Biomedical subjects

C K Lea

Publications and source records attributed to C K Lea.

8 recordsLinked to original sources

PubMed1999

Macrophage colony stimulating-factor transcripts are differentially regulated in rat bone-marrow by gender hormones.

There are at least three forms of macrophage colony-stimulating factor (M-CSF), a cytokine that is critical for osteoclast formation; and evidence exists that the membrane-bound form is involved in this process. We wished to test the hypothesis that the expression of the membrane form of M-CSF is modulated by the presence of gender steroids. This was achieved by analyzing M-CSF messenger RNA and protein in the bone-marrow of estrogen- and androgen-replete, and -deficient female rats. We found that the 1.4-kb M-CSF transcript was not detected in sham-operated rats but that the 4.6-kb transcript was expressed in abundance. In contrast, these transcripts were differentially expressed in ovariectomized rats, and this effect was reversed by 17beta-estradiol treatment. Administration of androstenedione to ovariectomized rats, so that androstenedione plasma levels were restored to just below that in sham-operated rats, also suppressed the expression of the 1.4-kb M-CSF transcript. This effect was abrogated by antiandrogen treatment, indicating that this was an androgen-mediated effect. The membrane-bound protein was detected in the bone-marrow of sham-operated rats and was elevated post ovariectomy, whereas ovariectomy had no effect on the soluble isoform. Our data support the hypothesis that the membrane form of M-CSF is modulated by gender hormones and that this isoform is involved in the estrogen- and androgen-mediated effects on the skeleton.

Anastrozole↗

PubMed1999

Ovarian androgens protect against bone loss in rats made oestrogen deficient by treatment with ICI 182,780.

We tested the hypothesis that ovarian androgens play a role in protecting against cancellous bone loss in oestrogen-deficient states and that conversion of androgens to oestrogens is not catalysed by aromatase P450 in the bone or bone-marrow microenvironment. We did this by administering the anti-oestrogen, ICI 182,780, alone and in combination with the anti-androgen, Casodex, and compared the effects on the skeleton with those of ovariectomy. We found that rats subjected to ovariectomy lost significantly greater cancellous bone volume compared with those treated with ICI 182,780, but that combination anti-oestrogen and anti-androgen therapy resulted in bone loss equivalent to that in ovariectomised animals. The skeletal-protective effect of preserving the ovaries in animals which had been chemically ovariectomised was attributed to suppression of osteoclast parameters. Taken together, these data suggest that a reduction in ovarian androgens accentuates the increase in osteoclast number and the reduction in cancellous bone volume which occurs in oestrogen-deficient states. Failure to detect transcripts for aromatase cytochrome P450 in the bone and bone-marrow of rats provides supportive evidence that androgens mediate their skeletal-protective effect directly and not by peripheral conversion to oestradiol.

Analysis of Variance↗

PubMed1998

Physiological plasma levels of androgens reduce bone loss in the ovariectomized rat.

The effect of androstenedione (ADIONE) slow-release pellets on cancellous bone volume (BV/TV) at the tibial metaphysis was investigated in ovariectomized (OVX) rats at various times from 21 to 180 days. Plasma levels of ADIONE and testosterone (T) in OVX rats were significantly reduced at 21 days and were restored close to levels in the sham rats with the 1.5-mg ADIONE pellet. OVX animals with and without ADIONE pellets resulted in close to a 50% reduction in BV/TV, by day 21. By day 180, OVX rats had only approximately 5% BV/TV, whereas that in ADIONE-treated OVX rats was significantly greater at approximately 12%. The reduced BV/TV was associated with increased bone resorption and formation. In a separate 90-day experiment, we found that the antiandrogen, Casodex, abrogated the ADIONE-induced skeletal-protective effect in OVX rats, whereas the antiaromatase, Arimidex, had no effect. This provides evidence that ADIONE protects against the development of osteopenia in the estrogen-deficient rat and mediates its effect through androgens and not estrogens.

Aging↗

PubMed1998

Androstenedione treatment reduces loss of cancellous bone volume in ovariectomised rats in a dose-responsive manner and the effect is not mediated by oestrogen.

We have tested the hypothesis that androstenedione (administered as 21-day, slow-release pellets) is converted to active sex steroids and reduces bone turnover in the ovariectomised rat model. We found that ovariectomy resulted in a minor but significant reduction in plasma concentrations of androstenedione and testosterone and a more significant reduction in oestrone (E1) and oestradiol (E2). This was associated with the expected substantial loss of metaphyseal cancellous bone volume. Androstenedione (1.5-100 mg) pellets increased the plasma concentrations of androstenedione and testosterone above those in the ovariectomised (ovx) rats in a dose-responsive manner, whereas E2 plasma concentrations were increased to a minor but significant degree above those in the ovx animals. Androstenedione reduced loss of cancellous bone volume in a dose-dependent fashion by reducing bone turnover. The 1.5, 5 and 100 mg androstenedione-induced effect on bone turnover was not abrogated by simultaneous treatment with Arimidex, an aromatase inhibitor. This implies that the skeletal-protective effect of androstenedione was not oestrogen-mediated.

Androstenedione↗

PubMed1997

Aromatase cytochrome P450 transcripts are detected in fractured human bone but not in normal skeletal tissue.

