ABSTRACT
INTRODUCTION: Neoadjuvant chemotherapies for breast cancer (BC) are effective but potentially cardiotoxic, and expose long survivors at risk of chemotherapy-related cardiac dysfunction (CTRCD). Unfortunately, early screening for CTRCD has actual diagnostic limits. Myocardial extracellular volume (mECV) is a radiological marker used in cardiac CT scans and cardiac magnetic resonance for diagnosis and follow-up of CTRCD. It can be measured in whole-body CT (WB-CT) scan, routinely performed in patients at high risk of relapse, to evaluate CTRCD occurrence during oncological follow-up. METHODS: 82 WB-CT scans were examined at baseline (T0) and during oncological follow-up at first year (T1) and fifth year (T5) after the end of neoadjuvant treatment. mECV was measured at 1 min (PP) and 5 min (DP) after contrast injection. 31 echocardiograms were retrieved in T1 to perform a linear correlation between mECV and left ventricular ejection fraction (LVEF). RESULTS: mECV values in T0 were similar between the two groups both in PP and in DP. Significant results were found for PP values in T1 (37.0 % vs 32 %, p = 0.0005) and in T5 (27.2 % vs 31.2 %, p = 0.025). A cut-off value of 35 % in PP proved significant in T1 (OR = 12.4, p = 0.004), while mECV was inversely correlated with LVEF both in PP (adj-S = -3.54, adj-p = 0.002) and in DP (adj-S = -2.51, adj-p = 0.0002), suggesting a synergistic action with the age at diagnosis (p < 0.0001, respectively). CONCLUSIONS: WB-CT scans performed during oncological reassessment in patients at high-risk of recurrence could be used for CTRCD screening in cardiovascular low-risk patients, especially in aging patients with mECV values above 35 %.
Subject(s)
Anthracyclines , Breast Neoplasms , Cardiotoxicity , Neoadjuvant Therapy , Tomography, X-Ray Computed , Humans , Female , Breast Neoplasms/drug therapy , Middle Aged , Neoadjuvant Therapy/adverse effects , Anthracyclines/adverse effects , Retrospective Studies , Cardiotoxicity/etiology , Cardiotoxicity/diagnostic imaging , Tomography, X-Ray Computed/methods , Adult , Aged , Whole Body Imaging/methods , Stroke Volume/drug effects , Echocardiography/methods , Predictive Value of Tests , Chemotherapy, Adjuvant/adverse effectsABSTRACT
Excision repair cross-complementation group 1 (ERCC1) is a key component in DNA repair mechanisms and may influence the tumor DNA-targeting effect of the chemotherapeutic agent oxaliplatin. Germline ERCC1 polymorphisms may alter the protein expression and published data on their predictive and prognostic value have so far been contradictory. In the present article we review available evidence on the clinical role and utility of ERCC1 polymorphisms and, in the absence of a 'perfect' trial, what we call the 'sliding doors' trial, we present the data of ERCC1 genotyping in our local patient population. We found a useful predictive value for oxaliplatin-induced risk of anemia.
