PMID- 19165496 OWN - NLM STAT- MEDLINE DCOM- 20090603 LR - 20211020 IS - 1435-702X (Electronic) IS - 0721-832X (Linking) VI - 247 IP - 5 DP - 2009 May TI - Rac1 activates HIF-1 in retinal pigment epithelium cells under hypoxia. PG - 633-9 LID - 10.1007/s00417-008-1031-0 [doi] AB - BACKGROUND: Upregulation of vascular endothelial growth factor (VEGF) in hypoxic retinal pigment epithelium (RPE) cells, mediated by hypoxia-inducible factor-1 (HIF-1) is responsible for choroidal neovascularization (CNV). HIF-1alpha is the inducible subunit of HIF-1, but the underlying mechanisms by which RPE cells sense a decrease in oxygen concentration and transduce this signal to HIF-1alpha are largely unknown. Rho family small GTPase Rac1, as a potential intermediate, possibly plays a pivotal role in activating HIF-1alpha in RPE cells under hypoxia. AIMS: To further define Rac1 playing an essential role in the induction of HIF-1alpha expression in RPE cells under hypoxia. METHODS: In this study, we examined the expression of HIF-1alpha and Rac1 in human RPE cells under hypoxia for 0, 1, 2, 4, 8, 12 and 24 h by RT-PCR and Western blot. To elucidate whether Rac1 is responsible for activating the expression of hypoxia-induced HIF-1alpha, human RPE cells were treated with Rac1 inhibitor NSC23766 under hypoxia for 0, 1, 2, 4, 8, 12 and 24 h, and expression of HIF-1alpha and Rac1 measured by RT-PCR and Western blot. RESULTS: The mRNA expression of HIF-1alpha and Rac1 in RPE cells significantly increased in a time-dependent manner, reaching the maximum at 4 h, and thereafter slowly declined. HIF-1alpha protein induction in human RPE cells was found after 1 h of hypoxia, reaching the maximum at 8 h, and then slowly declined. In response to hypoxia, the levels of Rac1 protein significantly increased, reaching the maximum at 4 h, and then slowly declined. After treatment with NSC23766, both HIF-1alpha and Rac1 expression were significantly inhibited in hypoxic RPE cells. CONCLUSIONS: Rac1 is crucial to activate HIF-1 in RPE cells under hypoxia, which may be a novel target other than VEGF and HIF-1 in developing CNV inhibitors. FAU - Zhang, Peng AU - Zhang P AD - Department of Ophthalmology, Xijing Hospital, Fourth Military Medical University, Xi'an, Shaanxi Province, 710032, PR China. FAU - Zhang, Xing AU - Zhang X FAU - Hao, Xiaofeng AU - Hao X FAU - Wang, Yusheng AU - Wang Y FAU - Hui, Yannian AU - Hui Y FAU - Wang, Haiyan AU - Wang H FAU - Hu, Dan AU - Hu D FAU - Zhou, Jian AU - Zhou J LA - eng PT - Journal Article PT - Research Support, Non-U.S. Gov't DEP - 20090123 PL - Germany TA - Graefes Arch Clin Exp Ophthalmol JT - Graefe's archive for clinical and experimental ophthalmology = Albrecht von Graefes Archiv fur klinische und experimentelle Ophthalmologie JID - 8205248 RN - 0 (Aminoquinolines) RN - 0 (HIF1A protein, human) RN - 0 (Hypoxia-Inducible Factor 1, alpha Subunit) RN - 0 (NSC 23766) RN - 0 (Pyrimidines) RN - 0 (RAC1 protein, human) RN - 0 (RNA, Messenger) RN - EC 3.6.5.2 (rac1 GTP-Binding Protein) SB - IM MH - Aminoquinolines/pharmacology MH - Blotting, Western MH - Cells, Cultured MH - Down-Regulation MH - Gene Expression Regulation/*physiology MH - Humans MH - Hypoxia/*metabolism MH - Hypoxia-Inducible Factor 1, alpha Subunit/antagonists & inhibitors/*genetics/metabolism MH - Immunoenzyme Techniques MH - Pyrimidines/pharmacology MH - RNA, Messenger/metabolism MH - Retinal Pigment Epithelium/drug effects/*metabolism MH - Reverse Transcriptase Polymerase Chain Reaction MH - Time Factors MH - rac1 GTP-Binding Protein/antagonists & inhibitors/*physiology EDAT- 2009/01/24 09:00 MHDA- 2009/06/06 09:00 CRDT- 2009/01/24 09:00 PHST- 2008/08/18 00:00 [received] PHST- 2008/12/22 00:00 [accepted] PHST- 2008/12/10 00:00 [revised] PHST- 2009/01/24 09:00 [entrez] PHST- 2009/01/24 09:00 [pubmed] PHST- 2009/06/06 09:00 [medline] AID - 10.1007/s00417-008-1031-0 [doi] PST - ppublish SO - Graefes Arch Clin Exp Ophthalmol. 2009 May;247(5):633-9. doi: 10.1007/s00417-008-1031-0. Epub 2009 Jan 23.