Raptor Pediatrics

Neonatal and juvenile raptors may differ from adults in their husbandry, disease predispositions, and medical therapies. There are differences between captive bred juveniles and those presented for rehabilitation to the wild, which must be taken into consideration for successful long-term outcomes. In captive settings, many metabolic and infectious diseases may be linked to problems with diet. The successful rehabilitation and release of wild raptor chicks requires special precautions beyond avoiding imprinting.

Organic farming reduces pesticide load in a bird of prey

Human activities have led to the contamination of all environmental compartments worldwide, including bird species. In birds, both the environment and maternal transfer lead to high inter-brood variability in contamination levels of pollutants, whereas intra-brood variability is generally low. However, most existing studies focused on heavy metals or persistent compounds and none, to our knowledge, addressed the variability in contamination levels of multiple pesticides and the factors influencing it. In this study, the number of pesticides detected (of 104 compounds searched) and the sum of their concentrations in the blood of 55 Montagu's harrier (Circus pygargus) nestlings from 22 nests sampled in 2021 were used as metrics of contamination levels. We investigated the effect of organic farming at the size of male's home range (i.e., 14 km2) and chicks' sex and hatching order on contamination levels. We did not find a difference between inter-brood and intra-brood variability in pesticide contamination levels, suggesting a different exposure of siblings through food items. While chicks' sex or rank did not affect their contamination level, we found that the percentage of organic farming around the nests significantly decreased the number of pesticides detected, although it did not decrease the total concentrations. This finding highlights the potential role of organic farming in reducing the exposure of birds to a pesticide cocktail.

How do life history and behaviour influence plastic ingestion risk in Canadian freshwater and terrestrial birds?

Plastic ingestion presents many potential avenues of risk for wildlife. Understanding which species and environments are most exposed to plastic pollution is a critical first step in investigating the One Health implications of plastic exposure. The objectives of this study were the following: 1) Utilize necropsy as part of ongoing passive disease surveillance to investigate ingested mesoplastics in birds collected in Ontario and Nunavut, and examine the relationships between bird-level factors and ingested debris; 2) evaluate microplastic ingestion compared to ingested mesodebris in raptors; and 3) identify potential sentinel species for plastic pollution monitoring in understudied freshwater and terrestrial (inland) environments. Between 2020 and 2022, 457 free-ranging birds across 52 species were received for postmortem examination. The upper gastrointestinal tracts were examined for mesoplastics and other debris (>2 mm) using standard techniques. Twenty-four individuals (5.3%) retained mesodebris and prevalence varied across species, with foraging technique, food type, and foraging substrate all associated with different metrics of debris ingestion. The odds of ingesting any type of anthropogenic mesodebris was nine times higher for non-raptorial species than for raptors. For a subset of raptors (N = 54) across 14 species, the terminal portion of the distal intestinal tract was digested with potassium hydroxide and microparticles were assessed using stereo-microscopy. Although only one of 54 (1.9%) raptors included in both analyses retained mesodebris in the upper gastrointestinal tract, 24 (44.4%) contained microparticles in the distal intestine. This study demonstrates that a variety of Canadian bird species ingest anthropogenic debris in inland systems, and suggests that life history and behaviour are associated with ingestion risk. For raptors, the mechanisms governing exposure and ingestion of mesoplastics appear to be different than those that govern microplastics. Herring gulls (Larus argentatus) and ring-billed gulls (Larus delawarensis) are proposed as ideal sentinels for plastic pollution monitoring in inland systems.

Ataxin-2 sequesters Raptor into aggregates and impairs cellular mTORC1 signaling

Ataxin-2 (Atx2) is a polyglutamine (polyQ) protein, in which abnormal expansion of the polyQ tract can trigger protein aggregation and consequently cause spinocerebellar ataxia type 2 (SCA2), but the mechanism underlying how Atx2 aggregation leads to proteinopathy remains elusive. Here, we investigate the molecular mechanism and cellular consequences of Atx2 aggregation by molecular cell biology approaches. We have revealed that either normal or polyQ-expanded Atx2 can sequester Raptor, a component of mammalian target of rapamycin complex 1 (mTORC1), into aggregates based on their specific interaction. Further research indicates that the polyQ tract and the N-terminal region (residues 1-784) of Atx2 are responsible for the specific sequestration. Moreover, this sequestration leads to suppression of the mTORC1 activity as represented by down-regulation of phosphorylated P70S6K, which can be reversed by overexpression of Raptor. As mTORC1 is a key regulator of autophagy, Atx2 aggregation and sequestration also induces autophagy by upregulating LC3-II and reducing phosphorylated ULK1 levels. This study proposes that Atx2 sequesters Raptor into aggregates, thereby impairing cellular mTORC1 signaling and inducing autophagy, and will be beneficial for a better understanding of the pathogenesis of SCA2 and other polyQ diseases.

mTOR Regulates Mineralocorticoid Receptor Transcriptional Activity by ULK1-Dependent and -Independent Mechanisms

The mineralocorticoid receptor (MR) is a transcription factor for genes mediating diverse, cell-specific functions, including trophic effects as well as promoting fluid/electrolyte homeostasis. It was reported that in intercalated cells, phosphorylation of the MR at serine 843 (S843) by Unc-51-like kinase (ULK1) inhibits MR activation and that phosphorylation of ULK1 by mechanistic target of rapamycin (mTOR) inactivates ULK1, and thereby prevents MR inactivation. We extended these findings with studies in M1 mouse cortical collecting duct cells stably expressing the rat MR and a reporter gene. Pharmacological inhibition of ULK1 dose-dependently increased ligand-induced MR transactivation, while ULK1 activation had no effect. Pharmacological inhibition of mTOR and CRISPR/gRNA gene knockdown of rapamycin-sensitive adapter protein of mTOR (Raptor) or rapamycin-insensitive companion of mTOR (Rictor) decreased phosphorylated ULK1 and ligand-induced activation of the MR reporter gene, as well as transcription of endogenous MR-target genes. As predicted, ULK1 inhibition had no effect on aldosterone-mediated transcription in M1 cells with the mutated MR-S843A (alanine cannot be phosphorylated). In contrast, mTOR inhibition dose-dependently decreased transcription in the MR-S843A cells, though not as completely as in cells with the wild-type MR-S843. mTOR, Raptor, and Rictor coprecipitated with the MR and addition of aldosterone increased their phosphorylated, active state. These results suggest that mTOR significantly regulates MR activity in at least 2 ways: by suppressing MR inactivation by ULK1, and by a yet ill-defined mechanism that involves direct association with MR. They also provide new insights into the diverse functions of ULK1 and mTOR, 2 key enzymes that monitor the cell's energy status.

Large-scale genotypic identification reveals density-dependent natal dispersal patterns in an elusive bird of prey

BACKGROUND

Natal dispersal, the distance between site of birth and site of first breeding, has a fundamental role in population dynamics and species' responses to environmental changes. Population density is considered a key driver of natal dispersal. However, few studies have been able to examine densities at both the natal and the settlement site, which is critical for understanding the role of density in dispersal. Additionally, the role of density on natal dispersal remains poorly understood in long-lived and slowly reproducing species, due to their prolonged dispersal periods and often elusive nature. We studied the natal dispersal of the white-tailed eagle (Haliaeetus albicilla) in response to local breeder densities. We investigated the effects of the number of active territories around the natal site on (a) natal dispersal distance and (b) the difference between natal and settlement site breeder density. We were interested in whether eagles showed tendencies of conspecific attraction (positive density-dependence) or intraspecific competition (negative density-dependence) and how this related to settlement site breeder density.

METHODS

We used a combination of long-term visual and genotypic identification to match individuals from their breeding site to their natal nest. We identified natal dispersal events for 355 individuals hatched between 1984 and 2015 in the Baltic Sea coast and Arctic areas of Finland. Of those, 251 were identified by their genotype.

RESULTS

Individuals born in high-density areas dispersed shorter distances than those born in low-density areas, but settled at lower density breeding sites in comparison to their natal site. Eagles born in low natal area densities dispersed farther but settled in higher density breeding sites compared to their natal site.

CONCLUSIONS

We show that eagles might be attracted by conspecifics (positive density-dependence) to identify high-quality habitats or find mates, but do not settle in the most densely populated areas. This indicates that natal dispersal is affected by an interplay of conspecific attraction and intraspecific competition, which has implications for population dynamics of white-tailed eagles, but also other top predators. Furthermore, our study demonstrates the value of long-term collection of both nestling and (non-invasive) adult DNA samples, and thereafter using genotype matching to identify individuals in long-lived and elusive species.

