G protein-coupled estrogen receptor 1 as a novel regulator of blood pressure

Endothelin receptor B is required for the blood pressure-lowering effect of G protein-coupled estrogen receptor 1 in ovariectomized rats

Activation of G protein-coupled estrogen receptor 1 (GPER1) elicits antihypertensive actions in different animal models. The endothelin-1 signaling system plays a fundamental role in blood pressure regulation. Lack of functional endothelin receptor B (ETB) evokes hypertension and salt sensitivity. GPER1 and ETB interact to promote urinary sodium excretion in female rats. We hypothesized that activation of GPER1 protects against hypertension and salt sensitivity induced by ETB antagonism in female rats. Female Sprague-Dawley rats were implanted with radiotelemetry. Animals were then subjected to ovariectomy and simultaneously implanted with minipumps to deliver either the GPER1 agonist G1 or its corresponding vehicle. Two weeks post surgery, we initiated treatment of rats with the ETB antagonist A-192621. Animals were maintained on a normal-salt diet and then challenged with a high-salt diet for an additional 5 days. Assessment of mean arterial blood pressure revealed an increase in vehicle-treated, but not G1-treated, rats in response to ovariectomy. A-192621 increased blood pressure in normal-salt diet-fed vehicle- and G1-treated rats. G1 improved the circadian blood pressure rhythms that were disrupted in A-192621-treated ovariectomized rats. Thus, although systemic GPER1 activation did not protect ovariectomized rats from hypertension and salt sensitivity induced by ETB antagonism, it maintained circadian blood pressure rhythms. Functional ETB is required to elicit the antihypertensive actions of GPER1. Additional studies are needed to improve our understanding of the interaction between G protein-coupled receptors in regulating circadian blood pressure rhythm.NEW & NOTEWORTHY Systemic G protein-coupled estrogen receptor 1 (GPER1) activation in rats prevents the increase in blood pressure evoked by ovariectomy. Blockade of endothelin receptor B negates the blood pressure-lowering impact of GPER1 in ovariectomized rats. Endothelin receptor B plays an important role in mediating the blood pressure-lowering action of GPER1 activation in female rats.

The Abl1 tyrosine kinase is a key player in doxorubicin-induced cardiomyopathy and its p53/p73 cell death mediated signaling differs in atrial and ventricular cardiomyocytes

BACKGROUND

Doxorubicin is an important anticancer drug, however, elicits dose-dependently cardiomyopathy. Given its mode of action, i.e. topoisomerase inhibition and DNA damage, we investigated genetic events associated with cardiomyopathy and searched for mechanism-based possibilities to alleviate cardiotoxicity. We treated rats at clinically relevant doses of doxorubicin. Histopathology and transmission electron microscopy (TEM) defined cardiac lesions, and transcriptomics unveiled cardiomyopathy-associated gene regulations. Genomic-footprints revealed critical components of Abl1-p53-signaling, and EMSA-assays evidenced Abl1 DNA-binding activity. Gene reporter assays confirmed Abl1 activity on p53-targets while immunohistochemistry/immunofluorescence microscopy demonstrated Abl1, p53&p73 signaling.

RESULTS

Doxorubicin treatment caused dose-dependently toxic cardiomyopathy, and TEM evidenced damaged mitochondria and myofibrillar disarray. Surviving cardiomyocytes repressed Parkin-1 and Bnip3-mediated mitophagy, stimulated dynamin-1-like dependent mitochondrial fission and induced anti-apoptotic Bag1 signaling. Thus, we observed induced mitochondrial biogenesis. Transcriptomics discovered heterogeneity in cellular responses with minimal overlap between treatments, and the data are highly suggestive for distinct cardiomyocyte (sub)populations which differed in their resilience and reparative capacity. Genome-wide footprints revealed Abl1 and p53 enriched binding sites in doxorubicin-regulated genes, and we confirmed Abl1 DNA-binding activity in EMSA-assays. Extraordinarily, Abl1 signaling differed in the heart with highly significant regulations of Abl1, p53 and p73 in atrial cardiomyocytes. Conversely, in ventricular cardiomyocytes, Abl1 solely-modulated p53-signaling that was BAX transcription-independent. Gene reporter assays established Abl1 cofactor activity for the p53-reporter PG13-luc, and ectopic Abl1 expression stimulated p53-mediated apoptosis.

