Expression Of Renin-angiotensin System Genes Research Articles

Neuronal ACE1 knockout disrupts the hippocampal renin angiotensin system leading to memory impairment and vascular loss in normal aging

Angiotensin I converting enzyme (ACE1) maintains blood pressure homeostasis by converting angiotensin I into angiotensin II in the renin-angiotensin system (RAS). ACE1 is expressed in the brain, where an intrinsic RAS regulates complex cognitive functions including learning and memory. ACE1 has been implicated in neurodegenerative disorders including Alzheimer's disease and Parkinson's disease, but the mechanisms remain incompletely understood. Here, we performed single-nucleus RNA sequencing to characterize the expression of RAS genes in the hippocampus and discovered that Ace is mostly expressed in CA1 region excitatory neurons. To gain a deeper understanding of the function of neuronal ACE1, we generated ACE1 conditional knockout (cKO) mice lacking ACE1 expression specifically in hippocampal and cortical excitatory neurons. Interestingly, ACE1 cKO mice exhibited hippocampus-dependent memory impairment in the Morris water maze, y-maze, and fear conditioning tests. Total ACE1 level was significantly reduced in the cortex and hippocampus of ACE1 cKO mice showing that excitatory neurons are the predominant cell type expressing ACE1 in the forebrain. Despite similar reductions in total ACE1 level in both the hippocampus and cortex, the RAS pathway was dysregulated in the hippocampus only. Importantly, ACE1 cKO mice exhibited age-related capillary loss selectively in the hippocampus. Here, we show selective vulnerability of the hippocampal microvasculature and RAS pathway to neuronal ACE1 knockout. Our results provide important insights into the function of ACE1 in the brain and demonstrate a connection between neuronal ACE1 and cerebrovascular function in the hippocampus.

Upregulation of miR-361-3p Is Associated With Impaired AT2 Receptor Expression in Cardiometabolic Diseases

Cardiometabolic homeostasis has been shown to be regulated by the brain Renin-Angiotensin System (RAS), including via epigenetic mechanisms. MicroRNA (miRNA) regulation is one of the most common mechanisms controlling the expression of RAS genes and has previously been implicated in hypertension, cardiac ischemia, and aging. Recently, we observed that hypercaloric diet (HCD) programming resulted in differentially expressed miRNA in the hypothalamus of only the male progeny, including miR-361-3p which is thought to target angiotensin-II type 2 receptors (AT2R). Here, we aimed to investigate whether miR-361-3p regulate AT2R expression in a mouse model of cardiometabolic disease (CMD) exhibiting hypertension, diabetes and obesity. C57BI/6J mice (3-week-old, both sexes, n=10) were fed a HCD (D12492. 60 kcal% Fat, Research Diets, USA) while weight and fasting blood glucose levels were measured weekly to ensure the acquisition of metabolic syndrome. At 12 weeks of age, the mice were infused subcutaneously (osmotic pump model 1004, Alzet) with Ang-II (600 ng/kg/min/4 weeks). BP, food intake and glycemia were recorded weekly while intraperitoneal glucose (GTT), insulin (ITT) tolerance tests and body composition (EchoMRI) were assessed at the end of the study. Gene expression of miR-361-3p (QRT-PCR) was increased in the hypothalamus of CMD male mice (2.0 ±0.5 vs.1.2 ±0.2, p<0.05) but not in females (2.7 ±0.8 vs.2.5 ±0.4, P>0.05). However, both sexes showed an increase in the heart (Males: 2.0 ±0.5 vs.1.0 ±0.3; Females: 1.6 ±0.4 vs. 0.8 ±0.2, p<0.05) which was associated with decreased AT2R cardiac expression (Capillary Western) in CMD male (0.9 ±0.0 vs.1.0 ±0.0, p<0.05) and females (0.1 ±0.0 vs.0.6 ±0.1, p<0.001). Together, our data suggest that in CMD, upregulation of miR-361-3p is associated with the decrease of AT2R in the heart, possibly contributing to impaired cardiac function in this model. This positions inhibitors of miR-361-3p as a possible new therapeutic strategy to control RAS overactivity in CMD. This work was supported in part by a research grant from the National Institutes of Health (HL163588). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Sexually Dimorphic Gene Expression in Rat Proximal Tubules Suggests Activation of the Intrarenal Renin Angiotensin System and Elevated Transport Rates in Males

