The VASP Road to NAFLD: A Macrophage Detour

RANKL Is Involved in Runx2-Triggered Hepatic Infiltration of Macrophages in Mice with NAFLD Induced by a High-Fat Diet

Background

Receptor activator of nuclear factor-κB (NF-κB) ligand (RANKL) is significant in the activation of inflammation. Runt-related transcription factor 2 (Runx2) promotes the hepatic infiltration of macrophages in nonalcoholic fatty liver disease (NAFLD). We studied how RANKL affects Runx2-triggered macrophage infiltration in NAFLD.

Method

30 male C57BL/6J mice at 4 weeks of age were utilized in this study, 20 mice received a high-fat diet (HFD), and 10 mice received standard rodent chow over 8 months. The histopathologic features of the liver were identified by H&E, Oil red O, and Masson staining. Runx2, RANKL, and F4/80 were analyzed by western blot, real-time PCR, and immunohistochemistry in vivo, respectively. Lentivirus or siRNA was utilized for transwell assay to investigate the role of RANKL in Runx2-induced macrophage migration in vitro.

Results

Compared to controls, during NAFLD development, HFD increased Runx2 and RANKL in vivo in NASH (P < 0.01). Meanwhile, a correlation between the expression of Runx2 and RANKL (P < 0.05) was evident. In addition, the hepatic infiltration of macrophages was increased upon HFD feeding, and analysis showed that the macrophage infiltration was correlated with the expression of Runx2 or RANKL (P < 0.05). In vitro, we found that overexpression or deficiency of Runx2 increased or decreased the production of RANKL in mHSCs. Then, transwell assay revealed that RANKL was involved in Runx2-induced macrophage migration.

Conclusions

Overall, RANKL is involved in Runx2-triggered macrophage migration during NAFLD pathogenesis, which may provide an underlying therapeutic target for NAFLD.

Cell-specific elevation of Runx2 promotes hepatic infiltration of macrophages by upregulating MCP-1 in high-fat diet-induced mice NAFLD

OBJECTIVE

We have demonstrated runt-related transcription factor 2 (Runx2) plays important role in atherosclerosis. It has been indicated that atherosclerosis shares the similar histopathology with nonalcoholic steatohepatitis (NASH), a progressive stage of nonalcoholic fatty liver disease (NAFLD), on macrophages infiltration. However, the function of Runx2 in NAFLD is completely unknown. Here, we investigated the underlying mechanism of Runx2 triggering macrophages infiltration in the development of NAFLD.

METHODS

Mice were fed with high-fat diet (HFD) for a long time. Histopathologic features, macrophages infiltration, expression of monocyte chemotactic protein 1 (MCP-1), and Runx2 were, respectively, analyzed in vivo. Lentivirus or short interfering RNA were transfected in murine hepatic stellate cells (HSCs) and the transwell assay was performed to verify the contribution of Runx2 for macrophages migration in vitro.

RESULTS

Long-term treatment with HFD induced the progression of NAFLD, and NASH was initiated from 8 months on diet. HFD increased the expression of F4/80 upon HFD feeding, indicated HFD promotes hepatic infiltration of macrophages in NAFLD. In addition, HFD upregulated the expression of MCP-1 and Runx2 during NAFLD development. Unexpectedly, Runx2 upregulation is cell-type depended in NAFLD, and only abundantly elevated in activated HSCs. Furthermore, we found that Runx2 could increase or decrease the expression of MCP-1 in HSCs, and regulate macrophages migration by influencing MCP-1 production in vitro.

CONCLUSIONS

Our results give evidence that the upregulation of Runx2 specific in activated HSCs promotes hepatic infiltration of macrophages by increasing MCP-1 expression in NAFLD, which reveals a novel mechanism and provides a cell-specific therapeutic target for NAFLD.

GQ-11: A new PPAR agonist improves obesity-induced metabolic alterations in LDLr-/- mice

BACKGROUND

Obesity and insulin resistance/diabetes are important risk factors for cardiovascular diseases and demand safe and efficacious therapeutics.

OBJECTIVE

To assess the effects of a new thiazolidine compound-GQ-11-on obesity and insulin resistance induced by a diabetogenic diet in LDL receptor-deficient (LDLr^-/-) mice.

METHODS

Molecular docking simulations of GQ-11, PPARα and PPARγ structures were performed. Male C57BL/6J LDLr^-/- mice fed a diabetogenic diet for 24 weeks were treated with vehicle, GQ-11 or pioglitazone or (20 mg/kg/day) for 28 days by oral gavage. Glucose tolerance test, insulin, HOMA-IR, adipokines (leptin, adiponectin) and the lipid profile were assessed after treatment. Adipose tissue was analysed by X-ray analysis and morphometry; gene and protein expression were evaluated by real-time PCR and western blot, respectively.

RESULTS

GQ-11 showed partial agonism to PPARγ and PPARα. In vivo, treatment with GQ-11 ameliorated insulin sensitivity and did not modify subcutaneous adipose tissue and body weight gain. In addition, GQ-11 restored adipokine imbalance induced by a diabetogenic diet and enhanced Glut-4 expression in the adipose tissue. Improved insulin sensitivity was also associated with lower levels of MCP-1 and higher levels of IL-10. Furthermore, GQ-11 reduced triglycerides and VLDL cholesterol and increased HDL-cholesterol by upregulation of Apoa1 and Abca1 gene expression in the liver.

CONCLUSION

GQ-11 is a partial/dual PPARα/γ agonist that demonstrates anti-diabetic effects. Additionally, it improves the lipid profile and ameliorates chronic inflammation associated with obesity in atherosclerosis-prone mice.

Self-Assembled pH-Responsive Polymeric Micelles for Highly Efficient, Noncytotoxic Delivery of Doxorubicin Chemotherapy To Inhibit Macrophage Activation: In Vitro Investigation

Self-assembled pH-responsive polymeric micelles, a combination of hydrophilic poly(ethylene glycol) segments and hydrogen bonding interactions within a biocompatible polyurethane substrate, can spontaneously self-assemble into highly controlled, nanosized micelles in aqueous solution. These newly developed micelles exhibit excellent pH-responsive behavior and biocompatibility, highly controlled drug (doxorubicin; DOX) release behavior, and high drug encapsulation stability in different aqueous environments, making the micelles highly attractive potential candidates for safer, more effective drug delivery in applications such as cancer chemotherapy. In addition, in vitro cell studies revealed the drug-loaded micelles possessed excellent drug entrapment stability and low cytotoxicity toward macrophages under normal physiological conditions (pH 7.4, 37 °C). When the pH of the culture media was reduced to 6.0 to mimic the acidic tumor microenvironment, the drug-loaded micelles triggered rapid release of DOX within the cells, which induced potent antiproliferative and cytotoxic effects in vitro. Importantly, fluorescent imaging and flow cytometric analyses confirmed the DOX-loaded micelles were efficiently delivered into the cytoplasm of the cells via endocytosis and then subsequently gradually translocated into the nucleus. Therefore, these multifunctional micelles could serve as delivery vehicles for precise, effective, controlled drug release to prevent accumulation and activation of tumor-promoting tumor-associated macrophages in cancer tissues. Thus, this unique system may offer a potential route toward the practical realization of next-generation pH-responsive therapeutic delivery systems.