Endoplasmic reticulum stress inhibition reduces hypertension through the preservation of resistance blood vessel structure and function

PDIA3 rs2788: An Independent Risk Factor for Hypertension and Its Interaction With Antihypertensive Medications

Hypertension is a multifactorial condition influenced by both genetic and environmental factors. Protein disulfide isomerase family A member 3 (PDIA3) is a key endoplasmic reticulum protein which may contribute to increased blood pressure. However, the relationship between PDIA3 polymorphisms and hypertension remain unclear. This study aims to explore the relationship between PDIA3 polymorphisms and hypertension. First, Mendelian randomization (MR) analyses were performed to assess the causal link between PDIA3 and hypertension. Second, key gene polymorphism on PDIA3 was identified using online databases and analyzed with Haploview software. Third, multivariate-adjusted logistic regression analyses were employed to evaluate the associations between PDIA3 rs2788 and hypertension. Finally, stratified analyses were conducted to further assess interactions between PDIA3 rs2788 and antihypertensive medications. MR analyses indicated a causal relationship between PDIA3 and hypertension. The rs2788 gene polymorphism locus on PDIA3 was identified using online databases and Haploview software. Multivariable-adjusted logistic regression analyses revealed that PDIA3 rs2788 was an independent risk for hypertension (OR: 4.603, 95% CI: 2.946-7.194; p < 0.001). Significant interactions were identified between PDIA3 and antihypertensive medications, particularly ACEI/ARB treatments (p = 0.013 for interaction). Similar findings were observed regarding the causal relationship between antihypertensive treatments and hypertension. PDIA3, particularly its rs2788 polymorphisms, may represent a novel biomarker for hypertension. These findings may contribute to the development of targeted screening strategies and personalized treatment approaches for hypertension management.

Follistatin lowers blood pressure and improves vascular structure and function in essential and secondary hypertension

Hypertension is characterized by resistance artery remodeling driven by oxidative stress and fibrosis. We previously showed that an activin A antagonist, follistatin, inhibited renal oxidative stress and fibrosis in a model of hypertensive chronic kidney disease. Here, we investigate the effects of follistatin on blood pressure and vascular structure and function in models of essential and secondary hypertension. 5/6 nephrectomised mice, a model of secondary hypertension, were treated with either exogenous follistatin or with a follistatin miRNA inhibitor to increase endogenous follistatin for 9 weeks. Blood pressure in mice was measured by tail cuff. Spontaneously hypertensive rats, a model of essential hypertension, were treated with follistatin for 8 weeks. Wistar Kyoto (WKY) rats were used as the normotensive control. Blood pressure in rats was measured by radiotelemetry. Mouse superior mesenteric arteries and rat first branch mesenteric arteries were isolated for structural and functional analyses. In both models, follistatin significantly lowered blood pressure and improved vascular structure, decreasing medial thickness and collagen content. Follistatin also reduced agonist-induced maximum contraction and improved endothelium-dependent relaxation. Increased vessel oxidative stress was attenuated by follistatin in both models. In ex vivo WKY vessels, activin A increased oxidative stress, augmented constriction, and decreased endothelium-dependent relaxation. Inhibition of oxidative stress restored vessel relaxation. This study demonstrates that follistatin lowers blood pressure and improves vascular structure and function in models of essential and secondary hypertension. Effects were likely mediated through its inhibition of activin A and oxidative stress. These data suggest a potential therapeutic role for follistatin as a novel antihypertensive agent. Follistatin, through antagonization of activin A, inhibits oxidative stress and improves vascular structure and function in resistance arteries from models of essential and secondary HTN. FST decreases collagen content and vascular ROS. Functionally, FST improves endothelium-dependent relaxation and decreases maximal vasoconstriction. Improved resistance artery structure and function are correlated with a decrease in BP in both models.

Nogo-B Promotes Endoplasmic Reticulum Stress-Mediated Autophagy in Endothelial Cells of Diabetic Nephropathy

Aims: Endothelial cells are the critical targets of injury in diabetic nephropathy (DN), and endothelial cell lesions contribute to the disease progression. Neurite outgrowth inhibitor B (Nogo-B), an endoplasmic reticulum (ER)-resident protein, plays a pivotal role in vascular remodeling after injury, and maintains the structure and function of the ER. Yet, the role of Nogo-B in the regulation of ER stress and endothelial cell injury remains largely unknown. Herein, we tested the hypothesis that Nogo-B activates ER stress-mediated autophagy and protects endothelial cells in DN. Results: The level of Nogo-B was decreased in glomerular endothelial cells in biopsy specimens from DN patients. In vivo and in vitro studies have shown that silencing Nogo-B activated ER stress signaling, and affected the expression of autophagy-related marker early growth response 1 and microtubule-associated protein light chain 3 (LC3) in endothelial cells in hyperglycemic condition. Conclusion and Innovation: These results denote that Nogo-B contributes to ER stress-mediated autophagy and protects endothelial cells in DN, providing new evidence for understanding the role of ER stress-mediated autophagy in endothelial cells of DN.

Implications of endoplasmic reticulum stress and autophagy in aging and cardiovascular diseases

The average lifespan of humans has been increasing, resulting in a rapidly rising percentage of older individuals and high morbidity of aging-associated diseases, especially cardiovascular diseases (CVDs). Diverse intracellular and extracellular factors that interrupt homeostatic functions in the endoplasmic reticulum (ER) induce ER stress. Cells employ a dynamic signaling pathway of unfolded protein response (UPR) to buffer ER stress. Recent studies have demonstrated that ER stress triggers various cellular processes associated with aging and many aging-associated diseases, including CVDs. Autophagy is a conserved process involving lysosomal degradation and recycling of cytoplasmic components, proteins, organelles, and pathogens that invade the cytoplasm. Autophagy is vital for combating the adverse influence of aging on the heart. The present report summarizes recent studies on the mechanism of ER stress and autophagy and their overlap in aging and on CVD pathogenesis in the context of aging. It also discusses possible therapeutic interventions targeting ER stress and autophagy that might delay aging and prevent or treat CVDs.

