Erythrocyte glycocalyx sensitivity to sodium is associated with salt sensitivity of blood pressure in women but not men

Background

While salt sensitivity of blood pressure (SSBP) is a risk factor for hypertension, end-organ damage and death, most studies are conducted in western countries and in White people. We previously found that the prevalence of SSBP in Blacks living in Sub-Saharan Africa is as high as 75-80% like what has been reported in the west. Erythrocyte glycocalyx sensitivity to sodium (eGCSS), a marker of sodium-induced damage to the erythrocyte and vascular endothelial glycocalyx is thought to be related to blood pressure perturbations associated with salt intake. We hypothesized that SSBP correlates with eGCSS differently in men and women in Black people.

Methods

We conducted a cross sectional study using data from our recent clinical trial from Livingstone University Teaching Hospital among 117 normotensive young adults. We used a "salt blood test" to determine eGCSS and an immediate pressor response to oral salt (IPROS) for the diagnosis of SSBP.

Results

The proportion of males were equal to females and the median age (interquartile range) of the participants was 29 (22-45) years. The eGCSS scores were higher in salt-resistant females compared to salt-sensitive females and males. eGCSS correlated negatively with SSBP (AOR 0.98, 95% CI 0.97-0.99, p = 0.008), however, this relationship was driven by female sex and abrogated by male sex. Although blood pressure elevations exhibited a sustained bimodal pattern in both sexes, in males, systolic and diastolic blood pressure never returned to baseline during the time course as it did in females.

Conclusion

In this study, eGCSS correlated negatively with SSBP in black women but not in black men and the pressor response to dietary salt was significantly higher in men compared to women. These results suggest that women tend to have a higher disruption of the vascular endothelial glycocalyx by an acute salt load, implying that acute changes in blood pressure may not be driven directly by the endothelial glycocalyx. Our findings suggest a novel mechanism linking eGCSS and SSBP with potential implications for sex differences in salt-induced cardiovascular disease.Clinical trial registration: https://clinicaltrials.gov/, identifier [NCT04844255].

Hypertension Related Co-Morbidities and Complications in Women of Sub-Saharan Africa: A Brief Review

Hypertension is the leading cause of cardiovascular disease in women, and sub-Saharan African (SSA) countries have some of the highest rates of hypertension in the world. Expanding knowledge of causes, management, and awareness of hypertension and its co-morbidities worldwide is an effective strategy to mitigate its harms, decrease morbidities and mortality, and improve individual quality of life. Hypertensive disorders of pregnancy (HDPs) are a particularly important subset of hypertension, as pregnancy is a major stress test of the cardiovascular system and can be the first instance in which cardiovascular disease is clinically apparent. In SSA, women experience a higher incidence of HDP compared with other African regions. However, the region has yet to adopt treatment and preventative strategies for HDP. This delay stems from insufficient awareness, lack of clinical screening for hypertension, and lack of prevention programs. In this brief literature review, we will address the long-term consequences of hypertension and HDP in women. We evaluate the effects of uncontrolled hypertension in SSA by including research on heart disease, stroke, kidney disease, peripheral arterial disease, and HDP. Limitations exist in the number of studies from SSA; therefore, we will use data from countries across the globe, comparing and contrasting approaches in similar and dissimilar populations. Our review highlights an urgent need to prioritize public health, clinical, and bench research to discover cost-effective preventative and treatment strategies that will improve the lives of women living with hypertension in SSA.

Activation of renal epithelial Na+ channels (ENaC) in infants with congenital heart disease

Introduction

This study was designed to measure the concentration and activity of urinary proteases that activate renal epithelial sodium channel (ENaC) mediated Na+ transport in infants with congenital heart disease, a potential mechanism for fluid retention.

Methods

Urine samples from infants undergoing cardiac surgery were collected at three time points: T1) pre-operatively, T2) 6-8 h after surgery, and T3) 24 h after diuretics. Urine was collected from five heathy infant controls. The urine was tested for four proteases and whole-cell patch-clamp testing was conducted in renal collecting duct M-1 cells to test whether patient urine increased Na+ currents consistent with ENaC activation.

Results

Heavy chain of plasminogen, furin, and prostasin were significantly higher in cardiac patients prior to surgery compared to controls. There was no difference in most proteases before and after surgery. Urine from cardiac patients produced a significantly greater increase in Na+ inward currents compared to healthy controls.

Conclusion

Urine from infants with congenital heart disease is richer in proteases and has the potential to increase activation of ENaC in the nephron to enhance Na+ reabsorption, which may lead to fluid retention in this population.

Enhanced central sympathetic tone induces heart failure with preserved ejection fraction (HFpEF) in rats

Heart failure with preserved ejection fraction (HFpEF) is a heterogenous clinical syndrome characterized by diastolic dysfunction, concentric cardiac left ventricular (LV) hypertrophy, and myocardial fibrosis with preserved systolic function. However, the underlying mechanisms of HFpEF are not clear. We hypothesize that an enhanced central sympathetic drive is sufficient to induce LV dysfunction and HFpEF in rats. Male Sprague-Dawley rats were subjected to central infusion of either saline controls (saline) or angiotensin II (Ang II, 20 ng/min, i.c.v) via osmotic mini-pumps for 14 days to elicit enhanced sympathetic drive. Echocardiography and invasive cardiac catheterization were used to measure systolic and diastolic functions. Mean arterial pressure, heart rate, left ventricular end-diastolic pressure (LVEDP), and ± dP/dt changes in responses to isoproterenol (0.5 μg/kg, iv) were measured. Central infusion of Ang II resulted in increased sympatho-excitation with a consequent increase in blood pressure. Although the ejection fraction was comparable between the groups, there was a decrease in the E/A ratio (saline: 1.5 ± 0.2 vs Ang II: 1.2 ± 0.1). LVEDP was significantly increased in the Ang II-treated group (saline: 1.8 ± 0.2 vs Ang II: 4.6 ± 0.5). The increase in +dP/dt to isoproterenol was not significantly different between the groups, but the response in -dP/dt was significantly lower in Ang II-infused rats (saline: 11,765 ± 708 mmHg/s vs Ang II: 8,581 ± 661). Ang II-infused rats demonstrated an increased heart to body weight ratio, cardiomyocyte hypertrophy, and fibrosis. There were elevated levels of atrial natriuretic peptide and interleukin-6 in the Ang II-infused group. In conclusion, central infusion of Ang II in rats induces sympatho-excitation with concurrent diastolic dysfunction, pathological cardiac concentric hypertrophy, and cardiac fibrosis. This novel model of centrally mediated sympatho-excitation demonstrates characteristic diastolic dysfunction in rats, representing a potentially useful preclinical murine model of HFpEF to investigate various altered underlying mechanisms during HFpEF in future studies.

Role of Nanoparticle-Conjugates and Nanotheranostics in Abrogating Oxidative Stress and Ameliorating Neuroinflammation

Oxidative stress is a deteriorating condition that arises due to an imbalance between the reactive oxygen species and the antioxidant system or defense of the body. The key reasons for the development of such conditions are malfunctioning of various cell organelles, such as mitochondria, endoplasmic reticulum, and Golgi complex, as well as physical and mental disturbances. The nervous system has a relatively high utilization of oxygen, thus making it particularly vulnerable to oxidative stress, which eventually leads to neuronal atrophy and death. This advances the development of neuroinflammation and neurodegeneration-associated disorders such as Alzheimer's disease, Parkinson's disease, epilepsy, dementia, and other memory disorders. It is imperative to treat such conditions as early as possible before they worsen and progress to irreversible damage. Oxidative damage can be negated by two mechanisms: improving the cellular defense system or providing exogenous antioxidants. Natural antioxidants can normally handle such oxidative stress, but they have limited efficacy. The valuable features of nanoparticles and/or nanomaterials, in combination with antioxidant features, offer innovative nanotheranostic tools as potential therapeutic modalities. Hence, this review aims to represent novel therapeutic approaches like utilizing nanoparticles with antioxidant properties and nanotheranostics as delivery systems for potential therapeutic applications in various neuroinflammation- and neurodegeneration-associated disease conditions.

Inhibition of Pyk2 Improves Cx43 Intercalated Disc Localization, Infarct Size, and Cardiac Function in Rats With Heart Failure

BACKGROUND

Heart failure causes changes in Cx43 (Connexin43) regulation that are associated with arrhythmic heart disease. Pyk2 (proline-rich tyrosine kinase 2) is activated in cardiomyopathies and phosphorylates Cx43 to decrease intercellular communication. This study was designed to determine if Pyk2 inhibition improves cardiac function in a myocardial infarction (MI)-induced heart failure model in rats.

METHODS

MI (ligation of left anterior descending artery) rats were treated with the Pyk2 inhibitor PF4618433. Hemodynamic and structural parameters were monitored in Sham (n=5), MI-vehicle (n=5), and MI-PF4618433 (n=8) groups. Heart tissues were collected after 6 weeks to assess Pyk2 and Cx43 protein level and localization.

RESULTS

PF4618433 produced no observed adverse effects and inhibited ventricular Pyk2. PF4618433 reduced the MI infarct size from 34% to 17% (P=0.007). PF4618433 improved stroke volume (P=0.031) and cardiac output (P=0.009) in comparison to MI-vehicle with values similar to the Sham group. PF4618433 also led to an increase in the ejection fraction (P=0.002) and fractional shortening (P=0.006) when compared with the MI-vehicle (32% and 35% improvement, respectively) yet were lower in comparison with the Sham group. Pyk2 inhibition decreased Cx43 tyrosine phosphorylation (P=0.043) and maintained Cx43 at the intercalated disc in the distal ventricle 6 weeks post-MI.

