Macrophages in Renal Injury and Repair

Proliferation of renal macrophage via MR/CSF1 pathway induced with aldosterone and inhibited by esaxerenone

Macrophage proliferation plays a critical role in kidney injury and repair, but due to their high plasticity and heterogeneity, the origins and subtypes of these proliferating cells remain unclear. This study investigates aldosterone-induced proliferation of renal macrophages, focusing on their origins, subtypes, and regulatory mechanisms using immunofluorescence, flow cytometry, and single-cell sequencing. The findings suggest that both resident and infiltrating macrophages proliferate in response to aldosterone, a significant proportion of which are renal resident macrophages, predominantly of the M1 subtype. The study also identifies the mineralocorticoid receptor/colony stimulation factor-1 (MR/CSF1) pathway as a key regulator of this process. Inhibition of this pathway through antagonists and inhibitors reduces macrophage proliferation and kidney damage, suggesting that targeting MR/CSF1 could be therapeutic against aldosterone-induced renal damage and inflammation.

Dynamic proteome and phosphoproteome profiling reveals regulatory mechanisms in LPS-stimulated macrophage inflammatory responses

Macrophage-mediated acute inflammation is crucial for pathogen clearance and tissue repair, yet the underlying molecular mechanisms remain inadequately understood. The present study focused on the dynamic profiles of the proteome and phosphoproteome of macrophages exposed to lipopolysaccharide within 1 h. Gene Set Enrichment Analysis (GSEA) identified significantly enriched pathways in fatty acid metabolism and translation during the early inflammatory phase. Further trend analysis of the differentially expressed proteins revealed patterns associated with translation regulation such as translation initiation. Importantly, the nascent chain experiment demonstrated no significant changes in overall gene translation levels during this phase. These data indicate that macrophages maintain intracellular protein homeostasis through translational regulation, with post-translational modifications (PTMs) playing a crucial role in the rapid cellular response to pathogen invasion. Phosphorylation is a key PTM that regulates protein functions in almost all cellular processes. Time-resolved phosphoproteome analysis identified 367 differentially expressed phosphopeptides involved in immune-related pathways that resist infection. Additionally, weighted gene co-expression network analysis (WGCNA) discovered core modules that regulate translation-related processes such as RNA export from nucleus. Moreover, conjoint analysis of the proteome and phosphoproteome identified the hub protein EF1B that exhibited the largest fold change and is also involved in translation. Our data not only provide a more comprehensive understanding of the dynamic molecular networks of acute macrophage inflammation but also provide a systematic proteomic resource for further studies.

Therapeutic potential of p-coumaric acid in alleviating renal fibrosis through inhibition of M2 macrophage infiltration and cellular communication

BACKGROUND

p-coumaric acid (p-CA), a hydroxycinnamic acid derivative, is recognized for its antioxidant and anti-inflammatory properties; however, its pharmacological effects on renal fibrosis remain insufficiently explored.

PURPOSE

This study aimed to evaluate the therapeutic potential of p-CA in renal fibrosis and elucidate its underlying mechanisms through extensive molecular and cellular analyses.

METHODS

Liquid chromatography-tandem mass spectrometry (LC-MS) was employed to analyze metabolic alterations associated with renal fibrosis induced by unilateral ureteral obstruction (UUO). Immune cell dynamics were assessed using cytometry by time of flight (CyTOF) and single-cell RNA sequencing (scRNA-seq). Further validation was performed using flow cytometry, Western blot (WB), quantitative real-time PCR (qRT-PCR), immunohistochemistry (IHC), and immunofluorescence (IF) to evaluate the renoprotective effects of p-CA at the cellular and molecular levels.

RESULTS

p-CA levels were significantly reduced in fibrotic renal tissues. Administration of exogenous p-CA restored renal function, alleviated tissue damage, and inhibited G2/M cell cycle arrest and epithelial-mesenchymal transition (EMT) in tubular epithelial cells (TECs). CyTOF and scRNA-seq analyses revealed that p-CA treatment decreased M2 macrophage proliferation, intercellular communication, and differentiation in fibrotic kidney tissues, resulting in reduced renal fibrosis. Additional experimental validations confirmed that p-CA specifically targeted M2 macrophages, suppressing their contribution to fibrotic progression.

CONCLUSIONS

p-CA exerts renoprotective effects by targeting M2 macrophages, disrupting their interaction with TECs, and attenuating fibrotic progression. These findings underscore the potential of p-CA as a novel therapeutic approach for renal fibrosis.

The polarization of macrophages participates in the repair after folic acid-induced acute kidney injury

Acute kidney injury (AKI) remains a major public health challenge, posing serious threats to human health. Increasing evidence indicates that renal cells undergo significant metabolic alterations following AKI, with inflammatory responses persisting throughout both injury and repair phases. Our previous research has demonstrated that heightened aerobic glycolysis after AKI leads to increased secretion of metabolic byproducts such as lactate, which plays a critical role in tissue repair. However, the relationship between metabolic reprogramming and inflammatory responses, as well as the underlying mechanisms, remain poorly understood. This study aims to clarify the regulatory effects of the glycolytic byproduct lactate on macrophage activation and phenotypic differentiation following AKI. We observed increased expression of M1/M2 macrophages and elevated secretion of inflammatory cytokines after folic acid-induced AKI. Immunofluorescence staining showed co-localization of macrophages with α-SMA. Manipulating lactate levels post-injury led to a decrease in macrophage expression and a reduction in fibroblast activation and proliferation, ultimately impairing renal tissue repair. These findings suggest that targeting lactate as a key regulator of macrophage phenotype differentiation may provide a theoretical and clinical foundation for therapeutic strategies in AKI repair.

SOX9: a key transcriptional regulator in organ fibrosis

The SOX9 gene locus is not only extensive but also intricate, and it could promote fibrosis in different organs or tissues, including cardiac fibrosis, liver fibrosis, kidney fibrosis, pulmonary fibrosis, as well as other organ fibrosis. Many disorders are associated with the process of fibrosis; moreover, fibrosis is a common symptom of chronic inflammatory diseases, characterized by the accumulation of excessive components in the extracellular matrix through different signaling pathways. The advanced stage of the fibrotic process leads to organ dysfunction and, ultimately, death. In this review, we first give an overview of the original structure and functions of SOX9. Second, we will discuss the role of SOX9 in fibrosis in various organs or tissues. Third, we describe and reveal the possibility of SOX9 as an antifibrotic treatment target. Finally, we will focus on the application of novel technologies for SOX9 and the subsequent investigation of fibrosis.

Epigenetic regulation of macrophage function in kidney disease: New perspective on the interaction between epigenetics and immune modulation

The interaction between renal intrinsic cells and macrophages plays a crucial role in the onset and progression of kidney diseases. In recent years, epigenetic mechanisms such as DNA methylation, histone modification, and non-coding RNA regulation have become essential windows for understanding these processes. This review focuses on how renal intrinsic cells (including tubular epithelial cells, podocytes, and endothelial cells), renal cancer cells, and mesenchymal stem cells influence the function and polarization status of macrophages through their own epigenetic alterations, and how the epigenetic regulation of macrophages themselves responds to kidney damage, thus participating in renal inflammation, fibrosis, and repair. Moreover, therapeutic studies targeting these epigenetic interaction mechanisms have found that the application of histone deacetylase inhibitors, histone methyltransferase inhibitors, various nanomaterials, and locked nucleic acids against non-coding RNA have positive effects on the treatment of multiple kidney diseases. This review summarizes the latest research advancements in these epigenetic regulatory mechanisms and therapies, providing a theoretical foundation for further elucidating the pathogenesis of kidney diseases and the development of novel therapeutic strategies.

Trametinib alleviates lipopolysaccharide-induced acute kidney injury by inhibiting macrophage polarization through the PI3K/Akt pathway

BACKGROUND

Sepsis-induced acute kidney injury (AKI) is a severe condition characterized by dysregulation of pro- and anti-inflammatory responses. Targeting macrophage polarization between pro-inflammatory M1 and anti-inflammatory M2 cells offers a potential therapeutic approach for AKI. Trametinib (TRAM), an inhibitor of the MEK1/2 signaling pathway, was evaluated for its impact on M1/M2 polarization in AKI.

METHODS

Wild-type (WT) mice were subjected to lipopolysaccharide (LPS)-induced AKI and intraperitoneally treated with dimethyl sulfoxide (DMSO) or TRAM (10 mg/kg) for three days. Renal function was assessed by measuring creatinine levels. While histopathological changes, RNA sequencing data, and serum cytokine levels were analyzed. Macrophage M1/M2 polarization in kidney tissues was examined using flow cytometry and immunohistochemistry. Murine bone marrow-derived macrophages (BMDMs) were polarized to the M1 or M2 phenotype in vivo and treated with or without TRAM (10 μM). M1/M2 polarization was analyzed via flow cytometry, and PI3K/Akt signaling was evaluated by western blotting.

RESULTS

TRAM significantly improved renal function, as demonstrated by reduced serum creatinine levels (p < 0.01) and ameliorated histopathological damage (p < 0.01). Flow cytometry and immunohistochemistry revealed that TRAM markedly inhibited pro-inflammatory M1 macrophage polarization (p < 0.001). Additionally, TRAM reduced serum level of IFN-γ (p < 0.01) and IL-17 (p < 0.001). In vitro, TRAM suppressed M1 polarization (p < 0.05) by inhibiting the PI3K/Akt signaling pathway.

CONCLUSION

TRAM mitigated LPS-induced AKI by suppressing M1 macrophage polarization via the PI3K/Akt pathway, highlighting its therapeutic potential for AKI and other inflammatory kidney diseases.

