Arminda Vilares

Genetic and biochemical markers in patients with Alzheimer's disease support a concerted systemic iron homeostasis dysregulation

Alzheimers disease (AD) is the most common form of dementia in the elderly individuals, resulting from a complex interaction between environmental and genetic factors. Impaired brain iron homeostasis has been recognized as an important mechanism underlying the pathogenesis of this disease. Nevertheless, the knowledge gathered so far at the systemic level is clearly insufficient. Herein, we used an integrative approach to study iron metabolism in the periphery, at both genotypic and phenotypic levels, in a sample of 116 patients with AD and 89 healthy control subjects. To assess the potential impact of iron metabolism on the risk of developing AD, genetic analyses were performed along with the evaluation of the iron status profile in peripheral blood by biochemical and gene expression studies. The results obtained showed a significant decrease of serum iron, ferritin, and transferrin concentrations in patients compared with the control subjects. Also, a significant decrease of ferroportin (SLC40A1) and both transferrin receptors TFRC and TFR2 transcripts was found in peripheral blood mononuclear cells from patients. At the genetic level, significant associations with AD were found for single nucleotide polymorphisms in TF, TFR2, ACO1, and SLC40A1 genes. Apolipoprotein E gene, a well-known risk factor for AD, was also found significantly associated with the disease in this study. Taken together, we hypothesize that the alterations on systemic iron status observed in patients could reflect an iron homeostasis dysregulation, particularly in cellular iron efflux. The intracellular iron accumulation would lead to a rise in oxidative damage, contributing to AD pathophysiology.

Effects of microcystin-LR on Saccharomyces cerevisiae growth, oxidative stress and apoptosis

Microcystins (MC) are cyanotoxins occurring globally, known for causing acute hepatotoxicity in humans/animals, tumor promotion in animals and potential carcinogenicity. The mechanism of MC toxicity is considered a multi-pathway process involving the inhibition of protein phosphatases PP1/PP2A and the production of reactive oxygen species (ROS). However, their mechanism of action is not fully characterized, thus hampering the complete hazard identification. In this study, we evaluated the effect of several microcystin-LR concentrations on the growth, ROS levels, antioxidant system response and apoptosis induction on Saccharomyces cerevisiae. Our results showed that the growth of S. cerevisiae was not inhibited when compared to control cells. However, the staining of cells with DHR123 and DHE revealed an intracellular increase of the ROS levels. This ROS increase resulted in an augment of catalase activity and inhibition of SOD. All these facts suggest that hydrogen peroxide was the main ROS induced by MCLR. Signs of apoptosis were also detected in the cells exposed to toxin. Our results show that S. cerevisiae VL3 displays MCLR toxicity effects known to occur in higher eukaryotes and confirmed that it can be a simple and good model to help further in the elucidation of MCLR molecular mechanisms of toxicity.

Decrease in APP and CP mRNA expression supports impairment of iron export in Alzheimer's disease patients.

Alzheimers disease (AD) is a neurodegenerative disorder of still unknown etiology and the leading cause of dementia worldwide. Besides its main neuropathological hallmarks, a dysfunctional homeostasis of transition metals has been reported to play a pivotal role in the pathogenesis of this disease. Dysregulation of iron (Fe) metabolism in AD has been suggested, particularly at the level of cellular iron efflux. Herein, we intended to further clarify the molecular mechanisms underlying Fe homeostasis in AD. In order to achieve this goal, the expression of specific Fe metabolism-related genes directly involved in Fe regulation and export was assessed in peripheral blood mononuclear cells (PBMCs) from 73AD patients and 74 controls by quantitative PCR. The results obtained showed a significant decrease in the expression of aconitase 1 (ACO1; P=0.007); ceruloplasmin (CP; P<0.001) and amyloid-beta precursor protein (APP; P=0.006) genes in AD patients compared with healthy volunteers. These observations point out to a significant downregulation in the expression of genes associated with ferroportin-mediated cellular Fe export in PBMCs from AD patients, when compared to controls. Taken together, these findings support previous studies suggesting impairment of Fe homeostasis in AD, which may lead to cellular Fe retention and oxidative stress, a typical feature of this disease.