title: Acid-sensing ion channel 1a regulates the survival of nucleus pulposus cells in the acidic environment of degenerated intervertebral discs.
abstract: OBJECTIVE
  Activation of acid-sensing ion channel 1a (ASIC1a) is responsible for tissue injury caused by acidosis in nervous systems. But its physiological and pathological roles in nucleus pulposus cells (NPCs) are unclear. The aim of this study is to investigate whether ASIC1a regulates the survival of NPCs in the acidic environment of degenerated discs.
  
  
  METHODS
  NPCs were isolated and cultured followed by immunofluorescent staining and Western-blot analysis for ASIC1a. Intracellular calcium ([Ca2+]i) was determined by Ca2+-imaging using Fura-2-AM. Cell necrosis, apoptosis, and senescence following acid exposure were determined using lactate dehydrogenase (LDH) release assay, annexin V-fluorescein isothiocyanate/propidium iodide dual-staining and cell cycle analysis, respectively, followed by Western-blot analysis for apoptosis-related proteins (Bax, Bcl-2, and caspase-3) and senescence-related proteins (p53, p21, and p16). Effects of treatment with psalmotoxin-1 (PcTX1, blocker of ASIC1a) on [Ca2+]iand cell survival were investigated.
  
  
  RESULTS
  ASIC1a was detected in healthy NPCs, and its expression was significantly higher in degenerated cells. When NPCs were treated with PcTX1, acid-induced increases in [Ca2+]iwere significantly inhibited. PcTX1 treatment also resulted in decreased LDH release, cell apoptosis and cell cycle arrest in acid condition. Acid exposure decreased the expression of Bcl-2 and increased the expression of Bax, cleaved caspase-3 and senescence-related proteins (p53, p21, and p16), which was inhibited by PcTX1.
  
  
  CONCLUSIONS
  The present findings suggest that further understanding of ASIC1a functionality may provide not only a novel insight into intervertebral disc biology but also a novel therapeutic target for intervertebral disc degeneration.
authors.affiliation: The Department of Orthopedics, Zhongda Hospital, Medical School of Southeast University, Nanjing, Jiangsu 210009, China.
authors.forename: Feng
authors.initials: F
authors.lastname: Cai
authors.affiliation: The Department of Orthopedics, Zhongda Hospital, Medical School of Southeast University, Nanjing, Jiangsu 210009, China.
authors.forename: Feng
authors.initials: F
authors.lastname: Wang
authors.affiliation: The Department of Orthopedics, Zhongda Hospital, Medical School of Southeast University, Nanjing, Jiangsu 210009, China.
authors.forename: Xin
authors.initials: X
authors.lastname: Hong
authors.affiliation: The Department of Orthopedics, Zhongda Hospital, Medical School of Southeast University, Nanjing, Jiangsu 210009, China.
authors.forename: Xin-Hui
authors.initials: XH
authors.lastname: Xie
authors.affiliation: The Department of Orthopedics, Zhongda Hospital, Medical School of Southeast University, Nanjing, Jiangsu 210009, China.
authors.forename: Rui
authors.initials: R
authors.lastname: Shi
authors.affiliation: The Department of Orthopedics, Zhongda Hospital, Medical School of Southeast University, Nanjing, Jiangsu 210009, China.
authors.forename: Zhi-Yang
authors.initials: ZY
authors.lastname: Xie
authors.affiliation: The Department of Orthopedics, Zhongda Hospital, Medical School of Southeast University, Nanjing, Jiangsu 210009, China.
authors.forename: Xiao-Tao
authors.initials: XT
authors.lastname: Wu
keywords: Acid-sensing ion channel 1a; Acidic; Apoptosis; Intervertebral disc; Nucleus pulposus cells; Senescence; degeneration