Knockdown of TRIM27 expression suppresses the dysfunction of mesangial cells in lupus nephritis by FoxO1 pathway

Protopanaxadiol improves lupus nephritis by regulating the PTX3/MAPK/ERK1/2 pathway

Lupus nephritis (LN) is a kidney disease that occurs after systemic lupus erythematosus (SLE) affects the kidneys. Pentraxin 3 (PTX3) is highly expressed in the serum of patients with LN. Renal PTX3 deposition is directly related to clinical symptoms such as proteinuria and inflammation. The excessive proliferation of mesangial cells (MCs) is one of the representative pathological changes in the progression of LN, which is closely related to its pathogenesis. Protopanaxadiol (PPD) is the main component of ginsenoside metabolism and has not been reported in LN. The aim of this study was to investigate the relationship between PTX3 and mesangial cell proliferation and to evaluate the potential role and mechanism of PPD in improving LN. PTX3 is highly expressed in the kidneys of LN patients and LN mice and is positively correlated with renal pathological indicators, including proteinuria and PCNA. The excessive expression of PTX3 facilitated the proliferation of MCs, facilitated the activation of the MAPK/ERK1/2 signaling pathway, and increased the expression of HIF-1α. Further studies showed that PPD can effectively inhibit the abnormal proliferation of MCs with high expression of PTX3 and significantly improve LN symptoms such as proteinuria in MRL/lpr mice. The mechanism may be related to the inhibition of the PTX3/MAPK/ERK1/2 pathway. In this study, both in vitro, in vivo, and clinical sample results show that PTX3 is involved in the regulation of MCs proliferation and the early occurrence of LN. Natural active compound PPD can improve LN by regulating the PTX3/MAPK/ERK1/2 pathway.

TRIM Expression in HNSCC: Exploring the Link Between Ubiquitination, Immune Infiltration, and Signaling Pathways Through Bioinformatics

Objective

Ubiquitination is an important post-translational modification. However, the significance of the TRIM family of E3 ubiquitin ligases in head and neck squamous cell carcinoma (HNSCC) has not been determined. In this study, the roles of TRIM E3 ubiquitin ligases in lymphovascular invasion in head and neck squamous cell carcinoma (HNSCC) were evaluated.

Materials and Methods

TRIM expression and related parameters were obtained from UbiBrowser2.0, UALCAN, TIMER, TISIDB, LinkedOmics, STRING, and GeneMANIA databases. Immunohistochemistry was used to confirm their expression.

Results

TRIM2, TRIM11, TRIM28, and TRIM56 were upregulated in HNSCC with lymphovascular invasion. TRIM expression was strongly associated with immune infiltration, including key treatment targets, like PD-1 and CTL4. Co-expressed genes and possible ubiquitination substrates included tumor-related factors. The TRIMs had predicted roles in ubiquitination-related pathways and vital signaling pathways, eg, MAPK, PI3K-Akt, and JAK-STAT signaling pathways.

Conclusion

Ubiquitination mediated by four TRIMs might be involved in the regulation of tumor immunity, laying the foundation for future studies of the roles of the TRIM family on the prediction and personalized medicine in HNSCC. The four TRIMs might exert oncogenic effects by promoting lymphovascular invasion in HNSCC.

Macrophages communicate with mesangial cells through the CXCL12/DPP4 axis in lupus nephritis pathogenesis

Lupus nephritis (LN) occurs in 50% of cases of systemic lupus erythematosus (SLE) and is one of the most serious complications that can occur during lupus progression. Mesangial cells (MCs) are intrinsic cells in the kidney that can regulate capillary blood flow, phagocytose apoptotic cells, and secrete vasoactive substances and growth factors. Previous studies have shown that various types of inflammatory cells can activate MCs for hyperproliferation, leading to disruption of the filtration barrier and impairment of renal function in LN. Here, we characterized the heterogeneity of kidney cells of LN mice by single-nucleus RNA sequencing (snRNA-seq) and revealed the interaction between macrophages and MCs through the CXC motif chemokine ligand 12 (CXCL12)/dipeptidyl peptidase 4 (DPP4) axis. In culture, macrophages modulated the proliferation and migration of MCs through this ligand-receptor interaction. In LN mice, treatment with linagliptin, a DPP4 inhibitor, effectively inhibited MC proliferation and reduced urinary protein levels. Together, our findings indicated that targeting the CXCL12/DPP4 axis with linagliptin treatment may serve as a novel strategy for the treatment of LN via the CXCL12/DPP4 axis.

