Increased RTN3 phenocopies nonalcoholic fatty liver disease by inhibiting the AMPK-IDH2 pathway

Deletion of Pyruvate Carboxylase in Tubular Epithelial Cell Promotes Renal Fibrosis by Regulating SQOR/cGAS/STING-Mediated Glycolysis

Renal fibrosis is a common pathway involved in the progression of various chronic kidney diseases to end-stage renal disease. Recent studies show that mitochondrial injury of renal tubular epithelial cells (RTECs) is a crucial pathological foundation for renal fibrosis. However, the underlying regulatory mechanisms remain unclear. Pyruvate carboxylase (PC) is a catalytic enzyme located within the mitochondria that is intricately linked with mitochondrial damage and metabolism. In the present study, the downregulation of PC in various fibrotic animal and human kidney samples is demonstrated. Renal proximal tubule-specific Pcx gene knockout mice (PcxcKO) has significant interstitial fibrosis compared to control mice, with heightened expression of extracellular matrix molecules. This is further demonstrated in a stable PC knock-out RTEC line. Mechanistically, PC deficiency reduces its interaction with sulfide:quinone oxidoreductase (SQOR), increasing the ubiquitination and degradation of SQOR. This leads to mitochondrial morphological and functional disruption, increased mtDNA release, activation of the cGAS-STING pathway, and elevated glycolysis levels, and ultimately, promotes renal fibrosis. This study investigates the molecular mechanisms through which PC deficiency induces mitochondrial injury and metabolic reprogramming in RTECs. This study provides a novel theoretical foundation and potential therapeutic targets for the pathogenesis and treatment of renal fibrosis.

Poria cocos: traditional uses, triterpenoid components and their renoprotective pharmacology

Poria cocos and its surface layer of Poria cocos (Schw.) Wolf (Polyporaceae), are used in traditional Chinese medicine for its diuretic and renoprotective effects. Phytochemical studies have shown that lanostane and 3,4-seco-lanostane tetracyclic triterpenoids are the main components of P. cocos and its surface layer. Accumulating evidence shows that triterpenoid components in P. cocos and its surface layer contribute to their renoprotective effect. The surface layer of P. cocos showed a stronger diuretic effect than P. cocos. The ethanol extract of the surface layer and its components improved acute kidney injury, acute kidney injury-to-chronic kidney disease transition and chronic kidney disease such as diabetic kidney disease, nephrotic syndrome and tubulointerstitial nephropathy, and protected against renal fibrosis. It has been elucidated that P. cocos and its surface layer exert a diuretic effect and improve kidney diseases through a variety of molecular mechanisms such as aberrant pathways TGF-β1/Smad, Wnt/β-catenin, IκB/NF-κB and Keap1/Nrf2 signaling as well as the activation of renin-angiotensin system, matrix metalloproteinases, aryl hydrocarbon receptor and endogenous metabolites. These studies further confirm the renoprotective effect of P. cocos and its surface layer and provide a beneficial basis to its clinical use in traditional medicine.

Early-life antibiotic exposure aggravates hepatic steatosis through enhanced endotoxemia and lipotoxic effects driven by gut Parabacteroides

Compelling evidence supports a link between early-life gut microbiota and the metabolic outcomes in later life. Using an early-life antibiotic exposure model in BALB/c mice, we investigated the life-course impact of prenatal and/or postnatal antibiotic exposures on the gut microbiome of offspring and the development of metabolic dysfunction-associated steatotic liver disease (MASLD). Compared to prenatal antibiotic exposure alone, postnatal antibiotic exposure more profoundly affected gut microbiota development and succession, which led to aggravated endotoxemia and metabolic dysfunctions. This was primarily resulted from the overblooming of gut Parabacteroides and hepatic accumulation of cytotoxic lysophosphatidyl cholines (LPCs), which acted in conjunction with LPS derived from Parabacteroides distasonis (LPS_PA) to induce cholesterol metabolic dysregulations, endoplasmic reticulum (ER) stress and apoptosis. Integrated serum metabolomics, hepatic lipidomics and transcriptomics revealed enhanced glycerophospholipid hydrolysis and LPC production in association with the upregulation of PLA2G10, the gene controlling the expression of the group X secretory Phospholipase A2s (sPLA2-X). Taken together, our results show microbial modulations on the systemic MASLD pathogenesis and hepatocellular lipotoxicity pathways following early-life antibiotic exposure, hence help inform refined clinical practices to avoid any prolonged maternal antibiotic administration in early life and potential gut microbiota-targeted intervention strategies.

