microRNA-4331 Promotes Transmissible Gastroenteritis Virus (TGEV)-induced Mitochondrial Damage Via Targeting RB1, Upregulating Interleukin-1 Receptor Accessory Protein (IL1RAP), and Activating p38 MAPK Pathway In Vitro

The proteomic analysis uncovers the cellular responses to the African swine fever virus membrane proteins p54, p17, and pB117L

African swine fever virus (ASFV) infection causes African swine fever (ASF), a highly contagious and fatal disease that poses severe threat to swine production. To gain insights into the host responses to ASFV, we generated recombinant adenovirus Ad5 expressing viral membrane proteins p54, p17, and pB117L individually and infected an alveolar cell line, 3D4/21, with these recombinant viruses. Then, the cell lysates were analyzed using label-free quantification proteomic analysis method. A total of 2158 differentially expressed proteins (DEPs) were identified, of which 817, 466, and 875 proteins were from Ad5-p54-, Ad5-p17-, Ad5-pB117L-infected 3D4/21 cells, respectively. Gene Ontology (GO) classification and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis revealed distinct yet interconnecting patterns of protein interaction networks. Specifically, the Ad5-p54 virus infection enriched the DEPs primarily involved in the metabolic pathways, endocytosis, adherens junction, and SNARE interactions in vesicular transport. The Ad5-p17 virus infection enriched the DEPs in endocytosis, ubiquitin-mediated proteolysis, N-Glycan biosynthesis, and apoptosis, while the Ad5-pB117L virus infection enriched the DEPs in metabolic pathways, endocytosis, oxidative phosphorylation, and focal adhesion. In summary, these results provide a comprehensive proteinomics analysis of the cellular responses to three ASFV membrane proteins, thus facilitating our understanding of ASFV pathogenesis.

Emerging role of microRNAs and long non-coding RNAs in COVID-19 with implications to therapeutics

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection which is commonly known as COVID-19 (COronaVIrus Disease 2019) has creeped into the human population taking tolls of life and causing tremendous economic crisis. It is indeed crucial to gain knowledge about their characteristics and interactions with human host cells. It has been shown that the majority of our genome consists of non-coding RNAs. Non-coding RNAs including micro RNAs (miRNAs) and long non-coding RNAs (lncRNAs) display significant roles in regulating gene expression in almost all cancers and viral diseases. It is intriguing that miRNAs and lncRNAs remarkably regulate the function and expression of major immune components of SARS-CoV-2. MiRNAs act via RNA interference mechanism in which they bind to the complementary sequences of the viral RNA strand, inducing the formation of silencing complex that eventually degrades or inhibits the viral RNA and viral protein expression. LncRNAs have been extensively shown to regulate gene expression in cytokine storm and thus emerges as a critical target for COVID-19 treatment. These lncRNAs also act as competing endogenous RNAs (ceRNAs) by sponging miRNAs and thus affecting the expression of downstream targets during SARS-CoV-2 infection. In this review, we extensively discuss the role of miRNAs and lncRNAs, describe their mechanism of action and their different interacting human targets cells during SARS-CoV-2 infection. Finally, we discuss possible ways how an interference with their molecular function could be exploited for new therapies against SARS-CoV-2.

An atlas of expression quantitative trait loci of microRNA in longissimus muscle of eight-way crossbred pigs

MicroRNAs (miRNAs) are key regulators of myocyte development and traits, yet insight into the genetic basis of variation in miRNA expression is still limited. Here, we present a systematic analysis of expression quantitative trait loci (eQTL) for miRNA profiling in longissimus muscle of pigs from an eight-breed crossed heterogeneous population. By integrating whole-genome sequencing and miRNAomics data, we map 54 cis- and 292 trans-eQTLs at high resolution that are associated with the expression of 54 and 92 miRNAs, respectively. Twenty-three trans-acting loci are identified to affect the expression of nine myomiRs (known muscle-specific miRNAs). MiRNAs in mammalian conserved miRNA clusters are found to be subjected to regulation by shared cis-eQTLs, while the expression of mature miRNA-5p/-3p counterparts is more likely to be regulated by different cis-eQTLs. Fine mapping and bioinformatics analyses pinpoint the peak cis-eSNP of miR-4331-5p, rs344650810, which is located in its seed region, as a causal variant for the changes in expression and function of this miRNA. Additionally, rs344650810 is significantly (P < 0.01) correlated with the density and percentage of type I muscle fibers. Altogether, this study provides a comprehensive atlas of miRNA-eQTLs in porcine skeletal muscle and new insights into regulatory mechanisms of miRNA expression.

