Rat Epithelial Cell Line Research Articles

Three-Dimensional Cell Culture of Epididymal Basal Cells and Organoids: A Novel Tool for Toxicology.

Spermatozoa are formed in the testis but must transit through the epididymis to acquire motility and the ability to fertilize. The epididymis is a single convoluted tubule comprising several anatomically and physiologically distinct regions. The pseudostratified epithelium consists of multiple cell types, including principal cells, clear cells, narrow cells, and apical cells, that line the lumen of the epididymis. Basal cells are present at the base of the epithelium, and halo cells, which includes macrophages/monocytes, mononuclear phagocytes, and T lymphocytes, are also present in the epithelium. Several aspects of this complex spermatozoan maturation process are well established, but a great deal remains poorly understood. Given that dysfunction of the epididymis has been associated with male infertility, in vitro tools to study epididymal function and epididymal sperm maturation are required. Our lab and others have previously developed human, rat, and mouse epithelial principal cell lines, which have been used to address certain questions, such as about the regulation of junctional proteins in the epididymis, as well as the toxicity of nonylphenols. Given that the epididymal epithelium comprises multiple cell types, however, a 3D in vitro model provides a more comprehensive and realistic tool that can be used to study and elucidate the multiple aspects of epididymal function. The purpose of this article is to provide detailed information regarding the preparation, maintenance, passaging, and immunofluorescent staining of rat epididymal organoids derived from adult basal cells, which we have demonstrated to be a type of adult stem cell in the rat epididymis. © 2024 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol 1: Isolation of epididymal cells Basic Protocol 2: Magnetic activated cell sorting and isolation of basal cells Basic Protocol 3: Preparation and culture of epididymal basal cell organoids Basic Protocol 4: Passage of epididymal basal cell organoids Basic Protocol 5: Freezing and thawing of epididymal basal cell organoids Basic Protocol 6: Immunofluorescent staining of epididymal basal cell organoids.

L-Theanine delays d-galactose-induced senescence by regulating the cell cycle and inhibiting apoptosis in rat intestinal cells.

Intestinal senescence is associated with several aging-related diseases. l-Theanine (LTA) has demonstrated strong potential as an antioxidant and antisenescence agent. This study investigated the regulatory effect of LTA on cellular senescence using an in vitro model of d-galactose (D-Gal)-induced senescence in the rat epithelial cell line, intestinal epithelioid cell-6 (IEC-6). Treatment of IEC-6 cells with 40 mg/mL D-Gal for 48 h resulted in the successful development of the senescent cell model. Compared with D-Gal alone, both LTA preventive and delayed intervention increased cell viability and the ratio of JC-1 monomers to aggregates, increased the antioxidant capacity, and decreased the advanced glycation end product (AGE) levels and the overall number of senescent cells. Preventive and delayed intervention with 1000 μM LTA alleviated the D-Gal-induced cell cycle arrest by regulating p38, p53, CDK4, and CDK6 expression at the mRNA and protein levels, and further induced CycD1 proteins. Moreover, LTA preventive intervention reduced apoptosis to a greater degree than delayed intervention by upregulating the expression of the receptors of AGEs, Bax, Bcl-2, and NF-κB at the mRNA and protein levels. Our findings indicate that LTA intervention could attenuate senescence in IEC-6 cells by regulating the cell cycle and inhibiting apoptosis. © 2023 Society of Chemical Industry.

Coactosin-like protein CLP/Cotl1 suppresses breast cancer growth through activation of IL-24/PERP and inhibition of non-canonical TGFβ signaling.

