Increased Plasma Norepinephrine Research Articles

Microglia Mediate Hypertension and Autonomic Dysfunction through Kinin B1 Receptor Activation

Reactive oxygen species and proinflammatory cytokines in the central nervous system can induce or exacerbate hypertension (HTN) and result in autonomic dysfunction. During HTN, activated microglia modulates autonomic neural activity in the paraventricular nucleus of the hypothalamus (PVN) by regulating neuroinflammation and blood pressure. We previously reported that enhanced kinin B1 receptor (B1R) expression in the brain is associated with increased neuroinflammation and autonomic dysfunction leading to the development of HTN. However, the functional role of B1R within microglia and signaling mechanisms during HTN have yet to be investigated. In this study, we tested the hypothesis that B1R blockade will reduce oxidative stress and mitochondrial dysfunction in microglia, resulting in an attenuation of hypertension and improved autonomic function. Male and female C57BL/6NJ wild-type (WT) and B1R global gene deficient mice (B1RKO) were administered angiotensin II (Ang II) (600 ng/kg/min; SC, 2 weeks) or saline (vehicle) via osmotic minipumps. Ang II infusion significantly increased mean arterial pressure (radiotelemetry) in WT mice (145 ±13 mmHg vs. 103 ±6, n=6, p<0.01), which was attenuated in B1RKO mice. Ang II induced HTN resulted in dysautonomia as indicated by significantly increased plasma norepinephrine levels (p<0.05, n=6) and decreased spontaneous baroreceptor reflex sensitivity (p<0.05, n=6). This further suggests that B1R contributes to impaired autonomic and baroreflex functions in HTN. In addition, CX3CR1 expression in the PVN revealed that microglia-neuron interactions may be increased during HTN. TMEM119 immunofluorescence revealed significant morphological changes in microglia in the PVN of Ang II infused mice compared to saline controls (p<0.05, n=3). To further define the role of microglia, we cultured primary microglia from neonatal mice and found that Ang II induces mitochondrial oxidative stress (MitoSOX) and decreases mitochondrial membrane potential (TMRE) (p<0.01, n=4), however use of B1R specific antagonist SSR240612 was able to reduce these responses. This data coincides with previous data published in primary hypothalamic neurons. To then explore the role of neuron-microglia interactions following Ang II stimulation, we established a direct co-culturing method and through immunocytochemistry, confirmed that levels of oxidative stress and inflammation were significantly increased in our co-culture model compared to when cultured individually (p<0.05, n=3). Pretreatment with B1R antagonist was able to attenuate these effects. This data indicates that autonomic and mitochondrial dysfunction may be regulated, in part, through the kinin B1 receptor in microglia and that neuron-microglia interactions can enhance these effects. This allows us to believe that B1R blockade may serve as a potential therapeutic target for HTN induced mitochondrial and autonomic dysfunction. This study was supported by the NHLBI/NIH 5R01HL153115 (S. Sriramula). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Circulating noradrenaline leads to release of neuropeptide Y from cardiac sympathetic nerve terminals via activation of β-adrenergic receptors.

Cardiac disease is marked by sympathoexcitation and elevated levels of noradrenaline (NA) and cotransmitter neuropeptide Y (NPY). Increased NPY levels are associated with a greater risk of ventricular arrhythmias and mortality. Nonetheless, the factors that cause NPY release remain poorly understood. We hypothesized that circulating catecholamines might lead to NPY release from myocardial sympathetic nerve terminals via a β-receptor-mediated mechanism that enhances sympathoexcitation. Ventricular interstitial NA and NPY levels were measured in six Yorkshire pigs after i.v. administration of NA (1mg) and before and after propranolol infusion (1mg/kg). Real-time interstitial NPY levels were measured using ventricular capacitive immunoprobes (CIs) affixed with NPY antibodies and quantified as the change in CI input current (INPY ) upon binding of NPY. Interstitial NA was measured with adjacent fast-scan cyclic voltammetry probes (INA ). A left ventricular pressure catheter and continuous ECGs were used for haemodynamic recordings, and an epicardial 56-electrode sock was used for measurements of activation recovery interval, a surrogate of action potential duration. Upon administration of NA, heart rate and left ventricular pressure increased, and activation recovery interval shortened. Notably, NA significantly increased interstitial myocardial NPY levels. After propranolol, changes in heart rate and activation recovery interval were largely mitigated. The INA increased to a similar extent post-propranolol vs. pre-propranolol, but changes in INPY were significantly reduced post-propranolol. Coronary sinus plasma analyses confirmed fast-scan cyclic voltammetry and CI findings. Hence, this study demonstrates that circulating NA induces NPY release from ventricular sympathetic nerve terminals, the mechanism for which is mediated via β-adrenergic receptors and can be blocked by the non-selective β-blocker, propranolol. KEY POINTS: Cardiovascular disease is characterized by sympathovagal imbalance, with increased plasma noradrenaline (NA) and neuropeptide Y (NPY) concentrations. Increased NPY levels are associated with increased ventricular arrhythmias and mortality in heart failure. Limited data are available on the specific factors that cause NPY release. In this study, fast-scan cyclic voltammetry and capacitive immunoprobes were used to allow for real-time in vivo measurements of interstitial myocardial neurotransmitters and neuropeptides, respectively. Using an in vivo porcine model with cardiac fast-scan cyclic voltammetry and capacitive immunoprobes, it was shown that systemic NA can increase ventricular interstitial NPY levels, suggesting that NA induces NPY release from postganglionic sympathetic nerves. The release of NPY was blocked by administration of the non-selective β-blocker propranolol, suggesting that release of NPY is dependent on activation of β-adrenergic receptors by NA.

