Unresolved inflammation is a major contributor to the development of heart failure following myocardial infarction (MI). Pro-resolving lipid mediators, such as resolvins (e.g. RvD1), are biosynthesized endogenously. The role of RvD1 in resolving post-MI inflammation has not been elucidated due to its unstable nature. Here, we have tested the role for two forms of RvD1, after incorporation into liposomes (Lipo-RvD1) and its free acid form (RvD1) in left ventricle (LV) and splenic remodeling post-MI. 8 to 12-week old male, C57BL/6J-mice were subjected to coronary artery ligation and Lipo-RvD1 or RvD1 (3µg/kg/day) was injected 3 hr post-MI for day (d)1 or until d5. No-MI mice and saline-injected MI mice served as controls. RvD1 injected groups showed improved fractional shortening post-MI; preserving transient changes in the splenic reservoir compared to MI-saline. RvD1-groups showed an early exit of neutrophils from LV and spleen at d5 post-MI with an increased expression of lipoxin A4 receptor; (ALX; synonym formyl peptide receptor; FPR2) compared to MI-saline group. The levels of pro-resolving mediators RvD1, RvD2, Maresin 1 (MaR1) and Lipoxin A4 (LXA4) were increased in spleens from RvD1 injected mice at d5 post-MI. RvD1 administration reduced macrophage density, ccr5 and cxcl5 levels at d5 post-MI compared to saline injected mice (both, p<0.05). Increased transcripts of mrc-1, arg-1 and Ym-1; (all, p<0.05) suggest macrophage-mediated clearance of necrotic cells in RvD1-groups. RvD1 reduced the pro-fibrotic genes (colla1, coll2a1 and tnc (all; p<0.05) and decreased collagen deposition, thereby reducing post-MI fibrosis and thus stabilizing the extracellular matrix. In summary, RvD1 and Lipo-RvD1 promote the resolution of acute inflammation initiated by MI, thereby delaying the onset of heart failure.

Myocardial infarction (MI) is the main cause for the progression of the left ventricle towards congestive heart failure. The optimal healing after MI requires timely induction and resolution of inflammation. Primarily, there have been a number of strategies applied to inhibit the post-MI inflammation but approaches that focus on the resolution of inflammation have sparsely been used in the treatment of heart failure. The early attempts to inhibit post-MI inflammation resulted in adverse outcomes that were realized in heart failure trials. We provide here an overview on the cyclooxygenase (COX)- and lipoxygenase (LOX)-derived lipid mediators that are either impairing or resolving the post-MI inflammation. With the evolution of lipidomics there has been emerging novel bioactive-specialized lipid mediators that promise to resolve chronic inflammation rather than promoting inhibition. The current review is focused on post-MI immune cells kinetics and the unexplored array of lipid mediators that are coordinated by COX and LOX. Thus, an emphasis on COX and LOX poses key questions and potential for the development of novel targets in the heart failure treatment strategy. This updated dynamic approach aims to fuse basic pre-clinical discoveries and translational bioactive lipid-based resolvin discoveries that could be potentially used in the clinic for the treatment of heart failure.

Post-myocardial infarction (MI), overactive inflammation is the hallmark of aging, however, the mechanism is unclear. We hypothesized that excess influx of omega 6 fatty acids may impair resolution, thus impacting the cardiosplenic and cardiorenal network post-MI. Young and aging mice were fed on standard lab chow (LC) and excess fatty acid (safflower oil; SO)-enriched diet for 2 months and were then subjected to MI surgery. Despite similar infarct areas and left ventricle (LV) dysfunction post-MI, splenic mass spectrometry data revealed higher levels of arachidonic acid (AA) derived pro-inflammatory metabolites in young-SO, but minimal formation of docosanoids, D- and E- series resolvins in SO-fed aged mice. The aged mice receiving excess intake of fatty acids exhibit; 1) decreased lipoxygenases (5-,12-, and 15) in the infarcted LV; 2) lower levels of 14HDHA, RvD1, RvD5, protectin D1, 7(S)maresin1, 8-,11-,18-HEPE and RvE3 with high levels of tetranor-12-HETEs; 3) dual population of macrophages (CD11blow/F480high and CD11bhigh/F480high) with increased pro-inflammatory (CD11b+F4/80+Ly6Chi) phenotype and; 4) increased kidney injury marker NGAL with increased expression of TNF-ɑ and IL-1β indicating MI-induced non-resolving response compared with LC-group. Thus, excess fatty acid intake magnifies the post-MI chemokine signaling and inflames the cardiosplenic and cardiorenal network towards a non-resolving microenvironment in aging.