The association between flavonoids intake and hypertension in U.S. adults: A cross-sectional study from The National Health and Nutrition Examination Survey

Although in vitro experiments have demonstrated the potential of flavonoid compounds in regulating blood pressure, there is still a lack of evidence from large population studies. We conducted a cross-sectional study using the National Health and Nutrition Examination Survey to investigate the relationship between flavonoid intake levels (natural log transformation) and hypertension events. A total of 15 752 participants aged over 20 years were included, and a weighted multivariable logistic regression analysis was performed to explore the relationship between total flavonoids, five sub types intake, and hypertension events. Smooth curve fitting was used to explore potential nonlinear relationships. Higher total flavonoids intake was associated with a lower risk of hypertension than the lowest group. The adjusted odds ratios (95% CIs) were 0.79 (0.70-0.88) for total flavonoids intake. Elevated total flavonoids intake levels were significantly and linearly associated with a lower risk of hypertension. For each unit increase in the total flavonoids intake level, the adjusted ORs for risk of hypertension decrease by 5% (OR 0.95; 95% CI, 0.92-0.98). In addition, in restricted cubic spline regression, we found that flavan-3-ols, anthocyanidins, and flavonols intake were linearly and negatively related to prevalence of hypertension. Flavones intake showed nonlinear associations with prevalence of hypertension with inflection points of -1.90. Within a certain range, a negative correlation exists between flavonoids intake and hypertension events. This finding provides insights into dietary modifications in the prevention of hypertension.

Endoplasmic reticulum stress-mediated cell death in cardiovascular disease

The endoplasmic reticulum (ER) plays a vital function in maintaining cellular homeostasis. Endoplasmic reticulum stress (ERS) can trigger various modes of cell death by activating the unfolded protein response (UPR) signaling pathway. Cell death plays a crucial role in the occurrence and development of diseases such as cancer, liver diseases, neurological diseases, and cardiovascular diseases. Several cardiovascular diseases including hypertension, atherosclerosis, and heart failure are associated with ER stress. ER stress-mediated cell death is of interest in cardiovascular disease. Moreover, an increasing body of evidence supports the potential of modulating ERS for treating cardiovascular disease. This paper provides a comprehensive review of the UPR signaling pathway, the mechanisms that induce cell death, and the modes of cell death in cardiovascular diseases. Additionally, we discuss the mechanisms of ERS and UPR in common cardiovascular diseases, along with potential therapeutic strategies.

Inhibition of endoplasmic reticulum stress restores the balance of renal RAS components and lowers blood pressure in the spontaneously hypertensive rats

BACKGROUND

Endoplasmic reticulum (ER) stress has been shown to play a critical role in the pathogenesis of hypertension. However, the underlying mechanisms for lowering blood pressure (BP) by suppressing ER stress remain unclear. Here, we hypothesized that inhibition of ER stress could restore the balance between RAS components and lower BP in spontaneously hypertensive rats (SHRs).

METHODS

Wistar-Kyoto (WKY) rats and SHRs received vehicle or 4-PBA, an ER stress inhibitor, in the drinking water for 4 weeks. BP was measured by tail-cuff plethysmography, and the expression of RAS components was examined by Western blot.

RESULTS

Compared with vehicle-treated WKY rats, vehicle-treated SHRs exhibited higher blood pressure and increased renal ER stress and oxidative stress, accompanied by impaired diuresis and natriuresis. Moreover, SHRs had higher ACE and AT₁R and lower AT₂R, ACE2, and MasR expressions in the kidney. Interestingly, 4-PBA treatment improved impaired diuresis and natriuresis and lowered blood pressure in SHRs, accompanied by reducing ACE and AT₁R protein expression and increasing AT₂R, ACE2, and MasR expression in the kidneys of SHRs. In addition, these changes were associated with the reduction of ER stress and oxidative stress.

CONCLUSIONS

These results suggest that the imbalance of renal RAS components was associated with increased ER stress in SHRs. Inhibition of ER stress with 4-PBA reversed the imbalance of renal RAS components and restored the impaired diuresis and natriuresis, which, at least in part, explains the blood pressure-lowering effects of 4-PBA in hypertension.

Follistatin-like 1 protects endothelial function in the spontaneously hypertensive rat by inhibition of endoplasmic reticulum stress through AMPK-dependent mechanism

OBJECTIVE

Endothelial dysfunction is a critical initiating factor in the development of hypertension and related complications. Follistatin-like 1 (FSTL1) can promote endothelial cell function and stimulates revascularization in response to ischemic insult. However, it is unclear whether FSTL1 has an effect on ameliorating endothelial dysfunction in spontaneously hypertensive rats (SHRs).

METHODS

Wistar Kyoto (WKY) and SHRs were treated with a tail vein injection of vehicle (1 mL/day) or recombinant FSTL1 (100 μg/kg body weight/day) for 4 weeks. Blood pressure was measured by tail-cuff plethysmograph, and vascular reactivity in mesenteric arteries was measured using wire myography.

RESULTS

We found that treatment with FSTL1 reversed impaired endothelium-dependent relaxation (EDR) in mesenteric arteries and lowered blood pressure of SHRs. Decreased AMP-activated protein kinase (AMPK) phosphorylation, elevated endoplasmic reticulum (ER) stress markers, increased reactive oxygen species (ROS), and reduction of nitric oxide (NO) production in mesenteric arteries of SHRs were also reversed by FSTL1 treatment. Ex vivo treatment with FSTL1 improved the impaired EDR in mesenteric arteries from SHRs and reversed tunicamycin (ER stress inducer)-induced ER stress and the impairment of EDR in mesenteric arteries from WKY rats. The effects of FSTL1 were abolished by cotreatment of compound C (AMPK inhibitor).

CONCLUSIONS

These results suggest that FSTL1 prevents endothelial dysfunction in mesenteric arteries of SHRs through inhibiting ER stress and ROS and increasing NO production via activation of AMPK signaling.

Oxidative Stress and Endoplasmic Reticular Stress Interplay in the Vasculopathy of Hypertension

Under physiologic conditions, reactive oxygen species (ROS) function as signalling molecules that control cell function. However, in pathologic conditions, increased generation of ROS triggers oxidative stress, which plays a role in vascular changes associated with hypertension, including endothelial dysfunction, vascular reactivity, and arterial remodelling (termed the vasculopathy of hypertension). The major source of ROS in the vascular system is NADPH oxidase (NOX). Increased NOX activity drives vascular oxidative stress in hypertension. Molecular mechanisms underlying vascular damage in hypertension include activation of redox-sensitive signalling pathways, post-translational modification of proteins, and oxidative damage of DNA and cytoplasmic proteins. In addition, oxidative stress leads to accumulation of proteins in the endoplasmic reticulum (ER) (termed ER stress), with consequent activation of the unfolded protein response (UPR). ER stress is emerging as a potential player in hypertension as abnormal protein folding in the ER leads to oxidative stress and dysregulated activation of the UPR promotes inflammation and injury in vascular and cardiac cells. In addition, the ER engages in crosstalk with exogenous sources of ROS, such as mitochondria and NOX, which can amplify redox processes. Here we provide an update of the role of ROS and NOX in hypertension and discuss novel concepts on the interplay between oxidative stress and ER stress.

