Biomedical subjects

A Porcellini

Publications and source records attributed to A Porcellini.

At least 19 recordsLinked to original sources

PubMed2006

The p85 regulatory subunit of PI3K mediates TSH-cAMP-PKA growth and survival signals.

Phosphatidylinositol 3-kinase (PI3K) is necessary for thyroid stimulating hormone (TSH)-induced cell cycle progression. To determine the molecular mechanism linking PI3K to TSH, we have identified a serine residue in p85alpha(PI3K) phosphorylated by protein kinase A (PKA) in vitro and in vivo. Expression of an alanine mutant (p85A) abolished cyclic AMP/TSH-induced cell cycle progression and was lethal in thyroid cells (FRTL-5). The aspartic version of the p85alpha(PI3K) (p85D) inhibited apoptosis following TSH withdrawal. The p85alpha(PI3K) wild type not the p85A bound PKA regulatory subunit RIIbeta in cells stimulated with cAMP or TSH. The binding of the aspartic version of p85alpha(PI3K) to RIIbeta was independent of cAMP or TSH stimulation. Similarly, binding of PI3K to p21Ras and activation of AKT, a downstream PI3K target, were severely impaired in cells expressing the p85A mutant. Finally, we found that the catalytic activity of PI3K was stimulated by TSH in cells expressing the wild-type p85alpha(PI3K) but not in cells expressing p85A. This latter mutant did not affect the epidermal growth factor-stimulated PI3K activity. We suggest that (1) TSH-cAMP-induced PKA phosphorylates p85alpha(PI3K) at serine 83, (2) phosphorylated p85alpha(PI3K) binds RIIbeta-PKA and targets PKAII to the membrane, and (3) PI3K activity and p21Ras binding to PI3K increase and activate PI3K downstream targets. This pathway is essential for the transmission of TSH-cAMP growth signals.

Animals↗

PubMed2006

p85 regulatory subunit of PI3K mediates cAMP-PKA and estrogens biological effects on growth and survival.

Cyclic adenosine 3'5' monophosphate (cAMP) and protein kinase A (PKA) cooperate with phosphatidylinositol 3' kinase (PI3K) signals in the control of growth and survival. To determine the molecular mechanism(s) involved, we identified and mutagenized a specific serine (residue 83) in p85alpha(PI3K), which is phosphorylated in vivo and in vitro by PKA. Expression of p85alpha(PI3K) mutants (alanine or aspartic substitutions) significantly altered the biological responses of the cells to cAMP. cAMP protection from anoikis was reduced in cells expressing the alanine version p85alpha(PI3K). These cells did not arrest in G1 in the presence of cAMP, whereas cells expressing the aspartic mutant p85D accumulated in G1 even in the absence of cAMP. S phase was still efficiently inhibited by cAMP in cells expressing both mutants. The binding of PI3K to Ras p21 was greatly reduced in cells expressing p85A in the presence or absence of cAMP. Conversely, expression of the aspartic mutant stimulated robustly the binding of PI3K to p21 Ras in the presence of cAMP. Mutation in the Ser 83 inhibited cAMP, but not PDGF stimulation of PI3K. Conversely, the p85D aspartic mutant amplified cAMP stimulation of PI3K activity. Phosphorylation of Ser 83 by cAMP-PKA in p85alpha(PI3K) was also necessary for estrogen signaling as expression of p85A or p85D mutants inhibited or amplified, respectively, the binding of estrogen receptor to p85alpha and AKT phosphorylation induced by estrogens. The data presented indicate that: (1) phosphorylation of Ser 83 in p85alpha(PI3K) is critical for cAMP-PKA induced G1 arrest and survival in mouse 3T3 fibroblasts; (2) this site is necessary for amplification of estrogen signals by cAMP-PKA and related receptors. Finally, these data suggest a general mechanism of PI3K regulation by cAMP, operating in various cell types and under different conditions.

Animals↗

PubMed2006

Allogeneic haematopoietic stem cell transplantation for metastatic renal carcinoma in Europe.

