Expression profiling reveals novel hypoxic biomarkers in peripheral blood of adult mice exposed to chronic hypoxia

A micropeptide TREMP encoded by lincR-PPP2R5C promotes Th2 cell differentiation by interacting with PYCR1 in allergic airway inflammation

BACKGROUND

Allergic asthma is largely dominated by Th2 lymphocytes. Micropeptides in Th2 cells and asthma remain unmasked. Here, we aimed to demonstrate a micropeptide, T-cell regulatory micropeptide (TREMP), in Th2 cell differentiation in asthma.

METHODS

TREMP translated from lincR-PPP2R5C was validated using Western blotting and mass spectrometry. TREMP knockout mice were generated using CRISPR/Cas9. Coimmunoprecipitation revealed that TREMP targeted pyrroline-5-carboxylate reductase 1 (PYCR1), which was further explored in vitro and in vivo. The levels of TREMP and PYCR1 in Th2 cells from clinical samples were determined by flow cytometry.

RESULTS

TREMP, encoded by lincR-PPP2R5C, was in the mitochondrion. The lentivirus encoding TREMP promoted Th2 cell differentiation. In contrast, Th2 differentiation was suppressed in TREMP-/- CD4+ T cells. In the HDM-induced model of allergic airway inflammation, TREMP was increased in pulmonary tissues. Allergic airway inflammation was relieved in TREMP-/- mice treated with HDM. Mechanistically, TREMP interacted with PYCR1, which regulated Th2 differentiation via glycolysis. Glycolysis was decreased in Th2 cells from TREMP-/- mice and PYCR1-/- mice. Similar to TREMP-/- mice, allergic airway inflammation was mitigated in HDM-challenged PYCR1-/- mice. Moreover, we measured TREMP and PYCR1 in asthma patients. And we found that, compared with those in healthy controls, the levels of TREMP and PYCR1 in Th2 cells were significantly increased in asthmatic patients.

CONCLUSIONS

The micropeptide TREMP encoded by lincR-PPP2R5C promoted Th2 differentiation in allergic airway inflammation by interacting with PYCR1 and enhancing glycolysis. Our findings highlight the importance of neglected micropeptides from noncoding RNAs in allergic diseases.

Effects of Drought and Flooding on Phytohormones and Abscisic Acid Gene Expression in Kiwifruit

Environmental extremes, such as drought and flooding, are becoming more common with global warming, resulting in significant crop losses. Understanding the mechanisms underlying the plant water stress response, regulated by the abscisic acid (ABA) pathway, is crucial to building resilience to climate change. Potted kiwifruit plants (two cultivars) were exposed to contrasting watering regimes (water logging and no water). Root and leaf tissues were sampled during the experiments to measure phytohormone levels and expression of ABA pathway genes. ABA increased significantly under drought conditions compared with the control and waterlogged plants. ABA-related gene responses were significantly greater in roots than leaves. ABA responsive genes, DREB2 and WRKY40, showed the greatest upregulation in roots with flooding, and the ABA biosynthesis gene, NCED3, with drought. Two ABA-catabolic genes, CYP707A i and ii were able to differentiate the water stress responses, with upregulation in flooding and downregulation in drought. This study has identified molecular markers and shown that water stress extremes induced strong phytohormone/ABA gene responses in the roots, which are the key site of water stress perception, supporting the theory kiwifruit plants regulate ABA to combat water stress.

Prevalence of Reticulocytosis in the Absence of Anemia in Dogs with Cardiogenic Pulmonary Edema Due to Myxomatous Mitral Valve Disease: A Retrospective Study

Myxomatous mitral valve disease (MMVD) is the most common heart disease in small breed dogs. Dogs with MMVD commonly show clinical signs of dyspnea due to cardiogenic pulmonary edema (CPE). Reticulocytosis in the absence of anemia (RAA) is a hematological finding in hypoxic conditions. We aimed to assess the prevalence of RAA in dogs with CPE due to MMVD, and evaluate whether RAA is reversible with amelioration of dyspnea. Twenty-nine client-owned dogs with CPE due to MMVD were included. Dogs who died within 6 weeks of the onset of CPE were included in the non-survival group, while the others comprised the survival group. Of the 21 dogs, RAA was observed in 17 dogs (80.9%). In the RAA group, the absolute reticulocyte count significantly decreased as CPE resolved (p < 0.001). The mean absolute reticulocyte count in the RAA group was 163.90 ± 50.77 on the first measurement and 78.84 ± 25.64 after resolution of CPE. In the RAA group, no significant differences in mean absolute reticulocyte count were observed between the survival and non-survival groups at either the first or second measurement. Our results indicate that RAA occurs in dogs with MMVD-related CPE and can resolve after resolution of CPE.

