Brain-Region-Specific Genes Form the Major Pathways Featuring Their Basic Functional Role: Their Implication in Animal Chronic Stress Model.

The analysis of RNA-Sec data from murine bulk tissue samples taken from five brain regions associated with behavior and stress response was conducted. The focus was on the most contrasting brain region-specific genes (BRSG) sets in terms of their expression rates. These BRSGs are identified as genes with a distinct outlying (high) expression rate in a specific region compared to others used in the study. The analysis suggested that BRSG sets form non-randomly connected compact gene networks, which correspond to the major neuron-mediated functional processes or pathways in each brain region. The number of BRSGs and the connection rate were found to depend on the heterogeneity and coordinated firing rate of neuron types in each brain region. The most connected pathways, along with the highest BRSG number, were observed in the Striatum, referred to as Medium Spiny Neurons (MSNs), which make up 95% of neurons and exhibit synchronous firing upon dopamine influx. However, the Ventral Tegmental Area/Medial Raphe Nucleus (VTA/MRN) regions, although primarily composed of monoaminergic neurons, do not fire synchronously, leading to a smaller BRSG number. The Hippocampus (HPC) region, on the other hand, displays significant neuronal heterogeneity, with glutamatergic neurons being the most numerous and synchronized. Interestingly, the two monoaminergic regions involved in the study displayed a common BRSG subnetwork architecture, emphasizing their proximity in terms of axonal throughput specifics and high-energy metabolism rates. This finding suggests the concerted evolution of monoaminergic neurons, leading to unique adaptations at the genic repertoire scale. With BRSG sets, we were able to highlight the contrasting features of the three groups: control, depressive, and aggressive mice in the animal chronic stress model. Specifically, we observed a decrease in serotonergic turnover in both the depressed and aggressive groups, while dopaminergic emission was high in both groups. There was also a notable absence of dopaminoceptive receptors on the postsynaptic membranes in the striatum in the depressed group. Additionally, we confirmed that neurogenesis BRSGs are specific to HPC, with the aggressive group showing attenuated neurogenesis rates compared to the control/depressive groups. We also confirmed that immune-competent cells like microglia and astrocytes play a crucial role in depressed phenotypes, including mitophagy-related gene Prkcd. Based on this analysis, we propose the use of BRSG sets as a suitable framework for evaluating case-control group-wise assessments of specific brain region gene pathway responses.

Age-Dependent Changes in the Relationships between Traits Associated with the Pathogenesis of Stress-Sensitive Hypertension in ISIAH Rats.

Hypertension is one of the most significant risk factors for many cardiovascular diseases. At different stages of hypertension development, various pathophysiological processes can play a key role in the manifestation of the hypertensive phenotype and of comorbid conditions. Accordingly, it is thought that when diagnosing and choosing a strategy for treating hypertension, it is necessary to take into account age, the stage of disorder development, comorbidities, and effects of emotional-psychosocial factors. Nonetheless, such an approach to choosing a treatment strategy is hampered by incomplete knowledge about details of age-related associations between the numerous features that may contribute to the manifestation of the hypertensive phenotype. Here, we used two groups of male F2(ISIAHxWAG) hybrids of different ages, obtained by crossing hypertensive ISIAH rats (simulating stress-sensitive arterial hypertension) and normotensive WAG rats. By principal component analysis, the relationships among 21 morphological, physiological, and behavioral traits were examined. It was shown that the development of stress-sensitive hypertension in ISIAH rats is accompanied not only by an age-dependent (FDR < 5%) persistent increase in basal blood pressure but also by a decrease in the response to stress and by an increase in anxiety. The plasma corticosterone concentration at rest and its increase during short-term restraint stress in a group of young rats did not have a straightforward relationship with the other analyzed traits. Nonetheless, in older animals, such associations were found. Thus, the study revealed age-dependent relationships between the key features that determine hypertension manifestation in ISIAH rats. Our results may be useful for designing therapeutic strategies against stress-sensitive hypertension, taking into account the patients' age.

Animal Models of Hypertension (ISIAH Rats), Catatonia (GC Rats), and Audiogenic Epilepsy (PM Rats) Developed by Breeding.

