Exposure Of Lens Epithelial Cells Research Articles

ZNF219 protects human lens epithelial cells against H2O2-induced injury via targeting SOX9 through activating AKT/GSK3β pathway.

Opacity of the lens caused by cataracts could lead to severe visual impairment and even blindness. Oxidative stress caused by exposure of lens epithelial cells to hydrogen peroxide (H2O2) can lead to DNA damage and impair cell function. Therefore, how to prevent lens epithelial cells from being harmed by H2O2 is an urgent problem. The ZNF219 gene belongs to the Kruppel like zinc finger gene family, which is involved in a variety of biological processes. In this study, we found the low expression of ZNF219 in H2O2-induced HLE-B3 cells. We further noticed ZNF219 could improve the survival rate of H2O2-induced HLE-B3 cells, and inhibit the apoptosis and oxidative stress response. Mechanically, ZNF219 protected human lens epithelial cells against H2O2-induced injury via targeting SOX9 through activating AKT/GSK3β pathway. We therefore thought ZNF219 was a key protective protein in the oxidative damage of human lens epithelial cells and the pathogenesis of cataract.

Lovastatin Alters TGF-β-Induced Epithelial-Mesenchymal Transition in Porcine Lens Epithelial Cells

Purpose: To determine whether lovastatin affects the epithelial-mesenchymal transition (EMT) in porcine lens epithelial cells (LECs) induced by transforming growth factor-β (TGF-β).Materials and Methods: Porcine LECs were cultured in Dulbecco’s Modified Eagle Medium (DMEM) for 24 h. The cultured cells were then exposed or not exposed to lovastatin (10 µM) for 18 h and then stimulated with or not stimulated with TGF-β2 (5 ng/ml) for 24 h. The expression of α-smooth muscle actin (α-SMA), a marker of myofibroblasts, was determined by real-time PCR, and the expression of α-SMA protein was determined by Western blot. The effect of lovastatin on the expression of the mRNA of collagen type 1 (COL1) was determined by real-time PCR. To assess cell contractility, LECs were cultured in collagen gel with or without pretreatment of lovastatin and exposure of TGF-β2. The longest and shortest diameters of the gels were measured and the area was determined.Results: Exposure of LECs to TGF-β2 increased the expression of the mRNA and protein of α-SMA and the mRNA of COL1A1. TGF-β2 increased the degree of contraction of collagen gel. These findings indicated that TGF-β2 promoted EMT, and the pretreatment of the LECs with lovastatin blocked these changes induced by TGF-β2.Conclusion: Lovastatin inhibits the TGF-β-induced EMT of cultured porcine LECs. This suggests that lovastatin should be considered as a new agent to prevent postoperative complications associated with EMT of LECs.

Poly(ADP-Ribose)Polymerase Inhibition Counteracts Cataract Formation and Early Retinal Changes in Streptozotocin-Diabetic Rats

This study evaluated the role for poly(ADP-ribose) polymerase (PARP) in diabetes-induced cataractogenesis and early retinal changes. Control and streptozotocin (STZ)-diabetic rats were treated with or without the PARP inhibitors 1,5-isoquinolinediol (ISO; 3 mg kg(-1) d(-1) intraperitoneally) and 10-(4-methyl-piperazin-1-ylmethyl)-2H-7-oxa-1,2-diaza-benzo[de]anthracen-3-1 (GPI-15427, 30 mg kg(-1) d(-1) orally) for 10 weeks after the first 2 weeks without treatment. Lens clarity was evaluated by indirect ophthalmoscopy and slit lamp examination, and retinal changes were evaluated by immunohistochemistry and Western blot analysis. In in vitro studies, cultured human lens epithelial cells and bovine retinal pericytes and endothelial cells were exposed to high glucose or palmitate. PARP is expressed in lens, and poly(ADP-ribosyl)ated proteins are primarily localized in the 38- to 87-kDa range of the protein spectrum, with several minor bands at 17 to 38 kDa. The 38- to 87-kDa and the 17- to 38-kDa poly(ADP-ribosyl)ated protein expression increased by 74% and 275%, respectively, after 4 weeks of diabetes and by approximately 65% early after exposure of lens epithelial cells to 30 mM glucose. Both PARP inhibitors delayed, but did not prevent, the formation of diabetic cataract. The number of TUNEL-positive nuclei in flatmounted retinas increased approximately 4-fold in STZ diabetic rats, and this increase was prevented by ISO and GPI-15427. Both PARP inhibitors reduced diabetes-induced retinal oxidative-nitrosative and endoplasmic reticulum stress and glial activation. GPI-15427 (20 microM) prevented oxidative-nitrosative stress and cell death in palmitate-exposed pericytes and endothelial cells. PARP activation is implicated in the formation of diabetic cataract and in early retinal changes. These findings provide a rationale for the development of PARP inhibitors for the prevention of diabetic ocular complications.

