Effects of growth factors, hormones, bacterial lipopolysaccharides, and lipotechoic acids on the clonal growth of normal ureteral epithelial cells in serum-free culture

Effect of growth factors on the proliferation and gene expression of human meibomian gland epithelial cells

PURPOSE

We hypothesize that growth factors, including epidermal growth factor (EGF) and bovine pituitary extract (BPE), induce proliferation, but not differentiation (e.g., lipid accumulation), of human meibomian gland epithelial cells. We also hypothesize that these actions involve a significant upregulation of genes linked to cell cycle processes, and a significant downregulation of genes associated with differentiation. Our objective was to test these hypotheses.

METHODS

Immortalized human meibomian gland and conjunctival epithelial cells were cultured for varying time periods in the presence or absence of EGF, BPE, EGF + BPE, or serum, followed by cell counting, neutral lipid staining, or RNA isolation for molecular biological procedures.

RESULTS

Our studies show that growth factors stimulate a significant, time-dependent proliferation of human meibomian gland epithelial cells. These effects are associated with a significant upregulation of genes linked to cell cycle, DNA replication, ribosomes, and translation, and a significant decrease in those related to cell differentiation, tissue development, lipid metabolic processes, and peroxisome proliferator-activated receptor signaling. Serum-induced differentiation, but not growth factor-related proliferation, elicits a pronounced lipid accumulation in human meibomian gland epithelial cells. This lipogenic response is unique, and is not duplicated by human conjunctival epithelial cells.

CONCLUSIONS

Our results demonstrate that EGF and BPE stimulate human meibomian gland epithelial cells to proliferate. Further, our findings show that action is associated with an upregulation of cell cycle and translation ontologies, and a downregulation of genetic pathways linked to differentiation and lipid biosynthesis.

Fetal calf serum heat inactivation and lipopolysaccharide contamination influence the human T lymphoblast proteome and phosphoproteome

BACKGROUND

The effects of fetal calf serum (FCS) heat inactivation and bacterial lipopolysaccharide (LPS) contamination on cell physiology have been studied, but their effect on the proteome of cultured cells has yet to be described. This study was undertaken to investigate the effects of heat inactivation of FCS and LPS contamination on the human T lymphoblast proteome. Human T lymphoblastic leukaemia (CCRF-CEM) cells were grown in FCS, either non-heated, or heat inactivated, having low (< 1 EU/mL) or regular (< 30 EU/mL) LPS concentrations. Protein lysates were resolved by 2-DE followed by phospho-specific and silver nitrate staining. Differentially regulated spots were identified by nano LC ESI Q-TOF MS/MS analysis.

RESULTS

A total of four proteins (EIF3M, PRS7, PSB4, and SNAPA) were up-regulated when CCRF-CEM cells were grown in media supplemented with heat inactivated FCS (HE) as compared to cells grown in media with non-heated FCS (NHE). Six proteins (TCPD, ACTA, NACA, TCTP, ACTB, and ICLN) displayed a differential phosphorylation pattern between the NHE and HE groups. Compared to the low concentration LPS group, regular levels of LPS resulted in the up-regulation of three proteins (SYBF, QCR1, and SUCB1).

CONCLUSION

The present study provides new information regarding the effect of FCS heat inactivation and change in FCS-LPS concentration on cellular protein expression, and post-translational modification in human T lymphoblasts. Both heat inactivation and LPS contamination of FCS were shown to modulate the expression and phosphorylation of proteins involved in basic cellular functions, such as protein synthesis, cytoskeleton stability, oxidative stress regulation and apoptosis. Hence, the study emphasizes the need to consider both heat inactivation and LPS contamination of FCS as factors that can influence the T lymphoblast proteome.

