Macrophage migration inhibitory factor (MIF) suppresses mitophagy through disturbing the protein interaction of PINK1-Parkin in sepsis-associated acute kidney injury.

Damage to renal tubular epithelial cells (RTECs) signaled the onset and progression of sepsis-associated acute kidney injury (SA-AKI). Recent research on mitochondria has revealed that mitophagy plays a crucial physiological role in alleviating injury to RTECs and it is suppressed progressively by the inflammation response in SA-AKI. However, the mechanism by which inflammation influences mitophagy remains poorly understood. We examined how macrophage migration inhibitory factor (MIF), a pro-inflammatory protein, influences the PINK1-Parkin pathway of mitophagy by studying protein-protein interactions when MIF was inhibited or overexpressed. Surprisingly, elevated levels of MIF were found to directly bind to PINK1, disrupting its interaction with Parkin. This interference hindered the recruitment of Parkin to mitochondria and impeded the initiation of mitophagy. Furthermore, this outcome led to significant apoptosis of RTECs, which could, however, be reversed by an MIF inhibitor ISO-1 and/or a new mitophagy activator T0467. These findings highlight the detrimental impact of MIF on renal damage through its disruption of the interaction between PINK1 and Parkin, and the therapeutic potential of ISO-1 and T0467 in mitigating SA-AKI. This study offers a fresh perspective on treating SA-AKI by targeting MIF and mitophagy.

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Acute kidney injury (AKI) is a common critical condition in clinical practice, characterized by a rapid decline in renal function within a short period. The pathogenesis of AKI is complex and has not been fully elucidated. In recent years, studies have found that the activation of endoplasmic reticulum stress (ERS) and the Nod-like receptor family pyrin domain containing 3 (NLRP3) inflammasome are closely related to the occurrence of AKI. When the kidneys is damaged, the internal environment of the kidney cells is disrupted, leading to the activation of ERS. Excessive ERS can induce apoptosis of renal cells, leading to the occurrence of AKI. Additionally, the NLRP3 inflammasome can mediate the recognition of endogenous and exogenous danger signal molecules by the host, subsequently activating caspase-1, pro-inflammatory cytokines such as IL-1ß and IL-18, inducing inflammatory responses, and promoting apoptosis of renal cells. In animal models of AKI, the upregulation of ERS markers is often accompanied by increased expression levels of NLRP3 inflammasome-related proteins, indicating that ERS can regulate the activation process of the NLRP3 inflammasome. Clarifying the role and mechanism of ERS and NLRP3 inflammasome in AKI is expected to provide new insights for the prevention and treatment of AKI.

DY131 activates ERRγ/TFAM axis to protect against metabolic disorders and acute kidney injury.

Renal tubular injury is considered as the main pathological feature of acute kidney injury (AKI), and mitochondrial dysfunction in renal tubular cells is implicated in the pathogenesis of AKI. The estrogen-related receptor γ (ERRγ) is a member of orphan nuclear receptors which plays a regulatory role in mitochondrial biosynthesis, energy metabolism and many metabolic pathways. Online datasets showed a dominant expression of ERRγ in renal tubules, but the role of ERRγ in AKI is still unknown. In the present study, we investigated the role of ERRγ in the pathogenesis of AKI and the therapeutic efficacy of ERRγ agonist DY131 in several murine models of AKI. ERRγ expression was reduced in kidneys of AKI patients and AKI murine models along with a negative correlation to the severity of AKI. Consistently, silencing ERRγ in vitro enhanced cisplatin-induced tubular cells apoptosis, while ERRγ overexpression in vivo utilizing hydrodynamic-based tail vein plasmid delivery approach alleviated cisplatin-induced AKI. ERRγ agonist DY131 could enhance the transcriptional activity of ERRγ and ameliorate AKI in various murine models. Moreover, DY131 attenuated the mitochondrial dysfunction of renal tubular cells and metabolic disorders of kidneys in AKI, and promoted the expression of the mitochondrial transcriptional factor A (TFAM). Further investigation showed that TFAM could be a target gene of ERRγ and DY131 might ameliorate AKI by enhancing ERRγ-mediated TFAM expression protecting mitochondria. These findings highlighted the protective effect of DY131 on AKI, thus providing a promising therapeutic strategy for AKI.

