Neurocovid-19: A clinical neuroscience-based approach to reduce SARS-CoV-2 related mental health sequelae

Coronavirus Disease 2019 (COVID-19), caused by SARS-CoV-2, is a disaster due to not only its psychosocial impact but it also to its direct effects on the brain. The latest evidence suggests it has neuroinvasive mechanisms, in addition to neurological manifestations, and as seen in past pandemics, long-term sequelae are expected. Specific and well-structured interventions are necessary, and that's why it's important to ensure a continuity between primary care, emergency medicine, and psychiatry. Evidence shows that 2003 SARS (Severe Acute Respiratory Syndrome) survivors developed persistent psychiatric comorbidities after the infection, in addition to Chronic Fatigue Syndrome. A proper stratification of patients according not only to psychosocial factors but also an inflammatory panel and SARS-Cov-2's direct effects on the central nervous system (CNS) and the immune system, may improve outcomes. The complexity of COVID-19's pathology and the impact on the brain requires appropriate screening that has to go beyond the psychosocial impact, taking into account how stress and neuroinflammation affects the brain. This is a call for a clinical multidisciplinary approach to treat and prevent Sars-Cov-2 mental health sequelae.

The Ionic DTI Model (iDTI) of Dynamic Diffusion Tensor Imaging (dDTI)

Measurements of water molecule diffusion along fiber tracts in CNS by diffusion tensor imaging (DTI) provides a static map of neural connections between brain centers, but does not capture the electrical activity along axons for these fiber tracts. Here, a modification of the DTI method is presented to enable the mapping of active fibers. It is termed dynamic diffusion tensor imaging (dDTI) and is based on a hypothesized “anisotropy reduction due to axonal excitation” (“AREX”). The potential changes in water mobility accompanying the movement of ions during the propagation of action potentials along axonal tracts are taken into account. Specifically, the proposed model, termed “ionic DTI model”, was formulated as follows.•

First, based on theoretical calculations, we calculated the molecular water flow accompanying the ionic flow perpendicular to the principal axis of fiber tracts produced by electrical conduction along excited myelinated and non-myelinated axons.

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Based on the changes in molecular water flow we estimated the signal changes as well as the changes in fractional anisotropy of axonal tracts while performing a functional task.

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The variation of fractional anisotropy in axonal tracts could allow mapping the active fiber tracts during a functional task.

Although technological advances are necessary to enable the robust and routine measurement of this electrical activity-dependent movement of water molecules perpendicular to axons, the proposed model of dDTI defines the vectorial parameters that will need to be measured to bring this much needed technique to fruition.

Microstructural abnormalities in subcortical reward circuitry of subjects with major depressive disorder

BACKGROUND

Previous studies of major depressive disorder (MDD) have focused on abnormalities in the prefrontal cortex and medial temporal regions. There has been little investigation in MDD of midbrain and subcortical regions central to reward/aversion function, such as the ventral tegmental area/substantia nigra (VTA/SN), and medial forebrain bundle (MFB).

METHODOLOGY/PRINCIPAL FINDINGS

We investigated the microstructural integrity of this circuitry using diffusion tensor imaging (DTI) in 22 MDD subjects and compared them with 22 matched healthy control subjects. Fractional anisotropy (FA) values were increased in the right VT and reduced in dorsolateral prefrontal white matter in MDD subjects. Follow-up analysis suggested two distinct subgroups of MDD patients, which exhibited non-overlapping abnormalities in reward/aversion circuitry. The MDD subgroup with abnormal FA values in VT exhibited significantly greater trait anxiety than the subgroup with normal FA values in VT, but the subgroups did not differ in levels of anhedonia, sadness, or overall depression severity.

CONCLUSIONS/SIGNIFICANCE

These findings suggest that MDD may be associated with abnormal microstructure in brain reward/aversion regions, and that there may be at least two subtypes of microstructural abnormalities which each impact core symptoms of depression.