Peripheral conversion of gender steroid precursors has been implicated in playing a role in bone turnover in postmenopausal women. It has been reported that aromatase cytochrome P450 (P450arom) is present in primary bone and bone marrow (BM), and that P450arom mRNA has been identified in cultured BM and osteoblast-like cell lines. However, there are no reports that P450arom transcripts have been detected in skeletal tissue that has not been cultured. We therefore elected to test for the presence of P450arom mRNA in primary human bone and BM in normal and fractured necks of femora using the reverse transcription-polymerase chain reaction method. Although the RNA extracted from these tissues was of good quality as demonstrated by the expression of transcripts for interleukin-6, P450arom transcripts failed to be detected in normal primary cortical bone and fatty BM containing trabecular bone. However, P450arom transcripts were detected in the latter when they were cultured. Transcripts for P450arom were also detected in total RNA extracted from six fractured necks of femora and semiquantitative PCR demonstrated that P450arom mRNA was present in similar abundance in the same amount of RNA analyzed from buttock adipose tissue and fractured bone/BM. P450arom mRNA expression was also detected in cultured peripheral blood leukocytes, suggesting that this might be the source of the enzyme. In these cultures no correlation was detected between the expression of P450arom mRNA and cell proliferation. PCR failure was excluded in cases when P450arom transcripts failed to be detected in bone/BM by coamplifying RNA from human and rat brain mRNA, known to express P450arom mRNA, using primers that detect both P450arom mRNA from both species. These products were analyzed by Southern blot using oligonucleotide probes, which label either human or rat P450arom cDNA. The blots confirmed the absence of P450arom in nonfractured human bone and BM and preclude PCR failure. Our results indicate that P450arom mRNA is not detected in either normal human bone or BM, but can be induced in this microenvironment under pathological conditions. We propose that tissue grown in vitro is analogous to a wound and this explains why P450arom transcripts were detected in cultured normal skeletal tissue, whereas they failed to be detected in primary normal bone and BM.

Animals↗

PubMed1996

Prevention of hyperacute rejection by removal of antibodies to HLA immediately before renal transplantation.

BACKGROUND: Many patients with circulating antibodies to human leucocyte antigens (anti-HLA) are highly sensitised against renal transplantation and are liable to immediate graft loss through hyperacute rejection. Our aim was to find out whether removal of anti-HLA immediately before renal transplantation prevented hyperacute graft rejection. METHODS: 13 highly sensitised patients underwent cadaveric renal transplants immediately after immunoadsorption (IA) treatment to remove anti-HLA. Before IA, 12 patients had a positive crossmatch against donor cells either by cytotoxic or flow-cytometric assay; results for one patient were equivocal. FINDINGS: Renal biopsy samples were obtained 20 min after removal of the vascular clamps in nine patients. There was no evidence of hyperacute rejection in six of the nine patients; the other three patients showed glomerular thrombosis but no other evidence of hyperacute rejection. Two of these three grafts were functioning at 31 months of follow-up. Six episodes of acute rejection occurred in five patients during the first month after transplantation and overall there were 13 rejection episodes in nine patients. At latest follow-up (median 26 months, range 9-42), 12 of 13 patients were alive and seven of 13 grafts were surviving with a median plasma creatinine concentration of 185 mumol/L (range 106-296) in the functioning grafts. No graft was lost as a result of classic hyperacute rejection. INTERPRETATION: Immediate pretransplant IA can prevent hyperacute rejection and provide an opportunity for successful transplantation in highly sensitised patients.

Adolescent↗

PubMed1996

Antibody removal and subsequent transplantation of a highly sensitised paediatric renal patient.

We report a successful renal transplant in a highly sensitised paediatric recipient following removal of HLA-specific antibodies by extracorporeal immunoadsorption. The immediate pretransplant cytotoxic titre against the donor was greater than 1:512; this was reduced to negativity by two immunoadsorption sessions prior to transplant surgery. We also describe the presence of unexpected non-HLA-specific antibody activities in this immunoadsorbed patient.

Autoantibodies↗

PubMed1996

The pharmacokinetics of anti-thymocyte globulin (ATG) following intravenous infusion in man.

The pharmacokinetics of the distribution and elimination of polyclonal rabbit antithymocyte globulin (ATG) following intravenous infusion was studied in patients who had received renal allografts. ATG concentration was measured using a new enzyme-linked immunoabsorbent assay (ELISA) for the Fc portion of rabbit IgG. Eleven patients received 14 courses of ATG supplied either by Fresenius (F-ATG) or Merieux (M-ATG) as a daily infusion of 2-6 mg/kg body weight for a therapeutic course lasting 5-10 days. The washout phase of ATG elimination was analysed over 0-300 days; results were well-fitted by a single exponential decay (r2 > 0.95) giving a mean elimination half-life (t0.5e) of 29.8 days (range 14.3-45.0, n = 9). Data for the first 4 days of treatment were analysed with linear regression to obtain a mean value for the apparent volume of distribution of ATG (Vd) of 0.12 l/kg body weight (range 0.07 to 0.17, n = 5). These results demonstrate that rabbit ATG has a long half-life in human plasma and an apparent volume of distribution of about twice plasma volume. The relationship between the concentration of ATG measured by this Fc receptor assay and its biological activity requires further study.

Animals↗