[Tubing and stopcock protector. Protective cover].
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Equipment and Supplies, Hospital↗
Biomedical subjects
F Dumont
Publications and source records attributed to F Dumont.
Is cyclophilin involved in the immunosuppressive and nephrotoxic mechanism of action of cyclosporin A?
In this report we have approached two questions relating to the mechanism of action of cyclosporin A (CsA). First, we address whether the major cytosolic protein for CsA, cyclophilin, is directly involved in mediating the immunosuppressive activity of this drug, and, in particular, whether inhibition of this protein's peptidyl-prolyl cis-trans isomerase (PPIase) activity results in inhibition of murine T cell activation. Second, we ask whether the nephrotoxicity observed with CsA is related to inhibition of PPIase-dependent pathways in cells other than lymphocytes. Using a series of 61 cyclosporin analogues, we generally found a good correlation between cyclophilin binding and immunosuppressive activity for the majority of analogues analyzed. However, a number of compounds of distinct structural classes were found that could interact with cyclophilin but were much less immunosuppressive than expected. The inability of these analogues to inhibit lymphocyte activation could not be explained by their failure to enter the cell and bind to cyclophilin under the conditions used in the cellular assays. Surprisingly, a nonimmunosuppressive analogue, MeAla-6, which bound well to cyclophilin and was active as a PPIase inhibitor, did not induce renal pathology in vivo. Furthermore, another analogue, MeBm2t, which was immunosuppressive in vitro, possessed little or no activity as a PPIase inhibitor. These findings pose serious questions concerning a direct role of cyclosporin in mediating CsA's immunosuppressive and nephrotoxic activities. In addition, they raise doubts about whether PPIase has a direct function in lymphocyte signal transduction.
Amino Acid Isomerases↗
The immunosuppressant FK506 selectively inhibits expression of early T cell activation genes.
FK506, a neutral macrolide with immunosuppressive properties, was shown to selectively and rapidly inhibit the accumulation of IL-2 mRNA, as well as the mRNAs of other early (E) phase T cell activation genes such as IL-3, IL-4, GM-CSF, TNF alpha, IFN-gamma, and c-myc in activated human peripheral blood T cells. The activity of FK506, when compared to Cyclosporin A, another immunosuppressant, was 10 to 100x more potent in its ability to inhibit IL-2 mRNA synthesis. FK506 inhibited IL-2 mRNA accumulation in Con A, Con A plus PMA, Ionomycin plus PMA, anti-CD3, and anti-CD3 plus PMA activated T cells. Transcripts from other T cell gene classes such as the immediate early (IE) phase gene, c-fos, the late phase (L) genes, transferrin receptor, IL-2R alpha-chain, and TNF-beta, and the constitutive class genes glyceraldehyde-3-phosphate dehydrogenase and class I MHC HLA-B7 were not affected by FK506. The macrolide Rapamycin, which is structurally related to FK506, had no inhibitory effect on IE, E, L, or constitutive class mRNAs, but it appeared to increase the levels of the E-phase transcripts that were inhibited in FK506 treated T cells. The effect of FK506 on inducible genes in non-T and non-lymphoid human cells was studied in LPS-induced monocytes and PMA or IL-1 activated synovial fibroblasts. FK506 did not affect expression of the mRNAs for IL-1 alpha or IL-1 beta in human monocytes, or of stromelysin, collagenase, or TIMP in synovial fibroblasts. Nuclear run-off transcription studies indicate that FK506 inhibits transcription of the IL-2 gene. These studies suggest that Cyclosporin A and FK506 may effect a common early event in the T cell activation pathway.
Base Sequence↗
A study of the correlation between cyclophilin binding and in vitro immunosuppressive activity of cyclosporine A and analogues.
In order to establish whether CyP is the pharmacologically relevant CsA receptor, the CyP binding v immunosuppressive activity was measured for an extensive, structurally varied group of CsA analogues. Overall, CyP binding was found to parallel immunosuppressive activity. Other than MeAla6-CsA, the few exceptions to the correlation could be ascribed to cellular metabolism. These results strongly implicate CyP or a related protein in the mechanism of action of cyclosporine.
Animals↗
Effects of ovariectomy and androgen treatment on the thymic pathology of NZB X SJL mice.
Aging (NZB X SJL)F1 (NS) mice provide a unique model of thymic pathology occurring in females but not in males and characterized by the intrathymic accumulation of mature T cells and B cells. Here, we studied the basis for the sex-related difference in the development of this thymic pathology. In the reverse (SJL X NZB)F1 hybrids, a similar pathology was also observed only in females which suggests that its sex-dependency does not involve sex-linked gene(s) but rather hormonal influences. Ovariectomy of NS females reduced but did not prevent the accumulation of T and B cells in the thymus indicating that estrogens play a minimal role in this thymic pathology. In contrast, chronic dihydrotestosterone (DHT)-treatment of females, started at 4 weeks of age, inhibited the development of thymic lesions. Consistently, orchidectomy of NS males induced the appearance of 'female-like' thymic lesions that could be prevented by DHT-treatment. This demonstrates that the absence of thymic disease in NS males primarily reflects an inhibitory action of androgens. Evidence was obtained that androgens also decrease the production of anti-ds DNA antibodies in NS mice.