Identification of Potential miRNA-mRNA Regulatory Network Associated with Pig Growth Performance in the Pituitaries of Bama Minipigs and Landrace Pigs

Pig growth performance is one of the criteria for judging pork production and is influenced by genotype and external environmental factors such as feeding conditions. The growth performance of miniature pigs, such as Bama minipigs, differs considerably from that of the larger body size pigs, such as Landrace pigs, and can be regarded as good models in pig growth studies. In this research, we identified differentially expressed genes in the pituitary gland of Bama minipigs and Landrace pigs. Through the pathway enrichment analysis, we screened the growth-related pathways and the genes enriched in the pathways and established the protein-protein interaction network. The RNAHybrid algorithm was used to predict the interaction between differentially expressed microRNAs and differentially expressed mRNAs. Four regulatory pathways (Y-82-ULK1/CDKN1A, miR-4334-5p-STAT3/PIK3R1/RPS6KA3/CAB39L, miR-4331-SCR/BCL2L1, and miR-133a-3p-BCL2L1) were identified via quantitative real-time PCR to detect the expression and correlation of candidate miRNAs and mRNAs. In conclusion, we revealed potential miRNA-mRNA regulatory networks associated with pig growth performance in the pituitary glands of Bama minipigs and Landrace pigs, which may help to elucidate the underlying molecular mechanisms of growth differences in pigs of different body sizes.

Transmissible Gastroenteritis Virus Infection Promotes the Self-Renewal of Porcine Intestinal Stem Cells via Wnt/β-Catenin Pathway

Intestinal stem cells (ISCs) play an important role in tissue repair after injury. A recent report delineates the effect of transmissible gastroenteritis virus (TGEV) infection on the small intestine of recovered pigs. However, the mechanism behind the epithelium regeneration upon TGEV infection remains unclear. To address this, we established a TGEV infection model based on the porcine intestinal organoid monolayer. The results illustrated that the porcine intestinal organoid monolayer was susceptible to TGEV. In addition, the TGEV infection initiated the interferon and inflammatory responses following the loss of absorptive enterocytes and goblet cells. However, TGEV infection did not disturb epithelial integrity but induced the proliferation of ISCs. Furthermore, TGEV infection activated the Wnt/β-catenin pathway by upregulating the accumulation and nuclear translocation of β-catenin, as well as promoting the expression of Wnt target genes, such as C-myc, Cyclin D1, Mmp7, Lgr5, and Sox9, which were associated with the self-renewal of ISCs. Collectively, these data demonstrated that the TGEV infection activated the Wnt/β-catenin pathway to promote the self-renewal of ISCs and resulted in intestinal epithelium regeneration. IMPORTANCE The intestinal epithelium is a physical barrier to enteric viruses and commensal bacteria. It plays an essential role in maintaining the balance between the host and intestinal microenvironment. In addition, intestinal stem cells (ISCs) are responsible for tissue repair after injury. Therefore, prompt self-renewal of intestinal epithelium will facilitate the rebuilding of the physical barrier and maintain gut health. In the manuscript, we found that the transmissible gastroenteritis virus (TGEV) infection did not disturb epithelial integrity but induced the proliferation of ISCs and facilitated epithelium regeneration. Detailed mechanism investigations revealed that the TGEV infection activated the Wnt/β-catenin pathway to promote the self-renewal of ISCs and resulted in intestinal epithelium regeneration. These findings will contribute to understanding the mechanism of intestinal epithelial regeneration and reparation upon viral infection.

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.

