Luis Fernando Hernández-Zimbrón

Amyloid-β Peptide Binds to Cytochrome C Oxidase Subunit 1

Extracellular and intraneuronal accumulation of amyloid-beta aggregates has been demonstrated to be involved in the pathogenesis of Alzheimers disease (AD). However, the precise mechanism of amyloid-beta neurotoxicity is not completely understood. Previous studies suggest that binding of amyloid-beta to a number of macromolecules has deleterious effects on cellular functions. Mitochondria were found to be the target for amyloid-beta, and mitochondrial dysfunction is well documented in AD. In the present study we have shown for the first time that Aβ 1–42 bound to a peptide comprising the amino-terminal region of cytochrome c oxidase subunit 1. Phage clone, selected after screening of a human brain cDNA library expressed on M13 phage and bearing a 61 amino acid fragment of cytochrome c oxidase subunit 1, bound to Aβ 1–42 in ELISA as well as to Aβ aggregates present in AD brain. Aβ 1–42 and cytochrome c oxidase subunit 1 co-immunoprecipitated from mitochondrial fraction of differentiated human neuroblastoma cells. Likewise, molecular dynamics simulation of the cytochrome c oxidase subunit 1 and the Aβ 1–42 peptide complex resulted in a reliable helix-helix interaction, supporting the experimental results. The interaction between Aβ 1–42 and cytochrome c oxidase subunit 1 may explain, in part, the diminished enzymatic activity of respiratory chain complex IV and subsequent neuronal metabolic dysfunction observed in AD.

Deciphering an interplay of proteins associated with amyloid β 1-42 peptide and molecular mechanisms of Alzheimer’s disease

Abstract Extracellular and intracellular accumulation of amyloid beta 1-42 peptide in different states of aggregation has been involved in the development and progression of Alzheimer’s disease. However, the precise mechanisms involved in amyloid beta peptide neurotoxicity have not been fully understood. There exists a wide variety of studies demonstrating the binding of amyloid beta peptide to a great variety of macromolecules and that such associations affect the cellular functions. This type of association involves proteins and receptors anchored to the plasma membrane of neurons or immune cells of the central nervous system as well as intracellular proteins that can alter intracellular transport, activate signaling pathways or affect proper mitochondrial function. In this review, we present some examples of such associations and the role played by these interactions, which are generally involved in the pathological progression of Alzheimer’s disease.

Identification of N-Terminally Truncated Pyroglutamate Amyloid-β in Cholesterol-Enriched Diet-Fed Rabbit and AD Brain

The main amyloid-β peptide (Aβ) variants detected in the human brain are Aβ1-40 and Aβ1-42; however, a significant proportion of Aβ in Alzheimers disease (AD) brain also consists of N-terminal truncated/modified species. AβN3(pE), Aβ peptide bearing amino-terminal pyroglutamate at position 3, has been demonstrated to be a major N-truncated/modified constituent of intracellular, extracellular, and vascular Aβ deposits in AD and Down syndrome brain tissue. It has been previously demonstrated that rabbits fed a diet enriched in cholesterol and given water containing trace copper levels developed AD-like pathology including intraneuronal and extracellular Aβ accumulation, tau hyperphosphorylation, vascular inflammation, astrocytosis, microgliosis, reduced levels of acetylcholine, as well as learning deficits and thus, may be used as a non-transgenic animal model of sporadic AD. In the present study, we have demonstrated for the first time the presence of AβN3(pE) in blood vessels in cholesterol-enriched diet-fed rabbit brain. In addition, we detected AβN3(pE) immunoreactivity in all postmortem AD brain samples studied. We believe that our results are potentially important for evaluation of novel therapeutic molecules/strategies targeting Aβ peptides in a suitable non-transgenic animal model.

