ACT Research
Our research programs focus on investigating the pathophysiology of brain aging, Alzheimer’s disease and related neurodegenerative disorders. We aim to advance the discovery of the cellular mechanisms and molecular pathways that are responsible for the onset and progression of these diseases, with the goal to develop therapeutic strategies and diagnostic biomarkers. The ACT is committed to translating studies of the basic biology of neurodegeneration, neuroinflammation and neurovascular pathology into new therapeutics and biomarkers, by implementing a comprehensive experimental approach which combines in vitro studies (brain cells), in vivo models of these diseases (transgenic mice), and human studies.
Fossati Lab
Cerebrovascular dysfunction and cardiovascular risk factors in Alzheimer’s disease (AD) and Cerebral Amyloid Angiopathy (CAA).
Our studies focus on establishing the mechanisms responsible for vascular endothelial cell death in Alzheimer’s disease and in the aging brain, which is often also subjected to cardiovascular/cerebrovascular risk factors such as hypertension, high levels of homocysteine, and hypoperfusion.
Our previous research assessed the effects of different variants of Amyloid b (Aβ) on neurovascular cell death pathways. These variants are linked to different forms of the disease, presenting with parenchymal and/or vascular deposition, and resulting preferentially in dementia and/or cerebral hemorrhage. Our work showed that different Aβ variants triggered mitochondrial apoptotic pathways with different kinetics, parallel to their aggregation propensity and to the formation of intermediate oligomeric and protofibrillar forms of the peptides, which are responsible for the apoptotic outcome. Different Aβ aggregation species such as oligomers and protofibrils also cause differential effects on the blood brain barrier (BBB), being preferentially associated with either endothelial cell death or BBB permeability.
We are currently evaluating how the presence of cardiovascular risk factors and cerebral hypoperfusion contribute to these mechanisms, and if the actions of these different challenges on neurovascular cells are synergistic in nature.
Mitochondria, caspases and death receptors in Aβ-induced brain vascular degeneration.
Our studies identified for the first time the TRAIL Death Receptors DR4 and DR5 as specific targets for Aβ oligomers in cerebral microvascular endothelial cells, demonstrating that DR4/5 were activated after Aβ challenge, and triggered extrinsic apoptotic pathways with involvement of mitochondrial dysfunction and caspase 8/9 activation. Aβ oligomers and protofibrils specifically functioned as alternative ligands for these receptors. These studies unveiled new targets for the protection of vascular cells against neurodegeneration, neuroinflammation, and vascular dysfunction in AD, including death receptors, mitochondrial dysfunction, and caspase activation pathways. We are currently testing if the presence of homocysteine or low oxygen and glucose affect these pathways in an additive or synergistic manner or if complementary cell death pathways are activated.
Targeting carbonic anhydrases in AD
Our research pioneered the use of the carbonic anhydrase inhibitors (CAI) methazolamide (MTZ) and acetazolamide (ATZ) to prevent Aβ-induced mitochondrial dysfunction in neurovascular cells. MTZ and ATZ are FDA-approved for different indications (such as glaucoma and high altitude sickness), and could be rapidly tested in controlled clinical trials in AD. Using these carbonic anhydrase inhibitors we prevented mitochondrial dysfunction, caspase activation and cell death in in vitro studies, as well as after acute brain Aβ injection in mice and in transgenic animal models of cerebral amyloidosis. We recently reported specific mitochondrial mechanisms responsible for this protection. We are currently aiming to expand these studies to models including tauopathy, and to investigate how particular isoforms of carbonic anhydrases (which are increased in the brain and in the mitochondria during aging and neurodegeneration) are relevant for AD pathology.
Study of biomarkers for AD, TBI and related disorders.
Our lab is also conducting multiple translational studies for biomarker discovery, focusing on the identification of biofluid biomarkers for Alzheimer’s disease (AD), traumatic brain injury (TBI), and related neurodegenerative or psychiatric disorders, in collaboration with multiple clinical studies and centers. Important current projects include clinical translational studies on the effect of cardiovascular risk factors on AD and cerebrovascular blood and imaging biomarkers, and studies on the effects of TBI on neurovascular degeneration and brain clearance, among others. For these studies, we use well established assays and novel technologies for the detection of blood biomarkers at very low concentrations, including the ultrasensitive Quanterix Simoa HD-X technology, that is available at the ACT.
Luna Lab
Synaptic mechanisms underlying neurological and psychiatric disorders of aging
The Laboratory on Synaptic Aging investigates how aged synapses—the neurobiological basis for all cognition and emotion—control behaviors related to late-life depression, Alzheimer’s disease, and related dementias. We aim to identify molecular mechanisms that rejuvenate synaptic function in the aged brain, with a clear view towards translating these findings to pharmacological treatments that rescue cognitive and affective impairments due to aging. We employ an integrative approach where: 1) evolutionarily conserved behaviors related to late-life depression and dementia are assessed in aged mice, 2) their synaptic mechanisms identified using electrophysiology, molecular biology, optogenetics, calcium/voltage/glutamate imaging, and 3) the therapeutic potential of these mechanisms determined using virus-driven gene manipulation, photopharmacology, and in vivo wireless optofluidics. A major objective of our research is the elucidation of synaptic mechanisms that underlie sex differences in order to develop targeted strategies that mitigate cognitive and emotional dysfunctions disorders of aging.
