Manon Buist-Homan

Pirfenidone (PFD) shows therapeutic potential for liver fibrosis, but its molecular mechanisms are not fully elucidated. Activation of hepatic stellate cells (HSCs) is central to liver fibrosis, making their targeted elimination a prime therapeutic strategy. Since amino acid metabolism governs both HSC activation and ferroptosis, we investigated whether PFD acts by reprogramming these metabolic pathways. Analysis of primary rat HSCs revealed that their in vitro activation induced fibrotic markers, including collagen type I and α-smooth muscle actin, as well as key metabolic enzymes. Specifically, we observed upregulation of glutaminase 1, initiating glutaminolysis to produce glutamate; serine hydroxymethyltransferase 2, which generates glycine from serine; and pyrroline-5-carboxylate synthase, the rate-limiting enzyme for de novo proline synthesis. Treatment with PFD suppressed HSC activation by reducing protein levels of these enzymes, an effect consistent with PFD’s inhibition of activating transcription factor 4 nuclear accumulation. This created a dual metabolic vulnerability, limiting amino acid precursors for both collagen synthesis and the master antioxidant glutathione (GSH). Consequently, while PFD alone was not cytotoxic, GSH depletion sensitized activated HSCs to ferroptosis. Co-treatment with the ferroptosis inducer erastin triggered a synergistic increase in reactive oxygen species, labile iron, and lipid peroxidation, culminating in cell death. This synergistic lethality was abrogated by the ferroptosis inhibitor ferrostatin-1 and the antioxidant N-acetylcysteine, confirming ferroptosis as the specific cell death modality. Our study uncovers a dual anti-fibrotic mechanism for PFD: PFD inhibits collagen synthesis by limiting key amino acid precursors and depletes GSH. This compromises antioxidant defenses, creating vulnerability to ferroptosis. Our findings establish a rationale for using PFD in combination therapies designed to eliminate activated HSCs.

Metabolic dysfunction associated with steatotic liver disease (MASLD) is the result of disturbed lipid metabolism. In MASLD, the accumulation of free fatty acids (FFAs) in hepatocytes causes lipotoxicity mediated by oxidative stress. Coffee compounds are known for their beneficial effects in MASLD; however, the mechanisms still need to be further explored. The aim of this study was to elucidate the protective mechanisms of coffee compounds against palmitate-induced lipotoxicity in primary hepatocytes. Methods: Primary hepatocytes were isolated from male Wistar rats and treated with palmitate (1 mmol/L) in combination with caffeine (CF: 1 mmol/L) or chlorogenic acid (CGA: 5 µmol/L). Mitochondrial ROS production, palmitate-induced necrosis, antioxidant response, ER stress markers and lipid droplet (LD) formation were assessed. Monoacylglycerols 2-SG (2-Stearolylglycerol), 2-OG (2-Oleoylglycerol) and SCD-1 (Stearoyl-CoA Desaturase 1) inhibitors were used to modulate LD formation. LD formation in steatotic Zucker rat hepatocytes was also investigated. Results: CF and CGA prevented palmitate-induced cell death and reduced ROS production. CF and CGA induced the antioxidant response, especially HO-1 expression, but had no significant effect on ER stress markers. CF and CGA increased LD formation in palmitate-treated cells. This effect was significantly reduced by 2-SG and SCD-1 inhibitors but enhanced by 2-OG. Lipid droplets were associated with lower palmitate toxicity and reduced ROS production. Conclusions: CF and CGA protect hepatocytes from lipotoxicity via modulation of the antioxidant response and enhance lipid droplet formation via an SCD-1-dependent mechanism. Oxidative stress-related toxicity in hepatocytes can be prevented by enhancing LD formation.

Aim: Extracellular vesicles (EVs) have gained significant attention for their diagnostic and therapeutic potential in various diseases, including liver disorders. This study focuses on optimizing the isolation and characterization of small EVs from plasma and serum samples in patients with liver diseases, aiming to advance our understanding and potential clinical applications of EVs. Methods: Blood samples were collected from patients with end-stage liver disease (ESLD) enlisted in the TransplantLines Cohort and Biobank Study, and healthy donors. We employed differential ultracentrifugation (DUC) to evaluate three distinct protocols: a 3-step DUC, a washing step omitted [samples without washing (WW)], and a contaminant-depleted plasma (CDP) protocol. RNA isolation methodologies were compared, involving the use of TRI-reagent or the commercial AllPrep DNA/RNA kit. Further insights into EV composition were obtained through proteomic analyses, comparing samples subjected to traditional cell lysis (L) with those processed without lysis (NL). Results: We successfully isolated EVs from both plasma and serum samples as confirmed by the presence of specific EV markers, including CD9, CD63, CD81, and tumor susceptibility gene 101 (TSG-101). While some contaminants remained, such as albumin and lipoproteins, the protocol selected to continue EVs analysis was the 3-step protocol. Transmission electron microscopy (TEM) and nanotracking analysis (NTA) further confirmed EVs presence. RNA extraction was achieved using TRI-reagent, but not with the commercial kit highlighting the importance of selecting an appropriate method for RNA isolation. Finally, proteomics analysis showed that lysed samples were significantly more enriched in proteins compared to non-lysed samples, although protein variability was still present in both groups. Conclusions: Optimizing EV isolation techniques is essential for harnessing their potential in liver disease diagnosis and therapy. Further refinement of purification methods, a deep characterization of our cohort and understanding the variability and cargo within EVs will be crucial for future biomarker discovery and therapeutic applications in liver-related diseases.