Intracellular iron accumulation throughout the progression of sepsis influences the phenotype and function of activated macrophages in renal tissue damage

Sepsis, the most common cause of acute kidney injury, remains a major socioeconomic burden. A dysregulated immune response leads to progressive organ dysfunction. Although numerous inflammatory pathways were described, most are still vague and need to be studied in terms of the mechanisms to improve the therapeutic intervention. We tackled the relationship between intracellular iron overload and macrophage polarization within 6, 24, and 72 h of sepsis induction. In our study, sepsis-induced kidney injury was caused by using the cecal ligation and puncture (CLP) model. Our results indicated severe renal tissue damage with a progressive increase in serum BUN and creatinine with architectural tissue damage and positive PAS staining. There was increased expression of CD8+ CD68+ M1 macrophage markers with upregulation of iNOS and co-expression of CD163+. Alternatively, Arg1+ Fizz1+ M2 macrophage markers were downregulated with increased iNOS/Arg1 ratio. TFR1, cubilin, and DMT1, as iron transport systems, were increased compared to sham but were significant after 72 h, while ZIP8 showed no significant change. There was a correlation between iron overload and M1 macrophage polarization with CD163+ phenotype, together with fibrotic changes. The intracellular iron overload with downregulation of ferritin was strongly related to macrophage polarization that was exaggerated at 72 h. Finally, early introduced therapy to target free iron during sepsis is a proposed novel solution for protecting the renal tissue from acute injury due to macrophage activation that may end up with chronic kidney injury, if not mortality.

Genetic deficiency or pharmacological inhibition of cGAS-STING signalling suppresses kidney inflammation and fibrosis

BACKGROUND AND PURPOSE

Chronic kidney disease (CKD) is characterised by inflammation, which can lead to tubular atrophy and fibrosis. The molecular mechanisms are not well understood. In this study, we investigated the functional role of the cyclic GMP-AMP synthase (cGAS)- stimulator of interferon genes (STING) signalling in renal inflammation and fibrosis.

EXPERIMENTAL APPROACH

Mice with global cGAS deficiency or global or myeloid cell-specific STING deficiency or wild-type mice treated with RU.521, a selective cGAS inhibitor, were used to examine the role of cGAS-STING signalling in renal inflammation and fibrosis in a preclinical model of obstructive nephropathy in vivo. Bone marrow-derived macrophages were used to determine whether tubular epithelial cell-derived DNA can activate cGAS-STING signalling in vitro.

KEY RESULTS

Following obstructive injury, cGAS-STING signalling was activated in the kidneys during the development of renal fibrosis. Mice with deficiency of cGAS or STING exhibited significantly less macrophage proinflammatory activation, myofibroblast formation, total collagen deposition, and extracellular matrix (ECM) protein production in the kidneys following obstructive injury. Pharmacological inhibition of cGAS with RU.521 reduced macrophage proinflammatory activation, suppressed myofibroblast formation, and attenuated kidney fibrosis following obstructive injury. Mechanistically, cGAS-STING signalling in macrophages is activated by double-stranded DNA released from damaged tubular epithelial cells, which induces inflammatory responses.

CONCLUSIONS AND IMPLICATIONS

Our study identifies the cGAS-STING signalling pathway as a critical regulator of macrophage proinflammatory activation during the development of renal fibrosis. Therefore, inhibition of cGAS-STING signalling may represent a novel therapeutic strategy for CKD.

Mechanism of dihydroartemisinin in the treatment of ischaemia/reperfusion-induced acute kidney injury via network pharmacology, molecular dynamics simulation and experiments

OBJECTIVE

To investigate whether dihydroartemisinin (DHA) attenuates ischaemia-reperfusion injury (IRI)-induced acute kidney injury (AKI) in mice by inhibiting oxidative stress and inflammation and to explore its potential molecular mechanisms.

MATERIALS AND METHODS

Network pharmacology analysis was used to screen relevant targets, and molecular docking of DHA with core targets was performed. Molecular dynamics simulation of the target with the lowest binding free energy, NQO1-DHA.The renal protective effect of DHA on the IRI-induced AKI mouse model was evaluated. The expression levels of NQO1, Nrf2 and other proteins were detected by Western blotting. The expression levels of Nrf2 and others were detected by immunohistochemistry (IHC) and immunofluorescence (IF).

RESULTS

Through network pharmacological analysis, we obtained that PI3K/AKT and MAPK signaling pathway may be related to DHA in the treatment of AKI.Molecular dynamics simulation indicated that NQO1 is an important target protein for DHA to exert nephroprotective effects.Moreover, the potential molecular mechanisms were verified by experiments.DHA reduced the serum creatinine (Scr) and urea nitrogen (BUN) levels in AKI mice, significantly improved AKI pathology, alleviated oxidative stress and inflammatory injury, which may be related to its activation of the Nrf2 pathway and regulation of macrophage polarization.

CONCLUSIONS

Through network pharmacology, molecular dynamics simulation and experimental validation, we initially investigated that DHA alleviate AKI by ameliorating oxidative stress and inflammatory damage, which may be related to its activation of the Nrf2 pathway and the regulation of macrophage polarisation, which lays the foundation for subsequent in-depth study of the specific mechanism of action.

Research hotspots and future trends in sepsis-associated acute kidney injury: a bibliometric and visualization analysis

Objectives

Sepsis-associated acute kidney injury (SA-AKI) commonly occurs in critically ill patients and is closely associated with adverse outcomes. A comprehensive analysis of the current research landscape in SA-AKI can help uncover trends and key issues in this field. This study aims to provide a scientific basis for research directions and critical issues through bibliometric analysis.

Methods

We searched all articles on SA-AKI indexed in the SCI-Expanded of WoSCC up to May 7, 2024, and conducted bibliometric and visual analyses using bibliometric software CiteSpace and VOSviewer.

Results

Over the past 20 years, there has been a steady increase in literature related to renal repair following AKI. China and the United States contribute over 60% of the publications, driving research in this field. The University of Pittsburgh is the most active academic institution, producing the highest number of publications. J. A. Kellum is both the most prolific and the most cited author in this area. "Shock" and "American Journal of Physiology-Renal Physiology" are the most popular journals, publishing the highest number of articles. Recent high-frequency keywords in this field include "septic AKI," "mitochondrial dysfunction," "inflammasome," "ferroptosis," and "macrophage." The terms "mitochondrial dysfunction," "inflammasome," "ferroptosis," and "macrophage" represent current research hotspots and potential targets in this area.

Conclusion

This is the first comprehensive bibliometric study to summarize the trends and advancements in SA-AKI research in recent years. These findings identify current research frontiers and hot topics, providing valuable insights for scholars studying SA-AKI.

Targeting Fibrosis: From Molecular Mechanisms to Advanced Therapies

As the final stage of disease-related tissue injury and repair, fibrosis is characterized by excessive accumulation of the extracellular matrix. Unrestricted accumulation of stromal cells and matrix during fibrosis impairs the structure and function of organs, ultimately leading to organ failure. The major etiology of fibrosis is an injury caused by genetic heterogeneity, trauma, virus infection, alcohol, mechanical stimuli, and drug. Persistent abnormal activation of "quiescent" fibroblasts that interact with or do not interact with the immune system via complicated signaling cascades, in which parenchymal cells are also triggered, is identified as the main mechanism involved in the initiation and progression of fibrosis. Although the mechanisms of fibrosis are still largely unknown, multiple therapeutic strategies targeting identified molecular mechanisms have greatly attenuated fibrotic lesions in clinical trials. In this review, the organ-specific molecular mechanisms of fibrosis is systematically summarized, including cardiac fibrosis, hepatic fibrosis, renal fibrosis, and pulmonary fibrosis. Some important signaling pathways associated with fibrosis are also introduced. Finally, the current antifibrotic strategies based on therapeutic targets and clinical trials are discussed. A comprehensive interpretation of the current mechanisms and therapeutic strategies targeting fibrosis will provide the fundamental theoretical basis not only for fibrosis but also for the development of antifibrotic therapies.

Inhibition of PKM2 by shikonin impedes TGF-β1 expression by repressing histone lactylation to alleviate renal fibrosis

BACKGROUND

Macrophage-myofibroblast transition (MMT) plays a significant role in the progression of renal fibrosis in chronic kidney disease (CKD), making inhibition of MMT a promising therapeutic strategy. Pyruvate kinase M2 (PKM2) and its metabolite lactate are implicated in the pathogenesis of renal fibrosis; however, the mechanisms through which they contribute to this process remain poorly understood.

PURPOSE

To investigate the effects of PKM2 inhibition by shikonin on renal fibrosis and the underly mechanisms.

METHODS

Mice were subjected to unilateral ureteral obstruction (UUO) to establish a CKD model. Renal fibrosis was assessed using histochemistry and western blotting. The MMT and histone lactylation levels were evaluated by immunofluorescence and western blotting. The interaction between the Tgfb1 promoter and lactylated histone H3 (K18) was examined using chromatin Immunoprecipitation (ChIP).

RESULTS

PKM2 expression was significantly elevated in the renal tubular cells of UUO mouse kidneys, resulting in increased pyruvate and lactate production. Similarly, lactate levels were elevated in TGF-β1-treated TCMK-1 cells and in the serum of CKD patients. In UUO mice, treatment with shikonin, a potent PKM2 inhibitor, effectively reduced lactate production, alleviated renal fibrosis, decreased TGF-β1 expression, and suppressed the MMT process. Mechanistic studies revealed that lactate treatment stimulates Tgfb1 expression in TCMK-1 cells. Consequently, TGF-β1 in conditioned media from lactate-treated TCMK-1 cells promoted M2 macrophage polarization and upregulated fibrotic gene expression in RAW264.7 cells. Pharmacological intervention demonstrated that TGF-β1 activates the Smad3 pathway to drive the MMT process. In TCMK-1 cells, both lactate treatment and PKM2 overexpression induced Tgfb1 expression by promoting histone H3K18 lactylation.

