WAG Rats Research Articles

The decreased expression of genes controlling the vascular tone in the kidneys of ISIAH rats with stress-induced arterial hypertension

The transcriptional activity of genes was studied in the kidneys of hypertensive ISIAH and normotensive WAG rats in order to detect genes significantly expressed in the kidneys of just one of the strains. Gene expression profiling was performed on the Illumina RatRef-12 Expression BeadChip microarray platform. The expression of three genes (Klk1, Klk1c10, and Kng1) related to the kallikrein-kinin system was significant in the WAG renal cortex but was not detected in hypertensive kidneys. The lower expression of these three genes and Gucy1a3 in the ISIAH renal cortex suggests the weakened function of the kallikrein-kinin system in hypertensive kidneys, which may cause blood circulation disturbances in renal glomeruli and mediate the development of hypertension in ISIAH rats. The functional annotation of the genes significantly expressed in the renal medulla of just one of the compared rat strains revealed genes involved in immune response regulation.

Regression of Walker 256 carcinosarcoma in vasopressin-deficient Brattleboro rats is accompanied by a changed laminin pattern.

Walker 256 carcinosarcoma is a transplantable model of rat carcinoma that originally appeared spontaneously in mammary glands. The growth rate of Walker 256 carcinosarcoma in vasopressin-deficient Brattleboro rats is lower than in WAG rats and their congenic hybrids with normal vasopressin levels. Study of tumor proteins detected essential alterations. Tumor regression starting at the 14th day in Brattleboro rats was accompanied by changes in the laminin pattern. At the 21st day, the concentration of α-chains became twice as low, while β-chains of laminin showed a sixfold increase compared to the initial equimolar correlation of bands. Congenic hybrids having one active copy of the vasopressin gene to provide a physiological level of hormone against the genetic background of Brattleboro rats show the same laminin alterations as WAG rats. They demonstrated a similar moderate increase of γ-chains and threefold growth of α- and β-chains of laminin in tumor tissue. It is supposed that vasopressin may be involved in the regulation of relevant local stimuli to trigger renovation of the laminin composition in a course of growing Walker 256 carcinosarcoma.

Candidate genes in quantitative trait loci associated with absolute and relative kidney weight in rats with Inherited Stress Induced Arterial Hypertension

BackgroundThe kidney mass is significantly increased in hypertensive ISIAH rats with Inherited Stress Induced Arterial Hypertension as compared with normotensive WAG rats. The QTL/microarray approach was carried out to determine the positional candidate genes in the QTL for absolute and relative kidney weight.ResultsSeveral known and predicted genes differentially expressed in ISIAH and WAG kidney were mapped to genetic loci associated with the absolute and relative kidney weight in 6-month old F2 hybrid (ISIAHxWAG) males. The knowledge-driven filtering of the list of candidates helped to suggest several positional candidate genes, which may be related to the structural and mass changes in hypertensive ISIAH kidney.In the current study, we showed that all loci found for absolute and relative kidney weight didn't overlap with significant or suggestive loci for arterial blood pressure level. So, the genes differentially expressed in ISIAH and WAG kidneys and located in these QTL regions associated with absolute and relative kidney weight shouldn't substantially influence the BP level in the 6 month-old ISIAH rats. However, in some cases, small effects may be suggested.ConclusionsThe further experimental validation of causative genes and detection of polymorphisms will provide opportunities to advance our understanding of the underlying nature of structural and mass changes in hypertensive ISIAH kidney.

Application of quantitative trait locus mapping and transcriptomics to studies of the senescence-accelerated phenotype in rats.

