LEFTYA Activates the Epithelial Na+ Channel (ENaC) in Endometrial Cells via Serum and Glucocorticoid Inducible Kinase SGK1.

BACKGROUND: Serum & glucocorticoid inducible kinase (SGK1) regulates several ion channels, including amiloride sensitive epithelial Na+ channel (ENaC). SGK1 and ENaC in the luminal endometrium epithelium, are critically involved in embryo implantation, although little is known about their regulation. The present study explored whether SGK1 and ENaC are modulated by LEFTYA, a negative regulator of uterine receptivity. METHODS: Expression levels were determined by qRT-PCR and Western blotting, ENaC channel activity by whole cell patch clamp and transepithelial current by Ussing chamber experiments. RESULTS: Treatment of Ishikawa cells, an endometrial adenocarcinoma model cell line of endometrial epithelial cells, with LEFTYA rapidly up-regulated SGK1 and ENaC transcript and protein levels. Induction of ENaC in response to LEFTYA was blunted upon co-treatment with the SGK1 inhibitor EMD638683. ENaC levels also significantly upregulated upon expression of a constitutively active, but not a kinase dead, SGK1 mutant in Ishikawa cells. LEFTYA increased amiloride sensitive Na+-currents in Ishikawa cells and amiloride sensitive transepithelial current across the murine endometrium. Furthermore, LEFTYA induced the expression of ENaC in the endometrium of wild-type but not of Sgk1-deficient mice. CONCLUSIONS: LEFTYA regulates the expression and activity of ENaC in endometrial epithelial cells via SGK1. Aberrant regulation of SGK1 and ENaC by LEFTYA could contribute to the pathogenesis of unexplained infertility.

LEFTY2 Controls Migration of Human Endometrial Cancer Cells via Focal Adhesion Kinase Activity (FAK) and miRNA-200a.

BACKGROUND: LEFTY2, a suppressor of cell proliferation, tumor growth, regulator of stemness and embryonic differentiation, is a negative regulator of cancer cell reprogramming. Malignant transformation may lead to migration requiring loss of adhesion and gain of migratory activity. Signaling involved in the orchestration of migration, proliferation and spreading of cells include focal adhesion kinase (FAK) and adhesion molecule E-cadherin. AIMS: The present study explored whether LEFTY2 influences the proliferation marker MKi67, FAK activity, E-cadherin abundance and migration of Ishikawa human endometrial carcinoma cells. Moreover, the study explored the involvement of microRNA-200a (miR-200a), which is known to regulate cellular adhesion by targeting E-Cadherin. METHODS: FAK activity was estimated from FAK phosphorylation quantified by Western blotting, migration utilizing a wound healing assay, miR-200a and MKi67 expression levels utilizing qRT-PCR, cell proliferation and apoptosis using BrdU and Annexin V staining, respectively, and E-Cadherin (E-Cad) abundance, using confocal microscopy. RESULTS: LEFTY2 (25 ng/ml, 48 hours) treatment was followed by decrease of MKi67 expression, FAK activity and migration. LEFTY2 upregulated miRNA-200a and E-Cad protein level in Ishikawa cells. The effect of LEFTY2 on migration was mimicked by FAK inhibitor PF 573228 (50 µM). Addition of LEFTY2 in the presence of PF-573228 did not result in a further significant decline of migration. CONCLUSION: In conclusion, LEFTY2 down-regulates MKi67 expression and FAK activity, up-regulates miR-200a and E-cadherin, and is thus a powerful negative regulator of endometrial cell proliferation and migration.

Lefty-1 alleviates TGF-ß1-induced fibroblast-myofibroblast transdifferentiation in NRK-49F cells.

