Search Results (5)

Background/Objectives: Visceral adipose tissue (VAT) may play a direct role in the development of metabolic dysfunction-associated steatotic liver disease (MASLD) and its progression to metabolic dysfunction-associated steatohepatitis (MASH). In this study, we employed untargeted proteomics analyses on paired biopsies from VAT and liver tissues of patients with obesity, MASLD, and MASH. Our objective was to investigate tissue-specific protein expression patterns in search of a potential proteomic signature associated with MASH in both VAT and liver tissue. Methods: VAT and liver tissue were collected from 70 subjects with severe obesity (SWOs) and nine control study subjects without obesity (CON). SWOs were stratified on the basis of liver histology into LS− (no liver steatosis), LS+ (liver steatosis), and MASH. Peptides were extracted from frozen tissue and were analyzed by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). Raw files were analyzed with Spectronaut, proteins were searched against the human FASTA Uniprot database, and the significantly expressed proteins in the two tissues were analyzed. The p-values were false discovery rate (FDR) corrected. Results: A total of 59 VAT and 42 liver proteins were significantly differentially expressed between the four groups: LS−, LS+, MASH, and CON. The majority were upregulated, and many were related to lipid metabolism. In VAT, only one protein, the mitochondrial sulfide:quinone oxidoreductase (SQOR), was significantly downregulated in the MASH group only. In liver tissue from patients with MASH, six proteins were significantly altered compared with the three other groups. Correlation analyses between the top 10 positive VAT and liver proteins were dominated by inflammatory and detoxification proteins. Conclusions: The presence of MASH was not reflected in the VAT proteome, and both the VAT and the liver proteome were generally affected more by the presence of obesity than by MASLD severity. Several immunomodulating proteins correlated significantly between VAT and liver tissue and could reflect common pathophysiological characteristics. Full article

Amyotrophic lateral sclerosis (ALS) is a fatal rare disease of progressive degeneration of motor neurons. The most common genetic mutation in ALS is the hexanucleotide repeat expansion (HRE) located in the first intron of the C9orf72 gene (C9-ALS). HRE can produce dipeptide repeat proteins (DPRs) such as poly glycine-alanine (GA) in a repeat-associated non-ATG (RAN) translation. GA-DPR has been shown to be toxic to motor neurons in various biological models. However, its effects on microglia involved in C9-ALS have not been reported. Here, we show that GA-DPR (GA₅₀) activates the NLR family pyrin domain containing 3 (NLRP3) inflammasome in a human HMC3 microglia model. MCC950 (specific inhibitor of the NLRP3) treatment can abrogate this activity. Next, using yeast two-hybrid screening, we identified sulfide quinone oxidoreductase (SQOR) as a GA₅₀ interacting protein. SQOR knockdown in HMC3 cells can significantly induce the activity of the NLRP3 inflammasome by upregulating the level of intracellular reactive oxygen species and the cytoplasmic escape of mitochondrial DNA. Furthermore, we obtained irisflorentin as an effective blocker of the interaction between SQOR and GA₅₀, thus inhibiting NLRP3 inflammasome activity in GA₅₀-expressing HMC3 cells. These results imply the association of GA-DPR, SQOR, and NLRP3 inflammasomes in microglia and establish a treatment strategy for C9-ALS with irisflorentin. Full article

The protective effects of hydrogen sulphide (H₂S) to limit oxidative injury and preserve mitochondrial function during sepsis, ischemia/reperfusion, and neurodegenerative diseases have prompted the development of soluble H₂S-releasing compounds such as GYY4137. Yet, the effects of GYY4137 on the mitochondrial function of endothelial cells remain unclear, while this cell type comprises the first target cell after parenteral administration. Here, we specifically assessed whether human endothelial cells possess a functional sulfide:quinone oxidoreductase (SQOR), to oxidise GYY4137-released H₂S within the mitochondria for electron donation to the electron transport chain. We demonstrate that H₂S administration increases oxygen consumption by human umbilical vein endothelial cells (HUVECs), which does not occur in the SQOR-deficient cell line SH-SY5Y. GYY4137 releases H₂S in HUVECs in a dose- and time-dependent fashion as quantified by oxygen consumption and confirmed by lead acetate assay, as well as AzMC fluorescence. Scavenging of intracellular H₂S using zinc confirmed intracellular and intramitochondrial sulfur, which resulted in mitotoxic zinc sulfide (ZnS) precipitates. Together, GYY4137 increases intramitochondrial H₂S and boosts oxygen consumption of endothelial cells, which is likely governed via the oxidation of H₂S by SQOR. This mechanism in endothelial cells may be instrumental in regulating H₂S levels in blood and organs but can also be exploited to quantify H₂S release by soluble donors such as GYY4137 in living systems. Full article

Hydrogen sulfide (H₂S) is a toxic gas that has important regulatory functions. In the colon, H₂S can be produced and detoxified endogenously. Both too little and too much H₂S exposure are associated with inflammatory bowel disease (IBD), a chronic intestinal disease mainly classified as Crohn’s disease (CD) and ulcerative colitis (UC). As the pathogenesis of IBD remains elusive, this study’s aim was to investigate potential differences in the expression of H₂S-metabolizing enzymes in normal aging and IBD. Intestinal mucosal biopsies of 25 adults and 22 children with IBD along with those of 26 healthy controls were stained immunohistochemically for cystathionine-γ-lyase (CSE), 3-mercapto-sulfurtransferase (3-MST), ethylmalonic encephalopathy 1 protein (ETHE1), sulfide:quinone oxidoreductase (SQOR) and thiosulfate sulfurtransferase (TST). Expression levels were calculated by multiplication of the staining intensity and percentage of positively stained cells. Healthy adults showed an overall trend towards lower expression of H₂S-metabolizing enzymes than healthy children. Adults with IBD also tended to have lower expression compared to controls. A similar trend was seen in the enzyme expression of children with IBD compared to controls. These results indicate an age-related decrease in the expression of H₂S-metabolizing enzymes and a dysfunctional H₂S metabolism in IBD, which was less pronounced in children. Full article

Hydrogen sulfide (H₂S) has been proposed to promote tumor growth. Elevated H₂S levels have been detected in human colorectal cancer (CRC) biopsies, resulting from the selective upregulation of cystathionine β-synthase (CBS). In contrast, the recently identified novel H₂S-generating enzyme, selenium-binding protein 1 (SELENBP1), is largely suppressed in tumors. Here, we provide the first comparative analysis of the four human H₂S-producing enzymes and the key H₂S-catabolizing enzyme, sulfide:quinone oxidoreductase (SQOR), in Caco-2 human colorectal adenocarcinoma cells. The gene expression pattern of proliferating Caco-2 cells parallels that of CRC, while confluent cells undergo spontaneous differentiation to a colonocyte-like phenotype. SELENBP1 and SQOR were strongly upregulated during spontaneous differentiation, whereas CBS was downregulated. Cystathionine γ-lyase and 3-mercaptopyruvate sulfurtransferase remained unaffected. Terminally differentiated cells showed an enhanced capacity to produce H₂S from methanethiol and homocysteine. Differentiation induced by exposure to butyrate also resulted in the upregulation of SELENBP1, accompanied by increased SELENBP1 promoter activity. In contrast to spontaneous differentiation, however, butyrate did not cause downregulation of CBS. In summary, SELENBP1 and CBS are reciprocally regulated during the spontaneous differentiation of Caco-2 cells, thus paralleling their opposing regulation in CRC. Butyrate exposure, while imitating some aspects of spontaneous differentiation, does not elicit the same expression patterns of genes encoding H₂S-modulating enzymes. Full article