Difference of gene expression profiles in spontaneous hypertensive rats and Wistar-Kyoto rats from two sources

Mas receptor is translocated to the nucleus upon agonist stimulation in brainstem neurons from spontaneously hypertensive rats but not normotensive rats

AIMS

Activation of the angiotensin (Ang)-(1-7)/Mas receptor (R) axis protects from sympathetic overactivity. Endocytic trafficking is an essential process that regulates receptor (R) function and its ultimate cellular responses. We investigated whether the blunted responses to Ang-(1-7) in hypertensive rats are associated to an alteration in MasR trafficking.

METHODS AND RESULTS

Brainstem neurons from Wistar-Kyoto (WKY) or spontaneously hypertensive rats (SHRs) were investigated for (i) Ang-(1-7) levels and binding and MasR expression, (ii) Ang-(1-7) responses (arachidonic acid and nitric oxide release and Akt and ERK1/2 phosphorylation), and (iii) MasR trafficking. Ang-(1-7) was determined by radioimmunoassay. MasR expression and functionality were evaluated by western blot and binding assays. MasR trafficking was evaluated by immunofluorescence. Ang-(1-7) treatment induced an increase in nitric oxide and arachidonic acid release and ERK1/2 and Akt phosphorylation in WKY neurons but did not have an effect in SHR neurons. Although SHR neurons showed greater MasR expression, Ang-(1-7)-elicited responses were substantially diminished presumably due to decreased Ang-(1-7) endogenous levels concomitant with impaired binding to its receptor. Through immunocolocalization studies, we evidenced that upon Ang-(1-7) stimulation MasRs were internalized through clathrin-coated pits and caveolae into early endosomes and slowly recycled back to the plasma membrane. However, the fraction of internalized MasRs into early endosomes was larger and the fraction of MasRs recycled back to the plasma membrane was smaller in SHR than in WKY neurons. Surprisingly, in SHR neurons but not in WKY neurons, Ang-(1-7) induced MasR translocation to the nucleus. Nuclear MasR expression and Ang-(1-7) levels were significantly greater in the nuclei of Ang-(1-7)-stimulated SHR neurons, indicating that the MasR is translocated with its ligand bound to it.

CONCLUSION

MasRs display differential trafficking in brainstem neurons from SHRs, which may contribute to the impaired responses to Ang-(1-7).

Genetic Model to Study the Co-Morbid Phenotypes of Increased Alcohol Intake and Prior Stress-Induced Enhanced Fear Memory

Posttraumatic Stress Disorder (PTSD) is a complex illness, frequently co-morbid with depression, caused by both genetics, and the environment. Alcohol Use Disorder (AUD), which also co-occurs with depression, is often co-morbid with PTSD. To date, very few genes have been identified for PTSD and even less for PTSD comorbidity with AUD, likely because of the phenotypic heterogeneity seen in humans, combined with each gene playing a relatively small role in disease predisposition. In the current study, we investigated whether a genetic model of depression-like behavior, further developed from the depression model Wistar Kyoto (WKY) rat, is a suitable vehicle to uncover the genetics of co-morbidity between PTSD and AUD. The by-now inbred WKY More Immobile (WMI) and the WKY Less Immobile (WLI) rats were generated from the WKY via bidirectional selective breeding using the forced swim test, a measure of despair-like behavior, as the functional selector. The colonies of the WMIs that show despair-like behavior and the control strain showing less or no despair-like behavior, the WLI, are maintained with strict inbreeding over 40 generations to date. WMIs of both sexes intrinsically self-administer more alcohol than WLIs. Alcohol self-administration is increased in the WMIs without sucrose fading, water deprivation or any prior stress, mimicking the increased voluntary alcohol-consumption of subjects with AUD. Prior Stress-Enhanced Fear Learning (SEFL) is a model of PTSD. WMI males, but not females, show increased SEFL after acute restraint stress in the context-dependent fear conditioning paradigm, a sexually dimorphic pattern similar to human data. Plasma corticosterone differences between stressed and not-stressed WLI and WMI male and female animals immediately prior to fear conditioning predict SEFL results. These data demonstrate that the WMI male and its genetically close, but behaviorally divergent control the WLI male, would be suitable for investigating the underlying genetic basis of comorbidity between SEFL and alcohol self-administration.

