This study used mice to evaluate whether coupling expression of corticotropin-releasing hormone (CRH) and angiotensin converting enzyme 2 (ACE2) creates central interactions that blunt endocrine and behavioral responses to psychogenic stress. Central administration of diminazene aceturate, an ACE2 activator, had no effect on restraint-induced activation of the hypothalamic-pituitary-adrenal (HPA) axis; however, mice that ubiquitously overexpress ACE2 had reduced plasma corticosterone (CORT) and pituitary expression of POMC mRNA. The Cre-LoxP system was used to restrict ACE2 overexpression to CRH synthesizing cells and probe whether HPA axis suppression was the result of central ACE2 and CRH interactions. Within the paraventricular nucleus of the hypothalamus (PVN), mice with ACE2 overexpression directed to CRH had a ≈2.5 fold increase in ACE2 mRNA, which co-localized with CRH mRNA. Relative to controls, mice overexpressing ACE2 in CRH cells had a decreased CORT response to restraint as well as decreased CRH mRNA in the PVN and CEA and POMC mRNA in the pituitary. Administration of ACTH similarly increased plasma CORT, indicating that the blunted HPA axis activation that accompanies ACE2 overexpression in CRH cells is centrally mediated. Anxiety-like behavior was assessed to determine whether the decreased HPA axis activation was predictive of anxiolysis. Mice with ACE2 overexpression directed to CRH cells displayed decreased anxiety-like behavior in the elevated plus maze and open field when compared to that of controls. Collectively, these results suggest that exogenous ACE2 suppresses CRH synthesis, which alters the central processing of psychogenic stress, thereby blunting HPA axis activation and attenuating anxiety-like behavior.

Activation of corticotropin-releasing hormone (CRH) type 2 receptors (CRHR2) in the nucleus of the solitary tract (NTS) contributes to the development of hypertension, but the source of CRH inputs to the NTS that increases blood pressure remains unknown. This study tested the hypothesis that activation of CRH-containing projections from the paraventricular nucleus of the hypothalamus (PVN) to the NTS increase blood pressure. We expressed channelrhodopsin 2 (ChR2), a light-sensitive ion channel, into CRH-containing neurons in the PVN. This was achieved by injecting Cre-inducible virus expressing ChR2 into the PVN of CRH-Cre mice. CRH-Cre mice are genetically modified mice expressing Cre recombinase only in neurons producing CRH. We found that optogenetic stimulation of CRH-containing somas in the PVN or CRH-containing fibers in the NTS originating from the PVN significantly increased blood pressure and heart rate. Microinjection of K-41498 (CRHR2 antagonist) into the NTS attenuated the pressor and tachycardiac responses induced by optogenetic stimulation of CRH-containing somas in the PVN. In vitro loose-patch recordings revealed that optogenetic stimulation of CRH-containing fibers in the NTS originating from the PVN significantly increased the discharge frequency of NTS neurons. This effect was attenuated by pretreatment of K-41498 and was abolished by pretreatment of kynurenic acid (nonselective glutamate receptor antagonist). These results suggest that activation of PVN-NTS CRH-containing projections increases blood pressure and heart rate. The cardiovascular responses may be mediated at least in part by the corelease of CRH and glutamate from NTS CRH-containing axons originating from the PVN. NEW & NOTEWORTHY Optogenetic stimulation of paraventricular nucleus of the hypothalamus (PVN) corticotropin-releasing hormone (CRH)-containing somas or nucleus of the solitary tract (NTS) CRH-containing fibers originating from the PVN increased blood pressure and heart rate. Corelease of CRH and glutamate from NTS CRH-containing axons originating from the PVN may contribute to the pressor and tachycardiac responses elicited by optogenetic stimulation of PVN CRH-containing somas.

Motivated by the potential of objective neurophysiological markers to index thalamocortical function in patients with severe psychiatric illnesses, we comprehensively characterized key non-rapid eye movement (NREM) sleep parameters across multiple domains, their interdependencies, and their relationship to waking event-related potentials and symptom severity. In 72 schizophrenia (SCZ) patients and 58 controls, we confirmed a marked reduction in sleep spindle density in SCZ and extended these findings to show that fast and slow spindle properties were largely uncorrelated. We also describe a novel measure of slow oscillation and spindle interaction that was attenuated in SCZ. The main sleep findings were replicated in a demographically distinct sample, and a joint model, based on multiple NREM components, statistically predicted disease status in the replication cohort. Although also altered in patients, auditory event-related potentials elicited during wake were unrelated to NREM metrics. Consistent with a growing literature implicating thalamocortical dysfunction in SCZ, our characterization identifies independent NREM and wake EEG biomarkers that may index distinct aspects of SCZ pathophysiology and point to multiple neural mechanisms underlying disease heterogeneity. This study lays the groundwork for evaluating these neurophysiological markers, individually or in combination, to guide efforts at treatment and prevention as well as identifying individuals most likely to benefit from specific interventions.

