Elevated Plasma Norepinephrine Levels Research Articles

Abstract 14993: Empagliflozin Exerts a Sympathoinhibitory Effect and Ameliorates Cardiorenal Injuries in a Rat Model of Hypertensive Heart Failure

Background: SGLT2 inhibitors may have protective effects on cardiac and renal injuries; however, their mechanisms remain unclear. Sympathetic activation has a crucial role in cardio/renal injuries. This study aimed to investigate whether empagliflozin can inhibit cardio/renal injuries through sympathoinhibition in a rat model of hypertensive heart failure. Methods: Male Dahl salt-sensitive rats were divided into low-salt (LS) and high-salt (HS) diet groups from 6 weeks of age. The rats in HS group were assigned to vehicle (HS-VEH) or empagliflozin (HS-EMPA) treatment group at 8 weeks. The effect of empagliflozin on central sympathetic regulation and cardio/renal injuries was assessed at 12 weeks (pre-heart failure phase), while its protective effect on heart failure was evaluated at 15 weeks in another cohort. Results: At 12 weeks , systolic blood pressure was similarly elevated in HS-VEH and HS-EMPA. Plasma norepinephrine levels were increased in HS-VEH compared to LS, and were suppressed in HS-EMPA, which was consistent with the neuronal activity of pre-sympathetic neurons in the brain. Increased left ventricular (LV) weight/body weight, plasma creatinine levels, renal fibrosis, and glomerular sclerosis in HS-VEH were attenuated in HS-EMPA. At 15 weeks , the high salt-induced blood pressure elevation was similar between HS-VEH and HS-EMPA. Although LV hypertrophy did not significantly differ, both decreased echocardiographic LV fractional shortening and increased lung weight observed in HS-VEH were attenuated in HS-EMPA. Elevated plasma creatinine and norepinephrine levels in HS-VEH were also attenuated in HS-EMPA. Conclusion: Empagliflozin inhibits sympathoexcitation and ameliorates cardio/renal injuries without lowering blood pressure in the hypertensive heart failure model. This sympathoinhibitory effect of empagliflozin observed in the pre-heart failure phase might contribute to the attenuation of heart failure progression.

Olfactory Receptor78 Participates in Carotid Body‐Dependent Sympathetic Activation and Hypertension in Murine Models of Obstructive Sleep Apnea

Olfactory receptor (Olfr) 78 participates in carotid body (CB) activation by acute hypoxia. We examined the role of Olfr78 in CB‐dependent sympathetic activation and hypertension in: 1) mice treated with chronic intermittent hypoxia (CIH) patterned after blood O2 profiles during obstructive sleep apnea (OSA) and 2) heme oxygenase‐2 (HO‐2) null mice, which exhibit OSA. CIH treated wild type (WT) mice showed: enhanced CB sensory nerve response to hypoxia and sensory long‐term facilitation (sLTF), hypertension, activation of the sympathetic nervous system as evidenced by spectral analysis of inter‐beat interval as well as elevated plasma nor‐epinephrine (NE) levels. All these responses were absent in Olfr78 null mice. HO‐2 null mice showed spontaneous apneas with an apnea index (AI) of 58±1.2 apneas/hour compared to AI of 8±0.8 apneas/hour in WT mice. CBs of HO‐2 null mice showed enhanced CB response to hypoxia and sLTF as well as elevated plasma NE levels and hypertension. The magnitude of hypertension correlated to AI in HO‐2 null mice (P<0.01). In striking contrast, HO‐2/Olfr78 double null mice showed stable breathing with an AI of 12±1.3 apneas/hour. HO‐2/Olfr78 double null mice showed absence of augmented CB response to hypoxia, sLTF, elevated plasma NE levels and hypertension. These results demonstrate that Olfr78 participates in CB activation and ensuing sympathetic nerve excitation and hypertension in two mouse models of OSA.