A case of suspected chimpanzee scavenging in the Issa Valley, Tanzania

Like humans, chimpanzees (Pan troglodytes) are well known for their vertebrate and invertebrate hunting, but they rarely scavenge. In contrast, while hunting and meat consumption became increasingly important during the evolution of the genus Homo, scavenging meat and marrow from carcasses of large mammals was also likely to be an important component of their subsistence strategies. Here, we describe a confrontational scavenging interaction between an adult male chimpanzee from the Issa Valley and a crowned eagle (Stephanoaetus coronatus), which resulted in the chimpanzee capturing and consuming the carcass of a juvenile bushbuck (Tragelaphus scriptus). We describe the interaction and contextualize this with previous scavenging observations from chimpanzees.

FARSB Facilitates Hepatocellular Carcinoma Progression by Activating the mTORC1 Signaling Pathway

Hepatocellular carcinoma (HCC) is a common malignant tumor with high mortality. Human phenylalanine tRNA synthetase (PheRS) comprises two α catalytic subunits encoded by the FARSA gene and two β regulatory subunits encoded by the FARSB gene. FARSB is a potential oncogene, but no experimental data show the relationship between FARSB and HCC progression. We found that the high expression of FARSB in liver cancer is closely related to patients' low survival and poor prognosis. In liver cancer cells, the mRNA and protein expression levels of FARSB are increased and promote cell proliferation and migration. Mechanistically, FARSB activates the mTOR complex 1 (mTORC1) signaling pathway by binding to the component Raptor of the mTORC1 complex to play a role in promoting cancer. In addition, we found that FARSB can inhibit erastin-induced ferroptosis by regulating the mTOR signaling pathway, which may be another mechanism by which FARSB promotes HCC progression. In summary, FARSB promotes HCC progression and is associated with the poor prognosis of patients. FARSB is expected to be a biomarker for early screening and treatment of HCC.

Mechanism of the Mitogen-Activated Protein Kinases/Mammalian Target of Rapamycin Pathway in the Process of Cartilage Endplate Stem Cell Degeneration Induced by Tension Load

STUDY DESIGN

Basic Research.

OBJECTIVE

Intervertebral disc degeneration (IVDD) is caused by the cartilage endplate (CEP). Cartilage endplate stem cell (CESC) is involved in the recovery of CEP degeneration. Tension load (TL) contributes a lot to the initiation and progression of IVDD. This study aims to investigate the regulatory mechanism of the Mitogen-activated protein kinases/Mammalian target of rapamycin (MAPK/mTOR) pathway during TL-induced CESC degeneration.

METHODS

CESCs were isolated from New Zealand big-eared white female rabbits (6 months old). FX-4000T cell stress loading system was applied to establish a TL-induced degeneration model of CESCs. Western blotting was used to detect the level of mTOR pathway-related proteins and autophagy markers LC3-Ⅱ, Beclin-1, and p62 in degenerative CESCs. The expression of MAPK pathway-related proteins JNK and extracellular signal-regulated kinases (ERK) in degenerated CESCs was inhibited by cell transfection to explore whether JNK and ERK play a regulatory role in TL-induced autophagy in CESCs.

RESULTS

In the CESC degeneration model, the mTOR pathway was activated. After inhibition of mTOR, the autophagy level of CESCs was increased, and the degeneration of CESCs was alleviated. The MAPK pathway was also activated in the CESC degeneration model. Inhibition of JNK expression may alleviate TL-induced CEP degeneration by inhibiting Raptor phosphorylation and activating autophagy. Inhibition of ERK expression may alleviate TL-induced CEP degeneration by inhibiting mTOR phosphorylation and activating autophagy.

CONCLUSION

Inhibition of JNK and ERK in the MAPK signaling family alleviated TL-induced CESC degeneration by inhibiting the phosphorylation of Raptor and mTOR in the mTOR pathway.

Raptor mediates the selective inhibitory effect of cardamonin on RRAGC-mutant B cell lymphoma

BACKGROUND

mTORC1 (mechanistic target of rapamycin complex 1) is associated with lymphoma progression. Oncogenic RRAGC (Rag guanosine triphosphatase C) mutations identified in patients with follicular lymphoma facilitate the interaction between Raptor (regulatory protein associated with mTOR) and Rag GTPase. It promotes the activation of mTORC1 and accelerates lymphomagenesis. Cardamonin inhibits mTORC1 by decreasing the protein level of Raptor. In the present study, we investigated the inhibitory effect and possible mechanism of action of cardamonin in RRAGC-mutant lymphoma. This could provide a precise targeted therapy for lymphoma with RRAGC mutations.

METHODS

Cell viability was measured using a cell counting kit-8 (CCK-8) assay. Protein expression and phosphorylation levels were determined using western blotting. The interactions of mTOR and Raptor with RagC were determined by co-immunoprecipitation. Cells overexpressing RagC wild-type (RagCWT) and RagC Thr90Asn (RagCT90N) were generated by lentiviral infection. Raptor knockdown was performed by lentivirus-mediated shRNA transduction. The in vivo anti-tumour effect of cardamonin was assessed in a xenograft model.

RESULTS

Cardamonin disrupted mTOR complex interactions by decreasing Raptor protein levels. RagCT90N overexpression via lentiviral infection increased cell proliferation and mTORC1 activation. The viability and tumour growth rate of RagCT90N-mutant cells were more sensitive to cardamonin treatment than those of normal and RagCWT cells. Cardamonin also exhibited a stronger inhibitory effect on the phosphorylation of mTOR and p70 S6 kinase 1 in RagCT90N-mutant cells. Raptor knockdown abolishes the inhibitory effects of cardamonin on mTOR. An in vivo xenograft model demonstrated that the RagCT90N-mutant showed significantly higher sensitivity to cardamonin treatment.

CONCLUSIONS

Cardamonin exerts selective therapeutic effects on RagCT90N-mutant cells. Cardamonin can serve as a drug for individualised therapy for follicular lymphoma with RRAGC mutations.

Raptor levels are critical for β-cell adaptation to a high-fat diet in male mice

OBJECTIVE

The essential role of raptor/mTORC1 signaling in β-cell survival and insulin processing has been recently demonstrated using raptor knock-out models. Our aim was to evaluate the role of mTORC1 function in adaptation of β-cells to insulin resistant state.

METHOD

Here, we use mice with heterozygous deletion of raptor in β-cells (βraHet) to assess whether reduced mTORC1 function is critical for β-cell function in normal conditions or during β-cell adaptation to high-fat diet (HFD).

RESULTS

Deletion of a raptor allele in β-cells showed no differences at the metabolic level, islets morphology, or β-cell function in mice fed regular chow. Surprisingly, deletion of only one allele of raptor increases apoptosis without altering proliferation rate and is sufficient to impair insulin secretion when fed a HFD. This is accompanied by reduced levels of critical β-cell genes like Ins1, MafA, Ucn3, Glut2, Glp1r, and specially PDX1 suggesting an improper β-cell adaptation to HFD.

CONCLUSION

This study identifies that raptor levels play a key role in maintaining PDX1 levels and β-cell function during the adaptation of β-cell to HFD. Finally, we identified that Raptor levels regulate PDX1 levels and β-cell function during β-cell adaptation to HFD by reduction of the mTORC1-mediated negative feedback and activation of the AKT/FOXA2/PDX1 axis. We suggest that Raptor levels are critical to maintaining PDX1 levels and β-cell function in conditions of insulin resistance in male mice.

Use of marine debris as nest material by ospreys

The use of anthropogenic debris as nest-building materials may affect nest function. We study ospreys (Pandion haliaetus) on an island with scarce vegetation and high availability of beached marine debris. We describe the anthropogenic debris in osprey nests, evaluate the factors affecting its prevalence and abundance, and test its potential effects on breeding parameters. We also quantify plastic entanglements among adults and nestlings. Of the 36 studied nests, 92 % included non-natural items, with plastic being the most frequent material (88.9 %). Nests that were bigger and closer to the coast had more anthropogenic items. The abundance of anthropogenic items in nests did not correlate with osprey breeding parameters. We recorded two live entangled adult females, which represent 3.9 % of the adult population. Monitoring the abundance of anthropogenic debris and its effects on wildlife is necessary to guarantee long-term viability of coastal wildlife.

O-GlcNAcylation of Raptor transduces glucose signals to mTORC1

The mechanistic target of rapamycin complex 1 (mTORC1) regulates metabolism and cell growth in response to nutrient levels. Dysregulation of mTORC1 results in a broad spectrum of diseases. Glucose is the primary energy supply of cells, and therefore, glucose levels must be accurately conveyed to mTORC1 through highly responsive signaling mechanisms to control mTORC1 activity. Here, we report that glucose-induced mTORC1 activation is regulated by O-GlcNAcylation of Raptor, a core component of mTORC1, in HEK293T cells. Mechanistically, O-GlcNAcylation of Raptor at threonine 700 facilitates the interactions between Raptor and Rag GTPases and promotes the translocation of mTOR to the lysosomal surface, consequently activating mTORC1. In addition, we show that AMPK-mediated phosphorylation of Raptor suppresses Raptor O-GlcNAcylation and inhibits Raptor-Rags interactions. Our findings reveal an exquisitely controlled mechanism, which suggests how glucose coordinately regulates cellular anabolism and catabolism.

