Sphingosine Kinase 1 Mediates Sexual Dimorphism in Fibrosis in a Mouse Model of NASH

Development of hepatic steatosis in normal and veinous livers of overfed female mule ducks

Following the various recent avian influenza crises, the shortage of male mule ducklings has led to the use of females, although these are not normally used mainly because of defects in the presentation of the final product. The aim of this study was to examine the evolution of hepatic steatosis induced by overfeeding in female mule ducks with or without a visible network of veins on the surface of lean or fatty livers. The overall evolution of hepatic steatosis (weight gain, gross biochemical composition) was strikingly similar in both types of liver. Histological observations confirm that in both types of livers, there is a steady increase in the accumulation of lipid droplets in hepatocytes throughout the period of overfeeding. At the same time, other parameters (fibrogenesis, measured by the accumulation of hydroxyproline; oxidative status, measured by the activities of the enzymes superoxide dismutase and catalase; contents of reduced and oxidised glutathione and level of hypoxia, measured with Hypoxia 1 and 2 Induced Factors) are also altered similarly in all samples. Nor did the overall activities of genes belonging to different metabolic pathways reveal any major differences when normal and veinous livers were compared. In conclusion, hepatic steatosis induced by overfeeding developed under very similar conditions in the normal and veinous livers of female mule ducks. However, these visible anatomical differences degrade the visual quality of the final product and make veinous livers less attractive to processors and consumers.

UV-aging process of titanium dioxide nanoparticles aggravates enterohepatic toxicity of bis(2-ethylhexyl)-2,3,4,5-tetrabromophthalate to zebrafish

The physicochemical characteristics of titanium dioxide nanoparticles (n-TiO2) may change during the aging process once discharged into aquatic environment. However, how the aging process affects their interactions with co-existing pollutants, as well as the joint toxicity has not been explored. This study investigated how UV-aging impacts n-TiO2 in aquatic environments and their interactions with bis(2-ethylhexyl)-2,3,4,5-tetrabromophthalate (TBPH), focusing on their joint toxicity in adult female zebrafish. UV-aging process significantly increased the specific area and hydrophobicity of n-TiO2, promoting the adsorption of TBPH. In vivo experiments revealed that aged n-TiO2 enhanced the bioaccumulation of TBPH in the liver and intestine, worsening hepatic steatosis and intestinal barrier damage. A combined analysis of hepatic lipidomic profiling and intestinal microbiota 16S rRNA sequencing revealed that co-exposure of aged n-TiO2 and TBPH altered gut microbial composition and abundances, facilitating the circulation of lipopolysaccharides (LPS) through the gut-liver axis. Subsequentially, the elevated LPS level in the liver activated the sphingolipid metabolic pathway, resulting in severer lipid metabolism disorders and hepatotoxicity. This study found that UV-aging increases the hydrophobicity and surface area of n-TiO2, enhancing their interaction with the TBPH, which leads to greater bioaccumulation and hepatoxicity through mechanisms involving changes in gut microbiomes and sphingolipid metabolism.

Sex-specific transcriptomic effects of low-dose inorganic arsenic exposure on bone marrow-derived macrophages

