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C P Redfern

Publications and source records attributed to C P Redfern.

At least 37 records · Page 2Linked to original sources
PubMed1997

9-cis retinoic acid--a better retinoid for the modulation of differentiation, proliferation and gene expression in human neuroblastoma.

To date, the clinical success of 13-cis or all-trans retinoic acid in the treatment of neuroblastoma has been disappointing. In vivo, 13-cis will isomerise to both all-trans and 9-cis retinoic acid, believed to be the main biologically-active isomers. In vitro studies with an N-type neuroblastoma cell line, SH SY 5Y, show that 9-cis is better than other isomers at both inducing morphological differentiation and inhibiting proliferation. RAR-beta, a gene which may mediate retinoic acid responsiveness and be of prognostic significance, is also more-effectively induced by 9-cis retinoic acid. 9-cis and all-trans retinoic acid do not have synergistic effects on SH SY 5Y cell proliferation and gene expression. A retinoid X receptor (RXR)-specific analogue of 9-cis retinoic acid had similar effects on gene expression to 9-cis retinoic acid alone. In view of these results, 9-cis retinoic acid or stable analogues of this retinoid may have potential for the treatment of neuroblastoma.

Alitretinoin↗
PubMed1996

Nuclear retinoid receptor expression in normal human endometrium throughout the menstrual cycle.

Previous work has shown that retinoic acid receptors (RARs) and retinoid X receptors (RXRs) are expressed in human endometrial epithelial and stromal cells. These nuclear receptors mediate the biological effects of retinoic acid, a vitamin A derivative which may have an important, though poorly characterized role in the functional differentiation of secretory epithelia. The aim of this study was to find out whether the expression of RAR and RXR mRNA in endometrial epithelial and stromal cells varies in relation to the menstrual cycle. The expression of RARs and RXRs was investigated by Northern blotting and, for stromal cells, there were no differences in expression of RAR-alpha, RAR-beta, RAR-gamma and RXR-alpha between the proliferative and secretory phases of the menstrual cycle. Similarly, for epithelial tissue, there were no significant differences between the proliferative and secretory phases with respect to the expression of RAR-alpha, RAR-gamma and RXR-alpha. However, RAR-beta was expressed at a 1.7-fold higher level in epithelial samples from the proliferative phase compared to the secretory phase. Overall, the levels of expression of RAR-alpha, RAR-beta and RAR-gamma were 1.7- to 4-fold higher in stromal cells compared to epithelial cells whereas RXR-alpha was expressed at a similar level in both cell types. We have previously suggested that retinoic acid has a role in endometrial differentiation or function which may be reflected by cyclical changes in intracellular retinoic acid levels. These data indicate that RARs and RXRs are expressed at a similar level throughout the menstrual cycle, with the possible exception of RAR-beta, implying that any menstrual cycle-related function of RARs in controlled by ligand availability rather than by changes in expression of the receptors.

Blotting, Northern↗
PubMed1995

Retinoic acid receptors and retinoid binding proteins in endometrial adenocarcinoma: differential expression of cellular retinoid binding proteins in endometrioid tumours.

Retinoic acid is apparently required for the normal differentiation of reproductive epithelium. Cellular abnormalities in retinoid homeostasis could be a factor in the development of endometrial malignancy. We have thus investigated the expression of nuclear retinoic acid receptors (RARs and RXRs) and cellular binding proteins for retinol (CRBP) and retinoic acid (CRABP) in endometrial adenocarcinoma of the endometrioid histological subtype. Ten grade I, II grade 2 and 10 grade 3 tumour samples, as well as 4 samples of severe atypical precancerous endometrial hyperplasia, were studied. No significant difference in expression of RAR-beta was detected in tumour samples compared with normal epithelial cells. RAR-gamma was significantly elevated in grade 1 and 2 carcinomas, but this may be due to greater stromal cell involvement in these lower grade tumours. There was significant elevation of CRBP I mRNA in tumour samples. Furthermore, although undetectable in normal endometrial epithelium, CRABP I was expressed in 3/II grade 2 and 9/10 grade 3 carcinomas, with expression being significantly higher where the primary tumour had invaded more than 50% of the total myometrial thickness. Analysis of 2 epithelial-like endometrial adenocarcinoma cell lines supported the idea that CRABP I expression is characteristic of poorly differentiated endometrial adenocarcinoma. Our data suggest that alterations in mechanisms of retinoid homeostasis are a feature of endometrial adenocarcinoma and may contribute to the severity of disease.