Disruption of neuronal RHEB signaling impairs oligodendrocyte differentiation and myelination through mTORC1-DLK1 axis

How neuronal signaling affects brain myelination remains poorly understood. We show dysregulated neuronal RHEB-mTORC1-DLK1 axis impairs brain myelination. Neuronal Rheb cKO impairs oligodendrocyte differentiation/myelination, with activated neuronal expression of the imprinted gene Dlk1. Neuronal Dlk1 cKO ameliorates myelination deficit in neuronal Rheb cKO mice, indicating that activated neuronal Dlk1 expression contributes to impaired myelination caused by Rheb cKO. The effect of Rheb cKO on Dlk1 expression is mediated by mTORC1; neuronal mTor cKO and Raptor cKO and pharmacological inhibition of mTORC1 recapitulate elevated neuronal Dlk1 expression. We demonstrate that both a secreted form of DLK1 and a membrane-bound DLK1 inhibit the differentiation of cultured oligodendrocyte precursor cells into oligodendrocytes expressing myelin proteins. Finally, neuronal expression of Dlk1 in transgenic mice reduces the formation of mature oligodendrocytes and myelination. This study identifies Dlk1 as an inhibitor of oligodendrocyte myelination and a mechanism linking altered neuronal signaling with oligodendrocyte dysfunction.

Regulation of mTOR Signaling: Emerging Role of Cyclic Nucleotide-Dependent Protein Kinases and Implications for Cardiometabolic Disease

The mechanistic target of rapamycin (mTOR) kinase is a central regulator of cell growth and metabolism. It is the catalytic subunit of two distinct large protein complexes, mTOR complex 1 (mTORC1) and mTORC2. mTOR activity is subjected to tight regulation in response to external nutrition and growth factor stimulation. As an important mechanism of signaling transduction, the 'second messenger' cyclic nucleotides including cAMP and cGMP and their associated cyclic nucleotide-dependent kinases, including protein kinase A (PKA) and protein kinase G (PKG), play essential roles in mediating the intracellular action of a variety of hormones and neurotransmitters. They have also emerged as important regulators of mTOR signaling in various physiological and disease conditions. However, the mechanism by which cAMP and cGMP regulate mTOR activity is not completely understood. In this review, we will summarize the earlier work establishing the ability of cAMP to dampen mTORC1 activation in response to insulin and growth factors and then discuss our recent findings demonstrating the regulation of mTOR signaling by the PKA- and PKG-dependent signaling pathways. This signaling framework represents a new non-canonical regulation of mTOR activity that is independent of AKT and could be a novel mechanism underpinning the action of a variety of G protein-coupled receptors that are linked to the mTOR signaling network. We will further review the implications of these signaling events in the context of cardiometabolic disease, such as obesity, non-alcoholic fatty liver disease, and cardiac remodeling. The metabolic and cardiac phenotypes of mouse models with targeted deletion of Raptor and Rictor, the two essential components for mTORC1 and mTORC2, will be summarized and discussed.

Inactivation of Minar2 in mice hyperactivates mTOR signaling and results in obesity

OBJECTIVE

Obesity is a complex disorder and is linked to chronic diseases such as type 2 diabetes. Major intrinsically disordered NOTCH2-associated receptor2 (MINAR2) is an understudied protein with an unknown role in obesity and metabolism. The purpose of this study was to determine the impact of Minar2 on adipose tissues and obesity.

METHOD

We generated Minar2 knockout (KO) mice and used various molecular, proteomic, biochemical, histopathology, and cell culture studies to determine the pathophysiological role of Minar2 in adipocytes.

RESULTS

We demonstrated that the inactivation of Minar2 results in increased body fat with hypertrophic adipocytes. Minar2 KO mice on a high-fat diet develop obesity and impaired glucose tolerance and metabolism. Mechanistically, Minar2 interacts with Raptor, a specific and essential component of mammalian TOR complex 1 (mTORC1) and inhibits mTOR activation. mTOR is hyperactivated in the adipocytes deficient for Minar2 and over-expression of Minar2 in HEK-293 cells inhibited mTOR activation and phosphorylation of mTORC1 substrates, including S6 kinase, and 4E-BP1.

CONCLUSION

Our findings identified Minar2 as a novel physiological negative regulator of mTORC1 with a key role in obesity and metabolic disorders. Impaired expression or activation of MINAR2 could lead to obesity and obesity-associated diseases.

Raptor couples mTORC1 and ERK1/2 inhibition by cardamonin with oxidative stress induction in ovarian cancer cells

Background

A balance on nutrient supply and redox homeostasis is required for cell survival, and increased antioxidant capacity of cancer cells may lead to chemotherapy failure.

Objective

To investigate the mechanism of anti-proliferation of cardamonin by inducing oxidative stress in ovarian cancer cells.

Methods

After 24 h of drug treatment, CCK8 kit and wound healing test were used to detect cell viability and migration ability, respectively, and the ROS levels were detected by flow cytometry. The differential protein expression after cardamonin administration was analyzed by proteomics, and the protein level was detected by Western blotting.

Results

Cardamonin inhibited the cell growth, which was related to ROS accumulation. Proteomic analysis suggested that MAPK pathway might be involved in cardamonin-induced oxidative stress. Western blotting showed that cardamonin decreased Raptor expression and the activity of mTORC1 and ERK1/2. Same results were observed in Raptor KO cells. Notably, in Raptor KO cells, the effect of cardamonin was weakened.

Conclusion

Raptor mediated the function of cardamonin on cellular redox homeostasis and cell proliferation through mTORC1 and ERK1/2 pathways.

The role of Raptor in lymphocytes differentiation and function

Raptor, a key component of mTORC1, is required for recruiting substrates to mTORC1 and contributing to its subcellular localization. Raptor has a highly conserved N-terminus domain and seven WD40 repeats, which interact with mTOR and other mTORC1-related proteins. mTORC1 participates in various cellular events and mediates differentiation and metabolism. Directly or indirectly, many factors mediate the differentiation and function of lymphocytes that is essential for immunity. In this review, we summarize the role of Raptor in lymphocytes differentiation and function, whereby Raptor mediates the secretion of cytokines to induce early lymphocyte metabolism, development, proliferation and migration. Additionally, Raptor regulates the function of lymphocytes by regulating their steady-state maintenance and activation.

The seasonal threat of lead exposure in bald eagles

Bald eagles often scavenge hunting remains embedded with lead bullet fragments, which debilitate and kill many eagles. Measuring blood lead concentrations (BLC) in free-flying bald eagles and those received by rehabilitators allows researchers to both actively and opportunistically monitor exposure. From 2012 to 2022, we captured 62 free-flying bald eagles and measured their BLC following the big-game hunting season in Montana, USA, which occurs from late October through late November. Between 2011 and 2022, we also measured the BLC of 165 bald eagles received by Montana's four raptor rehabilitation centers. Most of the free-flying bald eagles (89 %) had BLC above background (≥10 μg/dL), and BLC of juveniles tended to be lower as winter progressed (ρ = -0.482, P = 0.017). Bald eagles received by rehabilitators had an almost identical prevalence of BLC above background (90 %) over that same timeframe (n = 48). However, those eagles in rehabilitation were more likely to have BLC exceeding the clinical threshold (≥ 60 μg/dL), which we observed only from November through May. Between June and October, 45 % of bald eagles in rehabilitation had sub-clinical BLC (10-59 μg/dL), suggesting that many eagles may live with BLC chronically above background concentrations. Hunters may help lower BLC in bald eagles by switching to lead-free bullets. Those mitigation efforts could be evaluated through a continued monitoring of BLC in both free-flying bald eagles and those received by rehabilitators.

Dysregulation of the mTOR pathway by mechlorethamine

Mechlorethamine (HN2) is a derivative of the chemical warfare agent sulfur mustard (SM) and cutaneous exposure to HN2 is associated with dermal-epidermal junction (DEJ) disruption (vesication). The primary purpose of the present study was to investigate the effect of HN2 on the mammalian target of rapamycin (mTOR) signaling pathway using an in vivo mouse ear vesicant model (MEVM). To this end, the ears of male C57BL/ 6 J mice were exposed to a single topical dose of HN2 (100 mM) or vehicle control (DMSO). Mice were then euthanized 30 min, 1 h or 24 h following exposure. Mouse ear skin exposed to HN2 and biopsied 24 h thereafter exhibited increased tissue expression of Raptor, an important member of the mTORC1 complex, relative to vehicle treated samples. HN2 reduced the downstream effectors phospho S6 (Ser 240/244) ribosomal protein and phospho 4E-BP1 (Thr 37/46) of the mTOR pathway in the epidermis at 30 min, 1 h and 24 h following HN2 exposure but not in the dermis. These results support the hypothesis that HN2-mediated cutaneous toxicity involves dysregulation of the mTOR signaling pathway in the epidermis.