Introduction: Sexual dimorphism affects various organ systems, including renal and cardiovascular. The renin-angiotensin system (RAS) plays a pivotal role in regulating fluid homeostasis and blood pressure, with males being generally more sensitive to the hypertensive actions of angiotensin II (AngII). Proximal tubules (PT)s reabsorb 60-70% of filtered water, sodium, and bicarbonate and present sexually dimorphic biology. In addition, PTs are a key element of the intrarenal RAS and the production site of angiotensinogen ( Agt, AGT) and derived bioactive peptides. These peptides exert autocrine, as well as paracrine effects in distal portions of the nephron, regulating salt and water reabsorption. Hypothesis: We hypothesize that the increased sensitivity to the hypertensive actions of AngII in males is due to activation of the intrarenal RAS. Methods: We used 3 male and 3 female pools of whole kidney single-cell RNAseq transcriptomes to study gene expression differences across sexes in different segments of the nephron. Results: We identified sex-differentially expressed genes (DEGs) in all segments of the nephron, with the majority of DEG mapping to the PT. Analyzing all three PT segments together, we found 86 upregulated genes in females and 104 in males. Pathway enrichment analysis using the Kyoto Encyclopedia of Genes and Genomes (KEGG) highlighted pathways associated with glutathione biosynthesis and metabolism in females, while males presented greater expression of genes associated with the tricarboxylic acid cycle and mineral absorption, including the γ-subunit of the Na,K-ATPase ( Fxyd2). Differential expression of genes on each sub-segment of the PTs, namely S1, S2, and S3, showed the following number of upregulated genes: Females: 39, 37, and 73 in S1, S2, and S3, respectively; and Males: 67, 57, and 105 in S1, S2, and S3, respectively. This data indicates that S3 exhibits the largest sexually dimorphic transcriptomes. Pathway enrichment on S3 DEG in both males and females showed similar enrichment terms as in whole PTs. However, at this resolution, males also present upregulation of RAS genes, including Agt, and two proteases involved in the metabolism of angiotensin peptides: aminopeptidase A ( Enpep, APA) and prolyl endopeptidase ( Prep, PEP). APA and PEP can both cleave AngII to bioactive peptides AngIII and Ang(1-7), respectively. Conclusion: We conclude that the intrarenal RAS is upregulated in male PT.S3. The increase in AGT and proteases capable of metabolizing AngII suggest that this peptide may be elevated. Analyzing the expression of RAS genes alone does not allow us to infer a resultant effect on Na handling, as AngII, AngIII, and Ang(1-7) could exert both natriuretic and anti-natriuretic effects. However, enrichment terms associated with mineral transport and energy demands suggest active mineral transport prevails in males. Funding sources: This work was supported in part by CWRU BGT670107 and NIH-NIDDK DK128304 grants to AGV. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Upregulation of the Renin-Angiotensin System Is Associated with Patient Survival and the Tumour Microenvironment in Glioblastoma.

Glioblastoma is a highly aggressive disease with poor survival outcomes. An emerging body of literature links the role of the renin-angiotensin system (RAS), well-known for its function in the cardiovascular system, to the progression of cancers. We studied the expression of RAS-related genes (ATP6AP2, AGTR1, AGTR2, ACE, AGT, and REN) in The Cancer Genome Atlas (TCGA) glioblastoma cohort, their relationship to patient survival, and association with tumour microenvironment pathways. The expression of RAS genes was then examined in 12 patient-derived glioblastoma cell lines treated with chemoradiation. In cases of glioblastoma within the TCGA, ATP6AP2, AGTR1, ACE, and AGT had consistent expressions across samples, while AGTR2 and REN were lowly expressed. High expression of AGTR1 was independently associated with lower progression-free survival (PFS) (p = 0.01) and had a non-significant trend for overall survival (OS) after multivariate analysis (p = 0.095). The combined expression of RAS receptors (ATP6AP2, AGTR1, and AGTR2) was positively associated with gene pathways involved in hypoxia, microvasculature, stem cell plasticity, and the molecular characterisation of glioblastoma subtypes. In patient-derived glioblastoma cell lines, ATP6AP2 and AGTR1 were upregulated after chemoradiotherapy and correlated with an increase in HIF1A expression. This data suggests the RAS is correlated with changes in the tumour microenvironment and associated with glioblastoma survival outcomes.

Altered Gene Expression Within the Renin-Angiotensin System in Normal Aging and Dementia.

The renin-angiotensin system (RAS) is dysregulated in Alzheimer's disease (AD). In this study, we have explored the hypothesis that an -age--related imbalance in brain RAS is a trigger for RAS dysregulation in AD. We characterized RAS gene expression in the frontal cortex from (i) a cohort of normal aging (n = 99, age range = 19-96 years) and (ii) a case-control cohort (n = 209) including AD (n = 66), mixed dementia (VaD + AD; n = 50), pure vascular dementia (VaD; n = 42), and age-matched controls (n = 51). The AD, mixed dementia, and age-matched controls were further stratified by Braak tangle stage (BS): BS0-II (n = 48), BSIII-IV (n = 44), and BSV-VI (n = 85). Gene expression was calculated by quantitative PCR (qPCR) for ACE1, AGTR1, AGTR2, ACE2, LNPEP, and MAS1 using the 2-∆∆Cq method, after adjustment for reference genes (RPL13 and UBE2D2) and cell-specific calibrator genes (NEUN, GFAP, PECAM). ACE1 and AGTR1, markers of classical RAS signaling, and AGTR2 gene expression were elevated in normal aging and gene expression in markers of protective downstream regulatory RAS signaling, including ACE2, MAS1, and LNPEP, were unchanged. In AD and mixed dementia, AGTR1 and AGTR2 gene expression were elevated in BSIII-IV and BSV-VI, respectively. MAS1 gene expression was reduced at BSV-VI and was inversely related to parenchymal Aβ and tau load. LNPEP gene expression was specifically elevated in VaD. These data provide novel insights into RAS signaling in normal aging and dementia.

