Rationale: The alarmin S100A9 has been identified as a potential therapeutic target in myocardial infarction. Short-term S100A9 blockade during the inflammatory phase post-myocardial infarction inhibits systemic and cardiac inflammation and improves cardiac function long term. Objective: To evaluate the impact of S100A9 blockade on postischemic cardiac repair. Methods and Results: We assessed cardiac function, hematopoietic response, and myeloid phagocyte dynamics in WT (wild type) C57BL/6 mice with permanent coronary artery ligation, treated with the specific S100A9 blocker ABR-238901 for 7 or 21 days. In contrast to the beneficial effects of short-term therapy, extended S100A9 blockade led to progressive deterioration of cardiac function and left ventricle dilation. The treatment reduced the proliferation of Lin ⁻ Sca-1 ⁺ c-Kit ⁺ hematopoietic stem and progenitor cells in the bone marrow and the production of proreparatory CD150 ⁺ CD48 ⁻ CCR2 ⁺ hematopoietic stem cells. Monocyte trafficking from the spleen to the myocardium and subsequent phenotype switching to reparatory Ly6C ^lo MerTK ^hi macrophages was also impaired, leading to inefficient efferocytosis, accumulation of apoptotic cardiomyocytes, and a larger myocardial scar. The transcription factor Nur77 (Nr4a1 [nuclear receptor subfamily 4 group A member 1]) mediates the transition from inflammatory Ly6C ^hi monocytes to reparatory Ly6C ^lo macrophages. S100A9 upregulated the levels and activity of Nur77 in monocytes and macrophages in vitro and in Ly6C ^hi/int monocytes in vivo, and S100A9 blockade antagonized these effects. Finally, the presence of reparatory macrophages in the myocardium was also impaired in S100A9 ^{−/ −} mice with permanent myocardial ischemia, leading to depressed cardiac function long term. Conclusions: We show that S100A9 plays an important role in both the inflammatory and the reparatory immune responses to myocardial infarction. Long-term S100A9 blockade negatively impacts cardiac recovery and counterbalances the beneficial effects of short-term therapy. These results define a therapeutic window targeting the inflammatory phase for optimal effects of S100A9 blockade as potential immunomodulatory treatment in acute myocardial infarction.

Background: Diabetes mellitus is linked to premature mortality of virtually all causes. Furin is a proprotein convertase broadly involved in the maintenance of cellular homeostasis; however, little is known about its role in the development of diabetes mellitus and risk of premature mortality.Objectives: To test if fasting plasma concentration of furin is associated with the development of diabetes mellitus and mortality.Methods: Overnight fasted plasma furin levels were measured at baseline examination in 4678 individuals from the population‐based prospective Malmö Diet and Cancer Study. We studied the relation of plasma furin levels with metabolic and hemodynamic traits. We used multivariable Cox proportional hazards models to investigate the association between baseline plasma furin levels and incidence of diabetes mellitus and mortality during 21.3–21.7 years follow‐up.Results: An association was observed between quartiles of furin concentration at baseline and body mass index, blood pressure and plasma concentration of glucose, insulin, LDL and HDL cholesterol (|0.11| ≤ β ≤ |0.31|, P < 0.001). Plasma furin (hazard ratio [HR] per one standard deviation increment of furin) was predictive of future diabetes mellitus (727 events; HR = 1.24, CI = 1.14–1.36, P < 0.001) after adjustment for age, sex, body mass index, systolic and diastolic blood pressure, use of antihypertensive treatment, alcohol intake and fasting plasma level of glucose, insulin and lipoproteins cholesterol. Furin was also independently related to the risk of all‐cause mortality (1229 events; HR = 1.12, CI = 1.05–1.19, P = 0.001) after full multivariable adjustment.Conclusion: Individuals with high plasma furin concentration have a pronounced dysmetabolic phenotype and elevated risk of diabetes mellitus and premature mortality.

