Discovery of genomic loci for liver health and steatosis reveals overlap with glutathione redox genetics.

Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver condition in the United States, encompassing a wide spectrum of liver pathologies including steatosis, steatohepatitis, fibrosis, and cirrhosis. Despite its high prevalence, there are no medications currently approved by the Food and Drug Administration for the treatment of NAFLD. Recent work has suggested that NAFLD has a strong genetic component and identifying causative genes will improve our understanding of the molecular mechanisms contributing to NAFLD and yield targets for future therapeutic investigations. Oxidative stress is known to play an important role in NAFLD pathogenesis, yet the underlying mechanisms accounting for disturbances in redox status are not entirely understood. To better understand the relationship between the glutathione redox system and signs of NAFLD in a genetically-diverse population, we measured liver weight, serum biomarkers aspartate aminotransferase (AST) and alanine aminotransferase (ALT), and graded liver pathology in a large cohort of Diversity Outbred mice. We compared hepatic endpoints to those of the glutathione redox system previously measured in the livers and kidneys of the same mice, and we screened for statistical and genetic associations using the R/qtl2 software. We discovered several novel genetic loci associated with markers of liver health, including loci that were associated with both liver steatosis and glutathione redox status. Candidate genes within each locus point to possible new mechanisms underlying the complex relationship between NAFLD and the glutathione redox system, which could have translational implications for future studies targeting NAFLD pathology.

Development of quantitative high-throughput screening assays to identify, validate, and optimize small-molecule stabilizers of misfolded ß-glucocerebrosidase with therapeutic potential for Gaucher disease and Parkinson's disease.

Glucocerebrosidase (GCase) is implicated in both a rare, monogenic disorder (Gaucher disease, GD) and a common, multifactorial condition (Parkinson's disease); hence, it is an urgent therapeutic target. To identify correctors of severe protein misfolding and trafficking obstruction manifested by the pathogenic L444P-variant of GCase, we developed a suite of quantitative, high-throughput, cell-based assays. First, we labeled GCase with a small pro-luminescent HiBiT peptide reporter tag, enabling quantitation of protein stabilization in cells while faithfully maintaining target biology. TALEN-based gene editing allowed for stable integration of a single HiBiT-GBA1 transgene into an intragenic safe-harbor locus in GBA1-knockout H4 (neuroglioma) cells. This GD cell model was amenable to lead discovery via titration-based quantitative high-throughput screening and lead optimization via structure-activity relationships. A primary screen of 10,779 compounds from the NCATS bioactive collections identified 140 stabilizers of HiBiT-GCase-L444P, including both pharmacological chaperones (ambroxol and non-inhibitory chaperone NCGC326) and proteostasis regulators (panobinostat, trans-ISRIB, and pladienolide B). Two complementary high-content imaging-based assays were deployed to triage hits: the fluorescence-quenched substrate LysoFix-GBA captured functional lysosomal GCase activity, while an immunofluorescence assay featuring antibody hGCase-1/23 provided direct visualization of GCase lysosomal translocation. NCGC326 was active in both secondary assays and completely reversed pathological glucosylsphingosine accumulation. Finally, we tested the concept of combination therapy, by demonstrating synergistic actions of NCGC326 with proteostasis regulators in enhancing GCase-L444P levels. Looking forward, these physiologically-relevant assays can facilitate the identification, pharmacological validation, and medicinal chemistry optimization of new chemical matter targeting GCase, ultimately leading to a viable therapeutic for two protein-misfolding diseases.

HEG1 Protects Against Atherosclerosis by Regulating Stable Flow-Induced KLF2/4 Expression in Endothelial Cells.

BACKGROUND: Atherosclerosis preferentially occurs in arterial regions of disturbed blood flow, and stable flow (s-flow) protects against atherosclerosis by incompletely understood mechanisms. METHODS: Our single-cell RNA-sequencing data using the mouse partial carotid ligation model was reanalyzed, which identified Heart-of-glass 1 (HEG1) as an s-flow-induced gene. HEG1 expression was studied by immunostaining, quantitive polymerase chain reaction, hybridization chain reaction, and Western blot in mouse arteries, human aortic endothelial cells (HAECs), and human coronary arteries. A small interfering RNA-mediated knockdown of HEG1 was used to study its function and signaling mechanisms in HAECs under various flow conditions using a cone-and-plate shear device. We generated endothelial-targeted, tamoxifen-inducible HEG1 knockout (HEG1iECKO) mice. To determine the role of HEG1 in atherosclerosis, HEG1iECKO and littermate-control mice were injected with an adeno-associated virus-PCSK9 [proprotein convertase subtilisin/kexin type 9] and fed a Western diet to induce hypercholesterolemia either for 2 weeks with partial carotid ligation or 2 months without the surgery. RESULTS: S-flow induced HEG1 expression at the mRNA and protein levels in vivo and in vitro. S-flow stimulated HEG1 protein translocation to the downstream side of HAECs and release into the media, followed by increased messenger RNA and protein expression. HEG1 knockdown prevented s-flow-induced endothelial responses, including monocyte adhesion, permeability, and migration. Mechanistically, HEG1 knockdown prevented s-flow-induced KLF2/4 (Kruppel-like factor 2/4) expression by regulating its intracellular binding partner KRIT1 (Krev interaction trapped protein 1) and the MEKK3-MEK5-ERK5-MEF2 pathway in HAECs. Compared with littermate controls, HEG1iECKO mice exposed to hypercholesterolemia for 2 weeks and partial carotid ligation developed advanced atherosclerotic plaques, featuring increased necrotic core area, thin-capped fibroatheroma, inflammation, and intraplaque hemorrhage. In a conventional Western diet model for 2 months, HEG1iECKO mice also showed an exacerbated atherosclerosis development in the arterial tree in both sexes and the aortic sinus in males but not in females. Moreover, endothelial HEG1 expression was reduced in human coronary arteries with advanced atherosclerotic plaques. CONCLUSIONS: Our findings indicate that HEG1 is a novel mediator of atheroprotective endothelial responses to flow and a potential therapeutic target.

