Tetramethylpyrazine (TMP), an Active Ingredient of Chinese Herb Medicine Chuanxiong, Attenuates the Degeneration of Trabecular Meshwork through SDF-1/CXCR4 Axis

Abstract

BackgroundA traditional Chinese medicine, Tetramethylpyrazine (TMP), has been prescribed as a complementary treatment for glaucoma to improve patient prognosis. However, the pharmacological mechanism of action of TMP is poorly understood. In previous studies, we demonstrated that TMP exerts potent inhibitory effects on neovascularization, suppresses the tumorigenic behavior of glioma cells, and protects neural cells by regulating CXCR4 expression. Here, we further investigated whether the SDF-1/CXCR4 pathway is also involved in the TMP-mediated activity in trabecular meshwork cells.Methodology/Principal FindingsCXCR4 expression was examined by quantitative real-time PCR in trabecular and iris specimens from 54 primary open-angle glaucoma (POAG) patients who required surgery and 19 non-glaucomatous donors. Our data revealed markedly elevated CXCR4 expression in the trabecular meshwork of POAG patients compared with that of controls. Consistently, CXCR4 expression was much higher in glaucomatous trabecular meshwork cells than in normal trabecular meshwork cells. Using RT-PCR and western blot assays, we determined that glaucoma-related cytokines and dexamethasone (DEX) also significantly up-regulated CXCR4 expression in primary human trabecular meshwork (PHTM) cells. Moreover, the TGF-β1-mediated induction of CXCR4 expression in PHTM cells was markedly down-regulated by TMP compared with control treatment (PBS) and the CXCR4 antagonist AMD3100. In addition, TMP could counteract the TGF-β1-induced effects on stress fiber accumulation and expansion of PHTM cells. TMP markedly suppressed the migration of PHTM cells stimulated by TGF-β1 in transwell and scratch wound assays. TMP also suppressed the extracellular matrix (ECM) accumulation induced by TGF-β2.ConclusionsOur findings demonstrate that CXCR4 might be involved in the pathogenetic changes in the trabecular meshwork of patients with POAG. Additionally, TMP might exert its beneficial effects in POAG patients by down-regulating CXCR4 expression.

Tetramethylpyrazine Attenuates Transdifferentiation of TGF-β2–Treated Human Tenon's Fibroblasts

“…Moreover, in 10% FBS, HTFs treated with TMP were less viable and expressed less PCNA, but were not apoptotic even at a high concentration (400 lM), indicating that the limiting effects of TMP were unlikely to be due to toxicity. This is consistent with our previous report showing that TMP has no cytotoxic effects on PHTM cells, 24 suggesting that it is clinically safe.…”

“…Evidence suggests that TMP may inhibit proliferation and migration of several cell types, including ECV304 and PHTM cells. 16,24 Trimethylpyrazine also delayed TGF-b2-induced migration of primary HTFs in our study, as evidenced by the transwell invasion assays. Interestingly, under serumfree conditions, TMP treatment alone had no effect on either proliferation or migration.…”

“…ocular diseases, including corneal neovascularization and glaucoma. [21][22][23][24] In the present study, our results indicate that TMP exhibits an inhibitory effect on the proliferation in profibrotic cytokine-treated HTFs. Moreover, in 10% FBS, HTFs treated with TMP were less viable and expressed less PCNA, but were not apoptotic even at a high concentration (400 lM), indicating that the limiting effects of TMP were unlikely to be due to toxicity.…”

“…These findings agree with previous studies of trabecular meshwork cells and ECV 304 cells. 16,24 In addition, it is well established that the actin cytoskeleton is associated with the vimentin filament system, which is involved in regulating cell shape and tissue homeostasis. 25 By immunofluorescence staining assay, more pronounced vimentin expression was observed in TGF-b2-treated HTFs, but counteracted by TMP treatment (vimentin content: con, 26.92 6 6.67; TMP, 19.11 6 3.48; TGF-b2, 77.52 6 9.39; TGF-b2 þ TMP, 42.67 6 8.38, *P < 0.01, #P < 0.01, Figs.…”

“…16,[21][22][23] In particular, our latest investigation implicated TMP in attenuation of TGF-b-induced pathologic changes in trabecular meshwork cells, showing that it inhibits cytoskeleton remodeling and ECM accumulation through the SDF/CXCR4 axis. 24 Prompted by these previous reports, we sought to characterize the bioactivity of TMP and its underlying mechanism. In the present study, fibrosis of HTFs was …”