Differences in autonomic innervation to the vertebrobasilar arteries in spontaneously hypertensive and Wistar rats

KEY POINTS

Essential hypertension is associated with hyperactivity of the sympathetic nervous system and hypoperfusion of the brainstem area controlling arterial pressure. Sympathetic and parasympathetic innervation of vertebrobasilar arteries may regulate blood perfusion to the brainstem. We examined the autonomic innervation of these arteries in pre-hypertensive (PHSH) and hypertensive spontaneously hypertensive (SH) rats relative to age-matched Wistar rats. Our main findings were: (1) an unexpected decrease in noradrenergic sympathetic innervation in PHSH and SH compared to Wistar rats despite elevated sympathetic drive in PHSH rats; (2) a dramatic deficit in cholinergic and peptidergic parasympathetic innervation in PHSH and SH compared to Wistar rats; and (3) denervation of sympathetic fibres did not alter vertebrobasilar artery morphology or arterial pressure. Our results support a compromised vasodilatory capacity in PHSH and SH rats compared to Wistar rats, which may explain their hypoperfused brainstem.

ABSTRACT

Neurogenic hypertension may result from brainstem hypoperfusion. We previously found remodelling (decreased lumen, increased wall thickness) in vertebrobasilar arteries of juvenile, pre-hypertensive spontaneously hypertensive (PHSH) and adult spontaneously hypertensive (SH) rats compared to age-matched normotensive rats. We tested the hypothesis that there would be a greater density of sympathetic to parasympathetic innervation of vertebrobasilar arteries in SH versus Wistar rats irrespective of the stage of development and that sympathetic denervation (ablation of the superior cervical ganglia bilaterally) would reverse the remodelling and lower blood pressure. Contrary to our hypothesis, immunohistochemistry revealed a decrease in the innervation density of noradrenergic sympathetic fibres in adult SH rats (P < 0.01) compared to Wistar rats. Unexpectedly, there was a 65% deficit in parasympathetic fibres, as assessed by both vesicular acetylcholine transporter (α-VAChT) and vasoactive intestinal peptide (α-VIP) immunofluorescence (P < 0.002) in PHSH rats compared to age-matched Wistar rats. Although the neural activity of the internal cervical sympathetic branch, which innervates the vertebrobasilar arteries, was higher in PHSH relative to Wistar rats, its denervation had no effect on the vertebrobasilar artery morphology or persistent effect on arterial pressure in SH rats. Our neuroanatomic and functional data do not support a role for sympathetic nerves in remodelling of the vertebrobasilar artery wall in PHSH or SH rats. The remodelling of vertebrobasilar arteries and the elevated activity in the internal cervical sympathetic nerve coupled with their reduced parasympathetic innervation suggests a compromised vasodilatory capacity in PHSH and SH rats that could explain their brainstem hypoperfusion.

Gene Expression and MicroRNA Expression Analysis in Small Arteries of Spontaneously Hypertensive Rats. Evidence for ER Stress

