The transcriptional factor PREB mediates MCP-1 transcription induced by cytokines in human vascular endothelial cells

Unfolded Protein Response-Related Signature Associates With the Immune Microenvironment and Prognostic Prediction in Osteosarcoma

Background: Osteosarcoma is a highly malignant bone tumor commonly occurring in adolescents with a poor 5-year survival rate. The unfolded protein response (UPR) can alleviate the accumulation of misfolded proteins to maintain homeostasis under endoplasmic reticulum stress. The UPR is linked to the occurrence, progression, and drug resistance of tumors. However, the function of UPR-related genes (UPRRGs) in disease progression and prognosis of osteosarcoma remains unclear.

Methods: The mRNA expression profiling and corresponding clinical features of osteosarcoma were acquired from TARGET and GEO databases. Consensus clustering was conducted to confirm different UPRRG subtypes. Subsequently, we evaluated the prognosis and immune status of the different subtypes. Functional analysis of GO, GSEA, and GSVA was used to reveal the molecular mechanism between the subtypes. Finally, four genes (STC2, PREB, TSPYL2, and ATP6V0D1) were screened to construct and validate a risk signature to predict the prognosis of patients with osteosarcoma.

Result: We identified two subtypes according to the UPRRG expression patterns. The subgroup with higher immune scores, lower tumor purity, and active immune status was linked to a better prognosis. Meanwhile, functional enrichment revealed that immune-related signaling pathways varied markedly in the two subtypes, suggesting that the UPR might influence the prognosis of osteosarcoma via influencing the immune microenvironment. Moreover, prognostic signature and nomogram models were developed based on UPRRGs, and the results showed that our model has an excellent performance in predicting the prognosis of osteosarcoma. qPCR analysis was also conducted to verify the expression levels of the four genes.

Conclusion: We revealed the crucial contribution of UPRRGs in the immune microenvironment and prognostic prediction of osteosarcoma patients and provided new insights for targeted therapy and prognostic assessment of the disease.

Role of ATP-binding cassette transporter A1 in suppressing lipid accumulation by glucagon-like peptide-1 agonist in hepatocytes

Objective

Adenosine triphosphate (ATP)-binding cassette transporter A1 (ABCA1) influences hepatic cholesterol transportation. Accumulation of hepatic cholesterol leads to fatty liver disease, which is improved by glucagon-like peptide 1 (GLP-1) in diabetes. Therefore, we analyzed the molecular mechanism in the regulation of hepatic ABCA1 by GLP-1 analogue exendin-4.

Methods

Hepatic ABCA1 expression and transcription were checked by western blotting, real-time polymerase chain reaction (PCR), and luciferase assay in HepG2 cells. Chromatin immunoprecipitation (ChIP) and site-directed mutagenesis were employed to determine transcriptional regulation of the ABCA1 gene. Prolactin regulatory element-binding (PREB)-transgenic mice were generated to access the effect of exendin-4 on improving lipid accumulation caused by a high-fat diet (HFD).

Results

Exendin-4 stimulated hepatic ABCA1 expression and transcription via the Ca²⁺/calmodulin (CaM)-dependent protein kinase kinase/CaM-dependent protein kinase IV (CaMKK/CaMKIV) pathway, whereas GLP-1 receptor antagonist exendin9-39 cancelled this effect. Therefore, exendin-4 decreased hepatic lipid content. ChIP showed that PREB could directly bind to the ABCA1 promoter, which was enhanced by exendin-4. Moreover, PREB stimulated ABCA1 promoter activity, and mutation of PREB-binding site in ABCA1 promoter cancelled exendin-4-enhanced ABCA1 promoter activity. Silencing of PREB attenuated the effect of exendin-4 and induced hepatic cholesterol accumulation. Blockade of CaMKK by STO-609 or siRNA cancelled the upregulation of ABCA1 and PREB induced by exendin-4. In vivo, exendin-4 or overexpression of PREB increased hepatic ABCA1 expression and decreased hepatic lipid accumulation and high plasma cholesterol caused by a HFD.

Conclusions

Our data shows that exendin-4 stimulates hepatic ABCA1 expression and decreases lipid accumulation by the CaMKK/CaMKIV/PREB pathway, suggesting that ABCA1 and PREB might be the therapeutic targets in fatty liver disease.

•

The GLP-1R agonist exendin-4 suppressed lipid accumulation by upregulating ABCA1 expression in hepatocytes.

•

Exendin-4 regulated the expression and transcription of hepatic ABCA1 via the CaMKK/CaMKIV/PREB pathway.

•

Overexpression of PREB or exendin-4 protected mouse liver from fatty liver by upregulation of ABCA1.