Polyunsaturated fatty acid (PUFA) intake has increased over the last 100 yr, contributing to the current obesogenic environment. Obesity and aging are prominent risk factors for myocardial infarction (MI). How obesity interacts with aging to alter the post-MI response, however, is unclear. We tested the hypothesis that obesity in aging mice would impair the resolution of post-MI inflammation. PUFA diet (PUFA aging group) feeding to 12-mo-old C57BL/6J mice for 5 mo showed higher fat mass compared with standard lab chow (LC)-fed young (LC young group; 3-5 mo old) or aging alone control mice (LC aging group). LC young, LC aging, and PUFA aging mice were subjected to coronary artery ligation to induce MI. Despite similar infarct areas post-MI, plasma proteomic profiling revealed higher VCAM-1 in the PUFA aging group compared with LC young and LC aging groups, leading to increased neutrophil infiltration in the PUFA aging group (P<0.05). Macrophage inflammatory protein-1γ and CD40 were also increased at day 1, and myeloperoxidase remained elevated at day 5, an observation consistent with delayed wound healing in the PUFA aging group. Lipidomic analysis showed higher levels of arachidonic acid and 12(S)-hydroxyeicosatetraenoic acid at day 1 post-MI in the PUFA aging group compared with the LC aging group (all P<0.05), thereby mediating neutrophil extravasation in the PUFA aging group. The inflammation-resolving enzymes 5-lipoxygenase, cyclooxygenase-2, and heme oxyegnase-1 were altered to delay wound healing post-MI in the PUFA aging group compared with LC young and LC aging groups. PUFA aging magnifies the post-MI inflammatory response and impairs the healing response by stimulating prolonged neutrophil trafficking and proinflammatory lipid mediators.

Inflammation promotes healing in myocardial infarction but if unresolved, it leads to heart failure. To define the inflammatory and resolving responses, we quantified leukocyte trafficking and specialized proresolving mediators (SPMs) in the infarcted left ventricle and spleen after myocardial infarction, with the goal of distinguishing inflammation from its resolution. Our data suggest that the spleen not only served as a leukocyte reservoir but also was the site where SPMs were actively generated after coronary ligation in mice. Before myocardial infarction, SPMs were more abundant in the spleen than in the left ventricle. At day 1 after coronary ligation, the spleen was depleted of leukocytes, a phenomenon that was associated with greater numbers of leukocytes in the infarcted left ventricle and increased generation of SPMs at the same site, particularly resolvins, maresin, lipoxins, and protectin. In addition, the infarcted left ventricle showed increased expression of genes encoding lipoxygenases and enhanced production of SPMs generated by these enzymes. We found that macrophages were necessary for SPM generation. The abundance of SPMs in the spleen before myocardial infarction and increased SPM concentrations in the infarcted left ventricle within 24 hours after myocardial infarction were temporally correlated with the resolution of inflammation. Thus, the acute inflammatory response coincided with the active resolving phase in post-myocardial infarction and suggests that further investigation into macrophage-derived SPMs in heart failure is warranted.