Landscape genomics of the streamside salamander: Implications for species management in the face of environmental change

Understanding spatial patterns of genetic differentiation and local adaptation is critical in a period of rapid environmental change. Climate change and anthropogenic development have led to population declines and shifting geographic distributions in numerous species. The streamside salamander, Ambystoma barbouri, is an endemic amphibian with a small geographic range that predominantly inhabits small, ephemeral streams. As A. barbouri is listed as near-threatened by the IUCN, we describe range-wide patterns of genetic differentiation and adaptation to assess the species' potential to respond to environmental change. We use outlier scans and genetic-environment association analyses to identify genomic variation putatively underlying local adaptation across the species' geographic range. We find evidence for adaptation with a polygenic architecture and a set of candidate SNPs that identify genes putatively contributing to local adaptation. Our results build on earlier work that suggests that some A. barbouri populations are locally adapted despite evidence for asymmetric gene flow between the range core and periphery. Taken together, the body of work describing the evolutionary genetics of range limits in A. barbouri suggests that the species may be unlikely to respond naturally to environmental challenges through a range shift or in situ adaptation. We suggest that management efforts such as assisted migration may be necessary in future.

Defence Responses Associated with Elicitor-Induced, Cultivar-Associated Resistance to Latania Scale in Kiwifruit

Latania scale insect is a pest of global significance affecting kiwifruit. The sessile insect (life stage: settled crawler-mature adult) is covered with a waxy cap that protects it from topical pesticides, so increasingly, a selection of resistant cultivars and application of elicitors are being used in pest control. Thus far, the application of a salicylic acid (SA) phytohormone pathway elicitor, acibenzolar-S-methyl (ASM), has been shown to reduce insect development (as indicated by cap size) on one kiwifruit cultivar ('Hayward'). To investigate how cultivar-associated resistance is affected by the ability to respond to different elicitors, we measured phytohormones (by LCMS) and gene expression (by qPCR and NanoString) on latania scale-tolerant 'Hort16A' and susceptible 'Hayward' kiwifruit over two seasons. Potted plants in the presence/absence of settled latania scales were treated with ASM (0.2 g/L) or methyl jasmonate (MeJA, 0.05% v/v), representing elicitors of the SA and JA signalling pathways, respectively. 'Hort16A' cultivar resistance to latania scale was associated with elevated expression of SA and SA-related defence genes (PR1 and two PR2 family genes) in the ASM treatment. MeJA treatments did not significantly affect insect development in 'Hayward' (latania scale did not survive on 'Hort16A') and did not correlate with phytohormone and gene expression measurements in either cultivar. 'Hayward' had greater concentrations than 'Hort16A' of inert storage forms of both SA and JA across all treatments. This information contributes to the selection of tolerant cultivars and the effective use of elicitors for control of latania scale in kiwifruit.

Integrated Use of Aureobasidium pullulans Strain CG163 and Acibenzolar-S-Methyl for Management of Bacterial Canker in Kiwifruit

An isolate of Aureobasidium pullulans (strain = CG163) and the plant defence elicitor acibenzolar-S-methyl (ASM) were investigated for their ability to control leaf spot in kiwifruit caused by Pseudomonassyringae pv. actinidiae biovar 3 (Psa). Clonal Actinidia chinensis var. deliciosa plantlets (‘Hayward’) were treated with ASM, CG163 or ASM + CG163 at seven and one day before inoculation with Psa. ASM (0.2 g/L) was applied either as a root or foliar treatments and CG163 was applied as a foliar spray containing 2 × 10⁷ CFU/mL. Leaf spot incidence was significantly reduced by all treatments compared with the control. The combination of ASM + CG163 had greater efficacy (75%) than either ASM (55%) or CG163 (40%) alone. Moreover, treatment efficacy correlated positively with the expression of defence-related genes: pathogenesis-related protein 1 (PR1), β-1,3-glucosidase, Glucan endo 1,3-β-glucosidase (Gluc_PrimerH) and Class IV chitinase (ClassIV_Chit), with greater gene upregulation in plants treated with ASM + CG163 than by the individual treatments. Pathogen population studies indicated that CG163 had significant suppressive activity against epiphytic populations of Psa. Endophytic populations were reduced by ASM + CG163 but not by the individual treatments, and by 96–144 h after inoculation were significantly lower than the control. Together these data suggest that ASM + CG163 have complementary modes of action that contribute to greater control of leaf spotting than either treatment alone.

