Investigating RNA expression profiles altered by nicotinamide mononucleotide therapy in a chronic model of alcoholic liver disease.

BACKGROUND: Chronic alcohol consumption is a significant cause of liver disease worldwide. Several biochemical mechanisms have been linked to the initiation and progression of alcoholic liver disease (ALD) such as oxidative stress, inflammation, and metabolic dysregulation, including the disruption of NAD+/NADH. Indeed, an ethanol-mediated reduction in hepatic NAD+ levels is thought to be one factor underlying ethanol-induced steatosis, oxidative stress, steatohepatitis, insulin resistance, and inhibition of gluconeogenesis. Therefore, we applied a NAD+ boosting supplement to investigate alterations in the pathogenesis of early-stage ALD. METHODS: To examine the impact of NAD+ therapy on the early stages of ALD, we utilized nicotinamide mononucleotide (NMN) at 500 mg/kg intraperitoneal injection every other day, for the duration of a Lieber-DeCarli 6-week chronic ethanol model in mice. Numerous strategies were employed to characterize the effect of NMN therapy, including the integration of RNA-seq, immunoblotting, and metabolomics analysis. RESULTS: Our findings reveal that NMN therapy increased hepatic NAD+ levels, prevented an ethanol-induced increase in plasma ALT and AST, and changed the expression of 25% of the genes that were modulated by ethanol metabolism. These genes were associated with a number of pathways including the MAPK pathway. Interestingly, our analysis revealed that NMN treatment normalized Erk1/2 signaling and prevented an induction of Atf3 overexpression. CONCLUSIONS: These findings reveal previously unreported mechanisms by which NMN supplementation alters hepatic gene expression and protein pathways to impact ethanol hepatotoxicity in an early-stage murine model of ALD. Overall, our data suggest further research is needed to fully characterize treatment paradigms and biochemical implications of NAD+-based interventions.

Quantifying Competition among Mitochondrial Protein Acylation Events Induced by Ethanol Metabolism.

Mitochondrial dysfunction is one of many key factors in the etiology of alcoholic liver disease (ALD). Lysine acetylation is known to regulate numerous mitochondrial metabolic pathways, and recent reports demonstrate that alcohol-induced protein acylation negatively impacts these processes. To identify regulatory mechanisms attributed to alcohol-induced protein post-translational modifications, we employed a model of alcohol consumption within the context of wild type (WT), sirtuin 3 knockout (SIRT3 KO), and sirtuin 5 knockout (SIRT5 KO) mice to manipulate hepatic mitochondrial protein acylation. Mitochondrial fractions were examined by label-free quantitative HPLC-MS/MS to reveal competition between lysine acetylation and succinylation. A class of proteins defined as "differential acyl switching proteins" demonstrate select sensitivity to alcohol-induced protein acylation. A number of these proteins reveal saturated lysine-site occupancy, suggesting a significant level of differential stoichiometry in the setting of ethanol consumption. We hypothesize that ethanol downregulates numerous mitochondrial metabolic pathways through differential acyl switching proteins. Data are available via ProteomeXchange with identifier PXD012089.

The absence of SIRT3 and SIRT5 promotes the acetylation of lens proteins and improves the chaperone activity of α-crystallin in mouse lenses.

Acetylation of lysine residues occurs in lens proteins. Previous studies have shown an improvement in the chaperone activity of αA-crystallin upon acetylation. Sirtuins are NAD+-dependent enzymes that can deacylate proteins. The roles of sirtuins in regulating the acetylation of lens proteins and their impacts on the function of α-crystallin are not known. Here, we detected sirtuin activity in mouse lenses, and SIRT3 and SIRT5 were present primarily in the mitochondria of cultured primary mouse lens epithelial cells. Western blotting showed higher levels of protein acetylation in the lenses of SIRT3 KO and SIRT5 KO mice than in lenses of WT mice. Mass spectrometry analyses revealed a greater number of acetylated lysine residues in α-crystallin isolated from the SIRT3 and SIRT5 KO lenses than from WT lenses. α-Crystallin isolated from SIRT3 and SIRT5 KO lenses displayed a higher surface hydrophobicity and higher chaperone activity than the protein isolated from WT lenses. Thus, SIRTs regulate the acetylation levels of crystallins in mouse lenses, and acetylation in lenses enhances the chaperone activity of α-crystallin.