Absence of Erythropoietin and Cardio‐respiratory Responses to Hypobaric Hypoxia in Olfactory Receptor 78 Null mice

Hypobaric hypoxia (HH) evokes a series of physiological adaptations, including carotid body (CB)–dependent ventilatory acclimatization to hypoxia (VAH), elevated blood pressure (BP), and stimulation of erythropoietin (Epo) gene in the kidney. Olfactory receptor 78 (Olfr78) is a G‐protein coupled receptor that has been implicated in CB response to acute hypoxia. Given that both CB and kidney express Olfr78, we tested the hypothesis that Olfr78 plays a role in the cardio‐respiratory and renal Epo gene responses to HH. Studies were performed on wild type (WT) and Olfr78 null mice reared in room air (control) or exposed to 18h of HH (0.4 atmospheres). HH treated WT exhibited: 1) VAH manifested as increased baseline breathing, and enhanced hypoxic ventilatory response (HVR; 12% O2); 2) elevated BP and plasma norepinephrine levels; and 3) increased baseline CB sensory nerve activity and augmented CB sensory nerve response to subsequent acute hypoxia‐ all these responses to HH are either markedly attenuated or absent in Olfr78 null mice. WT mice responded to HH with activation of the renal Epo gene expression and elevated plasma Epo levels, and these effects were attenuated or absent in Olfr78 null mice. The attenuated Epo activation by HH was accompanied with markedly reduced hypoxia‐inducible factor (HIF)‐2α protein and reduced activation of HIF‐2 target gene Sod‐1 in Olfr78 null mice, suggesting impaired transcriptional activation of HIF‐2 contributes to attenuated Epo responses to HH. These results suggest a role for Olfr78 in physiological adaptations to HH experienced at high altitude

Depression of Non-Neuronal Cholinergic System May Play a Role in Co-Occurrence of Subjective Daytime Sleepiness and Hypertension in Patients with Obstructive Sleep Apnea Syndrome.

PurposeSimultaneous occurrence of hypertension and excessive daytime sleepiness (EDS) is very common in obstructive sleep apnea syndrome (OSAS), although no study has specifically addressed this issue. The present study explored the risk factors for co-occurrence of OSAS-related EDS and hypertension.Patients and MethodsA total of 161 OSAS patients were studied after undergoing an eight-hour in-laboratory polysomnography for one night. The OSAS severity assessment depends on the number of breathing disturbances per hour of sleep. EDS was defined using the Epworth Sleepiness Scale (ESS) scores of ≥13. Hypertension was defined according to direct cuff blood pressure (BP) measurements. Beat-to-beat R-R interval data were incorporated in polysomnography for heart rate variability analysis. The low-frequency/high-frequency band ratio was used to reflect sympathovagal balance. The study participants were divided into four groups based on the presence of EDS and/or hypertension: EDS with hypertension (n = 53), EDS without hypertension (n = 27), no EDS with hypertension (n = 38), and no EDS or hypertension (n = 43). Clinical, polysomnographic and heart rate data were compared and studied among the four groups. Plasma acetylcholine (ACh) levels were assessed to explore the effects of the non-neuronal cholinergic system and the co-occurrence of EDS and hypertension.ResultsPatients with EDS and hypertension had more severe OSAS severity indices compared to control patients. Increased cardiac sympathovagal imbalance and nocturnal hypoxemia regulated the presence of EDS and hypertension. Further plasma biomarker analysis revealed that both ESS scores and BP levels were associated with significantly elevated plasma norepinephrine, interleukin-6 and superoxide dismutase levels and significantly decreased ACh levels. Logistic regression analyses showed that ACh was the only factor significantly associated with co-occurrence of EDS and hypertension after controlling for confounders using odds ratio of 0.932, with a 95% confidence interval of 0.868 to 1.000 (P = 0.049).ConclusionThe results suggested that OSAS coupled with both EDS and hypertension is a more severe phenotype of the respiratory disorder. The presence of EDS and hypertension was accompanied by sympathovagal imbalance, and co-occurrence of these two conditions may be related to decreased plasma ACh levels.

Hyperadrenergic Orthostatic Hypotension With Pure Peripheral Sympathetic Denervation Associated With Sjogren’s Syndrome

Hyperadrenergic orthostatic hypertension (hyper OH), defined as OH with elevated levels of upright plasma norepinephrine (NE), is assumed to be a clinical expression of peripheral sympathetic denervation (PSD). Primary Sjogren’s syndrome (pSS) is an autoimmune disease that not only affects the exocrine glands but also develops autonomic neuropathy with PSD. We present a hyper OH with PSD possibly associated with pSS and successfully treated with intravenous immunoglobulin (IVIg). The case was a 60-year-old man who developed recurrent syncope on rapid standing from a sitting position. Head-up tilt test and NE infusion test showed hyper OH with PSD. This case report raises the possible associations between hyper OH and autonomic neuropathy as pSS developed.