MicroRNA­17­5p alleviates sepsis­related acute kidney injury in mice by modulating inflammation and apoptosis.

Septic acute kidney injury (AKI) is considered as a severe and frequent complication that occurs during sepsis. Mounting evidence has confirmed the pivotal pathogenetic roles of microRNA (miRNA or miR) in sepsis­induced AKI; however, the role of miRNAs and their underlying mechanisms in sepsis­induced AKI have not been entirely understood. The present study aimed to elucidate the functions of special miRNAs during sepsis­induced AKI and its underlying mechanism. First, a number of differently expressed miRNAs was identified based on the microarray dataset GSE172044. Subsequently, lipopolysaccharide (LPS) was used to induce AKI in mice, and the role of miR­17­5p on AKI was clarified. Finally, the related molecular mechanisms were further examined by western blotting and immunohistochemical analysis. MiR­17­5p was found to be continuously decreased and reached the bottom at h 24 after AKI in mice. Functionally, injection of agomiR­17­5p could observably improve renal injury and survival rate, as well as inhibit inflammatory cytokine production and renal cell apoptosis in mice after AKI. On the contrary, injection of antagomiR­17­5p aggravated LPS­induced renal injury, inflammation and apoptosis in mice after AKI. Moreover, transforming growth factor ß receptor 2 (TGFßR2) was identified as a direct target of miR­17­5p, and its downstream phosphorylated Smad3 was also suppressed by miR­17­5p upregulation. Taken together, these results demonstrated that miR­17­5p overexpression may exhibit a beneficial effect by attenuating LPS­induced inflammation and apoptosis via regulating the TGFßR2/TGF­ß/Smad3 signaling pathway, indicating that miR­17­5p could act as a potential target for sepsis treatment.

Clinical impact of Wnt5a expression on persistence of acute kidney injury in patients with urosepsis.

Abnormal Wnt5a expression is associated with dysregulated inflammation and organ dysfunction. However, the effect of Wnt5a activation on the duration of organ dysfunction remains unclear. This prospective study investigated the association between Wnt5a levels and persistent acute kidney injury (AKI) in patients with urosepsis. Serum creatinine and Wnt5a levels were measured on days 1 and 5 and at discharge in 87 patients diagnosed with urosepsis. Patients with urosepsis were classified into an improving acute kidney injury (AKI) group and a persistent or worsening AKI group according to the AKI stage on days 1 and 5. AKI recovery was defined as a discharge-to-baseline serum creatinine ratio of <1.5. Twenty-eight patients with urosepsis (32.2%) had persistent or worsening AKI, and their Wnt5a levels were higher on days 1 and 5 and at discharge than those with improving AKI. The association between Wnt5a levels and persistent or worsening AKI was maintained after adjusting for age, sex, baseline serum creatinine levels, and disease severity. Moreover, elevated Wnt5a levels were associated with an increased risk of major adverse kidney events. High Wnt5a levels at discharge were associated with unrecovered AKI and participants with AKI recovery had a steeper Wnt5a slope over time than those without recovery, irrespective of age, sex, baseline serum creatinine level, or disease severity. Assessment of Wnt5a expression was helpful in predicting AKI persistence and adverse outcomes in patients with urosepsis. Therefore, Wnt5a may serve as a valuable bio-marker for identifying the risk of persistence of AKI.

Selenoprotein-P1 (SEPP1) Expression in Human Proximal Tubule Cells after Ischemia-Reperfusion Injury: An In Vitro Model.