Research into genetic and physiological mechanisms of widespread disorders such as arterial hypertension as well as neuropsychiatric and other human diseases is urgently needed in academic and practical medicine and in the field of biology. Nevertheless, such studies have many limitations and pose difficulties that can be overcome by using animal models. To date, for the purposes of creating animal models of human pathologies, several approaches have been used: pharmacological/chemical intervention; surgical procedures; genetic technologies for creating transgenic animals, knockouts, or knockdowns; and breeding. Although some of these approaches are good for certain research aims, they have many drawbacks, the greatest being a strong perturbation (in a biological system) that, along with the expected effect, exerts side effects in the study. Therefore, for investigating the pathogenesis of a disease, models obtained using genetic selection for a target trait are of high value as this approach allows for the creation of a model with a "natural" manifestation of the pathology. In this review, three rat models are described: ISIAH rats (arterial hypertension), GC rats (catatonia), and PM rats (audiogenic epilepsy), which are developed by breeding in the Laboratory of Evolutionary Genetics at the Institute of Cytology and Genetics (the Siberian Branch of the Russian Academy of Sciences).

Elucidation of the Landscape of Alternatively Spliced Genes and Features in the Dorsal Striatum of Aggressive/Aggression-Deprived Mice in the Model of Chronic Social Conflicts.

Both aggressive and aggression-deprived (AD) individuals represent pathological cases extensively studied in psychiatry and substance abuse disciplines. We employed the animal model of chronic social conflicts curated in our laboratory for over 30 years. In the study, we pursued the task of evaluation of the key events in the dorsal striatum transcriptomes of aggression-experienced mice and AD species, as compared with the controls, using RNA-seq profiling. We evaluated the alternative splicing-mediated transcriptome dynamics based on the RNA-seq data. We confined our attention to the exon skipping (ES) events as the major AS type for animals. We report the concurrent posttranscriptional and posttranslational regulation of the ES events observed in the phosphorylation cycles (in phosphoproteins and their targets) in the neuron-specific genes of the striatum. Strikingly, we found that major neurospecific splicing factors (Nova1, Ptbp1, 2, Mbnl1, 2, and Sam68) related to the alternative splicing regulation of cAMP genes (Darpp-32, Grin1, Ptpn5, Ppp3ca, Pde10a, Prkaca, Psd95, and Adora1) are upregulated specifically in aggressive individuals as compared with the controls and specifically AD animals, assuming intense switching between isoforms in the cAMP-mediated (de)phosphorylation signaling cascade. We found that the coding alternative splicing events were mostly attributed to synaptic plasticity and neural development-related proteins, while the nonsense-mediated decay-associated splicing events are mostly attributed to the mRNA processing of genes, including the spliceosome and splicing factors. In addition, considering the gene families, the transporter (Slc) gene family manifested most of the ES events. We found out that the major molecular systems employing AS for their plasticity are the 'spliceosome', 'chromatin rearrangement complex', 'synapse', and 'neural development/axonogenesis' GO categories. Finally, we state that approximately 35% of the exon skipping variants in gene coding regions manifest the noncoding variants subject to nonsense-mediated decay, employed as a homeostasis-mediated expression regulation layer and often associated with the corresponding gene expression alteration.

Effects of Positive Fighting Experience and Its Subsequent Deprivation on the Expression Profile of Mouse Hippocampal Genes Associated with Neurogenesis.