CONCLUSIONS

Our findings indicate that PKM2-induced excessive lactate production renal tubular cells contributes to renal fibrosis. Lactate promotes histone lactylation, leading to TGF-β1 expression in these cells, which subsequently activates the Smad3 pathway in macrophages, driving the MMT and fibrosis in the kidney. Therefore, targeting PKM2, as with shikonin treatment, may represent an effective therapeutic strategy for managing renal fibrosis in CKD.

The Kidney Precision Medicine Project and Single-Cell Biology of the Injured Proximal Tubule

Single-cell RNA sequencing (scRNA-seq) has led to major advances in our understanding of proximal tubule subtypes in health and disease. The proximal tubule serves essential functions in overall homeostasis, but pathologic or physiological perturbations can affect its transcriptomic signature and corresponding tasks. These alterations in proximal tubular cells are often described within a scRNA-seq atlas as cell states, which are pathophysiological subclassifications based on molecular and morphologic changes in a cell's response to that injury compared with its native state. This review describes the major cell states defined in the Kidney Precision Medicine Project's scRNA-seq atlas. It then identifies the overlap between the Kidney Precision Medicine Project and other seminal works that may use different nomenclature or cluster proximal tubule cells at different resolutions to define cell state subtypes. The goal is for the reader to understand the key transcriptomic markers of important cellular injury and regeneration processes across this highly dynamic and evolving field.

A Newly Identified Protective Role of C5a Receptor 1 in Kidney Tubules against Toxin-Induced Acute Kidney Injury

Acute kidney injury (AKI) remains a major reason for hospitalization with limited therapeutic options. Although complement activation is implicated in AKI, the role of C5a receptor 1 (C5aR1) in kidney tubular cells is unclear. Herein, aristolochic acid nephropathy (AAN) and folic acid nephropathy (FAN) models were used to establish the role of C5aR1 in kidney tubules during AKI in germline C5ar1-/-, myeloid cell-specific, and kidney tubule-specific C5ar1 knockout mice. After aristolochic acid and folic acid injection, C5ar1-/- mice had increased AKI severity and a higher degree of tubular injury. Macrophage depletion in C5ar1-/- mice or myeloid cell-specific C5ar1 deletion did not affect the outcomes of aristolochic acid-induced AKI. RNA-sequencing data from renal tubular epithelial cells (RTECs) showed that C5ar1 deletion was associated with the down-regulation of mitochondrial metabolism and ATP production transcriptional pathways. Metabolic studies confirmed reduced mitochondrial membrane potential at baseline and increased mitochondrial oxidative stress after injury in C5ar1-/- RTECs. Moreover, C5ar1-/- RTECs had enhanced glycolysis, glucose uptake, and lactate production on injury, corroborated by metabolomics analysis of kidneys from AAN mice. Kidney tubule-specific C5ar1 knockout mice recapitulated exacerbated AKI observed in C5ar1-/- mice in AAN and FAN. These data indicate that C5aR1 signaling in kidney tubules exerts renoprotective effects against toxin-induced AKI by limiting overt glycolysis and maintaining mitochondrial function, thereby revealing a novel link between the complement system and tubular cell metabolism.

Nrf2 inhibits M1 macrophage polarization to ameliorate renal ischemia-reperfusion injury through antagonizing NF-κB signaling

Renal ischemia-reperfusion injury (IRI) is a condition that arises from a sudden interruption of the blood flow to the kidney for a period of time followed by restoration of the blood supply. This process contributes to acute kidney injury (AKI), increases morbidity and mortality, and is a major risk factor for chronic kidney disease (CKD). Nuclear factor erythroid-derived 2-like 2 (Nrf2) has been shown to exhibit strong anti-oxidative and anti-inflammatory effects, which are reciprocally regulated by the pro-inflammatory actions of nuclear factor-kappa B (NF-κB) signaling. In this study, we established a model of AKI caused by renal IRI in mice lacking the Nrf2 gene (KO-Nrf2) and mice pre-injected with ML385 (Nrf2 inhibitor). In addition, LPS- or IL-4-induced M1- or M2-type polarized macrophages (RAW264.7), respectively, were also treated with Nrf2 activation and inhibition. The results demonstrated a more pronounced activation of the NF-κB signaling pathway in the Nrf2 inhibition model, accompanied by a more severe inflammatory effect. In cultured macrophages and renal IRI mice, Nrf2 inhibition activated M1 macrophage polarization, thereby increasing the release of proinflammatory cell factors (iNOS and TNF-α) and aggravating renal IRI. Notably, the inhibitory effect of Nrf2 on M1 macrophage polarization was related to the downregulation of the NF-κB signaling pathway activity, resulting in partial relief of renal IRI. Consequently, our findings indicated that Nrf2 inhibits M1 macrophage polarization to ameliorate renal IRI through antagonizing NF-κB signaling. Targeted activation of Nrf2 may be one of the important strategies for renal IRI treatment.

Macrophage Infiltration Correlated with IFI16, EGR1 and MX1 Expression in Renal Tubular Epithelial Cells Within Lupus Nephritis-Associated Tubulointerstitial Injury via Bioinformatics Analysis

Objective

A comprehensive bioinformatics analysis was conducted to investigate potential new diagnostic biomarkers and immune infiltration characteristics associated with tubulointerstitial injury in lupus nephritis (LN), and to examine possible correlations between key genes and infiltrating immune cells.

Methods

The GSE32591, GSE113342, and GSE200306 datasets were downloaded from the Gene Expression Omnibus database and differentially expressed genes (DEGs) were identified in the pooled dataset. Support vector machine-recursive feature elimination analysis and the least absolute shrinkage and selection operator regression model were used to screen for possible markers, and the compositional patterns of the 22 types of immune cell fractions in LN were determined using CIBERSORT. Finally, Western blotting, quantitative real-time polymerase chain reaction, and multiple immunofluorescence methods were used to confirm the significance of these feature genes in MRL/lpr mice and patients with LN.

Results

Seventeen DEGs were identified, of which 11 were considerably upregulated and six were markedly downregulated. Kyoto Encyclopedia of Genes and Genomes pathway analysis revealed significant enrichment in pertussis, complement and coagulation cascades, systemic lupus erythematosus, and other pathways. Based on the machine learning results, we identified IFI16, EGR1 and MX1 were key diagnostic genes for tubulointerstitial injury associated with LN. Immune cell infiltration analysis revealed that IFI16, EGR1 and MX1 were associated with M1 macrophages. Finally, the association between IFI16, EGR1, MX1 and macrophages in MRL/lpr mice and patients with LN were verified.

Conclusion

This study suggests that IFI16, EGR1 and MX1 which are highly expressed in renal tubular epithelial cells in LN and are associated with macrophage infiltration, may be a novel diagnostic and therapeutic target.

The Effects of Aldosterone on Hypertension-Associated Kidney Injury in a Tg-hAS Mouse Model

Hypertension remains a global health challenge due to its high prevalence and association with premature morbidity and mortality. Aldosterone, a mineralocorticoid hormone, and its receptor, the mineralocorticoid receptor (MR), are highly implicated in hypertension pathogenesis. Aldosterone synthase is the sole enzyme responsible for producing aldosterone in humans. We established transgenic mice carrying the human aldosterone synthase gene (cyp11B2) and showed dramatically increased levels of aldosterone in female hemizygotes. High-salt diets persistently increased blood pressure in these mice, and salt-induced hypertension was significantly ameliorated by reducing aldosterone levels via an aldosterone synthase inhibitor or blocking MR via an MR inhibitor. Since both hypertension and hyperaldosteronism specifically induce chronic kidney disease, in this model, we demonstrated that chronic high-salt diets induced hypertension in this mouse line and resulted in kidney inflammation and injury. Both the aldosterone synthase inhibitor and the MR antagonist markedly blocked high-salt-diet-mediated kidney injury. Thus, this transgenic mouse line can be used to study the pathogenic mechanisms underlying aldosterone and its receptor and to screen therapeutic compounds for aldosterone-mediated hypertension and related complications, such as kidney disease, in humans.

Integrated Analysis of Gene Expression and Immune Cell Infiltration Reveals Dysregulated Genes and miRNAs in Acute Kidney Injury

Acute Kidney Injury (AKI) is a multifaceted condition characterised by rapid deterioration of renal function, often precipitated by diverse etiologies. A comprehensive understanding of the molecular underpinnings of AKI is pivotal for identifying potential diagnostic markers and therapeutic targets. This study utilised bioinformatics to elucidate gene expression and immune infiltration in AKI. Publicly available mRNA and miRNA datasets were harnessed to discern differentially expressed genes (DEGs) and miRNAs in AKI. The CIBERSORT algorithm was employed to quantify immune cell infiltration in AKI samples. Functional enrichment analyses were conducted to unravel the implicated biological processes. Furthermore, the expression of identified genes and miRNAs was validated by quantitative real-time PCR in an AKI model. Our study revealed significant dysregulation of three genes (Aspn, Clec2h, Tmigd1) and two miRNAs (mmu-miR-21a-3p, mmu-miR-223-3p) in AKI, each with p < 0.0001. These molecular markers are implicated in immune responses, tissue remodelling, and inflammation. We observed notable disturbances in specific immune cells, including activated and immature dendritic cells, M1 macrophages, and subsets of T cells (Treg, Th1, Th17). These alterations correlated significantly with AKI pathology, with dendritic cells and M1 macrophages showing p < 0.01, and T cell subsets demonstrating p < 0.05. These results highlight the intricate involvement of the immune system in AKI and indicate significant enrichment of pathways related to immune response, inflammation, and tissue remodelling, pointing to their pivotal roles in AKI pathophysiology. Our study underscored the significance of immune cell infiltration and dysregulated gene and miRNA expression in AKI. The identified genes (Clec2h, Aspn, and Tmigd1) and miRNAs (mmu-miR-21a-3p and mmu-miR-223-3p) offer potential diagnostic markers and therapeutic avenues for AKI. Subsequent investigations targeting these genes and miRNAs, along with the elucidated pathways, may augment the clinical management and outcomes for AKI patients.

