Publications -- Yang Liu

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12503/31720

This collection is limited to articles published under the terms of a creative commons license or other open access publishing agreement since 2016. It is not intended as a complete list of the author's works.

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    Fibronectin extra domain A (FN-EDA) causes glaucomatous trabecular meshwork, retina, and optic nerve damage in mice
    (BioMed Central Ltd., 2022-05-26) Mavlyutov, Timur A.; Myrah, Justin J.; Chauhan, Anil K.; Liu, Yang; McDowell, Colleen M.
    BACKGROUND: Elevated intraocular pressure (IOP) is a major risk factor for the development and progression of primary open angle glaucoma and is due to trabecular meshwork (TM) damage. Here, we investigate the role of an endogenous Toll-like receptor 4 (TLR4) ligand, FN-EDA, in the development of glaucoma utilizing a transgenic mouse strain (B6.EDA(+/+)) that constitutively expresses only FN containing the EDA isoform. METHODS: Eyes from C57BL6/J (wild-type), B6.EDA+/+ (constitutively active EDA), B6.EDA-/- (EDA null) mice were processed for electron microscopy and consecutive images of the entire length of the TM and Schlemm's canal (SC) from anterior to posterior were collected and montaged into a single image. ECM accumulation, basement membrane length, and size and number of giant vacuoles were quantified by ImageJ analysis. Tlr4 and Iba1 expression in the TM and ONH cells was conducted using RNAscope in situ hybridization and immunohistochemistry protocols. IOP was measured using a rebound tonometer, ON damage assessed by PPD stain, and RGC loss quantified in RBPMS labeled retina flat mounts. RESULTS: Ultrastructure analyses show the TM of B6.EDA(+/+) mice have significantly increased accumulation of ECM between TM beams with few empty spaces compared to C57BL/6 J mice (p < 0.05). SC basement membrane is thicker and more continuous in B6.EDA(+/+) mice compared to C57BL/6 J. No significant structural differences are detected in the TM of EDA null mice. Tlr4 and Iba1 expression is increased in the TM of B6.EDA(+/+) mice compared to C57BL/6 J eyes (p < 0.05). IOP is significantly higher in B6.EDA(+/+) mice compared to C57BL/6 J eyes (p < 0.001), and significant ON damage (p < 0.001) and RGC loss (p < 0.05) detected at 1 year of age. Tlr4 mRNA is expressed in mouse ONH cells, and is present in ganglion cell axons, microglia, and astrocytes. There is a significant increase in the area occupied by Iba-1 positive microglia cells in the ONH of B6.EDA(+/+) mice compared to C57BL/6 J control eyes (p < 0.01). CONCLUSIONS: B6.EDA(+/+) mice have increased ECM accumulation in the TM, elevated IOP, enhanced proinflammatory changes in the ONH, loss of RGCs, and ONH damage. These data suggest B6.EDA(+/+) mice recapitulate many aspects of glaucomatous damage.
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    Early-Onset Glaucoma in egl1 Mice Homozygous for Pitx2 Mutation
    (MDPI, 2022-02-22) Kodati, Bindu; Merchant, Shawn A.; Millar, J. Cameron; Liu, Yang
    Mutations in PITX2 cause Axenfeld-Rieger syndrome, with congenital glaucoma as an ocular feature. The egl1 mouse strain carries a chemically induced Pitx2 mutation and develops early-onset glaucoma. In this study, we characterized the glaucomatous features in egl1 mice. The eyes of egl1 and C57BL/6J control mice were assessed by slit lamp examination, total aqueous humor outflow facility, intraocular pressure (IOP) measurement, pattern electroretinography (PERG) recording, and histologic and immunohistochemistry assessment beginning at 3 weeks and up to 12 months of age. The egl1 mice developed elevated IOP as early as 4 weeks old. The IOP elevation was variable and asymmetric within and between the animals. The aqueous humor outflow facility was significantly reduced in 12-month-old animals. PERG detected a decreased response at 2 weeks after the development of IOP elevation. Retinal ganglion cell (RGC) loss was detected after 8 weeks of IOP elevation. Slit lamp and histologic evaluation revealed corneal opacity, iridocorneal adhesions (anterior synechiae), and ciliary body atrophy in egl1 mice. Immunohistochemistry assessment demonstrated glial cell activation and RGC axonal injury in response to IOP elevation. These results show that the eyes of egl1 mice exhibit anterior segment dysgenesis and early-onset glaucoma. The egl1 mouse strain may represent a useful model for the study of congenital glaucoma.
