Biomedical subjects

M A Mariggiò

Publications and source records attributed to M A Mariggiò.

At least 19 recordsLinked to original sources

PubMed2006

Organ-specific manganese toxicity: a comparative in vitro study on five cellular models exposed to MnCl(2).

Manganese (Mn) is both an essential nutrient and a toxicant, with specific effects on liver and kidney (acute exposure) and on central nervous system (CNS) (chronic exposure). Mn neurotoxicity includes neurobehavioral disorders and extra-pyramidal motor dysfunctions (manganism), possibly due to focal injuries to the basal ganglia. Even if widely investigated, the molecular mechanisms responsible for Mn toxicity remain to be clarified. Aim of this study was to identify suitable in vitro models to investigate these molecular pathways. To this purpose we compared the effect of manganese chloride on four cell lines, representative of the main target organs of Mn toxicity in vivo. HepG2 and MDCK cell lines were selected for liver and kidney, respectively; glial GL15 and neuronal SHSY5Y cells were used as models of CNS components. To complete the "motor system" model, skeletal muscle C2C12 cells were also included. Our results demonstrate that hepatic, renal, glial and neuronal cell types differently react to Mn, mirroring the specific in vivo response of the tissue they represent. This confirms their value as suitable in vitro models to study Mn-related toxic events. Interestingly, also muscle C2C12 cells showed a noticeable sensitivity to Mn, preferential targets being differentiated myotubes.

Animals↗

PubMed2004

Cooperation in signal transduction of extracellular guanosine 5' triphosphate and nerve growth factor in neuronal differentiation of PC12 cells.

Guanosine 5' triphosphate (GTP), acting synergistically with the nerve growth factor (NGF), enhances the proportion of neurite-bearing cells in cultures of PC12 rat pheochromocytoma cells. We studied the transduction mechanisms activated by GTP in PC12 cells and found that addition of GTP (100 microM) increased intracellular calcium concentration ([Ca(2+)](i)) in cells that were between 60 and 70% confluent. Addition of GTP also enhanced activation of NGF-induced extracellular regulated kinases (ERKs) and induced Ca(2+) mobilization. This mobilization, due to the activation of voltage-sensitive and ryanodine-sensitive calcium channels, as well as pertussis toxin-sensitive purinoceptors, modulates Ca(2+)-activated K(+) channels not involved in activation of ERKs. The results presented here indicate that GTP-triggered [Ca(2+)](i) increase may be a key event in GTP signal transduction, which can modulate activity of ERKs. The physiological importance of the GTP effect lies in its capacity to interact with the NGF-activated pathway to enhance neurite outgrowth from PC12 cells.

Animals↗

PubMed2004

P-cadherin expression predicts clinical outcome in oral squamous cell carcinomas.

P-cadherin, a transmembrane molecule similar to E-cadherin involved in the cell-cell adhesion, and catenins form complexes between its cytoplasmic domain and the cytoskeleton. Five cell lines, 108 specimens of oral squamous cell carcinomas (OSCC), 9 metastasis and 10 of normal oral mucosa were examined to evaluate P-cadherin expression and cellular localization by immunohistochemistry and western-blotting. In normal oral mucosa there was a membranous expression only in basal and parabasal layers. 91 cases (84%) showed membranous/cytoplasmic positivity, whereas 17 cases (16%) were negative. In particular, while well-differentiated carcinomas showed P-cadherin upregulation, the protein was homogeneously hypo- or unexpressed in low-differentiated carcinomas. There was a statistically significant correlation between P-cadherin expression and tumour grading: G3 tumours had a lower score than G1-G2 tumours (P<0.05). When analysed for prognostic significance, patients with no P-cadherin expression (score 0) had poorer overall and diseases-free survival rates than the P-cadherin-expressing group (score 1) (P=0.0463 and P=0.0471, respectively). Western blotting analysis of cell lines and tissue samples confirmed immunohistochemical findings. When cell staining pattern of positive cases was examined, 52 cases showed a prevalent membranous pattern, while 39 had a prevalent cytoplasmic pattern. Cases with prevalent cytoplasmic staining showed high rates of lymph node metastases (P>0.05), and regional relapse (P <0.05) and poorer survival rates than the group with prevalent membranous expression (P<0.0001). An absent P-cadherin expression could constitute a hallmark of aggressive biological behaviour in oral squamous cell carcinoma.