CONCLUSIONS

The tyrosine kinase Abl1 is of critical importance in doxorubicin induced cardiomyopathy, and we propose its inhibition as means to diminish risk of cardiotoxicity.

Cycling matters: Sex hormone regulation of vascular potassium channels

Sex hormones and the reproductive cycle (estrus in rodents and menstrual in humans) have a known impact on arterial function. In spite of this, sex hormones and the estrus/menstrual cycle are often neglected experimental factors in vascular basic preclinical scientific research. Recent research by our own laboratory indicates that cyclical changes in serum concentrations of sex -hormones across the rat estrus cycle, primary estradiol, have significant consequences for the subcellular trafficking and function of KV. Vascular potassium channels, including KV, are essential components of vascular reactivity. Our study represents a small part of a growing field of literature aimed at determining the role of sex hormones in regulating arterial ion channel function. This review covers key findings describing the current understanding of sex hormone regulation of vascular potassium channels, with a focus on KV channels. Further, we highlight areas of research where the estrus cycle should be considered in future studies to determine the consequences of physiological oscillations in concentrations of sex hormones on vascular potassium channel function.

Aromatase enzyme: Paving the way for exploring aromatization for cardio-renal protection

Documented male-female differences in the risk of cardiovascular and chronic kidney diseases have been largely attributed to estrogens. The cardiovascular and renal protective effects of estrogens are mediated via the activation of estrogen receptors (ERα and ERβ) and G protein-coupled estrogen receptor, and involve interactions with the renin-angiotensin-aldosterone system. Aromatase, also called estrogen synthase, is a cytochrome P-450 enzyme that plays a pivotal role in the conversion of androgens into estrogens. Estrogens are biosynthesized in gonadal and extra-gonadal sites by the action of aromatase. Evidence suggests that aromatase inhibitors, which are used to treat high estrogen-related pathologies, are associated with the development of cardiovascular events. We review the potential role of aromatization in providing cardio-renal protection and highlight several meta-analysis studies on cardiovascular events associated with aromatase inhibitors. Overall, we present the potential of aromatase enzyme as a fundamental contributor to cardio-renal protection.

SGK1 Target Genes Involved in Heart and Blood Vessel Functions in PC12 Cells

Serum and glucocorticoid-regulated kinase 1 (SGK1) is expressed in neuronal cells and involved in the pathogenesis of hypertension and metabolic syndrome, regulation of neuronal function, and depression in the brain. This study aims to identify the cellular mechanisms and signaling pathways of SGK1 in neuronal cells. In this study, the SGK1 inhibitor GSK650394 is used to suppress SGK1 expression in PC12 cells using an in vitro neuroscience research platform. Comparative transcriptomic analysis was performed to investigate the effects of SGK1 inhibition in nervous cells using mRNA sequencing (RNA-seq), differentially expressed genes (DEGs), and gene enrichment analysis. In total, 12,627 genes were identified, including 675 and 2152 DEGs at 48 and 72 h after treatment with GSK650394 in PC12 cells, respectively. Gene enrichment analysis data indicated that SGK1 inhibition-induced DEGs were enriched in 94 and 173 genes associated with vascular development and functional regulation and were validated using real-time PCR, Western blotting, and GEPIA2. Therefore, this study uses RNA-seq, DEG analysis, and GEPIA2 correlation analysis to identify positive candidate genes and signaling pathways regulated by SGK1 in rat nervous cells, which will enable further exploration of the underlying molecular signaling mechanisms of SGK1 and provide new insights into neuromodulation in cardiovascular diseases.

G protein-coupled estrogen receptor 1 regulates renal endothelin-1 signaling system in a sex-specific manner