Altered renin-angiotensin system gene expression in airways of antigen-challenged mice: ACE2 downregulation and unexpected increase in angiotensin 1–7

ObjectiveEvidence suggest that the renin-angiotensin system (RAS) is activated in people with asthma, although its pathophysiological role is unclear. Angiotensin-converting enzyme 2 (ACE2) is the major enzyme that converts angiotensin II to angiotensin 1–7 (Ang-1–7), and is also known as a receptor of SARS-CoV-2. The current study was conducted to identify the change in RAS-related gene expression in airways of a murine asthma model. MethodsThe ovalbumin (OA)-sensitized mice were repeatedly challenged with aerosolized OA to induce asthmatic reaction. Twenty-four hours after the last antigen challenge, the main bronchial smooth muscle (BSM) tissues were isolated. ResultsThe KEGG pathway analysis of differentially expressed genes in our published microarray data revealed a significant change in the RAS pathway in the antigen-challenged mice. Quantitative RT-PCR analyses showed significant increases in the angiotensin II-generating enzymes (Klk1, Klk1b3 and Klk1b8) and a significant decrease in Ace2. Surprisingly, ELISA analyses revealed a significant increase in Ang-1–7 levels in bronchoalveolar lavage (BAL) fluids of the antigen-challenged animals, while no significant change in angiotensin II was observed. Application of Ang-1–7 to the isolated BSMs had no effect on their isometrical tension. ConclusionThe expression of Ace2 was downregulated in the BSMs of OA-challenged mice, while Klk1, Klk1b3 and Klk1b8 were upregulated. Despite the downregulation of ACE2, the level of its enzymatic product, Ang-1–7, was increased in the inflamed airways, suggesting the existence of an unknown ACE2-independent pathway for Ang-1–7 production. The functional role of Ang-1–7 in the airways remains unclear.

INVESTIGATING NEW THERAPEUTIC OPPORTUNITIES FOR HYPERTENSION THROUGH TRANSCRIPTOMIC AND PROTEOMIC ANALYSIS OF THE KIDNEY RENIN-ANGIOTENSIN SYSTEM

Objective: We systematically characterised the expression of all renin-angiotensin system (RAS) genes in the human kidney and searched in silico for new pharmacological therapeutic opportunities to modify RAS. Design and method: We compiled data from open access resources to characterise all components of the RAS pathway. We used transcriptomic profiles of 73 human kidney tissues from the Genotype-Tissue Expression Project, integrated genome-wide DNA genotypes and RNA-sequencing-derived transcriptome profiles of 478 human kidneys from Human Kidney Tissue Resource and, kidney tissue proteomics from 72 samples recruited by Clinical Proteomic Tumour Analysis Consortium. Additionally, we used an independent single-cell RNA sequencing data and gene expression datasets curated from the Kidney Precision Medicine Project (KPMP) and Enrichr (web-based enrichment analysis tool). Lastly, we integrated the Connectivity Map and Drug Gene Interaction Database to identify drug repurposing opportunities for treatment of hypertension targeting the RAS genes. Results: We identified 37 genes encoding components of the RAS pathway with measurable expression in human kidney tissue. 15% of these gene-pairs demonstrated a positive (r>0.5) correlation in kidney expression most consistent with a functionally integrated network of interacting molecules. Angiotensinogen (AGT), the key component of the pathway - showed the highest level of mRNA expression in the liver, and we demonstrated that its hepatic mRNA expression correlates most strongly with its mRNA expression in the kidney (r = 0.71, P = 2.60e-06). Expression levels of mRNA for 92% of RAS genes correlated positively with their protein abundance in the kidney, where renin had the strongest positive correlation (r = 0.64, P<0.01). Enrichr and KPMP revealed that RAS gene expression was enriched in mesangial and epithelial cell types. Existing genetic evidence for correlation between glutamyl aminopeptidase (ENPEP) and systolic blood pressure might relate to its capacity to generate angiotensin III acting on dilator angiotensin II type 2 receptors. This raises potential repurposing opportunities for ENPEP inhibitors like firibastat and tosedostat for the treatment of hypertension. Conclusions: Collectively, this study confirmed synchronized expression of RAS genes in the kidney at both mRNA and protein levels and identified new therapeutic opportunities for treatment of hypertension, through drug repurposing.

Evaluating the brain renin‐angiotensin system (RAS) and sex differences in pre‐clinical models of Alzheimer’s Disease