RasGRP4 aggravates ischemia-reperfusion injury in diabetic kidneys by mediating communication between macrophages and T cells

Diabetes mellitus (DM) is acknowledged as an independent risk factor for acute kidney injury. Ras guanine nucleotide-releasing protein-4 (RasGRP4) exerts a notable role in modulating immune-inflammatory responses and kidney disease progression in diabetes. Herein, we delved into the specific role and mechanism of RasGRP4 in diabetic renal ischemia-reperfusion injury. Diabetes was induced by a high-fat diet and streptozocin (STZ) injections, followed by creating an ischemia-reperfusion kidney injury via renal pedicle clamping and reperfusion. In vitro, a high glucose and hypoxia-reoxygenation modeled cellular inflammatory injury. We found RasGRP4-KO mice, compared with C57BL/6J (WT) mice, showed markedly less renal dysfunction and fibrosis in diabetic ischemia-reperfusion injury. There was a significant decrease in the renal infiltration of M1 macrophages and Th17 cells, along with downregulated IL-17 pathway proteins and effectors. In vitro, RasGRP4 deletion restrained M1 macrophage polarization and Th17 cell differentiation, inhibiting the IL-17 signaling pathway in HK-2 cells. Hyperglycemia intensified renal inflammation state. Together, RasGRP4, through the regulation of interactions among M1 macrophages, CD4+ T cells, and HK-2 cells, formed a cascade that intensified the inflammatory storm activity, ultimately exacerbating the inflammatory injury of diabetic ischemia-reperfusion kidneys. DM intensified this inflammatory injury mechanism, worsening the injury from renal ischemia-reperfusion.

Exosomes From Human Umbilical Cord Stem Cells Suppress Macrophage-to-myofibroblast Transition, Alleviating Renal Fibrosis

Renal fibrosis, a progressive scarring of the kidney, lacks effective treatment. Human umbilical cord mesenchymal stem cell-derived exosomes (HucMSC-Exos) hold promise for treating kidney diseases due to their anti-inflammatory properties. This study investigates their potential to lessen renal fibrosis by targeting macrophage-to-myofibroblast transformation (MMT), a key driver of fibrosis. We employed a mouse model of unilateral ureteral obstruction (UUO) and cultured cells exposed to transforming growth factor-β (TGF-β) to mimic MMT. HucMSC-Exos were administered to UUO mice, and their effects on kidney function and fibrosis were assessed. Additionally, RNA sequencing and cellular analysis were performed to elucidate the mechanisms by which HucMSC-Exos inhibit MMT. HucMSC-Exos treatment significantly reduced kidney damage and fibrosis in UUO mice. They downregulated markers of fibrosis (Collagen I, vimentin, alpha-smooth muscle actin) and suppressed MMT (α-SMA + F4/80 + cells). Furthermore, ARNTL, a specific molecule, emerged as a potential target of HucMSC-Exos in hindering MMT and consequently preventing fibrosis. HucMSC-Exos effectively lessen renal fibrosis by suppressing MMT, suggesting a novel therapeutic strategy for managing kidney damage and fibrosis.

HBSP inhibits tubular cell pyroptosis and apoptosis, promotes macrophage M2 polarization, and protects LPS-induced acute kidney injury

Sepsis-associated acute kidney injury (AKI) has high morbidity and mortality, but without cause-specific treatment. Erythropoietin derived Helix B surface peptide (HBSP) alleviates AKI, whereas its underlying mechanisms remain to be further explored. Here, the effects of HBSP on pyroptosis, apoptosis, macrophage polarization and repair were investigated in lipopolysaccharide (LPS)-induced AKI mouse model and cultured kidney epithelial cells. Systemic inflammation, compromised renal function and histology were demonstrated in LPS-treated mice, with upregulated pyroptotic and apoptotic key proteins in the kidneys including GSDMD-N, cleaved IL-1β, IL-18 and caspase-3. These proteins were localized in tubular areas and colocalized with aquaporin-1 (AQP1), with increased F4/80+ M1 macrophages. However, HBSP mitigated pyroptosis, apoptosis and inflammation, and promoted macrophage M2 polarization. In addition, HMGB1 and erythropoietin receptor (EPOR) were increased by LPS and decreased by HBSP, both of which were positively correlated with pyroptotic and apoptotic proteins. Moreover, HBSP reduced TNF-α and IL-6 mRNA levels, as well as pyroptosis and apoptosis in LPS-stimulated TCMK-1 cells. In conclusion, HBSP inhibited tubular pyroptosis and apoptosis, EPOR expression, promoted macrophage M2 polarization, and protected against LPS-induced AKI. These findings provide new mechanistic insights into the renoprotection of HBSP, and facilitate its potential for clinical applications and therapeutic strategies in sepsis-associated AKI.

Dietary sodium modulates mTORC1-dependent trained immunity in macrophages to accelerate CKD development

Chronic Kidney Disease (CKD) is a significant global health issue linked to dietary habits, especially high salt intake. However, the precise mechanisms driving this progression remain incompletely understood. This study reveals that a high-salt diet intensifies macrophage trained immunity, leading to a marked pro-inflammatory response upon repeated pathogenic exposures, as evidenced by increased renal damage and fibrosis. Under high-salt conditions, there was an induction of CD45+F4/80+ macrophage infiltration into the renal tissue, accompanied by heightened production of inflammatory cytokines. Distinct responses were observed between circulating and resident renal macrophages to a high-salt diet, with a notable upsurge in the migration of pro-inflammatory macrophages, driven by CCL2-CCR2 signaling and aberrant mTORC1 pathway activation. Treatment with rapamycin-liposome effectively reduced this inflammatory cascade by mitigating mTORC1 signaling. Transplantation of monocytes from CKD mice with a high-salt diet significantly exacerbates renal inflammatory damage in the host mice, showing increased migratory tendency and inflammatory activity. The cell co-culture experiment further confirmed that macrophages derived from CKD mice, particularly those under conditions of high salt exposure, significantly induced apoptosis and inflammatory responses in renal tubular cells. Taken together, recurrent exposure to LPS elicits the activation of trained immunity, consequently augmenting inflammatory response of monocytes/macrophages in the involved kidneys. The high-salt diet exacerbates this phenomenon, attributable at least in part to the overactivation of the mTORC1 pathway. This research emphasizes the importance of dietary modulation and targeted immunological interventions in slowing CKD progression, providing new insights into mTORC1-mediated pathophysiological mechanisms and potential management strategies for CKD.

Exosomes on the development and progression of renal fibrosis

Renal fibrosis is a prevalent pathological alteration that occurs throughout the progression of primary and secondary renal disorders towards end-stage renal disease. As a complex and irreversible pathophysiological phenomenon, it includes a sequence of intricate regulatory processes at the molecular and cellular levels. Exosomes are a distinct category of extracellular vesicles that play a crucial role in facilitating intercellular communication. Multiple pathways are regulated by exosomes produced by various cell types, including tubular epithelial cells and mesenchymal stem cells, in the context of renal fibrosis. Furthermore, research has shown that exosomes present in bodily fluids, including urine and blood, may be indicators of renal fibrosis. However, the regulatory mechanism of exosomes in renal fibrosis has not been fully elucidated. This article reviewed and analysed the various mechanisms by which exosomes regulate renal fibrosis, which may provide new ideas for further study of the pathophysiological process of renal fibrosis and targeted treatment of renal fibrosis with exosomes.

Exploring macrophage heterogeneity in IgA nephropathy: Mechanisms of renal impairment and current therapeutic targets

The lack of understanding of the mechanism of renal injury in IgA nephropathy (IgAN) hinders the development of personalized treatment plans and targeted therapies. Improved insight into the cause of renal dysfunction in IgAN is necessary to enhance the effectiveness of strategies for slowing the progression of the disease. This study examined single cell RNA sequencing (scRNA seq) and bulk-RNA seq data and found that the gene expression of renal intrinsic cells (RIC) was significantly changed in patients with renal impairment, with a primary focus on energy metabolism. We discovered a clear metabolic reprogramming of RIC during renal function impairment (RF) using the 'scMetabolism' package, which manifested as a weakening of oxidative phosphorylation, alterations in fatty acid metabolism, and changes in glycolysis. Cellular communication analysis revealed that communication between macrophages (Ma) and RIC became more active and impacted cell function through the ligand-receptor-transcription factor (L-R-TF) axis in patients with RF. Our studies showed a notable upsurge in the expression of gene CLU and the infiltration of CLU+ Ma in patients with RF. CLU is a multifunctional protein, extensively involved in processes such as cell apoptosis and immune responses. Data obtained from the Nephroseq V5 database and multiplex immunohistochemistry (mIHC) were used to validate the findings, which were found to be robustly correlated with estimated glomerular filtration rate (eGFR) of the IgAN patients, as demonstrated by linear regression (LR). This study provides new insights into the cellular and molecular changes that occur in IgAN during renal impairment, revealing that elevated expression of CLU and CLU+ Ma percolation are common features in patients with RF. These findings offer potential targets and strategies for personalized management and targeted therapy of IgAN.

