Identification and characterization of ARID1A-interacting proteins in renal tubular cells and their molecular regulation of angiogenesis

Trigonelline prevents high-glucose-induced endothelial-to-mesenchymal transition, oxidative stress, mitochondrial dysfunction, and impaired angiogenic activity in human endothelial EA.hy926 cells

Trigonelline (TRIG) is a natural compound in an alkaloid family found in diverse plants. This compound exerts anti-inflammatory, anti-allergic, anti-oxidative and anti-fibrotic activities in several disease models. However, its beneficial role in endothelial injury, especially induced by diabetes, is unclear. We, therefore, evaluated the effects of TRIG on the cellular proteome of human endothelial (EA.hy926) cells followed by functional validation in high-glucose (HG)-induced endothelial deteriorations. Label-free quantification using nanoLC-ESI-Qq-TOF MS/MS revealed 40 downregulated and 29 upregulated proteins induced by TRIG. Functional enrichment analysis using DAVID and REVIGO tools suggested the involvement of these altered proteins in several biological processes and molecular functions, particularly cell-cell adhesion, ATP metabolic process, cell redox homeostasis, cadherin binding, and ATP hydrolysis activity. Experimental validation showed that HG triggered endothelial-to-mesenchymal transition (EndMT) (as demonstrated by increased spindle index and mesenchymal markers, i.e., fibronectin and vimentin, and decreased endothelial markers, i.e., PECAM-1 and VE-cadherin), increased oxidized proteins, and reduced intracellular ATP, active mitochondria, endothelial tube/mesh formation and VEGF secretion. However, TRIG successfully abolished all these defects induced by HG. These data indicate that TRIG prevents HG-induced EndMT, oxidative stress, mitochondrial dysfunction, and impaired angiogenic activity in human endothelial cells.

Proteomic insights into the regulatory function of ARID1A in colon cancer cells

The AT-rich interacting domain-containing protein 1A (ARID1A) is a tumor suppressor gene that has been implicated in several cancers, including colorectal cancer (CRC). The present study used a proteomic approach to elucidate the molecular mechanisms of ARID1A in CRC carcinogenesis. Stable ARID1A-overexpressing SW48 colon cancer cells were established using lentivirus transduction and the successful overexpression of ARID1A was confirmed by western blotting. Label-free quantitative proteomic analysis using liquid chromatography-tandem mass spectrometry identified 705 differentially altered proteins in the ARID1A-overexpressing cells, with 310 proteins significantly increased and 395 significantly decreased compared with empty vector control cells. Gene Ontology enrichment analysis highlighted the involvement of the altered proteins mainly in the Wnt signaling pathway. Western blotting supported these findings, as a decreased protein expression of Wnt target genes, including c-Myc, transcription factor T cell factor-1/7 and cyclin D1, were observed in ARID1A-overexpressing cells. Among the altered proteins involved in the Wnt signaling pathway, the interaction network analysis revealed that ARID1A exhibited a direct interaction with E3 ubiquitin-protein ligase zinc and ring finger 3 (ZNRF3), a negative regulator of the Wnt signaling pathway. Further analyses using the The Cancer Genome Atlas colon adenocarcinoma public dataset revealed that ZNRF3 expression significantly impacted the overall survival of patients with CRC and was positively correlated with ARID1A expression. Finally, an increased level of ZNRF3 in ARID1A-overexpressing cells was confirmed by western blotting. In conclusion, the findings of the present study suggest that ARID1A negatively regulates the Wnt signaling pathway through ZNRF3, which may contribute to CRC carcinogenesis.

The protective effect of caffeine against oxalate-induced epithelial-mesenchymal transition in renal tubular cells via mitochondrial preservation

Mitochondrial dysfunction is one of the key mechanisms for developing chronic kidney disease (CKD). Hyperoxaluria and nephrolithiasis are also associated with mitochondrial dysfunction. Increasing evidence has shown that caffeine, the main bioactive compound in coffee, exerts both anti-fibrotic and anti-lithogenic properties but with unclear mechanisms. Herein, we address the protective effect of caffeine against mitochondrial dysfunction during oxalate-induced epithelial-mesenchymal transition (EMT) in renal cells. Analyses revealed that oxalate successfully induced EMT in MDCK renal cells as evidenced by the increased expression of several EMT-related genes (i.e., Snai1, Fn1 and Acta2). Oxalate also suppressed cellular metabolic activity and intracellular ATP level, but increased reactive oxygen species (ROS). Additionally, oxalate reduced abundance of active mitochondria and induced mitochondrial fragmentation (fission). Furthermore, oxalate decreased mitochondrial biogenesis and content as evidenced by decreased expression of sirtuin-1 (SIRT1), peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α), cytochrome c oxidase subunit 4 (COX4), and total mitochondrial proteins. Nonetheless, these oxalate-induced deteriorations in MDCK cells and their mitochondria were successfully hampered by caffeine. Knockdown of Snai1 gene by small interfering RNA (siRNA) completely abolished the effects of oxalate on suppression of cellular metabolic activity, intracellular ATP and abundance of active mitochondria, indicating that these oxalate-induced renal cell deteriorations were mediated through the Snai1 EMT-related gene. These data, at least in part, unveil the anti-fibrotic mechanism of caffeine during oxalate-induced EMT in renal cells by preserving mitochondrial biogenesis and function.