AbstractBackgroundHypertension is linked to Alzheimer’s Disease (AD) risk, although the mechanisms remain unclear. The renin angiotensin system (RAS), critical for blood pressure homeostasis, is thought to contribute to AD pathology, and targeted RAS therapies are under current clinical investigation. To further evaluate the neurobiological mechanisms of RAS in AD, the current study leveraged two transgenic AD mouse models to compare the behavioral and cognitive deficits and the brain RAS in male and female mice.MethodsA triple‐transgenic mouse model of AD (3xTg‐AD), which exhibits both amyloid beta and tau pathology, was used for in‐house assays, while an RNA‐sequencing database using a novel mouse model on a genetically diverse background (AD‐BXD) (GEO accession number GSE119215) was used to compare expression levels of hippocampal RAS genes at 6 and 14 mos. Morris water maze (MWM) and Y‐maze alternation tests were performed at early (3‐4 mos) and middle (5‐6 mos) time points on 3xTg‐AD mice (n = 8/sex/age/genotype), followed by collection of plasma and whole brain.ResultsCompared to controls, beginning at 3.5 months, 3xTg‐AD male and female mice exhibited deficits in learning assessed by MWM escape latency (p<0.01). However, beginning at 6 months, only 3xTg‐AD females had deficits in memory assessed by Y‐maze alternation below 50% (i.e. chance) (p<0.05). Sex‐dependent deficits are consistent with variability in phenotype beginning at early time points. Next we assessed hippocampal RNA‐sequencing data from the AD‐BXD database. These data demonstrated a sex‐dependent increase in expression of counter‐regulatory RAS genes ACE (p<0.0001) and ACE2 (p<0.05) and decrease in MasR (p<0.01) when comparing 6 and 14 month females, as compared to males and wild‐type controls. There was no change in classical RAS gene expression, indicating that variation in expression of neuroprotective but not classical RAS genes may be more pronounced in aging female mice.ConclusionOur results demonstrate sex and stage‐specific behavioral deficits in the 3xTg‐AD model, which may be linked to changes in hippocampal regulation of the counter‐regulatory arm of brain RAS. Additional studies are needed to further evaluate underlying mechanisms for the role of the neuroprotective arm of the brain RAS in AD and its biomarker and therapeutic targeting potential.

Coordinated expression of the renin-angiotensin genes in the lumbar spinal cord: Lateralization and effects of unilateral brain injury.

In spite of its apparent symmetry, the spinal cord is asymmetric in its reflexes and gene expression patterns including leftward expression bias of the opioid and glutamate genes. To examine whether this is a general phenomenon for neurotransmitter and neurohormonal genes, we here characterized expression and co-expression (transcriptionally coordinated) patterns of genes of the renin-angiotensin system (RAS) that is involved in neuroprotection and pathological neuroplasticity in the left and right lumbar spinal cord. We also tested whether the RAS expression patterns were affected by unilateral brain injury (UBI) that rewired lumbar spinal neurocircuits. The left and right halves of the lumbar spinal cord were analysed in intact rats, and rats with left- or right-sided unilateral cortical injury, and left- or right-sided sham surgery. The findings were (i) lateralized expression of the RAS genes Ace, Agtr2 and Ren with higher levels on the left side; (ii) the asymmetry in coordination of the RAS gene expression that was stronger on the right side; (iii) the decay in coordination of co-expression of the RAS and neuroplasticity-related genes induced by the right-side but not left-side sham surgery and UBI; and (iv) the UBI-induced shift to negative regulatory interactions between RAS and neuroplasticity-related genes on the contralesional spinal side. Thus, the RAS genes may be a part of lateralized gene co-expression networks and have a role in a side-specific regulation of spinal neurocircuits.

Effect of Angiotensin‐converting Enzyme Inhibition on Systemic and Renal RAS Components in a Hyperandrogenemic Rat Model of PCOS

Polycystic Ovary Syndrome (PCOS) is characterized by androgen excess, oligo/anovulation, and polycystic ovaries. Obesity, insulin resistance (IR) and increased blood pressure (BP) are associated with PCOS. Therapeutic options for PCOS are limited and the mechanisms responsible for the cardiometabolic complications seen in PCOS are uncertain. It is unclear if androgen-mediated increases in BP contribute to obesity and/or IR in PCOS. The renin angiotensin system (RAS), a regulator of BP, is affected by androgens and is associated with increased BP in PCOS. To investigate the role of androgens and the contribution of the RAS in PCOS, RAS inhibition via an angiotensin-converting enzyme inhibitor (ACEi) was performed in a PCOS-like rat model. We hypothesized that ACEi would attenuate obesity and IR in PCOS. Female SD rats (4 week old) received dihydrotestosterone (DHT, 7.5 mg/ 90 days) pellets (HAF) subcutaneously or sham surgeries (CON). The rats were then assigned tap water or tap water with the ACEi, enalapril (ENA) (250mg/L) for n=10/group. At the end of the study (16 week old) body weight (BW), body composition by EchoMRI, and IR by HOMA-IR were assessed. Renal RAS gene expression was assessed by qPCR. BP was measured by radiotelemetry and plasma and renal ACE and ACE2 activities were assessed. HAF had increased BW, fat mass and IR vs CON. ENA reduced BW in only HAF. Overall, ENA decreased fat mass, and the decrease in HAF neared significance. ENA did not attenuate IR in HAF. In HAF, angiotensinogen (Agt) mRNA was increased in the renal cortex and medulla, while ACE and angiotensin II receptor type 1a (Atr1a) mRNA was increased in the medulla vs CON. In HAF, ENA had no impact on renal Agt, ACE or Atr1a mRNA. ACE2 mRNA was increased in the medulla of HAF vs CON, and ENA increased medulla ACE2 mRNA in both HAF and CON. HAF had increased BP, and ENA decreased BP in both HAF and CON by a similar degree. Overall, ENA decreased plasma ACE activity but only increased plasma ACE2 activity in HAF. ENA increased cortical ACE2 activity in both HAF and CON. In summary, ACEi therapy in a PCOS model reduced BW, BP and adiposity but had no impact on IR. Renal classic RAS gene expression is upregulated in the HAF but unchanged by ENA. Furthermore, only ACE2 mRNA expression was altered in the HAF with ENA. In addition, the expression of other RAS component genes that were unchanged by ACEi in HAF were significantly impacted by ACEi in CON. This reveals a complex interaction between androgen exposure and renal RAS component gene expression. Increased BP in the HAF did not correlate with plasma or renal ACE or ACE2 activities. Chronic RAS inhibition may be a promising therapeutic approach for androgen-mediated increases in BP and obesity in AE-PCOS, though additional therapy would be needed for IR.