Effects of the environmental conditions and seasonality on a population survey of the Andean condor Vultur gryphus in the tropical Andes

Background

Among the New World vultures, the Andean condor is considered one of the most culturally and ecologically important species. However, their populations are declining over their entire distributional range. In response, conservation strategies have been implemented in many countries to reverse the increasing extinction risk of this species. The initiatives rely on extensive population surveys to gather basic information necessary to implement policies and to intervene efficiently. Still, there is a need to standardize the surveys based on seasonality and suitable environmental conditions throughout the species distribution. Here, we provide the first assessment of how daily temperature, rainfall, and seasonality influence surveys of Andean condors on a communal roost in the central Peruvian Andes.

Methods

Using an autoregressive generalized linear model, we associated environmental variables with visual surveys of adult and young condors at three different times of the day and three times a week between June 2014 and March 2015.

Results

We found that both adults and young Andean condors showed a threefold reduction in the use of the communal roost after the beginning of the rainy season. Colder and drier days (dry season) are preferable for surveying, as we expect the total number of condors using communal roosts to reduce under rainy (rainfall = -0.53 ± 0.16) and warmer days (temperature = -0.04 ± 0.02) days. Therefore, the significant variation in the use of roosts across seasons and hours should be carefully accounted for in national surveys, at the risk of undermining the full potential of the communal roost surveys. Moreover, we also found a strong bias towards immatures (about 76%) in the adult:immature ratio and a remarkable absence of Andean condors during the wet season. These results suggest that the species might be using other unknown communal roosts hierarchically. Such results provide key information for selecting priority areas for conservation and selecting the best time to survey this species in the tropical Andes. Finally, it may open a fruitful avenue for further research on the protection of the Andean condor.

Blood parasites (Trypanosoma, Leucocytozoon, Haemoproteus) in the Eurasian sparrowhawk (Accipiter nisus): diversity, incidence and persistence of infection at the individual level

BACKGROUND

A high prevalence of parasites may result from life-long persistence of infection or from high reinfection rates. We have studied blood parasites in a breeding population of the accipitrid raptor, Eurasian sparrowhawk (Accipiter nisus), to determine parasite diversity and turnover.

METHODS

During this 7-year study, 210 adult Eurasian sparrowhawks breeding in the city of Prague were checked for parasites using several diagnostic methods.

RESULTS

In both female and male raptors, parasites of the genus Leucocytozoon were the most prevalent (92% and 85%, respectively) followed in decreasing order of prevalence by those of genus Trypanosoma (74% and 68%, respectively) and genus Haemoproteus (46% and 16%, respectively). The prevalence of all parasites increased with age in both sexes, with the females at each respective age having the higher prevalence. There was a positive association between Haemoproteus and Leucocytozoon infections. Persistence at the individual level was higher than incidence for Trypanosoma and Haemoproteus. In the case of Leucocytozoon and Trypanosoma, most individuals probably become infected in their first year of life or even before dispersal from the nest. The detected parasites belonged to Trypanosoma avium sensu stricto, Leucocytozoon sp. (haplotypes ACNI1 and ACNI3) and Leucocytozoon mathisi (haplotype ACNI4) and two new lineages of the Haemoproteus elani complex (ACCNIS6 and ACCNIS7). Detailed analysis of parasite lineages in individuals that were repeatedly sampled revealed lineage turnover that would otherwise remain hidden. Phylogenetic analysis revealed that the detected Haemoproteus belongs to a phylogenetically distant group whose taxonomic position requires further analysis.

CONCLUSIONS

All three genera of blood parasites persist in infected individuals, thus enabling sustainability of vector transmission cycles. Prevalence increases with age; however, there is a high turnover of Leucocytozoon lineages. No clear evidence of parasite-induced mortality was found, and most of the individuals were infected early in life, particularly in the case of Leucocytozoon.

Temporal trends in PFAS concentrations in livers of a terrestrial raptor (common buzzard; Buteo buteo) collected in Belgium during the period 2000-2005 and in 2021

Per- and polyfluoroalkyl substances (PFAS) are anthropogenic chemicals that have been globally distributed. Biological time series data suggest variation in temporal PFAS concentrations due to regulations and the phase-out of multiple PFAS analytes. Nonetheless, biomonitoring temporal trends of PFAS concentrations in raptors has only been done sporadically in Europe at a national scale. In the present study, we examined the concentrations of 28 PFAS in livers of common buzzard (Buteo buteo) collected in Belgium in the period 2000-2005 and in 2021. Despite the regulations and phase-out, the ΣPFAS concentrations remained similar in the livers over the past 20 years. However, over time the abundance of perfluorooctane sulfonate (PFOS), dominant in livers collected in 2000-2005, to the ΣPFAS concentration decreased from 46% to 27%, whereas the abundance of perfluorotetradecanoic acid (PFTeDA), dominant in 2021, increased from 19% to 43%. The PFOS concentrations in the present study did not exceed the Toxicity Reference Values (TRVs), which were determined in liver on the characteristics of an avian top predator. The absence of temporal changes in PFAS concentrations is hypothesized to be due to a lagged response in environmental concentrations compared to atmospheric concentrations.

Phosphorylation of the novel mTOR substrate Unkempt regulates cellular morphogenesis

Mechanistic target of rapamycin (mTOR) is a protein kinase that integrates multiple inputs to regulate anabolic cellular processes. For example, mTOR complex 1 (mTORC1) has key functions in growth control, autophagy, and metabolism. However, much less is known about the signaling components that act downstream of mTORC1 to regulate cellular morphogenesis. Here, we show that the RNA-binding protein Unkempt, a key regulator of cellular morphogenesis, is a novel substrate of mTORC1. We show that Unkempt phosphorylation is regulated by nutrient levels and growth factors via mTORC1. To analyze Unkempt phosphorylation, we immunoprecipitated Unkempt from cells in the presence or the absence of the mTORC1 inhibitor rapamycin and used mass spectrometry to identify mTORC1-dependent phosphorylated residues. This analysis showed that mTORC1-dependent phosphorylation is concentrated in a serine-rich intrinsically disordered region in the C-terminal half of Unkempt. We also found that Unkempt physically interacts with and is directly phosphorylated by mTORC1 through binding to the regulatory-associated protein of mTOR, Raptor. Furthermore, analysis in the developing brain of mice lacking TSC1 expression showed that phosphorylation of Unkempt is mTORC1 dependent in vivo. Finally, mutation analysis of key serine/threonine residues in the serine-rich region indicates that phosphorylation inhibits the ability of Unkempt to induce a bipolar morphology. Phosphorylation within this serine-rich region thus profoundly affects the ability of Unkempt to regulate cellular morphogenesis. Taken together, our findings reveal a novel molecular link between mTORC1 signaling and cellular morphogenesis.

A review of raptor carcass persistence trials and the practical implications for fatality estimation at wind farms

Bird and bat turbine collision fatalities are a principal biodiversity impact at wind energy facilities. Raptors are a group at particular risk and often the focus of post-construction fatality monitoring programs. To estimate fatalities from detected carcasses requires correction for biases, including for carcasses that are removed or decompose before the following search. This is addressed through persistence trials, where carcasses are monitored until no longer detectable or the trial ends. Sourcing sufficient raptor carcasses for trials is challenging and surrogates that are typically used often have shorter persistence times than raptors. We collated information from raptor carcass persistence trials to evaluate consistencies between trials and assess the implications of using persistence values from other studies in wind facility fatality estimates. We compiled individual raptor carcass persistence times from published sources along with information on methods and location, estimated carcass persistence using GenEst and ran full fatality estimates using the carcass persistence estimates and mock datasets for other information. We compiled results from 22 trials from 17 sites across four terrestrial biomes, with trials lasting between 7 and 365 days and involving between 11 and 115 carcasses. Median carcass persistence was estimated at 420 days (90% confidence interval (CI) of 290 to 607 days) for the full dataset. Persistence time varied significantly between trials (trial-specific persistence estimates of 14 (5-42) days to 1,586 (816-3,084) days) but not between terrestrial biomes. We also found no significant relationship between either the number of carcasses in the trial or trial duration and estimated carcass persistence. Using a mock dataset with 12 observed fatalities, we estimated annual fatalities of 25 (16-33) or 26 (17-36) individuals using a 14- or 28-day search interval respectively using global dataset. When using trial-specific carcass persistence estimates and the same mock dataset, estimated annual fatalities ranged from 22 (14-30) to 37 (21-63) individuals for a 14-day search interval, and from 22 (15-31) to 47 (26-84) individuals for a 28-day search interval. The different raptor carcass persistence rates between trials translated to small effects on fatality estimates when using recommended search frequencies, since persistence rates were generally much longer than the search interval. When threatened raptor species, or raptors of particular concern to stakeholders are present, and no site-specific carcass persistence estimates are available, projects should use the lowest median carcass persistence estimate from this study to provide precautionary estimates of fatalities. At sites without threatened species, or where the risk of collision to raptors is low, the global median carcass persistence estimate from this review could be used to provide a plausible estimate for annual raptor fatalities.