Age-Related Macular Degeneration: New Paradigms for Treatment and Management of AMD

Age-related macular degeneration (AMD) is a well-characterized and extensively studied disease. It is currently considered the leading cause of visual disability among patients over 60 years. The hallmark of early AMD is the formation of drusen, pigmentary changes at the macula, and mild to moderate vision loss. There are two forms of AMD: the “dry” and the “wet” form that is less frequent but is responsible for 90% of acute blindness due to AMD. Risk factors have been associated with AMD progression, and they are taking relevance to understand how AMD develops: (1) advanced age and the exposition to environmental factors inducing high levels of oxidative stress damaging the macula and (2) this damage, which causes inflammation inducing a vicious cycle, altogether causing central vision loss. There is neither a cure nor treatment to prevent AMD. However, there are some treatments available for the wet form of AMD. This article will review some molecular and cellular mechanisms associated with the onset of AMD focusing on feasible treatments for each related factor in the development of this pathology such as vascular endothelial growth factor, oxidative stress, failure of the clearance of proteins and organelles, and glial cell dysfunction in AMD.

Syntaxin 5 Overexpression and β-Amyloid 1–42 Accumulation in Endoplasmic Reticulum of Hippocampal Cells in Rat Brain Induced by Ozone Exposure

Oxidative stress is a risk factor for Alzheimers disease and it is currently accepted that oxidative damage precedes the overproduction of A42 peptide. We have reported that ozone causes oxidative stress inducing neurodegeneration in the brain of rats. It is associated with A42 overproduction and intracellular accumulation in hippocampus. Organelles like mitochondria, intracellular membranes, and endoplasmic reticulum have been identified as sites of A42 production and accumulation affecting cellular metabolism. However whether ozone exposure induces overproduction and/or accumulation of A42 in endoplasmic reticulum has not been studied. We evaluated this effect in the endoplasmic reticulum of hippocampal cells of rats exposed chronically to low doses of ozone (0.25 ppm) at 7, 15, 30, 60, and 90 days. The effect of the presence of A42 in endoplasmic reticulum was analyzed evaluating the expression of the chaperone Syntaxin 5. Our results show an accumulation of A42 peptide in this organelle. It was observed by immunofluorescence and by WB in endoplasmic fractions from hippocampal cells of rats at 60 and 90 days of treatment. Significant overexpression of the chaperone Syntaxin 5 at 60 and 90 days of treatment was observed (⁎ P < 0.05). These results indicate that the exposure to environmental pollutants could be involved as a risk factor for neurodegenerative processes.

Beta Amyloid Peptides: Extracellular and Intracellular Mechanisms of Clearance in Alzheimer’s Disease

Alzheimer’s disease (AD) is a neurodegenerative disease and the most common form of dementia, characterized by the overproduction and accumulation of different amyloidβ peptide peptides (Aβ) within different areas in the brain conducting to memory loss and dementia. The Aβ cascade hypothesis of AD was originally proposed by Selkoe in 1991 by the theory that accumulation of Aβ42 is the initial trigger for neurodegenera‐ tion. The Aβ cascade hypothesis assumes that changes in the production or accumula‐ tion of Aβ are responsible for AD pathology. Different Aβ clearance mechanisms are also affected by AD pathology. Studies from the past years have revealed that the blocking of Aβ production is not effective for reducing the brain Aβ levels. However, the relevance of Aβ clearance in AD, especially in late-onset sporadic AD (LOAD), has been height‐ ened, and the study of the Aβ clearance mechanisms has elucidated new possible therapeutic targets. This chapter summarizes recent data underlying the idea of the reduced Aβ clearance and subsequent Aβ spread in AD. We discuss the Aβ clearance mechanisms altered in AD, and the Aβ clearance through autophagy in more detail, a more recent mechanism proposed, and the new strategies to eliminate Aβ42 inducing autophagy.

Current Anti-Integrin Therapy for Ocular Disease

ABSTRACT The integrin family of cell adhesion molecules mediates homeostasis, signal transduction, and various other interactions between the cell and the extracellular matrix. Integrins are type-1 transmembrane glycoproteins located on the cell surface, widely expressed in leukocytes, which play an important role in the inflammatory pathway. The purpose of this review is to summarize the current state of anti-integrin therapy and to assess ongoing clinical trials in ocular disease. We performed a search on PubMed, CINAHL, and Embase for the published literature available using the MeSH terms: “integrin therapy” and “αLβ2,” “α4β1” and “α4β7,” “αvβ3,” “αvβ5,” and “αvβ1” and/or “ophthalmology,” and “clinical trials.” We used no language restrictions. We generated searches to account for synonyms of these keywords and MESH headings as follows: (1) “integrin,” “therapy,” or “treatment”; (2) “clinical trials,” “ophthalmology,” or “ocular.” In addition, the analysis included phase 2 and phase 3 clinical trials with a minimal follow-up of six months. Integrin antagonists have shown their capacity to improve signs and symptoms of patients with dry eye disease, age-related macular degeneration, diabetic macular edema, and vitreomacular traction.

