Renin Expression In Kidney Research Articles

Abstract 026: Three-dimensional Visualization And Evaluation Of Differences In Renin Expression In Kidneys Exposed In Vivo To Either Low Or High Arterial Pressure

Background: Renin cells are essential for the regulation of blood pressure (BP). In adult mammals, renin cells are present in small numbers in the juxtaglomerular area, but when homeostasis is threatened, such as by hypotension, additional cells along the renal arterioles are recruited to synthesize and release renin. However, there have been no studies to date that have shown changes in the distribution of renin cells in response to changes in BP by three-dimensional (3D) imaging. Objective: Establish a method to visualize and measure renin cells, and comparison of renin expression differences in kidneys exposed to hypo- or hypertension in 3D. Methods: We used our new mouse model ( Ren1 c-tdTomato ) that expresses renin and the fluorescent tdTomato under the control of the endogenous renin gene environment. To test whether we could detect differences in the distribution of renin in response to changes in BP, we subjected Ren1 c-tdTomato mice to aortic coarctation at 3 months of life. The right and left kidneys (RK, LK) are exposed to high and low BPs, respectively. We harvested kidneys after 72 hours and performed tissue-clearing. We used light sheet microscopy for imaging and the Imaris software for 3D reconstruction and data analysis. We defined the 3D renin cell index (3D-RI) as total volume of renin cells (μm 3 ) divided by total number of glomeruli. We extracted 10 cubes of 500 μm square each from the L and R renal cortex, calculated their individual 3D-RI and compared them. Results: With tissue-clearing-based 3D imaging, renin cells were clearly visualized, allowing observation of their distribution and appearance at a one-cell resolution. In the LK exposed to hypotension, several afferent arterioles were identified where renin cells extended close to their branching point. Further, the average value of the 3D-RI was significantly higher in LK (21460 ±6303) than in RK (12838 ± 4632; p = 0.003). Conclusion: Using our new Ren1 c-tdTomato mouse and 3D imaging technology we detected differences in renin cells appearance and distribution in kidneys exposed to hypo- or hypertension. Combined with spatial single cell multiomics, 3D visualization of renin cells will open new avenues for understanding how vascular cells acquire their positional identity in health and disease.

Interactive effects of high temperature and pesticide exposure on oxidative status, apoptosis, and renin expression in kidney of goldfish: Molecular and cellular mechanisms of widespread kidney damage and renin attenuation.

One of many noteworthy consequences of increasing societal reliance on pesticides is their predominance in aquatic environments. These pernicious chemicals interact with high temperatures from global climate change, heat waves, and natural variations to create unstable environments that negatively impact organisms' health. To understand these conditions, we examined the dose-dependent effects of environmentally relevant pesticide mixtures (metolachlor, linuron, isoproturon, tebuconazole, aclonifen, atrazine, pendimethalin, and azinphos-methyl) combined with elevated temperatures (22 control vs. 32°C for 4-week exposure) on renin, dinitrophenyl protein (DNP, an indicator of reactive oxygen species, ROS), 3-nitrotyrosine protein (NTP, an indicator of reactive nitrogen species, RNS), superoxidase dismutase (SOD, an antioxidant), and catalase (CAT, an antioxidant) expressions in the kidneys of goldfish (Carassius auratus). Histopathological analysis showed widespread damage to kidney tissues in high temperature and pesticide co-exposure groups, including rupture of the epithelial layer, hemorrhaging, and degeneration of tubular epithelium. Quantitative real-time polymerase chain reaction (qRT-PCR) and immunohistochemical analyses demonstrated significant declines in renin receptor-like mRNA and protein expressions in kidney tissues under combined exposure to high temperature and pesticides compared with controls; conversely, expression of DNP, NTP, SOD, and CAT increased in kidney tissues under the same conditions. Apoptotic cells were also increased in co-exposure groups as assessed by in situ terminal deoxynucleotidyl transferase dUTP nick labeling (TUNEL) assay. The enhanced apoptosis in kidneys of heat and pesticides co-exposed fish was associated with increased caspase-3 (a protease enzyme) mRNA levels. Our results demonstrated that high temperature and pesticides induced oxidative/nitrative stress (i.e., ROS/RNS), damaged tissues, increased cellular apoptosis, and suppressed renin expression in kidneys of goldfish.

