Atypical P2X receptor pharmacology in two human osteoblast-like cell lines
S M Alqallaf1, B A J Evans, E J Kidd
1Welsh School of Pharmacy, Cardiff University, King Edward VII Avenue, Cardiff, UK.
Background And Purpose:
The expression and function of P2X(7) receptors in osteoclasts is well established, but less is known about their role in osteoblast-like cells. A study in P2X(7) receptor knockout mice suggested the involvement of these receptors in bone formation. We have investigated the expression and pharmacology of several P2X receptors in two human osteosarcoma cell lines to see if they could be involved in bone turnover in man.
Experimental Approach:
Reverse transcriptase-polymerase chain reaction and Western blotting were used to study P2X(2), P2X(4) and P2X(7) receptor expression at mRNA and protein levels, respectively, in human osteoblast-like cells. P2X(7) receptor pharmacology was studied by measuring pore formation in the presence of different agonists and antagonists using the YO-PRO 1 uptake method.
Key Results:
P2X(4) and P2X(7) receptor mRNA and protein were found to be expressed by these cell lines. No evidence was found for P2X(4)/P2X(7) receptor heteropolymerization. 2'-3'-O-(4-benzoylbenzoyl)adenosine 5'-triphosphate (DBzATP) was equipotent to ATP and the antagonists used were either ineffective or weakly blocked pore formation.
Conclusions And Implications:
This study demonstrates that P2X(4) and P2X(7) receptors are expressed by human osteoblast-like cells. The affinities of the different agonists suggest that the P2X(7) receptor is mainly responsible for pore formation although P2X(4) receptors may also be involved. The low affinity of DBzATP and the weak action of the antagonists support the previously described atypical pharmacology of the P2X(7) receptor in osteoblasts. Targeting the P2X(7) receptor in osteoblasts could represent a promising new treatment for bone diseases such as osteoporosis and rheumatoid arthritis.
Insights
Human osteoblast-like cells express P2X(4) and P2X(7) receptors, key players in bone turnover. Targeting P2X(7) receptors may offer new treatments for bone diseases like osteoporosis.
Area of Science:
- Cell Biology
- Pharmacology
- Bone Biology
Background:
- P2X(7) receptors are known in osteoclasts, but their role in osteoblast-like cells is less understood.
- Previous studies in knockout mice suggest P2X(7) receptors involvement in bone formation.
- Osteosarcoma cell lines serve as models for human osteoblast-like cells.
Purpose of the Study:
- Investigate P2X receptor expression and pharmacology in human osteoblast-like cells.
- Determine the potential role of P2X receptors in human bone turnover.
- Assess P2X(7) receptor function and drug interactions in this cell type.
Main Methods:
- Utilized reverse transcriptase-polymerase chain reaction (RT-PCR) for mRNA analysis.
- Employed Western blotting to detect protein expression of P2X(2), P2X(4), and P2X(7) receptors.
- Assessed P2X(7) receptor pore formation using YO-PRO 1 uptake assays with various agonists and antagonists.
Main Results:
- P2X(4) and P2X(7) receptor mRNA and protein were detected in human osteoblast-like cells.
- No evidence of P2X(4)/P2X(7) receptor heteropolymerization was observed.
- DBzATP showed equipotent activity to ATP, and tested antagonists had limited effect on pore formation, indicating atypical P2X(7) receptor pharmacology.
Conclusions:
- P2X(4) and P2X(7) receptors are expressed in human osteoblast-like cells, suggesting a role in bone turnover.
- P2X(7) receptors are primarily responsible for pore formation, with potential involvement of P2X(4) receptors.
- Targeting P2X(7) receptors in osteoblasts presents a potential therapeutic strategy for bone diseases like osteoporosis and rheumatoid arthritis.