Sympathetic dysfunction is associated with worse fatigue and early and subtle symptoms in heart failure: an exploratory sex-stratified analysis.

Physical symptoms impact patients with heart failure (HF) despite treatment advancements; however, our understanding of the pathogenic mechanisms underlying HF symptoms remains limited, including sex differences therein. The objective of this study was to quantify associations between sympathetic markers [norepinephrine (NE) and 3,4-dihydroxyphenylglycol (DHPG)] and physical symptoms in patients with HF and to explore sex differences in these associations. We performed a secondary analysis of combined data from two studies: outpatients with HF (n = 111), and patients prior to left ventricular assist device implantation (n = 38). Physical symptoms were measured with the Heart Failure Somatic Perception Scale (HFSPS) dyspnoea and early/subtle symptom subscales and the Functional Assessment in Chronic Illness Therapy Fatigue Scale (FACIT-F) to capture dyspnoea, early symptoms of decompensation, and fatigue. Norepinephrine and DHPG were measured with high-performance liquid chromatography with electrochemical detection. Multivariate linear regression was used to quantify associations between symptoms and sympathetic markers. The sample (n = 149) was 60.8 ± 15.7 years, 41% women, and 71% non-ischaemic aetiology. Increased plasma NE and NE:DHPG ratio were associated with worse FACIT-F scores (P = 0.043 and P = 0.013, respectively). Increased plasma NE:DHPG ratio was associated with worse HFSPS early/subtle symptoms (P = 0.025). In sex-stratified analyses, increased NE:DHPG ratio was associated with worse FACIT-F scores (P = 0.011) and HFSPS early/subtle scores (P = 0.022) among women but not men. In patients with HF, sympathetic dysfunction is associated with worse fatigue and early/subtle physical symptoms with associations stronger in women than men.

240-LB: Unrestrained Sympathetic Signaling Is a Key Driver of Obesity-Induced Insulin Resistance

Obesity is the major driver of type 2 diabetes. The mechanisms that account for overnutrition induced insulin resistance are yet to be delineated as impaired cellular insulin signaling may or may not account for the impaired insulin action. We find that overnutrition rapidly impairs insulin action and increase plasma norepinephrine, suggesting heightened activation of the sympathetic nervous system (SNS), possibly due to brain insulin resistance as earlier studies from our group suggested. Here, we hypothesize that unrestrained SNS activity (SNA) is a key driver of obesity induced insulin resistance. To test this hypothesis, we examined a mouse model of inducible and peripherally restricted tyrosine hydroxylase (th) gene deletion (THΔper) that have profoundly lower catecholamine levels in peripheral tissues is protected from high fat diet (HFD) induced insulin resistance. Despite similar food intake, obesity and cellular insulin signaling in liver and adipose tissue, THΔper mice were protected from both short-term and long-term HFD feeding-induced glucose intolerance, increases in plasma catecholamines and hyperglucagonemia. Hyperinsulinemic euglycemic clamp studies revealed that overnutrition induced hepatic insulin resistance was markedly ameliorated in the THΔper mice, even though cellular insulin signaling in liver and adipose tissue was comparable. Moreover, THΔper mice were protected from HFD-induced adipose tissue dysfunction characterized by reduced lipogenic capacity, unrestrained lipolysis and increased low-grade inflammation as well as hepatic steatosis, possibly due to decreased lipolytic flux and hepatic de novo lipogenesis. In addition, fibrosis genes were markedly reduced in the liver of the THΔper mice, suggesting that reducing SNA can prevent metabolic dysfunction-associated fatty liver disease. These results demonstrate that unrestrained SNA is a pivotal driver of insulin resistance, hyperglucagonemia and metabolic dysfunction in obesity. Disclosure K. Sakamoto: None. G. Maurizi: None. B. Chen: None. A. Shawkat: None. L. Patlolla: None. A. Tahiri: None. A. Butera: None. C. Buettner: None.

Cerebrovascular regulation in patients with vasovagal syncope and autonomic failure due to familial amyloidotic polyneuropathy.

While there is strong evidence for autonomic involvement in cerebrovascular function acutely, long-term role of autonomic nervous system in cerebrovascular function has been controversial. We assessed autoregulation in 10 healthy individuals, nine patients with vasovagal syncope (VVS), and nine with Familial Amyloidotic Polyneuropathy (FAP), in response to head-up tilt test (HUTT). Arterial blood pressure heart rate, cardiac output, and bilateral cerebral blood flow velocity (CBFV) at the M1 segment of middle cerebral artery (transcranial Doppler ultrasound) were recorded during supine rest and 70° HUTT. Autoregulation was quantified using a validated nonlinear and nonparametric approach based on projection pursuit regression. Plasma adrenaline and noradrenaline were also measured at rest and during HUTT. During supine rest and HUTT, plasma noradrenaline content was lower in FAP patients. During HUTT, VVS patients had a hyperadrenergic status; CBFV decreased in all groups, which was greater in FAP patients (p<0.01). Healthy controls responded to HUTT with a reduction in CBFV responses to increases (p=0.01) and decreases (p<0.01) in arterial pressure without any change in the range or effectiveness of autoregulation. VVS patients responded to HUTT with a reduction in falling (p=0.02), but not rising slope (p=0.40). Autoregulatory range (p<0.01) and effectiveness increased (p=0.09), consistent with the rapid increase in levels of catecholamines. In FAP patients, the level of increase in range of autoregulation was significantly related to the magnitude of increase in plasma noradrenaline in response to HUTT (R2=0.26, p=0.05). Autonomic dysfunction affects the cerebral autoregulatory response orthostatic to challenge.

