Plasma exosomes are enriched in Hsp70 and modulated by stress and cortisol in rainbow trout

Exosome: From biology to drug delivery

In recent years, different advancements have been observed in nanosized drug delivery systems. Factors such as stability, safety and targeting efficiency cause hindrances in the clinical translation of these synthetic nanocarriers. Therefore, researchers employed endogenous nanocarriers like exosomes as drug delivery vehicles that have an inherent ability to target more efficiently after appropriate functionalization and show higher biocompatibility and less immunogenicity and facilitate penetration through the biological barriers more quickly than the other available carriers. Exosomes are biologically derived lipid bilayer-enclosed nanosized extracellular vesicles (size ranges from 30 to 150 nm) secreted from both prokaryotic and eukaryotic cells and appears significantly in the extracellular space. These EVs (extracellular vesicles) can exist in different sources, including mammals, plants and microorganisms. Different advanced techniques have been introduced for the isolation of exosomes to overcome the existing barriers present with conventional methods. Extensive research on the application of exosomes in therapeutic delivery for treating various diseases related to central nervous system, bone, cancer, skin, etc. has been employed. Several studies are on different stages of clinical trials, and many exosomes patents have been registered.

Is serum-derived exosomal hTERT transcript a marker of oncogenic activity in primary brain tumors? An exploratory study

BACKGROUND

In order to proliferate indefinitely, all tumors require a telomere maintenance mechanism. The expression of human telomerase reverse transcriptase (hTERT) enables telomere maintenance and provides cancer cells with limitless replicative potential. As such, it may serve as an attractive biomarker for oncogenic activity. This study explored whether a liquid biopsy that analyses blood derived exosomal hTERT transcript (e-hTERT-trans) may serve as such a biomarker in gliomas and meningiomas when compared to healthy controls.

METHODS

Exosomes were isolated from the pre-operative sera of patients' samples stored in the biobank of both Rabin and Sheba Medical Centers. The levels of e-hTERT-trans were measured in 81 healthy controls, 117 meningiomas, 17 low-grade gliomas, and 61 glioblastomas. Clinical parameters of the patients were collected retrospectively and compared to the levels of the e-hTERT-trans.

RESULTS

The upper normal limit of controls e-hTERT-trans was 1.85 relative quantitation (RQ). The rate of detection increased with rising tumor grade and correlated with tumor recurrence in meningiomas: mean RQ without recurrence (2.17 ± 11.7) versus with recurrence (3.59 ± 4.42; p = 0.002). In glioblastomas, preoperative measurements correlated with tumor volume and with the disease course on serial sampling.

CONCLUSIONS

We demonstrated for the first time that the expression of e-hTERT-trans transcript can be measured in the serum of primary brain tumors. This exosomal marker carries the potential to serve as a biomarker once used in conjunction with other clinical and radiological parameters. Future studies are required to investigate whether the sensitivity could be augmented and whether it can be implemented into routine patients care.

Isolation and characterization of the morphology, size and particle number of rainbow trout (Oncorhynchus mykiss) and zebrafish (Danio rerio) cell line derived large and small extracellular vesicles

Extracellular vesicles (EVs) are 50-1,000 nm lipid bilayer-bound vesicles, released into the extracellular environment by various cell types for intercellular communication purposes. The quantitative and qualitative characteristics of EVs can be affected by stress and pathological conditions. The majority of extracellular vesicle (EV) studies have been performed on mammalian cell lines or bodily fluids. EVs have been previously described from bodily fluids like plasma, serum or mucus in different fish species, however the available knowledge of fish cell line derived EVs is limited and in the vast majority of studies, the overall focus is on small EVs (< 200 nm). We isolated large and small extracellular vesicles from zebrafish (Danio rerio) liver (ZFL), rainbow trout (Oncorhynchus mykiss) liver (RTL-W1), gill (RTgill-W1) and intestinal epithelial (RTgutGC) cell lines using stepwise centrifugation and characterized the size and morphology of EVs. Here we demonstrated that large and small extracellular vesicles can be successfully isolated using stepwise centrifugation from the serum-free medium of the selected piscine cell lines after a 24-h incubation period. The size distribution of large and small EVs isolated from the piscine cell lines suggest that large and small EV groups show high diversity in size ranges, containing heterogenous subpopulations in sizes, and the results highly depend on the applied method and whether filtration steps were included following the isolation. The spherical morphology of EVs was verified by transmission electron microscopy.

Proteomics analysis of circulating small extracellular vesicles: Focus on the contribution of EVs to tumor metabolism

The term small extracellular vesicle (sEV) is a comprehensive term that includes any type of cell-derived, membrane-delimited particle that has a diameter < 200 nm, and which includes exosomes and smaller microvesicles. sEVs transfer bioactive molecules between cells and are crucial for cellular homeostasis and particularly during tumor development, where sEVs provide important contributions to the formation of the premetastic niche and to their altered metabolism. sEVs are thus legitimate targets for intervention and have also gained increasing interest as an easily accessible source of biomarkers because they can be rapidly isolated from serum/plasma and their molecular cargo provides information on their cell-of origin. To target sEVs that are specific for a given cell/disease it is essential to identify EV surface proteins that are characteristic of that cell/disease. Mass-spectrometry based proteomics is widely used for the identification and quantification of sEV proteins. The methods used for isolating the sEVs, preparing the sEV sample for proteomics analysis, and mass spectrometry analysis, can have a strong influence on the results and requires careful consideration. This review provides an overview of the approaches used for sEV proteomics and discusses the inherent compromises regarding EV purity versus depth of coverage. Additionally, it discusses the practical applications of the methods to unravel the involvement of sEVs in regulating the metabolism of pancreatic ductal adenocarcinoma (PDAC). The metabolic reprogramming in PDAC includes enhanced glycolysis, elevated glutamine metabolism, alterations in lipid metabolism, mitochondrial dysfunction and hypoxia, all of which are crucial in promoting tumor cell growth. A thorough understanding of these metabolic adaptations is imperative for the development of targeted therapies to exploit PDAC's vulnerabilities.