Association of a polymorphism near CREB1 with differential aversion processing in the insula of healthy participants

CONTEXT

Previous functional neuroimaging studies have identified a network of brain regions that process aversive stimuli, including anger. A polymorphism near the cyclic adenosine monophosphate response element binding protein gene (CREB1) has recently been associated with greater self-reported effort at anger control as well as risk for antidepressant treatment-emergent suicidality in men with major depressive disorder, but its functional effects have not been studied.

OBJECTIVE

To determine whether this genetic variant is associated with altered brain processing of and behavioral avoidance responses to angry facial expressions.

DESIGN AND PARTICIPANTS

A total of 28 white participants (mean age, 29.2 years; 13 women) were screened using the Structured Clinical Interview for DSM-IV to exclude any lifetime Axis I psychiatric disorder and were genotyped for rs4675690, a single-nucleotide polymorphism near CREB1.

MAIN OUTCOME MEASURES

Blood oxygenation level-dependent signal by functional magnetic resonance imaging in the amygdala, insula, anterior cingulate, and orbitofrontal cortex during passive viewing of photographs of faces with emotional expressions. To measure approach and avoidance responses to anger, an off-line key-press task that traded effort for viewing time assessed valuation of angry faces compared with other expressions.

RESULTS

The CREB1-linked single-nucleotide polymorphism was associated with significant differential activation in an extended neural network responding to angry and other facial expressions. The CREB1-associated insular activation was coincident with activation associated with behavioral avoidance of angry faces.

CONCLUSIONS

A polymorphism near CREB1 is associated with responsiveness to angry faces in a brain network implicated in processing aversion. Coincident activation in the left insula is further associated with behavioral avoidance of these stimuli.

Decreased volume of the brain reward system in alcoholism

BACKGROUND

Reinforcement of behavioral responses involves a complex cerebral circuit engaging specific neuronal networks that are modulated by cortical oversight systems affiliated with emotion, memory, judgment, and decision making (collectively referred to in this study as the "extended reward and oversight system" or "reward network"). We examined whether reward-network brain volumes are reduced in alcoholics and how volumes of subcomponents within this system are correlated with memory and drinking history.

METHODS

Morphometric analysis was performed on magnetic resonance brain scans in 21 abstinent long-term chronic alcoholic men and 21 healthy control men, group-matched on age, verbal IQ, and education. We derived volumes of total brain and volumes of cortical and subcortical reward-related structures including the dorsolateral-prefrontal, orbitofrontal, cingulate cortices, and the insula, as well as the amygdala, hippocampus, nucleus accumbens septi (NAc), and ventral diencephalon.

RESULTS

Morphometric analyses of reward-related regions revealed decreased total reward-network volume in alcoholic subjects. Volume reduction was most pronounced in right dorsolateral-prefrontal cortex, right anterior insula, and right NAc, as well as left amygdala. In alcoholics, NAc and anterior insula volumes increased with length of abstinence, and total reward-network and amygdala volumes correlated positively with memory scores.

CONCLUSIONS

The observation of decreased reward-network volume suggests that alcoholism is associated with alterations in this neural reward system. These structural reward system deficits and their correlation with memory scores elucidate underlying structural-functional relationships between alcoholism and emotional and cognitive processes.

fMRI of sensitization to angry faces

This study examined what is communicated by facial expressions of anger and mapped the neural substrates, evaluating the motivational salience of these stimuli. During functional magnetic resonance imaging, angry and neutral faces were presented to human subjects. Across experimental runs, signal adaptation was observed. Whereas fearful faces have reproducibly evoked response habituation in amygdala and prefrontal cortex, angry faces evoked sensitization in the insula, cingulate, thalamus, basal ganglia, and hippocampus. Complementary offline rating and keypress experiments determined an aversive rank ordering of angry, fearful, neutral, and happy faces and revealed behavioral sensitization to the angry faces. Subjects rated angry faces, in contrast to other face categories such as fear, as significantly more likely to directly inflict harm. Furthermore, they rated angry faces as significantly less likely to produce positive emotional outcomes than the other face categories. Together these data argue that angry faces, a directly aversive stimulus, produce a sensitization response.

