Targeting peroxisome proliferator-activated receptor γ proteasomal degradation by magnolol is a potential avenue for adipogenesis-mediated metabolic homeostasis.

OBJECTIVE: Adipogenesis has been recognized as an attractive avenue for maintaining systemic homeostasis, with peroxisome proliferator-activated receptor γ (PPARγ) showing predominant roles in this process. This study aims to identify promising drug candidates by targeting PPARγ for adipogenesis-based metabolic homeostasis and to clarify the detailed mechanisms. METHODS: Molecular events contributing to adipogenesis were screened, which identified PPARγ as having the predominant role. Promising agents of adipogenesis agonism were screened using a PPARγ-based luciferase reporter assay. The functional capacity and molecular mechanisms of magnolol were intensively examined using 3T3-L1 preadipocytes and dietary models. RESULTS: This study found that F-box only protein 9 (FBXO9)-mediated lysine 11 (K11)-linked ubiquitination and proteasomal degradation of PPARγ are critically required during adipogenesis and systemic homeostasis. Notably, magnolol was identified as a potent adipogenesis activator by stabilizing PPARγ. The pharmacological mechanisms investigations clarified that magnolol directly binds to PPARγ and markedly interrupts its interaction with FBXO9, leading to a decline in K11-linked ubiquitination and proteasomal degradation of PPARγ. Clinically important, magnolol treatment significantly facilitates adipogenesis in vitro and in vivo. CONCLUSIONS: The downregulation of K11-linked ubiquitination of PPARγ caused by FBOX9 is essentially required for adipogenesis, while targeting PPARγ-FBXO9 interaction provides a new avenue for the therapy of adipogenesis-related metabolic disorder.

Network-based analysis identifies key regulatory transcription factors involved in skin aging.

Skin aging is a complex process involving intricate genetic and environmental factors. In this study, we performed a comprehensive analysis of the transcriptional regulatory landscape of skin aging in canines. Weighted Gene Co-expression Network Analysis (WGCNA) was employed to identify aging-related gene modules. We subsequently validated the expression changes of these module genes in single-cell RNA sequencing (scRNA-seq) data of human aging skin. Notably, basal cell (BC), spinous cell (SC), mitotic cell (MC), and fibroblast (FB) were identified as the cell types with the most significant gene expression changes during aging. By integrating GENIE3 and RcisTarget, we constructed gene regulation networks (GRNs) for aging-related modules and identified core transcription factors (TFs) by intersecting significantly enriched TFs within the GRNs with hub TFs from WGCNA analysis, revealing key regulators of skin aging. Furthermore, we demonstrated the conserved role of CTCF and RAD21 in skin aging using an H2O2-stimulated cell aging model in HaCaT cells. Our findings provide new insights into the transcriptional regulatory landscape of skin aging and unveil potential targets for future intervention strategies against age-related skin disorders in both canines and humans.

A high-throughput drug screening identifies luteolin as a therapeutic candidate for pathological cardiac hypertrophy and heart failure.

Background: Pathological cardiac hypertrophy is commonly resulted from sustained pressure overload and/or metabolic disorder and eventually leads to heart failure, lacking specific drugs in clinic. Here, we aimed to identify promising anti-hypertrophic drug(s) for heart failure and related metabolic disorders by using a luciferase reporter-based high-throughput screening. Methods: A screen of the FDA-approved compounds based on luciferase reporter was performed, with identified luteolin as a promising anti-hypertrophic drug. We systematically examined the therapeutic efficacy of luteolin on cardiac hypertrophy and heart failure in vitro and in vivo models. Transcriptome examination was performed to probe the molecular mechanisms of luteolin. Results: Among 2,570 compounds in the library, luteolin emerged as the most robust candidate against cardiomyocyte hypertrophy. Luteolin dose-dependently blocked phenylephrine-induced cardiomyocyte hypertrophy and showed extensive cardioprotective roles in cardiomyocytes as evidenced by transcriptomics. More importantly, gastric administration of luteolin effectively ameliorated pathological cardiac hypertrophy, fibrosis, metabolic disorder, and heart failure in mice. Cross analysis of large-scale transcriptomics and drug-target interacting investigations indicated that peroxisome proliferator activated receptor γ (PPARγ) was the direct target of luteolin in the setting of pathological cardiac hypertrophy and metabolic disorders. Luteolin can directly interact with PPARγ to inhibit its ubiquitination and subsequent proteasomal degradation. Furthermore, PPARγ inhibitor and PPARγ knockdown both prevented the protective effect of luteolin against phenylephrine-induced cardiomyocyte hypertrophy in vitro. Conclusion: Our data clearly supported that luteolin is a promising therapeutic compound for pathological cardiac hypertrophy and heart failure by directly targeting ubiquitin-proteasomal degradation of PPARγ and the related metabolic homeostasis.

