title: Early apoptotic vascular signaling is determined by Sirt1 through nuclear shuttling, forkhead trafficking, bad, and mitochondrial caspase activation.
abstract: Complications of diabetes mellitus (DM) weigh heavily upon the endothelium that ultimately affect multiple organ systems. These concerns call for innovative treatment strategies that employ molecular pathways responsible for cell survival and longevity. Here we show in a clinically relevant model of DM with elevated D-glucose that endothelial cell (EC) SIRT1 is vital for the prevention of early membrane apoptotic phosphatidylserine externalization and subsequent DNA degradation supported by studies with modulation of SIRT1 activity and gene knockdown of SIRT1. Furthermore, during elevated D-glucose exposure, we show that SIRT1 is sequestered in the cytoplasm of ECs, but specific activation of SIRT1 shuttles the protein to the nucleus to allow for cytoprotection. The ability of SIRT1 to avert apoptosis employs the activation of protein kinase B (Akt1), the post-translational phosphorylation of the forkhead member FoxO3a, the blocked trafficking of FoxO3a to the nucleus, and the inhibition of FoxO3a to initiate a "pro-apoptotic" program as shown by complimentary gene knockdown studies of FoxO3a. Vascular apoptotic oversight by SIRT1 extends to the direct modulation of mitochondrial membrane permeability, cytochrome c release, Bad activation, and caspase 1 and 3 activation, since inhibition of SIRT1 activity and gene knockdown of SIRT1 significantly accentuate cascade progression while SIRT1 activation abrogates these apoptotic elements. Our work identifies vascular SIRT1 and its control over early apoptotic membrane signaling, Akt1 activation, post-translational modification and trafficking of FoxO3a, mitochondrial permeability, Bad activation, and rapid caspase induction as new avenues for the treatment of vascular complications during DM.
authors.affiliation: Division of Cellular and Molecular Cerebral Ischemia, Wayne State University School of Medicine, Detroit, Michigan 48201, USA.
authors.forename: Jinling
authors.initials: J
authors.lastname: Hou
authors.forename: Zhao Zhong
authors.initials: ZZ
authors.lastname: Chong
authors.forename: Yan Chen
authors.initials: YC
authors.lastname: Shang
authors.forename: Kenneth
authors.initials: K
authors.lastname: Maiese
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D001549:Benzamides / Q000494:pharmacology; D001808:Blood Vessels / Q000166:cytology*; D001921:Brain / Q000166:cytology; D002227:Carbazoles / Q000494:pharmacology; D053148:Caspase 3 / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D045304:Cytochromes c / Q000378:metabolism; D053938:DNA Fragmentation / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D042783:Endothelial Cells / Q000187:drug effects / Q000648:ultrastructure*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors / Q000378:metabolism*; D005947:Glucose / Q000494:pharmacology; D008297:Male; D008928:Mitochondria / Q000187:drug effects / Q000502:physiology; D009284:Naphthols / Q000494:pharmacology; D010718:Phosphatidylserines / Q000378:metabolism; D021381:Protein Transport / Q000187:drug effects; D034741:RNA, Small Interfering / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D000077185:Resveratrol; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D056564:Sirtuin 1 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D013267:Stilbenes / Q000494:pharmacology; D013347:Subcellular Fractions / Q000187:drug effects / Q000378:metabolism; D051025:bcl-Associated Death Protein / Q000378:metabolism*
chemical_list: C550547:6-chloro-2,3,4,9-tetrahydro-1H-carbazole-1-carboxamide; C494821:Bad protein, rat; D001549:Benzamides; D002227:Carbazoles; D004791:Enzyme Inhibitors; C499515:FOXO3 protein, rat; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors; D009284:Naphthols; D010718:Phosphatidylserines; D034741:RNA, Small Interfering; D013267:Stilbenes; D051025:bcl-Associated Death Protein; C439060:sirtinol; D045304:Cytochromes c; D053148:Caspase 3; C488368:Sirt1 protein, rat; D056564:Sirtuin 1; D005947:Glucose; D000077185:Resveratrol