PubMed Health⌕ Search

Biomedical subjects

A P Soler

Publications and source records attributed to A P Soler.

At least 19 recordsLinked to original sources
PubMed2001

Abnormal ornithine decarboxylase activity in transgenic mice increases tumor formation and infertility.

A transgenic mouse line carrying ornithine decarboxylase cDNA as the transgene under the control of a mouse mammary tumor virus long terminal repeat (MMTV LTR) promoter was generated in order to study whether ornithine decarboxylase transgene expression will have any physiological or pathological effect during the entire life of a transgenic mouse. The high frequency of infertile animals and the loss of pups made the breeding of homozygous mice unsuccessful. However, a colony of heterozygous transgenic mice was followed for 2 years. In adult heterozygous transgenic mice, ornithine decarboxylase activity was significantly increased in the testis, seminal vesicle and preputial gland when compared to non-transgenic controls. In contrast, ornithine decarboxylase activity was decreased in the kidney and prostate of transgenic mice. No significant changes in ornithine decarboxylase activity were found in the ovary and mammary gland and only moderate changes in ornithine decarboxylase activity were detected in the heart, brain, pancreas and lung. The most common abnormalities found in adult animals (12 males and 20 females) of the transgenic line were inflammatory processes, including pancreatitis, hepatitis, sialoadenitis and pyelonephritis. Spontaneous tumors were observed in eight animals, including two benign tumors (one dermatofibroma, one liver hemangioma) and six malignant tumors (one lymphoma, one intestinal and three mammary adenocarcinomas and one adenocarcinoma in the lung). No significant pathological changes were found in 17 nontransgenic controls.

Animals↗
PubMed2001

Cadherin junctions in mammary tumors.

Cadherins are the transmembrane component of adherens junctions found between interacting cells in tissues. The cadherins bind cells to one another in a specific manner and link to the actin cytoskeleton through intracellular catenins. In addition to promoting strong cell-cell adhesion, cadherins appear to initiate and modify intracellular signaling pathways. The loss of E-cadherin function in epithelial cells is thought to be an important step in tumorigenesis. Moreover, anomalous expression of inappropriate cadherins in epithelial cells alters their behavior and may contribute to the tumorigenic phenotype. For breast cancer the decreased expression of E-cadherin alone may have limited value as a prognostic indicator; however, examining the repertoire of cadherins and catenins expressed by tumors may provide useful prognostic information.

Animals↗
PubMed2001

Overexpression of neural cell adhesion molecule in Chagas' myocarditis.

The expression of the neural cell adhesion molecule (NCAM) was studied in normal human myocardium and in Chagas' disease myocarditis. We found that NCAM is expressed in the conduction system as well as the myocardium in the fetal heart, but its expression is restricted to the conduction system and absent in the adult myocardium. Chagas' disease is an American endemic disease caused by the Trypanosoma cruzi parasite, which produces myocarditis and a blockade of the conduction system, resulting in cardiac dysfunction. We studied the expression of NCAM in paraffin-embedded human heart tissues from 34 autopsies of patients with Chagas' myocarditis and from murine and canine experimental acute Chagas' myocarditis, using a polyclonal anti-NCAM antibody and immunohistochemistry. Our results show a dramatic upregulation of NCAM expression in the intercalated discs of cardiomyocytes in acute and chronic Chagas' myocarditis. Surprisingly, the NCAM signal was detected in intracellular nests of amastigote forms of the parasite, within infected cardiomyocytes of human and experimental Chagas' myocarditis. In contrast, cardiac cell-cell adhesion proteins, N-cadherin and beta-catenin, were found in intercalated discs distorted by the infection but absent from the amastigote nests. Proteins reactive to several antibodies against NCAM were detected by Western immunoblotting in cultured T cruzi parasites and in trypomastigote forms of T cruzi extracted from the blood of infected mice. The upregulation of NCAM in Chagas' myocarditis and the expression of NCAM or a NCAM-like protein by T cruzi suggest that NCAM may act as a receptor for tissue targeting and cellular invasion by T cruzi in Chagas' disease.

Animals↗
PubMed2001

Alterations induced by E-cadherin and beta-catenin antibodies during the development of Bufo arenarum (Anura-Bufonidae).