The hippocampus is known as the brain region implicated in visuospatial processes and processes associated with learning and short- and long-term memory. An important functional characteristic of the hippocampus is lifelong neurogenesis. A decrease or increase in adult hippocampal neurogenesis is associated with a wide range of neurological diseases. We have previously shown that in adult male mice with a chronic positive fighting experience in daily agonistic interactions, there is an increase in the proliferation of progenitor neurons and the production of young neurons in the dentate gyrus (in hippocampus), and these neurogenesis parameters remain modified during 2 weeks of deprivation of further fights. The aim of the present work was to identify hippocampal genes associated with neurogenesis and involved in the formation of behavioral features in mice with the chronic experience of wins in aggressive confrontations, as well as during the subsequent 2-week deprivation of agonistic interactions. Hippocampal gene expression profiles were compared among three groups of adult male mice: chronically winning for 20 days in the agonistic interactions, chronically victorious for 20 days followed by the 2-week deprivation of fights, and intact (control) mice. Neurogenesis-associated genes were identified whose transcription levels changed during the social confrontations and in the subsequent period of deprivation of fights. In the experimental males, some of these genes are associated with behavioral traits, including abnormal aggression-related behavior, an abnormal anxiety-related response, and others. Two genes encoding transcription factors (Nr1d1 and Fmr1) were likely to contribute the most to the between-group differences. It can be concluded that the chronic experience of wins in agonistic interactions alters hippocampal levels of transcription of multiple genes in adult male mice. The transcriptome changes get reversed only partially after the 2-week period of deprivation of fights. The identified differentially expressed genes associated with neurogenesis and involved in the control of a behavior/neurological phenotype can be used in further studies to identify targets for therapeutic correction of the neurological disturbances that develop in winners under the conditions of chronic social confrontations.

The Dysfunction of Carcinogenesis- and Apoptosis-Associated Genes that Develops in the Hypothalamus under Chronic Social Defeat Stress in Male Mice.

Chronic social stress caused by daily agonistic interactions in male mice leads to a mixed anxiety/depression-like disorder that is accompanied by the development of psychogenic immunodeficiency and stimulation of oncogenic processes concurrently with many neurotranscriptomic changes in brain regions. The aim of the study was to identify carcinogenesis- and apoptosis-associated differentially expressed genes (DEGs) in the hypothalamus of male mice with depression-like symptoms and, for comparison, in aggressive male mice with positive social experience. To obtain two groups of animals with the opposite 20-day social experiences, a model of chronic social conflict was used. Analysis of RNA-Seq data revealed similar expression changes for many DEGs between the aggressive and depressed animals in comparison with the control group; however, the number of DEGs was significantly lower in the aggressive than in the depressed mice. It is likely that the observed unidirectional changes in the expression of carcinogenesis- and apoptosis-associated genes in the two experimental groups may be a result of prolonged social stress (of different severity) caused by the agonistic interactions. In addition, 26 DEGs were found that did not change expression in the aggressive animals and could be considered genes promoting carcinogenesis or inhibiting apoptosis. Akt1, Bag6, Foxp4, Mapk3, Mapk8, Nol3, Pdcd10, and Xiap were identified as genes whose expression most strongly correlated with the expression of other DEGs, suggesting that their protein products play a role in coordination of the neurotranscriptomic changes in the hypothalamus. Further research into functions of these genes may be useful for the development of pharmacotherapies for psychosomatic pathologies.

Advances of Brain Transcriptomics.

Advancements in RNA sequencing technology in past decade have underlined its power for elucidating the brain gene networks responsible for various stressful factors, as well as the pathologies associated with both genetically determined neurodegenerative diseases and those acquired during the lifespan [...].

Identification of Hypothalamic Long Noncoding RNAs Associated with Hypertension and the Behavior/Neurological Phenotype of Hypertensive ISIAH Rats.

Long noncoding RNAs (lncRNAs) play an important role in the control of many physiological and pathophysiological processes, including the development of hypertension and other cardiovascular diseases. Nonetheless, the understanding of the regulatory function of many lncRNAs is still incomplete. This work is a continuation of our earlier study on the sequencing of hypothalamic transcriptomes of hypertensive ISIAH rats and control normotensive WAG rats. It aims to identify lncRNAs that may be involved in the formation of the hypertensive state and the associated behavioral features of ISIAH rats. Interstrain differences in the expression of seven lncRNAs were validated by quantitative PCR. Differential hypothalamic expression of lncRNAs LOC100910237 and RGD1562890 between hypertensive and normotensive rats was shown for the first time. Expression of four lncRNAs (Snhg4, LOC100910237, RGD1562890, and Tnxa-ps1) correlated with transcription levels of many hypothalamic genes differentially expressed between ISIAH and WAG rats (DEGs), including genes associated with the behavior/neurological phenotype and hypertension. After functional annotation of these DEGs, it was concluded that lncRNAs Snhg4, LOC100910237, RGD1562890, and Tnxa-ps1 may be involved in the hypothalamic processes related to immune-system functioning and in the response to various exogenous and endogenous factors, including hormonal stimuli. Based on the functional enrichment analysis of the networks, an association of lncRNAs LOC100910237 and Tnxa-ps1 with retinol metabolism and an association of lncRNAs RGD1562890 and Tnxa-ps1 with type 1 diabetes mellitus are proposed for the first time. Based on a discussion, it is hypothesized that previously functionally uncharacterized lncRNA LOC100910237 is implicated in the regulation of hypothalamic processes associated with dopaminergic synaptic signaling, which may contribute to the formation of the behavioral/neurological phenotype and hypertensive state of ISIAH rats.