Adenocarcinoma↗
PubMed1995

Gene expression and neuroblastoma cell differentiation in response to retinoic acid: differential effects of 9-cis and all-trans retinoic acid.

Retinoic acid has considerable potential for the chemoprevention and chemotherapy of cancer. Neuroblastoma cells differentiate in response to retinoic acid in vitro, an observation that has led to clinical trials using either the 13-cis or all-trans isomers of retinoic acid. We review the effects of retinoic acid on neuroblastoma, and the potential involvement of nuclear retinoic acid receptors (RARs) and retinoid X receptors (RXRs). 9-cis retinoic acid is a ligand for RXRs, and we review recent data on the differential effects of 9-cis and all-trans retinoic acid on neuroblastoma differentiation and proliferation in vitro, and possible mechanisms of action via hetero- and homodimers of RARs and RXRs. Although there is uncertainty whether or not 9-cis retinoic acid produces its biological effects primarily via RXR homodimers, in vitro data suggest that this isomer of retinoic acid or stable analogues may have considerable potential for the treatment of resistant, disseminated neuroblastoma.

Antineoplastic Agents↗
PubMed1995

Variation in the expression of cellular retinoid binding proteins in human endometrium throughout the menstrual cycle.

Human endometrium is a glandular epithelial tissue with a substantial underlying stroma. Under the influence of ovarian steroids, endometrium undergoes a cyclical pattern of proliferation followed by secretory differentiation. Since retinoids promote the differentiation of many epithelia to secretory phenotypes they may be involved in controlling the secretory differentiation of human endometrial epithelium. Cytosolic binding proteins for retinol (cellular retinol binding protein) and retinoic acid (cellular retinoic acid binding protein) may play an important part in regulating the availability of retinoic acid to its nuclear receptors and we have therefore asked whether expression of mRNA for these proteins varies in relation to endometrial differentiation. In a series of 54 endometrial biopsies, both endometrial epithelial and stromal cells expressed mRNA for cellular retinol binding protein type I at a constant level throughout the menstrual cycle. Cellular retinoic acid binding protein type II was also expressed but the level of expression varied dramatically, being elevated in the proliferative phase and depressed during the secretory phase of the menstrual cycle in both epithelial and stromal cells. These data suggest that cytosolic binding proteins modulate the supply of retinoic acid to the nuclei of endometrial cells during the menstrual cycle and that retinoic acid is involved in the cyclical control of endometrial differentiation.

Amino Acid Sequence↗
PubMed1995

Menstrual cycle related differences in the proliferative responses of cultured human endometrial stromal cells to retinoic acid.

Although ovarian-derived steroid hormones are central to the control of endometrial growth and secretory differentiation, all-trans retinoic acid, a derivative of vitamin A, may also play an important role. Since the retinoids can inhibit the proliferation of both fibroblasts and epithelial cells in experimental systems, we investigated whether the proliferation of endometrial stromal cells was inhibited by all-trans retinoic acid. A sensitive spectrophotometric assay was used to show that the proliferation rates of primary cultures of endometrial stromal fibroblasts varied with the timing of biopsy, and that all-trans retinoic acid inhibited the growth of late secretory phase cells but had no effect on cells sampled at other times. Furthermore, since the expression of mRNA encoding cellular retinoic acid binding protein type II decreases in endometrial stromal cells in the secretory phase, a rise in intracellular all-trans retinoic acid concentrations could be fundamental to the control of endometrial stromal cell proliferation and differentiation in vivo.

Analysis of Variance↗
PubMed1994

Concentration-dependent effects of 9-cis retinoic acid on neuroblastoma differentiation and proliferation in vitro.

The observation that neuroblastoma cells differentiate in response to retinoic acid (RA) in vitro has led to clinical trials using either 13-cis or all-trans RA. Since 9-cis RA may also have important biological functions, we have compared the potential of RA isomers to induce differentiation and inhibit cell proliferation of SH SY 5Y neuroblastoma cells. 9-cis RA at high concentrations is better at inducing morphological differentiation than either all-trans or 13-cis RA and as effective at inhibiting proliferation. Hence, 9-cis RA or stable analogues may have important therapeutic potential in the treatment of neuroblastoma.