Background and Objectives: Selenium deficiency represents a risk factor for the occurrence of severe diseases, such as acute kidney injury (AKI). Recently, selenoprotein-p1 (SEPP1), a selenium transporter, mainly released by the liver, has emerged as a promising plasmatic biomarker of AKI as a consequence of cardio-surgery operations. The aim of the present study was to investigate, on an in vitro model of hypoxia induced in renal tubular cells, HK-2, the effects of sodium selenite (Na2SeO3) and to evaluate the expression of SEPP1 as a marker of injury. Materials and Methods: HK-2 cells were pre-incubated with 100 nM Na2SeO3 for 24 h, and then, treated for 24 h with CoCl2 (500 µM), a chemical hypoxia inducer. The results were derived from an ROS assay, MTT, and Western blot analysis. Results: The pre-treatment determined an increase in cells' viability and a reduction in reactive oxygen species (ROS), as shown by MTT and the ROS assay. Moreover, by Western blot an increase in SEPP1 expression was observed after hypoxic injury as after adding sodium selenite. Conclusions: Our preliminary results shed light on the possible role of selenium supplementation as a means to prevent oxidative damage and to increase SEPP1 after acute kidney injury. In our in vitro model, SEPP1 emerges as a promising biomarker of kidney injury, although further studies in vivo are necessary to validate our findings.

Air pollution aggravates renal ischaemia-reperfusion-induced acute kidney injury.

Chronic kidney disease (CKD) has emerged as a significant global public health concern. Recent epidemiological studies have highlighted the link between exposure to fine particulate matter (PM2.5) and a decline in renal function. PM2.5 exerts harmful effects on various organs through oxidative stress and inflammation. Acute kidney injury (AKI) resulting from ischaemia-reperfusion injury (IRI) involves biological processes similar to those involved in PM2.5 toxicity and is a known risk factor for CKD. The objective of this study was to investigate the impact of PM2.5 exposure on IRI-induced AKI. Through a unique environmentally controlled setup, mice were exposed to urban PM2.5 or filtered air for 12 weeks before IRI followed by euthanasia 48 h after surgery. Animals exposed to PM2.5 and IRI exhibited reduced glomerular filtration, impaired urine concentration ability, and significant tubular damage. Further, PM2.5 aggravated local innate immune responses and mitochondrial dysfunction, as well as enhancing cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) pathway activation. This increased renal senescence and suppressed the anti-ageing protein klotho, leading to early fibrotic changes. In vitro studies using proximal tubular epithelial cells exposed to PM2.5 and hypoxia/reoxygenation revealed heightened activation of the STING pathway triggered by cytoplasmic mitochondrial DNA, resulting in increased tubular damage and a pro-inflammatory phenotype. In summary, our findings imply a role for PM2.5 in sensitising proximal tubular epithelial cells to IRI-induced damage, suggesting a plausible association between PM2.5 exposure and heightened susceptibility to CKD in individuals experiencing AKI. Strategies aimed at reducing PM2.5 concentrations and implementing preventive measures may improve outcomes for AKI patients and mitigate the progression from AKI to CKD. © 2024 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

TREM2 deficiency aggravates renal injury by promoting macrophage apoptosis and polarization via the JAK-STAT pathway in mice.

The triggering receptor expressed on myeloid cells 2 (TREM2) is an immune receptor that affects cellular phenotypes by modulating phagocytosis and metabolism, promoting cell survival, and counteracting inflammation. Its role in renal injury, in particular, unilateral ureteral obstruction (UUO) or ischemia-reperfusion injury (IRI)-induced renal injury remains unclear. In our study, WT and Trem2-/- mice were employed to evaluate the role of TREM2 in renal macrophage infiltration and tissue injury after UUO. Bone marrow-derived macrophages (BMDM) from both mouse genotypes were cultured and polarized for in vitro experiments. Next, the effects of TREM2 on renal injury and macrophage polarization in IRI mice were also explored. We found that TREM2 expression was upregulated in the obstructed kidneys. TREM2 deficiency exacerbated renal inflammation and fibrosis 3 and 7 days after UUO, in association with reduced macrophage infiltration. Trem2-/- BMDM exhibited increased apoptosis and poorer survival compared with WT BMDM. Meanwhile, TREM2 deficiency augmented M1 and M2 polarization after UUO. Consistent with the in vivo observations, TREM2 deficiency led to increased polarization of BMDM towards the M1 proinflammatory phenotype. Mechanistically, TREM2 deficiency promoted M1 and M2 polarization via the JAK-STAT pathway in the presence of TGF-ß1, thereby affecting cell survival by regulating mTOR signaling. Furthermore, cyclocreatine supplementation alleviated cell death caused by TREM2 deficiency. Additionally, we found that TREM2 deficiency promoted renal injury, fibrosis, and macrophage polarization in IRI mice. The current data suggest that TREM2 deficiency aggravates renal injury by promoting macrophage apoptosis and polarization via the JAK-STAT pathway. These findings have implications for the role of TREM2 in the regulation of renal injury that justify further evaluation.