Adult↗

PubMed2004

HSP 27 as possible prognostic factor in patients with oral squamous cell carcinoma.

UNLABELLED: HSP27 belongs to the Heat shock protein (HSP) family, which plays essential functions in cells under physiological conditions and prevents stress-induced cellular damage. The aim of this study was to investigate the biological role of HSP27 in oral tumorigenesis. MATERIALS AND METHODS: Seventy-nine cases of oral squamous cell carcinoma and 10 cases of normal mucosa were analysed for HSP27 expression by immunohistochemistry. Moreover, the western blot analysis was performed on two cases of normal mucosa and five cases of OSCC. RESULTS: Normal oral mucosa showed a suprabasal expression of HSP27. Twenty-four cases of SCC (30.7%) showed a diffuse staining for HSP27, and 48 cases (60.3%) showed instead a decrease in staining, which was diffuse, homogeneous, or with alternation of positive and negative areas in a single tumor ("mosaic" pattern). Only 7 cases of OSCC (7.5%) were completely negative for HSP27. Frequency of lymph node metastases was higher in HSP27-negative tumours (3/7, 42.8%) than in HSP-reduced (16/48, 33.3%) or positive ones (5/26, 19.2%). Regard staging, stages I and II had a higher score than stages III and IV (stage I > stage II > stage III > stage IV). There was also a statistically significant correlation between HSP27 expression and grade: HSP27 expression was reduced in poorly differentiated tumours (P < 0.05). When analysed for prognostic significance, patients with negative/reduced HSP27 expression had poorer survival rates than the group with positive HSP27 expression (P < 0.05). The statistical analysis of these findings showed no significant correlation between HSP27 expression, sex, and tumour size. CONCLUSION: Cases with reduced expression were more aggressive and poorly differentiated. These data suggest that HSP27 expression may be useful in order to identify cases of oral squamous cell carcinoma with more aggressive and invasive phenotype providing novel diagnostic and prognostic information on individual patient survival with oral cancers.

Adult↗

PubMed2003

Survivin expression in oral squamous cell carcinoma.

A series of 110 cases of oral squamous cell carcinoma (SCC) together with six lymph node and one distant metastatic lesions was analysed for expression of survivin, a recent apoptosis inhibitor, by immunohistochemistry and Western blotting. In total, 91 cases (82.7%) of carcinoma and all metastasis (seven cases, 100%) were positive for survivin expression, with weighted survivin scores ranging from 1 to 4. In contrast, normal oral epithelium did not express survivin. There was no significant correlation between survivin expression and age, sex, tumour size, the presence of lymph node and distant metastases. Survivin expression was increased in poorly differentiated tumours, even if differences were not statistically significant. In contrast, when analysed for prognostic significance, patients with low survivin expression had statistically significant better survival rates than the group with high survivin expression (P<0.05). These data suggest that survivin expression may identify cases of oral SCC with more aggressive and invasive phenotype.

Adult↗

PubMed2002

p120(cat) Delocalization in cell lines of oral cancer.