OVERPRODUCTION OF DIFFERENT β-AMYLOID PEPTIDES IN RETINA, OPTIC NERVE AND VISUAL CORTEX IN HEALTHY AGING AND ALZHEIMER'S DISEASE

(CsA). Patch-clamp results suggest that Ab-suppression of Kv1.1 involves both PP2B-dephosphorylation and direct protein-protein interaction of Ab with Kv1.1 channel subunits. Exposure of inside-out single Kv1.1 in ripped-off oocyte patches to application of purified, catalytically-active PP2B produced gradual reductions in p(open), followed by abrupt disappearance of Kv1.1 activity. Application of Ab to the intracellular face of Kv1.1 channels also produced dramatic reductions in p(open). Additional results indicate that 2 mM of Ab(25-35) suppressed Kv1.1 currents by w40%. Using “tip-dip” artificial membrane methods, 1 mM Ab(25-35) exposure eliminated Kv1.1 channel activity when applied to the intracellular face. Conclusions: The toxic Ab fragments (1-42) and (25-35) suppress the voltage-gated potassium channel, Kv1.1. Suppression of Kv1.1 and related K channels presynaptically could lead to larger and longer action potentials, allowing more influx of Ca, increased release of glutamate, and possibly the beginning of a disruption of Ca homeostasis. Postsynaptically, the increased glutamate release, through activation of AMPA and NMDA receptors, may contribute to excitotoxicity.

Molecular Age-Related Changes in the Anterior Segment of the Eye

Purpose To examine the current knowledge about the age-related processes in the anterior segment of the eye at a biological, clinical, and molecular level. Methods We reviewed the available published literature that addresses the aging process of the anterior segment of the eye and its associated molecular and physiological events. We performed a search on PubMed, CINAHL, and Embase using the MeSH terms “eye,” “anterior segment,” and “age.” We generated searches to account for synonyms of these keywords and MESH headings as follows: (1) “Eye” AND “ageing process” OR “anterior segment ageing” and (2) “Anterior segment” AND “ageing process” OR “anterior segment” AND “molecular changes” AND “age.” Results. Among the principal causes of age-dependent alterations in the anterior segment of the eye, we found the mutation of the TGF-β gene and loss of autophagy in addition to oxidative stress, which contributes to the pathogenesis of degenerative diseases. Conclusions In this review, we summarize the current knowledge regarding some of the molecular mechanisms related to aging in the anterior segment of the eye. We also introduce and propose potential roles of autophagy, an important mechanism responsible for maintaining homeostasis and proteostasis under stress conditions in the anterior segment during aging.

Markers of Alzheimer’s Disease in Primary Visual Cortex in Normal Aging in Mice

Aging is the principal risk factor for the development of Alzheimers disease (AD). The hallmarks of AD are accumulation of the amyloid-β peptide 1–42 (Aβ42) and abnormal hyperphosphorylation of Tau (p-Tau) protein in different areas of the brain and, more recently reported, in the visual cortex. Recently, Aβ42 peptide overproduction has been involved in visual loss. Similar to AD, in normal aging, there is a significant amyloid deposition related to the overactivation of the aforementioned mechanisms. However, the mechanisms associated with visual loss secondary to age-induced visual cortex affectation are not completely understood. Young and aged mice were used as model to analyze the presence of Aβ42, p-Tau, glial-acidic fibrillary protein (GFAP), and presenilin-2, one of the main enzymes involved in Aβ42 production. Our results show a significant increase of Aβ42 deposition in aged mice in the following cells and/or tissues: endothelial cells and blood vessels and neurons of the visual cortex; they also show an increase of the expression of GFAP and presenilin-2 in this region. These results provide a comprehensive framework for the role of Aβ42 in visual loss due to inflammation present with aging and offer some clues for fruitful avenues for the study of healthy aging.