Hyperphosphorylation induces self-assembly of tau into tangles of paired helical filaments/straight filaments.

The microtubule-associated protein tau is a family of six isoforms that becomes abnormally hyperphosphorylated and accumulates in the form of paired helical filaments (PHF) in the brains of patients with Alzheimer's disease (AD) and patients with several other tauopathies. Here, we show that the abnormally hyperphosphorylated tau from AD brain cytosol (AD P-tau) self-aggregates into PHF-like structures on incubation at pH 6.9 under reducing conditions at 35 degrees C during 90 min. In vitro dephosphorylation, but not deglycosylation, of AD P-tau inhibits its self-association into PHF. Furthermore, hyperphosphorylation induces self-assembly of each of the six tau isoforms into tangles of PHF and straight filaments, and the microtubule binding domains/repeats region in the absence of the rest of the molecule can also self-assemble into PHF. Thus, it appears that tau self-assembles by association of the microtubule binding domains/repeats and that the abnormal hyperphosphorylation promotes the self-assembly of tau into tangles of PHF and straight filaments by neutralizing the inhibitory basic charges of the flanking regions.

[Hormone replacement therapy in ischemic heart disease prevention in women. Arguments against]. / Tratamiento hormonal sustitutivo en la prevención de la cardiopatía isquémica en la mujer. Argumentos en contra.

Hormone replacement therapy is one of the most difficult issues women and their doctors face. Epidemiological studies have consistently found that women using hormone replacement therapy are at a substantially lower risk of developing coronary heart disease. Observational data are supported by findings demonstrating that hormone replacement therapy improves several risk factors o coronary heart disease, specially the favourable changes in lipid profile. However, no study has clearly established hormones help prevent heart disease. In women without heart disease, the benefits of hormone replacement therapy are unclear. However, recent clinical trials have sown that the use of hormone replacement therapy does not provide cardiovascular benefits in women with established heart disease.