Endogenous IRAK-M Attenuates Postinfarction Remodeling Through Effects on Macrophages and Fibroblasts

Abstract

Objective Effective post-infarction repair requires timely suppression of innate immune signals to prevent the catastrophic consequences of uncontrolled inflammation on cardiac geometry and function. In macrophages, Interleukin Receptor-Associated Kinase (IRAK)-M acts as a functional decoy preventing uncontrolled TLR/Interleukin-1-mediated responses. Our study investigates the role of IRAK-M as a negative regulator of the post-infarction inflammatory response and as a modulator of cardiac remodeling. Methods and results In WT mouse infarcts IRAK-M was upregulated in infiltrating macrophages and fibroblasts exhibiting a biphasic response. When compared to wildtype animals, infarcted IRAK-M −/− mice had enhanced adverse remodeling and worse systolic dysfunction; however, acute infarct size was comparable between groups. Adverse remodeling in IRAK-M −/− animals was associated with enhanced myocardial inflammation and protease activation. The protective actions of IRAK-M involved phenotypic modulation of macrophages and fibroblasts. IRAK-M −/− infarcts showed increased infiltration with pro-inflammatory CD11b+/Ly6Chi monocytes; leukocytes harvested from IRAK-M null infarcts exhibited accentuated cytokine expression. In vitro, IRAK-M expression was upregulated in cytokine-stimulated murine cardiac fibroblasts and suppressed their matrix-degrading properties without affecting their inflammatory activity. Conclusions Endogenous IRAK-M attenuates adverse post-infarction remodeling suppressing leukocyte inflammatory activity, while inhibiting fibroblast-mediated matrix degradation.

Lack of specificity of fibroblast-specific protein 1 in cardiac remodeling and fibrosis

“…The resulting single-cell suspensions were washed with HBSS supplemented with 0.2% (wt/vol) BSA and 1% (wt/vol) FCS and centrifuged. Cells were stained and analyzed using flow cytometry as previously described by our laboratory (10). The following dyes and antibodies were used: LIVE/DEAD Fixable Violet Dead Cell Stain single-color dyes (Invitrogen), APC-Cy7-conjugated anti-CD45, Alexa Fluor 700-conjugated anti-CD3 (both from BD Phamingen), PerCP/Cy5.5-labeled anti-CD31, PE/Cy7-labeled anti-F4/80 (both from Biolegend), and Cy3-conjugated anti-␣-SMA (Sigma).…”

“…Macrophages and fibroblasts were isolated from control and infarcted hearts (CD11b-negative control, n ϭ 5; macrophages control, n ϭ 7; CD11b-negative infarct 24 h, n ϭ 8; CD11b-negative infarct 7 days, n ϭ 8; macrophages infarct 24 h, n ϭ 8; and macrophages infarct 7 days, n ϭ 8) for RNA extraction as previously described (10). Briefly, single cell suspensions were obtained from infarcted hearts (1 h ischemia followed by 24 h or 7 days of reperfusion) or healthy hearts as described in Isolation of noncardiomyocytes from control, pressure-overloaded, and infarcted hearts and flow cytometry.…”

Inorganic nitrite modulates miRNA signatures in acute myocardial in vivo ischemia/reperfusion

“…This analysis yielded the miRNAs miR-146b, miR-339-3p, and miR-433 to be predicted to target the 3 0 UTR binding site of Irak-M, which was 1.3-fold up-regulated after only 5 min of reperfusion in the nitrite treated group (Table 4). Increased levels of Irak-M are consistent with decreased levels of the above-mentioned miRNAs, due to less inhibition of their target gene Irak-M. IRAK-M is established to be an important negative regulator of pro-inflammatory signaling pathways [27,28]. To validate the expression levels of these three miRNAs as well as the transcript level of Irak-M, we performed single tube real-time qRT-PCRs as well as immunoblotting for IRAK-M protein level.…”

“…IRAK-M is an important negative regulator of pro-inflammatory signaling pathways by inhibiting cytokine expression [27,28]. In the scope of acute myocardial infarction, IRAK-M was previously shown to be up-regulated in macrophages and fibroblasts after 6 h of reperfusion leading to a diminished adverse post-infarction remodeling and limited fibroblasts-mediated matrix degradation [27,28]. A timely activation of the antiinflammatory response within the "late" phase of reperfusion is crucial for cardiac repair.…”

Efeito do tratamento crônico do metotrexato associado à nanoemulsão de LDE no remodelamento cardíaco por infarto do miocárdio em ratos Wistar

“…Estudos experimentais discutem se a inflamação pode estender a injúria isquêmica (Briaud et al, 2001;Chen et al, 2012). Entretanto, o processo inflamatório está certamente envolvido na dilatação e fibrose cardíaca, conduzindo eventos-chave na patogênese da IC pós-infarto (Frangogiannis, 2014 parede ventricular e a cicatrização tecidual podem influenciar no processo de dilatação cardíaca e posteriormente na IC (Hanemaaijer et al, 1993;Cohn, 2000;Frangogiannis, 2014 (Kucharz et al, 1982;Jensen et al, 1990;Ward, 2000).…”