UNLABELLED: p120(cat) is a novel component of the catenin family, a cytoplasmic molecule closely associated with the cell-cell adhesion molecule E (epithelial)-cadherin, by forming complexes between the cytoplasmic domain of E-cadherin and the cytoskeleton. Recent studies suppose a role for this molecule in human cancers and to date none report its expression in oral squamous cell carcinomas (SCCs). The goal of this study was to evaluate the role of this protein in the oral carcinogenetic process. A linked streptavidin-biotin-alkaline phosphatase technique was used to examine the immunoreactivity and cellular localisation of p120(cat) in five oral epithelial cell lines (NCTC 2544, normal and immortalized keratinocytes; KB, a poorly differentiated SCC cell line; OSC 20, a well differentiated oral SCC cell line; CAL 33 and CAL 27, moderately differentiated oral SCC cell lines) and 10 normal oral epithelium biopsies. RESULTS: As already reported for E-cadherin, beta- and gamma-catenin, p120 expression showed a homogeneous membranous localization in normal oral specimens. The intensity of staining for p120 progressively increased from basal and parabasal layers toward the intermediate spinous layer. No staining for p120 was observed in the upper layer. NCTC showed a membranous positivity. OSC 20, CAL 33 and CAL 27 showed a membranous positivity, even if polarized to cell-cell adhesion sites, in 40-50% of cells. OSC 20, CAL 33 and CAL 27 cells showed also a cytoplasmic delocalization. All positive KB cells showed a prevalent cytoplasmic staining and 10% of these cells showed a nuclear delocalization. In cancer cells, p120 showed an inverse relationship with the degree of differentiation for a progressive displacement of the signal toward the cytoplasm or nucleus in dedifferentiated cells. In conclusions, this nuclear delocalization for p120 could suppose its potential involvement in signalling and cancer transformation.

Carcinoma, Squamous Cell↗

PubMed2001

Nicotine effects on polymorphonuclear cell apoptosis and lipopolysaccharide-induced monocyte functions. A possible role in periodontal disease?

Apoptosis provides a mechanism for clearance of unwanted cells in a variety of situations in which programmed or physiological cell death occurs; but the premature death of defensive cells could promote infection, inflammation and concomitant disease. We detected high values of apoptosis in polymorphonuclear cells (PMN) elicited from crevicular sulci of smokers affected by adult periodontitis. To learn more about the effects of nicotine on the periodontal environment, we studied its ability to modulate the apoptosis of two phagocytic lines, PMN and mononuclear cells, which are continuously recruited from gingival vessels to prevent or control plaque extension. Brief exposure of PMN to nicotine concentrations ranging from 0.01 to 0.3% shortened, in a dose-dependent relationship, the lag culture time required to observe at fluorescent microscopy the morphological traces of apoptosis. These observations were confirmed by specific tools of apoptosis: DNA fragmentation on gel electrophoresis and expression of the apoptosis-signaling receptor Fas/Apo-1. The apoptotic effect excited by nicotine on these first line defensive cells may be an important feature of the pathogenesis of periodontal disease. As for mononuclear leukocytes, nicotine was unable to induce apoptotic modifications on cells observed up to 72 h culture time, but the drug inhibited IL-1beta release and procoagulant activity (PCA) expression. The conflicting role played by these lipopolysaccharide (LPS)-induced monocyte functions in the inflammatory process is a further intrigue in the mechanism by which nicotine compromises the oral health.

Apoptosis↗

PubMed2000

New structural analogues of Tubulozole induce apoptosis, [Ca2+]i modifications and cytoskeletal disorganization in glial (GL15) and neuronal-like (PC12) cell lines.

The synthesis and the biological activity of (+/-)-cis- and (+/-)-trans-[4-[[2-(1,1'-biphenyl-4-yl)-2-(1H-imidazol-1-ylmethyl)-1, 3-dioxolan-4-yl]methylthio]phenyl]carbamic acid ethyl esters (2a and 2b) are discussed. They were designed as structural analogues of Tubulozole, a synthetic tubulin polymerisation inhibitor with antimitotic properties. Biological tests were carried out on PC12, a neuronal-like cell line derived from rat pheochromocytoma, and on GL15, a cell line derived from human glioblastoma. The exposure (from 5 to 20 h) of GL15 and PC12 cells to different concentrations (0.1-1000 microM; IC50 approximately 1 microM) of 2a or 2b resulted in a drastic decrease in the number of viable cells without an apparent effect on the cell distribution in the various phases of the cell cycle. Compound 2a or 2b (10 microM) induced cell death by activating apoptosis. This was correlated with the activation of an oscillating Ca(2+)-dependent mechanism which increased the intracellular calcium concentration ([Ca2+]i) via Ca(2+)-release from internal stores. Moreover, 2a (10 microM) also induced severe damage of cytoskeletal F-actin filaments after a 5 h incubation in GL15 cells. This was also observed but to a smaller extent, for 2b. Under the same experimental conditions, PC12 cells showed similar actin deregulation.