CONCLUSIONS

Unlike other attempts to decrease Cx43 remodeling after MI-induced heart failure, inhibition of Pyk2 activity maintained Cx43 at the intercalated disc. This may have aided in the reduced infarct size (acute time frame) and improved cardiac function (chronic time frame). Additionally, we provide evidence that Pyk2 is activated following MI in human left ventricle, implicating a novel potential target for therapy in patients with heart failure.

Neurogenic Background for Emotional Stress-Associated Hypertension

PURPOSE OF REVIEW

The response to natural stressors involves both cardiac stimulation and vascular changes, primarily triggered by increases in sympathetic activity. These effects lead to immediate flow redistribution that provides metabolic support to priority target organs combined with other key physiological responses and cognitive strategies, against stressor challenges. This extremely well-orchestrated response that was developed over millions of years of evolution is presently being challenged, over a short period of time. In this short review, we discuss the neurogenic background for the origin of emotional stress-induced hypertension, focusing on sympathetic pathways from related findings in humans and animals.

RECENT FINDINGS

The urban environment offers a variety of psychological stressors. Real or anticipatory, emotional stressors may increase baseline sympathetic activity. From routine day-to-day traffic stress to job-related anxiety, chronic or abnormal increases in sympathetic activity caused by emotional stressors can lead to cardiovascular events, including cardiac arrhythmias, increases in blood pressure and even sudden death. Among the various alterations proposed, chronic stress could modify neuroglial circuits or compromise antioxidant systems that may alter the responsiveness of neurons to stressful stimuli. These phenomena lead to increases in sympathetic activity, hypertension and consequent cardiovascular diseases. The link between anxiety, emotional stress, and hypertension may result from an altered neuronal firing rate in central pathways controlling sympathetic activity. The participation of neuroglial and oxidative mechanisms in altered neuronal function is primarily involved in enhanced sympathetic outflow. The significance of the insular cortex-dorsomedial hypothalamic pathway in the evolution of enhanced overall sympathetic outflow is discussed.

Glycocalyx-Sodium Interaction in Vascular Endothelium

The glycocalyx generally covers almost all cellular surfaces, where it participates in mediating cell-surface interactions with the extracellular matrix as well as with intracellular signaling molecules. The endothelial glycocalyx that covers the luminal surface mediates the interactions of endothelial cells with materials flowing in the circulating blood, including blood cells. Cardiovascular diseases (CVD) remain a major cause of morbidity and mortality around the world. The cardiovascular risk factors start by causing endothelial cell dysfunction associated with destruction or irregular maintenance of the glycocalyx, which may culminate into a full-blown cardiovascular disease. The endothelial glycocalyx plays a crucial role in shielding the cell from excessive exposure and absorption of excessive salt, which can potentially cause damage to the endothelial cells and underlying tissues of the blood vessels. So, in this mini review/commentary, we delineate and provide a concise summary of the various components of the glycocalyx, their interaction with salt, and subsequent involvement in the cardiovascular disease process. We also highlight the major components of the glycocalyx that could be used as disease biomarkers or as drug targets in the management of cardiovascular diseases.

C-type natriuretic peptide (CNP) in the paraventricular nucleus-mediated renal sympatho-inhibition

Volume reflex produces sympatho-inhibition that is mediated by the hypothalamic paraventricular nucleus (PVN). However, the mechanisms for the sympatho-inhibitory role of the PVN and the neurochemical factors involved remain to be identified. In this study, we proposed C-type natriuretic peptide (CNP) as a potential mediator of this sympatho-inhibition within the PVN. Microinjection of CNP (1.0 μg) into the PVN significantly decreased renal sympathetic nerve activity (RSNA) (−25.8% ± 1.8% vs. −3.6% ± 1.5%), mean arterial pressure (−15.0 ± 1.9 vs. −0.1 ± 0.9 mmHg) and heart rate (−23.6 ± 3.5 vs. −0.3 ± 0.9 beats/min) compared with microinjection of vehicle. Picoinjection of CNP significantly decreased the basal discharge of extracellular single-unit recordings in 5/6 (83%) rostral ventrolateral medulla (RVLM)-projecting PVN neurons and in 6/13 (46%) of the neurons that were not antidromically activated from the RVLM. We also observed that natriuretic peptide receptor type C (NPR-C) was present on the RVLM projecting PVN neurons detected by dual-labeling with retrograde tracer. Prior NPR-C siRNA microinjection into the PVN significantly blunted the decrease in RSNA to CNP microinjections into the PVN. Volume expansion-mediated reduction in RSNA was significantly blunted by prior administration of NPR-C siRNA into the PVN. These results suggest a potential role for CNP within the PVN in regulating RSNA, specifically under physiological conditions of alterations in fluid balance.

Sex differences in hypertension among people living with HIV after initiation of antiretroviral therapy

Background

Hypertension is common in people living with HIV (PLWH) on antiretroviral therapy (ART). In the general population and in experimental animal models, the incidence of hypertension is greater in males than in females, especially during the premenopausal period. However, it is not known whether there are sex differences in hypertension associated with HIV and ART, and the factors contributing to incident hypertension among PLWH have not been well characterized. In this study, we aimed to determine the time course, sex differences and factors associated with incident hypertension in PLWH initiating ART.

Methods and results

We conducted a retrospective study in which we used programmatic data from the ART registry to identify sex differences in the determinants of incident hypertension among PLWH initiating the ART regimen from Livingstone University Teaching Hospital in Zambia and followed for 8 years. Males developed hypertension earlier, 2 years after initiating ART, compared to 6 years in females. In multivariable analysis, increasing age, baseline systolic blood pressure and baseline mean arterial pressure (MAP) were associated with increased risk for developing incident hypertension. Also, participants who switched to the integrase strand transfer inhibitor, dolutegravir (DTG) or the protease inhibitor, lopinavir boosted with ritonavir were 2 and 3 times more likely to develop hypertension when compared to those on non-nucleoside reverse transcriptase inhibitors (NNRTIs). However, these relationships were abrogated by sex, as self-reported male sex was the major contributor in predicting incident hypertension. While none of the factors remained significantly associated with incident hypertension upon multivariate analysis among females, body mass index (BMI), and use of protease inhibitors remained strongly associated with hypertension among males.

Conclusion

Our results indicate that the use of protease inhibitors and BMI are important predictors of incident hypertension among males. Thus, blood pressure and BMI should be closely monitored, particularly in males living with HIV on protease inhibitors. In addition, identifying specific factors that protect females from developing hypertension early is important but remains to be determined.

Extracellular volume fraction by computed tomography predicts long-term prognosis among patients with cardiac amyloidosis

Objective

This study sought to investigate the association of extracellular volume fraction by computed tomography (ECVCT), myocardial remodeling and mortality in patients with systemic amyloidosis.

Background

Light chain (AL) and transthyretin (ATTR) amyloid fibrils are deposited in the extracellular space of the myocardium, resulting in heart failure and premature mortality. Extracellular expansion can be quantified by CT, offering a rapid and cost-effective alternative to cardiovascular magnetic resonance (CMR), especially among patients with cardiac devices or on renal dialysis.

Methods

Patients with confirmed systemic amyloidosis and varying degrees of cardiac involvement underwent ECG-gated cardiac CT. ECVCT was analysed in the inter-ventricular septum. All patients also underwent clinical assessment, ECG, echocardiography, serum amyloid protein component (SAP) and/or technetium-99m (99mTc) 3,3-diphosphono-1,2-propanodicarboxylic acid scintigraphy. ECVCT was compared across different extents of cardiac infiltration (ATTR Perugini Grade / AL Mayo Class) and evaluated for its association with myocardial remodelling and all-cause mortality.

Results

72 patients were studied (AL n=35, ATTR n=37; age 67 (59–76) years, 71% males). Mean septal ECVCT was 42.7±13.1% and 55.8±10.9% in AL and ATTR, respectively, and correlated with indexed left ventricular (LV) mass (r=0.426, p<0.001), LV ejection fraction [LVEF, (r=0.460, p<0.001)], NT-proBNP (r=0.563, p<0.001) and hsTnT (r=0.546, p=0.02). ECVCT increased with cardiac amyloid involvement in both AL and ATTR (Figure 1). Over a mean follow-up of 5.3±2.4 years, 40 deaths occurred (AL 14 [35%]; ATTR 26 [65%]). ECVCT was independently associated with all-cause mortality in ATTR (not AL) after adjustment for age and IV septal wall thickness (HR: 1.046, 95% CI: 1.003–1.090, p=0.037).

Conclusion

Cardiac amyloid burden quantified by ECVCT is associated with adverse cardiac remodelling as well as all-cause mortality among ATTR amyloid patients. ECVCT may address the need for better identification and risk stratification of amyloid patients, using a widely-accessible imaging modality (Figure 2).

Funding Acknowledgement

Type of funding sources: None.

Hypertension and human immunodeficiency virus: A paradigm for epithelial sodium channels?

Hypertension is a risk factor for end organ damage and death and is more common in persons with HIV compared to the general population. Several mechanisms have been studied in the pathogenesis of hypertension. Current evidence suggests that the epithelial sodium channel (ENaC) plays a key role in regulating blood pressure through the transport of sodium and water across membranes in the kidney tubules, resulting in retention of sodium and water and an altered fluid balance. However, there is scarcity of information that elucidates the role of ENaC in HIV as it relates to increasing the risk for development or pathogenesis of hypertension. This review summarized the evidence to date implicating a potential role for altered ENaC activity in contributing to hypertension in patients with HIV.