Both tissue-resident macrophages and monocytes recruited from the bone marrow that transform into tissue-resident cells play critical roles in mediating homeostasis as well as in the pathology of inflammatory diseases. Inorganic arsenic (iAs) is the most common drinking water contaminant worldwide and represents a major public health concern. There are numerous diseases caused by iAs exposure in which macrophages are involved, including cardiovascular disease, cancer, and increased risk of (respiratory) infectious diseases. Notably, prenatal iAs exposure is also associated with negative birth outcomes and developmental immunotoxicity (DIT) contributing to long-term adverse outcomes of these immune-related diseases. Therefore, understanding the effects of iAs exposure on macrophages, particularly during immune development or tissue injury and inflammation, can help us better grasp the full range of arsenic immunotoxicity and better design therapeutic targets for iAs-induced diseases particularly in exposed populations. In contrast to prior published studies which often only focused on the effect of iAs on mature macrophages after development, in this study, we analyzed the transcriptome of M0-, M1- and M2-polarized male and female murine bone marrow-derived macrophages (BMDMs) which were exposed to iAs during the differentiation phase, as a model to study iAs (developmental) immunotoxicity. We identified differentially expressed genes by iAs in a sex- and stimulation-dependent manner and used bioinformatics tools to predict protein-protein interactions, transcriptional regulatory networks, and associated biological processes. Overall, our data suggest that M1-stimulated, especially female-derived, BMDMs are most susceptible to iAs exposure during differentiation. Most notably, we observed significant downregulation of major proinflammatory transcription factors, like IRF8, and its downstream targets, as well as genes encoding proteins involved in pattern recognition and antigen presentation, such as TLR7, TLR8, and H2-D1, potentially providing causal insight regarding the role of (early-life) arsenic exposure in perturbing immune responses to infectious diseases. We also observed significant downregulation of genes involved in processes crucial to coordinating a proinflammatory response including leukocyte migration, differentiation, and cytokine and chemokine production and response. Finally, we discovered that 24 X-linked genes were dysregulated in iAs-exposed female stimulation groups compared to only 3 across the iAs-exposed male stimulation groups. These findings elucidate the potential mechanisms underlying the sex-differential iAs-associated immune-related disease risk.

Sphingosine kinase 2 and p62 regulation are determinants of sexual dimorphism in hepatocellular carcinoma

OBJECTIVE

Hepatocellular carcinoma (HCC) is the third leading cause of cancer mortality, and its incidence is increasing due to endemic obesity. HCC is sexually dimorphic in both humans and rodents with higher incidence in males, although the mechanisms contributing to these correlations remain unclear. Here, we examined the role of sphingosine kinase 2 (SphK2), the enzyme that regulates the balance of bioactive sphingolipid metabolites, sphingosine-1-phosphate (S1P) and ceramide, in gender specific MASH-driven HCC.

METHODS

Male and female mice were fed a high fat diet with sugar water, a clinically relevant model that recapitulates MASH-driven HCC in humans followed by physiological, biochemical cellular and molecular analyses. In addition, correlations with increased risk of HCC recurrence were determined in patients.

RESULTS

Here, we report that deletion of SphK2 protects both male and female mice from Western diet-induced weight gain and metabolic dysfunction without affecting hepatic lipid accumulation or fibrosis. However, SphK2 deficiency decreases chronic diet-induced hepatocyte proliferation in males but increases it in females. Remarkably, SphK2 deficiency reverses the sexual dimorphism of HCC, as SphK2-/- male mice are protected whereas the females develop liver cancer. Only in male mice, chronic western diet induced accumulation of the autophagy receptor p62 and its downstream mediators, the antioxidant response target NQO1, and the oncogene c-Myc. SphK2 deletion repressed these known drivers of HCC development. Moreover, high p62 expression correlates with poor survival in male HCC patients but not in females. In hepatocytes, lipotoxicity-induced p62 accumulation is regulated by sex hormones and prevented by SphK2 deletion. Importantly, high SphK2 expression in male but not female HCC patients is associated with a more aggressive HCC differentiation status and increased risk of cancer recurrence.

CONCLUSIONS

This work identifies SphK2 as a potential regulator of HCC sexual dimorphism and suggests SphK2 inhibitors now in clinical trials could have opposing, gender-specific effects in patients.