AM1638, a GPR40-Full Agonist, Inhibited Palmitate- Induced ROS Production and Endoplasmic Reticulum Stress, Enhancing HUVEC Viability in an NRF2-Dependent Manner

BACKGRUOUND

G protein-coupled receptor 40 (GPR40) is a key molecule in diabetes and fatty liver, but its role in endothelial dysfunction remains unclear. Our objective in this study was to determine whether GPR40 agonists protect endothelial cells against palmitatemediated oxidative stress.

METHODS

Human umbilical vein endothelial cells (HUVECs) were used to investigate effects of various GPR40 agonists on vascular endothelium.

RESULTS

In HUVECs, AM1638, a GPR40-full agonist, enhanced nuclear factor erythroid 2-related factor 2 (NRF2) translocation to the nucleus and heme oxygenase-1 (HO-1) expression, which blocked palmitate-induced superoxide production. Those antioxidant effects were not detected after treatment with LY2922470 or TAK875, GPR40-partial agonists, suggesting that GPR40 regulates reactive oxygen species (ROS) removal in a ligand-dependent manner. We also found that palmitate-induced CCAAT/enhancer-binding protein homologous protein expression; X-box binding protein-1 splicing, nuclear condensation, and fragmentation; and caspase-3 cleavage were all blocked in an NRF2-dependent manner after AM1638 treatment. Both LY2922470 and TAK875 also improved cell viability independent of the NRF2/ROS pathway by reducing palmitate-mediated endoplasmic reticulum stress and nuclear damage. GPR40 agonists thus have beneficial effects against palmitate in HUVECs. In particular, AM1638 reduced palmitate-induced superoxide production and cytotoxicity in an NRF2/HO-1 dependent manner.

CONCLUSION

GPR40 could be developed as a good therapeutic target to prevent or treat cardiovascular diseases such as atherosclerosis.

Role of ROS-mediated PERK/ATF4 signaling activation in extracorporeal tube formation injury of human umbilical vein endothelial cells induced by cooking oil fume PM2.5 exposure

Cooking oil fume-derived PM2.5 (COF-PM2.5) is a major source of indoor air contamination in China, which has been demonstrated to be a hazard factor of cardiovascular and cerebrovascular diseases. This study aimed to investigate the role of ROS-mediated PERK/ATF4 signaling activation in COF-PM2.5-inhibited extracorporeal tube formation in human umbilical vein endothelial cells (HUVECs). HUVECs were treated with 100 μg/mL COF-PM2.5 at different times, with or without 100 nM PERK activity inhibitor GSK2606414 (GSK) or 200 μM antioxidant N-acetylcysteine (NAC) pretreatment. Our results showed that COF-PM2.5 exposure can inhibit extracorporeal tube formation and down-regulate VEGFR2 expression in HUVECs. Furthermore, our data indicated that COF-PM2.5 exposure can activate the PERK/ATF4 signaling in HUVECs. Mechanistically, pretreatment with GSK interdicted PERK/ATF4 signaling, thereby reversing COF-PM2.5-downregulated VEGFR2 protein expression in HUVECs. Furthermore, NAC reversed VEGFR2 expression downregulated induced by COF-PM2.5 by inhibiting the upregulation of intracellular ROS levels and PERK/ATF4 signaling in HUVECs. As above, COF-PM2.5 exposure could induce ROS release from HUVECs, which in turn activate the endoplasmic reticulum PERK/ATF4 signaling and inhibit tube formation of HUVECs.

Non-Invasive Retinal Blood Vessel Wall Measurements with Polarization-Sensitive Optical Coherence Tomography for Diabetes Assessment: A Quantitative Study

Diabetes affects the structure of the blood vessel walls. Since the blood vessel walls are made of birefringent organized tissue, any change or damage to this organization can be evaluated using polarization-sensitive optical coherence tomography (PS-OCT). In this paper, we used PS-OCT along with the blood vessel wall birefringence index (BBI = thickness/birefringence2) to non-invasively assess the structural integrity of the human retinal blood vessel walls in patients with diabetes and compared the results to those of healthy subjects. PS-OCT measurements revealed that blood vessel walls of diabetic patients exhibit a much higher birefringence while having the same wall thickness and therefore lower BBI values. Applying BBI to diagnose diabetes demonstrated high accuracy (93%), sensitivity (93%) and specificity (93%). PS-OCT measurements can quantify small changes in the polarization properties of retinal vessel walls associated with diabetes, which provides researchers with a new imaging tool to determine the effects of exercise, medication, and alternative diets on the development of diabetes.

Soluble and insoluble protein aggregates, endoplasmic reticulum stress, and vascular dysfunction in Alzheimer's disease and cardiovascular diseases

Dementia refers to a particular group of symptoms characterized by difficulties with memory, language, problem-solving, and other thinking skills that affect a person's ability to perform everyday activities. Alzheimer's disease (AD) is the most common form of dementia, affecting about 6.2 million Americans aged 65 years and older. Likewise, cardiovascular diseases (CVDs) are a major cause of disability and premature death, impacting 126.9 million adults in the USA, a number that increases with age. Consequently, CVDs and cardiovascular risk factors are associated with an increased risk of AD and cognitive impairment. They share important age-related cardiometabolic and lifestyle risk factors, that make them among the leading causes of death. Additionally, there are several premises and hypotheses about the mechanisms underlying the association between AD and CVD. Although AD and CVD may be considered deleterious to health, the study of their combination constitutes a clinical challenge, and investigations to understand the mechanistic pathways for the cause-effect and/or shared pathology between these two disease constellations remains an active area of research. AD pathology is propagated by the amyloid β (Aβ) peptides. These peptides give rise to small, toxic, and soluble Aβ oligomers (SPOs) that are nonfibrillar, and it is their levels that show a robust correlation with the extent of cognitive impairment. This review will elucidate the interplay between the effects of accumulating SPOs in AD and CVDs, the resulting ER stress response, and their role in vascular dysfunction. We will also address the potential underlying mechanisms, including the possibility that SPOs are among the causes of vascular injury in CVD associated with cognitive decline. By revealing common mechanistic underpinnings of AD and CVD, we hope that novel experimental therapeutics can be designed to reduce the burden of these devastating diseases. Graphical abstract Alzheimer's disease (AD) pathology leads to the release of Aβ peptides, and their accumulation in the peripheral organs has varying effects on various components of the cardiovascular system including endoplasmic reticulum (ER) stress and vascular damage. Image created with BioRender.com.