Coactosin-like protein (CLP, or Cotl1), is an F-actin-binding protein, whose role in cancer is largely unknown. Here we show that CLP/Cotl1 is highly expressed in a rat epithelial breast cancer cell line (FE1.3) compared with its mesenchymal counterpart (FE1.2). Knockdown of CLP/Cotl1 in FE1.3 cells increased cell proliferation, whereas its overexpression in FE1.2 cells inhibited proliferation in culture and reduced tumor growth in xenograft assays in mice. Mechanistically, we identified two major pathways through which CLP/Cotl1 exerts its suppressive effects. First, CLP/Cotl1 re-expression in FE1.2 and in human MCF7 breast cancer cells induced expression of the growth-suppressor gene interleukin-24 (IL-24), which independently of p53 upregulates the tumor-suppressor genes p53 apoptosis effector related to PMP-22 (PERP) and p21cip1. Second, overexpression of CLP/Cotl1 potentiated the growth-suppressive effect of transforming growth factor-β1 (TGFβ1), leading to downregulation of TGFβ-responsive genes vascular growth factor A/B (VEGFA/VEGFB), hypoxia inducing factor 1α (HIF-1α) and trombospondin 1 (TSP1), which mediate various hallmarks of cancer progression including angiogenesis, invasion and metastasis. CLP/Cotl1 inhibited TGFβ signaling via a non-canonical signaling involving IL-24-instigated inhibition of mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) phosphorylation and subsequent post-transcriptional downregulation of SMAD2 and SMAD4. We also showed that CLP/COTL1 expression sensitizes breast cancer cells to chemotherapeutic drugs, and this was further enhanced by addition of exogenous TGFβ1. CLP/Cotl1 expression is lost in many human malignancies including prostate, uterine and breast cancers. Thus, our results uncover a novel tumor-suppressor role for CLP/Cotl1 and identify the downstream effectors interleukin 24 (IL-24)/PERP and IL-24/MAPK/ERK/TGFβ as potential targets for precision therapy.

Enteric epithelial cells support growth of Hymenolepis diminuta in vitro and trigger TH2-promoting events in a species-specific manner

Knowledge of the gut epithelium in modulating immune responses to cestode parasites is scant. Hymenolepis diminuta causes no damage to its rodent host and is expelled from mice. Hymenolepis diminuta (scolex+2cm strobila) was cultured with rat (IEC6), human (T84) or mouse (IEC4) epithelial cell lines: all promoted worm survival, but those cultured on IEC6 (rat is a permissive host) were the healthiest. In contrast, production of Th2 polarising cytokines, IL-17e, IL-33 and TSLP, was greatest in IEC4 cells, less in T84 epithelia and almost negligible in IEC6 cells. Thus, the enteric epithelium is a key determinant of the response to infection with H. diminuta and is predictive of host permissiveness.

The role of miR-200a in mammalian epithelial cell transformation.

Cancer is a multistep disease that begins with malignant cell transformation and frequently culminates in metastasis. MicroRNAs (miRNAs) are small regulatory 21-25 nt RNA molecules and are frequently deregulated in cancer. miR-200a is a member of the miR-200 family, which are known inhibitors of the epithelial-to-mesenchymal transition. As such, the tumor-suppressive role of miR-200a in oncogenesis has been well documented; however, recent studies have found a proliferative role for this miRNA as well as a prometastatic role in the later steps of cancer progression. Little is known about the role of this miRNA in the early stages of cancer, namely, malignant cell transformation. Here, we show that miR-200a alone transforms an immortalized rat epithelial cell line, and miR-200a cooperates with Ras to enhance malignant transformation of an immortalized human epithelial cell line. Furthermore, miR-200a induces cell transformation and tumorigenesis in immunocompromised mice by cooperating with a Ras mutant that activates only the RalGEF effector pathway, but not Ras mutants activating PI3K or Raf effector pathways. This transformative ability is in accordance with miR-200a targeting Fog2 and p53 to activate Akt and directly repress p53 protein levels, respectively. These results demonstrate an oncogenic role for miR-200a and provide a specific cellular context where miR-200a acts as an oncomiR rather than a tumor suppressor by cooperating with an oncogene in malignant cell transformation.

