Department of Orthopedics, Renmin Hospital of Wuhan University, 430060 Wuhan, China; Central Laboratory, Renmin Hospital of Wuhan University, 430060, Wuhan, China.
Department of Orthopedics, Renmin Hospital of Wuhan University, 430060 Wuhan, China.
Pharmacol Res. 2020 May;155:104690. doi: 10.1016/j.phrs.2020.104690. Epub 2020 Feb 11.
The innate immune system drives inflammatory joint damage in osteoarthritis (OA) and regulates cartilage repair. Berberine chloride (BBR) is an isoquinoline alkaloid that shows immunomodulatory activity in a variety of cell lines. However, the immunomodulatory mechanisms of BBR in chondrocytes during OA are largely unknown. Herein, we assessed the ability of BBR to mediate chondroprotection through its effects on innate immunity. We found that BBR up-regulated the expression of surfactant protein D (SP-D) in OA cartilage, a key regulator of inflammation and innate immunity both in the airways and extrapulmonary tissues, including joint cartilage. To further explore these findings, we used recombinant adeno-associated virus (rAAV)-mediated knockdown of SP-D. Silencing was assessed in rat model of surgically-induced OA in the presence or absence of BBR treatment, 10 weeks post-surgery. We observed a clear improvement in histological scores of BBR-treated animals compared to those treated with BBR and the rAAV-SP-D vector. In addition, animals co-treated with BBR + recombinant human SP-D (rhSP-D) exhibited significantly lower histological scores than those treated with BBR alone. BBR treatment led to significantly reduced immune cell infiltration mediated through TLR4, F4/80, CD68 and CD34, whilst SP-D silencing reversed this improvement. In contrast, rhSP-D treatment enhanced the protective phenotype. We further explored how BBR influences SP-D and other OA-associated genes in vitro. We observed an up-regulation of SP-D and a marked decline in TRAF6, TLR4, MD-2 and MyD88 expression, as well as NF-κB p65 and IκBα phosphorylation in chondrocytes treated with sodium nitroprusside. siRNAs specific for SP-D were able to partially reverse this phenotype, whilst both rhSP-D and the TLR4 inhibitor TAK-242 enhanced the effects. Together, these results are consistent with a model wherein SP-D has therapeutic potential for OA treatment. Concomitantly, BBR modulates immune responses and decreases cartilage degradation. These findings suggest that BBR achieves this function through releasing SP-D from MD2/SP-D complexes and through the inhibition of TLR4/NF-κB signaling.
固有免疫系统驱动骨关节炎（OA）中的炎症性关节损伤，并调节软骨修复。盐酸小檗碱（BBR）是一种异喹啉生物碱，在多种细胞系中显示出免疫调节活性。然而，BBR 在 OA 软骨细胞中的免疫调节机制在很大程度上尚不清楚。在此，我们评估了 BBR 通过对固有免疫的影响介导软骨保护的能力。我们发现 BBR 上调 OA 软骨中表面活性剂蛋白 D（SP-D）的表达，SP-D 是气道和肺外组织（包括关节软骨）中炎症和固有免疫的关键调节剂。为了进一步探索这些发现，我们使用重组腺相关病毒（rAAV）介导的 SP-D 敲低。在手术后 10 周，在存在或不存在 BBR 治疗的情况下，在大鼠手术诱导的 OA 模型中评估沉默。与用 BBR 和 rAAV-SP-D 载体治疗的动物相比，用 BBR 治疗的动物的组织学评分明显改善。此外，与单独用 BBR 治疗的动物相比，用 BBR+重组人 SP-D（rhSP-D）共同治疗的动物的组织学评分明显更低。BBR 治疗导致 TLR4、F4/80、CD68 和 CD34 介导的免疫细胞浸润显著减少，而 SP-D 沉默逆转了这种改善。相反，rhSP-D 治疗增强了保护表型。我们进一步探讨了 BBR 如何在体外影响 SP-D 和其他 OA 相关基因。我们观察到 SP-D 的上调以及 TRAF6、TLR4、MD-2 和 MyD88 表达以及 NF-κB p65 和 IκBα 磷酸化的显著下降，在用硝普钠处理的软骨细胞中。SP-D 的特异性 siRNA 能够部分逆转这种表型，而 rhSP-D 和 TLR4 抑制剂 TAK-242 均增强了这种作用。总的来说，这些结果与 SP-D 具有治疗 OA 的潜力的模型一致。同时，BBR 调节免疫反应并减少软骨降解。这些发现表明，BBR 通过从 MD2/SP-D 复合物中释放 SP-D 并通过抑制 TLR4/NF-κB 信号传导来实现此功能。
