ursodoxicoltaurine and Cataract

Epithelial‑to‑mesenchymal transition (EMT) of human lens epithelial cells (HLECs) serve an important role in cataract formation. The endoplasmic reticulum stress response (ER stress) has been demonstrated to regulate EMT in a number of tissues. The aim of the present study was to demonstrate the role of ER stress on EMT in HLECs. HLECs were treated with tunicamycin (TM) or thapsigargin (TG) to disturb ER homeostasis, and 4‑phenylbutyric acid (PBA) or sodium tauroursodeoxycholate (TUDCA) to restore ER homeostasis. Cell morphology was evaluated after 24 h. The long axis and aspect ratio of the cells were analyzed using ImageJ software. The results demonstrated that HLECs adopted an elongated morphology following treatment with TG, and the cellular aspect ratio increased. However, this morphological change was not observed following combination treatment with TG and PBA. Western blot analysis and immunofluorescence staining were used to measure the protein expression levels. A wound‑healing assay was performed to evaluate cell migration. Treatment with TM or TG increased the expression of the ER stress markers glucose‑regulated protein 78, phosphorylated eukaryotic initiation factor 2α, activating transcription factor (ATF)6, ATF4 and inositol‑requiring protein 1α and the EMT markers fibronectin, vimentin, α‑smooth muscle actin and neural cadherin. Furthermore, treatment with TM or TG decreased the expression of the epithelial cell marker epithelial cadherin and enhanced cell migration, which effects were inhibited following treatment with PBA or TUDCA. These results indicates that enhanced ER stress induced EMT and subsequently increased cell migration in HLECs in vitro.

Topics: Cataract; Cell Line; Endoplasmic Reticulum Stress; Epithelial Cells; Epithelial-Mesenchymal Transition; Eye Proteins; Humans; Lens, Crystalline; Phenylbutyrates; Taurochenodeoxycholic Acid; Thapsigargin; Tunicamycin

Many cataractogenic stresses also induce endoplasmic reticulum (ER) stress in lens epithelial cells (LECs), which appears to be one of the universal inducers of cell death. In galactosemic rats, activation of ER stress results in the activation of the unfolded protein response (UPR)-dependent death pathway, production of reactive oxygen species (ROS), and cell death. All are induced and precede cataract formation. Cellular osmolytes such as 4-phenylbutyric acid (PBA), trimethylamine N-oxide (TMAO), and tauroursodeoxychoric acid (TUDCA) are known to suppress the induction of ER stress. We investigated whether these small molecules prevent cataract formation in galactose-fed rat lenses.. Cultured LECs were treated with galactose and each cellular osmolyte. Sprague-Dawley rats were fed a 50% galactose chow for 15 days with or without cellular osmolyte treatment. Similarly, selenite was injected subcutaneously into rats with or without cellular osmolytes. Calcein AM and ethidium homodimer-1 (EthD) were used to detect live and dead cells, respectively. The cellular osmolytes, PBA, TMAO, and TUDCA were tested for their ability to suppress LEC death and cataract formation.. Cellular osmolytes rescued cultured human LECs which were treated with the ER stressors. We administered these osmolytes either orally or by injection into galactosemic Sprague-Dawley rats. These rats had significantly reduced LEC death and partially delayed hypermature cataract formation. Since the UPR was not activated in cultured LECs treated with selenite, we used the selenite nuclear cataract as a UPR-independent death pathway control. In selenite-induced nuclear cataract in rats, cellular osmolytes did not prevent LEC death and did not alleviate cataract formation.. These results further establish that ER stress and LEC death play a vital role in certain types of cataract formation. In addition, cellular osmolytes may be potential prophylactic drugs for some types of cataracts.

Topics: Animals; Body Weight; Cataract; Cell Death; Cell Survival; Cells, Cultured; Disease Models, Animal; Endoplasmic Reticulum; Epithelial Cells; Galactose; Galactosemias; Humans; Lens, Crystalline; Methylamines; Phenylbutyrates; Protein Folding; Rats; Rats, Sprague-Dawley; Sodium Selenite; Taurochenodeoxycholic Acid; Tunicamycin; Up-Regulation