Effects of vagotomy on cardiovascular and heart rate variability alterations following chronic normobaric hypoxia in adult rabbits

BACKGROUND

chronic hypoxia increases basal ventilation and pulmonary vascular resistance, with variable changes in arterial blood pressure and heart rate, but it's impact on heart rate variability and autonomic regulation have been less well examined. We studied changes in arterial blood pressure, heart rate and heart rate variability (HRV) in rabbits subjected to chronic normobaric hypoxia (CNH; PB ~ 719 mmHg; F_IO₂ ~ 9.2%) for 14 days and assess the effect of autonomic control by acute bilateral vagal denervation.

RESULTS

exposure to CNH stalled animal weight gain and increased the hematocrit, without affecting heart rate or arterial blood pressure. Nevertheless, Poincaré plots of the electrocardiographic R-R intervals showed a reduced distribution parallel to the line of identity, which interpreted as reduced long-term HRV. In the frequency domain, CNH reduced the very-low- (< 0.2 Hz) and high-frequency components (> 0.8 Hz) of the R-R spectrograms and produced a prominent component in the low-frequency component (0.2-0.5 Hz) of the power spectrum. In control and CNH exposed rabbits, bilateral vagotomy had no apparent effect on the short- and long-term HRV in the Poincaré plots. However, bilateral vagotomy differentially affected higher-frequency components (> 0.8 Hz); reducing it in control animals without modifying it in CNH-exposed rabbits.

CONCLUSIONS

These results suggest that CNH exposure shifts the autonomic balance of heart rate towards a sympathetic predominance without modifying resting heart rate or arterial blood pressure.

Gene expression is implicated in the ability of pikas to occupy Himalayan elevational gradient

Species are shifting their ranges due to climate change, many moving to cooler and higher locations. However, with elevation increase comes oxygen decline, potentially limiting a species’ ability to track its environment depending on what mechanisms it has available to compensate for hypoxic stress. Pikas (Family Ochotonidae), cold-specialist small mammal species, are already undergoing elevational range shifts. We collected RNA samples from one population of Ochotona roylei in the western Himalaya at three sites– 3,600, 4,000, and 5,000 meters–and found no evidence of significant population genetic structure nor positive selection among sites. However, out of over 10,000 expressed transcripts, 26 were significantly upregulated at the 5,000 m site and were significantly enriched for pathways consistent with physiological compensation for limited oxygen. These results suggest that differences in gene expression may play a key role in enabling hypoxia tolerance on this local scale, indicating elevational flexibility that may facilitate successful range shifts in response to climate change.

Transcriptomic analysis identifies a role of PI3K-Akt signalling in the responses of skeletal muscle to acute hypoxia in vivo

KEY POINTS

Changes in gene expression that occur within hours of exposure to hypoxia in in vivo skeletal muscles remain unexplored. Two hours of hypoxia caused significant down-regulation of extracellular matrix genes followed by a shift at 6 h to altered expression of genes associated with the nuclear lumen while respiratory and blood gases were stabilized. Enrichment analysis of mRNAs classified by stability rates suggests an attenuation of post-transcriptional regulation within hours of hypoxic exposure, where PI3K-Akt signalling was suggested to have a nodal role by pathway analysis. Experimental measurements and bioinformatic analyses suggested that the dephosphorylation of Akt after 2 h of hypoxic exposure might deactivate RNA-binding protein BRF1, hence resulting in the selective degradation of mRNAs.

ABSTRACT

The effects of acute hypoxia have been widely studied, but there are few studies of transcriptional responses to hours of hypoxia in vivo, especially in hypoxia-tolerant tissues like skeletal muscles. We used RNA-seq to analyse gene expression in plantaris muscles while monitoring respiration, arterial blood gases, and blood glucose in mice exposed to 8% O2 for 2 or 6 h. Rapid decreases in blood gases and a slower reduction in blood glucose suggest stress, which was accompanied by widespread changes in gene expression. Early down-regulation of genes associated with the extracellular matrix was followed by a shift to genes associated with the nuclear lumen. Most of the early down-regulated genes had mRNA half-lives longer than 2 h, suggesting a role for post-transcriptional regulation. These transcriptional changes were enriched in signalling pathways in which the PI3K-Akt signalling pathway was identified as a hub. Our analyses indicated that gene targets of PI3K-Akt but not HIF were enriched in early transcriptional responses to hypoxia. Among the PI3K-Akt targets, 75% could be explained by a deactivation of adenylate-uridylate-rich element (ARE)-binding protein BRF1, a target of PI3K-Akt. Consistent decreases in the phosphorylation of Akt and BRF1 were experimentally confirmed following 2 h of hypoxia. These results suggest that the PI3K-Akt signalling pathway might play a role in responses induced by acute hypoxia in skeletal muscles, partially through the dephosphorylation of ARE-binding protein BRF1.

