Myeloid Differentiation Protein 2 Mediates Angiotensin II-Induced Liver Inflammation and Fibrosis in Mice.

Yi Zhang,Hui Liu,Yali Zhang,Jiayu Qi,Guang Liang,Hongjin Chen,Wenjing Jia,Wentao Zhang,Wenxin Zhang

doi:10.3390/molecules25010025

Abstract

Angiotensin II (Ang II) participates in the pathogenesis of liver injury. Our previous publications reported that myeloid differentiation protein 2 (MD2) mediates Ang II-induced cardiac and kidney inflammation by directly binding to Ang II. Thus, we hypothesize that MD2 is critical to Ang II-induced liver injury. Subcutaneous injections of Ang II for 8 weeks were adopted to build the liver injury model. With a specific MD2 inhibitor L6H21 and MD2 knockout mice, we reported that MD2 inhibition and knockout significantly mitigate liver inflammation and fibrosis in mice injected with Ang II. To be more specific, the functional and pathological damages induced by Ang II were mitigated by L6H21 or MD2 knockout. MD2 knockout or L6H21 administration inhibited the Ang II-induced upregulation of fibrosis markers, inflammatory cytokines, and adhesion molecules in gene or protein levels. The activation of NF-κB and Extracellular signal-regulated kinases (ERK) induced by Ang II was also reversed by L6H21 treatment or MD2 deficiency. Note that the co-immunoprecipitation study showed that L6H21 downregulated the ANG II-induced toll-like receptor 4 (TLR4)/MD2 complex in liver tissues while having no effects on MD2 expression. Our results reported the critical role of MD2 in the progress of liver injury and suggested that MD2 is a potential therapeutic target for liver injury.

Highlights

Liver injury-correlated diseases are among the commonest health problems, with almost 800,000 deaths each year worldwide [1]
A mouse liver injury model was built by injections of Angiotensin II (Ang II) (1.4 mg/kg/day in a phosphate buffer, pH 7.2) continued for 8 weeks, and the myeloid differentiation protein 2 (MD2) protein level in liver tissue was upregulated (Figure 1A)
These results revealed that MD2 might participate in Ang II-induced liver injury

Summary

Introduction

Liver injury-correlated diseases are among the commonest health problems, with almost 800,000 deaths each year worldwide [1]. Continuous liver injury induces hepatic inflammation and fibrosis, resulting in cirrhosis, liver failure, or hepatocellular carcinoma. Numerous factors, covering high-fat diets, alcohol, carbon tetrachloride, drugs, ischemia, and reperfusion, can induce liver injury [2]. Clinical and experimental studies have progressively highlighted the renin–angiotensin system (RAS) in hepatic diseases [3,4]. Angiotensin (Ang) II, the major RAS component, has been shown to regulate inflammation and fibrosis in various diseases (e.g., liver injury) [3,5]. Prolonged infusion of Ang II into normal rats can induce stellate cell activation and proinflammatory effects in the liver, which is independent of the rise in arterial pressure [6]. Whether there is a critical protein participating in the process remains unclear

Methods

Results

Discussion

Conclusion