Subject(s)
Colorectal Neoplasms/drug therapy , Colorectal Neoplasms/enzymology , DNA-Binding Proteins/genetics , Endonucleases/genetics , Animals , Antineoplastic Combined Chemotherapy Protocols/therapeutic use , Colorectal Neoplasms/genetics , DNA Repair , DNA, Neoplasm/genetics , DNA-Binding Proteins/chemistry , Endonucleases/chemistry , Female , Humans , Middle Aged , Organoplatinum Compounds/administration & dosage , Oxaliplatin , Polymorphism, Single Nucleotide , Prognosis , Replication Protein C/chemistry , Replication Protein C/genetics , Transcription Factors/chemistry , Transcription Factors/geneticsABSTRACT
BACKGROUND: Dyslipidemia is a well-known risk factor for the development of atherothrombosis; however, its involvement in venous thromboembolism (VTE) is still debated. Low levels of HDL cholesterol (HDL-C) have been found to be associated with VTE, which is a common complication of cancer and its treatment. VTE incidence is increased in cancer patients, especially those undergoing chemotherapy. OBJECTIVE: We sought to investigate the value of pretreatment HDL-C in the risk prediction of future VTE in a population of ambulatory cancer patients undergoing chemotherapy. PATIENTS AND METHODS: Blood lipid composition was retrospectively evaluated in 592 consecutive patients with primary (n = 373) or relapsing/recurrent (n = 219) solid cancers at the start of a new chemotherapy regimen (12% neoadjuvant, 31% adjuvant, 57% metastatic). RESULTS: VTE occurred during chemotherapy in 38 patients (median time-to-event: 3 months). Mean HDL-C levels were lower in patients who developed VTE during chemotherapy (41 mg dL(-1) ; standard deviation [SD] 13 mg dL(-1) ) than in those who did not (48 mg dL(-1) ; SD 14 mg dL(-1) ). Cox proportional hazard survival analysis showed that HDL-C levels ≤ 43 mg dL(-1) were able to significantly predict a first VTE episode, with a hazard ratio of 2.87 (95% confidence interval 1.45-5.68). Moreover, patients with HDL-C levels ≤ 43 mg dL(-1) had worse 1-year VTE-free survival (86%) than those with HDL-C levels > 43 mg dL(-1) (96%; log rank test, 3.14). CONCLUSIONS: Patients with low HDL-C levels have a three-fold higher risk of developing a first VTE episode during chemotherapy. Baseline analysis of HDL-C levels might be of clinical value in predicting VTE in cancer outpatients treated with anticancer drugs.
Subject(s)
Antineoplastic Agents/administration & dosage , Cholesterol, HDL/blood , Neoplasms/complications , Venous Thromboembolism/blood , Aged , Antineoplastic Agents/therapeutic use , Disease-Free Survival , Dyslipidemias/blood , Female , Humans , Incidence , Male , Middle Aged , Neoplasm Recurrence, Local , Neoplasms/blood , Neoplasms/drug therapy , Predictive Value of Tests , Proportional Hazards Models , Retrospective Studies , Risk Factors , Venous Thromboembolism/complicationsABSTRACT
Venous thromboembolism (VTE) is a frequent complication of lung cancer and its treatment, especially in the advanced stages of disease. The risk of a pro-thrombotic state might increase through the activation of hemostasis, occurring both via the induction of a pro-coagulant activity and with platelet involvement, ultimately leading to the development of metastases. Despite the acknowledgement of an increased thrombophilic condition in cancer patients, and the experimental evidence that heparin compounds may have direct anticancer benefits, there is no univocal consent regarding VTE prevention in cancer outpatients receiving therapy. Thus, many authors highlighted the need for the development of stratification techniques to identify at-risk patients who might benefit from thromboprophylaxis. Clinical risk models were developed and validated, in order to assign high-risk patients to a proper thromboprophylaxis regimen that, however, might not be justified in all clusters. Besides, efforts have been devoted to identify candidate biomarkers that may be used in VTE risk assessment, although none has been recognized, so far, as a predictor for VTE in lung cancer patients. In this review, we will summarize the latest information concerning this very controversial topic, with focus on some of the proposed strategies to select the appropriate patients for prophylaxis.
Subject(s)
Lung Neoplasms/complications , Venous Thromboembolism/diagnosis , Venous Thromboembolism/etiology , Anticoagulants/therapeutic use , Chemoprevention , Disease Progression , Hemostasis , Humans , Incidence , Lung Neoplasms/blood , Lung Neoplasms/drug therapy , Lung Neoplasms/pathology , Neoplasm Staging , Prognosis , Risk , Venous Thromboembolism/epidemiology , Venous Thromboembolism/prevention & controlABSTRACT
Visceral obesity is characterized by increased risk of cardiovascular disease as well as higher incidence of malignancies, including colorectal cancer (CRC), although the mechanisms linking excess adiposity with cancer are only partly characterized. Visceral obesity is currently acknowledged as a chronic inflammatory disorder and a growing body of evidence demonstrates the interconnections between obesity-related secretion pattern of adipo/cytokines and CRC. Specific molecules derived from the visceral adipose tissue (VAT), including adiponectin, leptin and resistin, are able to establish a positive feedback loop, thus increasing the proinflammatory and insulin resistant state and promoting tumorigenesis. Interestingly, these molecules have emerged as novel prognostic factors and therapeutic targets. This review will focus on current molecular and clinical evidence linking VAT-related inflammation to CRC initiation and progression, and summarize the role of dietary factors and lifestyle interventions aimed at promoting weight control and physical activity on CRC prevention and prognosis.
