Young Investigator Talks
Wednesday · Oct 7
9:00 to 11:00
Aβ promotes amyloidogenic processing of APP through a Go/βγ signaling.
BACE1 cleavage on amyloid precursor protein (APP), is rate-limiting on Aβ biosynthesis. Some in vitro studies have demonstrated that exogenous Aβ triggers its own production by a mechanism which are unclear. Our previous findings suggest that APP acts as a pathologic receptor of Aβ, able to provoke neurodegeneration through Go/βγ intracellular signaling. In this work, we evaluated the role of APP/Go/βγ signaling, induced by aggregates of Aβ, promoting the encounter and interaction of APP with BACE1. Using quantitative colocalization, we found that fibrillar Aβ (fAβ) provoked an increase in the localization of APP and BACE1 in recycling endosomes (RE). Employing mutant forms of APP, we verified that this event is dependent of the interaction of APP with fAβ and with Go intracellular. Likewise, pharmacological inhibition of βγ with gallein, abrogated the Aβ-dependent convergence of endogenous APP and BACE1 in hippocampal neurons. Using Bimolecular Fluorescence Complementation (BiFC) technique in human neurons derivate from IPSCs, we found that fAβ and oligomeric Aβ (oAβ) were able to increment the APP/BACE1 interaction in RE; effect that was avoided by gallein. Finally, we correlated changes in APP and BACE1 interaction with changes in β-processing of APP by WB. Collectively, these findings uncover a feed-forward mechanism of amyloidogenesis that might contribute to amyloid pathology in early stages of Alzheimer’s disease and suggest that gallein might have clinical relevance
Oxidative distress in Alzheimer Disease human organoids
Instituto de Biología Celular y Neurociencia “Profesor Eduardo de Robertis” IBCN (UBA-CONICET)
While highly polarized neurons deal with physiological changes in local levels of reactive oxygen species (ROS), it is known that in early stages of Alzheimer disease (AD) imbalances in the management of ROS occur, promoting abnormal macromolecules oxidation. To test the association of increased oxidation and intracellular dynamic defects in the progression of AD we developed human brain organoids from iPSC control and APP Swedish mutation (APPSwe). We characterized organoid cell composition and AD pathological hallmarks, such as amyloid-like deposits stained with antibodies and classical Congo-red. Furthermore, we observed, in APPSwe organoids, an increase in Aβ reactive area as well as a decrease in full length APP levels by western blot and immunostaining. In addition, we developed a technique for microinjecting organoids with viral vectors or probes to measure mitochondrial dynamics and morphology, superoxide anion levels and reactive oxygen species. We found a significant increase of superoxide anion levels in live imaging of APPSwe organoids. We also described an increase in Glutaredoxin-2 reactive area and integrated intensity, suggesting changes in thiol-based regulation in AD. Our results highlight the relevance of modeling neurological diseases using complex tissue arrangements, and points to a clear impairment in oxidative stress pathways that, if modulated, could be used as a therapeutic strategy for treatment of abnormal oxidation in AD.
Early life stress and the programing of stress-coping abilities in juvenile rats
MARIA EUGENIA PALLARÉS
1. Laboratorio de Programación Perinatal del Neurodesarrollo. Instituto de Biología Celular y Neurociencias “Prof. E. de Robertis” (IBCN)- Facultad de Medicina, Universidad de Buenos Aires.
2. Laboratorio de Neurobiología del Estrés. Instituto de Investigaciones Biotecnológicas (IIB). UNSAM. CONICET.
Prenatal stress (PS) predisposes individuals to develop emotional disorders in later life, including depression and anxiety, which might be mediated by dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis response. However, to date, little studies have examined the effects of PS on stress coping abilities of younger individuals and it relevance for the early onset of stress-related disorders. In here we assessed the impact of PS on the emergence of anxiety-/depressive- like behaviors and HPA response to an acute stress in juvenile rats. We explored possible underlying molecular bases by changes in candidate stress-related genes and DNA-methylation levels in the hippocampus, a key structure in stress regulation. Also, we tested patterns of maternal behavior within early lactation.
Stress during pregnancy enhanced pup-directed behavior of stressed dams. In the offspring, PS rats had enhanced stress-coping abilities than non-prenatally stressed rats. In the hippocampus, PS increased the expression of bdnf-IV and crhr1 although several sex differences changes on glucocorticoids and on BDNF receptors expressions were found. PS changes the hippocampal epigenetic landscape only in male offspring.
Our results show that PS and maternal behavior induce dynamic alterations in the offspring that should be adaptive at younger ages, but potentially maladaptive in later life, highlighting the importance of including an ontogenetic approach when assessing the effects of PS.