Exosomes in the Diagnosis and Treatment of Renal Cell Cancer

Renal cell carcinoma (RCC) is the most prevalent type of kidney cancer originating from renal tubular epithelial cells, with clear cell RCC comprising approximately 80% of cases. The primary treatment modalities for RCC are surgery and targeted therapy, albeit with suboptimal efficacies. Despite progress in RCC research, significant challenges persist, including advanced distant metastasis, delayed diagnosis, and drug resistance. Growing evidence suggests that extracellular vesicles (EVs) play a pivotal role in multiple aspects of RCC, including tumorigenesis, metastasis, immune evasion, and drug response. These membrane-bound vesicles are released into the extracellular environment by nearly all cell types and are capable of transferring various bioactive molecules, including RNA, DNA, proteins, and lipids, aiding intercellular communication. The molecular cargo carried by EVs renders them an attractive resource for biomarker identification, while their multifarious role in the RCC offers opportunities for diagnosis and targeted interventions, including EV-based therapies. As the most versatile type of EVs, exosomes have attracted much attention as nanocarriers of biologicals, with multi-range signaling effects. Despite the growing interest in exosomes, there is currently no widely accepted consensus on their subtypes and properties. The emerging heterogeneity of exosomes presents both methodological challenges and exciting opportunities for diagnostic and clinical interventions. This article reviews the characteristics and functions of exosomes, with a particular reference to the recent advances in their application to the diagnosis and treatment of RCC.

Bridging the extracellular vesicle knowledge gap: insights from non-mammalian vertebrates, invertebrates, and early-diverging metazoans

Extracellular vesicles (EVs) are lipid-enclosed structures that facilitate intercellular communication by transferring cargo between cells. Although predominantly studied in mammals, extracellular vesicles are ubiquitous across metazoans, and thus research in non-mammalian models is critical for fully elucidating extracellular vesicles biology. Recent advances demonstrate that extracellular vesicles mediate diverse physiological processes in non-mammalian vertebrates, including fish, amphibians, and reptiles. Piscine extracellular vesicles promote fin regeneration in zebrafish and carry heat shock proteins regulated by stress. Frog extracellular vesicles containing microRNAs modulate angiogenesis, while turtle extracellular vesicles coordinate reproductive functions. Venom from snakes contains extracellular vesicles that mirror the whole venom composition and interact with mammalian cells. Invertebrates also possess extracellular vesicles involved in immunity, development, and pathogenesis. Molluscan extracellular vesicles participate in shell formation and host interactions. Arthropod models, including Drosophila, genetically dissect conserved pathways controlling extracellular vesicles biogenesis and signalling. Nematode extracellular vesicles regulate larval development, animal communication, and ageing via conserved extracellular vesicles proteins. Ancient metazoan lineages utilise extracellular vesicles as well, with cnidarian extracellular vesicles regulating immunity and regeneration. Ultimately, expanding extracellular vesicles research beyond typical biomedical models to encompass phylogenetic diversity provides an unparalleled perspective on the conserved versus specialised aspects of metazoan extracellular vesicles roles over ∼500 million years. With a primary focus on the literature from the past 5 years, this review aims to reveal fundamental insights into EV-mediated intercellular communication mechanisms shaping animal physiology.

Liquid Biopsy at the Frontier of Kidney Diseases: Application of Exosomes in Diagnostics and Therapeutics

In the era of precision medicine, liquid biopsy techniques, especially the use of urine analysis, represent a paradigm shift in the identification of biomarkers, with considerable implications for clinical practice in the field of nephrology. In kidney diseases, the use of this non-invasive tool to identify specific and sensitive biomarkers other than plasma creatinine and the glomerular filtration rate is becoming crucial for the diagnosis and assessment of a patient's condition. In recent years, studies have drawn attention to the importance of exosomes for diagnostic and therapeutic purposes in kidney diseases. Exosomes are nano-sized extracellular vesicles with a lipid bilayer structure, composed of a variety of biologically active substances. In the context of kidney diseases, studies have demonstrated that exosomes are valuable carriers of information and are delivery vectors, rendering them appealing candidates as biomarkers and drug delivery vehicles with beneficial therapeutic outcomes for kidney diseases. This review summarizes the applications of exosomes in kidney diseases, emphasizing the current biomarkers of renal diseases identified from urinary exosomes and the therapeutic applications of exosomes with reference to drug delivery and immunomodulation. Finally, we discuss the challenges encountered when using exosomes for therapeutic purposes and how these may affect its clinical applications.

Exosomal microRNAs regulate the heat stress response in sea cucumber Apostichopus japonicus

Exosomes are small extracellular vesicles that contain nucleic acids such as microRNAs and may participate in important biological processes. We made the initial report of exosomes from sea cucumber Apostichopus japonicus, that were classically cup-shaped and had an average size of 74.65 nm, and identified specific exosome biomarkers (HSP70, TSG101, and CD9). We explored changes in the global expression of microRNAs in exosomes from the commercially important A. japonicus under normal conditions and heat-stressed conditions for 3 and 7 d. We found that heat stress increased exosome production and modified the expression profiles of the microRNAs that they contained. Novel_mir31, novel_mir132, novel_mir26, miR-92_1, and novel_mir27 were commonly found to be differentially expressed in three comparison groups, indicating their importance in the heat stress response. The microRNA expression levels were validated by qPCR. Function analysis of the target genes of these microRNAs indicated they were involved mainly in replication and repair in the initial response of A. japonicus to heat stress exposure. Conversely, during acclimation to the high temperature conditions, the target genes of the differentially expressed microRNAs were primarily involved in metabolism adjustments. Our results will contribute to a better understanding of the regulatory roles of exosomes in sea cucumber, and provide insights into the functions of sea cucumber exosome-shuttled microRNAs against environmental stresses exacerbated by global warming.

