The circular RNA hsa_circ_0003091 regulates sepsis-induced lung injury by sponging the miR-149/Smad2 axis

Emerging role and clinical applications of circular RNAs in human diseases

Circular RNAs (circRNAs) are a large family of non-coding RNAs characterized by a single-stranded, covalently closed structure, predominantly synthesized through a back-splicing mechanism. While thousands of circRNAs have been identified, only a few have been functionally characterized. Although circRNAs are less abundant than other RNA types, they exhibit exceptional stability due to their covalently closed structure and demonstrate high cell and tissue specificity. CircRNAs play a critical role in maintaining cellular homeostasis by influencing gene transcription, translation, and post-translation processes, modulating the immune system, and interacting with mRNA, miRNA, and proteins. Abnormal circRNA expression has been associated with a wide range of human diseases and various infections. Due to their remarkable stability in body fluids and tissues, emerging research suggests that circRNAs could serve as diagnostic and therapeutic biomarkers for these diseases. This review focuses on the emerging role of circRNAs in various human diseases, exploring their biogenesis, molecular functions, and potential clinical applications as diagnostic and therapeutic biomarkers with current evidence, challenges, and future perspectives. The key theme highlights the significance of circRNAs in regulating gene expression, their involvement in diseases like cancer, neurodegenerative disorders, cardiovascular diseases, and diabetes, and their potential use in translational medicine for developing novel therapeutic strategies. We also discuss recent clinical trials involving circRNAs. Thus, this review is important for both basic researchers and clinical scientists, as it provides updated insights into the role of circRNAs in human diseases, aiding further exploration and advancements in the field.

The Therapeutic Potential of Exosome Therapy in Sepsis Management: Addressing Complications and Improving Outcomes"

Infection occurs when pathogens penetrate tissues, reproduce, and trigger a host response to both the infectious agents and their toxins. A diverse array of pathogens, including viruses and bacteria, can cause infections. The host's immune system employs several mechanisms to combat these infections, typically involving an innate inflammatory response. Inflammation is a complex biological reaction that can affect various parts of the body and is a key component of the response to harmful stimuli. Sepsis arises when the body's response to infection leads to widespread damage to tissues and organs, potentially resulting in severe outcomes or death. The initial phase of sepsis involves immune system suppression. Early identification and targeted management are crucial for improving sepsis outcomes. Common treatment approaches include antibiotics, intravenous fluids, blood cultures, and monitoring urine output. This study explores the potential of exosome therapy in enhancing the management and alleviation of sepsis symptoms.

CircIRAK3 Promotes Neutrophil Extracellular Trap Formation by Improving the Stability of ELANE mRNA in Sepsis

Excessive formation of neutrophil extracellular traps (NETs) has been shown to exacerbate inflammatory injury and organ damage in patients with sepsis. Circular RNAs (circRNAs) abnormally expressed in immune cells of sepsis patients, and play an important role in the pathogenesis of dysregulated immune responses. However, the functions of circRNAs in NET formation during sepsis remain unknown. Here, we identified circIRAK3, a novel circRNA that was upregulated in peripheral blood neutrophils of sepsis patients. Combining clinical data, we revealed that elevated circIRAK3 was positively correlated with blood NET levels. Furthermore, knockdown and overexpression in differentiated HL-60 (dHL-60) neutrophil-like cells demonstrated that circIRAK3 promoted NET formation. In addition, we found that circIRAK3 promoted NET formation via positively regulating elastase expression in dHL-60 cells when treated with inflammatory stimuli. Mechanistically, circIRAK3 directly interacted with ELAVL1 to improve ELANE mRNA stability and consequently promote elastase protein expression. In summary, our study reveals that circIRAK3 promotes NET formation in sepsis by increasing ELANE mRNA levels.