A Liver-Derived Rat Epithelial Cell Line from Biliary Origin Acquires Hepatic Functions Upon Sequential Exposure to Hepatogenic Growth Factors and Cytokines

Withdrawal of promising drug candidates is often due to the detection of liver toxicity. In particular the parenchymal liver cells or hepatocytes are targeted since they are the major sites of drug transport and of metabolite formation and thus also the place where not only detoxification, but also activation of new chemical (NCE) and biological (NBE) entities may occur. Therefore, primary hepatocyte- based cultures are currently the preferred in vitro model to screen for liver toxicity. However, within a few days, they undergo dedifferentiation with loss of liver-specific functionality, including xenobiotic biotransformation capacity, making them only suitable for short-term applications. A plausible alternative to primary hepatocyte cultures that can be maintained for longer periods of time could be the use of liver-derived epithelial cell lines and their optimized derivatives. Therefore, in the present study, we evaluated the stability and the hepatic differentiation potential of a neonatal liver-derived rat epithelial cell line from biliary origin (rLEC). Undifferentiated rLEC stably express the hepatic progenitor markers CEBPA, FOXA2, GJA1, ONECUT1, KRT18 and KRT19 for at least 15 consecutive passages after cryopreservation. Upon sequential exposure to hepatogenic growth factors and cytokines, rLEC generate functional hepatic progeny, expressing mature hepatic markers including Alb, Ahr, Car, C/ebpα, Cx32, Foxa2, Hnf1α, Hnf1β and Onecut1. Furthermore, an active polarization is observed for the hepatic drug transporters Oatp4 and Ntcp. rLEC-derived hepatic cells also acquire the ability to store glycogen, express genes encoding for key hepatic enzymes as shown by Affymetrix microarray data, and display stable CYP1A1/2- and CYP2B1/2-dependent activities for several weeks at levels comparable to those observed in cultured primary rat hepatocytes. The acquisition of such a stable and active biotransformation capacity is key for the applicability of liver-based in vitro models for long-term toxicity testing.

Abstract 3701: Dimethylbenzanthracene (DMBA) and DMBA dihydrodiol mutagenicity in rat epithelial and fibroblast cell lines, and its inhibition by combinations of nutraceuticals

Abstract 7,12-Dimethylbenzanthracene (DMBA) is a potent mammary carcinogen in rats. Combinations of non-toxic nutraceutical agents, administered at or near physiological levels, were investigated for their abilities to inhibit the mutagenicity of DMBA or DMBA-dihydrodiol (DMBAD, a primary metabolite and proximate mutagen of DMBA) in vitro, in rat mammary epithelial and fibroblast cells derived from a lacI (BigBlue) Fischer rat (McDiarmid, H.M., Douglas, G.R., Coomber, B.L., and Josephy, P.D. Epithelial and fibroblast cell lines cultured from the transgenic BigBlue rat: an in vitro mutagenesis assay. Mutat. Res., 497: 39-47, 2001). In the epithelial cells, DMBA was not appreciably mutagenic at concentrations up to 4 µM, but DMBAD, was significantly mutagenic at ten-fold lower concentrations. These results indicate that the epithelial cells can bioactivate the intermediate, DMBAD, but cannot effect the complete biotransformation of DMBA to its ultimate mutagenic metabolite, DMBA-dihydrodiolepoxide. In the fibroblast cell line, in contrast, DMBA was mutagenic at concentrations as low as 20 nM and DMBAD was even more potent than DMBA. Several combinations of nutraceuticals (dietary components providing health benefits) were tested for their abilities to inhibit mutagenesis in these cell lines; the concentrations tested were based on reported serum concentrations and these were used to establish 1x concentrations. The agents and their 1x concentrations were: resveratrol (Res), 2.4 μM; sulforaphane (Sul), 0.06 μM; antioxidant mix (α- and γ-tocopherol, 30 μM, plus vitamin C, 68 μM – VCE); α-lipoic acid (LA), 2 μM; epigallocatechin gallate (EGCG), 0.7 μM; and N-acetylcysteine (NAC), 12 μM. None of the agents or their combinations, tested at 1 – 3 x concentrations, showed any cytotoxicity. In both epithelial and fibroblast cells, Sul and Res alone slightly inhibited mutagenesis at 2x concentrations; no other agents had observable effects. All binary combinations of Res, LA, and Sul, at 2x concentrations, inhibited mutagenesis; the Res + Sul combination was particularly effective (ca. 50% inhibition). These results suggest a role for fibroblast cells in the bioactivation of carcinogens, implicating the microenvironment, and indicate that combinations of nutraceuticals can inhibit mutagenesis by polycyclic aromatic hydrocarbons. Supported by the Susan Komen Foundation grant # KG080836 (JBG) and NSERC Canada (PDJ). Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3701. doi:10.1158/1538-7445.AM2011-3701