E(epithelial)-cadherin is a member of a calcium-dependent family of cell surface glycoproteins involved in cell-cell adhesion and morphogenesis. Catenins are a large family of proteins that connect the cadherins to the cytoskeleton. They are important for cadherin function and for transducing signals involved in specification of cell fate during embryogenesis. The best characterized catenins include alpha-, beta-, gamma-, and p120-catenin. Using specific antibodies, we studied the expression and distribution of E-cadherin, and alpha- and beta-catenin in developmental stages of Bufo arenarum toad. The three proteins were found co-localized in stages 19 to 41 of development. Surprisingly, E-cadherin was the only of these three proteins found earlier than stage 19. To test whether E-cadherin and beta-catenin have a functional role in Bufo arenarum embryogenesis, stage 17 whole embryos were incubated with anti-E-cadherin and beta-catenin antibodies. Both anti-E-cadherin and anti-beta-catenin antibodies induced severe morphological alterations. However, while alterations produced by the anti-beta-catenin antibody, showed some variability from the most severe (neural tube and notochord duplication) to a simple delay in development, the alterations with anti-E-cadherin were homogeneous. These observations suggest a critical role for E-cadherin and beta-catenin in the early embryonic development of the Bufo arenarum toad. Our results are consistent with the developmental role of these proteins in other species. One of the most surprising findings was the blockage with the anti-beta-catenin antibodies on later embryo stages, and we hypothesize that the partial axes duplication could be mediated by the notochord induction.

Animals↗
PubMed2000

Wnt-1 dependent activation of the survival factor NF-kappaB in PC12 cells.

Expression of the Wnt-1 oncogene in PC12 cells induces morphological and biochemical changes, including up-regulation of cell adhesion and lack of differentiation in response to growth factors. The survival of PC12 cells is known to be mediated in part by phosphatidylinositol-3 kinase (PI-3 kinase)-dependent activation of the transcription factor nuclear factor-kappaB (NF-kappaB). We investigated the effect of Wnt-1 expression on cell survival and NF-kappaB activation using PC12 cells expressing Wnt-1 (PC12/Wnt1) and a reporter vector in which firefly luciferase expression is under the control of NF-kappaB consensus sequences. Serum deprivation caused apoptosis and decreased NF-kappaB activity in wild type PC12 cells. PC12/Wnt-1 cells showed less apoptosis in the absence of serum, and the levels of NF-kappaB activity were higher than in wild type PC12 cells. NF-kappaB activity was also increased by the transient expression of Wnt-1 in PC12 cells and it was completely inhibited in both PC12 and PC12/Wnt-1 cells by a dominant negative mutant IkappaB-alpha that has been shown to prevent NF-kappaB activation. Agents known to inhibit NF-kappaB-induced apoptosis in PC12 as well as in PC12/Wnt-1 cells, indicating a role of NF-kappaB activation in the anti-apoptotic effect of Wnt-1. Inhibition of PI-3 kinase with wortmannin, or with a dominant negative p85 regulatory subunit of the PI-3 kinase, blocked NF-kappaB activity in PC12 cells but caused only partial inhibition in PC12/Wnt-1 cells. The effect of Wnt-1 in activating NF-kappaB can be mimicked by inhibition of glycogen synthase kinase-3beta (GSK-3beta) with lithium or with a dominant negative GSK-3beta. Our results show that expression of Wnt-1 increases survival of PC12 cells in the absence of serum by activating the anti-apoptotic factor NF-kappaB. Wnt-1-induced activation of NF-kappaB is partially independent of PI-3 kinase and can be mimicked by inhibition of GSK-3beta.

Androstadienes↗
PubMed2000

Regulation of protein kinase C-delta and -epsilon isoforms by phorbol ester treatment of LLC-PK1 renal epithelia.

