Alcohol exposure suppresses ribosome biogenesis and causes nucleolar stress in cranial neural crest cells

In vivo protein half-life analysis identifies the SREBF1-SLC27a5 axis governs antioxidant response in preclinical alcoholic rat model

BACKGROUND

ALD causes liver dysfunction with inflammation, steatosis, and fibrosis. While abstinence reverses damage, its effect on protein half-lives remains unclear. This study examines site-specific protein half-life changes, transcription regulation, and recovery mechanisms.

METHOD

Long-Evans rats were fed ethanol or control diets for 24 weeks to induce ALD, with some switched to a control diet for 7 days to model abstinence. Protein half-lives, pathways, and transcription factors were analyzed using deuterium labeling and were validated in ALD rats, abstinent rats, and human biopsies.

RESULTS

Liver histology showed increased steatosis (28 %) and fibrosis (15 %) in ALD rats, both reduced with abstinence (<20 %, <12 %, p < 0.05). Liver function and lipid profiles improved, while alcohol-metabolizing and inflammatory markers were decreased (>1.5-fold, p < 0.05) following abstinence. ALD induced change in protein half-life specific to liver (82↑, 54↓), intestine (26↑, 30↓), and plasma (11↑, 17↓). Abstinence modulated; liver (64↑, 62↓), intestine (13↑, 25↓), and plasma (10↑, 12↓; FC > 1.5, p < 0.05). Specifically, abstinence reversed protein half-lives linked to lipid metabolism in the liver, neurodegeneration in the intestine, and NET formation in plasma (p < 0.05). Abstinence restored protein half-lives of Cyp2d10, Ugt1a1, Slc27a5, and Hsp90b1, regulated by Srebf1. Proteomic validation confirmed increased Acat1, Ugt1a1, and Slc27a5 in ALD, linked to steatosis and inflammation, which decreased with abstinence. Severe alcoholic hepatitis patients also documented that abstinence work on modulating protein turnover under the Srebf1-Slc27a5 axis and thereby ameliorate liver damage.

CONCLUSION

Alcohol abstinence modulates protein half-lives through Srebf1-Slc27a5 axis, reducing inflammation, steatosis, and oxidative stress, potentially aiding in alcohol-induced liver damage treatment.

Alcohol Exposure May Increase Prenatal Choline Needs Through Redirection of Choline into Lipid Synthesis Rather than Methyl Donation

Background: Prenatal alcohol exposure (PAE) can reduce fetal growth and cause neurodevelopmental disability. Prenatal choline supplements attenuate PAE-induced behavioral and growth deficits; however, the underlying mechanisms are unknown. Alcohol alters nutrient metabolism and potentially increases nutrient needs. Here, we investigate how alcohol affects choline metabolism in the maternal-fetal dyad and the role of supplemental choline. Methods: Pregnant C57BL/6J mice were assigned to one of four groups: alcohol-exposed (3 g/kg alcohol/day) or control +/- 100 mg/kg choline daily from embryonic day (E)8.5-17.5. We performed an exploratory hypothesis-generating analysis of targeted metabolomics on choline-related metabolites in the maternal liver, plasma, placenta, and fetal brain at E17.5 and Spearman correlation analyses to determine their association with gestational and fetal growth outcomes. Results: Although choline levels were largely unaffected by alcohol or choline, alcohol increased many lipid products in the CDP-choline pathway; this was not normalized by choline. Alcohol increased placental CDP-ethanolamine and reduced the maternal hepatic SAM/SAH ratio as well as dimethylglycine and the serine/glycine ratio across the dyad, suggesting a functional insufficiency in methyl donor pools. These outcomes were rescued by supplemental choline. Correlation analyses among choline metabolites and fetal growth outcomes suggest that maternal plasma methionine, serine, and the serine/glycine ratio may be predictive of maternal-fetal choline status. Conclusions: The increased hepatic lipid synthesis that characterizes chronic alcohol exposure may draw choline into phospholipid biosynthesis at the expense of its use as a methyl donor. We propose that PAE increases choline needs, and that its supplementation is necessary to fulfill these competing demands for lipid and methyl use.

Alcohol induces p53-mediated apoptosis in neural crest by stimulating an AMPK-mediated suppression of TORC1, S6K, and ribosomal biogenesis

Prenatal alcohol exposure is a leading cause of permanent neurodevelopmental disability and can feature distinctive craniofacial deficits that partly originate from the apoptotic deletion of craniofacial progenitors, a stem cell lineage called the neural crest (NC). We recently demonstrated that alcohol causes nucleolar stress in NC through its suppression of ribosome biogenesis (RBG) and this suppression is causative in their p53/MDM2-mediated apoptosis. Here, we show that this nucleolar stress originates from alcohol's activation of AMPK, which suppresses TORC1 and the p70/S6K-mediated stimulation of RBG. Alcohol-exposed cells of the pluripotent, primary cranial NC line O9-1 were evaluated with respect to their S6K, TORC1, and AMPK activity. The functional impact of these signals with respect to RBG, p53, and apoptosis were assessed using gain-of-function constructs and small molecule mediators. Alcohol rapidly (<2 hr) increased pAMPK, pTSC2, and pRaptor, and reduced both total and pS6K in NC cells. These changes persisted for at least 12 hr to 18 hr following alcohol exposure. Attenuation of these signals via gain- or loss-of-function approaches that targeted AMPK, S6K, or TORC1 prevented alcohol's suppression of rRNA synthesis and the induction of p53-stimulated apoptosis. We conclude that alcohol induces ribosome dysbiogenesis and activates their p53/MDM2-mediated apoptosis via its activation of pAMPK, which in turn activates TSC2 and Raptor to suppress the TORC1/S6K-mediated promotion of ribosome biogenesis. This represents a novel mechanism underlying alcohol's neurotoxicity and is consistent with findings that TORC1/S6K networks are critical for cranial NC survival.

Alcohol induces p53-mediated apoptosis in neural crest by stimulating an AMPK-mediated suppression of TORC1, S6K, and ribosomal biogenesis

Prenatal alcohol exposure is a leading cause of permanent neurodevelopmental disability and can feature distinctive craniofacial deficits that partly originate from the apoptotic deletion of craniofacial progenitors, a stem cell lineage called the neural crest (NC). We recently demonstrated that alcohol causes nucleolar stress in NC through its suppression of ribosome biogenesis (RBG) and this suppression is causative in their p53/MDM2-mediated apoptosis. Here, we show that this nucleolar stress originates from alcohol's activation of AMPK, which suppresses TORC1 and the p70/S6K-mediated stimulation of RBG. Alcohol-exposed cells of the pluripotent, primary cranial NC line O9-1 were evaluated with respect to their S6K, TORC1, and AMPK activity. The functional impact of these signals with respect to RBG, p53, and apoptosis were assessed using gain-of-function constructs and small molecule mediators. Alcohol rapidly (<2hr) increased pAMPK, pTSC2, and pRaptor, and reduced both total and pS6K in NC cells. These changes persisted for at least 12hr to 18hr following alcohol exposure. Attenuation of these signals via gain- or loss-of-function approaches that targeted AMPK, S6K, or TORC1 prevented alcohol's suppression of rRNA synthesis and the induction of p53-stimulated apoptosis. We conclude that alcohol induces ribosome dysbiogenesis and activates their p53/MDM2-mediated apoptosis via its activation of pAMPK, which in turn activates TSC2 and Raptor to suppress the TORC1/S6K-mediated promotion of ribosome biogenesis. This represents a novel mechanism underlying alcohol's neurotoxicity and is consistent with findings that TORC1/S6K networks are critical for cranial NC survival.