Small arteries are known to develop functional and structural alterations in hypertension. However, the mechanisms of this remodeling are not fully understood. We hypothesized that altered gene expression is associated with the development of hypertension in mesenteric arteries of spontaneously hypertensive rats (SHR). Three sublines of SHR and normotensive Wistar Kyoto rats (WKY) were studied at 6 weeks and 5 months of age. MiRNA and mRNA microarray experiments were performed and analyzed with bioinformatical tools, including Ingenuity Pathway Analysis (IPA). Principal component analysis showed a clear separation in both miRNA and mRNA expression levels between both ages studied, demonstrating strong age-related changes in expression. At the miRNA level, IPA identified differences between SHR and WKY related to metabolic diseases, cellular growth, and proliferation. The mRNAs differentially expressed between SHR and WKY were related to metabolism, cellular movement and proliferation. The most strongly upregulated gene (9.2-fold) was thrombospondin 4 (Thbs4), a protein involved in the endoplasmic reticulum (ER) stress response that activates transcription factor 6α (ATF6α). ATF6α downstream targets were also differentially expressed in SHR vs. WKY. Differential expression of THBS4, the cleaved form of ATF6α, and two of its targets were further confirmed at the protein level by western blot. In summary, these data revealed a number of genes (n = 202) and miRNAs (n = 3) in mesenteric arteries of SHR that had not been related to hypertension previously. The most prominent of these, Thbs4, is related to vascular ER stress that is associated with hypertension.

Peripheral gene expression profile of mechanical hyperalgesia induced by repeated cold stress in SHRSP5/Dmcr rats

Repeated cold stress (RCS) is known to transiently induce functional disorders associated with hypotension and hyperalgesia. In this study, we investigated the effects of RCS (24 and 4 °C alternately at 30-min intervals during the day and 4 °C at night for 2 days, followed by 4 °C on the next 2 consecutive nights) on the thresholds for cutaneous mechanical pain responses and on peripheral expression of "pain-related genes" in SHRSP5/Dmcr rats, which are derived from stroke-prone spontaneously hypertensive rats. To define genes peripherally regulated by RCS, we detected changes in the expression of pain-related genes in dorsal root ganglion cells by PCR-based cDNA subtraction analysis or DNA microarray analysis, and confirmed the changes by RT-PCR. We found significantly changed expression in eight pain-related genes (upregulated: Fyn, St8sia1, and Tac 1; downregulated: Ctsb, Fstl1, Itpr1, Npy, S100a10). At least some of these genes may play key roles in hyperalgesia induced by RCS.

The stroke-prone spontaneously hypertensive rat: still a useful model for post-GWAS genetic studies?

The stroke-prone spontaneously hypertensive rat (SHRSP) is a unique genetic model of severe hypertension and cerebral stroke. SHRSP, as well as the spontaneously hypertensive rat, the parental strain of SHRSP, has made a tremendous contribution to cardiovascular research. However, the genetic mechanisms underlying hypertension and stroke in these rats have not yet been clarified. Recent studies using whole-genome sequencing and comprehensive gene expression analyses combined with classical quantitative trait loci analyses provided several candidate genes, such as Ephx2, Gstm1 and Slc34a1, which still need further evidence to define their pathological roles. Currently, genome-wide association studies can directly identify candidate genes for hypertension in the human genome. Thus, genetic studies in SHRSP and other rat models must be focused on the pathogenetic roles of 'networks of interacting genes' in hypertension, instead of searching for individual candidate genes.

High blood pressure-lowering and vasoprotective effects of milk products in experimental hypertension

Milk casein-derived angiotensin-converting enzyme (ACE)-inhibitory tripeptides isoleucine-proline-proline (Ile-Pro-Pro) and valine-proline-proline (Val-Pro-Pro) have been shown to have antihypertensive effects in human subjects and to attenuate the development of hypertension in experimental models. The aim of the present study was to investigate the effect of a fermented milk product containing Ile-Pro-Pro and Val-Pro-Pro and plant sterols on already established hypertension, endothelial dysfunction and aortic gene expression. Male spontaneously hypertensive rats (SHR) with baseline systolic blood pressure (SBP) of 195 mmHg were given either active milk (tripeptides and plant sterols), milk or water ad libitum for 6 weeks. SBP was measured weekly by the tail-cuff method. The endothelial function of mesenteric arteries was investigated at the end of the study. Aortas were collected for DNA microarray study (Affymetrix Rat Gene 1.0 ST Array). The main finding was that active milk decreased SBP by 16 mmHg compared with water (178 (sem 3) v. 195 (sem 3) mmHg; P < 0·001). Milk also had an antihypertensive effect. Active milk improved mesenteric artery endothelial dysfunction by NO-dependent and endothelium-derived hyperpolarising factor-dependent mechanisms. Treatment with active milk caused mild changes in aortic gene expression; twenty-seven genes were up-regulated and eighty-two down-regulated. Using the criteria for fold change (fc) <  0·833 or > 1·2 and P < 0·05, the most affected (down-regulated) signalling pathways were hedgehog, chemokine and leucocyte transendothelial migration pathways. ACE expression was also slightly decreased (fc 0·86; P = 0·047). In conclusion, long-term treatment with fermented milk enriched with tripeptides and plant sterols decreases SBP, improves endothelial dysfunction and affects signalling pathways related to inflammatory responses in SHR.