MicroRNA-212-5p, an anti-proliferative miRNA, attenuates hypoxia and sugen/hypoxia-induced pulmonary hypertension in rodents

MicroRNAs (miRNA, miR-) play important roles in disease development. In this study, we identified an anti-proliferative miRNA, miR-212-5p, that is induced in pulmonary artery smooth muscle cells (PASMCs) and lungs of pulmonary hypertension (PH) patients and rodents with experimental PH. We found that smooth muscle cell (SMC)-specific knockout of miR-212-5p exacerbated hypoxia-induced pulmonary vascular remodeling and PH in mice, suggesting that miR-212-5p may be upregulated in PASMCs to act as an endogenous inhibitor of PH, possibly by suppressing PASMC proliferation. Extracellular vesicles (EVs) have been shown recently to be promising drug delivery tools for disease treatment. We generated endothelium-derived EVs with an enriched miR-212-5p load, 212-eEVs, and found that they significantly attenuated hypoxia-induced PH in mice and Sugen/hypoxia-induced severe PH in rats, providing proof of concept that engineered endothelium-derived EVs can be used to deliver miRNA into lungs for treatment of severe PH.

Isolation and characterization of plasma-derived exosomes from olive flounder (Paralichthys olivaceus) and their wound healing and regeneration activities

Exosomes have garnered enormous interest for their role in physiological and pathological processes and their potential for therapeutic and diagnostic applications. In this study, exosomes were isolated from plasma of olive flounder (Paralichthys olivaceus) and their physiochemical and morphological characteristics, as well as wound healing and regeneration activities were determined. Isolated exosomes had typical characteristics, including average particle diameter (151.82 ± 9.17 nm), concentration (6.31 × 10¹⁰ particles/mL) with a membrane-bound, cup-shaped morphology. Exosome marker proteins, tetraspanins (CD63, CD9, and CD81), and acetylcholinesterase were detected, indicating the presence of exosomes in olive flounder plasma. Exosomes exhibited no toxicity in in vitro and in vivo studies, even at the highest treatment concentrations (100 and 400 μg/mL, respectively), confirming their suitability for further functional studies. Following exosome treatment (50 and 100 μg/mL), substantial cell migration with rapid closure of the open wound area in in vitro scratch wound healing assay and faster zebrafish larvae fin regeneration rate was observed compared to that of the vehicle. Moreover, exosomes exhibited immunomodulatory properties associated with wound healing, based on mRNA expression patterns in fathead minnow (FHM) cells. In conclusion, exosomes isolated from olive flounder plasma using ultracentrifugation exhibited minimal toxicity and enhanced wound healing and tissue regeneration activities. Identification and in-depth investigation of olive flounder plasma-derived exosome constituents will support the development of exosomes as an efficient therapeutic carrier system for fish medicine in the future.

Research Progress on Exosomes in Osteonecrosis of the Femoral Head

Osteonecrosis of the femoral head (ONFH) is a progressive disease that often necessitates hip replacement if hip preservation therapy fails. ONFH places a heavy economic burden and severe psychological pressure on patients. At present, ONFH is treated by either surgical or non‐surgical methods. In clinical practice, stem cells combined with surgery has achieved some positive results, but many problems remain to be resolved. Exosomes are small vesicles of 30–150 nm, which are rich in various nucleic acids, proteins, and small molecules depending on the cells from which they are derived. A growing number of studies have found that exosomes play an important role in tissue damage repair. In comparison with stem cells, exosomes have lower immunogenicity. Also, exosomes can promote cell proliferation and inhibit tumor growth. In addition, exosomes can also be used as natural carriers of drugs. Many studies have shown that exosomes have therapeutic effects in hormone‐induced ONFH. Exosomes have the effect of promoting vascular regeneration and show good application prospects in ONFH. Here, we present a review of studies on the application of exosomes in ONFH to provide a reference for future research.

A Role for Exchange of Extracellular Vesicles in Porcine Spermatogonial Co-Culture

Spermatogonial stem cells (SSCs) provide the basis for lifelong male fertility through self-renewal and differentiation. Prepubertal male cancer patients may be rendered infertile by gonadotoxic chemotherapy and, unlike sexually mature men, cannot store sperm. Alternatively, testicular biopsies taken prior to treatment may be used to restore fertility in adulthood. Testicular SSC populations are limited, and in vitro culture systems are required to increase numbers of SSCs for treatment, demanding culture systems for SSC propagation. Using the pig as a non-rodent model, we developed culture systems to expand spermatogonia from immature testis tissue, comparing different feeders (Sertoli cells, peritubular myoid cells (PMCs) and pig fetal fibroblasts (PFFs)). Spermatogonia co-cultured with Sertoli cells, PMCs and PFFs had comparable rates of proliferation and apoptosis. To elucidate the mechanism behind the beneficial nature of feeder layers, we investigated the role of extracellular vesicles in crosstalk between spermatogonia and feeder cells. Sertoli cell-released exosomes are incorporated by spermatogonia, and inhibition of exosomal release reduces spermatogonial proliferation. Together, these results show that PMCs, PFFs and Sertoli cells promote spermatogonial proliferation in co-culture, with exosomal exchange representing one possible mechanism. Further characterization of exosomal cargo may ultimately allow the development of feeder-free culture systems for clinical use.