Objective—: Matrix metalloproteinases (MMPs) degrade extracellular matrix proteins and play important roles in development and tissue repair. They have also been shown to have both protective and pathogenic effects in atherosclerosis, and experimental studies have suggested that MMP-12 contributes to plaque growth and destabilization. The objective of this study was to investigate the associations between circulating MMPs, atherosclerosis burden, and incidence of cardiovascular disease with a particular focus on type 2 diabetes mellitus. Approach and Results—: Plasma levels of MMP-1, -3, -7, -10, and -12 were analyzed by the Proximity Extension Assay technology in 1500 subjects participating in the SUMMIT (surrogate markers for micro- and macrovascular hard end points for innovative diabetes tools) study, 384 incident coronary cases, and 409 matched controls in the Malmö Diet and Cancer study and in 205 carotid endarterectomy patients. Plasma MMP-7 and -12 were higher in subjects with type 2 diabetes mellitus, increased with age and impaired renal function, and was independently associated with prevalent cardiovascular disease, atherosclerotic burden (as assessed by carotid intima-media thickness and ankle-brachial pressure index), arterial stiffness, and plaque inflammation. Baseline MMP-7 and -12 levels were increased in Malmö Diet and Cancer subjects who had a coronary event during follow-up. Conclusions—: The plasma level of MMP-7 and -12 are elevated in type 2 diabetes mellitus, associated with more severe atherosclerosis and an increased incidence of coronary events. These observations provide clinical support to previous experimental studies, demonstrating a role for these MMPs in plaque development, and suggest that they are potential biomarkers of atherosclerosis burden and cardiovascular disease risk.

Inflammation is a key factor in atherosclerosis. The transcription factor interferon regulatory factor-5 (IRF5) drives macrophages towards a pro-inflammatory state. We investigated the role of IRF5 in human atherosclerosis and plaque stability. Bulk RNA sequencing from the Carotid Plaque Imaging Project biobank were used to mine associations between major macrophage associated genes and transcription factors and human symptomatic carotid disease. Immunohistochemistry, proximity extension assays, and Helios cytometry by time of flight (CyTOF) were used for validation. The effect of IRF5 deficiency on carotid plaque phenotype and rupture in ApoE^−/− mice was studied in an inducible model of plaque rupture. Interferon regulatory factor-5 and ITGAX/CD11c were identified as the macrophage associated genes with the strongest associations with symptomatic carotid disease. Expression of IRF5 and ITGAX/CD11c correlated with the vulnerability index, pro-inflammatory plaque cytokine levels, necrotic core area, and with each other. Macrophages were the predominant CD11c-expressing immune cells in the plaque by CyTOF and immunohistochemistry. Interferon regulatory factor-5 immunopositive areas were predominantly found within CD11c⁺ areas with a predilection for the shoulder region, the area of the human plaque most prone to rupture. Accordingly, an inducible plaque rupture model of ApoE^−/−Irf5^−/− mice had significantly lower frequencies of carotid plaque ruptures, smaller necrotic cores, and less CD11c⁺ macrophages than their IRF5-competent counterparts. Using complementary evidence from data from human carotid endarterectomies and a murine model of inducible rupture of carotid artery plaque in IRF5-deficient mice, we demonstrate a mechanistic link between the pro-inflammatory transcription factor IRF5, macrophage phenotype, plaque inflammation, and its vulnerability to rupture. Macrophages perform both pro- and anti-atherogenic functions depending on their transcriptional status and activation. Using human carotid endarterectomies and a murine model of inducible rupture of carotid plaque, we show that the transcription factor interferon regulatory factor-5 (IRF5) promotes macrophage activation with the production of chemokines CCL2 and CCL4, and the expression of the integrin CD11c ,while it disables the production of proteins required for the uptake of apoptotic cells within the plaque (efferocytosis) such as MFEG8 and the integrin ITGB3. In doing so, IRF5 promotes inflammation and increases the necrotic core size enhancing plaque vulnerability to rupture. MFGE8, Milk fat globule—epidermal growth factor—factor VIII; CCL2, C–C motif chemokine ligand 2; CCL4, C–C motif chemokine ligand 4; ITGB3, Integrin subunit beta 3.