Cardiorenal Syndrome: The Role of Neural Connections Between the Heart and the Kidneys

The maintenance of cardiovascular homeostasis is highly dependent on tightly controlled interactions between the heart and the kidneys. Therefore, it is not surprising that a dysfunction in one organ affects the other. This interlinking relationship is aptly demonstrated in the cardiorenal syndrome. The characteristics of the cardiorenal syndrome state include alterations in neurohumoral drive, autonomic reflexes, and fluid balance. The evidence suggests that several factors contribute to these alterations. These may include peripheral and central nervous system abnormalities. However, accumulating evidence from animals with experimental models of congestive heart failure and renal dysfunction as well as humans with the cardiorenal syndrome suggests that alterations in neural pathways, from and to the kidneys and the heart, including the central nervous system are involved in regulating sympathetic outflow and may be critically important in the alterations in neurohumoral drive, autonomic reflexes, and fluid balance commonly observed in the cardiorenal syndrome. This review focuses on studies implicating neural pathways, particularly the afferent and efferent signals from the heart and the kidneys integrating at the level of the paraventricular nucleus in the hypothalamus to alter neurohumoral drive, autonomic pathways, and fluid balance. Further, it explores the potential mechanisms of action for the known beneficial use of various medications or potential novel therapeutic manipulations for the treatment of the cardiorenal syndrome. A comprehensive understanding of these mechanisms will enhance our ability to treat cardiorenal conditions and their cardiovascular complications more efficaciously and thoroughly.

A Critical Role for the Paraventricular Nucleus of the Hypothalamus in the Regulation of the Volume Reflex in Normal and Various Cardiovascular Disease States

PURPOSE OF REVIEW

This review focuses on studies implicating forebrain neural pathways and neuromodulator systems, particularly, the nitric oxide system within the paraventricular nucleus of the hypothalamus in regulating neurohumoral drive, autonomic pathways, and fluid balance.

RECENT FINDINGS

Accumulating evidence from animals with experimental models of hypertension and heart failure as well as humans with hypertension suggests that alterations in central neural pathways, particularly, within the PVN neuromodulated by neuronal nitric oxide, are involved in regulating sympathetic outflow particularly to the kidney resulting in alterations in fluid balance commonly observed in hypertension and heart failure states. The characteristics of the hypertensive and heart failure states include alterations in neuronal nitric oxide within the PVN to cause an increase in renal sympathetic nerve activity to result in sodium and fluid retention in these diseases. A comprehensive understanding of these mechanisms will enhance our ability to treat hypertensive and heart failure conditions and their cardiovascular complications more efficiently.

Enhanced Expression and Function of Renal SGLT2 (Sodium-Glucose Cotransporter 2) in Heart Failure: Role of Renal Nerves

BACKGROUND

Recent clinical studies demonstrate that SGLT2 (sodium-glucose cotransporter 2) inhibitors ameliorate heart failure (HF). The present study was conducted to assess the expression and function of renal SGLT2 and the influence of enhanced renal sympathetic tone in HF.

METHODS

Four weeks after coronary artery ligation surgery to induce HF, surgical bilateral renal denervation (RDN) was performed in rats. Four groups of rats (Sham-operated control [Sham], Sham+RDN, HF and HF+RDN; n=6/group) were used. Immunohistochemistry and Western blot analysis were performed to evaluate the renal SGLT2 expression. One week after RDN (5 weeks after induction of HF), intravenous injection of SGLT2 inhibitor dapagliflozin were performed to assess renal excretory responses. In vitro, human embryonic kidney cells were used to investigate the fractionation of SGLT2 after norepinephrine treatment.

RESULTS

In rats with HF, (1) SGLT2 expression in the proximal tubule of the kidney was increased; (2) the response of increases in urine flow, sodium excretion, and glucose excretion to dapagliflozin were greater; and (3) RDN attenuated renal SGLT2 expression and normalized renal functional responses to dapagliflozin. In vitro, norepinephrine promoted translocation of SGLT2 to the cell membrane.

CONCLUSIONS

These results indicate that the enhanced tonic renal sympathetic nerve activation in HF increases the expression and functional activity of renal SGLT2. Potentiated trafficking of SGLT2 to cell surface in renal proximal tubules mediated by norepinephrine may contribute to this functional activation of SGLT2 in HF. These findings provide critical insight into the underlying mechanisms for the beneficial effects of SGLT2 inhibitors on HF reported in the clinical studies.

Neurogenic Hypertension Mediated Mitochondrial Abnormality Leads to Cardiomyopathy: Contribution of UPRmt and Norepinephrine-miR- 18a-5p-HIF-1α Axis

Aims: Hypertension increases the risk of heart disease. Hallmark features of hypertensive heart disease is sympathoexcitation and cardiac mitochondrial abnormality. However, the molecular mechanisms for specifically neurally mediated mitochondrial abnormality and subsequent cardiac dysfunction are unclear. We hypothesized that enhanced sympatho-excitation to the heart elicits cardiac miR-18a-5p/HIF-1α and mitochondrial unfolded protein response (UPRmt) signaling that lead to mitochondrial abnormalities and consequent pathological cardiac remodeling. Methods and Results: Using a model of neurogenic hypertension (NG-HTN), induced by intracerebroventricular (ICV) infusion of Ang II (NG-HTN; 20 ng/min, 14 days, 0.5 μl/h, or Saline; Control, 0.9%) through osmotic mini-pumps in Sprague-Dawley rats (250-300 g), we attempted to identify a link between sympathoexcitation (norepinephrine; NE), miRNA and HIF-1α signaling and UPRmt to produce mitochondrial abnormalities resulting in cardiomyopathy. Cardiac remodeling, mitochondrial abnormality, and miRNA/HIF-1α signaling were assessed using histology, immunocytochemistry, electron microscopy, Western blotting or RT-qPCR. NG-HTN demonstrated increased sympatho-excitation with concomitant reduction in UPRmt, miRNA-18a-5p and increased level of HIF-1α in the heart. Our in silico analysis indicated that miR-18a-5p targets HIF-1α. Direct effects of NE on miRNA/HIF-1α signaling and mitochondrial abnormality examined using H9c2 rat cardiomyocytes showed NE reduces miR-18a-5p but increases HIF-1α. Electron microscopy revealed cardiac mitochondrial abnormality in NG-HTN, linked with hypertrophic cardiomyopathy and fibrosis. Mitochondrial unfolded protein response was decreased in NG-HTN indicating mitochondrial proteinopathy and proteotoxic stress, associated with increased mito-ROS and decreased mitochondrial membrane potential (ΔΨm), and oxidative phosphorylation. Further, there was reduced cardiac mitochondrial biogenesis and fusion, but increased mitochondrial fission, coupled with mitochondrial impaired TIM-TOM transport and UPRmt. Direct effects of NE on H9c2 rat cardiomyocytes also showed cardiomyocyte hypertrophy, increased mitochondrial ROS generation, and UPRmt corroborating the in vivo data. Conclusion: In conclusion, enhanced sympatho-excitation suppress miR-18a-5p/HIF-1α signaling and increased mitochondrial stress proteotoxicity, decreased UPRmt leading to decreased mitochondrial dynamics/OXPHOS/ΔΨm and ROS generation. Taken together, these results suggest that ROS induced mitochondrial transition pore opening activates pro-hypertrophy/fibrosis/inflammatory factors that induce pathological cardiac hypertrophy and fibrosis commonly observed in NG-HTN.

Therapeutic effects of masitinib on abnormal mechanoreception in a mouse model of tourniquet-induced extremity ischemia-reperfusion

Tourniquets are widely used to stop extremity hemorrhage, but their use and subsequent release can result in nerve damage and degeneration, leading to neurological deficits. Increasing evidence has suggested a pivotal role of inflammation in nerve damage and abnormal mechanoreception. In this study, we investigated the therapeutic effects of masitinib (Mas), an anti-neuroinflammatory drug, on the mechanoreception of sensory neurons in a mouse model of tourniquet-induced hind paw ischemia-reperfusion (tourniquet/IR). C57BL/6 mice were subjected to 3 h of ischemia by placing a rubber band at the ankle joint and evaluated for subsequent reperfusion injury on day 1, 3, 7, 14, and 28 based on the experiments. Treatment with Mas (28 mg/kg/day, i.p.) began on the day of IR induction and lasted for 1, 3, 7, 14, or 28 days. Tourniquet/IR caused sensory nerve denervation in the skin of paw pads and abolished the hind paw mechanoreception to mechanical stimulation during the first 3 days of reperfusion. Sensory nerves gradually reinnervated in the skin of paw pads and allodynia began to appear on day 7. The maximum reaction occurred on day 14 and was maintained throughout the study period. Treatment with Mas mitigated nerve damage and improved hind paw mechanoreception to mechanical stimulation by decreasing the production of reactive oxygen species (ROS) during the early stages of tourniquet/IR. Mas also alleviated allodynia and decreased inflammatory cytokines (IL-1β and TNFα) in the skin of paw pads from days 7-28. Our data suggest that treatment with Mas significantly ameliorated paw numbness and allodynia in mouse hind paw tourniquet/IR.

Role of Renal Sympathetic Nerves in GLP-1 (Glucagon-Like Peptide-1) Receptor Agonist Exendin-4-Mediated Diuresis and Natriuresis in Diet-Induced Obese Rats

Background

The gut‐derived hormone GLP‐1 (glucagon‐like peptide‐1) exerts beneficial effects against established risk factors for chronic kidney disease. GLP‐1 influences renal function by stimulating diuresis and natriuresis and thus lowering arterial blood pressure. The role of the sympathetic nervous system has been implicated as an important link between obesity with elevated arterial pressure and chronic kidney disease. The primary aim of this study was to determine the contribution of renal sympathetic nerves on intrapelvic GLP‐1‐mediated diuresis and natriuresis in high‐fat diet (HFD)‐induced obese rats.

