title: Hyperhomocysteinemia causes ER stress and impaired autophagy that is reversed by Vitamin B supplementation.
abstract: Hyperhomocysteinemia (HHcy) is a well-known risk factor for stroke; however, its underlying molecular mechanism remains unclear. Using both mouse and cell culture models, we have provided evidence that impairment of autophagy has a central role in HHcy-induced cellular injury in the mouse brain. We observed accumulation of LC3B-II and p62 that was associated with increased MTOR signaling in human and mouse primary astrocyte cell cultures as well as a diet-induced mouse model of HHcy, HHcy decreased lysosomal membrane protein LAMP2, vacuolar ATPase (ATP6V0A2), and protease cathepsin D, suggesting that lysosomal dysfunction also contributed to the autophagic defect. Moreover, HHcy increased unfolded protein response. Interestingly, Vitamin B supplementation restored autophagic flux, alleviated ER stress, and reversed lysosomal dysfunction due to HHCy. Furthermore, the autophagy inducer, rapamycin was able to relieve ER stress and reverse lysosomal dysfunction caused by HHcy in vitro. Inhibition of autophagy by HHcy exacerbated cellular injury during oxygen and glucose deprivation and reperfusion (OGD/R), and oxidative stress. These effects were prevented by Vitamin B co-treatment, suggesting that it may be helpful in relieving detrimental effects of HHcy in ischemia/reperfusion or oxidative stress. Collectively, these findings show that Vitamin B therapy can reverse defects in cellular autophagy and ER stress due to HHcy; and thus may be a potential treatment to reduce ischemic damage caused by stroke in patients with HHcy.
authors.affiliation: Laboratory of Hormonal Regulation, Cardiovascular and Metabolic Disorders Program, Duke-NUS Medical School, Singapore 169857, Singapore.|Stroke Trial Unit, Department of Neurology, Singapore General Hospital, Outram Road, Singapore 169608, Singapore.|National Neuroscience Institute, 11 Jalan Tan Tock Seng, Singapore 308433, Singapore.
authors.forename: Madhulika
authors.initials: M
authors.lastname: Tripathi
authors.affiliation: National Neuroscience Institute, 11 Jalan Tan Tock Seng, Singapore 308433, Singapore.
authors.forename: Cheng Wu
authors.initials: CW
authors.lastname: Zhang
authors.affiliation: Laboratory of Hormonal Regulation, Cardiovascular and Metabolic Disorders Program, Duke-NUS Medical School, Singapore 169857, Singapore.
authors.forename: Brijesh Kumar
authors.initials: BK
authors.lastname: Singh
authors.affiliation: Laboratory of Hormonal Regulation, Cardiovascular and Metabolic Disorders Program, Duke-NUS Medical School, Singapore 169857, Singapore.
authors.forename: Rohit Anthony
authors.initials: RA
authors.lastname: Sinha
authors.affiliation: Newcastle University Medicine Malaysia (NUMed, Malaysia) No. 1 Jalan Sarjana, Iskandar Puteri (formerly Nusajaya), Johor 179200, Malaysia.
authors.forename: Kyaw Thu
authors.initials: KT
authors.lastname: Moe
authors.affiliation: Stroke Trial Unit, Department of Neurology, Singapore General Hospital, Outram Road, Singapore 169608, Singapore.|National Neuroscience Institute, 11 Jalan Tan Tock Seng, Singapore 308433, Singapore.
authors.forename: Deidre Anne
authors.initials: DA
authors.lastname: DeSilva
authors.affiliation: Laboratory of Hormonal Regulation, Cardiovascular and Metabolic Disorders Program, Duke-NUS Medical School, Singapore 169857, Singapore.
authors.forename: Paul Michael
authors.initials: PM
authors.lastname: Yen
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D001343:Autophagy / Q000187:drug effects*; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D004032:Diet; D019587:Dietary Supplements; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects*; D005492:Folic Acid / Q000494:pharmacology; D005947:Glucose / Q000172:deficiency; D006801:Humans; D020138:Hyperhomocysteinemia / Q000188:drug therapy / Q000473:pathology*; D008247:Lysosomes / Q000187:drug effects / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008869:Microtubule-Associated Proteins; D008954:Models, Biological; D018384:Oxidative Stress / Q000187:drug effects; D010100:Oxygen; D015427:Reperfusion Injury / Q000473:pathology; D000071456:Sequestosome-1 Protein / Q000378:metabolism; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism; D014805:Vitamin B 12 / Q000494:pharmacology* / Q000627:therapeutic use
chemical_list: C480860:Map1lc3b protein, mouse; D008869:Microtubule-Associated Proteins; D000071456:Sequestosome-1 Protein; C101343:Sqstm1 protein, mouse; D005492:Folic Acid; D058570:TOR Serine-Threonine Kinases; D005947:Glucose; D014805:Vitamin B 12; D010100:Oxygen