Epinephrine Is Required for Normal Cardiovascular Responses to Stress in the Phenylethanolamine N-Methyltransferase Knockout Mouse

Peripheral to brain and hippocampus crosstalk induced by exercise mediates cognitive and structural hippocampal adaptations

Endurance exercise leads to robust increases in memory and learning. Several exercise adaptations occur to mediate these improvements, including in both the hippocampus and in peripheral organs. Organ crosstalk has been becoming increasingly more present in exercise biology, and studies have shown that peripheral organs can communicate to the hippocampus and mediate hippocampal changes. Both learning and memory as well as other hippocampal functional-related changes such as neurogenesis, cell proliferation, dendrite morphology and synaptic plasticity are controlled by these exercise responsive peripheral proteins. These peripheral factors, also called exerkines, are produced by several organs including skeletal muscle, liver, adipose tissue, kidneys, adrenal glands and circulatory cells. Previous reviews have explored some of these exerkines including muscle-derived irisin and cathepsin B (CTSB), but a full picture of peripheral to hippocampus crosstalk with novel exerkines such as selenoprotein 1 (SEPP1) and platelet factor 4 (PF4), or old overlooked ones such as lactate and insulin-like growth factor 1 (IGF-1) is still missing. We provide 29 different studies of 14 different exerkines that crosstalk with the hippocampus. Thus, the purpose of this review is to explore peripheral exerkines that have shown to exert hippocampal function following exercise, demonstrating their particular effects and molecular mechanisms in which they could be inducing adaptations.

Aerobic training increases renal antioxidant defence and reduces angiotensin II levels, mitigating the high mortality in SHR-STZ model

OBJECTVE

The purpose of the research was to investigate the effects of aerobic training on renal function, oxidative stress, intrarenal renin-angiotensin system, and mortality of hypertensive and diabetic (SHR-STZ) rats.

MATERIALS AND METHODS

Blood pressure, creatinine, urea levels, urinary glucose, urine volume, and protein excretion were reduced in trained SHR-STZ rats.

RESULTS

Aerobic training not only attenuated oxidative stress but also elevated the activity of antioxidant enzymes in the kid'ney of SHR-STZ rats. Training increased intrarenal levels of angiotensin-converting enzymes (ACE and ACE2) as well as the neprilysin (NEP) activity, along with decreased intrarenal angiotensin II (Ang II) levels. Aerobic training significantly improved the survival of STZ-SHR rats.

CONCLUSION

The protective role of aerobic training was associated with improvements in the renal antioxidative capacity, reduced urinary protein excretion along with reduced intrarenal Ang II and increased NEP activity. These findings might reflect a better survival under the combined pathological conditions, hypertension, and diabetes.

Traditional medicinal use is linked with apparency, not specialized metabolite profiles in the order Caryophyllales

PREMISE

Better understanding of the relationship between plant specialized metabolism and traditional medicine has the potential to aid in bioprospecting and untangling of cross-cultural use patterns. However, given the limited information available for metabolites in most plant species, understanding medicinal use-metabolite relationships can be difficult. The order Caryophyllales has a unique pattern of lineages of tyrosine- or phenylalanine-dominated specialized metabolism, represented by mutually exclusive anthocyanin and betalain pigments, making Caryophyllales a compelling system to explore the relationship between medicine and metabolites by using pigment as a proxy for dominant metabolism.

METHODS

We compiled a list of medicinal species in select tyrosine- or phenylalanine-dominant families of Caryophyllales (Nepenthaceae, Polygonaceae, Simmondsiaceae, Microteaceae, Caryophyllaceae, Amaranthaceae, Limeaceae, Molluginaceae, Portulacaceae, Cactaceae, and Nyctaginaceae) by searching scientific literature until no new uses were recovered. We then tested for phylogenetic clustering of uses using a "hot nodes" approach. To test potential non-metabolite drivers of medicinal use, like how often humans encounter a species (apparency), we repeated the analysis using only North American species across the entire order and performed phylogenetic generalized least squares regression (PGLS) with occurrence data from the Global Biodiversity Information Facility (GBIF).

RESULTS

We hypothesized families with tyrosine-enriched metabolism would show clustering of different types of medicinal use compared to phenylalanine-enriched metabolism. Instead, wide-ranging, apparent clades in Polygonaceae and Amaranthaceae are overrepresented across nearly all types of medicinal use.

CONCLUSIONS

Our results suggest that apparency is a better predictor of medicinal use than metabolism, although metabolism type may still be a contributing factor.

Molecular pathways underlying sympathetic autonomic overshooting leading to fear and traumatic memories: looking for alternative therapeutic options for post-traumatic stress disorder

The sympathoadrenal medullary system and the hypothalamic-pituitary-adrenal axis are both activated upon stressful events. The release of catecholamines, such as dopamine, norepinephrine (NE), and epinephrine (EPI), from sympathetic autonomic nerves participate in the adaptive responses to acute stress. Most theories suggest that activation of peripheral β-adrenoceptors (β-ARs) mediates catecholamines-induced memory enhancement. These include direct activation of β-ARs in the vagus nerve, as well as indirect responses to catecholamine-induced glucose changes in the brain. Excessive sympathetic activity is deeply associated with memories experienced during strong emotional stressful conditions, with catecholamines playing relevant roles in fear and traumatic memories consolidation. Recent findings suggest that EPI is implicated in fear and traumatic contextual memories associated with post-traumatic stress disorder (PTSD) by increasing hippocampal gene transcription (e.g., Nr4a) downstream to cAMP response-element protein activation (CREB). Herein, we reviewed the literature focusing on the molecular mechanisms underlying the pathophysiology of memories associated with fear and traumatic experiences to pave new avenues for the treatment of stress and anxiety conditions, such as PTSD.

Glucoregulatory disruption in male mice offspring induced by maternal transfer of endocrine disrupting brominated flame retardants in DE-71

Introduction

Polybrominated diphenyl ethers (PBDEs) are commercially used flame retardants that bioaccumulate in human tissues, including breast milk. PBDEs produce endocrine and metabolic disruption in experimental animals and have been associated with diabetes and metabolic syndrome (MetS) in humans, however, their sex-specific diabetogenic effects are not completely understood. Our past works show glucolipid dysregulation resulting from perinatal exposure to the commercial penta-mixture of PBDEs, DE-71, in C57BL/6 female mice.

Methods

As a comparison, in the current study, the effects of DE-71 on glucose homeostasis in male offspring was examined. C57BL/6N dams were exposed to DE-71 at 0.1 mg/kg/d (L-DE-71), 0.4 mg/kg/d (H-DE-71), or received corn oil vehicle (VEH/CON) for a total of 10 wks, including gestation and lactation and their male offspring were examined in adulthood.