Soluble epoxide hydrolase in the generation and maintenance of high blood pressure in spontaneously hypertensive rats

We hypothesized that perinatal inhibition of soluble epoxide hydrolase (SEH), which metabolizes epoxyeicosatrienoic acids in the arachidonic acid (AA) cascade, with an orally active SEH inhibitor, 12-(3-adamantan-1-yl-ureido)-dodecanoic acid (AUDA), would persistently reduce blood pressure (BP) in adult SHR despite discontinuation of AUDA at 4 wk of age. Renal cytoplasmic epoxide hydrolase-2 (Ephx2) gene expression was enhanced in SHR vs. WKY from 2 days to 24 wk. Effects of perinatal treatment with AUDA, supplied to SHR dams until 4 wk after birth, on BP in female and male offspring and renal oxylipin metabolome in female offspring were observed and contrasted to female SHR for direct effects of AUDA (8-12 wk). Briefly, inhibition of SEH was effective in persistently reducing BP in female SHR when applied during the perinatal phase. This was accompanied by marked increases in major renal AA epoxides and decreases in renal lipoxygenase products of AA. Early inhibition of SEH induced a delayed increase in renal 5-HETE at 24 wk, in contrast to a decrease at 2 wk. Inhibition of SEH in female SHR from 8 to 12 wk did not reduce BP but caused profound decreases in renal 15(S)-HETrE, LTB4, TBX2, 5-HETE, and 20-HETE and increases in TriHOMEs. In male SHR, BP reduction after perinatal AUDA was transient. Thus, Ephx2 transcription and SEH activity in early life may initiate mechanisms that eventually contribute to high BP in adult female SHR. However, programmed BP-lowering effects of perinatal SEH inhibition in female SHR cannot be simply explained by persistent reduction in renal SEH activity but rather by more complex and temporally dynamic interactions between the renal SEH, lipoxygenase, and cyclooxygenase pathways.

Consequences of perinatal treatment with L-arginine and antioxidants for the renal transcriptome in spontaneously hypertensive rats

Treating spontaneously hypertensive rats (SHR) with L-arginine, taurine, and vitamins C and E (ATCE) during nephrogenesis (2 weeks before to 4 weeks after birth) persistently lowers blood pressure. Hypothetically, differential gene expression in kidney of SHR vs. normotensive Wistar-Kyoto rats (WKY) is partially corrected by maternal ATCE in SHR. Differential gene expression in 2-days, 2-weeks, and 48-week-old rats was studied using oligonucleotide chips. Transcription factor binding sites (TFBS) of differentially expressed genes were analyzed in silico. Differential gene expression varied between SHR+ATCE and SHR, suggesting both direct and indirect effects; but, few genes were modulated toward WKY level and there was little overlap between ages. TFBS analysis suggests less Elk-1-driven gene transcription in both WKY and SHR+ATCE vs. SHR at 2 days and 2 weeks. Concluding, in SHR, persistent antihypertensive effects of maternal ATCE are not primarily due to persistent corrective transcription. Less Elk-1-driven transcription at 2 days and 2 weeks may be involved.

