Sorbonne Université, INSERM UMR 938, Centre de Recherche Saint-Antoine, Hôpital Saint-Antoine, Assistance Publique - Hôpitaux de Paris (AP-HP), Paris, France.
Department of Rheumatology, Assistance Publique - Hôpitaux de Paris (AP-HP), Saint-Antoine Hospital, Paris, France.
Front Immunol. 2022 Apr 8;13:842538. doi: 10.3389/fimmu.2022.842538. eCollection 2022.
Osteoarthritis (OA) is a whole-joint disease characterized by a low-grade inflammation that is involved in both cartilage degradation and subchondral bone remodeling. Since subchondral bone has a cholinergic innervation and that acetylcholine (Ach) might have an anti-inflammatory effect through the α7 nicotinic Ach receptor (α7nAchR), we aimed (i) to determine the expression of non-neuronal cholinergic system and nicotinic receptor subunits by murine and human osteoblasts, (ii) to address the role of α7nAchR in osteoblastic response to inflammation, and (iii) to study the role of α7nAchR in a spontaneous aging OA model.
Primary cultures of WT and α7nAchR knock-out mice (Chrna7) murine osteoblasts and of subchondral bone human OA osteoblasts were performed. The expressions of the non-neuronal cholinergic system and of the nAchR subunits were assessed by PCR. , IL1β-stimulated WT, Chrna7, and human osteoblasts were pretreated with nicotine. At 24 h, expressions of interleukin-6 (IL6) and metalloproteinase-3 and -13 (MMP), RANK-ligand (RANKL), and osteoprotegerin (OPG) were quantified by qPCR and ELISA. Spontaneous aging OA was evaluated and compared between male WT and Chrna7 mice of 9 and 12 months.
Murine WT osteoblasts express the main components of the cholinergic system and α7 subunit composing α7nAchR. Nicotine partially prevented the IL1β-induced expression and production of IL6, MMP3, and RANKL in WT osteoblasts. The effect for IL6 and MMP was mediated by α7nAchR since nicotine had no effect on Chrna7 osteoblasts while the RANKL decrease persisted. Chrna7 mice displayed significantly higher cartilage lesions than their WT counterparts at 9 and 12 months, without difference in subchondral bone remodeling. Human OA osteoblasts also expressed the non-neuronal cholinergic system and α7 subunit as well as CHRFAM7A, the dominant negative duplicate of Chrna7. Nicotine pretreatment did not significantly reduce IL6 and MMP3 production in IL-1β-stimulated human osteoarthritic osteoblasts ( = 4), possibly due to CHRFAM7A.
Cholinergic system counteracts murine osteoblastic response to IL-1β through α7nAchR. Since α7nAchR deletion may limit cartilage degradation during murine age-related OA, enhancing cholinergic system could be a new therapeutic target in OA but may depend on CHRFAM7A expression.
骨关节炎（OA）是一种全关节疾病，其特征为低度炎症，涉及软骨降解和软骨下骨重塑。由于软骨下骨具有胆碱能神经支配，而乙酰胆碱（Ach）可能通过α7 烟碱型 Ach 受体（α7nAchR）发挥抗炎作用，我们旨在：（i）确定鼠和人成骨细胞中非神经元胆碱能系统和烟碱受体亚单位的表达；（ii）研究α7nAchR 在成骨细胞炎症反应中的作用；（iii）研究α7nAchR 在自发性衰老 OA 模型中的作用。
进行 WT 和 α7nAchR 敲除（Chrna7）小鼠成骨细胞和软骨下骨人 OA 成骨细胞的原代培养。通过 PCR 评估非神经元胆碱能系统和 nAchR 亚单位的表达。用尼古丁预处理 IL1β 刺激的 WT、Chrna7 和人成骨细胞。24 小时后，通过 qPCR 和 ELISA 定量测定白细胞介素 6（IL6）和基质金属蛋白酶 3 和 13（MMP）、核因子-κB 受体激活因子配体（RANKL）和骨保护素（OPG）的表达。评估自发性衰老 OA，并比较 9 个月和 12 个月雄性 WT 和 Chrna7 小鼠之间的差异。
鼠 WT 成骨细胞表达胆碱能系统的主要成分和组成α7nAchR 的α7 亚单位。尼古丁部分阻止了 WT 成骨细胞中 IL1β 诱导的 IL6、MMP3 和 RANKL 的表达和产生。该作用通过α7nAchR 介导，因为尼古丁对 Chrna7 成骨细胞没有作用，而 RANKL 的减少仍然存在。Chrna7 小鼠在 9 个月和 12 个月时的软骨病变明显高于 WT 小鼠，但软骨下骨重塑无差异。人 OA 成骨细胞也表达非神经元胆碱能系统和 α7 亚单位以及 Chrna7 的显性负重复制物 CHRFAM7A。尼古丁预处理并未显著减少 IL1β 刺激的人骨关节炎成骨细胞中 IL6 和 MMP3 的产生（= 4），这可能是由于 CHRFAM7A 的存在。
胆碱能系统通过α7nAchR 拮抗鼠成骨细胞对 IL-1β 的反应。由于α7nAchR 缺失可能会限制鼠年龄相关性 OA 期间的软骨降解，因此增强胆碱能系统可能成为 OA 的新治疗靶点，但这可能取决于 CHRFAM7A 的表达。