Results

Compared to VEH/CON, DE-71 exposure produced hypoglycemia after a 11 h fast (H-DE-71). An increased fast duration from 9 to 11 h resulted in lower blood glucose in both DE-71 exposure groups. In vivo glucose challenge showed marked glucose intolerance (H-DE-71) and incomplete clearance (L- and H-DE-71). Moreover, L-DE-71-exposed mice showed altered glucose responses to exogenous insulin, including incomplete glucose clearance and/or utilization. In addition, L-DE-71 produced elevated levels of plasma glucagon and the incretin, active glucagon-like peptide-1 (7-36) amide (GLP-1) but no changes were detected in insulin. These alterations, which represent criteria used clinically to diagnose diabetes in humans, were accompanied with reduced hepatic glutamate dehydrogenase enzymatic activity, elevated adrenal epinephrine and decreased thermogenic brown adipose tissue (BAT) mass, indicating involvement of several organ system targets of PBDEs. Liver levels of several endocannabinoid species were not altered.

Discussion

Our findings demonstrate that chronic, low-level exposure to PBDEs in dams can dysregulate glucose homeostasis and glucoregulatory hormones in their male offspring. Previous findings using female siblings show altered glucose homeostasis that aligned with a contrasting diabetogenic phenotype, while their mothers displayed more subtle glucoregulatory alterations, suggesting that developing organisms are more susceptible to DE-71. We summarize the results of the current work, generated in males, considering previous findings in females. Collectively, these findings offer a comprehensive account of differential effects of environmentally relevant PBDEs on glucose homeostasis and glucoregulatory endocrine dysregulation of developmentally exposed male and female mice.

Cell Networks in Endocrine/Neuroendocrine Gland Function

Reproduction, growth, stress, and metabolism are determined by endocrine/neuroendocrine systems that regulate circulating hormone concentrations. All these systems generate rhythms and changes in hormone pulsatility observed in a variety of pathophysiological states. Thus, the output of endocrine/neuroendocrine systems must be regulated within a narrow window of effective hormone concentrations but must also maintain a capacity for plasticity to respond to changing physiological demands. Remarkably most endocrinologists still have a "textbook" view of endocrine gland organization which has emanated from 20^th century histological studies on thin 2D tissue sections. However, 21^st -century technological advances, including in-depth 3D imaging of specific cell types have vastly changed our knowledge. We now know that various levels of multicellular organization can be found across different glands, that organizational motifs can vary between species and can be modified to enhance or decrease hormonal release. This article focuses on how the organization of cells regulates hormone output using three endocrine/neuroendocrine glands that present different levels of organization and complexity: the adrenal medulla, with a single neuroendocrine cell type; the anterior pituitary, with multiple intermingled cell types; and the pancreas with multiple intermingled cell types organized into distinct functional units. We give an overview of recent methodologies that allow the study of the different components within endocrine systems, particularly their temporal and spatial relationships. We believe the emerging findings about network organization, and its impact on hormone secretion, are crucial to understanding how homeostatic regulation of endocrine axes is carried out within endocrine organs themselves. © 2022 American Physiological Society. Compr Physiol 12:3371-3415, 2022.

Targeting Adrenergic Receptors in Metabolic Therapies for Heart Failure

The heart has a reduced capacity to generate sufficient energy when failing, resulting in an energy-starved condition with diminished functions. Studies have identified numerous changes in metabolic pathways in the failing heart that result in reduced oxidation of both glucose and fatty acid substrates, defects in mitochondrial functions and oxidative phosphorylation, and inefficient substrate utilization for the ATP that is produced. Recent early-phase clinical studies indicate that inhibitors of fatty acid oxidation and antioxidants that target the mitochondria may improve heart function during failure by increasing compensatory glucose oxidation. Adrenergic receptors (α1 and β) are a key sympathetic nervous system regulator that controls cardiac function. β-AR blockers are an established treatment for heart failure and α1A-AR agonists have potential therapeutic benefit. Besides regulating inotropy and chronotropy, α1- and β-adrenergic receptors also regulate metabolic functions in the heart that underlie many cardiac benefits. This review will highlight recent studies that describe how adrenergic receptor-mediated metabolic pathways may be able to restore cardiac energetics to non-failing levels that may offer promising therapeutic strategies.

Epinephrine May Contribute to the Persistence of Traumatic Memories in a Post-traumatic Stress Disorder Animal Model

The importance of catecholamines in post-traumatic stress disorder (PTSD) still needs to be explored. We aimed to evaluate epinephrine’s (EPI) causal role and molecular mechanism for the persistence of PTSD traumatic memories. Wild-type (WT) and EPI-deficient mice (phenylethanolamine-N-methyltransferase-knockout mice, Pnmt-KO) were induced with PTSD and behavioral tests were performed. Some Pnmt-KO mice were administered with EPI or vehicle. Catecholamines were quantified by HPLC-ED. Nr4a1, Nr4a2, and Nr4a3 mRNA expression were evaluated by real-time PCR in hippocampus samples. It was observed an increase in EPI and freezing behavior, and a decrease in open arm entries in the elevated plus-maze test and time spent in the light in the light–dark test in WT mice in the PTSD-induction group compared to control. After induction of PTSD, Pnmt-KO mice showed a decrease in freezing, as well as an increase in open arm entries and transitions between compartments compared to WT. After PTSD induction, Pnmt-KO mice administered with EPI showed an increase in freezing compared with the vehicle. On day 0 of PTSD induction, it was observed an increase in mRNA expression of Nr4a2 and Nr4a3 genes in the hippocampus of WT mice compared to control, contrary to Pnmt-KO mice. In conclusion, our data suggest that EPI may be involved in the persistence of traumatic memories in PTSD, possibly through enhancement of the expression of Nr4a2 and Nr4a3 genes in the hippocampus. Peripheral administration of EPI restored contextual traumatic memories in Pnmt-KO mice, which suggests a causal role for EPI. The persistence of contextual traumatic memories may contribute to anxiety-like behavior and resistance of traumatic memory extinction in this PTSD mice model.

Epistasis between phenylethanolamine N-methyltransferase and β2-adrenergic receptor influences extracellular epinephrine level and associates with the susceptibility to allergic asthma

BACKGROUND

Reduced extracellular epinephrine level often associates with asthma-related symptoms; however, the correlation between asthma and genetic variants in genes participating in the epinephrine signalling pathway remains unclear.

OBJECTIVE

To characterize the functions of single nucleotide polymorphisms (SNPs) in phenylethanolamine N-methyltransferase (PNMT) and β2-adrenergic receptor (ADRB2), and to study the effects, including both direct and epistatic, of these SNPs on serum epinephrine level and asthma susceptibility.