Hypoxia increased malondialdehyde from membrane damages is highly correlated to HIF-1α but not to renin expression in rat kidney

Systemic hypoxia lead to deplete amount of ATP in tissues that is caused by inefficiency of ATP production in anaerobic glycolysis. Furthermore, degradation of ATP will activate xanthine oxidase activity, that has side effect free radical production and oxidative stress. In addition, hypoxia is known lead to HIF-1α stabilities by reducing prolyl hydroxylase activity and renin expression. Higher renin expression can cause hypertension. This research aim is to reveal how strong oxidative stress damages of systemic hypoxia (MDA) correlated to HIF-1α and renin expression in kidney tissue. This experimental study conducted using rats induced by hypoxic states for 1 day, 3 days, 7 days, and 14 days with gas mix 10% O2, 90% N2 to proof systemic hypoxia, produce free radical damaged (malondialdehyde/MDA), increase expression of HIF-1α and renin mRNA relative expression. MDA was measured by spectrophotometric method, HIF-1α by Immunohysto chemistry, and renin mRNA using RT-PCR. Results showed that in systemic hypoxia MDA were increased significantly in 7 and 14 days of hypoxia, but in 14days MDA level was lower than 7 days hypoxia. HIF-1α increased during hypoxia. Relative expression of renin mRNA was increased during systemic hypoxia and the peak was at 3day hypoxia. MDA has strong correlation to HIF-1α than to renin mRNA relative expression. We conclude that MDA as product of membrane damage caused by free radicals has strong correlation to HIF-1α in systemic hypoxia.

Development of renal renin-expressing cells does not involve PDGF-B-PDGFR-βsignaling

Apart from their endocrine functions renin-expressing cells play an important functional role as mural cells of the developing preglomerular arteriolar vessel tree in the kidney. The recruitment of renin-expressing cells from the mesenchyme to the vessel wall is not well understood. Assuming that it may follow more general lines of pericyte recruitment to endothelial tubes we have now investigated the relevance of the platelet-derived growth factor (PDGF)-B-PDGFR-β signaling pathway in this context. We studied renin expression in kidneys lacking PDGFR-β in these cells and in kidneys with reduced endothelial PDGF-B expression. We found that expression of renin in the kidneys under normal and stimulated conditions was not different from wild-type kidneys. As expected, PDGFR-β immunoreactivity was found in mesangial, adventitial and tubulo-interstitial cells but not in renin-expressing cells. These findings suggest that the PDGF-B-PDGFR-β signaling pathway is not essential for the recruitment of renin-expressing cells to preglomerular vessel walls in the kidney.

A Clinical Link Between Peroxisome Proliferator-Activated Receptor γ and the Renin–Angiotensin System

A mechanistic link between peroxisome proliferator-activated receptor γ (PPARγ) and the renin–angiotensin system (RAS) has been previously proposed, but clinical evidence supporting the relationship is incomplete. In the current issue of Arteriosclerosis, Thrombosis, and Vascular Biology , Caron-Debarle et al show that 4 patients with familial partial lipodystrophy associated with early-onset severe hypertension carry mutations in PPARγ that impair its ability to act as a ligand-activated transcription factor. Cells isolated from these patients, and cells transfected with the same mutations in PPARγ, exhibit activation of the cellular RAS, increased production of reactive oxygen species (ROS), and markers of inflammation, all of which are dependent on the angiotensin-II (Ang-II) AT1 receptor (AT1R). This translational study further supports a role for PPARγ as a regulator of blood pressure through its ability to modulate the RAS. See accompanying article on page 829 PPARγ is a ligand-activated transcription factor and target of the thiazolidinedione (TZD) class of antidiabetes mellitus medications. PPARγ is best recognized for its role in adipogenesis, but is also a regulator of systemic metabolism as evidenced by the pleiotropic abnormalities (lipodystrophy, insulin-resistance, and metabolic syndrome) caused by PPARγ mutations.1–3 Clinical studies of TZD use in type 2 diabetes mellitus, including the PROactive (PROspective pioglitAzone Clinical Trial In macroVascular Events) trial, documented improved endothelial function and modest, but significant reductions in blood pressure.4 Some of the same mutations that cause lipodystrophy and diabetes mellitus also cause severe hypertension and preeclampsia in human patients3 and in knock-in mice.5,6 Evidence suggests that PPARγ activity in the vascular endothelium and smooth muscle are important regulators of endothelial function, smooth muscle contraction, and systemic blood pressure.7,8 Data suggesting a role for PPARγ in regulating blood pressure led many to search for downstream …