Dynamic Regulation of Brain Renin Angiotensin System During Fear Memory Reconsolidation

Background Dysregulation of the renin angiotensin system (RAS) has been linked to autonomic dysfunction, fear -related disorders (i.e., PTSD) and increased cardiovascular disease (CVD) risk. We recently demonstrated that following reactivation of a fear memory, the peripheral administration of losartan, an angiotensin type 1 receptor blocker (Agtr1) blocker, disrupted long term cue-dependent fear memory. In order to further analyze the role of brain RAS in fear memory processes, here we examined brain RAS gene expression patterns in the basolateral amygdala (BLA), a brain region essential for fear or threat related memory. We hypothesized that peripheral losartan administration would interfere with the reconsolidation of memory by altering the expression of central RAS and other downstream signaling genes involved in fear memory. Methods Pavlovian auditory fear conditioning, whole-genome RNA-sequencing and RT-qPCR on brain tissue punches were combined to analyze gene expression patterns at early (40mins) and late (4hr) phases of reconsolidation and also after acute losartan treatment (10mg/kg, i.p). Results Following auditory cued fear memory retrieval, mRNA expression of immediate early genes (IEGs) - fos, Egr-1 and Arc in the BLA were rapidly increased at 40mins (2-3-fold, p<0.001; n=8) and returned to baseline at 4hrs. At these same early (40 min) activation and late (4hrs) time-points, RAS gene expression (mRNA) patterns in the BLA and synaptic plasticity genes were also dynamically regulated in a time-dependent manner. Compared to our control (non-retrieval group), at 40 min, we observed 2-3-fold mRNA changes in levels of the angiotensin peptide pre-cursor angiotensinogen - Agt (3-fold p<0.025, n=6) and the angiotensin II converting to angiotensin 1-7 cleaving enzyme - Ace2 (2-fold, p<0.05, n=8) which both returned to control levels at 4 hours. In contrast, at the receptor level, the angiotensin II type 1 receptor (Agtr1) was increased at 4 hours, but not 40 min while the type 2 receptor (Agtr2) was increased at both time points. The mRNA level of brain derived neurotrophic factor (Bdnf), an important synaptic plasticity modulator and downstream to angiotensin II signaling, was also elevated (1-fold, p<0.005, n=8) at 40mins. These gene expression patterns were distinct only for BLA as other brain regions of CA1, PVN and PFC showed no significant change. Finally, we determined whether post-retrieval losartan effects RAS genes in the BLA. We found that losartan prevented the rapid increase in Agt expression (p<0.05, n=8) and further increased Ace2 levels (p<0.01, n=8). Conclusion These results demonstrate that following retrieval of a fear memory, brain Agt expression is dynamically regulated in the basolateral amygdala and its expression is also influenced by losartan administration. These results contribute to further understanding the role of brain RAS in modulating central fear memory processes which may have important translational implications for advancing novel therapeutics for PTSD.

Epigenetic Programming Induces Changes in Metabolic and Gene Expression and Reverses the Effects of Ang‐II Infusion in Male Mice

