John W. Deming Department of Medicine, Tulane University School of Medicine, New Orleans, Louisiana, USA.
University of Alabama at Birmingham, Birmingham, Alabama, USA.
JCI Insight. 2020 Jul 23;5(14):137191. doi: 10.1172/jci.insight.137191.
Free light chains (FLCs) induce inflammatory pathways in proximal tubule cells (PTCs). The role of TLRs in these responses is unknown. Here we present findings on the role of TLRs in FLC-induced PTC injury. We exposed human kidney PTC cultures to κ and λ FLCs and used cell supernatants and pellets for ELISA and gene expression studies. We also analyzed tissues from Stat1-/- and littermate control mice treated with daily i.p. injections of a κ FLC for 10 days. FLCs increased the expression of TLR2, TLR4, and TLR6 via HMGB1, a damage-associated molecular pattern. Countering TLR2, TLR4, and TLR6 through GIT-27 or specific TLR siRNAs reduced downstream cytokine responses. Blocking HMGB1 through siRNA or pharmacologic inhibition, or via STAT1 inhibition, reduced FLC-induced TLR2, TLR4, and TLR6 expression. Blocking endocytosis of FLCs through silencing of megalin/cubilin, with bafilomycin A1 or hypertonic sucrose, attenuated FLC-induced cytokine responses in PTCs. IHC showed decreased TLR4 and TLR6 expression in kidney sections from Stat1-/- mice compared with their littermate controls. PTCs exposed to FLCs released HMGB1, which induced expression of TLR2, TLR4, and TLR6 and downstream inflammation. Blocking FLCs' endocytosis, Stat1 knockdown, HMGB1 inhibition, and TLR knockdown each rescued PTCs from FLC-induced injury.
游离轻链 (FLC) 可诱导近端肾小管细胞 (PTC) 产生炎症途径。TLRs 在这些反应中的作用尚不清楚。本文介绍了 TLRs 在 FLC 诱导的 PTC 损伤中的作用。我们将人肾 PTC 培养物暴露于 κ 和 λ FLC 中，并使用细胞上清液和沉淀进行 ELISA 和基因表达研究。我们还分析了用 κ FLC 每日腹腔注射治疗 10 天的 Stat1-/-和同窝对照小鼠的组织。FLC 通过高迁移率族蛋白 B1（一种损伤相关分子模式）增加 TLR2、TLR4 和 TLR6 的表达。通过 GIT-27 或特异性 TLR siRNA 拮抗 TLR2、TLR4 和 TLR6 可降低下游细胞因子反应。通过 siRNA 或药物抑制或通过 STAT1 抑制降低 FLC 诱导的 TLR2、TLR4 和 TLR6 表达，从而阻断 HMGB1。通过沉默巨球蛋白/cubilin 并用巴弗洛霉素 A1 或高渗蔗糖阻断 FLC 的内吞作用，可减轻 PTC 中 FLC 诱导的细胞因子反应。免疫组化显示，与同窝对照小鼠相比，Stat1-/-小鼠肾脏切片中 TLR4 和 TLR6 的表达减少。暴露于 FLC 的 PTC 释放 HMGB1，诱导 TLR2、TLR4 和 TLR6 的表达及下游炎症。阻断 FLC 的内吞作用、Stat1 敲低、HMGB1 抑制和 TLR 敲低均可使 PTC 免受 FLC 诱导的损伤。
