Circular RNA CircEZH2 Suppresses Transmissible Gastroenteritis Coronavirus-induced Opening of Mitochondrial Permeability Transition Pore via Targeting MiR-22 in IPEC-J2

Polygonum cillinerve polysaccharide inhibits transmissible gastroenteritis virus by regulating microRNA-181

Transmissible gastroenteritis virus (TGEV) is an important pathogen capable of altering the expression profile of cellular miRNA. In this study, the potential of Polygonum cillinerve polysaccharide (PCP) to treat TGEV-infected piglets was evaluated through in vivo experiments. High-throughput sequencing technology was employed to identify 9 up-regulated and 17 down-regulated miRNAs during PCP-mediated inhibition of TGEV infection in PK15 cells. Additionally, miR-181 was found to be associated with target genes of key proteins in the apoptosis pathway. PK15 cells were treated with various concentrations of PCP following transfection with miR-181 mimic or inhibitor. Real-time PCR assessed the impact on TGEV replication, while electron microscopy (TEM) and Hoechst fluorescence staining evaluated cellular functionality. Western blot analysis was utilized to assess the expression of key signaling factors-cytochrome C (cyt C), caspase 9, and P53-in the apoptotic signaling pathway. The results showed that compared with the control group, 250 μg/mL PCP significantly inhibited TGEV gRNA replication and gene N expression (P < 0.01). Microscopic examination revealed uniform cell morphology and fewer floating cells in PCP-treated groups (250 and 125 μg/mL). TEM analysis showed no typical virus structure in the 250 μg/mL PCP group, and apoptosis staining indicated a significant reduction in apoptotic cells at this concentration. Furthermore, PCP may inhibit TGEV-induced apoptosis via the Caspase-dependent mitochondrial pathway following miR-181 transfection. These findings provide a theoretical basis for further exploration into the mechanism of PCP's anti-TGEV properties.

CircMYO1B/miR-155 pathway is a common mechanism of stress-induced immunosuppression affecting immune response to three vaccines in chicken

Stress-induced immunosuppression (SIIS) can weaken the immune response effect of poultry vaccination, and bring huge hidden dangers and economic losses to the poultry industry. However, the detailed molecular mechanisms are still not fully understood. Unveiling the common mechanism of SIIS affecting the immune response to different vaccines is critical for detecting and minimizing the losses caused by SIIS. This study used glucocorticoid dexamethasone (Dex) to simulate SIIS, and three classic avian vaccines (including avian influenza virus (AIV), Newcastle disease virus (NDV), and infectious bursal disease virus (IBDV)) were used to induce immune responses in chicken. Quantitative real-time PCR (qRT-PCR) revealed the expression characteristics and functions of circMYO1B and miR-155 in the processes of SIIS affecting the immune response to the aforementioned avian vaccines, as well as their targeted regulatory relationship. Subsequent bioinformatics analysis predicted FOS, one of the potential target genes of miR-155. The results showed that circMYO1B/miR-155 pathway served as a key common mechanism by which SIIS affected the immune response to the three vaccines. Both heart and proventriculus appeared to be the crucial tissues for this process, with five days post immunization (dpi) emerging as the primary time of interest. Moreover, mitogen-activated protein kinase (MAPK) signaling system played a key role in modulating the immune response subsequent to SIIS administration. Our findings provide new insights into the immune function of competitive endogenous RNA (ceRNA), which have important function in the detection and treatment of SIIS affecting vaccine immunity.

The Roles of CircRNAs in Mitochondria

Mitochondria participate in varieties of cellular events. It is widely accepted that human mitochondrial genome encodes 13 proteins, 2 rRNAs, and 22 tRNAs. Gene variation derived from human nuclear genome cannot completely explain mitochondrial diseases. The advent of high-throughput sequencing coupled with novel bioinformatic analyses decode the complexity of mitochondria-derived transcripts. Recently, circular RNAs (circRNAs) from both human mitochondrial genome and nuclear genome have been found to be located at mitochondria. Studies about the roles and molecular mechanisms underlying trafficking of the nucleus encoded circRNAs to mitochondria and mitochondria encoded circRNAs to the nucleus or cytoplasm in mammals are only beginning to emerge. These circRNAs have been associated with a variety of diseases, especially cancers. Here, we discuss the emerging field of mitochondria-located circRNAs by reviewing their identification, expression patterns, regulatory roles, and functional mechanisms. Mitochondria-located circRNAs have regulatory roles in cellular physiology and pathology. We also highlight future perspectives and challenges in studying mitochondria-located circRNAs, as well as their potential biomedical applications.