Integrated Analysis of WES and scRNA-Seq Data Reveals the Genetic Basis of Immune Dysregulation in Unexplained Recurrent Pregnancy Loss

OBJECTIVE

This study aimed to identify genetic variants and their functional consequences underlying Unexplained Recurrent Pregnancy Loss (uRPL) through comprehensive genomic and transcriptomic analyses.

METHODS

We recruited 13 Chinese uRPL patients and performed Whole Exome Sequencing (WES) on chorionic villi samples from miscarriage tissues. Additionally, we conducted an integrative analysis using single-cell RNA sequencing data from decidual immune cells to examine expression patterns.

RESULTS

WES analysis pinpointed variants in the four MUC genes (MUC4, MUC6, MUC16, and MUC17), six lipid metabolism genes in immune cells (ABCA4, ABCA7, ABCB5, ABCC8, ADGRV1, and ANK3), and two structural genes (PIEZO1 and PKD1), whose variants impair mucosal barriers and lipid homeostasis, thereby leading to immune dysregulation and contributing to uRPL. To delve deeper into the effects of these genetic variants on cellular expression patterns, we undertook an integrative analysis using a single-cell dataset from decidual immune cells in uRPL cases. We observed significant dysregulation of lipid metabolism within immune cells, reduced heat shock protein expression, and enhanced chemokine signaling in uRPL samples, indicating a pro-inflammatory state.

CONCLUSIONS

In summary, our study reveals a complex interplay between genetic variants and immune cell dysfunctions in uRPL, emphasizing the role of identified genetic variants in driving pro-inflammatory states. These findings provide a comprehensive view of the molecular mechanisms underlying uRPL, opening paths for novel therapeutic interventions and improved clinical management.

RTN3 regulates collagen biosynthesis and profibrotic macrophage differentiation to promote pulmonary fibrosis via interacting with CRTH2

BACKGROUND

As an endoplasmic reticulum (ER) protein, Reticulum 3 (RTN3) has been reported to play a crucial role in neurodegenerative diseases, lipid metabolism, and chronic kidney disease. The involvement of RTN3 in idiopathic pulmonary fibrosis (IPF), a progressive and fatal interstitial lung disease, remains unexplored.

METHODS

In this study, we explored the role of RTN3 in pulmonary fibrosis using public datasets, IPF patient samples, and animal models. We investigated its pathogenic mechanisms in lung fibroblasts and alveolar macrophages.

RESULTS

We found decreased levels of RTN3 in IPF patients, bleomycin-induced mice, and TGFβ-treated cell lines. RTN3-null mice exhibited more severe pulmonary fibrosis phenotypes in old age or after bleomycin treatment. Collagen synthesis was significantly increased in RTN3-null mice lung tissues and lung fibroblasts. Mechanistic studies revealed that RTN3 deficiency reduced the ER-anchored CRTH2 in lung fibroblasts, which serves as an antifibrotic molecule via antagonizing collagen biosynthesis. Simultaneously, RTN3 deficiency reduced the autophagy degradation of CRTH2 which acts as an activator of profibrotic macrophage differentiation. Both effects of RTN3 and CRTH2 in lung fibroblasts and alveolar macrophages aggravated age-or bleomycin-induced pulmonary fibrosis. Additionally, we also identified a mutation of RTN3 in patients with ILD.

CONCLUSIONS

Our research demonstrated that RTN3 plays a significant role in the lung, and reduction of RTN3 levels may be a risk factor for IPF and related diseases.

Heat shock proteins (HSPs) in non-alcoholic fatty liver disease (NAFLD): from molecular mechanisms to therapeutic avenues

Non-alcoholic fatty liver disease (NAFLD), a spectrum of liver conditions characterized by fat accumulation without excessive alcohol consumption, represents a significant global health burden. The intricate molecular landscape underlying NAFLD pathogenesis involves lipid handling, inflammation, oxidative stress, and mitochondrial dysfunction, with endoplasmic reticulum (ER) stress emerging as a key contributor. ER stress triggers the unfolded protein response (UPR), impacting hepatic steatosis in NAFLD and contributing to inflammation, fibrosis, and progression to NASH and eventually hepatocellular carcinoma (HCC). Heat shock proteins (HSPs), including small HSPs such as HSP20 and HSP27, HSP60, HSP70, GRP78, and HSP90, are integral to cellular stress responses. They aid in protein folding, prevent aggregation, and facilitate degradation, thus mitigating cellular damage under stress conditions. In NAFLD, aberrant HSP expression and function contribute to disease pathogenesis. Understanding the specific roles of HSP subtypes in NAFLD offers insights into potential therapeutic interventions. This review discusses the involvement of HSPs in NAFLD pathophysiology and highlights their therapeutic potential. By elucidating the molecular mechanisms underlying HSP-mediated protection in NAFLD, this article aims to pave the way for the development of targeted therapies for this prevalent liver disorder.