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ObjectiveRecently, we observed that the specialized proresolving mediator (SPM) entity resolvin D1 activates lipoxin A4/formyl peptide receptor 2 (ALX/FPR2), which facilitates cardiac healing and persistent inflammation is a hallmark of impaired cardiac repair in aging. Splenic leukocyte-directed SPMs are essential for the safe clearance of inflammation and cardiac repair after injury; however, the target of SPMs remains undefined in cardiac healing and repair.MethodsTo define the mechanistic basis of ALX/FPR2 as a resolvin D1 target, ALX/FPR2-null mice were examined extensively. The systolic-diastolic heart function was assessed using echocardiography, leukocytes were phenotyped using flow cytometry, and SPMs were quantitated using mass spectrometry. The presence of cardiorenal syndrome was validated using histology and renal markers.ResultsLack of ALX/FPR2 led to the development of spontaneous obesity and diastolic dysfunction with reduced survival with aging. After cardiac injury, ALX/FPR2−/− mice showed lower expression of lipoxygenases (−5, −12, −15) and a reduction in SPMs in the infarcted left ventricle and spleen, indicating nonresolving inflammation. Reduced SPM levels in the infarcted heart and spleen are suggestive of impaired cross-talk between the injured heart and splenic leukocytes, which are required for the resolution of inflammation. In contrast, cyclooxygenases (−1 and −2) were over amplified in the infarcted heart. Together, these results suggest interorgan signaling in which the spleen acts as both an SPM biosynthesizer and supplier in acute heart failure. ALX/FPR2 dysfunction magnified obesogenic cardiomyopathy and renal inflammation (↑NGAL, ↑TNF-α, ↑CCL2, ↑IL-1β) with elevated plasma creatinine levels in aging mice. At the cellular level, ALX/FPR2−/− mice showed impairment of macrophage phagocytic function ex-vivo with expansion of neutrophils after myocardial infarction.ConclusionsLack of ALX/FPR2 induced obesity, reduced the life span, amplified leukocyte dysfunction, and facilitated profound interorgan nonresolving inflammation. Our study shows the integrative and indispensable role of ALX/FPR2 in lipid metabolism, cardiac inflammation–resolution processes, obesogenic aging, and renal homeostasis.

PRIP-Interacting protein with methyl transferase domain (PIMT) serves as a molecular bridge between CREB-binding protein (CBP)/ E1A binding protein p300 (Ep300) -anchored histone acetyl transferase and the Mediator complex sub-unit1 (Med1) and modulates nuclear receptor transcription. Here, we report that ERK2 phosphorylates PIMT at Ser298 and enhances its ability to activate PEPCK promoter. We observed that PIMT is recruited to PEPCK promoter and adenoviral-mediated over-expression of PIMT in rat primary hepatocytes up-regulated expression of gluconeogenic genes including PEPCK. Reporter experiments with phosphomimetic PIMT mutant (PIMTS298D) suggested that conformational change may play an important role in PIMT-dependent PEPCK promoter activity. Overexpression of PIMT and Med1 together augmented hepatic glucose output in an additive manner. Importantly, expression of gluconeogenic genes and hepatic glucose output were suppressed in isolated liver specific PIMT knockout mouse hepatocytes. Furthermore, consistent with reporter experiments, PIMTS298D but not PIMTS298A augmented hepatic glucose output via up-regulating the expression of gluconeogenic genes. Pharmacological blockade of MAPK/ERK pathway using U0126, abolished PIMT/Med1-dependent gluconeogenic program leading to reduced hepatic glucose output. Further, systemic administration of T4 hormone to rats activated ERK1/2 resulting in enhanced PIMT ser298 phosphorylation. Phosphorylation of PIMT led to its increased binding to the PEPCK promoter, increased PEPCK expression and induction of gluconeogenesis in liver. Thus, ERK2-mediated phosphorylation of PIMT at Ser298 is essential in hepatic gluconeogenesis, demonstrating an important role of PIMT in the pathogenesis of hyperglycemia.