METHODS

Single nucleotide polymorphisms functions were characterized through in vitro luciferase assay. ADRB2 gene expression level in peripheral blood mononuclear cell (PBMC) was measured by transcriptome sequencing and expression microarray on two separate Asian cohorts (NUS-UTAR, n = 278 and NUS-TA, n = 58). Serum epinephrine level was assessed on a Singapore Chinese cohort (NUS-SH, n = 314) with 155 asthmatic and 159 non-asthmatic subjects. A separate Singapore Chinese cohort (NUS-G, n = 3009) was genotyped to show disease association (direct and epistatic effect) of functional SNPs in PNMT and ADRB2.

RESULTS

Reduced serum epinephrine level was associated with increased asthma risk in Singapore Chinese. The minor allele of rs876493 was shown to increase PNMT promoter activity and reduce asthma risk. Multiple SNPs in ADRB2 forms a haplotype that was associated with the differential promoter activity of this gene. In this haplotype, rs11168070 was associated directly with ADRB2 expression in PBMCs. Both minor alleles from rs876493 and rs11168070 contribute synergistically to reduce asthma risk and increase serum epinephrine level.

CONCLUSION AND CLINICAL RELEVANCE

Epistatic interaction between genetic variants from PNMT (rs876493) and ADRB2 (rs11168070) is associated with serum epinephrine level and the susceptibility of asthma. Our findings improved the current understanding of the genetic basis of this disease, while genotypic states of these SNPs may serve as potential biomarkers to predict susceptibility to the disease.

Dexamethasone Causes Hypertension in Rats Even Under Chemical Blockade of Peripheral Sympathetic Nerves

Synthetic glucocorticoids (GCs) are widely used to treat inflammatory conditions. However, chronic use of GCs can lead to hypertension. The cause of this undesired side effect remains unclear. Previously, we developed an in vivo rat model to study the mechanisms underlying hypertension induced by the chronic administration of the potent synthetic GC, dexamethasone (DEX) and found that the catecholamine biosynthetic pathway plays an important role. In the current study, we used this model to investigate the role of the adrenal medulla, renal nerves, and other peripheral sympathetic nerves in DEX-induced hypertension. After 5 days of baseline telemetric recording of mean arterial pressure (MAP) and heart rate (HR), rats were subjected to one of the following treatments: renal denervation (RDNX), adrenal medullectomy (ADMX), 6-hydroxydopamine (6-OHDA, 20 mg/kg, i.p.) to induce chemical sympathectomy, or a combination of ADMX and 6-OHDA. On day 11, the animals received vehicle (VEH) or DEX in drinking water for 7 days, with the latter causing an increase in MAP in control animals. ADMX and RDNX by themselves exacerbated the pressor effect of DEX. In the chemical sympathectomy group, DEX still caused a rise in MAP but the response was lower (ΔMAP of 6-OHDA/DEX < VEH/DEX, p = 0.039). However, when ΔMAP was normalized to day 10, 6-OHDA + DEX did not show any difference from VEH + DEX, certainly not an increase as observed in DEX + ADMX or RDNX groups. This indicates that sympathetic nerves do not modulate the pressor effect of DEX. TH mRNA levels increased in the adrenal medulla in both VEH/DEX (p = 0.009) and 6-OHDA/DEX (p = 0.031) groups. In the 6-OHDA group, DEX also increased plasma levels of norepinephrine (NE) (p = 0.016). Our results suggest that the activation of catecholamine synthetic pathway could be involved in the pressor response to DEX in animals even under chemical sympathectomy with 6-OHDA.

Metabolic modulation predicts heart failure tests performance

The metabolic changes that accompany changes in Cardiopulmonary testing (CPET) and heart failure biomarkers (HFbio) are not well known. We undertook metabolomic and lipidomic phenotyping of a cohort of heart failure (HF) patients and utilized Multiple Regression Analysis (MRA) to identify associations to CPET and HFBio test performance (peak oxygen consumption (Peak VO₂), oxygen uptake efficiency slope (OUES), exercise duration, and minute ventilation-carbon dioxide production slope (VE/VCO₂ slope), as well as the established HF biomarkers of inflammation C-reactive protein (CRP), beta-galactoside-binding protein (galectin-3), and N-terminal prohormone of brain natriuretic peptide (NT-proBNP)). A cohort of 49 patients with a left ventricular ejection fraction < 50%, predominantly males African American, presenting a high frequency of diabetes, hyperlipidemia, and hypertension were used in the study. MRA revealed that metabolic models for VE/VCO₂ and Peak VO₂ were the most fitted models, and the highest predictors’ coefficients were from Acylcarnitine C18:2, palmitic acid, citric acid, asparagine, and 3-hydroxybutiric acid. Metabolic Pathway Analysis (MetPA) used predictors to identify the most relevant metabolic pathways associated to the study, aminoacyl-tRNA and amino acid biosynthesis, amino acid metabolism, nitrogen metabolism, pantothenate and CoA biosynthesis, sphingolipid and glycerolipid metabolism, fatty acid biosynthesis, glutathione metabolism, and pentose phosphate pathway (PPP). Metabolite Set Enrichment Analysis (MSEA) found associations of our findings with pre-existing biological knowledge from studies of human plasma metabolism as brain dysfunction and enzyme deficiencies associated with lactic acidosis. Our results indicate a profile of oxidative stress, lactic acidosis, and metabolic syndrome coupled with mitochondria dysfunction in patients with HF tests poor performance. The insights resulting from this study coincides with what has previously been discussed in existing literature thereby supporting the validity of our findings while at the same time characterizing the metabolic underpinning of CPET and HFBio.

Circulating Histone Concentrations Differentially Affect the Predominance of Left or Right Ventricular Dysfunction in Critical Illness

OBJECTIVES

Cardiac complications are common in critical illness and associated with grave consequences. In this setting, elevated circulating histone levels have been linked to cardiac injury and dysfunction in experimental models and patients with sepsis. The mechanisms underlying histone-induced cardiotoxicity and the functional consequences on left ventricle and right ventricle remain unclear. This study aims to examine dose-dependent effects of circulating histones on left ventricle and right ventricle function at clinically relevant concentrations.

DESIGN

Prospective laboratory study with in vitro and in vivo investigations.

SETTING

University research laboratory.

SUBJECTS

Twelve-week old male C57BL/6N mice.

INTERVENTIONS

Cultured cardiomyocytes were incubated with clinically relevant histone concentrations, and a histone infusion mouse model was also used with hemodynamic changes characterized by echocardiography and left ventricle/right ventricle catheter-derived variables. Circulating histones and cardiac troponin levels were obtained from serial blood samples.