Subject(s)
Colorectal Neoplasms/etiology , Inflammation/etiology , Obesity/complications , Adipokines/metabolism , Colorectal Neoplasms/metabolism , Colorectal Neoplasms/mortality , Cytokines/metabolism , Humans , Inflammation/metabolism , Insulin Resistance , Intra-Abdominal Fat/metabolism , Vascular Diseases/etiology , Vascular Diseases/metabolismSubject(s)
Antineoplastic Combined Chemotherapy Protocols/adverse effects , Blood Coagulation Tests , Neoplasms/diagnosis , Thrombin/metabolism , Venous Thromboembolism/diagnosis , Aged , Antineoplastic Combined Chemotherapy Protocols/administration & dosage , Disease-Free Survival , Female , Follow-Up Studies , Humans , Male , Middle Aged , Neoplasms/complications , Neoplasms/drug therapy , Neoplasms/mortality , Neoplasms/physiopathology , Predictive Value of Tests , Protein C/metabolism , Sensitivity and Specificity , Venous Thromboembolism/etiology , Venous Thromboembolism/mortality , Venous Thromboembolism/physiopathology , Venous Thromboembolism/prevention & controlABSTRACT
BACKGROUND: Homocysteinemia has been associated with oncogenic risk. This study was designed to investigate the homocysteine (Hcy) genotype/phenotype interactions together with the inflammatory and nutritional status of cancer patients. PATIENTS AND METHODS: The Hcy levels were analyzed in 47 cancer patients in association with methylenetetrahydrofolate reductase (MTHFR) polymorphisms, folate and inflammatory markers. RESULTS: The MTHFR C677T and A1298C genotype distributions did not differ from those predicted by the Hardy-Weinberg distribution. Conversely, the Hcy levels were higher in the cancer patients (p=0.04), who were also characterized by low-grade inflammation. The Hcy levels correlated with the interleukin-6 (IL-6) (p=0.001), tumor necrosis factor-alpha (TNF-alpha) (p=0.042) and folate (p<0.0001) levels of the patients. Multivariate analysis showed that TNF-alpha (p=0.014) and folate (p=0.019) were independent predictors of elevated Hcy levels in the cancer patients. CONCLUSION: The MTHFR polymorphisms do not significantly contribute to tHcy (total Hcy) levels in cancer patients, and cancer-related inflammation may be associated with elevated tHcy levels, possibly involving a TNF-alpha mediated pathway.
Subject(s)
Breast Neoplasms/blood , Colorectal Neoplasms/blood , Homocysteine/blood , Adult , Breast Neoplasms/enzymology , Breast Neoplasms/genetics , Case-Control Studies , Colorectal Neoplasms/enzymology , Colorectal Neoplasms/genetics , Female , Folic Acid/blood , Humans , Inflammation Mediators/blood , Male , Methylenetetrahydrofolate Reductase (NADPH2)/genetics , Middle Aged , Nutritional Status , Polymorphism, Single NucleotideABSTRACT
BACKGROUND: Patients treated with aspirin may have a reduced sensitivity to its antiplatelet effect. The mechanism accounting for such a reduced sensitivity might involve an impaired interaction of aspirin with cyclooxygenase-1 (COX)-1. OBJECTIVE: We sought to investigate whether platelets from patients under chronic treatment with aspirin still produce TxA2 and whether there is any relationship between the eventual persistent TxA2 formation and platelet aggregation. Finally, whether platelet-derived TxA2 can be inhibited by in vitro addition of aspirin. METHODS: Collagen-induced platelet aggregation and thromboxane-A2 (TxA2) were measured in 196 patients treated with aspirin (100-330 mg day(-1)) because of previous vascular events or presence of risk factors of atherosclerosis. RESULTS: Collagen-induced TxA2 production of the entire cohort was 128.7 +/- 21.6 pg 10(-8) cells, and was significantly correlated with platelet aggregation (Spearman's correlation coefficient = 0.44; P < 0.0001). Patients in the highest quartile of TxA2 showed higher platelet response to collagen (P < 0.0001) when compared with those in the lowest quartile. In a subgroup of 96 patients, platelets were treated in vitro with a TxA2 receptor antagonist (13-azaprostanoic acid) or aspirin before stimulation with collagen. 13-APA acid significantly inhibited platelet aggregation. Aspirin reduced (-72.9%) TxA2 production in patients with TxA2 values above the median but it was ineffective in those with TxA2 values below the median. CONCLUSION: In some patients chronically treated with aspirin platelet production of TxA2 may persist and account for enhanced platelet aggregation. Incomplete inhibition of COX-1 seems to be implicated in persistent TxA2 production.
