Biomedical subjects

Maria Marino

Publications and source records attributed to Maria Marino.

28 records · Page 2Linked to original sources

PubMed2003

Biphasic estradiol-induced AKT phosphorylation is modulated by PTEN via MAP kinase in HepG2 cells.

We reported previously in HepG2 cells that estradiol induces cell cycle progression throughout the G1-S transition by the parallel stimulation of both PKC-alpha and ERK signaling molecules. The analysis of the cyclin D1 gene expression showed that only the MAP kinase pathway was involved. Here, the presence of rapid/nongenomic, estradiol-regulated, PI3K/AKT signal transduction pathway, its modulation by the levels of the tumor suppressor PTEN, its cross-talk with the ERK pathway, and its involvement in DNA synthesis and cyclin D1 gene promoter activity have all been studied in HepG2 cells. 17beta-Estradiol induced the rapid and biphasic phosphorylation of AKT. These phosphorylations were independent of each other, being the first wave of activation independent of the estrogen receptor (ER), whereas the second was dependent on ER. Both activations were dependent on PI3K activity; furthermore, the ERK pathway modulated AKT phosphorylation by acting on the PTEN levels. The results showed that the PI3K pathway, as well as ER, were strongly involved in both G1-S progression and cyclin D1 promoter activity by acting on its proximal region (-254 base pairs). These data indicate that in HepG2 cells, different rapid/nongenomic estradiol-induced signal transduction pathways modulate the multiple steps of G1-S phase transition.

Cyclin D1↗

PubMed2003

The age-related accumulation of dolichol in rat liver may correlate with expectation of life.

In order to test the hypothesis that the ageing-related alteration in membrane lipids might reflect the biological age of rodents, the levels of liver dolichol were assayed by the HPLC procedure in male ad-libitum fed (AL) Sprague-Dawley rats aged 2, 6, 12 and 24 months, and in 24-month-old rats on anti-aging food-restrictions (FR) differing in duration and in their effects on longevity. Results showed that the effects on liver dolichol of FR initiated at 2, 6 and 12 months of age, or initiated at 2 and interrupted at 18 months of age were significantly different, and reflected the differences in the effects of FR on expectation of life (the longer the expected residual lifespan the lower the content in liver dolichol). The conclusion is that assay of the quantity of dolichol in the liver tissue may be used as a marker of the biological age of the animal and therefore as an important biomarker of ageing.

Aging↗

PubMed2003

Does palmitoylation target estrogen receptors to plasma membrane caveolae?

The human nuclear estrogen receptors (i.e., ERalpha and ERbeta), as other transcriptional factors, regulate cellular processes inducing genomic events. In addition, the binding of 17beta-estradiol to ERs induces different membrane initiating non-genomic signaling. The non-genomic effects of ER are independent of transcriptional activity of the receptor and have been attributed to membrane ERs belonging to a signaling complex localized in caveolae. Here, we postulate that S-acylation of cysteine residue(s) present in the ligand binding domain of ERalpha and ERbeta may play a critical role in the membrane caveolar localization of the receptor and in the formation of the 'steroid signalosome'.

Acylation↗

PubMed2003

Synergism between genomic and non genomic estrogen action mechanisms.

The 17beta-estradiol (E2) action mechanism for inducing target gene expression can be attributed to both the direct binding of its receptor (ER) to specific sequences, the estrogen response element (ERE), and to the interaction between ER and other DNA-binding transcription factors. At the present meagre information is available for the role played by the rapid hormone action mechanism(s) (i.e., activation of ERK, PI(3)K, PKC-alpha) in modulating E2-induced gene promoter activity. Here the involvement of the rapid non genomic mechanism in triggering the transcriptional activity of two E2-regulated target genes in human hepatoma HepG2 cells has been studied, taking into consideration the cyclin D1 (ERE-devoid) and the complement protein 3 (ERE-containing) promoter-luciferase report constructs. The results indicate that the activation of the ERK pathway is essential for the E2-induced activity of both promoters, whereas the other rapid E2-induced membrane-starting signal transduction pathways (i.e., PI(3)K and PKC-alpha) were differently required. These results permit the amplification of the E2 action mechanism by the addition of synergy between the non genomic and genomic molecular actions of the E2-induced gene transcription.

