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Caihong Huang, He Wang, Juxin Pan, Dan Zhou, Wensheng Chen, Wei Li, Yongxiong Chen, Zuguo Liu; Benzalkonium Chloride Induces Subconjunctival Fibrosis Through the COX-2–Modulated Activation of a TGF-β1/Smad3 Signaling Pathway. Invest. Ophthalmol. Vis. Sci. 2014;55(12):8111-8122. doi: 10.1167/iovs.14-14504.
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The purpose is to investigate the mechanism of subconjunctival fibrosis caused by benzalkonium chloride (BAC), which is the most common preservative in ophthalmic preparations.
The left eyes of male Sprague-Dawley rats were topically treated with 0.01% BAC or PBS twice daily for 1 month. Primary conjunctival fibroblasts (CFs) were exposed for 24 hours to 0.00005% BAC, 0.000075% BAC, 0.000075% BAC + LY2157299 (a selective transforming growth factor β receptor type I inhibitor); 0.000075% BAC + NS-398 (a selective cyclooxygenase-2 inhibitor) and PBS, respectively. The pathological changes of the bulbar conjunctival tissue of rats were examined using hematoxylin-eosin (HE), Van Gieson's (vG), periodic acid-Schiff (PAS) stains, or immunohistochemisty (IHC). The expression of the extracellular matrix (ECM), the transforming growth factor β (TGF-β) signaling pathway–related molecules, and cyclooxygenase-2 (COX-2) in bulbar conjunctival tissues and CFs were detected using Western blot (WB) and quantitative real-time RT-PCR (qRT-PCR).
Rats treated with 0.01% BAC exhibited a slight increase of the fibroblast density and a more compact collagen deposition in the bulbar subepithelial connective tissues in comparison with rats treated with PBS. Western blot and qRT-PCR analyses showed that the expression of ECM, TGF-β signaling pathway–related molecules, and COX-2 were markedly increased in the bulbar conjunctival tissues of rats exposed to 0.01% BAC and in CFs exposed to 0.00005% and 0.000075% BAC. In conjunctival fibroblasts, BAC-induced ECM expression was clearly decreased by LY2157299, while the BAC-induced activation of the TGF-β1/Smad3 signaling pathway was greatly attenuated by NS-398.
Subconjunctival fibrosis BAC-induced is a consequence of excessive ECM production of CFs through the COX-2–modulated activation of a TGF-β1/Smad3 signaling pathway.
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