Stress Reactivity, Susceptibility to Hypertension, and Differential Expression of Genes in Hypertensive Compared to Normotensive Patients.

Although half of hypertensive patients have hypertensive parents, known hypertension-related human loci identified by genome-wide analysis explain only 3% of hypertension heredity. Therefore, mainstream transcriptome profiling of hypertensive subjects addresses differentially expressed genes (DEGs) specific to gender, age, and comorbidities in accordance with predictive preventive personalized participatory medicine treating patients according to their symptoms, individual lifestyle, and genetic background. Within this mainstream paradigm, here, we determined whether, among the known hypertension-related DEGs that we could find, there is any genome-wide hypertension theranostic molecular marker applicable to everyone, everywhere, anytime. Therefore, we sequenced the hippocampal transcriptome of tame and aggressive rats, corresponding to low and high stress reactivity, an increase of which raises hypertensive risk; we identified stress-reactivity-related rat DEGs and compared them with their known homologous hypertension-related animal DEGs. This yielded significant correlations between stress reactivity-related and hypertension-related fold changes (log2 values) of these DEG homologs. We found principal components, PC1 and PC2, corresponding to a half-difference and half-sum of these log2 values. Using the DEGs of hypertensive versus normotensive patients (as the control), we verified the correlations and principal components. This analysis highlighted downregulation of ß-protocadherins and hemoglobin as whole-genome hypertension theranostic molecular markers associated with a wide vascular inner diameter and low blood viscosity, respectively.

Correlation of Expression Changes between Genes Controlling 5-HT Synthesis and Genes Crh and Trh in the Midbrain Raphe Nuclei of Chronically Aggressive and Defeated Male Mice.

Midbrain raphe nuclei (MRNs) contain a large number of serotonergic neurons associated with the regulation of numerous types of psychoemotional states and physiological processes. The aim of this work was to study alterations of the MRN transcriptome in mice with prolonged positive or negative fighting experience and to identify key gene networks associated with the regulation of serotonergic system functioning. Numerous genes underwent alterations of transcription in the MRNs of male mice that either manifested aggression or experienced social defeat in daily agonistic interactions. The expression of the Tph2 gene encoding the rate-limiting enzyme of the serotonin synthesis pathway correlated with the expression of many genes, 31 of which were common between aggressive and defeated mice and were downregulated in the MRNs of mice of both experimental groups. Among these common differentially expressed genes (DEGs), there were genes associated with behavior, learning, memory, and synaptic signaling. These results suggested that, in the MRNs of the mice, the transcriptome changes associated with serotonergic regulation of various processes are similar between the two groups (aggressive and defeated). In the MRNs, more DEGs correlating with Tph2 expression were found in defeated mice than in the winners, which is probably a consequence of deeper Tph2 downregulation in the losers. It was shown for the first time that, in both groups of experimental mice, the changes in the transcription of genes controlling the synthesis and transport of serotonin directly correlate with the expression of genes Crh and Trh, which control the synthesis of corticotrophin- and thyrotropin-releasing hormones. Our findings indicate that CRH and TRH locally produced in MRNs are related to serotonergic regulation of brain processes during a chronic social conflict.

Reduced Expression of Slc Genes in the VTA and NAcc of Male Mice with Positive Fighting Experience.