BACKGROUND: LLC-PK1 renal epithelia are a widely used model for proximal tubular physiology and differentiation. Protein kinase C (PKC) has been observed to play a role in both processes. This study examines the subcellular distribution and down-regulation of PKC-delta and PKC-epsilon isoforms in phorbol ester-treated LLC-PK1 epithelia. METHODS: Cells were treated with 10-7 mol/L 12-O-tetradecanoyl phorbol 13-acetate (TPA) for up to seven days and were extracted as total cell lysates as well as cytosolic, membrane-associated (Triton-X soluble) and a third (Triton-X insoluble) fraction. The expression and cellular localization of PKC-delta and PKC-epsilon isoforms were then detected using Western immunoblot and immunofluorescence. RESULTS: Based on the use of an anti-PKC-delta monoclonal antibody, TPA was observed to cause a rapid decrease in total PKC-delta content, which then returned to near control levels by seven days of treatment. Immunofluorescence indicated that PKC-delta had a cytoskeletal localization within the cells, and a subtle cytoskeletal rearrangement occurred upon exposure to TPA. Western immunoblots showed that PKC-delta did not undergo the expected membrane translocation upon activation by TPA, but simply disappeared immediately from the cytosolic compartment. Conventional cell fractionation procedures such as homogenization and Triton extraction prior to Western immunoblot will, however, fail to evaluate completely PKC-delta in LLC-PK1 epithelia because of the highly stringent measures necessary to extract PKC-delta from the cytoskeletal compartment of these cells. Furthermore, we observed that a second (polyclonal) PKC-delta antibody may recognize phosphorylated forms of PKC-delta, which went unrecognized by the other antibody. PKC-epsilon was present in the cytosol, membrane, and Triton-X-insoluble fractions of the cells. TPA treatment resulted in a partial translocation of PKC-epsilon to both the membrane and Triton-X-insoluble fractions of the cell, but total PKC-epsilon remained essentially unchanged. CONCLUSIONS: The present data indicate that the localization of PKC-delta and subsequent redistribution within the LLC-PK1 cells in response to TPA treatment is highly unique and distinct from that of PKC-epsilon and PKC-alpha. An important methodological finding is that one given antibody may not recognize all phosphoproteins of a given PKC isoform.

Animals↗
PubMed2000

Lack of correlation between serum levels of E- and P-cadherin fragments and the presence of breast cancer.

Breast cancers often show reduced expression of the transmembrane cell-cell adhesion protein, E-cadherin. In addition, approximately half of breast carcinomas express P-cadherin, which correlates with poor survival. A large fragment of the E-cadherin extracellular domain can be detected in serum, and it has been proposed that an increase in serum E-cadherin can denote the presence of a tumor. In this study, we tested the possibility that serum E- or P-cadherin levels might be useful diagnostic or prognostic indicators in breast cancer. However, we found no indication that the level of serum E-cadherin correlated with the presence of breast cancer. In addition, although we successfully detected a fragment of P-cadherin in serum, we found that its level was considerably lower than that of E-cadherin and did not correlate with the presence of P-cadherin-positive breast cancer.

Breast↗
PubMed2000

Protein kinase C activation leads to dephosphorylation of occludin and tight junction permeability increase in LLC-PK1 epithelial cell sheets.

Activation of protein kinase C by exposure of LLC-PK1 renal epithelial cells to 10(-7) M TPA, a tumor promoting phorbol ester, results in a rapid and sustained increase in paracellular permeability as evidenced by a decrease in transepithelial electrical resistance. Occludin, the first identified transmembrane protein to be localized to the tight junction of both epithelial and endothelial cells is thought play an important role in tight junction barriers. Although transepithelial electrical resistance fell to less than 20% of initial values within 1 hour of TPA exposure, transmission electron microscopy showed no change in the gross morphology of the tight junction of cells treated with 10(-7) M TPA for up to 2 hours. Immunofluorescence microscopy revealed a more rapid change in the membrane distribution of ZO-1 compared to occludin in the TPA-treated cells. Immunoblot analysis indicated that occludin levels in total cell lysates as well as cytosolic, membrane (Triton-X soluble) and cytoskeletal (Triton-X insoluble) fractions remained unchanged for at least 2 hours in cells treated with 10(-7) M TPA compared to their corresponding control cells. As the phosphorylation state of occludin is thought to be important in both tight junction assembly and regulation, the effect of phorbol ester treatment on the phosphorylation of occludin was investigated. Surprisingly, activation of protein kinase C with 10(-7) M TPA resulted in a time-dependent decrease in threonine phosphorylation of occludin which correlated closely with the rapid decrease in transepithelial electrical resistance. This dephosphorylation of occludin, occurring after activation of a serine/threonine kinase by TPA, suggested that protein kinase C was not acting directly on this tight junction target protein. If occludin dephosphorylation is involved in increasing tight junction permeability, then protein kinase C is apparently further upstream in the signaling pathway regulating epithelial barrier function, with a downstream serine/threonine phosphatase acting upon occludin.

Animals↗
PubMed2000

Nuclear localization of E-cadherin expression in Merkel cell carcinoma.