Decreased absolute amygdala volume in cocaine addicts

The amygdala is instrumental to a set of brain processes that lead to cocaine consumption, including those that mediate reward and drug craving. This study examined the volumes of the amygdala and hippocampus in cocaine-addicted subjects and matched healthy controls and determined that the amygdala but not the hippocampus was significantly reduced in volume. The right-left amygdala asymmetry in control subjects was absent in the cocaine addicts. Topological analysis of amygdala isosurfaces (population averages) revealed that the isosurface of the cocaine-dependent group undercut the anterior and superior surfaces of the control group, implicating a difference in the corticomedial and basolateral nuclei. In cocaine addicts, amygdala volume did not correlate with any measure of cocaine use. The amygdala symmetry coefficient did correlate with baseline but not cocaine-primed craving. These findings argue for a condition that predisposes the individual to cocaine dependence by affecting the amygdala, or a primary event early in the course of cocaine use.

To die or to sleep, perhaps to dream

Establishing social contacts is the raison d'être of neurons throughout their entire life span. To form and retain functional connections, neuronal differentiation and death are ruthlessly regulated in development and kept strictly under control in post-mitotic systems. Derangements in neural networks affect neuronal populations at large. Therefore, failure to retain synaptic connectivity is linked to dysfunction and often followed by neuronal death. Loss of neurons is a predominant feature of neurodegenerative disease. Nevertheless, neuronal cell death is not an obligate requirement for neural dysfunction at the level of distributed circuits or local circuits. Although more or less wide spread neuronal loss can occur after acute insults such as brain ischemia or invasion of the brain by pathogens, neuronal death is a hallmark of end-stage neurodegenerative and psychiatric disease. The relative contributions made by loss of synaptic connectivity versus cell death for these diseases are still debated. Here these processes are discussed in relation to acute and chronic CNS disorders.

Acute cortisol administration triggers craving in individuals with cocaine dependence

Stress is often mentioned as a factor in the development of drug abuse. Twelve cocaine dependent individuals were administered a stress hormone, cortisol, along with cocaine and saline via intravenous boluses, in a double-blind, counterbalanced fashion. Self-reports of mood states were collected prior to, during, and 20 minutes after each bolus was administered. Cortisol produced significant increases in craving while cocaine significantly elevated all subjective ratings (ie, craving, high, rush, and low). These pilot data suggest that cortisol can induce a state that is associated with drug abuse.

Chronic ingestion of ethanol up-regulates NMDAR1 receptor subunit immunoreactivity in rat hippocampus

We examined the effects of chronic ethanol exposure on the levels of N-methyl-D-aspartate receptor subunit 1 (NMDAR1) protein, an essential component of N-methyl-D-aspartate glutamate receptors, in rat brain. By immunoblotting procedures using a specific antibody for the NMDAR1 subunit, we found that ethanol dramatically up-regulated (by 65%) NMDAR1 immunoreactivity in the hippocampus but not in the nucleus accumbens, cerebral cortex, or striatum. In contrast, ethanol did not alter the levels of glutamate receptor subunit (GLUR) 1 or GLUR2 protein, subunits that make up the alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid glutamate receptor, in the hippocampus. Because ethanol can potentially influence many different neurotransmitter systems, we examined whether chronic treatment with several psychotropic drugs with different pharmacological profiles (cocaine, haloperidol, SCH 23390, imipramine, and morphine) could mimic the effect of ethanol. None of these agents increased hippocampal NMDAR1 subunit immunoreactivity after chronic administration. Increased NMDAR1 subunit levels in the hippocampus after chronic ethanol exposure may represent an important neurochemical substrate for some of the features associated with ethanol dependence and withdrawal.

