RESUMO
To investigate the possibility that cell contact could initiate a series of signals in both the host cell and the flagellate protozoan Trypanosoma cruzi, we studied [32P]-phospholipid turnover during parasite interaction with cellular membranes in vitro. Lipid alterations were produced in the parasite during the initial period of contact with the plasma membranes of human erythrocytes. In the presence of calcium an increment in phosphatidylethanolamine was observed with a concomitant decrease in phosphatidic acid fractions, whereas these modifications were not observed in the absence of calcium. There was an evident decrease in phosphatidylcholine and a shift in the phosphatidylinositol/lysophosphatidylethanolamine fraction among the phospholipids of major turnover in the absence or presence of calcium. Among the minor labeled species, lysophosphatidylcholine reached levels that duplicated control values, whereas the amounts of lysophosphatidylinositol, phosphatidylinositol 4-phosphate, and phosphatidylinositol 4,5-bisphosphate diminished by over 50%. All of these variations indicate that the parasite's contact with plasma membranes induces changes involving T. cruzi phospholipids and suggest the participation of these compounds in the activation of intracellular mechanisms that might be important during the life cycle of this parasite.
Assuntos
Membrana Eritrocítica/parasitologia , Fosfolipídeos/metabolismo , Trypanosoma cruzi/metabolismo , Animais , Adesão Celular , Humanos , Ácidos Fosfatídicos/metabolismo , Fosfatidilcolinas/metabolismo , Fosfatidiletanolaminas/metabolismo , Fosfatidilinositóis/metabolismo , Transdução de SinaisRESUMO
In a previous work, our group reported that Albino Swiss male mice inoculated with T. cruzi to develop acute lethal infection by day 15 decreased parasitemia and survived when treated with total brain gangliosides (GT; 1 mg, daily). In this paper, GT were replaced by GM1 in 0.1 mg dose that caused diminished parasitemia from day 15 to 30 and survival of 80% by day 120 p.i. Treatment with GT 0.15 mg was ineffective. This indicates that GT effect was due to GM1 and that more sialyl residues on the same lipid moiety produces adverse results. GM1 was compared to other sialylated molecules: fetuine and colominic acid. Both of them increased parasitemias and death by day 16 p.i., suggesting that sialic residues favor parasite replication. Asialo-GM1 (0.1 mg daily) was also adverse. This pointed to GM1 not to other ganglioside or sphingolipid or sialoprotein as the active agent. Gangliosides are [Ca+2]i modulators, so GM1 was compared to nifedipine which blocks calcium channels only in the host. Nifedipine treated mice behaved as controls. It is proposed that if GM1 calcium modulation is involved it must be on the parasite rather than on the host. Electrocardiographic (ECG) records show that while infected mice die with bradycardia, treated mice survive and recover normal frequency. Uninfected treated mice showed no electrocardiographic alterations.
Assuntos
Cardiomiopatia Chagásica/tratamento farmacológico , Doença de Chagas/tratamento farmacológico , Gangliosídeo G(M1)/uso terapêutico , Coração/fisiologia , Animais , Bloqueadores dos Canais de Cálcio/farmacologia , Bloqueadores dos Canais de Cálcio/uso terapêutico , Cardiomiopatia Chagásica/parasitologia , Cardiomiopatia Chagásica/fisiopatologia , Doença de Chagas/parasitologia , Doença de Chagas/fisiopatologia , Eletrocardiografia , Gangliosídeo G(M1)/administração & dosagem , Gangliosídeo G(M1)/química , Gangliosídeo G(M1)/farmacologia , Coração/parasitologia , Masculino , Camundongos , Nifedipino/farmacologia , Nifedipino/uso terapêutico , Parasitemia/tratamento farmacológico , Parasitemia/parasitologiaRESUMO
Ganglioside treatment of mice during their acute infection with Trypanosoma cruzi promoted long-term survival and clearance of parasites from the bloodstream and organs. Additionally, such treatment completely prevented the clinical manifestations of the infection, and progression into the chronic stages of the disease, for at least 18 months post-infection. Trypanosoma cruzi must invade nucleated cells to survive and reproduce within the mammalian host, and it has been suggested that ganglioside treatment inhibits the parasite's phospholipase A2 enzymes (PLA2), which are involved in membrane destabilization. However, since total brain gangliosides were not toxic to the parasite, either in xenic or axenic cultures, it seems unlikely that their action in vivo relates to their inhibition of PLA2. Other possible mechanisms of action are discussed.
Assuntos
Doença de Chagas/tratamento farmacológico , Gangliosídeos/uso terapêutico , Doença Aguda , Animais , Técnicas de Cultura de Células , Doença de Chagas/patologia , Camundongos , Miocárdio/patologia , Parasitemia/tratamento farmacológico , Reação em Cadeia da Polimerase , Taxa de Sobrevida , Trypanosoma cruzi/efeitos dos fármacos , Trypanosoma cruzi/crescimento & desenvolvimentoRESUMO
Vitamin D deficiency affects the lipid composition and Ca2+ uptake of intestinal basolateral membranes from chick intestine. The increased cholesterol content causes an increase in the molar ratio cholesterol/phospholipid. Phospholipid classes remain unchanged, but the percentages of arachidonic acid from the from the major phospholipid fractions are increased. After 24 hours of oral administration of 2,000 IU of cholecalciferol to vitamin D-deficient chicks, the cholesterol values do not change, but the amount of arachidonic acid returns to normal values. Ca2+ uptake driven by ATP is diminished in vesicles from intestinal basolateral membranes of vitamin D-deficient chicks. Cholecalciferol treatment returns these values to the controls which might be due mainly to the increased number of Ca2+ pump units. In conclusion, changes in lipid composition and in Ca2+ pump caused by vitamin D deficiency seems to play a role in the decrease of vesicular Ca2+ transport. A single dose of cholecalciferol restores only partially the lipid-protein changes produced by vitamin D deficiency.