Propionibacterium acnes activates the IGF-1/IGF-1R system in the epidermis and induces keratinocyte proliferation

Propionibacterium acnes has a major role in the development of acne lesions. IGF-1 stimulates the proliferation of keratinocytes via an activation of the IGF-1 receptor (IGF-1R). Zinc has been proven to work efficiently against inflammatory acne and to modulate the IGF-1 system. Our objectives were to study the modulation of IGF-1 and IGF-1R expression by P. acnes extracts and to determine their modulation by zinc gluconate. In vivo, we analyzed biopsies of acne lesions and healthy skin, and in vitro we used skin explants incubated with two P. acnes extracts--membrane fraction (MF) and cytosolic proteins--with or without zinc. IGF-1 and IGF-1R expression was evaluated using immunohistochemistry, and the IGF-1 production in supernatants was measured by ELISA. Then, IGF-1 and IGF-1R mRNA levels were analyzed using quantitative PCR on normal human epidermal keratinocytes (NHEKs). IGF-1 and IGF-1R were overexpressed in acne lesions. MF increased IGF-1 and IGF-1R expression in the epidermis of explants and was associated with an overexpression of both Ki-67 and filaggrin. Zinc had the effect of downregulating IGF-1 and IGF-1R levels. These observations were confirmed at the mRNA level for IGF-1R in NHEKs. These results demonstrate that P. acnes can induce the formation of comedones by stimulating the IGF/IGF-1R system. Moreover, zinc downregulates this pathway.

Compensatory paracrine mechanisms that define the urothelial response to injury in partial bladder outlet obstruction

Diseases and conditions affecting the lower urinary tract are a leading cause of dysfunctional sexual health, incontinence, infection, and kidney failure. The growth, differentiation, and repair of the bladder's epithelial lining are regulated, in part, by fibroblast growth factor (FGF)-7 and -10 via a paracrine cascade originating in the mesenchyme (lamina propria) and targeting the receptor for FGF-7 and -10 within the transitional epithelium (urothelium). The FGF-7 gene is located at the 15q15-q21.1 locus on chromosome 15 and four exons generate a 3.852-kb mRNA. Five duplicated FGF-7 gene sequences that localized to chromosome 9 were predicted not to generate functional protein products, thus validating the use of FGF-7-null mice as an experimental model. Recombinant FGF-7 and -10 induced proliferation of human urothelial cells in vitro and transitional epithelium of wild-type and FGF-7-null mice in vivo. To determine the extent that induction of urothelial cell proliferation during the bladder response to injury is dependent on FGF-7, an animal model of partial bladder outlet obstruction was developed. Unbiased stereology was used to measure the percentage of proliferating urothelial cells between obstructed groups of wild-type and FGF-7-null mice. The stereological analysis indicated that a statistical significant difference did not exist between the two groups, suggesting that FGF-7 is not essential for urothelial cell proliferation in response to partial outlet obstruction. In contrast, a significant increase in FGF-10 expression was observed in the obstructed FGF-7-null group, indicating that the compensatory pathway that functions in this model results in urothelial repair.

The effect of endotoxin on functional parameters of mammary CID-9 cells

The effect of endotoxin on mammary CID-9 cells, which differentiate in culture and express beta-casein, was investigated. Cells in culture supplemented with lactogenic hormones and dripped with EMS-Matrix (EMS-drip), were treated daily with endotoxin (0.5-500 microg/ml). Endotoxin at concentrations of less or equal to 10 microg/ml did not affect cell growth and viability up to 5 days post endotoxin treatment. Endotoxin (0.01-10 microg/ml) was added to the culture medium, upon confluence, and functional parameters were examined within 48 h post endotoxin treatment. Nuclear factor-kappaB (NF-kappaB) (p52) increased in nuclear extracts from endotoxin-stimulated cells within 1 h of treatment, while beta-casein mRNA and protein expression decreased in a concentration-dependent manner at 24 and 48 h post treatment. Zymography showed that the 72 and 92 kDa gelatinase activity increased in cells at 24 and 48 h post endotoxin treatment at 10 and 50 microg/ml. At the latter concentration, the active form of 72 kDa gelatinase was induced at 48 h. Interleukin-6 and tumor necrosis factor-alpha levels increased at 1-3 h post endotoxin treatment and peaked at 6 h in cells on plastic and EHS-drip. Nerve growth factor (NGF) levels increased in control and endotoxin-treated cells in a time-dependent manner, and endotoxin increased NGF levels in culture at 6 and 9 h post endotoxin treatment. This study shows that endotoxin activated NF-kappaB, suppressed beta-casein expression and upregulated gelatinases, cytokines and NGF. This model could be used to investigate the role of mammary cells in initiating and propagating inflammation and to test candidate molecules for potential anti-inflammatory properties.