Unwinding circular RNA's role in inflammatory pulmonary diseases

Circular RNAs (circRNAs) have emerged as pivotal regulators of gene expression and cellular processes in various physiological and pathological conditions. In recent years, there has been a growing interest in investigating the role of circRNAs in inflammatory lung diseases, owing to their potential to modulate inflammation-associated pathways and contribute to disease pathogenesis. Inflammatory lung diseases, like asthma, chronic obstructive pulmonary disease (COPD), and COVID-19, pose significant global health challenges. The dysregulation of inflammatory responses demonstrates a pivotal function in advancing these diseases. CircRNAs have been identified as important players in regulating inflammation by functioning as miRNA sponges, engaging with RNA-binding proteins, and participating in intricate ceRNA networks. These interactions enable circRNAs to regulate the manifestation of key inflammatory genes and signaling pathways. Furthermore, emerging evidence suggests that specific circRNAs are differentially expressed in response to inflammatory stimuli and exhibit distinct patterns in various lung diseases. Their involvement in immune cell activation, cytokine production, and tissue remodeling processes underscores their possible capabilities as therapeutic targets and diagnostic biomarkers. Harnessing the knowledge of circRNA-mediated regulation in inflammatory lung diseases could lead to the development of innovative strategies for disease management and intervention. This review summarizes the current understanding of the role of circRNAs in inflammatory lung diseases, focusing on their regulatory mechanisms and functional implications.

Functional roles of circular RNAs in lung injury

Lung injury leads to respiratory dysfunction, low quality of life, and even life-threatening conditions. Circular RNAs (circRNAs) are endogenous RNAs produced by selective RNA splicing. Studies have reported their involvement in the progression of lung injury. Understanding the roles of circRNAs in lung injury may aid in elucidating the underlying mechanisms and provide new therapeutic targets. Thus, in this review, we aimed to summarize and discuss the characteristics and biological functions of circRNAs, and their roles in lung injury from existing research, to provide a theoretical basis for the use of circRNAs as a diagnostic and therapeutic target for lung injury.

CircEXOC5 Aggravates Sepsis-Induced Acute Lung Injury by Promoting Ferroptosis Through the IGF2BP2/ATF3 Axis

BACKGROUND

Patients with sepsis resulting in acute lung injury (ALI) usually have increased mortality. Ferroptosis is a vital regulator in sepsis-induced ALI. Exploring the association of ferroptosis and sepsis-induced ALI is crucial for the management of sepsis-induced ALI.

METHODS

Whole blood was collected from sepsis patients. Mice were treated with cecal ligation and puncture (CLP) to model sepsis. Primary murine pulmonary microvascular endothelial cells were treated with lipopolysaccharide as a cell model. Ferroptosis was evaluated by analyzing levels of iron, malonaldehyde, glutathione, nonheme iron, ferroportin, ferritin, and GPX4. Hematoxylin and eosin and Masson's trichrome staining were applied to examine lung injury and collagen deposition. Cell apoptosis was analyzed by caspase-3 activity and TUNEL assays. Gene regulatory relationship was verified using RNA pull-down and immunoprecipitation assays.

RESULTS

CircEXOC5 was highly expressed in sepsis patients and CLP-treated mice, in which knockdown alleviated CLP-induced pulmonary inflammation and injury, and ferroptosis. CircEXOC5 recruited IGF2BP2 to degrade ATF3 mRNA. The demethylase ALKBH5 was responsible for circEXOC5 upregulation through demethylation. CircEXOC5 silencing significantly improved sepsis-induced ALI and survival rate of mice by downregulating ATF3.

CONCLUSIONS

ALKBH5-mediated upregulation of circEXOC5 exacerbates sepsis-induced ALI by facilitating ferroptosis through IGF2BP2 recruitment to degrade ATF3 mRNA.

circFLNA promotes intestinal injury during abdominal sepsis through Fas-mediated apoptosis pathway by sponging miR-766-3p

BACKGROUND

Intra-abdominal infections are the second most common cause of sepsis in the intensive care unit. Intestinal epithelial injury due to abdominal sepsis results in a variety of pathological changes, such as intestinal bacteria and toxins entering the blood, leading to persistent systemic inflammation and multiple organ dysfunction. The increased apoptosis of intestinal epithelial cells induced by sepsis further exacerbates the progression of sepsis. Although several studies have revealed that circRNAs are involved in intestinal epithelial injury in sepsis, few studies have identified the roles of circRNAs in intestinal epithelial apoptosis.