MAFB in Macrophages Regulates Prostaglandin E2-Mediated Lipid Mediator Class Switch through ALOX15 in Ischemic Acute Kidney Injury

Monocytes and macrophages express the transcription factor MAFB (V-maf musculoaponeurotic fibrosarcoma oncogene homolog B) and protect against ischemic acute kidney injury (AKI). However, the mechanism through which MAFB alleviates AKI in macrophages remains unclear. In this study, we induced AKI in macrophage lineage-specific Mafb-deficient mice (C57BL/6J) using the ischemia-reperfusion injury model to analyze these mechanisms. Our results showed that MAFB regulates the expression of Alox15 (arachidonate 15-lipoxygenase) in macrophages during ischemic AKI. The expression of ALOX15 was significantly decreased at the mRNA and protein levels in macrophages that infiltrated the kidneys of macrophage-specific Mafb-deficient mice at 24 h after ischemia-reperfusion injury. ALOX15 promotes the resolution of inflammation under acute conditions by producing specialized proresolving mediators by oxidizing essential fatty acids. Therefore, MAFB in macrophages promotes the resolution of inflammation in ischemic AKI by regulating the expression of Alox15. Moreover, MAFB expression in macrophages is upregulated via the COX-2/PGE2/EP4 pathway in ischemic AKI. Our in vitro assay showed that MAFB regulates the expression of Alox15 under the COX-2/PGE2/EP4 pathway in macrophages. PGE2 mediates the lipid mediator (LM) class switch from inflammatory LMs to specialized proresolving mediators. Therefore, MAFB plays a key role in the PGE2-mediated LM class switch by regulating the expression of Alox15. Our study identified a previously unknown mechanism by which MAFB in macrophages alleviates ischemic AKI and provides new insights into regulating the LM class switch in acute inflammatory conditions.

Protective effects of pioglitazone in renal ischemia-reperfusion injury (RIRI): focus on oxidative stress and inflammation

BACKGROUND

Renal ischemia-reperfusion injury (RIRI) is a critical phenomenon that compromises renal function and is the most serious health concern related to acute kidney injury (AKI). Pioglitazone (Pio) is a known agonist of peroxisome proliferator-activated receptor-gamma (PPAR-γ). PPAR-γ is a nuclear receptor that regulates genes involved in inflammation, metabolism, and cellular differentiation. Activation of PPAR-γ is associated with antiinflammatory and antioxidant effects, which are relevant to the pathophysiology of RIRI. This study aimed to investigate the protective effects of Pio in RIRI, focusing on oxidative stress and inflammation.

METHODS

We conducted a comprehensive literature search using electronic databases, including PubMed, ScienceDirect, Web of Science, Scopus, and Google Scholar.

RESULTS

The results of this study demonstrated that Pio has antioxidant, anti-inflammatory, and anti-apoptotic activities that counteract the consequences of RIRI. The study also discussed the underlying mechanisms, including the modulation of various pathways such as TNF-α, NF-κB signaling systems, STAT3 pathway, KIM-1 and NGAL pathways, AMPK phosphorylation, and autophagy flux. Additionally, the study presented a summary of various animal studies that support the potential protective effects of Pio in RIRI.

CONCLUSION

Our findings suggest that Pio could protect the kidneys from RIRI by improving antioxidant capacity and decreasing inflammation. Therefore, these findings support the potential of Pio as a therapeutic strategy for preventing RIRI in different clinical conditions.

Identification of a Novel ECM Remodeling Macrophage Subset in AKI to CKD Transition by Integrative Spatial and Single-Cell Analysis

The transition from acute kidney injury (AKI) to chronic kidney disease (CKD) is a critical clinical issue. Although previous studies have suggested macrophages as a key player in promoting inflammation and fibrosis during this transition, the heterogeneity and dynamic characterization of macrophages are still poorly understood. Here, we used integrated single-cell RNA sequencing and spatial transcriptomic to characterize the spatiotemporal heterogeneity of macrophages in murine AKI-to-CKD model of unilateral ischemia-reperfusion injury. A marked increase in macrophage infiltration at day 1 was followed by a second peak at day 14 post AKI. Spatiotemporal profiling revealed that injured tubules and macrophages co-localized early after AKI, whereas in late chronic stages had spatial proximity to fibroblasts. Further pseudotime analysis revealed two distinct lineages of macrophages in this transition: renal resident macrophages differentiated into the pro-repair subsets, whereas infiltrating monocyte-derived macrophages contributed to chronic inflammation and fibrosis. A novel macrophage subset, extracellular matrix remodeling-associated macrophages (EAMs) originating from monocytes, linked to renal fibrogenesis and communicated with fibroblasts via insulin-like growth factors (IGF) signalling. In sum, our study identified the spatiotemporal dynamics of macrophage heterogeneity with a unique subset of EAMs in AKI-to-CKD transition, which could be a potential therapeutic target for preventing CKD development.

Complex Pathophysiology of Acute Kidney Injury (AKI) in Aging: Epigenetic Regulation, Matrix Remodeling, and the Healing Effects of H2S

The kidney is an essential excretory organ that works as a filter of toxins and metabolic by-products of the human body and maintains osmotic pressure throughout life. The kidney undergoes several physiological, morphological, and structural changes with age. As life expectancy in humans increases, cell senescence in renal aging is a growing challenge. Identifying age-related kidney disorders and their cause is one of the contemporary public health challenges. While the structural abnormalities to the extracellular matrix (ECM) occur, in part, due to changes in MMPs, EMMPRIN, and Meprin-A, a variety of epigenetic modifiers, such as DNA methylation, histone alterations, changes in small non-coding RNA, and microRNA (miRNA) expressions are proven to play pivotal roles in renal pathology. An aged kidney is vulnerable to acute injury due to ischemia-reperfusion, toxic medications, altered matrix proteins, systemic hemodynamics, etc., non-coding RNA and miRNAs play an important role in renal homeostasis, and alterations of their expressions can be considered as a good marker for AKI. Other epigenetic changes, such as histone modifications and DNA methylation, are also evident in AKI pathophysiology. The endogenous production of gaseous molecule hydrogen sulfide (H2S) was documented in the early 1980s, but its ameliorative effects, especially on kidney injury, still need further research to understand its molecular mode of action in detail. H2S donors heal fibrotic kidney tissues, attenuate oxidative stress, apoptosis, inflammation, and GFR, and also modulate the renin-angiotensin-aldosterone system (RAAS). In this review, we discuss the complex pathophysiological interplay in AKI and its available treatments along with future perspectives. The basic role of H2S in the kidney has been summarized, and recent references and knowledge gaps are also addressed. Finally, the healing effects of H2S in AKI are described with special emphasis on epigenetic regulation and matrix remodeling.

APP-CD74 axis mediates endothelial cell-macrophage communication to promote kidney injury and fibrosis

Background

Kidney injuries often carry a grim prognosis, marked by fibrosis development, renal function loss, and macrophage involvement. Despite extensive research on macrophage polarization and its effects on other cells, like fibroblasts, limited attention has been paid to the influence of non-immune cells on macrophages. This study aims to address this gap by shedding light on the intricate dynamics and diversity of macrophages during renal injury and repair.

Methods

During the initial research phase, the complexity of intercellular communication in the context of kidney injury was revealed using a publicly available single-cell RNA sequencing library of the unilateral ureteral obstruction (UUO) model. Subsequently, we confirmed our findings using an independent dataset from a renal ischemia-reperfusion injury (IRI) model. We treated two different types of endothelial cells with TGF-β and co-cultured their supernatants with macrophages, establishing an endothelial cell and macrophage co-culture system. We also established a UUO and an IRI mouse model. Western blot analysis, flow cytometry, immunohistochemistry and immunofluorescence staining were used to validate our results at multiple levels.

Results

Our analysis revealed significant changes in the heterogeneity of macrophage subsets during both injury processes. Amyloid β precursor protein (APP)-CD74 axis mediated endothelial-macrophage intercellular communication plays a dominant role. In the in vitro co-culture system, TGF-β triggers endothelial APP expression, which subsequently enhances CD74 expression in macrophages. Flow cytometry corroborated these findings. Additionally, APP and CD74 expression were significantly increased in the UUO and IRI mouse models. Immunofluorescence techniques demonstrated the co-localization of F4/80 and CD74 in vivo.

Conclusion

Our study unravels a compelling molecular mechanism, elucidating how endothelium-mediated regulation shapes macrophage function during renal repair. The identified APP-CD74 signaling axis emerges as a promising target for optimizing renal recovery post-injury and preventing the progression of chronic kidney disease.

Activation of the α7nAChR by GTS-21 mitigates septic tubular cell injury and modulates macrophage infiltration

The most common and serious complication among hospitalized and critically ill patients is sepsis-associated acute kidney damage (S-AKI), which raises the risk of comorbidities and is linked to a high mortality rate. Cholinergic anti-inflammatory pathway (CAP), an anti-inflammatory pathway mediated by the vagus nerve, acetylcholine, and α7 nicotinic acetylcholine receptors (α7nAChRs), offers new perspectives for the treatment of S-AKI. In this study, we investigated the role of CAP and α7nAChR in kidney injury by employing an LPS-induced septic kidney injury mouse model and GTS-21 intervention. C57BL/6 mice were injected with LPS, with or without GTS-21, in different subgroups. Kidney function was assessed by plasma creatinine, histology, and markers of kidney injury 24 h after intervention. The results demonstrated that GTS-21 could inhibit the systemic inflammatory response and directly protect the tubular cell injury from LPS. To explore the novel gene involved in this response, RNA sequencing of the renal proximal tubular epithelial cell (HK-2), pretreated with LPS and GTS-21, was conducted. The results indicate that GTS-21 administration reduces LPS-induced cytokines and chemokines secretion by HK-2, including CCL20, a potent chemokine attracting monocytes/macrophages. Furthermore, a macrophage transmigration assay revealed that GTS-21 inhibits macrophage transmigration by downregulating the expression of CCL20 in HK-2 cells. In conclusion, GTS-21, as an α7nAChR agonist, emerges as a noteworthy and versatile treatment for S-AKI. Its dual function of directly protecting renal tubular cells and regulating inflammatory responses represents a major advancement in the treatment of sepsis-induced AKI. This finding might pave the way for novel approaches to improving patient outcomes and reducing death rates in sepsis-related complications.