Adrenal Gland Neoplasms↗

PubMed2000

Extracellular guanosine 5' triphosphate enhances nerve growth factor-induced neurite outgrowth via increases in intracellular calcium.

Extracellular guanosine 5' triphosphate (GTP) enhances nerve growth factor-dependent neurite outgrowth from rat pheochromocytoma (PC12) cells; cultures of PC12 cells exposed to GTP and nerve growth factor together contain significantly more neurite-bearing cells than do those exposed to either nerve growth factor or GTP alone [Gysbers J. W. and Rathbone M. P. (1996) Int. J. devl Neurosci. 14, 19-34]. PC12 cells contain specific cell surface binding sites for extracellular GTP, which do not bind ATP or uridine 5' triphosphate. Exposure of PC12 cells to extracellular GTP (300microM) produced a robust and sustained increase in intracellular Ca(2+) ([Ca(2+)](i)), different from the transient response to the addition of ATP. The GTP-induced [Ca(2+)](i) increase was blocked by the L-type calcium channel inhibitor, nifedipine. The L-type Ca(2+) channel inhibitors, nifedipine or verapamil, also inhibited the enhancement of neurite outgrowth by GTP, but did not affect neurite outgrowth stimulated by nerve growth factor alone. Pre-treatment of PC12 cells with ryanodine (0.5-50microM) depleted calcium from internal stores and prevented the further release of calcium by GTP. Similarly, pre-treatment of PC12 cells with thapsigargin (an inhibitor of internal store Ca(2+)/ATPase) or dantrolene (which blocks Ca(2+) release from some of these stores) also reduced the enhancement of neurite outgrowth by GTP. Therefore, Ca(2+)-induced Ca(2+) release from specific stores, present in PC12 cells, is involved in the enhancement of nerve growth factor-induced neurite outgrowth by GTP, possibly acting at specific binding sites on the cell surface. GTP is proving to be an important extracellular trophic modulator in the central nervous system. These studies show that the neuritogenic actions of GTP involve moderate but sustained increases in intracellular Ca(2+) which are likely due to activation of L-type Ca(2+) channels and Ca(2+)-induced Ca(2+) release from intracellular stores. These effects of extracellular GTP are likely mediated at the cell surface and may be related to specific GTP binding sites which are distinct from G-proteins and from hitherto described purine nucleotide (P2) receptors. These data indicate a mechanism whereby the neuritogenic effects of GTP are mediated and emphasize the importance of considering GTP as a neurotrophic mediator.

Animals↗

PubMed2000

Calcium and fos involvement in brain-derived Ca(2+)-binding protein (S100)-dependent apoptosis in rat phaeochromocytoma cells.

Brain-derived calcium-binding protein S100 induces apoptosis in a significant fraction of rat phaeochromocytoma (PC12) cells. We used single cell techniques (patch clamp, videomicroscopy and immunocytochemistry) to clarify some of the specific aspects of S100-induced apoptosis, the modality(ies) of early intracellular Ca2+ concentration increase and the expression of some classes of genes (c-fos, c-jun, bax, bcl-x, p-15, p-21) known to be implicated in apoptosis of different cells. The results show that S100: (1) causes an increase of [Ca2+]i due to an increased conductance of L-type Ca2+ channels; (2) induces a sustained increase of the Fos levels which is evident since the first time point tested (3 h) and remains elevated until to the last time point (72 h). All these data suggest that S100-derived apoptosis in PC12 cells may be the consequence of a system involving an increase in L-type Ca2+ channel conductance with consequent [Ca2+]i increase which up-regulates, directly or indirectly, the expression of Fos.