Regional, cellular, and ultrastructural distribution of N-methyl-D-aspartate receptor subunit 1 in monkey hippocampus

The regional, cellular, and subcellular distributions of N-methyl-D-aspartate (NMDA) receptor subunit 1, NMDAR-1, were investigated in monkey hippocampus by using a monoclonal antibody directed against a fusion protein corresponding to aa 660-811 of NMDAR-1. The data indicate that many neurons in each subfield of the hippocampus contain NMDAR-1 protein, although the intensity and distribution of immunoreactivity varied across regions, strata, and cellular compartments. In stratum lucidum of CA3, mossy fiber axons were immunoreactive for NMDAR-1, which may correspond to previously hypothesized presynaptic receptors. NMDAR-1-labeled postsynaptic profiles were present in stratum radiatum of CA3 but were largely absent from stratum lucidum. Such intraneuronal segregation of glutamate receptor subunits or classes may be spatially correlated with afferent systems that exhibit laminar segregation and terminate in different portions of the postsynaptic dendritic tree. For example, in CA3 pyramidal cells, NMDA receptors are postsynaptic in distal apical dendrites (stratum radiatum) where NMDA-dependent long-term potentiation in rats is mediated by associational/commissural afferents, and are absent from proximal apical dendrites (stratum lucidum), where NMDA-independent long-term potentiation is mediated by the mossy fiber input.

Protein chemical characterization and immunocytochemical localization of the NMDA receptor subunit NMDA R1

In the rat central nervous system, the mRNA encoding the N-methyl-D-aspartate receptor subunit R1 is the most ubiquitously distributed among the cloned subunit mRNAs of this glutamate receptor subtype. The N-methyl-D-aspartate R1 mRNA is very abundantly expressed and N-methyl-D-aspartate R1 coexpression is necessary for functional expression of all other cloned N-methyl-D-aspartate receptor subunits. Therefore, the R1 subunit is likely to be an essential component of all known N-methyl-D-aspartate receptors in rat brain. By employing sequence specific polyclonal antibodies, we demonstrate that rat brain N-methyl-D-aspartate R1, as well as recombinantly expressed receptor protein, has an apparent molecular mass of 116 kDa in sodium dodecyl sulfate polyacrylamide gel electrophoresis. The receptor protein is heavily glycosylated. It is specifically localized to the central nervous system, and it co-enriches with synaptic membranes upon subcellular fractionation of the cerebral cortex. Chemical cross-linking of synaptic membrane proteins shows that the N-methyl-D-aspartate R1 protein is part of a receptor protein complex with a molecular mass of 730 kDa. By using immunocytochemical methods, we demonstrate a widespread but distinct distribution of N-methyl-D-aspartate R1 in neurons of the rat brain, with prominent immunostaining in certain layers of the cerebral cortex, in the hippocampus and dentate gyrus, as well as in the cerebellum.

Expression of endogenous NMDAR1 transcripts without receptor protein suggests post-transcriptional control in PC12 cells

Expression of RNA for the NMDAR1 subunit of the N-methyl-D-aspartate receptor was detected by Northern hybridization in both nerve growth factor-differentiated and undifferentiated rat pheochromocytoma (PC12) cells. The NMDA receptor type 1 (NMDAR1) message in PC12 cells was similar in size to that expressed in hippocampal neurons. PC12 cell cDNAs that were amplified by polymerase chain reaction with primers flanking the coding region of NMDAR1 corresponded to the NMDAR1 splice variant NMDA receptor type 1 isoform C (NMDAR1C). Using calcium imaging or patch-clamp recording, no functional NMDA-gated ion channels were found in PC12 cells. A monoclonal antibody against NMDAR1 was developed in order to investigate whether or not NMDAR1 protein was present in PC12 cells. Only trace amounts of NMDAR1 protein were found in native PC12 cells. However, expression of NMDAR1 protein was detected in PC12 cells that were transfected with an expression vector containing an NMDAR1C clone under control of a cytomegalovirus promoter. These findings suggest that the expression of NMDAR1 protein in PC12 cells may be controlled by post-transcriptional mechanisms. The PC12 cell line may serve as a model system for the study of the transcriptional, post-transcriptional, and translational regulation of NMDAR1. Furthermore, the presence of NMDAR1 RNA in a particular cell type may not necessarily indicate expression of NMDAR1 protein.