Isolation and Characterization of Plasma-Derived Exosomes from the Marine Fish Rock Bream (Oplegnathus fasciatus) by Two Isolation Techniques

Exosomes are important mediators of intercellular communication and modulate many physiological and pathological processes. Knowledge of secretion, content, and biological functions of fish exosomes during pathological infection is still scarce due to lack of suitable standardized isolation techniques. In this study, we aimed to isolate exosomes from the plasma of marine fish, rock bream (Oplegnathus fasciatus), by two isolation methods: differential ultracentrifugation (UC) and a commercial membrane affinity spin column technique (kit). Morphological and physicochemical characteristics of the isolated exosomes were determined by these two methods, and the efficiencies of the two methods were compared. Exosomes isolated by both methods were in the expected size range (30–200 nm) and had a characteristic cup-shape in transmission electron microscopy observation. Moreover, more intact exosomes were identified using the kit-based method than UC. Nanoparticle tracking analysis demonstrated a heterogeneous population of exosomes with a mean particle diameter of 114.6 ± 4.6 and 111.2 ± 2.2 nm by UC and a kit-based method, respectively. The particle concentration obtained by the kit method (1.05 × 1011 ± 1.23 × 1010 particles/mL) was 10-fold higher than that obtained by UC (4.90 × 1010 ± 2.91 × 109 particles/mL). The kit method had a comparatively higher total protein yield (1.86 mg) and exosome protein recovery (0.55 mg/mL plasma). Immunoblotting analysis showed the presence of exosome marker proteins (CD81, CD63, and HSP90) in the exosomes isolated by both methods and suggests the existence of exosomes. However, the absence of cytotoxicity or adverse immune responses to fish and mammalian cells by the exosomes isolated by the UC procedure indicates its suitability for functional studies in vitro. Overall, our basic characterization results indicate that the kit-based method is more suitable for isolating high-purity exosomes from fish plasma, whereas UC has higher safety in terms of yielding exosomes with low toxicity. This study provides evidence for the existence of typical exosomes in rock beam plasma and facilitates the selection of an efficient exosome isolation procedure for future applications in disease diagnosis and exosome therapy as fish medicine.

Extracellular vesicles derived from endothelial cells in hypoxia contribute to pulmonary artery smooth muscle cell proliferation in-vitro and pulmonary hypertension in mice

In the lung, communication between pulmonary vascular endothelial cells (PVEC) and pulmonary artery smooth muscle cells (PASMC) is essential for the maintenance of vascular homeostasis. In pulmonary hypertension (PH), the derangement in their cell-cell communication plays a major role in the pathogenesis of pulmonary vascular remodeling. In this study, we focused on the role of PVEC-derived extracellular vesicles (EV), specifically their microRNA (miRNA, miR-) cargo, in the regulation of PASMC proliferation and vascular remodeling in PH. We found that the amount of pro-proliferative miR-210-3p was increased in PVEC-derived EV in hypoxia (H-EV), which contributes to the H-EV-induced proliferation of PASMC and the development of PH.

Current status of research on exosomes in general, and for the diagnosis and treatment of kidney cancer in particular

Kidney cancer is a common urological tumour. Owing to its high prevalence and mortality rate, it is the third most malignant tumour of the urinary system, followed by prostate and bladder cancers. It exerts a high degree of malignancy, and most of the distant metastasis occurs at an early stage; it is insensitive to chemoradiotherapy and easily develops drug resistance. The current treatment for kidney cancer mainly includes surgery, interventional embolization and targeted therapy; however, the treatment efficacy is poor. In recent years, the role of exosomes as mediators of intercellular communication and information exchange in the tumour microenvironment in tumour pathogenesis has attracted much attention. Exosomes are rich in bioactive substances such as nucleic acids, proteins and lipids and are involved in angiogenesis, immune regulation, drug resistance, formation of pre-metastatic niche, invasion and metastasis. This article reviews the ongoing research and applications of exosomes for the diagnosis and treatment of kidney cancer.

Evidence for a Novel Antiviral Mechanism of Teleost Fish: Serum-Derived Exosomes Inhibit Virus Replication through Incorporating Mx1 Protein

Exosomes are associated with cancer progression, pregnancy, cardiovascular diseases, central nervous system-related diseases, immune responses and viral pathogenicity. However, study on the role of exosomes in the immune response of teleost fish, especially antiviral immunity, is limited. Herein, serum-derived exosomes from mandarin fish were used to investigate the antiviral effect on the exosomes of teleost fish. Exosomes isolated from mandarin fish serum by ultra-centrifugation were internalized by mandarin fish fry cells and were able to inhibit Infectious spleen and kidney necrosis virus (ISKNV) infection. To further investigate the underlying mechanisms of exosomes in inhibiting ISKNV infection, the protein composition of serum-derived exosomes was analyzed by mass spectrometry. It was found that myxovirus resistance 1 (Mx1) was incorporated by exosomes. Furthermore, the mandarin fish Mx1 protein was proven to be transferred into the recipient cells though exosomes. Our results showed that the serum-derived exosomes from mandarin fish could inhibit ISKNV replication, which suggested an underlying mechanism of the exosome antivirus in that it incorporates Mx1 protein and delivery into recipient cells. This study provided evidence for the important antiviral role of exosomes in the immune system of teleost fish.