Profile and Functional Prediction of Plasma Exosome-Derived CircRNAs From Acute Ischemic Stroke Patients

Stroke is one of the major causes of death and long-term disability, of which acute ischemic stroke (AIS) is the most common type. Although circular RNA (circRNA) expression profiles of AIS patients have been reported to be significantly altered in blood and peripheral blood mononuclear cells, the role of exosome-containing circRNAs after AIS is still unknown. Plasma exosomes from 10 AIS patients and 10 controls were isolated, and through microarray and bioinformatics analysis, the profile and putative function of circRNAs in the plasma exosomes were studied. A total of 198 circRNAs were differentially quantified (|log2 fold change| ≥ 1.00, p < 0.05) between AIS patients and controls. The levels of 12 candidate circRNAs were verified by qRT-PCR, and the quantities of 10 of these circRNAs were consistent with the data of microarray. The functions of host genes of differentially quantified circRNAs, including RNA and protein process, focal adhesion, and leukocyte transendothelial migration, were associated with the development of AIS. As a miRNA sponge, differentially quantified circRNAs had the potential to regulate pathways related to AIS, like PI3K-Akt, AMPK, and chemokine pathways. Of 198 differentially quantified circRNAs, 96 circRNAs possessing a strong translational ability could affect cellular structure and activity, like focal adhesion, tight junction, and endocytosis. Most differentially quantified circRNAs were predicted to bind to EIF4A3 and AGO2—two RNA-binding proteins (RBPs)—and to play a role in AIS. Moreover, four of ten circRNAs with verified levels by qRT-PCR (hsa_circ_0112036, hsa_circ_0066867, hsa_circ_0093708, and hsa_circ_0041685) were predicted to participate in processes of AIS, including PI3K-Akt, AMPK, and chemokine pathways as well as endocytosis, and to be potentially useful as diagnostic biomarkers for AIS. In conclusion, plasma exosome-derived circRNAs were significantly differentially quantified between AIS patients and controls and participated in the occurrence and progression of AIS by sponging miRNA/RBPs or translating into proteins, indicating that circRNAs from plasma exosomes could be crucial molecules in the pathogenesis of AIS and promising candidates as diagnostic biomarkers and therapeutic targets for the condition.

Oxidative Stress: A Putative Link Between Lower Urinary Tract Symptoms and Aging and Major Chronic Diseases

Aging and major chronic diseases are risk factors for lower urinary tract symptoms (LUTS). On the other hand, oxidative stress (OS) is one of the fundamental mechanisms of aging and the development of chronic diseases. Therefore, OS might be a candidate mechanism linking these two clinical entities. This article aims to summarize the studies on the prevalence of LUTS, the role of OS in aging and chronic diseases, and the potential mechanisms supporting the putative link. A comprehensive literature search was performed to identify recent reports investigating LUTS and OS in major chronic diseases. In addition, studies on the impact of OS on the lower urinary tract, including bladder, urethra, and prostate, were collected and summarized. Many studies showed LUTS are prevalent in aging and major chronic diseases, including obesity, metabolic syndrome, diabetes, cardiovascular disease, hypertension, obstructive sleep apnea, autoimmune diseases, Alzheimer’s disease, and Parkinson’s disease. At the same time, OS is a key component in the pathogenesis of those chronic diseases and conditions. Recent studies also provided evidence that exacerbated OS can cause functional and/or structural changes in the bladder, urethra, and prostate, leading to LUTS. The reviewed data support the concept that OS is involved in multiple risk factors-associated LUTS, although further studies are needed to confirm the causative relationship. The specific ROS/RNS and corresponding reactions/pathways involved in chronic diseases and associated LUTS should be identified in the future and could serve as therapeutic targets.

Down-regulation of AMPK/PPARδ signalling promotes endoplasmic reticulum stress-induced endothelial dysfunction in adult rat offspring exposed to maternal diabetes

AIMS

Exposure to maternal diabetes is associated with increased prevalence of hypertension in the offspring. The mechanisms underlying the prenatal programming of hypertension remain unclear. Because endoplasmic reticulum (ER) stress plays a key role in vascular endothelial dysfunction in hypertension, we investigated whether aberrant ER stress causes endothelial dysfunction and high blood pressure in the offspring of dams with diabetes.

METHODS AND RESULTS

Pregnant Sprague-Dawley rats were intraperitoneally injected with streptozotocin (35 mg/kg) or citrate buffer at Day 0 of gestation. Compared with control mother offspring (CMO), the diabetic mother offspring (DMO) had higher blood pressure and impaired endothelium-dependent relaxation in mesenteric arteries, accompanied by decreased AMPK phosphorylation and PPARδ expression, increased ER stress markers, and reactive oxygen species (ROS) levels. The inhibition of ER stress reversed these aberrant changes in DMO. Ex vivo treatment of mesenteric arteries with an AMPK agonist (A769662) or a PPARδ agonist (GW1516) improved the impaired EDR in DMO and reversed the tunicamycin-induced ER stress, ROS production, and EDR impairment in mesenteric arteries from CMO. The effects of A769662 were abolished by co-treatment with GSK0660 (PPARδ antagonist), whereas the effects of GW1516 were unaffected by Compound C (AMPK inhibitor).

CONCLUSION

These results suggest an abnormal foetal programming of vascular endothelial function in offspring of rats with maternal diabetes that is associated with increased ER stress, which can be ascribed to down-regulation of AMPK/PPARδ signalling cascade.

Mitochondria-Associated Membranes (MAMs): A Novel Therapeutic Target for Treating Metabolic Syndrome

Mitochondria-associated Endoplasmic Reticulum (ER) Membranes (MAMs) are the cellular structures that connect the ER and mitochondria and mediate communication between these two organelles. MAMs have been demonstrated to be involved in calcium signaling, lipid transfer, mitochondrial dynamic change, mitophagy, and the ER stress response. In addition, MAMs are critical for metabolic regulation, and their dysfunction has been reported to be associated with metabolic syndrome, including the downregulation of insulin signaling and the accelerated progression of hyperlipidemia, obesity, and hypertension. This review covers the roles of MAMs in regulating insulin sensitivity and the molecular mechanism underlying MAM-regulated cellular metabolism and reveals the potential of MAMs as a therapeutic target in treating metabolic syndrome.

miR-1283 Contributes to Endoplasmic Reticulum Stress in the Development of Hypertension Through the Activating Transcription Factor-4 (ATF4)/C/EBP-Homologous Protein (CHOP) Signaling Pathway

Background

Hypertension-related microRNA(miR)-1283 and its target gene, activating transcription factor-4 (ATF4), can regulate vascular endothelial dysfunction. This study aimed to explore whether miR-1283 prevents hypertension through targeting ATF4.

