Inhibitory effect of PXR on ammonia-induced hepatocyte autophagy via P53

Pregnane X Receptor Signaling Pathway and Vitamin K: Molecular Mechanisms and Clinical Relevance in Human Health

This review explores the likely clinical impact of Pregnane X Receptor (PXR) activation by vitamin K on human health. PXR, initially recognized as a master regulator of xenobiotic metabolism in liver, emerges as a key regulator influencing intestinal homeostasis, inflammation, oxidative stress, and autophagy. The activation of PXR by vitamin K highlights its role as a potent endogenous and local agonist with diverse clinical implications. Recent research suggests that the vitamin K-mediated activation of PXR highlights this vitamin's potential in addressing pathophysiological conditions by promoting hepatic detoxification, fortifying gut barrier integrity, and controlling pro-inflammatory and apoptotic pathways. PXR activation by vitamin K provides an intricate association with cancer cell survival, particularly in colorectal and liver cancers, to provide new insights into potential novel therapeutic strategies. Understanding the clinical implications of PXR activation by vitamin K bridges molecular mechanisms with health outcomes, further offering personalized therapeutic approaches for complex diseases.

Pregnane X receptor activation alleviates renal fibrosis in mice via interacting with p53 and inhibiting the Wnt7a/β-catenin signaling

Renal fibrosis is a common pathological feature of chronic kidney disease (CKD) with various etiologies, which seriously affects the structure and function of the kidney. Pregnane X receptor (PXR) is a member of the nuclear receptor superfamily and plays a critical role in regulating the genes related to xenobiotic and endobiotic metabolism in mammals. Previous studies show that PXR is expressed in the kidney and has protective effect against acute kidney injury (AKI). In this study, we investigated the role of PXR in CKD. Adenine diet-induced CKD (AD) model was established in wild-type and PXR humanized (hPXR) mice, respectively, which were treated with pregnenolone-16α-carbonitrile (PCN, 50 mg/kg, twice a week for 4 weeks) or rifampicin (RIF, 10 mg·kg-1·d-1, for 4 weeks). We showed that both PCN and RIF, which activated mouse and human PXR, respectively, improved renal function and attenuated renal fibrosis in the two types of AD mice. In addition, PCN treatment also alleviated renal fibrosis in unilateral ureter obstruction (UUO) mice. On the contrary, PXR gene deficiency exacerbated renal dysfunction and fibrosis in both adenine- and UUO-induced CKD mice. We found that PCN treatment suppressed the expression of the profibrotic Wnt7a and β-catenin in AD mice and in cultured mouse renal tubular epithelial cells treated with TGFβ1 in vitro. We demonstrated that PXR was colocalized and interacted with p53 in the nuclei of tubular epithelial cells. Overexpression of p53 increased the expression of Wnt7a, β-catenin and its downstream gene fibronectin. We further revealed that p53 bound to the promoter of Wnt7a gene to increase its transcription and β-catenin activation, leading to increased expression of the downstream profibrotic genes, which was inhibited by PXR. Taken together, PXR activation alleviates renal fibrosis in mice via interacting with p53 and inhibiting the Wnt7a/β-catenin signaling pathway.

Transcriptional Regulation of Hepatic Autophagy by Nuclear Receptors

Autophagy is an adaptive self-eating process involved in degradation of various cellular components such as carbohydrates, lipids, proteins, and organelles. Its activity plays an essential role in tissue homeostasis and systemic metabolism in response to diverse challenges, including nutrient depletion, pathogen invasion, and accumulations of toxic materials. Therefore, autophagy dysfunctions are intimately associated with many human diseases such as cancer, neurodegeneration, obesity, diabetes, infection, and aging. Although its acute post-translational regulation is well described, recent studies have also shown that autophagy can be controlled at the transcriptional and post-transcriptional levels. Nuclear receptors (NRs) are in general ligand-dependent transcription factors consisting of 48 members in humans. These receptors extensively control transcription of a variety of genes involved in development, metabolism, and inflammation. In this review, we discuss the roles and mechanisms of NRs in an aspect of transcriptional regulation of hepatic autophagy, and how the NR-driven autophagy pathway can be harnessed to treat various liver diseases.