MicroRNA-22-3p displaces critical host factors from the 5' UTR and inhibits the translation of Coxsackievirus B3 RNA

Coxsackievirus B3 (CVB3) is known to cause acute myocarditis and pancreatitis in humans. We investigated the microRNAs (miRNAs) that can potentially govern the viral life cycle by binding to the untranslated regions (UTRs) of CVB3 RNA. MicroRNA-22-3p was short-listed, as its potential binding site overlapped with the region crucial for recruiting internal ribosome entry site trans-acting factors (ITAFs) and ribosomes. We demonstrate that miR-22-3p binds CVB3 5' UTR, hinders recruitment of key ITAFs on viral mRNA, disrupts the spatial structure required for ribosome recruitment, and ultimately blocks translation. Likewise, cells lacking miR-22-3p exhibited heightened CVB3 infection compared to wild type, confirming its role in controlling infection. Interestingly, miR-22-3p level was found to be increased at 4 hours post-infection, potentially due to the accumulation of viral 2A protease in the early phase of infection. 2Apro enhances the miR-22-3p level to dislodge the ITAFs from the SD-like sequence, rendering the viral RNA accessible for binding of replication factors to switch to replication. Furthermore, one of the cellular targets of miR-22-3p, protocadherin-1 (PCDH1), was significantly downregulated during CVB3 infection. Partial silencing of PCDH1 reduced viral replication, demonstrating its proviral role. Interestingly, upon CVB3 infection in mice, miR-22-3p level was found to be downregulated only in the small intestine, the primary target organ, indicating its possible role in influencing tissue tropism. It appears miR-22-3p plays a dual role during infection by binding viral RNA to aid its life cycle as a viral strategy and by targeting a proviral protein to restrict viral replication as a host response.IMPORTANCECVB3 infection is associated with the development of end-stage heart diseases. Lack of effective anti-viral treatments and vaccines for CVB3 necessitates comprehensive understanding of the molecular players during CVB3 infection. miRNAs have emerged as promising targets for anti-viral strategies. Here, we demonstrate that miR-22-3p binds to 5' UTR and inhibits viral RNA translation at the later stage of infection to promote viral RNA replication. Conversely, as host response, it targets PCDH1, a proviral factor, to discourage viral propagation. miR-22-3p also influences CVB3 tissue tropism. Deciphering the multifaced role of miR-22-3p during CVB3 infection unravels the necessary molecular insights, which can be exploited for novel intervening strategies to curb infection and restrict viral pathogenesis.

Advances in the understanding of circRNAs that influence viral replication in host cells

Circular RNAs (circRNAs) are non-coding RNAs discovered in recent years, which are produced by back-splicing involving the 3' and 5' ends of RNA molecules. There is increasing evidence that circRNAs have important roles in cancer, neurological diseases, cardiovascular and cerebrovascular diseases, and other diseases. In addition, host circRNAs and virus-encoded circRNAs participate in the body's immune response, with antiviral roles. This review summarizes the mechanisms by which host and viral circRNAs interact during the host immune response. Comprehensive investigations have revealed that host circRNAs function as miRNA sponges in a particular manner, primarily by inhibiting viral replication. Viral circRNAs have more diverse functions, which generally involve promoting viral replication. In addition, in contrast to circRNAs from RNA viruses, circRNAs from DNA viruses can influence host cell migration, proliferation, and apoptosis, along with their effects on viral replication. In summary, circRNAs have potential as diagnostic and therapeutic targets, offering a foundation for the diagnosis and treatment of viral diseases.

Integrated analysis of microRNA and messenger RNA expression profiles reveals functional microRNA in infectious bovine rhinotracheitis virus-induced mitochondrial damage in Madin-Darby bovine kidney cells

BACKGROUND

Studies have confirmed that Infectious bovine rhinotracheitis virus (IBRV) infection induces mitochondrial damage. MicroRNAs (miRNAs) are a class of noncoding RNA molecules, which are involved in various biological processes and pathological changes associated with mitochondrial damage. It is currently unclear whether miRNAs participate in IBRV-induced mitochondrial damage in Madin-Darby bovine kidney (MDBK) cells.