Demographic studies reveal lower prevalence of hypertension among premenopausal females compared to age-matched males. The kidney plays a central role in the maintenance of sodium (Na⁺) homeostasis and consequently blood pressure. Renal endothelin-1 (ET-1) is a pro-natriuretic peptide that contributes to sex differences in blood pressure regulation and Na⁺ homeostasis. We recently showed that activation of renal medullary G protein-coupled estrogen receptor 1 (GPER1) promotes ET-1-dependent natriuresis in female, but not male, rats. We hypothesized that GPER1 upregulates the renal ET-1 signaling system in females, but not males. To test our hypothesis, we determined the effect of GPER1 deletion on ET-1 and its downstream effectors in the renal cortex, outer and inner medulla obtained from 12-16-week-old female and male mice. GPER1 knockout (KO) mice and wildtype (WT) littermates were implanted with telemetry transmitters for blood pressure assessment, and we used metabolic cages to determine urinary Na⁺ excretion. GPER1 deletion did not significantly affect 24-h mean arterial pressure (MAP) nor urinary Na⁺ excretion. However, GPER1 deletion decreased urinary ET-1 excretion in females but not males. Of note, female WT mice had greater urinary ET-1 excretion than male WT littermates, whereas no sex differences were observed in GPER1 KO mice. GPER1 deletion increased inner medullary ET-1 peptide content in both sexes but increased outer medullary ET-1 content in females only. Cortical ET-1 content increased in response to GPER1 deletion in both sexes. Furthermore, GPER1 deletion notably increased inner medullary ET receptor A (ET_A) and decreased outer medullary ET receptor B (ET_B) mRNA expression in male, but not female, mice. We conclude that GPER1 is required for greater ET-1 excretion in females. Our data suggest that GPER1 is an upstream regulator of renal medullary ET-1 production and ET receptor expression in a sex-specific manner. Overall, our study identifies the role of GPER1 as a sex-specific upstream regulator of the renal ET-1 system.

Dynamic Evolution of Cardiac Function and Glucose and Lipid Metabolism in Ovariectomized Rats and the Intervention Effect of Erxian Decoction

Aims

Abnormal changes in cardiac function have been reported in menopausal women, but there are few clinical studies on this topic. Erxian decoction (EXD) is a classic prescription that is widely used in the treatment of female menopausal diseases. The purpose of this study was to investigate the dynamic evolution of cardiac function and glucose and lipid metabolism in ovariectomized (OVX) rats and the intervention effect of EXD.

Materials and Methods

The OVX climacteric rat model was established by bilateral ovariectomy. After successful modeling, the rats were randomly divided into four groups: the sham operation (SHAM) group (equal volumes of purified water), OVX group (equal volumes of purified water), estradiol (E₂) group (1.8 × 10^-4 g/kg), and EXD group (9 g/kg). Each group of rats was treated for 16 weeks. At the 4^th, 8^th, 12^th, and 16^th weeks after treatment, the cardiac function of the rats in each group was evaluated by ultrasound. The coaxial method was used to measure blood pressure (BP). Serum endothelin-1 (ET-1) and angiotensin-2 (Ang II) levels were determined by the enzyme-linked immunosorbent assay (ELISA). The strip method was used to measure fasting blood glucose (FBG). The serum total cholesterol (TC) and triglyceride (TG) levels of rats were measured with the oxidase method. Direct methods were used to measure serum high-density lipoprotein (HDL-C) and low-density lipoprotein (LDL-C) levels. At week 16 of dosing, serum E₂ levels were determined by E₂ radioimmunoassay. The myocardium and uterus of the rats in each group were stained with HE (hematoxylin-eosin). The ultrastructure of the rat myocardium was observed by electron microscopy.

Results

After the 16^th week of treatment, the serum E₂ level decreased (P < 0.05), and the uterus was atrophied in OVX rats. The cardiac ejection fraction (EF%) decreased at 4 weeks after treatment, and systolic and diastolic function decreased after 12 weeks. After the 16^th week, the EF%, which reflects the "pump" function of the heart, decreased significantly (P < 0.05 or P < 0.01). At the 4^th, 8^th, 12^th, and 16^th weeks of treatment, the systolic blood pressure (SBP), diastolic blood pressure (DBP), and mean pressure (MBP) of the rats in the OVX group increased with time (P < 0.05 or P < 0.01). The serum ET-1 and Ang II levels of rats in the OVX group increased (P < 0.05 or P < 0.01). In the OVX group, FBG was increased (P < 0.05 or P < 0.01), and blood lipids, especially LDL-C, were significantly increased (P < 0.05 or P < 0.01). After the 16^th week of treatment, the myocardial tissue of OVX rats showed obvious pathological changes. EXD significantly increased serum E₂ levels (P < 0.01), decreased ET-1 and Ang II levels (P < 0.01), reduced the cardiac function risk factors BP, FBG, and blood lipids, and significantly improved cardiac function and structural changes in OVX rats (P < 0.05 or P < 0.01).

Conclusions

EXD can improve abnormal cardiac structure and function in OVX rats.