Material/Methods

Transcriptome sequencing was performed after overexpression or inhibition of miR-1283 in human amniotic epithelial cells (HAECs). After miR-1283 was overexpressed or inhibited in HAECs, ATF4^+/− and wild-type mice were induced with a high-salt diet. We detected the expression of ATF4, C/EBP-homologous protein (CHOP), BH3-interacting domain death agonist (BID), Bcl-2, Bcl-2-like protein 11 (BIM), Bcl-2-like protein 1 (BCL-X), and caspase-3 by PCR and western blotting. We detected the changes of vasoactive substances including nitric oxide (NO), endothelin 1 (ET-1), endothelial protein C receptor (EPCR), thrombin (TM), and von Willebrand factor (vWF) by ELISA.

Results

Compared with that of the miR-1283- inhibited group, NO was higher in the miR-1283 overexpression group, while the expression of ET-1, EPCR, TM, and vWF were lower. Similarly, compared with that of the miR-1283 inhibited group, the expression of ATF4, CHOP, BID, BIM, and caspase-3 in the miR-1283 overexpression group was downregulated, while the expression of BCL-2 and BCL-X was upregulated (P<0.05). In vivo experiments showed the lack of ATF4 gene could prevent hypertension in mice induced by high-salt diet and protect endothelial function.

Conclusions

The mechanism of regulating blood pressure and endothelial function of the miR-1283/ATF4 axis was related to inhibiting endoplasmic reticulum stress and cell apoptosis through the ATF4/CHOP signaling pathway. Therefore, the miR-1283/ATF4 axis may be a target for the prevention and treatment of hypertension.

Oxidative Stress and Hypertension

A link between oxidative stress and hypertension has been firmly established in multiple animal models of hypertension but remains elusive in humans. While initial studies focused on inactivation of nitric oxide by superoxide, our understanding of relevant reactive oxygen species (superoxide, hydrogen peroxide, and peroxynitrite) and how they modify complex signaling pathways to promote hypertension has expanded significantly. In this review, we summarize recent advances in delineating the primary and secondary sources of reactive oxygen species (nicotinamide adenine dinucleotide phosphate oxidases, uncoupled endothelial nitric oxide synthase, endoplasmic reticulum, and mitochondria), the posttranslational oxidative modifications they induce on protein targets important for redox signaling, their interplay with endogenous antioxidant systems, and the role of inflammasome activation and endoplasmic reticular stress in the development of hypertension. We highlight how oxidative stress in different organ systems contributes to hypertension, describe new animal models that have clarified the importance of specific proteins, and discuss clinical studies that shed light on how these processes and pathways are altered in human hypertension. Finally, we focus on the promise of redox proteomics and systems biology to help us fully understand the relationship between ROS and hypertension and their potential for designing and evaluating novel antihypertensive therapies.

Endoplasmic reticulum stress and unfolded protein response in cardiovascular diseases

Cardiovascular diseases (CVDs), such as ischaemic heart disease, cardiomyopathy, atherosclerosis, hypertension, stroke and heart failure, are among the leading causes of morbidity and mortality worldwide. Although specific CVDs and the associated cardiometabolic abnormalities have distinct pathophysiological and clinical manifestations, they often share common traits, including disruption of proteostasis resulting in accumulation of unfolded or misfolded proteins in the endoplasmic reticulum (ER). ER proteostasis is governed by the unfolded protein response (UPR), a signalling pathway that adjusts the protein-folding capacity of the cell to sustain the cell's secretory function. When the adaptive UPR fails to preserve ER homeostasis, a maladaptive or terminal UPR is engaged, leading to the disruption of ER integrity and to apoptosis. ER stress functions as a double-edged sword, with long-term ER stress resulting in cellular defects causing disturbed cardiovascular function. In this Review, we discuss the distinct roles of the UPR and ER stress response as both causes and consequences of CVD. We also summarize the latest advances in our understanding of the importance of the UPR and ER stress in the pathogenesis of CVD and discuss potential therapeutic strategies aimed at restoring ER proteostasis in CVDs.

Detection of Protein Aggregation and Proteotoxicity Induced by Angiotensin II in Vascular Smooth Muscle Cells

ABSTRACT

Disruption of protein quality control occurs with aging and cardiovascular pathologies including arterial stiffness and hypertension. Angiotensin II (Ang II) is believed to induce endoplasmic reticulum stress in vascular smooth muscle cells (VSMCs), thus contributing to vascular remodeling and dysfunction. However, whether Ang II increases formation of protein aggregates and mediates proteotoxicity in VSMCs remain obscure. Accordingly, this study aimed to establish a quantitative method of protein aggregate detection induced by Ang II and to investigate their potential involvement in inflammatory and senescence responses. Proteostat staining showed increased aggregate numbers per cell on Ang II exposure. Immunoblot analysis further showed an increase in preamyloid oligomer presence in a detergent insoluble protein fraction purified from VSMCs stimulated with Ang II. Moreover, these responses were attenuated by treatment with chemical chaperone, 4-phenylbutyrate. 4-phenylbutyrate further blocked Ang II-induced senescence associated β-galactosidase activity and THP-1 monocyte adhesion in VSMCs. These data suggest that Ang II induces proteotoxicity in VSMCs which likely contributes to aging and inflammation in the vasculature.

Enhanced Myogenic Constriction in the SHR Preglomerular Vessels Is Mediated by Thromboxane A2 Synthesis

Background

Spontaneously Hypertensive Rats (SHR) have chronically elevated blood pressures at 30 weeks of age (systolic: 191.0 ± 1.0, diastolic: 128.8 ± 0.9). However, despite this chronic malignant hypertension, SHR kidneys remain relatively free of pathology due to having an augmented myogenic constriction (MC). We hypothesized that the enhanced MC in the SHR preglomerular vessels was due to increased prostaglandin and decreased nitric oxide (NO) synthesis, providing renal protection.