Bacterial components inhibit fibroblast proliferation in vitro

Perigraft fluid from Staphylococcus epidermidis infected grafts in a mouse model significantly inhibits fibroblast proliferation (60-98% at 7 and 28 days), compared with perigraft fluid from sterile grafts. The fibroblast inhibitor was trypsin-heat resistant and dependent primarily upon the bacteria, not the host proinflammatory mediators or the vascular graft biomaterial. We tested the inhibitory properties of S. epidermidis strains RP62A (slime producer) and RP62NA (nonslime producer) and Staphylococcus aureus strain 502a, using an in vitro tritiated thymidine murine fibroblast (ATCC CCL-12) proliferation assay. Whole killed bacteria, disrupted bacteria (live and killed), bacterial supernatants, and purified cell wall products (peptidoglycan, teichoic acid, and lipoteichoic acid from disrupted bacteria) were studied. Significant fibroblast inhibition occurred for all three bacterial strains with disrupted bacteria (live or killed) and cell free bacteria derived supernatants. The fibroblast inhibitor from disrupted slime producing S. epidermidis was trypsin-heat resistant. The fibroblast inhibitor from disrupted S. aureus and supernatants for all three bacterial strains at 1 x 10(7) were trypsin-heat sensitive. Fibroblast inhibition was not dependent upon bacterial viability and not mediated by bacterial cell wall products. In conclusion, components of slime and nonslime producing S. epidermidis and S. aureus inhibit fibroblast proliferation.

Primary uroepithelial cultures. A model system to analyze umbrella cell barrier function

Despite almost 25 years of effort, the development of a highly differentiated and functionally equivalent cell culture model of uroepithelial cells has eluded investigators. We have developed a primary cell culture model of rabbit uroepithelium that consists of an underlying cell layer that interacts with a collagen substratum, an intermediate cell layer, and an upper cell layer of large (25-100 micrometer) superficial cells. When examined at the ultrastructural level, the superficial cells formed junctional complexes and had an asymmetric unit membrane, a hallmark of terminal differentiation in bladder umbrella cells. These cultured "umbrella" cells expressed uroplakins and a 27-kDa uroepithelial specific antigen that assembled into detergent-resistant asymmetric unit membrane particles. The cultures had low diffusive permeabilities for water (2.8 x 10(-4) cm/s) and urea (3.0 x 10(-7) cm/s) and high transepithelial resistance (>8000 Omega cm2) was achieved when 1 mM CaCl2 was included in the culture medium. The cell cultures expressed an amiloride-sensitive sodium transport pathway and increases in apical membrane capacitance were observed when the cultures were osmotically stretched. The described primary rabbit cell culture model mimics many of the characteristics of uroepithelium found in vivo and should serve as a useful tool to explore normal uroepithelial function as well as dysfunction as a result of disease.

Osteopontin stimulates a subpopulation of quiescent human prostate epithelial cells with high proliferative potential to divide in vitro

BACKGROUND

Osteopontin (OPN) is a secreted extracellular matrix (ECM) protein found in bone, as well as associated with epithelial cells. The main objective of these studies was to test in vitro the hypothesis that interaction with OPN stimulates proliferation of a quiescent subpopulation of prostate epithelial cells with high proliferative potential.

METHODS

To simulate conditions that restrict proliferation and inhibit terminal differentiation of basal cells in vivo, control cultures grew on substrate coated with collagen (CO) or fibronectin (FN), in medium containing low levels of growth factors.

RESULTS

Under growth-restricting conditions, most prostate epithelial cells with high proliferative potential, seeded in control secondary cultures, were quiescent within the time frame of the studies, as indicated by the small number of large colonies in these cultures. Growing prostate epithelial cells (PR) under the same growth-restricting conditions, but on substrate coated with OPN instead of CO or FN, stimulated proliferation of a subpopulation of single cells with high proliferative ability as indicated by: 1) dose-dependent increase in the percentage of single cells incorporating bromodeoxyuridine, i.e., proliferating PR; and 2) subsequent dose-dependent increase in the percentage of large colonies. The OPN effect was not merely due to preferential attachment to OPN, because PR attachment to OPN, CO, or FN was identical. PR attachment to OPN was inhibited in the presence of GRGDTP or an antibody against the integrin subunit alphav, but not in the presence of an RGES peptide or a nonspecific IgG.

