Auto- and paracrine rewiring of NIX-mediated mitophagy by insulin-like growth factor-binding protein 7 in septic AKI escalates inflammation-coupling tubular damage

Downregulation of the immunoproteasome subunit PSMB8 attenuates sepsis-associated acute kidney injury through the NF-κB pathway

Sepsis-associated acute kidney injury (S-AKI) is a prevalent and life-threatening complication in hospitalized and critically ill patients. Recent researches indicates that immunoproteasome, especially proteasome 20S subunit beta 8 (PSMB8), is highly associated with various kidney diseases. This study aims to investigate the potential involvement of PSMB8 in S-AKI and its impact on apoptosis and inflammation. The model of S-AKI induced by LPS (10 mg/kg) was assessed by histological examination. ELISA and Real-time PCR were used to detect the levels of inflammatory cytokines in the renal cortex. The role of shPSMB8 in LPS-induced apoptosis was detected by flow cytometry. Finally, western blot was performed to assess the NF-κB signaling pathway related proteins, and the nuclear translocation of NF-kB P65 was detected by immunofluorescence microscopy. PSMB8 knockdown substantially protected against renal injury by reducing blood urea nitrogen and creatinine levels and ameliorating inflammation. PSMB8 knockdown inhibited renal expression of interleukin (IL)-1β, IL-6, tumor necrosis factor-α (TNF-α) and COX-2 to improve inflammatory response. Mechanistic studies demonstrated that downregulation of PSMB8 blocked LPS-induced S-AKI phosphorylation and nuclear translocation of NF-κB P65. Collectively, our results suggest that inhibition of PSMB8 significantly contributes to S-AKI via regulation of NF-κB. These findings reveal the pathogenic role of PSMB8 in AKI and suggest a novel therapeutic target for the condition.

Downregulation of IGFBP7 Alleviates LPS-induced Inflammation and Apoptosis in WI-38 Cells via Enhancing Mitophagy

Pediatric pneumonia is an inflammatory disease with a very high incidence. IGF binding protein 7 (IGFBP7) plays an important role in inflammatory diseases. However, the role of IGFBP7 in pediatric pneumonia and its mechanism have not been reported. Human embryonic lung (WI-38) cells were induced by lipopolysaccharide (LPS) to construct the cell inflammatory injury model. Subsequently, the expression of IGFBP7 was detected by qPCR and western blot. Next, IGFBP7 interference plasmid was constructed, and cell viability and apoptosis were detected by CCK8, flow cytometry and western blot. ELISA and other techniques were used to detect the inflammatory level. Autophagy and mitochondrial activities were detected by immunofluorescence and other techniques, and mitophagy-related proteins were detected by western blot. To further investigate the regulatory mechanism of IGFBP7, we administered cyclosporin A, a mitophagy inhibitor, and then detected apoptosis and inflammation. The expression of IGFBP7 was significantly increased in LPS-induced WI-38 cells. Interference with IGFBP7 expression in LPS-induced cells significantly increased cell activity, decreased apoptosis and cellular inflammation levels. During this process, mitophagy was enhanced. Further addition of cyclosporin A significantly reversed the protective effect of IGFBP7 knockdown. To be concluded, inhibition of IGFBP7 alleviates LPS-induced inflammation and apoptosis in WI-38 cells via enhancing mitophagy.

Molecular mechanisms of Sepsis attacking the immune system and solid organs

Remarkable progress has been achieved in sepsis treatment in recent times, the mortality rate of sepsis has experienced a gradual decline as a result of the prompt administration of antibiotics, fluid resuscitation, and the implementation of various therapies aimed at supporting multiple organ functions. However, there is still significant mortality and room for improvement. The mortality rate for septic patients, 22.5%, is still unacceptably high, accounting for 19.7% of all global deaths. Therefore, it is crucial to thoroughly comprehend the pathogenesis of sepsis in order to enhance clinical diagnosis and treatment methods. Here, we summarized classic mechanisms of sepsis progression, activation of signal pathways, mitochondrial quality control, imbalance of pro-and anti- inflammation response, diseminated intravascular coagulation (DIC), cell death, presented the latest research findings for each mechanism and identify potential therapeutic targets within each mechanism.

The multifaceted role of insulin-like growth factor binding protein 7

Insulin-like growth factor binding protein 7 (IGFBP7) serves as a crucial extracellular matrix protein, exerting pivotal roles in both physiological and pathological processes. This comprehensive review meticulously delineates the structural attributes of IGFBP7, juxtaposing them with other members within the IGFBP families, and delves into the expression patterns across various tissues. Furthermore, the review thoroughly examines the multifaceted functions of IGFBP7, encompassing its regulatory effects on cell proliferation, apoptosis, and migration, elucidating the underlying mechanistic pathways. Moreover, it underscores the compelling roles in tumor progression, acute kidney injury, and reproductive processes. By rigorously elucidating the diverse functionalities and regulatory networks of IGFBP7 across various physiological and pathological contexts, this review aims to furnish a robust theoretical framework and delineate future research trajectories for leveraging IGFBP7 in disease diagnosis, therapeutic interventions, and pharmaceutical innovations.