BackgroundEtiology of complex disorders, such as cataract and neurodegenerative diseases including age-related macular degeneration (AMD), remains poorly understood due to the paucity of animal models, fully replicating the human disease. Previously, two quantitative trait loci (QTLs) associated with early cataract, AMD-like retinopathy, and some behavioral aberrations in senescence-accelerated OXYS rats were uncovered on chromosome 1 in a cross between OXYS and WAG rats. To confirm the findings, we generated interval-specific congenic strains, WAG/OXYS-1.1 and WAG/OXYS-1.2, carrying OXYS-derived loci of chromosome 1 in the WAG strain. Both congenic strains displayed early cataract and retinopathy but differed clinically from OXYS rats. Here we applied a high-throughput RNA sequencing (RNA-Seq) strategy to facilitate nomination of the candidate genes and functional pathways that may be responsible for these differences and can contribute to the development of the senescence-accelerated phenotype of OXYS rats.ResultsFirst, the size and map position of QTL-derived congenic segments were determined by comparative analysis of coding single-nucleotide polymorphisms (SNPs), which were identified for OXYS, WAG, and congenic retinal RNAs after sequencing. The transferred locus was not what we expected in WAG/OXYS-1.1 rats. In rat retina, 15442 genes were expressed. Coherent sets of differentially expressed genes were identified when we compared RNA-Seq retinal profiles of 20-day-old WAG/OXYS-1.1, WAG/OXYS-1.2, and OXYS rats. The genes most different in the average expression level between the congenic strains included those generally associated with the Wnt, integrin, and TGF-β signaling pathways, widely involved in neurodegenerative processes. Several candidate genes (including Arhgap33, Cebpg, Gtf3c1, Snurf, Tnfaip3, Yme1l1, Cbs, Car9 and Fn1) were found to be either polymorphic in the congenic loci or differentially expressed between the strains. These genes may contribute to the development of cataract and retinopathy.ConclusionsThis study is the first RNA-Seq analysis of the rat retinal transcriptome generated with 40 mln sequencing read depth. The integration of QTL and transcriptomic analyses in our study forms the basis of future research into the relationship between the candidate genes within the congenic regions and specific changes in the retinal transcriptome as possible causal mechanisms that underlie age-associated disorders.

Features of the immune proteasome expression in ascite Zajdela hepatoma after implantation into Brattleboro rats with the hereditary defect of arginine-vasopressin synthesis

The expression of the total proteasome pool, immune proteasome subunits LMP2 and LMP7, TAP1 and TAP2 transporters, as well as RT1A molecule of MHC class I was investigated in the ascite Zajdela hepatoma at the 10th day after implantation into Brattleboro rats with the hereditary defect of hypothalamic arginine-vasopressin synthesis (AVP) and into WAG rats with normal AVP expression. In Zajdela hepatoma cells implanted into Brattleboro rats the 3-fold increase of the total proteasome pool and LMP2 level and 8-fold increase of the LMP7 level was detected by Western blotting as compared to those in WAG rats. Differences in the LMP2 and LMP7 expression suggest variations in their functions, namely the important role of LMP7 in anti-tumor immunity. The growth of Zajdela hepatoma in WAG rats was accompanied by the decreased level of total proteasome pool as well as immune proteasome expression as compared to those in Brattleboro rats during the regression of tumor. The analysis of TAP1 and TAP2 revealed the pronounced expression of these peptide transporters in Zajdela hepatoma cells implanted into Brattleboro and WAG rats. The expression level of RT1A molecule of MHC class I was increased 3 times in Zajdela hepatoma cells implanted into Brattleboro rats as compared to WAG rats. Moreover, flow cytometric analysis of CD4- and CD8-lymphocytes number in the spleen of Brattleboro and WAG rats was performed at the 10th day after implantation of Zajdela hepatoma. The increased number of CD4- and CD8-lymphocytes was observed in the spleen of Brattleboro as compared to WAG. The increased subpopulations of cytotoxic T-lymphocytes and T-helpers might promote the tumor regression in Brattleboro rats. The reduced populations of CD4- and CD8-lymphocytes in the spleen of WAG rats were accompanied by the splenomegaly and tumor progression. The data obtained suggest that AVP deficiency in Brattleboro rats leads to the increase of the immune proteasome and MHC class I expression in Zajdela hepatoma cells, resulting in tumor immunogenicity and its elimination by the adaptive immunity.

Behavior of rat neonates with inherited stress induced arterial hypertension

The hypertensive status of the mother can affect the behavioral traits of its offspring in early ontogeny. Rats with inherited stress-induced arterial hypertension (ISIAH) exhibit a delay in locomotor activity development as compared with WAG rats during the first week of life, but they show a higher locomotor activity in the open field test during the second week of development. Using the method of principal components, a higher level of exploratory behavior and a higher adaptability of ISIAH rat neonates as compared to WAG neonates were shown in the third week of postnatal development. Vibrissa growth and hair coat formation did not differ between the strains by the end of the second week.

