Fenofibrate regulates retinal endothelial cell survival through the AMPK signal transduction pathway
Introduction
Fibric acid derivatives, which are peroxisome proliferator-activated receptor α (PPARα) agonists, have beneficial effects on lipid profiles, including lowering triglycerides and increasing high-density lipoprotein cholesterol, and in reducing coronary vascular events in large clinical trials (Frick et al., 1997, Robins et al., 2003). Treatment with fenofibrate, one of the most widely used fibric acid derivatives, reduces the angiographic progression of coronary artery disease in type 2 diabetes (Diabetes Atherosclerosis Intervention Study Investigators, 2001). Fenofibrates also improved endothelial dysfunction in patients with type 2 diabetes with dyslipidemia (Playford et al., 2002). The mechanisms for the vascular benefit of fenofibrates are unclear, but probably involve direct anti-inflammatory effects including the modulation of the expression of several cytokines and adhesion molecules and anti-atherosclerotic effects (Israelian-Konaraki and Reaven, 2005).
AMP-activated protein kinase (AMPK) is a ubiquitously expressed enzyme whose activity is increased by adipocyte-derived hormones, including leptin and adiponectin, as well as by pathological stresses such as hypoxia, glucose deprivation, and hyperosmolarity (Hardie and Carling, 1997, Carling, 2004). Activated AMPK phosphorylates multiple target genes, including several biosynthetic enzymes such as acetyl-CoA carboxylase (ACC), hydroxymethylglutaryl-CoA reductase, glycogen synthase, and endothelial nitric oxide synthase (eNOS) (Chen et al., 1999). AMPK has an important role in the cardiovascular protection. For example, AMPK activation by α-lipoic acid prevents endothelial dysfunction in insulin-resistant rats (Lee et al., 2005). AMPK also protects against myocardial injury and apoptosis in the ischemic heart (Russell et al., 2004, Shibata et al., 2005). A recent study suggests that fenofibrate activates AMPK and increases eNOS phosphorylation in human umbilical vein endothelial cells (Murakami et al., 2006). However, the effect of fenofibrate on endothelial cell survival has not been fully investigated. The objectives of the present study were to examine whether fenofibrate activates AMPK and promotes anti-apoptotic effects in human retinal endothelial cells. We found that the AMPK signaling plays an important role in the fenofibrate-mediated endothelial cell survival.
Section snippets
Reagents
Fenofibrate and WY-14643 were purchased from Sigma Chemical Co. (St Louis, MO). MK 886 was obtained from Alexis Biochemicals (San Diego, CA). Compound C was from Calbiochem. (La Jolla, CA). Fenofibrate, WY-14643, MK 886, and Compound C were dissolved in dimethyl sulfoxide (DMSO). Antibodies against AMPK, p-AMPK-α-Thr172, ACC, p-ACC-Ser79 were from Cell Signaling Technology (Beverly, MA). Endothelial basal medium (EBM-2) and endothelial cell growth medium (EGM-2) were from Cambrex (East
Fenofibrate protects HRECs from serum deprivation-induced apoptosis
Serum deprivation caused cell death in HRECs, as evidenced by more floating and less adherent cells seen with phase-contrast microscopy (Fig. 1A). Approximately 40% of total cells undergo cell death at 36 h during serum deprivation. As shown in Fig. 1B, addition of fenofibrate (10–50 μM) reversed the serum deprivation associated cell death in a concentration-dependent manner (P < 0.01). To verify that cell death was mediated by apoptosis, cells were subjected to DAPI staining. As shown in Fig. 1C,
Discussion
In the present study, we demonstrated that in HRECs fenofibrate is anti-apoptotic and its action is mediated in part by AMPK signaling. The survival of endothelial cells is critical for the maintenance of microvascular integrity. It has been reported that retinal endothelial cells die prematurely and undergo apoptosis in both human and experimental diabetes (Mizutani et al., 1996). Acellular or nonperfused capillaries can lead to sight-threatening proliferative retinopathy. A recent report has
Acknowledgements
We thank Professor E. Dale Abel and Dr. Adam R. Wende of the School of Medicine, University of Utah for critically reading the manuscript, and Dr. Jeong-Ki Min of the Department of Biochemistry College of Sciences, Yonsei University for very helpful discussion and advice. This work was supported by the Korea Research Foundation Grant funded by the Korean Government (KRF-2005-003-E00104).
References (44)
- et al.
The AMP-activated protein kinase prevents ceramide synthesis de novo and apoptosis in astrocytes
FEBS Lett.
(2001) The AMP-activated protein kinase cascade—a unifying system for energy control
Trends Biochem. Sci.
(2004)- et al.
AMP-activated protein kinase phosphorylation of endothelial NO synthase
FEBS Lett
(1999) - et al.
