Downregulation of circ-ZNF644 alleviates LPS-induced HK2 cell injury via miR-335-5p/HIPK1 axis

KLF15 ATTENUATES LIPOPOLYSACCHARIDE-INDUCED APOPTOSIS AND INFLAMMATORY RESPONSE IN RENAL TUBULAR EPITHELIAL CELLS VIA PPARΔ

ABSTRACT

Background: The kidney is the most commonly affected organ in sepsis patients, and Krüppel-like transcription factor 15 (KLF15) has a kidney-protective effect and is highly enriched in the kidneys. This study aims to explore the role of KLF15 in sepsis-related acute kidney injury. Methods: A septic injury model in HK2 cells was established through the administration of lipopolysaccharide (LPS), followed by the transfection of an overexpression plasmid for KLF15. Cell viability was assessed using Cell Counting Kit-8 assay, and apoptosis was measured via flow cytometry. The levels of inflammatory cytokines were detected using ELISA, and western blot assay was employed to assess the expression of KLF15, PPARδ, as well as inflammatory and apoptosis-related proteins. The interaction between KLF15 and PPARδ was confirmed through the utilization of online databases and immunoprecipitation experiments. The mechanism was further validated using PPARδ agonists and small interfering RNA. Results: LPS-induced HK2 cells showed downregulated expression of KLF15 and PPARδ, along with decreased viability, accompanied by increased levels of apoptosis, TNFα, IL-1β, and IL-6. Additionally, LPS upregulated the expression of Bax, cytoplasmic cytochrome C [Cytc (cyt)], Cox-2, and p-NF-κB-p65 in HK2 cells, while simultaneously downregulating the expression of Bcl2 and mitochondrial cytochrome c [Cytc (mit)]. immunoprecipitation experiment revealed a possible interaction between KLF15 and PPARδ in HK2 cells. Ov-KLF15, Ov-PPARδ, or administration of PPARδ agonists effectively alleviated the aforementioned alterations induced by LPS. However, interference with PPARδ significantly attenuated the protective effect of Ov-KLF15 on HK2 cells. Conclusion: KLF15 attenuates LPS-induced apoptosis and inflammatory responses in HK2 cells via PPARδ.

A Systematic Review and Meta-Analysis of MicroRNA as Predictive Biomarkers of Acute Kidney Injury

Acute kidney injury (AKI) affects 10-15% of hospitalised patients and arises after severe infections, major surgeries, or exposure to nephrotoxic drugs. AKI diagnosis based on creatinine level changes lacks specificity and may be delayed. MicroRNAs are short non-coding RNA secreted by all cells. This review of studies measuring miRNAs in AKI aimed to verify miRNAs as diagnostic markers. The study included data from patients diagnosed with AKI due to sepsis, ischaemia, nephrotoxins, radiocontrast, shock, trauma, and cardiopulmonary bypass. Out of 71 studies, the majority focused on AKI in sepsis patients, followed by cardiac surgery patients, ICU patients, and individuals receiving nephrotoxic agents or experiencing ischaemia. Studies that used untargeted assays found 856 differentially regulated miRNAs, although none of these were confirmed by more than one study. Moreover, 68 studies measured miRNAs by qRT-PCR, and 2 studies reported downregulation of miR-495-3p and miR-370-3p in AKI patients with sepsis after the AKI diagnosis. In three studies, upregulation of miR-21 was reported at the time of the AKI diagnosis with a significant pooled effect of 0.56. MiR-21 was also measured 19-24 h after cardiac surgery in three studies. However, the pooled effect was not significant. Despite the considerable research into miRNA in AKI, there is a knowledge gap in their applicability as diagnostic markers of AKI in humans.