Aging↗
Effects of intraventricular injections of gamma-aminobutyric acid and related substances on feeding behavior in satiated sheep.
Feed intake was measured following injections of gamma-aminobutyric acid (GABA), muscimol (a GABA agonist), and picrotoxin (a GABA antagonist) into the lateral ventricles of satiated sheep. Doses ranging from 0.20 to 3200 nmol of GABA did not affect feeding behavior at 15, 30, 60, and 120 min postinjection. A dose of 160 nmol of muscimol induced a marked increase in feeding, comparable to that provoked by an injection of 78 mumol of pentobarbital. Muscimol-induced feeding was blocked effectively by a preinjection of picrotoxin. These observations implicate that neurons sensitive to gamma-aminobutyric acid may be involved in the control of feeding behavior in ruminants.
Animals↗
Sex-dependent systemic lupus erythematosus-like syndrome in (NZB X SJL)F1 mice.
(NZB X SJL)F1 (NS) mice were previously shown to develop sex-dependent thymic abnormalities in the course of aging. The possible occurrence in these mice of various autoimmune manifestations characteristic of a systemic lupus erythematosus (SLE)-like syndrome is investigated. Female NS mice died faster and exhibited antinuclear (AN), anti-ds-DNA antibodies and circulating immune complexes earlier in life and in greater amounts than male NS mice. At 12 months of age immunoglobulin deposits were detected in the renal glomeruli and at the dermo-epidermal junction of the skin. These deposits were more frequent and more intense in females than in males. In addition, proteinuria was found to rise with aging in females but not in males. These data demonstrate that NS mice suffer from SLE symptoms which, like the thymic abnormalities, are influenced by sex-related factors. The study of castrated males and females and of androgen-treated females suggests that androgens exert an inhibitory effect on these SLE symptoms. Preliminary genetic analysis further indicates a probable polygenic control of these SLE symptoms in NS females.
Aging↗
Thymic abnormalities induced by castration in aged (NZB X SJL)F1 male mice: distinct effects of early and late castration.
Female but not male (NZB X SJL)F1 (NS) hybrid mice develop thymic abnormalities during aging. To determine the possible participation of androgens in this sex-related difference, we investigated the effect of androgen deprivation, as can be achieved by orchidectomy, on the cellular composition of the thymus of old NS males. Mice were orchidectomized at ages ranging from 3 weeks to 9 months and their thymuses were studied at the ages of 12 or 18 months. Phenotypic characterization of the intrathymic lymphocyte population was carried out using flow cytofluorometry analysis. Orchidectomy performed early in life (3 weeks-3 months) resulted, at 12 months of age, in thymic alterations (expansion of dull Thy-1+ cells, emergence of surface immunoglobulin-bearing cells) resembling those occurring spontaneously in old NS females. In contrast, when orchidectomy was performed later in life (6-9 months), there was a numerical increase of all thymocyte subsets but no major qualitative abnormality at either 12 or 18 months of age. Therefore, the absence of thymic disease in intact NS males may reflect primarily a suppressive effect of androgens that can be reversed by early but not by late orchidectomy.
Animals↗
Studies of congenitally immunologically mutant New Zealand mice. VIII. Cell-surface phenotype of spleen cells of Xid and nude mice.
Surface immunoglobulin on spleen cells from NZB and NZB/W mice and congenic mice bearing the nude or X-linked immune defective (Xid) gene was examined by flow microfluorometry with regard to both the frequency of positive cells and density expressed on the cell. These data indicate that although the frequency of unseparated sIg+ B lymphocytes is equivalent among all of these groups of mice, the densities of sIgM and sIgD are different. Spleen cells from these mice were also separated by free-flow electrophoresis and analyzed in a similar manner. This analysis demonstrated the absence of a subpopulation of B lymphocytes with a low electrophoretic mobility and low expression of sIgM. These studies suggest that maturational and/or activation states of the B cells in mice bearing the Xid or nude genes are different from those seen in the parent strains of mice. Such alterations in cell-surface antigens correlate with the differences in the natural history of immunopathology of the autoimmune disease in these congenic colonies of New Zealand mice.
Animals↗
Electrophoretic fractionation of murine lymphoid cells. I. Enrichment of peripheral T lymphocyte subsets with distinct surface phenotypes.