Subject(s)
Aspirin/pharmacology , Blood Platelets/metabolism , Drug Resistance , Thromboxane A2/biosynthesis , Aged , Aspirin/administration & dosage , Cardiovascular Diseases/blood , Cardiovascular Diseases/drug therapy , Collagen , Cyclooxygenase 1/drug effects , Dose-Response Relationship, Drug , Female , Humans , Male , Middle Aged , Platelet Aggregation/drug effects , Thromboxane A2/antagonists & inhibitors , Thromboxane A2/physiologySubject(s)
Endothelial Growth Factors/blood , Intercellular Signaling Peptides and Proteins/blood , Lymphokines/blood , Platelet Activation , Antithrombin III , Arteriosclerosis/etiology , Female , Humans , Male , P-Selectin/blood , Peptide Hydrolases/blood , Vascular Endothelial Growth Factor A , Vascular Endothelial Growth FactorsABSTRACT
Gangliosides are sialic acid-containing glycosphingolipids present in the outer leaflet of the plasma membrane of many cell types where they modulate adhesive processes. The main population of glycolipids in resting platelets is represented by ganglioside M3 (GM3). It has been demonstrated that following platelet activation ganglioside D3 (GD3) is rapidly formed from the GM3 pool. The present study was designed to evaluate the link between platelet activation and GD3 expression and to verify whether this ganglioside might play a role in modulating signal transduction events. Our results suggest that following platelet activation, GD3 is rapidly expressed on the platelet surface and internalised to the cytoskeleton where it transiently associates first with the Src family tyrosine kinase Lyn then with the Fc receptor gamma chain. This sequence of events ultimately leads to an enhanced CD32 (the Fc receptor isoform present in platelets) expression on the platelet membrane. These data drive us to speculate that GD3 might act as second messenger in the activatory cascade, which leads to CD32 expression and triggers platelet adhesion and spreading to the subendothelial matrix.
Subject(s)
Blood Platelets/metabolism , Gangliosides/metabolism , Platelet Activation , Receptors, IgG/metabolism , Adenosine Diphosphate/pharmacology , Arachidonic Acid/metabolism , Arachidonic Acid/pharmacology , Arachidonic Acids/pharmacology , Blood Platelets/drug effects , Blotting, Western , Cells, Cultured , Collagen/pharmacology , Cytoskeleton/drug effects , Cytoskeleton/metabolism , Enzyme Inhibitors/pharmacology , Gangliosides/immunology , Gangliosides/pharmacology , Humans , Phospholipases A/antagonists & inhibitors , Phospholipases A/metabolism , Receptors, IgG/drug effects , src-Family Kinases/drug effects , src-Family Kinases/metabolismABSTRACT
We studied the effect of nickel ions on platelet function because hypernickelemia has been found in patients with acute myocardial infarction. We previously demonstrated that nickel can activate an intracellular pathway leading to cytoskeleton reorganization consequent to tyrosine phosphorylation of p60(src) in human platelets independently of integrin alpha-IIb-beta(3). Moreover, in von Willebrand factor-stimulated platelets, the tyrosine phosphorylation of pp60(c-src) is closely associated with the activation of phosphatidylinositol 3-kinase (PIK), and two adhesion receptors, glycoprotein (Gp)Ib and GpIIb/IIIa(alpha-IIb-beta(3)), are involved. In our study, 1 and 5 mM nickel in the presence of fibrinogen induced platelet aggregation (independently of protein kinase C activation) and secretion. The pretreatment with a PIK inhibitor, wortmannin, strongly decreased nickel-induced platelet aggregation. Platelet treatment with mocarhagin, a cobra venom metalloproteinase that cleaves GpIba, significantly reduced aggregation induced by 5 mM without affecting the response to other agonists such as adenosine diphosphate (ADP). Moreover, nickel caused PIK translocation to the cytoskeleton. Taken together, these observations suggest a partial involvement of both integrins alpha-IIb-beta(3) and GpIb-V-IX complex in Ni(2+)-induced platelet activation.
