Menopausal symptoms in epithelial ovarian cancer survivors: a GINECO VIVROVAIRE2 study.

OBJECTIVE: We have previously shown that epithelial ovarian cancer (EOC) and its treatments have negative effects on long-term quality of life (QoL) and fatigue. The present multicenter study investigated the main menopausal symptoms and gynecological management of EOC survivors (EOCS). METHODS: 166 patients with relapse-free ≥3 years after the end of treatment attended a consultation with a gynecologist, including a questionnaire related to vasomotor symptoms (VMS) and sexuality, a clinical examination, a blood sample and an osteodensitometry. QoL, fatigue, insomnia and mood disorders were measured with validated questionnaires and correlated to VMS. VMS and QoL were assessed according to natural menopause (NM) or surgical menopause (SM). RESULTS: Mean age at the survey was 62 [21-83] years and stage III/IV (48%). Mean delay since the end of treatment was 6 years. Fifty-nine patients (36%) had SM. Half of patients reported VMS. Seventy-two percent of EOCS with SM had VMS compared to 41% with NM (P < .001). VMS were not associated with poor global QoL, fatigue, insomnia or mood disorders. Two-thirds of EOCS reported a decrease in libido. Patients with SM showed a greater decrease in libido than NM (P < .02). Fourteen percent of them had osteoporosis and 50% osteopenia. Among the 85 patients with VMS, 80 did not receive HRT after cancer treatment. At the time of the survey, only 7 (4%) patients were receiving hormone replacement therapy (HRT). CONCLUSIONS: VMS and sexual disorders are frequently reported by EOCS, particularly among patients with SM. Most EOCS with menopausal symptoms could benefit from HRT to improve these symptoms.

In vivo imaging of CNS microglial activation/macrophage infiltration with combined [18F]DPA-714-PET and SPIO-MRI in a mouse model of relapsing remitting experimental autoimmune encephalomyelitis.

PURPOSE: To evaluate the feasibility and sensitivity of multimodality PET/CT and MRI imaging for non-invasive characterization of brain microglial/macrophage activation occurring during the acute phase in a mouse model of relapsing remitting multiple sclerosis (RR-MS) using [18F]DPA-714, a selective radioligand for the 18-kDa translocator protein (TSPO), superparamagnetic iron oxide particles (SPIO), and ex vivo immunohistochemistry. METHODS: Experimental autoimmune encephalomyelitis (EAE) was induced in female SJL/J mice by immunization with PLP139-151. Seven symptomatic EAE mice and five controls underwent both PET/CT and MRI studies between 11 and 14 days post-immunization. SPIO was injected i.v. in the same animals immediately after [18F]DPA-714 and MRI acquisition was performed after 24 h. Regional brain volumes were defined according to a mouse brain atlas on co-registered PET and SPIO-MRI images. [18F]DPA-714 standardized uptake value (SUV) ratios (SUVR), with unaffected neocortex as reference, and SPIO fractional volumes (SPIO-Vol) were generated. Both SUVR and SPIO-Vol values were correlated with the clinical score (CS) and among them. Five EAE and four control mice underwent immunohistochemical analysis with the aim of identifying activated microglia/macrophage and TSPO expressions. RESULTS: SUVR and SPIO-Vol values were significantly increased in EAE compared with controls in the hippocampus (p < 0.01; p < 0.02, respectively), thalamus (p < 0.02; p < 0.05, respectively), and cerebellum and brainstem (p < 0.02), while only SPIO-Vol was significantly increased in the caudate/putamen (p < 0.05). Both SUVR and SPIO-Vol values were positively significantly correlated with CS and among them in the same regions. TSPO/Iba1 and F4/80/Prussian blue staining immunohistochemistry suggests that increased activated microglia/macrophages underlay TSPO expression and SPIO uptake in symptomatic EAE mice. CONCLUSIONS: These preliminary results suggest that both activated microglia and infiltrated macrophages are present in vulnerable brain regions during the acute phase of PLP-EAE and contribute to disease severity. Both [18F]DPA-714-PET and SPIO-MRI appear suitable modalities for preclinical study of neuroinflammation in MS mice models.

