Valproic acid suppresses collagen by selective regulation of Smads in conjunctival fibrosis.
Overproduction of type I collagen is associated with a wide range of fibrotic diseases as well as surgical failure such as in glaucoma filtration surgery (GFS). Its modulation is therefore of clinical importance. Valproic acid (VPA) is known to reduce collagen in a variety of tissues with unclear mechanism of action. In this report, we demonstrate that VPA inhibited collagen production in both conjunctival fibroblasts and the mouse model of GFS. In fibroblasts, VPA decreased type I collagen expression which intensified with longer drug exposure and suppressed steady-state type I collagen promoter activity. Moreover, VPA decreased Smad2, Smad3 and Smad4 but increased Smad6 expression with a similar intensity-exposure profile. Reduction of Smad3 using small hairpin RNA and/or overexpression of Smad6 resulted in decreased collagen expression which was exacerbated when VPA was simultaneously present. Furthermore, fibrogenic TGF-β2 failed to induce collagen when VPA was present, as opposed to the myofibroblast markers, beta-actin, alpha-smooth muscle actin and tenascin-C, which were elevated by TGF-β2. VPA suppressed p3TP-Lux luciferase activity and selectively rescued Smad6 expression from suppression by TGF-β2. Notably, SMAD6 overexpression reduced the effectiveness of TGF-β2 in inducing collagen expression. In corroboration, VPA inhibited type I collagen but increased Smad6 expression in the late phase of wound healing in the mouse model of GFS. Taken together, our data indicate that VPA has the capacity to effectively suppress both steady-state and fibrogenic activation of type I collagen expression by modulating Smad expression. Hence, VPA is potentially applicable as an anti-fibrotic therapeutic by targeting collagen. Key message: • VPA modulates type I collagen expression via members of the Smad family. • VPA suppresses Smad2, Smad3 and Smad4 but upregulates Smad6. • Smad3 and Smad6 are involved in VPA regulation of steady-state collagen expression. • Smad6 is involved in VPA modulation of TGF-β-stimulated collagen expression. • VPA reduces collagen and upregulates Smad6 in the mouse model of glaucoma filtration surgery.
Ocular Therapeutics and Drug Delivery, Singapore Eye Research Institute, Singapore, Singapore. seet.li.fong@seri.com.sg.|Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore. seet.li.fong@seri.com.sg.|Duke-NUS Graduate Medical School Singapore, Singapore, Singapore. seet.li.fong@seri.com.sg.
Li-Fong
LF
Seet
Ocular Therapeutics and Drug Delivery, Singapore Eye Research Institute, Singapore, Singapore.
Li Zhen
LZ
Toh
Ocular Therapeutics and Drug Delivery, Singapore Eye Research Institute, Singapore, Singapore.
Sharon N
SN
Finger
Ocular Therapeutics and Drug Delivery, Singapore Eye Research Institute, Singapore, Singapore.
Stephanie W L
SW
Chu
Department of Biomedical Sciences, College of Medicine, Florida State University, Tallahassee, FL, USA.
Branko
B
Stefanovic
Ocular Therapeutics and Drug Delivery, Singapore Eye Research Institute, Singapore, Singapore. tina.wong.t.l@snec.com.sg.|Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore. tina.wong.t.l@snec.com.sg.|Duke-NUS Graduate Medical School Singapore, Singapore, Singapore. tina.wong.t.l@snec.com.sg.|Glaucoma Service, Singapore National Eye Center, 11 Third Hospital Avenue, Singapore, 168751, Singapore. tina.wong.t.l@snec.com.sg.|School of Materials Science and Engineering, Nanyang Technological University, Singapore, Singapore. tina.wong.t.l@snec.com.sg.
Tina T
TT
Wong
D000818:Animals; D002478:Cells, Cultured; D024042:Collagen Type I / Q000032:analysis / Q000235:genetics*; D003228:Conjunctiva / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology*; D004791:Enzyme Inhibitors / Q000494:pharmacology* / Q000627:therapeutic use; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D005355:Fibrosis; D005786:Gene Expression Regulation / Q000187:drug effects*; D005901:Glaucoma / Q000150:complications / Q000601:surgery; D051379:Mice; D008810:Mice, Inbred C57BL; D051785:Smad Proteins / Q000235:genetics*; D053781:Transforming Growth Factor beta2 / Q000378:metabolism; D014635:Valproic Acid / Q000494:pharmacology* / Q000627:therapeutic use
D024042:Collagen Type I; D004791:Enzyme Inhibitors; D051785:Smad Proteins; D053781:Transforming Growth Factor beta2; D014635:Valproic Acid
Collagen; Conjunctiva; Fibrosis; SMAD; TGF‐β2; Valproic acid