The role of neurogenesis and its downstream synaptic targets during aging
Adult hippocampal neurogenesis is a powerful form of plasticity that has a significant impact on cognition and emotion. Using electrophysiology, optogenetics, pharmacology, and behavior, we have found that new neurons (≤6 weeks old) bidirectionally modulate the synaptic strengths of incoming contextual versus spatial information to shape distinct neural representations in the dentate gyrus of young adult mice. Depending on cognitive demand, new neurons could rapidly inhibit or excite the dentate gyrus via postsynaptic metabotropic glutamate receptor 2 or ionotropic NMDA-type glutamate receptors, respectively. This bidirectional modulation could underlie the pivotal role neurogenesis plays in regulating memory and mood. Indeed, by taking this unique function into account, we were able to predict dentate activity patterns after an active place avoidance and a novel object recognition task.
Neurogenesis drastically declines with aging, depression, and Alzheimer’s disease. Stimulating neurogenesis in mice mitigates behavioral impairments caused by normal aging or disorders of aging. However, there is debate as to the feasibility of rejuvenating neurogenesis in aged humans. Importantly, pharmacologic compounds designed to stimulate neurogenesis can also increase cell proliferation which could increase the risk for cancer. We are therefore employing our multidisciplinary tools to test the therapeutic potential of instead targeting downstream synaptic targets of new neurons and leveraging them to rescue memory and mood. This approach effectively takes advantage of neurogenesis-dependent plasticity without having to manipulate it directly. Our studies therefore hold great promise for developing novel synaptic strategies that could effectively and safely ameliorate cognitive and emotional dysregulation caused by late-life depression, Alzheimer’s disease, and other related forms of dementia.
Lyssenko Lab
The neuroprotective functions of ABCA7 in Alzheimer’s disease
A major emphasis of my research program is the genes that are involved in lipid metabolism and are associated with Alzheimer’s disease (AD) in human genome and gene studies. The genes linked to disease in human genome-wide association studies (GWAS) have immediate relevance to human pathophysiology and are causative because inheritance of the risk and protection alleles at the variants in these genes is random during meiosis. The leading gene of interest is ABCA7, which encodes adenosine triphosphate-binding cassette transporter subfamily A member 7 and has been associated with AD in all major GWAS in African and European ancestry populations. Loss-of-function and other damaging mutations in ABCA7 are also associated with a greater risk of AD. ABCA7 is a large 12-pass integral membrane protein. It is an extruder that forces lipids out of cell membranes to form extracellular lipoprotein particles with apolipoproteins, such as apo E. We conduct question-driven research into the biochemical and pathophysiological functions of ABCA7 using human specimens, mouse models and immortalized, primary and iPSC-derived cells. We recently showed that there is a group of individuals with exceptionally low ABCA7 protein levels in the cerebrum who develop AD neuropathologic changes in their 60s and 70s. Also recently, we demonstrated that ABCA7 mediates formation of lipoprotein particles with a distinct phospholipid composition and is regulated by inflammation in human microglial cells. The ongoing research efforts encompass development of a method to assess cerebral ABCA7 levels in live human individuals, making of a humanized constitutive over-expression and a humanized inducible tissue-specific expression ABCA7 mouse models and application of integrated lipidomics and transcriptomics to identify the ABCA7 cargo lipid.
Emerging Alzheimer’s disease risk and protection factors that bear on neural lipidostasis
We recently proposed that altered lipidostasis is a causative factor in the AD pathogenesis. To improve our understanding of normal and pathogenic lipidostasis, we investigate lipid metabolism-related genes that were linked with AD in the AD GWAS and exome sequencing investigations but had not been previously implicated in the disease pathogenesis. Such genes are ATPase phospholipid transporting 8B4 (ATP8B4) and the genes at the AD-associated locus in the p13.2 band of chromosome 17 (Chr17). ATP8B4 encodes a member of the subfamily IV in the P-type ATPase superfamily. It is a large 12-pass integral membrane protein that is thought to regulate transbilayer phospholipid asymmetry by flipping certain phospholipids from one monolayer of the bilayer to the other. The AD-associated variants at the ATP8B4 locus have not reached the genome-wide level of significance in the AD GWAS, but rare damaging mutations in ATP8B4 have been shown to associate with a greater risk of AD. We currently investigate ATP8B4 expression in human neural cell lines and the cerebrum of individuals without and with AD neuropathologic changes. The locus in the p13.2 band of Chr17 has been consistently identified as a risk factor for AD in the AD GWAS. There are a number of genes at the locus, and the risk effect has been assigned to different genes by different GWAS. We conduct in vitro screens of the genes at the locus to identify which one(s) affect AD risk.
