title: Pyrroloquinoline quinone protects nucleus pulposus cells from hydrogen peroxide-induced apoptosis by inhibiting the mitochondria-mediated pathway.
abstract: OBJECTIVE
  Intervertebral disc cell apoptosis has been suggested to play a key role in promoting disc degeneration, and many studies have shown that the mechanism may be related to oxidative stress. Pyrroloquinoline quinone (PQQ), a redox cofactor for bacterial dehydrogenases, possesses the potential to scavenge reactive oxygen species (ROS) and inhibit cell apoptosis. The objective of this study was to evaluate the effects of PQQ on cultured rat nucleus pulposus (NP) cells under conditions of oxidative injury induced by hydrogen peroxide (H2O2) and to investigate the underlying mechanisms in vitro.
  
  
  METHODS
  Cell viability was determined by CCK8 assay. Changes in the apoptosis rate, intracellular ROS levels and the mitochondrial membrane potential were measured by flow cytometry. Extracellular matrix (ECM)-related proteins (collagen-2 and aggrecan) and apoptosis-related proteins (Bcl-2, Bax, cytochrome c, and caspase-3) were investigated by western blotting.
  
  
  RESULTS
  The results show that NP cells pretreated with PQQ before H2O2 exposure exhibited increased cell viability, decreased ROS formation, maintained mitochondrial membrane potential, and reduced apoptosis. In the presence of PQQ, ECM production was maintained by the cells despite being in an apoptotic environment. In addition, pretreatment with PQQ increased the expression of Bcl-2, inhibited the release of mitochondrial cytochrome c, and decreased the expressions of Bax and cleaved caspase-3.
  
  
  CONCLUSIONS
  Our results suggest that PQQ can protect rat NP cells against oxidative stress via a mitochondria-mediated pathway. PQQ might be useful as a potential pharmaceutical agent in the prevention of intervertebral disc degeneration.
authors.affiliation: Department of Orthopaedics, Zhu Jiang Hospital, Southern Medical University, No. 253, Gongye Big Road, Guangzhou, 510280, China.
authors.forename: Lianjun
authors.initials: L
authors.lastname: Yang
authors.forename: Zijie
authors.initials: Z
authors.lastname: Rong
authors.forename: Mingjun
authors.initials: M
authors.lastname: Zeng
authors.forename: Yanlin
authors.initials: Y
authors.lastname: Cao
authors.forename: Xumeng
authors.initials: X
authors.lastname: Gong
authors.forename: Lijun
authors.initials: L
authors.lastname: Lin
authors.forename: Yong
authors.initials: Y
authors.lastname: Chen
authors.forename: Wei
authors.initials: W
authors.lastname: Cao
authors.forename: Lixin
authors.initials: L
authors.lastname: Zhu
authors.forename: Weiren
authors.initials: W
authors.lastname: Dong
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D016166:Free Radical Scavengers / Q000494:pharmacology*; D006861:Hydrogen Peroxide / Q000009:adverse effects*; D007403:Intervertebral Disc / Q000166:cytology / Q000187:drug effects*; D055959:Intervertebral Disc Degeneration / Q000378:metabolism / Q000517:prevention & control; D008297:Male; D008928:Mitochondria / Q000187:drug effects* / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects*; D045542:PQQ Cofactor / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D016166:Free Radical Scavengers; D017382:Reactive Oxygen Species; D045542:PQQ Cofactor; D006861:Hydrogen Peroxide