Plasma Norepinephrine Levels Research Articles

Downregulation of Neuronal Nitric Oxide Synthase (nNOS) within the Paraventricular Nucleus in Ins2Akita-type-1 Diabetic Mice Contributes to Sympatho-excitation

Activation of both renin-angiotensin system (RAS) and the sympathetic system is the primary etiologic event in developing cardiovascular complications in diabetes mellitus (DM). However, the precise mechanisms for sympathetic activation in DM have not been elucidated. Here we attempted to investigate diabetes-linked cardiovascular dysregulation due to angiotensin II (Ang II)-mediated reduction in neuronal nitric oxide (NO) synthase (nNOS) within the paraventricular neuleus (PVN). In the present study, we used Ins2+/-Akita (a spontaneous, insulin-dependent genetic diabetic non-obese murine model) and wild-type (WT) littermates mice as controls. At 14 weeks of age, we found the Akita mice had increased renal sympathetic nerve activity and elevated levels of plasma norepinephrine. There was decreased expression of nNOS protein (Akita 0.43 ± 0.11 vs. WT 0.75 ± 0.05, P < 0.05) in the PVN of Akita mice. Akita mice had increased expression of angiotensin-converting enzyme (ACE) (Akita 0.58 ± 0.05 vs. WT 0.34 ± 0.04, P < 0.05) and Ang II type 1 receptor (Akita 0.49 ± 0.03 vs. WT 0.29 ± 0.09, P < 0.05), decreased expressions of ACE2 (Akita 0.17 ± 0.05 vs. WT 0.27 ± 0.03, P < 0.05) and angiotensin (1-7) Mas receptor (Akita 0.46 ± 0.02 vs. WT 0.77 ± 0.07, P < 0.05). Futher, there were increased protein levels of protein inhibitor of nNOS (PIN) (Akita 1.75 ± 0.08 vs. WT 0.71 ± 0.09, P < 0.05) with concomitantly decreased catalytically active dimers of nNOS (Akita 0.11 ± 0.04 vs. WT 0.19 ± 0.02, P < 0.05) in the PVN in Akita mice. Our studies suggest that activation of the excitatory arm of RAS, leads to a decrease NO, causing an over-activation of the sympathetic drive in DM.

The impact of inflammatory and oxidative stress biomarkers on the sympathetic nervous system in severe coronary atherosclerosis.

The present study aimed at evaluating the association between sympathetic nervous system activation (SNS) and the severity of coronary artery disease (CAD). In addition, we tested the hypothesis that inflammation and oxidative stress influence the SNS activation. Adult patients with severe CAD scheduled for coronary artery bypass graft (CABG) surgery were enrolled. SYNTAX I score was calculated based on coronary angiography. Systemic activation of the SNS was estimated through circulating levels of norepinephrine (NE). Plasma levels of pro-inflammatory cytokines (IL 1β, IL 6 and HIF 1α) and oxidative stress molecules (SOD-1 and LOX-1) were obtained prior to surgery. Circulating NE levels were significantly correlated with the severity of CAD, as assessed by the SYNTAX I score (p 0.002; r 0.329). Elevated levels of circulating pro-inflammatory markers were significantly correlated with increased NE concentrations (for IL-1β: p < 0.001, r = 0.49; for IL-6 and NE: p = 0.003, r = 0.32; for HIF-1α and NE: p = 0.049, r = 0.21). Additionally, oxidative stress molecules were associated with circulating NE levels (for SOD-1 and NE: p = 0.016, r = 0.26; for LOX-1 and NE: p = 0.004, r = 0.31). In patients with CAD referred for CABG, SNS activation, indicated by plasma NE levels, was correlated with disease severity as assessed by the SYNTAX I score, as well as with markers of inflammation and oxidative stress. This suggests that inflammation, oxidative stress, and SNS activation form an interconnected network, with each component influencing the others. It might be of interest to develop a scoring system including inflammation and oxidative stress markers to identify patients that require a more aggressive approach to lower inflammation, oxidative stress and modulate the sympathetic nervous system. This could be of use especially in the setting of a scheduled intervention -such as CABG surgery.

Tyrosine hydroxylase-positive neurons in the rostral ventrolateral medulla mediate sympathetic activation in sepsis