Development of hepatic steatosis in male and female mule ducks after respective force-feeding programs

Male and female mule ducks were subjected to a force-feeding diet to induce liver steatosis as it is generally done only with male ducks for the production of foie gras. The different biochemical measurements indicated that the course of hepatic steatosis development was present in both sexes and associated with a huge increase in liver weight mainly due to the synthesis and accumulation of lipids in hepatocytes. In livers of male and female ducks, this lipid accumulation was associated with oxidative stress and hypoxia. However, certain specific modifications (kinetics of lipid droplet development and hepatic inflammation) indicate that female ducks may tolerate force-feeding less well, at least at the hepatic level. This is in contradiction with what is generally reported concerning hepatic steatosis induced by dietary disturbances in mammals but could be explained by the very specific conditions imposed by force-feeding. Despite this, force-feeding female ducks seems entirely feasible, provided that the final quality of the product is as good as that of the male ducks, which will remain to be demonstrated in future studies.

Noninvasive scores are poorly predictive of histological fibrosis in paediatric fatty liver disease

OBJECTIVES

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease in children. Roughly a quarter of paediatric patients with NAFLD develop nonalcoholic steatohepatitis and fibrosis. Here, we evaluated the diagnostic accuracy of previously published noninvasive fibrosis scores to predict liver fibrosis in a large European cohort of paediatric patients with NAFLD.

METHODS

The 457 patients with biopsy-proven NAFLD from 10 specialized centers were included. We assessed diagnostic accuracy for the prediction of any (F ≥ 1), moderate (F ≥ 2) or advanced (F ≥ 3) fibrosis for the AST/platelet ratio (APRI), Fibrosis 4 score (FIB-4), paediatric NAFLD fibrosis score (PNFS) and paediatric NAFLD fibrosis index (PNFI).

RESULTS

Patients covered the full spectrum of fibrosis (F0: n = 103; F1: n = 230; F2: n = 78; F3: n = 44; F4: n = 2). None of the scores were able to accurately distinguish the presence of any fibrosis from no fibrosis. For the detection of moderate fibrosis, area under the receiver operating characteristic curve (AUROC) were: APRI: 0.697, FIB-4: 0.663, PNFI: 0.515, PNFS: 0.665, while for detection of advanced fibrosis AUROCs were: APRI: 0.759, FIB-4: 0.611, PNFI: 0.521, PNFS: 0.712. Fibrosis scores showed no diagnostic benefit over using ALT ≤ 50/ > 50 IU/L as a cut-off.

CONCLUSIONS

Established fibrosis scores lack diagnostic accuracy to replace liver biopsy for staging of fibrosis, giving similar results as compared to using ALT alone. New diagnostic tools are needed for Noninvasive risk-stratification in paediatric NAFLD.

Overexpression of ORMDL3 confers sexual dimorphism in diet-induced non-alcoholic steatohepatitis

OBJECTIVE

The bioactive sphingolipid metabolites ceramide and sphingosine-1-phosphate (S1P) accumulate with overnutrition and have been implicated in non-alcoholic steatohepatitis (NASH) development. ORMDL3, a negative regulator of the rate-limiting step in ceramide biosynthesis, has been identified as an obesity-related gene. Therefore, we assessed the role of ORMDL3 in diet-induced obesity and development of NASH.

METHODS

Globally overexpressing Ormdl3-Flag transgenic mice (ORMDL3TG) were fed a western high-fat, carbohydrate and cholesterol enriched diet, with high fructose-glucose drinking water. Physiological, biochemical and sphingolipidomic analyses were employed to measure the effect of ORMDL3 overexpression on NASH development.

RESULTS

ORMDL3TG male but not female mice fed a western high-fat diet and sugar water had exacerbated adipocyte hypertrophy together with increased severity of white adipose inflammation and fibrosis. Hepatic steatosis, dyslipidemia, impaired glucose homeostasis, hyperinsulinemia, and insulin resistance were significantly more severe only in obese ORMDL3TG male mice that accompanied dramatic liver fibrosis, inflammation, and formation of hepatic crown-like structures, which are unique features of human and murine NASH. Obesogenic diet induces ORMDL expression in male mice but reduces it in females. Mechanistically, overexpression of Ormdl3 lowered the levels of S1P and ceramides only in obese female mice and antithetically increased them in tissues of obese males. ORMDL3TG male mice exhibited a much greater induction of the UPR, propagating ER stress that contributed to their early development of NASH.

