Identification of circRNA and mRNA expression profiles and functional networks of vascular tissue in lipopolysaccharide-induced sepsis

CIRCVMA21-RELATED PATHWAY ALLEVIATES LIPOPOLYSACCHARIDE-INDUCED HK-2 CELL INJURY

ABSTRACT

Background : It is reported that circVMA21 has an inhibition effect on sepsis-induced acute kidney injury (AKI). Therefore, the underlying molecular mechanisms of circVMA21 in AKI are worthy of further investigation. Material and Methods : Lipopolysaccharide (LPS) was used to induce HK2 cell injury. CircVMA21, miR-337-3p and ZEB2 expression was tested by qRT-PCR. Cell growth was detected by CCK8 assay, EdU assay, and flow cytometry. Protein levels were examined by western blot. The levels of inflammatory factors and oxidative stress markers were measured to evaluate cell inflammatory response and oxidative stress. RNA relationship as verified by dual-luciferase reporter assay, RIP assay, and RNA pull-down assay. Results : CircVMA21 had decreased expression in AKI patients. Overexpressed circVMA21 alleviated LPS-induced HK2 cell inflammation, apoptosis, and oxidative stress. Moreover, circVMA21 sponged miR-337-3p, and miR-337-3p targeted ZEB2. The inhibitory effect of circVMA21 on LPS-induced HK2 cell injury was reversed by miR-337-3p overexpression, and ZEB2 overexpression abolished the promotion effect of miR-337-3p on LPS-induced HK2 cell injury. Conclusions : CircVMA21 could inhibit LPS-induced HK2 cell injury via miR-337-3p/ZEB2 axis.

UMI-77 Modulates the Complement Cascade Pathway and Inhibits Inflammatory Factor Storm in Sepsis Based on TMT Proteomics and Inflammation Array Glass Chip

Sepsis is a systemic inflammatory response syndrome caused by infection, which has no specific drug at present. UMI-77 can significantly improve the survival rate of septic mice; the detailed role of UMI-77 and its underlying mechanisms in sepsis are not clear. Inflammation array glass chip and proteomic analyses were performed to elucidate the latent mechanism of UMI-77 in the treatment of sepsis. The results showed that 7.0 mg/kg UMI-77 improved the 5 day survival rate in septic mice compared to the LPS group (60.964 vs 9.779%) and ameliorated the pathological conditions. Inflammation array glass chip analysis showed that sepsis treatment with UMI-77 may eventually through the suppression of the characteristic inflammatory storm-related cytokines such as KC, RANTES, LIX, IL-6, eotaxin, TARC, IL-1β, and so on. Proteomics analysis showed that 213 differential expression proteins and complement and coagulation cascades were significantly associated with the process for the UMI-77 treatment of sepsis. The top 10 proteins including Apoa2, Tgfb1, Serpinc1, Vtn, Apoa4, Cat, Hp, Serpinf2, Fgb, and Serpine1 were identified and verified, which play important roles in the mechanism of UMI-77 in the treatment of sepsis. Our findings indicate that UMI-77 exerts an antisepsis effect by modulating the complement cascade pathway and inhibiting inflammatory storm factors.

CIRCTDRD9 CONTRIBUTES TO SEPSIS-INDUCED ACUTE LUNG INJURY BY ENHANCING THE EXPRESSION OF RAB10 VIA DIRECTLY BINDING TO MIR-223-3P