‘Actin-reactive’ discriminated from ‘non-actin-reactive’ smooth muscle autoantibody by immunofluorescence reactivity with rat epithelial cell line

To compare smooth muscle antibody (SMA) patterns in tissue sections with patterns in an immunofluorescence assay (IFA) using a rat intestinal epithelial cell line and results from an F-actin IgG ELISA. SMA positive sera (n = 188) were classified by immunofluorescence staining of rodent kidney, stomach and liver sections as SMA-T (tubules) (n = 124) or SMA-V (vessels) (n = 64). The F-actin pattern on the rat epithelial cell line was identified by immunofluorescence staining of actin cables that was confirmed by dual immunofluorescence co-localisation with phalloidin. Of 124 SMA-T positive sera, 123 reacted with the epithelial cell line and 120 with F-actin by ELISA, giving sensitivity for detection of anti-F-actin antibody of 99% and 97%, respectively. Of 64 SMA-V positive sera, four reacted with the epithelial cell line (6%) and 41 with F-actin by ELISA (64%). Tests of 493 normal blood donors and 100 disease controls yielded specificities of 584/593 (98.5%) and 562/593 (94.8%) for the cell line IFA and F-actin ELISA, respectively. The rat epithelial cell line IFA is a robust diagnostic assay for anti-F-actin antibody that can either replace the routine screening for actin-reactive SMA-T antibody in tissue sections or be used as a confirmatory assay for anti-F-actin antibody after screening by F-actin ELISA or on rodent tissue sections by IFA.

N-acetylcysteine inhibits alveolar epithelial-mesenchymal transition

The ability of transforming growth factor-beta1 (TGF-beta1) to induce epithelial-mesenchymal transition (EMT) in alveolar epithelial cells (AEC) in vitro and in vivo, together with the demonstration of EMT in biopsies of idiopathic pulmonary fibrosis (IPF) patients, suggests a role for TGF-beta1-induced EMT in disease pathogenesis. We investigated the effects of N-acetylcysteine (NAC) on TGF-beta1-induced EMT in a rat epithelial cell line (RLE-6TN) and in primary rat alveolar epithelial cells (AEC). RLE-6TN cells exposed to TGF-beta1 for 5 days underwent EMT as evidenced by acquisition of a fibroblast-like morphology, downregulation of the epithelial-specific protein zonula occludens-1, and induction of the mesenchymal-specific proteins alpha-smooth muscle actin (alpha-SMA) and vimentin. These changes were inhibited by NAC, which also prevented Smad3 phosphorylation. Similarly, primary alveolar epithelial type II cells exposed to TGF-beta1 also underwent EMT that was prevented by NAC. TGF-beta1 decreased cellular GSH levels by 50-80%, whereas NAC restored them to approximately 150% of those found in TGF-beta1-treated cells. Treatment with glutathione monoethyl ester similarly prevented an increase in mesenchymal marker expression. Consistent with its role as an antioxidant and cellular redox stabilizer, NAC dramatically reduced intracellular reactive oxygen species production in the presence of TGF-beta1. Finally, inhibition of intracellular ROS generation during TGF-beta1 treatment prevented alveolar EMT, but treatment with H2O2 alone did not induce EMT. We conclude that NAC prevents EMT in AEC in vitro, at least in part through replenishment of intracellular GSH stores and limitation of TGF-beta1-induced intracellular ROS generation. We speculate that beneficial effects of NAC on pulmonary function in IPF may be mediated by inhibitory effects on alveolar EMT.