Engineering extracellular vesicles for cancer therapy: recent advances and challenges in clinical translation

Extracellular vesicles (EVs) are receiving increasing attention in recent years in the field of cancer treatment. EVs contain specific contents closely related to their donor cells, such as miRNAs, proteins and dsDNAs. As endogenous vesicles, EVs naturally have the characteristics of low toxicity and low immunogenicity and can stably pass through the circulatory system to reach the recipient cells, which make them good carriers to deliver therapeutic agents such as nucleic acid sequences and chemotherapeutics. In many preclinical studies and clinical trials, EVs have demonstrated their unlimited advantages in the field of cancer therapy. However, there are still some challenges that restrict their clinical application, such as yield, heterogeneity, safety, and specificity. In this review, we will focus on the latest breakthrough of EVs in the field of cancer treatment and discuss the challenges in the clinical translation of EVs.

Cortisol modulates calcium release-activated calcium channel gating in fish hepatocytes

Glucocorticoids (GCs) are rapidly released in response to stress and play an important role in the physiological adjustments to re-establish homeostasis. The mode of action of GCs for stress coping is mediated largely by the steroid binding to the glucocorticoid receptor (GR), a ligand-bound transcription factor, and modulating the expression of target genes. However, GCs also exert rapid actions that are independent of transcriptional regulation by modulating second messenger signaling. However, a membrane-specific protein that transduces rapid GCs signal is yet to be characterized. Here, using freshly isolated hepatocytes from rainbow trout (Oncorhynchus mykiss) and fura2 fluorescence microscopy, we report that stressed levels of cortisol rapidly stimulate the rise in cytosolic free calcium ([Ca²⁺]i). Pharmacological manipulations using specific extra- and intra-cellular calcium chelators, plasma membrane and endoplasmic reticulum channel blockers and receptors, indicated extracellular Ca²⁺ entry is required for the cortisol-mediated rise in ([Ca²⁺]i). Particularly, the calcium release-activated calcium (CRAC) channel gating appears to be a key target for the rapid action of cortisol in the ([Ca²⁺]i) rise in trout hepatocytes. To test this further, we carried out in silico molecular docking studies using the Drosophila CRAC channel modulator 1 (ORAI1) protein, the pore forming subunit of CRAC channel that is highly conserved. The result predicts a putative binding site on CRAC for cortisol to modulate channel gating, suggesting a direct, as well as an indirect regulation (by other membrane receptors) of CRAC channel gating by cortisol. Altogether, CRAC channel may be a novel cortisol-gated Ca²⁺ channel transducing rapid nongenomic signalling in hepatocytes during acute stress.

The Proteome and Citrullinome of Hippoglossus hippoglossus Extracellular Vesicles-Novel Insights into Roles of the Serum Secretome in Immune, Gene Regulatory and Metabolic Pathways

Extracellular vesicles (EVs) are lipid bilayer vesicles which are released from cells and play multifaceted roles in cellular communication in health and disease. EVs can be isolated from various body fluids, including serum and plasma, and are usable biomarkers as they can inform health status. Studies on EVs are an emerging research field in teleost fish, with accumulating evidence for important functions in immunity and homeostasis, but remain to be characterised in most fish species, including halibut. Protein deimination is a post-translational modification caused by a conserved family of enzymes, named peptidylarginine deiminases (PADs), and results in changes in protein folding and function via conversion of arginine to citrulline in target proteins. Protein deimination has been recently described in halibut ontogeny and halibut serum. Neither EV profiles, nor total protein or deiminated protein EV cargos have yet been assessed in halibut and are reported in the current study. Halibut serum EVs showed a poly-dispersed population in the size range of 50–600 nm, with modal size of EVs falling at 138 nm, and morphology was further confirmed by transmission electron microscopy. The assessment of EV total protein cargo revealed 124 protein hits and 37 deiminated protein hits, whereof 15 hits were particularly identified in deiminated form only. Protein interaction network analysis showed that deimination hits are involved in a range of gene regulatory, immune, metabolic and developmental processes. The same was found for total EV protein cargo, although a far wider range of pathways was found than for deimination hits only. The expression of complement component C3 and C4, as well as pentraxin-like protein, which were identified by proteomic analysis, was further verified in EVs by western blotting. This showed that C3 is exported in EVs at higher levels than C4 and deiminated C3 was furthermore confirmed to be at high levels in the deimination-enriched EV fractions, while, in comparison, C4 showed very low detection in deimination-enriched EV fractions. Pentraxin was exported in EVs, but not detected in the deimination-enriched fractions. Our findings provide novel insights into EV-mediated communication in halibut serum, via transport of protein cargo, including post-translationally deiminated proteins.

Cloning and identification of grass carp transcription factor HSF1 and its characterization involving the production of fish HSP70

In mammals, heat shock transcription factor 1 (HSF1) is well documented as the critical transcript factor to regulate heat shock protein 70 (HSP70) expression under different stresses, such as heat shock or bacterial infection. In fish, Hsf1 responses to physiological and environmental stresses and regulates Hsp70 expression under thermal exposure. However, the functional role of Hsf1 in Hsp70 production is still elusive under bacterial infection. In the present study, a coding sequence of grass carp hsf1 (gchsf1) gene was cloned and identified. Using Ctenopharyngodon idellus kidney (CIK) cells as the model, we found that lipopolysaccharide (LPS) exerted stimulatory effects on the expression of grass carp hsp70 (gchsp70) and hsf1, implying possible relationship of Hsp70 and Hsf1 under immune stimulation in fish. To validate the hypothesis, overexpression of gcHsf1 was performed in CIK cells, and the effects of overexpressing gcHsf1 on the expression of gcHsp70 in the absence or presence of LPS were examined. Results showed that LPS significantly upregulated the transcription and protein synthesis of gcHsp70, and these stimulatory effects were further amplified when overexpression of gcHsf1 was performed. Furthermore, luciferase reporter assays in CIK cells revealed that both overexpression of Hsf1 and LPS upregulated gchsp70 transcription, and their combined treatment further enhanced the gchsp70 promoter activity. Moreover, the regions responsive to these treatments were mapped to the promoter of gchsp70. Besides transcriptional level and cellular protein contents, gcHsp70 secretion was measured by competitive ELISA, uncovering that gcHsf1 enhanced the release of gcHsp70 induced by LPS in the same cells. These data not only demonstrated the enhancement of Hsf1 in Hsp70 production but also initially revealed the involvement of Hsf1-Hsp70 axis in mediating inflammatory response in fish.

