PMID- 29608906 OWN - NLM STAT- MEDLINE DCOM- 20190325 LR - 20200306 IS - 1096-0007 (Electronic) IS - 0014-4835 (Print) IS - 0014-4835 (Linking) VI - 178 DP - 2019 Jan TI - Excess homocysteine upregulates the NRF2-antioxidant pathway in retinal Muller glial cells. PG - 228-237 LID - S0014-4835(18)30139-8 [pii] LID - 10.1016/j.exer.2018.03.022 [doi] AB - This study evaluated the effects of elevated homocysteine (Hcy) on the oxidative stress response in retinal Muller glial cells. Elevated Hcy has been implicated in retinal diseases including glaucoma and optic neuropathy, which are characterized by retinal ganglion cell (RGC) loss. To understand the mechanisms of Hcy-induced RGC loss, in vitro and in vivo models have been utilized. In vitro isolated RGCs are quite sensitive to elevated Hcy levels, while in vivo murine models of hyperhomocysteinemia (HHcy) demonstrate a more modest RGC loss ( approximately 20%) over a period of many months. This differential response to Hcy between isolated cells and the intact retina suggests that the retinal milieu invokes mechanisms that buffer excess Hcy. Oxidative stress has been implicated as a mechanism of Hcy-induced neuron loss and NRF2 is a transcription factor that plays a major role in regulating cytoprotective responses to oxidative stress. In the present study we investigated whether HHcy upregulates NRF2-mediated stress responses in Muller cells, the chief retinal glial cell responsible for providing trophic support to retinal neurons. Primary Muller cells were exposed to L-Hcy-thiolactone [50muM-10mM] and assessed for viability, reactive oxygen species (ROS), and glutathione (GSH) levels. Gene/protein levels of Nrf2 and levels of NRF2-regulated antioxidants (NQO1, CAT, SOD2, HMOX1, GPX1) were assessed in Hcy-exposed Muller cells. Unlike isolated RGCs, isolated Muller cells are viable over a wide range of Hcy concentrations [50 muM - 1 mM]. Moreover, when exposed to elevated Hcy, Muller cells demonstrate decreased oxidative stress and decreased ROS levels. GSH levels increased by approximately 20% within 24 h exposure to Hcy. Molecular analyses revealed 2-fold increase in Nrf2 expression. Expression of antioxidant genes Nqo1, Cat, Sod2, Hmox1, Gpx1 increased significantly. The consequences of Hcy exposure were evaluated also in Muller cells harvested from Nrf2(-/-) mice. In contrast to WT Muller cells, in which oxidative stress decreased upon exposure to Hcy, the Nrf2(-/-) Muller cells showed a significant increase in oxidative stress. Our data suggest that at least during early stages of Hhcy, a cytoprotective response may be in place, mediated in part by NRF2 in Muller cells. CI - Copyright (c) 2018 Elsevier Ltd. All rights reserved. FAU - Navneet, Soumya AU - Navneet S AD - Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, Augusta, GA, United States; James and Jean Culver Vision Discovery Institute, Augusta University, Augusta, GA, United States. FAU - Cui, Xuezhi AU - Cui X AD - Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, Augusta, GA, United States; James and Jean Culver Vision Discovery Institute, Augusta University, Augusta, GA, United States. FAU - Zhao, Jing AU - Zhao J AD - Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, Augusta, GA, United States; James and Jean Culver Vision Discovery Institute, Augusta University, Augusta, GA, United States. FAU - Wang, Jing AU - Wang J AD - Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, Augusta, GA, United States; James and Jean Culver Vision Discovery Institute, Augusta University, Augusta, GA, United States. FAU - Kaidery, Navneet Ammal AU - Kaidery NA AD - Department of Pharmacology and Toxicology, Medical College of Georgia, Augusta University, Augusta, GA, United States. FAU - Thomas, Bobby AU - Thomas B AD - Department of Pharmacology and Toxicology, Medical College of Georgia, Augusta University, Augusta, GA, United States. FAU - Bollinger, Kathryn E AU - Bollinger KE AD - Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, Augusta, GA, United States; James and Jean Culver Vision Discovery Institute, Augusta University, Augusta, GA, United States; Department of Ophthalmology, Medical College of Georgia, Augusta University, Augusta, GA, United States. FAU - Yoon, Yisang AU - Yoon Y AD - Department of Physiology, Medical College of Georgia, Augusta University, Augusta, GA, United States. FAU - Smith, Sylvia B AU - Smith SB AD - Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, Augusta, GA, United States; James and Jean Culver Vision Discovery Institute, Augusta University, Augusta, GA, United States; Department of Ophthalmology, Medical College of Georgia, Augusta University, Augusta, GA, United States. Electronic address: sbsmith@augusta.edu. LA - eng GR - R01 EY012830/EY/NEI NIH HHS/United States GR - R01 EY027406/EY/NEI NIH HHS/United States GR - R01 EY028103/EY/NEI NIH HHS/United States GR - R01 NS101967/NS/NINDS NIH HHS/United States PT - Journal Article PT - Research Support, N.I.H., Extramural PT - Research Support, Non-U.S. Gov't DEP - 20180331 PL - England TA - Exp Eye Res JT - Experimental eye research JID - 0370707 RN - 0 (NF-E2-Related Factor 2) RN - 0 (Nfe2l2 protein, mouse) RN - 0 (Radiation-Protective Agents) RN - 0LVT1QZ0BA (Homocysteine) RN - D5H88XF24X (homocysteine thiolactone) RN - GAN16C9B8O (Glutathione) SB - IM MH - Animals MH - Antioxidant Response Elements/physiology MH - Cell Survival MH - Ependymoglial Cells/*drug effects/metabolism/pathology MH - Glutathione/metabolism MH - Homocysteine/*analogs & derivatives/pharmacology MH - Mice MH - Mice, Inbred C57BL MH - NF-E2-Related Factor 2/genetics/*metabolism MH - Oxidative Stress/drug effects MH - Radiation-Protective Agents/*pharmacology MH - Up-Regulation PMC - PMC6167214 MID - NIHMS956689 OTO - NOTNLM OT - Exfoliative glaucoma OT - Hyperhomocysteinemia OT - Mouse OT - Optic neuropathy OT - Oxidative stress OT - Retinal glial cells EDAT- 2018/04/03 06:00 MHDA- 2019/03/26 06:00 PMCR- 2020/01/01 CRDT- 2018/04/03 06:00 PHST- 2018/02/21 00:00 [received] PHST- 2018/03/14 00:00 [revised] PHST- 2018/03/22 00:00 [accepted] PHST- 2018/04/03 06:00 [pubmed] PHST- 2019/03/26 06:00 [medline] PHST- 2018/04/03 06:00 [entrez] PHST- 2020/01/01 00:00 [pmc-release] AID - S0014-4835(18)30139-8 [pii] AID - 10.1016/j.exer.2018.03.022 [doi] PST - ppublish SO - Exp Eye Res. 2019 Jan;178:228-237. doi: 10.1016/j.exer.2018.03.022. Epub 2018 Mar 31.