Taurine treatment prevents derangement of the hepatic γ-glutamyl cycle and methylglyoxal metabolism in a mouse model of classical homocystinuria: regulatory crosstalk between thiol and sulfinic acid metabolism.

Cystathionine ß-synthase-deficient homocystinuria (HCU) is a poorly understood, life-threatening inborn error of sulfur metabolism. Analysis of hepatic glutathione (GSH) metabolism in a mouse model of HCU demonstrated significant depletion of cysteine, GSH, and GSH disulfide independent of the block in trans-sulfuration compared with wild-type controls. HCU induced the expression of the catalytic and regulatory subunits of γ-glutamyl ligase, GSH synthase (GS), γ-glutamyl transpeptidase 1, 5-oxoprolinase (OPLAH), and the GSH-dependent methylglyoxal detoxification enzyme, glyoxalase-1. Multiple components of the transcription factor nuclear factor (erythroid-derived 2)-like 2 (Nrf2)-mediated antioxidant-response regulatory axis were induced without any detectable activation of Nrf2. Metabolomic analysis revealed the accumulation of multiple γ-glutamyl amino acids and that plasma ophthalmate levels could serve as a noninvasive marker for hepatic redox stress. Neither cysteine, nor betaine treatment was able to reverse the observed enzyme inductions. Taurine treatment normalized the expression levels of γ-glutamyl ligase C/M, GS, OPLAH, and glyoxalase-1, and reversed HCU-induced deficits in protein glutathionylation by acting to double GSH levels relative to controls. Collectively, our data indicate that the perturbation of the γ-glutamyl cycle could contribute to multiple sequelae in HCU and that taurine has significant therapeutic potential for both HCU and other diseases for which GSH depletion is a critical pathogenic factor.-Maclean, K. N., Jiang, H., Aivazidis, S., Kim, E., Shearn, C. T., Harris, P. S., Petersen, D. R., Allen, R. H., Stabler, S. P., Roede, J. R. Taurine treatment prevents derangement of the hepatic γ-glutamyl cycle and methylglyoxal metabolism in a mouse model of classical homocystinuria: regulatory crosstalk between thiol and sulfinic acid metabolism.

Quantitative Analysis and Discovery of Lysine and Arginine Modifications.

Post-translational modifications (PTMs) affect protein function, localization, and stability, yet very little is known about the ratios of these modifications. Here, we describe a novel method to quantitate and assess the relative stoichiometry of Lys and Arg modifications (QuARKMod) in complex biological settings. We demonstrate the versatility of this platform in monitoring recombinant protein modification of peptide substrates, PTMs of individual histones, and the relative abundance of these PTMs as a function of subcellular location. Lastly, we describe a product ion scanning technique that offers the potential to discover unexpected and possibly novel Lys and Arg modifications. In summary, this approach yields accurate quantitation and discovery of protein PTMs in complex biological systems without the requirement of high mass accuracy instrumentation.

Characterizing Sirtuin 3 Deacetylase Affinity for Aldehyde Dehydrogenase 2.

Mitochondrial aldehyde dehydrogenase (ALDH2) plays a central role in the detoxification of reactive aldehydes generated through endogenous and exogenous sources. The biochemical regulation of enzyme activity through post-translational modification provides an intricate response system regulating mitochondrial detoxification pathways. ALDH2 is a known target of lysine acetylation, which arises as a consequence of mitochondrial bioenergetic flux and sirtuin deacetylase activity. The mitochondrial deacetylase Sirtuin 3 (SIRT3) has been reported to alter ALDH2 lysine acetylation status, yet the mechanism and consequence of this interaction remain unknown. The in vitro results presented here provide a novel biochemical approach using stable-isotope dilution mass spectrometry to elucidate which lysine residues are targeted by SIRT3 for deacetylation. Furthermore, HPLC-MS/MS and computational modeling elucidate a potential role for acetyl-Lys369 on ALDH2 in perturbing normal ß-nicotinamide adenine dinucleotide (NAD+) cofactor binding.

