Al-Siyabi, S. | Search bioRxiv

bioRxiv2026

Acidosis-triggered fatty acid overload induces endothelial cell dysfunction.

Vascular ischemia is characterized not only by hypoxia but also by acidosis, which affects endothelial cells (ECs) due to increased H+ production from glycolysis and a deficit in H+ washout. We recently documented that an acidic environment facilitates the flip-flop transport of the non-ionized form of fatty acids (FAs) across the plasma membrane of cancer cells. In this study, we investigated how acidosis influences the capacity of highly glycolytic ECs to manage FAs and participates to endothelial dysfunction. We first tracked lipid droplet (LD) formation using Oil Red O staining and holotomographic microscopy. Purified monounsaturated oleate but also a mixture of FAs that reflect in vivo serum composition, resulted in dose- and time-dependent LD accumulation through FA transporter-independent mechanisms. Acid-exposed ECs exhibited enhanced mitochondrial respiration fueled by FAs, and endoplasmic reticulum (ER) stress, as indicated by the expression of ATF4 and CHOP. This phenotype was further associated with elevated reactive oxygen species production, which correlated with reduced nitric oxide (NO) availability. FA removal from EC culture media promoted lipolysis from LDs, supported by ATGL lipase induction which however slowed under acidic conditions. While ER stress persisted upon FA washout, NO availability was restored to levels comparable to those in FA-unexposed ECs. This observation coincided with dynamic mobilization of antioxidant defenses in acid-exposed ECs, as evidenced by low levels of reduced glutathione and enhanced cystine uptake, alongside a decrease in carnitine and FA-fueled mitochondrial respiration. Collectively, these data underscore the vulnerability of ECs to passive FA capture promoted by local acidosis, thereby contributing to a silent source of endothelial dysfunction in the postprandial state or during chronic exposure to elevated lipid levels.

cell biology↗

bioRxiv2025

Hepatic ADMA/PRMT1 axis regulation is associated with NO-dependent endothelial dysfunction in MASH

Metabolic dysfunction-associated steatohepatitis (MASH) is a severe form of fatty liver disease and a recognized cardiovascular risk factor, yet the mechanisms linking hepatic pathology to vascular dysfunction remain poorly understood. We aimed to investigate whether MASH impairs endothelial function via nitric oxide (NO)-dependent mechanisms and to identify potential liver-derived mediators involved in this process. Endothelial function was assessed in two murine MASH models, Foz mice fed a high-fat diet and C57BL/6JRj mice fed a western diet with fructose, by using wire myography, while blood pressure was monitored via telemetry. NO pathway was further investigated through eNOS expression and activation and Hb-NO measurements. ADMA metabolism was analyzed in both liver tissue and plasma by LC-MS and gene expressions. Additionally, bovine aortic endothelial cells (BAECs) were treated with mouse plasma to measure the circulating factors effects on eNOS activation and the role of oxidative stress. Both models exhibited impaired NO-dependent vasorelaxation without evidence of atherosclerosis. In Foz mice, this impairment was associated with reduced eNOS expression and activation. Surprisingly, plasma Hb-NO levels did not reflect vascular NO deficiency, likely due to elevated hepatic iNOS expression. In both models, hepatic and plasma ADMA levels were increased, concomitant with hepatic upregulation of Prmt1. BAECs exposed to plasma from MASH mice showed reduced eNOS activation independent of oxidative stress. Our findings reveal that MASH is consistently associated with NO-dependent endothelial dysfunction, with ADMA emerging as a key liver-derived mediator. The PRMT1/ADMA/NO axis may represent a mechanistic link between liver pathology and vascular impairment, positioning ADMA as a potential biomarker and therapeutic target for cardiovascular risk associated with MASH. HighlightsO_LIMASH is associated with impaired NO-dependent endothelial function in two distinct MASH models. C_LIO_LICirculating factors disrupt the NOS/NO pathway independently of oxidative stress C_LIO_LIReduced plasma Hb-NO levels do not accurately reflect NO-dependent endothelial dysfunction in a context of MASH. C_LIO_LIElevated plasma and hepatic ADMA levels associated with hepatic prmt1 upregulation are consistently observed in both MASH models. C_LIO_LIThe PRMT1/ADMA/NO axis emerges as a key liver-mediated mechanism driving endothelial dysfunction in MASH C_LI

physiology↗