A Novel Small Molecule Regulator of Guanine Nucleotide Exchange Activity of the ADP-ribosylation Factor and Golgi Membrane Trafficking

An image-based phenotypic screen was developed to identify small molecule regulators of intracellular traffic. Using this screen we found that AG1478, a previously known inhibitor of epidermal growth factor receptor, had epidermal growth factor receptor-independent activity in inducing the disassembly of the Golgi in human cells. Similar to brefeldin A (BFA), a known disrupter of the Golgi, AG1478 inhibits the activity of small GTPase ADP-ribosylation factor. Unlike BFA, AG1478 exhibits low cytotoxicity and selectively targets the cis-Golgi without affecting endosomal compartment. We show that AG1478 inhibits GBF1, a large nucleotide exchange factor for the ADP-ribosylation factor, in a Sec7 domain-dependent manner and mimics the phenotype of a GBF1 mutant that has an inactive mutation. The treatment with AG1478 leads to the recruitment of GBF1 to the vesicular-tubular clusters adjacent to the endoplasmic reticulum exit sites, a step only transiently observed previously in the presence of BFA. We propose that the treatment with AG1478 delineates a membrane trafficking intermediate step that depends upon the Sec7 domain.

Glutamine Regulates the Human Epithelial Intestinal HCT-8 Cell Proteome under Apoptotic Conditions

Glutamine plays a key role in the metabolism of rapidly dividing cells, including enterocytes and lymphocytes, which may contribute to its beneficial clinical effects. Gut mucosal homeostasis is achieved through a balance between cell proliferation and apoptosis. In T cells, glutamine up-regulates antiapoptotic proteins and down-regulates proapoptotic proteins. In gut mucosa, glutamine prevents apoptosis in rat epithelial cell lines, whereas glutamine starvation induces apoptosis through caspase activation. Finally glutamine specifically prevents tumor necrosis factor-alpha-related apoptosis in the human intestinal cell line HT-29. Comparative functional proteomics enables the characterization of each differentially expressed protein in intestinal cells in response to modifications of nutritional environment. The influence of glutamine on intestinal proteome expression in apoptotic conditions has not been studied and evaluated. This comparative proteomics study was performed in the human epithelial intestinal cell line HCT-8 under experimental apoptotic conditions to investigate the influence of glutamine on protein expression during apoptosis. The pharmaconutritional effects of glutamine were determined under 2 mm (physiological concentration) and 10 mm (pharmaconutritional concentration) conditions. About 1,800 protein spots were revealed in both conditions. Comparative assessments indicated that 28 proteins were differentially expressed significantly (i.e. at least 2-fold modulated and Student's t test with p </= 0.05) in response to an increase of glutamine concentration in the culture medium. Twenty-four proteins were identified by mass spectrometry and associated databases. From these proteins, 34% are involved in cell cycle and apoptosis mechanisms, 17% are involved in signal transduction, and 13% are involved in cytoskeleton organization. These data were integrated in a proposed schema of the interactome under apoptotic conditions. In conclusion, this study provides the first holistic picture of proteome modulation by glutamine in a human enterocytic cell line under apoptotic conditions and supports further evaluation of nutritional modulation of human intestinal proteome in various pathological conditions where apoptosis may be involved.

Characterization of P-glycoprotein and multidrug resistance proteins in rat kidney and intestinal cell lines

The activity of P-glycoprotein (Pgp/MDR1/ABCB1) and multidrug resistance proteins (MRP/ABCC) influence the pharmacokinetics and bioavailability of many drugs. Few suitable cell lines for the study of drug transport exist. Additional non-human cell lines may help clarify species differences and contribute to the current knowledge of drug transport. The aim of the present study was to characterize three rat epithelial cell lines for transporter expression and activity. Transporter expression was assessed in intestinal IEC-6 and renal GERP and NRK-52E cells using RT-PCR and Western blot analysis. Pgp and Mrp transport activity were analyzed by measuring calcein accumulation and glutathione- S-bimane efflux, respectively. The three cell lines showed Pgp expression and Pgp-dependent transport, both decreasing with culture time after reaching confluency. Besides Pgp, cells expressed Mrp1, Mrp3, Mrp4, and Mrp5, while Mrp2 and Mrp6 were absent. In addition, they showed temperature- and Mrp-dependent efflux of glutathione- S-bimane. Exposure to a panel of different inhibitors showed that this efflux was probably mediated by Mrp4. In conclusion, the three rat epithelial cell lines investigated showed Pgp and Mrp expression and transport. Mrp dependent transport was most likely mediated by Mrp4. In future, these cell lines may be used as in vitro models to study drug transport.