BACKGROUND: An allogeneic antitumour effect has been reported for various cancers. We evaluated the experience of allogeneic haematopoietic stem cell transplantation (HSCT) for renal cell carcinoma (RCC) in 124 patients from 21 European centres. PATIENTS AND METHODS: Reduced intensity conditioning and peripheral blood stem cells from an HLA-identical sibling (n = 106), a mismatched related (n = 5), or an unrelated (n = 13) donor were used. Immunosuppression was cyclosporine alone, or combined with methotrexate or mycophenolate mofetil. Donor lymphocyte infusions (DLI) were given to 42 patients. The median follow-up was 15 (range 3-41) months. RESULTS: All but three patients engrafted. The cumulative incidence of moderate to severe, grades II-IV acute GVHD was 40% and for chronic GVHD it was 33%. Transplant-related mortality was 16% at one year. Complete (n = 4) or partial (n = 24) responses, median 150 (range 42-600) days post-transplant, were associated with time from diagnosis to HSCT, mismatched donor and acute GVHD II-IV. Factors associated with survival included chronic GVHD (hazards ratio, HR 4.12, P < 0.001), DLI (HR 3.39, P < 0.001), <3 metastatic sites (HR 2.61, P = 0.002) and a Karnofsky score >70 (HR 2.33, P = 0.03). Patients (n = 17) with chronic GVHD and given DLI had a 2-year survival of 70%. CONCLUSION: Patients with metastatic RCC, less than three metastatic locations and a Karnofsky score >70% can be considered for HSCT. Posttransplant DLI and limited chronic GVHD improved the patient survival.

Adolescent↗

PubMed2005

Upfront high-dose sequential therapy (HDS) versus VACOP-B with or without HDS in aggressive non-Hodgkin's lymphoma: long-term results by the NHLCSG.

BACKGROUND: There is not univocal concordance for using high-dose sequential therapy (HDS) as first-line treatment for aggressive non-Hodgkin's lymphoma (NHL). We designed this study to evaluate the usefulness of HDS followed by high-dose therapy (HDT) with autologous stem cell transplantation as front-line treatment in different subsets of aggressive NHL. PATIENTS AND METHODS: Among 223 patients aged 15-60 years with aggressive, advanced stage NHL, 106 patients were randomized to VACOP-B (etoposide, doxorubicin, cyclophosphamide, vincristine, prednisone, bleomycin) for 12 weeks (plus HDS/HDT in case of persistent disease) (arm A), and 117 patients to VACOP-B for 8 weeks plus upfront HDS/HDT (arm B). RESULTS: According to the intention-to-treat analysis, the complete response rate was 75% for arm A and 72.6% for arm B. With a median follow-up of 62 months there was no difference in 7-year probability of survival (60% and 57.8%; P = 0.5), disease-free survival (DFS) (62% and 71%; P = 0.2) and progression-free survival (PFS) (44.9% and 40.9%; P = 0.7) between the two arms. Subgroup analyses confirmed that the best results in terms of survival, DFS and PFS were achieved by patients with large B-cell NHL without bone marrow (BM) involvement, independently of the treatment arm. Results were poorer in other categories of patients and poorest in patients with BM involvement. CONCLUSIONS: Aggressive NHL patients do not benefit from upfront HDS/HDT.

Adolescent↗

PubMed2001

Inhibition of MAPK activity, cell proliferation, and anchorage-independent growth by N-Ras antisense in an N-ras-transformed human cell line.

Mammalian ras genes encode a family of plasma membrane-bound proteins that function as intermediates in signal transduction pathways involved in cell growth and differentiation. Ras oncogene is frequently involved in neoplastic transformation of different cellular histotypes. In this study, we tested the ability of antisense oligodeoxyribonucleotides (AS-ODN) that have mixed phosphodiester/phosphorothioate backbone, targeted against human N-Ras, to inhibit N-ras gene expression and to specifically interfere with the Ras-dependent activity of mitogen-activated protein kinase (MAPK) in two human cell lines carrying an endogenous N-ras mutated allele at codon 61. Three AS-ODN that inhibit basal MAPK activity have been identified. Moreover, AS-ODN treatment resulted in potent antiproliferative effects in cell culture and great inhibition of N-ras mRNA levels in one of two cell lines. These studies suggest that antisense molecules, targeted against N-Ras, could be of considerable value as a tool to study the N-Ras-specific transduction pathway.