Animals↗

PubMed2000

Reduction of cisplatin nephrotoxicity by procainamide: does the formation of a cisplatin-procainamide complex play a role?

Procainamide protects mice bearing P388 leukemic cells against the toxicity of cisplatin without diminishing antitumor activity. The mechanism of action of procainamide protection was investigated both in vitro and in vivo. HPLC studies showed that procainamide forms a complex with cisplatin in vitro that has a UV spectrum similar to that of DPR, a triamine platinum complex that contains procaine as ligand. We report here the effect of the reaction product of cisplatin and procainamide on both cisplatin-induced DNA interstrand cross-links (ISCLs) and on the total DNA platination of isolated DNA. Total DNA platination in vitro of isolated DNA was increased by 113% (P <.01) and 17% (P <.05) after incubation times of 1.75 and 6 h, respectively, compared with products from the reaction of cisplatin with water. Furthermore, the reaction product of cisplatin and procainamide was bound to DNA to a significantly greater extent than was cisplatin itself. ISCLs were decreased by 41% when this drug combination was incubated with DNA for 1.75 h, but no changes were observed after incubation for 6 h. We also examined the influence of the time interval between administration of cisplatin and procainamide on normal kidney injury, the renal distribution and urinary excretion of platinum, and the formation of cisplatin-DNA adducts in renal tissue of Sprague-Dawley rats after i.p. administration of 7.5 mg/kg cisplatin either with or without procainamide. The plasma concentrations of urea and creatinine and kidney histology demonstrated that procainamide provided effective protection in vivo in the rat when administered either simultaneously or at 0.5 and 1 h before or after cisplatin. The protection was accompanied by both higher renal levels of platinum and cisplatin-DNA adducts and by an increase in the formation of ISCLs. Moreover, a dose-dependent reduction of urinary excretion and concentration of platinum was also observed. We propose that procainamide, after accumulation in the kidney, may coordinate with cisplatin to form a less toxic DPR-like complex that renders rats less susceptible to cisplatin-induced toxicity.

Animals↗

PubMed1999

Rapid desensitization of PC12 cells stimulated with high concentrations of extracellular S100.

Undifferentiated PC12 cells undergo apoptosis, via a calcium-induced calcium release mechanism, when the calcium-binding protein purified from bovine brain (native S100) is present in micromolar concentration in the medium. This process begins when S100 binds to specific membrane binding sites and involves up to 50% of the cell population. In the experiments reported here, we demonstrate that, by utilizing [3H]S100, the S100 protein can be displaced from its binding sites only during the first 10 min of incubation. This fact is due to an internalization mechanism, having a time-course with a plateau after 10-20 min of incubation. The native form of S100 is a mixture of two different S100 isoforms: S100A1 (20%) and S100B (80%). Using confocal microscopy and monoclonal antibodies, we demonstrated that only one of these isoforms, S100A1, was autoexpressed in more than 50% of the PC12 cells analysed. After cell incubation with 2 microM native S100, S100B also appears in PC12 cells, with a maximum presence after 10 min of incubation. This fact seems to indicate that this isoform, at least, is effectively translocated when stimulated with external native S100. From the data reported, it is possible to hypothesize that, in PC12 cells, a possible homeostatic mechanism is present that can counteract the effect of a continuously applied lethal stimulus (stimuli) on cell viability.

Animals↗

PubMed1999

Cisplatin combined with tiopronin or sodium thiosulfate: cytotoxicity in vitro and antitumor activity in vivo.