CONTEXT: Cadherins are cell-cell adhesion proteins that act as tumor suppressor genes and have a critical role in cell sorting and tissue formation during organogenesis. The pattern of cadherin expression constitutes a useful diagnostic and prognostic tool in the evaluation of tumors and for determining the histogenesis of tumor cells. We have previously characterized the cell types of several tumors based on the expression of individual cadherins. OBJECTIVE: To investigate the expression of cadherins in Merkel cell carcinomas. DESIGN: Paraffin immunohistochemical analysis of the 3 best-studied cadherins was performed on 35 cases of Merkel cell carcinoma. RESULTS: E-cadherin was expressed in 34 (97%) of 35 Merkel cell carcinomas examined, N-cadherin was expressed in 22 (63%) of 35 cases, and P-cadherin was expressed in 15 (43%) of 35 cases. This frequency of cadherin expression was similar to a group of small cell and neuroendocrine tumors from other primary sites. Interestingly, the localization of E-cadherin expression was unique in Merkel cell carcinomas compared with other primary neuroendocrine tumors. Merkel cell carcinomas showed marked preference for nuclear versus membrane localization, whereas small cell tumors from other sites showed fewer cases of nuclear E-cadherin expression. The nuclear localization of E-cadherin did not correlate with cadherin-associated protein beta-catenin nuclear expression. CONCLUSIONS: Our findings show that E-cadherin is the most frequently expressed cadherin in Merkel cell carcinoma, followed in frequency by N-cadherin then P-cadherin. The pattern of nuclear E-cadherin expression is more frequent for Merkel cell carcinoma than small cell tumors of other primary sites. These observations suggest that E-cadherin expression and function are altered in Merkel cell carcinoma, and this finding has potential use in the differential diagnosis of these tumors.

Breast Neoplasms↗
PubMed2000

Expression of N-CAM-180 and N-cadherin during development in two South-American anuran species (Bufo arenarum and Hyla nana).

Cadherins and N-CAM are Ca++-dependent and Ca++-independent cell adhesion molecules respectively. These molecules play a key role in morphogenesis and histogenesis. We determined the spatiotemporal pattern of N-cadherin and N-CAM-180 kDa expression by immunohistochemistry during development in two South-American anuran species (Bufo arenarum, toad and Hyla nana, frog). Both N-cadherin and N-CAM were not detectable during early developmental stages. Expression of N-cadherin appeared between the inner and the outer ectoderm layers at stages 19-20. At stages 24-25, N-cadherin was expressed in the neural tube and the heart. In early tadpoles, N-cadherin expression increased along with the central nervous system (CNS) morphogenesis, and reached its maximum level at metamorphic climax stage. N-Cadherin expression was not uniformly distributed. At stage 42, olfactory placodes and retina expressed N-cadherin. Contrary to N-CAM, the strongly myelinated cranial nerves were not labeled. N-Cadherin was present in several mesoderm derivatives such as the notochord, heart and skeletal muscle. The non-neural ectoderm and the endoderm were always negative. Expression of N-CAM appeared first in the neural tube at stages 24-25 and the level of expression became uniform from pre-metamorphic to metamorphic climax tadpoles. At this latter stage, a clear N-CAM immunolabeling appeared in the nerve terminals of pharynx and heart. N-Cadherin and N-CAM were found mainly co-expressed in the CNS from early tadpole to metamorphic climax tadpole. Our results show that the expression of N-CAM and N-cadherin is evolutionary conserved. Their increased expression during late developmental stages suggests that N-CAM and N-cadherin are involved in cell contact stabilization during tissue formation.

Animals↗
PubMed1999

N-cadherin distinguishes pleural mesotheliomas from lung adenocarcinomas: a ThinPrep immunocytochemical study.

BACKGROUND: Cadherins are a family of cell-cell adhesion proteins. The homotypic binding of cadherins is critical for cell sorting and tissue formation during organogenesis. Different cadherin subtypes show lineage specific tissue expression, which has been exploited to differentiate histologically similar tumors of varying ontogeny. By applying immunohistochemistry to tissue sections, the authors have previously documented the utility of N-cadherin in distinguishing between pleural mesotheliomas and lung adenocarcinomas, based on the observation that N-cadherin is expressed in the former disease but not in the latter. Because the diagnosis of these diseases is frequently rendered on cytologic material rather than tissue biopsies, the authors wanted to assess the utility of N-cadherin immunocytochemistry in evaluating material prepared with ThinPrep. METHODS: The authors examined the cytologic material from 12 patients for the expression of N-cadherin using immunocytochemistry. Four patients had mesotheliomas and eight had adenocarcinomas. ThinPrep slides of the patients' pleural fluid were prepared and stained with the monoclonal antibody 13A9, which is specific for N-cadherin. RESULTS: Of the 12 cases studied, all 4 cases of pleural mesothelioma expressed N-cadherin in a specific cell-cell membrane location, and all 8 cases of lung adenocarcinoma were negative for N-cadherin. CONCLUSIONS: These results show that the N-cadherin specific antibody 13A9 is a suitable marker in material prepared with ThinPrep for the differentiation of pleural mesotheliomas from lung adenocarcinomas. This antibody should be included in the diagnostic immunocytochemical panel for evaluation of these malignancies.