A range of several psychiatric medications targeting the activity of solute carrier (SLC) transporters have proved effective for treatment. Therefore, further research is needed to elucidate the expression profiles of the Slc genes, which may serve as markers of altered brain metabolic processes and neurotransmitter activities in psychoneurological disorders. We studied the Slc differentially expressed genes (DEGs) using transcriptomic profiles in the ventral tegmental area (VTA), nucleus accumbens (NAcc), and prefrontal cortex (PFC) of control and aggressive male mice with psychosis-like behavior induced by repeated experience of aggression accompanied with wins in daily agonistic interactions. The majority of the Slc DEGs were shown to have brain region-specific expression profiles. Most of these genes in the VTA and NAcc (12 of 17 and 25 of 26, respectively) were downregulated, which was not the case in the PFC (6 and 5, up- and downregulated, respectively). In the VTA and NAcc, altered expression was observed for the genes encoding the transporters of neurotransmitters as well as inorganic and organic ions, amino acids, metals, glucose, etc. This indicates an alteration in transport functions for many substrates, which can lead to the downregulation or even disruption of cellular and neurotransmitter processes in the VTA and NAcc, which are attributable to chronic stimulation of the reward systems induced by positive fighting experience. There is not a single Slc DEG common to all three brain regions. Our findings show that in male mice with repeated experience of aggression, altered activity of neurotransmitter systems leads to a restructuring of metabolic and neurotransmitter processes in a way specific for each brain region. We assume that the scoring of Slc DEGs by the largest instances of significant expression co-variation with other genes may outline a candidate for new prognostic drug targets. Thus, we propose that the Slc genes set may be treated as a sensitive genes marker scaffold in brain RNA-Seq studies.

Hypothalamic Norepinephrine Concentration and Heart Mass in Hypertensive ISIAH Rats Are Associated with a Genetic Locus on Chromosome 18.

The relationship between activation of the sympathetic nervous system and cardiac hypertrophy has long been known. However, the molecular genetic basis of this association is poorly understood. Given the known role of hypothalamic norepinephrine in the activation of the sympathetic nervous system, the aim of the work was to carry out genetic mapping using Quantitative Trait Loci (QTL) analysis and determine the loci associated both with an increase in the concentration of norepinephrine in the hypothalamus and with an increase in heart mass in Inherited Stress-Induced Arterial Hypertension (ISIAH) rats simulating the stress-sensitive form of arterial hypertension. The work describes a genetic locus on chromosome 18, in which there are genes that control the development of cardiac hypertrophy associated with an increase in the concentration of norepinephrine in the hypothalamus, i.e., genes involved in enhanced sympathetic myocardial stimulation. No association of this locus with the blood pressure was found. Taking into consideration previously obtained results, it was concluded that the contribution to the development of heart hypertrophy in the ISIAH rats is controlled by different genetic loci, one of which is associated with the concentration of norepinephrine in the hypothalamus (on chromosome 18) and the other is associated with high blood pressure (on chromosome 1). Nucleotide substitutions that may be involved in the formation or absence of association with blood pressure in different rat strains are discussed.

Dorsal Striatum Transcriptome Profile Profound Shift in Repeated Aggression Mouse Model Converged to Networks of 12 Transcription Factors after Fighting Deprivation.

Both aggressive and aggression-deprived (AD) species represent pathologic cases intensely addressed in psychiatry and substance abuse disciplines. Previously, we reported that AD mice displayed a higher aggressive behavior score than the aggressive group, implying the manifestation of a withdrawal effect. We employed an animal model of chronic social conflicts, curated in our lab for more than 30 years. In the study, we pursued the task of evaluating key events in the dorsal striatum transcriptome of aggression experienced mice and AD species compared to controls using RNA-Seq profiling. Aggressive species were subjected to repeated social conflict encounters (fights) with regular positive (winners) experience in the course of 20 consecutive days (A20 group). This led to a profoundly shifted transcriptome expression profile relative to the control group, outlined by more than 1000 differentially expressed genes (DEGs). RNA-Seq cluster analysis revealed that elevated cyclic AMP (cAMP) signaling cascade and associated genes comprising 170 differentially expressed genes (DEGs) in aggressive (A20) species were accompanied by a downturn in the majority of other metabolic/signaling gene networks (839 DEGs) via the activation of transcriptional repressor DEGs. Fourteen days of a consecutive fighting deprivation period (AD group) featured the basic restoration of the normal (control) transcriptome expression profile yielding only 62 DEGs against the control. Notably, we observed a network of 12 coordinated DEG Transcription Factor (TF) activators from 62 DEGs in total that were distinctly altered in AD compared to control group, underlining the distinct transcription programs featuring AD group, partly retained from the aggressive encounters and not restored to normal in 14 days. We found circadian clock TFs among them, reported previously as a withdrawal effect factor. We conclude that the aggressive phenotype selection with positive reward effect (winning) manifests an addiction model featuring a distinct opioid-related withdrawal effect in AD group. Along with reporting profound transcriptome alteration in A20 group and gaining some insight on its specifics, we outline specific TF activator gene networks associated with transcriptional repression in affected species compared to controls, outlining Nr1d1 as a primary candidate, thus offering putative therapeutic targets in opioid-induced withdrawal treatment.