Methods

SHR and Wistar Kyoto (WKY) arcuate and mesenteric arteries were treated with indomethacin (prostaglandin synthesis inhibitor), N omega-nitro-L-arginine (L-NNA, NO synthase inhibitor), and nifedipine (L-type calcium channel blocker); and MC was measured in these vessels. The role of endothelium in MC was examined by removing endothelium from WKY and SHR preglomerular and mesenteric arteries using human hair, and measuring MC. We also studied the source of prostaglandin in the SHR by treating endothelium-removed arcuate arteries with indomethacin and furegrelate (thromboxane synthase inhibitor).

Results

MC was enhanced in the SHR preglomerular vessels but not the mesenteric arteries. Indomethacin and LNNA removed the enhanced MC in the SHR. Nifedipine also inhibited MC in both WKY and SHR arcuate and mesenteric arteries. Removing endothelium did not change MC in either arcuate or mesenteric arteries of WKY and SHR rats; and did not remove the augmented MC in the SHR arcuate arteries. Indomethacin and furegrelate decreased MC in endothelium-removed SHR arcuate arteries and obliterated the enhanced MC in the SHR.

Conclusion

The enhanced MC in the SHR arcuate arteries was due to thromboxane A2 synthesis from the tunica media and/or adventitia layers. MC was not dependent on endothelium, but was dependent on L-type calcium channels. Nevertheless, SHR arcuate arteries displayed differential intracellular calcium signaling compared to the WKYs.

78 kDa Glucose-Regulated Protein Attenuates Protein Aggregation and Monocyte Adhesion Induced by Angiotensin II in Vascular Cells

Investigations of vascular smooth muscle cell (VSMC) phenotypic modulation due to angiotensin II (AngII) stimulation are important for understanding molecular mechanisms contributing to hypertension and associated vascular pathology. AngII induces endoplasmic reticulum (ER) stress in VSMCs, which has been implicated in hypertensive vascular remodeling. Under ER stress, 78 kDa glucose-regulated protein (GRP78) acts as an endogenous chaperone, as well as a master controller of unfolded protein response (UPR) to maintain protein quality control. However, the potential downstream consequences of ER stress induced by AngII on protein quality control and pro-inflammatory phenotype in VSMCs remain elusive. This study aims to identify protein aggregation as evidence of the disruption of protein quality control in VSMCs, and to test the hypothesis that preservation of proteostasis by overexpression of GRP78 can attenuate the AngII-induced pro-inflammatory phenotype in VSMCs. Increases in protein aggregation and enhanced UPR were observed in VSMCs exposed to AngII, which were mitigated by overexpression of GRP78. Moreover, GRP78 overexpression attenuated enhanced monocyte adhesion to VSMCs induced by AngII. Our results thus indicate that the prevention of protein aggregation can potentially mitigate an inflammatory phenotype in VSMCs, which may suggest an alternative therapy for the treatment of AngII-associated vascular disorders.

Oxidative Stress: A Unifying Paradigm in Hypertension

The etiology of hypertension involves complex interactions among genetic, environmental, and pathophysiologic factors that influence many regulatory systems. Hypertension is characteristically associated with vascular dysfunction, cardiovascular remodelling, renal dysfunction, and stimulation of the sympathetic nervous system. Emerging evidence indicates that the immune system is also important and that activated immune cells migrate and accumulate in tissues promoting inflammation, fibrosis, and target-organ damage. Common to these processes is oxidative stress, defined as an imbalance between oxidants and antioxidants in favour of the oxidants that leads to a disruption of oxidation-reduction (redox) signalling and control and molecular damage. Physiologically, reactive oxygen species (ROS) act as signalling molecules and influence cell function through highly regulated redox-sensitive signal transduction. In hypertension, oxidative stress promotes posttranslational modification (oxidation and phosphorylation) of proteins and aberrant signalling with consequent cell and tissue damage. Many enzymatic systems generate ROS, but NADPH oxidases (Nox) are the major sources in cells of the heart, vessels, kidneys, and immune system. Expression and activity of Nox are increased in hypertension and are the major systems responsible for oxidative stress in cardiovascular disease. Here we provide a unifying concept where oxidative stress is a common mediator underlying pathophysiologic processes in hypertension. We focus on some novel concepts whereby ROS influence vascular function, aldosterone/mineralocorticoid actions, and immunoinflammation, all important processes contributing to the development of hypertension.

Protein Misfolding and Endoplasmic Reticulum Stress in Chronic Lung Disease: Will Cell-Specific Targeting Be the Key to the Cure?

Chronic lung disease accounts for a significant global burden with respect to death, disability, and health-care costs. Due to the heterogeneous nature and limited treatment options for these diseases, it is imperative that the cellular and molecular mechanisms underlying the disease pathophysiology are further understood. The lung is a complex organ with a diverse cell population, and each cell type will likely have different roles in disease initiation, progression, and resolution. The effectiveness of a given therapeutic agent may depend on the net effect on each of these cell types. Over the past decade, it has been established that endoplasmic reticulum stress and the unfolded protein response are involved in the development of several chronic lung diseases. These conserved cellular pathways are important for maintaining cellular proteostasis, but their aberrant activation can result in pathology. This review discusses the current understanding of endoplasmic reticulum stress and the unfolded protein response at the cellular level in the development and progression of various chronic lung diseases. We highlight the need for increased understanding of the specific cellular contributions of unfolded protein response activation to these pathologies and suggest that the development of cell-specific targeted therapies is likely required to further decrease disease progression and to promote resolution of chronic lung disease.

Endoplasmic reticulum stress inhibition blunts the development of essential hypertension in the spontaneously hypertensive rat

Essential hypertension is the leading cause of premature death worldwide. However, hypertension’s cause remains uncertain. endoplasmic reticulum (ER) stress has recently been associated with hypertension, but it is unclear whether ER stress causes hypertension. To clarify this question, we examined if ER stress occurs in blood vessels before the development of hypertension and if ER stress inhibition would prevent hypertension development. We used the spontaneously hypertensive rat (SHR) as a model of human essential hypertension and the Wistar-Kyoto (WKY) rat as its normotensive control. Resistance arteries collected from young rats determined that ER stress was present in SHR vessels before the onset of hypertension. To assess the effect of ER stress inhibition on hypertension development, another subset of rats were treated with 4-phenylbutyric acid (4-PBA; 1 g·kg−1·day−1) for 8 wk from 5 wk of age. Blood pressure was measured via radiotelemetry and compared with untreated SHR and WKY rats. Mesenteric resistance arteries were collected and assessed for structural and functional changes associated with hypertension. Systolic and diastolic blood pressures were significantly lower in the 4-PBA-treated SHR groups than in untreated SHRs. Additionally, 4-PBA significantly decreased the media-to-lumen ratio and ER stress marker expression, improved vasodilatory response, and reduced contractile responses in resistance arteries from SHRs. Overall, ER stress inhibition blunted the development of hypertension in the SHR. These data add evidence to the hypothesis that a component of hypertension in the SHR is caused by ER stress.