RESULTS

In the present study, we used high-throughput sequencing technology, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis to screen for mitochondria-related miRNAs and messenger RNAs (mRNAs). In total, 279 differentially expressed miRNAs and 832 differentially expressed mRNAs were identified in 6 hours (IBRV1) versus 24 hours (IBRV2) after IBRV infection in MDBK cells. GO and KEGG enrichment analysis revealed that 42 differentially expressed mRNAs and 348 target genes of differentially expressed miRNAs were correlated with mitochondrial damage, and the miRNA-mitochondria-related target genes regulatory network was constructed to elucidate their potential regulatory relationships. Among the 10 differentially expressed miRNAs, 8 showed expression patterns consistent with the high-throughput sequencing results. Functional validation results showed that overexpression of miR-10a and miR-182 aggravated mitochondrial damage, while inhibition of miR-10a and miR-182 alleviated mitochondrial damage.

CONCLUSIONS

This study not only revealed the expression changes of miRNAs and mRNAs in IBRV-infected MDBK cells, but also revealed possible biological regulatory relationship between them. MiR-10a and miR-182 may have the potential to be developed as biomarkers for the diagnosis and treatment of IBRV. Together, Together, these data and analyses provide additional insights into the roles of miRNA and mRNA in IBRV-induced mitochondria damage.

Functional Involvement of circRNAs in the Innate Immune Responses to Viral Infection

Effective viral clearance requires fine-tuned immune responses to minimize undesirable inflammatory responses. Circular RNAs (circRNAs) are a class of non-coding RNAs that are abundant and highly stable, formed by backsplicing pre-mRNAs, and expressed ubiquitously in eukaryotic cells, emerging as critical regulators of a plethora of signaling pathways. Recent progress in high-throughput sequencing has enabled a better understanding of the physiological and pathophysiological functions of circRNAs, overcoming the obstacle of the sequence overlap between circRNAs and their linear cognate mRNAs. Some viruses also encode circRNAs implicated in viral replication or disease progression. There is increasing evidence that viral infections dysregulate circRNA expression and that the altered expression of circRNAs is critical in regulating viral infection and replication. circRNAs were shown to regulate gene expression via microRNA and protein sponging or via encoding small polypeptides. Recent studies have also highlighted the potential role of circRNAs as promising diagnostic and prognostic biomarkers, RNA vaccines and antiviral therapy candidates due to their higher stability and lower immunogenicity. This review presents an up-to-date summary of the mechanistic involvement of circRNAs in innate immunity against viral infections, the current understanding of their regulatory roles, and the suggested applications.

The potential role and mechanism of circRNA/miRNA axis in cholesterol synthesis

Cholesterol levels are an initiating risk factor for atherosclerosis. Many genes play a central role in cholesterol synthesis, including HMGCR, SQLE, HMGCS1, FDFT1, LSS, MVK, PMK, MVD, FDPS, CYP51, TM7SF2, LBR, MSMO1, NSDHL, HSD17B7, DHCR24, EBP, SC5D, DHCR7, IDI1/2. Especially, HMGCR, SQLE, FDFT1, LSS, FDPS, CYP51, and EBP are promising therapeutic targets for drug development due to many drugs have been approved and entered into clinical research by targeting these genes. However, new targets and drugs still need to be discovered. Interestingly, many small nucleic acid drugs and vaccines were approved for the market, including Inclisiran, Patisiran, Inotersen, Givosiran, Lumasiran, Nusinersen, Volanesorsen, Eteplirsen, Golodirsen, Viltolarsen, Casimersen, Elasomeran, Tozinameran. However, these agents are all linear RNA agents. Circular RNAs (circRNAs) may have longer half-lives, higher stability, lower immunogenicity, lower production costs, and higher delivery efficiency than these agents due to their covalently closed structures. CircRNA agents are developed by several companies, including Orna Therapeutics, Laronde, and CirCode, Therorna. Many studies have shown that circRNAs regulate cholesterol synthesis by regulating HMGCR, SQLE, HMGCS1, ACS, YWHAG, PTEN, DHCR24, SREBP-2, and PMK expression. MiRNAs are essential for circRNA-mediated cholesterol biosynthesis. Notable, the phase II trial for inhibiting miR-122 with nucleic acid drugs has been completed. Suppressing HMGCR, SQLE, and miR-122 with circRNA_ABCA1, circ-PRKCH, circEZH2, circRNA-SCAP, and circFOXO3 are the promising therapeutic target for drug development, specifically the circFOXO3. This review focuses on the role and mechanism of the circRNA/miRNA axis in cholesterol synthesis in the hope of providing knowledge to identify new targets.