Sus_circPAPPA2 Regulates Fat Deposition in Castrated Pigs through the miR-2366/GK Pathway

CircRNAs play an important role in fat deposition, and testosterone-deficient boars exhibit significantly increased fat deposition; however, the mechanism by which testosterone regulates fat deposition through circRNAs remains unclear. In this study, circRNA-seq of backfat and abdominal fat from castrated and intact full-sib Yorkshire pigs was performed. The GO and KEGG enrichment analyses revealed that the host genes of the dorsal DE circRNAs were mainly involved in fatty acid transport, while in abdominal tissues, these genes were mainly involved in adipogenesis and inflammation. The interaction among sus_circPAPPA2, ssc-miR-2366 and GK was verified by dual fluorescence experiments and in porcine preadipocytes. The overexpression of sus_circPAPPA2 significantly inhibited the differentiation of preadipocytes. The expression of sus_circPAPPA2 was increased after adding 100 nM of testosterone, and preadipocyte differentiation was significantly inhibited. Testosterone can affect preadipocyte differentiation by upregulating the expression of sus_circPAPPA2, sponging miR-2366 and regulating the expression of genes, such as GK. These results indicate that testosterone can regulate the expression of adipocyte differentiation- and lipid metabolism-related genes by regulating the expression of circRNA, and ceRNA networks are different in the testosterone regulation of adipose deposition in different parts. This study provides basic data enhancing the understanding of the interaction between the hormone environment and mir-2366/GK to regulate trait performance in pigs.

Integrated Analysis of the ceRNA Network and M-7474 Function in Testosterone-Mediated Fat Deposition in Pigs

Castration can significantly enhance fat deposition in pigs, and the molecular mechanism of fat deposition caused by castration and its influence on fat deposition in different parts of pigs remain unclear. RNA-seq was performed on adipose tissue from different parts of castrated and intact Yorkshire pigs. Different ceRNA networks were constructed for different fat parts. GO and KEGG pathway annotations suggested that testosterone elevates cell migration and affects differentiation and apoptosis in back fat, while it predisposes animals to glycolipid metabolism disorders and increases the expression of inflammatory cytokines in abdominal fat. The interaction between M-7474, novel_miR_243 and SGK1 was verified by dual fluorescence experiments. This ceRNA relationship has also been demonstrated in porcine preadipocytes. Overexpression of M-7474 significantly inhibited the differentiation of preadipocytes compared to the control group. When 100 nM testosterone was added during preadipocyte differentiation, the expression of M-7474 was increased, and preadipocyte differentiation was significantly inhibited. Testosterone can affect preadipocyte differentiation by upregulating the expression of M-7474, sponging novel-miR-243, and regulating the expression of genes such as SGK1. At the same time, HSD11B1 and SLC2A4 may also be regulated by the corresponding lncRNA and miRNA, which ultimately affects glucose uptake by adipocytes and leads to obesity.

Chicken Peripheral Blood Mononuclear Cells Response to Avian Leukosis Virus Subgroup J Infection Assessed by Single-Cell RNA Sequencing

Chicken peripheral blood mononuclear cells (PBMCs) exhibit wide-ranging cell types, but current understanding of their subclasses, immune cell classification, and function is limited and incomplete. Here we performed single-cell RNA sequencing (scRNA-seq) of PBMCs in Avian leukosis virus subgroup J (ALV-J) infected and control chickens at 21 days post infection (DPI) to determine chicken PBMCs subsets and their specific molecular and cellular characteristics. Eight cell populations and their potential marker genes were identified in PBMCs. T cell populations had the strongest response to (ALV-J) infection, based on the detection of the largest number of differentially expressed genes (DEGs), and could be further grouped into four subsets: activated CD4⁺ T cells, Th1-like cells, Th2-like cells, and cytotoxic CD8⁺ T cells. Furthermore, pseudotime analysis results suggested that chicken CD4⁺ T cells could potentially differentiate into Th1-like and Th2-like cells. Moreover, ALV-J infection activated CD4⁺ T cell was probably inclined to differentiate into Th1-like cells. Compared to the control PBMCs, ALV-J infection also had an obvious impact on PBMCs composition. B cells showed inconspicuous response and their numbers decreased in PBMCs from ALV-J infected chicken. Proportions of cytotoxic Th1-like cells and CD8⁺ T cells increased in the T cell population of PBMCs from ALV-J infected chicken, which were potentially key mitigating effectors against ALV-J infection. More importantly, our results provide a rich resource of gene expression profiles of chicken PBMCs subsets for a systems-level understanding of their function in homeostatic condition as well as in response to viral infection.