AimSepsis results in high mortality and is associated with organ dysfunction caused by infection. The present study aimed to elucidate whether early-stage sympathetic activation is associated with the prognosis of sepsis and its possible mechanisms. MethodsPatients with sepsis and healthy controls were included. Sepsis in rats was induced by lipopolysaccharide. Dexmedetomidine, a α2-adrenergic receptor agonist, was used in patients and rats with sepsis to evaluate the role of the sympathetic nervous system in sepsis. Holter monitoring was used to detect heart rate variability, while plasma samples were obtained to measure levels of norepinephrine and inflammatory markers. Mean arterial pressure, heart rate, and renal sympathetic nerve activity were recorded. Immunofluorescence was used to detect the activation of neurons in the rostral ventrolateral medulla (RVLM). ResultsIn patients with sepsis, plasma levels of norepinephrine and interleukin-1β were higher compared with those in controls and positively correlated with acute physiology and chronic health evaluation (APACHEII). SDNN and SDANN were significantly reduced as well as negatively correlated with APACHEII. Meanwhile, rats with sepsis showed increased of sympathetic outflow and plasma levels of norepinephrine, with increased c-fos levels in the RVLM. Treatment with dexmedetomidine could improve prognosis. Lesion of tyrosine hydroxylase-positive neurons in the RVLM attenuated sympathetic activation and target organs damage in septic rats as well as improved survival. ConclusionThe results suggest that tyrosine hydroxylase-positive neurons in the RVLM might contribute to the prognosis of sepsis via activation of the sympathetic nervous system, while dexmedetomidine could ameliorate sepsis via inhibiting sympathetic activation.

Impact of Dexmedetomidine on Hemodynamics, Plasma Catecholamine Levels, and Delirium Incidence Among Intubated Patients in the ICU--A Randomized Controlled Trial.

To investigate the impact of various sedative medications on hemodynamics and plasma levels of epinephrine (E) and norepinephrine (NE) in mechanically ventilated patients postoperatively in the intensive care unit (ICU). Ninety-seven patients admitted to the ICU undergoing postoperative mechanical ventilation with tracheal intubation and continuous analgesic sedation following general anesthesia were randomly assigned to either the observation group (dexmedetomidine) (n = 49) or the control group (propofol) (n = 48) in this randomized controlled trial. Upon transfer to the ICU, vital signs (heart rate [HR], respiratory rate [RR], mean arterial pressure [MAP]) were recorded prior to the initiation of the sedation treatment (T0), at one-hour post sedation (T1) and two hours following tracheal extubation (T2), plasma levels of epinephrine (E) and norepinephrine (NE) were measured at these time points. The incidence of delirium was recorded in both groups. MAP between the two groups at both T0 and T1 At T2 plasma NE and HR were found to be lower in the observation group compared to the control group (P < 0.001). Among the patients receiving antihypertensive medication in the ICU, NE levels were significantly lower in the observation group compared to the control group (P = 0.019) Among the patients not receiving antihypertensive medication, both NE (P < 0.001) and MAP (P = 0.001) levels were lower in the observation group compared to the control group. The incidence of delirium in the observation group (dexmedetomidine) was not significantly different from that in the control group (propofol). With dexmedetomidine sedation, blood pressure fluctuated less, plasma catecholamine levels were lower, and sympathetic inhibition was stronger in patients before and after extubation. However, it did not significantly reduce the incidence of postoperative delirium.

Moderately cool environment with rain and wind increases cold strain and energy expenditure via carbohydrate oxidation during running exercise.

Outdoor exercise often proceeds despite rain and wind in cool conditions. The aim of this study was to investigate the effects of rain with wind on physiological responses during running exercise at 70% V̇O<inf>2max</inf> in cool conditions. Eleven healthy men exercised on a treadmill at 70% V̇O<inf>2max</inf> intensity for 60 min under conditions of 10 mm/h rain and 3 m/sec wind (RW) or not (CON) at 10°C in a climatic chamber able to simulate various temperature, humidity, rain, and wind conditions. Body temperature, expired air, and blood samples were measured at rest and exercise. Rectal temperature, mean weighted skin temperature, and thermal sensation were all significantly lower in RW than in CON during exercise (all P<0.05). Oxygen uptake was significantly higher in RW than in CON during exercise (all P<0.05). Participants' rating of perceived exertion was significantly higher in RW than in CON at 50 and 60 min (P<0.05). Respiratory exchange ratio was significantly higher in RW than in CON at 10, 20, and 40 min. Plasma lactate concentration and plasma norepinephrine levels were significantly higher in RW than in CON during exercise (both P<0.05). Rain with wind intensified body heat loss, and energy expenditure and carbohydrate oxidation increased as the body cooled. These conditions may decrease exercise performance.

Abstract P173: Pivotal Role for the Kinin B1R in CB1 Receptor Mediated Neuroinflammation and Pressor Response