circEZH2E2 /E3 is a dual suppressor of miR363/miR708 to promote EZH2 expression and prostate cancer progression

The histone methyltransferase enhancer of zeste homolog 2 (EZH2) is overexpressed in a variety of malignancies including prostate cancer (PCa) and may play important roles in tumor progression. Gene copy number gains, enhanced transcription, and a few circRNAs have been reported to upregulate EZH2. It was not known whether EZH2 itself generates circRNAs that promote its own expression. We here report the identification of circEZH2^E2/E3 that is derived from exons 2 and 3 of the EZH2 gene and overexpressed in PCa. We show that circEZH2^E2/E3 functions as a dual inhibitor for both miR363 and miR708 that target the EZH2 3'UTR and CDS, respectively, resulting in the upregulation of EZH2 expression and hence the downregulation of EZH2-repressed genes (e.g., CDH1 and DAB2IP), and enhancement of PCa cell proliferation, migration, invasion, and xenograft PCa growth. Overexpression of circEZH2^E2/E3 is significantly correlated with higher tumor grade, tumor progression, and unfavorable progression-free and disease-specific survival in PCa patients. These findings show a novel autoenhancing EZH2-circEZH2^E2/E3 -miR363/miR708-EZH2 regulatory loop, by which circEZH2^E2/E3 plays important roles in PCa tumorigenesis and progression by upregulating EZH2, and may have potential diagnostic, prognostic, and therapeutic uses in PCa management.

New insights on circular RNAs and their potential applications as biomarkers, therapeutic agents, and preventive vaccines in viral infections: with a glance at SARS-CoV-2

The occurrence of viral infections and approaches to handling them are very challenging and require prompt diagnosis and timely treatment. Recently, genomic medicine approaches have come up with the discovery of the competing endogenous RNA (ceRNA) network, including microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs) on the basis of gene silencing. CircRNAs, as a group of non-encoded RNAs, make a loop-like structure by back-splicing through 3′ and 5′ ends. They are stable, abundant, specific, and highly conserved and can be quickly generated at large scales in vitro. CircRNAs have the potential to contribute in several cellular processes in a way that some serve as microRNA sponges, cellular transporters, protein-binding RNAs, transcriptional regulators, and immune system modulators. CircRNAs can even play an important role in modulating antiviral immune responses. In the present review, circRNAs’ biogenesis, function, and biomarker and therapeutic potential as well as their prospective applications as vaccines against viral infections such as SARS-CoV-2 are explained. By considering their unique properties, their potential to be used as novel vaccines, biomarkers, and a therapeutic approach appears possible.

circEZH2 inhibits opening of mitochondrial permeability transition pore via interacting with PiC and up-regulating RSAD2

Transmissible gastroenteritis virus (TGEV) infection can lead to mitochondrial damage in porcine intestinal epithelial cells-jejunum 2 (IPEC-J2) cell line. The abnormal opening of mitochondrial permeability transition pore (mPTP) is the most important factor for mitochondrial damage. We previously demonstrated that circEZH2 could inhibit the abnormal opening of mPTP by binding miR-22. However, circEZH2 binding to miR-22 cannot completely enable mPTP opening to recover to normal level compared with the control group. So, we assume that circEZH2 also regulates the mPTP opening in other ways. To prove it, we identified the differentially expressed proteins (DEPs) caused by circEZH2 and circEZH2-interacting proteins by liquid chromatography-tandem mass spectrometry (LC-MS/MS). It turns out there are 123 DEPs (0.83 ≤ fold change ≥ 1.2) upon overexpression circEZH2 and 200 proteins interacted with circEZH2. The kyoto encyclopedia of genes and genomes (KEGG) analysis, gene ontology (GO) analysis, subcellular localization analysis, and protein interaction network results show that the DEPs and circEZH2-interacting proteins may involve in the regulation of mPTP opening. RNA immunoprecipitation (RIP) assay and flow cytometry (FCM) results indicate that circEZH2 can inhibit the opening of mPTP by interacting with Pi carrier (PiC, also named SLC25A3). Quantitative real-time polymerase chain reaction (qRT-PCR), western blotting, and FCM results reveal that circEZH2 can inhibit mPTP opening by promoting the expression of radical s-adenosyl methionine domain-containing protein 2 (RSAD2). In addition, PiC can promote RSAD2 expression. The data indicate that circEZH2 inhibits TGEV-induced mPTP opening by interacting with PiC and upregulating RSAD2.

