Angiotensin II increases vesicular trafficking in brain neurons

SARS-CoV-2 Dissemination Through Peripheral Nerves Explains Multiple Organ Injury

Coronavirus disease (CoVID-19), caused by recently identified severe acute respiratory distress syndrome coronavirus 2 (SARS-CoV-2), is characterized by inconsistent clinical presentations. While many infected individuals remain asymptomatic or show mild respiratory symptoms, others develop severe pneumonia or even respiratory distress syndrome. SARS-CoV-2 is reported to be able to infect the lungs, the intestines, blood vessels, the bile ducts, the conjunctiva, macrophages, T lymphocytes, the heart, liver, kidneys, and brain. More than a third of cases displayed neurological involvement, and many severely ill patients developed multiple organ infection and injury. However, less than 1% of patients had a detectable level of SARS-CoV-2 in the blood, raising a question of how the virus spreads throughout the body. We propose that nerve terminals in the orofacial mucosa, eyes, and olfactory neuroepithelium act as entry points for the brain invasion, allowing SARS-CoV-2 to infect the brainstem. By exploiting the subcellular membrane compartments of infected cells, a feature common to all coronaviruses, SARS-CoV-2 is capable to disseminate from the brain to periphery via vesicular axonal transport and passive diffusion through axonal endoplasmic reticula, causing multiple organ injury independently of an underlying respiratory infection. The proposed model clarifies a wide range of clinically observed phenomena in CoVID-19 patients, such as neurological symptoms unassociated with lung pathology, protracted presence of the virus in samples obtained from recovered patients, exaggerated immune response, and multiple organ failure in severe cases with variable course and dynamics of the disease. We believe that this model can provide novel insights into CoVID-19 and its long-term sequelae, and establish a framework for further research.

The angiotensin-converting enzyme inhibitor perindopril treatment alters cardiovascular and subjective effects of methamphetamine in humans

A variety of medications have been assessed for their potential efficacy for the treatment of methamphetamine dependence. We conducted this study in an attempt to evaluate the potential of a novel class of medications, angiotensin-converting enzyme inhibitors, as treatments for methamphetamine dependence. All participants met the Diagnostic and Statistical Manual of Mental Disorders, fourth edition, third revision (DSM-IV-TR) criteria for methamphetamine abuse or dependence and were not seeking treatment at the time of study entry. The study was conducted using a double-blind design. Subjects received a baseline series of intravenous (IV) doses of methamphetamine (15 mg and 30 mg) and placebo. Subjects received a second identical series of methamphetamine doses 3 and 5 days after initiation of once-daily oral placebo or perindopril treatment. The dose of perindopril was 2 mg, 4mg, or 8 mg administered in the morning. Perindopril treatment was tolerated well. There were no main effects of perindopril on methamphetamine-induced changes in cardiovascular or subjective effects. There were significant perindoprilmethamphetamine interactions for diastolic blood pressure and for ratings of "Any Drug Effect", indicating inverted U dose-effect functions for these indices.

Impaired Autofeedback Regulation of Hypothalamic Norepinephrine Release in Experimental Uremia

Chronic renal failure (CRF) is associated with multiple hypothalamic dysfunctions, including reduced secretion of gonadotropin-releasing hormone (GnRH). Because GnRH release is tightly controlled by sympathetic neuronal input, a possible alteration of local noradrenergic neurotransmission in experimental CRF was evaluated. Basal, stimulated, and autoinhibited norepinephrine (NE) release was assessed in hypothalamic and hippocampal tissue slices obtained from 5/6-nephrectomized and control rats. Autoinhibition-free NE release from brain slices, prelabeled with [3H]NE and superfused with physiologic buffer, was stimulated by six electrical pulses, 100 Hz (pseudo-one-pulse stimulation). Autoinhibited NE release was induced by 90 pulses at 3 Hz. The release of tritiated NE was measured upon addition of increasing concentrations of unlabeled NE to exogenously activate the inhibitory alpha2-autoreceptor. Although neither basal nor stimulated NE release differed between the groups, significantly lower pIC50 and Imax estimates of the concentration-response curves of exogenous NE on [3H]NE release were observed in CRF rats, suggesting a diminished autoinhibition of hypothalamic noradrenergic terminals in CRF. Western blotting of tissue homogenates disclosed a significantly reduced abundance of alpha2-autoreceptor protein in hypothalamic tissue from CRF rats. These abnormalities were selectively observed in the hypothalamus, whereas noradrenergic autoinhibition seemed unaltered in the hippocampus. The results suggest a diminished autoinhibition of hypothalamic NE release in CRF. Although impaired hypothalamic NE autoinhibition does not explain reduced GnRH secretion in CRF, it may be involved in the pathogenesis of sympathetic hyperactivity associated with this condition.