Gene Expression Changes in the Ventral Tegmental Area of Male Mice with Alternative Social Behavior Experience in Chronic Agonistic Interactions.

Daily agonistic interactions of mice are an effective experimental approach to elucidate the molecular mechanisms underlying the excitation of the brain neurons and the formation of alternative social behavior patterns. An RNA-Seq analysis was used to compare the ventral tegmental area (VTA) transcriptome profiles for three groups of male C57BL/6J mice: winners, a group of chronically winning mice, losers, a group of chronically defeated mice, and controls. The data obtained show that both winners and defeated mice experience stress, which however, has a more drastic effect on defeated animals causing more significant changes in the levels of gene transcription. Four genes (Nrgn, Ercc2, Otx2, and Six3) changed their VTA expression profiles in opposite directions in winners and defeated mice. It was first shown that Nrgn (neurogranin) expression was highly correlated with the expression of the genes involved in dopamine synthesis and transport (Th, Ddc, Slc6a3, and Drd2) in the VTA of defeated mice but not in winners. The obtained network of 31 coregulated genes, encoding proteins associated with nervous system development (including 24 genes associated with the generation of neurons), may be potentially useful for studying their role in the VTA dopaminergic neurons maturation under the influence of social stress.

Single-Nucleotide Polymorphisms (SNPs) Both Associated with Hypertension and Contributing to Accelerated-Senescence Traits in OXYS Rats.

Aging is a major risk factor of numerous human diseases. Adverse genetic variants may contribute to multiple manifestations of aging and increase the number of comorbid conditions. There is evidence of links between hypertension and age-related diseases, although the genetic relationships are insufficiently studied. Here, we investigated the contribution of hypertension to the development of accelerated-senescence syndrome in OXYS rats. We compared transcriptome sequences of the prefrontal cortex, hippocampus, and retina of OXYS rats with the genotypes of 45 rat strains and substrains (which include models with hypertension) to find single-nucleotide polymorphisms (SNPs) both associated with hypertension and possibly contributing to the development of age-related diseases. A total of 725 polymorphisms were common between OXYS rats and one or more hypertensive rat strains/substrains being analyzed. Multidimensional scaling detected significant similarities between OXYS and ISIAH rat genotypes and significant differences between these strains and the other hypertensive rat strains/substrains. Nonetheless, similar sets of SNPs produce a different phenotype in OXYS and ISIAH rats depending on hypertension severity. We identified 13 SNPs causing nonsynonymous amino-acid substitutions having a deleterious effect on the structure or function of the corresponding proteins and four SNPs leading to functionally significant structural rearrangements of transcripts in OXYS rats. Among them, SNPs in genes Ephx1, Pla2r1, and Ccdc28b were identified as candidates responsible for the concomitant manifestation of hypertension and signs of accelerated aging in OXYS rats.

Single-Nucleotide Polymorphisms Associated with the Senescence-Accelerated Phenotype of OXYS Rats: A Focus on Alzheimer's Disease-Like and Age-Related-Macular-Degeneration-Like Pathologies.