Long-term fatigue and quality of life among epithelial ovarian cancer survivors: a GINECO case/control VIVROVAIRE I study.

BACKGROUND: Few data are available on long-term fatigue (LTF) and quality of life (QoL) among epithelial ovarian cancer survivors (EOCS). In this case-control study, we compared LTF, symptoms and several QoL domains in EOCS relapse-free ≥3 years after first-line treatment and age-matched healthy women. PATIENTS AND METHODS: EOCS were recruited from 25 cooperative GINECO centers in France. Controls were randomly selected from the electoral rolls. All participants completed validated self-reported questionnaires: fatigue (FACIT-F), QoL (FACT-G/O), neurotoxicity (FACT-Ntx), anxiety/depression (HADS), sleep disturbance (ISI), and physical activity (IPAQ). Severe LTF (SLTF) was defined as a FACIT-F score <37/52. Univariate and multivariate logistic regressions were conducted to analyze SLTF and its influencing factors in EOCS. RESULTS: A total of 318 EOCS and 318 controls were included. EOCS were 63-year-old on average, with FIGO stage I/II (50%), III/IV (48%); 99% had received platinum and taxane chemotherapy, with an average 6-year follow-up. There were no differences between the two groups in socio-demographic characteristics and global QoL. EOCS had poorer FACIT-F scores (40 versus 45, P < 0.0001), lower functional well-being scores (18 versus 20, P = 0.0002), poorer FACT-O scores (31 versus 34 P < 0.0001), and poorer FACT-Ntx scores (35 versus 39, P < 0.0001). They also reported more SLTF (26% versus 13%, P = 0.0004), poorer sleep quality (63% versus 47%, P = 0.0003), and more depression (22% versus 13%, P = 0.01). Fewer than 20% of EOCS and controls exercised regularly. In multivariate analyses, EOCS with high levels of depression, neurotoxicity, and sleep disturbance had an increased risk of developing SLTF (P < 0.01). CONCLUSION: Compared with controls, EOCS presented similar QoL but persistent LTF, EOC-related symptoms, neurotoxicity, depression, and sleep disturbance. Depression, neuropathy, and sleep disturbance are the main conditions associated with severe LTF.

Clinical validation of a prognostic tool in a population of outpatients treated for incurable cancer undergoing anticancer therapy: PRONOPALL study.

BACKGROUND: In 2008, a study of the characteristics of hospitalised patients led to the development of a prognostic tool that distinguished three populations with significantly different 2-month survival rates. The goal of our study aimed at validating prospectively this prognostic tool in outpatients treated for cancer in terminal stage, based on four factors: performance status (ECOG) (PS), number of metastatic sites, serum albumin and lactate dehydrogenase. PATIENTS AND METHODS: PRONOPALL is a multicentre study of current care. About 302 adult patients who met one or more of the following criteria: life expectancy under 6 months, performance status ≥ 2 and disease progression during the previous chemotherapy regimen were included across 16 institutions between October 2009 and October 2010. Afterwards, in order to validate the prognostic tool, the score was ciphered and correlated to patient survival. RESULTS: Totally 262 patients (87%) were evaluable (27 patients excluded and 13 unknown score). Median age was 66 years [37-88], and women accounted for 59%. ECOG PS 0-1 (46%), PS 2 (37%) and PS 3-4 (17%). The primary tumours were: breast (29%), colorectal (28%), lung (13%), pancreas (12%), ovary (11%) and other (8%). About 32% of patients presented one metastatic site, 35% had two and 31% had more than two. The median lactate dehydrogenase level was 398 IU/l [118-4314]; median serum albumin was 35 g/l [13-54]. According to the PRONOPALL prognostic tool, the 2-month survival rate was 92% and the median survival rate was 301 days [209-348] for the 130 patients in population C, 66% and 79 days [71-114] for the 111 patients in population B, and 24% and 35 days for [14-56] the 21 patients in population A. These three populations survival were statistically different (P <0.0001). CONCLUSION: PRONOPALL study confirms the three prognostic profiles defined by the combination of four factors. This PRONOPALL score is a useful decision-making tool in daily practice.

