The spatiotemporal activities of astrocyte Ca2+ signaling in mature neuronal circuits remain unclear. We used genetically encoded Ca2+ and glutamate indicators as well as pharmacogenetic and ...electrical control of neurotransmitter release to explore astrocyte activity in the hippocampal mossy fiber pathway. Our data revealed numerous localized, spontaneous Ca2+ signals in astrocyte branches and territories, but these were not driven by neuronal activity or glutamate. Moreover, evoked astrocyte Ca2+ signaling changed linearly with the number of mossy fiber action potentials. Under these settings, astrocyte responses were global, suppressed by neurotransmitter clearance, and mediated by glutamate and GABA. Thus, astrocyte engagement in the fully developed mossy fiber pathway was slow and territorial, contrary to that frequently proposed for astrocytes within microcircuits. We show that astrocyte Ca2+ signaling functionally segregates large volumes of neuropil and that these transients are not suited for responding to, or regulating, single synapses in the mossy fiber pathway.
•Astrocyte branches/territories were studied using optical and pharmacogenetic tools•Spontaneous astrocyte Ca2+ signals were not due to action potentials or glutamate•Evoked astrocyte Ca2+ signals were slow, territorial and triggered by spike trains•Astrocyte Ca2+ signaling was tightly gated by neurotransmitter clearance
Haustein et al. use optical and genetic methods to explore the rules under which astrocytes are engaged in a model neuronal circuit. The findings show that astrocytes listen to synapses during bursts of action potentials in mossy fiber axons.
Epicardial cells are cardiac progenitors that give rise to the majority of cardiac fibroblasts, coronary smooth muscle cells, and pericytes during development. An integral phase of epicardial fate ...transition is epithelial-to-mesenchymal transition (EMT) that confers motility. We uncover an essential role for the protein arginine methyltransferase 1 (PRMT1) in epicardial invasion and differentiation. Using scRNA-seq, we show that epicardial-specific deletion of Prmt1 reduced matrix and ribosomal gene expression in epicardial-derived cell lineages. PRMT1 regulates splicing of Mdm4, which is a key controller of p53 stability. Loss of PRMT1 leads to accumulation of p53 that enhances Slug degradation and blocks EMT. During heart development, the PRMT1-p53 pathway is required for epicardial invasion and formation of epicardial-derived lineages: cardiac fibroblasts, coronary smooth muscle cells, and pericytes. Consequently, this pathway modulates ventricular morphogenesis and coronary vessel formation. Altogether, our study reveals molecular mechanisms involving the PRMT1-p53 pathway and establish its roles in heart development.
Display omitted
•PRMT1 drives epicardial EMT and invasion in vitro and in vivo•PRMT1-p53 pathway controls the formation of epicardial-derived lineages•PRMT1-p53 regulates ventricular morphogenesis and coronary vessel formation•PRMT1 modulates alternative splicing of Mdm4 and decreases p53 stability
Jackson-Weaver et al. show that PRMT1 drives epicardial invasion and differentiation in heart development. PRMT1 regulates splicing of Mdm4 and decreases p53 stability, which enhances Slug degradation to block epicardial EMT. The PRMT1-p53 axis is required for epicardial invasion and formation of epicardial-derived lineages during development.
The endothelial glycocalyx (EGX) contributes to the permeability barrier of vessels and regulates the coagulation cascade. EGX damage, which occurs in numerous disease states, including sepsis and ...trauma, results in endotheliopathy. While influenza and other viral infections are known to cause endothelial dysfunction, their effect on the EGX has not been described. We hypothesized that the H1N1 influenza virus would cause EGX degradation. Human umbilical vein endothelial cells (HUVECs) were exposed to varying multiplicities of infection (MOI) of the H1N1 strain of influenza virus for 24 hours. A dose-dependent effect was examined by using an MOI of 5 (n = 541), 15 (n = 714), 30 (n = 596), and 60 (n = 653) and compared to a control (n = 607). Cells were fixed and stained with FITC-labelled wheat germ agglutinin to quantify EGX. There was no difference in EGX intensity after exposure to H1N1 at an MOI of 5 compared to control (6.20 vs. 6.56 Arbitrary Units (AU), p = 0.50). EGX intensity was decreased at an MOI of 15 compared to control (5.36 vs. 6.56 AU, p<0.001). The degree of EGX degradation was worse at higher doses of the H1N1 virus; however, the decrease in EGX intensity was maximized at an MOI of 30. Injury at MOI of 60 was not worse than MOI of 30. (4.17 vs. 4.47 AU, p = 0.13). The H1N1 virus induces endothelial dysfunction by causing EGX degradation in a dose-dependent fashion. Further studies are needed to characterize the role of this EGX damage in causing clinically significant lung injury during acute viral infection.
The goal of this study was to determine if IL-22:Fc would Acute Respiratory Distress Syndrome (ARDS).