Cell Differentiation↗
PubMed1994

Differential effects of 9-cis and all-trans retinoic acid on the induction of retinoic acid receptor-beta and cellular retinoic acid-binding protein II in human neuroblastoma cells.

The objective of this study was to compare the properties of 9-cis and all-trans retinoic acid with respect to the induction of expression of retinoic acid receptor beta (RAR-beta) and cellular retinoic acid-binding protein (CRABP) II in human neuroblastoma SH SY 5Y cells. RAR-beta and CRABP II mRNA was induced by both all-trans and 9-cis retinoic acid in SH SY 5Y cells. Induction was rapid, detectable within 2-4 h, and inhibited by actinomycin D. Time-courses of induction for RAR-beta and CRABP II differed: RAR-beta mRNA levels reached a maximum 4-6 h after adding all-trans or 9-cis retinoic acid, whereas CRABP II mRNA levels increased over at least 18 h. These differences were attributed to the longer half-life of CRABP II mRNA (20 h) compared with RAR-beta mRNA (3.9 h). The dose-response characteristics of all-trans and 9-cis retinoic acid were different: all-trans was effective at nanomolar concentrations, whereas 10-fold higher levels of 9-cis retinoic acid were required to achieve comparable induction of RAR-beta and CRABP II. Conversely, at high concentrations, 9-cis retinoic acid gave a greater induction of RAR-beta and CRABP II than all-trans. The induction of RAR-beta and CRABP II by all-trans retinoic acid was maintained in the subsequent absence of all-trans retinoic acid, whereas induction by 9-cis retinoic acid was dependent on its continued presence in the culture medium. These results suggest that, at high concentrations, 9-cis retinoic acid may produce its transcriptional effects via retinoid X receptor (RXR) homodimers. This has implications for the cellular functions of 9-cis retinoic acid and its use as a biological response modifier.

Dactinomycin↗
PubMed1994

Changes in oncogene mRNA expression during human keratinocyte differentiation.

The nuclear proto-oncogenes are involved in transcriptional regulation and control many cell processes. The role of changes in proto-oncogene expression in controlling the balance between proliferation and differentiation was studied in cultured keratinocytes. Normal human keratinocytes were grown in the serum-free medium MCDB153 with an extracellular calcium concentration of 70 microM. After treatment with different differentiation conditions, cellular RNA was size-fractionated on agarose gels and transferred to nylon membranes which were subsequently hybridized with c-myc, c-jun, and H-ras 32P-labelled probes. Relative RNA loading was assessed using probes for beta-actin and ribosomal 18s RNA. Inducing differentiation by increasing the calcium concentration of the medium from 70 microM to 1.5 mM resulted in a marked decrease in c-myc RNA levels to 26% of control levels within 8 h. After 48 h in 1.5 mM calcium, c-myc levels had recovered to approximately 50% of control levels. There was a gradual reduction in c-jun levels to 56% of control levels by 4 days. Treatment with 10 nM TPA, which also induces keratinocyte differentiation, reduced c-myc RNA levels to 70% of control levels during the first 4 h, but thereafter c-myc levels remained approximately constant for a further 20 h. TGF beta (2 ng/ml), which inhibits keratinocyte growth without inducing differentiation, did not alter c-myc RNA levels over a 4-day period. There were no changes in c-myc levels following the addition of retinoic acid and none of the conditions altered H-ras levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Calcium↗
PubMed1994

Oestrogen and progesterone do not regulate the expression of retinoic acid receptors and retinoid 'X' receptors in human endometrial stromal cells in vitro.

Elucidation of the gene structure for retinoic acid receptor-beta (RAR-beta) has suggested a potential role for oestrogen in regulating the expression of RAR-beta. We have previously shown that all three RAR types are expressed in human endometrial stromal cells in vitro and that RAR-beta expression is induced in response to retinoic acid. The aim of this study was to ask whether oestradiol and progesterone could play a part in regulating the expression of RARs in human endometrial stromal cells and to establish the patterns of expression of a related group of nuclear retinoid receptors, retinoid 'X' receptors (RXRs) and their potential for regulation by steroid hormones. The RAR expression patterns of endometrial stromal cells, grown in steroid-free medium, did not change in response to the presence of steroid hormones. Furthermore, the retinoic acid-mediated induction of RAR-beta was not affected by oestradiol or progesterone, and was dependent on the continued presence of retinoic acid. Of the three RXR types, only RXR-alpha was detectably expressed in stromal cells in vitro and the expression of RXR-alpha did not change in response to steroid hormones or retinoic acid. These data indicate that oestradiol and progesterone are not important in the regulation of RAR and RXR expression in human endometrial stromal cells.