Imaging of brain TSPO expression in a mouse model of amyotrophic lateral sclerosis with (18)F-DPA-714 and micro-PET/CT.

PURPOSE: To evaluate the feasibility and sensitivity of (18)F-DPA-714 for the study of microglial activation in the brain and spinal cord of transgenic SOD1(G93A) mice using high-resolution PET/CT and to evaluate the Iba1 and TSPO expression with immunohistochemistry. METHODS: Nine symptomatic SOD1(G93A) mice (aged 117 ± 12.7 days, clinical score range 1 - 4) and five WT SOD1 control mice (aged 108 ± 28.5 days) underwent (18)F-DPA-714 PET/CT. SUV ratios were calculated by normalizing the cerebellar (rCRB), brainstem (rBS), motor cortex (rMCX) and cervical spinal cord (rCSC) activities to that of the frontal association cortex. Two WT SOD1 and six symptomatic SOD1(G93A) mice were studied by immunohistochemistry. RESULTS: In the symptomatic SOD1(G93A) mice, rCRB, rBS and rCSC were increased as compared to the values in WT SOD1 mice, with a statistically significantly difference in rBS (2.340 ± 0.784 vs 1.576 ± 0.287, p = 0.014). Immunofluorescence studies showed that TSPO expression was increased in the trigeminal, facial, ambiguus and hypoglossal nuclei, as well as in the spinal cord, of symptomatic SOD1(G93A) mice and was colocalized with increased Iba1 staining. CONCLUSION: Increased (18)F-DPA-714 uptake can be detected with high-resolution PET/CT in the brainstem of transgenic SOD1(G93A) mice, a region known to be a site of degeneration and increased microglial activation in amyotrophic lateral sclerosis, in agreement with increased TSPO expression in the brainstem nuclei shown by immunostaining. Therefore, (18)F-DPA-714 PET/CT might be a suitable tool to evaluate microglial activation in the SOD1(G93A) mouse model.

PET/CT in cancer research: from preclinical to clinical applications.

The identification of genetic and biochemical mechanisms underlying tumor growth and progression along with the unraveling of human genoma provided a plethora of new targets for cancer detection, treatment and monitoring. Simultaneously, the extraordinary development of a number of imaging technologies, including hybrid systems, allowed the visualization of biochemical, molecular and physiological aberrations linked to underlying mutations in a given tumor. In vivo evaluation of complex biological processes such as proliferation, apoptosis, angiogenesis, metastasis, gene expression, receptor-ligand interactions, transport of substrates and metabolism of nutrients in human cancers is feasible using PET/CT and radiolabeled molecular probes. Some of these compounds are in preclinical phases of evaluation whereas others have been already applied in clinical settings. Here we provide prominent examples on how some biological processes and target expression can be visualized by PET/CT in animal tumor models and cancer patients for the noninvasive detection of well-known markers of tumor aggressiveness, invasiveness and resistance to treatment and for the evaluation of tumor response to therapy.

Molecular imaging of tumor microenvironment: challenges and perspectives.

Tumor microenvironment consists of a number of components including host resident stromal cells, infiltrating immune cells and extracellular matrix. The architecture surrounding tumor cells is not static but is subjected to a continuous remodeling in response to the dynamic interplay between tumor and stromal cells and to the production of extracellular proteases. In addition all these microenvironmental components along with cancer cells are exposed to abnormal physiologic conditions such as hypoxia and acidic extracellular pH that may induce both adaptive and constitutive changes in cancer and stromal cells. In this review, we will primarily focus on the possibility to visualize in vivo tumor microenvironment components and conditions as well as interactions with cancer cells. The major goal is to highlight the difficulties and the opportunities of this approach and how each imaging technology helps to overcome specific challenge.