Methods and Results

Obesity was induced in rats by HFD for 12 weeks, followed by either surgical bilateral renal denervation or chronic subcutaneous endopeptidase neprilysin inhibition by sacubitril for a week. Diuretic and natriuretic responses to intrapelvic administration of the GLP‐1R (GLP‐1 receptor) agonist exendin‐4 were monitored in anesthetized control and HFD rats. Renal GLP‐1R expression and neprilysin expression and activity were measured. The effects of norepinephrine on the expression of GLP‐1R and neprilysin in kidney epithelial LLC‐PK1 cells were also examined. We found that diuretic and natriuretic responses to exendin‐4 were significantly reduced in the HFD obese rats compared with the control rats (cumulative urine flow at 40 minutes, 387±32 versus 650±65 µL/gkw; cumulative sodium excretion at 40 minutes, 42±5 versus 75±10 µEq/gkw, P<0.05). These responses in the HFD rats were restored after ablation of renal nerves (cumulative urine flow at 40 minutes, 625±62 versus 387±32 µL/gkw; cumulative sodium excretion at 40 minutes, 70±9 versus 42±5 µEq/gkw, P<0.05). Renal denervation induced significant reductions in arterial pressure and heart rate responses to intrapelvic GLP‐1 in the HFD rats. Renal denervation also significantly increased the GLP‐1R expression and reduced neprilysin expression and activity in renal tissues from the HFD rats. Chronic subcutaneous neprilysin inhibition by sacubitril increased GLP‐1–induced diuretic and natriuretic effects in the HFD rats. Finally, exposure of the renal epithelial cells to norepinephrine in vitro led to downregulation of GLP‐1R expression but upregulation of neprilysin expression and activity.

Conclusions

These results suggest that renal sympathetic nerve activation contributes to the blunted diuretic and natriuretic effects of GLP‐1 in HFD obese rats. This study provides significant novel insight into the potential renal nerve–neprilysin–GLP‐1 pathway involved in renal dysfunction during obesity that leads to hypertension.

A comparison of acute mouse hindlimb injuries between tourniquet- and femoral artery ligation-induced ischemia-reperfusion

The tourniquet or femoral artery ligation is widely used to stop extremity hemorrhage or create a bloodless operating field in the combat scenario and civilian setting. However, these procedures with subsequent reperfusion also induce ischemia-reperfusion (IR) injuries. To fully evaluate animal models of limb IR injuries, we compared tourniquet- and femoral artery ligation-induced IR injuries in the hindlimb of mice. In C57/BL6 mice, 3 h of unilateral hindlimb ischemia was induced by placement of a rubber band at the hip joint or a surgical ligation of the femoral artery. The tourniquet or femoral artery ligation was then released, allowing for 24 h of reperfusion. Compared to the femoral artery ligation/IR, the tourniquet/IR induced more severe skeletal muscle damage, including muscle necrosis and interruption of muscle fibers. There was no gastrocnemius muscle contraction in tourniquet/IR, while femoral artery ligation/IR markedly weakened gastrocnemius muscle contraction. Motor nerve terminals disappeared, and endplate potentials (EPPs) were undetectable in tourniquet/IR, whereas femoral artery ligation/IR only induced mild impairment of motor nerve terminals and decreased the amplitude of EPPs. Additionally, western blot data showed that proinflammatory cytokine levels (IL-1β and TNF-α) were higher in the tourniquet/IR than that in femoral artery ligation/IR. Moreover, tourniquet/IR caused significant tissue edema and dilation of lymphatic vessels in the hindlimb, compared to femoral artery ligation/IR. The above data demonstrated that tourniquet/IR-induced acute hindlimb injuries are more severe than those induced by femoral artery ligation/IR. This suggests that future investigators should determine which hindlimb IR model (tourniquet/IR or femoral artery ligation/IR) is optimal depending on the purpose of their study.

Outcomes of trans-catheter versus surgical aortic valve replacement for patients with classic low-flow low-gradient aortic stenosis

Background

Classical low-flow low-gradient aortic stenosis (cLFLG-AS) is frequently encountered within clinical practice [1], and is often associated with high mortality [2]. Whilst aortic valve replacement can improve outcomes, there is a lack of real-world data guiding the decision between trans-catheter aortic valve implantation (TAVI) or surgical aortic valve replacement (SAVR) in this specific patient cohort.

Purpose

To compare outcomes between TAVI and SAVR in patients with cLFLG-AS.

Methods

cLFLG-AS was defined by an aortic valve area &lt;1cm2, mean gradient &lt;40mmHg or peak velocity &lt;4m/s and left ventricular ejection fraction &lt;50%. All patients who met cLFLG-AS criteria who underwent TAVI or SAVR at our tertiary referral centre between 2015 and 2020 were included. Inverse probability weighting was used to adjust for differences in baseline characteristics and the non-random assignment of treatment modalities. The primary end-point was all-cause mortality. Secondary end-points were procedure-related permanent pacemaker implantation, renal replacement therapy (RRT) and stroke.

Results

322 patients were included (220 TAVI and 102 SAVR). Baseline characteristics were: male sex 70%, mean gradient 30mmHg (23–35), aortic valve area 0.8cm2 (0.6–0.9). Patients undergoing TAVI were older than the SAVR group (81.3±8.5 vs 70.6±11.1 years, p&lt;0.0001) with higher Logistic Euroscore (19.3 (11.8–32.3) vs 7.1 (3.7–14.1), p&lt;0.0001) (figure 1).

At median follow-up of 2.7 years (1.5–4.1), 99 patients had died; 70 (31.8%) had TAVI and 29 (28.4%) had SAVR. Both unweighted and weighted Kaplan-Meier curve analysis was performed; there was similar survival between SAVR and TAVI (log rank test 0=0.27 and p=0.4 respectively) (figure 2).

Adjusted hazard ratio (HR) for mortality with SAVR was 0.78 unweighted (95% CI 0.5–1.21; p=0.27) and 0.66 weighted (95% CI 0.26–1.64; p=0.37).

In terms of contributory procedural factors, concomitant multiple valve intervention in the SAVR group independently affected mortality (HR 5.47, 95% CI 2.52–11.51, p&lt;0.001).

There was no difference in permanent pacemaker insertion or stroke across the two groups, but rates of RRT were higher in SAVR cohort (13.7% vs 0%, p&lt;0.001).

Conclusions

Despite the TAVI cohort being both older and at higher risk, there was no observed difference in mortality between TAVI and SAVR in the mid-term. Deciding upon intervention choice can therefore be based upon criteria other than the specific presence of a classic low-flow low-gradient state.

Funding Acknowledgement

Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): Clinical training research fellowship from the British Heart Foundation Baseline characteristics by treatmentKaplan-Meier curves for TAVI vs SAVR

Splenic denervation attenuates repeated social defeat stress-induced T-lymphocyte inflammation

Background

Post-traumatic stress disorder (PTSD) is a devastating psychological disorder. Patients with PTSD canonically demonstrate an increased risk for inflammatory diseases, as well as increased sympathetic tone and norepinephrine (NE) outflow. Yet, the exact etiology and causal nature of these physiologic changes remain unclear. Previously, we demonstrated that exogenous NE alters mitochondrial superoxide in T-lymphocytes to produce a pro-inflammatory T-helper 17 (TH17) phenotype, and observed similar TH17 polarization in a preclinical model of PTSD. Therefore, we hypothesized sympathetic-driven neuroimmune interactions could mediate psychological trauma-induced T-lymphocyte inflammation.

Methods

Repeated social defeat stress (RSDS) is a preclinical murine model that recapitulates the behavioral, autonomic, and inflammatory aspects of PTSD. Targeted splenic denervation (Dnx) was performed to deduce the contribution of splenic sympathetic nerves to RSDS-induced inflammation. Eighty-five C57BL/6J mice underwent Dnx or sham-operation, followed by RSDS or control paradigms. Animals were assessed for behavioral, autonomic, inflammatory, and redox profiles.

Results

Dnx did not alter the antisocial or anxiety-like behavior induced by RSDS. In circulation, RSDS Dnx animals exhibited diminished levels of T-lymphocyte-specific cytokines (IL-2, IL-17A, and IL-22) compared to intact animals, whereas other non-specific inflammatory cytokines (e.g., IL-6, TNF-α, and IL-10) were unaffected by Dnx. Importantly, Dnx specifically ameliorated the increases in RSDS-induced T-lymphocyte mitochondrial superoxide, TH17 polarization, and pro-inflammatory gene expression with minimal impact to non-T-lymphocyte immune populations.

Conclusions

Overall, our data suggest that sympathetic nerves regulate RSDS-induced splenic T-lymphocyte inflammation, but play less of a role in the behavioral and non-T-lymphocyte inflammatory phenotypes induced by this psychological trauma paradigm.

Comparative evaluation of isoflurane and sevoflurane in avian patients

Background and Aim:

Literature comparing the use of isoflurane and sevoflurane inhalation anesthetic agents in birds is scarce. This study aimed to evaluate the comparison of isoflurane and sevoflurane during induction, maintenance, and recovery of anesthesia in avian patients.

Materials and Methods:

In this study, 24 injured avian patients (n=24) were selected randomly and divided into four groups during kite flying festival. In the present study, isoflurane and sevoflurane were used as induction and maintenance anesthetic agents, with and without butorphanol tartrate premedication agent in all the birds. Different physiological parameters were evaluated, namely, cloacal temperature (°F), heart rate (beats/min), respiratory rate (breaths/min), and SpO₂ (%) were recorded at 0, 10, 20 min, and at recovery time. The quality of anesthesia was assessed on the basis of induction time, quality of induction, production of analgesia, muscle relaxation, body reflexes, recovery time, quality of recovery, sitting, standing, and complete recovery time (CRT).