Determinants of the calcium permeation of ligand-gated cation channels

Fast synaptic transmission in the vertebrate brain is mediated by ligand-gated channel receptors. As some of these receptors have been implicated in learning and memory, it is important to understand their mechanism of action at a molecular level. Excitatory receptors are members of large gene families of related channels that are gated by acetylcholine, serotonin, and the most abundant neurotransmitter, glutamate. Within the last year, a number of important studies have focused on the ability of these channels to flux calcium ions. Calcium entry into neurons through some of these channels triggers biochemical cascades, which can lead to changes in synaptic efficacy, presumed to be a requisite for memory formation, or if it occurs in excess, to cell death. Recent studies that attempt to determine the channel structures responsible for this calcium conductance will be discussed.

Coagulation factors X, Xa, and protein S as potent mitogens of cultured aortic smooth muscle cells

Smooth muscle cells (SMCs) in the rat carotid artery leave the quiescent state and proliferate after balloon catheter injury. The precise signals responsible for this SMC mitogenesis need to be elucidated. Although platelet-derived growth factor (PDGF), a potent SMC mitogen, is released from activated platelets, damaged endothelium, and macrophages, it cannot be solely responsible for this proliferation. In search of other SMC growth factors, we have examined several proteins of the coagulation cascade. At nanomolar concentrations, factors X, Xa, and protein S promote cultured rat aortic SMC mitosis. In contrast, factor IX is only weakly mitogenic, whereas factor VII and protein C fail to stimulate SMC division. Protein S, the most mitogenic of these coagulation cascade factors, stimulates DNA synthesis in cultured SMCs with a time course similar to that of PDGF-AA and without the delay observed for transforming growth factor beta. Antistasin and tick anticoagulant peptide, two specific factor Xa inhibitors, inhibit SMC mitogenesis due to Xa and protein S. Coagulation factors that possess mitogenic activity may contribute to intimal SMC proliferation after vascular injury as a result of angioplasty or vascular compromise during atherogenesis.

The characterization and localization of the glutamate receptor subunit GluR1 in the rat brain

The cloning of cDNAs that encode functional glutamate receptors makes it possible to produce antibodies that can be used as high-affinity probes for the localization and characterization of these receptors in the mammalian brain. We have made antibodies to different regions of the first cloned member of this family, GluR1, using bacterially overproduced antigen. On Western blots, these antisera detect glycoprotein(s) of 105 kDa present in crude membranes of the hippocampus and cerebellum. The 105-kDa band is associated with postsynaptic densities, and it is observed in cultured cells upon transfection with the GluR1 cDNA. Although glutamate receptors are thought to be the most prevalent excitatory ligand-gated ion channel in the mammalian brain, immunohistochemistry reveals that the receptors recognized by these antisera are localized predominantly in neurons of the cerebellum and some structures of the limbic system, including the hippocampus, the central nucleus of the amygdala, and portions of the septum. This pattern of expression is, in general, consistent with the distribution of GluR1 mRNA as determined by in situ hybridization histochemistry. Our results suggest that glutamate excitatory circuits recognized by these antisera are predominantly found in regions of the limbic system that are reciprocally interconnected.

Receptors coupled to ionic channels: the glutamate receptor family

Glutamate-gated ion channels belong to a complex family of receptors containing several pharmacological subtypes. They are thought to be essential for the acquisition of associative memory and for activity-dependent synaptogenesis, and have been implicated in several central nervous system diseases. Within the past year, molecular cloning of the first glutamate receptor channel and several related subunits has opened new approaches for understanding the basis of these important phenomena.