The cannabinoid receptors CB1R and CB2R are involved in blood pressure (BP) regulation and CB1R is implicated in the incidence of hypertension. CB1R is highly expressed in the brain but both receptors are also expressed in the heart. Prior research has demonstrated that CB1R mediates significant cardiovascular responses, including elevated BP, heightened plasma norepinephrine levels, and increased sympathetic nerve activity. Furthermore, the activation of the kinin B1 receptor (B1R) mediates similar effects when studied independently. However, the role of B1R in CB1R-mediated BP regulation and the associated signaling mechanisms remain unknown. In this study, we tested the hypothesis that B1R plays a pivotal role in CB1R-mediated pressor response, oxidative stress and neuroinflammation. To test this, we used both in vivo mouse models and in vitro primary hypothalamic neurons. Male C57BL/6NJ wild-type (WT) and B1R knockout mice (B1RKO) underwent surgical carotid artery and jugular vein catheterization to measure BP in conscious state. Following stabilization of BP for at least 90 minutes, the CB1R agonist WIN55,212-2 (300 ug/kg; i.v., WIN) or its vehicle was administered, and recordings continued for 45 minutes. WIN increased BP in WT mice (25±7 mmHg vs baseline), but this effect was blunted in B1RKO mice (n=3, p&lt;0.05). Moreover, administration of WIN led to an augmentation of CB1R expression in the paraventricular nucleus of WT mice, but not in B1RKO mice, thereby indicating the involvement of B1R in CB1R signaling (p&lt;0.05, n=3 mice/group). WT, but not B1RKO, mice treated with WIN displayed a significant increase in oxidative stress levels (p&lt;0.05, n=3 mice/group), as indicated by dihydroethidium staining. To further confirm the role of B1R blockade on CB1R signaling, we cultured primary hypothalamic neurons, as neurons express the highest levels of CB1R in the brain. Neurons were stimulated with WIN (1 uM) both with and without a B1R selective antagonist (SSR240612, 10uM). The results indicated that WIN incubation for 24 hours increased CB1R expression, inflammation, and oxidative stress compared to vehicle treated, and these responses were abrogated by prior B1R blockade (p&lt;0.05, n=5/group), consistent with the in vivo observations. These data provide novel evidence that B1R is implicated in CB1R-mediated proinflammatory responses and serves as a potential therapeutic target to reduce CB1R induced effects.

P180 CONTRIBUTION OF AFFERENT RENAL NERVES TO HYPERTENSION AND HYPERTENSIVE HEART FAILURE

Background and Objective: Renal nerves contain efferent and afferent fibers. This study aimed to investigate the contribution of afferent renal nerves to the development of hypertension and hypertensive heart failure in several rat models of hypertension. Methods: Selective afferent renal nerve denervation (ARDN) or sham operation was performed in the following models: (1) SHRSP at 9 weeks; (2) 4% high-salt diet (HS)-fed SHRSP at 8 weeks (HS from 8 weeks); and (3) 8% HS-fed Dahl salt-sensitive rats at 9 weeks (HS from 6 weeks). Dahl rats fed 0.3% low-salt diet were controls for (3). Blood pressure (BP) was measured by telemetry in (1) and (2), and by tail-cuff method in (3). Results: (1) Mean BP was elevated from 9 weeks to 11 weeks in sham-SHRSP (155.2±2.0 vs 144.0±1.9 mmHg, n=10, p&lt;0.05). Mean BP in ARDN-SHRSP (157.8±2.7 mmHg, n=10) did not differ from sham-SHRSP at 11 weeks. (2) Mean BP increased from 8 weeks to 11 weeks in HS-sham-SHRSP (191.5±8.1 vs 126.5±4.0 mmHg, n=6, p&lt;0.05). Mean BP in HS-ARDN-SHRSP (186.0±7.1 mmHg, n=6) did not differ from HS-sham-SHRSP at 11 weeks. (3) Systolic BP increased (243.6±7.0 vs 140.0±2.7 mmHg, n=9 each, p&lt;0.05) and echocardiographic left ventricular (LV) fractional shortening decreased (25.9±1.7 vs 48.8±0.4%, p&lt;0.05) in HS-sham-Dahl rats compared to low-salt controls at 16 weeks (“HFrEF” phase). LV weight, lung weight, and LV fibrosis were significantly increased in HS-sham-Dahl rats compared to controls. ARDN attenuated these changes except for BP. At 12 weeks (pre-HFrEF phase), plasma norepinephrine levels increased in HS-sham-Dahl rats compared to controls and were attenuated by ARDN (controls 188.7±16.5, HS-sham 563.8±82.7, HS-ARDN 327.4±50.2 pg/ml; n=15, 12, 14; p&lt;0.05). Conclusions: Signals from afferent renal nerves contribute to sympathoexcitation and the development of HFrEF without affecting BP in Dahl salt-sensitive hypertensive rats, but not to the development of hypertension in SHRSP and HS-fed SHRSP.

Dexmedetomidine Improves Microcirculatory Alterations in Patients With Initial Resuscitated Septic Shock.