Mammalian Target of Rapamycin Inhibition Decreases Angiotensin II-Induced Steroidogenesis in HAC15 Human Adrenocortical Carcinoma Cells

BACKGROUND

Mammalian target of rapamycin (mTOR) inhibitors suppress adrenal cortical carcinoma cell proliferation and cortisol production; the relationship between mTOR and aldosterone production has not been examined.

METHODS

HAC15 cells were incubated with an mTOR activator and several inhibitors including AZD8055 (AZD) in the presence and absence of angiotensin II (AngII). The expression of rapamycin-sensitive adapter protein of mTOR (Raptor) and rapamycin-insensitive companion of mTOR (Rictor), adaptor proteins of mTOR complex 1 and 2, respectively, were studied in the HAC15 cells and deleted by CRISPR/gRNA.

RESULTS

The mTOR inhibitors decreased aldosterone induced by AngII. Inhibition of mTOR by AZD significantly suppressed AngII-induced aldosterone and cortisol formation in a dose-dependent manner, whereas the mTOR activator MHY had no effect. AZD did not alter forskolin-induced aldosterone production showing that it is specific to the AngII signaling pathway. AngII-mediated ERK and mTOR activation were suppressed by AZD, along with a concomitant dose-dependent reduction of AngII-induced steroidogenic enzymes including steroidogenic acute regulatory protein, 3β-hydroxysteroid dehydrogenase-type 2, CYP17A1, and aldosterone synthase protein. Furthermore, mTOR components ribosomal protein S6 kinase (P70S6K) and protein kinase B phosphorylation levels were decreased by AZD. As mTOR exerts its main effects by forming complexes with adaptor proteins Raptor and Rictor, the roles of these individual complexes were studied. We found an increase in the phosphorylation of Raptor and Rictor by AngII and that their CRISPR/gRNA-mediated knockdown significantly attenuated AngII-induced aldosterone and cortisol production.

CONCLUSION

mTOR signaling has a critical role in transducing the AngII signal initiating aldosterone and cortisol synthesis in HAC15 cells and that inhibition of mTOR could be a therapeutic option for conditions associated with excessive renin-angiotensin system-mediated steroid synthesis.

Disruption of mTORC1 rescues neuronal overgrowth and synapse function dysregulated by Pten loss

Phosphatase and tensin homolog deleted on chromosome 10 (PTEN) is a negative regulator of AKT/mTOR signaling pathway. Mutations in PTEN are found in patients with autism, epilepsy, or macrocephaly. In mouse models, Pten loss results in neuronal hypertrophy, hyperexcitability, seizures, and ASD-like behaviors. The underlying molecular mechanisms of these phenotypes are not well delineated. We determined which of the Pten loss-driven aberrations in neuronal form and function are orchestrated by downstream mTOR complex 1 (mTORC1). Rapamycin-mediated inhibition of mTORC1 prevented increase in soma size, migration, spine density, and dendritic overgrowth in Pten knockout dentate gyrus granule neurons. Genetic knockout of Raptor to disrupt mTORC1 complex formation blocked Pten loss-mediated neuronal hypertrophy. Electrophysiological recordings revealed that genetic disruption of mTORC1 rescued Pten loss-mediated increase in excitatory synaptic transmission. We have identified an essential role for mTORC1 in orchestrating Pten loss-driven neuronal hypertrophy and synapse formation.

Stimulation of protein synthesis by optogenetic and chemical induction of excitatory synaptic plasticity in hippocampal somatostatin interneurons

Somatostatin-expressing interneurons (SOM-INs) are a major subpopulation of GABAergic cells in CA1 hippocampus that receive excitation from pyramidal cells (PCs) and provide feedback control of synaptic inputs onto PC dendrites. Excitatory synapses from PCs onto SOM-INs (PC-SOM synapses) exhibit long-term potentiation (LTP) mediated by type 1a metabotropic glutamate receptors (mGluR1a). LTP at PC-SOM synapses translates in lasting regulation of metaplasticity of entorhinal and CA3 synaptic inputs on PCs and contributes to hippocampus-dependent learning. A persistent form of PC-SOM synapse LTP lasting hours is prevented by blockers of transcription and translation, and a more transient form of PC-SOM synapse LTP lasting tens of minutes requires mTORC1-signaling, suggesting an involvement of protein synthesis. However, the role of protein synthesis in these forms of plasticity has not been directly demonstrated. Here we use the SUrface SEnsing of Translation (SUnSET) assay of protein synthesis to directly show that the induction protocols for both forms of LTP at PC-SOM synapses stimulate protein synthesis in SOM-INs. Moreover, protein synthesis stimulated by persistent LTP induction was prevented in mice with a SOM-IN conditional knock-out of Raptor, an essential component of mTORC1, indicating a critical role of mTORC1 in the control of translation in PC-SOM synapse plasticity. Moreover, protein synthesis induced by both forms of LTP may share common mechanisms as transient LTP induction occluded further stimulation of protein synthesis by persistent LTP induction. Our findings highlight a crucial role of protein synthesis and its control by mTORC1 in SOM-INs that is important for hippocampus-dependent memory function.

ZNF143 regulates autophagic flux to alleviate myocardial ischemia/reperfusion injury through Raptor

The exact role of autophagy in myocardial ischemia/reperfusion (I/R) injury is still controversial. Excessive or insufficient autophagy may lead to cell death. Therefore, how to regulate autophagic balance during myocardial ischemia/reperfusion is critical to the treatment of myocardial I/R injury. Raptor is an mTOR regulatory related protein and closely related to the induction of autophagy. ZNF143 is widely expressed in various cells and acts as a transcription factor, which is involved in the regulation of autophagy, cell growth and development. In this study, we aimed to explore the mechanism by which ZNF143 regulated autophagy in myocardial I/R injury and the relationship between ZNF143 and Raptor. In our results, we found that ZNF143 expression was down-regulated in myocardial I/R. Inhibition of ZNF143 expression further enhanced autophagy and restored the deficiency of autophagic flux caused by myocardial I/R, subsequently alleviating myocardial I/R injury. On the other hand, overexpression of ZNF143 up-regulated Raptor expression and reduced autophagic activity, consequently exacerbating myocardial I/R injury. Taken together, our study revealed that ZNF143 might be a key target of the regulation of autophagy and a novel therapeutic target of myocardial I/R injury.

Temporal Trends of Organochlorine and Perfluorinated Contaminants in a Terrestrial Raptor in Northern Europe Over 34 years (1986-2019)

Fourteen legacy organochlorine (OC) contaminants and 12 perfluoroalkyl substances (PFASs) were measured in eggs of tawny owls (Strix alueco) in central Norway (1986-2019). We expected OCs to have reached stable equilibrium levels due to bans, and that recent phase-out of some PFASs would have slowed the increase of these compounds. ∑OC comprised on average approximately 92% of the measured compounds, whereas ∑PFAS accounted for approximately 8%. However, whereas the ∑OC to ∑PFAS ratio was approximately 60 in the first 5 years of the study, it was only approximately 11 in the last 5 years. Both OC pesticides and polychlorinated biphenyls (PCBs) showed substantial declines over the study period (~85%-98%): hexachlorocyclohexanes and chlordanes seemed to be levelling off, whereas p,p'-dichlorodiphenyldichloroethylene (p,p'-DDE) and hexachlororbenzene (HCB), and most PCB congeners still seemed to decline at a more or less constant rate. While the concentration of perfluorooctane sulfonic acid (PFOS), the dominating PFAS, was reduced by approximately 43%, other perfluorinated sulfonates (PFSAs) showed only minor changes. Moreover, the median concentrations of seven perfluorinated carboxylic acids (PFCAs) increased approximately five-fold over the study period. Perfluorononanoic acid and perfluoroundecanoate acid, however, seemed to be levelling off in recent years. In contrast, perfluorododecanoic acid, perfluorodecanoate acid, perfluorotridecanoic acid, and perfluorotetradecanoic acid seemed to increase more or less linearily. Finally, perfluorooctanoic acid (PFOA) was increasingly likely to be detected over the study period. Hence, most legacy OCs and PFOS have not reached a lower threshold with stable background levels, and voluntary elimination of perfluoroalkyl carboxylates still has not resulted in declining levels in tawny owls in central Norway. Environ Toxicol Chem 2022;41:1508-1519. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Loss of Raptor induces Sertoli cells into an undifferentiated state in mice