Chronic Ethanol Metabolism Inhibits Hepatic Mitochondrial Superoxide Dismutase via Lysine Acetylation.

BACKGROUND: Chronic ethanol (EtOH) consumption is a major cause of liver disease worldwide. Oxidative stress is a known consequence of EtOH metabolism and is thought to contribute significantly to alcoholic liver disease (ALD). Therefore, elucidating pathways leading to sustained oxidative stress and downstream redox imbalances may reveal how EtOH consumption leads to ALD. Recent studies suggest that EtOH metabolism impacts mitochondrial antioxidant processes through a number of proteomic alterations, including hyperacetylation of key antioxidant proteins. METHODS: To elucidate mechanisms of EtOH-induced hepatic oxidative stress, we investigate a role for protein hyperacetylation in modulating mitochondrial superoxide dismutase (SOD2) structure and function in a 6-week Lieber-DeCarli murine model of EtOH consumption. Our experimental approach includes immunoblotting immunohistochemistry (IHC), activity assays, mass spectrometry, and in silico modeling. RESULTS: We found that EtOH metabolism significantly increased the acetylation of SOD2 at 2 functionally relevant lysine sites, K68 and K122, resulting in a 40% decrease in enzyme activity while overall SOD2 abundance was unchanged. In vitro studies also reveal which lysine residues are more susceptible to acetylation. IHC analysis demonstrates that SOD2 hyperacetylation occurs near zone 3 within the liver, which is the main EtOH-metabolizing region of the liver. CONCLUSIONS: Overall, the findings presented in this study support a role for EtOH-induced lysine acetylation as an adverse posttranslational modification within the mitochondria that directly impacts SOD2 charge state and activity. Last, the data presented here indicate that protein hyperacetylation may be a major factor contributing to an imbalance in hepatic redox homeostasis due to chronic EtOH metabolism.

MicroRNA 218 acts as a tumor suppressor by targeting multiple cancer phenotype-associated genes in medulloblastoma.

Aberrant expression of microRNAs has been implicated in many cancers. We recently demonstrated differential expression of several microRNAs in medulloblastoma. In this study, the regulation and function of microRNA 218 (miR-218), which is significantly underexpressed in medulloblastoma, was evaluated. Re-expression of miR-218 resulted in a significant decrease in medulloblastoma cell growth, cell colony formation, cell migration, invasion, and tumor sphere size. We used C17.2 neural stem cells as a model to show that increased miR-218 expression results in increased cell differentiation and also decreased malignant transformation when transfected with the oncogene REST. These results suggest that miR-218 acts as a tumor suppressor in medulloblastoma. MicroRNAs function by down-regulating translation of target mRNAs. Targets are determined by imperfect base pairing of the microRNA to the 3'-UTR of the mRNA. To comprehensively identify actual miR-218 targets, medulloblastoma cells overexpressing miR-218 and control cells were subjected to high throughput sequencing of RNA isolated by cross-linking immunoprecipitation, a technique that identifies the mRNAs bound to the RNA-induced silencing complex component protein Argonaute 2. High throughput sequencing of mRNAs identified 618 genes as targets of miR-218 and included both previously validated targets and many targets not predicted computationally. Additional work further confirmed CDK6, RICTOR, and CTSB (cathepsin B) as targets of miR-218 and examined the functional role of one of these targets, CDK6, in medulloblastoma.

Integrated genomic analysis identifies the mitotic checkpoint kinase WEE1 as a novel therapeutic target in medulloblastoma.