Abstract P210: Central Blockade Of Tumor Necrosis Factor-Á-Converting Enzyme (tace) Ameliorates Neuroinflammation, Sympathetic Excitation And Cardiac Dysfunction In Heart Failure Rat

TACE is a key metalloprotease involved in ectodomain shedding of tumor necrosis factor (TNF)-α and transforming growth factor (TGF)-α. We previously reported that TACE-mediated production of TNF-α in the hypothalamic paraventricular nucleus (PVN) contributes to the sympathetic excitation in heart failure (HF). Additionally, the upregulated TGF-α in the PVN transactivates the epidermal growth factor receptor (EGFR) to activate extracellular signal-regulated kinase (ERK) 1/2 in HF. Here we sought to determine whether central inhibition of TACE attenuates neuroinflammation and prevents the progress of HF. Male rats underwent coronary artery ligation to induce HF or sham surgery (Sham). These rats were treated with bilateral PVN microinjection of a TACE siRNA or control siRNA while some rats received a 4-week intracerebroventricular (ICV) infusion of TACE inhibitor TAPI-0 or vehicle. Compared with Sham rats, HF rats treated with control siRNA, had higher (*P<0.05) levels of TNF-α (7.88±1.32* vs 2.77±0.98 pg/mL) and TGF-α (28.27±2.76* vs 11.62±2.48 pg/mL) in cerebrospinal fluid, and increased mRNA expression of TACE (2.53±0.30* vs 1.04±0.12), TNF-α (3.43±0.55* vs 1.03±0.11), TNF-α receptor 1 (2.32±0.27* vs 1.07±0.19), cyclooxygenase-2 (2.96±0.31* vs 1.10±0.19) and TGF-α (2.68±0.41* vs 1.06±0.14) in the PVN, but these levels were markedly reduced (39-54%*) in TACE siRNA-treated HF rats. Compared with control HF rats, HF rats treated with TACE siRNA had reduced expression of phosphorylated (p-) NF-κB p65 (1.27±0.14 vs 0.84±0.07*), p-EGFR (0.52±0.05 vs 0.37±0.04*) and p-ERK1/2 (1.06±0.10 vs 0.62±0.09*) in the PVN. Moreover, the elevated plasma norepinephrine levels, lung/body weight, heart/body weight and left ventricular (LV) end-diastolic pressure along with decreased LV dP/dt max in HF rats-treated with control siRNA were significantly attenuated in HF rats treated with TACE siRNA. Treatments with TACE siRNA in the PVN also improved the indicators of cardiac hypertrophy and fibrosis of HF. ICV infusion of TAPI-0 had the similar effects with PVN TACE siRNA on these variables in HF. These data indicate that central interventions suppressing TACE activity ameliorate neuroinflammation, sympathetic activation and cardiac dysfunction in HF.

Gene expression profiles T helper cell chemokines, cytokines and transcription factors in the genital tract of a stress mouse model during Chlamydia muridarum infection

A stress mouse model established in our laboratory showed that prolonged exposure of mice to cold water-induced stress results in elevated plasma norepinephrine levels, increased intensity of Chlamydia muridarum genital infection, and decreased functions of the immune system. The current study was designed to test whether Active Hexose Correlated Compound (AHCC) modulates the gene expression profiles of chemokines associated with either Thelper 1 (Th1) or Th2 in the stress model. We hypothesized that oral administration of AHCC feeding up-regulates the gene expression profiles of Th1 chemokines and Th1 transcription factors and increases the secretion of cytokines in Th cells and lysates of the genital tract. During the stressing period of 21 days, we mice either 300 mg/kg of AHCC or PBS per day using a gavage feeding technique. We used real PCR to determine gene expression of chemokines favoring Th1 or Th2 chemokines and cytokines. We used ELISA to assess cytokine production in the genital tract lysates. Oral administration of AHCC to stressed mice resulted in the up-regulation of Th1 chemokines. The level of mRNA fold-changes of CXCL10 (+2.2 fold), CXCL9 (+1.8 fold), and CCL5 (+2.fold) was observed. Moreover, AHCC feeding resulted in a significant increase in productions of interleukin-1b, and interleukin 10(IL-10) in the genital tract of stressed mice. However, the production of TNF-a and IL-6 were undetectable by ELISA. Although further study is needed, preliminary data suggest that AHCC feeding favors the production of protective cytokines in our stress mouse model. (Supported by NIH Grant P20GM103434 to the West Virginia IDeA Network for Biomedical Research Excellence and NIH Grant P20GM103434 awarded to Bluefield State College).