MEASUREMENTS AND MAIN RESULTS

IV histone infusion caused time-dependent cardiac troponin elevation to indicate cardiac injury. At moderate sublethal histone doses (30 mg/kg), left ventricular contractile dysfunction was the prominent abnormality with reduced ejection fraction and prolonged relaxation time. At high doses (≥ 60 mg/kg), pulmonary vascular obstruction induced right ventricular pressure increase and dilatation, but left ventricular end-diastolic volume improved because of reduced blood return from the lungs. Mechanistically, histones induced profound calcium influx and overload in cultured cardiomyocytes with dose-dependent detrimental effects on intracellular calcium transient amplitude, contractility, and rhythm, suggesting that histones directly affect cardiomyocyte function adversely. However, increasing histone-induced neutrophil congestion, neutrophil extracellular trap formation, and thrombosis in the pulmonary microvasculature culminated in right ventricular dysfunction. Antihistone antibody treatment abrogated histone cardiotoxicity.

CONCLUSIONS

Circulating histones significantly compromise left ventricular and right ventricular function through different mechanisms that are dependent on histone concentrations. This provides a translational basis to explain and target the spectral manifestations of cardiac dysfunction in critical illness.

Acute and chronic psychological stress as risk factors for cardiovascular disease: Insights gained from epidemiological, clinical and experimental studies

Cardiovascular disease (CVD) remains a leading cause of death worldwide and identification and therapeutic modulation of all its risk factors is necessary to ensure a lower burden on the patient and on society. The physiological response to acute and chronic stress exposure has long been recognized as a potent modulator of immune, endocrine and metabolic pathways, however its direct implications for cardiovascular disease development, progression and as a therapeutic target are not completely understood. More and more attention is given to the bidirectional interaction between psychological and physical health in relation to cardiovascular disease. With atherosclerosis being a chronic disease starting already at an early age the contribution of adverse early life events in affecting adult health risk behavior, health status and disease development is receiving increased attention. In addition, experimental research into the biological pathways involved in stress-induced cardiovascular complications show important roles for metabolic and immunologic maladaptation, resulting in increased disease development and progression. Here we provide a concise overview of human and experimental animal data linking chronic and acute stress to CVD risk and increased progression of the underlying disease atherosclerosis.

Attenuated aortic vasodilation and sympathetic prejunctional facilitation in epinephrine-deficient mice: selective impairment of β2-adrenoceptor responses

It has been suggested that there is a link between epinephrine synthesis and the development of β2-adrenoceptor-mediated effects, but it remains to be determined whether this development is triggered by epinephrine. The aim of this study was to characterize β-adrenoceptor-mediated relaxation and facilitation of norepinephrine release in the aorta of phenylethanolamine-N-methyltransferase-knockout (Pnmt-KO) mice. Catecholamines were quantified by reverse-phase high-performance liquid chromatography-electrochemical detection. Aortic rings were mounted in a myograph to determine concentration-response curves to selective β1- or β2-adrenoceptor agonists in the absence or presence of selective β1- or β2-adrenoceptor antagonists. Aortic rings were also preincubated with [(3)H]norepinephrine to measure tritium overflow elicited by electrical stimulation in the presence of increasing concentrations of nonselective β- or selective β2-adrenoceptor agonists. β2-Adrenoceptor protein density was evaluated by Western blotting and β2-adrenoceptor localization by immunohistochemistry. Epinephrine is absent in Pnmt-KO mice. The potency and the maximal effect of the β2-adrenoceptor agonist terbutaline were lower in Pnmt-KO than in wild-type (WT) mice. The selective β2-adrenoceptor antagonist ICI 118,551 [(±)-erythro-(S*,S*)-1-[2,3-(dihydro-7-methyl-1H-inden-4-yl)oxy]-3-[(1-methylethyl)amino]-2-butanol hydrochloride] antagonized the relaxation caused by terbutaline in WT but not in Pnmt-KO mice. Isoproterenol and terbutaline induced concentration-dependent increases in tritium overflow in WT mice only. β2-Adrenoceptor protein density was decreased in membrane aorta homogenates of Pnmt-KO mice, and this finding was supported by immunofluorescence confocal microscopy. In conclusion, epinephrine is crucial for β2-adrenoceptor-mediated vasodilation and facilitation of norepinephrine release. In the absence of epinephrine, β2-adrenoceptor protein density was decreased in aorta cell membranes, thus potentially hindering its functional activity.

Neuropeptide y gates a stress-induced, long-lasting plasticity in the sympathetic nervous system

Acute stress evokes the fight-or-flight reflex, which via release of the catecholamine hormones affects the function of every major organ. Although the reflex is transient, it has lasting consequences that produce an exaggerated response when stress is reexperienced. How this change is encoded is not known. We investigated whether the reflex affects the adrenal component of the sympathetic nervous system, a major branch of the stress response. Mice were briefly exposed to the cold-water forced swim test (FST) which evoked an increase in circulating catecholamines. Although this hormonal response was transient, the FST led to a long-lasting increase in the catecholamine secretory capacity measured amperometrically from chromaffin cells and in the expression of tyrosine hydroxylase. A variety of approaches indicate that these changes are regulated postsynaptically by neuropeptide Y (NPY), an adrenal cotransmitter. Using immunohistochemistry, RT-PCR, and NPY(GFP) BAC mice, we find that NPY is synthesized by all chromaffin cells. Stress failed to increase secretory capacity in NPY knock-out mice. Genetic or pharmacological interference with NPY and Y1 (but not Y2 or Y5) receptor signaling attenuated the stress-induced change in tyrosine hydroxylase expression. These results indicate that, under basal conditions, adrenal signaling is tonically inhibited by NPY, but stress overrides this autocrine negative feedback loop. Because acute stress leads to a lasting increase in secretory capacity in vivo but does not alter sympathetic tone, these postsynaptic changes appear to be an adaptive response. We conclude that the sympathetic limb of the stress response exhibits an activity-dependent form of long-lasting plasticity.

Mild Transient Hypercapnia as a Novel Fear Conditioning Stimulus Allowing Re-Exposure during Sleep

Introduction

Studies suggest that sleep plays a role in traumatic memories and that treatment of sleep disorders may help alleviate symptoms of posttraumatic stress disorder. Fear-conditioning paradigms in rodents are used to investigate causal mechanisms of fear acquisition and the relationship between sleep and posttraumatic behaviors. We developed a novel conditioning stimulus (CS) that evoked fear and was subsequently used to study re-exposure to the CS during sleep.