BACKGROUND: Medulloblastoma is the most common type of malignant brain tumor that afflicts children. Although recent advances in chemotherapy and radiation have improved outcomes, high-risk patients do poorly with significant morbidity. METHODS: To identify new molecular targets, we performed an integrated genomic analysis using structural and functional methods. Gene expression profiling in 16 medulloblastoma patient samples and subsequent gene set enrichment analysis indicated that cell cycle-related kinases were associated with disease development. In addition a kinome-wide small interfering RNA (siRNA) screen was performed to identify kinases that, when inhibited, could prevent cell proliferation. The two genome-scale analyses were combined to identify key vulnerabilities in medulloblastoma. The inhibition of one of the identified targets was further investigated using RNAi and a small molecule inhibitor. RESULTS: Combining the two analyses revealed that mitosis-related kinases were critical determinants of medulloblastoma cell proliferation. RNA interference (RNAi)-mediated knockdown of WEE1 kinase and other mitotic kinases was sufficient to reduce medulloblastoma cell proliferation. These data prompted us to examine the effects of inhibiting WEE1 by RNAi and by a small molecule inhibitor of WEE1, MK-1775, in medulloblastoma cell lines. MK-1775 inhibited the growth of medulloblastoma cell lines, induced apoptosis and increased DNA damage at nanomolar concentrations. Further, MK-1775 was synergistic with cisplatin in reducing medulloblastoma cell proliferation and resulted in an associated increase in cell death. In vivo MK-1775 suppressed medulloblastoma tumor growth as a single agent. CONCLUSIONS: Taken together, these findings highlight mitotic kinases and, in particular, WEE1 as a rational therapeutic target for medulloblastoma.

Quantifying Protein Acetylation in Diabetic Nephropathy from Formalin-Fixed Paraffin-Embedded Tissue.

PURPOSE: Diabetic kidney disease (DKD) is a serious complication of diabetes mellitus and a leading cause of chronic kidney disease and end-stage renal disease. One potential mechanism underlying cellular dysfunction contributing to kidney disease is aberrant protein post-translational modifications. Lysine acetylation is associated with cellular metabolic flux and is thought to be altered in patients with diabetes and dysfunctional renal metabolism. EXPERIMENTAL DESIGN: A novel extraction and LC-MS/MS approach was adapted to quantify sites of lysine acetylation from formalin-fixed paraffin-embedded (FFPE) kidney tissue and from patients with DKD and non-diabetic donors (n = 5 and n = 7, respectively). RESULTS: Analysis of FFPE tissues identified 840 total proteins, with 225 of those significantly changing in patients with DKD. Acetylomic analysis quantified 289 acetylated peptides, with 69 of those significantly changing. Pathways impacted in DKD patients revealed numerous metabolic pathways, specifically mitochondrial function, oxidative phosphorylation, and sirtuin signaling. Differential protein acetylation in DKD patients impacted sirtuin signaling, valine, leucine, and isoleucine degradation, lactate metabolism, oxidative phosphorylation, and ketogenesis. CONCLUSIONS AND CLINICAL RELEVANCE: A quantitative acetylomics platform was developed for protein biomarker discovery in formalin-fixed and paraffin-embedded biopsies of kidney transplant patients suffering from DKD.

Inhibition of cyclin-dependent kinase 6 suppresses cell proliferation and enhances radiation sensitivity in medulloblastoma cells.

Medulloblastoma accounts for 20 % of all primary pediatric intracranial tumors. Current treatment cures 50-80 % of patients but is associated with significant long-term morbidity and thus new therapeutic targets are needed. One such target is cyclin-dependent kinase 6 (CDK6), a serine/threonine kinase that plays a vital role in cell cycle progression and differentiation. CDK6 is overexpressed in medulloblastoma patients and is associated with an adverse prognosis. To investigate the role of CDK6 in medulloblastoma, we assayed the effect of CDK6 inhibition on proliferation by depleting expression with RNA interference (RNAi) or by inhibiting kinase function with a small molecule inhibitor, PD0332991. Cell proliferation was assessed by colony focus assay or by the xCELLigence system. We then investigated the impact of CDK6 inhibition on differentiation of murine neural stem cells by immunofluorescence of relevant markers. Finally we evaluated the effects of PD0332991 treatment on medulloblastoma cell cycle and radiosensitivity using colony focus assays. Gene expression analysis revealed that CDK6 mRNA expression is higher than normal cerebellum in fifteen out of sixteen medulloblastoma patient samples. Inhibition of CDK6 by RNAi significantly decreased medulloblastoma cell proliferation and colony forming potential. Interestingly, CDK6 inhibition by RNAi increased differentiation in murine neural stem cells. PD0332991 treatment significantly decreased medulloblastoma cell proliferation and led to a G0/G1 cell cycle arrest. Furthermore, PD0332991 pretreatment sensitized medulloblastoma cells to ionizing radiation. Our findings suggest that targeting CDK6 with small molecule inhibitors may prove beneficial in the treatment of medulloblastoma, especially when combined with radiation.