Base Sequence↗
PubMed1994

Cellular retinoid binding proteins and nuclear retinoic acid receptors in endometrial epithelial cells.

Retinoic acid, one of the most potent of the naturally occurring retinoids (retinol and derivatives), is required in vivo for the maintenance of epithelial cell growth. This study describes the pattern of expression of nuclear retinoic acid receptors (RARs and RXRs), and cellular binding proteins for retinol and retinoic acid (CRBP I, CRABP I and II), in endometrial epithelial cells. The effects of retinoic acid on the expression of these receptors in endometrial epithelial cells have also been studied and compared with its effects in endometrial stromal cells. Messenger RNA for RAR-alpha, RAR-beta, RAR-gamma, RXR-alpha, CRBP I and CRABP II was detected by Northern blotting of total RNA extracted from cultured epithelial cells. In comparison with stromal cell RNA that was used as an internal standard, CRBP I appeared to be more abundant in epithelial cells, whereas CRABP II appeared to be more abundant in the stromal cells. This implies that the intracellular concentration of retinoic acid may be maintained at higher levels in epithelial cells compared to stromal cells. In addition, the response of the two cell types to retinoic acid differs: RAR-beta is induced in stromal cells treated with all-trans retinoic acid but not in epithelial cells. From these data we suggest that retinoid physiology differs between endometrial epithelial and stromal cells. Furthermore, by analogy with other studies, we propose that retinoic acid may be maintained at a higher intracellular concentration in endometrial epithelial cells to facilitate differentiation to a glandular phenotype.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Production of interleukin 1 receptor antagonist and interleukin 1 during haemodialysis with cellulose membranes.

An in vivo cross-over study has investigated plasma and cellular levels of IL-1 (IL-1 alpha IL-1 beta and IL-1Ra) when using Cuprophan (C) and cellulose triacetate (CTA) membranes to assess the roles of complement activation and dialysate endotoxin content in the induction of cytokines during the dialysis procedure. The mean C5a level during Cuprophan dialysis was 29.9 +/- 0.63 ng/ml (Mean +/- SEM), while for the cellulose triacetate dialysis was 3.09 +/- 0.7 ng/ml. The endotoxin content of the dialysate was 0.31 +/- 0.34 EU/ml and 0.68 +/- 1.39 EU/ml. These two factors failed to produce measurable changes in plasma or cellular IL-1 alpha and IL-1 beta levels during treatment. The plasma IL-1Ra levels predialysis were similar to those for normal controls (CTA 769 +/- 156 ng/ml, C739 +/- 93, normal controls 635 +/- 33) with a considerable day to day variation. A membrane independent fall in plasma IL-1Ra at 15 minutes was noted (CTA 420 +/- 92 ng/ml, C 503 +/- 139) with a return to pre-dialysis levels by the end of treatment. Cellular IL-1Ra levels pre-dialysis were similar to the normal group--(CTA 1904 +/- 291 ng/ml, C 1564 +/- 292 and normal control 1971 +/- 368). However, on average, the values when using cellulose triacetate were 655 +/- 623 pg/ml higher than for Cuprophan (p = 0.03). These findings indicate that the measurement of plasma cytokine levels is of limited use in the study of cytokine induction by the haemodialysis procedure and that IL-1Ra may be a better indicator of the host response to cytokine stimuli during treatment. However, a considerable inter-patient and intra-treatment variation is present and further studies are required to elucidate the factors involved.

Aged↗
PubMed1993

Retinoic acid receptor expression during the in vitro differentiation of human neuroblastoma.

Neuroblastoma cells differentiate in response to retinoic acid and cyclic AMP. We have examined the expression of retinoic acid receptors (RARs) in relation to neuroblastoma differentiation and show that short term exposure of SK N SH, SH SY 5Y AND GI LI N cells to physiological concentrations of retinoic acid results in induction of RAR-beta, particularly the lower transcript. Cyclic AMP has no effect on retinoic acid mediated induction and does not alter RAR expression patterns. These data are discussed in the light of evidence that retinoic acid and cyclic AMP act either on different control pathways or at different points within a common pathway.