Results:

The mean±standard error value of induction time was 230.00±32.55, 280.00±25.29, 180.00±21.90, and 260.00±36.87 s, respectively, in Groups I, II, III, and IV. The feather plucking, pharyngeal, and toe pinching reflexes were noticed, when the birds were passing through the light plane of anesthesia during induction. Comparison of cloacal temperature at the time of recovery between Group-I versus Group-III revealed a significant difference (p<0.05). Comparison of mean respiratory rates at the time of recovery between Group-II versus Group-IV revealed a significant difference (p<0.05). Excellent quality of recovery was observed in all the groups of anesthetic protocols. Sitting, standing, and CRT were observed shortest in avian patients maintained with sevoflurane as compared to isoflurane.

Conclusion:

The quality of induction of anesthesia was rapid in avian patients when induced with sevoflurane as compared to isoflurane. Rapid onset of induction and recovery of anesthesia were found with sevoflurane followed by isoflurane. Induction and maintenance of anesthesia in avian patients with sevoflurane resulted in the lowest time required for sitting, standing, and CRT.

Myocardial fibrosis quantification by cardiac CT predicts outcome in severe aortic stenosis

Funding Acknowledgements

Type of funding sources: Foundation. Main funding source(s): British Heart Foundation

Background

Myocardial extracellular volume (ECV) increases with fibrosis, oedema or infiltration. ECV by CMR predicts all-cause and cardiovascular mortality in severe AS after valve intervention. Previous studies have shown that ECV can be reliably quantified by computed tomography (ECVCT), but these studies have not differentiated between ECV elevation due to fibrosis or cardiac amyloid deposition (13-16% of patients with severe AS). 

Purpose

We hypothesised that ECVCT quantification, performed as part of a transcatheter aortic valve implantation (TAVI) work-up CT, predicts survival in patients with severe AS without cardiac amyloid (lone AS).

Methods

Patients aged ≥75, with severe AS, referred for TAVI at Barts Heart Centre (as part of ATTRact-AS (NCT03029026)) underwent CT as part of their clinical work-up. All patients had 99mTc-3,3-diphosphono-1,2-propanodicarboxylic acid (DPD) scintigraphy and those with a positive result were excluded.  CT was performed on a 128-slice dual-source 3rdgeneration scanner (Siemens Somatom FORCE) and ECVCT was acquired during the TAVI work-up CT using additional pre- and 3-minute post-contrast ‘axial shuttle mode’ acquisitions (no additional contrast).  ECVCT was calculated from the Hounsfield units (HU) and a venous haematocrit (HCT): ECVCT = (1-HCT) x (ΔHUmyo/ΔHUblood).

Results

Following exclusion of 16 patients with cardiac uptake on DPD, 93 patients (41% male, aged 85 ± 5 years) were included in the study.  All patients had severe AS (AV Vmax 4.12 ± 0.63m/s, mean AV gradient 42 ± 14mmHg, AVA 0.71 ± 0.23cm2). The mean HCT was 0.38 ± 0.04 and total dose-length product for additional research scans was 364 ± 41 mGy.cm. 76 patients (82%) underwent TAVI. ECVCT was 32 ± 3% in the entire cohort, which we then split into those with a ‘higher’ ECVCT (&gt;34%, n = 23, representing the highest quartile) and those with a ‘lower’ ECVCT (≤34%, n = 70, representing the lower quartiles). Over a median follow-up of 25 months (IQR 17-34 months) there were 27 deaths (29%), of whom 11 did not undergo TAVI (41%). There were 10 deaths in the 23 patients (44%) with a higher ECVCT, compared to 17 in the 70 patients (24%) with a lower ECVCT (p = 0.03, figure 1). This mortality difference remained significant when those patients who did not undergo TAVI were excluded (p = 0.03).

Conclusions

Myocardial fibrosis quantified by ECVCT is associated with a significantly worse prognosis in lone AS, even after patients with AS-amyloid are excluded. ECVCT can be performed as a simple addition to the TAVI work-up CT and provides additional prognostic information.

Abstract Figure.

Structural basis of acquired resistance to selpercatinib and pralsetinib mediated by non-gatekeeper RET mutations

BACKGROUND

Selpercatinib (LOXO-292) and pralsetinib (BLU-667) are highly potent RET-selective protein tyrosine kinase inhibitors (TKIs) for treating advanced RET-altered thyroid cancers and non-small-cell lung cancer (NSCLC). It is critical to analyze RET mutants resistant to these drugs and unravel the molecular basis to improve patient outcomes.

PATIENTS AND METHODS

Cell-free DNAs (cfDNAs) were analyzed in a RET-mutant medullary thyroid cancer (MTC) patient and a CCDC6-RET fusion NSCLC patient who had dramatic response to selpercatinib and later developed resistance. Selpercatinib-resistant RET mutants were identified and cross-profiled with pralsetinib in cell cultures. Crystal structures of RET-selpercatinib and RET-pralsetinib complexes were determined based on high-resolution diffraction data collected with synchrotron radiation.

RESULTS

RETG810C/S mutations at the solvent front and RETY806C/N mutation at the hinge region were found in cfDNAs of an MTC patient with RETM918T/V804M/L, who initially responded to selpercatinib and developed resistance. RETG810C mutant was detected in cfDNAs of a CCDC6-RET-fusion NSCLC patient who developed acquired resistance to selpercatinib. Five RET kinase domain mutations at three non-gatekeeper residues were identified from 39 selpercatinib-resistant cell lines. All five selpercatinib-resistant RET mutants were cross-resistant to pralsetinib. X-ray crystal structures of the RET-selpercatinib and RET-pralsetinib complexes reveal that, unlike other TKIs, these two RET TKIs anchor one end in the front cleft and wrap around the gate wall to access the back cleft.

CONCLUSIONS

RET mutations at the solvent front and the hinge are resistant to both drugs. Selpercatinib and pralsetinib use an unconventional mode to bind RET that avoids the interference from gatekeeper mutations but is vulnerable to non-gatekeeper mutations.

Central Ang II (Angiotensin II)-Mediated Sympathoexcitation: Role for HIF-1α (Hypoxia-Inducible Factor-1α) Facilitated Glutamatergic Tone in the Paraventricular Nucleus of the Hypothalamus

Central infusion of Ang II (angiotensin II) has been associated with increased sympathetic outflow resulting in neurogenic hypertension. In the present study, we appraised whether the chronic increase in central Ang II activates the paraventricular nucleus of the hypothalamus (PVN) resulting in elevated sympathetic tone and altered baro- and chemoreflexes. Further, we evaluated the contribution of HIF-1α (hypoxia-inducible factor-1α), a transcription factor involved in enhancing the expression of N-methyl-D-aspartate receptors and thus glutamatergic-mediated sympathetic tone from the PVN. Ang II infusion (20 ng/minute, intracerebroventricular, 14 days) increased mean arterial pressure (126±9 versus 84±4 mm Hg), cardiac sympathetic tone (96±7 versus 75±6 bpm), and decreased cardiac parasympathetic tone (16±2 versus 36±3 versus bpm) compared with saline-infused controls in conscious rats. The Ang II-infused group also showed an impaired baroreflex control of heart rate (-1.50±0.1 versus -2.50±0.3 bpm/mm Hg), potentiation of the chemoreflex pressor response (53±7 versus 30±7 mm Hg) and increased number of FosB-labeled cells (53±3 versus 19±4) in the PVN. Concomitant with the activation of the PVN, there was an increased expression of HIF-1α and N-Methyl-D-Aspartate-type1 receptors in the PVN. Further, Ang II-infusion showed increased renal sympathetic nerve activity (20.5±2.3% versus 6.4±1.9% of Max) and 3-fold enhanced renal sympathetic nerve activity responses to microinjection of N-methyl-D-aspartate (200 pmol) into the PVN of anesthetized rats. Further, silencing of HIF-1α in NG108 cells abrogated the expression of N-methyl-D-aspartate-N-methyl-D-aspartate-type1 induced by Ang II. Taken together, our studies suggest a novel Ang II-HIF-1α-N-methyl-D-aspartate receptor-mediated activation of preautonomic neurons in the PVN, resulting in increased sympathetic outflow and alterations in baro- and chemoreflexes.

MMP9 inhibition increases autophagic flux in chronic heart failure

Increased matrix metalloprotease 9 (MMP9) after myocardial infarction (MI) exacerbates ischemia-induced chronic heart failure (CHF). Autophagy is cardioprotective during CHF; however, whether increased MMP9 suppresses autophagic activity in CHF is unknown. This study aimed to determine whether increased MMP9 suppressed autophagic flux and MMP9 inhibition increased autophagic flux in the heart of rats with post-MI CHF. Sprague-Dawley rats underwent either sham surgery or coronary artery ligation 6-8 wk before being treated with MMP9 inhibitor for 7 days, followed by cardiac autophagic flux measurement with lysosomal inhibitor bafilomycin A1. Furthermore, autophagic flux was measured in vitro by treating H9c2 cardiomyocytes with two independent pharmacological MMP9 inhibitors, salvianolic acid B (SalB) and MMP9 inhibitor-I, and CRISPR/cas9-mediated MMP9 genetic ablation. CHF rats showed cardiac infarct, significantly increased left ventricular end-diastolic pressure (LVEDP), and increased MMP9 activity and fibrosis in the peri-infarct areas of left ventricular myocardium. Measurement of the autophagic markers LC3B-II and p62 with lysosomal inhibition showed decreased autophagic flux in the peri-infarct myocardium. Treatment with SalB for 7 days in CHF rats decreased MMP9 activity and cardiac fibrosis but increased autophagic flux in the peri-infarct myocardium. As an in vitro corollary study, measurement of autophagic flux in H9c2 cardiomyocytes and fibroblasts showed that pharmacological inhibition or genetic ablation of MMP9 upregulates autophagic flux. These data are consistent with our observations that MMP9 inhibition upregulates autophagic flux in the heart of rats with CHF. In conclusion, the results in this study suggest that the beneficial outcome of MMP9 inhibition in pathological cardiac remodeling is in part mediated by improved autophagic flux.NEW & NOTEWORTHY This study elucidates that the improved cardiac extracellular matrix (ECM) remodeling and cardioprotective effect of matrix metalloprotease 9 (MMP9) inhibition in chronic heart failure (CHF) are via increased autophagic flux. Autophagy is cardioprotective; however, the mechanism of autophagy suppression in CHF is unknown. We for the first time demonstrated here that increased MMP9 suppressed cardiac autophagy and ablation of MMP9 increased cardiac autophagic flux in CHF rats. Restoring the physiological level of autophagy in the failing heart is a challenge, and our study addressed this challenge. The novelty and highlights of this report are as follows: 1) MMP9 regulates cardiomyocyte and fibroblast autophagy, 2) MMP9 inhibition protects CHF after myocardial infarction (MI) via increased cardiac autophagic flux, 3) MMP9 inhibition increased cardiac autophagy via activation of AMP-activated protein kinase (AMPK)α, Beclin-1, Atg7 pathway and suppressed mechanistic target of rapamycin (mTOR) pathway.