CUX1 attenuates the apoptosis of renal tubular epithelial cells induced by contrast media through activating the PI3K/AKT signaling pathway.

OBJECTIVE: Contrast media (CM) is a commonly applied drug in medical examination and surgery. However, contrast-induced acute kidney injury (CIAKI) poses a severe threat to human life and health. Notably, the CUT-like homeobox 1 (CUX1) gene shows protective effects in a variety of cells. Therefore, the objective of this study was to provide a new target for the treatment of CIAKI through exploring the role and possible molecular mechanism of CUX1 in CIAKI. METHOD: Blood samples were collected from 20 patients with CIAKI and healthy volunteers. Human kidney 2 (HK-2) cells were incubated with 200 mg/mL iohexol for 6 h to establish a contrast-induced injury model of HK-2 cells. Subsequently, qRT-PCR was used to detect the relative mRNA expression of CUX1; CCK-8 and flow cytometry to assess the proliferation and apoptosis of HK-2 cells; the levels of IL(interleukin)-1ß, tumor necrosis factor alpha (TNF-α) and malondialdehyde (MDA) in cells and lactate dehydrogenase (LDH) activity in cell culture supernatant were detect; and western blot to observe the expression levels of CUX1 and the PI3K/AKT signaling pathway related proteins [phosphorylated phosphoinositide 3-kinase (p-PI3K), PI3K, phosphorylated Akt (p-AKT), AKT]. RESULTS: CUX1 expression was significantly downregulated in blood samples of patients with CIAKI and contrast-induced HK-2 cells. Contrast media (CM; iohexol) treatment significantly reduced the proliferation of HK-2 cells, promoted apoptosis, stimulated inflammation and oxidative stress that caused cell damage. CUX1 overexpression alleviated cell damage by significantly improving the proliferation level of HK-2 cells induced by CM, inhibiting cell apoptosis, and reducing the level of LDH in culture supernatant and the expression of IL-1ß, TNF-α and MDA in cells. CM treatment significantly inhibited the activity of PI3K/AKT signaling pathway activity. Nevertheless, up-regulating CUX1 could activate the PI3K/AKT signaling pathway activity in HK-2 cells induced by CM. CONCLUSION: CUX1 promotes cell proliferation, inhibits apoptosis, and reduces inflammation and oxidative stress in CM-induced HK-2 cells to alleviate CM-induced damage. The mechanism of CUX1 may be correlated with activation of the PI3K/AKT signaling pathway.

Usp9x contributes to the development of sepsis-induced acute kidney injury by promoting inflammation and apoptosis in renal tubular epithelial cells via activation of the TLR4/nf-κb pathway.

As a pattern recognition receptor, Toll-like receptor 4 (TLR4) is crucial for the development and progression of acute kidney injury (AKI). This study aims to explore whether the deubiquitinase Usp9x influences the TLR4/NF-B pathway to cause sepsis-induced acute kidney injury (S-AKI). The model of AKI was established in Sprague-Dawley rats using the cecal ligation and puncture (CLP) method, while renal tubular epithelial cell NRK-52E was stimulated with lipopolysaccharide (LPS) in vitro. All plasmids were transfected into NRK-52E cells according to the indicated group. The deubiquitinase of TLR4 was predicted by the online prediction software Ubibrowser. Subsequently, Western blot and Pearson correlation analysis identified Usp9x protein as a potential candidate. Co-IP analysis verified the interaction between TLR4 and Usp9x. Further research revealed that overexpression of Usp9x inhibited degradation of TLR4 protein by downregulating its ubiquitination modification levels. Both in vivo and in vitro experiments observed that interference with Usp9x effectively alleviated the inflammatory response and apoptosis of renal tubular epithelial cells (RTECs) induced by CLP or LPS, whereas overexpression of TLR4 reversed this situation. Transfection with sh-Usp9x in NRK-52E cells suppressed the expression of proteins associated with the TLR4/NF-κB pathway induced by LPS. Moreover, the overexpression of TLR4 reversed the effect of sh-Usp9x transfection. Therefore, the deubiquitinase Usp9x interacts with TLR4, leading to the upregulation of its expression through deubiquitination modification, and the activation of the TLR4/NF-κB signaling pathway, thereby promoting inflammation and apoptosis in renal tubular epithelial cells and contributing to sepsis-induced acute kidney injury.

