Targeting Mechanics-Induced Fibroblast Activation through CD44-RhoA-YAP Pathway Ameliorates Crystalline Silica-Induced Silicosis

Abstract

Silicosis is pneumoconiosis of the lung, usually resulting from prolonged exposure to crystalline silica (CS). The hallmark of silicosis is excessive extracellular matrix (ECM) deposition produced by activated fibroblasts. Recent work demonstrated that excessive ECM-forming mechanical cues play an essential role in promoting fibroblast activation and perpetuating fibrotic pathologies. However, the detailed molecular mechanism still needs to be uncovered. Methods : NIH-3T3 fibroblasts were cultured on either 1 kappa (soft) or 60 kappa (stiff) gel-coated coverslips. A series of knockdown and reverse experiments in vitro were performed to establish the signaling for mechanics-induced fibroblast activation. An experimental model of silicosis was established by one-time intratracheal instillation of CS suspension. The cluster of differentiation 44 (CD44) antibody (IM7), dihydrotanshinone I (DHI) and verteporfin (VP) were used to explore the effect of CD44-RhoA-YAP signaling blockade on mechanics-induced fibroblast activation and CS-induced pulmonary fibrosis. Results : Matrix stiffness could induce nuclear translocation of the Yes-associated protein (YAP) through CD44 in fibroblasts. This effect required RhoA activity and F-actin cytoskeleton polymerization but was independent of Hippo pathway kinases, Mst 1 and Lats 1, forming CD44-RhoA-YAP signaling pathway. Pharmacological upstream blocking by CD44 antibody or downstream blockade of YAP by DHI or VP could attenuate fibroblast migration, invasion, proliferation, and collagen deposition. Furthermore, CD44-RhoA-YAP signaling blockade could alleviate CS-induced fibrosis and improve pulmonary function in vivo . Conclusion : CD44-RhoA-YAP signaling mediates mechanics-induced fibroblast activation. Targeting this pathway could ameliorate crystalline silica-induced silicosis and provide a potential therapeutic strategy to mitigate fibrosis.

Trehalose Alleviates Crystalline Silica-Induced Pulmonary Fibrosis via Activation of the TFEB-Mediated Autophagy-Lysosomal System in Alveolar Macrophages

“…CS particulates (Min-U-Sil 5 ground silica with size distribution of 97% < 5 µm diameter, 80% < 3 µm diameter, and median diameter 1.4 µm) were purchased form the U.S. Silica Company (Frederick, MD, USA). The pretreatment of CS and the establishment of silicosis animal models were performed as previously described [25,26]. The schematic representation for the in vivo treatment schedule is presented in Figure S1.…”

YAP is essential for TGF‐β‐induced retinal fibrosis in diabetic rats via promoting the fibrogenic activity of Müller cells

“…YAP has been shown to be involved in the regulation of the TGF‐β1 signalling pathway, potentially through directly binding Smad2/3 to enhance renal fibroblast activation 32 . Moreover, overexpression of YAP has been demonstrated in lung, renal and liver fibrosis 33‐35 . It is worth noting that YAP has been linked to the TGF‐β1/Smad pathway in mouse models of kidney fibrosis 36 .…”

“…32 Moreover, overexpression of YAP has been demonstrated in lung, renal and liver fibrosis. [33][34][35] It is worth noting that YAP has been linked to the TGF-β1/Smad pathway in mouse models of kidney fibrosis. 36 Consistent with previous studies, our findings also indicated that YAP plays an important role in TGF-β1mediated retinal fibrosis.…”

Inhibition of miR-155-5p Exerts Anti-Fibrotic Effects in Silicotic Mice by Regulating Meprin α

“…To observe the anti-fibrotic effect of miR-155-5p, specific pathogen-free male C57BL/6 mice weighting 15 ± 3 g at 8 weeks of age were purchased from Vital River Laboratory Animal Technology. Animals were randomly divided into three groups as follows (n = 6): agonist miRNA negative control (agomiR-NC), 0.05 mL of 0.9% saline containing 5 nmol ago-NC; silica plus agomiR-NC, 0.05 mL of 0.9% saline containing 5 nmol ago-NC plus 2.5 mg SiO 2 ; silica plus agomiR-155-5p group, 0.05 mL of 0.9% saline containing 5 nmol agomiR-155-5p plus 2.5 mg SiO 2 administered via trachea instillation 23 , 24 . Subsequently, 2.5 nmol of ago-NC or agomiR-155-5P was injected via the tail vein at 1 week after silica treatment.…”