Regulation of mouse-renin gene by apurinic/apyrimidinic-endonuclease 1 (APE1/Ref-1) via recruitment of histone deacetylase 1 corepressor complex

Apurinic/apyrimidinic-endonuclease 1 (APE1) heterozygous mice have chronically elevated blood pressure. Renin of the renin-angiotensin (ANG) system for blood pressure maintenance regulates production of ANG II, a vasoactive hormone. Renin expression and secretion from kidney juxtaglomerular cells are regulated by intracellular calcium. Our objective in this study is to investigate APE1's regulatory role in renin expression. Effect of APE1 on calcium-mediated modulation of renin expression was examined by real-time reverse transcriptase-PCR, Western analysis and renin promoter-dependent luciferase activity in APE1-knockdown, APE1-overexpressing or control mouse kidney As4.1 cells. Furthermore, coimmunoprecipitation and chromatin immunoprecipitation assays were utilized to examine the association of APE1 with histone deacetylase (HDAC)1 corepressor complex and their recruitment to renin enhancer. Finally, kidney renin mRNA level and plasma-renin activity were measured in wild-type and APE1-heterozygous mice. Here we show that APE1 is involved in calcium-mediated repression of renin gene. Our results further indicate that APE1 is a component of HDAC1 corepressor complex bound to renin-enhancer region. Increase in intracellular calcium ion concentration enhances the association of APE1 with HDAC1 corepressor complex and their recruitment to the enhancer region. Furthermore, APE1's N-terminal region is critical for formation and recruitment of the enhancer-bound corepressor complex. Increased renin expression in kidneys and higher plasma-renin activity in APE1 heterozygous mice further supports APE1's corepressor role in vivo. This study uncovers APE1's function as a novel negative regulator of renin expression, and thereby in blood pressure maintenance.

Renin Enhancer Is Crucial for Full Response in Renin Expression to an In Vivo Stimulus

We showed recently that deletion of a strong enhancer located 2.7 kb upstream of the renin gene in mice produces a strain with mild hypotension and salt-sensitivity. Here we set out to compare responses in renin expression in kidney and extrarenal tissues in these "REKO" mice. REKO and wild-type mice were placed on a low NaCl/enalapril regimen for 1 week, and then Ren-1(c) mRNA and renin enzyme activities were measured in tissues and plasma. In untreated REKO mice, renin and Ren-1(c) mRNA were reduced significantly in kidney, submandibular gland, adrenal, heart, and brain. In situ hybridization indicated a marked reduction in Ren-1(c) mRNA in juxtaglomerular cells and granular ducts of submandibular gland. After the chronic stimulus response in renal Ren-1(c) mRNA in REKO mice was blunted by 54% compared with wild-type mice, and was accompanied by almost complete exhaustion of renin stores. Response in plasma renin was blunted by 47%, this being mirrored in heart (54% decline), in which renin is derived mostly from the bloodstream. In adrenal a 55% reduction was seen. These data are consistent with inability of REKO mice to adequately replenish renal renin stores during chronic stimulation of renin secretion. In conclusion, the renin enhancer is critical for replenishment of renin stores and response in renin to a chronic in vivo stimulus.

Molecular phenotyping for analyzing subtle genetic effects in mice: application to an angiotensinogen gene titration.

The angiotensinogen M235T polymorphism in humans is linked to differential expression of the human angiotensinogen gene (AGT) gene and hypertension, but the homeostatic responses resulting from this polymorphism are not known. We therefore investigated how mice respond to five genetically determined levels of mouse angiotensinogen gene (Agt) expression covering the range associated with the M235T variants. By using high-throughput molecular phenotyping, tissue RNAs were assayed for expression of 10 genes important in hypertension. Significant positive and negative responses occurred in both sexes as Agt expression increased twofold, including a three-fold increase in aldosterone synthase expression in adrenal gland, and a two-fold decrease in renin expression in kidney. In males, cardiac expression of the precursor of atrial natriuretic peptide B and of adrenomedullin also increased approximately twofold. The relative expression of all genes studied except Agt differed significantly in the two sexes, and several unexpected relationships were encountered. A highly significant correlation between renal expression of the angiotensin type 1a receptor and kallikrein, independent of Agt genotype, is present in females (P < 0.0001) but not males (P = 0.4). The correlation between blood pressure (BP) and liver Agt expression within the five Agt genotypes is significant in females (P = 0.0005) but not in males (P = 0.2), whereas correlation of BP with differences between the genotypes is less in females (P = 0.06) than in males (P = 0.001). The marked gender differences in gene expression in wild-type mice and the changes induced by moderate alterations in Agt expression and BP emphasize the need to look for similar differences in humans.