Animals↗

PubMed2001

Loss of heterozygosity at the RET protooncogene locus in a case of multiple endocrine neoplasia type 2A.

We describe a patient affected by multiple endocrine neoplasia type 2A (MEN 2A) bearing a heterozygous germline mutation (Cys(634)Arg) in exon 11 and an additional somatic mutation of the RET protooncogene. A large intragenic deletion, spanning exon 4 to exon 16, affected the normal allele and was detected by quantitative PCR, Southern blot analysis, and screening of several polymorphic markers. This deletion causes RET loss of heterozygosity exclusively in the metastasis, thus suggesting a role for this second mutational event in tumor progression. No additional mutations were found in the other exons analyzed. We provide the first evidence that RET, a dominant oncogene, is affected by a germline mutation and by an additional somatic deletion of the wild-type allele. This unusual genetic profile may be related to the clinical course and very poor outcome.

Adolescent↗

PubMed2001

Cemp, a mitoxantrone containing combination, in the treatment of intermediate and high grade non-hodgkin's lymphoma: an effective and non toxic therapeutic alternative for adult and elderly patients.

Here we report the results of a randomised multicenter phase III clinical trial which assesses the therapeutic efficacy and tolerability of a chemotherapy protocol CEMP (cyclophosphamide, etoposide, mitoxantrone and prednisone) in adult and elderly patients with advanced intermediate and high-grade NHL. Between October 1991 and October 1995, 139 patients, aged 55 to 79 years, with diffuse intermediate and high-grade lymphoma, were enrolled. A considerable percentage of patients had clinically aggressive disease: 32.4% had systemic symptoms, 79% had stage III or IV disease, 33.8% had bone marrow involvement, 46% had splenic involvement and 42.5% had increased values of serum lactate dehydrogenate. Complete remission was achieved in 70 of the 139 patients (51.9%) and PR in 12 (16.6%) with an overall response of 68.5%. The overall response survival rate at 6 years was 39%, whereas DFS rate was 48.7% and PFS rate was 28.5%. At four years 49% of the patients were still in CR. Dividing the patients in two groups, under and over 65 years of age, we obtained the same results as far as overall response is concerned. No toxic deaths occurred, neither cardiac, renal nor liver complications happened. CEMP regimen is an effective and safe protocol with good results in elderly people, well comparable to those achieved in younger ones.

Actuarial Analysis↗

PubMed2001

Short-term effects of olanzapine in Huntington disease.

OBJECTIVE: The aim was to describe the short-term (6 months) effects of olanzapine on behavioral and motor clinical manifestations in a group of 11 patients with Huntington disease. METHOD: An open-pilot study of olanzapine (5 mg) in patients with clinical and genetic diagnosis of Huntington disease was used. The Unified Huntington Disease Rating Scale for clinical assessment and the Total Functional Capacity score for the disease-stage evaluation were used. A statistical analysis was performed to compare the effects of olanzapine on the Unified Huntington Disease Rating Scale scores at time 0 (baseline) and at time 1 (6 months). Comparisons of motor scores, of single behavioral items, and of TFC scores were performed within the group. RESULTS: The behavioral assessment score of items regarding depression, anxiety, irritability, and obsessions showed a significant improvement (range of p, 0.0134-0.048). Given the total behavioral scores (sum of all the items investigated), five patients significantly improved their behavioral score after a 6-month treatment (range of p, 0.013-0.047). Choreic movements improved, although not significantly (0.05 < or = p < or = 1). CONCLUSIONS: Olanzapine is a potentially useful antipsychotic drug, with significant short-term effects on behavioral changes, mainly in patients with severe psychiatric symptoms at the onset. It might be considered as a possible therapeutic choice for treatment of Huntington disease.

Administration, Oral↗

PubMed2001

The early growth response gene EGR-1 behaves as a suppressor gene that is down-regulated independent of ARF/Mdm2 but not p53 alterations in fresh human gliomas.

