Inhibition of phosphorylation of troponin I in rat heart by adenosine and 5'-chloro-5'-deoxyadenosine

Rare Clinical Symptoms in Hairy Cell Leukemia: An Overview

BACKGROUND

Hairy cell leukemia (HCL) is a rare indolent B-cell lymphoid malignancy. The majority of patients are asymptomatic and HCL is usually diagnosed incidentally during a routine blood cell count. In symptomatic patients, typical symptoms are related to pancytopenia and splenomegaly. In this review, we present rare clinical symptoms in patients with HCL.

METHODS

A literature search was conducted of PubMed, Web of Science and Google Scholar for articles concerning hairy cell leukemia, leukemia cutis, bone lesions, neurological manifestations, pulmonary symptoms, ocular manifestations, cardiac manifestation and rare symptoms. Publications from January 1980 to August 2024 were scrutinized. Additional relevant publications were obtained by reviewing the references from the chosen articles.

RESULTS

Extramedullary and extranodal manifestations of classic HCL are rare. However, leukemic involvement in the skin, bone, central nervous system, gastrointestinal tract, heart, kidney, liver, lung, ocular system and other organs have been reported.

Insuffisances cardiaques d’origine médicamenteuse (en dehors des anthracyclines)

The principal drugs implicated in or disclosing cardiac insufficiency are drawn from a review of the literature and observations by the French national pharmacovigilance database, from 1984 to April 2003. Several pharmacological classes are identified: in addition to antimitotic drugs, such as anthracyclines, many drugs are implicated in cardiac insufficiency, e.g. immunomodulators, anti-inflammatory drugs (including coxibs), antiarrhythmic drugs, anaesthetic drugs, antipsychotic drugs, and antidiabetic drugs (including glitazones). It is usual to classify these drugs according to three categories: (i) drugs likely to cause cardiac insufficiency de novo (such as cyclophosphamide, paclitaxel, mitoxantrone, interferons, interleukin-2 etc.); (ii) drugs likely to worsen preexisting cardiac insufficiency (such as antiarrhythmics, beta-blockers, calcium antagonists, nonsteroidal and steroidal anti-inflammatory drugs, sympathomimetic drugs etc.); and (iii) drugs only occasionally causing cardiac insufficiency. This review shows that this classification is, in fact, artificial. If cardiac toxicity is a constant concern when using antimitotic drugs or some immunomodulator drugs, it is advisable to exercise caution in the use of many other drugs when treating patients with cardiac insufficiency, even if the clinical situation is well controlled. In particular, drug-drug interactions and patient medical history must be taken into account.

Intracellular localization and functional effects of P21-activated kinase-1 (Pak1) in cardiac myocytes

We investigated intracellular localization and substrate specificity of P21-activated kinase-1 (Pak1) in rat cardiac myocytes. Pak1 is a serine/threonine protein kinase that is activated by Rac1/Cdc42 and important in signaling of stress responses. Yet the localization and in vivo function of Pak1 in heart cells is poorly understood. Studies reported here indicate that Pak1 physically interacts with protein phosphatase 2a and localizes to the Z-disk, cell membrane, intercalated disc, and nuclear membrane of adult rat heart myocytes. We compared levels of phosphorylation of cardiac troponin I (cTnI) in control myocytes with phosphorylation of cTnI and myosin binding protein C (C-protein) in myocytes with increased Pak1 activity. The increase in activity was induced by infection of myocytes with a recombinant adenovirus (AdPak1) containing cDNA for a constitutively active Pak1. Control cells were infected with a virus (AdLacZ) containing LacZ. Basal levels of phosphorylation of cTnI and C-protein were relatively high in the myocytes infected with AdLacZ. However, phosphorylation of cTnI and C-protein in cells expressing constitutively active Pak1 was significantly reduced compared with those expressing LacZ. Measurement of Ca2+ tension relations in single myocytes demonstrated that this reduction in phosphorylation of cTnI and C-protein was associated with the predicted increase in sensitivity to Ca2+. Our data provide evidence for a novel pathway of phosphatase regulation in cardiac myocytes.