Extracellular adenosine activates AMP-dependent protein kinase (AMPK)

Adenosine monophosphate (AMP)-activated protein kinase (AMPK) is a heterotrimeric complex that senses intracellular energy status and exerts rapid regulation on energy-demanding and -consuming metabolic pathways. Although alterations in the intracellular adenosine nucleotide pool are traditionally assumed to be the consequence of changes in energy metabolism, in this study we have addressed the question of whether extracellular adenosine contributes to AMPK regulation. In the intestinal rat epithelial cell line IEC-6, addition of adenosine rapidly increases AMP intracellular concentrations and upregulates alpha1AMPK, thus promoting phosphorylation of its downstream target acetyl-CoA carboxylase (ACC). The effect of adenosine on AMPK signaling is completely blocked by transducing IEC-6 cells with an adenoviral vector expressing a mutated alpha1 subunit, resulting in a dominant-negative effect on endogenous AMPK activity. These effects are blocked by 5'-iodotubercidine (5'-ITU), an inhibitor of adenosine kinase. Moreover, inhibition of adenosine transport through the concentrative adenosine plasma membrane transporter CNT2 with formycin B results in the blockade of adenosine-mediated AMPK signaling. Extracellular adenosine is equally able to activate AMPK and promote ACC phosphorylation in liver parenchymal cell models in a manner that is also inhibited by 5'-ITU. In summary, this study shows that adenosine, when added at physiological concentrations, activates AMPK and promotes ACC phosphorylation. Adenosine must be transported and phosphorylated to exert its action. Thus, nucleoside transporters might be novel players in the complex regulation of AMPK and energy metabolism.

Association of RON tyrosine kinase with the Jaagsiekte sheep retrovirus envelope glycoprotein

The envelope (Env) of Jaagsiekte sheep retrovirus (JSRV) functions as an oncoprotein. One of the mechanisms of JSRV-induced cell transformation that has been proposed for epithelial cells involves JSRV Env binding Hyaluronidase 2 (the JSRV receptor), thereby inducing its degradation and allowing the release and activation of RON tyrosine kinase which is normally suppressed by HYAL-2. In this study, we report that HYAL-2 and RON are not critical for the JSRV Env-induced transformation of the rat epithelial cell line IEC-18, while the cytoplasmic tail of the JSRV Env is critical to transform this cell line. We have also determined that RON can associate with the JSRV Env under normal and stringent conditions. In addition, the cytoplasmic tail of the JSRV and the enJS5F16 (non oncogenic JSRV-related endogenous retrovirus) Env proteins appears to have a major influence on the activation status of RON. Thus, it appears that the interaction of the JSRV Env with RON is more complex than previously thought and requires further investigation.