Disruption in glutathione metabolism and altered energy production in the liver and kidney after ischemic acute kidney injury in mice.

Acute kidney injury (AKI) is a systemic disease that affects energy metabolism in various remote organs in murine models of ischemic AKI. However, AKI-mediated effects in the liver have not been comprehensively assessed. After inducing ischemic AKI in 8-10-week-old, male C57BL/6 mice, mass spectrometry metabolomics revealed that the liver had the most distinct phenotype 24 h after AKI versus 4 h and 7 days. Follow up studies with in vivo [13C6]-glucose tracing on liver and kidney 24 h after AKI revealed 4 major findings: (1) increased flux through glycolysis and the tricarboxylic (TCA) cycle in both kidney and liver; (2) depleted hepatic glutathione levels and its intermediates despite unchanged level of reactive oxygen species, suggesting glutathione consumption exceeds production due to systemic oxidative stress after AKI; (3) hepatic ATP depletion despite unchanged rate of mitochondrial respiration, suggesting increased ATP consumption relative to production; (4) increased hepatic and renal urea cycle intermediates suggesting hypercatabolism and upregulation of the urea cycle independent of impaired renal clearance of nitrogenous waste. Taken together, this is the first study to describe the hepatic metabolome after ischemic AKI in a murine model and demonstrates that there is significant liver-kidney crosstalk after AKI.

H-151 attenuates lipopolysaccharide-induced acute kidney injury by inhibiting the STING-TBK1 pathway.

Sepsis is a severe systemic infectious disease that often leads to multi-organ dysfunction. One of the common and serious complications of sepsis is renal injury. In this study, we aimed to investigate the potential mechanistic role of a novel compound called H-151 in septic kidney injury. We also examined its impact on renal function and mouse survival rates. Initially, we confirmed abnormal activation of the STING-TBK1 signaling pathway in the kidneys of septic mice. Subsequently, we treated the mice with H-151 and observed significant improvement in sepsis-induced renal dysfunction. This was evidenced by reductions in blood creatinine and urea nitrogen levels, as well as a marked decrease in inflammatory cytokine levels. Furthermore, H-151 substantially improved the seven-day survival rate of septic mice, indicating its therapeutic potential. Importantly, H-151 also exhibited an inhibitory effect on renal apoptosis levels, further highlighting its mechanism of protecting against septic kidney injury. These study findings not only offer new insights into the treatment of septic renal injury but also provide crucial clues for further investigations into the regulatory mechanisms of the STING-TBK1 signaling pathway and potential drug targets.

Hypoxia-inducible factor prolyl hydroxylase inhibitor alleviates heatstroke-induced acute kidney injury by activating BNIP3-mediated mitophagy.

Hypoxia-induced inflammation and apoptosis are important pathophysiological features of heat stroke-induced acute kidney injury (HS-AKI). Hypoxia-inducible factor (HIF) is a key protein that regulates cell adaptation to hypoxia. HIF-prolyl hydroxylase inhibitor (HIF-PHI) stabilizes HIF to increase cell adaptation to hypoxia. Herein, we reported that HIF-PHI pretreatment significantly improved renal function, enhanced thermotolerance, and increased the survival rate of mice in the context of HS. Moreover, HIF-PHI could alleviate HS-induced mitochondrial damage, inflammation, and apoptosis in renal tubular epithelial cells (RTECs) by enhancing mitophagy in vitro and in vivo. By contrast, mitophagy inhibitors Mdivi-1, 3-MA, and Baf-A1 reversed the renoprotective effects of HIF-PHI. Mechanistically, HIF-PHI protects RTECs from inflammation and apoptosis by enhancing Bcl-2 adenovirus E18 19-kDa-interacting protein 3 (BNIP3)-mediated mitophagy, while genetic ablation of BNIP3 attenuated HIF-PHI-induced mitophagy and abolished HIF-PHI-mediated renal protection. Thus, our results indicated that HIF-PHI protects renal function by upregulating BNIP3-mediated mitophagy to improve HS-induced inflammation and apoptosis of RTECs, suggesting HIF-PHI as a promising therapeutic agent to treat HS-AKI.