Brain fog in neuropathic postural tachycardia syndrome may be associated with autonomic hyperarousal and improves after water drinking.

BackgroundBrain fog is a common and highly disturbing symptom for patients with neuropathic postural tachycardia syndrome (POTS). Cognitive deficits have been measured exclusively in the upright body position and mainly comprised impairments of higher cognitive functions. The cause of brain fog is still unclear today. This study aimed to investigate whether increased autonomic activation might be an underlying mechanism for the occurrence of brain fog in neuropathic POTS. We therefore investigated cognitive function in patients with neuropathic POTS and a healthy control group depending on body position and in relation to catecholamine release as a sensitive indicator of acute stress. The second aim was to test the effect of water intake on cardiovascular regulation, orthostatic symptoms, cognitive function and catecholamine release.MethodsThirteen patients with neuropathic POTS and 15 healthy control subjects were included. All participants completed a total of four rounds of cognitive testing: two before and two after the intake of 500 ml still water, each first in the supine position and then during head-up tilt. At the end of each cognitive test, a blood sample was collected for determination of plasma catecholamines. After each head-up tilt phase participants were asked to rate their current symptoms on a visual analogue scale.ResultsWorking memory performance in the upright body position was impaired in patients, which was associated with self-reported symptom severity. Patients had elevated plasma norepinephrine independent of body position and water intake that increased excessively in the upright body position. The excessive increase of plasma norepinephrine was related to heart rate and symptom severity. Water intake in patients decreased norepinephrine concentrations and heart rate, and improved symptoms as well as cognitive performance.ConclusionBrain fog and symptom severity in neuropathic POTS are paralleled by an excessive norepinephrine secretion. Bolus water drinking down-regulates norepinephrine secretion and improves general symptom severity including brain fog.

Glucose infusion suppresses acute restraint stress-induced peripheral and central sympathetic responses in rats.

Acute restraint stress (RS) induces sympathetic activation such as elevating plasma catecholamines, resulting in increase in blood glucose. We aimed to investigate whether glucose infusion affects the RS-induced sympathetic responses. Plasma catecholamines were measured by high-performance liquid chromatography with electrochemical detection. Blood glucose levels were measured with a glucometer and a glucose assay kit. Cardiac parameters were measured by echocardiographic and hemodynamic analysis. Prostanoid levels in the paraventricular nucleus of hypothalamus (PVN) microdialysates were measured by liquid chromatography-ion trap tandem mass spectrometry analysis. RS significantly increased plasma noradrenaline and adrenaline. Intravenous infusion of a 5% glucose solution significantly attenuated the RS-induced elevation of plasma adrenaline but did not alter the plasma noradrenaline. Glucose administration during RS suppressed the progression of cardiac impairment by attenuating the decline rates in left ventricular diastolic, end-diastolic volume, stroke volume, fractional shortening, and ejection fraction. Both Intravenous and intracerebroventricular infusion of glucose solution significantly attenuated the RS-induced elevation of thromboxane B2 (TxB2) (a metabolite of TxA2) levels in the PVN but did not alter prostaglandin E2 levels in the PVN. Our results demonstrate that glucose infusion suppresses RS-induced elevation of plasma adrenaline and left ventricular dysfunction. In the brain, glucose infusion suppresses RS-induced production of TxA2 in the PVN.

Blockade of Microglial Activation in Hypothalamic Paraventricular Nucleus Improves High Salt-Induced Hypertension.

It has been shown that activated microglia in brain releasing proinflammatory cytokines (PICs) contribute to the progression of cardiovascular diseases. In this study, we tested the hypothesis that microglial activation in hypothalamic paraventricular nucleus (PVN), induced by high-salt diet, increases the oxidative stress via releasing PICs and promotes sympathoexcitation and development of hypertension. High-salt diet was given to male Dahl salt-sensitive rats to induce hypertension. Those rats were bilaterally implanted with cannula for PVN infusion of minocycline, a selective microglial activation blocker, or artificial cerebrospinal fluid for 4 weeks. High-salt diet elevated mean arterial pressure of Dahl salt-sensitive rats. Meanwhile, elevations of renal sympathetic nerve activity and central prostaglandin E2, as well as increase of plasma norepinephrine, were observed in those hypertensive rats. Tumor necrosis factor-α, interleukin-1β (IL-1β), and IL-6 increased in the PVN of those rats, associated with a significant activation of microglia and prominent disruption of redox balance, which was demonstrated by higher superoxide and NAD(P)H oxidase 2 (NOX-2) and NAD(P)H oxidase 4 (NOX-4), and lower Cu/Zn superoxide dismutase in PVN. PVN infusion of minocycline attenuated all hypertension-related alterations described above. This study indicates that high salt leads to microglial activation within PVN of hypertensive rats, and those activated PVN microglia release PICs and trigger the production of reactive oxygen species, which contributes to sympathoexcitation and development of hypertension. Blockade of PVN microglial activation inhibits inflammation and oxidative stress, therefore attenuating the development of hypertension induced by high-salt diet.