Prostaglandin E2 receptor EP3 subtype in the paraventricular hypothalamic nucleus mediates corticotropin-releasing factor-induced elevation of plasma noradrenaline levels in rats

Corticotropin-releasing factor (CRF) plays an important role in sympathetic regulation. Centrally administered CRF elevates plasma catecholamine levels, resulting in CRF-dependent hypertension and tachycardia. We previously reported that brain thromboxane A2 mediates CRF-induced elevation of plasma adrenaline levels, whereas prostanoids other than thromboxane A2 mediate elevations in plasma noradrenaline levels. However, the mechanism by which CRF induces elevations in plasma noradrenaline levels remains unknown. Previous studies have revealed that brain prostaglandin (PG) E2, but not other PGs, causes sympathetic activation. In this study, we examined the roles of brain PGE2 and its receptors in CRF-induced elevation of plasma noradrenaline levels in rats. Our results showed that intracerebroventricular pretreatment with an antagonist of the PGE2 receptor EP3 subtype, but not other subtypes, suppressed CRF-induced elevations in plasma noradrenaline levels. We also examined the role of PGE2 and EP3 receptors in the paraventricular hypothalamic nucleus (PVN), the major integrative center for sympathetic regulation, in CRF-induced elevation of plasma noradrenaline levels. Centrally administered CRF increased PGE2 levels in PVN microdialysates, and microinjection of an EP3 receptor agonist into the PVN elevated plasma noradrenaline levels. Bilateral blockade of EP3 receptors in the PVN suppressed the elevation of plasma noradrenaline levels evoked by intracerebroventricular administration and PVN-microinjection of CRF. Our results suggest that CRF stimulates PGE2 release into the PVN that activates EP3 receptors in the PVN, resulting in the elevation of plasma noradrenaline levels.

MON-386 Finding Truth from Two False-Positives

Certain medications can interfere with catecholamines levels and result in a misleading diagnosis of pheochromocytoma. Tricyclic antidepressants, alpha-blockers, beta-blockers, and acetaminophens are the most common cause of falsely elevated levels of catecholamines. To confirm and localize pheochromocytoma, 123I-Metaiodobenzylguanidine (123I-MIBG) scintigraphy scan is usually performed following a biochemical test if CT or MRI has failed to detect the tumor. Here we describe a 48-year-old African-American male who was found to have a medication-related elevation in catecholamines with positive 123I-MIBG adrenal uptake. He was referred to the endocrinology clinic for elevated plasma epinephrine, norepinephrine, and dopamine levels. His primary care physician obtained catecholamines levels for recurrent episodes of anxiety, sweating, and dizziness. No history of hypertension was noted. His medications include alprazolam for anxiety, hydrocodone/acetaminophen for chronic back pain, valproic acid for mood-stablilizing, and escitalopram for depression. At the first visit, his blood pressure was 162/110. Otherwise, an unremarkable physical exam was noted. Initial blood work at an outside facility showed plasma dopamine > 3000 pg/mL (Ref 0-20 pg/mL), epinephrine 6827 pg/mL (Ref 0-62 pg/mL), and norepinephrine 51919 pg/mL (Ref 80-520 pg/mL). The patient underwent MRI of the abdomen and pelvis before the referral, which was unremarkable, and had an 123I-MIBG scan that showed increased accumulation over the left adrenal gland; none was seen over the right adrenal gland. We withheld his medications except for alprazolam. Catecholamine levels were retested after four weeks and showed normal plasma epinephrine, norepinephrine, metanephrine, and normetanephrine levels. The 123I-MIBG scan is highly sensitive and specific for the detection of pheochromocytoma. However, 123I-MIBG uptake can also be seen in normal adrenal medulla (16% of scans after 48 h). The pattern of 123I-MIBG uptake may be asymmetrical between the left and right adrenals, and therefore, caution should be applied in interpreting the images obtained, particularly to avoid unnecessary or misguided surgery. This case demonstrates a unilateral 123I-MIBG adrenal uptake possibly associated with medications. It is expected that the uptake would be bilateral, given the systemic effect of the medications. Nonetheless, in this case, unilateral adrenal uptake was found. Medication-induced catecholamine elevation has to be ruled out before further investigation for pheochromocytoma. This step is crucial given the non-specific symptoms of pheochromocytoma and the possibility of having false catecholamines elevation and false 123I-MIBG uptake, both of which further challenge the diagnosis of pheochromocytoma.