Adenocarcinoma↗
PubMed1999

Distinct cadherin profiles in special variant carcinomas and other tumors of the breast.

The cadherins are homotypic adhesion proteins that are important in cell sorting during organogenesis. Classical cadherins include several different types that show tissue-specific expression. Cell lineage-specific expression of different cadherin subtypes can differentiate morphologically similar but histogenetically distinct tumors. We examined by immunohistochemistry in paraffin sections, the expression of E (epithelial), N- (neural), and P- (placental) cadherin in 36 unusual tumors of the breast (22 medullary carcinomas, 5 metaplastic carcinomas, 2 carcinosarcomas, 4 phyllodes tumors, and 3 periductal stromal tumors). All carcinomas stain with E-cadherin (22 of 22 medullary and 5 of 5 metaplastic). E-cadherin also stained the epithelial component but not the sarcomatous areas of 2 of 2 cases of carcinosarcomas. E-cadherin was not detected in the stromal tumors (phyllodes, periductal stromal tumor). N-cadherin was most frequently expressed in sarcomatoid metaplastic carcinomas (5 of 5), and variably in other tumors, including the sarcomatous area of carcinosarcoma (1 of 2), and 6 of 22 medullary carcinomas. P-cadherin was frequently identified in medullary carcinomas (20 of 22), in 5 of 5 metaplastic carcinomas, and in the proliferating stroma and benign epithelium of 3 of 3 periductal stromal, but not in phyllodes tumors (0 of 4). All sarcomatoid metaplastic carcinomas co-expressed all 3 classical cadherins. Our results show that these breast tumors have unique patterns of cadherin expression suggesting different histogenetic origin or lines of differentiation. The cadherin profiles in these tumors may be useful for classification and diagnosis.

Breast Neoplasms↗
PubMed1999

Activation of NF-kappaB is necessary for the restoration of the barrier function of an epithelium undergoing TNF-alpha-induced apoptosis.

Tumor necrosis factor-alpha (TNF) induces apoptosis in confluent LLC-PK1 epithelial cells, but also activates NF-kappaB, a negative regulator of apoptosis. The presence of increased TNF-induced apoptosis causes a transient increase in epithelial permeability, but the epithelial barrier function recovers, as assessed by measuring the transepithelial electrical resistance, the paracellular flux of mannitol and by the electron microscopic evaluation of the penetration of the electron-dense dye ruthenium red across the tight junctions. The integrity of the epithelial cell layer is maintained by rearrangement of non-apoptotic cells in the monolayer and by the phagocytosis of apoptotic fragments. To study the role of NF-kappaB in an epithelium exposed to TNF, NF-kappaB was inhibited in LLC-PK1 epithelial cells with either the dietary compound, curcumin, or by transfection with a dominant negative mutant inhibitor I kappaB alpha. Replacement of serine 32 and 36 by alanine has been shown to prevent its phosphorylation and degradation, blocking NF-kappaB activation. Inhibition of NF-kappaB altered the morphology of TNF-induced apoptotic cells, which showed lack of fragmentation and membrane blebbings, and absence of phagocytosis by neighboring cells. TNF treatment of NF-kappaB-inhibited cells also caused altered distribution of the tight junction-associated protein ZO-1, increased epithelial leakiness, and impaired the recovery of the epithelial barrier function, which normally occurs 6 hours after TNF treatment of LLC-PK1 cells. These data demonstrate that NF-kappaB activation is required for the maintenance of the barrier function of an epithelium undergoing TNF-induced apoptosis.

Animals↗
PubMed1999

Increased tight junctional permeability is associated with the development of colon cancer.