Enzyme Activation↗

PubMed2002

Age-related changes of cholesterol and dolichol biosynthesis in rat liver.

Ageing has been defined as a gradually decreased ability to maintain homeostatic potential and increased risk to die, associated with a tissue accumulation of altered proteins and lipids. Among other, increased concentration of an isoprenoid compound, dolichol (Dol), in mammalian tissues during ageing has been reported and it has been considered as a new biomarker of ageing. However, the mechanism and the role of this accumulation is still unknown. Aim of this work was to study the mechanism of age-dependent Dol accumulation in the liver analysing the activity of the hepatic rate-limiting enzyme of isoprenoid biosynthesis, the 3-hydroxy 3-methylglutaryl CoA reductase (HMGCoA reductase), the Dol synthesis by mevalonate (MVA), the Dol level in the plasma, and the cholesterol (Chol) synthesis and content of ageing rat fed ad libitum (AL) or subjected to the effect of food restriction. Since the caloric restrictions are the most reproducible way to slow ageing and to extend life span, animals on these nutritional regimens were used to study ageing related mechanisms. The data show that during ageing the hepatic Dol accumulation is associated with an increase of HMGCoA reductase activity, which is affected by diet restriction, and with an increase of MVA incorporation in Dol and Chol, which is not. In addition, the liver of aged rats maintains the capability to regulate its Chol content and to modify Chol delivery into the blood.

Aging↗

PubMed2002

Role of tyrosine kinase signaling in estrogen-induced LDL receptor gene expression in HepG2 cells.

The expression of the low-density lipoprotein receptor (LDL-r) gene is stimulated by estrogen in vivo, although its promoter does not contain a classical estrogen-responsive element, suggesting an alternative mechanism of estrogen-regulated expression of this gene. The aim of this work was to assess whether estrogen-stimulated transcription of the LDL-r gene depends on tyrosine kinase (TK) and protein kinase C (PKC) activation, both signaling pathways being activated by estrogen in vivo and in hepatoma cells. Therefore, in HepG2 cells cotransfected with estrogen receptor-alpha, estrogen-stimulated transcription of LDL-r-promoter reporter plasmid was analyzed in the absence and presence of TK and PKC inhibitors. The expression of LDL-r was also compared with the transcription of the complement gene, which contains a classical estrogen-responsive element sequence. Our results demonstrate that the induction of LDL-r expression by estrogen requires longer stimulation than that necessary for complement induction. Moreover, basal transcription of the LDL-r gene depends on PKC activity, while estrogen-stimulated activation of the LDL-r-promoter requires TK activity, pointing to a role of these non-classical estrogen-stimulated pathways in the transcriptional regulation of the LDL-r.

Enzyme Activation↗

PubMed2002

Agmatine oxidation by copper amine oxidase.

The product of agmatine oxidation catalyzed by Pisum sativum L. copper amine oxidase has been identified by means of one- and two-dimensional (1)H-NMR spectroscopy to be N-amidino-2-hydroxypyrrolidine. This compound inhibits competitively rat nitric oxide synthase type I and type II (NOS-I and NOS-II, respectively) and bovine trypsin (trypsin) activity, values of Ki being (1.1 +/- 0.1) x 10(-5) m (at pH 7.5 and 37.0 degrees C), (2.1 +/- 0.1) x 10(-5) m (at pH 7.5 and 37.0 degrees C), and (8.9 +/- 0.4) x 10(-5) m (at pH 6.8 and 21.0 degrees C), respectively. Remarkably, the affinity of N-amidino-2-hydroxypyrrolidine for NOS-I, NOS-II and trypsin is significantly higher than that observed for agmatine and clonidine binding. Furthermore, N-amidino-2-hydroxypyrrolidine and agmatine are more efficient than clonidine in displacing [(3)H]clonidine (= 1.0 x 10(-8) m) from specific binding sites in heart rat membranes, values of IC50 being (1.3 +/- 0.4) x 10(-9) m and (2.2 +/- 0.4) x 10(-8) m, respectively (at pH 7.4 and 37.0 degrees C).