The Effects of Swine Coronaviruses on ER Stress, Autophagy, Apoptosis, and Alterations in Cell Morphology

Swine coronaviruses include the following six members, namely porcine epidemic diarrhea virus (PEDV), transmissible gastroenteritis virus (TGEV), porcine delta coronavirus (PDCoV), swine acute diarrhea syndrome coronavirus (SADS-CoV), porcine hemagglutinating encephalomyelitis virus (PHEV), and porcine respiratory coronavirus (PRCV). Clinically, PEDV, TGEV, PDCoV, and SADS-CoV cause enteritis, whereas PHEV induces encephalomyelitis, and PRCV causes respiratory disease. Years of studies reveal that swine coronaviruses replicate in the cellular cytoplasm exerting a wide variety of effects on cells. Some of these effects are particularly pertinent to cell pathology, including endoplasmic reticulum (ER) stress, unfolded protein response (UPR), autophagy, and apoptosis. In addition, swine coronaviruses are able to induce cellular changes, such as cytoskeletal rearrangement, alterations of junctional complexes, and epithelial-mesenchymal transition (EMT), that render enterocytes unable to absorb nutrients normally, resulting in the loss of water, ions, and protein into the intestinal lumen. This review aims to describe the cellular changes in swine coronavirus-infected cells and to aid in understanding the pathogenesis of swine coronavirus infections. This review also explores how the virus exerted subcellular and molecular changes culminating in the clinical and pathological findings observed in the field.

A new circular RNA-encoded protein BIRC6-236aa inhibits transmissible gastroenteritis virus (TGEV)-induced mitochondrial dysfunction

Transmissible gastroenteritis virus (TGEV), a member of the coronavirus family, is the pathogen responsible for transmissible gastroenteritis, which results in mitochondrial dysfunction in host cells. Previously, we identified 123 differentially expressed circular RNAs (cRNA)from the TGEV-infected porcine intestinal epithelial cell line jejunum 2 (IPEC-J2). Previous bioinformatics analysis suggested that, of these, circBIRC6 had the potential to regulate mitochondrial function. Furthermore, mitochondrial permeability transition, a key step in the process of mitochondrial dysfunction, is known to be caused by abnormal opening of mitochondrial permeability transition pores (mPTPs) regulated by the voltage-dependent anion-selective channel protein 1 (VDAC)–Cyclophilin D (CypD) complex. Therefore, in the present study, we investigated the effects of circBIRC6-2 on mitochondrial dysfunction and opening of mPTPs. We found that TGEV infection reduced circBIRC6-2 levels, which in turn reduced mitochondrial calcium (Ca²⁺) levels, the decrease of mitochondrial membrane potential, and opening of mPTPs. In addition, we also identified ORFs and internal ribosomal entrance sites within the circBIRC6-2 RNA. We demonstrate circBIRC6-2 encodes a novel protein, BIRC6-236aa, which we show inhibits TGEV-induced opening of mPTPs during TGEV infection. Mechanistically, we identified an interaction between BIRC6-236aa and VDAC1, suggesting that BIRC6-236aa destabilizes the VDAC1–CypD complex. Taken together, the results suggest that the novel protein BIRC6-236aa encoded by cRNA circBIRC6-2 inhibits mPTP opening and subsequent mitochondrial dysfunction by interacting with VDAC1.