Decreased NHE3 activity in intestinal epithelial cells in TGEV and PEDV-induced piglet diarrhea

Transmissible gastroenteritis (TGE) and porcine epidemic diarrhea (PED) are highly transmissible intestinal infections caused by transmissible gastroenteritis virus (TGEV) and porcine epidemic diarrhea virus (PEDV), respectively. They are clinically associated with vomiting, diarrhea, and dehydration in piglets. An imbalance in Na⁺ uptake by intestinal epithelial cells causes TGEV/PEDV-induced diarrhea. However, the mechanism by which TGEV/PEDV-infection in piglets causes Na⁺ imbalance diarrhea has not been elucidated. In the present study, we demonstrated that specific inhibition of NHE3 activity caused small intestinal bulging, intestinal wall thinning and severe diarrhea in piglets, consistent with the signs of TGEV/PEDV infection. This study further elucidated the role of NHE3 in TGEV/PEDV-induced diarrhea. In this study, small intestinal epithelial cells (IPEC-J2) were used as a model of infection. The results showed that TGEV/PEDV infection reduced NHE3 activity and Na⁺ uptake in IPEC-J2 cells. Further studies revealed that the use of NHE3-specific inhibitors could reduce the amount of cell membrane NHE3, thereby decreasing Na⁺ uptake and ultimately leading to diarrhea. Transcriptomic studies performed on obtained jejunal tissues were also consistent with pre-laboratory results. This study will provide a basis for understanding Na⁺ imbalance diarrhea caused by TGEV/PEDV, as well as for elucidating the diarrheal pathogenesis of other members of α-animal coronaviruses.

Reduced activity of intestinal surface Na+/H+ exchanger NHE3 is a key factor for induction of diarrhea after PEDV infection in neonatal piglets

Porcine epidemic diarrhea virus (PEDV; family Coronaviridae, genus Alphacoronavirus) causes acute diarrhea and vomiting, dehydration, and high mortality in neonatal piglets. Despite extensive research focusing on the pathogenesis of PEDV infection, the molecular pathogenesis of PEDV-induced diarrhea in piglets remains unclear. Na⁺/H⁺ exchanger 3 (NHE3), the main exchanger of electroneutral sodium in intestinal epithelial cells, is closely associated with the occurrence of diarrhea. To date, there is no study on whether diarrhea caused by PEDV infection is related to the activity of NHE3. In the present study, it was found that the expression level of cell membrane protein NHE3 significantly decreased after PEDV infection, whereas the total level of protein expression was not significantly changed. The Na⁺/H⁺ transport rate and the mRNA abundance of NHE3 decreased; the NHE3 activity decreased gradually with increasing infection time. In vivo, after PEDV infection of newborn piglets, rupture of intestinal villi and interstitial degeneration of intestinal epithelial cells in different intestinal segments were observed by hematoxylin-eosin staining. Immunohistochemical and immunofluorescence methods were used to observe the decreased expression of NHE3 protein on the membrane of intestinal epithelial cells in the jejunum and ileum. Taken together, these data indicate that PEDV infection reduces NHE3 activity in intestinal epithelial cells, hindering Na⁺ transport and thus causing diarrhea.

Proteomics-Based Approach Reveals the Involvement of SERPINB9 in Recurrent and Relapsed Multiple Myeloma

Multiple myeloma (MM) is a common hematological malignancy with poorly understood recurrence and relapse mechanisms. Notably, bortezomib resistance leading to relapse makes MM treatment significantly challenging. To clarify the drug resistance mechanism, we employed a quantitative proteomics approach to identify differentially expressed protein candidates implicated in bortezomib-resistant recurrent and relapsed MM (RRMM). Bone marrow aspirates from five patients newly diagnosed with MM (NDMM) were compared with those from five patients diagnosed with bortezomib-resistant RRMM using tandem mass tag-mass spectrometry (TMT-MS). Subcellular localization and functional classification of the differentially expressed proteins were determined by gene ontology, Kyoto Encyclopedia of Genes and Genomes pathway, and hierarchical clustering analyses. The top candidates identified were validated with parallel reaction monitoring (PRM) analysis using tissue samples from 11 NDMM and 8 RRMM patients, followed by comparison with the NCBI Gene Expression Omnibus (GEO) dataset of 10 MM patients and 10 healthy controls (accession no.: GSE80608). Thirty-four differentially expressed proteins in RRMM, including proteinase inhibitor 9 (SERPINB9), were identified by TMT-MS. Subsequent functional enrichment analyses of the identified protein candidates indicated their involvement in regulating cellular metabolism, apoptosis, programmed cell death, lymphocyte-mediated immunity, and defense response pathways in RRMM. The top protein candidate SERPINB9 was confirmed by PRM analysis and western blotting as well as by comparison with an NCBI GEO dataset. We elucidated the proteome landscape of bortezomib-resistant RRMM and identified SERPINB9 as a promising novel therapeutic target. Our results provide a resource for future studies on the mechanism of RRMM.