Isoflavone daidzein ameliorates renal dysfunction and fibrosis in a postmenopausal rat model: Intermediation of angiotensin AT1 and Mas receptors and microRNAs 33a and 27a

OBJECTIVES

Chronic kidney disease (CKD), accompanied by renal dysfunction, fibrosis, and apoptosis, is highly prevalent in postmenopausal women. We tested the hypothesis that isoflavone daidzein may ameliorate renal dysfunction and fibrosis through angiotensin II type 1 (AT1R) and angiotensin 1-7 (MasR) receptors in association with microRNAs 33a and 27a.

MATERIALS AND METHODS

Two weeks before the initiation of the experiments, rats (n=84) underwent ovariectomy (OVX). Then, unilateral ureteral obstruction (UUO) was performed in OVX rats, and animals were allocated to the following groups (n=21): sham vehicle (dimethyl sulfoxide; DMSO 1%), UUO vehicle, UUO+17β-estradiol (E2), and UUO+daidzein. Each group encompassed three subgroups (n=7) treated with saline, A779 (MasR antagonist), or losartan (AT1R antagonist) for 15 days. The fractional urine excretion of sodium (FE_Na+) and potassium (FE_K+), renal failure index (RFI), renal interstitial fibrosis (RIF index), glomerulosclerosis, miR-33a, and miR-27a expressions and their target genes were analyzed. Apoptosis was measured via cleaved caspase-3 immunohistochemistry.

RESULTS

UUO increased kidney weight, FE_Na+, FE_K+, urine calcium, RFI, RIF index, glomerulosclerosis, and cleaved caspase-3. Moreover, expression of renal miR-33a and miR-27a, collagen3A1 mRNA, and protein were up-regulated post-UUO. Daidzein treatment alleviated the harmful effects of UUO especially in co-treatment with losartan. They also masked the anticipated worsening effects of A779 on UUO.

CONCLUSION

Compared with E2, daidzein efficiently ameliorated renal dysfunction, fibrosis, and apoptosis through modulation of miR-33a and miR-27a expression and their crosstalk with AT1R and MasR. Therefore, daidzein might be a promising candidate for treating CKD in postmenopausal and older women.

Does G Protein-Coupled Estrogen Receptor 1 Contribute to Cisplatin-Induced Acute Kidney Injury in Male Mice?

Nephrotoxicity is the dose-limiting side-effect of the chemotherapeutic agent cisplatin (Cp). Recent evidence points to renal protective actions of G protein-coupled estrogen receptor 1 (GPER1). In addition, it has been shown that GPER1 signaling elicits protective actions against acute ischemic injuries that involve multiple organ systems; however, the involvement of GPER1 signaling in Cp-induced acute kidney injury (AKI) remains unclear. This study tested whether genetic deletion of GPER1 exacerbates Cp-induced AKI in male mice. We subjected male mice, homozygous (homo) and heterozygous (het) knockout for the GPER1 gene, and wild-type (WT) littermates to Cp or saline injections and assessed markers for renal injury on the third day after injections. We also determined serum levels of proinflammatory markers in saline and Cp-treated mice. Given the protective role of heme oxygenase-1 (HO-1) in Cp-mediated apoptosis, we also investigated genotypic differences in renal HO-1 abundance, cell death, and proliferation by Western blotting, the TUNEL assay, and Ki67 immunostaining, respectively. Cp increased serum creatinine, urea, and neutrophil gelatinase-associated lipocalin (NGAL) levels, the renal abundance of kidney injury molecule-1, and NGAL in all groups. Cp-induced AKI resulted in comparable histological evidence of injury in all genotypes. WT and homo mice showed greater renal HO-1 abundance in response to Cp. Renal HO-1 abundance was lower in Cp-treated homo, compared to Cp-treated WT mice. Of note, GPER1 deletion elicited a remarkable increase in renal apoptosis; however, no genotypic differences in cell proliferation were observed. Cp augmented kidney Ki67-positive counts, regardless of the genotype. Overall, our data do not support a role for GPER1 in mediating Cp-induced renal injury. GPER1 deletion promotes renal apoptosis and diminishes HO-1 induction in response to Cp, suggesting that GPER1 may play cytoprotective and anti-apoptotic actions in AKI. GPER1-induced regulation of HO-1 and apoptosis may offer novel therapeutic targets for the treatment of AKI.

mTOR inhibitor improves testosterone-induced myocardial hypertrophy in hypertensive rats