NEW & NOTEWORTHY In this study, 4-phenylbutyric acid’s (4-PBA’s) molecular chaperone capability was used to inhibit endoplasmic reticulum (ER) stress in the small arteries of young spontaneously hypertensive rats (SHRs) and reduce their hypertension. These effects are likely mediated through 4-PBA's effects to reduce resistant artery contractility and increase nitric oxide-mediated endothelial vasodilation through a process preventing endothelial dysfunction. Overall, ER stress inhibition blunted the development of hypertension in this young SHR model. This suggests that a component of the increase in blood pressure found in SHRs is due to ER stress. However, it is important to note that inhibition of ER stress was not able to fully restore the blood pressure to normal, suggesting that a component of hypertension may not be due to ER stress. This study points to the inhibition of ER stress as an important new physiological pathway to lower blood pressure, where other known approaches may not achieve blood pressure-lowering targets.

4-Sodium phenyl butyric acid has both efficacy and counter-indicative effects in the treatment of Col4a1 disease

Mutations in the collagen genes COL4A1 and COL4A2 cause Mendelian eye, kidney and cerebrovascular disease including intracerebral haemorrhage (ICH), and common collagen IV variants are a risk factor for sporadic ICH. COL4A1 and COL4A2 mutations cause endoplasmic reticulum (ER) stress and basement membrane (BM) defects, and recent data suggest an association of ER stress with ICH due to a COL4A2 mutation. However, the potential of ER stress as a therapeutic target for the multi-systemic COL4A1 pathologies remains unclear. We performed a preventative oral treatment of Col4a1 mutant mice with the chemical chaperone phenyl butyric acid (PBA), which reduced adult ICH. Importantly, treatment of adult mice with the established disease also reduced ICH. However, PBA treatment did not alter eye and kidney defects, establishing tissue-specific outcomes of targeting Col4a1-derived ER stress, and therefore this treatment may not be applicable for patients with eye and renal disease. While PBA treatment reduced ER stress and increased collagen IV incorporation into BMs, the persistence of defects in BM structure and reduced ability of the BM to withstand mechanical stress indicate that PBA may be counter-indicative for pathologies caused by matrix defects. These data establish that treatment for COL4A1 disease requires a multipronged treatment approach that restores both ER homeostasis and matrix defects. Alleviating ER stress is a valid therapeutic target for preventing and treating established adult ICH, but collagen IV patients will require stratification based on their clinical presentation and mechanism of their mutations.

Inhibition of endoplasmic reticulum stress protected DOCA-salt hypertension-induced vascular dysfunction

Hypertension has complex vascular pathogenesis and therefore the molecular etiology remains poorly elucidated. Endoplasmic reticulum stress (ERS), which is a condition of the unfolded/misfolded protein accumulation in the endoplasmic reticulum, has been defined as a potential target for cardiovascular disease. In the present study, the effects of ERS inhibition on hypertension-induced alterations in the vessels were investigated. In male Wistar albino rats, hypertension was induced through unilateral nephrectomy, deoxycorticosterone-acetate (DOCA) injection (20 mg/kg, twice a week) and 1% NaCl with 0.2% KCI added to drinking water for 12 weeks. An ERS inhibitor, tauroursodeoxycolic acid (TUDCA) (150 mg/kg/day, i.p.), was administered for the final four weeks. ERS inhibition in DOCA-salt induced hypertension was observed to have reduced systolic blood pressure, improved endothelial dysfunction, enhanced plasma nitric oxide (NO) level, reduced protein expressions of phosphorylated-double-stranded RNA-activated protein kinase-like endoplasmic reticulum kinase (pPERK), 78 kDa glucose-regulated protein (GRP78), Inositol trisphosphate receptor1 (IP₃R1) and Epidermal growth factor receptor (EGFR), increased expressions of endoplasmic reticulum Ca²⁺-ATPase2 (SERCA2) and B cell lymphoma2 (Bcl2) in vessels. These findings suggest that the beneficial effects of ERS inhibition on hypertension may be related to protection of vessel functions through restoration of endoplasmic reticulum calcium homeostasis, and apoptotic and mitotic pathways.

Vascular Nox (NADPH Oxidase) Compartmentalization, Protein Hyperoxidation, and Endoplasmic Reticulum Stress Response in Hypertension

Vascular Nox (NADPH oxidase)-derived reactive oxygen species and endoplasmic reticulum (ER) stress have been implicated in hypertension. However, relationships between these processes are unclear. We hypothesized that Nox isoforms localize in a subcellular compartment-specific manner, contributing to oxidative and ER stress, which influence the oxidative proteome and vascular function in hypertension. Nox compartmentalization (cell fractionation), O₂^- (lucigenin), H₂O₂ (amplex red), reversible protein oxidation (sulfenylation), irreversible protein oxidation (protein tyrosine phosphatase, peroxiredoxin oxidation), and ER stress (PERK [protein kinase RNA-like endoplasmic reticulum kinase], IRE1α [inositol-requiring enzyme 1], and phosphorylation/oxidation) were studied in spontaneously hypertensive rat (SHR) vascular smooth muscle cells (VSMCs). VSMC proliferation was measured by fluorescence-activated cell sorting, and vascular reactivity assessed in stroke-prone SHR arteries by myography. Noxs were downregulated by short interfering RNA and pharmacologically. In SHR, Noxs were localized in specific subcellular regions: Nox1 in plasma membrane and Nox4 in ER. In SHR, oxidative stress was associated with increased protein sulfenylation and hyperoxidation of protein tyrosine phosphatases and peroxiredoxins. Inhibition of Nox1 (NoxA1ds), Nox1/4 (GKT137831), and ER stress (4-phenylbutyric acid/tauroursodeoxycholic acid) normalized SHR vascular reactive oxygen species generation. GKT137831 reduced IRE1α sulfenylation and XBP1 (X-box binding protein 1) splicing in SHR. Increased VSMC proliferation in SHR was normalized by GKT137831, 4-phenylbutyric acid, and STF083010 (IRE1-XBP1 disruptor). Hypercontractility in the stroke-prone SHR was attenuated by 4-phenylbutyric acid. We demonstrate that protein hyperoxidation in hypertension is associated with oxidative and ER stress through upregulation of plasmalemmal-Nox1 and ER-Nox4. The IRE1-XBP1 pathway of the ER stress response is regulated by Nox4/reactive oxygen species and plays a role in the hyperproliferative VSMC phenotype in SHR. Our study highlights the importance of Nox subcellular compartmentalization and interplay between cytoplasmic reactive oxygen species and ER stress response, which contribute to the VSMC oxidative proteome and vascular dysfunction in hypertension.