Stable flow-induced expression of KLK10 inhibits endothelial inflammation and atherosclerosis.

Atherosclerosis preferentially occurs in arterial regions exposed to disturbed blood flow (d-flow), while regions exposed to stable flow (s-flow) are protected. The proatherogenic and atheroprotective effects of d-flow and s-flow are mediated in part by the global changes in endothelial cell (EC) gene expression, which regulates endothelial dysfunction, inflammation, and atherosclerosis. Previously, we identified kallikrein-related peptidase 10 (Klk10, a secreted serine protease) as a flow-sensitive gene in mouse arterial ECs, but its role in endothelial biology and atherosclerosis was unknown. Here, we show that KLK10 is upregulated under s-flow conditions and downregulated under d-flow conditions using in vivo mouse models and in vitro studies with cultured ECs. Single-cell RNA sequencing (scRNAseq) and scATAC sequencing (scATACseq) study using the partial carotid ligation mouse model showed flow-regulated Klk10 expression at the epigenomic and transcription levels. Functionally, KLK10 protected against d-flow-induced permeability dysfunction and inflammation in human artery ECs, as determined by NFκB activation, expression of vascular cell adhesion molecule 1 and intracellular adhesion molecule 1, and monocyte adhesion. Furthermore, treatment of mice in vivo with rKLK10 decreased arterial endothelial inflammation in d-flow regions. Additionally, rKLK10 injection or ultrasound-mediated transfection of Klk10-expressing plasmids inhibited atherosclerosis in Apoe-/- mice. Moreover, KLK10 expression was significantly reduced in human coronary arteries with advanced atherosclerotic plaques compared to those with less severe plaques. KLK10 is a flow-sensitive endothelial protein that serves as an anti-inflammatory, barrier-protective, and anti-atherogenic factor.

Role of flow-sensitive microRNAs and long noncoding RNAs in vascular dysfunction and atherosclerosis.

Atherosclerosis is the primary underlying cause of myocardial infarction, ischemic stroke, and peripheral artery disease. The disease preferentially occurs in arterial regions exposed to disturbed blood flow, in part, by altering expression of flow-sensitive coding- and non-coding genes. In this review, we summarize the role of noncoding RNAs, [microRNAs (miRNAs) and long noncoding RNAs(lncRNAs)], as regulators of gene expression and outline their relationship to the pathogenesis of atherosclerosis. While miRNAs are small noncoding genes that post-transcriptionally regulate gene expression by targeting mRNA transcripts, the lncRNAs regulate gene expression by diverse mechanisms, which are still emerging and incompletely understood. We focused on multiple flow-sensitive miRNAs such as, miR-10a, -19a, -23b, -17~92, -21, -663, -92a, -143/145, -101, -126, -712, -205, and -155 that play a critical role in endothelial function and atherosclerosis by targeting inflammation, cell cycle, proliferation, migration, apoptosis, and nitric oxide signaling. Flow-dependent regulation of lncRNAs is just emerging, and their role in vascular dysfunction and atherosclerosis is unknown. Here, we discuss the flow-sensitive lncRNA STEEL along with other lncRNAs studied in the context of vascular pathophysiology and atherosclerosis such as MALAT1, MIAT1, ANRIL, MYOSLID, MEG3, SENCR, SMILR, LISPR1, and H19. Also discussed is the use of these noncoding RNAs as potential biomarkers and therapeutics to reduce and regress atherosclerosis.

Muscle stem cell dysfunction impairs muscle regeneration in a mouse model of Down syndrome.

Down syndrome, caused by trisomy 21, is characterized by a variety of medical conditions including intellectual impairments, cardiovascular defects, blood cell disorders and pre-mature aging phenotypes. Several somatic stem cell populations are dysfunctional in Down syndrome and their deficiencies may contribute to multiple Down syndrome phenotypes. Down syndrome is associated with muscle weakness but skeletal muscle stem cells or satellite cells in Down syndrome have not been investigated. We find that a failure in satellite cell expansion impairs muscle regeneration in the Ts65Dn mouse model of Down syndrome. Ts65Dn satellite cells accumulate DNA damage and over express Usp16, a histone de-ubiquitinating enzyme that regulates the DNA damage response. Impairment of satellite cell function, which further declines as Ts65Dn mice age, underscores stem cell deficiencies as an important contributor to Down syndrome pathologies.