A Previously Undiscovered Circular RNA, circTNFAIP3, and Its Role in Coronavirus Replication

Circular RNAs (circRNAs) are a newly discovered class of noncoding RNAs (ncRNAs) present in various tissues and cells. However, the functions of most circRNAs have not been verified experimentally. Here, using deltacoronavirus as a model, differentially expressed circRNAs in cells with or without deltacoronavirus infection were analyzed by RNA sequencing to characterize the cellular responses to RNA virus infection. More than 57,000 circRNA candidates were detected, and seven significantly dysregulated circRNAs were quantitated by real-time reverse transcription-PCR. We discovered a previously unidentified circRNA derived from the TNFAIP3 gene, named circTNFAIP3, which is distributed and expressed widely in various tissues. RNA viruses, including deltacoronaviruses, rather than DNA viruses tend to activate the expression of endogenous circTNFAIP3. Overexpression of circTNFAIP3 promoted deltacoronavirus replication by reducing the apoptosis, while silencing of circTNFAIP3 inhibited deltacoronavirus replication by enhancing the apoptosis. In summary, our work provides useful circRNA-related information to facilitate investigation of the underlying mechanism of deltacoronavirus infection and identifies a novel circTNFAIP3 that promotes deltacoronavirus replication via regulating apoptosis.

The potential use of microRNAs as a therapeutic strategy for SARS-CoV-2 infection

Coronavirus disease 2019 (COVID-19) is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). To date, there is no effective therapeutic approach for treating SARS-CoV-2 infections. MicroRNAs (miRNAs) have been recognized to target the viral genome directly or indirectly, thereby inhibiting viral replication. Several studies have demonstrated that host miRNAs target different sites in SARS-CoV-2 RNA and constrain the production of essential viral proteins. Furthermore, miRNAs have lower toxicity, are more immunogenic, and are more diverse than protein-based and even plasmid-DNA-based therapeutic agents. In this review, we emphasize the role of miRNAs in viral infection and their potential use as therapeutic agents against COVID-19 disease. The potential of novel miRNA delivery strategies, especially EDV™ nanocells, for targeting lung tissue for treatment of SARS-CoV-2 infection is also discussed.

Transcriptome analysis reveals that hydrogen sulfide exposure suppresses cell proliferation and induces apoptosis through ciR-PTPN23/miR-15a/E2F3 signaling in broiler thymus

The immune organs, like thymus, are one of the targets of hydrogen sulfide (H₂S). Previously we reported that H₂S induced the differential expression of mRNAs that implicating apoptosis in thymus, however, the roles of noncoding RNAs (ncRNAs) in H₂S-induced thymus injury are still unknown. Pollution gases could alter the expression of ncRNAs, which have been shown to play important roles in many physiological and pathophysiological processes, including immune activity. This study revealed that H₂S exposure induced 9 differentially expressed circRNAs and 15 differentially expressed miRNAs in chicken thymus. Furthermore, the circRNA - miRNA - mRNA network was constructed. We discovered that circR-PTPN23 - miR-15a - E2F3 was involved in the cell cycle and apoptosis. Further, an in vitro H₂S exposure model was established using HD11 cell line and demonstrated that H₂S suppressed cell proliferation and induced apoptosis. Moreover, ciR-PTPN23 and E2F3 were downregulated, but miR-15a was upregulated in both the thymus and HD11 cell line after H₂S exposure. Bioinformatics analysis revealed that ciR-PTPN23 directly bound to miR-15a and that E2F3 was the target gene of miR-15a. Knocking down ciR-PTPN23 suppressed HD11 proliferation and caused G1 arrest and apoptosis, however, this phenomenon could be partially reversed by ciR-PTPN23 overexpression or miR-15a silencing. In summary, the ciR-PTPN23 - miR-15a - E2F3 axis was involved in H₂S-induced cell proliferation suppression and apoptosis.

Transmissible gastroenteritis virus ORF3b up-regulates miR-885-3p to counteract TNF-α production via inhibiting NF-κB pathway

Transmissible gastroenteritis (TGE) is an acute viral disease and characterized as severe acute inflammation response that leads to diarrhea, vomiting, and high lethality of piglets. Transmissible gastroenteritis virus (TGEV), a member of coronavirus, is the pathogen of TGE. We previously found NF-κB pathway was activated and 65 miRNAs were changed in response to inflammation caused by TGEV in cell line porcine intestinal epithelial cells-jejunum 2 (IPEC-J2). Bioinformatics results showed that these altered miRNAs were relevant to inflammation. In this study, the candidate targets of differentially expressed (DE) miRNAs were predicted and analyzed using Kyoto Encyclopedia of Genes and Genomes (KEGG) database. Based on the results of KEGG analysis, miR-885-3p might participate in regulating activation of NF-κB pathway and TNF pathway. To study the function of miR-885-3p, miR-885-3p mimics and inhibitors were artificially synthesized and respectively used for overexpression and silence of miR-885-3p in cells. Our results showed that miR-885-3p inhibited NF-κB signaling pathway and tumor necrosis factor-α (TNF-α) production. B-cell CLL/lymphoma 10 (Bcl-10) was identified as the target of miR-885-3p, and promoted NF-κB pathway activation and TNF-α production. It was found that TGEV open reading frame 3b (TGEV-ORF3b) suppressed Bcl-10 expression, activation of NF-κB pathway, and TNF-α production by uniquely up-regulated miR-885-3p expression. Overall, the results indicated that TGEV-ORF3b counteracted NF-κB pathway and TNF-α via regulating miR-885-3p and Bcl-10.