Investigating gut microbiota-blood and urine metabolite correlations in early sepsis-induced acute kidney injury: insights from targeted KEGG analyses.

Background: The interplay between gut microbiota and metabolites in the early stages of sepsis-induced acute kidney injury (SA-AKI) is not yet clearly understood. This study explores the characteristics and interactions of gut microbiota, and blood and urinary metabolites in patients with SA-AKI. Methods: Utilizing a prospective observational approach, we conducted comparative analyses of gut microbiota and metabolites via metabolomics and metagenomics in individuals diagnosed with SA-AKI compared to those without AKI (NCT06197828). Pearson correlations were used to identify associations between microbiota, metabolites, and clinical indicators. The Comprehensive Antibiotic Resistance Database was employed to detect antibiotic resistance genes (ARGs), while Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways informed on metabolic processes and microbial resistance patterns. Results: Our study included analysis of four patients with SA-AKI and five without AKI. Significant disparities in bacterial composition were observed, illustrated by diversity indices (Shannon index: 2.0 ± 0.4 vs. 1.4 ± 0.6, P = 0.230; Simpson index: 0.8 ± 0.1 vs. 0.6 ± 0.2, P = 0.494) between the SA-AKI group and the non-AKI group. N6, N6, N6-Trimethyl-L-lysine was detected in both blood and urine metabolites, and also showed significant correlations with specific gut microbiota (Campylobacter hominis and Bacteroides caccae, R > 0, P < 0.05). Both blood and urine metabolites were enriched in the lysine degradation pathway. We also identified the citrate cycle (TCA cycle) as a KEGG pathway enriched in sets of differentially expressed ARGs in the gut microbiota, which exhibits an association with lysine degradation. Conclusions: Significant differences in gut microbiota and metabolites were observed between the SA-AKI and non-AKI groups, uncovering potential biomarkers and metabolic changes linked to SA-AKI. The lysine degradation pathway may serve as a crucial link connecting gut microbiota and metabolites.

Identification of proteins related to SIS3 by iTRAQ and PRM-based comparative proteomic analysis in cisplatin-induced acute kidney injury.

Background: Cisplatin is a commonly used nephrotoxic drug and can cause acute kidney injury (AKI). In the present study, isobaric tags for relative and absolute quantification (iTRAQ) and parallel reaction monitoring (PRM)-based comparative proteomics were used to analyze differentially expressed proteins (DEPs) to determine the key molecular mechanism in mice with cisplatin-induced AKI in the presence or absence of SIS3, a specific p-smad3 inhibitor, intervention. Methods: The cisplatin-induced AKI mouse model was established and treated with SIS3. We used iTRAQ to search for DEPs, PRM to verify key DEPs and combined Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) for bioinformatics analysis. We then assessed lipid deposition, malondialdehyde (MDA) and reactive oxygen species (ROS) and detected the expression of SREBF1, SCD1, CPT1A, PPARα and NDRG1 in vitro. Results: Proteomic analysis showed that the identified DEPs were mainly enriched in energy metabolism pathways, especially in lipid metabolism. When SIS3 was applied to inhibit the phosphorylation of Smad3, the expression of NDRG1 and fatty acid oxidation key proteins CPT1A and PPARα increased, the expression of lipid synthesis related proteins SREBF1 and SCD1 decreased and the production of lipid droplets, MDA and ROS decreased. Conclusion: SIS3 alleviates oxidative stress, reduces lipid accumulation and promotes fatty acid oxidation through NDRG1 in cisplatin-induced AKI. Our study provides a new candidate protein for elucidating the molecular mechanisms of fatty acid metabolism disorders in cisplatin-induced acute kidney injury.