Recent evidence suggests hypertension may be secondary to chronic inflammation that results from hypoactive neuro-immune regulatory mechanisms. To further understand this association, we used systemic lupus erythematosus (SLE) as a model of inflammation-induced hypertension. In addition to prevalent inflammatory kidney disease and hypertension, SLE patients suffer from dysautonomia in the form of decreased efferent vagal tone. Based on this, the cholinergic anti-inflammatory pathway, an endogenous vagus-to-spleen mechanism that, when activated results in decreases in systemic inflammation, may be compromised in SLE. We hypothesized that stimulation of the cholinergic anti-inflammatory pathway via pharmacological potentiation of the efferent vagus nerve would reduce inflammation and halt the development of hypertension and renal injury in SLE. Female NZBWF1 mice, an established model of murine SLE, and female control mice were treated with galantamine (4 mg/kg daily ip), an acetylcholinesterase inhibitor, or saline for 14 days. At the end of therapy, carotid catheters were surgically implanted and were used to measure mean arterial pressure before the animals were euthanized. Chronic galantamine administration attenuated both splenic and renal cortical inflammation, which likely explains why the hypertension and renal injury (i.e., glomerulosclerosis and fibrosis) typically observed in murine SLE was attenuated following therapy. Based on this, the anti-inflammatory, antihypertensive, and renoprotective effects of galantamine may be mediated through activation of the cholinergic anti-inflammatory pathway. It is possible that dysfunction of the cholinergic anti-inflammatory pathway exists in SLE at the level of the efferent vagus nerve and promoting restoration of its activity through central cholinergic receptor activation may be beneficial.

Sex is an important biological variable that impacts diverse physiological and pathological processes, including the progression of diabetic nephropathy. Diabetic nephropathy is one of the most common complications of diabetes mellitus and is the leading cause of end-stage renal disease. The endothelial nitric oxide synthase-deficient (eNOS−/−) db/ db mouse is an appropriate and valuable model to study mechanisms in the development of diabetic nephropathy because of the similarities of the features of diabetic kidney disease in this model to those in humans. The aim of the present study was to determine whether there was a sex difference in renal injury in eNOS−/− db/ db mice. Both male and female eNOS−/− db/ db mice showed hyperglycemia, obesity, and renal hypertrophy. However, there was no significant difference in those variables between male and female mice. Furthermore, both male and female diabetic mice showed progressive albuminuria and significantly greater levels of serum creatinine and blood urea nitrogen compared with the same sex of wild-type mice (nondiabetic controls). Although all three variables in female eNOS−/− db/ db mice had a tendency to be greater than those in male eNOS−/− db/ db mice, those sex differences were not statistically significant. Moreover, both male and female eNOS−/− db/ db mice showed significant mesangial expansion, higher glomerular injury scores, profound renal fibrosis, and substantial accumulation of fibronectin and collagen type IV proteins. However, sex differences in those structural changes were not observed. Similarly, survival rates of male and female eNOS−/− db/ db mice were comparable. Taken together, the results from the present study suggest no sex difference in renal structural and functional damage in eNOS−/− db/ db mice.

This study tested the hypothesis that corticotropin-releasing hormone (CRH) receptors in the nucleus of the solitary tract (NTS) contribute to the hypertension induced by intermittent hypoxia (IH) exposure in rats. Initial studies using in situ hybridization revealed low mRNA level of CRH type 1 receptor (CRHR1) but high mRNA level of CRH type 2 receptor (CRHR2) in the NTS. Calcium imaging studies on NTS slice preparations using Fura-2-acetoxymethyl ester demonstrated that CRH induced a transient increase of intracellular calcium level. The CRH-induced calcium response was reproduced in the presence of TTX but was abolished by depletion of extracellular calcium or by the L-type calcium channel blocker nifedipine. The CRH-induced calcium influx was attenuated by the CRHR2 antagonist K41498 but not by the CRHR1 antagonist NBI-35965. Calcium influx can be induced by the CRHR2 agonist Urocortin II but not by the CRHR1 agonist Stressin I. IH exposure did not affect CRHR1 mRNA level but significantly decreased CRHR2 mRNA level and the CRH-induced calcium influx in the NTS. Further in vivo studies showed that intra-4th ventricle infusion of K41498 did not affect the basal blood pressure but significantly attenuated the IH-induced hypertension; intra-4th ventricle infusion of Urocortin II significantly increased basal blood pressure and exacerbated the IH-induced hypertension. Collectively, these results suggest that CRHR2 in the NTS contributes to the IH-induced hypertension; down-regulation of CRHR2 and CRHR2-mediated calcium influx in the NTS may serve as an adaptive response to protect against the IH-induced hypertension.