The study was to investigate the effects of dexmedetomidine on microcirculation in patients with early septic shock despite initial resuscitation. This was a single-center prospective study. Patients with early septic shock despite initial fluid resuscitation who still required norepinephrine to maintain target arterial pressure were enrolled. Hemodynamic and gas analysis variables, sublingual microcirculatory parameters were measured at baseline, and during the infusion of dexmedetomidine for 1 h (0.7mcg/kg/h). To elucidate the possible mechanisms of the effect of dexmedetomidine on microcirculation, after interim analysis, the dose-effect relationship of dexmedetomidine on microcirculation and catecholamine level were investigated at baseline, 1h after stabilization at different doses of dexmedetomidine (0.7 and 0.3 mcg/kg/h), and 2h after dexmedetomidine cessation. Forty-four patients with septic shock were enrolled after initial resuscitation. Compared with baseline, total and perfused vascular densities were statistically increased after infusion of dexmedetomidine, which was correlated with the dose of dexmedetomidine. During dexmedetomidine infusion, plasma norepinephrine, and dopamine level were significantly decreased. Changes in plasma norepinephrine level contributed to dexmedetomidine infusion were well correlated with changes in total and perfused vascular densities. In adult patients with resuscitated septic shock, dexmedetomidine improved microcirculation, which might be associated with plasma catecholamine level. However, double-blinded large sample studies should be performed to verify the results.

Acute hypoxic conditions preceding endotoxin administration result in an increased proinflammatory cytokine response in healthy men.

Tissues often experience hypoxia at sites of inflammation due to malperfusion, massive immune cell recruitment, and increased oxygen consumption. Organisms adapt to these hypoxic conditions through the transcriptional activation of various genes. In fact, there is significant crosstalk between the transcriptional responses to hypoxia and inflammatory processes. This interaction, named inflammatory hypoxia, plays a crucial role in various diseases including malignancies, chronic inflammatory lung diseases, and sepsis. To further elucidate the crosstalk between hypoxia and inflammation in vivo and assess its potential for innovative therapies, our study aimed at investigating the impact of acute hypoxic conditions on inflammation-induced immune responses. To this end, we exposed healthy human subjects to hypoxia either before (hypoxia priming) or after a single intravenous (i.v.) injection of 0.4 ng/kg LPS. Our data show that hypoxia exposure prior to LPS injection (hypoxia priming) amplified the proinflammatory response. This was reflected by an increase in body temperature, plasma noradrenaline levels, and the production of proinflammatory cytokines (i.e., IL-6 and TNF-α), compared with LPS control conditions. These effects were not observed when participants were exposed to hypoxia after LPS administration, demonstrating that the interaction between hypoxia and inflammation highly depends on the timing of both stimuli. Our findings suggest that acute hypoxia (i.e., hypoxia priming) modulates transient inflammation, leading to an enhanced proinflammatory response in healthy human subjects. This highlights the need for further investigations to understand the pathology of various hypoxia-inducible factor (HIF)-associated inflammatory diseases and to develop suitable, innovative therapies.NEW & NOTEWORTHY To our knowledge, this is the first in vivo study investigating the effects of hypoxia preceding (hypoxia priming) or following LPS administration on the endotoxin-induced inflammatory response in healthy human subjects. The data show that hypoxia priming amplified the proinflammatory response, reflected by an increased body temperature, increased plasma noradrenaline levels, and higher production of proinflammatory cytokines (i.e., IL-6 and TNF-α) compared with LPS control conditions.

Altered brain activity associated with premature ejaculation improved by electroacupuncture in rats.

Premature ejaculation (PE) is linked with abnormal brain activity that is modifiable by electroacupuncture (EA). In this study we aimed to explore the central pathological mechanism underlying EA in treating PE. Six-week-old male Sprague-Dawley rats were divided into a PE group (n = 8) and a control group (n = 8) according to ejaculatory frequency during copulatory behavior. All rats underwent EA at the Zusanli acupoint (ST-36) for 4weeks. Magnetic resonance imaging data were collected before and after EA. The behavioral parameters, plasma norepinephrine levels, fractional amplitude of low frequency fluctuation (fALFF), and regional homogeneity (ReHo) were evaluated. The PE group ejaculated more times with shorter latency compared with controls. After EA, the ejaculation frequency of the PE group decreased, and the ejaculation latency period increased, with no changes observed in the control group. Norepinephrine levels were higher in the PE group than in the controls and were positively correlated with ejaculation frequency and negatively correlated with ejaculation latency. The PE group showed lower fALFF in the right striatum and higher ReHo in the brainstem compared with controls. After EA, controls showed decreased fALFF in the right striatum, left olfactory bulb, and dorsal fornix and increased ReHo in the right interpeduncular nucleus, as well as decreased ReHo in the left striatum, prelimbic system, right basal forebrain region, septal region, and olfactory bulb, while the model group exhibited increased fALFF in the right hypothalamic region, decreased fALFF in the left globus pallidum and right basal forebrain region and increased ReHo in the right interpeduncular nucleus, as well as decreased ReHo in the left striatum, olfactory bulb, basal forebrain region, dentate gyrus, right dysgranular insular cortex, and striatum. Compared with the controls after EA, the model group showed increased ReHo of the right hypothalamic region and decreased ReHo of the right dysgranular insular cortex. These findings might enhance the understanding of PE and contribute to new, targeted therapies for PE. The therapeutic effects might be achieved by EA inhibiting the activity in brain regions involved in ejaculatory behavior. However, the curative effect of acupuncture might be underestimated due to some curative effects of sham acupuncture used in the control group. In conclusion, the ejaculatory frequency of rats may be reduced and ejaculation latency could be extended by EA at ST-36, which might be achieved by the effects of this treatment on brain activity.

