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The angiotensin-converting enzyme 2 (ACE2) has emerged as a critical regulator of the renin–angiotensin system (RAS), which plays important roles in cardiovascular homeostasis by regulating vascular tone, fluid and electrolyte balance. ACE2 functions as a carboxymonopeptidase hydrolyzing the cleavage of a single C-terminal residue from Angiotensin-II (Ang-II), the key peptide hormone of RAS, to form Angiotensin-(1-7) (Ang-(1-7)), which binds to the G-protein–coupled Mas receptor and activates signaling pathways that counteract the pathways activated by Ang-II. ACE2 is expressed in a variety of tissues and overwhelming evidence substantiates the beneficial effects of enhancing ACE2/Ang-(1-7)/Mas axis under many pathological conditions in these tissues in experimental models. This review will provide a succinct overview on current strategies to enhance ACE2 as therapeutic agent, and discuss limitations and future challenges. ACE2 also has other functions, such as acting as a co-factor for amino acid transport and being exploited by the severe acute respiratory syndrome coronaviruses (SARS-CoVs) as cellular entry receptor, the implications of these functions in development of ACE2-based therapeutics will also be discussed.

Emerging evidence implicates an interplay among multiple organs such as brain, vasculature, gut and lung in the development of established pulmonary arterial hypertension (PAH). This has led us to propose that activated microglia mediated-enhanced sympathetic activation contributes to PAH pathophysiology. Since enhanced sympathetic activity is observed in human PAH and the gut is highly innervated by sympathetic nerves that regulate its physiological functions, we hypothesized that PAH would be associated with gut pathophysiology. A monocrotaline rat model of PAH was utilized to investigate the link between gut pathology and PAH. Haemodynamics, histology, immunocytochemistry and 16S RNA gene sequencing were used to assess cardiopulmonary functions, gut pathology and gut microbial communities respectively. Monocrotaline treatment caused increased right ventricular systolic pressure, haemodynamics and pathological changes associated with PAH. PAH animals also showed profound gut pathology that included increased intestinal permeability, increased muscularis layer, decreased villi length and goblet cells. These changes in gut pathology were associated with alterations in microbial communities, some unique to PAH animals. Furthermore, enhanced gut–neural communication involving the paraventricular nucleus of the hypothalamus and increased sympathetic drive were observed. In conclusion, our data show the presence of gut pathology and distinct changes in gut microbiota and increased sympathetic activity in PAH. They suggest that dysfunctional gut–brain crosstalk could be critical in PAH and considered a future therapeutic target for PAH., Impaired gut–brain communication in pulmonary arterial hypertension https://bit.ly/2LpvWvY

We have previously found that in utero exposure to excess maternal cortisol (1 mg/kg/day) in late gestation increases the incidence of stillbirth during labor and produces fetal bradycardia at birth. In the interventricular septum, mitochondrial DNA (mt-DNA) was decreased, and transcriptomics and metabolomics were consistent with altered mitochondrial metabolism. The present study uses transcriptomics to model effects of increased maternal cortisol on fetal biceps femoris. Transcriptomic modeling revealed that pathways related to mitochondrial metabolism were downregulated, whereas pathways for regulation of reactive oxygen species and activation of the apoptotic cascade were upregulated. Mt-DNA and the protein levels of cytochrome C were significantly decreased in the biceps femoris. RT-PCR validation of the pathways confirmed a significant decrease in SLC2A4 mRNA levels and a significant increase in PDK4, TXNIP, ANGPTL4 mRNA levels, suggesting that insulin sensitivity of the biceps femoris muscle may be reduced in cortisol offspring. We also tested for changes in gene expression in diaphragm by rt-PCR. PDK4, TXNIP, and ANGPTL4 mRNA were also increased in the diaphragm, but SLC2A4, cytochrome C protein, and mt-DNA were unchanged. Comparison of the change in gene expression in biceps femoris to that in cardiac interventricular septum and left ventricle showed few common genes and little overlap in specific metabolic or signaling pathways, despite reduction in mt-DNA in both heart and biceps femoris. Our results suggest that glucocorticoid exposure alters expression of nuclear genes important to mitochondrial activity and oxidative stress in both cardiac and skeletal muscle tissues, but that these effects are tissue-specific.