We have previously reported that the thiol compound tiopronin protects rat kidneys in vitro against the toxic activity of cisplatin. The influence of tiopronin and sodium thiosulfate (STS) on the cytotoxicity of cisplatin has been investigated on P388 leukemic cells in vitro after 3 days. The combination has also been investigated in vivo in BDF1 mice bearing a P388 s.c. tumor. In contrast to STS, tiopronin did not significantly reduce the cytotoxic activity of cisplatin in vitro and nor did it affect the uptake of platinum (cisplatin-derived), binding to DNA or the percentage of interstrand cross-links (%ISCL) formation. The co-administration of cisplatin (4 mg/kg) and tiopronin (150 and 300 mg/kg) to BDF1 female mice bearing a s.c. P388 tumor produced a significant reduction in tumor growth similar to that of a single 6 mg/kg dose of cisplatin. Interestingly, pre-incubation in vitro of either tiopronin or STS for 2 h with the species formed from cisplatin by hydrolysis demonstrated their ability in inhibiting the cytotoxicity of these reactive platinum products. These results indicate that tiopronin does not reduce the cytotoxicity of cisplatin in vitro, as STS does. This may be, at least partly, because of a different effect of the two thiol compounds on the cellular uptake and binding of platinum to DNA. Notably, tiopronin substantially reduced tumor growth in mice treated with a non-toxic dose of cisplatin (p < or = 0.0277), suggesting some positive influence of this thiol compound on the antitumor properties of cisplatin. The ability of tiopronin to protect in vitro against the cytotoxicity of the aquation products of cisplatin may be related to its nephroprotective effect.

Animals↗

PubMed1998

Sulfide enhancement of PMN apoptosis.

Hydrogen sulfide is a toxic metabolite released by several bacterial agents under anaerobic conditions. In the present paper, we investigated the effects of sulfide on polymorphonuclear cell (PMN) apoptosis, a mechanism suggested for limiting the toxic potential of neutrophils in inflammatory sites. We showed that 1 mM sulfide (concentration not conditioning PMN viability) is able to enhance the apoptotic fate of human granulocytes by increasing: i) the number of cells containing pyknotic nuclei, ii) the internucleosomal cleavage, and, iii) the intensity of tubulin immunofluorescence staining. The sulfide effect is partially prevented by ionomycin and this finding is consistent with the hypothesis of the inhibiting role played by high levels of cytosolic calcium in PMN apoptosis modulating.

Apoptosis↗

PubMed1997

Nerve growth factor inhibits apoptosis induced by S-100 binding in neuronal PC12 cells.

When grown for seven days in a medium containing nerve growth factor (100 ng/ml), 10% horse serum and 5% fetal bovine serum PC12 cells stopped dividing, extended neurites and assumed a neuronal phenotype. Withdrawal of nerve growth factor from these cells resulted in loss of neurites and apoptotic changes in many cells. The apoptotic changes were exacerbated if the cells were also exposed to 1-2 microM S-100, a calcium binding protein purified from bovine brain. After exposure to S-100, the PC12 cells underwent characteristic apoptotic changes. Within 2 in neurites retracted, the cell body shrunk and submembranous accumulation of condensed cytoplasmic material was observed. DNA ladders were present after 24-48 h and 60% of the cells became hypodiploid after 72 h. S-100 induced apoptosis by binding to specific sites (Kd = 189 nM) on PC12 cells and this caused a rise in [Ca2+]i due to a transmembrane capacitative flux followed by the depletion of internal stores. This increase was reversed if 5 microM nifedipine, a specific L-type Ca2+ channel inhibitor, was added to the medium after S-100 and completely abolished if the cells were pretreated with 5 microM thapsigargin, an inhibitor of endoplasmic reticulum Ca(2+)-ATPase. The presence of nerve growth factor in the culture medium completely blocked the apoptotic changes induced by S-100, probably due to interaction of nerve growth factor and S-100 at the same binding sites. These data indicate that nerve growth factor not only prevents apoptosis during cell development, but also apoptosis induced by endogenous substances such as S-100.

Animals↗

PubMed1997

Sulfide influence on polymorphonuclear functions: a possible role for Ca2+ involvement.