PURPOSE: EGR-1 is an immediate early gene with diverse functions that include the suppression of growth. EGR-1 is down-regulated many cancer cell types, suggesting a tumor suppressor role, and may critically involve the p53 pathway. The aim of this work was to measure the expression of EGR-1 and the p16/INK4a/ARF-Mdm2-p53 pathway status in fresh human gliomas. EXPERIMENTAL DESIGN: Thirty-one human gliomas with different grades of malignancy were investigated for Egr-1 mRNA and the protein expression, frequency, and spectrum of p53 gene mutations, mdm2 gene amplification, and p16/INK4a/ARF allele loss. RESULTS: The amplification of Mdm2 and the deletion of the p16/INK4a gene was found in 3 and 5 cases, respectively, whereas mutations of p53, including two novel mutations, were observed in 10 other cases. The three types of changes occurred strictly mutually exclusively, emphasizing that these genes operate in a common pathway critical to glioma progression. EGR-1 mRNA was significantly down-regulated in astrocytomas (14.7 +/- 5.1%) and in glioblastomas (33.6 +/- 10.0%) versus normal brain. Overall, EGR-1 mRNA was strongly suppressed (average, 15.2 +/- 13.9%) in 27 of 31 cases (87%), independent of changes in p16/INK4a/ARF and Mdm2; whereas 4 of 31 cases with residual EGR-1 expression as well as the highest EGR-1 variance segregated with p53 mutations. Immunohistochemical analyses confirmed the suppression of EGR-1 protein. CONCLUSIONS: These results indicate that EGR-1 is commonly suppressed in gliomas independent of p16/INK4a/ARF and Mdm2 and that suppression is less crucial in tumors bearing p53 mutations, and these results implicate an EGR-1 growth regulatory mechanism as a target of inactivation during tumor progression.

Blotting, Northern↗

PubMed2000

The localization and activity of cAMP-dependent protein kinase affect cell cycle progression in thyroid cells.

cAMP signals are received and transmitted by multiple isoforms of cAMP-dependent protein kinases (PKAs), typically determined by their specific regulatory subunits. We describe changes in the cAMP signal transduction pathway during cell cycle progression in synchronized rat thyroid cells. Both PKA type II (PKAII) localization and nuclear cAMP signaling are significantly modified during G(0) and G(1)-S transitions. G(1) is characterized by PKA activation and amplified cAMP signal transduction. This is associated with a decrease in the concentration of RI and RII regulatory subunits and enhanced anchoring of PKAII to the Golgi-centrosome region. Just prior to S, the cAMP pathway is depressed. Up-regulation of the pathway by exogenous cAMP in G(1) inhibited the subsequent decay of the Cdk inhibitor p27 and delayed the onset of S phase. Forced translocation of endogenous PKAII to the cytosol down-regulated cAMP signaling, advancing the timing of p27 decay and inducing premature exit from G(1). These data indicate that membrane-bound PKA amplifies the transduction of cAMP signals in G(1) and that the length of G(1) is influenced by cAMP-PKA.

Animals↗

PubMed2000

Defective suppression of the aldosterone biosynthesis during stroke permissive diet in the stroke-prone phenotype of the spontaneously hypertensive rat.

Previous studies have shown that short-term high salt intake unmasks blunted plasma aldosterone suppression in stroke-prone spontaneously hypertensive rats (SHRsp). The aim of this study was to evaluate the response of aldosterone biosynthesis and production to a sustained exposure to the stroke-permissive Japanese-style diet (JD) in young stroke-prone and stroke-resistant SHRs. For this purpose, 6-week old male rats from both strains were divided into 2 dietary groups and received regular diet (SHR = 37, SHRsp = 32) or the JD and 1% saline to drink (SHR = 34, SHRsp = 30) for 4 weeks. All measurements were carried out at the end of the dietary periods. After JD, plasma aldosterone levels were significantly decreased in SHR (from 357.8 +/- 57 to 163.3 +/- 31.5 pg/ml, p < 0.05) but markedly increased in SHRsp (from 442 +/- 56.5 to 739 +/- 125.7 pg/ml, p < 0.05). Consistently, the adrenal aldosterone synthase expression was reduced by JD in SHR (p < 0.05), whereas it was even slightly raised by JD in SHRsp so that, at the end of JD, aldosterone synthase mRNA was 5-fold higher in SHRsp than in SHR. Urinary sodium excretion (mEq/24h) achieved lower levels in SHRsp, so that fractional excretion of sodium was 80.2 +/- 9% in SHR and 40.3 +/- 8% in SHRsp (p < 0.05) in balance studies performed at the end of JD. These different responses of mineralocorticoid biosynthesis and urinary sodium excretion to JD were not accounted for by different adaptations of the renin-angiotensin and atrial natriuretic peptide systems, of serum potassium levels, or of adrenal 11beta-hydroxylase expression in the two strains. Systolic blood pressure was comparable in both strains throughout the experiment. These results demonstrate enhanced aldosterone biosynthesis, associated with reduced urinary excretion of sodium in response to JD in SHRsp before the onset of stroke. This abnormality may play a role in the higher susceptibility to stroke of this model.

