Nlrp3 Deficiency Alleviates Lipopolysaccharide-Induced Acute Kidney Injury via Suppressing Renal Inflammation and Ferroptosis in Mice

Targeting the epigenetic regulation of ferroptosis: a potential therapeutic approach for sepsis-associated acute kidney injury

Sepsis is a syndrome of organ dysfunction caused by the invasion of pathogenic microorganisms. In clinical practice, patients with sepsis are prone to concurrent acute kidney injury, which has high morbidity and mortality rates. Thus, understanding the pathogenesis of sepsis-associated acute kidney injury is of significant clinical importance. Ferroptosis is an iron-dependent programmed cell death pathway, which is proved to play a critical role in the process of sepsis-associated acute kidney injury through various mechanisms. Epigenetic regulation modulates the content and function of nucleic acids and proteins within cells through various modifications. Its impact on ferroptosis has garnered increasing attention; however, the role of epigenetic regulation targeting ferroptosis in sepsis-associated acute kidney injury has not been fully elucidated. Growing evidence suggests that epigenetic regulation can modulate ferroptosis through complex pathway networks, thereby affecting the development and prognosis of sepsis-associated acute kidney injury. This paper summarizes the impact of ferroptosis on sepsis-associated acute kidney injury and the regulatory mechanisms of epigenetic regulation on ferroptosis, providing new insights for the targeted therapy of sepsis-associated acute kidney injury.

ALPK1 signaling pathway activation by HMGB1 drives microglial pyroptosis and ferroptosis and brain injury after acute ischemic stroke

Pyroptosis and ferroptosis emerge as remarkable contributors to neuronal death and inflammation following ischemic stroke. High mobility group box 1 (HMGB1), a principal damage-associated molecular pattern (DAMP), is implicated in pyroptosis and ferroptosis post-stroke. Our previous research has demonstrated that alpha kinase 1 (ALPK1), a novel cytoplasmic pattern recognition receptor (PRR), plays an important role in mediating inflammatory damage following ischemic stroke. However, the interaction between ALPK1 and HMGB1, and their combined impact on pyroptosis and ferroptosis post-ischemic stroke remain unexplored, which is what this study aims to investigate. Initially, we observed that ALPK1 ablation attenuated ischemic brain injury of transient middle cerebral artery occlusion (tMCAO) mice. Moreover, recombinant HMGB1 (rHMGB1) stimulation induced the greatest upregulation of ALPK1 expression in microglia compared to astrocytes and neurons. Further investigation using co-immunofluorescence, co-immunoprecipitation, pull-down assay, and molecular docking revealed an interaction between HMGB1 and ALPK1. Additionally, the exacerbation of ischemic brain injury and the induction of microglial pyroptosis and ferroptosis by rHMGB1 treatment in tMCAO mice were significantly mitigated through ALPK1 deficiency by inhibiting the NLRP3/Caspase-1/GSDMD and JAK2/STAT3 signaling pathways. The inhibitory effects of ALPK1 deficiency on pyroptosis and ferroptosis induced by rHMGB1 in microglial cells were further substantiated. Finally, glycyrrhizic acid (GA), an inhibitor of HMGB1, exhibited significant neuroprotective effects in both tMCAO mice and BV2 cells subjected to oxygen-glucose deprivation/reperfusion (OGD/R) by downregulating ALPK1 expression and inhibiting microglial pyroptosis and ferroptosis. Collectively, these findings suggest that HMGB1 may interact with ALPK1 to drive microglial pyroptosis and ferroptosis via the activation of the ALPK1/NF-κB/NLRP3/GSDMD and JAK2/STAT3 signaling pathways, thereby exacerbating brain injury following acute ischemic stroke.

Total Alkaloids of Rhizoma Corydalis regulates gut microbiota and restores gut immune barrier to ameliorate cognitive dysfunction in diabetic rats

Background and objectives

Given the widespread dysbiosis of gut microbiota in patients with T2DM, it has been found that the microbiota-gut-brain axis plays an influential regulatory role in diabetic cognitive dysfunction, and improving gut dysbiosis may be a potential strategy for treating diabetic cognitive dysfunction. Total Alkaloids of Rhizoma Corydalis (TAC) is the main active component extracted from Rhizoma Corydalis. Pharmacological studies have demonstrated its significant pharmacological effects on the cardiovascular and cerebrovascular systems, and berberine, the main component of TAC, has a certain regulatory effect on gut microbiota.

Materials and methods

Rats were randomly divided into Control group, Model group, TAC-low group, TAC-mid group and TAC-high group. Cognitive function of diabetic rats was evaluated through behavioral testing using the Morris water maze experiment. The relative abundance of gut bacteria in rat feces was determined via 16S rRNA analysis. IHC and Western blot techniques were employed to assess IL-22, IL-23, Reg3g, ZO-1, occludin 1 expression in the colon tissue; GPX4, xCT, NLRP3, Caspase-1 p20, GSDMD-N were detected in the hippocampus.