The Canonical Intrinsic Mitochondrial Death Pathway Has a Non-apoptotic Role in Signaling Lens Cell Differentiation

The mitochondrial cell death pathway is known for its role in signaling apoptosis. Here, we describe a novel function for the mitochondrial cell death pathway in signaling initiation of differentiation in the developing lens. Most remarkably, we induced lens cell differentiation by short-term exposure of lens epithelial cells to the apoptogen staurosporine. Activation of apoptosis-related pathways induced lens epithelial cells to express differentiation-specific markers and to undergo morphogenetic changes that led to formation of the lens-like structures known as lentoids. The fact that multiple stages of differentiation are expressed at a single stage of development in the embryonic lens made it possible to precisely determine the timing of expression of proteins associated with the apoptotic pathway. We discovered that there was high expression in the lens equatorial epithelium (the region of the lens in which differentiation is initiated) of pro-apoptotic molecules such as Bax and Bcl-x(S) and release of cytochrome c from mitochondria. Furthermore, we found significant caspase-3-like activity in the equatorial epithelium, yet this activity was far lower than that associated with lens cell apoptosis. These apoptotic pathways are likely regulated by the concurrent expression of prosurvival molecules, including Bcl-2 and Bcl-x(L); phosphorylation of Bad; and high expression of inhibitor of apoptosis proteins chicken IAP1, IAP3, and survivin. This finding suggests that prosurvival pathways allow pro-apoptotic molecules to function as molecular switches in the differentiation process without tipping the balance toward apoptosis. We call this process apoptosis-related Bcl-2- and caspase-dependent (ABC) differentiation.

Activity of Ubiquitin-dependent Pathway in Response to Oxidative Stress: UBIQUITIN-ACTIVATING ENZYME IS TRANSIENTLY UP-REGULATED

Relations between the ubiquitin pathway and cellular stress have been noted, but data regarding responses of the ubiquitin pathway to oxidative stress are scanty. This paper documents the response of this pathway to oxidative stress in lens cells. A brief exposure of lens epithelial cells to physiologically relevant levels of H2O2 induces a transient increase in activity of the ubiquitin-dependent pathway. Ubiquitin conjugation activity was maximal and increased 3. 5-9.2-fold over the activity noted in untreated cells by 4 h after removal of H2O2. By 24 h after removal of H2O2, ubiquitin conjugation activity returned to the level noted in untreated cells. In parallel to the changes in ubiquitin conjugation activity, the activity of ubiquitin-activating enzyme (E1), as determined by thiol ester formation, increased 2-6.7-fold during recovery from oxidation. Addition of exogenous E1 resulted in an increase in ubiquitin conjugation activity and in the levels of ubiquitin carrier protein (E2)-ubiquitin thiol esters in both the untreated cells and the H2O2-treated cells. These data suggest that E1 is the rate-limiting enzyme in the ubiquitin conjugation process and that the increases in ubiquitin conjugation activity which are induced upon recovery from oxidation are primarily due to increased E1 activity. The oxidation- and recovery-induced up-regulation of E1 activity is primarily due to post-synthetic events. Substrate availability and up-regulation of E2 activities also appear to be related to the enhancement in ubiquitinylation upon recovery from oxidative stress. The oxidation-induced increases in ubiquitin conjugation activity were associated with an increase in intracellular proteolysis, suggesting that the transient increase in ubiquitinylation noted upon recovery from oxidative stress may play a role in removal of damaged proteins from the cells.