Phytohormone and Putative Defense Gene Expression Differentiates the Response of 'Hayward' Kiwifruit to Psa and Pfm Infections

Pseudomonas syringae pv. actinidiae (Psa) and Pseudomonas syringae pv. actinidifoliorum (Pfm) are closely related pathovars infecting kiwifruit, but Psa is considered one of the most important global pathogens, whereas Pfm is not. In this study of Actinidia deliciosa 'Hayward' responses to the two pathovars, the objective was to test whether differences in plant defense responses mounted against the two pathovars correlated with the contrasting severity of the symptoms caused by them. Results showed that Psa infections were always more severe than Pfm infections, and were associated with highly localized, differential expression of phytohormones and putative defense gene transcripts in stem tissue closest to the inoculation site. Phytohormone concentrations of jasmonic acid (JA), jasmonate isoleucine (JA-Ile), salicylic acid (SA) and abscisic acid were always greater in stem tissue than in leaves, and leaf phytohormones were not affected by pathogen inoculation. Pfm inoculation induced a threefold increase in SA in stems relative to Psa inoculation, and a smaller 1.6-fold induction of JA. Transcript expression showed no effect of inoculation in leaves, but Pfm inoculation resulted in the greatest elevation of the SA marker genes, PR1 and glucan endo-1,3-beta-glucosidase (β-1,3-glucosidase) (32- and 25-fold increases, respectively) in stem tissue surrounding the inoculation site. Pfm inoculation also produced a stronger response than Psa inoculation in localized stem tissue for the SA marker gene PR6, jasmonoyl-isoleucine-12-hydrolase (JIH1), which acts as a negative marker of the JA pathway, and APETALA2/Ethylene response factor 2 transcription factor (AP2 ERF2), which is involved in JA/SA crosstalk. WRKY40 transcription factor (a SA marker) was induced equally in stems by wounding (mock inoculation) and pathovar inoculation. Taken together, these results suggest that the host appears to mount a stronger, localized, SA-based defense response to Pfm than Psa.

Inactivation of tristetraprolin in chronic hypoxia provokes the expression of cathepsin B

Macrophages play important roles in many diseases and are frequently found in hypoxic areas. A chronic hypoxic microenvironment alters global cellular protein expression, but molecular details remain poorly understood. Although hypoxia-inducible factor (HIF) is an established transcription factor allowing adaption to acute hypoxia, responses to chronic hypoxia are more complex. Based on a two-dimensional differential gel electrophoresis (2D-DIGE) approach, we aimed to identify proteins that are exclusively expressed under chronic but not acute hypoxia (1% O2). One of the identified proteins was cathepsin B (CTSB), and a knockdown of either HIF-1α or -2α in primary human macrophages pointed to an HIF-2α dependency. Although chromatin immunoprecipitation (ChIP) experiments confirmed HIF-2 binding to a CTSB enhancer in acute hypoxia, an increase of CTSB mRNA was evident only under chronic hypoxia. Along those lines, CTSB mRNA stability increased at 48 h but not at 8 h of hypoxia. However, RNA stability at 8 h of hypoxia was enhanced by a knockdown of tristetraprolin (TTP). Inactivation of TTP under prolonged hypoxia was facilitated by c-Jun N-terminal kinase (JNK), and inhibition of this kinase lowered CTSB mRNA levels and stability. We postulate a TTP-dependent mechanism to explain delayed expression of CTSB under chronic hypoxia.

Inhaled formaldehyde induces DNA-protein crosslinks and oxidative stress in bone marrow and other distant organs of exposed mice

Formaldehyde (FA), a major industrial chemical and ubiquitous environmental pollutant, has been classified as a leukemogen. The causal relationship remains unclear, however, due to limited evidence that FA induces toxicity in bone marrow, the site of leukemia induction, and in other distal organs. Although induction of DNA-protein crosslinks (DPC), a hallmark of FA toxicity, was not previously detected in the bone marrow of FA-exposed rats and monkeys in studies published in the 1980s, our recent studies showed increased DPC in the bone marrow, liver, kidney, and testes of exposed Kunming mice. To confirm these preliminary results, in the current study we exposed BALB/c mice to 0, 0.5, 1.0, and 3.0 mg m(-3) FA (8 hr per day, for 7 consecutive days) by nose-only inhalation and measured DPC levels in bone marrow and other organs of exposed mice. As oxidative stress is a potential mechanism of FA toxicity, we also measured glutathione (GSH), reactive oxygen species (ROS), and malondialdehyde (MDA), in the bone marrow, peripheral blood mononuclear cells, lung, liver, spleen, and testes of exposed mice. Significant dose-dependent increases in DPC, decreases in GSH, and increases in ROS and MDA were observed in all organs examined (except for DPC in lung). Bone marrow was among the organs with the strongest effects for DPC, GSH, and ROS. In conclusion, exposure of mice to FA by inhalation induced genotoxicity and oxidative stress in bone marrow and other organs. These findings strengthen the biological plausibility of FA-induced leukemogenesis and systemic toxicity.