Role of AMPK mediated pathways in autophagy and aging

AMPK is an important kinase regulating energy homeostasis and also a key protein involved in a variety of signal transduction pathways. It plays a vitally regulatory role in cellular senescence. Activation of AMPK can delay or block the aging process, which is of great significance in the treatment of cardiovascular diseases and other aging related diseases, and provides a potential target for new indications such as Alzheimer's disease. Therefore, AMPK signaling pathway plays an important role in aging research. The in-depth study of AMPK activators will provide more new directions for the treatment of age-related maladies and the development of innovative drugs. Autophagy is a process that engulfs and degrades own cytoplasm or organelles. Thereby, meeting the metabolic demands and updating certain organelles of the cell has become a hotspot in the field of anti-aging in recent years. AMPK plays an important role between autophagy and senescence. In our review, the relationship among AMPK signaling, autophagy and aging will be clarified through the interaction between AMPK and mTOR, ULK1, FOXO, p53, SIRT1, and NF -κB.

Prevention of D-GalN/LPS-induced ALI by 18β-glycyrrhetinic acid through PXR-mediated inhibition of autophagy degradation

Acute liver injury (ALI) has multiple causes and results in liver dysfunction. Severe or persistent liver injury eventually leads to liver failure and even death. Pregnane X receptor (PXR)-null mice present more severe liver damage and lower rates of autophagy. 18β-glycyrrhetinic acid (GA) has been proposed as a promising hepatoprotective agent. We hypothesized that GA significantly alleivates D-GalN/LPS-induced ALI, which involved in PXR-mediated autophagy and lysosome biogenesis. We found that GA can significantly decrease hepatocyte apoptosis and increase the hepatic autophagy marker LC3-B. Ad-mCherry-GFP-LC3 tandem fluorescence, RNA-seq and real-time PCR indicated that GA may stabilize autophagosomes and lysosomes and inhibit autophagosome-lysosome fusion. Simultaneously, GA markedly activates PXR, even reversing the D-GalN/LPS-induced reduction of PXR and its downstream genes. In contrast, GA has a weak protective effect in pharmacological inhibition of PXR and PXR-null mice, which significantly affected apoptosis- and autophagy-related genes. PXR knockout interferes with the stability of autophagosomes and lysosomes, preventing GA reducing the expression of lysosomal genes such as Cst B and TPP1, and suppressing autophagy flow. Therefore, we believe that GA increases autophagy by inhibiting autophagosome-lysosome fusion and blocked autophagy flux via activation of PXR. In conclusion, our results show that GA activates PXR to regulate autophagy and lysosome biogenesis, represented by inhibiting autophagosome-lysosome fusion and stabilization of lysosome. These results identify a new mechanism by which GA-dependent PXR activation reduces D-GalN/LPS-induced acute liver injury.

The Effects of Autophagy-Related Genes and lncRNAs in Therapy and Prognosis of Colorectal Cancer

Cellular autophagy plays an important role in the occurrence and development of colorectal cancer (CRC). Whether autophagy-related genes and lncRNAs can be used as ideal markers in CRC is still controversial. The purpose of this study is to identify novel treatment and prognosis markers of CRC. We downloaded transcription and clinical data of CRC from the GEO (GSE40967, GSE12954, GSE17536) and TCGA database, screened for differentially autophagy-related genes (DEAGs) and lncRNAs, constructed prognostic model, and analyzed its relationship with immune infiltration. TCGA and GEO datasets (GSE12954 and GSE17536) were used to validate the effect of the model. Oncomine database and Human Protein Atlas verified the expression of DEAGs. We obtained a total of 151 DEAGs in three verification sets collaboratively. Then we constructed a risk prognostic model through Lasso regression to obtain 15 prognostic DEAGs from the training set and verified the risk prognostic model in three verification sets. The low-risk group survived longer than the high-risk group. Age, gender, pathological stage, and TNM stage were related to the prognostic risk of CRC. On the other hand, BRAF status, RFS event, and tumor location are considered as most significant risk factors of CRC in the training set. Furthermore, we found that the immune score of the low-risk group was higher. The content of CD8 + T cells, active NK cells, macrophages M0, macrophages M1, and active dendritic cells was noted more in the high-risk group. The content of plasma cells, resting memory CD4 + T cells, resting NK cells, resting mast cells, and neutrophil cells was higher in the low-risk group. After all, the Oncomine database and immunohistochemistry verified that the expression level of most key autophagy-related genes was consistent with the results that we found. In addition, we obtained six lncRNAs co-expressed with DEAGs from the training set and found that the survival time was longer in the low-risk group. This finding was verified in the verification set and showed same trend to the results mentioned above. In the final analysis, these results indicate that autophagy-related genes and lncRNAs can be used as prognostic and therapeutic markers for CRC.