GABAB receptors in the hypothalamic paraventricular nucleus mediate β-adrenoceptor-induced elevations of plasma noradrenaline in rats

In the brain, various neurotransmitters such as noradrenaline and GABA regulate peripheral sympathetic functions. Previously, it has been reported that both β-adrenoceptor activation and GABAB receptor activation in the brain are involved in the elevation of plasma noradrenaline levels. However, it is unknown whether these pathways interact with each other. In the present study, we examined the relationship between the central actions of β-adrenoceptor activation and GABAB receptor activation with regard to plasma noradrenaline responses using urethane-anesthetized rats. Intracerebroventricular pretreatment with the GABAA receptor antagonist bicuculline did not affect the β-adrenoceptor agonist isoproterenol-induced elevation of plasma noradrenaline levels. In contrast, pretreatment with the GABAB receptor antagonist CGP 35348 suppressed the isoproterenol-induced elevation of noradrenaline levels. Intracerebroventricular pretreatment with the β-adrenoceptor antagonist propranolol did not alter the GABAB receptor agonist baclofen-induced elevation of plasma noradrenaline levels. We next examined the central effects of β-adrenoceptor activation on GABA release in the paraventricular hypothalamic nucleus (PVN), the major integrative center for sympathetic regulation in the brain. Intracerebroventricular administration of isoproterenol increased GABA content in PVN dialysates. In addition, baclofen microinjected unilaterally into the PVN resulted in elevated plasma levels of noradrenaline, but not adrenaline. Finally, unilateral blockade of GABAB receptors in the PVN suppressed the isoproterenol-induced elevation of plasma noradrenaline level. Our results suggest that activation of β-adrenoceptors in the brain, likely in the PVN, induces GABA release in the PVN, which in turn activates GABAB receptors in the PVN, leading to elevated plasma noradrenaline.

BDNF contributes to the skeletal muscle anti-atrophic effect of exercise training through AMPK-PGC1α signaling in heart failure mice.

IntroductionExercise training is a coadjuvant therapy in preventive cardiology, and it delays cardiac dysfunction and exercise intolerance in heart failure (HF). However, the mechanisms underlying muscle function improvement and cardioprotection are poorly understood. In this study, we tested whether exercise training would counteract skeletal muscle atrophy via activation of the BDNF pathway in myocardial infarction (MI)-induced HF mice.Material and methodsA cohort of male Sham-operated and MI mice were assigned into 8-week moderate exercise training, and untrained counterparters were used as control. Exercise capacity, plasma norepinephrine (NE) level, heart rate (HR), fractional shortening (FS) and ejection fraction (EF) were measured. The protein expression of BDNF, p-TrkB, p-AMPK and PGC1α were analyzed by Western blot.ResultsCompared with the Sham-operated mice, MI mice displayed reduced total distance run and elevated plasma NE level (both p < 0.05). Exercise training significantly improved distance run and plasma NE levels in HF mice (both p < 0.05). Significantly increased HR, decreased FS and EF were observed in the MI group as compared to the Sham-operated group, and exercise training prevent the hemodynamic status and systolic dysfunction in MI mice (all p < 0.05). The expression of BDNF, p-TrkB, p-AMPK and PGC1α were significantly decreased in the skeletal muscle from MI compared to Sham-operated mice, which were significantly increased by exercise training (all p < 0.05). In addition, BDNF siRNA markedly decreased the protein level of p-AMPK and PGC1α in C2C12 myoblasts.ConclusionsTaken together, our data provide evidence for exercise training may counteract HF-induced muscle atrophy through induced activation of BDNF pathway.