Assuntos
Cálcio/metabolismo , Membrana Celular/metabolismo , Mucosa Intestinal/metabolismo , Lipídeos/química , Deficiência de Vitamina D/metabolismo , Trifosfato de Adenosina/metabolismo , Animais , Transporte Biológico , Cálcio/farmacocinética , Membrana Celular/química , Membrana Celular/efeitos dos fármacos , Galinhas , Colecalciferol/farmacologia , Colesterol/metabolismo , Duodeno/efeitos dos fármacos , Duodeno/metabolismo , Ácidos Graxos/análise , Ácidos Graxos/metabolismo , Intestinos/efeitos dos fármacos , Metabolismo dos Lipídeos , Fosfatidilinositóis/análise , Fosfatidilinositóis/metabolismo , Deficiência de Vitamina D/tratamento farmacológicoRESUMO
The ability of Trypanosoma cruzi to induce erythrocyte membrane destabilization in vitro was studied. Epimastigote forms adhered to human erythrocytes and caused fusion or lysis of the red cells, depending on the conditions of the interaction. Red cells were fused in the presence of calcium, while haemolysis was induced in the absence of the cation. Dextran 60 C facilitated fusion but delayed lysis. Optimum pH and temperature for fusion were 7.4 and 37 degrees C, respectively. Lipid alterations were produced in the plasma membrane of the red cell during the interaction with the parasite. A Ca(2+)-independent increase of lysophospholipids and free fatty acids was common to both the lysis and fusion processes. A relative increase of 1,2-diacylglycerides was unique to the fusion process and these changes were dependent on Ca2+. The transfer of free fatty acids and lysophospholipids from T. cruzi to erythrocyte membranes was demonstrated using parasites pre-labelled with radioactive phospholipids. Pre-treatment of parasites with exogenous phospholipase A2 abolished the fusogenicity, while lysis was increased. Neither fusion nor haemolysis occurred when the parasites were pre-treated with fatty acid free albumin, phospholipase A2 inhibitors or when these compounds were present in the medium during the parasite-erythrocyte interaction. Our results suggest that T. cruzi induces erythrocyte membrane destabilization in vitro by transfer of lipid material in a calcium independent manner and that this ion is necessary for other membrane alterations that lead to erythrocyte fusion.
Assuntos
Membrana Eritrocítica/metabolismo , Eritrócitos/parasitologia , Fusão de Membrana , Lipídeos de Membrana/metabolismo , Trypanosoma cruzi/fisiologia , Animais , Cálcio/farmacologia , Fusão Celular/efeitos dos fármacos , Crithidia fasciculata/fisiologia , Ácido Edético/farmacologia , Membrana Eritrocítica/efeitos dos fármacos , Membrana Eritrocítica/ultraestrutura , Eritrócitos/citologia , Eritrócitos/ultraestrutura , Ácidos Graxos não Esterificados/metabolismo , Humanos , Concentração de Íons de Hidrogênio , Leishmania/fisiologia , Lisofosfolipídeos/metabolismo , Magnésio/farmacologia , Fusão de Membrana/efeitos dos fármacos , Temperatura , Fatores de TempoRESUMO
Albino Swiss male mice were inoculated with Trypanosoma cruzi, Tulahuen strain trypomastigotes, and separated into three groups: control, without treatment; control, treated with Nifurtimox 25 mg/day; and experimental, treated with total brain gangliosides 1 mg/day, intramuscular. The treatment was started immediately after infection and maintained for 4 weeks. Parasitemia was determined twice a week and histopathological analyses of hearts were performed. The parasitemia was significantly lowered by the ganglioside treatment. All untreated mice died by day 14 post infection. Survival at day 30 was 96% for mice in the experimental group. Hearts from untreated animals showed acute chagasic myocarditis, while those from mice treated with gangliosides presented only minor mononuclear infiltration. The effect of gangliosides is probably due to interference of parasite penetration into the host cells.
Assuntos
Doença de Chagas/tratamento farmacológico , Gangliosídeos/uso terapêutico , Animais , Doença de Chagas/patologia , Modelos Animais de Doenças , Masculino , Camundongos , Miocárdio/patologia , Trypanosoma cruzi/efeitos dos fármacosRESUMO
Human erythrocytes were fused by Trypanosoma cruzi from 7 and 14 day old culture (stationary and declination phases, respectively) while only lysis was induced by 4 day old culture parasite (exponential phase). Lysis and erythrocyte fusion were studied by phase contrast microscopy, measuring of hemolysis and gel electrophoresis. The fusogenicity is Ca2+-dependent while lysis is delayed in the absence of exogenous Ca2+. The proteolysis of erythrocyte protein bands 1, 2, 2.1, 2.3 and 3 are common features of both fusion and lysis processes. Nevertheless the breakdown rate of ankyrin (band 2.1) and band 3 are different in fused or in lysed cells. The lysis process is associated with a faster degradation of band 2.1 and increase of band 2.3 than in the case of the fusion process. By contrast, degradation of band 3 occurs faster in the fusion than in the lytic event. Treatment of fusogenic parasites but not erythrocytes with TPCK, soybean trypsin inhibitor or FCS inhibited to some extent the fusion process and the decrease of bands 1, 2, 2.1, 2.3 and 3. The results suggest that proteases from fusogenic parasites may be directly or indirectly involved in the proteolysis of band 2.1 in a way related to induction of fusion.