Fibroblast activation and proliferation are important for fibroblast-myofibroblast transdifferentiation, a crucial process in the pathological changes that define renal interstitial fibrosis. The left-right determination factor (Lefty) is an important cytokine of the transforming growth factor (TGF)-ß family, with two variants, Lefty-1 and Lefty-2, in mice. Lefty has diverse functions, such as the regulation of embryonic development, the inhibition of TGF-ß1 signaling, and the suppression of tumor activity. However, whether Lefty-1 influences fibroblast activation and proliferation, and consequently prevents fibroblast-myofibroblast transdifferentiation, remains unclear. This study aimed to investigate whether Lefty-1 can attenuate TGF-ß1-induced fibroblast-myofibroblast transdifferentiation in normal rat kidney interstitial fibroblast cells (NRK-49F), as well as the mechanisms underlying any effects. Results showed that the typical fibroblast cell morphology of NRK-49F cells was altered after TGF-ß1 treatment and that Lefty-1 significantly prevented this change in a dose-dependent manner. Further analyses demonstrated decreased proliferating cell nuclear antigen, cyclin D1, collagen I(A1), alpha-smooth muscle actin, and fibronectin expression. Lefty-1 further induced remarkable reductions in TGF-ß1-induced Smad3 and mitogen-activated protein kinase-10/c-Jun N-terminal kinase (JNK-3) signaling, and enhanced expression of the antifibrotic factor bone morphogenetic protein (BMP)-5. However, without TGF-ß1, Lefty-1 had no effect on Smad3, JNK-3, and BMP-5 activation and fibroblast-myofibroblast transdifferentiation. Taken together, these findings indicate that Lefty-1 can alleviate TGF-ß1-mediated activation and the proliferation of fibroblasts. Furthermore, Lefty-1 may prevent fibroblast-myofibroblast transdifferentiation in part via modulations of Smad3, JNK-3, and BMP-5 activities in the TGF-ß/BMP signaling pathway.

Lefty A protein inhibits TGF-ß1-mediated apoptosis in human renal tubular epithelial cells.

This study aimed to examine the effects of Lefty A protein on transforming growth factor-ß1 (TGF-ß1)-mediated apoptosis in human renal tubular epithelial cells (HK-2). HK-2 cells were transfected with the human Lefty gene to induce the secretion of endogenous Lefty A protein. Following exposure of the HK-2 cells to recombinant human TGF-ß1 (10 ng/ml), p-Smad2/3 protein levels were examined by western blot analysis, and cellular apoptosis was detected by flow cytometry 6, 12, 24 and 48 h following TGF-ß1 treatment. Coculture of renal tubular epithelial cells with TGF-ß1 resulted in a significant increase in p-Smad2/3 protein levels and the rate of cell apoptosis, which were attenuated by liposome-mediated transfection with the Lefty gene. Lefty A protein was able to inhibit the TGF-ß1/Smad signaling pathway and markedly attenuate TGF-ß1-mediated apoptosis in human renal tubular epithelial cells. Taken together, these results indicated that the TGF-ß1/Smad signaling pathway most likely mediates apoptosis in renal tubular epithelial cells. In addition, Lefty A protein is capable of inhibiting the TGF-ß1/Smad pathway to reduce TGF-ß1/Smad-mediated apoptosis in renal tubular epithelial cells. This study may provide novel insights into the prevention and treatment of urinary tract obstruction disease using Lefty A protein.

Characterization and retinal neuron differentiation of WERI-Rb1 cancer stem cells.

PURPOSE: The evidence is increasing that cancer stem cells (CSCs) expressing embryonic and neuronal stem cell markers are present in human retinoblastoma (Rb). This study was conducted to determine whether stem-like cancer cells (SLCCs) in Rb express retinal stem cell-related genes and whether SLCCs can directly differentiate into retinal neurons. METHODS: The cancer stem cell characteristics in WERI-Rb1 cells were determined with Hoechst 33,342 staining, clone formation assay, and CD133 flow cytometry. The expression of embryonic stem cell and retinal stem cell-related genes was analyzed with real-time PCR and immunofluorescence. The SLCCs were induced to differentiate into retinal neurons by the addition of Dickkopf-related protein 1 and Lefty-A. RESULTS: A small but persistent population of cells excluding Hoechst dye in a verapamil-sensitive manner exhibited a cancer stem cell-like phenotype. The SLCCs displayed highly clonogenic abilities and increased CD133 expression with isolation and expansion in culture in serum-free medium. By comparing the expression of stem cell markers, we found Oct3/4 was more highly expressed in the SLCCs than in human embryonic stem cells. Together with the properties of intrinsic retinal stem cell-related gene expression, we found SLCCs can be induced into neuron-like cells that express glial fibrillary acidic protein and rhodopsin (a photoreceptor cell marker). CONCLUSIONS: These findings provide new insight into cancer stem cells and used a strategy of an artificial change of cancer stem cell fate with transcription factors.