Norepinephrine levels in children with single ventricle circulation

Elevated plasma norepinephrine levels are a strong independent predictor of mortality in adults with heart failure with systolic dysfunction, and provide the mechanistic basis to its therapeutic paradigm. The pathogenesis of heart failure in the single ventricle circulation is unknown. It remains controversial whether conventional neurohormonal blockade in this population is beneficial. We hypothesize that norepinephrine levels can be elevated in children with single ventricle circulation and that it is associated with a poor outcome.Norepinephrine levels were collected from 22 consecutive single ventricle and 7 control patients at the time of catheterization. The disease group was followed for the development of heart failure and a composite outcome of death or transplant.Median age at norepinephrine level was 2.4years (interquartile range 93days–16.8years) and follow-up duration was 9.8years (range 75days–10.5years), during which 5 patients (23%) met a composite outcome of either death (n=4) or transplantation (n=1). While ventricular dysfunction and individual invasive hemodynamic parameters were not predictive of subsequent composite outcome, a norepinephrine level >369pg/mL at time of catheterization was associated with a decreased freedom from the composite outcome.In this study of children with single ventricle circulation, elevated norepinephrine levels were observed and were associated with a poor outcome. Consideration should be given to the further study of the role of neurohormonal activation and potentially its blockade, currently used for heart failure from systolic dysfunction, in the management of this high risk congenital heart disease population.

Plasma Catecholamine Profile of Subarachnoid Hemorrhage Patients with Neurogenic Cardiomyopathy

Purpose: To investigate the connection between sympathetic function and neurogenic cardiomyopathy (NC), and to determine whether NC is mediated primarily by circulating adrenal epinephrine (EPI) or neuronally transmitted norepinephrine (NE), following subarachnoid hemorrhage (SAH). Methods: This is a prospective observational investigation of consecutive severe-grade SAH patients. All participants had transthoracic echocardiography and serological assays for catecholamine levels - dopamine (DA), NE and EPI - within 48 h of hemorrhage onset. Clinical and serological independent predictors of NC were determined using multivariate logistic regression analyses, and the accuracy of predictors was assessed by receiver operating characteristic (ROC) curves. Multivariate linear regression analyses were used to evaluate correlations among the catecholamines. Results: The investigation included a total of 94 subjects: the mean age was 55 years, 81% were female and 57% were Caucasian. NC was identified in approximately 10% (9/94) of cases. Univariate analyses revealed associations between NC and worse clinical severity (p = 0.019), plasma DA (p = 0.018) and NE levels (p = 0.024). Plasma NE correlated with DA levels (ρ = 0.206, p = 0.046) and EPI levels (ρ = 0.392, p < 0.001), but was predicted only by plasma EPI in bivariate [parameter estimate (PE) = 1.95, p < 0.001] and multivariate (PE = 1.89, p < 0.001) linear regression models. Multivariate logistic regression analyses consistently demonstrated the predictive value of clinical grade for NC (p < 0.05 for all analyses) except in models incorporating plasma NE, where NC was independently predicted by NE level (OR 1.25, 95% CI 1.01-1.55) over clinical grade (OR 4.19, 95% CI 0.874-20.1). ROC curves similarly revealed the greater accuracy of plasma NE [area under the curve (AUC) 0.727, 95% CI 0.56-0.90, p = 0.02] over clinical grade (AUC 0.704, 95% CI 0.55-0.86, p = 0.05) for identifying the presence or absence of NC. Conclusions: Following SAH, the development of NC is primarily related to elevated plasma NE levels. Findings implicate a predominantly neurogenic process mediated by neuronal NE (and not adrenal EPI), but cannot exclude synergy between the catecholamines.

Elevated plasma norepinephrine level and sick sinus syndrome in patients with lone atrial fibrillation

ObjectivePlasma norepinephrine (NE) level can be a guide to mortality in patients with heart failure. This study aimed to evaluate the significance of plasma NE level compared with plasma natriuretic...

Adrenal Lymphangioma Masquerading as a Catecholamine Producing Tumor.

Objective. To report the unusual case of an adrenal lymphangioma presenting in a patient with an adrenal cystic lesion and biochemical testing concerning for pheochromocytoma. The pertinent diagnostic and imaging features of adrenal lymphangiomas are reviewed. Methods. We describe a 59-year-old patient who presented with hyperhidrosis and a 2.2 by 2.2 cm left adrenal nodule. Biochemical evaluation revealed elevated plasma-free normetanephrine, urine normetanephrine, urine vanillylmandelic acid, and urine norepinephrine levels. Elevated plasma norepinephrine levels were not suppressed appropriately with clonidine administration. Results. Given persistent concern for pheochromocytoma, the patient underwent adrenalectomy. The final pathology was consistent with adrenal lymphangioma. Conclusions. Lymphangiomas are benign vascular lesions that can very rarely occur in the adrenal gland. Imaging findings are generally consistent with a cyst but are nonspecific. Excluding malignancy in patients presenting with adrenal cysts can be difficult. Despite its benign nature, the diagnosis of adrenal lymphangioma may ultimately require pathology.