Enhanced activity of central adrenergic neurons in two-kidney, one clip hypertension in Sprague–Dawley rats

The present study was aimed at investigating whether two-kidney, one clip (2K1C) hypertension is associated with an enhanced central adrenergic activity. Rats were made 2K1C hypertensive, and the expression of Fos-like immunoreactivity (FLI) and phenylethanalamine N-methyltransferase (PNMT)-immunoreactivity was determined in the brain areas related to the cardiovascular regulation. In 2K1C hypertension, the basal Fos-immunoreactivity was significantly increased in rostral ventrolateral medulla (RVLM), paraventricular nucleus (PVN), and supraoptic nucleus (SON). PNMT-immunoreactivities were noted in RVLM, but not in PVN or SON. Intracerebroventricular administration of angiotensin II (AII) markedly increased Fos-immunoreactivities, the degree of which was greater in hypertension. Furthermore, AII increased the ratio of PNMT-positive/Fos-positive neurons in RVLM in hypertension. It is suggested that the responsiveness to AII of the central adrenergic system is enhanced in 2K1C hypertension.

Gene expression profiles in the rat central nervous system induced by JP-8 jet fuel vapor exposure

Jet propulsion fuel-8 (JP-8) is the predominant fuel for military land vehicles and aircraft used in the US and NATO. Occupational exposure to jet fuel in military personnel has raised concern for the health risk associated with such exposure in the Department of Defense. Clinical studies of humans chronically exposed to jet fuel have suggested both neurotoxicity and neurobehavioral deficits. We utilized rat neurobiology U34 array to measure gene expression changes in whole brain tissue of rats exposed repeatedly to JP-8, under conditions that simulated possible occupational exposure (6 h/day for 91 days) to JP-8 vapor at 250, 500, and 1000 mg/m(3), respectively. Our studies revealed that the gene expression changes of exposure groups can be divided into two main categories according to their functions: (1). neurotransmitter signaling pathways; and (2). stress response. The implications of these gene expression changes are discussed.

Viral vectors as tools for studies of central cardiovascular control

During the last few years physiological genomics has been the most rapidly developing area of physiology. Given the current ease of obtaining information about nucleotide sequences found in genomes and the vast amount of readily available clones, one of the most pertinent tasks is to find out about the roles of the individual genes and their families under normal and pathological conditions. Viral gene delivery into the brain is a powerful tool, which can be used to address a wide range of questions posed by physiological genomics including central nervous mechanisms regulating the cardio-vascular system. In this paper, we will give a short overview of current data obtained in this field using viral vectors and then look critically at the technology of viral gene transfer.

Heterogeneous co-localization of AT1A receptor and Fos protein in forebrain neuronal populations responding to acute hydromineral deficit

The present study investigates co-localization of AT(1A) receptor subtype and Fos protein in neuronal populations of the lamina terminalis (LT) that have been recruited during acute Na(+) and water depletion mediated by furosemide injections. For that purpose, we combined high cellular resolution of in situ hybridization technique to reveal neurons expressing AT(1A) receptor gene (AT(1A) mRNA) with the specificity of Fos protein immunoreactivity as a marker of neuronal activation (Fos-ir). As expected, furosemide treatment dramatically increased the density of Fos-immunoreactive neuronal population in all the regions of the LT compared to control (saline-injected animals). Distribution analysis of Fos-ir neurons and AT(1A) receptor-expressing neurons performed consecutively to furosemide-induced Na(+) and water depletion indicated that double-labeled neurons (AT(1A) mRNA+Fos-ir) represented the majority (67%) of the neuronal population that expressed AT(1A) receptor in the rim of the vascular organ of the lamina terminalis (OVLT). Double-labeled neurons amounted about 60% of the neurons that expressed AT(1A) receptor in the core of the subfornical organ (SFO) and 34% in the periphery of the SFO. In the median preoptic nucleus (MnPO), the density of the double-labeled neuronal population observed in the furosemide-treated animals remained weak compared to the control group of animals. Double-labeled neuronal population estimated in the MnPO of the furosemide-treated group of animals represented 17% of the neurons that express AT(1A) receptor gene. Our results report a heterogeneous distribution of the neuronal populations that co-localize AT(1A) receptor and Fos protein in the lamina terminalis after an acute Na(+) and water depletion. This study gives anatomical support to a direct action of endogenous AngII on c-fos transcription via binding on AT(1A) receptor in specific areas of the circumventricular organs (rim of the OVLT and core of the SFO). In the MnPO, our data indicate that intracellular signaling pathways unlikely couple AT(1A) receptor with c-fos transcription. The expression of Fos protein in this nucleus might be therefore secondary to the recruitment of excitatory inputs different from AngII. This observation underlines the complexity of molecules and neurocircuits in the preoptic region that are involved in the control of acute Na(+) and water deficit.