Behavioral and genetic evidence for a novel animal model of Attention-Deficit/Hyperactivity Disorder Predominantly Inattentive Subtype

Background

According to DSM-IV there are three subtypes of Attention-Deficit/Hyperactivity Disorder, namely: ADHD predominantly inattentive type (ADHD-PI), ADHD predominantly Hyperactive-Impulsive Type (ADHD-HI), and ADHD combined type (ADHD-C). These subtypes may represent distinct neurobehavioral disorders of childhood onset with separate etiologies. The diagnosis of ADHD is behaviorally based; therefore, investigations into its possible etiologies should be based in behavior. Animal models of ADHD demonstrate construct validity when they accurately reproduce elements of the etiology, biochemistry, symptoms, and treatment of the disorder. Spontaneously hypertensive rats (SHR) fulfill many of the validation criteria and compare well with clinical cases of ADHD-C. The present study describes a novel rat model of the predominantly inattentive subtype (ADHD-PI).

Methods

ADHD-like behavior was tested with a visual discrimination task measuring overactivity, impulsiveness and inattentiveness. Several strains with varied genetic background were needed to determine what constitutes a normal comparison. Five groups of rats were used: SHR/NCrl spontaneously hypertensive and WKY/NCrl Wistar/Kyoto rats from Charles River; SD/NTac Sprague Dawley and WH/HanTac Wistar rats from Taconic Europe; and WKY/NHsd Wistar/Kyoto rats from Harlan. DNA was analyzed to determine background differences in the strains by PCR genotyping of eight highly polymorphic microsatellite markers and 2625 single nucleotide polymorphisms (SNPs).

Results

Compared to appropriate comparison strains (WKY/NHsd and SD/NTac rats), SHR/NCrl showed ADHD-C-like behavior: striking overactivity and poor sustained attention. Compared to WKY/NHsd rats, WKY/NCrl rats showed inattention, but no overactivity or impulsiveness. WH/HanTac rats deviated significantly from the other control groups by being more active and less attentive than the WKY/NHsd and SD/NTac rats. We also found substantial genomic differences between the WKY/NCrl and WKY/NHsd rats for eight short tandem repeat loci and 2625 SNPs. About 33.5 percent of the genome differs between the two WKY rat substrains, with large stretches of divergence on each chromosome.

Discussion

These data provide solid behavioral and genetic evidence that the WKY/NCrl and WKY/NHsd rats should be considered as separate substrains. Moreover, the behavioral features of the WKY/NCrl rat indicate that it should be a useful model for ADHD-PI, the primarily inattentive subtype of ADHD. The SD/NTac and the WH/HanTac rats show significant genetic and/or behavioral differences from WKY/NHsd rats and appear not to be appropriate controls in studies using the SHR/NCrl. The present results support the conclusion that SHR/NCrl is the best validated animal model of ADHD-C. The overactivity, impulsiveness and deficient sustained attention of the SHR/NCrl strain are independent behaviors. Thus, overactivity does not account for this strain's impulsiveness and deficient sustained attention. Finally, the present study shows that great care has to be exercised to select the model and comparison groups.

Differential renal gene expression in prehypertensive and hypertensive spontaneously hypertensive rats

Development of hypertension stems from both environmental and genetic factors wherein the kidney plays a central role. Spontaneously hypertensive rats (SHR) and the nonhypertensive Wistar-Kyoto (WKY) controls are widely used as a model for studying hypertension. The present study examined the renal gene expression profiles between SHR and WKY at a prehypertensive stage (3 wk of age) and hypertensive stage (9 wk of age). Additionally, age-related changes in gene expression patterns were examined from 3 to 9 wk in both WKY and SHR. Five to six individual kidney samples of the same experimental group were pooled together, and quadruplicate hybridizations were performed using the National Institute of Environmental Health Sciences Rat version 2.0 Chip, which contains ∼6,700 genes. Twenty two genes were found to be differentially expressed between SHR and WKY at 3 wk of age, and 104 genes were differentially expressed at 9 wk of age. Soluble epoxide hydrolase ( Ephx2) was found to be significantly upregulated in SHR at both time points and was the predominant outlier. Conversely, elastase 1 ( Ela1) was found to be the predominant gene downregulated in SHR at both time points. Analysis of profiles at 3 vs. 9 wk of age identified 508 differentially expressed genes in WKY rats. In contrast, only 211 genes were found to be differentially expressed during this time period in SHR. The altered gene expression patterns observed in the age-related analysis suggested significant differences in the vascular extracellular matrix system between SHR and WKY kidney. Together, our data highlight the complexity of hypertension and the numerous genes involved in and affected by this condition.