Circular RNA CircZNF644 Facilitates Circulating Follicular Helper T Cells Response in Patients with Graves' Disease

Aberrant accumulation of circulating follicular helper T cells (cTfh) has been found in the peripheral blood mononuclear cells (PBMCs) of Graves' disease (GD) patients. However, the underlying mechanism that contributes to the imbalance of cTfh cells remains unknown. Previously, studies described a GD-related circular RNAs (circRNAs)-circZNF644 that might be associated with cTfh cells. This study aimed to investigate the role of circZNF644 on cTfh cells in GD patients. Here, we found that circZNF644 was highly stable expression in the PBMCs of GD patients, which was positively correlated with the serum levels of TSH receptor autoantibodies (TRAb). Knockdown of circZNF644 caused a reduction of the proportion of cTfh cells in vitro. Mechanistically, circZNF644 served as a ceRNA for miR-29a-3p to promote ICOS expression, resulting in increased cTfh cells. In the PBMCs of GD patients, circZNF644 expression was positively correlated with ICOS expression and the percentage of cTfh cells, but negatively related to miR-29a-3p expression. Additionally, a strong relationship between circZNF644 and IL-21 was revealed in GD patients, and silencing of circZNF644 inhibited IL-21 expression. Our study elucidated that elevated expression of circZNF644 is a key feature in the development of GD and may contribute to the pathogenic role of cTfh cells in GD.

Potential therapeutic applications of circular RNA in acute kidney injury

Acute kidney injury (AKI) is a common clinical syndrome characterized by a rapid deterioration in renal function, manifested by a significant increase in creatinine and a sharp decrease in urine output. The incidence of morbidity and mortality associated with AKI is on the rise, with most patients progressing to chronic kidney disease or end-stage renal disease. Treatment options for patients with AKI remain limited. Circular RNA (circRNA) is a wide and diverse class of non-coding RNAs that are present in a variety of organisms and are involved in gene expression regulation. Studies have shown that circRNA acts as a competing RNA, is involved in disease occurrence and development, and has potential as a disease diagnostic and prognostic marker. CircRNA is involved in the regulation of important biological processes, including apoptosis, oxidative stress, and inflammation. This study reviews the current status and progress of circRNA research in the context of AKI.

Fatty Acid Binding Protein-4 Silencing Inhibits Ferroptosis to Alleviate Lipopolysaccharide-induced Injury of Renal Tubular Epithelial Cells by Blocking Janus Kinase 2/Signal Transducer and Activator of Transcription 3 Signaling

Sepsis-induced kidney injury (SAKI) has been frequently established as a prevailing complication of sepsis which is linked to unfavorable outcomes. Fatty acid-binding protein-4 (FABP4) has been proposed as a possible target for the treatment of SAKI. In the current work, we aimed to explore the role and underlying mechanism of FABP4 in lipopolysaccharide (LPS)-induced human renal tubular epithelial cell damage. In LPS-induced human kidney 2 (HK2) cells, FABP4 expression was tested by the reverse transcription-quantitative polymerase chain reaction and Western blot. Cell counting kit-8 method assayed cell viability. Inflammatory levels were detected using the enzyme-linked immunosorbent assay. Immunofluorescence staining measured the nuclear translocation of nuclear factor kappa B p65. Thiobarbituric acid-reactive substances assay and C11 BODIPY 581/591 probe were used to estimate the level of cellular lipid peroxidation. Fe2+ content was examined by the kit. In addition, the expression of proteins related to inflammation-, ferroptosis- and Janus kinase 2 (JAK2)/signal transducer, and activator of transcription 3 (STAT3) signaling was detected by the Western blot analysis. The results revealed that FABP4 was significantly upregulated in LPS-treated HK2 cells, the knockdown of which elevated the viability, whereas alleviated the inflammation and ferroptosis in HK2 cells challenged with LPS. In addition, down-regulation of FABP4 inactivated JAK2/STAT3 signaling. JAK2/STAT3 stimulator (colivelin) and ferroptosis activator (Erastin) partially restored the effects of FABP4 interference on LPS-triggered inflammation and ferroptosis in HK2 cells. Together, FABP4 knockdown inhibited ferroptosis to alleviate LPS-induced injury of renal tubular epithelial cells through suppressing JAK2/STAT3 signaling.

Circ_0040994 depletion alleviates lipopolysaccharide-induced HK2 cell injury through miR-17-5p/TRPM7 axis

BACKGROUND

Sepsis is a fatal systemic inflammatory disease that causes septic acute kidney injury (AKI). In this work, we explored the roles of circ_0040994 in lipopolysaccharide (LPS)-induced human kidney-2 (HK2) cell injury.