Cardiometabolic diseases are highly prevalent chronic illnesses associated with high risk morbidities. Maternal epigenetic programming modulates gene expression in offspring thus affecting their disease susceptibility later in life. The renin-angiotensin system (RAS) contributes to cardiometabolic homeostasis however, its over-activation is associated with cardiometabolic dysfunctions. Previously, we showed that perinatal exposure to high fat diet (HFD) leads to elevated BP, heart rate, fasting blood glucose (FBG) and weight gain in addition to elevated brain AT1R and ADAM17 gene expression exclusively in males. We hypothesize that perinatal HFD exposure leads to changes in RAS gene expression in peripheral tissues and these changes could be accentuated by low dose Angiotensin-II (Ang-II) revealing a stronger cardiometabolic dysfunction. C57BL6/J dams were fed a HFD or regular diet (RD) for 1 month and mated with RD-fed males. After weaning, offspring were put on RD resulting in two groups; HFD-RD (programmed) and RD-RD (control). At 3 months, offspring underwent 24 h BP recording (telemetry) and glucose tolerance test (GTT). Half of the mice in each group were then implanted with an osmotic pump filled with Ang-II (200 ng/kg/min/2 weeks) resulting in 4 groups; HFD-RD, RD-RD, HFD-RD+Ang-II, RD-RD+Ang-II. BP (24 h) was recorded weekly and GTT was repeated after the 2nd week for the Ang-II-treated mice. For all groups, Liver, muscle and adipose tissues were harvested and selected genes expression was quantified using qPCR. HFD-RD males exhibited higher FBG than RD-RD males (172.7 ±6 vs. 145.2 ±5 mg/dL, p=0.01) and higher blood glucose at 15 min (387.8 ±17 vs. 303.4 ±30 mg/dL, p=0.04). Surprisingly, only HFD-RD+Ang-II males showed lowered FBG level compared to HFD-RD males (139.7 ±8 mg/dL vs. 172.7 ±6, p=0.007) and at 15 min (279.8 ±19 mg/dL vs. 387.8 ±17, p=0.006). Interestingly, no metabolic changes were seen in females in any of the groups. In addition, Ang-II infusion had no effect on hemodynamic parameters in treated groups. Regarding gene expression, HFD-RD showed upregulation of insulin receptor (p=0.0019), ACE2 (p=0.008), and ADAM17 (p=0.04) in the liver compared to RD-RD. Conversely, in HFD-RD+Ang-II, insulin receptor and ACE2 were downregulated in the liver (p<0.0001) relative to HFD-RD. In muscle tissue, while ADAM17 was upregulated in RD-RD+Ang-II (p=0.039), there was no change in ADAM17 expression in HFD-RD+Ang-II. Additionally, AT1 receptor was strongly upregulated in RD-RD+Ang-II (p<0.0001) with a slight upregulation in HFD-RD+Ang-II (p=0.03). We conclude that perinatal exposure to HFD leads to a pre-diabetic state evident by elevated FBG, disturbed first phase insulin secretion, changes in insulin receptor and RAS gene expression exclusively in male mice. This programming reverses the effects of Ang-II, possibly switching signaling towards another angiotensin receptor involved in a protective mechanism.

New angiotensin-converting enzyme inhibitory peptide from Coix prolamin and its influence on the gene expression of renin-angiotensin system in vein endothelial cells

Coix seed, which is a traditional Chinese medicine, has been used to treat hypertension for thousands of years. It has been shown that Coix prolamin peptides display high levels of angiotensin I converting enzyme (ACE) inhibitory activity. Hence, we purified the ACE inhibitory peptides from Coix prolamin hydrolysates and evaluated the influence of the most potent peptide on the renin-angiotensin system (RAS) genes expression in human umbilical vein endothelial cells (HUVECs). In this study, Coix prolamin peptides were sequentially separated by ultrafiltration, ion exchange chromatography, gel filtration chromatography and RP-HPLC, while the peptide structure was analyzed by mass spectrometry. Next, in silico proteolysis, pharmacophore and molecular docking were further applied to screen and optimize the structure of peptides. Finally, a novel ACE inhibitory peptide VDMF was obtained, in which its influence on the gene expression of RAS signaling pathway in AngⅡ-injury HUVECs was evaluated by quantitative real-time PCR. VDMF significantly down-regulated ACE, AngII type 1 receptor (AT1R) and ACE2 mRNA expression in comparation with model group, while up-regulating Mas gene expression. Hence, we obtained a novel antihypertensive candidate that was derived from the Coix peptides, which could involve a multi-modulation mechanism that regulates blood pressure.

Abstract MP04: High Fat Diet Exposure Induces Epigenetic Modulation In The Brain Renin Angiotensin System

Cardiometabolic Diseases (CMD) are one of the highest causes of morbidity and mortality worldwide. In-utero, environmental insults can program brain’s progeny through changes in gene expression level affecting cardiometabolic functions. Methylation and demethylation of DNA take place by DNA methyltransferase (DNMT) and Ten eleven translocation (TET) enzymes, respectively. Expression of renin angiotensin system (RAS) on pre-autonomic neurons in the hypothalamus is believed to play a pivotal role in sympathetic activity controlling metabolic and blood pressure (BP) homeostasis. We hypothesize that perinatal exposure to high fat high sucrose diet (HFHSD) programs the brain RAS through methylation mechanisms that lead to autonomic dysfunction and hypersensitivity to CMD. C57BL6/J dams were fed HFHSD or regular diet (RD) and mated with RD sires. After weaning, offspring were raised on RD. Three-month old progeny underwent 24 h BP recording (telemetry), measurement of fasted blood glucose (FBG), assessment of autonomic function (pharmacological) and baroreflex sensitivity (sequence method). Mice were then sacrificed, and brains harvested for quantification of mRNA levels of DNMT, TET and RAS components in the hypothalamus. HFHSD-exposed male offspring showed elevation in systolic BP (140.2 ±1.9 vs. 131.2 ±2.4 mmHg, p=0.006), heart rate (611.3 ±7.8 vs 562.5 ±7 bpm, p&lt;0.0001) and FBG (172.7 ±6.3 vs. 142.6 ±6.3 mg/dl, p=0.018) but not females. Cardiac sympathetic activity was higher in HFHSD-exposed mice (-148 ±11.5 vs. -35.2 ±4.7 bpm, p&lt;0.05). Surprisingly, sympathetic vascular tone was only increased in HFHSD-exposed females (-64.6 ±5.7 vs. -36.7 ±2.9 mmHg, p&lt;0.05) while spontaneous baroreflex gain was improved in HFHSD-exposed males (5.3 ±0.7 vs. 2.6 ±0.4 msec/mmHg, p&lt;0.05). In the brain, DNMT1, DNMT3a and TET1, 2 and 3 mRNA expression were downregulated (p&lt;0.05) while AT 1a R and ACE2 genes were upregulated (p=0.02) in HFHSD-exposed mice. We conclude that perinatal exposure to a hypercaloric diet epigenetically programs the progeny’s brain through methylation leading to a pre-hypertensive and pre-diabetic phenotype associated with changes in the expression of RAS genes which could eventually result in increased susceptibility to CMD.