Transcriptome analysis and kidney research: Toward systems biology

An enormous amount of data has been generated in kidney research using transcriptome analysis techniques. In this review article, we first describe briefly the principles and major characteristics of several of these techniques. We then summarize the progress in kidney research that has been made by using transcriptome analysis, emphasizing the experience gained and the lessons learned. Several technical issues regarding DNA microarray are highlighted because of the rapidly increased use of this technology. It appears clear from this brief survey that transcriptome analysis is an effective and important tool for question-driven exploratory science. To further enhance the power of this and other high throughput, as well as conventional approaches, in future studies of the kidney, we propose a multidimensional systems biology paradigm that integrates investigation at multiple levels of biologic regulation toward the goal of achieving a global understanding of physiology and pathophysiology.

Cardiovascular Genomics and Oxidative Stress

The majority of modifiable cardiovascular risk factors are complex, polygenic, or at least oligogenic traits, with genetic and environmental determinants playing important roles in disease risk and its phenotypic expression. The Human Genome Project and subsequent mouse and rat genome data have provided powerful tools to commence the dissection of genetic determinants of hypertension and other cardiovascular risk factors. Despite several new methodologies such as genome-wide scans, genome-wide gene expression profiling, and proteomic screens, it is fair to say that the progress of genetic studies designed as nonhypothesis driven has been relatively slow. On the other hand, several interesting candidate pathways have been identified, where investigators allowed for hypothesis-driven functional studies. One example of such pathway is vascular oxidative stress with its extensive network of genes and proteins, many with proven contributions to cardiovascular disease. Therefore, in parallel to genome-wide or proteome-wide studies, it will be constructive to pursue “pathwayomics” defined here as functional studies of a candidate pathway for disease pathogenesis.

Novel mechanism of brain soluble epoxide hydrolase‐mediated blood pressure regulation in the spontaneously hypertensive rat

The role of soluble epoxide hydrolase (sEH) in the central control of blood pressure (BP) has not been elucidated in spite of peripheral sEH overexpression being linked to hypertension. Thus, our objective was to investigate the involvement of brain sEH in BP control. sEH expression in the hypothalamus and brain stem, two cardioregulatory brain areas, was increased in the spontaneously hypertensive rat (SHR) compared to the Wistar Kyoto (WKY) rat. Inhibition of the enzyme by intracerebroventricular (icv) delivery of AUDA further increased both BP and heart rate (HR) by 32 +/- 6 mmHg and 54 +/- 10 bpm, respectively, (P<0.05) in the SHR. Analysis of waveform telemetry data revealed a decrease in spontaneous baroreceptor reflex gain following sEH inhibition, indicating the sustained increase in BP may be due to a decrease in baroreceptor reflex function. The hypertensive effect of sEH inhibition is likely a result of an increase in epoxyeicosatrienoic acid (EET)-mediated generation of ROS. This view is supported by the following: 1) Inhibition of EET formation attenuates AUDA-induced increase in BP; 2) delivery of an EET agonist increases BP and HR in the WKY rat, and 3) inhibition of NAD(P)H oxidase by gp91ds-tat prevents AUDA-induced increases in BP and HR. Finally, electrophysiological studies demonstrate that AUDA increased neuronal firing rate exclusively in the SHR, an effect completely abolished by gp91ds-tat. These observations suggest that EETs and sEH inhibition are involved in increasing BP in the SHR. We suggest that an increased expression of sEH is a futile central nervous system response in protection against hypertension.