Click chemistry-based thiol redox proteomics reveals significant cysteine reduction induced by chronic ethanol consumption.

In the U.S., alcohol-associated liver disease (ALD) impacts millions of people and is a major healthcare burden. While the pathology of ALD is unmistakable, the molecular mechanisms underlying ethanol hepatotoxicity are not fully understood. Hepatic ethanol metabolism is intimately linked with alterations in extracellular and intracellular metabolic processes, specifically oxidation/reduction reactions. The xenobiotic detoxification of ethanol leads to significant disruptions in glycolysis, ß-oxidation, and the TCA cycle, as well as oxidative stress. Perturbation of these regulatory networks impacts the redox status of critical regulatory protein thiols throughout the cell. Integrating these key concepts, our goal was to apply a cutting-edge approach toward understanding mechanisms of ethanol metabolism in disrupting hepatic thiol redox signaling. Utilizing a chronic murine model of ALD, we applied a cysteine targeted click chemistry enrichment coupled with quantitative nano HPLC-MS/MS to assess the thiol redox proteome. Our strategy reveals that ethanol metabolism largely reduces the cysteine proteome, with 593 cysteine residues significantly reduced and 8 significantly oxidized cysteines. Ingenuity Pathway Analysis demonstrates that ethanol metabolism reduces specific cysteines throughout ethanol metabolism (Adh1, Cat, Aldh2), antioxidant pathways (Prx1, Mgst1, Gsr), as well as many other biochemical pathways. Interestingly, a sequence motif analysis of reduced cysteines showed a correlation for hydrophilic, charged amino acids lysine or glutamic acid nearby. Further research is needed to determine how a reduced cysteine proteome impacts individual protein activity across these protein targets and pathways. Additionally, understanding how a complex array of cysteine-targeted post-translational modifications (e.g., S-NO, S-GSH, S-OH) are integrated to regulate redox signaling and control throughout the cell is key to the development of redox-centric therapeutic agents targeted to ameliorate the progression of ALD.

Polo-like kinase 1 (PLK1) inhibition suppresses cell growth and enhances radiation sensitivity in medulloblastoma cells.

BACKGROUND: Medulloblastoma is the most common malignant brain tumor in children and remains a therapeutic challenge due to its significant therapy-related morbidity. Polo-like kinase 1 (PLK1) is highly expressed in many cancers and regulates critical steps in mitotic progression. Recent studies suggest that targeting PLK1 with small molecule inhibitors is a promising approach to tumor therapy. METHODS: We examined the expression of PLK1 mRNA in medulloblastoma tumor samples using microarray analysis. The impact of PLK1 on cell proliferation was evaluated by depleting expression with RNA interference (RNAi) or by inhibiting function with the small molecule inhibitor BI 2536. Colony formation studies were performed to examine the impact of BI 2536 on medulloblastoma cell radiosensitivity. In addition, the impact of depleting PLK1 mRNA on tumor-initiating cells was evaluated using tumor sphere assays. RESULTS: Analysis of gene expression in two independent cohorts revealed that PLK1 mRNA is overexpressed in some, but not all, medulloblastoma patient samples when compared to normal cerebellum. Inhibition of PLK1 by RNAi significantly decreased medulloblastoma cell proliferation and clonogenic potential and increased cell apoptosis. Similarly, a low nanomolar concentration of BI 2536, a small molecule inhibitor of PLK1, potently inhibited cell growth, strongly suppressed the colony-forming ability, and increased cellular apoptosis of medulloblastoma cells. Furthermore, BI 2536 pretreatment sensitized medulloblastoma cells to ionizing radiation. Inhibition of PLK1 impaired tumor sphere formation of medulloblastoma cells and decreased the expression of SRY (sex determining region Y)-box 2 (SOX2) mRNA in tumor spheres indicating a possible role in targeting tumor initiating cells. CONCLUSIONS: Our data suggest that targeting PLK1 with small molecule inhibitors, in combination with radiation therapy, is a novel strategy in the treatment of medulloblastoma that warrants further investigation.