The role of ABCA1 in age-related macular degeneration
ABCA1 encodes adenosine triphosphate-binding cassette transporter subfamily A member 1, a protein closely related to ABCA7 in the amino acid sequence. ABCA1 is a risk factor for AD and age-related macular degeneration (AMD). ABCA1 mediates formation of high-density lipoprotein (HDL) and removes cholesterol from the cell. The alleles that are associated with a higher ABCA1 activity are also associated with a greater risk of AMD, suggesting that hyperactive ABCA1 contributes to AMD pathogenesis, possibly by promoting cholesterol and phospholipid deposition in the Bruch’s membrane. We are testing the latter hypothesis by making a mouse model over-expressing human ABCA1 specifically in the retinal pigment epithelium.
Pratico’ Lab
The neurobiology of 12/15-Lipoxygenase
The 12/15-Lipoxygenase (12/15LO) is an enzyme widely expressed in the central nervous system where its levels increase in an age-dependent manner. Previously, we demonstrated that this protein is up-regulated in brains from Alzheimer’s disease patients in specific regions known to be vulnerable to neurodegenerative insults (i.e., hippocampus and frontal cortex) and at an early stage of the disease suggesting an active involvement in its pathogenesis. In support of this hypothesis we showed that this protein acts as an endogenous regulator of Amyloid beta peptide formation by controlling APP processing via the transcriptional regulation of beta-secretase pathway via the transcription factor Sp1. Current efforts are focused on testing the hypothesis that this protein is a viable therapeutic target for Alzheimer’s disease, and investigating its functional role in the post-transcriptional regulation of tau protein and the development of its neuropathology (i.e., neurofibrillary tangles).
Diet and the risk of Alzheimer’s disease
Another area of research is the role that certain dietary factors may play in the onset of Alzheimer’s disease. In particular, we are investigating the functional role that high circulating levels of homocysteine, also known as hyper-homocysteinemia, a known risk factor for Alzheimer’s disease has on the development of its phenotype using different transgenic mouse models of the disease (i.e., the Tg2576 and 3xTg mice). These studies are designed to understand how hyper-homocysteinemia accelerates the amyloid pathology, tau hyper-phosphorylation, synaptic function, memory and learning deficits.
In addition, we are investigating the effect on brain health of one of the major component of the Mediterranean diet, which is known to have beneficial effects on human health. In particular, we have been focusing our attention on the extra virgin olive oil (EVOO) as the mediator of those benefits. By using relevant transgenic mouse models of Alzheimer’s and related tauopathies we have been studying the molecular and cellular mechanism(s) that are responsible for the beneficial effects that EVOO displays on the development of the neuropathological phenotype with particular emphasis on the autophagy machinery and its regulation.
Neuroninflammation and Neurodegeneration
Besides the accumulation of amyloid-beta peptides and highly phosphorylated tau protein deposits, substantial evidence has mounted showing that abnormal inflammatory reactions in the brain are another cardinal manifestation of Alzheimer’s disease. Leukotrienes are bioactive lipid mediators, major metabolic products of the enzyme 5-Lipoxygenase (5LO), which can trigger immune cells chemotaxis and initiate potent pro-inflammatory reactions. This enzymatic pathway is highly expressed in neurons and glial cells, and its levels are up-regulated in Alzheimer’s disease patients as well as animal models of the disease. Previously, we have demonstrated that 5LO directly modulates the development of amyloid pathology together with the behavioral deficits in these models. Current work in the lab is now focusing on its mechanistic role in regulating tau metabolism and synaptic function by implementing models that express only tau neuropathology. To reach this goal we are implementing an in vitro and in vivo approach targeting 5LO with specific pharmacological and genetic suppressor(s) and inducer(s) of this enzyme.
Environment and neurodegeneration
Emerging evidence has showed that he majority of the cases of Alzheimer’s disease and other neurodegenerative diseases are the result of a combination between genetic risk factor with environmental elements that directly influence their onset. The core of this research program is to investigate the role that environment may play in the pathogenesis of Alzheimer’s disease, tauopathies and Parkinson’s disease. To this end, we focus on chronic environmental stressors and implement different experimental paradigms in wild type as well as transgenic animal models of these diseases. In particular, we have been investigating how social isolation, circadian rhythm disruption, and sleep deprivation may induce neuropathological modification, impair synaptic function and integrity, and ultimately memory and learning deficits.
Down syndrome: Mechanisms and Pathways
Because of an extra copy of the APP gene on chromosome 21, Down syndrome individuals develop high levels of Ab peptides and Alzheimer’s disease-like brain amyloidosis early in life. By using in vitro and in vivo models of the disease, we are investigating novel pathways potentially involved in the pathogenesis of the syndrome which can eventually be tested as therapeutic targets. Further, we are interested in understanding how and if alterations in the transport and traffic system for specific proteins (i.e., APP, BACE-1) within the neurons can modulate the earliest