Norepinephrine mediates heart block during severe hypoglycemia in male rats.

Hypoglycemia is common in people with type 1 diabetes. Sometimes, severe hypoglycemia can be fatal. The underlying mechanisms by which severe hypoglycemia can lead to death are unclear. The sympathetic nervous system is thought to be proarrhythmic. We hypothesized that norepinephrine is the main mediator of severe hypoglycemia-induced fatal cardiac arrhythmias. To test this hypothesis, adult, non-diabetic Sprague-Dawley rats were subjected to hyperinsulinemic-severe hypoglycemic clamps (3 h, 10-15 mg/dL) during two different experiments: (1) intracerebroventricular (ICV) norepinephrine (n = 26) or artificial cerebrospinal fluid (aCSF) (n = 20) infusion or (2) blockade of norepinephrine release by intraperitoneal reserpine (n = 20) or control (n = 29). In experiment 1, brain norepinephrine infusion during severe hypoglycemia led to a 2.5-fold increase in third-degree heart block and a 24% incidence of ST elevation compared to no ST elevation in aCSF controls. In experiment 2, reserpine successfully reduced plasma and cardiac norepinephrine levels. During severe hypoglycemia, reserpine completely prevented second and third-degree heart block and T wave increases, a marker of myocardial infarction, compared to controls. In conclusion, norepinephrine increases while reserpine, used to reduce norepinephrine nerve terminal release, reduces heart block and markers of myocardial infarction during severe hypoglycemia.

Temporal Dynamics of Plasma Catecholamines, Metabolic and Immune Markers, and the Corticosterone:DHEA Ratio in Farmed Crocodiles before and after an Acute Stressor.

Commercial crocodilian farms face significant economic and livestock losses attributed to stress, which may be linked to their adopted husbandry practices. The development of appropriate and modernized husbandry guidelines, particularly those focused on stress mitigation, is impeded by the limited understanding of the crocodilian stress response. Fifteen grower Nile crocodiles were subjected to simulated acute transport stress, with blood samples collected at various intervals post-stress. Plasma levels of corticosterone (CORT), dehydroepiandrosterone (DHEA), adrenaline, and noradrenaline were determined using high-performance liquid chromatography. Glucose and lactate were measured using portable meters and the heterophil-to-lymphocyte ratio (HLR) was determined via differential leucocyte counts. Significant differences were elicited after the stressor, with acute fluctuations observed in the fast-acting catecholamines (adrenaline and noradrenaline) when compared to the baseline. Downstream effects of these catecholamines and CORT appear to be associated with a persistent increase in plasma glucose and HLR. Lactate also showed acute fluctuations over time but returned to the baseline by the final measurement. DHEA, which is used in a ratio with CORT, showed fluctuations over time with an inverted release pattern to the catecholamines. The study highlights the temporal dynamics of physiological markers under acute stress, contributing to our understanding of crocodilian stress and potentially informing improved farming practices for conservation and sustainable management.

Butyrate attenuates sympathetic activation in rats with chronic heart failure by inhibiting microglial inflammation in the paraventricular nucleus.

Sympathetic activation is a hallmark of heart failure and the underlying mechanism remains elusive. Butyrate is generated by gut microbiota and influences numerous physiological and pathological processes in the host. The present study aims to investigate whether the intestinal metabolite butyrate reduces sympathetic activation in rats with heart failure (HF) and the underlying mechanisms involved. Sprague-Dawley rats (220‒250 g) are anaesthetized with isoflurane, and the left anterior descending artery is ligated to model HF. Then, the rats are treated with or without butyrate sodium (NaB, a donor of butyrate, 10 g/L in water) for 8 weeks. Blood pressure and renal sympathetic nerve activity (RSNA) are recorded to assess sympathetic outflow. Cardiac function is improved (mean ejection fraction, 22.6%±4.8% vs 38.3%±5.3%; P<0.05), and sympathetic activation is decreased (RSNA, 36.3%±7.9% vs 23.9%±7.6%; P<0.05) in HF rats treated with NaB compared with untreated HF rats. The plasma and cerebrospinal fluid levels of norepinephrine are decreased in HF rats treated with NaB. The infusion of N-methyl-D-aspartic acid (NMDA) into the paraventricular nucleus (PVN) of the hypothalamus of HF model rats increases sympathetic nervous activity by upregulating the NMDA receptor. Microglia polarized to the M2 phenotype and inflammation are markedly attenuated in the PVN of HF model rats after NaB administration. In addition, HF model rats treated with NaB exhibit enhanced intestinal barrier function and increased levels of GPR109A, zona occludens-1 and occludin, but decreased levels of lipopolysaccharide-binding protein and zonulin. In conclusion, butyrate attenuates sympathetic activation and improves cardiac function in rats with HF. The improvements in intestinal barrier function, reductions in microglia-mediated inflammation and decreases in NMDA receptor 1 expression in the PVN are all due to the protective effects of NaB.