Differential transcriptional activity of kidney genes in hypertensive ISIAH and normotensive WAG rats

Transcriptional activity of the kidney genes was compared in hypertensive ISIAH and normotensive WAG rats using the oligonucleotide microarray technique. Most of differentially expressed genes were downregulated in ISIAH kidney both in renal cortex and medulla. According to functional annotation the kidney function in ISIAH rats is based on altered expression of many genes working in stress-related mode. The alterations in gene expression are likely related to both pathophysiological and compensatory mechanisms. The further studies of genes differentially expressed in ISIAH and WAG kidney will help to reveal new hypertensive genes and mechanisms specific for stress-induced arterial hypertension.

Senescence-accelerated OXYS rats: A genetic model of premature aging and age-related diseases

A genetic model of accelerated senescence and the associated diseases in the OXYS strain of rats was established by selection and inbreeding of Wistar rats sensitive to the cataractogenic effects of galactose. In the first five generations, the development of a cataract was induced by galactose overconsumption, and, subsequently, the selection was carried out for early spontaneous cataract, genetically linked with the latter animals that inherited a set of features of premature aging. At present, there is already the 103rd generation of OXYS rats that develop retinopathy at young age, similar to age-related macular degeneration in humans, osteoporosis, arterial hypertension, accelerated thymus involution, sarcopenia, and neurodegenerative changes in the brain with the features characteristic for Alzheimer’s disease, in addition to cataracts. This review discusses possible mechanisms of their accelerated senescence: the results of comparison of retinal transcriptomes between OXYS and Wistar (control group) rats at different ages, studies of the markers of Alzheimer’s disease in the retina and in certain brain regions, and the results of development of congenic strains of animals through a transfer of loci of chromosome 1 from OXYS to WAG rats that are associated with the signs of accelerated senescence. The uniqueness of OXYS rats lies in the complex composition of manifestations of the traits; accordingly, this rat model can be used not only for studies of the mechanisms of aging and pathogenesis of age-related diseases but also for objective evaluation of new methods of treatment and prevention.

Genetic loci for spleen weight and blood pressure in ISIAH rats with inherited stress-induced arterial hypertension

Recently, the important role of the spleen function in hypertension development was demonstrated. In this study, the genetic control of absolute and relative spleen weight was investigated to reveal the genetic loci common for spleen traits and for arterial blood pressure at rest and under the emotional stress conditions in the ISIAH rats with inherited stress-induced arterial hypertension. The search for genetic loci for absolute and relative spleen weight was performed on 6-month old F2 (ISIAH x WAG) hybrid males derived from a cross of hypertensive ISIAH and normotensive WAG rats. One significant QTL mapped on chromosome 1 and 5 suggestive loci were found for relative spleen weight. Four suggestive loci were detected for absolute spleen weight. All detected loci were novel. The significant QTL on chromosome 1 was common for relative spleen weight and arterial blood pressure at rest and under the emotional stress conditions in ISIAH rats. The results suggest that the manifestation ofthe stress-sensitive arterial hypertension in ISIAH rats may be related to the changes in genetic control of the spleen function.

Rats of hypertensive ISIAH strain are resistant to the development of metabolic syndrome induced by high-fat diet.

We studied the influence of high-fat diet on the development of metabolic syndrome in rats of hypertensive ISIAH strain and normotensive WAG strain. In contrast to ISIAH rats, high-fat diet in WAG rats led visceral obesity, glucose tolerance, and dyslipidemia. DNA-binding activity of the peroxisome proliferator-activated receptor α (PPARα) decreased in the liver of WAG rats and increased in ISIAH rats. Blood levels of TNF-α, IL-6, and corticosterone increased more significantly in WAG rats. Corticosterone content in the adrenal glands was more markedly reduced in WAG rats. High-fat diet had no effect on BP in ISIAH and WAG rats. It was concluded that ISIAH rats can be used as a genetic model in studies of the mechanism of resistance to the metabolic syndrome.

Elevated expression of the Ephx2 mRNA in the kidney of hypertensive ISIAH rats

Epoxyeicosatrienoic acids (EETs) have antihypertensive properties and play a role in maintaining the renal microvascular function. EETs mediate vasodilation of rat preglomerular microvessels and activate ion channels. Ephx2 codes for a soluble epoxide hydrolase (sEH), which catalyzes EET degradation. The renal cortex and medulla were tested for Ephx2 mRNA level in ISIAH rats with hereditary stress-sensitive hypertension and in normotensive WAG rats at rest and in emotional stress. Ephx2 transcriptional activity in ISIAH rats was significantly higher than in WAG rats at rest and in stress by both microarray analysis and realtime PCR. The results implicated Ephx2 in controlling and modulating the vascular tone in the kidney in both hypertensive ISIAH and normotensive WAG rats.