The effect of mitochondrial transplantation therapy from different gender on inhibiting cell proliferation of malignant melanoma

Today mitochondria are considered much more than a energy plant in cells. Mitochondrial transplantation therapy has been an active research area for treating mitochondria-associated diseases from animal studies to clinical trials. However, the specific mechanism involved in the anti-tumor activity of healthy mitochondria remain to be characterized. Here we investigate the signal mechanism and gender difference of mitochondrial transplantation therapy against malignant melanoma. In the study, we administrated intact mitochondria extracted from mouse livers respectively to the mice bearing malignantly subcutaneous and metastatic melanoma, and identified the signal mechanism responsible for the mitochondrial treatment through transcriptomic analysis. Meanwhile, the efficiency of female mitochondria and male mitochondria was compared in the cultured melanoma cells and transplanted melanoma in mice. The results suggested that the mitochondria significantly inhibited the tumor cell proliferation in vitro through cell cycle arrest and induction of cell apoptosis. In the melanoma-bearing mice, the mitochondria retard the tumor growth and lung migration, and the transcriptomic analysis indicated that general chromosome silencing was strongly associated with the mitochondria against melanoma after the mitochondrial transplantation on the metastasis melanoma. Moreover, the anti-tumor activity of mitochondria from female animals was more efficient in comparison to the males, and the female mitochondria could probably induce more persuasive mitochondria-nuclear communication than the mitochondria from male mice. The study identifies the anti-tumor mechanism of the mitochondrial transplantation therapy, and provides a novel insight into the effect of mitochondria from different gender.

Research progress of circRNA as a biomarker of sepsis: a narrative review

Objective

Explore the possibility of circRNAs as markers of sepsis.

Background

Sepsis is an abnormal immune response of our body to infection that can lead to organ failure and death. Although the research on sepsis has been extensive in the past few years, sepsis-associated morbidity and mortality are still increasing. Early diagnosis and early treatment are important for patients with sepsis. Although many markers, including procalcitonin and C-reactive protein, have been proposed as diagnostic indicators of sepsis, there are still challenges in the early diagnosis and treatment of sepsis due to the lack of sensitivity and specificity of these substances. Recently, a large number of studies have found that circular RNAs (circRNAs) participate in a variety of biological functions, such as immune response, regulating the expression of miRNAs, and they are closely related to the occurrence and development of many diseases, including sepsis. However, the clear mechanism of the role of circRNAs has not been fully elucidated. An increasing number of studies have confirmed that circRNAs have potential in the diagnosis and treatment of sepsis. By studying the regulatory mechanism of circRNAs in sepsis, we can search for new molecular intervention targets for the treatment of sepsis, which is conducive to the development of new molecular therapeutic drugs for sepsis.

Methods

In the present study, we summarize and analyze the role of circRNAs in the pathogenesis of sepsis and discuss the possibility of circRNA as a biomarker for the diagnosis of sepsis.

Conclusions

The biological characteristics of circRNAs and their role in the occurrence and development of sepsis make them possible markers of sepsis.

The role of circular RNAs in viral infection and related diseases

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CircRNAs are formed by pre-mRNA through “back-splicing”.

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CircRNAs regulate host immune response and virus replication.

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CircRNAs have potential as diagnostic markers or treatment targets for viral infection.