PTEN/AKT/mTOR pathway involvement in autophagy, mediated by miR-99a-3p and energy metabolism in ammonia-exposed chicken bursal lymphocytes

Emission of atmospheric ammonia (NH₃) is an environmental challenge because of its harmful effects on humans and animals including birds. Among all organisms, NH₃ is highly sensitive to birds. Autophagy plays a critical role in Bursa of fabricius (BF)-mediated immune responses against various hazardous substances. Therefore, we designed our work to demonstrate whether NH₃ can induce autophagy in broiler chicken BF. In this study, the downregulated levels of mammalian target of rapamycin and light chain-3 (LC-Ⅰ), as well as the upregulated levels of phosphate and tensin homology (PTEN), protein kinase B (AKT), autophagy related-5, light chain-3 (LC3-Ⅱ), Becline-1, and Dynein, were found. Our results of transmission electron microscopy displayed signs of autophagosomes/autophagic lysosomes, and immunofluorescence assay displayed that NH₃ exposure reduced the relative amount of CD8⁺ B-lymphocyte in chicken BF. Exposure of NH₃ led to energy metabolism disturbance by decreasing mRNA levels of glucose metabolism factors aconitase-2, hexokinase-1, hexokinase-2, lactate dehydrogenase-A, lactate dehydrogenase-B, pyruvate kinase, phosphofructokinase and succinate dehydrogenase complex unit-B, and adenosine triphosphates (ATPase) activities (Na⁺/K⁺ ATPase, Ca²⁺ ATPase, Mg²⁺ ATPase, and Ca/Mg²⁺ ATPase). Moreover, phosphate and tensin homology was found as target gene of microRNA-99a-3p which confirmed that high concentration of NH₃ caused autophagy in chicken BF. In summary, these findings suggested that ammonia induced autophagy via miR-99a-3p, the reduction of ATPase activity, and the alteration of autophagy-related factors, and energy metabolism mediation in BF. Our findings provide information to assess the harmful effects of NH₃ on chicken and clues for human health pathophysiology.

High ammonia exposure regulates lipid metabolism in the pig skeletal muscle via mTOR pathway

Ambient ammonia exposure has been known to perturb lipid metabolism in farm animals, but the underlying mechanism is unclear. The current study was conducted to investigate how ambient ammonia exposure influences lipid metabolism in the pig model. Twelve pigs were randomly divided into two groups, either exposed to 0 or 35 mg/m³ atmospheric ammonia for 25 days. Serum ammonia remained unchanged (p > 0.05), but increased serum urea concentration was found (p < 0.05) after ammonia exposure. Ammonia exposure also caused an increased C18:0, C18:2n6c, C18:3n6, C18:3n3, C20:0, C20:2, C20:3n6, C20:3n3, C22:0 concentrations and fat content in the longissimus dorsi muscle (p < 0.05), and also serum total triglyceride (p = 0.0294) and ApoB (p = 0.0061) contents. Analysis of serum free amino acids profile revealed that concentrations of ornithine, tyrosine, asparagine, histidine, phenylalanine, leucine, isoleucine, glutamine and valine were significantly increased in the pigs exposed to 35 mg/m³ ammonia (p < 0.05). RNA-Seq analysis showed that genes encoding enzymes involved in lipid synthesis (FASN, SCD and FADS1) and uptake (LDLR) were up-regulated, whereas genes related to lipolysis (PNPLA4, ANGPTL4 and CEL), transport (CPT1A, CPT1B and CPT2) and β-oxidation (ACADL, ACADVL, UCP2 and UCP3) were down-regulated. Furthermore, exposure to 35 mg/m³ atmospheric ammonia increased expression of mTOR (p = 0.0377) and its downstream P70S6K (p = 0.0139) and p-P70S6K (p = 0.0431), but decreased AMPK (p < 0.0001) and p-AMPK (p = 0.0071) in the longissimus dorsi muscle. In conclusion, high concentration of atmospheric ammonia exposure greatly interferes with amino acid metabolism, resulting in increased BCAAs and aromatic amino acids. The increased BCAAs production can up-regulate lipid synthesis and down-regulate β-oxidation by activating mTOR signaling and inhibiting AMPK signaling.