Results

The cognitive function of diabetic rats decreased significantly. TAC demonstrated a significant reduction in inflammatory factors in serum, hippocampus, and colon, thus alleviating inflammation. Additionally, it effectively decreased ferroptosis induced by NLRP3 and reduced pathological damage in the hippocampus of diabetic rats. After treatment, the differential microbiota such as Lachnoclotridium and Bacteroides. TAC improved gut barrier permeability and integrity in rats while remodeling gut mucosal homeostasis. Moreover, pyroptosis and ferroptosis caused by the inflammatory cascade in the rat hippocampus were also significantly inhibited.

Conclusion

The combination of high lipid and high glucose with STZ can result in gut microbiota disturbance, damage gut immune barrier, decreased gut mucosal permeability and integrity, aggravated gut inflammation, further spread inflammatory factors to brain tissue, cause inflammatory cascade reaction of encephalopathy, and ultimately resulting in neuronal ferroptosis and cognitive dysfunction in diabetes mellitus. Our study suggests that TAC may regulate gut microbiota, restore gut immune homeostasis, improve gut barrier permeability and integrity, inhibit brain tissue inflammatory cascade, reduce neuronal ferroptosis, and thus improve diabetes. This provides new targets for its treatment strategy.

Regulation of pyroptosis and ferroptosis by mitophagy in chronic kidney disease

Chronic kidney disease (CKD) is a chronic progressive disease characterized by kidney injury or declining renal function. With its insidious onset and significant harm, CKD has become a major global public health concern. Abnormal cell death can directly or indirectly contribute to kidney injury, among which excessive pyroptosis and ferroptosis are central events in CKD pathogenesis. These two forms of cell death may interact through mechanisms such as reactive oxygen species release, further aggravating renal damage. Mitophagy, a selective autophagic process that removes damaged mitochondria, plays an important role in maintaining cellular homeostasis. In CKD, mitophagy is impaired; however, enhancing mitophagy signaling pathways can alleviate inflammation, reduce iron accumulation and lipid peroxidation in renal cells. This suggests that mitophagy may be a key regulator of pyroptosis and ferroptosis in kidney cells and holds potential as a novel target for the prevention, diagnosis, and treatment of CKD.

Isoquercitrin Inhibits Lung Cancer Cell Growth Through Triggering Pyroptosis and Ferroptosis

Isoquercitrin possesses anti-tumor activity in several types of cancers, however, its effects and underlying mechanisms on lung cancer have not been reported. Human lung cancer cell lines as well as normal lung epithelial BEAS-2B cells were treated with isoquercitrin. The influences of isoquercitrin in vitro were evaluated by determining cell viability, apoptosis, pyroptosis, and ferroptosis. Additionally, A549 tumor-bearing mice were generated to explore the anti-cancer effect of isoquercitrin in vivo. We found that isoquercitrin dose-dependently reduced lung cancer cells' viability, with no toxicity against BEAS-2B cells. Isoquercitrin at 40 μM and 80 μM was used in vitro. Isoquercitrin increased apoptosis, elevated NLRP3 inflammasome activation-mediated pyroptosis, and promoted ferroptosis in lung cancer cells. NLRP3 knockdown and caspase-1 selective inhibitor VX-765 attenuated isoquercitrin-induced pyroptosis and ferroptosis, but not apoptosis. Furthermore, isoquercitrin accelerated ROS generation, while ROS inhibitor N-acetylcysteine abrogated isoquercitrin-induced apoptosis, NLRP3 related-pyroptosis and ferroptosis. In vivo, isoquercitrin (1 mg/kg and 5 mg/kg) inhibited tumor growth, increased apoptosis, NLRP3-related pyroptosis, ferroptosis and ROS generation in tumors. Taken together, isoquercitrin inhibits lung cancer growth by triggering ROS/NLRP3-mediated pyroptosis and ferroptosis, with ROS also directly inducing apoptosis. This suggests that isoquercitrin might be a potential therapeutic agent for lung cancer.