The physiological response to hypoxia in the fetus has been extensively studied with regard to redistribution of fetal combined ventricular output and sparing of oxygen delivery to fetal brain and heart. Previously, we have shown that the fetal brain is capable of mounting changes in gene expression that are consistent with tissue inflammation. The present study was designed to use transcriptomics and systems biology modeling to test the hypothesis that ketamine reduces or prevents the upregulation of inflammation-related pathways in hypothalamus and hippocampus after transient hypoxic hypoxia. Chronically catheterized fetal sheep (122 ± 5 days gestation) were subjected to 30 min hypoxia (relative reduction in PaO2∼50%) caused by infusion of nitrogen into the inspired gas of the pregnant ewe. RNA was isolated from fetal hypothalamus and hippocampus collected 24 h after hypoxia, and was analyzed for gene expression using the Agilent 15.5 k ovine microarray. Ketamine, injected 10 min prior to hypoxia, reduced the cerebral immune response activation to the hypoxia in both brain regions. Genes both upregulated by hypoxia and downregulated by ketamine after hypoxia were significantly associated with gene ontology terms and KEGG pathways that are, themselves, associated with the tissue response to exposure to bacteria. We conclude that the results are consistent with interruption of the cellular response to bacteria by ketamine. Fil: Chang, Eileen I.. University of Florida; Estados Unidos Fil: Zarate, Miguel A.. University of Florida; Estados Unidos Fil: Arndt, Thomas J.. University of Florida; Estados Unidos Fil: Richards, Elaine M.. University of Florida; Estados Unidos Fil: Rabaglino, Maria Belen. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Ciencias de la Salud. Universidad Nacional de Córdoba. Instituto de Investigaciones en Ciencias de la Salud; Argentina Fil: Keller Wood, Maureen. University of Florida; Estados Unidos Fil: Wood, Charles E.. University of Florida; Estados Unidos

Crosstalk between the gut microbiota and the host has attracted considerable attention owing to its involvement in diverse diseases. Chronic kidney disease (CKD) is commonly associated with hypertension and is characterized by immune dysregulation, metabolic disorder and sympathetic activation, which are all linked to gut dysbiosis and altered host–microbiota crosstalk. In this Review, we discuss the complex interplay between the brain, the gut, the microbiota and the kidney in CKD and hypertension and explain our brain–gut–kidney axis hypothesis for the pathogenesis of these diseases. Consideration of the role of the brain–gut–kidney axis in the maintenance of normal homeostasis and of dysregulation of this axis in CKD and hypertension could lead to the identification of novel therapeutic targets. In addition, the discovery of unique microbial communities and their associated metabolites and the elucidation of brain–gut–kidney signalling are likely to fill fundamental knowledge gaps leading to innovative research, clinical trials and treatments for CKD and hypertension. Increasing evidence suggests an important role of the gut microbiota in the development of hypertension and chronic kidney disease. In this Review, the authors explain their brain–gut–kidney axis hypothesis for the pathogenesis of these diseases.

Despite major advances in pharmacological and device-based therapies, systemic hypertension (HTN) continues to be the major, modifiable risk factor for most cardiovascular disease and a leading cause of morbidity and mortality. Treatment resistant HTN (RH) is present in ≈15% to 20% of hypertensive patients, with few treatment options. These facts provide an opportunity to develop novel hypotheses to advance this field. Over 60 years ago, Irvine Page1 proposed a mosaic theory where interplay of multiple factors integrate to increase blood pressure (BP). This fostered establishment of cellular, molecular, and physiological mechanisms altered in HTN. However, how these diverse factors integrate to impair BP control remains a challenge. Furthermore, why some factors are prohypertensive in one individual and not in another, and where prohypertensive signals originate, remains an enigma. In this Viewpoint, we propose that the gut and gut microbiota could be one missing link and provide a potential unifying concept. We summarize most recent evidence for involvement of gut microbiota in BP control and HTN. We present our thoughts on the current state and relevant knowledge gaps to be addressed to determine whether targeting gut microbiota and related pathology would be a next frontier in HTN therapeutics. Gut dysbiosis and microbial functions contribute to pathological effects beyond the gastrointestinal system. Gut microbiota play a role in BP regulation, and gut dysbiosis has been observed in multiple animal models of HTN.2–5 Our group was among the first to document HTN-associated gut dysbiosis and an increased Firmicutes/Bacteroidetes ratio.2,3 This was associated with a decrease in acetate- and butyrate-producing bacteria and an increase in the lactate-producing bacteria. High-fiber diet and acetate supplementation correct gut dysbiosis, increase the abundance of acetate-producing bacteria, and are associated with lower BP in DOCA-salt mice.5 Stroke-prone spontaneously hypertensive rats exhibit …