Increased MCP-1 gene expression in monocytes of severe OSA patients and under intermittent hypoxia

PURPOSE

Obstructive sleep apnea (OSA) is known to be a risk factor of coronary artery disease. Monocyte chemoattractant protein-1 (MCP-1), as a critical factor for monocyte infiltration, is known to play a role in the development of atherosclerosis. This study aimed to investigate the effect of intermittent hypoxia, the hallmark of OSA, on the MCP-1 expression of monocytes.

METHODS

Peripheral blood was sampled from 61 adults enrolled for suspected OSA. RNA was prepared from the isolated monocytes for the analysis of MCP-1. The effect of in vitro intermittent hypoxia on the regulation and function of MCP-1 was investigated on THP-1 monocytic cells and human monocytes. The mRNA and secreted protein levels were investigated by RT/real-time PCR and enzyme-linked immunosorbent assay, respectively.

RESULTS

Monocytic MCP-1 gene expression was found to be increased significantly in severe OSA patients. In vitro intermittent hypoxia was demonstrated to increase the mRNA and protein expression levels of MCP-1 dose- and time-dependently in THP-1 monocytic cells. The MCP-1 mRNA expression in monocytes isolated from OSA patient was induced to a much higher level compared to that from normal control. Pre-treatment with inhibitor for p42/44 MAPK or p38 MAPK suppressed the activation of MCP-1 expression by intermittent hypoxia.

CONCLUSIONS

This is the first study to demonstrate the increase of MCP-1 gene expression in monocytes of severe OSA patients. In addition, monocytic MCP-1 gene expression can be induced under intermittent hypoxia.

Transcriptional factor prolactin regulatory element-binding protein-mediated gene transcription of ABCA1 via 3',5'-cyclic adenosine-5'-monophosphate

OBJECTIVE

Prolactin regulatory element-binding (PREB) protein is a transcription factor that regulates prolactin promoter activity in the rat anterior pituitary. The PREB protein is not only expressed in the anterior pituitary but also in the cardiovascular system, including vascular smooth muscle cells (SMCs). However, the role of PREB in SMCs is not clearly understood. The ATP-binding cassette transporter A1 (ABCA1) regulates lipid efflux from peripheral cells to apolipoproteins. In the present study, we have examined the role of PREB in regulating ABCA1 expression mediated by 3',5'-cyclic adenosine-5'-monophosphate (cAMP).

METHODS AND RESULTS

PREB was expressed in the rats SMC line CRL-2018. ABCA1 expression was found to be regulated by cAMP, which stimulated the expression of PREB in a dose-dependent manner. Conversely, over-expression of PREB, which was induced by a PREB-expressing adenovirus, increased the expression of the ABCA1 protein in CRL-2018 cells. In addition, PREB stimulated the activity of the luciferase reporter protein that was under the control of the ABCA1 promoter. Chromatin immunoprecipitation assay showed that PREB mediates its transcriptional activity by directly binding to the ABCA1 promoter region. Finally, we used siRNA to inhibit PREB expression in the cells and demonstrated that the knockdown of PREB expression attenuated the effects of cAMP on ABCA1 expression.

CONCLUSIONS

In summary, our data showed that PREB regulates the cAMP-mediated transcription of the ABCA1 gene in vascular SMCs.

Is recurrent epistaxis from Kiesselbach's area (REKAS) in any relationship to the hemorrhoidal disease?

Vascular diseases are a major threat to human health nowadays. Hypertension, cardiovascular disease and varicose vain disease including hemorrhoids, are now increasingly recognized as inflammatory diseases. The role of inflammation cytokines in the pathogenesis of these diseases is very important. The lamina propria in the nasal mucosa is rich in blood vessels and humoral mediators. Recurrent epistaxis from Kiesselbach's area syndrome (REKAS) was first mentioned as early as 1985. It has been found that 90% of patients suffering from recurrent epistaxis from Kiesselbach area syndrome simultaneously suffered from hemorrhoids. Clinical observations suggest a possible mutual pathophysiologic relationship between Kiesselbach's and anorectal venous plexus. This relationship is also suggested in the reverse direction: significantly more than two thirds of primarily hemorrhoidal patients (83.01%) showed simultaneous vascular dilatations within their Kiesselbach plexuses, but none of these patients had ever have recurrent nose bleeds. There is one more thing they did not have (contrary to REKAS group)--anterior septal deformity. Furthermore, REKAS and hemorrhoidal disease, despite being different clinical entities, frequently appear in the primarily REKAS patients or their closest relatives (more than 90% out of all!). At the same time, all of REKAS patients did have a certain degree of the anterior septal deformity, which primarily hemorrhoidal patients did not have at all. Therefore we presume that Kiesselbach's vascular plexus in the Little's area of the nasal septum belongs to the same group as anorectal venous plexus does (others of this group are brain, esophagus, and lower leg venous system). We also presume that the anterior septal deformity is a crucial factor for the onset of the inflammation of the nasal vestibule skin (vestibulitis nasi), while vestibulitis nasi precipitates the onset of typical recurrent nose bleeds from the Kiesselbach's plexus.