Cell surface trafficking of the antidepressant-sensitive norepinephrine transporter revealed with an ectodomain antibody

The antidepressant-sensitive L-norepinephrine (NE) transporter (NET;SLC6A2) is a critical determinant of neurotransmitter inactivation following NE release at synapses. Although regulated trafficking of NET has been documented in transfected cells, a lack of reagents suitable for reporting native NET surface exposition has limited validation of this concept in neurons. In the current report, we document the utility of a novel antibody (43408) directed at conserved sequences in the NET second extracellular loop. Using human NET (hNET) stably transfected cells, we document loss of NET surface expression following acute (30 min) phorbol ester treatments. In superior cervical ganglion (SCG) cultures, NET surface expression is prominent on varicosities defined by FM1-43 labeling of living neurons or synaptophysin labeling of fixed preparations. Moreover, NET surface density can be rapidly augmented by brief depolarization (5 min, 40 mM K(+)). Similarly, in brainstem cultures, we demonstrate an increase in NET surface labeling following either depolarization or angiotensin II stimulation. These findings provide the first evidence for regulated trafficking of NET in neurons and support the suggestion that activity-dependent NET trafficking may provide additional modulatory capacity for noradrenergic signaling.

Cross-talk between AT(1) and AT(2) angiotensin receptors in rat anococcygeus smooth muscle

Schild regressions for the selective AT(1) and AT(2) receptor antagonists, losartan and PD123319 (S-[+]-1-[(4-dimethylamino]-3-methylphenyl)methyl]-5-[diphenylacetyl]-4,5,6,7-tetrahydro-1H-imidazol[4,5-c]pyridine-6-carboxilic acid), respectively, were calculated to analyze the heterogeneity of receptor populations in the rat anococcygeus muscle. For a one-receptor system, the Schild regression has a slope of unity and an intercept of K(B) for competitive antagonists. However, in a two-receptor system, a deviation from the single-receptor plot will occur. This is predicated on the assumption that the secondary receptor is less sensitive to the antagonist than the primary receptor. Results showed that the Schild regression for losartan did not produce a slope of unity, and PD123319 did not produce any effect. However, tissue incubation with losartan plus PD123319 resulted in a Schild regression that has a slope of unity and a pK(B) of 9.32. In the presence of prazosin, an alpha(1)-adrenoceptor antagonist, losartan did not produce any effect. Conversely, PD123319 enhanced the angiotensin II (Ang II)-induced contraction in a concentration-dependent fashion, suggesting an inhibitory AT(2)-mediated effect. This effect was confirmed with assays that showed a relaxant response induced by Ang II on precontracted tissues incubated with prazosin. PD123319 and N(G)-nitro-L-arginine methyl ester [nitric-oxide (NO) synthase inhibitor)] markedly inhibited the relaxant response of Ang II. In contrast, losartan did not produce any significant effect. Consequently, results show that the mechanism underlying the AT(2)-mediated effect is highly dependent on NO generation. Results indicate the presence of a heterogeneous angiotensin receptor population in the rat anococcygeus muscle following a negative cross-talk relationship between the AT(1) and AT(2) subtypes.

Obligatory role of protein kinase Cbeta and MARCKS in vesicular trafficking in living neurons

Neurotransmitter release from neurons involves both vesicular trafficking and subsequent fusion of synaptic vesicles with the plasma membrane. The mechanisms involving the formation and fusion of vesicles that allow the exocytotic release of transmitters are understood well. Little is known, however, about the signaling mechanism involved in the trafficking of vesicles along the neurites. In this study, we used real-time confocal microscopy to search for evidence that vesicular trafficking in neurons requires the activation of protein kinase Cbeta (PKCbeta) and the myristoylated alanine-rich C kinase substrate (MARCKS) signaling pathway. Dopamine-beta-hydroxylase fused to green fluorescent protein has been used to trace vesicular movement. Angiotensin II, an established neuromodulatory hormone, stimulates translocation of green fluorescent protein-dopamine-beta-hydroxylase vesicles from the cell body to neurites. This translocation was blocked by an antisense oligonucleotide to PKCbeta and MARCKS. Stimulation of PKC by other means, such as phorbol-12-myristate-13-acetate or carbachol, also resulted in the redistribution of fluorescence in a manner similar to that observed for angiotensin II. These observations demonstrate that PKCbeta-MARCKS signaling may be a general mechanism for the stimulation of vesicular trafficking in brain neurons.