Neuroendocrine transcriptome in genetic hypertension: multiple changes in diverse adrenal physiological systems

The genetic basis of hypertension in the genetically/hereditary hypertensive (BPH/2) mouse strain is incompletely understood, although a recent genome scan uncovered evidence for several susceptibility loci. To probe the neuroendocrine transcriptome in this disease model, 12 488 probe set microarray experiments were performed on mRNA transcripts from adrenal glands of juvenile (prehypertensive) and adult BPH/2 (hypertensive), as well as the genetically/hereditary low-blood pressure (BPL/1), strains at both time points. To determine the impact of strain (BPH/2 versus BPL/1), age (juvenile versus adult), and the interaction of strain and age on gene expression levels, we performed standard 2-factor ANOVA and computed a concordance coefficient to assess the reproducibility of gene expression measurements among replicates. Of genes with significant (P<0.05) differential expression, 2647 showed strain differences, 982 showed age differences, and 757 exhibited strain-by-age interaction. Fold-changes in gene expression assayed by microarray were confirmed in a subset by real-time polymerase chain reaction (R=0.739, P=0.0094). We used a systems biology approach to evaluate alterations in contributing biochemical pathways and we statistically quantified these global pathway disturbances using the Kolmogorov-Smirnov goodness-of-fit test. We found widespread, indeed global, alterations in patterns of gene expression in diverse systems of BPH/2: in sympathochromaffin transcripts suggesting increased sympathetic stimulation; in vasoconstrictor/vasodilator systems; global reductions in carbohydrate intermediary metabolism; and increases in oxidative stress, with changes in oxygen radical forming and disposition enzymes. These analyses highlight widespread derangements in diverse physiological pathways, providing multiple avenues for further investigation into the pathogenesis of genetic hypertension.

Functional genomics as an emerging strategy for the investigation of central mechanisms in experimental hypertension

Centrally mediated increases in sympathetic nerve activity and attenuated arterial baroreflexes contribute to the pathogenesis of hypertension. Despite the characterization of cellular and physiological mechanisms that regulate blood pressure and alterations that contribute to hypertension, the genetic and molecular basis of this pathophysiology remains poorly understood. Strategies to identify genes that contribute to central pathophysiologic mechanisms in hypertension include integrative biochemistry and physiology as well as functional genomics. This article summarizes recent progress in applying functional genomics to elucidate the genetic basis of altered central blood pressure regulatory mechanisms in hypertension. We describe approaches others and we have undertaken to investigate gene expression profiles in hypertensive models in order to identify genes that contribute to the pathogenesis of hypertension. Finally, we provide the readers a roadmap for negotiating the route from experimental findings of gene expression profiling to translating their therapeutic potential. The combination of gene expression profiling and the phenotypic characterization of in vitro and in vivo loss or gain of function experiments for candidate genes have the potential to identify genes involved in the pathogenesis of hypertension and may present novel targets for therapy.

Pyridoxine 5′-phosphate oxidase is a candidate gene responsible for hypertension in Dahl-S rats

To identify candidate genes responsible for hypertension in Dahl salt-sensitive rats (Dahl-S), an oligonucleotide microarray analysis was performed to find differentially expressed genes in kidneys of Dahl-S and Lewis rats. We obtained 101 F2 male rats from Dahl-S and Lewis rats and performed precise measurements of blood pressure (BP) and heart rate by telemetric monitoring at 14 weeks of age after 9 weeks of salt-loading. The correlation analysis between genotypes of differentially expressed genes and BP in F2 rats indicated that pyridoxine 5'-phosphate oxidase (Pnpo) and catecholamine-O-methyltransferease (Comt) showed a highly significant association with BP. However, in the case of Comt, the Dahl-S genotype correlated with low BP. Short/branched chain acyl-CoA dehydrogenase and Sah also showed a significant association with systolic blood pressure. The present study provided evidence that Pnpo is a candidate gene responsible for hypertension in Dahl-S rats.