Subject(s)
Environmental Pollutants/pharmacology , Nickel/pharmacology , Platelet Activation/drug effects , Platelet Glycoprotein GPIb-IX Complex/drug effects , Platelet Membrane Glycoproteins , Cytoskeleton/drug effects , Cytoskeleton/physiology , Humans , Immunoblotting , Myocardial Infarction/etiology , Occupational Exposure/adverse effectsABSTRACT
Cyclic nucleotides, such as cAMP, are known to inhibit the multistep cascade that results in platelet aggregation. In the present study we provide evidence that it is possible to bypass cAMP inhibitory effect on fibrinogen binding site exposure induced by the thromboxane A2 synthetic analogue U46619, the snake venom toxin convulxin, or by the direct PKC activator OAG, by concomitantly activating a G1-coupled receptor by means of epinephrine or by inducing cytosolic calcium influx by means of ionomycin. In fact, in our study we demonstrate that, in iloprost-treated platelets, the inhibition of both platelet aggregation and fibrinogen binding was overcome by adding epinephrine or ionomycin. To further confirm this, we used the cAMP analogue dibutyryl cAMP and we obtained platelet aggregation in response to U46619, convulxin or OAG plus epinephrine. Moreover, a complete inhibition of platelet aggregation in the presence of high concentrations of cAMP was observed only in the case of U46619, while a small percentage of aggregation persisted when convulxin or OAG were used, due to the small amount of ADP that both convulxin and OAG are able to release. Since PKC inhibition didn't allow platelet aggregation to occur in response to the concomitant activation of U46619 or convulxin, plus epinephrine or ionomycin, we can conclude that cAMP-induced inhibition of aggregation can be counteracted by the simultaneous activation of PKC in the presence of an activated G1-coupled receptor or of an induced calcium influx.
Subject(s)
Cyclic AMP/metabolism , Lectins, C-Type , Platelet Activation/drug effects , Platelet Glycoprotein GPIIb-IIIa Complex/metabolism , 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid/pharmacology , Blood Platelets/cytology , Blood Platelets/drug effects , Crotalid Venoms/pharmacology , Cyclic AMP/pharmacology , Cytosol/chemistry , Diglycerides/pharmacology , Epinephrine/pharmacology , Fibrinogen/metabolism , GTP-Binding Protein alpha Subunits, Gi-Go/metabolism , Humans , Iloprost/pharmacology , Platelet Aggregation/drug effects , Platelet Aggregation Inhibitors/pharmacologyABSTRACT
OBJECTIVE: To investigate if markers of exposure to foodborne and orofecal microbes versus airborne viruses are associated with atopy and respiratory allergies. DESIGN: Retrospective case-control study. PARTICIPANTS: 240 atopic cases and 240 non-atopic controls from a population sample of 1659 participants, all Italian male cadets aged 17-24. SETTING: Air force school in Caserta, Italy. MAIN OUTCOME MEASURES: Serology for Toxoplasma gondii, Helicobacter pylori, hepatitis A virus, measles, mumps, rubella, chickenpox, cytomegalovirus, and herpes simplex virus type 1; skin sensitisation and IgE antibodies to relevant airborne allergens; total IgE concentration; and diagnosis of allergic asthma or rhinitis. RESULTS: Compared with controls there was a lower prevalence of T gondii (26% v 18%, P=0.027), hepatitis A virus (30% v 16%, P=0.004), and H pylori (18% v 15%, P=0.325) in atopic participants. Adjusted odds ratios of atopy decreased with a gradient of exposure to H pylori, T gondii, and hepatitis A virus (none, odds ratio 1; one, 0. 70; two or three, 0.37; P for trend=0.000045) but not with cumulative exposure to the other viruses. Conversely, total IgE concentration was not independently associated with any infection. Allergic asthma was rare (1/245, 0.4%) and allergic rhinitis infrequent (16/245, 7%) among the participants (245/1659) exposed to at least two orofecal and foodborne infections (H pylori, T gondii, hepatitis A virus). CONCLUSION: Respiratory allergy is less frequent in people heavily exposed to orofecal and foodborne microbes. Hygiene and a westernised, semisterile diet may facilitate atopy by influencing the overall pattern of commensals and pathogens that stimulate the gut associated lymphoid tissue thus contributing to the epidemic of allergic asthma and rhinitis in developed countries.