Randomized phase II study of docetaxel plus estramustine and single-agent docetaxel in patients with metastatic hormone-refractory prostate cancer.

BACKGROUND: Docetaxel (Taxotere)-based regimens are the new standard therapy in advanced hormone-refractory prostate cancer (HRPC). A synergistic activity has been shown with docetaxel in combination with estramustine in vitro; however, the benefit of this combination remains controversial in clinical practice. We assessed the activity and safety of docetaxel alone and docetaxel-estramustine in HRPC. PATIENTS AND METHODS: Patients (n = 92) with metastatic HRPC and rising prostate-specific antigen (PSA) while receiving androgen suppression were randomized to 3-weekly treatment with either docetaxel 75 mg/m(2), day 1 (D), or docetaxel 70 mg/m(2), day 2, plus oral estramustine 280 mg twice daily, days 1-5 (DE). RESULTS: Ninety-one patients were treated (DE 47, D 44). A PSA response occurred in 68% (primary endpoint met) and 30% of patients, respectively. Median PSA response duration was 6.0 months in both groups. Median time to progression was 5.7 and 2.9 months, and median survival was 19.3 and 17.8 months in the DE and D arms, respectively. Hematologic and non-hematologic toxic effects were mild and similar in both arms. One patient in each group withdrew due to toxicity. Quality of life was similar in both groups. CONCLUSION: Combining estramustine with docetaxel in this schedule is an active and well-tolerated treatment option in HRPC.

Nuclear imaging in cancer theranostics.

The combination of a diagnostic test with a therapeutic entity is termed theranostics. The diagnostic test aims at identifying patients who will likely benefit from a specific therapeutic intervention, fail to respond or eventually manifest side effects to a given drug. The appropriate selection of patients for innovative therapies would promote an enrichment of patient population that can potentiate clinical trials and, eventually, accelerate the drug development process. For these reasons, many drug companies adopted a theranostic approach as a new and promising avenue for drug development. From an historical perspective, the concepts underlying the theranostic strategy are well known in nuclear medicine and constituted the basis of many nuclear imaging procedures currently used in clinical practice. Nevertheless the adoption of these concepts by regulatory authorities is a real progress and reflects the remarkable advances in the development of drugs against molecular targets. In this respect, the oncological field provides the strongest evidence of the clinical need to link diagnostics to therapeutics. Here, we review the contribution that non-invasive nuclear imaging may give to cancer theranostics and report prominent examples of nuclear imaging procedures that can be coupled to specific therapies. The main focus lies on imaging procedures that can identify patients who will benefit from molecularly targeted therapy or are going to fail to respond to standard treatment.

MIBI as prognostic factor in breast cancer.

Evaluation of treatment response is of primary importance in the management of patients with cancer. Both positron- and g-emitting compounds have been used to monitor changes in tumor metabolism or viability after therapy. The use of (99m)Tc-labeled lipophilic cations raised the possibility to predict the tumor response to treatment and to identify patients who will become refractory to subsequent therapy. In particular, many studies have shown the prognostic value of (99m)Tc-MIBI scan in different types of malignancy including breast and lung cancer, lymphoma and sarcoma. The ability of (99m)Tc-MIBI to interact with P-glycoprotein, allowing the functional assessment of the multidrug resistant phenotype, is one of the mechanisms underlying its prognostic value. Additional mechanisms of cell resistance, mainly involving alterations of apoptosis, may affect (99m)Tc-MIBI uptake in tumors. Therefore, either an enhanced tracer clearance or a reduced early uptake of (99m)Tc-MIBI indicate a poor response to therapy. In both cases, (99m)Tc-MIBI scan may ensure that the further management strategy will be effective in individual cancer patients.

Radiolabeling approaches for cholecystokinin B receptor imaging.