Characterization of miRNAs in Extracellular Vesicles Released From Atlantic Salmon Monocyte-Like and Macrophage-Like Cells

Cell-derived extracellular vesicles (EVs) participate in cell-cell communication via transfer of molecular cargo including genetic material like miRNAs. In mammals, it has previously been established that EV-mediated transfer of miRNAs can alter the development or function of immune cells, such as macrophages. Our previous research revealed that Atlantic salmon head kidney leukocytes (HKLs) change their morphology, phagocytic ability and miRNA profile from primarily “monocyte-like” at Day 1 to primarily “macrophage-like” at Day 5 of culture. Therefore, we aimed to characterize the miRNA cargo packaged in EVs released from these two cell populations. We successfully isolated EVs from Atlantic salmon HKL culture supernatants using the established Vn96 peptide-based pull-down. Isolation was validated using transmission electron microscopy, nanoparticle tracking analysis, and Western blotting. RNA-sequencing identified 19 differentially enriched (DE) miRNAs packaged in Day 1 versus Day 5 EVs. Several of the highly abundant miRNAs, including those that were DE (e.g. ssa-miR-146a, ssa-miR-155 and ssa-miR-731), were previously identified as DE in HKLs and are associated with macrophage differentiation and immune response in other species. Interestingly, the abundance relative of the miRNAs in EVs, including the most abundant miRNA (ssa-miR-125b), was different than the miRNA abundance in HKLs, indicating selective packaging of miRNAs in EVs. Further study of the miRNA cargo in EVs derived from fish immune cells will be an important next step in identifying EV biomarkers useful for evaluating immune cell function, fish health, or response to disease.

Plasma exosomes protect against cerebral ischemia/reperfusion injury via exosomal HSP70 mediated suppression of ROS

AIMS

Ischemic stroke is the leading cause of severe disability and death worldwide. As the pathogenesis of stroke has not been clearly elucidated and the ability of current therapeutic drugs on crossing the blood-brain barrier (BBB) is extremely low, there is no effective strategy to treat stroke. We aim at investigating the specific advantages of using plasma exosomes (Pla-Exo) for targeting ischemic brain and exploring its underlying mechanism in neuroprotection.

MAIN METHODS

Pla-Exo was obtained by a gradient ultracentrifugation of fresh plasma. The quantification of penetrated Pla-Exo through BBB was investigated in vitro BBB model, furthermore, the effects of Pla-Exo and exosomal HSP70 on cerebral ischemia/reperfusion injury were evaluated.

KEY FINDINGS

Pla-Exo enhanced BBB crossing by specific interaction between Pla-Exo inherited heat shock protein 70 (HSP70) and endothelial Toll-like receptor 4 (TLR4). As expected, Pla-Exo increased HSP70 expression in the ischemic region through the transfer of HSP70, and led to HSP70 mediated suppression of ROS, thus alleviating cerebral ischemia/reperfusion (I/R) injury by attenuating the deterioration of BBB and preventing mitochondria damage.

SIGNIFICANCE

These findings indicated that Pla-Exo can provide protection against ischemia-reperfusion injury via the regulation of HSP70 and it should be further studied as a potential candidate for protection against ischemic injury.

Acute air exposure modulates the microRNA abundance in stress responsive tissues and circulating extracellular vesicles in rainbow trout (Oncorhynchus mykiss)

The hypothalamic-pituitary-interrenal axis is an important regulator of stress and metabolism in teleosts. Cortisol is secreted by the head kidney where it increases gluconeogenesis in the liver to increase circulating glucose levels. MicroRNAs (miRNAs) are small, non-coding RNA molecules that bind to the 3' untranslated region of specific mRNA to regulate their expression. MicroRNAs can also be secreted into circulation by association with extracellular vesicles (EVs) where they can influence the phenotype of other tissues. In this study, adult rainbow trout were exposed to a 3-minute acute air stress and allowed to recover for 1-, 3-, or 24-h to determine how miRNAs were altered. MicroRNAs measured in this study were chosen based on their high relative abundance in tissues that drive the stress response (miR-21a-3p, let-7a-5p, miR-143-3p) or their role in regulating DNA methylation (miR-29a-3p). In general, miRNAs increased in circulating EVs during the recovery period while decreasing in head kidney and liver at the same timepoints. Predicted targets for these miRNAs were analyzed using KEGG and DAVID functional enrichment analysis. Pathways involved in metabolism and cell signaling were predicted to be upregulated. Future studies can use these results to investigate how pathways are regulated after stress. Overall, our results indicate that miRNAs are regulated during teleost stress responses and could be supporting the cortisol-mediated changes that occur.

Integrative Modeling and Visualization of Exosomes

Information from proteomics, microscopy, and structural biology are integrated to create structural models of exosomes, small vesicles released from cells. Three visualization methods are employed and compared: 2D painting of a cross section using traditional media, manual creation of a cross section using the mesoscale 2.5D digital painting software cellPAINT, and generation of a 3D atomic model using the mesoscale modeling program cellPACK.