An overview of circulating and urinary biomarkers capable of predicting the transition of acute kidney injury to chronic kidney disease

INTRODUCTION

Acute kidney injury (AKI) defined by a substantial decrease in kidney function within hours to days and is often irreversible with higher risk to chronic kidney disease (CKD) transition.

AREAS COVERED

The authors discuss the diagnostic and predictive utilities of serum and urinary biomarkers on AKI and on the risk of AKI-to-CKD progression. The authors focus on the relevant literature covering evidence of circulating and urinary biomarkers' capability to predict the transition of AKI to CKD.

EXPERT OPINION

Based on the different modalities of serum and urinary biomarkers, multiple biomarker panel seems to be potentially useful to distinguish between various types of AKI, to detect the severity and the risk of AKI progression, to predict the clinical outcome and evaluate response to the therapy. Serum/urinary neutrophil gelatinase-associated lipocalin (NGAL), serum/urinary uromodulin, serum extracellular high mobility group box-1 (HMGB-1), serum cystatin C and urinary liver-type fatty acid-binding protein (L-FABP) were the most effective in the prediction of AKI-to-CKD transition regardless of etiology and the presence of critical state in patients. The current clinical evidence on the risk assessments of AKI progression is mainly based on the utility of combination of functional, injury and stress biomarkers, mainly NGAL, L-FABP, HMGB-1 and cystatin C.

Pellino1 orchestrates gut-kidney axis to perpetuate septic acute kidney injury through activation of STING pathway and NLRP3 inflammasome

AIMS

Intestinal barrier dysfunction is the initial and propagable factor of sepsis in which acute kidney injury (AKI) has been considered as a common life-threatening complication. Our recent study identifies the regulatory role of Pellino1 in tubular death under inflammatory conditions in vitro. The objective of our current study is to explore the impact of Pellino1 on gut-kidney axis during septic AKI and uncover the molecular mechanism (s) underlying this process.

MATERIALS AND METHODS

Immunohistochemistry (IHC) was conducted to evaluate Pellino1 and NOD-like receptor thermal protein domain associated protein 3 (NLRP3) levels in renal biopsies from critically ill patients with a clinical diagnosis of sepsis. Functional and mechanistic studies were characterized in septic models of the Peli-knockout (Peli1-/-) mice by histopathological staining, enzyme-linked immunosorbent assay (ELISA), flow cytometry, immunofluorescence, biochemical detection, CRISPR/Cas9-mediated gene editing and intestinal organoid.

KEY FINDINGS

Pellino1, together with NLRP3, are highly expressed in renal biopsies from critically ill patients diagnosed with sepsis and kidney tissues of septic mice. The Peli1-/- mice with sepsis become less prone to develop AKI and have markedly compromised NLRP3 activation in kidney. Loss of Peli1 endows septic mice refractory to intestinal inflammation, barrier permeability and enterocyte apoptosis that requires stimulator of interferons genes (STING) pathway. Administration of STING agonist DMXAA deteriorates AKI and mortality of septic Peli1-/- mice in the presence of kidney-specific NLRP3 reconstitution.

SIGNIFICANCE

Our studies suggest that Pellino1 has a principal role in orchestrating gut homeostasis towards renal pathophysiology, thus providing a potential therapeutic target for septic AKI.

Targeting SLC22A5 fosters mitophagy inhibition-mediated macrophage immunity against septic acute kidney injury upon CD47-SIRPα axis blockade

Efferocytosis of apoptotic neutrophils (PMNs) by macrophages is helpful for inflammation resolution and injury repair, but the role of efferocytosis in intrinsic nature of macrophages during septic acute kidney injury (AKI) remains unknown. Here we report that CD47 and signal regulatory protein alpha (SIRPα)-the anti-efferocytotic 'don't eat me' signals-are highly expressed in peripheral blood mononuclear cells (PBMCs) from patients with septic AKI and kidney samples from mice with polymicrobial sepsis and endotoxin shock. Conditional knockout (CKO) of SIRPA in macrophages ameliorates AKI and systemic inflammation response in septic mice, accompanied by an escalation in mitophagy inhibition of macrophages. Ablation of SIRPA transcriptionally downregulates solute carrier family 22 member 5 (SLC22A5) in the lipopolysaccharide (LPS)-stimulated macrophages that efferocytose apoptotic neutrophils (PMNs). Targeting SLC22A5 renders mitophagy inhibition of macrophages in response to LPS stimuli, improves survival and deters development of septic AKI. Our study supports further clinical investigation of CD47-SIRPα signalling in sepsis and proposes that SLC22A5 might be a promising immunotherapeutic target for septic AKI.

Mechanism and role of mitophagy in the development of severe infection

Mitochondria produce adenosine triphosphate and potentially contribute to proinflammatory responses and cell death. Mitophagy, as a conservative phenomenon, scavenges waste mitochondria and their components in the cell. Recent studies suggest that severe infections develop alongside mitochondrial dysfunction and mitophagy abnormalities. Restoring mitophagy protects against excessive inflammation and multiple organ failure in sepsis. Here, we review the normal mitophagy process, its interaction with invading microorganisms and the immune system, and summarize the mechanism of mitophagy dysfunction during severe infection. We highlight critical role of normal mitophagy in preventing severe infection.