Subject(s)
Air Microbiology , Asthma/microbiology , Feces/microbiology , Food Microbiology , Mouth/microbiology , Respiratory Hypersensitivity/microbiology , Adolescent , Adult , Animals , Asthma/epidemiology , Asthma/parasitology , Case-Control Studies , Feces/parasitology , Humans , Hygiene , Immunoglobulin E/analysis , Italy/epidemiology , Male , Mouth/parasitology , Respiratory Hypersensitivity/epidemiology , Respiratory Hypersensitivity/parasitology , Retrospective Studies , ToxoplasmaABSTRACT
It has recently been suggested that the concomitant activation of two distinct G protein-coupled receptors (G(i) and G(q)) is essential for platelet aggregation: in fact, the thromboxane A2 synthetic agonist, U46619, which causes the selective activation of Gq, is not able to elicit fibrinogen receptor exposure unless ADP or epinephrine is present. In the present study we demonstrate that a direct Gq activation is not required for platelet aggregation and that the activation of an enzyme downstream of Gq, such as phospholipase C (PLC) or protein-kinase C (PKC), is sufficient for such a process. In fact, platelet aggregation occurred in response to the snake venom toxin convulxin, which activates the PLC isoform PLCgamma2 or to cytosolic PKC activator phorbol 12-myristate 13-acetate (PMA) provided a Gi protein-coupled receptor was activated by ADP or epinephrine. The evidence that the PKC inhibitor, Ro 31-8220 did not suppress platelet aggregation in response to convulxin plus ADP or epinephrine led us to conclude that PLC and PKC are both involved in platelet aggregation, although not concomitantly, provided a Gi protein-coupled receptor is activated.
Subject(s)
GTP-Binding Proteins/metabolism , Lectins, C-Type , Platelet Aggregation , Protein Kinase C/metabolism , Type C Phospholipases/metabolism , Adenosine Diphosphate/pharmacology , Aspirin/pharmacology , Chelating Agents/pharmacology , Crotalid Venoms/pharmacology , Egtazic Acid/analogs & derivatives , Egtazic Acid/pharmacology , Enzyme Activation , Epinephrine/pharmacology , Humans , Indoles/pharmacology , Platelet Aggregation Inhibitors/pharmacology , Tetradecanoylphorbol Acetate/pharmacologyABSTRACT
OBJECTIVE: Patients with hypertension tend to have a high prevalence of atherothrombotic accidents. Platelet hyperactivity is frequently associated with hypertension. Because the vascular disease associated with hypertension evolves over the years, we investigated platelet activity parameters in a population of older hypertensive patients with no other risk factors for cardiovascular disease. PARTICIPANTS: We studied 34 older, nonsmoking patients (mean age 74 +/- 5 years) with uncomplicated hypertension before and after the normalization of blood pressure (BP) was achieved with the angiotensin-converting enzyme inhibitor quinapril alone or in combination with the Ca2+ antagonist nifedipine. MEASUREMENTS: Platelet aggregation, P-selectin (CD62) expression on the platelet surface, serum levels of Interleukin-1beta (IL-1beta) and of Interleukin-6 (IL-6), as well as plasma levels of soluble P-selectin and Endothelin-1 (ET-1), were analyzed. RESULTS: All platelet hyperactivity parameters were reduced significantly with the normalization of BP at the end of antihypertensive drug treatment (systolic/diastolic: 186.2 +/- 2.7/103.4 +/- 1.1 mm Hg vs 135.0 +/- 1.3/85.9 +/- 1.9 mm Hg; P < .001). Those factors more strictly associated with endothelium injury, such as ET-1 and IL-6, did not show variations. A significant correlation (Spearman Rank test) was observed among all platelet function parameters and blood pressure values. CONCLUSIONS: This study demonstrated that even in a population of older hypertensive patients with no other risk factor for atherogenic disease, normalization of blood pressure induces a significant reduction of the parameters of enhanced platelet hyperactivity independent of the action exerted, at the platelet level, by the antihypertensive drugs.