Targeting Aurora Kinase A enhances radiation sensitivity of atypical teratoid rhabdoid tumor cells.

Atypical teratoid/rhabdoid tumors (ATRT) are rare, highly malignant, embryonal CNS tumors with a poor prognosis. Therapy relies on highly toxic chemotherapy and radiotherapy. To improve outcomes and decrease morbidity, more targeted therapy is required. Gene expression analysis revealed elevated expression of multiple kinases in ATRT tissues. Aurora Kinase A was one of the candidate kinases. The objective of this study was to evaluate the impact of Aurora Kinase A inhibition in ATRT cell lines. Our analysis revealed that inhibition of Aurora Kinase A induces cell death in ATRT cells and the small molecule inhibitor MLN 8237 sensitizes these cells to radiation. Furthermore, inhibition of Aurora Kinase A resulted in decreased activity of pro-proliferative signaling pathways. These data indicate that inhibition of Aurora Kinase A is a promising small molecule target for ATRT therapy.

Biochemical Mechanisms of Sirtuin-Directed Protein Acylation in Hepatic Pathologies of Mitochondrial Dysfunction.

Mitochondrial protein acetylation is associated with a host of diseases including cancer, Alzheimer's, and metabolic syndrome. Deciphering the mechanisms regarding how protein acetylation contributes to disease pathologies remains difficult due to the complex diversity of pathways targeted by lysine acetylation. Specifically, protein acetylation is thought to direct feedback from metabolism, whereby nutritional status influences mitochondrial pathways including beta-oxidation, the citric acid cycle, and the electron transport chain. Acetylation provides a crucial connection between hepatic metabolism and mitochondrial function. Dysregulation of protein acetylation throughout the cell can alter mitochondrial function and is associated with numerous liver diseases, including non-alcoholic and alcoholic fatty liver disease, steatohepatitis, and hepatocellular carcinoma. This review introduces biochemical mechanisms of protein acetylation in the regulation of mitochondrial function and hepatic diseases and offers a viewpoint on the potential for targeted therapies.

Redox state and the sirtuin deacetylases are major factors that regulate the acetylation status of the stress protein NQO1.

The stress induced protein NQO1 can participate in a wide range of biological pathways which are dependent upon the interaction of NQO1 with protein targets. Many of the protein-protein interactions involving NQO1 have been shown to be regulated by the pyridine nucleotide redox balance. NQO1 can modify its conformation as a result of redox changes in pyridine nucleotides and sites on the C-terminal and helix seven regions of NQO1 have been identified as potential areas that may be involved in redox-dependent protein-protein interactions. Since post-translational modifications can modify the functionality of proteins, we examined whether redox-dependent conformational changes induced in NQO1 would alter lysine acetylation. Recombinant NQO1 was incubated with and without NADH then acetylated non-enzymatically by acetic anhydride or S-acetylglutathione (Ac-GSH). NQO1 acetylation was determined by immunoblot and site-specific lysine acetylation was quantified by mass spectrometry (MS). NQO1 was readily acetylated by acetic anhydride and Ac-GSH. Interestingly, despite a large number of lysine residues (9%) in NQO1 only a small subset of lysines were acetylated and the majority of these were located in or near the functional C-terminal or helix seven regions. Reduction of NQO1 by NADH prior to acetylation resulted in almost complete protection of NQO1 from lysine acetylation as confirmed by immunoblot analysis and MS. Lysines located within the redox-active C-terminus and helix seven regions were readily acetylated when NQO1 was in an oxidized conformation but were protected from acetylation when NQO1 was in the reduced conformation. To investigate regulatory mechanisms of enzymatic deacetylation, NQO1 was acetylated by Ac-GSH then exposed to purified sirtuins (SIRT 1-3) or histone deacetylase 6 (HDAC6). NQO1 could be deacetylated by all sirtuin isoforms and quantitative MS analysis performed using SIRT2 revealed very robust deacetylation of NQO1, specifically at K262 and K271 in the C-terminal region. No deacetylation of NQO1 by HDAC6 was detected. These data demonstrate that the same subset of key lysine residues in the C-terminal and helix seven regions of NQO1 undergo redox dependent acetylation and are regulated by sirtuin-mediated deacetylation.