Canine mesenchymal stem cell-derived exosomes attenuate renal ischemia-reperfusion injury through miR-146a-regulated macrophage polarization

Introduction

The most common factor leading to renal failure or death is renal IR (ischemia-reperfusion). Studies have shown that mesenchymal stem cells (MSCs) and their exosomes have potential therapeutic effects for IR injury by inhibiting M1 macrophage polarization and inflammation. In this study, the protective effect and anti-inflammatory mechanism of adipose-derived mesenchymal stem cell-derived exosomes (ADMSC-Exos) after renal IR were investigated.

Method

Initially, ADMSC-Exos were intravenously injected into IR experimental beagles, and the subsequent assessment focused on inflammatory damage and macrophage phenotype. Furthermore, an in vitro inflammatory model was established by inducing DH82 cells with LPS. The impact on inflammation and macrophage phenotype was then evaluated using ADMSC and regulatory miR-146a.

Results

Following the administration of ADMSC-Exos in IR canines, a shift from M1 to M2 macrophage polarization was observed. Similarly, in vitro experiments demonstrated that ADMSC-Exos enhanced the transformation of LPS-induced macrophages from M1 to M2 type. Notably, the promotion of macrophage polarization by ADMSC-Exos was found to be attenuated upon the inhibition of miR-146a in ADMSC-Exos.

Conclusion

These findings suggest that miR-146a plays a significant role in facilitating the transition of LPS-induced macrophages from M1 to M2 phenotype. As a result, the modulation of macrophage polarization by ADMSC-Exos is achieved via the encapsulation and conveyance of miR-146a, leading to diminished infiltration of inflammatory cells in renal tissue and mitigation of the inflammatory reaction following canine renal IR.

PBMC therapy reduces cell death and tissue fibrosis after acute kidney injury by modulating the pattern of monocyte/macrophage survival in tissue

In this study, we investigated if the therapeutic potential of peripheral blood mononuclear cell (PBMC) therapy in a murine model of ischemic AKI is related with the survival pattern of monocyte/macrophages in tissue. CD-1 mice were subjected to bilateral renal ischemia followed by reperfusion to induce AKI. M2-polarized PBMCs isolated from CD-1 mice were administered intravenously at different time points post-injury. Our results demonstrate that early administration of PBMC therapy attenuates renal tissue damage, reduces tissue cell death and prevents fibrosis development. Reduction of tissue pyroptosis was observed by reduction on NLRP3 inflammasome activation and decreasing IL-1beta and Caspase-1 expression in the kidney. Furthermore, the therapy was shown to mitigate ferroptosis by inducing GPX4 overexpression. Early administration of PBMCs increased the survival pattern of renal tissue-macrophages, promoting a "pro-survival phenotype" resulting in decreased pyroptotic marker NLRP3, IL-1beta and Caspase 1 and increased anti-ferroptotic gene GPX4. Conversely, delayed administration of PBMC therapy exhibits diminished efficacy in preventing cell death and fibrosis in tissue and provoked a decrease in the pro-survival phenotype of both monocyte /macrophages in tissue. Our findings highlight the therapeutic potential of PBMC therapy in mitigating AKI and preventing CKD progression by modulating tissue-resident macrophage survival and reducing their cell death pathways. The fact that the effectiveness of the therapy depends on the time of administration after the injury underscores the importance of early intervention in AKI management.

Paricalcitol prevents MAPK pathway activation and inflammation in adriamycin-induced kidney injury in rats

BACKGROUND

Activation of the mitogen-activated protein kinase (MAPK) pathway induces uncontrolled cell proliferation in response to inflammatory stimuli. Adriamycin (ADR)-induced nephropathy (ADRN) in rats triggers MAPK activation and pro-inflammatory mechanisms by increasing cytokine secretion, similar to chronic kidney disease (CKD). Activation of the vitamin D receptor (VDR) plays a crucial role in suppressing the expression of inflammatory markers in the kidney and may contribute to reducing cellular proliferation. This study evaluated the effect of pre-treatment with paricalcitol on ADRN in renal inflammation mechanisms.

METHODS

Male Sprague-Dawley rats were implanted with an osmotic minipump containing activated vitamin D (paricalcitol, Zemplar, 6 ng/day) or vehicle (NaCl 0.9%). Two days after implantation, ADR (Fauldoxo, 3.5 mg/kg) or vehicle (NaCl 0.9%) was injected. The rats were divided into four experimental groups: control, n = 6; paricalcitol, n = 6; ADR, n = 7 and, ADR + paricalcitol, n = 7.

RESULTS

VDR activation was demonstrated by increased CYP24A1 in renal tissue. Paricalcitol prevented macrophage infiltration in the glomeruli, cortex, and outer medulla, prevented secretion of tumor necrosis factor-α, and interleukin-1β, increased arginase I and decreased arginase II tissue expressions, effects associated with attenuation of MAPK pathways, increased zonula occludens-1, and reduced cell proliferation associated with proliferating cell nuclear antigen expression. Paricalcitol treatment decreased the stromal cell-derived factor 1α/chemokine C-X-C receptor type 4/β-catenin pathway.

CONCLUSIONS

Paricalcitol plays a renoprotective role by modulating renal inflammation and cell proliferation. These results highlight potential targets for treating CKD.

Mechanism of Chaihuang-Yishen formula to attenuate renal fibrosis in the treatment of chronic kidney disease: Insights from network pharmacology and experimental validation

Renal fibrosis represents a pivotal characteristic of chronic kidney disease (CKD), for which effective interventions are currently lacking. The Src kinase activates the phosphatidylinositol-3 kinases (PI3K)/Akt1 pathway to promote renal fibrosis, casting a promising target for anti-fibrosis treatment. Chaihuang-Yishen formula (CHYS), a traditional Chinese medicinal prescription, has a validated efficacy in the treatment of CKD, however, with the underlying mechanism unresolved. This study aimed to uncover the pharmacological mechanisms mediating the effect of CHYS in treating renal fibrosis using network pharmacology followed by experimental validation. The chemical compounds of CHYS were retrieved from the Traditional Chinese Medicine Systems Pharmacology (TCMSP) database or published literature, followed by the prediction of their targets using SwissTargetPrediction software. Disease (CKD/renal fibrosis)-related targets were retrieved from the Genecards database. Protein-protein interaction (PPI) network was generated using the drug-disease common targets and visualized in Cytoscape software. The drug-disease targets were further subjected to Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses by Metascape software. Additionally, the compound-target-pathway network was established in Cytosape to identify key compounds, targets, and pathways. Network pharmacology analysis screened out 96 active compounds and 837 potential targets within the 7 herbal/animal medicines of CHYS, among which 237 drug-disease common targets were identified. GO and KEGG analysis revealed the enrichment of fibrosis-related biological processes and pathways among the 237 common targets. Compound-target-pathway network analysis highlighted protein kinases Src and Akt1 as the top two targets associated with the anti-renal fibrosis effects of CHYS. In UUO mice, treatment with CHYS attenuates renal fibrosis, accompanied by suppressed expression and phosphorylation activation of Src. Unlike Src, CHYS reduced Akt1 phosphorylation without affecting its expression. In summary, network pharmacology and in vivo evidence suggest that CHYS exerts its anti-renal fibrosis effects, at least in part, by inhibiting the Src/Akt1 signaling axis.

Cyclic Adenosine Monophosphate Signaling in Chronic Kidney Disease: Molecular Targets and Therapeutic Potentials

Chronic kidney disease (CKD) is characterized by a steady decline in kidney function and affects roughly 10% of the world's population. This review focuses on the critical function of cyclic adenosine monophosphate (cAMP) signaling in CKD, specifically how it influences both protective and pathogenic processes in the kidney. cAMP, a critical secondary messenger, controls a variety of cellular functions, including transcription, metabolism, mitochondrial homeostasis, cell proliferation, and apoptosis. Its compartmentalization inside cellular microdomains ensures accurate signaling. In kidney physiology, cAMP is required for hormone-regulated activities, particularly in the collecting duct, where it promotes water reabsorption through vasopressin signaling. Several illnesses, including Fabry disease, renal cell carcinoma, nephrogenic diabetes insipidus, Bartter syndrome, Liddle syndrome, diabetic nephropathy, autosomal dominant polycystic kidney disease, and renal tubular acidosis, have been linked to dysfunction in the cAMP system. Both cAMP analogs and phosphodiesterase inhibitors have the potential to improve kidney function and reduce kidney damage. Future research should focus on developing targeted PDE inhibitors for the treatment of CKD.

The role of macrophages in fibrosis of chronic kidney disease

Macrophages are widely distributed throughout various tissues of the body, and mounting evidence suggests their involvement in regulating the tissue microenvironment, thereby influencing disease onset and progression through direct or indirect actions. In chronic kidney disease (CKD), disturbances in renal functional homeostasis lead to inflammatory cell infiltration, tubular expansion, glomerular atrophy, and subsequent renal fibrosis. Macrophages play a pivotal role in this pathological process. Therefore, understanding their role is imperative for investigating CKD progression, mitigating its advancement, and offering novel research perspectives for fibrosis treatment from an immunological standpoint. This review primarily delves into the intrinsic characteristics of macrophages, their origins, diverse subtypes, and their associations with renal fibrosis. Particular emphasis is placed on the transition between M1 and M2 phenotypes. In late-stage CKD, there is a shift from the M1 to the M2 phenotype, accompanied by an increased prevalence of M2 macrophages. This transition is governed by the activation of the TGF-β1/SMAD3 and JAK/STAT pathways, which facilitate macrophage-to-myofibroblast transition (MMT). The tyrosine kinase Src is involved in both signaling cascades. By thoroughly elucidating macrophage functions and comprehending the modes and molecular mechanisms of macrophage-fibroblast interaction in the kidney, novel, tailored therapeutic strategies for preventing or attenuating the progression of CKD can be developed.