Aldosterone↗

PubMed2000

VACOP-B, high-dose cyclophosphamide and high-dose therapy with peripheral blood progenitor cell rescue for aggressive non-Hodgkin's lymphoma with bone marrow involvement: a study by the non-Hodgkin's Lymphoma Co-operative Study Group.

BACKGROUND AND OBJECTIVE: Sequential treatment with the addition of high-dose therapy (HDT) and peripheral blood progenitor cell (PBPC) rescue has been reported to be active as front-line therapy in aggressive non-Hodgkin's lymphoma (NHL) with bone marrow (BM) involvement. We designed an intensive sequential therapy as front-line therapy in this subset of patients and conducted a phase II study. DESIGN AND METHODS: Patients with aggressive non-Hodgkin's lymphoma and BM involvement at diagnosis received 8 weeks of VACOP-B chemotherapy as induction therapy. The second phase included high-dose cyclophosphamide (HDCY) (7 g/m(2)) with granulocyte colony-stimulating factor (G-CSF) followed by leukaphereses. The third phase included HDT according to the BEAM protocol or melphalan (140 mg/m(2)) plus total body irradiation (8 Gy in a single dose). RESULTS: Forty patients were included in the study. According to the intention-to-treat, after VACOP-B, 11 (27.5%) and 22 (55%) patients achieved complete remission (CR) and partial remission (PR), respectively. Thirty-four received HDCY. After HDCY, 18 patients (45%) were in CR and 13 (32.5%) in PR. Twenty-nine underwent HDT plus peripheral blood cell rescue (PBPC) rescue. At the completion of treatment 29 patients (72.5%) were in CR, and 3 patients (7.5%) in PR. The actuarial 3-year overall survival, disease free survival and failure free survival are 48%, 55% and 40%, respectively. Overall severe toxicity was 7.5%. INTERPRETATION AND CONCLUSIONS: This phase II study suggests that the intensified treatment described is feasible and active in aggressive NHL with BM involvement. A randomized trial is now underway to test this approach.

Adolescent↗

PubMed1999

The type and the localization of cAMP-dependent protein kinase regulate transmission of cAMP signals to the nucleus in cortical and cerebellar granule cells.

cAMP signals are received and transmitted by multiple isoforms of cAMP-dependent protein kinases, typically determined by their specific regulatory subunits. In the brain the major regulatory isoform RIIbeta and the RII-anchor protein, AKAP150 (rat) or 75 (bovine), are differentially expressed. Cortical neurons express RIIbeta and AKAP75; conversely, granule cerebellar cells express predominantly RIalpha and RIIalpha. Cortical neurons accumulate PKA catalytic subunit and phosphorylated cAMP responsive element binding protein very efficiently into nuclei upon cAMP induction, whereas granule cerebellar cells fail to do so. Down-regulation of RIIbeta synthesis by antisense oligonucleotides inhibited cAMP-induced nuclear signaling in cortical neurons. Expression in cerebellar granule cells of RIIbeta and AKAP75 genes by microinjection of specific expression vectors, markedly stimulated cAMP-induced transcription of the lacZ gene driven by a cAMP-responsive element promoter. These data indicate that the composition of PKA in cortical and granule cells underlies the differential ability of these cells to transmit cAMP signals to the nucleus.