No therapies exist for ARDS and treatment is purely supportive. Interleukin-22 (IL-22) plays an ...integral component in recovery of the lung from infection. IL-22:Fc is a recombinant protein with a human FC immunoglobulin that increases the half-life of IL-22.
ARDS was induced in C57BL/6 mice with intra-tracheal lipopolysaccharide (LPS) at a dose of 33.3 or 100 ug. In the low-dose LPS group (LDG), IL-22:FC was administered via tail vein injection at 30 minutes (n = 9) and compared to sham (n = 9). In the high-dose LPS group (HDG), IL-22:FC was administered (n = 11) then compared to sham (n = 8). Euthanasia occurred after bronchioalveolar lavage (BAL) on post-injury day 4.
In the LDG, IL-22:FC resulted in decreased protein leak (0.15 vs. 0.25 ug/uL, p = 0.02). BAL protein in animals receiving IL-22:Fc in the HDG was not different. For the HDG, animals receiving IL-22:Fc had lower BAL cell counts (539,636 vs 3,147,556 cells/uL, p = 0.02). For the HDG, IL-6 (110.6 vs. 527.1 pg/mL, p = 0.04), TNF-α (5.87 vs. 25.41 pg/mL, p = 0.04), and G-CSF (95.14 vs. 659.6, p = 0.01) levels were lower in the BAL fluid of IL-22:Fc treated animals compared to sham.
IL-22:Fc decreases lung inflammation and lung capillary leak in ARDS. IL-22:Fc may be a novel therapy for ARDS.
Hemorrhagic shock has recently been shown to cause shedding of a carbohydrate surface layer of endothelial cells known as the glycocalyx. This shedding of the glycocalyx is thought to be a mediator ...of the coagulopathy seen in trauma patients. Clinical studies have demonstrated increases in shed glycocalyx in the blood after trauma, and animal studies have measured glycocalyx disruption in blood vessels in the lung, skeletal muscle, and mesentery. However, no study has measured glycocalyx disruption across a wide range of vascular beds to quantify the primary locations of this shedding.
In the present study, we used a rat model of hemorrhagic shock and resuscitation to more comprehensively assess glycocalyx disruption across a range of organs. Glycocalyx disruption was assessed by fluorescent-labeled wheat germ agglutinin or syndecan-1 antibody staining in flash frozen tissue.
We found that our model did elicit glycocalyx shedding, as assessed by an increase in plasma syndecan-1 levels. In tissue sections, we found that the greatest glycocalyx disruption occurred in vessels in the lung and intestine. Shedding to a lesser extent was observed in vessels of the brain, heart, and skeletal muscle. Liver vessel glycocalyx was unaffected, and kidney vessels, including the glomerular capillaries, displayed an increase in glycocalyx. We also measured reactive oxygen species (ROS) in the endothelial cells from these organs, and found that the greatest increase in ROS occurred in the two beds with the greatest glycocalyx shedding, the lungs, and intestine. We also detected fibrin deposition in lung vessels following hemorrhage-resuscitation.
We conclude that the endothelium in the lungs and intestine are particularly susceptible to the oxidative stress of hemorrhage-resuscitation, as well as the resulting glycocalyx disruption. Thus, these two vessel beds may be important drivers of coagulopathy in trauma patients.
RATIONALE:Myogenic tone, an important regulator of vascular resistance, is dependent on vascular smooth muscle (VSM) depolarization, can be modulated by endothelial factors, and is increased in ...several models of hypertension. Intermittent hypoxia (IH) elevates blood pressure and causes endothelial dysfunction. Hydrogen sulfide (H2S), a recently described endothelium-derived vasodilator, is produced by the enzyme cystathionine γ-lyase (CSE) and acts by hyperpolarizing VSM.
OBJECTIVE:Determine whether IH decreases endothelial H2S production to increase myogenic tone in small mesenteric arteries.
METHODS AND RESULTS:Myogenic tone was greater in mesenteric arteries from IH than sham control rat arteries, and VSM membrane potential was depolarized in IH in comparison with sham arteries. Endothelium inactivation or scavenging of H2S enhanced myogenic tone in sham arteries to the level of IH. Inhibiting CSE also enhanced myogenic tone and depolarized VSM in sham but not IH arteries. Similar results were seen in cerebral arteries. Exogenous H2S dilated and hyperpolarized sham and IH arteries, and this dilation was blocked by iberiotoxin, paxilline, and KCl preconstriction but not glibenclamide or 3-isobutyl-1-methylxanthine. Iberiotoxin enhanced myogenic tone in both groups but more in sham than IH. CSE immunofluorescence was less in the endothelium of IH than in sham mesenteric arteries. Endogenouse H2S dilation was reduced in IH arteries.
CONCLUSIONS:IH appears to decrease endothelial CSE expression to reduce H2S production, depolarize VSM, and enhance myogenic tone. H2S dilatation and hyperpolarization of VSM in small mesenteric arteries requires BKCa channels.