Special sensitization pattern in adenosine-induced myocardial responses after thyroxine-treatment

Chronic thyroxine treatment reduces the susceptibility of atrial myocardium to adenosine. While the possible role of membrane adenosine receptors in this action is supported by several studies, the involvement of intracellular adenosine mechanisms has not been defined. The present experiments were carried out in electrically driven euthyroid and hyperthyroid guinea pig atrial myocardium. The extracellular and intracellular actions of adenosine were analyzed pharmacologically by the use of specific blockers of membrane adenosine transport and intracellular adenosine deaminase (ADA). The involvement of phosphoprotein phosphatase, phospholamban, and sarcoplasmic reticulum Ca2+ ATPase (SERCA) in the adenosine-induced responses was also studied. The major findings were as follows: i) pD(2)- and E(max)-values for adenosine-induced decrease of mechanical activity were significantly reduced after an 8-day thyroxine treatment in atrial tissues; ii) in atria of thyroxine-treated animals, membrane purine transport inhibitors (dipyridamole, NBTI) induced similar leftward shifts in concentration-response curves for adenosine in both euthyroid and hyperthyroid atrial myocardium without altering the depressed E(max) values; iii) the leftward displacement evoked by inhibitors of intracellularly located ADA (coformycin, EHNA) was more striking in hyperthyroid than euthyroid myocardia. ADA inhibitors induced a complete reversal of the maximum adenosine actions; iv) inhibition by cantharidin of phosphoprotein phosphatases (after inhibition of ADA) reduced the adenosine-induced responses. This inhibition was stronger in hyperthyroid atria; v) pharmacological elimination of sarcoplasmic reticulum Ca2+ ATPase by cyclopiazonic acid did not alter the cardiac responses to adenosine and this was independent of thyroid status. It is suggested that distinct modulation of the extra- and intracellular adenosine actions is present in eu- and hyperthyroid hearts. In the latter, a predominance of intracellular adenosine mechanisms can be proposed.

Cardiotoxicity of chemotherapeutic agents: incidence, treatment and prevention

Cytostatic antibiotics of the anthracycline class are the best known of the chemotherapeutic agents that cause cardiotoxicity. Alkylating agents such as cyclophosphamide, ifosfamide, cisplatin, carmustine, busulfan, chlormethine and mitomycin have also been associated with cardiotoxicity. Other agents that may induce a cardiac event include paclitaxel, etoposide, teniposide, the vinca alkaloids, fluorouracil, cytarabine, amsacrine, cladribine, asparaginase, tretinoin and pentostatin. Cardiotoxicity is rare with some agents, but may occur in >20% of patients treated with doxorubicin, daunorubicin or fluorouracil. Cardiac events may include mild blood pressure changes, thrombosis, electrocardiographic changes, arrhythmias, myocarditis, pericarditis, myocardial infarction, cardiomyopathy, cardiac failure (left ventricular failure) and congestive heart failure. These may occur during or shortly after treatment, within days or weeks after treatment, or may not be apparent until months, and sometimes years, after completion of chemotherapy. A number of risk factors may predispose a patient to cardiotoxicity. These are: cumulative dose (anthracyclines, mitomycin); total dose administered during a day or a course (cyclophosphamide, ifosfamide, carmustine, fluorouracil, cytarabine); rate of administration (anthracyclines, fluorouracil); schedule of administration (anthracyclines); mediastinal radiation; age; female gender; concurrent administration of cardiotoxic agents; prior anthracycline chemotherapy; history of or pre-existing cardiovascular disorders; and electrolyte imbalances such as hypokalaemia and hypomagnesaemia. The potential for cardiotoxicity should be recognised before therapy is initiated. Patients should be screened for risk factors, and an attempt to modify them should be made. Monitoring for cardiac events and their treatment will usually depend on the signs and symptoms anticipated and exhibited. Patients may be asymptomatic, with the only manifestation being electrocardiographic changes. Continuous cardiac monitoring, baseline and regular electrocardiographic and echocardiographic studies, radionuclide angiography and measurement of serum electrolytes and cardiac enzymes may be considered in patients with risk factors or those with a history of cardiotoxicity. Treatment of most cardiac events induced by chemotherapy is symptomatic. Agents that can be used prophylactically are few, although dexrazoxane, a cardioprotective agent specific for anthracycline chemotherapy, has been approved by the US Food and Drug Administration. Cardiotoxicity can be prevented by screening and modifying risk factors, aggressively monitoring for signs and symptoms as chemotherapy is administered, and continuing follow-up after completion of a course or the entire treatment. Prompt measures such as discontinuation or modification of chemotherapy or use of appropriate drug therapy should be initiated on the basis of changes in monitoring parameters before the patient exhibits signs and symptoms of cardiotoxicity.