CD8 T cells induce the peritubular capillary rarefaction during AKI to CKD transition.

Acute kidney injury (AKI) transformed to chronic kidney disease (CKD) is a critical clinical issue characterized by tubulointerstitial inflammation (TII) and fibrosis. However, the exact mechanism remains largely unclear. In this study, we used single-cell RNA sequencing (scRNA-seq) to obtain a high-resolution profile of T cells in AKI to CKD transition with a mice model of unilateral ischemia-reperfusion injury (uIRI). We found that T cells accumulated increasingly with the progression of AKI to CKD, which was categorized into 9 clusters. A notably increased proportion of CD8 T cells via self-proliferation occurred in the early stage of AKI was identified. Further study revealed that the CD8 T cells were recruited through CXCL16-CXCR6 pathway mediated by macrophages. Notably, CD8 T cells induced endothelial cell apoptosis via Fas ligand-Fas signaling. Consistently, increased CD8 T cell infiltration accompanied with peritubular capillaries (PTCs) rarefaction was observed in uIRI mice. More impressively, the loss of PTCs and renal fibrosis was remarkably ameliorated after the elimination of CD8 T cells. In summary, our study provides a novel insight into the role of CD8 T cells in the transition from AKI to CKD via induction of PTCs rarefaction, which could suggest a promising therapeutic target for AKI.

Protective roles of thrombomodulin in cisplatin-induced nephrotoxicity through the inhibition of oxidative and endoplasmic reticulum stress.

Cisplatin is an effective chemotherapeutic agent widely used for the treatment of various solid tumors. However, cisplatin has an important limitation in its use; currently, there is no method to ameliorate cisplatin-induced acute kidney injury (AKI). Thrombomodulin (TM) is well known not only for its role as a cofactor in the clinically important natural anticoagulation pathway but also for its anti-inflammatory properties. Here, we investigated the effects of TM in cisplatin-induced AKI. In mice intraperitoneally injected with 15 mg/kg cisplatin, TM (10 mg/kg) or PBS was administered intravenously at 24 h after cisplatin injection. TM significantly attenuated cisplatin-induced nephrotoxicity with the suppressed elevation of blood urea nitrogen and serum creatinine, and reduced histological damages. Actually, TM treatment significantly alleviated oxidative stress-induced apoptosis by reducing reactive oxygen species (ROS) levels in cisplatin-treated renal proximal tubular epithelial cells (RPTECs) in vitro. Furthermore, TM clarified cisplatin-induced apoptosis by reducing caspase-3 levels. In addition, TM attenuated the endoplasmic reticulum (ER) stress signaling pathway in both renal tissues and RPTECs to protect the kidneys from cisplatin-induced AKI. These findings suggest that TM is a potential protectant against cisplatin-induced nephrotoxicity through suppressing ROS generation and ER stress in response to cisplatin.

[The role and mechanism of multifunctional molecule SLPI in regulating ischemia-reperfusion induced acute kidney injury and repair].

The secretory leukocyte protease inhibitor (SLPI) is mainly produced by immune cells and various epithelial cells, and is regulated by a variety of cytokines, such as transforming growth factor ß1, interleukin 1ß and tumor necrosis factor α. In addition to commonly known anti-protease activity, it has been found in recent years that SLPI plays essential roles in anti-apoptosis, regulating cell cycle, cell differentiation and proliferation, and inhibiting inflammatory response. SLPI can also assist the immune system to clear pathogens/damaged cells by enhancing the phagocytic function of phagocytes, so as to ameliorate tissue damage and promote repair. Moreover, recent studies have shown that the change of SLPI level in the serum of patients post cardiovascular surgery has a high diagnostic value in predicting the occurrence of acute kidney injury, suggesting that SLPI is involved in ischemia-reperfusion (IR) induced acute kidney injury. In this review, we summarized the expression, regulation, signaling pathways and associated biological events of SLPI in different organ injury models, and also discussed and evaluated the potential role of SLPI in renoprotection against IR induced acute kidney injury and its potential as a new biomarker.