In mammals, testis development is triggered by the expression of the sex-determining Y-chromosome gene SRY to commit the Sertoli cell (SC) fate at gonadal sex determination in the fetus. Several genes have been identified to be required to promote the testis pathway following SRY activation (i.e., SRY box 9 (SOX9)) in an embryo; however, it largely remains unknown about the genes and the mechanisms involved in stabilizing the testis pathway after birth and throughout adulthood. Herein, we report postnatal males with SC-specific deletion of Raptor demonstrated the absence of SC unique identity and adversely acquired granulosa cell-like characteristics, along with loss of tubular architecture and scattered distribution of SCs and germ cells. Subsequent genome-wide analysis by RNA sequencing revealed a profound decrease in the transcripts of testis genes (i.e., Sox9, Sox8, and anti-Mullerian hormone (Amh)) and, conversely, an increase in ovary genes (i.e., LIM/Homeobox gene 9 (Lhx9), Forkhead box L2 (Foxl2) and Follistatin (Fst)); these changes were further confirmed by immunofluorescence and quantitative reverse-transcription polymerase chain reaction. Importantly, co-immunofluorescence demonstrated that Raptor deficiency induced SCs dedifferentiation into a progenitor state; the Raptor-mutant gonads showed some ovarian somatic cell features, accompanied by enhanced female steroidogenesis and elevated estrogen levels, yet the zona pellucida 3 (ZP3)-positive terminally feminized oocytes were not observed. In vitro experiments with primary SCs suggested that Raptor is likely involved in the fibroblast growth factor 9 (FGF9)-induced formation of cell junctions among SCs. Our results established that Raptor is required to maintain SC identity, stabilize the male pathway, and promote testis development.

Telomere length in relation to persistent organic pollutant exposure in white-tailed eagle (Haliaeetus albicilla) nestlings from Sweden sampled in 1995-2013

Telomeres are used as biomarkers of vertebrate health because of the link between their length, lifespan, and survival. Exposure to environmental stressors appears to alter telomere dynamics, but little is known about telomere length and persistent organic pollutant (POP) exposure in wildlife. The white-tailed eagle (WTE; Haliaeetus albicilla) is an avian top predator that accumulates high levels of POPs and may subsequently suffer adverse health effects. Here we study the Baltic WTE population that is well documented to have been exposed to large contaminant burdens, thereby making it a promising candidate species for analyzing pollutant-mediated effects on telomeres. We investigated telomere lengths in WTE nestlings (n = 168) over 19 years and examined legacy POP concentrations (organochlorines and polybrominated diphenyl ethers) in whole blood and serum as potential drivers of differences in telomere length. Although we detected significant year-to-year variations in telomere lengths among the WTE nestlings, telomere lengths did not correlate with any of the investigated POP concentrations of several classes. Given that telomere lengths did not associate with POP contamination in the Baltic WTE nestlings, we propose that other environmental and biological factors, which likely fluctuate on a year-to-year basis, could be more important drivers of telomere lengths in this population.

Sarcocystis calchasi and other Sarcocystidae detected in predatory birds in California, USA

Outbreaks of neurological disease associated with Sarcocystis calchasi have been observed in captive and free-ranging rock pigeons (Columba livia) in Europe and the United States as well as in wild Brandt's cormorants (Phalacrocorax penicillatus) and captive psittacines in California, USA. Experimental and field studies have identified northern goshawks (Accipiter gentilis) and European sparrowhawks (A. nisus) as definitive hosts in Europe while the definitive hosts elsewhere remain unknown. In this study, we aimed to identify the potential definitive host(s) of S. calchasi through molecular analysis of intestinal samples from seven predatory (n = 85) and one omnivorous (n = 11) bird species in California. In total, apicomplexan-generic 28S rRNA PCR products were obtained and sequenced for 42 raptors. Three of 16 (18.8%) Cooper's hawks (A. cooperii) and two of 26 (5.6%) red-tailed hawks (Buteo jamaicensis) also tested positive for the S. calchasi-specific ITS1 PCR and sequencing of the 28S rRNA PCR product was 100% homologous to S. calchasi. In addition to S. calchasi (5.9%; 5/85), other Sarcocystis spp. detected in raptors included: S. jamaicensis (21.2%; 18/85), S. columbae (8.2%; 7/85), S. turdusi (7.1%; 6/85), and S. halieti (4.7; 4/85%). Infections with closely related S. jamaicensis and S. (Frenkelia) microti (9.4%; 8/85) could not be distinguished for eight raptors. Eumonospora henryae (1.2%; 1/85) was detected in one raptor. Our results indicate for the first time that S. calchasi may have a definitive host range in North America that includes at least two raptors, Cooper's hawks and red-tailed hawks, within the family Accipitridae.

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Cooper's hawks and red-tailed hawks likely definitive hosts for Sarcocystis calchasi.

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Raptors may be infected with a diversity of closely related Sarcocystis spp.

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More research needed to clarify life cycles for bird-infecting Sarcocystis spp.

A novel survey of raptor collections in Europe and their potential to provide samples for pan-European contaminant monitoring

This paper provides a novel survey of current collections of frozen raptor carcasses and tissue samples in natural history museums (NHMs), environmental specimen banks (ESBs) and other research collections (ORCs e.g. at universities and research institutes) across Europe and assesses the extent to which collections might support pan-European raptor biomonitoring through the provision of samples for contaminant analyses. The paper is based on questionnaire responses received in late 2018 and early 2019 from 116 institutions. Issues covered include the number of raptor carcasses and diversity of raptor species arriving annually at collections, the number of carcasses stored in freezers, the extent to which collections retain frozen tissue samples, what records are kept of carcasses and tissue samples, constraints to expanding collections of frozen carcasses and tissues and the extent to which collections currently engage in ecotoxicological research and monitoring. Our findings show that collections in Europe receive well over 5000 raptor carcasses per annum, and that NHMs are the key recipients of raptor carcasses for most countries. Collections in Europe probably hold well over 10,000 raptor carcasses in their freezers, offering a substantial resource of frozen raptor carcasses and tissues from recent years. Moreover, these carcasses include good specimen numbers for species that have been prioritized for pan-European contaminant monitoring. Collections are becoming digitized aiding access to samples. However, freezer capacity is a key constraint to retention of carcasses, and contaminant biomonitoring is novel for most NHMs. Our findings on the repository and availability of frozen raptor carcasses and tissues held by collections in Europe can enable greater use of these specimens for pan-European contaminant monitoring in support of better chemicals management. We highlight opportunities to further optimize raptor collections for pan-European contaminant monitoring.

Activation of Akt-mTORC1 signalling reverts cancer-dependent muscle wasting

BACKGROUND

Cancer-related muscle wasting occurs in most cancer patients. An important regulator of adult muscle mass and function is the Akt-mTORC1 pathway. While Akt-mTORC1 signalling is important for adult muscle homeostasis, it is also a major target of numerous cancer treatments. Which role Akt-mTORC1 signalling plays during cancer cachexia in muscle is currently not known. Here, we aimed to determine how activation or inactivation of the pathway affects skeletal muscle during cancer cachexia.

METHODS

We used inducible, muscle-specific Raptor ko (mTORC1) mice to determine the effect of reduced mTOR signalling during cancer cachexia. On the contrary, in order to understand if skeletal muscles maintain their anabolic capacity and if activation of Akt-mTORC1 signalling can reverse cancer cachexia, we generated mice in which we can inducibly activate Akt specifically in skeletal muscles.

RESULTS

We found that mTORC1 signalling is impaired during cancer cachexia, using the Lewis lung carcinoma and C26 colon cancer model, and is accompanied by a reduction in protein synthesis rates of 57% (P < 0.01). Further reduction of mTOR signalling, as seen in Raptor ko animals, leads to a 1.5-fold increase in autophagic flux (P > 0.001), but does not further increase muscle wasting. On the other hand, activation of Akt-mTORC1 signalling in already cachectic animals completely reverses the 15-20% loss in muscle mass and force (P < 0.001). Interestingly, Akt activation only in skeletal muscle completely normalizes the transcriptional deregulation observed in cachectic muscle, despite having no effect on tumour size or spleen mass. In addition to stimulating muscle growth, it is also sufficient to prevent the increase in protein degradation normally observed in muscles from tumour-bearing animals.