Subject(s)
Antihypertensive Agents/therapeutic use , Blood Pressure/drug effects , Hypertension/physiopathology , Platelet Activation/physiology , Tetrahydroisoquinolines , Aged , Angiotensin-Converting Enzyme Inhibitors/therapeutic use , Arteriosclerosis/etiology , Blood Pressure/physiology , Calcium Channel Blockers/therapeutic use , Endothelin-1/blood , Female , Humans , Hypertension/complications , Hypertension/drug therapy , Interleukin-1/blood , Interleukin-6/blood , Isoquinolines/therapeutic use , Male , Nifedipine/therapeutic use , P-Selectin/blood , Platelet Activation/drug effects , Platelet Aggregation/drug effects , Platelet Aggregation/physiology , Prevalence , Prodrugs/therapeutic use , QuinaprilABSTRACT
U46619 is a potent platelet agonist, its binding to the thromboxane A2 receptor resulting in Gq-binding protein-mediated responses; nevertheless, it is unable to cause platelet aggregation, unless released ADP is present. In this study we demonstrate that Gi activation is the step U46619 lacks to cause platelet aggregation; in fact, when platelets were treated with an ADP scavenger system, the response to U46619 was restored by the addition of epinephrine, which activates platelets via a Gi protein. The concomitant activation of Gi and Gq proteins does not require increased cytosolic calcium to cause aggregation, as assessed by the fact that platelets treated with the intracellular calcium chelator BAPTA were able to respond to U46619 provided ADP or epinephrine was present. Moreover, as the calcium ionophore ionomycin, at low concentrations, potentiated the response to U46619 but not to epinephrine, we may conclude that calcium influx preferentially activates a Gi downstream signalling pathway.
Subject(s)
Calcium/physiology , Cytosol/metabolism , GTP-Binding Protein alpha Subunits, Gi-Go/blood , Platelet Aggregation , Receptors, Purinergic P2/blood , Adenosine Diphosphate/physiology , Calcium/blood , Chelating Agents/pharmacology , Egtazic Acid/analogs & derivatives , Egtazic Acid/pharmacology , GTP-Binding Proteins/blood , Humans , Platelet Activation/drug effects , Platelet Aggregation/drug effects , Receptors, Purinergic P2Y1ABSTRACT
It has been previously suggested that tyrosine phosphorylation of p62, p68, and p130 might be necessary for the platelet shape change to occur. In preliminary studies we observed that high concentrations (30 microM) of a protein kinase C inhibitor, Ro 31-8220, selectively suppressed p130 tyrosine phosphorylation induced by thrombin, the thromboxane synthetic analogue (U46619) and ADP. Therefore, we have investigated the correlation, if any, between p130 tyrosine phosphorylation and platelet shape change induced by the same agonists in the presence of Ro 31-8220. Our results demonstrated that high concentrations of this compound almost completely abolished p130 tyrosine phosphorylation, whereas they had no effect on platelet shape change, thus proving a dissociation between these two phenomena. Our data support the hypothesis that a role in platelet shape change might be played by tyrosine phosphorylation of proteins other than p130.
Subject(s)
Blood Platelets/cytology , Blood Platelets/physiology , Blood Proteins/physiology , Proteins , Cell Size/physiology , Crk-Associated Substrate Protein , Humans , Phosphorylation , Retinoblastoma-Like Protein p130 , Signal Transduction , TyrosineABSTRACT
In a suspension of thrombin degranulated platelets (TDP), ADP and epinephrine can induce platelet aggregation, whereas the synthetic agonist of the thromboxane/endoperoxide receptor U46619 causes only shape change. However, U46619 can enhance platelet aggregation induced by ADP and epinephrine. In this paper, we have measured fibrinogen binding in relation to phospholipase C (PLC) activation and calcium mobilization in TDP activates by ADP, epinephrine and U46619. ADP caused fibrinogen binding in TDP but neither activated PLC nor caused a calcium mobilization. The requirement for ADP in inducing exposure of fibrinogen binding sites was not absolute since the combination of epinephrine and U46619 produced an increase in fibrinogen binding. U46619 caused significant PLC activation and cytosolic calcium release but not fibrinogen binding. These results suggest that in TDP the exposure of fibrinogen binding sites, after agonist activation, is independent of both PLC activation and calcium mobilization.