The Role of TRIM Proteins in Vascular Disease

There are more than 80 different tripartite motifs (TRIM) proteins within the E3 ubiquitin ligase subfamily, including proteins that regulate intracellular signaling, apoptosis, autophagy, proliferation, inflammation, and immunity through the ubiquitination of target proteins. Studies conducted in recent years have unraveled the importance of TRIM proteins in the pathophysiology of vascular diseases. In this review, we describe the effects of TRIM proteins on vascular endothelial cells, smooth muscle cells, heart, and lungs. In particular, we discuss the potential mechanisms by which TRIMs regulate diseases and shed light on the potential therapeutic applications of TRIMs.

Sweroside attenuates podocyte injury and proteinuria in part by activating Akt/BAD signaling in mice

In this study, we investigated the effects of sweroside on podocyte injury in diabetic nephropathy (DN) mice and elucidated its molecular mechanisms. We conducted in vivo experiments using a C57BL/6 mice model of DN to explore the effects of sweroside on proteinuria and podocyte injury in DN mice. In in vitro experiments, conditionally immortalized mouse podocytes were treated with high glucose and sweroside, and the protective effects of sweroside on podocyte injury were analyzed. In vitro, Akt/BAD pathways were detected using gene siRNA silencing assays and found to be involved in the protective roles of sweroside in high glucose-mediated podocyte injury. In vivo, sweroside significantly decreased albuminuria in DN mice (p < 0.01). periodic acid-Schiff staining showed that sweroside alleviated the glomerular volume and mesangium expansion in DN mice. Consistently, western blot and reverse transcription-polymerase chain reaction analyses showed that the profibrotic molecule expression in the glomeruli declined in sweroside-treated DN mice. Immunofluorescent results showed that sweroside preserved nephrin and podocin expression, and transmission electron microscopy showed that sweroside attenuated podocyte injury. In DN mice, sweroside decreased podocyte apoptosis, and increased nephrin, podocin expression and decreased desmin and HIF1α expression. These results confirmed that sweroside ameliorated albuminuria, glomerulomegaly, and glomerulosclerosis in these mice. Experiments in vitro revealed that sweroside improved HG-induced podocyte injury and apoptosis. Sweroside stimulated activation of the Akt/BAD pathway and upregulated Bcl-2-associated death promoter (BAD) and p-Akt. Overall, sweroside protected podocytes from injury and prevented the progression of DN, providing a novel strategy for the treatment of DN.

Knockdown of DEC2 expression inhibits the proliferation of mesangial cells through suppressed glycolysis and p38 MAPK/Erk pathway in lupus nephritis

BACKGROUND

To elucidate the mechanism by which DEC2 modulates the proliferation of mesangial cells (MCs) in lupus nephritis (LN).

METHODS

The 32-week-old female Fcgr2b-/- mice and their serum-treated MCs were used as in vivo and in vitro LN model. MCs knocked down of DEC2 and overexpressed with DEC2 were also established. The expression of DEC2 was measured in the kidneys of Fcgr2b-/- mice and LN serum-treated MCs using RT-qPCR and Western blot. MCs proliferation was detected by 5-ethynyl-2'-deoxyuridine (EdU) labeling assay and PCNA expression using immunofluorescence. The glucose metabolism was evaluated in LN serum-treated MCs, and the levels of lactate production, glucose consumption, ATP production and mitochondrial membrane potential were assayed. The glycolysis and mitochondrial respiration function of the MCs were measured using the Extracellular Flux Analyzer. The extracellular acidification rate (ECAR) and oxygen consumption rate (OCR) were dynamically monitored and multiple important bioenergetic parameters can be calculated. The expression of Toll like receptor 4 (TLR4) and glucose transporter 1 (GLUT1) were detected in the MCs. Multiple signaling proteins were screened.

RESULTS

DEC2 was found overexpressed in the kidney of Fcgr2b-/- LN mice. Knockdown of DEC2 inhibited LN serum-induced MCs proliferation. DEC2 was associated with the glucose metabolism in LN serum-treated MCs. DEC2 regulated glycolysis in LN serum-treated MCs. DEC2 was associated with mitochondrial fitness in LN serum treated MCs. DEC2 activated MCs glycolysis through TLR4 and glucose transporter 1 (GLUT1) regulation. DEC2 regulated MCs proliferation through two signaling pathways including dependent and independent of glycolysis, which located in the downstream of TLR4 signaling.

CONCLUSION

Knockdown of DEC2 expression inhibits the proliferation of MCs through suppressed glycolysis and p38 MAPK/ERK pathway in LN.