Angiotensin-converting enzyme 2 influences pancreatic and renal function in diabetic mice

AbstractType 1 diabetes is a T-cell mediated autoimmune disease characterized by pancreatic beta cells destruction. Angiotensin-converting enzyme 2 (ACE2), a component of renin–angiotensin system (RAS) has been identified in pancreas from type 2 diabetic mice and its overexpression prevents beta cell dysfunction. We studied the effect of ACE2 deletion on pancreatic and renal function in the nonobese diabetic mice, a model that mimics type 1 diabetes. ACE2-deficient NOD mice and the respective controls were generated. Pancreas function and immunohistochemistry studies were performed. Renal function and RAS gene expression were also analyzed. Renal proximal tubular cells were obtained from these animals to dissect the effect of ACE2 deficiency in these cells. In NOD mice, ACE2 deletion significantly worsened glucose homeostasis, decreased islet insulin content, increased beta cell oxidative stress, and RIPK1-positive islets as compared with control mice. Angiotensin-converting enzyme and angiotensin II type 1 receptor (AT1R) were also increased in ACE2-deficient mice. In kidneys of 30-day diabetic mice, ACE2 deletion decreased podocyte number within the glomeruli, and altered renal RAS gene expression in tubules. ACE2 deletion influenced the expression of fibrosis-related genes in isolated primary renal proximal tubular cells before diabetes onset in NOD mice. Our findings suggest that ACE2 deletion may have a deleterious impact on beta cell and renal function, by promoting oxidative stress and increasing necroptosis mediators. In addition, this effect is accompanied by RAS alterations in both pancreas and renal proximal tubular cells, indicating that ACE2 may exert a renopancreatic protective effect on type 1 diabetes, which is activated before diabetes starts.This study examined the contribution of ACE2 in diabetes onset and the role of ACE2 in the progression of diabetic nephropathy in NOD mouse. ACE2 loss leads to an impaired glucose and insulin homeostasis, RAS activation, increase in oxidative stress, and RIPK1 within the pancreas. In the kidney, ACE2 deletion induced podocyte loss, RAS modulation, and renal fibrosis activation in an early phase of diabetes.

Angiotensin-(1-7) Improves Integrated Cardiometabolic Function in Aged Mice.

Angiotensin (Ang)-(1-7) is a beneficial renin–angiotensin system (RAS) hormone that elicits protective cardiometabolic effects in young animal models of hypertension, obesity, and metabolic syndrome. The impact of Ang-(1-7) on cardiovascular and metabolic outcomes during aging, however, remains unexplored. This study tested the hypothesis that Ang-(1-7) attenuates age-related elevations in blood pressure and insulin resistance in mice. Young adult (two-month-old) and aged (16-month-old) male C57BL/6J mice received Ang-(1-7) (400 ng/kg/min) or saline for six-weeks via a subcutaneous osmotic mini-pump. Arterial blood pressure and metabolic function indices (body composition, insulin sensitivity, and glucose tolerance) were measured at the end of treatment. Adipose and cardiac tissue masses and cardiac RAS, sympathetic and inflammatory marker gene expression were also measured. We found that chronic Ang-(1-7) treatment decreased systolic and mean blood pressure, with a similar trend for diastolic blood pressure. Ang-(1-7) also improved insulin sensitivity in aged mice to levels in young mice, without effects on glucose tolerance or body composition. The blood pressure–lowering effects of Ang-(1-7) in aged mice were associated with reduced sympathetic outflow to the heart. These findings suggest Ang-(1-7) may provide a novel pharmacological target to improve age-related cardiometabolic risk.

Activation of the renin-angiotensin system in high fructose-induced metabolic syndrome.

