RESUMO
It is highly controversial to define the role of angiotensin-converting enzyme (ACE) polymorphisms in essential hypertension. We studied a group of patients in whom hypertension was the major side effect of treatment by cyclosporine A (CsA). This study group comprised 227 Italian patients with nephrotic syndrome, 103 of which were treated with CsA and had different outcome. Forty-nine patients developed serious hypertension that was reversed after withdrawal of drug. ACE haplotypes were determined by a combination of molecular and statistical methods after verifying genotypes of six intragenic single nucleotide polymorphisms in 304 Italian blood donors and assembling them in clades (A, B, C) that include 95% of observed haplotypes. The association between ACE clade combinations and serum enzymatic levels confirmed the previous results about a role of an unidentified genetic variant at the 5' of the intragenic recombination site located near intron 7. ACE clades were then determined in patients, and regression methods were used to analyze variables associated with CsA responsivity and progression to renal failure. ACE genotype and responsiveness to CsA were strictly associated, because homozygosis for ACE B clade was able to influence CsA sensitivity. This highlights the role of 5' variants, which differentiate clades B and C. Other genetic markers were tested to search for possible additive effects. We found that PAI-1 4G allele was associated with progression to renal failure in the group of CsA-treated patients. Our results are in agreement with the hypothesis, raised after experimental results obtained in mouse models, that the effect of ACE polymorphisms on blood pressure is detectable once environmental factors, like CsA treatment in our case, overcome physiological homeostatic mechanisms.
Assuntos
Ciclosporina/efeitos adversos , Inibidores Enzimáticos/efeitos adversos , Haplótipos/genética , Hipertensão/induzido quimicamente , Hipertensão/enzimologia , Peptidil Dipeptidase A/genética , Locos de Características Quantitativas , Adolescente , Adulto , Pressão Sanguínea , Estudos de Casos e Controles , Criança , Pré-Escolar , Feminino , Genótipo , Humanos , Lactente , Masculino , Peptidil Dipeptidase A/sangue , Fenótipo , Inibidor 1 de Ativador de Plasminogênio/genética , Polimorfismo Genético , Insuficiência Renal/induzido quimicamente , Insuficiência Renal/tratamento farmacológico , Estudos Retrospectivos , Resultado do TratamentoRESUMO
A new peptide was purified from the venom of the Venezuelan scorpion Tityus discrepans, by high-performance liquid chromatography and its amino acid sequence was completed by Edman degradation and mass spectrometry analysis. It contains 38 amino acid residues with a molecular weight of 4177.7 atomic mass units, tightly folded by three disulfide bridges, and has a pyroglutamic acid at the N-terminal region. This peptide, named Discrepin, was shown to block preferentially the IA currents of the voltage-dependent K+ -channel of rat cerebellum granular cells in culture. The K+ -currents are inhibited in an apparently irreversible manner, whose 50% inhibitory effect is reached with a 190 nM toxin concentration. The systematic nomenclature proposed for this toxin is alpha-KTx15.6.
Assuntos
Cerebelo/efeitos dos fármacos , Neurotoxinas/química , Peptídeos/química , Canais de Potássio/efeitos dos fármacos , Venenos de Escorpião/química , Escorpiões/química , Sequência de Aminoácidos , Animais , Células Cultivadas , Cerebelo/citologia , Dissulfetos , Cinética , Dados de Sequência Molecular , Peso Molecular , Neurotoxinas/genética , Neurotoxinas/isolamento & purificação , Neurotoxinas/farmacologia , Técnicas de Patch-Clamp , Peptídeos/isolamento & purificação , Peptídeos/metabolismo , Peptídeos/farmacologia , Ratos , Ratos Wistar , Venenos de Escorpião/genética , Venenos de Escorpião/isolamento & purificação , Venenos de Escorpião/farmacologia , Homologia de Sequência de Aminoácidos , SolubilidadeRESUMO
By means of high performance liquid chromatography (HPLC) the soluble venom of the Amazonian scorpion Tityus cambridgei was fractionated into over 50 different components. Four toxic and/or lethal peptides to mice were obtained in pure form and sequenced. Mass spectrometry analysis showed molecular weights of 7310, 7151, 7259 and 7405, respectively, for toxins Tc48a, Tc49a, Tc54 and Tc49b. The N-terminal amino acid sequence was obtained for the three first toxins mentioned, whereas the full primary structure was determined for Tc49b. It contains 64 amino acid residues, closely packed by four disulfide bridges. Sequence comparison analysis showed similarities around 50% with other toxins from scorpions of the genus Tityus of Brazil. It is lethal to mice at doses of 20 microg per 20 g mouse. The toxin was shown to affect the Na(+)-currents permeability of rat cerebellum granular cells in culture. Almost a complete elimination of current was observed with 100 nM toxin concentration. This effect was partially reversible. Furthermore, this toxin does not modify the function of the Shaker B K(+)-channels expressed on Sf9 cells, nor does it modify the Na(+)-channel function in a similar manner as those reported for the alpha-scorpion toxins purified from other scorpions.