CONCLUSIONS

Integrin-mediated OPN/PR interaction stimulates proliferation of a quiescent subpopulation of prostate epithelial cells with high proliferative potential, possibly stem cells.

Evidence for altered proliferative ability of progenitors of urothelial cells in interstitial cystitis

Secondary cultures of basal urothelial cells isolated from patients with stress incontinence (7 patients), neurogenic bladder (2 patients), interstitial cystitis (IC) (27 patients), bladder rupture (1 patient) and bacterial cystitis (3 patients) grew under growth restricting conditions. All groups displayed reproducible colony size distribution, reflecting the proliferative potential distribution in the population of progenitor cells seeded. The percentage of large colonies (> 6 cells/colony), progeny of basal cells with high proliferative potential, was low in cultures from control patients with stress incontinence, neurogenic bladder or bladder rupture. Exposure of cultures from control patients with stress incontinence to lipoteichoic acid from Streptococcus faecalis, in vitro, increased the percentage of large colonies to levels statistically indistinguishable from those in untreated IC cultures. This supported the possibility that exposure of progenitors of urothelial cells to infection in vivo may cause the persistent increase in the percentage of large colonies in 80% of the IC patients tested. Given these findings, it was not surprising that the percentage of large colonies was also high in cultures from patients with acute bacterial cystitis. In conclusion, the present findings support the theoretical model for the etiology of IC we proposed based on our studies in normal urothelial cells (Elgavish et al., Journal of Cellular Physiology 169: 42-51, 52-65, 66-77, 1996): (1) The proliferative ability of a subpopulation of progenitors of urothelial cells is increased in IC; and (2) This change may be the result of recurrent exposure of progenitors of urothelial cells to injury due, possibly but not exclusively, to infection and chronic inflammation. We propose to use this change as a diagnostic tool for IC.

A subpopulation of human urothelial cells is stimulated to proliferate by treatment in vitro with lipoteichoic acid, a cell wall component of Streptococcus faecalis

Urinary tract infection with gram-positive bacteria is common. Avenues for ingress of bacteria into the bladder include luminal and suburothelial infection. Terminally differentiated superficial urothelial cells lining the lumen of the bladder are often shed in response to infection. In contrast, infection-induced altered function of progenitors of urothelial cells residing in the basal layer of the urothelium is likely to have long lasting effects on the structure and function of the urothelium. The main objective of the present studies was to investigate in vitro the possibility that exposure to lipoteichoic acid, a cell wall component of the gram-positive Streptococcus faecalis (LT-2), stimulates basal urothelial cells to proliferate. To simulate conditions that restrict proliferation and inhibit terminal differentiation of urothelial cells in the basal layer, secondary cultures of urothelial cells (UT) were grown on collagen or fibronectin coated substrate in medium containing low levels of Ca2+ (0.2 mM) and growth factors (0.005% bovine pituitary extract [BPE]). Under these conditions, UT cultures displayed a highly reproducible colony size distribution, possibly due to the fact that colonies were progeny of basal cells with various proliferative potentials, retained in vitro. In cultures grown under growth-restricting conditions the majority of progenitors appeared to be quiescent, just like stem cells in the basal layer of the urothelium. Thus, the population of large colonies (more than six cells/colony), was small when a steady state of growth was achieved, 3-7 days after seeding. Growth factors (0.005-0.5% BPE) caused a dose-dependent increase in this population of large colonies. Moreover, treatment of UT grown under growth-restricting conditions (0.005% BPE) with LT-2 increased steady-state levels of the population of large colonies to levels obtained in cultures growing under optimal conditions with respect to growth factors. These results indicated that the subpopulation of progenitors, quiescent under normal conditions, could be stimulated to proliferate. Two lines of evidence were consistent with the possibility that treatment with LT-2 stimulated proliferation of the subpopulation of progenitors and that large colonies were the progeny of this subpopulation of single cells: (1) treatment with LT-2 increased the percentage of single cells that incorporated bromodeoxyuridine (i.e., proliferated) in a time-dependent manner. (2) An increase in the percentage of large colonies was found following LT-2-triggered proliferation of single cells. We propose that, under normal conditions, cells produced in response to LT-2-triggered proliferation of stem cells are removed from the system due to an increased rate of differentiation followed by apoptosis. Recurrent infection and inflammation may not allow these processes to proceed effectively, resulting in chronic injury to the bladder. Moreover, under conditions in which stem cells accumulate mutations that incapacitate their progeny to undergo apoptosis, LT-triggered proliferation could be a contributing factor to tumorigenesis.

