PMID- 32566653
OWN - NLM
STAT- MEDLINE
DCOM- 20210322
LR  - 20210322
IS  - 2314-6141 (Electronic)
IS  - 2314-6133 (Print)
VI  - 2020
DP  - 2020
TI  - Involvement of the G-Protein-Coupled Receptor 4 in the Increased Expression of 
      RANK/RANKL/OPG System and Neurotrophins by Nucleus Pulposus Cells under the 
      Degenerated Intervertebral Disc-Like Acidic Microenvironment.
PG  - 1328436
LID - 10.1155/2020/1328436 [doi]
LID - 1328436
AB  - Intervertebral disc (IVD) degeneration is associated with local inflammation and 
      increased expression of neurotrophins. Acidic microenvironment is believed to 
      cause the progression of IVD degeneration. However, there is a paucity of 
      information regarding the relationship between acidic microenvironment and the 
      inflammation and expression of neurotrophins in IVD. G-protein-coupled receptor 4 
      (GPR4) is a pH-sensing receptor, which can activate the inflammation and increase 
      the expression levels of nerve growth factor in acidic microenvironment. In this 
      study, culture media with pH 7.2 (representing the normal IVD-like acidic 
      condition) and pH 6.5 (degenerated IVD-like acidic condition) were prepared. The 
      gene and protein expression levels of GPR4 in SD rat nucleus pulposus cells were 
      determined under the acidic conditions. And cyclic AMP (cAMP), the second 
      messenger of GPR4, was assayed. Furthermore, the expression levels of receptor 
      activator of nuclear factor kappa B (RANK), RANKL ligand (RANKL), osteoprotegerin 
      (OPG), nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and 
      neurotrophin-3 (NT-3) were also determined. To clarify the involvement of GPR4 in 
      the upregulation of the expression of RANK/RANKL/OPG system and neurotrophins, 
      gene knockdown and forced expression of GPR4 and inhibiting its downstream cAMP 
      accumulation and Ca(2+) mobilization were performed. The alternation of the 
      expression levels of matrix metalloproteinase-3 (MMP-3), MMP-13, and 
      aggrecanase-2 (ADAMTS-5) were evaluated by RT-PCR and western blot. The results 
      showed that GPR4 was expressed in rat nucleus pulposus cells, and the expression 
      was upregulated under the degenerated IVD-like acidic microenvironment. cAMP 
      accumulation levels were increased under the degenerated IVD-like acidic culture 
      conditions. The expression levels of RANK, RANKL, OPG, NGF, and BNDF were 
      significantly upregulated under the degenerated IVD-like acidic microenvironment. 
      GPR4 knockdown and reduction of cAMP by the inhibitor SQ22536 abolished the 
      upregulation of the expression of RANK, RANKL, OPG, NGF, and BNDF under the 
      degenerated IVD-like acidic microenvironment. On the opposite, acidosis-induced 
      cAMP accumulation and upregulation of RANK, RANKL, OPG, NGF, and BNDF were 
      further promoted by GPR4 overexpression. The expression levels of MMP-3, MMP-13, 
      and ADAMTS-5 were upregulated under the degenerated IVD-like acidic condition, 
      which can be promoted or attenuated by GPR4 overexpression or knockdown, 
      respectively. We concluded that GPR4-mediated cAMP accumulation was involved in 
      the increased expression of RANK/RANKL/OPG system and neurotrophins by nucleus 
      pulposus cells under the degenerated IVD-like acidic microenvironment.
CI  - Copyright (c) 2020 Hao Li et al.
FAU - Li, Hao
AU  - Li H
AUID- ORCID: 0000-0002-5274-9350
AD  - Department of Orthopedics, 2nd Affiliated Hospital, School of Medicine, Zhejiang 
      University, Hangzhou, China.
FAU - Liu, Huafei
AU  - Liu H
AD  - Department of Orthopedics, 2nd Affiliated Hospital, School of Medicine, Zhejiang 
      University, Hangzhou, China.
FAU - Zhang, Ning
AU  - Zhang N
AUID- ORCID: 0000-0003-1241-5281
AD  - Department of Orthopedics, 2nd Affiliated Hospital, School of Medicine, Zhejiang 
      University, Hangzhou, China.
FAU - Zhu, Zemin
AU  - Zhu Z
AD  - Department of Orthopaedics, Changxing District of 2nd Affiliated Hospital, School 
      of Medicine, Zhejiang University, Huzhou, China.
LA  - eng
PT  - Journal Article
DEP - 20200529
PL  - United States
TA  - Biomed Res Int
JT  - BioMed research international
JID - 101600173
RN  - 0 (Gpr4 protein, rat)
RN  - 0 (Nerve Growth Factors)
RN  - 0 (Osteoprotegerin)
RN  - 0 (RANK Ligand)
RN  - 0 (Receptor Activator of Nuclear Factor-kappa B)
RN  - 0 (Receptors, G-Protein-Coupled)
RN  - 0 (Tnfrsf11b protein, rat)
RN  - E0399OZS9N (Cyclic AMP)
RN  - SY7Q814VUP (Calcium)
SB  - IM
MH  - Animals
MH  - Calcium/metabolism
MH  - Cells, Cultured
MH  - Cellular Microenvironment/physiology
MH  - Cyclic AMP/metabolism
MH  - Intervertebral Disc Degeneration/*metabolism
MH  - Nerve Growth Factors/*metabolism
MH  - *Nucleus Pulposus/cytology/metabolism
MH  - Osteoprotegerin/metabolism
MH  - RANK Ligand/*metabolism
MH  - Rats
MH  - Rats, Sprague-Dawley
MH  - Receptor Activator of Nuclear Factor-kappa B/metabolism
MH  - Receptors, G-Protein-Coupled/*metabolism
PMC - PMC7277045
COIS- The authors declare that there are no conflicts of interest regarding the 
      publication of this paper.
EDAT- 2020/06/23 06:00
MHDA- 2021/03/23 06:00
PMCR- 2020/05/29
CRDT- 2020/06/23 06:00
PHST- 2020/01/28 00:00 [received]
PHST- 2020/03/22 00:00 [revised]
PHST- 2020/04/01 00:00 [accepted]
PHST- 2020/06/23 06:00 [entrez]
PHST- 2020/06/23 06:00 [pubmed]
PHST- 2021/03/23 06:00 [medline]
PHST- 2020/05/29 00:00 [pmc-release]
AID - 10.1155/2020/1328436 [doi]
PST - epublish
SO  - Biomed Res Int. 2020 May 29;2020:1328436. doi: 10.1155/2020/1328436. eCollection 
      2020.