microRNA-125b Promotes HMGB1-Induced Inflammation Post Myocardial Infarction through Selectively Targeting Macrophages

Abstract: Myocardium inflammation triggered by damage associated molecular patterns (DAMPs)， such as HMGB1， is a key progress in pathogenesis of myocardial infarction (MI). However， the molecular mechanisms involved remain obscure. This study is to investigate the role of miR-125b on inflammation post-MI. Firstly， the expression of miR-125b and inflammatory cytokines including IL-1β， IL-6， IL-12， TNF-α were detected in the early MI， meanwhile， the levels of endogenous HMGB1 released were detected by immunohistochemical staining and immunofluorescence. Furthermore， recombinant mouse HMGB1 (rmHMGB1) were  constructed. miR-125b overexpression adenovirus and control adenovirus vector were constructed to infect H9C2 myocardial cells and 10T1/2 fibroblast cells in vitro as well as heart tissue after MI in vivo; miR-125b mimic  or control mimic were compounded to transfect primary-isolated macrophages from  mice. CD11b magnetic bead was performed to select cardiac macrophages post MI. The levels of cytokines IL-1β， IL-6， IL-12， TNF-α were detected via the qPCR and ELISA. The phosphorylation levels of NF-κB P65， MAPK JNK， MAPK P38 and MAPK ERK in inflammatory response were detected by western blot. The results showed that the expression of miR-125b were upregulated in the early MI， while endogenous HMGB1 released and a mass of cytokines producted in myocardial tissue. overexpressed-miR-125b promoted the production of inflammatory cytokines in cardiac macrophages after MI; the expression levels of IL-1β， IL-6， IL-12， TNF-α induced by rmHMGB1 varied in H9C2 myocardial cells， 10T1/2 fibroblasts and the primary macrophages， but overexpressed-miR-125b only played a selective up-regulation role on the  production of inflammatory cytokines in the macrophages， the reason might be related to the  activation of  P65 in macrophages. The results revealed that miR-125b positively regulated the inflammatory response induced by endogenous HMGB1 in macrophages after MI， but it didn’t have significant role on inflammation in myocardial cells and fibroblasts.

CSTR: 32200.14.cjcb.2016.12.0008