Neglected PTM in Animal Adipogenesis: E3-mediated Ubiquitination

Ubiquitination is a widespread post-transcriptional modification (PTM) that occurs during protein degradation in eukaryotes and participates in almost all physiological and pathological processes, including animal adipogenesis. Ubiquitination is a cascade reaction regulated by the activating enzyme E1, conjugating enzyme E2, and ligase E3. Several recent studies have reported that E3 ligases play important regulatory roles in adipogenesis. However, as a key influencing factor for the recognition and connection between the substrate and ubiquitin during ubiquitination, its regulatory role in adipogenesis has not received adequate attention. In this review, we summarize the E3s' regulation and modification targets in animal adipogenesis, explain the regulatory mechanisms in lipogenic-related pathways, and further analyze the existing positive results to provide research directions of guiding significance for further studies on the regulatory mechanisms of E3s in animal adipogenesis.

NQO1 alleviates renal fibrosis by inhibiting the TLR4/NF-κB and TGF-β/Smad signaling pathways in diabetic nephropathy

OBJECTIVE

Diabetic nephropathy (DN) is one of the main complications of diabetes, and inflammation and fibrosis play an important role in its progression. NAD(P)H: quinone oxidoreductase 1 (NQO1) protects cells from oxidative stress and damage caused by toxic quinones. In the present study, we aimed to investigate the protective effects of NQO1 against diabetes-induced renal inflammation and fibrosis and the underlying mechanisms.

METHODS

In vivo, the kidneys of type 2 diabetes model db/db mice were infected with adeno-associated virus vectors to induce NQO1 overexpression. In vitro, human renal tubular epithelial (HK-2) cells transfected with NQO1 pcDNA3.1(+) were cultured under high-glucose (HG) conditions. Gene and protein expression was assessed by quantitative real-time PCR, Western blotting, immunofluorescence, and immunohistochemical staining. Mitochondrial reactive oxygen species (ROS) were detected with MitoSOX Red.

RESULT

Our study revealed that the expression of NQO1 was markedly downregulated and that Toll-like receptor (TLR)4 and TGF-β1 expression was upregulated in vivo and in vitro under diabetic conditions. Overexpression of NQO1 suppressed proinflammatory cytokine (IL-6, TNF-α, MCP-1) secretion, extracellular matrix (ECM) (collagen IV, fibronectin) accumulation and epithelial-mesenchymal transition (EMT) (α-SMA, E-cadherin) in the db/db mouse kidneys and HG-cultured HK-2 cells. Furthermore, NQO1 overexpression ameliorated HG-induced TLR4/NF-κB and TGF-β/Smad pathways activation. Mechanistic studies demonstrated that a TLR4 inhibitor (TAK-242) suppressed the TLR4/NF-κB signaling pathway, proinflammatory cytokine secretion, EMT and ECM-related protein expression in HG-exposed HK-2 cells. In addition, we found that the antioxidants N-acetylcysteine (NAC) and tempol increased the expression of NQO1 and decreased the expression of TLR4, TGF-β1, Nox1, and Nox4 and ROS production in HK-2 cells cultured under HG conditions.

CONCLUSIONS

These data suggest that NQO1 alleviates diabetes-induced renal inflammation and fibrosis by regulating the TLR4/NF-κB and TGF-β/Smad signaling pathways.

Identification of genetic variants associated with diabetic kidney disease in multiple Korean cohorts via a genome-wide association study mega-analysis

BACKGROUND

The pathogenesis of diabetic kidney disease (DKD) is complex, involving metabolic and hemodynamic factors. Although DKD has been established as a heritable disorder and several genetic studies have been conducted, the identification of unique genetic variants for DKD is limited by its multiplex classification based on the phenotypes of diabetes mellitus (DM) and chronic kidney disease (CKD). Thus, we aimed to identify the genetic variants related to DKD that differentiate it from type 2 DM and CKD.

METHODS

We conducted a large-scale genome-wide association study mega-analysis, combining Korean multi-cohorts using multinomial logistic regression. A total of 33,879 patients were classified into four groups-normal, DM without CKD, CKD without DM, and DKD-and were further analyzed to identify novel single-nucleotide polymorphisms (SNPs) associated with DKD. Additionally, fine-mapping analysis was conducted to investigate whether the variants of interest contribute to a trait. Conditional analyses adjusting for the effect of type 1 DM (T1D)-associated HLA variants were also performed to remove confounding factors of genetic association with T1D. Moreover, analysis of expression quantitative trait loci (eQTL) was performed using the Genotype-Tissue Expression project. Differentially expressed genes (DEGs) were analyzed using the Gene Expression Omnibus database (GSE30529). The significant eQTL DEGs were used to explore the predicted interaction networks using search tools for the retrieval of interacting genes and proteins.

RESULTS

We identified three novel SNPs [rs3128852 (P = 8.21×10^-25), rs117744700 (P = 8.28×10^-10), and rs28366355 (P = 2.04×10^-8)] associated with DKD. Moreover, the fine-mapping study validated the causal relationship between rs3128852 and DKD. rs3128852 is an eQTL for TRIM27 in whole blood tissues and HLA-A in adipose-subcutaneous tissues. rs28366355 is an eQTL for HLA-group genes present in most tissues.