Circular RNAs (circRNAs) are a class of non-coding RNAs with a special covalently closed circular structure, which is formed by precursor mRNA (pre-mRNA) through “back-splicing”. CircRNAs are more stable than linear RNAs because they are resistant to exoribonucleases. Viral infections often cause abnormal expression of circRNAs, which could serve as novel biomarkers for the diagnosis of viral infections by detecting specific circRNAs in cells, body fluids, or tissues. CircRNAs also play a critical role in regulating host immune response and virus replication. Here, we reviewed the production and function of circRNAs, mainly focusing on their regulation on virus infection, to provide novel insights into the potential role of circRNAs as diagnostic marker or treatment targets for viral infection.

Circular RNAs: New Epigenetic Signatures in Viral Infections

Covalent closed circular RNAs (circRNAs) can act as a bridge between non-coding RNAs and coding messenger RNAs. CircRNAs are generated by a back-splicing mechanism during post-transcriptional processing and are abundantly expressed in eukaryotic cells. CircRNAs can act via the modulation of RNA transcription and protein production, and by the sponging of microRNAs (miRNAs). CircRNAs are now thought to be involved in many different biological and pathological processes. Some studies have suggested that the expression of host circRNAs is dysregulated in several types of virus-infected cells, compared to control cells. It is highly likely that viruses can use these molecules for their own purposes. In addition, some viral genes are able to produce viral circRNAs (VcircRNA) by a back-splicing mechanism. However, the viral genes that encode VcircRNAs, and their functions, are poorly studied. In this review, we highlight some new findings about the interaction of host circRNAs and viral infection. Moreover, the potential of VcircRNAs derived from the virus itself, to act as biomarkers and therapeutic targets is summarized.

The emerging role and significance of circular RNAs in viral infections and antiviral immune responses: possible implication as theranostic agents

Circular RNAs (circRNAs) are ubiquitously expressed, covalently closed rings, produced by pre-mRNA splicing in a reversed order during post-transcriptional processing. Circularity endows 3'-5'-linked circRNAs with stability and resistance to exonucleolytic degradation which raises the question whether circRNAs may be relevant as potential therapeutic targets or agents. High stability in biological systems is the most remarkable property and a major criterion for why circRNAs could be exploited for a range of RNA-centred medical applications. Even though various biological roles and regulatory functions of circRNAs have been reported, their in-depth study is challenging because of their circular structure and sequence-overlap with linear mRNA counterparts. Moreover, little is known about their role in viral infections and in antiviral immune responses. We believe that an in-depth and detailed understanding of circRNA mediated viral protein regulations will increase our knowledge of the biology of these novel molecules. In this review, we aimed to provide a comprehensive basis and overview on the biogenesis, significance and regulatory roles of circRNAs in the context of antiviral immune responses and viral infections including hepatitis C virus infection, hepatitis B virus infection, hepatitis delta virus infection, influenza A virus infection, Epstein-Barr virus infection, kaposi's sarcoma herpesvirus infection, human cytomegalovirus infection, herpes simplex virus infection, human immunodeficiency virus infection, porcine epidemic diarrhoea virus infection, ORF virus infection, avian leukosis virus infection, simian vacuolating virus 40 infection, transmissible gastroenteritis coronavirus infection, and bovine viral diarrhoea virus infection. We have also discussed the critical regulatory role of circRNAs in provoking antiviral immunity, providing evidence for implications as therapeutic agents and as diagnostic markers.

Identification, characterization, and functional prediction of circular RNAs in maize

Circular RNAs (circRNAs) are a new type of intracellular regulator that have been widely identified in animals and plants by high-throughput sequencing. However, there are still few functional studies on circRNAs in plants. To better understand maize circRNAs and their potential functions, we identified 1199 circRNAs in maize from RiboMinus RNA-Seq transcriptome data, and found distinct features of splicing site selection bias, longer flanking introns, and miniature inverted-repeat transposable element (MITE) insertions in flanking introns in maize circRNAs compared to other plant circRNAs. In total, 31 and 36 orthologous circRNAs were identified in rice and maize, respectively, but the orthologous parental genes could not produce orthologous circRNAs, mostly because of long-sequence insertions/deletions at flanking introns and approximately 24.3% of them contained MITE sequences. The majority of maize circRNAs showed high diversity of expression under different treatments and/or in different genetic backgrounds, implying that circRNAs could be involved in various regulatory networks. Twenty-six ecircRNAs were predicted to contain one or more target mimics, and 229 circRNAs had high coding potential, indicating that circRNAs could perform peptide-encoding functions in plants. These results will broaden understanding of the roles of circRNAs in plants and support further functional work on maize.