Transient hypoxia in pregnancy stimulates a physiological reflex response that redistributes blood flow and defends oxygen delivery to the fetal brain. We designed the present experiment to test the hypotheses that transient hypoxia produces damage of the cerebral cortex and that ketamine, an antagonist of NMDA receptors and a known anti‐inflammatory agent, reduces the damage. Late gestation, chronically catheterized fetal sheep were subjected to a 30‐min period of ventilatory hypoxia that decreased fetal PaO 2 from 17 ± 1 to 10 ± 1 mmHg, or normoxia (PaO 2 17 ± 1 mmHg), with or without pretreatment (10 min before hypoxia/normoxia) with ketamine (3 mg/kg, i.v.). One day (24 h) after hypoxia/normoxia, fetal cerebral cortex was removed and mRNA extracted for transcriptomics and systems biology analysis ( n = 3–5 per group). Hypoxia stimulated a transcriptomic response consistent with a reduction in cellular metabolism and an increase in inflammation. Ketamine pretreatment reduced both of these responses. The inflammation response modeled with transcriptomic systems biology was validated by immunohistochemistry and showed increased abundance of microglia/macrophages after hypoxia in the cerebral cortical tissue that ketamine significantly reduced. We conclude that transient hypoxia produces inflammation of the fetal cerebral cortex and that ketamine, in a standard clinical dose, reduces the inflammation response.

Previous studies in our laboratory have shown that a modest chronic increase in maternal cortisol concentrations impairs maternal glucose metabolism and increases the incidence of perinatal stillbirth. The dramatic outcomes prevented our ability to study the effects of maternal hypercortisolemia on neonatal growth, glucose metabolism, and hypothalamo-pituitary-adrenal axis response. Therefore, we developed a model in which pregnant ewes are infused for 12 h/day at 0.5 mg·kg(-1)·day(-1) from day 115 of gestation until delivery (~145), elevating nighttime plasma cortisol concentrations. This pattern of elevation of cortisol mimics that in patients with elevated evening cortisol concentrations, as in Cushing's syndrome or chronic depression. Plasma cortisol, glucose, insulin, and electrolytes were measured during pregnancy and postpartum in control and cortisol-infused ewes and their postnatal lambs for the first 14 days after delivery. Neonatal growth and plasma ACTH, aldosterone, renin activity, and electrolytes, and organ weights at 14 days of age were also measured. Infusion of cortisol increased maternal plasma cortisol during pregnancy but not postpartum, and did not alter neonatal ACTH or cortisol. Although maternal glucose and insulin concentrations were not changed by the maternal infusion of cortisol, neonatal plasma glucose was increased and plasma insulin was decreased compared to those in the control group. Neonatal ponderal index and kidney weight were reduced, left ventricular wall thickness was increased, and plasma sodium and creatinine were increased after maternal cortisol infusion. These results suggest that excess maternal cortisol concentrations in late gestation alter growth, glucose and insulin regulation, and organ maturation in the neonate.

Septa from sheep hearts at 130 days gestation, term, and 14-day-old lambs were used to model the changes in gene expression patterns during the perinatal period using Agilent 15k ovine microarrays. We used Bioconductor for R to model five major patterns of coexpressed genes. Gene ontology and transcription factor analyses using Webgestalt modeled the biological significances and transcription factors of the gene expression patterns. Modeling indicated a decreased expression of genes associated with anatomical development and differentiation during this period, whereas those associated with increased protein synthesis and growth associated with maturation of the endoplasmic reticulum rose to term but did not further increase from the near term expression. Expression of genes associated with cell responsiveness, for example, immune responses, decreased at term but expression returned by postnatal day 14. Changes in genes related to metabolism showed differential substrate-associated patterns: those related to carbohydrate metabolism rose to term and remained stable thereafter, whereas those associated with fatty acid oxidation facility rose throughout the period. The timing of many of these maturational processes was earlier in relation to birth than in the rodent. The importance of the transcription factors, estrogen-related receptors, and v-myc avian myelocytomatosis viral oncogene homolog was also highlighted in the pattern of gene expression during development of the perinatal sheep heart. Fil: Richards, Elaine M.. University of Florida; Estados Unidos Fil: Rabaglino, Maria Belen. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; Argentina. Universidad Nacional de Río Cuarto. Facultad de Agronomía y Veterinaria; Argentina Fil: Antolic, Andrew. University of Florida; Estados Unidos Fil: Wood, Charles E.. University of Florida; Estados Unidos Fil: Keller Wood, Maureen. University of Florida; Estados Unidos