1006. Effect on Expression of Including Binding Sites for the ELAV-Like Proteins HuD and HuR in Transgene Cassettes

ELAV-like (embryonic lethal abnormal vision) proteins are RNA- binding proteins first described in Drosophila. ELAV proteins are necessary for neuronal differentiation and maintenance. The human ELAV-like family includes HuB, HuC, Hel-N1, HuD and HuR and consists of three RNA-recognition motifs through which they bind with high affinity and specificity to target mRNAs with AU-rich elements. HuR is expressed in all cells, while HuD is considered neural specific. To optimize vectors for clinical application, we initially evaluated the expression patterns of several viral and mammalian promoters (Zheng and Baum, Mol. Ther., 2005). Since ELAV-like proteins can regulate mRNA stability and/or translation, we hypothesized that inclusion of binding sites for some ELAV-like proteins in expression cassettes could improve transgene expression. To test this, we selected two such binding sites (from p53 and vascular endothelial growth factor [VEGF]) for HuR, and seven binding sites for HuD (from c-fos, IL-3, c-myc-1, c-myc-2, tau, adenovirus IVa2 and growth-associated protein 43 [GAP-43]). Binding sites were inserted into the pACEF1a-luc-bGH expression plasmid, which includes the human elongation factor 1a (EF1a) promoter, luciferase cDNA (luc) and the bovine growth hormone poly A (bGH) in the expression cassette, between the luciferase cDNA and bGH poly A. The 293 and A5 (rat epithelial) cell lines were transfected with plasmids in vitro with LipofectamineTM 2000. We compared expression from these plasmids to that from expression plasmids containing the common SV40 poly A and either the EF1a or cytomegalovirus (CMV) promoter (pACEF1a-luc and pACCMV-luc; i.e., without any ELAV-like protein binding sites). In 293 cells, 24 or 48 hours post-transfection, pACCMV-luc resulted in 3 - 4 fold higher expression than pACEF1a-luc-bGH without ELAV-like protein binding sites. Addition of the p53 binding site to pACEF1a-luc-bGH increased luciferase expression 20 - 30% in 293 cells. The other ELAV-like protein binding sites either had no effect or decreased luciferase expression in 293 cells. In A5 cells, however, pACEF1a- luc-bGH containing the p53 binding site had the highest luciferase activity 24 or 48 hours post-transfection, markedly higher (2 - 3 fold) than that seen with either pACCMV-luc or pACEF1a-luc. pACEF1a-luc-bGH with binding sites from c-myc-2, VEGF and IL-3 also led to increased luciferase expression (45 - 120%) in A5 cells 48 hours post-transfection. These data support our hypothesis, especially in the A5 rat epithelial cell line. The pACEF1a-luc-bGH plasmids containing p53, c-myc-2, VEGF and IL-3 binding sites will next be tested to see if their beneficial effects are realized in vivo.

Adenomatous polyposis coli localization is both cell type and cell context dependent

The adenomatous polyposis coli (APC) tumor suppressor protein is mutated in most colorectal carcinomas. In addition to its role in WNT signaling it is proposed to be involved in both cell migration and mitosis. Although a variety of studies have shown an APC localization along lateral membranes of adjacent epithelial cells the existence of a cortical APC localization in mammalian cells remains controversial. To address this we have used matched rat epithelial (NRK-52E) and fibroblast (NRK-49F) cell lines to investigate the localization of APC. Subconfluent cultures of NRK-52E and -49F cells displayed microtubule-associated APC populations by immunostaining. However, confluent NRK-52E, but not -49F monolayers, exhibited a cortical APC distribution. Cortical APC localized in close proximity to a number of cell junction proteins in a microtubule-independent manner while calcium switch experiments suggested that APC was recruited to the cortex only when junction assembly was complete. Confluent NRK-49F and -52E cells also showed contrasting APC localizations in response to monolayer wounding. Our data suggests APC cortical localization is a feature of confluent epithelioid cells and that the subcellular distribution of APC is therefore dependent upon both cell type and context.

Attenuation of apoptosis in enterocytes by blockade of potassium channels

Apoptosis plays an important role in maintaining the balance between proliferation and cell loss in the intestinal epithelium. Apoptosis rates may increase in intestinal pathologies such as inflammatory bowel disease and necrotizing enterocolitis, suggesting pharmacological prevention of apoptosis as a therapy for these conditions. Here, we explore the feasibility of this approach using the rat epithelial cell line IEC-6 as a model. On the basis of the known role of K+ efflux in apoptosis in various cell types, we hypothesized that K+ efflux is essential for apoptosis in enterocytes and that pharmacological blockade of this efflux would inhibit apoptosis. By probing intracellular [K+] with the K+-sensitive fluorescent dye and measuring the efflux of 86Rb+, we found that apoptosis-inducing treatment with the proteasome inhibitor MG-132 leads to a twofold increase in K+ efflux from IEC-6 cells. Blockade of K+ efflux with tetraethylammonium, 4-aminopyridine, stromatoxin, chromanol 293B, and the recently described K+ channel inhibitor 48F10 prevents DNA fragmentation, caspase activation, release of cytochrome c from mitochondria, and loss of mitochondrial membrane potential. Thus K+ efflux occurs early in the apoptotic program and is required for the execution of later events. Apoptotic K+ efflux critically depends on activation of p38 MAPK. These results demonstrate for the first time the requirement of K+ channel-mediated K+ efflux for progression of apoptosis in enterocytes and suggest the use of K+ channel blockers to prevent apoptotic cell loss occurring in intestinal pathologies.