Calycosin inhibited MIF-mediated inflammatory chemotaxis of macrophages to ameliorate ischemia reperfusion-induced acute kidney injury

BACKGROUND

Inflammatory macrophage infiltration plays a critical role in acute kidney disease induced by ischemia-reperfusion (IRI-AKI). Calycosin is a natural flavone with multiple bioactivities. This study aimed to investigate the therapeutic role of calycosin in IRI-AKI and its underlying mechanism.

METHODS

The renoprotective and anti-inflammatory effects of calycosin were analyzed in C57BL/6 mice with IRI-AKI and lipopolysaccharide (LPS)-stimulated RAW 264.7 cells. RNA-seq was used for mechanism investigation. The molecular target of calycosin was screened by in silico methods and validated by surface plasmon resonance (SPR). Macrophage chemotaxis was analyzed using Transwell and agarose gel spot assays.

RESULTS

Calycosin treatment significantly reduced serum creatinine and urea nitrogen and attenuated tubular destruction in IRI-AKI mice. Additionally, calycosin markedly suppressed NF-κB signaling activation and the expression of inflammatory mediators IL-1β and TNF-α in IRI-AKI kidneys and LPS-stimulated RAW 264.7 cells. Interestingly, RNA-seq revealed calycosin remarkably downregulated chemotaxis-related pathways in RAW 264.7 cells. Among the differentially expressed genes, Ccl2/MCP-1, a critical chemokine mediating macrophage inflammatory chemotaxis, was downregulated in both LPS-stimulated RAW 264.7 cells and IRI-AKI kidneys. Consistently, calycosin treatment attenuated macrophage infiltration in the IRI-AKI kidneys. Importantly, in silico target prediction, molecular docking, and SPR assay demonstrated that calycosin directly binds to macrophage migration inhibitory factor (MIF). Functionally, calycosin abrogated MIF-stimulated NF-κB signaling activation and Ccl2 expression and MIF-mediated chemotaxis in RAW 264.7 cells.

CONCLUSIONS

In summary, calycosin attenuates IRI-AKI by inhibiting MIF-mediated macrophage inflammatory chemotaxis, suggesting it could be a promising therapeutic agent for the treatment of IRI-AKI.

Depleting profibrotic macrophages using bioactivated in vivo assembly peptides ameliorates kidney fibrosis

Managing renal fibrosis is challenging owing to the complex cell signaling redundancy in diseased kidneys. Renal fibrosis involves an immune response dominated by macrophages, which activates myofibroblasts in fibrotic niches. However, macrophages exhibit high heterogeneity, hindering their potential as therapeutic cell targets. Herein, we aimed to eliminate specific macrophage subsets that drive the profibrotic immune response in the kidney both temporally and spatially. We identified the major profibrotic macrophage subset (Fn1+Spp1+Arg1+) in the kidney and then constructed a 12-mer glycopeptide that was designated as bioactivated in vivo assembly PK (BIVA-PK) to deplete these cells. BIVA-PK specifically binds to and is internalized by profibrotic macrophages. By inducing macrophage cell death, BIVA-PK reshaped the renal microenvironment and suppressed profibrotic immune responses. The robust efficacy of BIVA-PK in ameliorating renal fibrosis and preserving kidney function highlights the value of targeting macrophage subsets as a potential therapy for patients with CKD.

Scutellarin alleviates renal ischemia-reperfusion injury by inhibiting the MAPK pathway and pro-inflammatory macrophage polarization

Renal ischemia-reperfusion injury (IRI) is an integral process in renal transplantation, which results in compromised graft survival. Macrophages play an important role in both the early inflammatory period and late fibrotic period in response to IRI. In this study, we investigated whether scutellarin (SCU) could protect against renal IRI by regulating macrophage polarization. Mice were given SCU (5-50 mg/kg) by gavage 1 h earlier, followed by a unilateral renal IRI. Renal function and pathological injury were assessed 24 h after reperfusion. The results showed that administration of 50 mg/kg SCU significantly improved renal function and renal pathology in IRI mice. In addition, SCU alleviated IRI-induced apoptosis. Meanwhile, it reduced macrophage infiltration and inhibited pro-inflammatory macrophage polarization. Moreover, in RAW 264.7 cells and primary bone marrow-derived macrophages (BMDMs) exposed to SCU, we found that 150 μM SCU inhibited these cells to polarize to an inflammatory phenotype induced by lipopolysaccharide (LPS) and interferon-γ (IFN-γ). However, SCU has no influence on anti-inflammatory macrophage polarization in vivo and in vitro induced by in interleukin-4 (IL-4). Finally, we explored the effect of SCU on the activation of the mitogen-activated protein kinase (MAPK) pathway both in vivo and in vitro. We found that SCU suppressed the activation of the MAPK pathway, including the extracellular signal-regulated kinase (ERK), Jun N-terminal kinase (JNK), and p38. Our results demonstrated that SCU protects the kidney against IRI by inhibiting macrophage infiltration and polarization toward pro-inflammatory phenotype via the MAPK pathway, suggesting that SCU may be therapeutically important in treatment of IRI.

The novel potential therapeutic target PSMP/MSMP promotes acute kidney injury via CCR2

Acute kidney injury (AKI) is a major worldwide health concern that currently lacks effective medical treatments. PSMP is a damage-induced chemotactic cytokine that acts as a ligand of CCR2 and has an unknown role in AKI. We have observed a significant increase in PSMP levels in the renal tissue, urine, and plasma of patients with AKI. PSMP deficiency improved kidney function and decreased tubular damage and inflammation in AKI mouse models induced by kidney ischemia-reperfusion injury, glycerol, and cisplatin. Single-cell RNA sequencing analysis revealed that Ly6Chi or F4/80lo infiltrated macrophages (IMs) were a major group of proinflammatory macrophages with strong CCR2 expression in AKI. We observed that PSMP deficiency decreased CCR2+Ly6Chi or F4/80lo IMs and inhibited M1 polarization in the AKI mouse model. Moreover, overexpressed human PSMP in the mouse kidney could reverse the attenuation of kidney injury in a CCR2-dependent manner, and this effect could be achieved without CCL2 involvement. Extracellular PSMP played a crucial role, and treatment with a PSMP-neutralizing antibody significantly reduced kidney injury in vivo. Therefore, PSMP might be a therapeutic target for AKI, and its antibody is a promising therapeutic drug for the treatment of AKI.

Lactate metabolism and acute kidney injury

ABSTRACT

Acute kidney injury (AKI) is a common clinically critical syndrome in hospitalized patients with high morbidity and mortality. At present, the mechanism of AKI has not been fully elucidated, and no therapeutic drugs exist. As known, glycolytic product lactate is a key metabolite in physiological and pathological processes. The kidney is an important gluconeogenic organ, where lactate is the primary substrate of renal gluconeogenesis in physiological conditions. During AKI, altered glycolysis and gluconeogenesis in kidneys significantly disturb the lactate metabolic balance, which exert impacts on the severity and prognosis of AKI. Additionally, lactate-derived posttranslational modification, namely lactylation, is novel to AKI as it could regulate gene transcription of metabolic enzymes involved in glycolysis or Warburg effect. Protein lactylation widely exists in human tissues and may severely affect non-histone functions. Moreover, the strategies of intervening lactate metabolic pathways are expected to bring a new dawn for the treatment of AKI. This review focused on renal lactate metabolism, especially in proximal renal tubules after AKI, and updated recent advances of lactylation modification, which may help to explore potential therapeutic targets against AKI.

Transcriptomics-based identification of TYROBP and TLR8 as novel macrophage-related biomarkers for the diagnosis of acute rejection after kidney transplantation

Macrophages play an important role in the development and progression of acute rejection after kidney transplantation. The study aims to investigate the biological role and significance of macrophage-associated genes (MAG) in acute rejection after kidney transplantation. We utilized transcriptome sequencing results from public databases related to acute rejection of kidney transplantation for comprehensive analysis and validation in animal experiments. We found that a large number of immune-related signaling pathways are activated in acute rejection. PPI protein interaction networks and machine learning were used to establish a Hub gene consisting of TYROBP and TLR8 for the diagnosis of acute rejection. The single-gene GSEA enrichment analysis and immune cell correlation analysis revealed a close correlation between the expression of Hub genes and immune-related biological pathways as well as the expression of multiple immune cells. In addition, the study of TF, miRNAs, and drugs provided a theoretical basis for regulating and treating the Hub genes in acute rejection. Finally, the animal experiments demonstrated once again that acute rejection can aggravate kidney tissue damage, apoptosis level, and increase the release of inflammatory factors. We established and validated a macrophage-associated diagnostic model for acute rejection after kidney transplantation, which can accurately diagnose the biological alterations in acute rejection after kidney transplantation.

Mincle receptor in macrophage and neutrophil contributes to the unresolved inflammation during the transition from acute kidney injury to chronic kidney disease

Background

Recent studies have demonstrated a strong association between acute kidney injury (AKI) and chronic kidney disease (CKD), while the unresolved inflammation is believed to be a driving force for this chronic transition process. As a transmembrane pattern recognition receptor, Mincle (macrophage-inducible C-type lectin, Clec4e) was identified to participate in the early immune response after AKI. However, the impact of Mincle on the chronic transition of AKI remains largely unclear.