Catheter-Based Renal Sympathetic Denervation Significantly Inhibits Atrial Fibrillation Induced by Electrical Stimulation of the Left Stellate Ganglion and Rapid Atrial Pacing

BackgroundSympathetic activity involves the pathogenesis of atrial fibrillation (AF). Renal sympathetic denervation (RSD) decreases sympathetic renal afferent nerve activity, leading to decreased central sympathetic drive. The aim of this study was to identify the effects of RSD on AF inducibility induced by hyper-sympathetic activity in a canine model.MethodsTo establish a hyper-sympathetic tone canine model of AF, sixteen dogs were subjected to stimulation of left stellate ganglion (LSG) and rapid atrial pacing (RAP) for 3 hours. Then animals in the RSD group (n = 8) underwent radiofrequency ablation of the renal sympathetic nerve. The control group (n = 8) underwent the same procedure except for ablation. AF inducibility, effective refractory period (ERP), ERP dispersion, heart rate variability and plasma norepinephrine levels were measured at baseline, after stimulation and after ablation.ResultsLSG stimulation combined RAP significantly induced higher AF induction rate, shorter ERP, larger ERP dispersion at all sites examined and higher plasma norepinephrine levels (P<0.05 in all values), compared to baseline. The increased AF induction rate, shortened ERP, increased ERP dispersion and elevated plasma norepinephrine levels can be almost reversed by RSD, compared to the control group (P<0.05). LSG stimulation combined RAP markedly shortened RR-interval and standard deviation of all RR-intervals (SDNN), Low-frequency (LF), high-frequency (HF) and LF/HF ratio (P<0.05). These changes can be reversed by RSD, compared to the control group (P<0.05).ConclusionsRSD significantly reduced AF inducibility and reversed the atrial electrophysiological changes induced by hyper-sympathetic activity.

Insulin restores myocardial presynaptic sympathetic neuronal integrity in insulin-resistant diabetic rats

BackgroundDiabetes is associated with increased sympathetic activity, elevated norepinephrine, impaired heart rate variability, and the added risk of cardiovascular mortality. The temporal development of sympathetic neuronal dysfunction, response to therapy, and relation to ventricular function is not well characterized. Methods and ResultsSympathetic neuronal integrity was serially investigated in high fat diet-fed streptozotocin diabetic rats using [11C]meta-hydroxyephedrine (HED) positron emission tomography at baseline, 8 weeks of diabetes, and after a further 8 weeks of insulin or insulin-sensitizing metformin therapy. Myocardial HED retention was reduced in diabetic rats (n = 16) compared to non-diabetics (n = 6) at 8 weeks by 52-57% (P = .01) with elevated plasma and myocardial norepinephrine levels. Echocardiography pulse-wave Doppler measurements demonstrated prolonged mitral valve deceleration and increased early-to-atrial filling velocity, consistent with diastolic dysfunction. Insulin but not metformin evoked recovery of HED retention and plasma norepinephrine (P < .05), whereas echocardiography measurements of diastolic function were not improved by either treatment. Relative expressions of norepinephrine reuptake transporter and β-adrenoceptors were lower in metformin-treated as compared to insulin-treated diabetic and non-diabetic rats. Diabetic rats exhibited depressed heart rate variability and impaired diastolic function which persisted despite insulin treatment. ConclusionsHED imaging provides sound estimation of sympathetic function. Effective glycemic control can recover sympathetic function in diabetic rats without the corresponding recovery of echocardiography indicators of diastolic dysfunction. HED positron emission tomography imaging may be useful in stratifying cardiovascular risk among diabetic patients and in evaluating the effect of glycemic therapy on the heart.

Protective effect of ischemic preconditioning on ischemia/reperfusion-induced acute kidney injury through sympathetic nervous system in rats