Angiotensin-converting enzyme 2 activator, DIZE in the basolateral amygdala attenuates the tachycardic response to acute stress by modulating glutamatergic tone

The basolateral amygdala (BLA) is critical in the control of the sympathetic output during stress. Studies demonstrated the involvement of the renin-angiotensin system components in the BLA. Angiotensin-(1-7) [Ang-(1-7)], acting through Mas receptors, reduces stress effects. Considering that angiotensin-converting enzyme 2 (ACE2) is the principal enzyme for the production of Ang-(1-7), here we evaluate the cardiovascular reactivity to acute stress after administration of the ACE2 activator, diminazene aceturate (DIZE) into the BLA. We also tested whether systemic treatment with DIZE could modify synaptic activity in the BLA and its effect directly on the expression of the N-methyl-d-aspartate receptors (NMDARs) in NG108 neurons in-vitro. Administration of DIZE into the BLA (200 pmol/100 nL) attenuated the tachycardia to stress (ΔHR, bpm: vehicle = 103 ± 17 vs DIZE = 49 ± 7 p = 0.018); this effect was inhibited by Ang-(1-7) antagonist, A-779 (ΔHR, bpm: DIZE = 49 ± 7 vs A-779 + DIZE = 100 ± 15 p = 0.04). Systemic treatment with DIZE attenuated the excitatory synaptic activity in the BLA (Frequency (Hz): vehicle = 2.9 ± 0.4 vs. DIZE =1.8 ± 0.3 p < 0.04). NG108 cells treated with DIZE demonstrated decreased expression of l subunit NMDAR-NR1 (NR1 expression (a.u): control = 0.534 ± 0.0593 vs. DIZE = 0.254 ± 0.0260) of NMDAR and increases of Mas receptors expression. These data demonstrate that DIZE attenuates the tachycardia evoked by acute stress. This effect results from a central action in the BLA involving activation of Mas receptors. The ACE2 activation via DIZE treatment attenuated the frequency of excitatory synaptic activity in the basolateral amygdala and this effect can be related with the decreases of the NMDAR-NR1 receptor expression.

Inhibition of Pyk2 and Src activity improves Cx43 gap junction intercellular communication

Identification of proteins that interact with Cx43 has been instrumental in the understanding of gap junction (GJ) regulation. An in vitro phosphorylation screen identified that Protein tyrosine kinase 2 beta (Pyk2) phosphorylated purified Cx43CT and this led us to characterize the impact of this phosphorylation on Cx43 function. Mass spectrometry identified Pyk2 phosphorylates Cx43 residues Y247, Y265, Y267, and Y313. Western blot and immunofluorescence staining using HeLa^Cx43 cells, HEK 293 T cells, and neonatal rat ventricular myocytes (NRVMs) revealed Pyk2 can be activated by Src and active Pyk2 interacts with Cx43 at the plasma membrane. Overexpression of Pyk2 increases Cx43 phosphorylation and knock-down of Pyk2 decreases Cx43 phosphorylation, without affecting the level of active Src. In HeLa^Cx43 cells treated with PMA to activate Pyk2, a decrease in Cx43 GJ intercellular communication (GJIC) was observed when assayed by dye transfer. Moreover, PMA activation of Pyk2 could be inhibited by the small molecule PF4618433. This partially restored GJIC, and when paired with a Src inhibitor, returned GJIC to the no PMA control-level. The ability of Pyk2 and Src inhibitors to restore Cx43 function in the presence of PMA was also observed in NRVMs. Additionally, an animal model of myocardial infarction induced heart failure showed a higher level of active Pyk2 activity and increased interaction with Cx43 in ventricular myocytes. Src inhibitors have been used to reverse Cx43 remodeling and improve heart function after myocardial infarction; however, they alone could not fully restore proper Cx43 function. Our data suggest that Pyk2 may need to be inhibited, in addition to Src, to further (if not completely) reverse Cx43 remodeling and improve intercellular communication.

Abstract MP49: Central Angiotensin II Mediates Neurogenic Hypertension Through Hif1-Alpha/NMDAR Axis In The Paraventricular Nucleus Of The Hypothalamus (PVN)

Central activation of the renin-angiotensin system and subsequent sympathoexcitation plays a pivotal role in the pathogenesis of hypertension. The specific neural substrates and the possible molecular mechanisms for the sympathoexcitation remain unclear. The glutamatergic activation via N-methyl-d-aspartate receptors (NMDAR) in the PVN enhances sympathetic outflow in hypertension. Previously, using Chromatin immunoprecipitation assay (ChiP) we have shown that Hypoxia-Inducible Factor-1 (heterodimer of HIF-1 α and HIF-1 β subunits ) binds to HREs elements in the NMDA-NR1(structural subunit of NMDAR) promoter in nucleus and increases transcription. In this study, central infusion of Ang II (20 ng/min, 14days, 0.5μl/h, i.c.v) through osmotic mini-pumps in Sprague-Dawley rats increased renal sympathetic nerve activity (20.5 ± 2.3 vs. 6.4 ± 1.9 % of Max) and mean arterial pressure (126 ± 9 vs. 84 ± 4 mmHg). At the same time, there was an increased expression of HIF-1α mRNA (2.79 fold) and HIF-1α protein (1.54 fold), as well as the expression of NMDA-NR1 mRNA (3.17 fold) and NMDA-NR1 protein levels (1.52 fold) in the PVN of Ang II infused group. Direct application of Ang II (1μM) induced an increase in the expression of HIF-1α protein (0.74 ± 0.03* vs. 0.50 ± 0.04) as well as decreased expression of prolyl hydroxylase domain protein 2 (an enzyme hydroxylating the proline residues of HIF-α, inducing subsequent ubiquitination and proteasomal degradation) (1.47 ± 0.14* vs. 0.50 ± 0.03) in NG108-15 neuronal cells. Tandem Ubiquitin-Binding Entities assay showed decreased HIF-α -Ub conjugates in Ang II-treated cells (0.65 ± 0.09* vs. 1.31 ± 0.10) suggesting a role for Ang II in post-translational stabilization of HIF-α. Further, silencing of HIF-1α (~60%) with siRNA in NG108-15 cells leads to a decrease in the expression of NMDA-NR1 induced by Ang II, compared with scrambled siRNA (0.47 ± 0.05* vs 0.80 ± 0.04). Taken together, these studies suggest that elevated central Ang II upregulates the expression of HIF-1α at transcriptional as well as post-translational level, which potentiates glutamatergic tone by enhanced expression of NMDA-NR1 in the PVN leading to heightened glutamatergic tone with a consequent increase in sympathetic outflow resulting in hypertension.

Nanoformulation of the superoxide dismutase mimic, MnTnBuOE-2-PyP5+, prevents its acute hypotensive response

Scavenging superoxide (O₂^•-) via overexpression of superoxide dismutase (SOD) or administration of SOD mimics improves outcomes in multiple experimental models of human disease including cardiovascular disease, neurodegeneration, and cancer. While few SOD mimics have transitioned to clinical trials, MnTnBuOE-2-PyP⁵⁺ (BuOE), a manganese porphyrin SOD mimic, is currently in clinical trials as a radioprotector for cancer patients; thus, providing hope for the use of SOD mimics in the clinical setting. However, BuOE transiently alters cardiovascular function including a significant and precipitous decrease in blood pressure. To limit BuOE's acute hypotensive action, we developed a mesoporous silica nanoparticle and lipid bilayer nanoformulation of BuOE (nanoBuOE) that allows for slow and sustained release of the drug. Herein, we tested the hypothesis that unlike native BuOE, nanoBuOE does not induce an acute hypotensive response, as the nanoformulation prevents BuOE from scavenging O₂^•- while the drug is still encapsulated in the formulation. We report that intact nanoBuOE does not effectively scavenge O₂^•-, whereas BuOE released from the nanoformulation does retain SOD-like activity. Further, in mice, native BuOE, but not nanoBuOE, rapidly, acutely, and significantly decreases blood pressure, as measured by radiotelemetry. To begin exploring the physiological mechanism by which native BuOE acutely decreases blood pressure, we recorded renal sympathetic nerve activity (RSNA) in rats. RSNA significantly decreased immediately following intravenous injection of BuOE, but not nanoBuOE. These data indicate that nanoformulation of BuOE, a SOD mimic currently in clinical trials in cancer patients, prevents BuOE's negative side effects on blood pressure homeostasis.