Multiple omics study identifies an interspecies conserved driver for nonalcoholic steatohepatitis.

Lipotoxicity is a recognized pathological trigger and accelerator of nonalcoholic steatohepatitis (NASH). However, the molecular basis of lipotoxicity-induced NASH remains elusive. Here, we systematically mapped the changes in hepatic transcriptomic landscapes in response to lipotoxic insults across multiple species. Conserved and robust activation of the arachidonic acid pathway, in particular the arachidonate 12-lipoxygenase (ALOX12) gene, was closely correlated with NASH severity in humans, macaques with spontaneously developed NASH, as well as swine and mouse dietary NASH models. Using gain- and loss-of-function studies, we found that ALOX12 markedly exacerbated NASH in both mice and Bama pig models. ALOX12 was shown to induce NASH by directly targeting acetyl-CoA carboxylase 1 (ACC1) via a lysosomal degradation mechanism. Overall, our findings reveal a key molecular driver of NASH pathogenesis and suggest that ALOX12-ACC1 interaction may be a therapeutic target in NASH.

A small molecule targeting ALOX12-ACC1 ameliorates nonalcoholic steatohepatitis in mice and macaques.

Nonalcoholic steatohepatitis (NASH) is a progressive liver disease and has become a leading indication for liver transplantation in the United States. The development of effective therapies for NASH is a major unmet need. Here, we identified a small molecule, IMA-1, that can treat NASH by interrupting the arachidonate 12-lipoxygenase (ALOX12)­acetyl-CoA carboxylase 1 (ACC1) interaction. IMA-1 markedly blocked diet-induced NASH progression in both male mice and Cynomolgus macaque therapeutic models. The anti-NASH efficacy of IMA-1 was comparable to ACC inhibitor in both species. Protein docking simulations and following functional experiments suggested that the anti-NASH effects of IMA-1 were largely dependent on its direct binding to a pocket in ALOX12 proximal to its ACC1-interacting surface instead of inhibiting ALOX12 lipoxygenase activity. IMA-1 treatment did not elicit hyperlipidemia, a known side effect of direct inhibition of ACC enzymatic activity, in both mice and macaques. These findings provide proof of concept across multiple species for the use of small molecule­based therapies for NASH.

A kinome screen reveals that Nemo-like kinase is a key suppressor of hepatic gluconeogenesis.

Antihyperglycemic therapy is an important priority for the treatment of type 2 diabetes (T2D). Excessive hepatic glucose production (HGP) is a major cause of fasting hyperglycemia. Therefore, a better understanding of its regulation would be important to develop effective antihyperglycemic therapies. Using a gluconeogenesis-targeted kinome screening approach combined with transcriptome analyses, we uncovered Nemo-like kinase (NLK) as a potent suppressor of HGP. Mechanistically, NLK phosphorylates and promotes nuclear export of CRTC2 and FOXO1, two key regulators of hepatic gluconeogenesis, resulting in the proteasome-dependent degradation of the former and the inhibition of the self-transcriptional activity and expression of the latter. Importantly, the expression of NLK is downregulated in the liver of individuals with diabetes and in diabetic rodent models and restoring NLK expression in the mouse model ameliorates hyperglycemia. Therefore, our findings uncover NLK as a critical player in the gluconeogenic regulatory network and as a potential therapeutic target for T2D.

STEAP3 (Six-Transmembrane Epithelial Antigen of Prostate 3) Inhibits Pathological Cardiac Hypertrophy.