Nitric oxide mediates the action of lipoteichoic acid on the function of human urothelial cells

Gram-positive bacteria are recognized pathogens in urinary tract infections. Lipoteichoic acids, major components of the cell wall of gram-positive bacteria, are important virulence attributes, but their mechanism of action is not well understood. We have postulated that infection-induced altered function of progenitors of urothelial cells (UT) residing in the basal layer is likely to have long-lasting effects on the architecture and function of the urothelium. Our earlier in vitro studies in UT of basal type, grown under growth restricting conditions, have shown that 1) treatment with lipoteichoic acid from Streptococcus faecalis (LT-2) stimulates a subpopulation of progenitors of urothelial cells to proliferate, and 2) resulting large colonies differentiated at an increased rate under conditions simulating those in the basal layer of the urothelium. The hypothesis underlying the present studies was that nitric oxide (NO) mediated LT-2 action on these functions of UT. Immunocytochemical studies using an antibody against inducible nitric oxide synthase (iNOS) confirmed expression of iNOS in LT-2-treated UT. Our hypothesis was tested by treating UT grown under growth restricting conditions (0.005% bovine pituitary extract) with LT-2 (25 micrograms/ml), in the presence or absence of inhibitors of NOS (1 mM NG-nitro-L-arginine methyl ester [L-NAME]; 1 microM dexamethasone [DEXA]) or 25 microM hemoglobin, a potent inactivator of NO. Treatment with LT-2 in the presence of these agents prevented the following effects of LT-2 alone: 1) the stimulatory effect on proliferation of single cells, as well as within the resulting large colonies; 2) the subsequent differentiation of large colonies resulting from this proliferative activity, as indicated by distribution of beta 1 subunit-containing integrins to cell-cell contacts; 3) the inhibitory effect on the subsequent ability of LT-2-treated UT to attach to extracellular matrix proteins. These studies suggest that induction of NOS by LT-2, initially aimed at restricting the replication of infectious agents, may have potential cost of damage to the host bladder by interfering with urothelial differentiation.

Long-term treatment with lipoteichoic acid from Streptococcus faecalis affects differentiation and expression and cellular distribution of beta 1 integrins in human urothelial cells