Regulatory peptides and their analogs are being extensively investigated as radiopharmaceuticals for cancer imaging. In particular, cholecystokinin (CCK) receptors of the subtype B (CCK-BR) have been shown to be overexpressed in certain neuroendocrine tumors including medullary thyroid cancer. Our recent work has focused on new methods to radiolabel the CCK8 peptide with (111)In or (99m)Tc for the purpose of developing radiopharmaceuticals for in vivo CCK-B receptor imaging. Labeling of CCK8 with (111)In was achieved at the N-terminus of the peptide by adding, in solid phase, a glutamate coupled diethylenetriaminepentaacetic acid (DTPA) moiety through a glycine linker, yielding DTPA-Glu-G-CCK8. For labeling with (99m)Tc, the CCK8 peptide was modified at its N-terminus by introducing, in the following order--cysteine, glycine, and a diphenylphosphinopropionyl moiety--giving a 10-residue peptide derivative, Phos-GC-CCK8. A cell culture model was developed for the purpose of evaluating the binding properties of these two ligands. The human epidermoid carcinoma cell line, A431, was transfected with a plasmid containing the full coding sequence of the human CCK-BR under a strong viral promoter, obtaining a number of receptors in the range of 2-5 x 10(6) per cell. Control cells were transfected with vector alone. An animal tumor model utilizing these two cell lines was developed to evaluate the specificity of interaction with the CCK-BR and biodistribution properties of the compounds. CCK-BR positive and control cells were subcutaneously injected in opposite flanks of CD1 female nude mice in order to obtain xenografts differing only in their ability to express CCK-B receptors. High performance liquid chromatography (HPLC) and other chromatographic methods were utilized to assess stability of the radiolabeled compounds after injection. Both (111)In-DTPA-Glu-G-CCK8 and (99m)Tc-Phos-GC-CCK8 showed similar binding affinities for cultured CCK-BR expressing cells, with dissociation constants in the range of 20-40 nM. With the two xenograft approach, we were able to demonstrate specific interaction with the receptor of both CCK analogs in our animal model. The data obtained shows rapid specific localization of both compounds on the CCK-BR overexpressing xenografts. Both tracers show rapid plasma clearance of unbound peptide. Clearance of (111)In-DTPA-Glu-G-CCK8 appears to be preferentially through the kidneys, whereas (99m)Tc-Phos-GC-CCK8 clearance occurs both through kidneys and the hepatobiliary system. Both our labeling approaches appear adequate for clinical use of peptide based radiopharmaceuticals, although (99m)Tc-Phos-GC-CCK8 shows elevated accumulation in the gastrointestinal tract, which causes high background activity.

Bone marrow uptake of 99mTc-MIBI in patients with multiple myeloma.

In a previous study, we showed the ability of technetium-99m methoxyisobutylisonitrile (99mTc-MIBI) scan to identify active disease in patients with multiple myeloma (Eur J Nucl Med 1998; 25: 714-720). In particular, a semiquantitative score of the extension and intensity of bone marrow uptake was derived and correlated with both the clinical status of the disease and plasma cell bone marrow infiltration. In order to estimate quantitatively 99mTc-MIBI bone marrow uptake and to verify the intracellular localization of the tracer, bone marrow samples obtained from 24 multiple myeloma patients, three patients with monoclonal gammopathy of undetermined significance (MGUS) and two healthy donors were studied for in vitro uptake. After centrifugation over Ficoll-Hypaque gradient, cell suspensions were incubated with 99mTc-MIBI and the uptake was expressed as the percentage of radioactivity specifically retained within the cells. The cellular localization of the tracer was assessed by micro-autoradiography. Twenty-two out of 27 patients underwent 99mTc-MIBI scan within a week of bone marrow sampling. Whole-body images were obtained 10 min after intravenous injection of 555 MBq of the tracer; the extension and intensity of 99mTc-MIBI uptake were graded using the semiquantitative score. A statistically significant correlation was found between in vitro uptake of 99mTc-MIBI and both plasma cell infiltration (Pearson's coefficient of correlation r=0.69, P<0.0001) and in vivo score (Spearman rank correlation coefficient r=0.60, P<0.01). No specific tracer uptake was found in bone marrow samples obtained from the two healthy donors. Micro-autoradiography showed localization of 99mTc-MIBI inside the plasma cells infiltrating the bone marrow. Therefore, our findings show that the degree of tracer uptake both in vitro and in vivo is related to the percentage of infiltrating plasma cells which accumulate the tracer in their inner compartments.