ER stress-induced adipocytes secrete-aldo-keto reductase 1B7-containing exosomes that cause nonalcoholic steatohepatitis in mice

Nonalcoholic steatohepatitis (NASH) is an increasingly prevalent liver disease linked to obesity and associated complications. Endoplasmic reticulum (ER) stress provokes dysfunction in lipid metabolism, which often leads to a progression of obesity-induced hepatic steatosis to NASH. However, the underlying mechanisms in which ER stress in adipose tissue induces hepatic pathology remain elusive. Here, we used male C57BL/6J mice to develop an animal model of NASH induced by a high fat (HFD) diet and methionine- and choline-deficient (MCD) diets. Using a gene-silencing approach with a recombinant lentiviral vector and extensive LC-MS/MS-based proteomics and lipidomics, we demonstrate that the ER stress-induced adipocyte-secreted exosome (ATEx) orchestrates lipid dynamics in the liver. We also noted that ATEx causes hepatic steatosis, inflammation, and fibrosis that lead to NASH through initial accumulation of glycerol and triglycerides in hepatocytes. We also determined that aldo-keto-reductase 1B7 (Akr1b7), a key mediator in liver lipid metabolism, is involved in ATEx-mediated NASH induction. Of note, Akr1b7 deficiency in ER stress-induced ATEx strongly protected the murine liver against HFD and MCD-induced NASH. Our results indicated that ER stress-induced, adipocyte-secreted ATEx triggers NASH by delivering exosomal AKR1B7 to, and elevating glycerol level, in hepatocytes. These findings suggest potential therapeutic strategie that target ATEx to prevent or manage obesity-induced NASH.

Regulatory role and mechanism of the inhibition of the Mcl-1 pathway during apoptosis and polarization of H37Rv-infected macrophages

BACKGROUND

Myeloid cell leukemia-1 (Mcl-1) plays an important role in the clearance of Mycobacterium tuberculosis (MTB) infection. It has the effect of anti-apoptosis, protecting macrophages that have engulfed pathogens and preventing pathogen clearance. Meanwhile, the MAPK signaling pathway plays a significant role in regulating Mcl-1 expression during tuberculosis infection. In the case of latent infection and active infection, the apoptosis and polarization of macrophages have a great influence during MTB infection, so we discussed the effect of Mcl-1 on apoptosis and polarization. Then, further discussed its mechanism.

METHODS

An infected RAW264.7 macrophage model was established to investigate the regulatory role and mechanism of the Mcl-1 pathway inhibition during apoptosis and polarization of H37Rv infection. First, Mcl-1 protein and mRNA was identified by western blotting and Real-Time Polymerase Chain Reaction (RT-PCR). RAW264.7 macrophage apoptosis was detected by flow cytometry. RT-PCR was utilized to detect Bax, Caspase-3, Cyt-c and Bcl-2 mRNA expression. Next, Then the expression levels of inflammation factors CD86, CD206, iNOS, Fizz1, IL-6, IL-10, TNF-α, and TGF-β was detected by ELISA. SEM was used to observe macrophages phenotype. Finally, Bax, Bcl-2 and Bcl-xl the expression was detected by western blotting. Confocal microscopy was used to analyze mitochondrial membrane potential using the JC-10 kit.

RESULTS

In this study, we found that inhibiting the Mcl-1 expression signaling pathway led to infection by different virulence Mycobacterium tuberculosis, as well as changes in Mcl-1 protein and mRNA expression. Concomitantly macrophage apoptosis rate also changed, While, two phenotypic states of M1 and M2 appeared in the infected cells. We also found that the mitochondrial pathway was activated, the expression of its related genes Bax, casepase3, and Cyt-c, increased, whereas that of Bcl-2 decreased, and the mitochondrial membrane depolarization function was changed.

CONCLUSIONS

We found that Mcl-1 affected the apoptosis and polarization of macrophages infected by Mycobacterium tuberculosis, mainly M1 in the early stage and M2 in the later stage. In addition, mitochondria played a crucial role in this process.