Gram-positive bacteria are recognized pathogens in urinary tract infections. Cellular mechanisms triggered by lipoteichoic acids (LTs), cell well components of gram-positive bacteria, have not been completely defined. We have postulated that infection-induced altered function of progenitors of urothelial cells residing in the basal layer is likely to have long lasting effects on the architecture and function of the urothelium. Our recent studies in vitro showed that treatment of poorly differentiated urothelial cells of basal type with LT from Streptococcus faecalis (LT-2) stimulated rapid proliferation of a subpopulation of progenitors of urothelial cells, supporting this possibility (Elgavish et al., 1996, J. Cell. Physiol., 169:42-51). The hypothesis underlying the present studies was that, following LT-triggered increase in proliferation of progenitors, the rate of differentiation of the resulting progeny was also stimulated. We proposed that this mechanism may allow rapid removal of cells from the injured area and replacement by cells that have not been exposed to infection. To simulate in vitro conditions in the basal layer that inhibit terminal differentiation, cells grew on fibronectin or collagen-coated substrate, in medium containing low Ca2+ (0.2 mM) and low levels of growth factors (0.005% bovine pituitary extract [BPE]). During the last 3 days in culture, cells grew in the same low Ca2+ (0.2 mM) medium, but without BPE, with or without LT-2. In a positive control group, cells grew during their last 3 days in culture in medium without BPE and LT-2 but in which levels levels of Ca2+ were higher (2 mM), a condition known to stimulate differentiation in other cell types. Several lines of evidence supported the possibility that long-term treatment with LT-2 stimulated progression of large colonies (i.e., the progeny resulting from LT-triggered proliferation) to a more differentiated state: (1) the rate of their differentiation, determined by criterion of intense cytokeratin 8 expression, was increased; (2) steady-state level of beta mRNA and expression of beta 1 subunit of integrins at the protein level were inhibited; (3) in contrast to large colonies in control cultures, the entire population of LT-2-treated large colonies contained beta 1 integrins distributed at cell-cell contacts. Raising extracellular Ca2+ concentration to 2 mM induced similar effects, suggesting that LT-2 may act by stimulating an increase in intracellular levels of Ca2+. However, further studies will be needed to elucidate the molecular mechanisms underlying the stimulatory effect of LT-2 on proliferation of progenitors of urothelial cells in the basal layer of the urothelium and subsequent differentiation of their progeny. We propose that these processes may have a causative role in the pathological changes that occur in the aftermath of chronic or recurrent suburothelial infection in the urinary bladder.

Induction of hepatic Ito cell nitric oxide production after acute endotoxemia

Nitric oxide is a highly reactive mediator released in the liver by hepatocytes, Kupffer cells and endothelial cells during endotoxin-induced inflammation. In this study we determined whether Ito cells also produce nitric oxide after exposure to endotoxin. For induction of endotoxemia, rats were injected intravenously with Escherichia coli lipopolysaccharide (2.5 mg/kg). Ito cells were isolated from the animals 48 hr later by means of in situ perfusion of the liver with protease and collagenase followed by purification on an arabinogalactan gradient. Ito cells from untreated and endotoxemic rats were found to produce low levels of nitric oxide in response to interferon-gamma. In both cell types, this response depended on L-arginine and was blocked by NG-monomethyl-L-arginine, a specific nitric oxide synthase inhibitor. Cells from rats treated with endotoxin produced significantly more nitric oxide than did cells from untreated animals; this was due, at least in part, to increased expression of protein for an inducible form of nitric oxide synthase. These cells also responded to stimulation with lipopolysaccharide in vitro, as well as the combination of interferon-gamma and lipopolysaccharide, which was synergistic in stimulating nitric oxide production. Tumor necrosis factor-alpha and macrophage colony-stimulating factor were also found to stimulate nitric oxide production by Ito cells from endotoxemic rats. In addition, in these cells, tumor necrosis factor-alpha synergized with interferon-gamma in inducing nitric oxide production. The combination of interferon-gamma and lipopolysaccharide was also found to inhibit Ito cell DNA synthesis, as measured on the basis of [3H]-thymidine uptake.(ABSTRACT TRUNCATED AT 250 WORDS)

Phenotypic and cytogenetic characterization of human bladder urothelia expanded in vitro

A simple method for the harvest of bladder cell types from surgical specimens was used to generate strains of normal human urothelial cells that could be reproducibly cultivated, passaged and extensively expanded in serum-free medium. Immunostaining of the bladder epithelial cells with broadly reacting anti-cytokeratin antibodies and with an anti-cytokeratin antibody specific to cytokeratin 7, a transitional cell marker, indicated that they expressed a stable epithelial phenotype with serial passage. Low levels of immunostaining for E-cadherin and low levels of E-cadherin messenger ribonucleic acid, as determined by Northern blot analysis, and strongly positive immunostaining with an anti-vimentin antibody indicated collectively that the uroepithelial cells express a nonbarrier-forming phenotype under these culture conditions. However, when the urothelial cells were implanted subcutaneously into athymic mice on biodegradable synthetic polymers, they formed multilayered structures, suggesting that they retain the capability to differentiate in a living host. The urothelial cells proliferated in an epidermal growth factor independent manner and expressed high levels of transforming growth factor-alpha and amphiregulin messanger ribonucleic acids, suggesting the possibility of autocrine regulation of growth by epidermal growth factor-like factors. Cytogenetic analysis indicated that urothelial cells cultured for 6 passages possessed a normal chromosomal complement. These results demonstrate that primary cultures of autologous human bladder epithelial cells can be extensively expanded in vitro and, consequently, might be used in cell transplantation strategies for genitourinary reconstruction.