The purpose of this work was to evaluate the efficiency of free-flow electrophoresis as a method for separating mouse lymphocyte subsets. The surface phenotype of the cells contained in the various fractions collected after electrophoresis of CBA/J lymph node cells was investigated by means of single- and 2-color flow cytofluorometry (FCF) analysis. In agreement with previous works, B cells (sIg+, Thy-1-) were found to segregate in the low mobility (LM) fractions and T cells (sIg-, Thy-1+) in the high-mobility (HM) fractions. While the mean fluorescence intensity of sIg staining did not significantly vary as a function of electrophoretic mobility (EPM) that of Thy-1 staining tended to decrease with increasing EPM. The distribution of Lyt-1+ cells was roughly parallel to that of Thy-1+ cells. However, 2-color FCF analysis suggested the existence, in addition to a major Thy-1+ Lyt-1+ subpopulation, of a minor subset of Thy-1- Lyt-1+ cells. Lyt-2+ cells made up a peak in the cathodic HM region where they were enriched by up to 3-fold, and a trail in the more anodic HM fractions. Two-color FCF analysis showed that all Lyt-2+ cells recovered in these various electrophoretic fractions expressed the Lyt-1 antigen. Taken together, these data demonstrate that free-flow electrophoresis provides a powerful tool for the delineation and substantial enrichment of phenotypically distinct mouse peripheral T cell subsets.
Animals↗
Alterations of the intrathymic lymphocyte population in aged (NZB X SJL)F1 female mice as revealed by the differential effects of hydrocortisone and cyclophosphamide treatments.
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Aging↗
Age-related alterations of the lymphocyte population in the thymus of (NZB x SJL)F1 mice: analysis by flow cytofluorometry.
(NZB x SJL)F1 (NS) female mice develop a marked hypertrophy of the thymus in the course of aging. The age-dependent evolution of the intrathymic lymphocyte population of these mice was monitored in comparison with that of the immunologically normal BALB/c and C57BL/6 strains. The expression of several lymphocyte markers on the surface of the thymic cells was quantitated using single- and two-color flow cytofluorometry analysis. Two main cell types could thus be identified in the thymus of 3-month-old mice: a major subset of bright Thy-1+, Lyt-1+2+, bright peanut agglutinin (PNA)+ lymphocytes and a minor subset of dull Thy-1+, Lyt-1+2-, dull PNA+ lymphocytes. In BALB/c and C57BL/6 mice, the frequencies of these cell types did not significantly vary between 3 and 18 months of age, despite a drop of thymic cellularity. In contrast, in NS female mice the proportion as well as the absolute number of dull Thy-1+, Lyt-1+2-, dull PNA+ cells increased while those of bright Thy-1+, Lyt-1+2+, bright PNA+ cells diminished during the same period. The emergence of new cell types could also be noted in the thymus of aging NS female mice. Thus, in addition to the appearance of dull PNA+, Lyt-2+ cells and of bright PNA+ cells devoid of T cell markers, there was a high frequency of non-T cells bearing surface immunoglobulin, Ia antigen and receptors for Fc. These data indicate that the thymic hypertrophy of NS female mice reflects the intrathymic accumulation of large numbers of phenotypically mature T and B cells. Such alterations were not detectable in NS male mice.
Aging↗
Accumulation of mature T and B cells and abnormalities of lymphocyte traffic in the thymus of aged NZB x SJL F1 female mice.
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Aging↗
Immunohistological study of the anterior pituitary gland - pars distalis and pars intermedia - in dwarf mice.
This immunohistological study of the anterior pituitary gland in Snell-Bagg dwarf mice demonstrates a total absence therein of somatotropin prolactin and thyrotropic cells. Gonadotropin, melanocorticotropic, LPH- and endorphin-positive cells are well developed; they appear to be hypertrophied and more numerous than in normal animals.
Adrenocorticotropic Hormone↗
Xenoantisera directed against the proliferating T-cells of MRL/Mp-lpr/lpr mice.
MRL/Mp-lpr/lpr (lpr/lpr) mice develop a generalized lymph node (LN) hypertrophy reflecting the expansion of a T-cell subset that seems to act as an accelerating factor for autoimmunity. In an attempt to produce antisera specific for this T-cell subset, NZW rabbits and Lewis rats were hyperimmunized with cells from hypertrophied lpr/lpr LN. The resulting xenoantisera were extensively absorbed with lymphoid cells from the congenic MRL/Mp +/+ (+/+) strain. As assessed by complement-dependent microcytotoxicity and indirect immunofluorescence using flow cytofluorometry analysis, these xenoantisera reacted with 70-90% of the cells in the enlarged LN of 4-month-old lpr/lpr mice but only with 10-35% of the cells in the normal-sized LN of age-matched +/+ mice or of 2-month-old lpr/lpr mice. These xenoantisera which appear to identify surface antigens associated with the proliferating lpr/lpr T-cells may prove useful to investigate the mechanism by which these cells contribute to the autoimmune disease of lpr/lpr mice.
Animals↗