Esaxerenone: blood pressure reduction and cardiorenal protection without reflex sympathetic activation in salt-loaded stroke-prone spontaneously hypertensive rats.

Mineralocorticoid receptor (MR) is involved in the mechanisms of blood pressure elevation, organ fibrosis, and inflammation. MR antagonists have been used in patients with hypertension, heart failure, or chronic kidney disease. Esaxerenone, a recently approved MR blocker with a nonsteroidal structure, has demonstrated a strong blood pressure-lowering effect. However, blood pressure reduction may lead to sympathetic activation through the baroreflex. The effect of esaxerenone on the sympathetic nervous system remains unclear. We investigated the effect of esaxerenone on organ damage and the sympathetic nervous system in salt-loaded stroke-prone spontaneously hypertensive rats (SHRSP), a well-established model of essential hypertension with sympathoexcitation and organ damage. Three-week administration of esaxerenone or hydralazine successfully attenuated the blood pressure elevation. Both esaxerenone and hydralazine comparably suppressed left ventricular hypertrophy and urinary albumin excretion. However, renal fibrosis and glomerular sclerosis were suppressed by esaxerenone but not hydralazine. Furthermore, plasma norepinephrine level, a parameter of systemic sympathetic activity, was significantly increased by hydralazine but not by esaxerenone. Consistent with these findings, the activity of the control centers of sympathetic nervous system, the parvocellular region of the paraventricular nucleus in the hypothalamus and the rostral ventrolateral medulla, was enhanced by hydralazine but remained unaffected by esaxerenone. These results suggest that esaxerenone effectively lowers blood pressure without inducing reflex sympathetic nervous system activation. Moreover, the organ-protective effects of esaxerenone appear to be partially independent of its blood pressure-lowering effect. In conclusion, esaxerenone demonstrates a blood pressure-lowering effect without concurrent sympathetic activation and exerts organ-protective effects in salt-loaded SHRSP. Esaxerenone has antihypertensive and cardiorenal protective effects without reflex sympathetic activation in salt-loaded stroke-prone spontaneously hypertensive rats.

Trimethylamine-N-oxide aggravated sympathetic activation in D-galactose induced aging rats by down-regulating P2Y12 receptor in microglia

This study aimed to determine whether trimethylamine N-oxide (TMAO) was involved in sympathetic activation in aging and the underline mechanisms. Our hypothesis is that TMAO reduces P2Y12 receptor and induces microglia-mediated inflammation in the paraventricular nucleus, then leading to sympathetic activation in aging. Eighteen young adults (20-40 years old) and sixteen old adults (65-90 years old) were involved in the study. Aging rats were established by injecting D-galactose (200 mg/kg/d) subcutaneously for 12 weeks. TMAO (120 mg/kg/d) or 1% 3, 3-dimethyl-l-butanol (DMB, a structural analog of choline, inhibiting TMA formation) was administrated in drinking water for 12 weeks to investigate their effects on neuroinflammation and sympathetic activation in aging rats. Heart rate variability was analyzed by 24 h ambulatory ECG multichannel recording system (CT-083S Holter ECG recorder, BENEWARE, Hangzhou) in young and old adults. The PowerLab 15T data acquisition system (AD Instruments, Australia) was used to record blood pressure and renal sympathetic nerve activity in the rats. Plasma levels of TMAO, noradrenaline, and IL-1β in old adults were higher than those in young group. In addition, standard deviation of all normal to normal intervals and standard deviation of the average of normal to normal intervals were lower in old adults and negative correlated with TMAO, which indicating sympathetic activation in old adults and related to the increased TMAO. Rats treatment with D-gal showed increased senescence-associated protein, microglia-mediated inflammation levels and decreased P2Y12 receptor in the paraventricular nucleus. Plasma levels of TMAO, noradrenaline, and IL-1β were increased, accompanied by enhanced renal sympathetic nerve activity. While TMAO supplementation aggravated the above phenomenons, and DMB abated them. These findings suggested that TMAO might contribute to the sympathetic hyperactivity of aging via downregulating P2Y12 receptor in microglia and increasing inflammation in the paraventricular nucleus. These results may provide a new target for the prevention and treatment of aging and aging-related diseases. This work was supported by the Program for the National Natural Science Foundationof China (32271155 and 31671185), the Science and Technology Project of the Hebei Education Department (ZD2021076), the Youth Top Talent Foundation of Hebei Province of China and the Program of Clinical Medicine Innovation Research Team of Hebei Medical University (2022LCTD-A1). 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.