Methods

We performed single-cell RNA sequencing (scRNA-seq) with the unilateral ischemia-reperfusion (UIR) murine model of AKI at days 1, 3, 14 and 28 after injury. Potential effects and mechanism of Mincle on renal inflammation and fibrosis were further validated in vivo utilizing Mincle knockout mice.

Results

The dynamic expression of Mincle in macrophages and neutrophils throughout the transition from AKI to CKD was observed. For both cell types, Mincle expression was significantly up-regulated on day 1 following AKI, with a second rise observed on day 14. Notably, we identified distinct subclusters of Minclehigh neutrophils and Minclehigh macrophages that exhibited time-dependent influx with dual peaks characterized with remarkable pro-inflammatory and pro-fibrotic functions. Moreover, we identified that Minclehigh neutrophils represented an "aged" mature neutrophil subset derived from the "fresh" mature neutrophil cluster in kidney. Additionally, we observed a synergistic mechanism whereby Mincle-expressing macrophages and neutrophils sustained renal inflammation by tumor necrosis factor (TNF) production. Mincle-deficient mice exhibited reduced renal injury and fibrosis following AKI.

Conclusion

The present findings have unveiled combined persistence of Minclehigh neutrophils and macrophages during AKI-to-CKD transition, contributing to unresolved inflammation followed by fibrosis via TNF-α as a central pro-inflammatory cytokine. Targeting Mincle may offer a novel therapeutic strategy for preventing the transition from AKI to CKD.

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.

CCR2 antagonist attenuates calcium oxalate-induced kidney oxidative stress and inflammation by regulating macrophage activation

C-C chemokine receptor type 2 (CCR2) is a monocyte chemokine associated with oxidative stress and inflammation. Kidney stones (KS) are composed of calcium oxalate (CaOx), which trigger renal oxidative stress and inflammatory. This study aims to evaluate the effects of CCR2 on KS in vivo and in vitro. Eight-week-old male C57BL/6J mice were intraperitoneally injected with glyoxylate (GOX) daily to establish a KS model, and along with CCR2 antagonist (INCB3344) treatment on days 2, 4, and 6. The results showed that CCR2 antagonist reduced renal injury markers (blood urea nitrogen and serum creatinine), alleviated renal tubular injury and CaOx crystal deposition. CCR2 antagonist also decreased CCR2 expression induced by GOX treatment and increased Nrf2 expression. GOX treatment promoted malondialdehyde (MDA) production, decreased glutathione (GSH) content, and inhibited catalase (CAT) and superoxide dismutase (SOD) activity, however, CCR2 antagonist attenuated the above effects of GOX. CCR2 antagonist had inhibitory effects on GOX-induced inflammatory cytokine expression (IL1B, IL6 and MCP1), and inhibited apoptosis by increasing Bcl-2 expression and decreasing Bax and cleaved-caspase 3 expression. In vitro experiments were performed by co-culture model of CaOx-induced damaged HK-2 cells and macrophage-like THP-1 cells. CCR2 antagonist inhibited CaOx-induced THP-1 cell M1 polarization by decreasing the TNF-α, IL6 and iNOS levels, and further alleviated CaOx-induced oxidative stress damage, inflammatory response and apoptosis of HK-2 cells. The study suggests that CCR2 antagonist may be resistant to CaOx crystals-induced oxidative stress and inflammation by inhibiting macrophage M1 polarization.

Integrative analysis of single-cell and bulk transcriptome data reveal the significant role of macrophages in lupus nephritis

OBJECTIVE

We attempted to identify abnormal immune cell components and signaling pathways in lupus nephritis (LN) and to identify potential therapeutic targets.

METHODS

Differentially expressed genes (DEGs) between LN and normal kidney tissues were identified from bulk transcriptome data, and functional annotation was performed. The phenotypic changes in macrophages and aberrant intercellular signaling communications within immune cells were imputed from LN scRNA-seq data using trajectory analysis and verified using immunofluorescence staining. Finally, lentivirus-mediated overexpression of LGALS9, the gene encoding Galectin 9, in THP-1 cells was used to study the functional effect of this gene on monocytic cells.

RESULTS

From bulk transcriptome data, a significant activation of interferon (IFN) signaling was observed, and its intensity showed a significantly positive correlation with the abundance of infiltrating macrophages in LN. Analysis of scRNA-seq data revealed 17 immune cell clusters, with macrophages showing the highest enrichment of intercellular signal communication in LN. Trajectory analysis revealed macrophages in LN undergo a phenotypic change from inflammatory patrolling macrophages to phagocytic and then to antigen-presenting macrophages, and secrete various pro-inflammatory factors and complement components. LGALS9 was found significantly upregulated in macrophages in LN, which was confirmed by the immunofluorescence assay. Gene functional study showed that LGALS9 overexpression in THP-1 cells significantly elicited pro-inflammatory activation, releasing multiple immune cell chemoattractants.

CONCLUSION

Our results present an important pathophysiological role for macrophages in LN, and our preliminary results demonstrate significant pro-inflammatory effects of LGALS9 gene in LN macrophages.

Pyxinol Fatty Acid Ester Derivatives J16 against AKI by Selectively Promoting M1 Transition to M2c Macrophages

Acute kidney injury (AKI) is a common, multicause clinical condition that, if ignored, often progresses to chronic kidney disease (CKD) and end-stage kidney disease, with a mortality rate of 40-50%. However, there is a lack of universal treatment for AKI. Inflammation is the basic pathological change of early kidney injury, and inflammation can exacerbate AKI. Macrophages are the primary immune cells involved in the inflammatory microenvironment of kidney disease. Therefore, regulating the function of macrophages is a crucial breakthrough for the AKI intervention. Our team chemically modified pyxinol, an ocotillol-type ginsenoside, to prepare PJ16 with higher solubility and bioavailability. In vitro, using a model of macrophages stimulated by LPS, it was found that PJ16 could regulate macrophage function, including inhibiting the secretion of inflammatory factors, promoting phagocytosis, inhibiting M1 macrophages, and promoting M1 transition to the M2c macrophage. Further investigation revealed that PJ16 may shield renal tubular epithelial cells (HK-2) damaged by LPS in vitro. Based on this, PJ16 was validated in the animal model of unilateral ureteral obstruction, which showed that it improves renal function and inhibits renal tissue fibrosis by decreasing inflammatory responses, reducing macrophage inflammatory infiltration, and preferentially upregulating M2c macrophages. In conclusion, our study is the first to show that PJ16 resists AKI and fibrosis by mechanistically regulating macrophage function by modulating the phenotypic transition from M1 to M2 macrophages, mainly M2c macrophages.

Toxicological effects of microplastics in renal ischemia-reperfusion injury

The widespread presence of microplastics (MPs) in the environment poses a significant threat to biological survival and human health. However, our understanding of the toxic effects of MPs on the kidneys remains limited. This study aimed to investigate the underlying mechanism of the toxic effects of MPs on the kidneys using an ischemia-reperfusion (IR) mouse model. Four-week-old ICR mice were exposed to 0.5 μm MPs for 12 weeks prior to IR injury. The results showed that MPs exposure could aggravate the IR-induced damage to renal tubules and glomeruli. Although there were no significant changes in blood urea nitrogen and serum creatinine levels 7 days after IR, MPs treatment resulted in a slight increase in both parameters. In addition, the expression levels of inflammatory factors (MCP-1 and IL-6) at the mRNA level, as well as macrophage markers (CD68 and F4/80), were significantly higher in the MPs + IR group than in the Sham group after IR. Furthermore, MPs exposure exacerbated IR-induced renal fibrosis. Importantly, the expression of pyroptosis-related genes, including NLRP3, ASC, GSDMD, cleaved caspase-1, and IL-18, was significantly upregulated by MPs, indicating that MPs exacerbate pyroptosis in the context of renal IR. In conclusion, our findings suggest that MPs exposure can aggravate renal IR-induced pyroptosis by activating NLRP3-GSDMD signaling.

Characterization of macrophages in ischemia-reperfusion injury-induced acute kidney injury based on single-cell RNA-Seq and bulk RNA-Seq analysis

Acute kidney injury (AKI) is a complex disease, with macrophages playing a vital role in its progression. However, the mechanism of macrophage function remains unclear and strategies targeting macrophages in AKI are controversial. To address this issue, we used single-cell RNA-seq analysis to identify macrophage sub-types involved in ischemia-reperfusion-induced AKI, and then screened for associated hub genes using intersecting bulk RNA-seq data. The single-cell and bulk RNA-seq datasets were obtained from the Gene Expression Omnibus (GEO) database. Screening of differentially-expressed genes (DEGs) and pseudo-bulk DEG analyses were used to identify common hub genes. Pseudotime and trajectory analyses were performed to investigate the progression of cell differentiation. CellChat analysis was performed to reveal the crosstalk between cell clusters. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses were used to identify enriched pathways in the cell clusters. Immunofluorescence and RT-PCR were preformed to validate the expression of the identified hub genes. Four hub genes, Vim, S100a6, Ier3, and Ccr1, were identified in the infiltrated macrophages between normal samples and those 3 days after ischemia-reperfusion renal injury (IRI); all were associated with the progression of IRI-induced AKI. Increased expression of Vim, S100a6, Ier3, and Ccr1 in infiltrated macrophages may be associated with inflammatory responses and may mediate crosstalk between macrophages and renal tubular epithelial cells under IRI conditions. Our results reveal that Ier3 may be critical in AKI, and that Vim, S100a6, Ier3, and Ccr1 may act as novel biomarkers and potential therapeutic targets for IRI-induced AKI.