Effects of Fatty Acid Amide Hydroxylase Inhibitor URB597 on the Catecholaminergic Activity of the Adrenal Medulla in Stressed Male and Female Rats

Introduction: The present study examined the effects of fatty acid amide hydrolase inhibitor URB597 on the level of plasma catecholamine and their content, synthesis, and degradation in the adrenal medulla of male and female rats subjected to chronic unpredictable stress (CUS). Material and Methods: Male and female Wistar rats were exposed to the 6 weeks of CUS and treated intraperitoneally with either 0.3 mg/kg/day of URB597 or vehicle in the last 2 weeks of stress protocol. Catecholamines’ plasma levels and catecholamines’ levels in adrenal medulla were examined using Elabscience ELISA kits. Western blot analysis was used to detect the protein in the medulla. Results: The results of our experiment showed that adrenal weights and catecholamine of unstressed control were higher in females and that CUS induced further enlargement of adrenal glands and catecholamine content and its synthesis compared to male rats. CUS caused an increase of plasma norepinephrine and depletion of norepinephrine content as well as unchanged synthesis and degradation of catecholamine in the adrenal medulla of male rats. URB597 reduced enlarged adrenals and catecholamine content and its synthesis in stressed female rats. URB597 reduces increased plasma norepinephrine and restores its content in the adrenal medulla, unchanging the expression of enzyme synthesis, while reduced protein levels of monoamine oxidase A in male rats are exposed to CUS. Discussion: Our results support the role of endocannabinoids as an antistress mechanism that inhibits elevated adrenomedullary activation and promotes its recovery to baseline in both male and female stressed rats.

Anti-hypotensive effect of “Yahom Navakot” in rats with orthostatic hypotension

Background and aimYahom Navakot (YN), is a Thai traditional medicine, consisting of 54 plants, for treating fainting and dizziness. Thus, YN might relieve orthostatic hypotension (OH) symptoms, but its therapeutic action is unclear. Therefore, this study evaluated YN in OH rats, using a head-up tilt test (HUT). Experimental procedureRats were anesthetized, and OH induced via a 90oHUT, before and after administering vehicle, a YN powder suspension (10, 100 mg/kg), a YN aqueous extract (100 mg/kg), and midodrine (5 mg/kg). The systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial blood pressure (MAP), pulse pressure (PP) and heart rate (HR) were determined via the carotid artery. Plasma noradrenaline (NA) was evaluated. YN-induced vasoconstriction of isolated rat aorta rings was determined using organ bath technique. Results and conclusionBaseline BP increased with the 100 mg/kg YN powder suspension, the YN aqueous extract or midodrine, while HR decreased, compared with vehicle and control. 90oHUT rapidly reduced SBP, DPB and MAP, but increased HR, for control and vehicle-treated groups, but BP was steady with the 100 mg/kg YN powder suspension, the YN aqueous extract or midodrine. The 90oHUT-increase in HR was most pronounced with the 100 mg/kg YN powder suspension (the traditional formulation). This accords with increased plasma NA. YN also induced vasoconstriction in rat aorta via α1-receptor activation. Thus, the anti-hypotensive action of YN involved a stimulating effect on the heart and blood vessels via sympathetic activation. The results support the traditional use of YN and demonstrated the effectiveness of YN for OH prevention.

Mercury in the human adrenal medulla could contribute to increased plasma noradrenaline in aging

Plasma noradrenaline levels increase with aging, and this could contribute to the sympathetic overactivity that is associated with essential hypertension and the metabolic syndrome. The underlying cause of this rise in noradrenaline is unknown, but a clue may be that mercury increases noradrenaline output from the adrenal medulla of experimental animals. We therefore determined the proportion of people from 2 to 104 years of age who had mercury in their adrenal medulla. Mercury was detected in paraffin sections of autopsied adrenal glands using two methods of elemental bioimaging, autometallography and laser ablation-inductively coupled plasma-mass spectrometry. Mercury first appeared in cells of the adrenal medulla in the 21–40 years group, where it was present in 52% of samples, and increased progressively in frequency in older age groups, until it was detected in 90% of samples from people aged over 80 years. In conclusion, the proportion of people having mercury in their adrenal medulla increases with aging. Mercury could alter the metabolism of catecholamines in the adrenal medulla that leads to the raised levels of plasma noradrenaline in aging. This retrospective autopsy study was not able to provide a definitive link between adrenal mercury, noradrenaline levels and hypertension, but future functional human and experimental studies could provide further evidence for these associations.