Ammonia inhalation-mediated mir-202-5p leads to cardiac autophagy through PTEN/AKT/mTOR pathway

Ammonia is a known environmental pollutant around the world. It leads to the deterioration of air quality and has adverse effects on human health. Although previous studies have demonstrated that ammonia caused some health problems to chickens, it is still unclear whether ammonia causes cardiac toxicity. The functional autophagy is very important for cardiac homeostasis. Therefore, the role of autophagy was investigated in the mechanism of chicken heart damage induced by environmental contaminant ammonia in our present study. The results from the oxidative stress index (SOD, GPx, H₂O₂, and MDA), NO content, iNOS activity, and transmission electron microscopy indicated that excess ammonia induced oxidative stress and autophagy in the chicken heart. The expression results from miR-202-5p and PTEN/AKT/mTOR (PTEN, LC3-I, LC3-II, p-AKT, AKT, Beclin1, Dynein, ATG5, p-mTOR and mTOR) signaling pathway-related genes further confirmed that excess ammonia induced cardiac autophagy. In conclusion, these results demonstrated that excess ammonia can cause cardiac damage and mediate mir-202-5p to regulate autophagy through PTEN/AKT/mTOR pathway in the chicken heart injury. Our findings will provide a new insight for better assessing the toxicity mechanism of environmental pollutants ammonia on the heart.

MIR155HG is a prognostic biomarker and associated with immune infiltration and immune checkpoint molecules expression in multiple cancers

In recent years, immune checkpoint inhibitor has achieved remarkable success in multiple cancer treatment. However, how to pre‐judge which patients are suitable for immune checkpoint inhibitor is a difficult problem. We use the existing public bioinformatics database to comprehensively analyze the relationship between clinical data of various cancers with immune checkpoint blocking molecules and long non‐coding RNAs (lncRNAs), and try to find the potential predictive value of lncRNA for immunotherapy with checkpoint inhibitors. In this study, we found that: (a) high expression of lncRNA MIR155 host gene (MIR155HG) was closely related to better overall survival (OS) in cholangiocarcinoma (CHOL), lung adenocarcinoma (LUAD), and skin cutaneous melanoma (SKCM), and have better disease‐free survival (DFS) in CHOL. Meanwhile, the high level of MIR155HG was associated with poorer OS in glioblastoma multiforme (GBM), kidney renal clear cell carcinoma (KIRC), brain lower grade glioma (LGG), and uveal melanoma (UVM). (b) The expression of MIR155HG was significantly correlated with infiltrating levels of immune cells and immune molecules, especially with immune checkpoint molecules such as programmed cell death protein 1 (PD‐1), PD‐1 ligand 1 (PD‐L1), and cytotoxic T lymphocyte‐associated antigen 4 (CTLA4) in most kinds of cancers. (c) Detection of clinical CHOL and liver hepatocellular carcinoma tissues confirmed that there was a strong positive correlation between MIR155HG expression and the levels of CTLA4 and PD‐L1. MIR155 host gene can be used as a prognostic marker in multiple cancers, and of great value in predicting the curative effect of immune checkpoint inhibitor therapy owing to it is closely related with immune cells infiltration and immune checkpoint molecules expression.