CONCLUSIONS

Here, we show that activation of Akt-mTORC1 signalling is sufficient to completely revert cancer-dependent muscle wasting. Intriguingly, these results show that skeletal muscle maintains its anabolic capacities also during cancer cachexia, possibly giving a rationale behind some of the beneficial effects observed in exercise in cancer patients.

Raptor Sedation and Anesthesia

Sedation and/or anesthesia is routinely and successfully used in raptors for a wide variety of procedures from the routine such as physical examination, radiographs, or venipuncture, to the more complex, such as orthopedic surgeries. Understanding the anatomy and physiology of raptor patients who present for care, and being fully prepared before the start of any procedure, can increase the success of anesthetic procedures. Recent advances in raptor sedation and anesthesia continue to improve the health and welfare of these avian patients.

Bird Medicine: Falconry as a Spiritual Salve

This paper is a personal reflection on the healing aspect of falconry. This is a particular style of bird medicine that offers healing in the personal, communal, environmental and transcendental realms. The ways in which this is so, are discussed from the perspective of falconry as a spiritual salve.

Molecular and Morphological Analyses of Leucocytozoon Parasites (Haemosporida: Leucocytozoidae) in Raptors From Thailand

INTRODUCTION

Leucocytozoon spp. causes a vector-borne disease that is nonpathogenic in domestic and wild birds. To date, there was no report of leucocytozoonosis in raptors from Thailand.

METHODS

This study was carried out to perform morphological and molecular analyses of Leucocytozoon in 400 raptors at a rehabilitation center at Kasetsart University, Thailand during a 7-year period. The nested PCR was used to amplify the cytochrome b gene of Leucocytozoon with primers HaemNF1 and HaemNR3 as the primary reaction.

RESULTS

The light microscopic examination revealed Leucocytozoon gametocytes in five raptors; three diurnal raptors [two Crested Goshawks (CGs, Accipiter trivirgatus) and one Eastern Imperial Eagle (EIE, Aquila heliaca)], and two nocturnal raptors (one Oriental Scops-Owl (OSO, Otus sunia,) and one Short-eared Owl, Asio flammeus) and two species were identified: Leucocytozoon danilewskyi in both owl species and L. californicus in two CGs. The PCR method revealed more infection rate (2.0%, 8/400) than the light microscopic method including one Barred Eagle-Owl (BEO, Bubo sumatranus), one Brown Hawk Owl (BHO, Ninox scutulata) and one OSO. A phylogeny revealed that sequences from one SEO and one OSO were clustered with L. danilewskyi and the three Leucocytozoon sequences from diurnal raptors were clustered with L. californicus. The other three sequences from a BHO, a BEO and an OSO were ambiguous.

CONCLUSION

This study combined morphological, morphometric and molecular phylogenetic analyses to identify L. danilewskyi in two species of owls, L. californicus in three diurnal raptors, and unknown species in three other owls, representing the first records of leucocytozoon infection in raptors from Thailand.

Raptor is critical for increasing the mitochondrial proteome and skeletal muscle force during hypertrophy

Loss of skeletal muscle mass and force is of critical importance in numerous pathologies, like age-related sarcopenia or cancer. It has been shown that the Akt-mTORC1 pathway is critical for stimulating adult muscle mass and function, however, it is unknown if mTORC1 is the only mediator downstream of Akt and which intracellular processes are required for functional muscle growth. Here, we show that loss of Raptor reduces muscle hypertrophy after Akt activation and completely prevents increases in muscle force. Interestingly, the residual hypertrophy after Raptor deletion can be completely prevented by administration of the mTORC1 inhibitor rapamycin. Using a quantitative proteomics approach we find that loss of Raptor affects the increases in mitochondrial proteins, while rapamycin mainly affects ribosomal proteins. Taken together, these results suggest that mTORC1 is the key mediator of Akt-dependent muscle growth and its regulation of the mitochondrial proteome is critical for increasing muscle force.

Occurrence and risks of PCDD/Fs and PCBs in three raptors from North China

Concentrations of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and polychlorinated biphenyls (PCBs) were investigated in muscle samples from common kestrels (Falco tinnunculus), eagle owls (Bubo bubo), and little owls (Athene noctua) collected in Beijing, China. The concentrations of PCDD/Fs were in the ranges of 22.7-5280, 67.5-1610, and 68.4-3180 pg/g lipid weight (lw), while levels of dioxin-like PCBs ranged from 4.91 to 1560, 8.08-294, and 28.2-3540 ng/g lw, in common kestrel, eagle owl, and little owl, respectively. The main PCDD/Fs congener was 2,3,4,7,8-PeCDF, and CB-153 dominated the seven indicator PCBs. PCB levels have shown a decreasing trend in the last decade for the common kestrel, but not for little owl in Beijing, which exhibited higher levels of pollutants and toxic equivalency (TEQ) values than the other two species. Concentrations of PCDD/Fs, dioxin-like PCBs, and indicator PCBs differed between fledgling and adult raptors for certain species. Raptors in this study generally had a higher TEQ than the no-observed-effect level in the literature, indicating significant exposure risks to PCDD/Fs and dioxin-like PCBs in raptors, especially in adult little owls.

Genomic bases underlying the adaptive radiation of core landbirds

BACKGROUND

Core landbirds undergo adaptive radiation with different ecological niches, but the genomic bases that underlie their ecological diversification remain unclear.

RESULTS

Here we used the genome-wide target enrichment sequencing of the genes related to vision, hearing, language, temperature sensation, beak shape, taste transduction, and carbohydrate, protein and fat digestion and absorption to examine the genomic bases underlying their ecological diversification. Our comparative molecular phyloecological analyses show that different core landbirds present adaptive enhancement in different aspects, and two general patterns emerge. First, all three raptorial birds (Accipitriformes, Strigiformes, and Falconiformes) show a convergent adaptive enhancement for fat digestion and absorption, while non-raptorial birds tend to exhibit a promoted capability for protein and carbohydrate digestion and absorption. Using this as a molecular marker, our results show relatively strong support for the raptorial lifestyle of the common ancestor of core landbirds, consequently suggesting a single origin of raptors, followed by two secondary losses of raptorial lifestyle within core landbirds. In addition to the dietary niche, we find at temporal niche that diurnal birds tend to exhibit an adaptive enhancement in bright-light vision, while nocturnal birds show an increased adaption in dim-light vision, in line with previous findings.

CONCLUSIONS

Our molecular phyloecological study reveals the genome-wide adaptive differentiations underlying the ecological diversification of core landbirds.

Analysis of lead distribution in avian organs by LA-ICP-MS: Study of experimentally lead-exposed ducks and kites

Lead poisoning of wild birds by ingestion of lead ammunition occurs worldwide. Histopathological changes in organs of lead-intoxicated birds are widely known, and lead concentration of each organ is measurable using mass spectrometry. However, detailed lead localization at the suborgan level has remained elusive in lead-exposed birds. Here we investigated the detailed lead localization in organs of experimentally lead-exposed ducks and kites by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). In both the ducks and kites, lead accumulated diffusely in the liver, renal cortex, and brain. Lead accumulation was restricted to the red pulp in the spleen. With regard to species differences in lead distribution patterns, it is noteworthy that intensive lead accumulation was observed in the arterial walls only in the kites. In addition, the distribution of copper in the brain was altered in the lead-exposed ducks. Thus, the present study shows suborgan lead distribution in lead-exposed birds and its differences between avian species for the first time. These findings will provide fundamental information to understand the cellular processes of lead poisoning and the mechanisms of species differences in susceptibility to lead exposure.

Reduced mTORC1-signaling in retinal ganglion cells leads to vascular retinopathy

BACKGROUND

The coordinated wiring of neurons, glia and endothelial cells into neurovascular units is critical for central nervous system development. This is best exemplified in the mammalian retina where interneurons, astrocytes and retinal ganglion cells sculpt their vascular environment to meet the metabolic demands of visual function. Identifying the molecular networks that underlie neurovascular unit formation is an important step towards a deeper understanding of nervous system development and function.

RESULTS

Here, we report that cell-to-cell mTORC1-signaling is essential for neurovascular unit formation during mouse retinal development. Using a conditional knockout approach we demonstrate that reduced mTORC1 activity in asymmetrically positioned retinal ganglion cells induces a delay in postnatal vascular network formation in addition to the production of rudimentary and tortuous vessel networks in adult animals. The severity of this vascular phenotype is directly correlated to the degree of mTORC1 down regulation within the neighboring retinal ganglion cell population.

CONCLUSIONS

This study establishes a cell nonautonomous role for mTORC1-signaling during retinal development. These findings contribute to our current understanding of neurovascular unit formation and demonstrate how ganglion cells actively sculpt their local environment to ensure that the retina is perfused with an appropriate supply of oxygen and nutrients.