Renal macrophages and NLRP3 inflammasomes in kidney diseases and therapeutics

Macrophages are exceptionally diversified cell types and perform unique features and functions when exposed to different stimuli within the specific microenvironment of various kidney diseases. In instances of kidney tissue necrosis or infection, specific patterns associated with damage or pathogens prompt the development of pro-inflammatory macrophages (M1). These M1 macrophages contribute to exacerbating tissue damage, inflammation, and eventual fibrosis. Conversely, anti-inflammatory macrophages (M2) arise in the same circumstances, contributing to kidney repair and regeneration processes. Impaired tissue repair causes fibrosis, and hence macrophages play a protective and pathogenic role. In response to harmful stimuli within the body, inflammasomes, complex assemblies of multiple proteins, assume a pivotal function in innate immunity. The initiation of inflammasomes triggers the activation of caspase 1, which in turn facilitates the maturation of cytokines, inflammation, and cell death. Macrophages in the kidneys possess the complete elements of the NLRP3 inflammasome, including NLRP3, ASC, and pro-caspase-1. When the NLRP3 inflammasomes are activated, it triggers the activation of caspase-1, resulting in the release of mature proinflammatory cytokines (IL)-1β and IL-18 and cleavage of Gasdermin D (GSDMD). This activation process therefore then induces pyroptosis, leading to renal inflammation, cell death, and renal dysfunction. The NLRP3-ASC-caspase-1-IL-1β-IL-18 pathway has been identified as a factor in the development of the pathophysiology of numerous kidney diseases. In this review, we explore current progress in understanding macrophage behavior concerning inflammation, injury, and fibrosis in kidneys. Emphasizing the pivotal role of activated macrophages in both the advancement and recovery phases of renal diseases, the article delves into potential strategies to modify macrophage functionality and it also discusses emerging approaches to selectively target NLRP3 inflammasomes and their signaling components within the kidney, aiming to facilitate the healing process in kidney diseases.

[Chlorogenic acid alleviates acute kidney injury in septic mice by inhibiting NLRP3 inflammasomes and the caspase-1 canonical pyroptosis pathway]

OBJECTIVE

To investigate the role of caspase-1-medicated canonical pyroptosis pathway in chlorogenic acid (CGA) treatment of acute kidney injury (AKI) in mice.

METHOD

Twenty-four C57Bl/6J mice were randomized into sham-operated group, cecal ligation and puncture (CLP) group, CLP+dexamethasone group (CLP+DXM group), and CLP+CGA group (n=6) and subjected to either sham operation (laparotomy only) or CLP. After modeling the mice received intravenous infusion of 10 mg/kg normal saline (in sham and CLP groups), 1 μg/kg dexamethasone or 15 mg/kg of chlorogenic acid for 6 h delivered using an intravenous pump. Eight hours after the infusion, renal morphology and histology, renal cell apoptosis, and the renal function parameters such as urea nitrogen (BUN), creatinine (Scr), and kidney injury molecule 1 (KIM-1) were compared among the 4 groups; the 7-day survival rates of the mice were recorded, and the expressions of NLRP3 inflammasomes and key proteins of the caspase-1 pathway in the renal tissue were detected.

RESULTS

CGA treatment significantly improved the 7-day survival rate, reduced renal pathologies of the septic mice (P < 0.05), and lowered the levels of BUN, Scr, KIM-1, NLRP3 inflammasome and expressions of key proteins of the caspase-1 pathway.

CONCLUSION

CGA alleviates AKI in mice with CLP-induced sepsis by inhibiting NLRP3 inflammasomes and the caspase-1 signaling pathway.

Bioinformatics analysis and experimental validation reveal the anti-ferroptosis effect of FZD7 in acute kidney injury

BACKGROUND

Ferroptosis plays an important role in acute kidney injury (AKI), but the specific regulatory mechanism of ferroptosis in AKI remains unclear. This study is expected to analyze ferroptosis-related genes (FRGs) in AKI and explore their underlying mechanisms.

RESULTS

A total of 479 differentially expressed genes (DEGs), including 196 up-regulated genes and 283 down-regulated genes were identified in the AKI chip GSE30718. 341 FRGs were obtained from the Genecard, OMIM and NCBI database. Totally 11 ferroptosis-related DEGs in AKI were found, in which 7 genes (CD44, TIGAR, RB1, LCN2, JUN, ARNTL, ACSL4) were up-regulated and 4 genes (FZD7, EP300, FOXC1, DLST) were down-regulated. Three core genes (FZD7, JUN, EP300) were obtained by PPI and KEGG analysis, among which the function of FZD7 in AKI is unclear. The WGCNA analysis found that FZD7 belongs to a module that was negatively correlated with AKI. Further basic experiments confirmed that FZD7 is down-regulated in mouse model of ischemia-reperfusion-AKI and cellular model of hypoxia-reoxygenation(H/R). In addition, knockdown of FZD7 could further aggravate the down-regulation of cell viability induced by H/R and Erastin, while overexpression of FZD7 can rescue its down-regulation to some extent. Furthermore, we verified that knockdown of FZD7 decreased the expression of GPX4 and overexpression of FZD7 increased the expression of GPX4, suggesting that FZD7 may inhibit ferroptosis by regulating the expression of GPX4 and plays a vital role in the onset and development of AKI.

CONCLUSIONS

This article revealed the anti-ferroptosis effect of FZD7 in acute kidney injury through bioinformatics analysis and experimental validation, suggesting that FZD7 is a promising target for AKI and provided more evidence about the vital role of ferroptosis in AKI.