Methods

Experiment 1 assessed physiological responses to a conditioned stimulus (mild transient hypercapnia, mtHC; 3.0% CO₂; n = 17)+footshock for the purpose of establishing a novel CS in male FVB/J mice. Responses to the novel CS were compared to tone+footshock (n = 18) and control groups of tone alone (n = 17) and mild transient hypercapnia alone (n = 10). A second proof of principle experiment re-exposed animals during sleep to mild transient hypercapnia or air (control) to study sleep processes related to the CS.

Results

Footshock elicited a response of acute tachycardia (30–40 bpm) and increased plasma epinephrine. When tone predicted footshock it elicited mild hypertension (1–2 mmHg) and a three-fold increase in plasma epinephrine. When mtHC predicted footshock it also induced mild hypertension, but additionally elicited a conditioned bradycardia and a smaller increase in plasma epinephrine. The overall mean 24 hour sleep–wake profile was unaffected immediately after fear conditioning.

Discussion

Our study demonstrates the efficacy of mtHC as a conditioning stimulus that is perceptible but innocuous (relative to tone) and applicable during sleep. This novel model will allow future studies to explore sleep-dependent mechanisms underlying maladaptive fear responses, as well as elucidate the moderators of the relationship between fear responses and sleep.

Impaired conditioned fear response and startle reactivity in epinephrine-deficient mice

Norepinephrine and epinephrine signaling is thought to facilitate cognitive processes related to emotional events and heightened arousal; however, the specific role of epinephrine in these processes is less known. To investigate the selective impact of epinephrine on arousal and fear-related memory retrieval, mice unable to synthesize epinephrine (phenylethanolamine N-methyltransferase knockout, PNMT-KO) were tested for contextual and cued-fear conditioning. To assess the role of epinephrine in other cognitive and arousal-based behaviors these mice were also tested for acoustic startle, prepulse inhibition, novel object recognition, and open-field activity. Our results show that compared with wild-type mice, PNMT-KO mice showed reduced contextual fear but normal cued fear. Mice exhibited normal memory performance in the short-term version of the novel object recognition task, suggesting that PNMT mice exhibit more selective memory effects on highly emotional and/or long-term memories. Similarly, open-field activity was unaffected by epinephrine deficiency, suggesting that differences in freezing are not related to changes in overall anxiety or exploratory drive. Startle reactivity to acoustic pulses was reduced in PNMT-KO mice, whereas prepulse inhibition was increased. These findings provide further evidence for a selective role of epinephrine in contextual-fear learning and support its potential role in acoustic startle.

Targeting of the enhanced green fluorescent protein reporter to adrenergic cells in mice

Adrenaline and noradrenaline are important neurotransmitter hormones that mediate physiological stress responses in adult mammals, and are essential for cardiovascular function during a critical period of embryonic/fetal development. In this study, we describe a novel mouse model system for identifying and characterizing adrenergic cells. Specifically, we generated a reporter mouse strain in which a nuclear-localized enhanced green fluorescent protein gene (nEGFP) was inserted into exon 1 of the gene encoding Phenylethanolamine n-methyltransferase (Pnmt), the enzyme responsible for production of adrenaline from noradrenaline. Our analysis demonstrates that this knock-in mutation effectively marks adrenergic cells in embryonic and adult mice. We see expression of nEGFP in Pnmt-expressing cells of the adrenal medulla in adult animals. We also note that nEGFP expression recapitulates the restricted expression of Pnmt in the embryonic heart. Finally, we show that nEGFP and Pnmt expressions are each induced in parallel during the in vitro differentiation of pluripotent mouse embryonic stem cells into beating cardiomyocytes. Thus, this new mouse genetic model should be useful for the identification and functional characterization of adrenergic cells in vitro and in vivo.

Stress-triggered changes in peripheral catecholaminergic systems

The sympathetic nervous system not only regulates cardiovascular and metabolic responses to stress but also is altered by stress. The sympathoneural and sympathoadrenomedullary systems are modified by different metabolic pathways and have different responses to short- and to long-term stressors. Stress also induces nonneuronal catecholamine enzymes, primarily through corticosteroids. Catecholamine synthetic enzymes are induced by different pathways in response to short- and long-term acting stressors, like cold exposure or immobilization, and differently in the sympathetic ganglia and the adrenal medulla. However, a long-term exposure to one stressor can increase the response to a second, different stressor. Tyrosine hydroxylase gene transcription increases after only 5min of immobilization through phosphorylation of CREB, but this response is short lived. However, repeated stress gives a longer-lived response utilizing transcription factors such as Egr-1 and Fra-2. Glucocorticoids and ACTH also induce sympathoneural enzymes leading to distinct patterns of short-term and long-lived activation of the sympathetic nervous system. Nonneuronal phenylethanolamine N-methyltransferase (PNMT) develops early in the heart and then diminishes. However, intrinsic cardiac adrenergic cells remain and nonneuronal PNMT is present in many cells of the adult organism and increases in response to glucocorticoids. Both stress-induced and administered glucocorticoids induce fetal PNMT and hypertension. Human stressors such as caring for an ill spouse or sleep apnea cause a persistent increase in blood norepinephrine, increased blood pressure, and downregulated catecholamine receptors. Hypertension is associated with a loss of slow-wave sleep, when sympathetic nerve activity is lowest. These findings indicate that stress-induced alteration of the sympathetic nervous system occurs in man as in experimental animals.

Activated plasma coagulation β-Factor XII-induced vasoconstriction in rats

By inducing BK (bradykinin)-stimulated adrenomedullary catecholamine release, bolus injection of the β-fragment of activated plasma coagulation Factor XII (β-FXIIa) transiently elevates BP (blood pressure) and HR (heart rate) of anaesthetized, vagotomized, ganglion-blocked, captopril-treated bioassay rats. We hypothesized that intravenous infusion of β-FXIIa into intact untreated rats would elicit a qualitatively similar vasoconstrictor response. BN (Brown Norway) rats received for 60 min either: (i) saline (control; n=10); (ii) β-FXIIa (85 ng/min per kg of body weight; n=9); or (iii) β-FXIIa after 2ADX (bilateral adrenalectomy; n=9). LV (left ventricular) volume and aortic BP were recorded before (30 min baseline), during (60 min) and after (30 min recovery) the infusion. TPR (total peripheral resistance) was derived from MAP (mean arterial pressure), SV (stroke volume) and HR. Saline had no haemodynamic effects. β-FXIIa infusion increased its plasma concentration 3-fold in both groups. In adrenally intact rats, β-FXIIa infusion increased MAP by 6% (5±2 mmHg) and TPR by 45% (0.50±0.12 mmHg/ml per min), despite falls in SV (−38±8 μl) and HR [−18±5 b.p.m. (beats/min)] (all P<0.05). In 2ADX rats, β-FXIIa had no HR effect, but decreased SV (−89±9 μl) and MAP (−4±1 mmHg), and increased TPR by 66% (0.59±0.15 mmHg/ml per min) (all P<0.05). After infusion, adrenally intact rats exhibited persistent vasoconstriction (MAP, 10±1 mmHg; TPR, 0.55±0.07 mmHg/ml per min; both P<0.05), whereas in 2ADX rats, MAP remained 5±1 mmHg below baseline (P<0.05) and TPR returned to baseline. End-study arterial adrenaline (epinephrine) concentrations in the three groups were 1.9±0.6, 9.8±4.1 and 0.6±0.2 nmol/l respectively. Thus, in neurally intact lightly anaesthetized untreated rats, β-FXIIa infusion induces both adrenal catecholamine-mediated and adrenally independent increases in peripheral resistance.