Estradiol (E2) is a well-known modulator of fetal neuroendocrine activity and has been proposed as a critical endocrine signal readying the fetus for birth and postnatal life. To investigate the modulatory role of E2 on fetal stress responsiveness and the response of the fetal brain to asphyxic stress, we subjected chronically catheterized fetal sheep to a transient (10 min) brachiocephalic artery occlusion (BCO) or sham occlusion. Half of the fetuses received subcutaneous pellets that increased plasma E2 concentrations within the physiological range. Hypothalamic mRNA was analyzed using the Agilent 8x15k ovine array (019921), processed and annotated as previously reported by our laboratory. Analysis of the data by ANOVA revealed that E2 differentially regulated (DR) 561 genes, and BCO DR 894 genes compared with control and E2+BCO DR 1,153 genes compared with BCO alone (all P < 0.05). E2 upregulated epigenetic pathways and downregulated local steroid biosynthesis but did not significantly involve genes known to directly respond to the estrogen receptor. Brachiocephalic occlusion upregulated kinase pathways as well as genes associated with lymphocyte infiltration into the brain and downregulated neuropeptide synthesis. E2 upregulated immune- and apoptosis-related pathways after BCO and reduced kinase and epigenetic pathway responses to the BCO. Responses to BCO are different from responses to hypoxic hypoxia suggesting that mechanisms of responses to these two forms of brain hypoxia are distinct. We conclude that cerebral ischemia caused by BCO might stimulate lymphocyte infiltration into the brain and that this response appears to be modified by estradiol. during the transition from intra- to extrauterine life, birth asphyxia is a common cause of cerebral ischemia (29), commonly resulting in the need for resuscitation of the neonate. Disturbances in cerebral blood flow can result from various manipulations in the neonatal intensive care unit, including hypocarbia secondary to mechanical ventilation (18), continuous positive airway pressure (16, 42), and extracorporeal membrane oxygenation (7). Reduction of cerebral blood flow in the neonate compromises oxygen delivery or, if severe, produces ischemia/reperfusion injury (10) and results in morbidity, including intraventricular hemorrhage (6) and long-term cognitive deficit (14). We have investigated the cardiovascular and endocrine responses to cerebral hypoperfusion in late-gestation chronically catheterized fetal sheep (31, 38, 39), in this animal model of late fetal development. This model allows us to investigate responses to stress in utero and better understand the native homeostatic mechanisms that promote survival after stress. We investigated the responses to severe brain asphyxia, produced by a transient occlusion of the brachiocephalic artery, the vessel that in sheep supplies blood flow to both carotid arteries. This manipulation produces a form of brain asphyxia and reperfusion that might be similar to transient umbilical cord occlusion or transient interruption of cerebral blood flow during surgery. Brachiocephalic occlusion stimulates cardiovascular and endocrine responses as direct responses to ischemia/reperfusion and as reflex responses to carotid chemoreceptor activity (21, 39). Glutamate neurotransmission appears to play an important role in mediating the fetal ACTH response to brachiocephalic artery occlusion (BCO) (19). Related to, and perhaps downstream from, N-methyl-D-aspartate (NMDA) neurotransmission is the influence of brain-derived prostaglandins, mediated by cyclooxygenase-2 [prostaglandin-endoperoxide synthase 2 (PTGS2)], which is upregulated in various brain regions after BCO (12). The availability of ovine gene array technology has provided investigators with the ability to broadly model the response of the fetal hypothalamus to BCO. We have recently annotated the Agilent 15k ovine array, and we have used it to measure gene expression in fetal hypothalamus in response to ventilatory hypoxia in late gestation (41). In the present experiment, we used this array to investigate the genomics of the ovine fetal hypothalamic responses to BCO and to estradiol, both alone and in combination. We hypothesized that the genomic response to estradiol is highly represented by genes known to be directly stimulated by the estrogen receptor (ER) and that the response to BCO is modulated by estradiol. Fil: Wood, Charles. University of Florida; Estados Unidos Fil: Rabaglino, Maria Belen. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. University of Florida; Estados Unidos Fil: Richards, Elaine. University of Florida; Estados Unidos Fil: Denslow, Nancy. University of Florida; Estados Unidos Fil: Zarate, Miguel A.. University of Florida; Estados Unidos Fil: Chang, Eileen. University of Florida; Estados Unidos