A Rat Endometrial Cell Line (R1-49E1) Expressing Estrogen Receptor-α Regulated by The Tet-Off System

Estrogens exert profound effects on target tissues. These effects are mediated by two estrogen receptors (ER(alpha) and ER(beta)) that bind to specific DNA sequences in estrogen-dependent genes. Other molecules such as growth factors, transcription factors and some oncoproteins might interact with the estrogen receptors and thus regulate the transcription of these genes. Currently there is no adequate cellular model to study these interactions. We transfected the human wild-type ER(alpha) to an ER-negative rat epithelial endometrial cell line (Rentr01) using a tetracycline-regulated gene expression system. The exogenous receptor was correctly translated, had an appropriate hormone-binding affinity, and bound well to estrogen response elements containing DNA. We obtained a new stable cell line that is ER(beta) negative but ER(alpha) positive (R1-49E1). The expression of receptor alpha can be regulated in a dose-response manner by addition of tetracycline in the culture medium. Estradiol treatment of ER(alpha)-containing cells apparently diminished cellular proliferation, and the exogenous receptor can induce the transcription of the endogenous progesterone receptor isoform B (PgR-B) gene. This epithelial cellular model may be useful to study the interaction between estrogens and other cell signaling pathways in epithelial endometrial cell physiology.

FGF-20 and DKK1 are transcriptional targets of β-catenin and FGF-20 is implicated in cancer and development

beta-catenin is the major effector of the canonical Wnt signaling pathway. Mutations in components of the pathway that stabilize beta-catenin result in augmented gene transcription and play a major role in many human cancers. We employed microarrays to identify transcriptional targets of deregulated beta-catenin in a human epithelial cell line (293) engineered to produce mutant beta-catenin and in ovarian endometrioid adenocarcinomas characterized with respect to mutations affecting the Wnt/beta-catenin pathway. Two genes strongly induced in both systems-FGF20 and DKK1-were studied in detail. Elevated levels of FGF20 RNA were also observed in adenomas from mice carrying the Apc(Min)allele. Both XFGF20 and Xdkk-1 are expressed early in Xenopus embryogenesis under the control of the Wnt signaling pathway. Furthermore, FGF20 and DKK1 appear to be direct targets for beta-catenin/TCF transcriptional regulation via LEF/TCF-binding sites. Finally, by using small inhibitory RNAs specific for FGF20, we show that continued expression of FGF20 is necessary for maintenance of the anchorage-independent growth state in RK3E cells transformed by beta-catenin, implying that FGF-20 may be a critical element in oncogenesis induced by the Wnt signaling pathway.

A new rat type I-like alveolar epithelial cell line R3/1: bleomycin effects on caveolin expression.

The study of function and regulation of the phenotype of alveolar type I (AT I) epithelial cells is limited by the rareness of suitable cell lines or primary cultures of this cell type. We describe in the present study the type I-like rat epithelial cell line R3/1. This cell line displays in vitro a phenotype with several characteristic features of AT I cells. R3/1 cells were analysed for mRNA and protein content of markers related to the AT I cell type (T1alpha, ICAM-1, connexin-43, caveolins-1 and -2) and AT II phenotypes [surfactant proteins (SPs) A, B, C and D]. The mRNAs for SPs were found to be at a low level. Moderate protein levels for SP-A and SP-B were found, and SP-C and SP-D proteins were not detectable. R3/1 cells are positive for CD44s, E-cadherin, cytokeratin, vimentin and RAGE, and bind the lectins BPA and SBA. For demonstration of the suitability of R3/1 cells for in vitro studies on epithelial injury, the cells were treated with bleomycin. As shown by real-time RT-PCR and immunoblotting, bleomycin-treatment of R3/1 cells resulted in a decrease in mRNA and protein for both caveolin-1 and caveolin-2 in comparison with controls. The AT I-like cell line R3/1 may serve as a promising tool for the study of lung cell biology.