The interface between coronaviruses and host cell RNA biology: Novel potential insights for future therapeutic intervention

Coronaviruses, including SARS-Cov-2, are RNA-based pathogens that interface with a large variety of RNA-related cellular processes during infection. These processes include capping, polyadenylation, localization, RNA stability, translation, and regulation by RNA binding proteins or noncoding RNA effectors. The goal of this article is to provide an in-depth perspective on the current state of knowledge of how various coronaviruses interact with, usurp, and/or avoid aspects of these cellular RNA biology machineries. A thorough understanding of how coronaviruses interact with RNA-related posttranscriptional processes in the cell should allow for new insights into aspects of viral pathogenesis as well as identify new potential avenues for the development of anti-coronaviral therapeutics. This article is categorized under: RNA in Disease and Development > RNA in Disease.

Transmissible gastroenteritis virus targets Paneth cells to inhibit the self-renewal and differentiation of Lgr5 intestinal stem cells via Notch signaling

Infection with transmissible gastroenteritis virus (TGEV) has been associated with villous atrophy within 48 h, which seriously disrupts intestinal homeostasis. However, the underlying mechanisms remain elusive. In this study, we found that TGEV infection severely disrupted intestinal homeostasis via inhibition of self-renewal and differentiation in Lgr5 intestinal stem cells (ISCs). Profoundly, TGEV-encoded NSP10/NSP16 protein complex-mediated the inactivation of Notch signaling provided a mechanistic explanation for this phenomenon. Initial invasions by TGEV-targeted Paneth cells through aminopeptidase N (APN) receptor, then inducing mitochondrial damage and ROS generation in them, ultimately causing Paneth cell decrease and loss of Notch factors (DII4 and Hes5), which are essential for Lgr5 ISCs self-renewal and differentiation. Interestingly, loss of Notch signaling induced goblet cells differentiation at the cost of absorptive enterocytes and promoted mucins secretion, which accelerated TGEV replication. Therefore, the more differentiation of goblet cells, the greater TGEV infection in jejunum. These results provide a detailed mechanistic pathway by which villous atrophy sharply occurs in TGEV-infected jejunum within 48 h. Thus, the pathogenesis of TGEV can be described as a "bottom up scenario", which is contrary to the traditional "top down" hypothesis. Together, our findings provide a potential link between diarrheal virus infection and crypt cells response that regulates Paneth cells function and Lgr5 ISCs fate and could be exploited for therapeutic application.

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

Transmissible gastroenteritis (TGE) is a contagious and infectious disease that is characterized by severe vomiting and diarrhea of swine , especially piglet, and caused by transmissible gastroenteritis coronavirus (TGEV) . TGEV infection provokes mitochondrial damage of porcine intestinal epthelial cell (IPEC), which is responsible for inflammation and cell death. In our previous study, we have demonstrated that circular RNA circEZH2 was down-regulated during TGEV infection and promoted the activation of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) via targeting miR-22 in porcine intestinal epithelial cell line (IPEC-J2). Activation of NF-κB is an important factor for mitochondrial damage. Mitochondrial permeability transition pore (mPTP) opening is a key reason for mitochondrial damage. So, we speculate that circEZH2 may regulate TGEV-induced mPTP opening via NF-kB pathway. In the present study, we found that mPTP opening of IPEC-J2 was occured during TGEV infection and suppressed by circEZH2 via attaching miR-22. Hexokinase 2 (HK2) and interleukin 6 (IL-6) were identified as the targets of miR-22. Silencing HK2 enhanced TGEV-induced mPTP opening, while no effect on NF-κB pathway. Silencing IL-6 promoted TGEV-induced mPTP opening and inhibited NF-κB pathway. Inhibitor of NF-κB increased TGEV-induced mPTP opening. The data revealed that TGEV-induced mPTP opening was regulated via two pathways: circEZH2/miR-22/HK2 axis and circEZH2/miR-22/IL-6/NF-κB axis.

Expression profile analysis of 5-day-old neonatal piglets infected with porcine Deltacoronavirus

BACKGROUND

Porcine deltacoronavirus (PDCoV) is a novel coronavirus that can cause diarrhea in nursing piglets. This study was aimed to investigate the roles of host differentially expressed genes on metabolic pathways in PDCoV infections.