Aberrant endoplasmic reticulum stress mediates coronary artery spasm through regulating MLCK/MLC2 pathway

Coronary artery spasm (CAS) is a pathophysiological phenomenon that may cause myocardial infarction and lead to circulatory collapse and death. Aberrant endoplasmic reticulum (ER) stress causes accumulation of misfolding proteins and has been reported to be involved in a variety of vascular diseases. The present study investigated the role of ER stress in the development of CAS and explored the possible molecular mechanisms. Initially, it was found that ER stress markers were elevated in response to drug-induced vascular smooth muscle cells (VSMCs) contraction. Pharmacologic activation of ER stress using Tunicamycin (Tm) persistently induced CAS and significantly promoted Pituitrin-induced CAS in mice as well as in a collagen gel contraction assay. On the contrary, pharmacologic inhibition of ER stress using 4-phenylacetic acid (4-PBA) completely blunted Pituitrin-induced CAS development in mice. Moreover, during the drug-induced VSMCs contraction, expression of ER stress markers were increased in parallel to those of myosin light chain kinase (MLCK) and phosphor-MLC2 (p-MLC2, at Ser19). After inhibiting MLCK activity by using its specific inhibitor ML-7, the ER stress activator Tm failed to activate the MLCK/MLC2 pathway and could neither trigger CAS in mice nor induce VSMCs contraction in vitro. Our results suggested that aberrant ER stress mediated CAS via regulating the MLCK/MLC2 pathway. ER stress activators might be more robust than the common drugs (Pituitrin or acetylcholine) as to induce vasocontraction and thus may serve as potential therapeutics against chronic bleeding, while its inhibitor might be useful for treatment of severe CAS caused by other medication.

Chronic intermittent hypobaric hypoxia provides vascular protection in the aorta of the 2-kidney, 1-clip rat model of hypertension

Many studies have demonstrated that chronic intermittent hypobaric hypoxia (CIHH) can reduce blood pressure in spontaneously hypertensive rats and renovascular hypertensive (RVH) rats in which endothelial dysfunction is determined as a critical factor. However, whether CIHH can regulate vasodilation of the aorta in RVH rats remains unknown. The purpose of this study was to investigate the effect of CIHH on impaired relaxation of the aorta in the 2-kidney, 1-clip (2K1C) RVH rat model. The results showed CIHH improved the impaired endothelium-dependent relaxation in the 2K1C rat aorta. The endothelial dysfunction was prevented by the p38 antagonist SB203580, but not by the ERK1/2 antagonist PD98059 or JNK antagonist SP600125. Furthermore, the expression of p-eNOS, HIF-1α, and HIF-2α increased while that of p-p38 and BMP-4 decreased in CIHH-treated aortas from 2K1C rats. Finally, the p-eNOS expression was upregulated and the p-p38 expression was downregulated by pre-incubation of SB203580 or the BMP-4 antagonist Noggin with the aorta. CIHH ameliorated the impairment of endothelium-dependent relaxation through upregulating the expression of p-eNOS, which may be mediated by the inhibition of BMP-4/p-p38 MAPK, and upregulating the expression of HIFs in the 2K1C rat aorta.

Endoplasmic reticulum stress in the pathogenesis of hypertension

What is the topic of this review? This review highlights the emerging role of disruptions in endoplasmic reticulum (ER) function, namely ER stress, as a contributor to hypertension. What advances does it highlight? This review presents an integrative view of ER stress in cardiovascular control systems, including systems within the brain, kidney and peripheral vasculature, as related to development of hypertension. The endoplasmic reticulum (ER) is a cellular organelle specialized in the synthesis, folding, assembly and modification of proteins. In situations of increased protein demand, complex signalling pathways, termed the unfolded protein response, influence a series of cellular feedback loops to control ER function strictly. Although this is initially a compensatory attempt to maintain cellular homeostasis, chronic activation of the unfolded protein response, known as ER stress, leads to sustained changes in cellular function. A growing body of literature points to ER stress in diverse cardioregulatory systems, including the brain, kidney and vasculature, as central to the development of hypertension. Here, these recent findings from essential and obesity-related forms of hypertension are highlighted in an integrative manner, with discussion of the potential upstream causes and downstream consequences of ER stress. Given that hypertension is a leading medical and socio-economic global challenge, emerging findings suggest that targeting ER stress might represent a viable strategy for the treatment of hypertensive disease.

Endoplasmic reticulum stress inhibition limits the progression of chronic kidney disease in the Dahl salt-sensitive rat

Proteinuria is one of the primary risk factors for the progression of chronic kidney disease (CKD) and has been implicated in the induction of endoplasmic reticulum (ER) stress. We hypothesized that the suppression of ER stress with a low molecular weight chemical chaperone, 4-phenylbutyric acid (4-PBA), would reduce the severity of CKD and proteinuria in the Dahl salt-sensitive (SS) hypertensive rat. To induce hypertension and CKD, 12-wk-old male rats were placed on a high-salt (HS) diet for 4 wk with or without 4-PBA treatment. We assessed blood pressure and markers of CKD, including proteinuria, albuminuria, and renal pathology. Furthermore, we determined if HS feeding resulted in an impaired myogenic response, subsequent to ER stress. 4-PBA treatment reduced salt-induced hypertension, proteinuria, and albuminuria and preserved myogenic constriction. Furthermore, renal pathology was reduced with 4-PBA treatment, as indicated by lowered expression of profibrotic markers and fewer intratubular protein casts. In addition, ER stress in the glomerulus was reduced, and the integrity of the glomerular filtration barrier was preserved. These results suggest that 4-PBA treatment protects against proteinuria in the SS rat by preserving the myogenic response and by preventing ER stress, which led to a breakdown in the glomerular filtration barrier. As such, alleviating ER stress serves as a viable therapeutic strategy to preserve kidney function and to delay the progression of CKD in the animal model under study.