Biomedical subjects

M M Sadeghi

Publications and source records attributed to M M Sadeghi.

6 recordsLinked to original sources

PubMed2004

Vascular cell adhesion molecule-1-targeted detection of endothelial activation in human microvasculature.

The hallmark of endothelial activation, an early and critical step in many alloimmune and inflammatory responses, is the transcriptional induction and expression of endothelial adhesion molecules (eg, vascular cell adhesion molecule-1 [VCAM-1]). We assessed the feasibility of VCAM-1-targeted in vivo detection of endothelial activation using I-125-labeled-F(ab')2 fragments of E1/6, a monoclonal antibody against human but not murine VCAM-1. The Kd and Bmax, determined by saturation binding in tumor necrosis factor (TNF)-activated human endothelial cells (ECs), were 3.2 +/- 0.6 nmol/L and 5600 +/- 300 binding sites per EC, respectively. Biodistribution and in vivo binding characteristics of I-125-E1/6 F(ab')2 were assessed in a novel chimeric human/mouse model, in which human skin (as a source of human microvasculature) is grafted onto SCID/beige mice. I-125-E1/6 F(ab')2 localized to TNF-activated human skin grafts as detected by autoradiography and gamma well-counting. Relative uptakes (uptake in human skin graft/uptake in the surrounding mouse skin) were, respectively, 2.6 +/- 0.8 (n = 14) and 1.6 +/- 0.3 (n = 12) for E1/6 and MOPC-21, an isotype-matched control antibody (P < .01). The preferential uptake in human skin graft was not due to differences in tissue vascularity assessed by Tc-99m-labeled murine red blood cells. In conclusion, the chimeric human/mouse model is a novel experimental tool for in vivo evaluation of human endothelial cell-specific radiopharmaceuticals. Although I-125-E1/6 F(ab')2 localized to human skin grafts, the limited number of VCAM-1 molecules/endothelial cell adversely affects its suitability as a target for in vivo imaging of endothelial activation.

Animals↗

PubMed2001

Inhibition of interferon-gamma-mediated microvascular endothelial cell major histocompatibility complex class II gene activation by HMG-CoA reductase inhibitors.

BACKGROUND: Graft vascular disease, a major cause of late graft failure in cardiac transplant patients, is associated with the presence of class II major histocompatibility complex molecules on the endothelium. 3-hydroxy-3-methylglutaryl (HMG)-CoA reductase inhibitors, e.g., simvastatin, have been shown to reduce the incidence of graft vascular disease. We studied the effect of simvastatin on interferon (IFN)-gamma-induced human leukocyte antigen (HLA)-DR expression in human microvascular endothelial cells (MVECs). METHODS AND RESULTS: Simvastatin pretreatment inhibited MVEC HILA-DR induction by IFN-gamma, as detected by flow cytometry. Simvastatin's inhibitory effect was reversed by the cholesterol synthesis pathway intermediates mevalonate and geranylgeranyl pyrophosphate but not squalene, indicating the involvement of protein prenylation in this process. Reverse transcription-polymerase chain reaction analysis demonstrated that induction of class II transactivator (CIITA), and consequently, HLA-DRalpha mRNA, is abrogated by simvastatin. Although signal transducer and activator of transcription (STAT)-1 is a critical CIITA gene transactivator, immunofluorescence studies, Western blotting, and electrophoretic mobility shift assays demonstrated that IFN-gamma-induced STAT-1 phosphorylation, nuclear translocation, and DNA binding are not affected by simvastatin. However, simvastatin inhibited IFN-gamma-induced transactivation of a CIITA promoter IV reporter construct, indicating the involvement of this promoter in the inhibitory effect of simvastatin. CONCLUSIONS: Simvastatin pretreatment inhibits CIITA and consequent HLA-DR induction by IFN-gamma in MVECs through interference with protein prenylation. This inhibitory effect occurs at the level of transcription and is directed, at least in part, at the CIITA promoter IV. These results explain some of the beneficial effects of HMG-CoA reductase inhibitors in cardiac transplantation.

Cholesterol↗

PubMed2000

Simvastatin modulates cytokine-mediated endothelial cell adhesion molecule induction: involvement of an inhibitory G protein.

Endothelial cell adhesion molecules (CAMs) E-selectin, ICAM-1, and VCAM-1 play variably important roles in immune-mediated processes. They are induced by the proinflammatory cytokines IL-1 and TNF-alpha, and NF-kappaB is required for the regulated expression of all three genes. Regulators of this pathway could potentially be potent immune modulators. We studied the effect of a 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor, simvastatin, on cytokine-induced expression of CAMs in HUVEC. Unexpectedly, pretreatment with simvastatin potentiated the induction of all three endothelial CAMs by IL-1 and TNF, but not LPS or PMA, as detected by flow cytometry. Northern blot analysis demonstrated an increase in steady state IL-1-induced E-selectin mRNA levels in cells pretreated with simvastatin. This was associated with an increase in nuclear translocation of NF-kappaB, as detected by EMSA. The effect of simvastatin was reversed by mevalonate and geranylgeranyl pyrophosphate but not squalene, indicating that an inhibitory prenylated protein is involved in endothelial responses to proinflammatory cytokines. Pertussis toxin mimicked the effect of simvastatin, and the G protein activator NaF inhibited the cytokine-induced expression of endothelial CAMs, indicating that a Gialpha protein is involved. These results demonstrate that cytokine-mediated activation of the endothelium, and specifically CAM induction, can be modulated by a heterotrimeric G protein-coupled pathway. This may represent a "basal tone" of endothelial inactivation, which can either be disinhibited or amplified, depending on the stimulus.