Blotting, Northern↗
PubMed1993

Ligand binding properties of human cellular retinoic acid binding protein II expressed in E. coli as a glutathione-S-transferase fusion protein.

To test the hypothesis that 9-cis-retinoic acid is a ligand for cellular retinoic acid binding protein II (CRABP II), human CRABP II was expressed as a glutathione-S-transferase fusion protein (GST-CRABP II) and a single affinity purification step used to extract it from bacterial lysates. GST-CRABP II bound all trans-retinoic acid with high affinity (Kd 14.2 +/- 6.5 nM), but 9-cis-retinoic acid bound poorly. These studies suggest that 9-cis-retinoic acid is not a ligand for CRABP II. Their ease of purification makes GST-CRABP fusion proteins useful tools for ligand binding studies with different retinoids.

Base Sequence↗
PubMed1993

Bradykinin stimulation of electrogenic ion transport in epithelial layers of cultured human endometrium.

Primary cultures of glandular endometrial epithelial cells grown on permeable supports formed monolayers with a high transepithelial electrical resistance [1096 +/- 83 omega.cm2 (n = 34)] and displayed electrogenic ion transport as demonstrated by an inward short circuit current (Isc; 20 +/- 2 microA/cm2). Bradykinin, 10(-8)-10(-6) M, added to either the basolateral or apical solutions enhanced the inward ISC. The concentration-response curves for bradykinin were bell-shaped in nature. The ISC response was more sensitive to apical addition of bradykinin and the maximum response was also greater with apical bradykinin. The increases in ISC were accompanied by two- to three-fold increases in transepithelial conductance. Apical addition of amiloride, 10(-4) M, reduced the unstimulated ISC by 80%. In the presence of amiloride, the response to both apical and basolateral bradykinin was reduced by > 50% in 8 out of 18 layers, and the mean response was reduced by approximately 25%. The data are consistent with a physiological role for bradykinin in the control of the intrauterine electrolyte environment, mediated in part by enhanced Na+ absorption.

Amiloride↗
PubMed1993

Ion transport by human endometrial epithelia in vitro.

Human glandular endometrial epithelial cells were cultured on porous tissue culture inserts to form tight, confluent layers. These layers generated time-dependent modifications in the ionic composition of both apical and basolateral solutions. Increases in sodium and chloride concentrations in the basolateral fluid were accompanied by reciprocal decreases in the concentrations of these ions in the apical fluid. The potassium concentration was increased in the apical, while decreased in the basolateral, solution. The total calcium concentration was slightly elevated in the apical, as compared with the basolateral fluid, while there were no alterations in pH. The endometrial layers demonstrated a significant transepithelial potential difference, and when this value was substituted in the Nernst equation a prediction of the passive distribution of ions across the cells was possible, indicating that none of the ions were in equilibrium. Addition of the sodium channel blocker amiloride to the medium bathing the cell layers reduced the modifications in ionic composition of apical and basolateral solutions. The data are consistent with other data indicating an amiloride-sensitive sodium-absorptive function for the endometrial epithelium. The ability of these primary cultures of endometrial epithelial cells to reduce the sodium while increasing the potassium concentration of the apical fluid is qualitatively in agreement with the low sodium and high potassium concentrations reported for human uterine fluid. The data suggest a role for the endometrial epithelium in generating and maintaining the distinctive ionic composition of the intra-uterine environment.

Adult↗
PubMed1993

Bombesin and gastrin-releasing peptide stimulate electrogenic ion transport in cultured human endometrial epithelial cell layers.

Electrogenic ion transport across human endometrial epithelial cells grown as polarized monolayers on permeable supports was measured as an inward short-circuit current (Isc; 16.2 +/- 1.1 microA/cm2). Bombesin (10(-7) M) and human gastrin-releasing peptide (GRP; 10(-7) M) caused transient enhancement of this Isc. These effects were largely restricted to the basolateral surface of the cells; responses to apical peptide were modest in comparison with those to basolateral peptide. GRP and other bombesin-related peptides may have a role in regulation of endometrial epithelial ion transport in vivo and thereby influence the intra-uterine environment.

Bombesin↗