Biomedical subjects

Gian Piero Pescarmona

Publications and source records attributed to Gian Piero Pescarmona.

5 recordsLinked to original sources

PubMed2006

Long-term exposure to dehydroepiandrosterone affects the transcriptional activity of the glucocorticoid receptor.

Although the antiglucocorticoid effects of dehydroepiandrosterone (DHEA) have been demonstrated in vivo in many systems, controversial results have been reported by in vitro studies. In order to elucidate the long-term antiglucocorticoid effects of DHEA in vitro in a context more physiological than what proposed by previous works, we set up a system consisting of a carcinoma cell line relying on endogenously produced glucocorticoid receptor (GR) and stably expressing a reporter gene ErbB-2 under the control of a GR-dependent MMTV promoter. These cells grown in presence of low levels of serum glucocorticoids (GC) showed a basal translocation and activity of endogenous GR. The cells reacted to high concentrations of dexamethasone increasing GR nuclear import, although down-regulating receptor expression, and enhancing GR-dependent transcriptional activity, as shown by EMSA assay and expression of the reporter gene ErbB-2. The response to GC was also functional since the increase of ErbB-2 boosted cellular growth. On the contrary, 72h of incubation with DHEA diminished basal GR-dependent reporter expression and abated cellular proliferation. Analysing molecular mechanisms responsible for this failed transcriptional activity, upon prolonged treatment with DHEA we observed a slow nuclear import of GR not followed by its recruitment to DNA. These data add novel information about the long-term effects of DHEA in vitro.

Animals↗

PubMed2006

Immune system and bone metabolism: Does thymectomy influence postmenopausal bone loss in humans?

Recent studies of animal models have suggested that an increase in the number of T cells due to both peripheral expansion and increased thymic T cell output plays a key role in the regulation of bone loss after ovariectomy. Osteoclastogenic cytokines which are either produced by T cells or activate T cells have also been implicated in ovx induced bone loss. Among them are TNF alpha and IL-7. The present study investigates the role of thymectomy (THX) and IL-7 in bone metabolism in humans. We studied T cells subsets, cytokine production and bone metabolism in 13 women thymectomized for Myasthenia gravis as compared to healthy controls. Our data demonstrate that the number of CD4+ and TNF-producing T cells is lower in THX women as compared to euthymic controls. However in THX women the residual T cells produce higher levels of IL-7 and RANKL. Furthermore, flow cytometry shows that IL-7 is produced by T and B cells. Serum levels of TNF alpha were unaffected by THX and both serum TNF alpha and the RANKL/OPG correlated inversely with BMD. There were no differences in bone turnover and bone mineral density between THX women and the controls. These data suggest that THX decreases the number of TNF-producing CD4+ T cells but does not alters serum TNF levels. The RANKL/OPG ratio and indices of bone metabolisms are also not affected by THX, although THX increases the levels of IL-7 and RANKL. Further studies are needed to clarify the role of thymus in bone metabolism and osteoclastogenesis in postmenopausal women.

Adolescent↗

PubMed2004

Spontaneous osteoclast formation from peripheral blood mononuclear cells in postmenopausal osteoporosis.

Osteoclasts are cells involved in bone reabsorbing and hence in postmenopausal bone loss. There is no evidence of increased in vitro spontaneous osteoclast formation in postmenopausal osteoporosis. The aim of our study was to evaluate spontaneous osteoclastogenesis in osteoporosis. Bone mineral density, markers of bone turnover, and cultures of peripheral blood mononuclear cells (PBMC) on dentine slices with or without the addition of 1,25-OH vitamin D3 ([10(-8) M]) were obtained from 18 osteoporotic women and 15 controls. To verify cytokine production by PBMC cultures, supernatants were collected on days 3 and 6 and tested for TNF-alpha and RANKL. The data obtained were compared between patients and controls by one-way ANOVA and correlated by Pearson's coefficient. We found a significant increase in osteoclast formation and bone reabsorbing activity in patients with respect to controls; in addition, the production of TNF-alpha and RANKL is significantly higher in patients. Furthermore, osteoclast number is inversely correlated with bone mineral density and directly with RANKL in culture supernatants. Our data demonstrated an increased spontaneous osteoclastogenesis in women affected by postmenopausal osteoporosis: this increase may be explained by the higher production of TNF-alpha and RANKL by PBMC cultures of osteoporotic patients.

Bone Density↗

PubMed2003

Infectious and inflammatory stimuli decrease endothelial nitric oxide synthase activity in vitro.

BACKGROUND: Perturbation of iron metabolism, especially the increase of serum ferritin levels, is often associated with both inflammation and hypertension. Changes in iron availability can affect an important regulator of vascular tone, the endothelial nitric oxide synthase (eNOS), activated by a heme-dependent dimerization. OBJECTIVE: To study the regulation of the anti-hypertensive eNOS in human endothelial cells, in correlation with iron metabolism alterations and stimuli triggering them in vivo, such as inflammation or infection. DESIGN: Cells were treated with stimuli mimicking infection or inflammation [lipopolysaccharide (LPS) and/or tumor necrosis factor alpha (TNFalpha)]. and iron shortage (succinylacetone and desferrioxamine). The effect on eNOS expression and activation was evaluated, as well as ferritin content. METHODS: eNOS protein expression was evaluated by separating the monomeric from the active dimeric form by low-temperature sodium dodecyl sulphate poly-acrylamide gel electrophoresis (SDS-PAGE), and mRNA was analyzed by semi-quantitative reverse transcriptase (RT)-polymerase chain reaction (PCR). As for LPS and TNFalpha, eNOS monomer decreased already after a 72-h treatment and further at 144 h, whereas the down-regulation of the dimer was slower, peaking at 144 h. Succinylacetone and desferrioxamine were effective only at 144 h. The mRNA levels were increasingly reduced after incubation, more markedly by LPS and TNFalpha together, whereas succinylacetone and desferrioxamine had no effect on transcription. We found that endothelial cells are not the source of increased ferritin production. CONCLUSIONS: The results of this study suggest a down-regulating effect of infectious and inflammatory stimuli on eNOS expression, both at the mRNA level and protein expression or stability and dimerization, enhanced by heme and iron shortage, and indicate eNOS as a possible link between infection and hypertension.

Bacterial Infections↗

PubMed2002

Synergistic effect of retinoic acid and dehydroepiandrosterone on differentiation of human neuroblastoma cells.

Retinoic acid (RA) affects many cell types by either promoting their survival or inducing their differentiation. Dehydroepiandrosterone (DHEA), a precursor for both androgenic and estrogenic steroids and abundantly produced by brain, is known as an inhibitor of cell proliferation. Differentiation of a human neuroblastoma cell line (SK-N-BE) was evaluated measuring growth rate, motility, neurite extension and GAP-43 expression. We report that DHEA enhances the differentiating effect of RA on neuroblastoma cells via a signalling that is not RA receptor-mediated. Instead, we show a differential expression of matrix metalloproteinases: RA enhances the activity of MMP-2, whereas MMP-9 expression is up-regulated by DHEA. The concerted modulation of these proteinases may support the neurite outgrowth observed after co-treatment with the two drugs.

Cell Differentiation↗