Arterial hypertension and brain damage--evidence from animal models (review)

Hypertension is an important risk factor for cerebrovascular disease including stroke and has also a role in the development of vascular cognitive impairment (VCI) and vascular dementia (VaD). Research on pathophysiology and treatment of hypertensive brain damage may benefit from the availability of animal models. This paper has reviewed the main animal models of hypertension in which brain damage is documented. Spontaneously hypertensive rats (SHR) represent the animal model more largely used. In these rats cerebrovascular changes, brain atrophy, loss of nerve cells in cerebrocortical areas, and glial reaction were documented. Several changes observed in SHR are similar to those found by in vivo imaging studies in essential hypertensives. It is documented that brain gets benefit from lowering abnormally elevated blood pressure and that reduction of hypertension protects brain from stroke and probably reduces the incidence of VaD. The influence of anti-hypertensive treatment on brain structure and function in animal models of hypertension is reviewed. Among classes of drugs investigated, dihydropyridine-type Ca2+ antagonists were those with a most documented protective effect on hypertensive brain damage. Limits and perspectives in the use of animal models for assessing brain damage caused by hypertension and protection from it are discussed.

DNA expression analysis: serial analysis of gene expression, microarrays and kidney disease

PURPOSE OF REVIEW

Expression profiling using serial analysis of gene expression and microarray technologies allows global description of expressed genes present in biological systems. Although relatively new technologies, each having been developed in the mid-1990s, both have become established and widely used tools for identification of gene networks and gene function.

RECENT FINDINGS

This review highlights DNA expression analyses published in 2002, emphasizing primarily serial analysis of gene expression and microarray technologies. We focus on the applicability of DNA expression analysis to renal disease, especially as some investigators have developed custom serial analysis of gene expression kidney libraries and kidney disease-specific 'designer chip' microarrays. Data analysis techniques and statistics are also discussed, since the challenge is generation of accurate messenger RNA profiles and interpretation of data in a manner that is both coherent and reproducible.

SUMMARY

Because kidney disease pathophysiology is complex, expression analysis can identify candidate nephropathy pathogenesis genes and gene networks, which eventually could become targets for therapeutic intervention.

Microarray analysis: a novel research tool for cardiovascular scientists and physicians

The massive increase in information on the human DNA sequence and the development of new technologies will have a profound impact on the diagnosis and treatment of cardiovascular diseases. The microarray is a micro-hybridisation based assay. The filter, called microchip or chip, is a special kind of membrane in which are spotted several thousands of oligonucleotides of cDNA fragments coding for known genes or expressed sequence tags. The resulting hybridisation signal on the chip is analysed by a fluorescent scanner and processed with a software package utilising the information on the oligonucleotide or cDNA map of the chip to generate a list of relative gene expression. Microarray technology can be used for many different purposes, most prominently to measure differential gene expression, variations in gene sequence (by analysing the genome of mutant phenotypes), or more recently, the entire binding site for transcription factors. Measurements of gene expression have the advantage of providing all available sequence information for any given experimental design and data interpretation in pursuit of biological understanding. This research tool will contribute to radically changing our understanding of cardiovascular diseases.

Gene expression profiling in hypertension research: a critical perspective

Recent advances in molecular biology and technology have made it possible to monitor the expression levels of virtually all genes simultaneously. As the tools for gene expression profiling have become more widely available, the number of investigators applying this technology in hypertension research, as in other fields of biomedical research, has grown rapidly. At the same time, numerous articles have been published that discuss the technical aspects of gene profiling and its promise for advancing research on the pathogenesis and treatment of multiple clinical disorders. However, much of the research carried out with gene expression profiling has been of a correlational or descriptive nature, and the true value of this technology is unclear. Despite the initial wave of enthusiasm for gene expression profiling, its actual utility for studying multifactorial disorders like hypertension remains to be established. In this review, we offer a critical perspective on the use of gene expression profiling in hypertension research and discuss some emerging strategies for taking this technology beyond the limits of correlational and descriptive studies.