Compelling evidence has described that the incidence of hypertension and left ventricular hypertrophy (LVH) in postmenopausal women is significantly increased worldwide. Our team's previous research identified that androgen was an underlying factor contributing to increased blood pressure and LVH in postmenopausal women. However, little is known about how androgens affect LVH in postmenopausal hypertensive women. The purpose of this study was to evaluate the role of mammalian rapamycin receptor (mTOR) signaling pathway in myocardial hypertrophy in androgen-induced postmenopausal hypertension and whether mTOR inhibitors can protect the myocardium from androgen-induced interference to prevent and treat cardiac hypertrophy. For that, ovariectomized (OVX) spontaneously hypertensive rats (SHR) aged 12 weeks were used to study the effects of testosterone (T 2.85 mg/kg/weekly i.m.) on blood pressure and myocardial tissue. On the basis of antihypertensive therapy (chlorthalidone 8 mg/kg/day ig), the improvement of blood pressure and myocardial hypertrophy in rats treated with different dose gradients of rapamycin (0.8 mg/kg/day vs 1.5 mg/kg/day vs 2 mg/kg/day i.p.) in OVX + estrogen (E 9.6 mg/kg/day, ig) + testosterone group was further evaluated. After testosterone intervention, the OVX female rats exhibited significant increments in the heart weight/tibial length (TL), area of cardiomyocytes and the mRNA expressions of ANP, β-myosin heavy chain and matrix metalloproteinase 9 accompanied by a significant reduction in the uterine weight/TL and tissue inhibitor of metalloproteinase 1. mTOR, ribosomal protein S6 kinase (S6K1), 4E-binding protein 1 (4EBP1) and eukaryotic translation initiation factor 4E in myocardial tissue of OVX + estrogen + testosterone group were expressed at higher levels than those of the other four groups. On the other hand, rapamycin abolished the effects of testosterone-induced cardiac hypertrophy, decreased the systolic and diastolic blood pressure of SHR, and inhibited the activation of mTOR/S6K1/4EBP1 signaling pathway in a concentration-dependent manner. Collectively, these data suggest that the mTOR/S6K1/4EBP1 pathway is an important therapeutic target for the prevention of LVH in postmenopausal hypertensive female rats with high testosterone levels. Our findings also support the standpoint that the mTOR inhibitor, rapamycin, can eliminate testosterone-induced cardiomyocyte hypertrophy.

Ischemic heart disease and cardioprotection: Focus on estrogenic hormonal setting and microvascular health

Ischemic Heart Disease (IHD) is a clinical condition characterized by insufficient blood flow to the cardiac tissue, and the consequent inappropriate oxygen and nutrients supply and metabolic waste removal in the heart. In the last decade a broad scientific literature has underlined the distinct mechanism of onset and the peculiar progress of IHD between female and male patients, highlighting the estrogenic hormonal setting as a key factor of these sex-dependent divergences. In particular, estrogen-activated cardioprotective pathways exert a pivotal role for the microvascular health, and their impairment, both physiologically and pathologically driven, predispose to vascular dysfunctions. Aim of this review is to summarize the current knowledge on the estrogen receptors localization and function in the cardiovascular system, particularly focusing on sex-dependent differences in microvascular vs macrovascular dysfunction and on the experimental models that allowed the researchers to reach the current findings and sketching the leading estrogen-mediated cardioprotective mechanisms.

Roles of Estrogens in the Healthy and Diseased Oviparous Vertebrate Liver

The liver is a vital organ that sustains multiple functions beneficial for the whole organism. It is sexually dimorphic, presenting sex-biased gene expression with implications for the phenotypic differences between males and females. Estrogens are involved in this sex dimorphism and their actions in the liver of several reptiles, fishes, amphibians, and birds are discussed. The liver participates in reproduction by producing vitellogenins (yolk proteins) and eggshell proteins under the control of estrogens that act via two types of receptors active either mainly in the cell nucleus (ESR) or the cell membrane (GPER1). Estrogens also control hepatic lipid and lipoprotein metabolisms, with a triglyceride carrier role for VLDL from the liver to the ovaries during oogenesis. Moreover, the activation of the vitellogenin genes is used as a robust biomarker for exposure to xenoestrogens. In the context of liver diseases, high plasma estrogen levels are observed in fatty liver hemorrhagic syndrome (FLHS) in chicken implicating estrogens in the disease progression. Fishes are also used to investigate liver diseases, including models generated by mutation and transgenesis. In conclusion, studies on the roles of estrogens in the non-mammalian oviparous vertebrate liver have contributed enormously to unveil hormone-dependent physiological and physiopathological processes.