Alzheimer's disease (AD) and age-related macular degeneration (AMD) are two complex incurable neurodegenerative disorders the common pathogenesis of which is actively discussed. There are overlapping risk factors and molecular mechanisms of the two diseases; at the same time, there are arguments in favor of the notion that susceptibility to each of these diseases is associated with a distinct genetic background. Here we identified single-nucleotide polymorphisms (SNPs) that are specific for senescence-accelerated OXYS rats, which simulate key characteristics of both sporadic AD and AMD. Transcriptomes of the hippocampus, prefrontal cortex, and retina (data of RNA-Seq) were analyzed. We detected SNPs in genes Rims2, AABR07072639.2, Lemd2, and AABR07045405.1, which thus can express significantly truncated proteins lacking functionally important domains. Additionally, 33 mutations in genes-which are related to various metabolic and signaling pathways-cause nonsynonymous amino acid substitutions presumably leading to disturbances in protein structure or functions. Some of the genes carrying these SNPs are associated with aging, neurodegenerative, and mental diseases. Thus, we revealed the SNPs can lead to abnormalities in protein structure or functions and affect the development of the senescence-accelerated phenotype of OXYS rats. Our data are consistent with the latest results of genome-wide association studies that highlight the importance of multiple pathways for the pathogenesis of AD and AMD. Identified SNPs can serve as promising research objects for further studies on the molecular mechanisms underlying this particular rat model as well as for the prediction of potential biomarkers of AD and AMD.

The differences in brain stem transcriptional profiling in hypertensive ISIAH and normotensive WAG rats.

BACKGROUND: The development of essential hypertension is associated with a wide range of mechanisms. The brain stem neurons are essential for the homeostatic regulation of arterial pressure as they control baroreflex and sympathetic nerve activity. The ISIAH (Inherited Stress Induced Arterial Hypertension) rats reproduce the human stress-sensitive hypertensive disease with predominant activation of the neuroendocrine hypothalamic-pituitary-adrenal and sympathetic adrenal axes. RNA-Seq analysis of the brain stems from the hypertensive ISIAH and normotensive control WAG (Wistar Albino Glaxo) rats was performed to identify the differentially expressed genes (DEGs) and the main central mechanisms (biological processes and metabolic pathways) contributing to the hypertensive state in the ISIAH rats. RESULTS: The study revealed 224 DEGs. Their annotation in databases showed that 22 of them were associated with hypertension and blood pressure (BP) regulation, and 61 DEGs were associated with central nervous system diseases. In accordance with the functional annotation of DEGs, the key role of hormonal metabolic processes and, in particular, the enhanced biosynthesis of aldosterone in the brain stem of ISIAH rats was proposed. Multiple DEGs associated with several Gene Ontology (GO) terms essentially related to modulation of BP were identified. Abundant groups of DEGs were related to GO terms associated with responses to different stimuli including response to organic (hormonal) substance, to external stimulus, and to stress. Several DEGs making the most contribution to the inter-strain differences were detected including the Ephx2, which was earlier defined as a major candidate gene in the studies of transcriptional profiles in different tissues/organs (hypothalamus, adrenal gland and kidney) of ISIAH rats. CONCLUSIONS: The results of the study showed that inter-strain differences in ISIAH and WAG brain stem functioning might be a result of the imbalance in processes leading to the pathology development and those, exerting the compensatory effects. The data obtained in this study are useful for a better understanding of the genetic mechanisms underlying the complexity of the brain stem processes in ISIAH rats, which are a model of stress-sensitive form of hypertension.

Stress, Genes, and Hypertension. Contribution of the ISIAH Rat Strain Study.

PURPOSE OF REVIEW: Acute psychoemotional stress is one of the causes of a sharp increase in blood pressure. However, the question if the stress may promote the hypertensive disease development is still open. This review aims, firstly, to show that the genetically determined enhanced responsiveness to stress is linked to sustained hypertension development and, secondly, to characterize the main physiological mechanisms and genetic factors implicated in the pathogenesis of stress-sensitive hypertension. RECENT FINDINGS: Recent findings helped to characterize the main neuroendocrine mechanisms and the specificity of the genetic background contributing to the stress-sensitive hypertension development in the ISIAH rats. The ISIAH rat strain, which is an original model of the stress-sensitive arterial hypertension, can be considered as "living" proof that the genetic predisposition to increased stress-reactivity can lead to the development of persistent stress-dependent arterial hypertension. The ISIAH rat strain is characterized by the genetically determined enhanced response of the neuroendocrine and renal regulatory systems to stress and is a suitable model that allows one to explore the genetic and physiological mechanisms involved in stress-sensitive hypertension development. There are common genetic loci (QTLs) associated with both basal and stress-induced blood pressure (BP) levels as well as QTLs associated with BP and other traits, which may be related to hypertension development in ISIAH rats. Multiple genes differentially expressed in the target organs/tissues of hypertensive ISIAH and normotensive control rats are associated with many biological processes and metabolic pathways involved in stress response and arterial hypertension. The genotype of ISIAH rats is characterized by numerous specific and common SNPs as compared with other models of hypertensive rats. The results of the studies are valuable for the search for genetic markers specific for stress-induced arterial hypertension, as well as for the selection of new molecular targets that may be potentially useful for prevention and/or therapy of hypertensive disease.