Coordinate up-regulation of Sp1 DNA-binding activity and urokinase receptor expression in breast carcinoma.

The regulatory mechanisms underlying the overexpression of urokinase-type plasminogen activator (uPA) and its receptor (uPAR) in highly invasive breast carcinomas remain poorly understood. In this study, we have simultaneously determined the level of uPAR and the activity of the transcription factor Sp1 in 14 breast carcinomas and 5 benign lesions. We found that uPAR levels and Sp1-binding activity are coordinately elevated in malignant tumors (r, 0.94; P < 0.001). On the contrary, undetectable or only barely detectable levels of uPAR and Sp1 activity were found in benign breast lesions. Finally, the engagement of uPAR by catalytically inactive uPA in the MDA-MB-231 breast carcinoma cell line results in a rapid up-regulation of Sp1-binding activity followed by an increase of uPAR protein. These results, taken together, suggest the existence of a uPA-dependent positive regulatory loop that may progressively enhance malignant breast cell invasiveness.

Urokinase receptor interacts with alpha(v)beta5 vitronectin receptor, promoting urokinase-dependent cell migration in breast cancer.

Perturbation of adhesive interactions at cell-substratum and cell-cell contact sites is a critical event in the multistep process of cancer invasion. Recent studies indicate that the urokinase receptor (uPAR) is associated in large molecular complexes with other molecules, such as integrins. To test the possibility that uPAR may physically and functionally interact with vitronectin (Vn) receptors, we determined the expression level of uPAR, alpha(v)beta3, and alpha(v)beta5 Vn receptors in 10 human breast carcinomas. Here, we show the ability of uPAR to physically associate with alpha(v)beta5 in the breast carcinomas examined. The functional effects of this interaction were studied using HT1080 human fibrosarcoma and MCF-7 human breast carcinoma cell lines, both exhibiting a urokinase-dependent physical association between uPAR and alpha(v)beta5. Both cell lines respond to urokinase or to its noncatalytic amino-terminal fragment by exhibiting remarkable cytoskeletal rearrangements that are mediated by alpha(v)beta5 and require protein kinase C activity. On the contrary, binding of Vn to alpha(v)beta5 results in the protein kinase C-independent formation of F-actin containing microspike-type structures. Furthermore, alpha(v)beta5 is required for urokinase-directed, receptor-dependent MCF-7 and HT1080 cell migration. These data show that uPAR association with alpha(v)beta5 leads to a functional interaction of these receptors and suggest that uPAR directs cytoskeletal rearrangements and cell migration by altering alpha(v)beta5 signaling specificity.

Dual modulation of Na/H antiport by atrial natriuretic factor in rat aortic smooth muscle cells.

The aim of the present work was to study the effect of the atrial natriuretic factor (ANF) on the Na/H antiport in rat aorta smooth muscle cells, evaluated as intracellular pH (pHi) recovery after an acid load with ammonium chloride. The Na/H antiport was studied using a fluorescent probe, sensitive to pHi, 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein. Our data indicate that ANF modulates the activity of the Na/H antiport in both a dose- and time-dependent manner. Hormone concentrations of 10(-10) M activate the antiport, increasing both the rate of recovery and the set point by approximately 0.2 pH units. This effect is mediated by diacylglycerol as a result of phospholipid hydrolysis by a phospholipase C, even if an involvement of adenosine 3',5'-cyclic monophosphate (cAMP) cannot be ruled out. ANF (10(-7) M) inhibits the antiport, decreasing both the rate of recovery and the set point by approximately 0.3 pH units, because of guanosine 3',5'-cyclic monophosphate production. Both inhibition and stimulation of pHi by ANF were more pronounced when the hormone was given before the acid load, perhaps because of the longer time exposure. We present new hypotheses on the mechanism of action of this paracrine/autocrine factor.

