Laboratório de Farmacologia e Neurobiologia, UMIB, Instituto de Ciências Biomédicas Abel Salazar - Universidade do Porto (ICBAS-UP), Portugal.
J Cell Physiol. 2011 May;226(5):1353-66. doi: 10.1002/jcp.22458.
Purines are important modulators of bone cell biology. ATP is metabolized into adenosine by human primary osteoblast cells (HPOC); due to very low activity of adenosine deaminase, the nucleoside is the end product of the ecto-nucleotidase cascade. We, therefore, investigated the expression and function of adenosine receptor subtypes (A(1) , A(2A) , A(2B) , and A(3) ) during proliferation and osteogenic differentiation of HPOC. Adenosine A(1) (CPA), A(2A) (CGS21680C), A(2B) (NECA), and A(3) (2-Cl-IB-MECA) receptor agonists concentration-dependently increased HPOC proliferation. Agonist-induced HPOC proliferation was prevented by their selective antagonists, DPCPX, SCH442416, PSB603, and MRS1191. CPA and NECA facilitated osteogenic differentiation measured by increases in alkaline phosphatase (ALP) activity. This contrasts with the effect of CGS21680C which delayed HPOC differentiation; 2-Cl-IB-MECA was devoid of effect. Blockade of the A(2B) receptor with PSB603 prevented osteogenic differentiation by NECA. In the presence of the A(1) antagonist, DPCPX, CPA reduced ALP activity at 21 and 28 days in culture. At the same time points, blockade of A(2A) receptors with SCH442416 transformed the inhibitory effect of CGS21680C into facilitation. Inhibition of adenosine uptake with dipyridamole caused a net increase in osteogenic differentiation. The presence of all subtypes of adenosine receptors on HPOC was confirmed by immunocytochemistry. Data show that adenosine is an important regulator of osteogenic cell differentiation through the activation of subtype-specific receptors. The most abundant A(2B) receptor seems to have a consistent role in cell differentiation, which may be balanced through the relative strengths of A(1) or A(2A) receptors determining whether osteoblasts are driven into proliferation or differentiation.
嘌呤是骨细胞生物学的重要调节剂。人原代成骨细胞（HPOC）将 ATP 代谢为腺苷；由于腺苷脱氨酶活性非常低，核苷是外核苷酸酶级联的终产物。因此，我们研究了腺苷受体亚型（A1、A2A、A2B 和 A3）在 HPOC 增殖和成骨分化过程中的表达和功能。腺苷 A1（CPA）、A2A（CGS21680C）、A2B（NECA）和 A3（2-Cl-IB-MECA）受体激动剂浓度依赖性地增加 HPOC 增殖。其选择性拮抗剂 DPCPX、SCH442416、PSB603 和 MRS1191 可阻止激动剂诱导的 HPOC 增殖。CPA 和 NECA 促进碱性磷酸酶（ALP）活性增加，从而促进成骨分化。这与 CGS21680C 的作用相反，CGS21680C 延迟 HPOC 分化；2-Cl-IB-MECA 则没有作用。用 PSB603 阻断 A2B 受体可阻止 NECA 诱导的成骨分化。在 A1 拮抗剂 DPCPX 的存在下，CPA 在培养的第 21 和 28 天降低了 ALP 活性。在相同的时间点，用 SCH442416 阻断 A2A 受体将 CGS21680C 的抑制作用转化为促进作用。用双嘧达莫抑制腺苷摄取会导致成骨分化的净增加。免疫细胞化学证实 HPOC 上存在所有亚型的腺苷受体。数据表明，通过激活特定亚型的受体，腺苷是成骨细胞分化的重要调节剂。最丰富的 A2B 受体似乎在细胞分化中具有一致的作用，这可能通过相对 A1 或 A2A 受体的强度来平衡，从而确定成骨细胞是被驱动进入增殖还是分化。
