Molecular Mechanisms Associated with Neurodegeneration of Neurotropic Viral Infection

Viral infections of the central nervous system (CNS) cause variable outcomes from acute to severe neurological sequelae with increased morbidity and mortality. Viral neuroinvasion directly or indirectly induces encephalitis via dysregulation of the immune response and contributes to the alteration of neuronal function and the degeneration of neuronal cells. This review provides an overview of the cellular and molecular mechanisms of virus-induced neurodegeneration. Neurotropic viral infections influence many aspects of neuronal dysfunction, including promoting chronic inflammation, inducing cellular oxidative stress, impairing mitophagy, encountering mitochondrial dynamics, enhancing metabolic rewiring, altering neurotransmitter systems, and inducing misfolded and aggregated pathological proteins associated with neurodegenerative diseases. These pathogenetic mechanisms create a multidimensional injury of the brain that leads to specific neuronal and brain dysfunction. The understanding of the molecular mechanisms underlying the neurophathogenesis associated with neurodegeneration of viral infection may emphasize the strategies for prevention, protection, and treatment of virus infection of the CNS.

Neuronal metabolism in learning and memory: The anticipatory activity perspective

Current research on the molecular mechanisms of learning and memory is based on the "stimulus-response" paradigm, in which the neural circuits connecting environmental events with behavioral responses are strengthened. By contrast, cognitive and systems neuroscience emphasize the intrinsic activity of the brain that integrates information, establishes anticipatory actions, executes adaptive actions, and assesses the outcome via regulatory feedback mechanisms. We believe that the difference in the perspectives of systems and molecular studies is a major roadblock to further progress toward understanding the mechanisms of learning and memory. Here, we briefly overview the current studies in molecular mechanisms of learning and memory and propose that studying the predictive properties of neuronal metabolism will significantly advance our knowledge of how intrinsic, predictive activity of neurons shapes a new learning event. We further suggest that predictive metabolic changes in the brain may also take place in non-neuronal cells, including those of peripheral tissues. Finally, we present a path forward toward more in-depth studies of the role of cell metabolism in learning and memory.

A novel integrated approach to estimate the mitochondrial content of neuronal cells and brain tissues

BACKGROUND

Mitochondria and their dynamics fuel most cellular processes both in physiological and pathological conditions. In the central nervous system, mitochondria sustain synaptic transmission and plasticity via multiple mechanisms which include their redistribution and/or expansion to higher energy demanding sites, sustaining activity changes and promoting morphological circuit adaptations.

NEW METHOD

To be able to evaluate changes in mitochondrial number and protein phenotype, we propose a novel methodological approach where the simultaneous analysis of both mitochondrial DNA and protein content is performed on each individual microsample, avoiding non-homogeneous loss of material.

RESULTS

We validated this method on neuronal-like cells and tissue samples and obtained estimates for the mitochondrial/genomic DNA ratio as well as for the abundance of protein counterparts. When the mitochondrial content per cell was evaluated in different brain areas, our results matched the known regional variation in aerobic-anaerobic metabolism. When long-term potentiation (LTP) was induced on hippocampal neurons, we detected increases in the abundance of mitochondria that correlated with the degree of synaptic enhancement.

CONCLUSIONS

Our approach can be effectively used to study the mitochondrial content andits changes in different brain cells and tissues.

The role of lipids in the central nervous system and their pathological implications in amyotrophic lateral sclerosis

Lipids play an important role in the central nervous system (CNS). They contribute to the structural integrity and physical characteristics of cell and organelle membranes, act as bioactive signalling molecules, and are utilised as fuel sources for mitochondrial metabolism. The intricate homeostatic mechanisms underpinning lipid handling and metabolism across two major CNS cell types; neurons and astrocytes, are integral for cellular health and maintenance. Here, we explore the various roles of lipids in these two cell types. Given that changes in lipid metabolism have been identified in a number of neurodegenerative diseases, we also discuss changes in lipid handling and utilisation in the context of amyotrophic lateral sclerosis (ALS), in order to identify key cellular processes affected by the disease, and inform future areas of research.

Maternal High-Fat Diet Modifies the Immature Hippocampus Vulnerability to Perinatal Asphyxia in Rats

BACKGROUND

High-fat diet (HFD) is a detrimental habit with harmful systemic consequences, including low-grade, long-lasting inflammation. During pregnancy, HFD can induce developmental changes. Moreover, HFD-related maternal obesity might enhance the risk of peripartum complications including hypoxic-ischemic encephalopathy secondary to perinatal asphyxia (PA).

OBJECTIVES

Following our previous results showing that PA increases neuroinflammation and neuronal injury in the immature hippocampus and modifies hippocampal epigenetic programming, we further aimed to establish the impact of maternal HFD on offspring hippocampus response to PA.

METHODS

We assessed hippocampal tumor necrosis factor alpha (TNFα), interleukin 1 beta -(IL-1b) and S-100B protein (S-100B), 24-48 h after PA exposure in postnatal day 6 Wistar rats, whose mothers received either the standard diet or HFD. The expression of small non-coding microRNA species miR124, miR132, miR134, miR146, and miR15a, as epigenetic markers for the maternal dietary influence on immature hippocampus response after PA, was determined 24 h after asphyxia exposure. Metabolic activity was measured using resazurin test in hippocampal cell suspension obtained 24 h after PA.

RESULTS

Our results indicate that maternal HFD additionally increases hippocampal TNFα, IL-1b, and S-100B after PA. Also, PA associated with maternal HFD induces miR124 upregulation and miR132 downregulation relative to PA only. Metabolic activity was increased in hippocampal cells from pups whose mothers received HFD.

CONCLUSION

HFD increases the PA-induced neuroinflammation and neuronal injury, and epigenetically influences homeostatic synaptic plasticity and neuronal tolerance to asphyxia, processes associated with a higher hippocampal cellular metabolism.