Petrosal ganglion responses to acetylcholine and ATP are enhanced by chronic normobaric hypoxia in the rabbit

In mammals, adaptation to chronic hypoxia requires the integrity of the arterial chemoreceptors, specially the carotid body (CB). Chronic hypoxia increases the sensibility of the CB by acting on the receptor cells, but there is limited information on the effects of chronic hypoxia on the sensory neurons that innervate the CB. Therefore, we studied the responses evoked by ACh and ATP, the main transmitters that generate the chemoafferent activity, on the petrosal ganglion (PG) of rabbits exposed to chronic normobaric hypoxia (CNH) during fourteen days. ATP and ACh increased the activity of PG neurons in a dose-dependent manner, in a similar way than in rabbits not exposed to hypoxia (naïve). However, the duration of the responses were significantly increased by CNH, with the mean maximal responses to ACh and ATP increased by a factor of two and four, respectively. Our results suggest that CNH increases duration of the responses by modifying the expression and/or content of ACh and ATP receptors.

Ventilatory chemosensory drive is blunted in the mdx mouse model of Duchenne Muscular Dystrophy (DMD)

Duchenne Muscular Dystrophy (DMD) is caused by mutations in the DMD gene resulting in an absence of dystrophin in neurons and muscle. Respiratory failure is the most common cause of mortality and previous studies have largely concentrated on diaphragmatic muscle necrosis and respiratory failure component. Here, we investigated the integrity of respiratory control mechanisms in the mdx mouse model of DMD. Whole body plethysmograph in parallel with phrenic nerve activity recordings revealed a lower respiratory rate and minute ventilation during normoxia and a blunting of the hypoxic ventilatory reflex in response to mild levels of hypoxia together with a poor performance on a hypoxic stress test in mdx mice. Arterial blood gas analysis revealed low PaO2 and pH and high PaCO2 in mdx mice. To investigate chemosensory respiratory drive, we analyzed the carotid body by molecular and functional means. Dystrophin mRNA and protein was expressed in normal mice carotid bodies however, they are absent in mdx mice. Functional analysis revealed abnormalities in Dejours test and the early component of the hypercapnic ventilatory reflex in mdx mice. Together, these results demonstrate a malfunction in the peripheral chemosensory drive that would be predicted to contribute to the respiratory failure in mdx mice. These data suggest that investigating and monitoring peripheral chemosensory drive function may be useful for improving the management of DMD patients with respiratory failure.

Electroretinographic assessment of retinal function at high altitude

Although hypoxia plays a key role in the pathophysiology of many common and well studied retinal diseases, little is known about the effects of high-altitude hypoxia on retinal function. The aim of the present study was to assess retinal function during exposure to high-altitude hypoxia using electroretinography (ERG). This work is related to the Tübingen High Altitude Ophthalmology (THAO) study. Electroretinography was performed in 14 subjects in Tübingen, Germany (341 m) and at high altitude at La Capanna Regina Margherita, Italy (4,559 m) using an extended protocol to assess functional integrity of various retinal layers. To place findings in the context of acute mountain sickness, correlations between ERG measurements and oxygen saturation, heart rate, and scores of acute mountain sickness (AMS) were calculated. At high altitude, the maximum response of the scotopic sensitivity function, the implicit times of the a- and b-wave of the combined rod-cone responses, and the implicit times of the photopic negative responses (PhNR) were significantly altered. A-wave slopes and i-waves were significantly decreased at high altitude. The strongest correlation was found for PhNR and O2 saturation (r = 0.68; P < 0.05). Of all tested correlations, only the photopic b-wave implicit time (10 cd·s/m(2)) was significantly correlated with severity of AMS (r = 0.57; P < 0.05). ERG data show that retinal function of inner, outer, and ganglion cell layer is altered at high-altitude hypoxia. Interestingly, the most affected ERG parameters are related to combined rod-cone responses, which indicate that phototransduction and visual processing, especially under conditions of rod-cone interaction, are primarily affected at high altitude.