METHODS

Circ_0040994, miR-17-5p and transient receptor potential melastatin 7 (TRPM7) expression were detected by qRT-PCR. Cell functions were examined by MTT assay, flow cytometry assay, western blot, ELISA assay, and oxidative stress assay. The molecular association was detected by dual-luciferase reporter assay.

RESULTS

Circ_0040994 was upregulated in the serum of septic AKI patients in comparison with the serum of healthy controls. Silencing circ_0040994 enhanced cell viability but inhibited cell apoptosis, cell inflammation and oxidative stress in LPS-triggered HK2 cells. Circ_0040994 acted as a miR-17-5p sponge to regulate the level of TRPM7. Moreover, miR-17-5p could alleviate LPS-induced HK2 cell injury by suppressing TRPM7.

CONCLUSION

Circ_0040994 downregulation alleviated LPS-induced HK2 cell injury through the miR-17-5p/TRPM7 axis.

Inhibition of sepsis-induced acute kidney injury via the circITCH-miR-579-3p-ZEB2 axis

Circular RNAs (circRNAs) are linked to the regulation of sepsis-induced acute kidney injury (AKI). However, the function of circITCH in the development of sepsis-induced AKI is still unclear. The levels of circITCH, miR-579-3p and ZEB2 were examined by real-time PCR and immunoblotting. Then, the roles of circITCH in cell viability, apoptosis, and inflammation in lipopolysaccharide (LPS)-treated HK-2 cells were evaluated. The further mechanism was investigated using rescue assays. CircITCH was downregulated in septic AKI patients and LPS-triggered HK-2 cells. CircITCH overexpression restored cell viability in LPS-treated HK-2 cells and restrained apoptosis and inflammatory cytokine production. CircITCH negatively regulated miR-579-3p, thereby upregulating ZEB2 expression. Taken together, circITCH alleviates LPS-induced HK-2 cell injury by regulating miR-579-3p/ZEB2 signal axis, which provides a theoretical basis for AKI therapy.

JMJD3 downregulates IL4i1 aggravating lipopolysaccharide-induced acute lung injury via H3K27 and H3K4 demethylation

The pro-inflammation M1 to anti-inflammation M2 macrophage ratio contribute to the severity of lipopolysaccharide (LPS)-induced acute lung injury (ALI). JMJD3 aggravates the inflammatory reaction through affecting epigenetic modification and macrophage's phenotype to deteriorate ALI. To explore the mechanism underlying the upregulation of the macrophage M1/M2 ratio through JMJD3, we developed an ALI mouse model using intratracheal LPS, LPS-stimulated RAW 264.7 cells, and inhibited JMJD3 using GSK-J4. H3K27me3 and H3K4me3 were investigated as JMJD3-mediated epigenetic alteration sites in vivo and in vitro. C/EBPβ and KDM5A were validated as linking factors between H3K27 and H3K4. IL4i1 was investigated as a JMJD3-mediated targeted gene to regulate the macrophage M1/M2 ratio. Chromatin immunoprecipitation was used to evaluate the relationship between H3K27me3 and C/ebpβ, C/EBPβ and Kdm5a, H3K4me3 and Il4i1. Inhibiting JMJD3 with GSK-J4 can relieve inflammation and pathological performance in ALI. JMJD3 can reduce IL4i1 expression to increase the macrophage M1/M2 ratio and aggravated ALI which process was mediated via JMJD3-indcued H3K27me3 and H3K4me3 demethylation, latter H3K4me3 demethylation inhibited IL4i1 transcription. Inhibiting JMJD3 with GSK-J4 can increase IL4i1 expression, subsequently decreasing the expressions of M1 and increasing of M2 in vivo. The over-expression IL4i1 in LPS-stimulated macrophage or inhibiting JMJD3 with GSK-J4 can both reverse the increase of the macrophage M1/M2 ratio in vitro. C/EBPβ and KDM5A were upregulated by LPS simulation, which linked JMJD3-induced H3K27-H3K4 demethylation. JMJD3 inhibited IL4i1 to increase the macrophage M1/M2 phenotype ratio and aggravate LPS-induced ALI. Using GSK-J4 to inhibit JMJD3 may facilitate the treatment of LPS-induced ALI.