Proteomic analysis of alcohol-associated hepatitis reveals glycoprotein NMB (GPNMB) as a novel hepatic and serum biomarker.

Alcohol consumption remains a leading cause of liver disease worldwide, resulting in a complex array of hepatic pathologies, including steatosis, steatohepatitis, and cirrhosis. Individuals who progress to a rarer form of alcohol-associated liver disease (ALD), alcohol-associated hepatitis (AH), require immediate life-saving intervention in the form of liver transplantation. Rapid onset of AH is poorly understood and the metabolic mechanisms contributing to the progression to liver failure remain undetermined. While multiple mechanisms have been identified that contribute to ALD, no cures exist and mortality from AH remains high. To identify novel pathways associated with AH, our group utilized proteomics to investigate AH-specific biomarkers in liver explant tissues. The goal of the present study was to determine changes in the proteome as well as epigenetic changes occurring in AH. Protein abundance and acetylomic analyses were performed utilizing nHPLC-MS/MS, revealing significant changes to proteins associated with metabolic and inflammatory fibrosis pathways. Here, we describe a novel hepatic and serum biomarker of AH, glycoprotein NMB (GPNMB). The anti-inflammatory protein GPNMB was significantly increased in AH explant liver and serum compared to healthy donors by 50-fold and 6.5-fold, respectively. Further, bioinformatics analyses identified an AH-dependent decrease in protein abundance across fatty acid degradation, biosynthesis of amino acids, and carbon metabolism. The greatest increases in protein abundance were observed in pathways for focal adhesion, lysosome, phagosome, and actin cytoskeleton. In contrast with the hyperacetylation observed in murine models of ALD, protein acetylation was decreased in AH compared to normal liver across fatty acid degradation, biosynthesis of amino acids, and carbon metabolism. Interestingly, immunoblot analysis found epigenetic marks were significantly increased in AH explants, including Histone H3K9 and H2BK5 acetylation. The increased acetylation of histones likely plays a role in the altered proteomic profile observed, including increases in GPNMB. Indeed, our results reveal that the AH proteome is dramatically impacted through unanticipated and unknown mechanisms. Understanding the origin and consequences of these changes will yield new mechanistic insight for ALD as well as identify novel hepatic and serum biomarkers, such as GPNMB.

Cystathionine γ-lyase promotes estrogen-stimulated uterine artery blood flow via glutathione homeostasis.

During pregnancy, estrogen (E2) stimulates uterine artery blood flow (UBF) by enhancing nitric oxide (NO)-dependent vasodilation. Cystathionine γ-lyase (CSE) promotes vascular NO signaling by producing hydrogen sulfide (H2S) and by maintaining the ratio of reduced-to-oxidized intracellular glutathione (GSH/GSSG) through l-cysteine production. Because redox homeostasis can influence NO signaling, we hypothesized that CSE mediates E2 stimulation of UBF by modulating local intracellular cysteine metabolism and GSH/GSSG levels to promote redox homeostasis. Using non-pregnant ovariectomized WT and CSE-null (CSE KO) mice, we performed micro-ultrasound of mouse uterine and renal arteries to assess changes in blood flow upon exogenous E2 stimulation. We quantified serum and uterine artery NO metabolites (NOx), serum amino acids, and uterine and renal artery GSH/GSSG. WT and CSE KO mice exhibited similar baseline uterine and renal blood flow. Unlike WT, CSE KO mice did not exhibit expected E2 stimulation of UBF. Renal blood flow was E2-insensitive for both genotypes. While serum and uterine artery NOx were similar between genotypes at baseline, E2 decreased NOx in CSE KO serum. Cysteine was also lower in CSE KO serum, while citrulline and homocysteine levels were elevated. E2 and CSE deletion additively decreased GSH/GSSG in uterine arteries. In contrast, renal artery GSH/GSSG was insensitive to E2 or CSE deletion. Together, these findings suggest that CSE maintenance of uterine artery GSH/GSSG facilitates nitrergic signaling in uterine arteries and is required for normal E2 stimulation of UBF. These data have implications for pregnancy pathophysiology and the selective hormone responses of specific vascular beds.

