ADAM8 deficiency in macrophages promotes angiogenesis to antagonize post-myocardial infarction cardiac injury
Authors: Ji Z , Guo J , Zuo W , Zhang R , Qu Y , Tao Z , Xu Y , Yao Y , Ma G 
Published: November 2023

Abstract

Background
A disintegrin and metallopeptidase domain 8 (ADAM8) may be closely related to the progress of cardiovascular diseases. ADAM8 was first found in macrophages from mice, and ADAM family is closely related to the secretion function of macrophages. Therefore, ADAM8 may affect the process of myocardial infarction (MI) by regulating macrophage function.

Purpose
This study aims to explore how ADAM8 regulating the function of macrophages to inhibit the cardiac repair after MI.

Methods
CRISPR/Cas9 system was used to generate macrophage-specific ADAM8 knockout mice (ADAM8flox/flox,Lyz2-Cre, ADAM8 mKO) and ADAM8flox/flox (control) . Bone marrow transplantation was performed and macrophage-specific ADAM8 overexpressed adeno-associated virus (AAV6-CD68-Adam8) was generated. Proteomics of hearts and RNA-sequencing of bone marrow derived macrophages (BMDM) was performed. Cellular and molecular assays were used to discover the underlying mechanisms of ADAM8 function.

Results
(1) ADAM8 in serum of AMI patients was significantly higher than control group. ADAM8 was highly expressed in cardiac macrophages after day 3 of AMI. (2) Compared with the control group, the expression of CD31 and VEGFA in the infarcted myocardium was significantly increased in ADAM8 mKO mice, indicating enhanced angiogenesis. The cardiac fibrosis was decreased and heart function was improved in ADAM8 mKO group. ADAM8 overexpression can reverse the increase of angiogenesis caused by ADAM8 mKO and promote cardiac fibrosis in mice. The bone marrow transplantation experiments also showed that donor of ADAM8 mKO mice had increased angiogenesis and reduced cardiac fibrosis in the infarcted area. (3) The proteomics of hearts in AMI day 14, showed the Cardiac muscle contraction pathway and the Citrate cycle (TCA cycle) pathway in ADAM8 mKO mice were both increased significantly, indicating improved cardiac function and maintained the metabolic stability of heart after MI. Myocardial injection in situ of anti-VEGFA antibody can reverse the angiogenesis induced by ADAM8 mKO, and deteriorate heart function. (4) The supernatants and protein lysates of ADAM8 KO BMDM showed the decreased level of VEGFA, and IL-1β/IL-18. (5) RNA-sequencing showed that AMPK signaling pathway and autophagy pathway were both significantly increased in ADAM8 KO BMDM treated with LPS. p-AMPK/AMPK and autophagy-related molecules were obviously elevated in ADAM8 KO BMDM. Application of autophagy inhibitor 3-Methyladenine (3-MA) could reverse ADAM8 KO induced secretion of VEGFA and IL-1β/IL-18.

Conclusions
Our study has discovered ADAM8 as a new regulator of myocardial infarction. ADAM8 KO may promoting VEGFA secretion and inhibiting inflammatory factors secretion of macrophages via AMPK/autophagy pathway, further promoting angiogenesis and reducing fibrosis of infarcted myocardium, and attenuating heart function and adverse remodeling. ADAM8 may be a new target for treating myocardial infarction.Schematic diagram