ABSTRACT

Background: The dysregulation of circular RNAs (circRNAs) is involved in various human diseases, including sepsis-induced acute lung injury (ALI). We aimed to investigate the role of circTDRD9 in the development of sepsis-induced ALI. Methods: Cell models of sepsis-induced ALI were established by treating A549 cells with LPS. The expression of circTDRD9, miR-223-3p, and RAB10 mRNA was measured by quantitative real-time PCR (qPCR). The levels of inflammatory factors were measured by ELISA. Oxidative stress-related indicators were monitored by using commercial detection kits. The expression of fibrosis-related proteins was detected by Western blot assay. Cell proliferation was assessed by EdU assay. The predicted binding relationship between miR-223-3p and circTDRD9 or RAB10 was verified by dual-luciferase reporter assay, RIP assay or pull-down assay. Results: CircTDRD9 was highly expressed in LPS-treated A549 cells. CircTDRD9 downregulation prevented LPS-induced inflammation, oxidative stress, cell proliferation inhibition, and cell fibrosis in A549 cells, whereas these effects were reversed by the inhibition of miR-223-3p, a target of circTDRD9. In addition, RAB10 was verified as a target of miR-223-3p, and RAB10 overexpression recovered LPS-induced inflammation, oxidative stress, cell proliferation inhibition, and cell fibrosis in A549 cells that were ameliorated by miR-223-3p restoration. Importantly, circTDRD9 positively regulated RAB10 expression by binding to miR-223-3p. Conclusion: CircTDRD9 overexpression was closely associated with LPS-induced ALI. CircTDRD9 contributed to LPS-induced ALI partly by upregulating RAB10 via binding to miR-223-3p.

CIRC_0114428 INFLUENCES THE PROGRESSION OF SEPTIC ACUTE KIDNEY INJURY VIA REGULATING MIR-370-3P/TIMP2 AXIS

ABSTRACT

Background: Septic acute kidney injury (AKI) is a serious complication of sepsis, which greatly threatened the life safety of critically ill patients. Recently, circular RNA is considered to be implicated in sepsis-induced renal cell damage. However, the role of circ_0114428 in sepsis AKI is still unclear. Methods: LPS was used to establish a sepsis-related AKI cell model. The expression of circ_0114428, microRNA (miR)-370-3p, tissue inhibitor of metalloproteinase-2 (TIMP2), Proliferating cell nuclear antigen, Bax, and Bcl-2 were detected by quantitative real-time polymerase chain reaction and Western blot. Cell counting kit 8 and enzyme-linked immunosorbent assay were used to measure cell proliferation ability and the secretion of inflammatory factors (tumor necrosis factor α, interleukin 1β, and interleukin 6), respectively. Cell cycle and apoptosis rate were analyzed by flow cytometry. Caspase-3 assay kits were used to detect Caspase-3 activity. Interaction between miR-370-3p and circ_0114428 or TIMP2 was analyzed by bioinformatics analysis, a dual-luciferase reporter assay, and RNA immunoprecipitation assay. Results: Circ_0114428 was upregulated in septic AKI serum samples and LPS-induced HK2 cells. The knockdown of circ_0114428 notably promoted cell proliferation and cycle, whereas it restrained cell inflammation and apoptosis in LPS-stimulated HK2 cells. Subsequent mechanism analysis revealed that miR-370-3p was a target of circ_0114428, and miR-370-3p inhibition could rescue the effects of circ_0114428 downregulation on LPS-induced cell injury. Meanwhile, TIMP2 was a target gene of miR-370-3p. miR-370-3p mimic could attenuate LPS-induced cell injury, whereas these impacts were overturned by overexpressed TIMP2. Furthermore, circ_0114428 enhanced TIMP2 protein expression by sponging miR-370-3p. Conclusion: Our data demonstrated that circ_0114428 contributed to septic AKI progression by regulating miR-370-3p-mediated TIMP2 expression, which provided a promising target for septic AKI treatment.

Long Noncoding RNA and mRNA Expression Profiles in Rats with LPS-induced Myocardial Dysfunction

Background

Sepsis is an uncontrolled systemic inflammatory response. Long noncoding RNAs (lncRNAs) are involved in the pathogenesis of sepsis. However, little is known about the roles of lncRNAs in sepsis-induced myocardial dysfunction.

Objective

We aimed to determine the regulatory mechanism of lncRNAs in sepsis-induced myocardial dysfunction.

Methods

In this study, we analysed the lncRNA and mRNA expression profiles using microarray analysis. Gene Ontology, Kyoto Encyclopedia of Genes and Genomes, protein-protein interaction network, and gene set enrichment analysis were used to evaluate the data. We also constructed coding and noncoding coexpression and competing endogenous RNA networks to investigate the mechanisms.