Vascular endothelial growth factor induces expression of the antiapoptotic proteins Bcl-2 and A1 in vascular endothelial cells
J. Biol. Chem.
(1998) - et al.
A role for caspase-1 in serum withdrawal-induced apoptosis of endothelial cells
Lab. Invest.
(2003) - et al.
Critical roles of AMP-activated protein kinase in the carcinogenic metal-induced expression of VEGF and HIF-1 proteins in DU145 prostate carcinoma
Biochem. Pharmacol.
(2006) - et al.
Growth inhibition and apoptosis in human Philadelphia chromosome-positive lymphoblastic leukemia cell lines by treatment with the dual PPARalpha/gamma ligand TZD18
Blood
(2006) - et al.
Sustained activation of AMP-activated protein kinase induces c-Jun N-terminal kinase activation and apoptosis in liver cells
FEBS Lett
(2002) - et al.
NFkappaB regulates plasma apolipoprotein A-I and high density lipoprotein cholesterol through inhibition of peroxisome proliferator-activated receptor alpha
J. Biol. Chem.
(2003) - et al.
Fenofibrate activates AMPK and increases eNOS phosphorylation in HUVEC
Biochem. Biophys. Res. Commun.
(2006)
Fibrate prevents cisplatin-induced proximal tubule cell death
Kidney Int.
Effect of fenofibrate on brachial artery flow-mediated dilatation in type 2 diabetes mellitus
Am. J. Cardiol.
Marked induction of the IAP family antiapoptotic proteins survivin and XIAP by VEGF in vascular endothelial cells
Biochem. Biophys. Res. Commun.
Vascular endothelial growth factors and angiogenesis in eye disease
Prog. Retin. Eye Res.
Glucose deprivation increases mRNA stability of vascular endothelial growth factor through activation of AMP-activated protein kinase in DU145 prostate carcinoma
J. Biol. Chem.
Vascular endothelial growth factor acts as a survival factor for newly formed retinal vessels and has implications for retinopathy of prematurity
Nat. Med.
Activation of the AMP-activated kinase by antidiabetes drug metformin stimulates nitric oxide synthesis in vivo by promoting the association of heat shock protein 90 and endothelial nitric oxide synthase
Diabetes
Effect of fenofibrate on progression of coronary-artery disease in type 2 diabetes: the Diabetes Atherosclerosis Intervention Study, a randomised study
Lancet
Oxidative stress inactivates VEGF survival signaling in retinal endothelial cells via PI 3-kinase tyrosine nitration
J. Cell Sci.
Role of vascular endothelial growth factor in regulation of physiological angiogenesis
Am. J. Physiol. Cell. Physiol.
Prevention of the angiographic progression of coronary and vein-graft atherosclerosis by gemfibrozil after coronary bypass surgery in men with low levels of HDL cholesterol. Lopid Coronary Angiography Trial (LOCAT) Study Group
Circulation
Akt promotes survival of cardiomyocytes in vitro and protects against ischemia-reperfusion injury in mouse heart
Circulation
Cited by (101)
Autophagy-nutrient sensing pathways in diabetic complications
2022, Pharmacological ResearchMetronomic anti-angiogenesis: The ideal companion of pH-centered treatments
2020, An Innovative Approach to Understanding and Treating Cancer: Targeting pH: From Etiopathogenesis to New Therapeutic AvenuesFenofibrate improves vascular endothelial function in diabetic mice
2019, Biomedicine and PharmacotherapyCitation Excerpt :In addition, AMPK was indicated as a drug target for diabetes mellitus, and previous experiments reported that fenofibrate can activate AMPK [54]. Activation of AMPK by fenofibrate could prevent apoptotic cell death induced by serum deprivation [55]. Although, the effect of fenofibrate on eNOS has been described in previous studies, and other studies have shown that fenofibrate normalizes endothelium-dependent relaxation in diabetic mice aortas through activating PPAR/LKB1/AMPK/eNOS signaling pathway, there has been no further verification at the cell level [56,14].
A non-invasive, multi-target approach to treat diabetic retinopathy
2019, Biomedicine and PharmacotherapyFenofibrate improves vascular endothelial function and contractility in diabetic mice
2019, Redox BiologyCitation Excerpt :We found that fenofibrate administration increased the protein expression of PPARα and AMPKα phosphorylation in aortas from diabetic mice. This result was consistent with previous cell experiments reporting that fenofibrate has a role in AMPKα activation [19,20], but the mechanism by which fenofibrate activates AMPK is poorly defined. Interestingly, a potentially important observation in our study is that fenofibrate administration upregulated LKB1 by transferring from the nucleus to the cytoplasm and increased phosphorylation of LKB1, thus activating AMPK in the cytosol.