CONCLUSIONS

We successfully identified SNPs (rs3128852, rs117744700, and rs28366355) associated with DKD and verified the causal association between rs3128852 and DKD. According to the in silico analysis, TRIM27 and HLA-A can define DKD pathophysiology and are associated with immune response and autophagy. However, further research is necessary to understand the mechanism of immunity and autophagy in the pathophysiology of DKD and to prevent and treat DKD.

Mesangial cell: A hub in lupus nephritis

Lupus nephritis (LN) is a severe renal disease caused by the massive deposition of the immune complexes (ICs) in renal tissue, acting as one of the significant organ manifestations of systemic lupus erythematosus (SLE) and a substantial cause of death in clinical patients. As mesangium is one of the primary sites for IC deposition, mesangial cells (MCs) constantly undergo severe damage, resulting in excessive proliferation and increased extracellular matrix (ECM) production. In addition to playing a role in organizational structure, MCs are closely related to in situ immunomodulation by phagocytosis, antigen-presenting function, and inflammatory effects, aberrantly participating in the tissue-resident immune responses and leading to immune-mediated renal lesions. Notably, such renal-resident immune responses drive a second wave of MC damage, accelerating the development of LN. This review summarized the damage mechanisms and the in situ immune regulation of MCs in LN, facilitating the current drug research for exploring clinical treatment strategies.

TRIM family contribute to tumorigenesis, cancer development, and drug resistance

The tripartite-motif (TRIM) family represents one of the largest classes of putative single protein RING-finger E3 ubiquitin ligases. TRIM family is involved in a variety of cellular signaling transductions and biological processes. TRIM family also contributes to cancer initiation, progress, and therapy resistance, exhibiting oncogenic and tumor-suppressive functions in different human cancer types. Moreover, TRIM family members have great potential to serve as biomarkers for cancer diagnosis and prognosis. In this review, we focus on the specific mechanisms of the participation of TRIM family members in tumorigenesis, and cancer development including interacting with dysregulated signaling pathways such as JAK/STAT, PI3K/AKT, TGF-β, NF-κB, Wnt/β-catenin, and p53 hub. In addition, many studies have demonstrated that the TRIM family are related to tumor resistance; modulate the epithelial–mesenchymal transition (EMT) process, and guarantee the acquisition of cancer stem cells (CSCs) phenotype. In the end, we havediscussed the potential of TRIM family members for cancer therapeutic targets.

Emerging roles of TRIM27 in cancer and other human diseases

As a member of the TRIM protein family, TRIM27 is a RING-mediated E3 ubiquitin ligase that can mark other proteins for degradation. Its ubiquitination targets include PTEN, IκBα and p53, which allows it to regulate many signaling pathways to exert its functions under both physiological and pathological conditions, such as cell proliferation, differentiation and apoptosis. During the past decades, TRIM27 was reported to be involved in many diseases, including cancer, lupus nephritis, ischemia-reperfusion injury and Parkinson’s disease. Although the research interest in TRIM27 is increasing, there are few reviews about the diverse roles of this protein. Here, we systematically review the roles of TRIM27 in cancer and other human diseases. Firstly, we introduce the biological functions of TRIM27. Next, we focus on the roles of TRIM27 in cancer, including ovarian cancer, breast cancer and lung cancer. At the same time, we also describe the roles of TRIM27 in other human diseases, such as lupus nephritis, ischemia-reperfusion injury and Parkinson’s disease. Finally, we discuss the future directions of TRIM27 research, especially its potential roles in tumor immunity.

Novel insight into the aetiology of rheumatoid arthritis gained by a cross-tissue transcriptome-wide association study

BACKGROUND

Although genome-wide association studies (GWASs) have identified more than 100 loci associated with rheumatoid arthritis (RA) susceptibility, the causal genes and biological mechanisms remain largely unknown.

METHODS

A cross-tissue transcriptome-wide association study (TWAS) using the unified test for molecular signaturestool was performed to integrate GWAS summary statistics from 58 284 individuals (14 361 RA cases and 43 923 controls) with gene-expression matrix in the Genotype-Tissue Expression project. Subsequently, a single tissue by using FUSION software was conducted to validate the significant associations. We also compared the TWAS with different gene-based methodologies, including Summary Data Based Mendelian Randomization (SMR) and Multimarker Analysis of Genomic Annotation (MAGMA). Further in silico analyses (conditional and joint analysis, differential expression analysis and gene-set enrichment analysis) were used to deepen our understanding of genetic architecture and comorbidity aetiology of RA.

