S100A8/A9 induces an inflammatory and pro-oxidant memory in bone morrow-derived leukocytes in experimental myocardial infarction
S A Manea, M L Vlad, R G Mares, M B Preda, L F Dudu, M R Fueriu, M Simionescu, A Manea, A SchiopuAbstract
Background
Evidence shows that myocardial infarction (MI) triggers a chain of cellular and molecular events that promote long-term cardiovascular complications, namely, accelerated atherosclerosis, recurrent MI, and heart failure. Hitherto, the precise mediators released by the ischemic myocardium post-MI, and the way by which these mediators fine tune molecular mechanisms further affecting the injured heart, blood vessels, and innate immune system remain poorly understood. Alarmin S100A8/A9 emerged as key trigger and amplifier of inflammation and oxidative stress during the acute inflammatory phase in MI. Yet, the role of S100A8/A9 as driver of long-lasting detrimental cardiovascular effects post-MI is not entirely explored.
Purpose
We aimed to investigate the potential implication of S100A8/A9 in mediating the imprinting of a transcriptional programme associated with an inflammatory and pro-oxidant phenotype in bone marrow-derived immune cells in experimental MI. To this purpose, we focused on two major processes, NLRP3 inflammasome priming and NADPH oxidase (Nox) expression.
Methods
Female C57BL/6J mice were subjected to sham or permanent surgical ligation of the left coronary artery to induce MI condition. Thereafter, the animals were randomly distributed intro experimental groups to receive via intraperitoneal injection, three daily doses of a selective S100A8/A9 inhibitor (30 mg/kg ABR-238901) or its vehicle (PBS). MI was confirm by echocardiographic analysis of cardiac function. Harvesting of left ventricle (LV) tissue specimens and bone morrow was done at 3 days and 21 days post-MI, respectively. CD45+ cells (leukocytes) were separated from bone marrow of mice and analysed by flow cytometry. Samples were examined by RNA sequencing, real-time PCR or Western blot.
Results
Significant increases in NLRP3, caspase-1, IL-1β, IL18, and Nox catalytic subunit gene or protein expression levels were determined in ischemic LV tissue specimens and bone marrow-derived CD45+ cells at 3 days post-MI, a condition that corresponds to acute inflammatory phase. Interestingly, the expression of NLRP3 and Nox components remained significantly up-regulated in CD45+ cells, during reparatory phase, namely, 21 days post-MI. Pharmacological inhibition of S100A8/A9 significantly reduced NLRP3 inflammasome priming and Nox expression at both 3 days and 21 days post-MI conditions.
Conclusion
Alarmin S100A8/A9, typically secreted by activated neutrophils in the inflammatory phase post-MI, leads to the imprinting of an inflammatory and pro-oxidant memory in the CD45+ bone morrow cells. S100A8/A9-oriented pharmacological intervention may become an important supportive therapeutic strategy to attenuate both acute and long-term inflammatory and pro-oxidant insults in myocardial infarction.