Cardiac protein phosphorylation: functional and pathophysiological correlates

Protein phosphorylation acts a pivotal mechanism in regulating the contractile state of the heart by modulating particular levels of autonomic control on cardiac force/length relationships. Early studies of changes in cardiac protein phosphorylation focused on key components of the excitation-coupling process, namely phospholamban of the sarcoplasmic reticulum and myofibrillar troponin I. In more recent years the emphasis has shifted towards the identification of other phosphoproteins, and more importantly, the delineation of the mechanistic and signaling pathways regulating the various known phosphoproteins. In addition to cAMP- and Ca(2+)-calmodulin-dependent kinase processes, these have included regulation by protein kinase C and the ever-emerging family of growth factor-related kinases such as the tyrosine-, mitogen- and stress-activated protein kinases. Similarly, the role of protein dephosphorylation by protein phosphatases has been recognized as integral in modulating normal cardiac cellular function. Recent studies involving a variety of cardiovascular pathologies have demonstrated that changes in the phosphorylation states of key cardiac regulatory proteins may underlie cardiac dysfunction in disease states. The emphasis of this comprehensive review will be on discussing the role of cardiac phosphoproteins in regulating myocardial function and pathophysiology based not only on in vitro data, but more importantly, from ex vivo experiments with corroborative physiological and biochemical evidence.

The development of congestive cardiac failure in a patient with hairy cell leukemia treated with 2-chlorodeoxyadenosine

Deoxyadenosines are closely related to adenosine and as such, may interfere with the cardiac adenylate cyclase pathway resulting in cardiac dysfunction. We report a rare case of a 42 year old man who developed transient cardiac failure following treatment with 2-CDA for hairy cell leukemia.

Characterization of a novel adenosine binding protein sensitive to cyclic AMP in rat brain cytosolic and particulate fractions

A novel binding site for the adenosine receptor agonist 5'-N-ethylcarboxamidoadenosine (NECA), which was enriched in rat forebrain, was characterized in cytosolic and particulate preparations. The site showed a pharmacological profile different from other [3H]NECA binding proteins and was named adenotin 2. [3H]NECA was bound in the presence of 100 microM 2-chloroadenosine with a Kd of 45.4 nM and a Bmax of 4711 fmol/mg in the cytosol and a Kd of 72.4 nM and a Bmax of 4844 fmol/mg in the crude membrane fraction. The presence of two different binding sites on adenotin 2 for [3H]NECA was shown in kinetic experiments. This protein showed identical pharmacological profiles in both subcellular preparations. [3H]NECA was displaced by purine analogues with a rank order of potency of NECA > 3'5' cyclic AMP (cAMP) > 5'-deoxy-5'-chloroadenosine > S-adenosylhomocysteine approximately 5'-deoxy-5'-methylthioadenosine (MeSA) > adenosine approximately adenine. cAMP inhibited [3H]NECA binding allosterically, whereas adenine and MeSA acted competitively. Inhibitors and activators of protein kinases such as N-(2-aminoethyl)-5-isoquinolinesulfonamide, Sp-adenosine cyclic monophophothioate and (8R*, 9S*, 11S*)-(-)-9-hydroxy-9-methoxy -carbonyl-8-methyl-2,3,9, 10-tetrahydro-8,11-epoxy-1H, 8H, 11H-2, 7b, 11a-triazadibenzo-(a,g)cycloocta(cde)-trinden-1-one (K 252a) interacted with [3H]NECA binding to adenotin 2 in nanomolar concentrations. Adenosine-5'-O-(3-thiotriphosphate) (100 microM) increased the affinity of [3H]NECA to a Kd of 9 nM and diminished the affinity of cAMP. The pharmacological characteristics of this novel binding site for [3H]NECA resemble those of the inhibition of phosphorylation processes by adenosine and its derivatives in heart and smooth muscle but are distinct from known adenosine receptors, adenosine binding proteins and protein kinases.