Tau protein phosphorylation in diverse brain areas of normal and CRH deficient mice: up-regulation by stress

Tau protein misfolding is a pathological mechanism, which plays a critical role in the etiopathogenesis of neurodegeneration. However, it is not entirely known what kind of stimuli can induce the misfolding. It is believed that physical and emotional stresses belong to such risk factors. Although the influence of stress on the onset and progression of Alzheimer's disease (AD) has already been proposed, the molecular links between stresses and AD are still unknown. We have therefore focused our attention on determination of the influence of acute immobilization stress (IMO) in normal mice and mice deficient in corticotropin-releasing hormone (CRH). Specifically, we have analyzed levels of hyperphosphorylated tau proteins, bearing the AD-specific phospho-epitopes (AT-8, pT181, and PHF-1), which are implicated in the pathogenesis of AD. We found that IMO induces transient hyperphosphorylation of tau proteins regardless of continuation of the stimulus. Concerning tau modifications, detailed analysis of the mouse brain revealed that neurons in different brain regions including frontal cortex, temporal cortex, hippocampal C1 and CA3 regions, dentate gyrus as well as nucleus basalis Meynert, and several brainstem nuclei such as locus coeruleus but also raphe nucleus and substantia nigra respond similarly to IMO. The strongest tau protein phosphorylation was observed after 30 min of IMO stress. Stress lasting for 120 min led either to the disappearance of tau hyperphosphorylation or to the induction of a second wave of hyperphosphorylation. Noteworthy is the magnitude of pathological phosphorylation of tau protein in CRH and glucocorticoids deficient mice, being much lower in comparison to that observed in wild-type animals, which suggests a critical role of CRH in the pathogenesis of AD. Thus, our results indicate that hyperphosphorylation of tau protein induced by stress may represent the pathogenic event upstream of tau protein misfolding, which leads to progression or eventually initiation of neurodegeneration. The data show that CRH plays an important role in stress induced hyperphosphorylation of tau protein, which might be either a direct effect of CRH innervations in the brain or an effect mediated via the hypothalamo-pituitary-adrenal axis.

Hypermorphic mutation of the voltage-gated sodium channel encoding gene Scn10a causes a dramatic stimulus-dependent neurobehavioral phenotype

The voltage-gated sodium channel Na(v)1.8 is known to function in the transmission of pain signals induced by cold, heat, and mechanical stimuli. Sequence variants of human Na(v)1.8 have been linked to altered cardiac conduction. We identified an allele of Scn10a encoding the α-subunit of Na(v)1.8 among mice homozygous for N-ethyl-N-nitrosourea-induced mutations. The allele creates a dominant neurobehavioral phenotype termed Possum, characterized by transient whole-body tonic immobility induced by pinching the skin at the back of the neck ("scruffing"). The Possum mutation enhanced Na(v)1.8 sodium currents and neuronal excitability and heightened sensitivity of mutants to cold stimuli. Striking electroencephalographic changes were observed concomitant with the scruffing-induced behavioral change. In addition, electrocardiography demonstrated that Possum mice exhibited marked sinus bradycardia and R-R variability upon scruffing, abrogated by infusion of atropine. However, atropine failed to prevent or mitigate the tonic immobility response. Hyperactive sodium conduction via Na(v)1.8 thus leads to a complex neurobehavioral phenotype, which resembles catatonia in schizophrenic humans and tonic immobility in other mammals upon application of a discrete stimulus; no other form of mechanosensory stimulus could induce the immobility phenotype. Our data confirm the involvement of Na(v)1.8 in transducing pain initiated by cold and additionally implicate Na(v)1.8 in previously unknown functions in the central nervous system and heart.

Cardiovascular effects of treadmill exercise in physiological and pathological preclinical settings

Exercise adaptations result from a coordinated response of multiple organ systems, including cardiovascular, pulmonary, endocrine-metabolic, immunologic, and skeletal muscle. Among these, the cardiovascular system is the most directly affected by exercise, and it is responsible for many of the important acute changes occurring during physical training. In recent years, the development of animal models of pathological or physiological cardiac overload has allowed researchers to precisely analyze the complex cardiovascular responses to stress in genetically altered murine models of human cardiovascular disease. The intensity-controlled treadmill exercise represents a well-characterized model of physiological cardiac hypertrophy because of its ability to mimic the typical responses to exercise in humans. In this review, we describe cardiovascular adaptations to treadmill exercise in mice and the most important parameters that can be used to quantify such modifications. Moreover, we discuss how treadmill exercise can be used to perform physiological testing in mouse models of disease and to enlighten the role of specific signaling pathways on cardiac function.

Endogenous epinephrine protects against obesity induced insulin resistance

Epinephrine (E) is a hormone released from the adrenal medulla in response to low blood sugar and other stresses. E and related β2-adrenergic agonists are used to treat asthma, but a side effect is high blood sugar. C57BL/6 mice prone to overfeeding induced type II diabetes had the PNMT gene knocked out to prevent E synthesis. These E deficient mice were very similar to control animals on a 14% fat diet. On a 40.6% fat diet they gained 20 to 33% more weight than control animals and increased their blood glucose response to a glucose tolerance test because they became resistant to insulin. Although the short term effect of β2-agonists such as E is to raise blood glucose, some long acting β2-agonists improve muscle glucose uptake. Endogenous E protects against overfeeding induced diabetes. Since adrenal E release can be impaired with aging and diabetes, endogenous E may help prevent adult onset diabetes.