Obstructive Sleep Apnea (OSA) is characterized by cessations in respiration that leads to the development of chronic hypertension. Hypertension persists into the waking period even during normal respiratory patterns, and can increase a patient's risk factor for heart disease and stroke. Previous studies have shown that experimental models of chronic intermittent hypoxia (CIH) can produce a sustained hypertension similar to that associated with OSA. It has been proposed that the peripheral and CNS renin‐angiotensin systems contribute to hypertension associated with CIH. Our working hypothesis is that increased circulating angiotensin II feeds into the forebrain thereby increasing excitatory signaling through the hypothalamus and hindbrain, creating a vicious cycle. The median preoptic nucleus (MnPO) is an integrative forebrain region that contributes to blood pressure regulation. The MnPO has projections to the paraventricular nucleus (PVN) of the hypothalamus. The PVN contains pre‐autonomic centers that project to regions in the hindbrain that regulate sympathetic outflow. We hypothesized that by lesioning pathway specific projections from the MnPO to the PVN, we could attenuate the sustained component of CIH‐induced hypertension. For these experiments, adult male Sprague‐Dawley rats (250–300 g bw) were anesthetized with isoflurane and stereotaxically injected bilaterally in the PVN with a retrograde AAV containing Cre (AAV9.CMV.HI.eGFP‐Cre.WPRE.SV40) and with the caspase‐3 virus (AAV5‐flex‐taCasp3‐TEVp) or a control virus (AAV5‐hSyn‐DIO‐mCherry) in the MnPO. After 1 week recovery, rats were instrumented with aortic radio telemetry and allowed an additional week recovery following surgery. Rats were then moved to new homecages and underwent baseline recording for 7 days before undergoing our 7‐day CIH protocol. The control group exposed to CIH developed chronic hypertension, however, caspase lesions blunted the sustained hypertension developed during CIH. Brain tissue processed for FosB immunohistochemistry (IHC) showed decreased expression with caspase‐induced inhibition in the MnPO and downstream autonomic‐regulating nuclei in the PVN and rostral ventral lateral medulla (RVLM). CIH significantly increased plasma advanced oxidative protein products (AOPP) levels in controls. This increase in AOPP levels was blocked in caspase‐lesioned rats comparable to normoxic control concentrations. In situ hybridization experiments indicate a reduction in angiotensin type 1a receptors (AT1aR) expression in the caspase‐lesioned group exposed to CIH compared to CIH controls. The results indicate that MnPO neurons that project to the PVN play a significant role in blood pressure regulation and in the development of persistent CIH‐induced hypertension. Support or Funding Information P01 HL088052 T32 AG020494 This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Aims These studies evaluate whether angiotensin type-2 receptors (AT2Rs) that are expressed on γ-aminobutyric acid (GABA) neurons in the nucleus of the solitary tract (NTS) represent a novel endogenous blood pressure lowering mechanism. Methods and Results Experiments combined advanced genetic and neuroanatomical techniques, pharmacology, electrophysiology and optogenetics in mice to define the structure and cardiovascular-related function of NTS neurons that contain AT2R. Using mice with Cre-recombinase directed to the AT2R gene, we discovered that optogenetic stimulation of AT2R-expressing neurons in the NTS increases GABA release and blood pressure. To evaluate the role of the receptor, per se, in cardiovascular regulation, we chronically delivered C21, a selective AT2R agonist, into the brains of normotensive mice and found that central AT2R activation reduces GABA-related gene expression and blunts the pressor responses induced by optogenetic excitation of NTS AT2R neurons. Next, using in situ hybridization, we found that the levels of Agtr2 mRNAs in GABAergic NTS neurons rise during experimentally-induced hypertension, and we hypothesized that this increased expression may be exploited to ameliorate the disease. Consistent with this, final experiments revealed that central administration of C21 attenuates hypertension, an effect that is abolished in mice lacking AT2R in GABAergic NTS neurons. Conclusions These studies unveil novel hindbrain circuits that maintain arterial blood pressure, and reveal a specific population of AT2R that can be engaged to alleviate hypertension. The implication is that these discrete receptors may serve as an access point for activating an endogenous depressor circuit. Translational perspective Hypertension is a widespread health problem and risk factor for cardiovascular disease and stroke. Although treatment options exist, many patients suffer from resistant hypertension, which is associated with enhanced sympathetic drive. Thus, many available therapeutics focus on dampening pressor mechanisms. The present studies take the alternative approach of treating hypertension by exploiting an endogenous depressor mechanism.