CONCLUSIONS

This study uncovered a previously unrecognized role for ORMDL3 in sexual dimorphism important for the development and progression of NASH.

Feline mammary carcinoma-derived extracellular vesicle promotes liver metastasis via sphingosine kinase-1-mediated premetastatic niche formation

BACKGROUND

Feline mammary carcinoma (FMC) is one of the most prevalent malignancies of female cats. FMC is highly metastatic and thus leads to poor disease outcomes. Among all metastases, liver metastasis occurs in about 25% of FMC patients. However, the mechanism underlying hepatic metastasis of FMC remains largely uncharacterized.

RESULTS

Herein, we demonstrate that FMC-derived extracellular vesicles (FMC-EVs) promotes the liver metastasis of FMC by activating hepatic stellate cells (HSCs) to prime a hepatic premetastatic niche (PMN). Moreover, we provide evidence that sphingosine kinase 1 (SK1) delivered by FMC-EV was pivotal for the activation of HSC and the formation of hepatic PMN. Depletion of SK1 impaired cargo sorting in FMC-EV and the EV-potentiated HSC activation, and abolished hepatic colonization of FMC cells.

CONCLUSIONS

Taken together, our findings uncover a previously uncharacterized mechanism underlying liver-metastasis of FMC and provide new insights into prognosis and treatment of this feline malignancy.

ORMDL in metabolic health and disease

Obesity is a key risk factor for the development of metabolic disease. Bioactive sphingolipid metabolites are among the lipids increased in obesity. Obesogenic saturated fatty acids are substrates for serine palmitoyltransferase (SPT) the rate-limiting step in de novo sphingolipid biosynthesis. The mammalian orosomucoid-like protein isoforms ORMDL1-3 negatively regulate SPT activity. Here we summarize evidence that dysregulation of sphingolipid metabolism and SPT activity correlates with pathogenesis of obesity. This review also discusses the current understanding of the function of SPT and ORMDL in obesity and metabolic disease. Gaps and limitations in current knowledge are highlighted together with the need to further understand how ORMDL3, which has been identified as an obesity-related gene, contributes to the pathogenesis of obesity and development of metabolic disease related to its physiological functions. Finally, we point out the needs to move this young field of research forward.

A Pathogenic Role of Non-Parenchymal Liver Cells in Alcohol-Associated Liver Disease of Infectious and Non-Infectious Origin

Now, much is known regarding the impact of chronic and heavy alcohol consumption on the disruption of physiological liver functions and the induction of structural distortions in the hepatic tissues in alcohol-associated liver disease (ALD). This review deliberates the effects of alcohol on the activity and properties of liver non-parenchymal cells (NPCs), which are either residential or infiltrated into the liver from the general circulation. NPCs play a pivotal role in the regulation of organ inflammation and fibrosis, both in the context of hepatotropic infections and in non-infectious settings. Here, we overview how NPC functions in ALD are regulated by second hits, such as gender and the exposure to bacterial or viral infections. As an example of the virus-mediated trigger of liver injury, we focused on HIV infections potentiated by alcohol exposure, since this combination was only limitedly studied in relation to the role of hepatic stellate cells (HSCs) in the development of liver fibrosis. The review specifically focusses on liver macrophages, HSC, and T-lymphocytes and their regulation of ALD pathogenesis and outcomes. It also illustrates the activation of NPCs by the engulfment of apoptotic bodies, a frequent event observed when hepatocytes are exposed to ethanol metabolites and infections. As an example of such a double-hit-induced apoptotic hepatocyte death, we deliberate on the hepatotoxic accumulation of HIV proteins, which in combination with ethanol metabolites, causes intensive hepatic cell death and pro-fibrotic activation of HSCs engulfing these HIV- and malondialdehyde-expressing apoptotic hepatocytes.