Results

In vivo lipopolysaccharide -induced sepsis rat model was established. A total of 387 lncRNAs and 1,952 mRNAs were identified as significantly changed in the left ventricle. Kyoto Encyclopedia of Genes and Genomes analysis of mRNAs showed that the upregulated genes were mainly enriched in the "complement and coagulation cascade pathway" and "immune-related biological processes" terms. Eight significantly changed lncRNAs detected by RT-qPCR may be responsible for these processes. A competing endogenous RNA network was generated, and the results indicated that eight lncRNAs were related to the "calcium ion binding" process.

Conclusion

These results demonstrate that crosstalk between lncRNAs and mRNAs may play important roles in the development of sepsis-induced myocardial dysfunction.

The Intricate Role of Non-Coding RNAs in Sepsis-Associated Disseminated Intravascular Coagulation

Disseminated Intravascular Coagulation (DIC) is a type of tissue and organ dysregulation in sepsis, due mainly to the effect of the inflammation on the coagulation system. Unfortunately, the underlying molecular mechanisms that lead to this disorder are not fully understood. Moreover, current biomarkers for DIC, including biological and clinical parameters, generally provide a poor diagnosis and prognosis. In recent years, non-coding RNAs have been studied as promising and robust biomarkers for a variety of diseases. Thus, their potential in the diagnosis and prognosis of DIC should be further studied. Specifically, the relationship between the coagulation cascade and non-coding RNAs should be established. In this review, microRNAs, long non-coding RNAs, and circular RNAs are studied in relation to DIC. Specifically, the axis between these non-coding RNAs and the corresponding affected pathway has been identified, including inflammation, alteration of the coagulation cascade, and endothelial damage. The main affected pathway identified is PI3K/AKT/mTOR axis, where several ncRNAs participate in its regulation, including miR-122-5p which is sponged by circ_0005963, ciRS-122, and circPTN, and miR-19a-3p which is modulated by circ_0000096 and circ_0063425. Additionally, both miR-223 and miR-24 were found to affect the PI3K/AKT pathway and were regulated by lncGAS5 and lncKCNQ1OT1, respectively. Thus, this work provides a useful pipeline of inter-connected ncRNAs that future research on their impact on DIC can further explore.

LncRNA-mRNA expression profile and functional network of vascular dysfunction in septic rats

BACKGROUND

We used microarrays to analyse the changes in long non-coding RNAs (lncRNAs) and mRNAs in aorta tissue in model rats with lipopolysaccharide-induced sepsis and determined the lncRNA-mRNA and lncRNA-miRNA-mRNA functional networks.

METHODS

Wistar rats were intraperitoneally injected with lipopolysaccharide, and the lncRNA and mRNA expression profiles in the aorta were evaluated using microarrays. The functions of the differentially expressed mRNAs were analysed using Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses. We then constructed coding/non-coding co-expression and competing endogenous RNA networks to study the mechanisms related to sepsis in rats.

RESULTS

We identified 503 differentially expressed lncRNAs and 2479 differentially expressed mRNAs in the model rats with lipopolysaccharide-induced sepsis. Mitochondrial fission process 1 (MTFP1) was the most significantly down-regulated mRNA. Bioinformatics analysis showed that the significantly down-regulated mRNAs in the sepsis models were in pathways related to mitochondrial structure, function, and energy metabolism. Coding/non-coding co-expression and competing endogenous RNA analyses were conducted using 12 validated lncRNAs in combination with all mRNAs. The coding/non-coding co-expression analysis showed that the 12 validated lncRNAs were mainly regulatory factors for abnormal energy metabolism, including mitochondrial structure damage and aberrant mitochondrial dynamics. The competing endogenous RNA analysis revealed that the potential functions of these 12 lncRNAs might be related to the inflammatory response.

CONCLUSION

We determined the differentially expressed lncRNAs and mRNAs in the aorta of septic rats using microarrays. Further studies on these lncRNAs will help elucidate the mechanism of sepsis at the genetic level and may identify potential therapeutic targets.