Pathological cardiac hypertrophy is one of the major predictors and inducers of heart failure, the end stage of various cardiovascular diseases. However, the molecular mechanisms underlying pathogenesis of pathological cardiac hypertrophy remain largely unknown. Here, we provided the first evidence that STEAP3 (Six-Transmembrane Epithelial Antigen of Prostate 3) is a key negative regulator of this disease. We found that the expression of STEAP3 was reduced in pressure overload-induced hypertrophic hearts and phenylephrine-induced hypertrophic cardiomyocytes. In a transverse aortic constriction-triggered mouse cardiac hypertrophy model, STEAP3 deficiency remarkably deteriorated cardiac hypertrophy and fibrosis, whereas the opposite phenotype was observed in the cardiomyocyte-specific STEAP3 overexpressing mice. Accordingly, STEAP3 significantly mitigated phenylephrine-induced cell enlargement in primary neonatal rat cardiomyocytes. Mechanistically, via RNA-seq and immunoprecipitation-mass screening, we demonstrated that STEAP3 directly bond to Rho family small GTPase 1 and suppressed the activation of downstream mitogen-activated protein kinase-extracellular signal-regulated kinase signaling cascade. Remarkably, the antihypertrophic effect of STEAP3 was largely blocked by overexpression of constitutively active mutant Rac1 (G12V). Our study indicates that STEAP3 serves as a novel negative regulator of pathological cardiac hypertrophy by blocking the activation of the Rac1-dependent signaling cascade and may contribute to exploring effective therapeutic strategies of pathological cardiac hypertrophy treatment.

Hepatocyte TNF Receptor-Associated Factor 6 Aggravates Hepatic Inflammation and Fibrosis by Promoting Lysine 6-Linked Polyubiquitination of Apoptosis Signal-Regulating Kinase 1.

Activation of apoptosis signal-regulating kinase 1 (ASK1) is a key driving force of the progression of nonalcoholic steatohepatitis (NASH) and represents an attractive therapeutic target for NASH treatment. However, the molecular and cellular mechanisms underlying ASK1 activation in the pathogenesis of NASH remain incompletely understood. In this study, our data unequivocally indicated that hyperactivated ASK1 in hepatocytes is a potent inducer of hepatic stellate cell (HSC) activation by promoting the production of hepatocyte-derived factors. Our previous serial studies have shown that the ubiquitination system plays a key role in regulating ASK1 activity during NASH progression. Here, we further demonstrated that tumor necrosis factor receptor-associated factor 6 (TRAF6) promotes lysine 6 (Lys6)-linked polyubiquitination and subsequent activation of ASK1 to trigger the release of robust proinflammatory and profibrotic factors in hepatocytes, which, in turn, drive HSC activation and hepatic fibrosis. Consistent with the in vitro findings, diet-induced liver inflammation and fibrosis were substantially attenuated in Traf6+/- mice, whereas hepatic TRAF6 overexpression exacerbated these abnormalities. Mechanistically, Lys6-linked ubiquitination of ASK1 by TRAF6 facilitates the dissociation of thioredoxin from ASK1 and N-terminal dimerization of ASK1, resulting in the boosted activation of ASK1-c-Jun N-terminal kinase 1/2 (JNK1/2)-mitogen-activated protein kinase 14(p38) signaling cascade in hepatocytes. Conclusion: These results suggest that Lys6-linked polyubiquitination of ASK1 by TRAF6 represents a mechanism underlying ASK1 activation in hepatocytes and a key driving force of proinflammatory and profibrogenic responses in NASH. Thus, inhibiting Lys6-linked polyubiquitination of ASK1 may serve as a potential therapeutic target for NASH treatment.

In vitro and in vivo investigation of the novel Dex-bHb as oxygen carriers.

The development of hemoglobin-based oxygen carriers (HBOCs) is a persistent and urgent need in biomedicine. As a potential HBOCs, Dextran-hemoglobin (Dex-bHb) has been developed over the past years. The novel Dex-bHb, whose thiol group of Cys-93(ß) was reversibly protected, was produced and the characteristics were evaluated in our previous study. Herein, blood compatibility was characterized in terms of the red blood cell aggregation and hemolysis rate in vitro, and Dex-bHb showed no obvious effects. After intravenous administration of Dex-bHb to golden Syrian hamsters with hemorrhages shock, it showed mean arterial pressure recovery, blood flow increase and the organ protection from serious hemorrhage injury. Consequently, Dex-bHb is hopeful to be a safe and available blood substitute.