Brain-Derived Extracellular Vesicles from Dahl Salt-Sensitive Rats with High Salt Diet Increase PVN and SON Vasopressin Levels in Sprague Dawley rats

Extracellular vesicles (EVs), naturally secreted by almost all cell types, encapsulate a broad spectrum of biological molecules, and ferry these contents to the local and distal recipient cells. Under disease conditions, EV-to-cell communication can lead to diverse cell responses and changes. Previously we have demonstrated that brain-derived EVs from hypertensive rats increased inflammation and oxidative stress in primary neurons and hypothalamic paraventricular nucleus (PVN) of the brain, however, the long-term effects of EVs are unclear. PVN is a key hub to mediate blood pressure via its endocrine and autonomic control. Increased vasopressin (AVP) levels have been found in Dahl salt sensitive hypertensive rats, which are produced by PVN and supraoptic nucleus (SON). In this study, we hypothesized that brain-derived EVs from hypertensive rats regulate blood pressure via AVP system. To test this hypothesis, we first labeled brain-derived EVs with Rhodamine dye (Rho-EVs) and studied their bio-distribution via intracerebroventricular (i.c.v.) injection into the normal Sprague Dawley (SD) rats. Rats were euthanized 24 hours after injection, and brain sections containing the PVN and SON regions were stained to test the colocalization of Rho-EVs with neurons (NeuN), astrocytes (GFAP) and microglia (Iba1). Then we injected brain-derived EVs obtained from hypertensive Dahl salt sensitive rats (DSS-EVs) and normotensive Sprague Dawley rats (SD-EVs) into the lateral ventricle (8 μg/rat) in the SD male rats, and the injection was repeated 2 weeks later. Blood pressure and heart rates of each rat were monitored each week using telemetry transducers. 4 weeks post first EVs injections, rats were euthanized, their blood were tested for plasma AVP and norepinephrine (NE) levels, and their brains were tested for AVP and Fos-related antigen 1 (Fra1) mRNA levels. Besides, we also performed biweekly PVN (800 ng/rat) and SON (800ng/rat) injections of DSS-EVs and SD-EVs and measured the AVP and/or Fra1 protein levels with immunostaining. Lastly, we determined the colocalization of Rho-EVs with AVP-containing cells in the PVN and SON. Results show that Rho-EVs are dominantly taken up by neurons in both PVN and SON regions. Biweekly i.c.v. injections of DSS-EVs do not increase blood pressure and heart rate. However, DSS-EVs significantly upregulate mRNA levels of AVP (2.4-fold) and Fra1 (2.5-fold) in the PVN compared to SD-EVs. There is an increasing trend of plasma AVP levels in DSS-EV-treated rats compared to control. Biweekly PVN injections of DSS-EVs significantly increase AVP (1.5-fold) protein levels relative to SD-EVs, and biweekly SON injections of DSS-EVs significantly increase AVP (1.5-fold) and Fra1 (2.6-fold) protein levels relative to SD-EVs. Lastly, we found that Rho-EVs are mainly colocalized with vasopressin-containing cells in the SON. These results suggest that brain-derived EVs cause SON and PVN neuron activation, which in turn may regulate AVP system during hypertensive development. R01HL163159 (Shan); R15HL150703 (Shan); AHA 1807047 (Bi). 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.

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&lt;0.01), which was attenuated in B1RKO mice. Ang II induced HTN resulted in dysautonomia as indicated by significantly increased plasma norepinephrine levels (p&lt;0.05, n=6) and decreased spontaneous baroreceptor reflex sensitivity (p&lt;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&lt;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&lt;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&lt;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.

Relation of catecholamines with oxidative stress in patients undergoing cardiac surgery before and after endotracheal intubation

Inroduction&#x0D; Endotracheal intubation is used to maintain the airway open so that oxygen, medicine, or anesthesia can be administered. Anesthesia and surgery boost the release of cross-regulating hormones through physiological responses and psychological stress. There is a strong link between psychological stress and oxidative stress, according to research.&#x0D; Objective: - The goal of this study was to determine the levels of catecholamines (adrenaline and noradrenaline) and oxidative stress before and after endotracheal intubation in patients undergoing cardiac surgery and to study association between them.&#x0D; Material &amp; Methods: - Total 30 patients undergoing cardiac surgery were enrolled. Blood samples were collected before and after endotracheal intubation. Plasma adrenaline and noradrenaline levels were estimated by ELISA. MDA &amp; SOD were estimated by spectrophotometric method.&#x0D; Results: - Mean levels of plasma adrenaline (p&lt; 0.01), noradrenaline (p&lt; 0.0001) and Serum MDA (p&lt; 0.0001) were significantly decreased while Serum SOD were significantly increased (p&lt; 0.0001) after endotracheal intubation as compared to before endotracheal intubation by laryngoscopy in patients undergoing cardiac surgery. We found significant positive correlation of MDA with adrenaline and nor-adrenaline before and after intubation. SOD activity was negatively correlated with MDA, adrenaline and noradrenaline before and after intubation&#x0D; Conclusion: Elevated levels of adrenaline, noradrenaline, MDA, and lower levels of SOD show that patients are stressed prior to endotracheal intubation, resulting in a stronger stress response and increased oxidative stress. After intubation, the levels of adrenaline and noradrenaline reduced, indicating a reduction of stress. Our study also shows a link between psychological and oxidative stress. For a better outcome and to avoid subsequent complications, it is preferable to evaluate stress levels and oxidative stress in patients undergoing cardiac surgery before and after endotracheal intubation.