Downregulating miR-432-5p exacerbates adriamycin-induced cardiotoxicity via activating the RTN3 signaling pathway

BACKGROUND

Adriamycin (ADR) is a widely used chemotherapy drug in clinical practice and it causes toxicity in the myocardium affecting its clinical use. miR-432-5p is a miRNA primarily expressed in myocardial cells and has a protective effect in the myocardium. We aim to explore the protective effect of miR-432-5p on ADR-caused impaired mitochondrial ATP metabolism and endoplasmic reticulum stress (ERs).

METHOD

The primary cardiomyocytes were obtained from neonatal mice and the ADR was added to cells, meanwhile, a mice model was constructed through intravenous ADR challenge, and expression levels of miR-432-5p were examined. Subsequently, the miR-432-5p was introduced in vitro and in vivo to explore its effect on the activity of mitochondrial ATP synthesis, autophagy, and ER stress. The bioinformatics analysis was performed to explore the target of miR-432-5p.

RESULTS

ADR decreased the expression of miR-432-5p in cardiomyocytes. It also decreases mitochondrial ATP production and activates the ER stress pathway by increasing the expression of LC3B, Beclin 1, cleaved caspase 3, and induces cardiac toxicity. miR-432-5p exogenous supplementation can reduce the cardiotoxicity caused by ADR, and its protective effect on cardiomyocytes depends on the down-regulation of the RTN3 signaling pathway in ER.

CONCLUSION

ADR can induce the low expression of miR-432-5p, and activate the RTN3 pathway in ER, increase the expression of LC3B, Beclin 1, cleaved caspase 3, CHOP, and RTN3, and induce cardiac toxicity.

Single-cell transcriptomic profiling reveals decreased ER protein Reticulon3 drives the progression of renal fibrosis

Chronic kidney disease (CKD) poses a significant global health dilemma, emerging from complex causes. Although our prior research has indicated that a deficiency in Reticulon-3 (RTN3) accelerates renal disease progression, a thorough examination of RTN3 on kidney function and pathology remains underexplored. To address this critical need, we generated Rtn3-null mice to study the consequences of RTN3 protein deficiency on CKD. Single-cell transcriptomic analyses were performed on 47,885 cells from the renal cortex of both healthy and Rtn3-null mice, enabling us to compare spatial architectures and expression profiles across 14 distinct cell types. Our analysis revealed that RTN3 deficiency leads to significant alterations in the spatial organization and gene expression profiles of renal cells, reflecting CKD pathology. Specifically, RTN3 deficiency was associated with Lars2 overexpression, which in turn caused mitochondrial dysfunction and increased reactive oxygen species levels. This shift induced a transition in renal epithelial cells from a functional state to a fibrogenic state, thus promoting renal fibrosis. Additionally, RTN3 deficiency was found to drive the endothelial-to-mesenchymal transition process and disrupt cell-cell communication, further exacerbating renal fibrosis. Immunohistochemistry and Western-Blot techniques were used to validate these observations, reinforcing the critical role of RTN3 in CKD pathogenesis. The deficiency of RTN3 protein in CKD leads to profound changes in cellular architecture and molecular profiles. Our work seeks to elevate the understanding of RTN3's role in CKD's narrative and position it as a promising therapeutic contender.

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.

RTN3 deficiency exacerbates cisplatin-induced acute kidney injury through the disruption of mitochondrial stability

Reticulum 3 (RTN3) is an endoplasmic reticulum (ER) protein that has been reported to act in neurodegenerative diseases and lipid metabolism. However, the role of RTN3 in acute kidney injury (AKI) has not been explored. Here, we employed public datasets, patient data, and animal models to explore the role of RTN3 in AKI. The underlying mechanisms were studied in primary renal tubular epithelial cells and in the HK2 cell line. We found reduced expression of RTN3 in AKI patients, cisplatin-induced mice, and cisplatin-treated HK2 cells. RTN3-null mice exhibit more severe AKI symptoms and kidney fibrosis after cisplatin treatment. Mitochondrial dysfunction was also found in cells with RTN3 knockdown or knockout. A mechanistic study revealed that RTN3 can interact with HSPA9 in kidney cells. RTN3 deficiency may disrupt the RTN3-HSPA9-VDAC2 complex and affect MAMs during ER-mitochondrion contact, which further leads to mitochondrial dysfunction and exacerbates cisplatin-induced AKI. Our study indicated that RTN3 was important in the kidney and that a decrease in RTN3 in the kidney might be a risk factor for the aggravation of AKI.

