Graduate Program in Pharmacology & Toxicology, School of Pharmacy, University of Connecticut, Storrs, CT 06269, USA.
Doctor of Pharmacy Program, School of Pharmacy, University of Connecticut, Storrs, CT 06269, USA.
Mediators Inflamm. 2020 Apr 21;2020:5919150. doi: 10.1155/2020/5919150. eCollection 2020.
TNIP1 protein is a widely expressed, cytoplasmic inhibitor of inflammatory signaling initiated by membrane receptors such as TLRs which recognize pathogen-associated and damage-associated molecular patterns (PAMPs and DAMPs). Keratinocyte TNIP1 deficiency sensitizes cells to PAMPs and DAMPs promoting hyperresponsive expression and secretion of cytokine markers (e.g., IL-8 and IL-6) relevant to cases of chronic inflammation, like psoriasis, where TNIP1 deficiency has been reported. Here, we examined the impact of TNIP1 deficiency on gene expression and cellular responses (migration and viability) relevant to acute inflammation as typically occurs in wound healing. Using siRNA-mediated TNIP1 expression knockdown in cultured HaCaT keratinocytes, we investigated TNIP1 deficiency effects on signaling downstream of TLR3 agonism with low-concentration poly (I:C), a representative PAMP/DAMP. The combination of TNIP1 knockdown and PAMP/DAMP signaling disrupted expression of specific keratinocyte differentiation markers (e.g., transglutaminase 1 and involucrin). These same conditions promoted synergistically increased expression of wound-associated markers (e.g., S100A8, TGF, and CCN2) suggesting potential benefit of increased inflammatory response from reduced TNIP1 protein. Unexpectedly, poly (I:C) challenge of TNIP1-deficient cells restricted reepithelialization and reduced cell viability. In these cells, there was not only increased expression for genes associated with inflammasome assembly (e.g., ASC, procaspase 1) but also for A20, a TNIP1 partner protein that represses cell-death signaling. Despite this possibly compensatory increase in A20 mRNA, there was a decrease in phospho-A20 protein, the form necessary for quenching inflammation. Hyperresponsiveness to poly (I:C) in TNIP1-deficient keratinocytes was in part mediated through p38 and JNK pathways. Taken together, we conclude that TNIP1 deficiency promotes enhanced expression of factors associated with promoting wound healing. However, the coupled, increased potential priming of the inflammasome and reduced compensatory activity of A20 has a net negative effect on overall cell recovery potential manifested by poor reepithelialization and viability. These findings suggest a previously unrecognized role for TNIP1 protein in limiting inflammation during successful progression through early wound healing stages.
TNIP1 蛋白是一种广泛表达的细胞质抑制剂，可抑制 TLR 等膜受体引发的炎症信号转导，TLR 可识别病原体相关和损伤相关的分子模式（PAMPs 和 DAMPs）。角质形成细胞中 TNIP1 的缺乏会使细胞对 PAMPs 和 DAMPs 敏感，从而促进细胞因子标志物（如 IL-8 和 IL-6）的过度表达和分泌，这些标志物与银屑病等慢性炎症病例相关，已有研究报道 TNIP1 缺乏与银屑病相关。在此，我们研究了 TNIP1 缺乏对与急性炎症相关的基因表达和细胞反应（迁移和活力）的影响，急性炎症通常发生在伤口愈合过程中。我们使用 siRNA 介导的 TNIP1 表达敲低，在培养的 HaCaT 角质形成细胞中研究了 TNIP1 缺乏对 TLR3 激动剂低浓度多聚（I：C）引发的信号转导的影响，多聚（I：C）是一种代表性的 PAMP/DAMP。TNIP1 敲低和 PAMP/DAMP 信号的组合破坏了特定角质形成细胞分化标志物（如转谷氨酰胺酶 1 和 involucrin）的表达。在这些相同的条件下，促进了与伤口相关的标志物（如 S100A8、TGF 和 CCN2）的协同表达增加，这表明 TNIP1 蛋白减少可能会增加炎症反应，从而带来益处。出乎意料的是，多聚（I：C）对 TNIP1 缺陷细胞的挑战限制了再上皮化并降低了细胞活力。在这些细胞中，不仅与炎症小体组装相关的基因（如 ASC、procaspase 1）的表达增加，而且 TNIP1 伴侣蛋白 A20 的表达也增加，A20 蛋白抑制细胞死亡信号。尽管 A20 mRNA 可能会代偿性增加，但磷酸化 A20 蛋白减少，而磷酸化 A20 蛋白是抑制炎症所必需的形式。TNIP1 缺陷角质形成细胞对多聚（I：C）的高反应性部分是通过 p38 和 JNK 途径介导的。总之，我们得出结论，TNIP1 缺乏会促进与促进伤口愈合相关的因子的表达增强。然而，炎症小体的潜在激活增加和 A20 的补偿性活性降低对整体细胞恢复潜力有负面影响，表现为再上皮化不良和活力降低。这些发现表明，TNIP1 蛋白在成功通过早期伤口愈合阶段期间限制炎症方面发挥了以前未被认识到的作用。