Extracellular vesicles from cod (Gadus morhua L.) mucus contain innate immune factors and deiminated protein cargo

Extracellular vesicles are released from cells and participate in cell communication via transfer of protein and genetic cargo derived from the parent cells. EVs play roles in normal physiology and immunity and are also linked to various pathological processes. Peptidylarginine deiminases (PADs) are phylogenetically conserved enzymes with physiological and pathophysiological roles. PADs cause post-translational protein deimination, resulting in structural and, in some cases, functional changes in target proteins and are also linked to EV biogenesis. This study describes for the first time EVs isolated from cod mucosa. Mucosal EVs were characterised by electron microscopy, nanoparticle tracking analysis and EV-specific surface markers. Cod mucosal EVs were found to carry PAD, complement component C3 and C-reactive proteins. C3 was found to be deiminated in both whole mucus and mucosal EVs, with some differences, and further 6 deiminated immune and cytoskeletal proteins were identified in EVs by LC-MS/MS analysis. As mucosal surfaces of teleost fish reflect human mucosal surfaces, these findings may provide useful insights into roles of EVs in mucosal immunity throughout phylogeny.

A review on protein markers of exosome from different bio-resources and the antibodies used for characterization

Exosomes are small membrane vesicles (ranging from 30 nm to 150 nm), secreted by different cell types upon fusion of multivesicular bodies (MVB) to the cell plasma membrane under a variety of normal and pathological conditions. Through transferring their cargos such as proteins, lipids and nucleic acids from donor cells to recipient cells, exosomes play a crucial role in cell-to-cell communication. Due to their presence in most body fluids (such as blood, breast milk, saliva, urine, bile, pancreatic juice, cerebrospinal and peritoneal fluids), and their role in carrying bioactive molecules from the cells of origin, exosomes have attracted great interest in their diagnostic and prognostic value for various diseases and therapeutic approaches. Although a large body of literature has documented the importance of exosomes over the past decade, there is no article systematically summarizing protein markers of exosome from different resources and the antibodies that are suited to characterize exosomes. In this review, we briefly summarize the exosome marker proteins, exosomal biomarkers for different diseases, and the antibodies suitable for different bio-resources exosomes characterization.

Circulating exosomal miRNAs in cardiovascular disease pathogenesis: New emerging hopes

Cardiovascular diseases (CVDs) are one of the leading causes of morbidity and mortality. Standard therapies have failed to significantly increase patients' survival. Moreover, the majority of conventional screening procedures are ineffective for the diagnosis of CVDs at early stages. Accumulating evidence suggests that numerous cell types release a class of nano-sized vesicles named exosomes into the extracellular space. Exosomes are widely distributed in various body fluids and contain a number of diverse biomolecules such as proteins, lipids, and both mRNA and noncoding RNAs which reflect host-cell molecular architecture. MicroRNAs (miRNAs), which can be found in exosomes, could be taken up by both neighboring and distal cells. Not only has recent evidence indicated the regulatory role of exosomal miRNAs in the pathogenesis of CVD, but it has also been shown that differential expression of exosomal miRNAs in CVDs has made them promising biomarkers for early detection of CVDs. Owing to these remarkable features, exosomal miRNAs have emerged as hot spots in research. This review summarizes the role of exosomal miRNAs in the pathogenesis of CVDs and discusses their potential application in the clinical setting as both therapeutic and diagnostic tools.

Early Developmental Stress Affects Subsequent Gene Expression Response to an Acute Stress in Atlantic Salmon: An Approach for Creating Robust Fish for Aquaculture?

Stress during early life has potential to program and alter the response to stressful events and metabolism in later life. Repeated short exposure of Atlantic salmon to cold water and air during embryonic (E), post-hatch (PH) or both phases of development (EPH) has been shown to alter the methylome and transcriptome and to affect growth performance during later life compared to untreated controls (CO). The aim of this study was to investigate how the transcriptome of these fish responds to subsequent acute stress at the start feeding stage, and to describe methylation differences that might steer these changes. EPH treated fish showed the strongest down-regulation of corticotropin releasing factor 1, up-regulation of glucocorticoid receptor and 3-oxo-5-alpha-steroid 4-dehydrogenase 2 gene expression and a suppressed cortisol response 3 hr after the acute stress, differences that could influence hormesis and be affecting how EPH fish cope and recover from the stress event. Growth hormone 2 and insulin-like growth factor 1 were more strongly down-regulated following acute stress in EPH treated fish relative to E, PH and CO fish. This indicates switching away from growth toward coping with stress following stressful events in EPH fish. Genes implicated in immune function such as major histocompatibility class 1A, T-cell receptor and toll-like receptor also responded to acute stress differently in EPH treated fish, indicating that repeated stresses during early life may affect robustness. Differential DNA methylation was detected in regions mapping <500 bases from genes differentially responding to acute stress suggesting the involvement of epigenetic mechanisms. Stress treatments applied during early development therefore have potential as a husbandry tool for boosting the productivity of aquaculture by affecting how fish respond to stresses at critical stages of production.

Exosomes: biogenesis, biologic function and clinical potential

Exosomes are nano-sized biovesicles released into surrounding body fluids upon fusion of multivesicular bodies and the plasma membrane. They were shown to carry cell-specific cargos of proteins, lipids, and genetic materials, and can be selectively taken up by neighboring or distant cells far from their release, reprogramming the recipient cells upon their bioactive compounds. Therefore, the regulated formation of exosomes, specific makeup of their cargo, cell-targeting specificity are of immense biological interest considering extremely high potential of exosomes as non-invasive diagnostic biomarkers, as well as therapeutic nanocarriers. In present review, we outline and discuss recent progress in the elucidation of the regulatory mechanisms of exosome biogenesis, the molecular composition of exosomes, and technologies used in exosome research. Furthermore, we focus on the potential use of exosomes as valuable diagnostic and prognostic biomarkers for their cell-lineage and state-specific contents, and possibilities as therapeutic vehicles for drug and gene delivery. Exosome research is now in its infancy, in-depth understanding of subcellular components and mechanisms involved in exosome formation and specific cell-targeting will bring light on their physiological activities.