PTX3 Protects Intestinal Mucosal Barrier Damage in Sepsis Through Toll-Like Receptor Signaling Pathway

This study aims to confirm the protective effect of Pentraxin 3 (PTX3) on intestinal mucosal barrier damage in sepsis in animal and cell models and explore its mechanism. Analysis of the GSE147775 gene set revealed that the level of PTX3 was upregulated in the lipopolysaccharide (LPS)-induced rat sepsis model. The mice sepsis model was established by cecal ligation perforation (CLP), and the cell inflammation model was induced by LPS. Cell apoptosis and the expression of apoptosis-related protein were detected by flow cytometry and Western blotting. The PTX3 level was significantly upregulated in the mice sepsis model. Intestinal mucosal barrier damage was aggravated and inflammatory factor expression was upregulated after PTX3 downregulation in sepsis mice. After upregulation of PTX3, intestinal mucosal barrier damage was alleviated and inflammatory factor expression was decreased in sepsis mice. Further data mining suggested that the anti-inflammatory effect of PTX3 might be realized through inhibition of the toll-like receptor (TLR) signaling pathway. Moreover, compared with the LPS group, downregulation of PTX3 increased cell apoptosis and the levels of BCL2-associated X (Bax), myeloperoxidase (MPO), tumor necrosis factor-alfa (TNF-α), interleukin 1 beta (IL-1β), and interferon-gamma (IFN-γ), and decreased the levels of B-cell lymphoma-2 (Bcl-2), zona occludens (ZO)-1, and occludin. On the contrary, overexpression of PTX3 reduced cell apoptosis and the levels of Bax, MPO, TNF-α, IL-1β, and IFN-γ. Moreover, downregulation of PTX3 reversed the inhibitive effects on cell apoptosis and inflammation and promotive effects on the levels of Zo-1 and occludin induced by CLI-095 (a TLR signaling pathway inhibitor). In the CLP-induced mice sepsis model and LPS-induced cell inflammation model, PTX3 inhibits inflammatory response and reduces intestinal mucosal barrier damage through the TLR signaling pathway.

Profiling the lncRNA-miRNA-mRNA interaction network in the submandibular gland of diabetic mice

BACKGROUND

Hyposalivation is one of the common symptoms of diabetes. Although long non-coding RNAs (lncRNAs) have recently been reported to play important roles in the pathogenesis of diabetes, the role of lncRNAs in diabetes-induced hyposalivation remains unknown.

METHODS

The present study aimed to explore the function of lncRNA-microRNA-mRNA regulatory network in the submandibular gland (SMGs) under the context of diabetes. LncRNA expression profile of the SMGs was analyzed using microarray technology. Differentially expressed lncRNAs were confirmed using real-time quantitative PCR. Bioinformatics analyses were performed, and Coding-non-coding gene co-expression (CNC) and competing endogenous RNA (ceRNA) networks were constructed to explore the potential mechanisms of diabetes-induced hyposalivation.

RESULTS

A total of 1273 differentially expressed lncRNAs (536 up-regulated and 737 downregulated) were identified in the SMGs tissues of db/db mice. CNC and ceRNA network analyses were performed based on five differentially expressed lncRNAs validated by real-time quantitative PCR. Gene Ontology analysis of target genes of CNC network revealed that "calcium ion binding" was a highly enriched molecular function. Kyoto Encyclopedia of Genes and Genomes pathway analysis of target genes of ceRNA network revealed that the "mammalian target of rapamycin signaling pathway" was significantly enriched.

CONCLUSIONS

On the whole, the findings of the present study may provide insight into the possible mechanism of diabetes-induced hyposalivation.

JNK/Itch Axis Mediates the Lipopolysaccharide-Induced Ubiquitin-Proteasome-Dependent Degradation of Ferritin Light Chain in Murine Macrophage Cells

Ferritin, which is composed of a heavy chain and a light chain, plays a critical role in maintaining iron homeostasis by sequestering iron. The ferritin light chain (FTL) is responsible for the stability of the ferritin complex. We have previously shown that overexpression of FTL decreases the levels of the labile iron pool (LIP) and reactive oxygen species (ROS) in lipopolysaccharide (LPS)-treated murine macrophage cells. The protein level of FTL was downregulated by LPS within a short treatment period. However, the mechanism underlying the LPS-induced changes in the FTL levels is not known. In the present study, we report that LPS induces the ubiquitin-proteasome-dependent degradation of FTL and that the mechanism of LPS-induced FTL degradation involves the JNK/Itch axis. We found that LPS downregulates the protein and mRNA levels of FTL in a time-dependent manner. The proteasome inhibitor MG-132 significantly reverses the LPS-induced decrease in FTL. Furthermore, we observed that LPS treatment cannot cause ubiquitination of the lysine site (K105 and K144) mutant of FTL. Interestingly, LPS-mediated ubiquitin-dependent degradation of FTL is significantly inhibited by the JNK-specific inhibitor SP600125. Moreover, LPS could upregulate the protein level of E3 ubiquitin ligase Itch, a substrate of JNK kinases. Immunoprecipitation analyses revealed an increase in the association of FTL with Itch, a substrate of JNK kinases, in response to LPS stimulation. SP600125 decreased LPS-induced Itch upregulation. Taken together, these results suggest that LPS stimulation leads to the degradation of FTL through the ubiquitin-proteasome proteolytic pathway, and this FTL degradation is mediated by the JNK/Itch axis in murine macrophage cells.

