title: Intermittent hypoxia reduces microglia proliferation and induces DNA damage in vitro.
abstract: OBJECTIVE
  Intermittent hypoxia (IH), caused by obstructive sleep apnea (OSA), could cause hippocampus or neuron damage through multiple signaling pathways, while the underlying mechanisms are still unclear. Thus, the present study aimed to explore the effect of IH on the biological functions of microglia cells.
  
  
  METHODS
  Cell proliferation of BV2 cells after exposure to IH were observed by MTT assay and then DNA damage was detected by comet assay. RNA-sequencing assay was performed in cells under IH condition and normal conditions to find out the differentially expressed genes, which were further confirmed by reverse transcriptase polymerase chain reaction (RT-PCR) and Western blot assay.
  
  
  RESULTS
  As results, IH inhibited the proliferation of BV2 cells, as well as caused DNA damage. RNA-sequencing assay revealed 4 differentially expressed genes (p21, Cyclin D1, Cyclin E2, and Gadd45α) which were associated with the network of P53 signaling pathways in BV2 cells, among which, p21 and Gadd45α were dramatically increased while Cyclin D1 and Cyclin E2 were both decreased significantly. Moreover, inflammatory factors including IL-6, TNF-α and iNOS were significantly up-regulated in microglia cells under IH conditions for 8 hr.
  
  
  CONCLUSIONS
  Our results indicated that IH could inhibit cyclin D1 and cyclin E2 expression via initiating multiple P53 pathways, which further blocked cell cycle transition and attenuated proliferative capability of BV2 cells. Meanwhile, IH activated inflammation reactions in BV2 cells. Present study elaborate the effects of IH on biological functions of microglia and provide theoretical foundation for further study on new therapy methods for OSA.
authors.affiliation: Department of Respiratory Medicine, Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China, 200092.
authors.forename: Song
authors.initials: S
authors.lastname: Liu
authors.affiliation: Department of Medical Oncology, Fudan University Shanghai Cancer Center; Department of Oncology, Shanghai Medical College, Fudan University, Shanghai, China, 200032.
authors.forename: Zhonghua
authors.initials: Z
authors.lastname: Wang
authors.affiliation: Department of Respiratory Medicine, Beijing Friendship Hospital, Capital Medical University, Beijing, China, 100050.
authors.forename: Bo
authors.initials: B
authors.lastname: Xu
authors.affiliation: Department of Neurology, Beijing Friendship Hospital, Capital Medical University, Beijing, China, 100050.
authors.forename: Kui
authors.initials: K
authors.lastname: Chen
authors.affiliation: Department of Respiratory Medicine, Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China, 200092.
authors.forename: Jinyuan
authors.initials: J
authors.lastname: Sun
authors.affiliation: Department of Respiratory Medicine, Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China, 200092.
authors.forename: Lianping
authors.initials: L
authors.lastname: Ren
keywords: Inflammatory cytokine; Intermittent hypoxia; Microglia; P53 signaling pathways