High fructose intake induces hyperglycemia and hypertension. However, the mechanism by which fructose induces metabolic syndrome is largely unknown. We hypothesized that high fructose intake induces activation of the renin-angiotensin system (RAS), resulting in hypertension and metabolic syndrome. We provided 11-week-old Sprague–Dawley rats with drinking water, with or without 20% fructose, for two weeks. We measured serum renin, angiotensin II (Ang II), and aldosterone (Aldo) using ELISA kits. The expression of RAS genes was determined by quantitative reverse transcription polymerase chain reaction. High fructose intake increased body weight and water retention, regardless of food intake or urine volume. After two weeks, fructose intake induced glucose intolerance and hypertension. High fructose intake increased serum renin, Ang II, triglyceride, and cholesterol levels, but not Aldo levels. High fructose intake increased the expression of angiotensinogen in the liver; angiotensin-converting enzyme in the lungs; and renin, angiotensin II type 1a receptor (AT1aR), and angiotensin II type 1b receptor (AT1bR) in the kidneys. However, expression of AT1aR and AT1bR in the adrenal glands did not increase in rats given fructose. Taken together, these results indicate that high fructose intake induces activation of RAS, resulting in hypertension and metabolic syndrome.

Training-Induced Deactivation of the AT1 Receptor Pathway Drives Autonomic Control and Heart Remodeling During the Transition From the Pre- to Hypertensive Phase in Spontaneously Hypertensive Rats.

The effects of hypertension and exercise training (T) on the sequential interplay between renin-angiotensin system (RAS), autonomic control and heart remodeling during the development of hypertension in spontaneously hypertensive rats (SHR), was evaluated.Methods and Results:Time course changes of these parameters were recorded in 4-week-old SHR submitted to a T or sedentary (S) protocol. Wistar Kyoto rats served as controls. Hemodynamic recordings were obtained in conscious rats at experimental weeks 0, 1, 2, 4, and 8. The left ventricle (LV) was collected to evaluate RAS gene and protein expression, cardiomyocytes' hypertrophy and collagen accumulation. Pre-hypertensive SHR exhibited augmented AT1R gene expression; at 5 weeks, they presented with elevated pressure, increased LV angiotensinogen and ACE mRNA expression, followed by sympathoexcitation (from the 8thweek onwards). Marked AT1R protein content, myocytes's hypertrophy, collagen deposition and increased pressure variability were observed in 12-week-old sedentary SHR. In addition to attenuating all these effects, T activated Mas receptor expression augmented parasympathetic modulation of the heart, and delayed the onset and reduced the magnitude, but did not block the development of genetic hypertension. The close temporal relationship between changes in the LV ACE-Ang II-AT1R axis, autonomic control and cardiac remodeling at both the establishment of hypertension and during exercise training reveals the essential role played by the AT1R pathway in driving cardiac remodeling and autonomic modulation during the transition from the pre- to hypertensive phase.

The Renin-Angiotensin System in the Central Nervous System and Its Role in Blood Pressure Regulation.

Purpose of the ReviewThe main goal of this article is to discuss how the development of state-of-the-art technology has made it possible to address fundamental questions related to how the renin-angiotensin system (RAS) operates within the brain from the neurophysiological and molecular perspective.Recent FindingsThe existence of the brain RAS remains surprisingly controversial. New sensitive in situ hybridization techniques and novel transgenic animals expressing reporter genes have provided pivotal information of the expression of RAS genes within the brain. We discuss studies using genetically engineered animals combined with targeted viral microinjections to study molecular mechanisms implicated in the regulation of the brain RAS. We also discuss novel drugs targeting the brain RAS that have shown promising results in clinical studies and trials.SummaryOver the last 50 years, several new physiological roles of the brain RAS have been identified. In the coming years, efforts to incorporate cutting-edge technologies such as optogenetics, chemogenetics, and single-cell RNA sequencing will lead to dramatic advances in our full understanding of how the brain RAS operates at molecular and neurophysiological levels.

Nrf2 Deficiency Upregulates Intrarenal Angiotensin-Converting Enzyme-2 and Angiotensin 1-7 Receptor Expression and Attenuates Hypertension and Nephropathy in Diabetic Mice

We investigated the role of nuclear factor erythroid 2-related factor 2 (Nrf2) in renin-angiotensin system (RAS) gene expression in renal proximal tubule cells (RPTCs) and in the development of systemic hypertension and kidney injury in diabetic Akita mice. We used adult male Akita Nrf2 knockout mice and Akita mice treated with trigonelline (an Nrf2 inhibitor) or oltipraz (an Nrf2 activator). We also examined rat immortalized RPTCs (IRPTCs) stably transfected with control plasmids or plasmids containing rat angiotensinogen (Agt), angiotensin-converting enzyme (ACE), angiotensin-converting enzyme-2 (Ace2), or angiotensin 1-7 (Ang 1-7) receptor (MasR) gene promoters. Genetic deletion of Nrf2 or pharmacological inhibition of Nrf2 in Akita mice attenuated hypertension, renal injury, tubulointerstitial fibrosis, and the urinary albumin/creatinine ratio. Furthermore, loss of Nrf2 upregulated RPTC Ace2 and MasR expression, increased urinary Ang 1-7 levels, and downregulated expression of Agt, ACE, and profibrotic genes in Akita mice. In cultured IRPTCs, Nrf2 small interfering RNA transfection or trigonelline treatment prevented high glucose stimulation of Nrf2 nuclear translocation, Agt, and ACE transcription with augmentation of Ace2 and MasR transcription, which was reversed by oltipraz. These data identify a mechanism, Nrf2-mediated stimulation of intrarenal RAS gene expression, by which chronic hyperglycemia induces hypertension and renal injury in diabetes.