Neuronal ER-Signalosome Proteins as Early Biomarkers in Prodromal Alzheimer's Disease Independent of Amyloid-β Production and Tau Phosphorylation

Neuronal Protection by Ha-RAS-GTPase Signaling through Selective Downregulation of Plasmalemmal Voltage-Dependent Anion Channel-1

The small GTPase RAS acts as a plasma membrane-anchored intracellular neurotrophin counteracting neuronal degeneration in the brain, but the underlying molecular mechanisms are largely unknown. In transgenic mice expressing constitutively activated V12-Ha-RAS selectively in neurons, proteome analysis uncovered a 70% decrease in voltage-dependent anion channel-1 (VDAC-1) in the cortex and hippocampus. We observed a corresponding reduction in the levels of mRNA splicing variant coding for plasma membrane-targeted VDAC-1 (pl-VDAC-1) while mRNA levels for mitochondrial membrane VDAC-1 (mt-VDAC-1) remained constant. In primary cortical neurons derived from V12-Ha-RAS animals, a decrease in pl-VDAC-1 mRNA levels was observed, accompanied by a concomitant reduction in the ferricyanide reductase activity associated with VDAC-1 protein. Application of MEK inhibitor U0126 to transgenic cortical neurons reconstituted pl-VDAC-1 mRNA to reach wild-type levels. Excitotoxic glutamate-induced cell death was strongly attenuated in transgenic V12-Ha-RAS overexpressing cortical cultures. Consistently, a neuroprotective effect could also be achieved in wild-type cortical cultures by the extracellular application of channel-blocking antibody targeting the N-terminus of VDAC-1. These results may encourage novel therapeutic approaches toward blocking pl-VDAC-1 by monoclonal antibody targeting for complementary treatments in transplantation and neurodegenerative disease.

Rafting on the Evidence for Lipid Raft-like Domains as Hubs Triggering Environmental Toxicants' Cellular Effects

The plasma membrane lipid rafts are cholesterol- and sphingolipid-enriched domains that allow regularly distributed, sub-micro-sized structures englobing proteins to compartmentalize cellular processes. These membrane domains can be highly heterogeneous and dynamic, functioning as signal transduction platforms that amplify the local concentrations and signaling of individual components. Moreover, they participate in cell signaling routes that are known to be important targets of environmental toxicants affecting cell redox status and calcium homeostasis, immune regulation, and hormonal functions. In this work, the evidence that plasma membrane raft-like domains operate as hubs for toxicants' cellular actions is discussed, and suggestions for future research are provided. Several studies address the insertion of pesticides and other organic pollutants into membranes, their accumulation in lipid rafts, or lipid rafts' disruption by polychlorinated biphenyls (PCBs), benzo[a]pyrene (B[a]P), and even metals/metalloids. In hepatocytes, macrophages, or neurons, B[a]P, airborne particulate matter, and other toxicants caused rafts' protein and lipid remodeling, oxidative changes, or amyloidogenesis. Different studies investigated the role of the invaginated lipid rafts present in endothelial cells in mediating the vascular inflammatory effects of PCBs. Furthermore, in vitro and in vivo data strongly implicate raft-localized NADPH oxidases, the aryl hydrocarbon receptor, caveolin-1, and protein kinases in the toxic mechanisms of occupational and environmental chemicals.

Compensatory Mechanisms in Early Alzheimer's Disease and Clinical Setting: The Need for Novel Neuropsychological Strategies

Despite advances in the detection of biomarkers and in the design of drugs that can slow the progression of Alzheimer's disease (AD), the underlying primary mechanisms have not been elucidated. The diagnosis of AD has notably improved with the development of neuroimaging techniques and cerebrospinal fluid biomarkers which have provided new information not available in the past. Although the diagnosis has advanced, there is a consensus among experts that, when making the diagnosis in a specific patient, many years have probably passed since the onset of the underlying processes, and it is very likely that the biomarkers in use and their cutoffs do not reflect the true critical points for establishing the precise stage of the ongoing disease. In this context, frequent disparities between current biomarkers and cognitive and functional performance in clinical practice constitute a major drawback in translational neurology. To our knowledge, the In-Out-test is the only neuropsychological test developed with the idea that compensatory brain mechanisms exist in the early stages of AD, and whose positive effects on conventional tests performance can be reduced in assessing episodic memory in the context of a dual-task, through which the executive auxiliary networks are 'distracted', thus uncover the real memory deficit. Furthermore, as additional traits, age and formal education have no impact on the performance of the In-Out-test.

Estrogen signaling via estrogen receptor alpha and its implications for neurodegeneration associated with Alzheimer's disease in aging women

Estrogen receptor alpha (ERα) is a transcription factor activated by estrogenic hormones to regulate gene expression in certain organs, including the brain. In the brain, estrogen signaling pathways are central for maintaining cognitive functions. Herein, we review the neuroprotective effects of estrogens mediated by ERα. The estrogen/ERα pathways are affected by the reduction of estrogens in menopause, and this event may be a risk factor for neurodegeneration associated with Alzheimer's disease in women. Thus, developing a better understanding of estrogen/ERα signaling may be critical for defining new biomarkers and potential therapeutic targets for Alzheimer's disease in women.

Roles of traditional chinese medicine regulating neuroendocrinology on AD treatment

The incidence of sporadic Alzheimer's disease (AD) is increasing in recent years. Studies have shown that in addition to some genetic abnormalities, the majority of AD patients has a history of long-term exposure to risk factors. Neuroendocrine related risk factors have been proved to be strongly associated with AD. Long-term hormone disorder can have a direct detrimental effect on the brain by producing an AD-like pathology and result in cognitive decline by impairing neuronal metabolism, plasticity and survival. Traditional Chinese Medicine(TCM) may regulate the complex process of endocrine disorders, and improve metabolic abnormalities, as well as the resulting neuroinflammation and oxidative damage through a variety of pathways. TCM has unique therapeutic advantages in treating early intervention of AD-related neuroendocrine disorders and preventing cognitive decline. This paper reviewed the relationship between neuroendocrine and AD as well as the related TCM treatment and its mechanism. The advantages of TCM intervention on endocrine disorders and some pending problems was also discussed, and new insights for TCM treatment of dementia in the future was provided.