The diversity and distribution of a bacterial community from Coffee Pots Hot Spring, a thermal spring in Yellowstone National Park with a temperature range of 39.3 to 74.1°C and pH range of 5.75 to ...6.91, were investigated by sequencing cloned PCR products and quantitative PCR (qPCR) of 16S rRNA and metabolic genes. The spring was inhabited by three Aquificae genera--Thermocrinis, Hydrogenobaculum, and SULFURIHYDROGENIBIUM:and members of the Alpha-, Beta-, and Gammaproteobacteria, Firmicutes, Acidobacteria, Deinococcus-Thermus, and candidate division OP5. The in situ chemical affinities were calculated for 41 potential metabolic reactions using measured environmental parameters and a range of hydrogen and oxygen concentrations. Reactions that use oxygen, ferric iron, sulfur, and nitrate as electron acceptors were predicted to be the most energetically favorable, while reactions using sulfate were expected to be less favorable. Samples were screened for genes used in ammonia oxidation (amoA, bacterial gene only), the reductive tricarboxylic acid (rTCA) cycle (aclB), the Calvin cycle (cbbM), sulfate reduction (dsrAB), nitrogen fixation (nifH), nitrite reduction (nirK), and sulfide oxidation (soxEF1) by PCR. Genes for carbon fixation by the rTCA cycle and nitrogen fixation were detected. All aclB sequences were phylogenetically related and spatially correlated to Sulfurihydrogenibium 16S rRNA gene sequences using qPCR (R² = 0.99). This result supports the recent finding of citrate cleavage by enzymes other than ATP citrate lyase in the rTCA cycle of the Aquificaceae family. We briefly consider potential biochemical mechanisms that may allow Sulfurihydrogenibium and Thermocrinis to codominate some hydrothermal environments.
Background: The effects of resuscitative endovascular balloon occlusion of the aorta (REBOA) on progression of traumatic brain injury (TBI) are unclear. Two hypotheses prevail: increased mean ...arterial pressure may improve cerebral perfusion, or cause cerebral edema due to elevated intracranial pressure. This study compares outcomes in hypotensive, blunt trauma patients with TBI treated with and without REBOA.
Methods: A retrospective analysis compared hypotensive (systolic blood pressure SBP >90) blunt trauma patients with TBI treated with REBOA to those treated without. Patients with spontaneous circulation at admission and at initiation of aortic occlusion were included. Patients requiring cardiopulmonary resuscitation in the emergency department (ED) were excluded. Radius matching used age, injury severity score (ISS), abbreviated injury score (AIS)head, and Glasgow coma score (GCS) and SBP at ED arrival.
Results: Of 232 patients, 135 were treated with REBOA and 97 without. REBOA patients were older and had higher ISS, AIS-head, AIS-chest and AIS- extremity. There was no difference in TBI severity, and mortality. In the matched analysis (n = 76 REBOA, n = 54 non-REBOA), there was no difference in ISS, AIS-head, pre-hospital, ED, or discharge GCS, ED SBP, or mortality. Despite longer hospital stays for REBOA patients, there was no difference in intensive care unit length of stay, rate of discharge home, or discharge GCS.
Conclusions: REBOA was used in more severely injured patients, but was not associated with higher mortality rate. REBOA should be considered for use in patients with non-compressible torso hemorrhage and concomitant TBI, as it did not increase mortality, and outcomes were similar to non-REBOA patients.
Metropolitan cities in the United States (US) suffer from higher rates of gun violence. However, the specific structural factors associated with increased gun violence are poorly defined. We ...hypothesized that firearm homicide in metropolitan cities would be impacted by black-white segregation index (SI).
This cross-sectional analysis evaluated 51 US metropolitan statistical areas (MSAs) using data from 2013-2017. Several measures of structural racism were examined, including the Brooking Institute's black-white SI. Demographic data was derived from the US Census Bureau, US Department of Education, and US Department of Labor. Crime data and firearm homicide mortality (FM) rates were obtained from the Federal Bureau of Investigation and the Centers for Disease Control. Spearman's Rho and linear regression were performed.
Firearm mortality was associated with multiple measures of structural racism and racial disparity, including white-black SI, unemployment rate, poverty rate, single parent household, percent black population, and crime rates. In regression analysis, percentage black population exhibited the strongest association with FM (β=0.42, p<0.001). Black-white segregation index (β=0.41, p=0.001) and percent children living in single-parent households (β=0.41, p=0.002) were also associated with higher FM. Firearm legislation scores were associated with lower FM (β=-0.20 p=0.02). High school and college graduation rates were not associated with FM and were not included in the final model.
Firearm homicide disproportionately impacts communities of color and is associated with measures of structural racism, such as white-black SI. Public health interventions targeting gun violence must address these systemic inequities. Furthermore, given the association between firearm mortality and single-parent households, intervention programs for at-risk youth may be particularly effective.
Level III; Retrospective Epidemiological Study.
PDF
