Search PubMed⌕ Search

Biomedical subjects

M Mirshahi

Publications and source records attributed to M Mirshahi.

115 records · Page 7Linked to original sources
PubMedDate not supplied

The blockade of mineralocorticoid hormone signaling provokes dramatic teratogenesis in cultured rat embryos.

Although the administration of adrenocortical hormones to pregnant rats provokes only limited effect on the growth and development of the fetus, the direct influence of these steroids on cultured embryos has never been studied. The disruption of cell signaling by ZK 91587, which specifically occupies the mineralocorticoid receptor, resulted within 2 days in significant and pronounced adverse effects on the total length, the somite number, the embryo curvature, the communication between vitelline and umbilical blood vessels in the allantoid, and the vascularization of the vitelline sac, in 244-hour Wistar rat embryos in culture. The average score of 16 organs declined in a dose-dependent manner, following exposure to ZK 91587, and this was totally reversed by 10 microM aldosterone which, by itself, did not at all influence the embryonic development. The organogenesis was inhibited in the order: hind limb > fore limb > optic stalk > brain > olfactory pit > otic vesicle. ZK 91587 was completely ineffective in embryos that had attained the age of 260 hours. Similar, but less dramatic, results were obtained with the mineralocorticoid antagonist RU 26752, and with the antiglucocorticoid RU 38486. Sprague-Dawley rat embryos responded in a manner similar to the Wistar conceptuses. Thus, steroid receptor-mediated cell signaling is of critical importance to the growth and development of cultured rat embryos, which form a new model system to unravel adrenocortical hormone action.

Animals↗
PubMedDate not supplied

Mineralocorticoid hormones exert dramatic effects on pluripotent human stem cell progeny.

The authors studied mineralocorticoid receptor (MCR)-mediated effects of steroids on CD34(+) progenitor cells. Reverse transcriptase-polymerase chain reaction (RT-PCR) analysis showed the presence of mRNA for both the MCR and the alpha subunit of the epithelial sodium channel, a member of the amiloride-sensitive sodium channel (ASSC) superfamily, in human CD41(+) megacaryoblastic cells derived from cultured bone marrow CD34(+) isolates, as well as in the human erythromegakaryoblastic leukemia (HEL) cell line. Immunofluorescence also revealed the presence of both the MCR and ASSC in circulating CD34(+) and medullar CD41(+) megacaryoblastic cells, the former as a nucleocytoplasmic protein and the latter as a membrane-bound protein, as expected from earlier studies using MCR-specific targets. In a selective medium, the formation of erythrocyte burst-forming units, and of the granulocyte-macrophage colony-forming units, by circulating CD34(+) cells was influenced by the agonists deoxycorticosterone and aldosterone, as well as by the antagonists RU 26752 and ZK 91587, targeted for the MCR. The multiplication of the leukemic HEL progeny, derived from CD41(+) cells, was similarly altered by these steroids targeted for the MCR. In contrast, in the optimal growth medium, the multiplication, and colony formation by bone marrow CD34(+) progenitor cells were not altered by either aldosterone or ZK 91587. These and other studies reveal that the receptor-mediated action of mineralocorticoids may influence the functional maturation of the hematopoietic progenitor lineage, contrary to the classical notion where the mineralotropic effect would be a unique feature of the epithelial cell.

Antigens, CD34↗
PubMedDate not supplied

Mineralocorticoid hormone signaling regulates the 'epithelial sodium channel' in fibroblasts from human cornea.

We investigated the regulation of sodium absorption by steroid hormones in embryologically diverse cells from the human eye. A cell extract from human corneal fibroblasts was positive for both the epithelial sodium channel (ENaC) and the mineralocorticoid receptor (MCR) as 82- to 85-kD and 102-kD bands, respectively, by the Western blot technique. In fluorescent, confocal and electron microscopy, the MCR was revealed as a nucleocytoplasmic protein, whereas the ENaC was almost exclusively membrane bound; both appeared aligned along actin filaments of corneal keratocytes, and both were widely colocalized in various cell types of human cornea in situ. Following reverse transcription and amplification of total RNA isolated from corneal fibroblasts, the ENaC and MCR genes in the PCR product were evident as predicted bands of 520 and 843 bp, respectively, whose sequence exhibited 100% identity with those from known human sources. The multiplication of corneal fibroblasts was influenced by both the MCR-specific antagonist RU 26752 and the natural hormone aldosterone, and these steroids also stimulated protein phosphorylation. In quantitative PCR, both the basal and aldosterone-induced levels of ENaC were diminished by the MCR-specific antagonist ZK 91587. Consequently, the ocular sodium channel appears to be regulated by steroid signalling in cells of diverse embryological origins, contrary to the existing notions where (a) this process would be limited exclusively to the epithelial cells and (b) ocular sodium transport would be regulated via the Na(+)-K(+)-ATPase in the basolateral membrane.