Genetic regulation of catecholamine synthesis, storage and secretion in the spontaneously hypertensive rat

Understanding catecholamine metabolism is crucial for elucidating the pathogenesis of hereditary hypertension. Here we integrated transcriptional and biochemical profiling with physiologic quantitative trait locus (eQTL and pQTL) mapping in adrenal glands of the HXB/BXH recombinant inbred (RI) strains, derived from the spontaneously hypertensive rat (SHR) and normotensive Brown Norway (BN.Lx). We found simultaneous down-regulation of five heritable transcripts in the catecholaminergic pathway in young (6 weeks) SHRs. We identified cis-acting eQTLs for Dbh, Pnmt (catecholamine biosynthesis) and Vamp1 (catecholamine secretion); enzymatic activities of Dbh and Pnmt paralleled transcripts, with pQTLs for activities mirroring eQTLs. We also detected trans-regulated expression of Vmat1 and Chga (both involved in catecholamine storage), with co-localization of these trans-eQTLs to the Pnmt locus. Pnmt re-sequencing revealed promoter polymorphisms that result in decreased response of the transfected SHR promoter to glucocorticoid, compared with BN.Lx. Of physiological pertinence, Dbh activity negatively correlated with systolic blood pressure in RI strains, whereas Pnmt activity was negatively correlated with heart rate. The finding of such cis- and trans-QTLs at an age before the onset of frank hypertension suggests that these heritable changes in biosynthetic enzyme expression represent primary genetic mechanisms for regulation of catecholamine action and blood pressure control in this widely studied model of hypertension.

Fetal and offspring arrhythmia following exposure to nicotine during pregnancy

Although recent studies have demonstrated prenatal nicotine can increase cardiovascular risk in the offspring, it is unknown whether exposure to nicotine during pregnancy also may be a risk for development of arrhythmia in the offspring. In addition, in previous studies of fetal arrhythmia affected by smoking, only two patterns, bradycardia and tachycardia, were observed. The present study examined acute effects of maternal nicotine on the fetal arrhythmia in utero, and chronic influence on offspring arrhythmia at adult stage following prenatal exposure to nicotine. Nicotine was administered to pregnant ewes and rats. In the fetal sheep, intravenous nicotine not only induced changes of fetal heart rate, but also caused cardiac cycle irregularity, single and multiple dropped cardiac cycles. Although maternal nicotine had no influence on fetal blood pH, lactic acid, hemocrit, Na(+), K(+) levels and plasma osmolality, fetal blood PO(2) levels were significantly decreased following maternal nicotine in ewes. In offspring rats at 4-5 months after birth, prenatal exposure to nicotine significantly increased heart rate and premature ventricular contraction in restraint stress. In addition, arrhythmias induced by injection of nicotine were higher in the offspring prenatal exposure to nicotine in utero. The results provide new evidence that exposure to nicotine in pregnancy can cause fetal arrhythmia in various patterns besides tachycardia and bradycardia, the possible mechanisms for nicotine-induced fetal arrhythmia included in utero hypoxia. Importantly, following exposure to nicotine significantly increased risk of arrhythmia in the adult offspring. The finding offers new insight for development of cardiac rhythm problems in fetal origins.

Increased spontaneous activity and reduced inotropic response to catecholamines in ventricular myocytes from footshock-stressed rats

Exposure to stressors has been shown to change atrial responsiveness to catecholamines, but it is not clear yet how it affects the ventricular myocardium, which plays a major role in the catecholamine-stimulated increase in cardiac output. Adult male rats were submitted to restraint (RST) or footshock (FS) sessions for 3 days. Reactivity to agonists of the beta-adrenergic pathway was analyzed in left ventricular myocytes isolated from stressed and control rats (CTR). Whereas no significant changes were detected after RST, enhancement of catecholamine-induced spontaneous activity, accompanied by decrease in inotropic maximal response, was observed in myocytes from FS rats. Changes were reversed by beta(1)-, but not by alpha(1)-or beta(2)-adrenoceptor (AR) blockade. Similar alterations were seen in response to forskolin. However, responsiveness to 3-isobutyl-1-methylxanthine and CaCl(2) was comparable in control and FS groups. A significant negative correlation was observed between the maximally stimulated spontaneous activity rate and contraction amplitude. Results indicate that: (a) enhanced automatism during adrenergic stimulation of myocytes from FS rats is mediated by beta(1)-ARs and seems to involve post-receptor mechanisms, probably decreased cAMP degradation; (b) the exaggerated spontaneous activity, which may contribute to generation of catecholaminergic arrhythmias, might limit the development of the inotropic response.

Heme Arginate Suppresses Cardiac Lesions and Hypertrophy in Deoxycorticosterone Acetate-Salt Hypertension

In hypertension, elevated levels of oxidative/inflammatory mediators including nuclear factor kappaB (NF-κB), activating protein (AP-1), c-Jun-NH2-terminal kinase (JNK), and cell-regulatory proteins such as transforming growth factor beta (TGF-β), trigger the mobilization of extracellular matrix (ECM) leading to fibrosis, hypertrophy and impairment of cardiac function. Although the heme oxygenase (HO) system is cytoprotective, its effects on cardiac fibrosis and hypertrophy in deoxycorticosterone acetate (DOCA-salt) hypertension are not completely elucidated. Here, we report cardioprotection by the HO inducer, heme arginate against histopathological lesions in DOCA-hypertension. Treatment with heme arginate restored physiological blood pressure, and abated cardiac hypertrophy (3.75 ± 0.12 vs. 3.19 ± 0.09 g/kg body wt; n =16, P < 0.01), left-to-right ventricular ratio (6.67 ± 0.62 vs. 4.39 ± 0.63; n = 16, P < 0.01), left ventricular mass (2.48 ± 0.14 vs. 2.01 ± 0.09 g/kg body wt; n = 16, P < 0.01) and left-ventricular wall thickness (2.82 ± 0.16 vs. 1.98 ± 0.14 mm; n = 16, P < 0.01), whereas the HO inhibitor, chromium mesoporphyrin, exacerbated hypertrophy and cardiac lesions. The suppression of cardiac hypertrophy was accompanied by a robust increase in HO-1, HO activity, cyclic guanosine monophosphate (cGMP), ferritin and the total antioxidant capacity, whereas 8-isoprostane, NF-κB, JNK, AP-1, TGF-β, fibronectin and collagen-I were significantly abated. Correspondingly, histopathological parameters that depict progressive cardiac damage, including fibrosis, interstitial/perivascular collagen deposition, scarring, muscle-fiber thickness, muscular hypertrophy and coronary-arteriolar thickening were abated. Our study suggests that upregulating the HO system lowers blood pressure, potentiates the antioxidant status in tissues, suppresses oxidative stress/mediators such as NF-κB, AP-1 and cJNK, and suppresses the mobilization of ECM proteins like TGF-β, collagen and fibronectin, with corresponding reduction of cardiac histopathological lesion and hypertrophy.

