Department of Oral and Maxillofacial Surgery, and Division of Neuroscience, University of California, San Francisco, San Francisco, California 94143.
Departments of Preventative and Restorative Dental Sciences and Oral and Maxillofacial Surgery, and Division of Neuroscience, University of California, San Francisco, San Francisco, California 94143.
J Neurosci. 2020 Aug 19;40(34):6477-6488. doi: 10.1523/JNEUROSCI.0166-20.2020. Epub 2020 Jul 14.
We evaluated the mechanism by which high-molecular-weight hyaluronan (HMWH) attenuates nociceptor sensitization, in the setting of inflammation. HMWH attenuated mechanical hyperalgesia induced by the inflammatory mediator prostaglandin E2 (PGE) in male and female rats. Intrathecal administration of an oligodeoxynucleotide antisense (AS-ODN) to mRNA for cluster of differentiation 44 (CD44), the cognate hyaluronan receptor, and intradermal administration of A5G27, a CD44 receptor antagonist, both attenuated antihyperalgesia induced by HMWH. In male rats, HMWH also signals via Toll-like receptor 4 (TLR4), and AS-ODN for TLR4 mRNA administered intrathecally, attenuated HMWH-induced antihyperalgesia. Since HMWH signaling is dependent on CD44 clustering in lipid rafts, we pretreated animals with methyl-β-cyclodextrin (MβCD), which disrupts lipid rafts. MβCD markedly attenuated HMWH-induced antihyperalgesia. Inhibitors for components of intracellular signaling pathways activated by CD44, including phospholipase C and phosphoinositide 3-kinase (PI3K), also attenuated HMWH-induced antihyperalgesia. Furthermore, application of HMWH attenuated PGE-induced sensitization of tetrodotoxin-resistant sodium current, in small-diameter dorsal root ganglion neurons, an effect that was attenuated by a PI3K inhibitor. Our results indicate a central role of CD44 signaling in HMWH-induced antihyperalgesia and suggest novel therapeutic targets, downstream of CD44, for the treatment of pain generated by nociceptor sensitization. High-molecular-weight-hyaluronan (HMWH) is used to treat osteoarthritis and other pain syndromes. In this study we demonstrate that attenuation of inflammatory hyperalgesia by HMWH is mediated by its action at cluster of differentiation 44 (CD44) and activation of its downstream signaling pathways, including RhoGTPases (RhoA and Rac1), phospholipases (phospholipases Cε and Cγ1), and phosphoinositide 3-kinase, in nociceptors. These findings contribute to our understanding of the antihyperalgesic effect of HMWH and support the hypothesis that CD44 and its downstream signaling pathways represent novel therapeutic targets for the treatment of inflammatory pain.
我们评估了高分子量透明质酸（HMWH）在炎症环境中减弱伤害感受器敏化的机制。HMWH 可减轻雄性和雌性大鼠中炎性介质前列腺素 E2（PGE）引起的机械性痛觉过敏。鞘内给予针对 CD44 信使 RNA 的寡脱氧核苷酸反义（AS-ODN），CD44 是透明质酸的同源受体，以及皮内给予 CD44 受体拮抗剂 A5G27，均可减轻 HMWH 引起的抗痛觉过敏。在雄性大鼠中，HMWH 还通过 Toll 样受体 4（TLR4）信号转导，鞘内给予 TLR4 mRNA 的 AS-ODN 可减轻 HMWH 引起的抗痛觉过敏。由于 HMWH 信号转导依赖于 CD44 在脂筏中的聚集，我们用甲基-β-环糊精（MβCD）预处理动物，MβCD 破坏脂筏。MβCD 显著减弱 HMWH 引起的抗痛觉过敏。CD44 激活的细胞内信号通路的成分抑制剂，包括磷脂酶 C 和磷酸肌醇 3-激酶（PI3K），也可减轻 HMWH 引起的抗痛觉过敏。此外，HMWH 的应用可减弱小直径背根神经节神经元中河豚毒素抗性钠电流对 PGE 诱导的敏化作用，而 PI3K 抑制剂可减弱这种作用。我们的结果表明 CD44 信号转导在 HMWH 引起的抗痛觉过敏中起中心作用，并提示 CD44 下游的新治疗靶点可用于治疗伤害感受器敏化引起的疼痛。高分子量透明质酸（HMWH）用于治疗骨关节炎和其他疼痛综合征。在这项研究中，我们证明 HMWH 通过其在 CD44 上的作用以及激活其下游信号通路（包括 RhoGTPases（RhoA 和 Rac1）、磷脂酶（磷脂酶 Cε 和 Cγ1）和磷酸肌醇 3-激酶）来减轻炎症性痛觉过敏。这些发现有助于我们了解 HMWH 的抗痛觉过敏作用，并支持 CD44 及其下游信号通路是治疗炎症性疼痛的新治疗靶点的假说。