Plasma brain natriuretic peptide level on admission predicts long-term outcome in patients with non-traumatic subarachnoid hemorrhage

IntroductionNon-traumatic subarachnoid hemorrhage (SAH) is a type of stroke that still has a high mortality rate. Some patients with SAH have electrocardiography (ECG) abnormalities or asymptomatic left ventricular apical ballooning, and requires intervention by cardiologists. However, the impact of cardiac abnormalities after SAH onset remains unclear. We investigated whether ECG abnormalities, myocardial damage, sympathetic nervous activity or echocardiographic left ventricular wall motion abnormalities (WMA) could provide additional risk stratification in patients with SAH. MethodsWe studied 118 SAH patients (78 women, age 63 ± 15) without a history of heart disease. Neurological grade (Hunt and Kosnik Grade) and clinical factors were evaluated. A standard 12-lead ECG, echocardiography and blood samples were obtained within 48 h after SAH onset. ECG abnormalities were defined as abnormal Q wave, ST elevation, giant T-wave inversion or QT prolongation. ResultsTwenty of 118 patients (17%) died during the follow-up (35 ± 31 months). Death was significantly associated with higher age (p < 0.0001), neurological grade (p < 0.0001), elevated BNP level (p < 0.0001), increased plasma norepinephrine levels (p < 0.0001) and WMA (p = 0.0070), while ECG abnormalities were not significantly associated. Neurological grade (p < 0.0001), age (p = 0.0047) and BNP (p = 0.0014, hazard ratio 1.0255 for each 1 pg/mL increase in BNP, 95%CI 1.0088 to 1.0499) were independently associated with death. Patients with BNP ≥ 96.6 had a higher risk of death (log- rank p < 0.0001). ConclusionPlasma BNP might provide an additional risk stratification in patients with non-traumatic SAH that requires intervention by cardiologists for both its prevention management after onset.

Upright Cheyne-Stokes Respiration in Patients With Heart Failure

BackgroundCheyne-Stokes respiration (CSR) is believed to only occur in supine and sleeping conditions, and thus, CSR treatment is applied to those specific states. Although CSR has also been described in patients with heart failure (HF) during wakefulness, its persistence in an upright position is still unknown. ObjectivesThe purpose of this study was to assess the predictors, clinical correlates, and prognostic value of diurnal CSR in upright position. MethodsOutpatients with systolic HF underwent a comprehensive evaluation, including short-term respiratory monitoring with a head-up tilt test to investigate the presence of upright CSR, assessment of chemoreflex response to hypoxia and hypercapnia, and 24-h cardiorespiratory recording. At follow-up, cardiac death was considered as the endpoint. ResultsOf 574 consecutive patients (left ventricular ejection fraction 32 ± 9%; age 65 ± 13 years; 80% men), 195 (34%) presented supine CSR only, 82 (14%) presented supine and upright CSR, and 297 patients (52%) had normal breathing. Patients with upright CSR had the greatest apnea-hypopnea and central apnea index (at daytime and nighttime), the worst hemodynamic profile and exercise performance, increased plasma norepinephrine and N-terminal pro–B-type natriuretic peptide, and chemosensitivity to hypercapnia, which was the only independent predictor of upright CSR (odds ratio: 3.96; 95% confidence interval [CI]: 1.45 to 10.76; p = 0.007 vs. normal breathing; odds ratio: 4.01; 95% CI: 1.54 to 10.46; p = 0.004 vs. supine CSR). At 8-year follow-up, patients with upright CSR had the worst outcome (log-rank = 14.05; p = 0.001) and the presence of upright CSR independently predicted 8-year cardiac death (hazard ratio: 2.39; 95% CI: 1.08 to 5.29; p = 0.032). ConclusionsUpright CSR in HF patients is predicted by increased chemosensitivity to hypercapnia and is associated with worse clinical conditions and with a greater risk of cardiac death.

Differences in correlations of depression and anhedonia with cardiovascular sympathetic functions during a head-up tilt test in drug-naïve Parkinson's disease patients.

Depression is a symptom of Parkinson's disease (PD) and may be correlated with cardiovascular sympathetic function. Anhedonia is an element of depression, but these symptoms can emerge independently in PD. A correlation of anhedonia with cardiovascular sympathetic function has rarely been examined. To compare correlations of depression and anhedonia with cardiovascular sympathetic function in drug-naive PD patients. Assessments of depression (Self-rating Depression Scale; SDS), anhedonia (Snaith-Hamilton Pleasure Scale; SHAPS), myocardial 123I-MIBG (123I-meta-iodobenzylguanidine) scintigraphy (heart to mediastinum (H/M) ratios in early and delayed images), and head-up tilt test (HUT) up to 60° for 10min were performed in 45 drug-naïve PD patients. During the HUT, blood pressure was measured every minute and the maximum decrease in systolic blood pressure (SBP) was determined. Plasma noradrenaline (NA) and arginine vasopressin (AVP) levels were examined at baseline and 10min after tilt, with subsequent calculation of increases in plasma NA and AVP levels in this 10min. Correlation coefficients were calculated among these assessment parameters. SDS significantly correlated with % maximum decrease in SBP (r = 0.344, p = 0.02), but not with H/M ratios in both images and increases in plasma NA and AVP levels. SHAPS did not correlate with the change in SBP, H/M ratios in both images, or plasma NA and AVP levels. Depression was correlated with the % maximum decrease in SBP during a 10-min HUT, but anhedonia did not show this relationship. This suggests that depression and anhedonia may have different pathophysiological backgrounds in drug-naïve PD patients.