METHODS

We used laser capture microdissection to obtain purified epithelial cells located in intestinal crypts from four patients with abdominal sepsis induced by intestinal perforation and four samples from age and sex-matched non-septic patients. Microarray analysis of circRNAs was conducted to assess differentially expressed circRNAs between patients with and without sepsis. Lastly, in vitro and in vivo assays were performed to study the mechanism of circFLNA in intestinal epithelial apoptosis during sepsis.

RESULTS

circFLNA was upregulated in the intestinal epithelium after abdominal sepsis induced by intestinal perforation. Inhibition of miR-766-3p impaired si-circFLNA-mediated inhibition of apoptosis and inflammation factor levels in lipopolysaccharide (LPS)-treated HIEC-6 cells. circFLNA aggravated apoptosis and inflammation through the Fas-mediated apoptosis pathway in both LPS-treated HIEC-6 cells and a mouse cecal ligation and puncture model.

CONCLUSION

Our findings showed that circFLNA promotes intestinal injury in abdominal sepsis through the Fas-mediated apoptosis pathway by sponging miR-766-3p. The circFLNA/miR-766-3p/Fas axis has potential as a novel therapeutic target for treating intestinal injury in sepsis.

Tocilizumab attenuates acute lung injury in rats with sepsis by regulating S100A12/NLRP3

OBJECTIVE

To investigate the mechanism of Tocilizumab (TCZ) in attenuating acute lung injury in rats with sepsis by regulating the S100A12/NLRP3 axis.

METHODS

A rat model of sepsis was constructed using cecal ligation and puncture (CLP). Rats were treated with TCZ, and their lung tissue was collected. H&E staining was used to detect pathologic damage to lung tissue, and lung wet/dry (W/D) weight ratio was measured to assess pulmonary edema. Lipid oxidation assay and superoxide dismutase (SOD) activity assay kits were used to measure malondialdehyde (MDA) and SOD levels. Primary rat pulmonary microvascular endothelial cells (MPVECs) were treated with lipopolysaccharide (LPS) to construct a rat model of sepsis, which was then treated with TCZ. The mRNA and protein expressions of S100A12/NLRP3 were detected by qRT-PCR and western blot, respectively. S100A12 knockdown and overexpression plasmids, and NLRP3 knockdown plasmids were constructed and transfected into sepsis cells to intervene in the levels of S100A12/NLRP3. The apoptosis rate was detected by apoptosis assay. The levels of IL-6, TNF-α, and IL-10 in cells and tissues were analyzed by ELISA.

RESULTS

Compared to the Sham group, the CLP group had increased W/D weight ratio of lung tissue, IL-6, TNF-α, and MDA levels, lowered IL-10 and SOD levels, and more severe tissue damage (all P<0.05). After TCZ treatment, the above indicators were improved. The expressions of S100A12/NLRP3 cells were increased in LPS-induced MPVECs, but decreased after TCZ treatment. LPS induced apoptosis, but TCZ reduced the apoptosis, weakened the secretion levels of IL-6 and TNF-α, and enhanced IL-10 secretion levels. Transfection to cause the overexpression of S100A12 or NLRP3 plasmid partially counteracted the effect of TCZ. Knockdown of S100A12 was transfected on the basis of overexpression of NLRP3, which weakened the countervailing effect of overexpressed NLRP3 on TCZ.

CONCLUSION

TCZ has a therapeutic effect on lung injury in rats with sepsis by reducing the expressions of S100A12/NLRP3.

Functions and clinical significance of circular RNAs in acute myeloid leukemia

Circular RNAs (circRNAs) are a class of covalently closed single-stranded RNA molecules. Four types of circRNAs have been reported in animal cells, and they have typical characteristics in their biogenesis, nuclear export and degradation. Advances in our understanding of the molecular functions of circRNAs in sponging microRNAs, modulating transcription, regulating RNA-binding proteins, as well as encoding proteins have been made very recently. Dysregulated circRNAs are associated with human diseases such as acute myeloid leukemia (AML). In this review, we focus on the recently described mechanisms, role and clinical significance of circRNAs in AML. Although great progress of circRNAs in AML has been achieved, substantial efforts are still required to explore whether circRNAs exert their biological function by other mechanisms such as regulation of gene transcription or serving as translation template in AML. It is also urgent that researchers study the machineries regulating circRNAs fate, the downstream effectors of circRNAs modulatory networks, and the clinical application of circRNAs in AML.