Bezafibrate Causes Depression of the Immune Response and Increases the Sensitivity to Endotoxin in Association with Low Level of HDL and PPARα Activity in Hypertensive ISIAH Rats

We studied the effect of bezafibrate on hepatic PPARα activity and immune parameters in hypertensive ISIAH rats in comparison with normotensive WAG rats under conditions of LPS treatment. Bezafibrate increased activity of PPARα in WAG rats, but not in ISIAH rats. As differentiated from WAG rats, bezafibrate produced a potent effect on the content of T cell subpopulations in the thymus and spleen of ISIAH rats. Administration of LPS after injection of bezafibrate caused death of 50% ISIAH animals (but not WAG rats), which was associated with low level of HDL cholesterol and increased triglyceride content. Our results suggest that the hypolipidemic treatment (e.g., bezafibrate) can increase the severity of complications in patients with infectious and inflammatory diseases in association with low level of HDL.

Effects of Experimental Desynchronosis on the Organs of Immune System in WAG and ISIAH Rats

We studied the influence of abnormal illumination regimen on cell composition of the central and peripheral organs of the immune system in ISIAH rats and control WAG rats. In ISIAH rats, 24-h illumination for 14 days led to more pronounced inhibition of cell proliferation and differentiation in the thymus and more pronounced decrease in splenocyte proliferation and T and B cell counts in the spleen in comparison with WAG rats; however, the level of antigen-presenting cells in the spleen of ISIAH increased. We concluded that ISIAH rats are more sensitive to abnormal illumination regimen than WAG rats. Twenty-four-hour illumination was associated with impairments of central differentiation of T cells and activation of systemic inflammation followed by impairment of differentiation regulation, which can aggravate metabolic dysfunctions in these animals.

Reactivity of the Immune System and Activities of PPARα and PPARγ in the Liver under Conditions of LPS-Induced Acute Infl ammatory Response in Hypertensive ISIAH Rats

The effects of LPS from E. coli on DNA-binding activities of PPARα and PPARγ in the liver and immune system parameters of were studied in hypertensive ISIAH rats and normotensive WAG rats. In ISIAH rats characterized by low basal level of PPARα, PPARγ, and HDL, the response of the peripheral immune system compartment to LPS was more pronounced and was not associated with decrease in DNA-binding activities of PPARα observed in WAG. Proinflammatory stimulus did not induce proliferative changes in the thymus of ISIAH rats, which can reflect impaired relationships between the central and peripheral organs of the immune system. The character of regulatory interactions between PPARα and immune cells can differ in various rat strains and depend on initial PPARα activity, HDL level, specific features of immune status, resistance to stress, and hormonal and metabolic background.

Structural Characteristics of Renomedullary Interstitial Cells of Hypertensive ISIAH Rats

The structural characteristics of the renal medulla and its interstitial cells were studied in hypertensive ISIAH rats (in comparison with normotensive WAG rats) in order to clear out the role of the renomedullary interstitial cells in the mechanisms of AP regulation. Morphometric electron microscopic analysis and immunohistochemical studies in ISIAH rats detected the initial signs of the renomedullary sclerosis. The renomedullary interstitial cells of ISIAH rats were characterized by higher numerical density and were larger in size, with a higher volumic share of their secretory granules. These structural features of the studied cells were regarded as signs of their more intense functional activity aimed at hypertension suppression.

Expression of Renin–Angiotensin System Genes in Brain Structures of ISIAH Rats with Stress-Induced Arterial Hypertension

We studied the expression of genes encoding angiotensinogen (Agt), renin (Ren), angiotensin-converting enzyme (ACE), and type 1 angiotensin receptor (AT1A) in the hypothalamus and medulla oblongata of hypertensive ISIAH rats and normotensive WAG rats. The amount of Agt mRNA in the hypothalamus of young ISIAH rats was increased by 30% compared to WAG controls. In the medulla oblongata of young ISIAH rats, the levels of mRNA of Agt and AT1A receptor were enhanced by 60% and 24%, respectively, compared to WAG rats. In adult animals, the expression of the studied genes did not differ from the control. It is concluded that changes in gene expression of the renin-angiotensin system in brain structures of ISIAH rats may contribute to the development of hypertension.