Correction to: Increased RTN3 phenocopies nonalcoholic fatty liver disease by inhibiting the AMPK-IDH2 pathway

[This corrects the article DOI: 10.1002/mco2.226.].

Haploinsufficiency of Lipin3 leads to hypertriglyceridemia and obesity by disrupting the expression and nucleocytoplasmic localization of Lipin1

Lipin proteins including Lipin 1-3 act as transcriptional co-activators and phosphatidic acid phosphohydrolase enzymes, which play crucial roles in lipid metabolism. However, little is known about the function of Lipin3 in triglyceride (TG) metabolism. Here, we identified a novel mutation (NM_001301860: p.1835A>T/p.D612V) of Lipin3 in a large family with hypertriglyceridemia (HTG) and obesity through whole-exome sequencing and Sanger sequencing. Functional studies revealed that the novel variant altered the half-life and stability of the Lipin3 protein. Hence, we generated Lipin3 heterozygous knockout (Lipin3-heKO) mice and cultured primary hepatocytes to explore the pathophysiological roles of Lipin3 in TG metabolism. We found that Lipin3-heKO mice exhibited obvious obesity, HTG, and non-alcoholic fatty liver disorder. Mechanistic study demonstrated that the haploinsufficiency of Lipin3 in primary hepatocytes may induce the overexpression and abnormal distribution of Lipin1 in cytosol and nucleoplasm. The increased expression of Lipin1 in cytosol may contribute to TG anabolism, and the decreased Lipin1 in nucleoplasm can reduce PGC1α, further leading to mitochondrial dysfunction and reduced TG catabolism. Our study suggested that Lipin3 was a novel disease-causing gene inducing obesity and HTG. We also established a relationship between Lipin3 and mitochondrial dysfunction.

Ferroptosis: an important player in the inflammatory response in diabetic nephropathy

Diabetic nephropathy (DN) is a chronic inflammatory disease that affects millions of diabetic patients worldwide. The key to treating of DN is early diagnosis and prevention. Once the patient enters the clinical proteinuria stage, renal damage is difficult to reverse. Therefore, developing early treatment methods is critical. DN pathogenesis results from various factors, among which the immune response and inflammation play major roles. Ferroptosis is a newly discovered type of programmed cell death characterized by iron-dependent lipid peroxidation and excessive ROS production. Recent studies have demonstrated that inflammation activation is closely related to the occurrence and development of ferroptosis. Moreover, hyperglycemia induces iron overload, lipid peroxidation, oxidative stress, inflammation, and renal fibrosis, all of which are related to DN pathogenesis, indicating that ferroptosis plays a key role in the development of DN. Therefore, this review focuses on the regulatory mechanisms of ferroptosis, and the mutual regulatory processes involved in the occurrence and development of DN and inflammation. By discussing and analyzing the relationship between ferroptosis and inflammation in the occurrence and development of DN, we can deepen our understanding of DN pathogenesis and develop new therapeutics targeting ferroptosis or inflammation-related regulatory mechanisms for patients with DN.

Cell therapy in end-stage liver disease: replace and remodel

Liver disease is prevalent worldwide. When it reaches the end stage, mortality rises to 50% or more. Although liver transplantation has emerged as the most efficient treatment for end-stage liver disease, its application has been limited by the scarcity of donor livers. The lack of acceptable donor organs implies that patients are at high risk while waiting for suitable livers. In this scenario, cell therapy has emerged as a promising treatment approach. Most of the time, transplanted cells can replace host hepatocytes and remodel the hepatic microenvironment. For instance, hepatocytes derived from donor livers or stem cells colonize and proliferate in the liver, can replace host hepatocytes, and restore liver function. Other cellular therapy candidates, such as macrophages and mesenchymal stem cells, can remodel the hepatic microenvironment, thereby repairing the damaged liver. In recent years, cell therapy has transitioned from animal research to early human studies. In this review, we will discuss cell therapy in end-stage liver disease treatment, especially focusing on various cell types utilized for cell transplantation, and elucidate the processes involved. Furthermore, we will also summarize the practical obstacles of cell therapy and offer potential solutions.