Agmatine↗

PubMed2002

Clonidine displacement from type 1 imidazoline receptor by p-aminobenzamidine, the prototype of trypsin-like serine protease inhibitors.

p-Aminobenzamidine inhibits competitively the catalytic activity of enzymes that recognize preferentially the L-arginyl side chain and related structures. Notably, p-aminobenzamidine is considered as the prototype of trypsin-like serine protease inhibitors. Furthermore, p-aminobenzamidine inhibits the catalytic activity of nitric oxide synthase type I and type II as well as copper amine oxidase. Taking into account the structural similarity between p-aminobenzamidine, agmatine (the putative endogenous ligand of the membrane type 1 imidazoline receptor (I1-R)), and N-amidino-2-hydroxypyrrolidine (the product of agmatine oxidation by copper amine oxidase), the [3H]clonidine displacement from I1-R in rat heart membranes by p-aminobenzamidine was investigated. p-Aminobenzamidine is as effective as agmatine and N-amidino-2-hydroxypyrrolidine and more effective than the antihypertensive drug clonidine to displace [3H]clonidine from I1-R. Therefore, trypsin-like serine protease inhibitors structurally related to p-aminobenzamidine should be administrated under careful control.

Adrenergic alpha-Agonists↗

PubMed2002

Distinct nongenomic signal transduction pathways controlled by 17beta-estradiol regulate DNA synthesis and cyclin D(1) gene transcription in HepG2 cells.

Estrogens induce cell proliferation in target tissues by stimulating progression through the G1 phase of the cell cycle. Activation of cyclin D(1) gene expression is a critical feature of this hormonal action. The existence of rapid/nongenomic estradiol-regulated protein kinase C (PKC-alpha) and extracellular signal-regulated kinase (ERK) signal transduction pathways, their cross talk, and role played in DNA synthesis and cyclin D(1) gene transcription have been studied herein in human hepatoma HepG2 cells. 17Beta-estradiol was found to rapidly activate PKC-alpha translocation and ERK-2/mitogen-activated protein kinase phosphorylation in this cell line. These actions were independent of each other, preceding the increase of thymidine incorporation into DNA and cyclin D(1) expression, and did not involve DNA binding by estrogen receptor. The results obtained with specific inhibitors indicated that PKC-alpha pathway is necessary to mediate the estradiol-induced G1-S progression of HepG2 cells, but it does not exert any effect(s) on cyclin D(1) gene expression. On the contrary, ERK-2 cascade was strongly involved in both G1-S progression and cyclin D(1) gene transcription. Deletion of its activating protein-1 responsive element motif resulted in attenuation of cyclin D(1) promoter responsiveness to estrogen. These results indicate that estrogen-induced cyclin D(1) transcription can occur in HepG2 cells independently of the transcriptional activity of estrogen receptor, sustaining the pivotal role played by nongenomic pathways of estrogen action in hormone-induced proliferation.

DNA↗

PubMed2002

Novel molecular targets for systemic lupus erythematosus.

For a long time the complement cascade has been believed to be the predominant pathway to inflammation and tissue destruction in autoimmune diseases such as systemic lupus erythematosus. Recently, new evidences show that FcRs may share the primacy with complement cascade, playing an equal or greater role in the disease process. The generation of specific mouse strains deficient in individual components has clarified the different role played by complement and Fc receptors in their interaction with ICs, illustrating that complement is essential for innate immunity against microbial pathogens, requiring natural antibodies to mediate its protective effects, whereas FcyRs have evolved as the principal system for coupling antigen-antibody complexes to effector cells and initiate the inflammatory cascade. Validation of FcRs as new therapeutic targets for autoimmune diseases, in particular for Systemic Lupus Erythematosus (SLE), has been provided by a large number of studies where the biological action of soluble forms of FcyRs or of monoclonal antibodies targeting Fc receptors has been assessed. Additional support to the role of FcRs in SLE has been provided by data obtained with compounds derived from combinatorial chemistry, such as TG19320, a tetrameric tripeptide which interferes with IgG/FcgammaR interaction in vitro and prevents glomerulonephritis in vivo in a SLE susceptible mouse strain. These findings might open the way to new therapeutic approaches for disorders where the role of FcRs has been established, including not only autoimmune diseases like systemic lupus erythematosus, rheumatoid arthritis, multiple myeloma, but also acquired immunodeficiency syndrome (AIDS).

Animals↗