Thermodynamic functions of molecular conformations of (2-fluoro-2-phenyl-1-ethyl)ammonium ion and (2-hydroxy-2-phenyl-1-ethyl)ammonium ion as models for protonated noradrenaline and adrenaline: first-principles computational study of conformations and thermodynamic functions for the noradrenaline and adrenaline models

This paper reports the structural and thermodynamic consequences of substitution of the OH group by the isoelectronic F-atom in the case of the adrenaline family of molecules. The conformational landscapes were explored for the two enantiomeric forms of N-protonated-beta-fluoro-beta-phenyl-ethylamine, also called (2-fluoro-2-phenyl-1-ethyl)-ammonium ion (Model 1) and that of N-protonated-beta-hydroxy-beta-phenyl-ethylamine, also referred to as (2-hydroxy-2-phenyl-1-ethyl)-ammonium (Model 2) models of noradrenaline and adrenaline molecules. These full conformational studies were carried out by first principles of quantum mechanical computations at the B3LYP/6-31G(d,p) and G3MP2B3 levels of theory, using the Gaussian03 program. Also, frequency calculations of the stable structures were performed at the B3LYP/6-31G(d,p), and G3MP2B3 levels of theory. The thermodynamic functions (U, H, S, and G) of the various stable conformations of the title compounds were calculated at these levels of theory for the R and S stereoisomers. Relative values of the thermodynamic functions have been calculated with respect of the chosen reference conformers in which all relevant dihedral angles assumed anti orientation for the Model 1 and Model 2. Through the combination of both point and axis chirality, the enantiomeric and diastereomeric relationships of the six structures for each molecule investigated were established. Intramolecular hydrogen bonding interactions have been studied by the atoms in molecules (AIM) analysis of the electron density. The aromaticity of phenyl group has been determined by a selective hydrogenation protocol. The pattern of the extent of aromacity, due intramolecular interactions, varies very little between the two models studied.

Epinephrine regulation of hemodynamics in catecholamine knockouts and the pithed mouse

Phenylethanolamine N-methyltransferase (PNMT) catalyzes synthesis of epinephrine (E) and is present in the brain, heart, and adrenal. E is a neurotransmitter and important hormone; however, its role in regulating cardiovascular dynamics is still unclear. We generated an E-deficient mouse model by knocking out the PNMT gene. The PNMT KO mouse had normal resting blood pressure, while treadmill exercise caused hypertension, suggesting an impaired response to stress in the absence of the stress hormone E. As PNMT occurs at a lower concentration in many extra-adrenal tissues including the brain, we set up a pithed mouse model to study the peripheral effects of E on cardiovascular dynamics, using pithing to eliminate central and reflex effects. The pithed mouse requires different surgical techniques and stimulation voltages than rats, and showed voltage- and frequency-dependent blood pressure responses to electrical stimuli. Stimulation with the alpha-adrenergic agonist phenylephrine gave a marked systolic pressor response, while the beta2 agonist salbutamol lowered diastolic blood pressure. The pithed PNMT KO mouse had an exaggerated blood pressure response to salbutamol, suggesting beta2 receptor supersensitivity. A targeted KO of tyrosine hydroxylase in PNMT-producing cells produced a mouse deficient in catecholamines in the adrenal. These targeted KO mice displayed significantly smaller pressor responses than pithed control mice. We find that E release during stress prevents an excessive increase in blood pressure.

Interaction among heme oxygenase, nuclear factor-kappaB, and transcription activating factors in cardiac hypertrophy in hypertension

Deoxycorticosterone acetate-induced hypertension is a volume overload and human primary aldosteronism model characterized by severe cardiac lesions attributed to elevated inflammation, oxidative stress, fibrosis, and hypertrophy. An important cytoprotective pathway that counteracts tissue insults is the heme oxygenase (HO) system. Although the HO-1 gene promoter contains consensus binding sites for proinflammatory/oxidative transcription factors like nuclear factor-kappaB, activating protein (AP)-1, and AP-2, the effects of HO inducers on these transcription factors in cardiac lesions of deoxycorticosterone acetate hypertension are not fully understood. Hemin therapy normalized systolic blood pressure and markedly reduced the left:right ventricular ratio, left ventricular wall thickness, and left ventricle:body weight ratio, whereas the HO blocker, chromium mesoporphyrin, exacerbated cardiac fibrosis/hypertrophy in deoxycorticosterone acetate-hypertensive rats. The cardioprotection by hemin was accompanied by increased HO-1, HO activity, cGMP, superoxide dismutase, catalase, the total antioxidant capacity alongside the reduction of 8-isoprostane, AP-1, AP-2, nuclear factor-kappaB, and c-Jun-NH(2)-terminal kinase, whereas chromium mesoporphyrin abolished the hemin effects. Furthermore, hemin therapy attenuated transforming growth factor-beta(1) and extracellular matrix proteins like fibronectin and collagen, with a corresponding reduction of histopathologic lesions, including longitudinal/cross-sectional muscle fiber thickness, scarring, muscular hypertrophy, coronary arteriolar thickening, and collagen deposition. The suppression of AP-1, AP-2, nuclear factor-kappaB, and c-Jun-NH(2)-terminal kinase proinflammatory/oxidative mediators in the left ventricle of hemin-treated animals is a novel observation that may account for cardioprotection in deoxycorticosterone acetate hypertension. By concomitantly upregulating HO activity and cGMP and potentiating the total antioxidant status, hemin therapy reduced hypertension, suppressed oxidative stress, and attenuated extracellular matrix and remodeling proteins, with a reduction of histopathologic lesions that characterize cardiac fibrosis, hypertrophy, and end-stage organ damage.

Cardiovascular responses to electrical stimulation of sympathetic nerves in the pithed mouse

The pithed rat model has been used extensively to study peripheral cardiovascular responses to electrical stimulation of the sympathetic nervous system, as pithing eliminates central and reflex effects. However, since the transgenic mouse has become a standard and economical model organism, an electrically stimulated pithed mouse would facilitate a variety of studies. We have developed surgical techniques, drug doses and stimulation parameters for an electrically stimulated pithed mouse to study peripheral sympathetic nerve effects on blood pressure. Similar to the pithed rat, the pithed mouse showed voltage and frequency-dependent blood pressure responses to a pulsed train of electrical stimuli. In addition, alpha-adrenergic stimulation with phenylephrine gave a marked systolic pressor response, while the beta2 agonist salbutamol lowered diastolic blood pressure. Furthermore, pithed transgenic mice unable to synthesize catecholamines in adrenergic cells displayed smaller pressor responses than pithed control mice. In summary, the electrically stimulated pithed mouse can be used to study peripheral effects of the sympathetic system on cardiovascular dynamics unencumbered by central responses.