Current Approaches and Future Directions for the Treatment of mTORopathies

The mechanistic target of rapamycin (mTOR) is a kinase at the center of an evolutionarily conserved signaling pathway that orchestrates cell growth and metabolism. mTOR responds to an array of intra- and extracellular stimuli and in turn controls multiple cellular anabolic and catabolic processes. Aberrant mTOR activity is associated with numerous diseases, with particularly profound impact on the nervous system. mTOR is found in two protein complexes, mTOR complex 1 (mTORC1) and 2 (mTORC2), which are governed by different upstream regulators and have distinct cellular actions. Mutations in genes encoding for mTOR regulators result in a collection of neurodevelopmental disorders known as mTORopathies. While these disorders can affect multiple organs, neuropsychiatric conditions such as epilepsy, intellectual disability, and autism spectrum disorder have a major impact on quality of life. The neuropsychiatric aspects of mTORopathies have been particularly challenging to treat in a clinical setting. Current therapeutic approaches center on rapamycin and its analogs, drugs that are administered systemically to inhibit mTOR activity. While these drugs show some clinical efficacy, adverse side effects, incomplete suppression of mTOR targets, and lack of specificity for mTORC1 or mTORC2 may limit their utility. An increased understanding of the neurobiology of mTOR and the underlying molecular, cellular, and circuit mechanisms of mTOR-related disorders will facilitate the development of improved therapeutics. Animal models of mTORopathies have helped unravel the consequences of mTOR pathway mutations in specific brain cell types and developmental stages, revealing an array of disease-related phenotypes. In this review, we discuss current progress and potential future directions for the therapeutic treatment of mTORopathies with a focus on findings from genetic mouse models.

Temporal trends of inorganic elements in a common kestrel (Falco tinnunculus) population from south west Spain

Historical variations (1966-2016) in the exposure to inorganic elements in raptors of South West Spain have been little studied. Therefore, uncertainty exists concerning whether environmental or anthropogenic inputs, as well as dietary strategy shift, may cause changes in exposure patterns. To address this gap, essential and non-essential inorganic elements were measured in Common kestrel (Falco tinnunculus) feathers from museum specimens and free-living individuals spanning a 50-year period. Moreover, stable isotopes of δ¹³C and δ¹⁵N were also measured as proxies of Common kestrel feeding ecology over time. In general, all elements showed significant increasing trends overtime, suggesting changes of inputs from local sources. Moreover, δ¹⁵N signatures were correlated to the variations in Al, Cr, Cu, Fe, K, Li, Mg, Mn, Ni, P, Pb, Rb, Sr, Ti, V and Zn concentrations, suggesting trophic changes in this kestrel population as well as possible biomagnification processes. Finally, some values of Cr, Mn and Pb were above the threshold concentrations of potential toxicity.

mTOR Signaling in Pulmonary Vascular Disease: Pathogenic Role and Therapeutic Target

Pulmonary arterial hypertension (PAH) is a progressive and fatal disease without a cure. The exact pathogenic mechanisms of PAH are complex and poorly understood, yet a number of abnormally expressed genes and regulatory pathways contribute to sustained vasoconstriction and vascular remodeling of the distal pulmonary arteries. Mammalian target of rapamycin (mTOR) is one of the major signaling pathways implicated in regulating cell proliferation, migration, differentiation, and protein synthesis. Here we will describe the canonical mTOR pathway, structural and functional differences between mTOR complexes 1 and 2, as well as the crosstalk with other important signaling cascades in the development of PAH. The pathogenic role of mTOR in pulmonary vascular remodeling and sustained vasoconstriction due to its contribution to proliferation, migration, phenotypic transition, and gene regulation in pulmonary artery smooth muscle and endothelial cells will be discussed. Despite the progress in our elucidation of the etiology and pathogenesis of PAH over the two last decades, there is a lack of effective therapeutic agents to treat PAH patients representing a significant unmet clinical need. In this review, we will explore the possibility and therapeutic potential to use inhibitors of mTOR signaling cascade to treat PAH.

mTORC1 silencing during intestinal epithelial Caco-2 cell differentiation is mediated by the activation of the AMPK/TSC2 pathway

The mechanistic target of rapamycin complex 1 (mTORC1) signaling is the prototypical pathway regulating protein synthesis and cell proliferation. The level of mTORC1 activity is high in intestinal stem cells located at the base of the crypts and thought to gradually decrease as transit-amplifying cells migrate out of the crypts and differentiate into enterocytes, goblet cells or enteroendocrine cells along the epithelium. The unknown mechanism responsible for the silencing of intestinal epithelium mTORC1 during cell differentiation was investigated in Caco-2 cells, which spontaneously differentiate into enterocytes in standard growth medium. The results show that TSC2, an upstream negative regulator of mTORC1 was central to mTORC1 silencing in differentiated Caco-2 cells. AMPK-mediated activation of TSC2 (Ser1387) and repression of Raptor (Ser792), an essential component of mTORC1, were stimulated in differentiated Caco-2 cells. ERK1/2-mediated repression of TSC2 (Ser664) seen in undifferentiated Caco-2 cells was lifted in differentiated cells. IRS-1-mediated activation of AKT (Thr308) phosphorylation was stimulated in differentiated Caco-2 cells and may be involved in cross-pathway repression of ERK1/2. Additionally, PRAS40 (Thr246) phosphorylation was decreased in differentiated Caco-2 cells compared to undifferentiated cells allowing dephosphorylated PRAS40 to displace Raptor thereby repressing mTORC1 kinase activity.

Using GPS tracking and stable multi-isotopes for estimating habitat use and winter range in Palearctic ospreys

We used both satellite tracking and carbon, nitrogen and sulphur stable isotopic analysis (SIA) to infer wintering ecology and habitat use of the Corsican osprey Pandion haliaetus population. A control sample of feathers from 75 individuals was collected within the osprey’s northern hemisphere breeding range, to assess the SIA variability across habitat types. An experimental set of SIA on feathers of 18 Corsican adults was examined to infer wintering ground locations and habitat types used during the non-breeding period. We calibrated the SIA using GPS/GSM tracks of 12 Mediterranean adults’ movements as wintering site references. We found 50% of individuals were resident and the other half migrated. Ospreys spent the winter at temperate latitudes and showed a high plasticity in habitat selection spread over the Mediterranean basin (marine bays, coastal lagoons/marshland, inland freshwater sites). Complementary to GPS tracking, SIA is, at a broad geographical scale, a reliable method to determine whether ospreys overwinter in a habitat different from that of their breeding area. This study proved that the integration of SIA and GPS/GSM tracking techniques was effective at overcoming the intrinsic limits of each method and achieving greater information for basic ecological studies of migratory birds in aquatic environments.

Raptor and rictor expression in patients with human papillomavirus-related oropharyngeal squamous cell carcinoma

Background

Despite reports of a link between human papillomavirus (HPV) infection and mechanistic target of rapamycin (mTOR) signaling activation, the role of the mTOR pathway, especially raptor and rictor, in HPV-related head and neck cancer is still unclear. The aim of the present study was to elucidate the role of the mTOR pathway in HPV-related oropharyngeal squamous cell carcinoma (OPSCC).

Methods

The present study involved two strategies. The first was to investigate the activity of mTOR and mTOR-related complexes in high-risk HPV-positive (UM-SCC47 and CaSki) and HPV-negative (SCC-4 and SAS) cancer cell lines. The second was to elucidate mTOR complex expression in 80 oropharyngeal cancer tissues and to examine the relationship between mTOR complex expression and survival in patients with OPSCC.

Results

The UM-SCC47 and CaSki cell lines showed high gene and protein expression of raptor. They also exhibited G1/S and G2/M phase cell cycle arrest following 24 h incubation with 6 μM temsirolimus, a rapamycin analog, and temsirolimus administration inhibited their growth. HPV-related OPSCC samples showed high gene and protein expression of raptor and rictor compared with HPV-unrelated OPSCC. In addition, HPV-related OPSCC patients with high raptor and rictor expression tended to have a worse prognosis than those with low or medium expression.

Conclusions

These results suggest that raptor and rictor have important roles in HPV-related OPSCC and that temsirolimus is a potential therapeutic agent for patients with HPV-related OPSCC. This is the first report to reveal the overexpression of raptor and rictor in HPV-related OPSCC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-07794-9.

Care of the Geriatric Raptor

Despite falconry having been practiced for centuries and with a wealth of published material on the husbandry of captive raptors over that period, there is a paucity of published material on the care of the geriatric raptor. Raptors are often a long-lived species and can suffer a range of age-related conditions that may impact on their welfare. This article seeks to cover some of these conditions and look at welfare considerations in the management of geriatric raptors, including quality-of-life assessments and euthanasia decision making.