Role of OPG/RANKL/RANK/TLR4 signaling pathway in sepsis-associated acute kidney injury.

BACKGROUND: Sepsis-associated acute kidney injury (SA-AKI) has high mortality rates. The osteoprotegerin (OPG)/receptor activator of nuclear factor-κB ligand (RANKL)/receptor activator of nuclear factor-κB (RANK)/Toll-like receptor 4 (TLR4) pathway and its potential role in SA-AKI pathogenesis remain to be fully understood. Herein, we addressed this issue using mouse models. METHODS: An SA-AKI mouse model was established using the cecal ligation and puncture method (CLP). Mice were grouped into sham, CLP model, CLP + recombinant RANKL, and CLP + anti-RANKL groups. Serum creatinine (Scr) and blood urea nitrogen (BUN) levels were measured to assess kidney function. ELISA was used to detect serum IL-1ß, TNF-α, and IL-6 levels. Real-time quantitative PCR and Western blot were used to detect the mRNA and protein expression levels of OPG, RANKL, RANK, and TLR4 in kidney tissues. HE staining was performed to evaluate the pathological changes. RESULTS: The CLP model group showed higher levels of Scr and BUN, indicating impaired kidney function in SA-AKI, compared to the sham group. Treatment with recombinant RANKL in the CLP + recombinant RANKL group reduced Scr and BUN levels, while anti-RANKL treatment in the CLP + anti-RANKL group elevated their levels. Moreover, the CLP model group had significantly increased IL-1ß, TNF-α, and IL-6 than the sham group, indicating elevated inflammation in SA-AKI. The CLP + recombinant RANKL group demonstrated decreased cytokine levels, whereas the CLP + anti-RANKL group showed an increase. Additionally, the histopathological evaluation revealed distinct kidney tissue damage in the CLP model group. Recombinant RANKL treatment reduced this damage, while anti-RANKL treatment exacerbated it. Mechanically, the mRNA and protein expression of RANKL were significantly decreased, while those of OPG, RANK, and TLR4 were significantly increased in the CLP model group and the CLP + anti-RANKL group. Interestingly, treatment with recombinant RANKL reversed these changes, as evidenced by significantly increased RANKL but decreased OPG, RANK, and TLR4. CONCLUSION: The OPG/RANKL/RANK/TLR4 pathway is involved in SA-AKI pathogenesis. Recombinant RANKL treatment attenuates the inflammatory response and kidney tissue damage in SA-AKI, possibly via regulating this pathway. This pathway shows promise as a therapeutic target for SA-AKI.

Efficacy of Trametinib in Alleviating Cisplatin-Induced Acute Kidney Injury: Inhibition of Inflammation, Oxidative Stress, and Tubular Cell Death in a Mouse Model.

Cisplatin, a platinum-based chemotherapeutic, is effective against various solid tumors, but its use is often limited by its nephrotoxic effects. This study evaluated the protective effects of trametinib, an FDA-approved selective inhibitor of mitogen-activated protein kinase kinase 1/2 (MEK1/2), against cisplatin-induced acute kidney injury (AKI) in mice. The experimental design included four groups, control, trametinib, cisplatin, and a combination of cisplatin and trametinib, each consisting of eight mice. Cisplatin was administered intraperitoneally at a dose of 20 mg/kg to induce kidney injury, while trametinib was administered via oral gavage at 3 mg/kg daily for three days. Assessments were conducted 72 h after cisplatin administration. Our results demonstrate that trametinib significantly reduces the phosphorylation of MEK1/2 and extracellular signal-regulated kinase 1/2 (ERK1/2), mitigated renal dysfunction, and ameliorated histopathological abnormalities. Additionally, trametinib significantly decreased macrophage infiltration and the expression of pro-inflammatory cytokines in the kidneys. It also lowered lipid peroxidation by-products, restored the reduced glutathione/oxidized glutathione ratio, and downregulated NADPH oxidase 4. Furthermore, trametinib significantly inhibited both apoptosis and necroptosis in the kidneys. In conclusion, our data underscore the potential of trametinib as a therapeutic agent for cisplatin-induced AKI, highlighting its role in reducing inflammation, oxidative stress, and tubular cell death.