Glucocorticoid Treatment Leads to Aberrant Ion and Macromolecular Transport in Regenerating Zebrafish Fins

Long-term glucocorticoid administration in patients undergoing immunosuppressive and anti-inflammatory treatment is accompanied by impaired bone formation and increased fracture risk. Furthermore, glucocorticoid treatment can lead to impaired wound healing and altered cell metabolism. Recently, we showed that exposure of zebrafish to the glucocorticoid prednisolone during fin regeneration impacts negatively on the length, bone formation, and osteoblast function of the regenerate. The underlying cellular and molecular mechanisms of impairment, however, remain incompletely understood. In order to further elucidate the anti-regenerative effects of continued glucocorticoid exposure on fin tissues, we performed proteome profiling of fin regenerates undergoing prednisolone treatment, in addition to profiling of homeostatic fin tissue and fins undergoing undisturbed regeneration. By using LC-MS (liquid chromatography-mass spectrometry) we identified more than 6,000 proteins across all tissue samples. In agreement with previous reports, fin amputation induces changes in chromatin structure and extracellular matrix (ECM) composition within the tissue. Notably, prednisolone treatment leads to impaired expression of selected ECM components in the fin regenerate. Moreover, the function of ion transporting ATPases and other proteins involved in macromolecule and vesicular transport mechanisms of the cell appears to be altered by prednisolone treatment. In particular, acidification of membrane-enclosed organelles such as lysosomes is inhibited. Taken together, our data indicate that continued synthetic glucocorticoid exposure in zebrafish deteriorates cellular trafficking processes in the regenerating fin, which interferes with appropriate tissue restoration upon injury.

The mineralocorticoid receptor is essential for stress axis regulation in zebrafish larvae

The mineralocorticoid receptor (MR) in mammals mediates the effects of aldosterone in regulating fluid balance and potassium homeostasis. While MR signalling is essential for survival in mammals, there is no evidence that MR has any physiological role in ray-finned fish. Teleosts lack aldosterone and emerging evidence suggest that cortisol mediates ion and fluid regulation by activating glucocorticoid receptor (GR) signalling. Consequently, a physiological role for MR signalling, despite its conserved and ancient origin, is still lacking. We tested the hypothesis that a key physiological role for MR signalling in fish is the regulation of stress axis activation and function. Using either MR or GR knockout zebrafish, our results reveal distinct and complementary role for these receptors in stress axis function. GR^-/- mutants were hypercortisolemic and failed to elicit a cortisol stress response, while MR^-/- mutants showed a delayed, but sustained cortisol response post-stressor. Both these receptors are involved in stress-related behaviour, as the loss of either receptors abolished the glucocorticoid-mediated larval hyperactivity to a light stimulus. Overall, the results underscore a key physiological role for MR signalling in ray-finned fishes, and we propose that the regulation of the highly conserved stress axis as the original function of this receptor.

Post-translational protein deimination in cod (Gadus morhua L.) ontogeny novel roles in tissue remodelling and mucosal immune defences?

Peptidylarginine deiminases (PADs) are calcium dependent enzymes with physiological and pathophysiological roles conserved throughout phylogeny. PADs promote post-translational deimination of protein arginine to citrulline, altering the structure and function of target proteins. Deiminated proteins were detected in the early developmental stages of cod from 11 days post fertilisation to 70 days post hatching. Deiminated proteins were present in mucosal surfaces and in liver, pancreas, spleen, gut, muscle, brain and eye during early cod larval development. Deiminated protein targets identified in skin mucosa included nuclear histones; cytoskeletal proteins such as tubulin and beta-actin; metabolic and immune related proteins such as galectin, mannan-binding lectin, toll-like receptor, kininogen, Beta2-microglobulin, aldehyde dehydrogenase, bloodthirsty and preproapolipoprotein A-I. Deiminated histone H3, a marker for anti-pathogenic neutrophil extracellular traps, was particularly elevated in mucosal tissues in immunostimulated cod larvae. PAD-mediated protein deimination may facilitate protein moonlighting, allowing the same protein to exhibit a range of biological functions, in tissue remodelling and mucosal immune defences in teleost ontogeny.

Isolation and Characterization of Serum Extracellular Vesicles (EVs) from Atlantic Salmon Infected with Piscirickettsia Salmonis

Secretion of extracellular vesicles (EVs) is a common feature of both eukaryotic and prokaryotic cells. Isolated EVs have been shown to contain different types of molecules, including proteins and nucleic acids, and are reported to be key players in intercellular communication. Little is known, however, of EV secretion in fish, or the effect of infection on EV release and content. In the present study, EVs were isolated from the serum of healthy and Piscirickettsia salmonis infected Atlantic salmon in order to evaluate the effect of infection on EV secretion. P. salmonis is facultative intracellular bacterium that causes a systemic infection disease in farmed salmonids. EVs isolated from both infected and non-infected fish had an average diameter of 230–300 nm, as confirmed by transmission electron microscopy, nanoparticle tracking, and flow cytometry. Mass spectrometry identified 180 proteins in serum EVs from both groups of fish. Interestingly, 35 unique proteins were identified in serum EVs isolated from the fish infected with P. salmonis. These unique proteins included proteasomes subunits, granulins, and major histocompatibility class I and II. Our results suggest that EV release could be part of a mechanism in which host stimulatory molecules are released from infected cells to promote an immune response.