Functional delivery of lncRNA TUG1 by endothelial progenitor cells derived extracellular vesicles confers anti-inflammatory macrophage polarization in sepsis via impairing miR-9-5p-targeted SIRT1 inhibition

The delivery of biomolecules by extracellular vesicles (EVs) derived from endothelial progenitor cells (EPCs) has been proven to ameliorate sepsis, yet the therapeutic mechanism remains to be elucidated. Taurine upregulated gene 1 (TUG1) is a long noncoding RNA (lncRNA) that is downregulated in sepsis. The current study was designed to explore the role of EPCs derived EVs transmitting TUG1 in macrophage polarization and macrophage-mediated inflammation in a cecal ligation and puncture (CLP)-induced sepsis mouse model. TUG1 was underexpressed in CLP-induced sepsis, and its reexpression induced anti-inflammatory macrophage polarization and suppressed macrophage-medicated inflammatory injury to the pulmonary vascular endothelium. EPCs derived EVs transmitted TUG1 to promote M2 macrophage polarization. Luciferase, RIP, and RNA pull-down assays showed that TUG1 could competitively bind to microRNA-9-5p (miR-9-5p) to upregulate the expression of sirtuin 1 (SIRT1). Furthermore, EPCs derived EVs transmitted TUG1 to promote M2 macrophage polarization through the impairment of miR-9-5p-dependent SIRT1 inhibition. Finally, EPCs derived EVs carrying TUG1 were verified to ameliorate sepsis-induced organ damage in the murine model. In summary, EPCs derived EVs transmit TUG1 to attenuate sepsis via macrophage M2 polarization. This study also highlights the proinflammatory mechanism associated with miR-9-5p-mediated inhibition of SIRT1, which contributes to a more comprehensive understanding of the pathogenesis of sepsis.

CircTLK1 modulates sepsis-induced cardiomyocyte apoptosis via enhancing PARP1/HMGB1 axis-mediated mitochondrial DNA damage by sponging miR-17-5p

Introduction

Septic cardiomyopathy is a common complication of sepsis with high morbidity and mortality, but lacks specific therapy. This study aimed to reveal the role of circTLK1 and its potential mechanisms in septic cardiomyopathy.

Materials and Methods

The in vitro and in vivo models of septic cardiomyopathy were established. Cell viability and apoptosis were detected by CCK8, TUNEL and flow cytometry, respectively. LDH, CK, SOD, MDA, ATP, 8‐OHdG, NAD+/NADH ratio, ROS level, mitochondrial membrane potential and cytochrome C distribution were evaluated using commercial kits. qRT‐PCR and western blotting were performed to detect RNA and protein levels. Mitochondrial DNA (mtDNA) copy number and transcription were assessed by quantitative PCR. Dual‐luciferase assay, RNA immunoprecipitation and co‐immunoprecipitation were performed to verify the interaction between circTLK1/PARP1 and miR‐17‐5p.

Results

CircTLK1, PARP1 and HMGB1 were up‐regulated in the in vitro and in vivo models of septic cardiomyopathy. CircTLK1 inhibition restrained LPS‐induced up‐regulation of PARP1 and HMGB1. Moreover, circTLK1 knockdown repressed sepsis‐induced mtDNA oxidative damage, mitochondrial dysfunction and consequent cardiomyocyte apoptosis by inhibiting PARP1/HMGB1 axis in vitro and in vivo. In addition, circTLK1 enhanced PARP1 expression via sponging miR‐17‐5p. Inhibition of miR‐17‐5p abolished the protective effects of circTLK1 silencing on oxidative mtDNA damage and cardiomyocyte apoptosis.