RESULTS

Twenty thousand six hundred seventy-four differentially expressed mRNAs were identified in 5-day-old piglets responded to PDCoV experimental infections. Many of these genes were correlated to the basic metabolism, such as the peroxisome proliferator-activated receptor (PPAR) signaling pathway which plays a critical role in digestion. At the same time, in the PPAR pathway genes of fatty acid-binding protein (FABP) family members were observed with remarkably differential expressions. The differential expressed genes were associated with appetite decrease and weight loss of PDCoV- affected piglets.

DISCUSSION

Fatty acid-binding protein 1 (FABP1) and fatty acid-binding protein 3 (FABP3) were found to be regulated by PDCoV. These two genes not only mediate fatty acid transportation to different cell organelles such as mitochondria, peroxisome, endoplasmic reticulum and nucleus, but also modulate fatty acid metabolism and storage as a signaling molecule outside the cell. Therefore, it can be preliminarily concluded that PPAR differential expression caused by PDCoV was mostly associated with weight loss and death from emaciation.

CONCLUSIONS

The host differentially expressed genes were associated with infection response, metabolism signaling and organismal systems signaling pathways. The genes of FABP family members in the PPAR signaling pathway were the most highly altered and played important roles in metabolism. Alteration of these genes were most likely the reason of weight loss and other clinical symptoms. Our results provided new insights into the metabolic mechanisms and pathogenesis of PDCoV infection.

METHODS

Animal experiment, Determination of viral growth by real-time RT-PCR, Histopathology, Immunohistochemical staining, Microarray analysis.

microRNA-222 Attenuates Mitochondrial Dysfunction During Transmissible Gastroenteritis Virus Infection

Transmissible gastroenteritis virus (TGEV) is a member of Coronaviridae family. Our previous research showed that TGEV infection could induce mitochondrial dysfunction and upregulate miR-222 level. Therefore, we presumed that miR-222 might be implicated in regulating mitochondrial dysfunction induced by TGEV infection. To verify the hypothesis, the effect of miR-222 on mitochondrial dysfunction was tested and we showed that miR-222 attenuated TGEV-induced mitochondrial dysfunction. To investigate the underlying molecular mechanism of miR-222 in TGEV-induced mitochondrial dysfunction, a quantitative proteomic analysis of PK-15 cells that were transfected with miR-222 mimics and infected with TGEV was performed. In total, 4151 proteins were quantified and 100 differentially expressed proteins were obtained (57 upregulated, 43 downregulated), among which thrombospondin-1 (THBS1) and cluster of differentiation 47 (CD47) were downregulated. THBS1 was identified as the target of miR-222. Knockdown of THBS1 and CD47 decreased mitochondrial Ca2+ level and increased mitochondrial membrane potential (MMP) level. Reversely, overexpression of THBS1 and CD47 elevated mitochondrial Ca2+ level and reduced mitochondrial membrane potential (MMP) level. Together, our data establish a significant role of miR-222 in regulating mitochondrial dysfunction in response to TGEV infection.

JS-K as a nitric oxide donor induces apoptosis via the ROS/Ca2+/caspase-mediated mitochondrial pathway in HepG2 cells

JS-K, (O²-(2, 4-dinitrophenyl) 1-[(4-ethoxycarbonyl) piperazin-1-yl] diazen 1-ium-1, 2-diolate), is a novel diazeniumdiolate-based nitric oxide donor prodrug. The present study investigated the relationship between reactive oxygen species (ROS) elevation, Ca²⁺ overload and mitochondrial disruption in JS-K-induced apoptosis. JS-K could significantly inhibit cell growth and induce apoptosis in a dose-dependent manner. Meanwhile, JS-K caused the accumulation of ROS, overload of Ca²⁺, decrease of mitochondrial membrane potential, release of cytochrome c (Cyt c) from mitochondria to the cytoplasm, increase of Bax-to-Bcl-2 ratio and activation of caspase- 9/3. NAC (an antioxidant) or BAPTA (an intracellular Ca²⁺ chelator) could partially reverse the above events, while BAPTA had little effect on the levels of ROS. Furthermore, pre-treatment with Carboxy-PTIO (a NO scavenger) significantly blocked the increasing of ROS, cytosolic Ca²⁺ and reversed the loss of mitochondrial membrane potential in JS-K-induced apoptosis. Taken together, the results suggested that NO released from JS-K could significantly induce HepG2 cell apoptosis through a ROS/Ca²⁺/caspase-mediated mitochondrial pathway.