Integrin-mediated adhesive properties of uroepithelial cells are inhibited by treatment with bacterial toxins

Gram-negative bacteria are a dominant cause of urinary tract infection, and their ability to produce toxins is an important virulence attribute. Cellular mechanisms triggered by the production of toxins in the lower urinary tract have not been completely defined. Ureteral epithelial cells (UT; A. Elgavish, Infect. Immun. 61: 3304-3312, 1993) have served as an in vitro model to explore the possibility that bacterial toxins act on UT by affecting integrin-mediated adhesive properties. The effect of treatment with lipopolysaccharides (LPS) from three strains of the gram-negative Escherichia coli [055:B5 (LPS-1), 0111:B4 (LPS-4), and 0127:B8 (LPS-5)] and lipoteichoic acids from two gram-positive bacteria, Streptococcus faecalis (LT-2) and Bacillus subtilis (LT-3), were examined. LPS-5 inhibited markedly UT attachment to collagen and fibronectin. LPS-4 had no effect, whereas LPS-1 inhibited UT attachment to collagen but not to fibronectin. The fact that LPS-5 and LT-2 inhibited an Arg-Gly-Asp sequence-sensitive component of UT attachment to fibronectin is consistent with the possibility that these toxins acted via a mechanism involving typical fibronectin receptors. UT spreading was inhibited markedly by LPS-1, LT-2, and LT-3, whereas LPS-4 and LPS-5 had no effect. Because clustering of integrins is a crucial step in integrin-mediated signal transduction, the possibility that toxins inhibited spreading by affecting clustering was tested. Treatment with LT-2, which inhibited spreading dramatically, abolished completely a UT cell population containing more than five to eight beta 1- or beta 4-subunit-containing integrin clusters.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of Escherichia coli and E. coli lipopolysaccharides on the function of human ureteral epithelial cells cultured in serum-free medium

Escherichia coli is the microorganism most commonly isolated from human urinary tract infections. Earlier studies by others have shown that bacterial attachment and production of toxins (e.g., lipopolysaccharides [LPS]) enhance recruitment of leukocytes to the infection site and mucosal inflammation. The mechanisms by which these changes occur have not been completely defined. In the present study, epithelial cell cultures isolated from the human ureter (UT cells) (A. Elgavish, J. J. Wille, F. Rahemtulla, and L. Debro, Am. J. Physiol. 261:C916-C926, 1991; J. J. Wille, J. Park, and A. Elgavish, J. Cell. Physiol. 150:52-58, 1992) served as a model system with which to explore the mechanisms of action of Escherichia coli and E. coli LPS in UT cells. E. coli adhered to UT cells and inhibited carrier-mediated sulfate uptake to half of that in untreated UT cells, suggesting that the intracellular pool of sulfate available for sulfation may be lower in infected cells and may lead to the production of undersulfated glycoconjugates. Incubation of UT cells with E. coli LPS inhibited carrier-mediated sulfate uptake to an extent similar to that caused by whole E. coli, indicating that the effect of E. coli on sulfate uptake may be mediated by LPS. LPS caused an increase in Na+ content in rapidly proliferating UT cells but not in quiescent cells. We postulated that this change in the intracellular ionic environment or changes coupled to it (e.g., pH or Ca2+ levels) may serve as a transducing signal. This possibility was supported by the fact that LPS stimulated clustering of ICAM-1 on the cell surface of rapidly proliferating but not quiescent UT cells. This study suggests that, in vivo, LPS stimulation of ICAM-1 clustering on the surface of the urothelium may allow more effective binding of leukocytes. This may be the mechanism underlying earlier findings in vivo indicating a role for LPS in the recruitment of leukocytes to the urinary tract as a host defense mechanism following urinary tract infection.