We have found that a series of brief renal ischemia and reperfusion (preconditioning), before the time of ischemia significantly attenuated the ischemia/reperfusion-induced acute kidney injury through endothelial nitric oxide synthase. In this study, we examined the effects of ischemic preconditioning on renal sympathetic nervous system and kidney function in ischemia/reperfusion-induced acute kidney injury with or without nitric oxide synthase inhibitor. Ischemia/reperfusion-induced acute kidney injury was made by clamping the left renal artery and vein for 45-min followed by reperfusion, 2 weeks after the contralateral nephrectomy. Ischemic preconditioning, consisting of three cycles of 2-min ischemia followed by 5-min reperfusion, was performed before the 45-min ischemia. Ischemic preconditioning suppressed the enhanced renal sympathetic nerve activity during ischemia and the elevated renal venous plasma norepinephrine level after reperfusion, and attenuated renal dysfunction and histological damage. The renoprotective effect of ischemic preconditioning was diminished by NG-nitro-L-arginine methyl ester (0.3mg/kg, i.v.), a nonselective nitric oxide synthase inhibitor, 5min before the start of ischemic preconditioning. Thus, ischemic preconditioning decreased renal sympathetic nerve activity and norepinephrine release probably through activating nitric oxide production, thereby improving ischemia/reperfusion-induced acute kidney injury.

Reversal of cardiac dysfunction and subcellular alterations by metoprolol in heart failure due to myocardial infarction

In order to examine the reversibility of heart failure due to myocardial infarction (MI) by β-adrenoceptor blockade, 12 weeks infarcted rats were treated with or without metoprolol (50 mg/kg/day) for 8 weeks. The depressed left ventricular (LV) systolic pressure, positive and negative rates of changes in pressure development, ejection fraction, fractional shortening and cardiac output, as well as increased LV end-diastolic pressure in 20 weeks MI animals were partially reversed by metoprolol. MI-induced decreases in septum (systolic) thickness as well as increase in LV posterior wall thickness and LV internal diameter were partially or fully reversible by metoprolol. Treatment of MI animals with metoprolol partially reversed the elevated levels of plasma norepinephrine and dopamine without affecting the elevated levels of epinephrine. Although sarcoplasmic reticular (SR) Ca(2+)-uptake, as well as protein content for SR Ca(2+)-pump and phospholamban, were reduced in the infarcted hearts; these changes were partially reversible with metoprolol. Depressed myofibrillar Ca(2+)-stimulated ATPase activity, as well as mRNA levels for SR Ca(2+)-pump, phospholamban and α-myosin heavy chain, were unaffected whereas increased mRNA level for β-myosin heavy chain was partially reversed by metoprolol. The results suggest that partial improvement of cardiac performance by β-adrenoceptor blockade at advanced stages of heart failure may be due to partial reversal of changes in SR Ca(2+)-pump function whereas partial to complete reverse cardiac remodeling may be due to partial reduction in the elevated levels of plasma catecholamines.

Central Nervous System Gαi 2 -Subunit Proteins Maintain Salt Resistance via a Renal Nerve–Dependent Sympathoinhibitory Pathway

In salt-resistant phenotypes, chronic elevated dietary sodium intake evokes suppression of renal sodium-retaining mechanisms to maintain sodium homeostasis and normotension. We have recently shown that brain Gαi 2 protein pathways are required to suppress renal sympathetic nerve activity and facilitate maximal sodium excretion during acute intravenous volume expansion in Sprague-Dawley rats. Here, we studied the role of brain Gαi 2 proteins in the endogenous central neural mechanisms acting to maintain fluid and electrolyte homeostasis and normotension during a chronic elevation in dietary salt intake. Naive or bilaterally renal denervated adult male Sprague-Dawley rats were randomly assigned to receive an intracerebroventricular scrambled or Gαi 2 oligodeoxynucleotide infusion and then subjected to either a normal salt (0.4%) or high-salt (8.0%) diet for 21 days. In scrambled oligodeoxynucleotide-infused rats, salt loading, which did not alter blood pressure, evoked a site-specific increase in hypothalamic paraventricular nucleus Gαi 2 protein levels and suppression of circulating norepinephrine content and plasma renin activity. In salt-loaded rats continuously infused intracerebroventricularly with a Gαi 2 oligodeoxynucleotide, animals exhibited sodium and water retention, elevated plasma norepinephrine levels, and hypertension, despite suppression of plasma renin activity. Furthermore, in salt-loaded bilaterally renal denervated rats, Gαi 2 oligodeoxynucleotide infusion failed to evoke salt-sensitive hypertension. Therefore, in salt-resistant rats subjected to a chronic high-salt diet, brain Gαi 2 proteins are required to inhibit central sympathetic outflow to the kidneys and maintain sodium balance and normotension. In conclusion, these data demonstrate a central role of endogenous brain, likely paraventricular nucleus-specific, Gαi 2 -subunit protein–gated signal transduction pathways in maintaining a salt-resistant phenotype.