RESULTS

We identified a total of 47 significant candidate genes for RA in both cross-tissue and single-tissue test after multiple testing correction, of which 40 TWAS-identified genes were verified by SMR or MAGMA. Among them, 13 genes were situated outside of previously reported significant loci by RA GWAS. Both TWAS-based and MAGMA-based enrichment analyses illustrated the shared genetic determinants among autoimmune thyroid disease, asthma, type I diabetes mellitus and RA.

CONCLUSION

Our study unveils 13 new candidate genes whose predicted expression is associated with risk of RA, providing new insights into the underlying genetic architecture of RA.

Tripartite motif 27 promotes cardiac hypertrophy via PTEN/Akt/mTOR signal pathways

Tripartite motif-containing 27 (Trim27) is highly expressed in tumor cells and regulates natural immunity and apoptosis. However, the effects of Trim27 in cardiac hypertrophy are not fully elucidated. In this study, we tried to explore the potential role of Trim27 in pressure overload-induced cardiac hypertrophy and the underlying mechanism. The results indicated that compared to sham operation (Sham) group, transverse aortic constriction (TAC) group showed significantly up-regulated Trim27 protein expression (P < 0.05). The neonatal rat cardiomyocytes (NRCMs) were isolated and stimulated with PBS, angiotensin (AngII) and phenylephrine (PE). NRCMs were collected to detect the protein expression of Trim27. The results were consistent with the results in vivo. Compared to PBS treatment, the expression of Trim27 protein in NRCMs was significantly increased after PE or AngII stimulation (P < 0.05, respectively). Knockout of Trim27 can reduce the size of cardiomyocytes and reduce the proteins expression of ANP, BNP, and β-MHC, improve cardiac function, and reverse myocardial hypertrophy (P < 0.05). Trim27 may be involved in regulating the development of cardiac hypertrophy. Further results showed that Trim27 can increase the protein expression of phosphorylation of Akt, GSK3β, mTOR, and P70s6k by interacting with PTEN (phosphatase tensin homolog). These findings revealed that Trim27 can promote cardiac hypertrophy by activating PTEN/Akt/GSK3β/mTOR signaling pathway.

NAD(P)H: quinone oxidoreductase 1 attenuates oxidative stress and apoptosis by regulating Sirt1 in diabetic nephropathy

Background

Diabetic nephropathy (DN) is one of the main complications of diabetes, and oxidative stress plays an important role in its progression. NAD(P)H: quinone oxidoreductase 1 (NQO1) protects cells from oxidative stress and toxic quinone damage. In the present study, we aimed to investigate the protective effects and underlying mechanisms of NQO1 on diabetes-induced renal tubular epithelial cell oxidative stress and apoptosis.

Methods

In vivo, the kidneys of db/db mice, which are a type 2 diabetes model, were infected with adeno-associated virus to induce NQO1 overexpression. In vitro, human renal tubular epithelial cells (HK-2 cells) were transfected with NQO1 pcDNA3.1(+) and cultured in high glucose (HG). Gene and protein expression was assessed by quantitative real-time PCR, western blotting, immunofluorescence analysis, and immunohistochemical staining. Reactive oxygen species (ROS) were examined by MitoSox red and flow cytometry. TUNEL assays were used to measure apoptosis.

Result

In vivo, NQO1 overexpression reduced the urinary albumin/creatinine ratio (UACR) and blood urea nitrogen (BUN) level in db/db mice. Our results revealed that NQO1 overexpression could significantly increase the ratio of NAD+/NADH and silencing information regulator 1 (Sirt1) expression and block tubular oxidative stress and apoptosis in diabetic kidneys. In vitro, NQO1 overexpression reduced the generation of ROS, NADPH oxidase 1 (Nox1) and Nox4, the Bax/Bcl-2 ratio and the expression of Cleaved Caspase-3 and increased NAD+/NADH levels and Sirt1 expression in HK-2 cells under HG conditions. However, these effects were reversed by the Sirt1 inhibitor EX527.

Conclusions

All these data suggest that NQO1 has a protective effect against oxidative stress and apoptosis in DN, which may be mediated by the regulation of Sirt1 through increasing intracellular NAD+/NADH levels. Therefore, NQO1 may be a new therapeutic target for DN.

Mesangial Cells in Lupus Nephritis

PURPOSE OF REVIEW

Mesangial cells are critical for the proper function of the glomerulus, playing roles in structural support and injury repair. However, they are also early responders to glomerular immune complex deposition and contribute to inflammation and fibrosis in lupus nephritis. This review highlights recent studies identifying signaling pathways and mediators in mesangial cell response to lupus-relevant stimuli.