Aldosterone↗
PubMedDate not supplied

Mineralocorticoid hormone receptor and the epithelial sodium channel in a human leukemic cell line.

A Cell extract from the HEL (human erythroblastic leukemia) cell line was positive for both the epithelial sodium channel (ENaC) and the mineralocorticoid receptor (MCR) as glycosylated 82-84 kDa bands, and a single 102 kDa band, respectively, in Western blots using polyclonal antibodies raised against these proteins. The immunofluorescent labeling of the MCR in all cell lines showed a nucleocytoplasmic localization of the receptor whereas the ENaC was exclusively membrane-bound. These results were confirmed by confocal microscopy. The expression of the MCR in HEL cells was evident as a predicted band of 843 bp (234 amino acids) after total RNA from HEL cells had been reverse transcribed and then amplified by PCR; the ENaC was similarly evident as a predicted band of 520 bp. In both cases, near 100% identity was observed between the deduced amino acid sequences of the PCR products and those from known human sources. The multiplication of HEL cells was influenced by antagonists (RU 26752, ZK 91587) targeted for specificity to the MCR and this was reversed by the natural hormone aldosterone. These steroids also provoked chromatin condensation in the HEL population.

Amino Acid Sequence↗
PubMedDate not supplied

Inhibition of S-antigen-induced experimental autoimmune uveoretinitis by active immunization against anti-idiotypic antibody to an S-antigen epitope.

Experimental autoimmune uveoretinitis (EAU) was induced in rnu/+ rats by one injection of retinal S-antigen (S-Ag) in complete Freund's adjuvant. Immunization of rats, before the S-Ag challenge, with a polyclonal antibody directed at the monoclonal antibody (mAb) S2D2, prevented the development of EAU in rats at clinical and histological levels. Lymph node cells from rats hyperimmunized with this anti-idiotype (anti-Id) S2D2 antibody were stimulated in vitro by anti-Id S2D2, S-Ag, and mAb S2D2. These findings suggest that anti-S2D2 antibody acts as an internal image at the T-cell level for the epitope of S-Ag recognized by mAb S2D2 (epitope S2). From these results, it appears that cells bearing receptors for the internal image of the epitope S2, which is not pathogenic when injected emulsified in adjuvants, are able to inhibit S-Ag-induced EAU.

Animals↗
PubMedDate not supplied

Modulation of experimental autoimmune uveoretinitis by adoptive transfer of cells from rats immunized with anti-S-antigen monoclonal antibody.

Preimmunization of rnu/+ rats with the mouse monoclonal antibody S2D2 against retinal S-antigen (S-Ag) leads to an anti-idiotypic (anti-Id) response and to protection against experimental autoimmune uveoretinitis (EAU) provoked by a subsequent challenge with S-Ag in complete Freund's adjuvant (CFA). Suppression of EAU can be passively transferred using lymph node and/or spleen cells from donors with active anti-Id immunity to naive rnu/+ recipients, prior to immunization with bovine S-Ag in CFA. In contrast, passive administration of IgG from S2D2-immunized rats did not produce suppression. High levels of anti-Id S2D2 antibodies were found: (1) in rats presenting an inhibited EAU after sensitization with S2D2 or after passive transfer of anti-S2D2 cells prior to the S-Ag immunization; and (2) in rats with a severe EAU after transfer of anti-S2D2 IgG associated with anti-S2D2 cells prior to the S-Ag challenge. No effect on the anti-S-Ag antibody level could be detected. These experiments suggest that EAU, a mostly T cell-dependent disease, can be down regulated by anti-Id lymphoid cells.

Animals↗