Decreased levels of hydrogen sulfide in the hypothalamic paraventricular nucleus contribute to sympathetic hyperactivity induced by cerebral infarction.

Paroxysmal sympathetic hyperactivity (PSH) is a common clinical feature secondary to ischemic stroke (IS), but its mechanism is poorly understood. We aimed to investigate the role of H2S in the pathogenesis of PSH. IS patients were divided into malignant (MCI) and non-malignant cerebral infarction (NMCI) group. IS in rats was induced by the right middle cerebral artery occlusion (MCAO). H2S donor (NaHS) or inhibitor (aminooxy-acetic acid, AOAA) were microinjected into the hypothalamic paraventricular nucleus (PVN). Compared with the NMCI group, patients in the MCI group showed PSH, including tachycardia, hypertension, and more plasma norepinephrine (NE) that was positively correlated with levels of creatine kinase, glutamate transaminase, and creatinine respectively. The 1-year survival rate of patients with high plasma NE levels was lower. The hypothalamus of rats with MCAO showed increased activity, especially in the PVN region. The levels of H2S in PVN of the rats with MCAO were reduced, while the blood pressure and renal sympathetic discharge were increased, which could be ameliorated by NaHS and exacerbated by AOAA. NaHS completely reduced the disulfide bond of NMDAR1 in PC12 cells. The inhibition of NMDAR by MK-801 microinjected in PVN of rats with MCAO also could lower blood pressure and renal sympathetic discharge. In conclusion, PSH may be associated with disease progression and survival in patients with IS. Decreased levels of H2S in PVN were involved in regulating sympathetic efferent activity after cerebral infarction. Our results might provide a new strategy and target for the prevention and treatment of PSH.

Activation of Cannabinoid Type 2 Receptor in Microglia Reduces Neuroinflammation through Inhibiting Aerobic Glycolysis to Relieve Hypertension.

Studies have shown that the chronic use of cannabis is associated with a decrease in blood pressure. Our previous studies prove that activating the cannabinoid type 2 (CB2) receptor in the brain can effectively reduce blood pressure in spontaneously hypertensive rats; however, the exact mechanism has not been clarified. The objective of this study is to demonstrate that activation of microglial CB2 receptors can effectively reduce the levels of TNF-α, IL-1β, and IL-6 in the paraventricular nucleus (PVN) through inhibiting aerobic glycolysis, thereby relieving hypertension. AngiotensinII (AngII) was administered to BV2 cells and C57 mice to induce hypertension and the release of proinflammatory cytokines. The mRNA and protein expression of the CB2 receptor, TNF-α, IL-1β, IL-6, and the PFK and LDHa enzymes were detected using RT-qPCR and Western blotting. The Seahorse XF Energy Metabolism Analyzer was used to measure the oxidative phosphorylation and aerobic glycolysis metabolic pathways in BV2 cells. The long-term effects of injecting JWH133, a selective CB2 receptor agonist, intraperitoneally on blood pressure were ascertained. ELISA was used to measure norepinephrine and lactic acid levels while immunofluorescence labeling was used to locate the CB2 receptor and c-Fos. By injecting pAAV-F4/80-GFP-mir30shRNA (AAV2-r-CB2shRNA) into the lateral cerebral ventricle, the CB2 receptor in microglia was specifically knocked down. Activation of CB2 receptors by the agonist JWH133 suppressed TNF-α, IL-1β, and IL-6 by inhibiting PFK and LDHa enzymes involved in glycolysis, as well as lactic acid accumulation, along with a reduction in glycoPER levels (marks of aerobic glycolysis) in AngII-treated BV2 cells. In AngII-treated mice, the administration of JWH133 specifically activated CB2 receptors on microglia, resulting in decreased expression levels of PFK, LDHa, TNF-α, IL-1β, and IL-6, subsequently leading to a decrease in c-Fos protein expression within PVN neurons as well as reduced norepinephrine levels in plasma, ultimately contributing to blood pressure reduction. The results suggest that activation of the microglia CB2 receptor decreases the neuroinflammation to relieve hypertension; the underlying mechanism is related to inhibiting aerobic glycolysis of microglia.