Возрастные структурно-функциональные особенности миоэндокринных клеток сердца у крыс в норме и при наследственной гипертензии

A qualitative and quantitative ultrastructural study of right atrial cardiomyocytes in WAG (normotensive control) and ISIAH (inherited stress-induced arterial hypertension) rats of different age (on day 18 of embryogenesis, on days 12 and 21 after birth, and at an age of 6 and 13 months) was performed. It was shown that, in embryos with an as yet incomplete atrial morphogenesis, secretory granules containing natriuretic peptides are actively formed, accumulated, and dissolved. In postnatal ontogeny, the secretory product is accumulated in atrial cells. In all ontogeny stages studied, the numerical density of secretory granules in the myoendocrine cells of hypertensive rats is greater and the qualitative composition of these granules is more diverse than in the control. It was established that, in atrial myocytes of ISIAH rats, the morphological signs of natriuretic peptide hypersecretion precede the development of genetically programmed high blood pressure. In adult hypertensive rats, hypertrophic and degenerative changes in myocytes are accompanied by excessive accumulation of secretory granules, some of which undergo intracellular degradation.

Fluoride penetration from three orthodontic adhesives: an experimental study

ObjectiveTo examine the prophylactic potential of 3 orthodontic bonding adhesives: Fuji Ortho SC, Illuminate, and Resilience.MethodsThirty-six Wistar Wag rats were randomly divided into 4 groups consisting of 9 rats each. One of the groups received no treatment and was used as a control. In the other groups, individual bands coated with one of the 3 adhesives were cemented to the lower incisors. Enamel samples were obtained after 6 and 12 weeks and analyzed using scanning electron microscopy in combination with energy dispersive spectrometry.ResultsSix weeks after band cementation, no fluoride was found in the enamel of the lower incisors. After 12 weeks, there was no fluoride in the enamel of teeth coated with the Resilience composite. However, in the case of the Illuminate composite and the resin-modified glass ionomer Fuji Ortho SC cement, the depth of fluoride penetration reached 2 µm and 4.8 - 5.7 µm, respectively.ConclusionsFluoride ions from orthodontic adhesives can be incorporated into the surface layer of the enamel. Orthodontists may apply orthodontic adhesives, such as the Fuji Ortho SC, to reduce the occurrence of caries during orthodontic treatment with fixed appliances.

Chromogranin Location in the Adrenal Glands of ISIAH Rats

Comparative immunohistochemical and electron microscopic study of the adrenals from hypertensive ISIAH rats and normotensive WAG rats (control) showed a more intense reaction to chromogranin A in the ISIAH adrenal in comparison with the control. Electron microscopy and morphometric analysis showed high volume and numerical densities of the secretory granules in chromaffin cells of hypertensive rats. The results indicate stimulation of the adrenal medullary substance in ISIAH rats. Presumably, intensive accumulation of chromogranin A and secretory granules in chromaffin cells of hypertensive rats reflects a certain imbalance of chromogranin A and catecholamines biogenesis, this, in turn, leading to stable stimulation of the sympathoadrenal component and higher stress sensitivity of these animals.

Influence of long-term administration of rutin on spatial memory as well as the concentration of brain neurotransmitters in aged rats

BackgroundThe present study was designed to investigate the behavioral and neurochemical effects of long-term oral rutin administration to old male WAG rats (100 and 200mg/kg b.w./day). Rutin is a well-known dietary flavonol glycoside with antioxidant and anti-inflammatory properties. MethodsFirst, spatial memory was assessed in the water maze and then the levels of neurotransmitters in selected brain regions were estimated. ResultsThere was enhanced spatial memory in aged rats pretreated with the smaller dose of rutin in the probe trial of the water maze, nevertheless, augmented levels of noradrenaline in the hippocampi of these animals were not correlated with improved spatial memory. The increased dopamine levels in the hypothalami of the same group of animals may suggest effects other than behavioral. ConclusionLong-term rutin pre-treatment may cause behavioral and neurochemical changes in aged WAG male rats.