•

MnTnBuOE-2-PyP⁵⁺ (BuOE) induces a rapid and significant decrease in blood pressure.

•

BuOE's hypotensive response is concomitant with reduced sympathetic nerve activity.

•

Nanoformulated BuOE (nanoBuOE) release of active drug is slow and sustained.

•

nanoBuOE prevents the BuOE-induced hypotensive and sympathoinhibition responses.

GLP-1 mediated diuresis and natriuresis are blunted in heart failure and restored by selective afferent renal denervation

Background

Glucagon-like peptide-1 (GLP-1) induces diuresis and natriuresis. Previously we have shown that GLP-1 activates afferent renal nerve to increase efferent renal sympathetic nerve activity that negates the diuresis and natriuresis as a negative feedback mechanism in normal rats. However, renal effects of GLP-1 in heart failure (HF) has not been elucidated. The present study was designed to assess GLP-1-induced diuresis and natriuresis in rats with HF and its interactions with renal nerve activity.

Methods

HF was induced in rats by coronary artery ligation. The direct recording of afferent renal nerve activity (ARNA) with intrapelvic injection of GLP-1 and total renal sympathetic nerve activity (RSNA) with intravenous infusion of GLP-1 were performed. GLP-1 receptor expression in renal pelvis, densely innervated by afferent renal nerve, was assessed by real-time PCR and western blot analysis. In separate group of rats after coronary artery ligation selective afferent renal denervation (A-RDN) was performed by periaxonal application of capsaicin, then intravenous infusion of GLP-1-induced diuresis and natriuresis were evaluated.

Results

In HF, compared to sham-operated control; (1) response of increase in ARNA to intrapelvic injection of GLP-1 was enhanced (3.7 ± 0.4 vs. 2.0 ± 0.4 µV s), (2) GLP-1 receptor expression was increased in renal pelvis, (3) response of increase in RSNA to intravenous infusion of GLP-1 was enhanced (132 ± 30% vs. 70 ± 16% of the baseline level), and (4) diuretic and natriuretic responses to intravenous infusion of GLP-1 were blunted (urine flow 53.4 ± 4.3 vs. 78.6 ± 4.4 µl/min/gkw, sodium excretion 7.4 ± 0.8 vs. 10.9 ± 1.0 µEq/min/gkw). A-RDN induced significant increases in diuretic and natriuretic responses to GLP-1 in HF (urine flow 96.0 ± 1.9 vs. 53.4 ± 4.3 µl/min/gkw, sodium excretion 13.6 ± 1.4 vs. 7.4 ± 0.8 µEq/min/gkw).

Conclusions

The excessive activation of neural circuitry involving afferent and efferent renal nerves suppresses diuretic and natriuretic responses to GLP-1 in HF. These pathophysiological responses to GLP-1 might be involved in the interaction between incretin-based medicines and established HF condition. RDN restores diuretic and natriuretic effects of GLP-1 and thus has potential beneficial therapeutic implication for diabetic HF patients.

Central angiotensin II-Protein inhibitor of neuronal nitric oxide synthase (PIN) axis contribute to neurogenic hypertension

Activation of renin-angiotensin- system, nitric oxide (NO•) bioavailability and subsequent sympathoexcitation plays a pivotal role in the pathogenesis of many cardiovascular diseases, including hypertension. Previously we have shown increased protein expression of PIN (a protein inhibitor of nNOS: neuronal nitric oxide synthase, known to dissociate nNOS dimers into monomers) with concomitantly reduced levels of catalytically active dimers of nNOS in the PVN of rats with heart failure. To elucidate the molecular mechanism by which Angiotensin II (Ang II) increases PIN expression, we used Sprague-Dawley rats (250-300 g) subjected to intracerebroventricular infusion of Ang II (20 ng/min, 0.5 μl/h) or saline as vehicle (Veh) for 14 days through osmotic mini-pumps and NG108-15 hybrid neuronal cell line treated with Ang II as an in vitro model. Ang II infusion significantly increased baseline renal sympathetic nerve activity and mean arterial pressure. Ang II infusion increased the expression of PIN (1.24 ± 0.04* Ang II vs. 0.65 ± 0.07 Veh) with a concomitant 50% decrease in dimeric nNOS and PIN-Ub conjugates (0.73 ± 0.04* Ang II vs. 1.00 ± 0.03 Veh) in the PVN. Substrate-dependent ligase assay in cells transfected with pCMV-(HA-Ub)8 vector revealed a reduction of HA-Ub-PIN conjugates after Ang II and a proteasome inhibitor, Lactacystin (LC), treatment (4.5 ± 0.7* LC Ang II vs. 9.2 ± 2.5 LC). TUBE (Tandem Ubiquitin-Binding Entities) assay showed decrease PIN-Ub conjugates in Ang II-treated cells (0.82 ± 0.12* LC Ang II vs. 1.21 ± 0.06 LC) while AT₁R blocker, Losartan (Los) treatment diminished the Ang II-mediated stabilization of PIN (1.21 ± 0.07 LC Los vs. 1.16 ± 0.04* LC Ang II Los). Taken together, our studies suggest that increased central levels of Ang II contribute to the enhanced expression of PIN leading to reduced expression of the dimeric form of nNOS, thus diminishing the inhibitory action of NO• on pre-autonomic neurons in the PVN resulting in increased sympathetic outflow.

Central Glucagon-like Peptide-1 Receptor Signaling via Brainstem Catecholamine Neurons Counteracts Hypertension in Spontaneously Hypertensive Rats

Glucagon-like peptide-1 receptor (GLP-1R) agonists, widely used to treat type 2 diabetes, reduce blood pressure (BP) in hypertensive patients. Whether this action involves central mechanisms is unknown. We here report that repeated lateral ventricular (LV) injection of GLP-1R agonist, liraglutide, once daily for 15 days counteracted the development of hypertension in spontaneously hypertensive rats (SHR). In parallel, it suppressed urinary norepinephrine excretion, and induced c-Fos expressions in the area postrema (AP) and nucleus tractus solitarius (NTS) of brainstem including the NTS neurons immunoreactive to dopamine beta-hydroxylase (DBH). Acute administration of liraglutide into fourth ventricle, the area with easy access to the AP and NTS, transiently decreased BP in SHR and this effect was attenuated after lesion of NTS DBH neurons with anti-DBH conjugated to saporin (anti-DBH-SAP). In anti-DBH-SAP injected SHR, the antihypertensive effect of repeated LV injection of liraglutide for 14 days was also attenuated. These findings demonstrate that the central GLP-1R signaling via NTS DBH neurons counteracts the development of hypertension in SHR, accompanied by attenuated sympathetic nerve activity.

Renal denervation improves sodium excretion in rats with chronic heart failure: effects on expression of renal ENaC and AQP2

Previously we have shown that increased expression of renal epithelial sodium channels (ENaC) may contribute to the renal sodium and water retention observed during chronic heart failure (CHF). The goal of this study was to examine whether renal denervation (RDN) changed the expressions of renal sodium transporters ENaC, sodium-hydrogen exchanger-3 proteins (NHE3), and water channel aquaporin 2 (AQP2) in rats with CHF. CHF was produced by left coronary artery ligation in rats. Four weeks after ligation surgery, surgical bilateral RDN was performed. The expression of ENaC, NHE3, and AQP2 in both renal cortex and medulla were measured. As a functional test for ENaC activation, diuretic and natriuretic responses to ENaC inhibitor benzamil were monitored in four groups of rats (Sham, Sham+RDN, CHF, CHF+RDN). Western blot analysis indicated that RDN (1 wk later) significantly reduced protein levels of α-ENaC, β-ENaC, γ-ENaC, and AQP2 in the renal cortex of CHF rats. RDN had no significant effects on the protein expression of kidney NHE3 in both Sham and CHF rats. Immunofluorescence studies of kidney sections confirmed the reduced signaling of ENaC and AQP2 in the CHF+RDN rats compared with the CHF rats. There were increases in diuretic and natriuretic responses to ENaC inhibitor benzamil in rats with CHF. RDN reduced the diuretic and natriuretic responses to benzamil in CHF rats. These findings suggest a critical role for renal nerves in the enhanced expression of ENaC and AQP2 and subsequent pathophysiology of renal sodium and water retention associated with CHF.NEW & NOTEWORTHY This is the first study to show in a comprehensive way that renal denervation initiated after a period of chronic heart failure reduces the expression of epithelial sodium channels and aquaporin 2 leading to reduced epithelial sodium channel function and sodium retention.

Does glucagon-like peptide-1 induce diuresis and natriuresis by modulating afferent renal nerve activity?

Glucagon-like peptide-1 (GLP-1), an incretin hormone, has diuretic and natriuretic effects. The present study was designed to explore the possible underlying mechanisms for the diuretic and natriuretic effects of GLP-1 via renal nerves in rats. Immunohistochemistry revealed that GLP-1 receptors were avidly expressed in the pelvic wall, the wall being adjacent to afferent renal nerves immunoreactive to calcitonin gene-related peptide, which is the dominant neurotransmitter for renal afferents. GLP-1 (3 μM) infused into the left renal pelvis increased ipsilateral afferent renal nerve activity (110.0 ± 15.6% of basal value). Intravenous infusion of GLP-1 (1 µg·kg^-1·min^-1) for 30 min increased renal sympathetic nerve activity (RSNA). After the distal end of the renal nerve was cut to eliminate the afferent signal, the increase in efferent renal nerve activity during intravenous infusion of GLP-1 was diminished compared with the increase in total RSNA (17.0 ± 9.0% vs. 68.1 ± 20.0% of the basal value). Diuretic and natriuretic responses to intravenous infusion of GLP-1 were enhanced by total renal denervation (T-RDN) with acute surgical cutting of the renal nerves. Selective afferent renal nerve denervation (A-RDN) was performed by bilateral perivascular application of capsaicin on the renal nerves. Similar to T-RDN, A-RDN enhanced diuretic and natriuretic responses to GLP-1. Urine flow and Na⁺ excretion responses to GLP-1 were not significantly different between T-RDN and A-RDN groups. These results indicate that the diuretic and natriuretic effects of GLP-1 are partly governed via activation of afferent renal nerves by GLP-1 acting on sensory nerve fibers within the pelvis of the kidney.