Conclusion

CircTLK1 sponged miR‐17‐5p to aggravate mtDNA oxidative damage, mitochondrial dysfunction and cardiomyocyte apoptosis via activating PARP1/HMGB1 axis during sepsis, indicating that circTLK1 may be a putative therapeutic target for septic cardiomyopathy.

Lipopolysaccharide Alters the m6A Epitranscriptomic Tagging of RNAs in Cardiac Tissue

N6-methyladenosine (m⁶A) modification plays important roles in the pathology of a variety of diseases. However, the roles of m⁶A modification in sepsis-induced myocardial dysfunction are not well defined. Rats were divided into control and lipopolysaccharide (LPS)-induced sepsis group. Global m⁶A levels of left ventricle tissue were measured by LC-MS/MS, and transcriptome-wide m⁶A modifications were profiled using epitranscriptomic microarrays (mRNAs and lncRNAs). Bioinformatics analysis was conducted to understand the functional implications of m⁶A modifications during sepsis. Methylated lncRNAs and mRNAs were measured by m⁶A single-base site qPCR. The global m⁶A levels in left ventricle tissue were significantly decreased in the LPS group. While 27 transcripts (23 mRNAs and four lncRNAs) were hypermethylated, 46 transcripts (39 mRNAs and 7 lncRNAs) were hypomethylated in the LPS group. The mRNA expression of writers and readers was significantly decreased in the LPS group. The m⁶A modification of Clec1b, Stk38l and Tnfrsf26 was associated with platelet activation and apoptotic pathways. Moreover, the decrease in m⁶A modification of lncRNA XR_346,771 may be related to cation import in cardiac tissue. Our data provide novel information regarding changes to m⁶A modifications in cardiac tissue during sepsis, and m⁶A modifications might be promising therapeutic targets.

Role of non-coding RNAs as biomarkers of deleterious cardiovascular effects in sepsis

The mechanisms occurring during sepsis that produce an increased risk of cardiovascular (CV) disease (CVD) are poorly understood. Even less information exists regarding CV dysfunction as a complication of sepsis, particularly for sepsis-induced cardiomyopathy. However, recent research has demonstrated that non-coding RNAs, including microRNAs, long non-coding RNAs, and circular RNAs, play a crucial role in genetic reprogramming, gene regulation, and inflammation during the development of CVD. Here we describe experimental findings showing the importance of non-coding RNAs mediating relevant mechanisms underlying CV dysfunction after sepsis, so contributing to sepsis-induced cardiomyopathy. Importantly, non-coding RNAs are critical novel regulators of CVD risk factors. Thus, they are potential candidates to improve diagnostics and prognosis of sepsis-induced cardiomyopathy and other CVD events occurring after sepsis and set the basis to design novel therapeutic strategies.

CircPTK2-miR-181c-5p-HMGB1: a new regulatory pathway for microglia activation and hippocampal neuronal apoptosis induced by sepsis

BACKGROUND

Circular RNA hsa_circ_0008305 (circPTK2), miR-181c-5p and High mobility group box-1 (HMGB1) had a targeted regulatory relationship through bioinformatics analysis. This study explained the effects of these genes in microglia and sepsis mice.

METHODS

Lipopolysaccharide (LPS) or Cecal Ligation and Puncture (CLP) was used to induce inflammation cell model or sepsis mouse model, as needed. Gene levels were measured by enzyme linked immunosorbent assay (ELISA), quantitative real-time PCR or Western blot, as required. Apoptosis was detected by TUNEL assay, and RNase R was used to test the stability of circPTK2. Targeting relationships between genes were analyzed using bioinformatics analysis and dual luciferase assay. Morris water maze test and mitochondrial membrane potential (MMP) detection were conducted to analyze the effects of genes on cognitive dysfunction of mice.