A Kinase Anchor Proteins↗

PubMed1999

Clinical sensitivity to anthracyclines in PH/BCR+ acute lymphoblastic leukemia.

Translocation t(9;22) or Philadelphia chromosome (Ph)/BCR-ABL rearrangement positive acute lymphoblastic leukemia (Ph/BCR+ ALL) is associated with a very short survival of about one year in most patients. We analyzed long-term outcome of 76 adults with Ph/BCR+ ALL, in order to detect which factors were associated with longer survival. Modifiable prognostic factors included type of treatment, allogeneic marrow transplant (allo-BMT), and early anthracycline dose intensity (high = H/A, low = L/A); unmodifiable factors were age, gender, FAB morphology, phenotype, blast count, P190/210 transcript, hepatospleno-lymphadenopathy, LDH level. Median patient age was 43 years (range 15-71). Four favorable prognostic factors (FPF) were found associated with greater likelihood of complete remission (blast count < 50 x 10(9)/l, p = 0.08), longer remission duration (age < 50 years, p < 0.001; H/A, p < 0.05), and lower relapse rate (allo-BMT, p = 0.017). Age and anthracycline dose intensity exerted a synergistic prognostic effect. According to the cumulative incidence of FPF in each patient (FPF 0-1 = 29, 2-3 = 42, 4 = 5), the probability of survival increased from nil to 0.22 to 0.60 at 5 years (p < 0.005). Adult Ph/BCR+ ALL is relatively sensitive to anthracyclines, which therefore should be prescribed at full dosage to patients not eligible to allo-BMT or in the waiting list for unrelated donor transplantation.

Adolescent↗

PubMed1999

Screening of thyrotropin receptor mutations by fine-needle aspiration biopsy in autonomous functioning thyroid nodules in multinodular goiters.

Multinodular goiter (MNG) is characterized by nodules of different size and function. Areas of increased function may emerge, appearing as single, or more frequently, multiple autonomously functioning thyroid nodules (AFTN). The molecular mechanism for the autonomous growth and function of these nodules has been related to mutations in the thyrotropin receptor (TSHR) that constitutively activate the adenylyl cyclase. We searched for mutations in a limited area of the TSHR gene, covering the major mutational hotspot, in 38 AFTNs found in 37 patients with MNGs. We used reverse transcriptase-polymerase chain reaction (RT-PCR) and restriction enzyme analysis of fine-needle aspiration biopsy (FNAB) samples to rapidly identify 4 of the more frequently occurring TSHR mutations: D619G, F631C, T632I and D633E. Mutations were identified in 5 nodules (1 D619G mutation and 4 T632I mutations). Subsequently, the entire transmembrane portion of the TSHR gene was sequenced in a random sample of 12 AFTN samples that were free of mutations by RT-PCR and restriction enzyme analysis. By direct sequencing we identified a new mutation, F666L, in the seventh transmembrane domain in a sample from 1 nodule. Analysis of FMA samples of AFTN is an effective approach to identify TSHR gene mutations because individual mutations may be associated with different growth and function in vitro, our approach might, allow correlation of a given mutation with the clinical behavior in vivo.

Adult↗

PubMed1999

Modulation of the AT2 subtype receptor gene activation and expression by the AT1 receptor in endothelial cells.