Epithelial tissues act as barriers between two fluid compartments, and the epithelial barrier function is provided by the epithelial cells and the tight junctions (TJs) that connect them. We have shown previously that chronic treatment of a cultured epithelial monolayer with phorbol ester tumor promoters induces an increase in transepithelial paracellular permeability and produces tumor-like polyps, suggesting an association between TJ permeability and tumor formation. In this study, we analyzed the association between TJ permeability and formation of tumors in vivo. The permeability of the TJs was assessed in normal human and rat colon epithelia and in colon tumors by measuring the transepithelial electrical resistance, the paracellular flux rate of D-[(14)C]mannitol and the electron microscopic evaluation of the penetration of the electron dense dye ruthenium red across the TJs. By these criteria, the TJs of human colon tumors, including carcinomas and adenomatous polyps, and the TJs of 1,2-dimethylhydrazine (DMH)-induced rat colon tumors were leakier than the TJs of normal colon. Treatment of rats with the carcinogen DMH induced a progressive increase in the number of aberrant colonic crypts, considered the putative pre-neoplastic colonic phenotype while increasing TJ permeability of the colon epithelium prior to the development of tumors. These results showed that increased TJ permeability of the colon epithelium and consequently a decrease in epithelial barrier function precede the development of colon tumors.

1,2-Dimethylhydrazine↗
PubMed1998

Tumor necrosis factor-alpha increases sodium and chloride conductance across the tight junction of CACO-2 BBE, a human intestinal epithelial cell line.

CACO-2 BBE was used to determine the response of a gastrointestinal epithelium to tumor necrosis factor-alpha (TNF). Incubation of CACO-2 BBE with TNF did not produce any effect on transepithelial resistance (TER) within the first 6 hr but resulted in a 40-50% reduction in TER and a 30% decrease in 1SC (short circuit current) relative to time-matched control at 24 hr. The decrease in TER was sustained up to 1 week following treatment with TNF and was not associated with a significant increase in the transepithelial flux of [14C]-D-mannitol or the penetration of ruthenium red into the lateral intercellular space. Dilution potential and transepithelial 22Na+ flux studies demonstrated that TNF-treatment of CACO-2 BBE cell sheets increased the paracellular permeability of the epithelium to Na+ and Cl-. The increased transepithelial permeability did not associate with an increase in the incidence of apoptosis. However, there was a TNF-dependent increase in [3H]-thymidine labeling that was not accompanied by a change in DNA content of the cell sheet. The increase in transepithelial permeability was concluded to be across the tight junction because: (i) 1 mM apical amiloride reduced the basolateral to apical flux of 22Na+, and (ii) dilution potential studies revealed a bidirectionally increased permeability to both Na+ and Cl-. These data suggest that the increase in transepithelial permeability across TNF-treated CACO-2 BBE cell sheets arises from an alteration in the charge selectivity of the paracellular conductive pathway that is not accompanied by a change in its size selectivity.

Caco-2 Cells↗
PubMed1998

Overexpression of protein kinase C-delta increases tight junction permeability in LLC-PK1 epithelia.

The Ca2+-independent delta-isoform of protein kinase C (PKC-delta) was overexpressed in LLC-PK1 epithelia and placed under control of a tetracycline-responsive expression system. In the absence of tetracycline, the exogenous PKC-delta is expressed. Western immunoblots show that the overexpressed PKC-delta is found in the cytosolic, membrane-associated, and Triton-insoluble fractions. Overexpression of PKC-delta produced subconfluent and confluent epithelial morphologies similar to that observed on exposure of wild-type cells to the phorbol ester 12-O-tetradecanoylphorbol-13-acetate. Transepithelial electrical resistance (RT) in cell sheets overexpressing PKC-delta was only 20% of that in cell sheets incubated in the presence of tetracycline, in which the amount of PKC-delta and RT were similar to those in LLC-PK1 parental cell sheets. Overexpression of PKC-delta also elicited a significant increase in transepithelial flux of D-[14C]mannitol and a radiolabeled 2 x 10(6)-molecular-weight dextran, suggesting with the RT decrease that overexpression increased paracellular, tight junctional permeability. Electron microscopy showed that PKC-delta overexpression results in a multilayered cell sheet, the tight junctions of which are almost uniformly permeable to ruthenium red. Freeze-fracture electron microscopy indicates that overexpression of PKC-delta results in a more disorganized arrangement of tight junctional strands. As with LLC-PK1 cell sheets treated with 12-O-tetradecanoylphorbol-13-acetate, the reduced RT, increased D-mannitol flux, and tight junctional leakiness to ruthenium red that are seen with PKC-delta overexpression suggest the involvement of PKC-delta in regulation of tight junctional permeability.

Animals↗