Exercise training augments neuronal nitric oxide synthase dimerization in the paraventricular nucleus of rats with chronic heart failure

Exercise training (ExT) is an established non-pharmacological therapy that improves the health and quality of life in patients with chronic heart failure (CHF). Exaggerated sympathetic drive characterizes CHF due to an imbalance of the autonomic nervous system. Neuronal nitric oxide synthase (nNOS) in the paraventricular nucleus (PVN) produce nitric oxide (NO•), which is known to regulate the sympathetic tone. Previously we have shown that during CHF, the catalytically active dimeric form of nNOS is significantly decreased with a concurrent increase in protein inhibitor of nNOS (PIN) expression, a protein that dissociates dimeric nNOS to monomers and facilitates its degradation. Dimerization of nNOS also requires (6R)-5,6,7,8-tetrahydrobiopterin (BH4) for stability and activity. Previously, we have shown that ExT improves NO-mediated sympathetic inhibition in the PVN; however, the molecular mechanism remains elusive. We hypothesized; ExT restores the sympathetic drive by increasing the levels and catalytically active form of nNOS by abrogating changes in the PIN in the PVN of CHF rats. CHF was induced in adult male Sprague-Dawley rats by coronary artery ligation, which reliably mimics CHF in patients with myocardial infarction. After 4 weeks of surgery, Sham and CHF rats were subjected to 3 weeks of progressive treadmill exercise. ExT significantly (p < 0.05) decreased PIN expression and increased dimer/monomer ratio of nNOS in the PVN of rats with CHF. Moreover, we found decreased GTP cyclohydrolase 1(GCH1) expression: a rate-limiting enzyme for BH4 biosynthesis in the PVN of CHF rats suggesting that perhaps reduced BH4 availability may also contribute to decreased nNOS dimers. Interestingly, CHF induced decrease in GCH1 expression was increased with ExT. Our findings revealed that ExT rectified decreased PIN and GCH1 expression and increased dimer/monomer ratio of nNOS in the PVN, which may lead to increase NO• bioavailability resulting in amelioration of activated sympathetic drive during CHF.

Specific Afferent Renal Denervation Prevents Reduction in Neuronal Nitric Oxide Synthase Within the Paraventricular Nucleus in Rats With Chronic Heart Failure

Renal denervation (RDN) has been shown to restore endogenous neuronal nitric oxide synthase (nNOS) in the paraventricular nucleus (PVN) and reduce sympathetic drive during chronic heart failure (CHF). The purpose of the present study was to assess the contribution of afferent renal nerves to the nNOS-mediated sympathetic outflow within the PVN in rats with CHF. CHF was induced in rats by ligation of the left coronary artery. Four weeks after surgery, selective afferent RDN (A-RDN) was performed by bilateral perivascular application of capsaicin on the renal arteries. Seven days after intervention, nNOS protein expression, nNOS immunostaining signaling, and diaphorase-positive stained cells were significantly decreased in the PVN of CHF rats, changes that were reversed by A-RDN. A-RDN reduced basal lumbar sympathetic nerve activity in rats with CHF (8.5%±0.5% versus 17.0%±1.2% of max). Microinjection of nNOS inhibitor L-NMMA (L-N^G-monomethyl arginine citrate) into the PVN produced a blunted increase in lumbar sympathetic nerve activity in rats with CHF. This response was significantly improved after A-RDN (Δ lumbar sympathetic nerve activity: 25.7%±2.4% versus 11.2%±0.9%). Resting afferent renal nerves activity was substantially increased in CHF compared with sham rats (56.3%±2.4% versus 33.0%±4.7%). These results suggest that intact afferent renal nerves contribute to the reduction of nNOS in the PVN. A-RDN restores nNOS and thus attenuates the sympathoexcitation. Also, resting afferent renal nerves activity is elevated in CHF rats, which may highlight a crucial neural mechanism arising from the kidney in the maintenance of enhanced sympathetic drive in CHF.

Abstract P340: Variable Pressor and Sympathetic Responsiveness Reflects Neurotransmitter Imbalance in the Paraventricular Nucleus that is Prevented by Loss of Renal Sensory Nerves

The paraventricular nucleus of the hypothalamus (PVN), a key regulator of sympathetic activity, is dependent on a balance of excitatory (NMDA) and inhibitory (nNOS) neurotransmission. Ischemic heart failure (HF), hypertension and renal disease are associated with excessive NMDA and reduced nNOS in the PVN. Individuals with essential hypertension have greater sympathetic tone and exaggerated pressor responsiveness to acute behavioral stress. We observed variable pressor responsiveness in Sprague-Dawley and Borderline Hypertensive rats (SDR and BHR). We hypothesized that those SDR or BHR with greater pressor responses to stress have greater NMDA and/or reduced nNOS activity in PVN. We proposed that renal denervation (RDN) or deafferentation resolves the difference in stress responses and the PVN imbalance. We recorded arterial pressure (AP), and, in some rats, cardiac output and sympathetic nerve activity. After recovery, SDR and BHR were exposed to acute stress (1 cm deep cold water) repeatedly. Average AP responses were greater in male BHR compared to SDR (X=60±2 vs 49±1 mmHg). Responses were divided between those with AP responses greater or lesser than these means. SDR with larger pressor responses (LP), had elevated NMDA NR1 mRNA and protein levels in the PVN and reduced nNOS mRNA (p<0.05). Likewise, in female BHR, larger AP responses (X=57±3 mmHg) LP had greater NMDA NR1 mRNA and protein in the PVN and reduced nNOS protein. Therefore, the imbalance in PVN exists in normotensive rats and correlates with greater AP and sympathetic responses predisposing an individual to cardiovascular disease. In related studies in male SDR and BHR, we examined the effects of RDN on acute stress responses to cold water and to air jet. In both rat strains, RDN or selective renal deafferentation with capsaicin or resiniferatoxin selectively prevented the exaggerated AP responses only in LP rats. Finally, RDN or deafferentation reversed the HF-induced increase in sympathetic nerve activity and the increase NADPH-diaphorase and nNOS staining and protein levels in the PVN. These data suggest that renal sensory nerves are responsible for variable excitatory and inhibitory influences in the PVN that contribute to the predisposition to cardiovascular disease.

Abstract 106: Central Angiotensin II Mediates Neurogenic Hypertension Through Post-Translational Regulation of Neuronal Nitric Oxide Synthase in the Paraventricular Nucleus of the Hypothalamus

Activation of renin-angiotensin- system, nitric oxide (NO) bioavailability and subsequent sympathoexcitation plays a pivotal role in the pathogenesis of many cardiovascular diseases including hypertension. Previously we have shown Ang II enhances PIN (a protein inhibitor of nNOS: neuronal nitric oxide synthase, known to dissociate nNOS dimers into monomers) mediated ubiquitination of nNOS in the PVN of rats with heart failure. To further elucidate the mechanism by which Ang II increases sympathetic outflow by regulating PIN mediated nNOS ubiquitination, we used Sprague-Dawley rats (250-300 g) subjected to intracerebroventricular infusion of Ang II (20 ng/min, 14days, 0.5μl/h) through osmotic mini-pumps and NG108-15 hybrid neuronal cell line treated with Ang II as an in vitro model. Ang II infusion increased baseline mean arterial pressure (126 ± 9* vs. 84 ± 4 mmHg) and renal sympathetic nerve activity (20.5 ± 2.3* vs. 6.4 ± 1.9 % of Max. Activity). Ang II infusion increased the expression of PIN (1.36 ± 0.04* Ang II vs. 0.81 ± 0.02 Veh) with a concomitant 52% decrease in dimeric nNOS and PIN-Ub conjugates (0.73 ± 0.04* Ang II vs. 1 ± 0.03 Veh) in the PVN. Further, Ang II-mediated increase in PIN expression(0.67±0.06* CHX AngII vs. 0.40±0.08 CHX 0h) was independent of CHX (protein synthesis inhibitor) mediated decrease in PIN expression (0.41±0.06* CHX AngII vs. 0.19±0.04 CHX 4h) suggesting Ang II-mediated post-translational stabilization of PIN. Substrate-dependent ligase assay in cells transfected with pCMV-(HA-Ub)8 vector revealed a reduction of HA-Ub-PIN conjugates after Ang II and proteasome inhibitor lactacystin (LC) treatment (4.5 ± 0.6* LC Ang II vs. 9.2 ± 2.2 LC). TUBE (Tandem Ubiquitin-Binding Entities) assay showed decrease PIN-Ub conjugates in Ang II-treated cells (0.82 ± 0.12* LC Ang II vs. 1.23 ± 0.05 LC) while AT1R blocker Losartan(Los) treatment diminishes the Ang II-mediated stabilization of PIN (1.21 ± 0.07 LC Los vs. 1.14 ± 0.04* LC AngII Los). Taken together, our studies suggest that increased central levels of Ang II contribute to the enhanced expression of PIN leading to reduced expression of the dimeric form of nNOS, thus diminishing the inhibitory action of NO on pre-autonomic neurons in the PVN resulting in an increase in sympathetic outflow.