Nrf2/HO-1 信号通路的抑制会导致骨关节炎中 NLRP3 炎性小体的过度激活。

INTRODUCTION: Osteoarthritis (OA) is an inflammatory disease of the joints that causes progressive disability in the elderly. Reactive oxygen species (ROS) play an important role in OA development; they may activate the NLRP3 inflammasome, thereby inducing the secretion of proinflammatory IL-1β and IL-18, leading to the aggravation of the downstream inflammatory response. Nrf2 is a key transcription factor that regulates the expression of antioxidant enzymes that protect against oxidative stress and tissue damage. We aimed to explore the underlying mechanism of OA development by investigating NLRP3, ASC, Nrf2, and HO-1 expression in synovia and their regulatory networks in OA. METHODS: Human total knee replacement samples were subjected to histology and micro-CT analysis to determine the pathological changes in the cartilage and subchondral bone and to assess the expression of inflammation-related markers in the synovial tissue by immunohistochemistry (IHC), qRT-PCR, and Western blot. To investigate these pathological changes in an OA animal model, adult Sprague-Dawley rats were subjected to anterior cruciate ligament transection and medial meniscectomy. Articular cartilage and subchondral bone changes and synovial tissue were also determined by the same methods used for the human samples. Finally, SW982 cells were stimulated with lipopolysaccharide (LPS) as an in vitro inflammatory cell model. The correlation between NLRP3 and Nrf2 expression was confirmed by knocking down NLRP3 or Nrf2. RESULTS: Cartilage destruction and subchondral bone sclerosis were found in the OA patients and OA model rats. Significantly increased expression levels of NLRP3, ASC, Nrf2, and HO-1 were found in the synovial tissue from OA patients. NLRP3, ASC, Nrf2, and HO-1 expression in the synovium was also upregulated in the OA group compared with the sham group. Furthermore, the NLRP3, Nrf2, HO-1, IL-1β, and IL-18 expression in LPS-treated SW982 cells was increased in a dose-dependent manner. As expected, the expression of NLRP3 was upregulated, and the expression of IL-1β and IL-18 was downregulated after Nrf2 silencing. However, knocking down NLRP3 did not affect the expression of Nrf2. CONCLUSIONS: ROS-induced oxidative stress may be the main cause of NLRP3 inflammasome activation and subsequent release of downstream factors during OA development. Nrf2/HO-1 signaling could be a key pathway for the activation of the NLRP3 inflammasome, which may contribute to the progression of OA. Herein, we discovered a novel role of Nrf2/HO-1 signaling in the production of NLRP3, which may facilitate the prevention and treatment of OA.

简介：骨关节炎（OA）是一种关节炎症性疾病，会导致老年人逐渐丧失活动能力。活性氧（ROS）在 OA 的发展中起着重要作用；它们可能激活 NLRP3 炎性小体，从而诱导促炎细胞因子 IL-1β 和 IL-18 的分泌，导致下游炎症反应加剧。Nrf2 是一种关键的转录因子，可调节抗氧化酶的表达，这些酶可抵抗氧化应激和组织损伤。我们旨在通过研究 OA 患者滑膜中 NLRP3、ASC、Nrf2 和 HO-1 的表达及其在 OA 中的调控网络，来探讨 OA 发展的潜在机制。

方法：对人类全膝关节置换样本进行组织学和 micro-CT 分析，以确定软骨和软骨下骨的病理变化，并通过免疫组织化学（IHC）、qRT-PCR 和 Western blot 检测滑膜组织中炎症相关标志物的表达。为了在 OA 动物模型中研究这些病理变化，对成年 Sprague-Dawley 大鼠进行前交叉韧带切断术和内侧半月板切除术。同样使用人类样本的方法来确定关节软骨和软骨下骨的变化以及滑膜组织。最后，用脂多糖（LPS）刺激 SW982 细胞作为体外炎症细胞模型。通过敲低 NLRP3 或 Nrf2 来验证 NLRP3 和 Nrf2 表达之间的相关性。

结果：在 OA 患者和 OA 模型大鼠中发现了软骨破坏和软骨下骨硬化。OA 患者滑膜组织中 NLRP3、ASC、Nrf2 和 HO-1 的表达水平显著升高。与假手术组相比，OA 组滑膜中 NLRP3、ASC、Nrf2 和 HO-1 的表达也上调。此外，LPS 处理的 SW982 细胞中 NLRP3、Nrf2、HO-1、IL-1β 和 IL-18 的表达呈剂量依赖性增加。正如预期的那样，Nrf2 沉默后 NLRP3 的表达上调，IL-1β 和 IL-18 的表达下调。然而，敲低 NLRP3 并不影响 Nrf2 的表达。

结论：ROS 诱导的氧化应激可能是 NLRP3 炎性小体激活和随后 OA 发展过程中下游因子释放的主要原因。Nrf2/HO-1 信号通路可能是 NLRP3 炎性小体激活的关键途径，可能有助于 OA 的进展。在此，我们发现了 Nrf2/HO-1 信号在 NLRP3 产生中的新作用，这可能有助于 OA 的预防和治疗。