SNARE proteins rescue impaired autophagic flux in Down syndrome.

Down syndrome (DS) is a chromosomal disorder caused by trisomy of chromosome 21 (Ts21). Unbalanced karyotypes can lead to dysfunction of the proteostasis network (PN) and disrupted proteostasis is mechanistically associated with multiple DS comorbidities. Autophagy is a critical component of the PN that has not previously been investigated in DS. Based on our previous observations of PN disruption in DS, we investigated possible dysfunction of the autophagic machinery in human DS fibroblasts and other DS cell models. Following induction of autophagy by serum starvation, DS fibroblasts displayed impaired autophagic flux indicated by autophagolysosome accumulation and elevated p62, NBR1, and LC3-II abundance, compared to age- and sex-matched, euploid (CTL) fibroblasts. While lysosomal physiology was unaffected in both groups after serum starvation, we observed decreased basal abundance of the Soluble N-ethylmaleimide-sensitive-factor Attachment protein Receptor (SNARE) family members syntaxin 17 (STX17) and Vesicle Associated Membrane Protein 8 (VAMP8) indicating that decreased autophagic flux in DS is due at least in part to a possible impairment of autophagosome-lysosome fusion. This conclusion was further supported by the observation that over-expression of either STX17 or VAMP8 in DS fibroblasts restored autophagic degradation and reversed p62 accumulation. Collectively, our results indicate that impaired autophagic clearance is a characteristic of DS cells that can be reversed by enhancement of SNARE protein expression and provides further evidence that PN disruption represents a candidate mechanism for multiple aspects of pathogenesis in DS and a possible future target for therapeutic intervention.

Cholestatic liver disease results increased production of reactive aldehydes and an atypical periportal hepatic antioxidant response.

Cholangiopathies such as primary sclerosing cholangitis (PSC) are chronic liver diseases characterized by increased cholestasis, biliary inflammation and oxidative stress. The objective of this study was to elucidate the impact of cholestatic injury on oxidative stress-related factors. Using hepatic tissue and whole cell liver extracts (LE) isolated from 11-week old C57BL/6J (WT) and Mdr2KO mice, inflammation and oxidative stress was assessed. Concurrently, specific targets of carbonylation were assessed in LE prepared from murine groups as well as from normal and human patients with end-stage PSC. Identified carbonylated proteins were further evaluated using bioinformatics analyses. Picrosirius red staining revealed extensive fibrosis in Mdr2KO liver, and fibrosis colocalized with increased periportal inflammatory cells and both acrolein and 4-HNE staining. Western blot analysis revealed elevated periportal expression of antioxidant proteins Cbr3, GSTµ, Prdx5, TrxR1 and HO-1 but not GCLC, GSTπ or catalase in the Mdr2KO group when compared to WT. From immunohistochemical analysis, increased periportal reactive aldehyde production colocalized with elevated staining of Cbr3, GSTµ and TrxR1 but surprisingly not with Nrf2. Mass spectrometric analysis revealed an increase in carbonylated proteins in the Mdr2KO and PSC groups compared to respective controls. Gene ontology and KEGG pathway analysis of carbonylated proteins revealed a propensity for increased carbonylation of proteins broadly involved in metabolic processes as well more specifically in Rab-mediated signal transduction, lysosomes and the large ribosomal subunit in human PSC. Western blot analysis of Rab-GTPase expression revealed no significant differences in Mdr2KO mice when compared to WT livers. In contrast, PSC tissue exhibited decreased levels of Rabs 4, 5 and increased abundance of Rabs 6 and 9a protein. Results herein reveal that cholestasis induces stage-dependent increases in periportal oxidative stress responses and protein carbonylation, potentially contributing to pathogenesis in Mdr2KO. Furthermore, during early stage cholestasis, there is cell-specific upregulation of some but not all, antioxidant proteins.