RECENT FINDINGS

Anti-dsDNA antibodies, serum, or plasma from individuals with lupus nephritis, or specific pathologic factors activated multiple signaling pathways. These pathways largely included JAK/STAT/SOCS, PI3K/AKT, and MAPK and led to induction of proliferation and expression of multiple proinflammatory cytokines, growth factors, and profibrotic factors. NFκB activation was a common mediator of response. Mesangial cells proliferate and express a wide array of proinflammatory/profibrotic factors in response to a variety of lupus-relevant pathologic stimuli. While some of the responses are similar, the mechanisms involved appear to be diverse depending on the stimulus. Future studies are needed to fully elucidate these mechanisms with respect to the diverse milieu of stimuli.

TRIM40 inhibits IgA1-induced proliferation of glomerular mesangial cells by inactivating NLRP3 inflammasome through ubiquitination

IgA nephropathy, as the most common type of glomerulonephritis, causes chronic renal disease and progresses into kidney failure. Aberrant IgA deposition in the glomerular mesangium induces NLRP3 inflammasome activation for massive local inflammation, and is recognized as the primary pathogenesis in IgA nephropathy. Tripartite motif (TRIM)-containing proteins are E3 ubiquitin ligases that possess crucial regulatory functions in innate immunity, but their functional roles in IgA nephropathy are still unclear. Here, we aimed to identify TRIM-containing proteins that regulate IgA nephropathy and their underlying mechanisms. An in vitro IgA1-induction model was established in glomerular mesangial cells (GMCs) and showed that IgA1 could promote GMC proliferation by activating NLRP3 inflammasome. TRIM40, which was downregulated by IgA1 and interacted with NLRP3, was recognized as a promising candidate. In addition, TRIM40 could suppress IgA1-induced GMC proliferation by inhibiting the activation of NLRP3 inflammasome. Based on coimmunoprecipitation and ubiquitination assays, we confirmed that TRIM40 could mediate the ubiquitination of NLRP3, which explained its regulatory effects on NLRP3 inflammasome and GMC proliferation. More importantly, a dominant-negative mutant of TRIM40 lacking the RING domain (ΔRING) did not affect NLRP3 ubiquitination, and had no effects on IgA1-induced GMC proliferation or NLRP3 inflammasome activation. This study revealed the biological functions of TRIM40 in IgA nephropathy, facilitating its application as therapeutic target for IgA nephropathy and other NLRP3 inflammasome-relevant diseases.

TRIM27 contributes to glomerular endothelial cell injury in lupus nephritis by mediating the FoxO1 signaling pathway

Tripartite motif-containing 27 (TRIM27) belongs to the triple motif (TRIM) protein family, which plays a role in a variety of biological activities. Our previous study showed that the TRIM27 protein was highly expressed in the glomerular endothelial cells of patients suffering from lupus nephritis (LN). However, whether TRIM27 is involved in the injury of glomerular endothelial cells in lupus nephritis remains to be clarified. Here, we detected the expression of the TRIM27 protein in glomerular endothelial cells in vivo and in vitro. In addition, the influence of TRIM27 knockdown on endothelial cell damage in MRL/lpr mice and cultured human renal glomerular endothelial cells (HRGECs) was explored. The results revealed that the expression of TRIM27 in endothelial cells was significantly enhanced in vivo and in vitro. Downregulating the expression of TRIM27 inhibited the breakdown of the glycocalyx and the injury of endothelial cells via the FoxO1 pathway. Moreover, HRGECs transfected with the WT-FoxO1 plasmid showed a reduction in impairment caused by LN plasma. Furthermore, suppression of the protein kinase B (Akt) pathway could attenuate damage by mediating the expression of TRIM27. Thus, the present study showed that TRIM27 participated in the injury of glomerular endothelial cells and served as a potential therapeutic target for the treatment of lupus nephritis.

FOXO1 expression in chondrocytes modulates cartilage production and removal in fracture healing

Fracture healing is a multistage process characterized by inflammation, cartilage formation, bone deposition, and remodeling. Chondrocytes are important in producing cartilage that forms the initial anlagen for the hard callus needed to stabilize the fracture site. We examined the role of FOXO1 by selective ablation of FOXO1 in chondrocytes mediated by Col2α1 driven Cre recombinase. Experimental mice with lineage-specific FOXO1 deletion (Col2α1Cre+FOXO1L/L) and negative control littermates (Col2α1Cre-FOXO1L/L) were used for in vivo, closed fracture studies. Unexpectedly, we found that in the early phases of fracture healing, FOXO1 deletion significantly increased the amount of cartilage formed, whereas, in later periods, FOXO1 deletion led to a greater loss of cartilage. FOXO1 was functionally important as its deletion in chondrocytes led to diminished bone formation on day 22. Mechanistically, the early effects of FOXO1 deletion were linked to increased proliferation of chondrocytes through enhanced expression of cell cycle genes that promote proliferation and reduced expression of those that inhibit it and increased expression of cartilage matrix genes. At later time points experimental mice with FOXO1 deletion had greater loss of cartilage, enhanced formation of osteoclasts, increased IL-6 and reduced numbers of M2 macrophages. These results identify FOXO1 as a transcription factor that regulates chondrocyte behavior by limiting the early expansion of cartilage and preventing rapid cartilage loss at later phases.