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    Glucocorticoid receptor GRbeta regulates glucocorticoid-induced ocular hypertension in mice
    (Springer Nature, 2018-01-16) Patel, Gaurang C.; Liu, Yang; Millar, J. Cameron; Clark, Abbot F.
    Prolonged glucocorticoid (GC) therapy can cause GC-induced ocular hypertension (OHT), which if left untreated progresses to iatrogenic glaucoma and permanent vision loss. The alternatively spliced isoform of glucocorticoid receptor GRbeta acts as dominant negative regulator of GR activity, and it has been shown that overexpressing GRbeta in trabecular meshwork (TM) cells inhibits GC-induced glaucomatous damage in TM cells. The purpose of this study was to use viral vectors to selectively overexpress the GRbeta isoform in the TM of mouse eyes treated with GCs, to precisely dissect the role of GRbeta in regulating steroid responsiveness. We show that overexpression of GRbeta inhibits GC effects on MTM cells in vitro and GC-induced OHT in mouse eyes in vivo. Ad5 mediated GRbeta overexpression reduced the GC induction of fibronectin, collagen 1, and myocilin in TM of mouse eyes both in vitro and in vivo. GRbeta also reversed DEX-Ac induced IOP elevation, which correlated with increased conventional aqueous humor outflow facility. Thus, GRbeta overexpression reduces effects caused by GCs and makes cells more resistant to GC treatment. In conclusion, our current work provides the first evidence of the in vivo physiological role of GRbeta in regulating GC-OHT and GC-mediated gene expression in the TM.
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    In vitro and in vivo neuroprotective effects of cJun N-terminal kinase inhibitors on retinal ganglion cells
    (BioMed Central Ltd., 2016-04-21) Kim, Byung-Jin; Silverman, Sean M.; Liu, Yang; Wordinger, Robert J.; Pang, Iok-Hou; Clark, Abbot F.
    BACKGROUND: The c-Jun N-terminal kinase (JNK) signaling pathway plays an important role in neuronal pathophysiology. Using JNK inhibitors, we examined involvement of the JNK pathway in cultured rat retinal ganglion cell (RGC) death and in mouse retinal ischemia/reperfusion (I/R) injury of the visual axis. The in vitro effects of JNK inhibitors were evaluated in cultured adult rat retinal cells enriched in RGCs. Retinal I/R was induced in C57BL/6J mice through elevation of intraocular pressure to 120 mmHg for 60 min followed by reperfusion. SP600125 was administered intraperitoneally once daily for 28 days. Phosphorylation of JNK and c-Jun in the retina was examined by immunoblotting and immunohistochemistry. The thickness of retinal layers and cell numbers in the ganglion cell layer (GCL) were examined using H&E stained retinal cross sections and spectral domain optical coherence tomography (SD-OCT). Retinal function was measured by scotopic flash electroretinography (ERG). Volumetric measurement of the superior colliculus (SC) as well as VGLUT2 and PSD95 expression were studied. RESULTS: JNK inhibitors SP600125 and TAT-JNK-III, dose-dependently and significantly (p < 0.05) protected against glutamate excitotoxicity and trophic factor withdrawal induced RGC death in culture. In the I/R model, phosphorylation of JNK (pJNK) in the retina was significantly (p < 0.05) increased after injury. I/R injury significantly (p < 0.05) decreased the thickness of retinal layers, including the whole retina, inner plexiform layer, and inner nuclear layer and cell numbers in the GCL. Administration of SP600125 for 28 days protected against all these degenerative morphological changes (p < 0.05). In addition, SP600125 significantly (p < 0.05) protected against I/R-induced reduction in scotopic ERG b-wave amplitude at 3, 7, 14, 21 and 28 days after injury. SP600125 also protected against the I/R-induced losses in volume and levels of synaptic markers in the SC. Moreover, the protective effects of SP600125 in the retina and SC were also detected even with only 7 days (Days 1-7 after I/R) of SP600125 treatment. CONCLUSIONS: Our results demonstrate the important role the JNK pathway plays in retinal degeneration in both in vitro and in vivo models and suggest that JNK inhibitors may be a useful therapeutic strategy for neuroprotection of RGCs in the retina.