Structure and distribution of the Notch protein in developing Drosophila

Antibodies to Notch show that it is a stable, high-molecular-weight transmembrane glycoprotein, with epidermal growth factor (EGF)-like elements exposed on the cell surface. The protein is phosphorylated variably on serines of the cytoplasmic domain. Individual Notch polypeptide chains appear to be associated with one another by disulfide bonds, suggesting that homotypic interaction of these proteins is required for function. Immunocytochemistry has revealed striking features of Notch expression that might clarify its function: Cells of the ventral neurogenic ectoderm become conspicuously labeled with the protein prior to embryonic neurogenesis, and Notch appears to be associated with cells destined for both neural and epidermal lineages. High levels of Notch become restricted to neuroblasts as they delaminate from the embryonic ectoderm and are apposed to mesoderm. Mesodermal cells express Notch also, suggesting a possible involvement in neurogenesis, or an unknown role in mesoderm differentiation. In larvae and pupae, a correlation of expression and neuroblast mitotic activity is seen for many cells. Notch produced by a dividing neuroblast may persist on derivative cells, including terminally differentiated neurons and nerve processes. In the larval eye imaginal disk, strong Notch expression appears in the morphogenetic furrow, uniformly on cell surfaces as they cluster to form ommatidia. Expression persists on ommatidia after release from the furrow. These patterns suggest a role for Notch in position-dependent development in both initiation and maintenance of cell-surface interactions. In the eye and embryonic ectoderm, uniform expression on cells interacting to produce different developmental lineages from a single primordium suggests that Notch alone may not be sufficient to elaborate cell fates.

Inhibition of lung tumor colonization by leech salivary gland extracts from Haementeria ghilianii

Salivary gland extract from the South American leech Haementeria ghilianii, administered i.v. on the same day as the i.v. inoculation of T241 sarcoma cells, completely suppresses colonization of the mediastinal lymph nodes and markedly reduces the number and size of lung tumor colonies produced by this tumor. Additional studies indicate that the extract contains various types of proteinase inhibitors and has the capacity to inhibit clotting and platelet aggregation by tumor material and collagen. Although not yet proved by direct evidence, these activities may be involved in the inhibitory effect of lung tumor colonization by the leech extract.

Molecular analysis of the c-myc locus in normal tissue and in avian leukosis virus-induced lymphomas

We isolated molecular clones of the provirus-host cell junctions (tumor junction fragments) from two avian leukosis virus-induced lymphomas and compared the structures of these clones with a clone of the normal c-myc gene. Restriction mapping and DNA sequencing demonstrated that normal proviral integration events occurred adjacent to c-myc in both tumors, without gross structural alteration of c-myc. The right long terminal repeat of an avian leukosis virus provirus is integrated upstream from the bulk of the c-myc coding sequences and oriented such that transcription can initiate within the long terminal repeat and proceed downstream into c-myc. A comparison of a tumor junction fragment with the v-myc gene showed that there are two regions of v-myc-related sequences (which are probably exons) separated by 1 kilobase of sequences unrelated to v-myc (probably an intron). A DNA sequence analysis of the tumor junction fragments suggested that integration had occurred in exons adjacent to splice donor sites. This suggests that there are additional exons and introns in c-myc. Based on these findings, a model is proposed for the genesis of the tumor-specific RNAs containing viral-5' and c-myc information in avian leukosis virus-induced lymphomas.

Prostacyclin: a potentially valuable agent for preserving myocardial tissue in acute myocardial ischemia

Prostacyclin, a potent, naturally occurring prostaglandin exerts a variety of cardiovascular and cellular actions of potential value in acute myocardial ischemia. These properties include the reduction of systemic blood pressure without changing heart rate, the lowering of coronary vascular and total peripheral resistance, the inhibition of platelet aggregation and the concomitant formation of thromboxane B2, and the reduction of the release of lysosomal enzymes.