Phosphatidylinositol- and phosphatidylcholine-dependent phospholipases C are involved in the mechanism of action of atrial natriuretic factor in cultured rat aortic smooth muscle cells.

We have investigated the involvement of specific phospholipase systems and their possible mutual relationship with the mechanism by which atrial natriuretic factor (ANF) increases phosphatidate (PA) and diacylglycerol (DAG) in rat aortic smooth muscle cells (RASMC), one of the major targets of this hormone. Our results indicate that ANF initially stimulates a phosphatidylinositol-dependent phospholipase C (PI-PLC) with a significant increase of DAG, enriched in arachidonate, and inositol trisphosphate (IP3) and then a phosphatidylcholine-dependent phospholipase C (PC-PLC) with formation of DAG, enriched in myristate, and phosphocholine (Pcho). Moreover, ANF stimulates PA formation at an intermediate stage between early and late DAG formation. The transphosphatidylation reaction, as well as its labeling ratio, demonstrate that phosphatidylcholine-dependent phospholipase D (PC-PLD) is not involved. Our experiments with R59022, a DAG kinase (DAGK) inhibitor, indicate that such an increase may be due to the phosphorylation of DAG derived from phosphatidylinositol (PI) hydrolysis. Our results show that phorbol 12-myristate 13 acetate (PMA) plays a significant role in late DAG formation and that Pcho is released concomitantly, suggesting there is a relationship between the two phospholipase Cs (PLCs) that occurs through a protein kinase C (PKC) translocation from cytosol to the plasma membrane. These findings are confirmed by the use of PKC inhibitors calphostin, H7, and staurosporine. The involvement of membrane phospholipid hydrolysis and the ensuing production of second messengers might explain the vasorelaxant effect of ANF.

Selective activation by atrial natriuretic factor of phosphatidylcholine-specific phospholipase activities in purified heart muscle plasma membranes.

We have characterized a membrane-bound phosphatidylcholine (PC) specific phospholipase C (PC-PLC) in plasma membranes from rat cardiac muscle, and have investigated the role of PC-PLC and PC-specific phospholipase D (PC-PLD) activities in the mechanism of action of atrial natriuretic factor (ANF). In purified sarcolemma, ANF stimulated over a wide range of concentrations with a maximum at 10(-11) M the hydrolysis of phosphatidylcholine through PC-PLD giving phosphatidate and choline, whereas higher concentrations of ANF (10(-10) M) preferentially stimulated PC breakdown through PC-PLC to form diacylglycerol and phosphocholine. To confirm the involvement of the PC-PLD in the mechanism of ANF action, we measured the transphosphatidylation reaction, a specific assay for this phospholipase which in the presence of ethanol catalyses the phosphatidylethanol formation from PC. ANF stimulated phosphatidylethanol formation with the same dose-response behavior as phosphatidate formation. The significant diacylglycerol increase at 10(-10) M ANF, in the presence of propranolol, a potent inhibitor of phosphatidate phosphatase which can hydrolyse phosphatidate to give diacylglycerol, suggested a direct involvement of PC-PLC. The use of GTP-gamma-S, a non hydrolysable analog of GTP, and of pertussis toxin showed the involvement of a pertussis toxin insensitive G protein in PC-PLC mediated ANF signal transduction. We suggest a differential effect of ANF on PC breakdown by phospholipases C and D depending on the concentration of the peptide.

Insulin-stimulated hydrolysis of phosphatidylcholine by phospholipase C and phospholipase D in cultured rat hepatocytes.