OBJECTIVE: To investigate whether angiotensin II type 2 (AT2) receptor (AT2-r) promoter activity and expression are modulated by angiotensin II (Ang II), and whether the AT1 receptor (AT1-r) is involved in this effect. DESIGN AND METHODS: Primary endothelial cells obtained from NEONATAL rat aorta, expressing both receptors, were transfected with the rat AT2-r promoter region cloned into a pCAT-reporter vector. The reporter-expression study was performed in a transient transfection assay system. Transfected cells were studied following angiotensin-converting enzyme inhibition to prevent endogenous formation of Ang II. Cells were subsequently stimulated for 6 h with Ang II, either alone or in combination with the AT1-r antagonist DuP753. AT2-r mRNA was assessed by RNase protection assay during the same pharmacological stimuli. RESULTS: Stimulation with Ang II caused an increase in promoter activity (+50%, P < 0.05 versus baseline), whereas mRNA expression was reduced by 50% (P < 0.05 versus baseline). Concomitant treatment with DuP753 and Ang II was associated with a 98% increase in promoter activity (P < 0.05 versus baseline). DuP753 also prevented the reduction in mRNA; it actually produced a 100% increase in AT2-r mRNA accumulation (P < 0.01 versus baseline). Studies with the AT2-r antagonist PD123319 indicate that the AT2-r is also involved in the regulation of AT2-r gene promoter activity. CONCLUSIONS: These data indicate that Ang II increases AT2-r promoter activity and decreases AT2-r mRNA accumulation in endothelial cells. The AT1 subtype receptor is involved in the modulation of both effects of Ang II. These findings suggest that changes in the expression of AT2 receptors may occur during treatment with AT1-r antagonists, and they indicate the existence of a cross-talk between AT1 and AT2 receptors.

Angiotensin II↗

PubMed1998

p53 genes mutated in the DNA binding site or at a specific COOH-terminal site exert divergent effects on thyroid cell growth and differentiation.

Expression of mutated versions of the p53 gene deranged the differentiation program of thyroid cells and resulted in deregulated growth. Specifically, p53 mutants in several residues of the DNA-binding region induced thyrotropin (TSH) -independent growth and inhibition of the expression of thyroid-specific genes. The loss of the differentiated phenotype invariably correlated with the blockage of the expression of the genes coding for the thyroid transcriptional factors PAX-8 and TTF2. Conversely, thyroid cells transfected with a p53 gene mutated at codon 392, located outside the DNA-binding region, stimulated the expression of differentiation genes in the absence of the TSH, and induced TSH-independent growth. cAMP intracellular levels were higher in thyroid cells transfected with the p53 gene mutated at the 392 site than in the untransfected thyroid cells, but lower in the cells transfected with the other mutated p53 genes. Fra-1 and c-jun were induced by p53, resulting in increased AP-1 levels. The results of this study suggest that p53 exerts effects on cAMP transduction pathway in thyroid cells, which are exquisitely sensitive to cAMP.

Animals↗

PubMed1998

Role of the angiotensin II AT2-subtype receptors in the blood pressure-lowering effect of losartan in salt-restricted rats.

OBJECTIVE: The aim of this study was to evaluate the potential role of the angiotensin II (Ang II) AT2 receptors (AT2) in the control of blood pressure (BP) in the rat and the effects of AT2 receptors on BP during AT1 receptor (AT1) antagonism. METHODS: The study was performed in 52 Sprague-Dawley rats, which were preliminarily salt-restricted (SR) to enhance circulating and tissue renin-angiotensin system activity. To explore whether AT2 plays a role in BP regulation, the BP effects of the selective AT2 and AT1 receptor antagonists PD123319 (PD) (50 microg/kg/min) and losartan (Los) (10 mg/kg/day), were studied. Seven rats were used as a control group. To define whether AT2 plays a role in the BP response observed during AT1 antagonism, 17 Los treated rats were divided into two groups: seven were treated with both antagonists (Los + PD) and 10 rats received Los + vehicle. The effects of both drugs were also studied in bilaterally nephrectomized rats (NX). All treatments were maintained for 1 week RESULTS: Los reduced BP significantly in both intact (P < 0.001) and NX (P < 0.05) rats, while PD increased BP in intact and NX rats (both P < 0.001). In the Los + PD group BP levels were significantly higher (P < 0.001 vs Los and Los + vehicle, P = ns vs pretreatment), while vehicle infusion did not modify the BP response to Los. CONCLUSION: The results show that in salt-restricted rats AT2 blockade offsets the BP-lowering effect of losartan and suggest that AT2 receptors contribute to the hypotensive effects of losartan. Thus, AT1 receptor antagonists such as losartan, which are becoming widely used in the clinical treatment of hypertension, may reduce BP not only by blockade of AT1 receptors, but also through the stimulation of AT2 receptors by the excess of angiotensin II.

Angiotensin II↗