Coumarin derivates have been proposed as a potential treatment for metabolic-dysfunction-associated fatty liver disease (MAFLD). However, the mechanisms underlying their beneficial effects remain unclear. In the present study, we explored the potential of the coumarin derivate esculetin in MAFLD, focusing on hepatocyte lipotoxicity and lipid accumulation. Primary cultures of rat hepatocytes were exposed to palmitic acid (PA) and palmitic acid plus oleic acid (OA/PA) as models of lipotoxicity and lipid accumulation, respectively. Esculetin significantly reduced oxidative stress in PA-treated hepatocytes, as shown by decreased total reactive oxygen species (ROS) and mitochondrial superoxide production and elevated expression of antioxidant genes, including Nrf2 and Gpx1. In addition, esculetin protects against PA-induced necrosis. Esculetin also improved lipid metabolism in primary hepatocytes exposed to nonlipotoxic OA/PA by decreasing the expression of the lipogenesis-related gene Srebp1c and increasing the expression of the fatty acid β-oxidation-related gene Ppar-α. Moreover, esculetin attenuated lipid accumulation in OA/PA-treated hepatocytes. The protective effects of esculetin against lipotoxicity and lipid accumulation were shown to be dependent on the inhibition of JNK and the activation of AMPK, respectively. We conclude that esculetin is a promising compound to target lipotoxicity and lipid accumulation in the treatment of MAFLD.

Liver fibrosis is a chronic disease associated with oxidative stress that has a great impact on the population mortality. Due to their antioxidant capacity, we evaluated the protective effect of Opuntia robusta fruit (Or) on liver fibrosis. A nutraceutical characterization of Or was performed and a model of fibrosis was induced with thioacetamide (TAA) in Wistar rats. Aminotransferases, reduced glutathione (GSH) and histopathology were evaluated. Or contained 436.5 ± 57 mg of Betacyanins equivalents/L., 793 mg of catechin equivalents (CAE)/100 g for flavonoids, 1118 mg of gallic acid equivalents (GAE)/100 g for total phenols, 141.14 mg/100 g for vitamin C and 429.9 μg/100 g for vitamin E. The antioxidant capacity of Or was: 2.27 mmol of Trolox^® equivalents (TE)/L (DPPH), 62.2 ± 5.0 μmol TE/g (ABTS^•+), 80.2 ± 11.7 μmol TE/g (FRAP), 247.9 ± 15.6 µmol TE/g (AAPH) and 15.0% of H₂O₂ elimination. An increase (p < 0.05) of aminotransferases and a decrease (p < 0.05) of hepatic GSH was observed in the TAA group compared to the control and the concomitant groups. Histopathology showed changes in the normal architecture of the liver treated with TAA compared to the concomitant treatments. Or contains bioactive components with antioxidant capacity, which can reduce fibrotic liver damage.

Barrett’s esophagus (BE) is the precursor of esophageal adenocarcinoma (EAC). Dysplastic BE (DBE) has a higher progression risk to EAC compared to non-dysplastic BE (NDBE). However, the miss rates for the endoscopic detection of DBE remain high. Fluorescence molecular endoscopy (FME) can detect DBE and mucosal EAC by highlighting the tumor-specific expression of proteins. This study aimed to identify target proteins suitable for FME. Publicly available RNA expression profiles of EAC and NDBE were corrected by functional genomic mRNA (FGmRNA) profiling. Following a class comparison between FGmRNA profiles of EAC and NDBE, predicted, significantly upregulated genes in EAC were prioritized by a literature search. Protein expression of prioritized genes was validated by immunohistochemistry (IHC) on DBE and NDBE tissues. Near-infrared fluorescent tracers targeting the proteins were developed and evaluated ex vivo on fresh human specimens. In total, 1976 overexpressed genes were identified in EAC (n = 64) compared to NDBE (n = 66) at RNA level. Prioritization and IHC validation revealed SPARC, SULF1, PKCι, and DDR1 (all p < 0.0001) as the most attractive imaging protein targets for DBE detection. Newly developed tracers SULF1-800CW and SPARC-800CW both showed higher fluorescence intensity in DBE tissue compared to paired non-dysplastic tissue. This study identified SPARC, SULF1, PKCι, and DDR1 as promising targets for FME to differentiate DBE from NDBE tissue, for which SULF1-800CW and SPARC-800CW were successfully ex vivo evaluated. Clinical studies should further validate these findings.