RESULTS

Lipopolysaccharide induction triggered the release of pro-inflammatory cytokines, the upregulation of HMGB1 and circPTK2, and the downregulation of miR-181c-5p in microglia. Overexpression of HMGB1 enhanced the effect of LPS, while silencing HMGB1 partially counteracted the effect of LPS. Moreover, miR-181c-5p was a target of circPTK2 and bound to HMGB1. MiR-181c-5p mimic partially reversed the functions of LPS and HMGB1 overexpression, reduced the levels of TNF-α, IL-1β, and HMGB1, and inhibited apoptosis. CircPTK2 knockdown had the same effect as miR-181c-5p up-regulation. In vivo, sicircPTK2 improved cognitive function, restored MMP level, inhibited apoptosis, reduced the levels of inflammatory factors and apoptotic factors, and increased the survival rate of CLP-induced mice.

CONCLUSION

Our research reveals that circPTK2 regulates microglia activation and hippocampal neuronal apoptosis induced by sepsis via miR-181c-5p-HMGB1 signaling.

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.

Circular RNA circ_0003420 mediates inflammation in sepsis-induced liver damage by downregulating neuronal PAS domain protein 4

OBJECTIVE

Our aim was to investigate whether circular RNA (circRNA) circ_0003420 mediates inflammation in sepsis-induced liver damage and to determine the mechanism involved.

MATERIALS AND METHODS

Liver tissue samples from patients with sepsis and healthy subjects were used to identify differentially expressed circRNAs. Additionally, Kupffer cells were treated with lipopolysaccharide (LPS) to establish an in vitro model of sepsis-induced liver damage. Cell viability and proliferation were measured with a cell counting kit-8 and 5-ethynyl-2'-deoxyuridine (EdU) labeling, respectively. Relative mRNA and protein levels of IL-6, IL-1β, tumor necrosis factor (TNF)-α, and neuronal PAS domain protein 4 (NPAS4) were determined via reverse-transcription quantitative PCR and western blotting, respectively.

RESULTS

We observed circ_0003420 upregulation accompanied by NPAS4 downregulation in liver samples from patients with sepsis-associated damage and in Kupffer cells treated with LPS. Results of in vitro experiments indicated that LPS treatment reduced cell viability and induced well-pronounced apoptosis and inflammatory signs. Circ_0003420 silencing counteracted LPS's influence on cell proliferation, apoptosis, and inflammation signs. Bioinformatics and a dual-luciferase reporter assay revealed that circ_0003420 targets NPAS4 mRNA and negatively correlates with NPAS4 expression. Moreover, NPAS4 knockdown recovered the apoptosis rate and expression levels of inflammatory cytokines in the LPS-treated circ_0003420 knockdown cells, whereas NPAS4 overexpression had similar effects on Kupffer cell properties as circ_0003420 silencing.

CONCLUSION

We demonstrate that circ_0003420 targets NPAS4 mRNA thereby mediating the cell damage and inflammation caused by LPS. This study provides a possible target for treatment of liver damage induced by sepsis.

Identification of circRNA and mRNA expression profiles and functional networks of vascular tissue in lipopolysaccharide-induced sepsis

Sepsis is the most common cause of death in intensive care units. This study investigated the circular RNA (circRNA) and mRNA expression profiles and functional networks of the aortic tissue in sepsis. We established a lipopolysaccharide (LPS)‐induced rat sepsis model. High‐throughput sequencing was performed on the aorta tissue to identify differentially expressed (DE) circRNAs and mRNAs, which were validated by real‐time quantitative polymerase chain reaction (RT‐qPCR). Bioinformatic analysis was carried out and coding and non‐coding co‐expression (CNC) and competing endogenous RNA (ceRNA) regulatory networks were constructed to investigate the mechanisms. In total, 373 up‐regulated and 428 down‐regulated circRNAs and 2063 up‐regulated and 2903 down‐regulated mRNAs were identified. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses of mRNAs showed that the down‐regulated genes were mainly enriched in the process of energy generation. CNC and ceRNA regulatory networks were constructed with seven DE circRNAs. The results of functional enrichment analysis of CNC target genes revealed the important role of circRNAs in inflammatory response. The ceRNA network also highlighted the significant enrichment in calcium signalling pathway. Significant alterations in circRNAs and mRNAs were observed in the aortic tissue of septic rats. In addition, CNC and ceRNA networks were established.