Accumulation of acidic renin isoforms in kidneys of cyclosporine-A-treated rats.

Chronic cyclosporin A (CsA) treatment results in major hemodynamic changes in the renal microvasculature and in expression of the intrarenal renin angiotensin system. Changes in renin expression in kidneys of CsA-treated rats include the recruitment of immunoreactive renin in afferent arterioles and in the juxtaglomerular apparatus. This study presents evidence that an acidic isoform of renin is increased in kidneys of CsA-treated rats. Immunoblots of rat kidney homogenate separated by polyacrylamide-gel electrophoresis and also by isoelectric focusing demonstrate the presence of an acidic isoform (pl 5.5 and estimated molecular weight of approximately 32 to 36 kd) seen in increased amounts in kidney homogenate from CsA-treated rats. Silver-stained two-dimensional gels of renin separated from kidney homogenate with pepstatin agarose confirm the presence of an acidic renin isoform in CsA-treated rats. In rats that received CsA for varied intervals of 1, 3, 5, and 8 wk, this acidic isoform is shown to significantly accumulate relative to duration of treatment with CsA when immunoreactive bands are analyzed by densitometric scanning (r2 = 0.90, P < 0.001). Renin enzymatic activity also increased in kidney homogenate of CsA-treated rats relative to duration of treatment with CsA (r2 = 0.486, P < 0.001). Prorenin in these same samples was significantly decreased compared with controls. The acidic renin isoform identified in kidney homogenate of CsA-treated rats may be involved in the vascular changes that are seen in this model.

The effect of captopril treatment and its withdrawal on the gene expression of the renin-angiotensin system.

The mRNA expression of renin, angiotensinogen and angiotensin converting enzyme (ACE) was determined in the kidneys and livers from spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY) during chronic treatment with captopril and following its withdrawal. Chronic captopril treatment was associated with a dramatic rise in renin mRNA in the kidney and an elevation in mRNA for ACE in the liver. The release from captopril treatment was associated with a reversal of the increase in kidney renin mRNA but no reversal of the sustained elevation of ACE mRNA in the liver. In situ hybridisation revealed a localisation of renin to the area of the juxtaglomerular apparatus in the kidneys from untreated animals, but recruitment of vascular sites of renin expression in kidneys from captopril-treated animals. In kidneys from released animals, renin mRNA expression was once again confined to the juxtaglomerular apparatus. ACE mRNA was expressed in hepatocytes throughout the livers from animals in all treatment groups. The results highlight a differential effect of captopril withdrawal upon the gene expression of the components of the renin-angiotensin system in kidney and liver.

Regulation of Tissue Renin and Angiotensin Gene Expressions

Recent studies employing molecular biological techniques demonstrate that renin and angiotensinogen genes are expressed in various tissues. We have observed tissue-specific regulation of renin and angiotensinogen gene expressions. Renin expression in kidney, heart, and adrenal are stimulated by sodium depletion and beta-adrenergic agonist. Submandibular gland and genital renins are not. Instead, the renin expression in these tissues are influenced by androgen and/or hormones that are activated during ontogeny. Genetic influence of tissue renin expression also exists, i.e., the submandibular gland, cardiac, and testicular renin activities are higher in the two gene strains, whereas kidney renin activity does not differ between different strains. Tissue-specific regulation of angiotensinogen mRNA is also observed when rats are placed on a low-sodium diet. Sodium depletion stimulates renin angiotensinogen mRNA expression but does not influence hepatic angiotensinogen mRNA levels. Tissue-specific regulation of renin angiotensin may have important functional implications. Increased local production of angiotensin should influence tissue angiotensin-mediated responses that may be independent of the circulating system.