Inhibition of microglial activation in rats attenuates paraventricular nucleus inflammation in Gαi2 protein-dependent, salt-sensitive hypertension.

New Findings • What is the central question of this study? We hypothesized that central inflammatory processes that involve activation of microglia and astrocytes contribute to the development of Gαi2 protein‐dependent, salt‐sensitive hypertension.• What is the main finding and its importance? The main finding is that PVN‐specific inflammatory processes, driven by microglial activation, appear to be linked to the development of Gαi2 protein‐dependent, salt‐sensitive hypertension in Sprague–Dawley rats. This finding might reveal new mechanistic targets in the treatment of hypertension. The central mechanisms underlying salt‐sensitive hypertension, a significant public health issue, remain to be established. Researchers in our laboratory have reported that hypothalamic paraventricular nucleus (PVN) Gαi2 proteins mediate the sympathoinhibitory and normotensive responses to high sodium intake in salt‐resistant rats. Given the recent evidence of central inflammation in animal models of hypertension, we hypothesized that PVN inflammation contributes to Gαi2 protein‐dependent, salt‐sensitive hypertension. Male Sprague–Dawley rats received chronic intracerebroventricular infusions of a targeted Gαi2 or control scrambled oligodeoxynucleotide (ODN) and were maintained for 7 days on a normal‐salt (NS; 0.6% NaCl) or high‐salt (HS; 4% NaCl) diet; in subgroups on HS, intracerebroventricular minocycline (microglial inhibitor) was co‐infused with ODNs. Radiotelemetry was used in subgroups of rats to measure mean arterial pressure (MAP) chronically. In a separate group of rats, plasma noradrenaline, plasma renin activity, urinary angiotensinogen and mRNA levels of the PVN pro‐inflammatory cytokines TNFα, IL‐1β and IL‐6 and the anti‐inflammatory cytokine IL‐10 were assessed. In additional groups, immunohistochemistry was performed for markers of PVN and subfornical organ microglial activation and cytokine levels and PVN astrocyte activation. High salt intake evoked salt‐sensitive hypertension, increased plasma noradrenaline, PVN pro‐inflammatory cytokine mRNA upregulation, anti‐inflammatory cytokine mRNA downregulation and PVN‐specific microglial activation in rats receiving a targeted Gαi2 but not scrambled ODN. Minocycline co‐infusion significantly attenuated the increase in MAP and abolished the increase in plasma noradrenaline and inflammation in Gαi2 ODN‐infused animals on HS. Our data suggest that central Gαi2 protein prevents microglial‐mediated PVN inflammation and the development of salt‐sensitive hypertension.

Coping Style of Pigs Is Associated With Different Behavioral, Neurobiological and Immune Responses to Stressful Challenges.

Based on the animal’s reaction to environmental challenges, consistent but different coping styles can be identified, which in turn may have consequences for health and welfare. Therefore, profound knowledge of the complex interrelationships between individual behavioral response patterns, underlying neurobiological mechanisms and immunological effects is required. The aim of this study was to examine whether pigs with different coping styles exhibit distinct behavioral, neurobiological and immune responses to stressful situations. Therefore, pigs (n = 40) were classified as proactive, reactive or intermediate animals according to a repeatedly-performed backtest, and behavioral, neuroendocrine and immune alterations were analyzed without any stress before weaning on day 28 and after a stress treatment on day 32. Our results show that the behavioral responses in an open-field/novel-object test characterized proactive pigs as more active. There were no significant differences in adrenocorticotropic hormone and cortisol concentrations between pigs with different coping characteristics. However, we found that proactive pigs displayed significantly increased plasma noradrenaline levels in response to stress, which may reflect a higher sympathetic reactivity of these animals. Furthermore, the present study revealed coping style differences in mRNA expression of mineralocorticoid, glucocorticoid, oxytocin and arginine vasopressin receptors and the immediate early gene c-fos in stress-related brain regions. While proactive pigs responded to stress with higher mRNA expression of arginine vasopressin, mineralocorticoid and glucocorticoid receptors, reactive pigs displayed higher oxytocin receptor and c-fos mRNA expression, indicating different neurobiological mechanisms of distinct coping styles in response to stressful challenges. Moreover, we also found humoral immune differences between proactive, intermediate and reactive animals. Proactive pigs had a higher total serum IgA concentration before and after stress treatment, with a significant increase in response to stress compared to reactive and intermediate pigs. In contrast, stress-induced IgM concentrations only increased in reactive and intermediate animals, suggesting that the effects of coping style on humoral immunity may differ depending on the specific function of the immunoglobulin classes. In conclusion, this multidisciplinary study expands the concept of coping style in farm animals, particularly in terms of individual stress reactivity and disease susceptibility, and thus contributes to the understanding of the biology of animal welfare.

Suppressed baroreflex peripheral arc overwhelms augmented neural arc and incapacitates baroreflex function in rats with pulmonary arterial hypertension.