Nitric Oxide and Immune Responses in Cancer: Searching for New Therapeutic Strategies

In recent years, there has been an increasing interest in understanding the mysterious functions of nitric oxide (NO) and how this pleiotropic signaling molecule contributes to tumorigenesis. This review attempts to expose and discuss the information available on the immunomodulatory role of NO in cancer and recent approaches to the role of NO donors in the area of immunotherapy. To address the goal, the following databases were searched to identify relevant literature concerning empirical evidence: The Cochrane Library, Pubmed, Medline, EMBASE from 1980 through March 2020. Valuable attempts have been made to develop distinctive NO-based cancer therapy. Although the data do not allow generalization, the evidence seems to indicate that low / moderate levels may favor tumorigenesis while higher levels would exert anti-tumor effects. In this sense, the use of NO donors could have an important therapeutic potential within immunotherapy, although there are still no clinical trials. The emerging understanding of NO-regulated immune responses in cancer may help unravel the recent features of this "double-edged sword" in cancer physiological and pathologic processes and its potential use as a therapeutic agent for cancer treatment. In short, in this review, we discuss the complex cellular mechanism in which NO, as a pleiotropic signaling molecule, participates in cancer pathophysiology. We also debate the dual role of NO in cancer and tumor progression, and clinical approaches for inducible nitric oxide synthase (iNOS) based therapy against cancer.

Landscape of GPCR expression along the mouse nephron

Kidney transport and other renal functions are regulated by multiple G protein-coupled receptors (GPCRs) expressed along the renal tubule. The rapid, recent appearance of comprehensive unbiased gene expression data in the various renal tubule segments, chiefly RNA sequencing and protein mass spectrometry data, has provided a means of identifying patterns of GPCR expression along the renal tubule. To allow for comprehensive mapping, we first curated a comprehensive list of GPCRs in the genomes of mice, rats, and humans (https://hpcwebapps.cit.nih.gov/ESBL/Database/GPCRs/) using multiple online data sources. We used this list to mine segment-specific and cell type-specific expression data from RNA-sequencing studies in microdissected mouse tubule segments to identify GPCRs that are selectively expressed in discrete tubule segments. Comparisons of these mapped mouse GPCRs with other omics datasets as well as functional data from isolated perfused tubule and micropuncture studies confirmed patterns of expression for well-known receptors and identified poorly studied GPCRs that are likely to play roles in the regulation of renal tubule function. Thus, we provide data resources for GPCR expression across the renal tubule, highlighting both well-known GPCRs and understudied receptors to provide guidance for future studies.

Activation of G protein-coupled estrogen receptor 1 ameliorates proximal tubular injury and proteinuria in Dahl salt-sensitive female rats

Recent evidence indicates a crucial role for G protein-coupled estrogen receptor 1 (GPER1) in the maintenance of cardiovascular and kidney health in females. The current study tested whether GPER1 activation ameliorates hypertension and kidney damage in female Dahl salt-sensitive (SS) rats fed a high-salt (HS) diet. Adult female rats were implanted with telemetry transmitters for monitoring blood pressure and osmotic minipumps releasing G1 (selective GPER1 agonist, 400 μg/kg/day ip) or vehicle. Two weeks after pump implantation, rats were shifted from a normal-salt (NS) diet (0.4% NaCl) to a matched HS diet (4.0% NaCl) for 2 wk. Twenty-four hour urine samples were collected during both diet periods and urinary markers of kidney injury were assessed. Histological assessment of kidney injury was conducted after the 2-wk HS diet period. Compared with values during the NS diet, 24-h mean arterial pressure markedly increased in response to HS, reaching similar values in vehicle-treated and G1-treated rats. HS also significantly increased urinary excretion of protein, albumin, nephrin (podocyte damage marker), and KIM-1 (proximal tubule injury marker) in vehicle-treated rats. Importantly, G1 treatment prevented the HS-induced proteinuria, albuminuria, and increase in KIM-1 excretion but not nephrinuria. Histological analysis revealed that HS-induced glomerular damage did not differ between groups. However, G1 treatment preserved proximal tubule brush-border integrity in HS-fed rats. Collectively, our data suggest that GPER1 activation protects against HS-induced proteinuria and albuminuria in female Dahl SS rats by preserving proximal tubule brush-border integrity in a blood pressure-independent manner.