,16). Although the metabolic effects of adiponectin in a variety of cell types have been closely associated with activation of 5-AMP– activated protein kinase (AMPK) (17 –19), diverse pat h- ways have been implicated in adiponectin signaling in the vasculature (2). Hyperglycemi a is a key factor in the develo pment of vascular comp licatio ns in pat ients with diabet es (20 ). Hyperglycemia sharply increases the production of reactive oxygen species (ROS), which pl ay a key role in endothelial dysfunction in diabetes (21,22). Systemic and vascular ROS production lead to reduced endothelial NO bioactivity, increased expression of cell surface adhesion molecules, and inflammatory changes that contribute to micr ovascular and macrovasc ular damage (23–27 ). Al- thou gh mos t studies have linked the sal utar y ef fects of adiponectin with obesity-linked insulin resistance and type 2 diabete s, epid emi olog ical dat a has als o implicated a potential role for adiponectin in coronary artery disease in type 1 diabetes (28). Recently, two studies (29,30) have also demonstrated a negative ass oci atio n between adiponectin and oxidative stress in human subjects, suggesting the possibil ity that one of the syst emic ef fects of adiponectin is to suppress ROS generation. From the 1 Dorrance Hamilton Research Laboratories, Division of Endocrinol- ogy, Diab etes and Meta bolic Disease s, Depa rtmen t of Medi cine, Jef ferso n Medical College of Thomas Jefferson University, Philadelphia, Pennsylvania; and the 2 Depa rtmen t of Phys iolog y, Jef ferso n Medical Colle ge of Thoma s Jefferson University, Philadelphia, Pennsylvania. Address correspondence and reprint requests to Barry J. Goldstein, MD, PhD, Director, Division of Endocrinology, Diabetes and Metabolic Diseases, Department of Medicine, Jefferson Medical College, Suite 349, 1020 Locust St., Philadelphia, PA 19107. E-mail: [email protected]. Received for publication 7 September 2005 and accepted in revised form 10 March 2006. AICAR, 5-aminoimidaz ole-4-carboxamide- 1- -D-ribof uran oside; AMPK, 5- AMP–activated protein kinase; ara-A, adenine-9- -D-arabinofuranoside; BAEC, bovine aorti c endothelial cell; fAd, full- lengt h adiponectin prote in; gAd, globular domain of human adiponectin; HUVEC, human umbilical vein endo- theli al cell; PKA, cAMP-depe ndent protein kinase; ROS, reactive oxygen species; TNF-, tumor necrosis factor-. DOI: 10.2337/db05-1174 © 2006 by the American Diabetes Association. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. 1840 DIABETES, VOL. 55, JUNE 2006

R_U_SQ_XU_Adiponectin

Documents

Transcript of R_U_SQ_XU_Adiponectin