Adjuvants, Immunologic↗

PubMed1995

Design, synthesis, and structure-activity relationship of novel dinucleotide analogs as agents against herpes and human immunodeficiency viruses.

A new acyclic nucleoside phosphonate (13) containing an adenine moiety was synthesized, which acted as an excellent inhibitor of calf mucosal adenosine deaminase. This inhibitory property allows it to exert great synergistic effect on certain antiviral agents (e.g., ara-A, 37). Phosphonate 13 was not phosphorylated by the bovine brain guanylate kinase nor by 5-phosphoribosyl 1-pyrophosphate synthetase. Syntheses of biologically active nucleotide phosphonate 40 and its phosphonoamidate derivative 42 were accomplished, which showed remarkable activity against herpes viruses and exhibited low host cell toxicity. 3'-Azido-nucleoside phosphonate 20 and 3'-fluoronucleoside phosphonate 32, as well as the corresponding dinucleotide analogs 47 and 48, and their respective phosphonoamidates 53-56 were also synthesized as new compounds, among which phosphonoamidates 53-56 showed potent activity against human immunodeficiency virus. Phosphonoamidates 55 and 56 bearing a methyl D-alaninate moiety exhibited less cellular toxicity than 53 and 54 bearing a methyl L-alaninate moiety. Nucleotide phosphonate 40 as well as dinucleotide phosphonates 47 and 48 were found susceptible to degradation by phosphodiesterases. Their respective phosphonoamidates 42 and 53-56, however, were completely resistant to snake venom and spleen enzymes.

Adenosine Deaminase Inhibitors↗

PubMed1994

Heterogeneous activation thresholds to cytokines in genetically distinct endothelial cells: evidence for diverse transcriptional responses.

It is well accepted that the induction of endothelial cell (EC) adhesion molecules is a critical component in acute inflammatory responses as well as allogeneic interactions in vascularized allografts and, possibly, atherogenesis. The "inflammatory triad" of interleukin 1 (IL-1), tumor necrosis factor, and lipopolysaccharide are potent stimulators of the EC activation/adhesion molecules intercellular adhesion molecule 1 (ICAM-1), endothelial-leukocyte adhesion molecule 1 (ELAM-1), and vascular cell adhesion molecule 1 (VCAM-1). To address whether there exist differing thresholds to cytokine-mediated EC activation, we utilized a panel of genetically distinct human umbilical vein EC lines, assessing their modulated EC surface expression and transcriptional responses to cytokines, with regard to the cell adhesion molecules (CAMs) ELAM-1, ICAM-1, and VCAM-1. With submaximal concentrations of cytokine, EC ELAM-1 surface expression varied from negligible to marked. This phenotypic response was maintained over numerous passages in culture and was observed in ex vivo organ culture analyses with cytokine-treated umbilical vein sections. Relative patterns of ELAM-1, ICAM-1, and VCAM-1 induction were similar in response to multiple stimuli (IL-1, tumor necrosis factor, and lipopolysaccharide, but not phorbol 12-myristate 13-acetate). Nuclear run-off experiments demonstrated that the "high responder" phenotype is a consequence of enhanced transcriptional activation of the CAM genes in response to IL-1 (1 unit/ml), whereas transcriptional responses in "low responders" are minimal. Despite the known involvement of NF-kappa B in endothelial CAM transcription, gel shift assays failed to demonstrate a correlation between the levels of IL-1-mediated nuclear NF-kappa B expression and CAM induction in high and low responding lines. We postulate that varying EC activation thresholds to cytokines observed here, in vitro, may be a critical determinant in the susceptibility to vasculopathic states.

Base Sequence↗

PubMed1986

Visceral nociception in developing rats.

Maturational changes in visceral nociception were measured in developing or adult rats challenged with hypertonic saline or acetylcholine. Chemically induced abdominal constrictions were absent in rats younger than 7 days of age, regardless of the dose of hypertonic saline or acetylcholine used. Age-related increases in the percent of animals responding, the number of abdominal constrictions emitted per responder, and total response duration occurred in animals 10-20 days of age, until adult-like patterns of responding were attained at the time of weaning. Additional changes in the percent animals responding, as well as in the frequency and total duration of abdominal constriction responses, were also seen in postweanling, but not in preweanling, animals. Five-day-old animals did emit audible vocalizations to the intraperitoneal insertion of a hypodermic needle, however, at a time when these animals failed to show observable responses to the noxious visceral stimuli. Hence, mechanisms mediating pain associated with intraperitoneal needle insertion may be functional during the first postnatal week, at a time when mechanisms mediating visceral pain appear to be immature. These differences may be caused by the differential maturation of sensory, neural, or motoric mechanisms important for hypodermic needle insertion versus visceral nociception.

Age Factors↗