Polymorphonuclear cells (PMN) of gingival sulcus play an important role in host defense against periodontal tissue-invading bacteria, but their phagocytic activity is conditioned by several virulence factors released by oral pathogens. In this report we have studied the influence of sulfide, a toxic bacterial metabolite, on the main PMN functions: chemotaxis, degranulation and oxidative burst. PMN exposed to sodium sulfide (up to 2 mM) used as a source of H2S showed a depression of the calcium-dependent cytoskeleton activities such as chemotaxis and azurophilic granule release induced by FMLP. No effect was observed on the calcium-independent specific granule release obtained by PMA. These data were in agreement with the sulfide inhibition of cytosolic free Ca2+ concentration [Ca2+]i increase normally induced by ionomycin. On the other hand, hydrogen sulfide was able to prime PMN for a stronger oxidative response both to calcium-dependent or calcium-independent stimulation. This finding may account for a more efficient oxidative killing under reoxygenation of the anaerobic infectious areas.

Calcium↗

PubMed1995

Platinum(II) complexes containing iminoethers: a trans platinum antitumour agent.

The biological activity of cis and trans complexes of formula [PtCl2(HN = C(OMe)Me)2] has been investigated. The iminoether ligands can have either E or Z configuration about the C = N double bond, therefore EE, EZ and ZZ isomers are obtainable. Substitution of iminoether with EE configuration for amine leads to unexpectedly high antitumor activity for the complex with trans geometry which turns out to be more active than the cis congener in the P388 leukaemia system. The same trans-EE complex shows an activity comparable to that of cisplatin in reducing the primary tumour mass and lung metastases in mice bearing Lewis lung carcinoma, thus representing a trans platinum complex active on both limphoproliferative and solid metastasizing murine tumours. Also the cytotoxicity, the inhibition of DNA synthesis and the mutagenic activity, which are greater for the cis- with respect to the trans-isomer in the amine complexes, are instead greater for the trans- than for the cis- isomer in the case of iminoether compounds. Binding to calf thymus DNA is slower for iminoether complexes than it is for amine complexes, however after 24 h reaction time the level of binding is similar for both types of complexes. Trans-EE, like trans-DDP, does not give the DNA conformational alterations (terbium fluorescence) typical of antitumour-active cis- platinum compounds, but, under strictly analogous experimental conditions, shows a greatly reduced DNA interstrand cross-linking ability (heat denaturation/renaturation assay) with respect to either trans-DDP or cis-EE and cis-DDP. The data in hand point to a new trans platinum antitumour complex with a mechanism of action different from that of cis-DDP and classical analogues.

Animals↗

PubMed1995

The S-100: a protein family in search of a function.

The S-100 is a group of low molecular weight (10-12 kD) calcium-binding proteins highly conserved among vertebrates. It is present in different tissues as dimers of homologous or different subunits (alpha, beta). In the nervous system, the S-100 exists as a mixture composed of beta beta and alpha beta dimers with the monomer beta represented more often. Its intracellular localisation is mainly restricted to the glial cytoplasmic compartment with a small fraction bound to membranes. In this compartment the S-100 acts as a potent inhibitor of phosphorylation on several substrates including the synaptosomal C-Kinase and Tau, a microtubule-associated protein. The S-100 in particular conditions, after binding with specific membrane sites (Kd = 0.2 microM; Bmax = 4.5 nM), is able to modify the activity of adenylate cyclase, probably via G-proteins. In addition, the Ca2+ homeostasis is also modulated by S-100 via an increase of specific membrane conductance and/or Ca2+ release from intracellular stores. "In vitro" and "in vivo" experiments showed that lower (nM) concentrations of extracellular S-100 beta act on glial and neuronal cells as a growth-differentiating factor. On the other hand, higher concentrations of the protein induce apoptosis of some cells such as the sympathetic-like PC12 line. Finally, data obtained from physiological (development, ageing) or pathological (dementia associated with Down's syndrome, Alzheimer's disease) conditions showed that a relationship could be established between the S-100 levels and some aspects of the statii.

Animals↗