Stress and hypertensive disease: adrenals as a link. Experimental study on hypertensive ISIAH rat strain.

OBJECTIVE: Association between stress and hypertensive disease is still a matter of debate. Can stress be the cause of hypertensive disease and, if so, what mechanisms are involved? To clarify this question, the Inherited stress-induced arterial hypertensive rat strain (ISIAH rat strain) with a stress related arterial hypertension was developed by selection for the enhanced blood pressure response to 0.5 h restraint stress. The main intention of this work is to confirm that the adrenals are a main link between stress and hypertensive disease. METHODS: Hypertensive ISIAH and normotensive WAG rats have been studied. The in vivo secretion rate of corticosterone, aldosterone, 11-Deoxycorticosterone (DOC), and 11-dehydrocorticosterone was measured in anesthetized rats by adrenal vein cannulation. The Dexamethasone/Adrenocorticotropic hormone (DEX/ACTH) test was performed and mRNA expression of Cyp11b1 and Cyp11b2 genes in adrenals was evaluated by real-time PCR. RESULTS: An increased secretion rate of corticosterone and DOC and higher peripheral plasma aldosterone concentration in ISIAH rats were revealed. Response of plasma aldosterone to the surgical stress (adrenal vein cannulation) in the ISIAH rats was significantly higher. The increase of corticosterone and aldosterone in response to ACTH was also higher in hypertensive rats. The basal mRNA expression of both Cyp11b1 and Cyp11b2 genes was increased in the ISIAH rats. The ratio 11-dehydrocorticosterone/corticosterone in ISIAH rats was low which indicates the weakening of 11-beta-Hydroxysteroid dehydrogenase (11-beta-HSD) type 2 converting corticosterone to cortisone. CONCLUSION: ISIAH rats may serve as a living proof that stress may produce sustained hypertension, and genetically determined enhanced stress responsiveness of corticosterone and, especially, aldosterone may play a crucial role in the mechanism of hypertension development.

Comparative transcriptional profiling of renal cortex in rats with inherited stress-induced arterial hypertension and normotensive Wistar Albino Glaxo rats.

BACKGROUND: The renal function plays a leading role in long-term control of arterial pressure. The comparative analysis of renal cortex transcriptome in ISIAH rats with inherited stress-induced arterial hypertension and normotensive WAG rats was performed using RNA-Seq approach. The goal of the study was to identify the differentially expressed genes (DEGs) related to hypertension and to detect the pathways contributing to the differences in renal functions in ISIAH and WAG rats. RESULTS: The analysis revealed 716 genes differentially expressed in renal cortex of ISIAH and WAG rats, 42 of them were associated with arterial hypertension and regulation of blood pressure (BP). Several Gene Ontology (GO) terms significantly enriched with DEGs suggested the existence of the hormone dependent interstrain differences in renal cortex function. Multiple DEGs were associated with regulation of blood pressure and blood circulation, with the response to stress (including oxidative stress, hypoxia, and fluid shear stress) and its regulation. Several other processes which may contribute to hypertension development in ISIAH rats were: ion transport, regulation of calcium ion transport, homeostatic process, tissue remodeling, immune system process and regulation of immune response. KEGG analysis marked out several pathways significantly enriched with DEGs related to immune system function, to steroid hormone biosynthesis, tryptophan, glutathione, nitrogen, and drug metabolism. CONCLUSIONS: The results of the study provide a basis for identification of potential biomarkers of stress-sensitive hypertension and for further investigation of the mechanisms that affect renal cortex function and hypertension development.