What is the central question of this study? The impact of pulmonary arterial hypertension on open-loop baroreflex function, which determines how powerfully and rapidly the baroreflex operates to regulate arterial pressure, remains poorly understood. What is the main finding and its importance? The gain of the baroreflex total arc, indicating the baroreflex pressure-stabilizing function, is markedly attenuated in rats with monocrotaline-induced pulmonary arterial hypertension. This is caused by a rightward shift of the baroreflex neural arc and a downward shift of the peripheral arc. These findings contribute greatly to our understanding of arterial pressure regulation by the sympathetic nervous system in pulmonary arterial hypertension. Sympathoexcitation has been documented in patients with established pulmonary arterial hypertension (PAH). Although the arterial baroreflex is the main negative feedback regulator of sympathetic nerve activity (SNA), the way in which PAH impacts baroreflex function remains poorly understood. In this study, we conducted baroreflex open-loop analysis in a rat model of PAH. Sprague-Dawley rats were injected with monocrotaline (MCT) s.c. to induce PAH (60mgkg-1 ; n=11) or saline as a control group (CTL; n=8). At 3.5weeks after MCT injection, bilateral carotid sinuses were isolated, and intrasinus pressure (CSP) was controlled while SNA at the coeliac ganglia and arterial pressure (AP) were recorded. To examine the static baroreflex function, CSP was increased stepwise while steady-state AP (total arc) and SNA (neural arc) responses to CSP and the AP response to SNA (peripheral arc) were measured. Monocrotaline significantly decreased the static gain of the baroreflex total arc at the operating AP compared with CTL (-0.80±0.31 versus -0.22±0.22, P<0.05). Given that MCT markedly increased plasma noradrenaline, an index of SNA, by approximately 3.6-fold compared with CTL, calibrating SNA by plasma noradrenaline revealed that MCT shifted the neural arc to a higher SNA level and shifted the peripheral arc downwards. Monocrotaline also decreased the dynamic gain of the baroreflex total arc (-0.79±0.16 versus -0.35±0.17, P<0.05), while the corner frequencies that reflect the speed of the baroreflex remained unchanged (0.06±0.02 versus 0.08±0.02Hz, n.s.). In rats with MCT-induced PAH, the suppressed baroreflex peripheral arc overwhelms the augmented neural arc and, in turn, attenuates the gain of the total arc, which determines the pressure-stabilizing capacity of the baroreflex.

Inhibition of Microgliosis with Minocycline Attenuates Central Inflammation Driving Gαi2 Protein Dependent Sympathetically Mediated Salt Sensitive Hypertension

AimPrevious work in our laboratory has established that hypothalamic PVNGαi2 proteins mediate sympathoinhibitory responses to high dietary sodium. Downregulation of these proteins is implicated in salt sensitive hypertension, and central inflammation may play a role in the pathogenesis of salt sensitive hypertension by increasing sympathetic outflow. We hypothesize that microglial‐mediatedPVN inflammation contributes to salt sensitive hypertension (HTN) that develops following central Gαi2 protein down regulation.Methods3‐month‐old male Sprague Dawley rats were implanted with I.C.V. cannulas fitted to osmotic minipumps to deliver an infusion of either Gαi2 or scrambled oligodeoxynucleotides (ODN) (25μg/5μl/day) and were then put on a 7‐day time course of either high (HS; 4% NaCl) or normal (NS; 0.6% NaCl) salt diets (n=6 per group), and instrumented on day 7 with a femoral cannula to measure blood pressure (BP) and obtain arterial blood for plasma norepinephrine (NE) analysis by ELISA. Rats were then sacrificed via transcardial perfusion and brains were extracted and fixed in 4% paraformaldehyde and 30% sucrose. Immunohistochemistry (IHC) was performed for markers of microglial activation and astrocyte activation, assessed via ImageJ analysis, and mRNA levels of pro‐inflammatory cytokines (PIC) TNFα, IL‐1β, and IL‐6 and anti‐inflammatory cytokine (AIC) IL‐10 in the PVN were analyzed. We additionally co‐infused a separate group of animals with minocycline, an inhibitor of microglial activation, and ODNs (n=6 per group), to abolish inflammatory responses and ran the same assessment for PIC upregulation, BP, and plasma NE.ResultsDownregulation of PVN Gαi2 proteins in combination with a HS diet resulted in significant increases in blood pressure, as well as significant increases in plasma NE. In our control, scrambled ODN infused animals on HS, there was a suppression of plasma NE as well as an increase in AICs. In contrast, PIC mRNA was significantly upregulated, while AIC mRNA was downregulated in response to Gαi2 ODN downregulation on HS diet. Microgliosis, but not astrogliosis, was seen in response to Gαi2 downregulation and HS diet, but neither were seen in scrambled ODN animals on HS or NS. Finally, minocycline co‐infusion caused complete restoration of PIC and AIC mRNA levels to baseline in Gαi2 ODN infused animals on HS diets, complete restoration of plasma NE content to baseline, and an approximately 50% reduction in the magnitude of hypertension.ConclusionsWe conclude that microgliosis, but not astrogliosis, mediates central inflammation driving Gαi2 protein mediated salt sensitive hypertension that lead to increases in global NE and systemic BP.Support or Funding InformationFunding Source: R01HL139867, R01 HL141406, K02 HL112718, R01 HL107330, R56 AG057687 0.6% NaCl SCR ODN 4% NaCl SCR ODN 4% NaCl SCR ODN + Mino 0.6% NaCl Gαi2 ODN 4% NaCl Gαi2 ODN 4% NaCl Gαi2 ODN + Mino MAP (mmHg) 123 ± 4 121 ± 3 119 ± 3 118 ± 4 144 ± 3 * 130 ± 4*# Plasma NE (nmol/L) 62 ± 7 38 ± 4* 42 ± 5* 59 ± 5 92 ± 7* 62 ± 6# IL‐1β mRNA fold increase 0.9 ± 0.2 0.8 ± 0.1 1.1 ± 0.2 1.1 ± 0.2 2.4 ± 0.4* 1.3 ± 0.3# TNFα mRNA fold increase 1.1 ± 0.1 1.0 ± 0.2 1.0 ± 0.1 1.3 ± 0.2 2.3 ± 0.5* 1.1 ± 0.2# IL‐6 mRNA fold increase 1.0 ± 0.2 0.9 ± 0.1 1.1 ± 0.1 1.0 ± 0.1 2.2 ± 0.3* 1.2 ± 0.2# IL‐10 mRNA fold increase 1.0 ± 0.1 1.3 ± 0.1 1.3 ± 0.2 1.1 ± 0.2 0.4 ± 0.1* 1.1 ± 0.2# Microglial Density in PVN (number/.04mm2) 26.6 ± 1.88 20.5 ± 2.44 ND 22 ± 3.11 35.33 ± 2.54 * ND Percent Activation Microglia 18.3 ± 0.024 13.4 ± 0.021 ND 16.8 ± 0.015 29.24 ± 0.01 * ND Astrocyte Density in PVN (% of tissue) 30.2 ± 0.0324 27.3 ± 0.021 ND 32.9 ± 0.034 26.6 ± 0.026 ND p&lt;0.05 vs. respective normal salt (0.6% NaCl) group; p&lt;0.05 vs. respective high salt (4% NaCl) group (N=4–6/group ± SEM). Mino = Minocycline. ND = not determined This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Antiarrhythmic and proarrhythmic effects of subcutaneous nerve stimulation in ambulatory dogs