Effect of forkhead box O1 in renal tubular epithelial cells on endotoxin-induced acute kidney injury

Mitochondrial damage in renal tubular epithelial cells (RTECs) is a hallmark of endotoxin-induced acute kidney injury (AKI). Forkhead box O1 (FOXO1) is responsible for regulating mitochondrial function and is involved in several kidney diseases. Here, we investigated the effect of FOXO1 on endotoxin-induced AKI and the related mechanism. In vivo, FOXO1 downregulation in mouse RTECs and mitochondrial damage were found in endotoxin-induced AKI. Overexpression of FOXO1 by kidney focal adeno-associated virus (AAV) delivery improved renal function and reduced mitochondrial damage. Peroxisome proliferator-activated receptor-γ coactivator 1-α (PGC1-α), a master regulator of mitochondrial biogenesis and function, was reduced in endotoxin-induced AKI, but the reduction was reversed by FOXO1 overexpression. In vitro, exposure to LPS led to a decline in HK-2 cell viability, mitochondrial fragmentation, and mitochondrial superoxide accumulation, as well as downregulation of FOXO1, PGC1-α, and mitochondrial complex I/V. Moreover, overexpression of FOXO1 in HK-2 cells increased HK-2 cell viability and PGC1-α expression, and it alleviated the mitochondrial injury and superoxide accumulation induced by LPS. Meanwhile, inhibition of FOXO1 in HK-2 cells by siRNA treatment decreased PGC1-α expression and HK-2 cell viability. Chromatin immunoprecipitation assays and PCR analysis confirmed that FOXO1 bound to the PGC1-α promoter in HK-2 cells. In conclusion, downregulation of FOXO1 in RTECs mediated endotoxin-induced AKI and mitochondrial damage. Overexpression of FOXO1 could improve renal injury and mitochondrial dysfunction, and this effect occurred at least in part as a result of PGC1-α signaling. FOXO1 might be a potential target for the prevention and treatment of endotoxin-induced AKI.

Tripartite Motif-Containing 27 Attenuates Liver Ischemia/Reperfusion Injury by Suppressing Transforming Growth Factor β-Activated Kinase 1 (TAK1) by TAK1 Binding Protein 2/3 Degradation

BACKGROUND AND AIMS

Hepatic ischemia-reperfusion (I/R) injury, which mainly involves inflammatory responses and apoptosis, is a common cause of organ dysfunction in liver transplantation (LT). As a critical mediator of inflammation and apoptosis in various cell types, the role of tripartite motif-containing (TRIM) 27 in hepatic I/R injury remains worthy of study.

APPROACH AND RESULTS

This study systemically evaluated the putative role of TRIM27/transforming growth factor β-activated kinase 1 (TAK1)/JNK (c-Jun N-terminal kinase)/p38 signaling in hepatic I/R injury. TRIM27 expression was significantly down-regulated in liver tissue from LT patients, mice subjected to hepatic I/R surgery, and hepatocytes challenged by hypoxia/reoxygenation (H/R) treatment. Subsequently, using global Trim27 knockout mice (Trim27-KO mice) and hepatocyte-specific Trim27 transgenic mice (Trim27-HTG mice), TRIM27 functions to ameliorate liver damage, reduce the inflammatory response, and prevent cell apoptosis. In parallel in vitro studies, activating TRIM27 also prevented H/R-induced hepatocyte inflammation and apoptosis. Mechanistically, TRIM27 constitutively interacted with the critical components, TAK1 and TAK1 binding protein 2/3 (TAB2/3), and promoted the degradation of TAB2/3, leading to inactivation of TAK1 and the subsequent suppression of downstream JNK/p38 signaling.

CONCLUSIONS

TRIM27 is a key regulator of hepatic I/R injury by mediating the degradation of TAB2/3 and suppression of downstream TAK1-JNK/p38 signaling. TRIM27 may be a promising approach to protect the liver against I/R-mediated hepatocellular damage in transplant recipients.

MYDGF attenuates podocyte injury and proteinuria by activating Akt/BAD signal pathway in mice with diabetic kidney disease

AIMS/HYPOTHESIS

Myeloid-derived growth factor (MYDGF), mainly secreted by bone marrow-derived cells, has been known to promote glucagon-like peptide-1 production and improve glucose/lipid metabolism in mouse models of diabetes, but little is known about the functions of MYDGF in diabetic kidney disease (DKD). Here, we investigated whether MYDGF can prevent the progression of DKD.