We have investigated the mechanism of action by which insulin increases phosphatidate (PA) and diacylglycerol (DAG) levels in cultured rat hepatocytes. Insulin initially stimulated phosphatidylcholine-dependent phospholipase D (PC-PLD) with a significant increase in both PA and intracellular as well as extracellular choline. The involvement of phospholipase D was confirmed by the formation of PC-derived phosphatidylethanol in the presence of ethanol. The DAG increase appeared to be biphasic. Only the early phase of DAG production was inhibited by propranolol, an inhibitor of the phosphatidate phosphatase (PAP) responsible for the conversion of PA into DAG, suggesting that initially the DAG increase is due to the PLD-PAP pathway. The delayed DAG increase was in parallel with increased intracellular and extracellular phosphocholine and probably derived directly from PC-PLC activity. Experiments performed in the presence of 1 microM phorbol 12-myristate 13-acetate (PMA) indicated that protein kinase C (PKC) mediated the insulin effect on PC-PLC, but not on PC-PLD. These findings were confirmed using the PKC inhibitors calphostin, H7 and staurosporine. The dual activation of these phospholipases with a biphasic elevation of DAG levels and activation of specific PKC isoenzymes could be necessary to elicit both early and delayed effects of insulin.

Modulation of the Na-H antiport by insulin: interplay between protein kinase C, tyrosine kinase, and protein phosphatases.

The insulin modulation of Na-H antiport in rat hepatocytes was studied using the fluorescent, pH-sensitive intracellular probe, 2',7' bis (carboxyethyl)-5(6)-carboxyfluorescein (BCECF). Our data show that insulin stimulates the Na-H antiport. The dose-response of insulin effect shows a behavior typical of other insulin responses: a maximum in the physiological range (1 nM) and smaller effects at higher and lower hormone concentrations. The time-course of activation is very fast at high hormone concentrations and slow, but reaching a higher value, for the physiological concentrations (0.26 +/- 0.05 and 0.18 +/- 0.022 pH units for 1 nM and 1 microM insulin respectively). The use of phorbol, 12-myristate, 13-acetate (PMA), a potent activator of protein kinase C and its inhibitor staurosporine, and the inhibitor of tyrosine kinase erbstatin analog, suggests that both protein kinase C and tyrosine kinase could be involved in the mechanism leading to Na-H antiport activation by insulin. We suggest that the activation of the antiport involves the two pathways depending on the hormone concentration. In particular, protein kinase C would mediate the effects of high hormone concentrations, acting as a growth factor, since staurosporine fully inhibited insulin 1 microM, but only partially 1 nM effects, and tyrosine kinase would mediate the effect of insulin 1 nM and only partially 1 microM. Okadaic acid 1 microM, a potent inhibitor of protein phosphatases, mimicked the hormone effects on the antiport and abolished the different time-course due to hormone concentration, suggesting a role of kinases and phosphatases in the signal transduction. The effect of all activators was abolished by amiloride analog, 5-(N-ethyl-N-isopropyl) amiloride (EIPA), confirming the specificity of these effects.

Insulin effect on isolated rat hepatocytes: diacylglycerol-phosphatidic acid interrelationship.

It is widely accepted that insulin action does not involve inositol phospholipid hydrolysis through the stimulation of a phosphatidylinositol-specific phospholipase C (PI-PLC). This consideration prompted us to investigate the insulin effect on the mechanism leading to the accumulation of diacylglycerol (DAG) and phosphatidic acid (PA) in rat hepatocytes. Basically, insulin induces: (i) a significant increase of both [3H]glycerol and fatty acid labelling of DAG; (ii) a significant increase of PA labelling preceding DAG labelling and paralleled by a decrease of phosphatidylcholine (PC) labelling. These observations, which suggest an insulin-dependent involvement of a phospholipase D, are strengthened by the increase of PC-derived phosphatidylethanol in presence of ethanol. Finally, the observation that the PA levels do not return to basal suggests that other mechanisms different from PC hydrolysis, such as the stimulation of direct synthesis of PA, may be activated.