High output subcutaneous nerve stimulation (ScNS) remodels the stellate ganglia and suppresses cardiac arrhythmia. The purpose of this study was to test the hypothesis that long duration low output ScNS causes cardiac nerve sprouting and increases plasma norepinephrine concentration and the duration of paroxysmal atrial tachycardia (PAT) in ambulatory dogs. We prospectively randomized 22 dogs (11 males and 11 females) into 5 different output groups for 2 months of ScNS: 0 mA (sham) (n = 6), 0.25 mA (n = 4), 1.5 mA (n = 4), 2.5 mA (n = 4), and 3.5 mA (n = 4). As compared with baseline, the changes in the durations of PAT episodes per 48 hours were significantly different among different groups (sham, -5.0 ± 9.5 seconds; 0.25 mA, 95.5 ± 71.0 seconds; 1.5 mA, -99.3 ± 39.6 seconds; 2.5 mA, -155.3 ± 87.8 seconds; and 3.5 mA, -76.3 ± 44.8 seconds; P< .001). The 3.5 mA group had a greater reduction in sinus heart rate than did the sham group (-29.8 ± 15.0 beats/min vs -14.5 ± 3.0 beats/min; P = .038). Immunohistochemical studies showed that the 0.25 mA group had a significantly increased while 2.5 mA and 3.5 mA stimulation had significantly reduced growth-associated protein 43 nerve densities in both atria and ventricles. The plasma norepinephrine concentrations in the 0.25 mA group was 5063.0 ± 4366.0 pg/mL, which was significantly higher than that in the other groups of dogs (739.3 ± 946.3; P = .009). There were no significant differences in the effects of simulation between males and females. In ambulatory dogs, low output ScNS causes cardiac nerve sprouting and increases plasma norepinephrine concentration and the duration of PAT episodes while high output ScNS is antiarrhythmic.

Multifocal pheochromocytoma-paraganglioma in a 29-year-old woman with cyanotic congenital heart disease

BackgroundMultifocal pheochromocytoma/paraganglioma presenting at an early age is commonly associated with a hereditary syndrome. Case ReportA 29-year-old woman was referred for evaluation of multifocal pheochromocytoma/paraganglioma. Interestingly, her family history did not include pheochromocytoma/paraganglioma, and comprehensive genetic testing for the well-documented pheochromocytoma/paraganglioma susceptibility genes was negative. Of note, this patient had a history of a complex cardiac defect resulting in cyanotic congenital heart disease and had never undergone operative repair. Thus she lived in a chronic hypoxic state with a baseline oxygen saturation of about 80%. Laboratory evaluation found marked increases in plasma norepinephrine and normetanephrines with normal epinephrine and metanephrines. Imaging revealed 4 aortocaval masses and a right adrenal mass. After appropriate preoperative preparation she underwent successful resection of each of the neoplasms, with pathologic testing revealing multifocal pheochromocytoma/paraganglioma. DiscussionThis case highlights a growing recognition of the potential development of pheochromocytoma/paraganglioma in patients with cyanotic congenital heart disease. The underlying pathophysiology and phenotypic similarities between pheochromocytoma/paraganglioma in patients with cyanotic congenital heart disease and those with mutations that lead to cellular pseudohypoxia are reviewed.