METHODS

In vivo experiments, both loss- and gain-of-function strategies were used to evaluate the effect of MYDGF on albuminuria and pathological glomerular lesions. We used streptozotocin-treated Mydgf knockout and wild-type mice on high fat diets to induce a model of DKD. Then, albuminuria, glomerular lesions and podocyte injury were evaluated in Mydgf knockout and wild-type DKD mice treated with adeno-associated virus-mediated Mydgf gene transfer. In vitro and ex vivo experiments, the expression of slit diaphragm protein nephrin and podocyte apoptosis were evaluated in conditionally immortalised mouse podocytes and isolated glomeruli from non-diabetic wild-type mice treated with recombinant MYDGF.

RESULTS

MYDGF deficiency caused more severe podocyte injury in DKD mice, including the disruption of slit diaphragm proteins (nephrin and podocin) and an increase in desmin expression and podocyte apoptosis, and subsequently caused more severe glomerular injury and increased albuminuria by 39.6% compared with those of wild-type DKD mice (p < 0.01). Inversely, MYDGF replenishment attenuated podocyte and glomerular injury in both wild-type and Mydgf knockout DKD mice and then decreased albuminuria by 36.7% in wild-type DKD mice (p < 0.01) and 34.9% in Mydgf knockout DKD mice (p < 0.01). Moreover, recombinant MYDGF preserved nephrin expression and inhibited podocyte apoptosis in vitro and ex vivo. Mechanistically, the renoprotection of MYDGF was attributed to the activation of the Akt/Bcl-2-associated death promoter (BAD) pathway.

CONCLUSIONS/INTERPRETATION

The study demonstrates that MYDGF protects podocytes from injury and prevents the progression of DKD, providing a novel strategy for the treatment of DKD. Graphical abstract.

Nestin protects podocyte from injury in lupus nephritis by mitophagy and oxidative stress

Podocyte injury is the main cause of proteinuria in lupus nephritis (LN). Nestin, an important cytoskeleton protein, is expressed stably in podocytes and is associated with podocyte injury. However, the role of nestin in the pathogenesis of proteinuria in LN remains unclear. The correlations among nestin, nephrin and proteinuria were analyzed in LN patients and MRL/lpr lupus-prone mice. The expression of nestin in mouse podocyte lines (MPCs) and MRL/lpr mice was knocked down to determine the role of nestin in podocyte injury. Inhibitors and RNAi method were used to explore the role of mitophagy and oxidative stress in nestin protection of podocyte from damage. There was a significantly negative correlation between nestin and proteinuria both in LN patients and MRL/lpr mice, whereas the expression of nephrin was positively correlated with nestin. Knockdown of nestin resulted in not only the decrease of nephrin, p-nephrin (Y1217) and mitophagy-associated proteins in cultured podocytes and the podocytes of MRL/lpr mice, but also mitochondrial dysfunction in podocytes stimulated with LN plasma. The expression and phosphorylation of nephrin was significantly decreased by reducing the level of mitophagy or production of reactive oxygen species (ROS) in cultured podocytes. Our findings suggested that nestin regulated the expression of nephrin through mitophagy and oxidative stress to protect the podocytes from injury in LN.

Detection of BKV encoded mature MicroRNAs in kidney transplant patients: Clinical and biologic insights

BACKGROUND

Polyomavirus BK (BKV) encodes two mature miRNAs that regulate the viral life cycle.

OBJECTIVES

This study investigated the autoregulatory and immunomodulatory effects of these miRNAs that have been defined in culture systems, but subject to only limited exploration in clinical samples.

METHODS

BKV-miR-B1-5p, BKV-miR-BJ1-3p, BKV DNA and BKV VP-1 mRNA levels were measured in 32 paired obtained plasma & urine samples from kidney transplant patients with (a) early stage infection manifesting as viruria, and (b) later stage infections complicated by viremia.

RESULTS

All patients showed abundant urine miRNAs (7.84E + 02-1.91E + 06 copies/ml, but plasma miRNA was below the limit of detection. There was no statistically significant difference in urinary miRNA levels between viruric and viremic patients. Median 5p miRNA load was 4-6 logs lower than the BKV genomic load. Higher miRNA levels in the urine were associated not with lower but higher urinary viral loads. BKV preferentially used the 3p miRNA for its interactions with host cell mRNAs. The mean ratio of 5p/3p in patients with viruria was 0.09, and 0.03 in patients with viremia.

CONCLUSIONS

The data suggest that immune evasion functions of BKV miRNAs over-ride the negative autoregulatory feedback effects in kidney transplant patients with active viral replication.