Department of Cell Biology & Anatomy, North Texas Eye Research Institute, University of North Texas Health Science Center, 3500 Camp Bowie Blvd., Fort Worth, TX 76107, USA.
Exp Eye Res. 2013 Aug;113:117-27. doi: 10.1016/j.exer.2013.05.011. Epub 2013 Jun 5.
The TGFβ/BMP signaling pathways are involved in glaucomatous damage to the trabecular meshwork (TM) leading to elevated intraocular pressure (IOP), which is a major risk factor for the development and progression of glaucoma. The BMP antagonist gremlin is elevated in glaucomatous TM cells and tissues and can directly elevate IOP. Gremlin utilizes the TGFβ2/SMAD pathway to induce TM extracellular matrix (ECM) proteins. The purpose of this study is to determine whether expression of the ECM cross-linking lysyl oxidase (LOX) genes is regulated by gremlin in cultured human TM cells. Human TM cells were treated with recombinant gremlin, and expression of the LOX genes was examined by quantitative RT-PCR and western immunoblotting. TM cells were pretreated with TGFBR inhibitors (LY364947 or SB431542), an inhibitor of the SMAD signaling pathway (SIS3), or with JNK (SP600125) and p38 MAPK (SB203580) inhibitors to identify the signaling pathway(s) involved in gremlin induction of LOX protein expression. All five LOX genes (LOX and LOXL1-4) were induced by gremlin. Gremlin induction of LOX genes and protein expression was blocked by TGFBR inhibitors as well as by inhibitors of the SMAD3, JNK and p38 MAPK signaling pathways. We conclude that gremlin employs both canonical TGFβ/SMAD and the non-canonical JNK and p38 MAPK signaling pathways to induce LOX genes and proteins in cultured human TM cells. Increased LOX levels may be at least partially responsible for gremlin-mediated IOP elevation and increased aqueous humor outflow resistance leading to glaucoma.
TGFβ/BMP 信号通路参与了小梁网（TM）的青光眼损伤，导致眼内压（IOP）升高，这是青光眼发展和进展的主要危险因素。BMP 拮抗剂 GREMLIN 在青光眼 TM 细胞和组织中升高，并可直接升高 IOP。GREMLIN 利用 TGFβ2/SMAD 通路诱导 TM 细胞外基质（ECM）蛋白。本研究的目的是确定 ECM 交联赖氨酰氧化酶（LOX）基因的表达是否受 GREMLIN 在培养的人 TM 细胞中的调节。用重组 GREMLIN 处理人 TM 细胞，并用定量 RT-PCR 和 Western 免疫印迹法检测 LOX 基因的表达。用 TGFBR 抑制剂（LY364947 或 SB431542）、SMAD 信号通路抑制剂（SIS3）或 JNK（SP600125）和 p38 MAPK（SB203580）抑制剂预处理 TM 细胞，以鉴定参与 GREMLIN 诱导 LOX 蛋白表达的信号通路。所有五个 LOX 基因（LOX 和 LOXL1-4）均被 GREMLIN 诱导。LOX 基因和蛋白表达的 GREMLIN 诱导被 TGFBR 抑制剂以及 SMAD3、JNK 和 p38 MAPK 信号通路抑制剂阻断。我们得出结论，GREMLIN 采用经典的 TGFβ/SMAD 和非经典的 JNK 和 p38 MAPK 信号通路在培养的人 TM 细胞中诱导 LOX 基因和蛋白。LOX 水平的增加可能至少部分是 GREMLIN 介导的 IOP 升高和房水流出阻力增加导致青光眼的原因。
