Vasundhara Kain

Resolvin D1 activates the inflammation resolving response at splenic and ventricular site following myocardial infarction leading to improved ventricular function

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 the 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 (3 μg/kg/day) was injected 3h 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 the 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.

Inflammation revisited: inflammation versus resolution of inflammation following myocardial infarction

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.

Obesity superimposed on aging magnifies inflammation and delays the resolving response after myocardial infarction

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.

Aging dysregulates D- and E-series resolvins to modulate cardiosplenic and cardiorenal network following myocardial infarction

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.

Simvastatin may induce insulin resistance through a novel fatty acid mediated cholesterol independent mechanism.

Statins are a class of oral drugs that are widely used for treatment of hypercholesterolemia. Recent clinical data suggest that chronic use of these drugs increases the frequency of new onset diabetes. Studies to define the risks of statin-induced diabetes and its underlying mechanisms are clearly necessary. We explored the possible mechanism of statin induced insulin resistance using a well-established cell based model and simvastatin as a prototype statin. Our data show that simvastatin induces insulin resistance in a cholesterol biosynthesis inhibition independent fashion but does so by a fatty acid mediated effect on insulin signaling pathway. These data may help design strategies for prevention of statin induced insulin resistance and diabetes in patients with hypercholesterolemia.

Cardiomyocyte-specific Bmal1 deletion in mice triggers diastolic dysfunction, extracellular matrix response, and impaired resolution of inflammation

The mammalian circadian clock consists of multiple transcriptional regulators that coordinate biological processes in a time-of-day-dependent manner. Cardiomyocyte-specific deletion of the circadian clock component, Bmal1 (aryl hydrocarbon receptor nuclear translocator-like protein 1), leads to age-dependent dilated cardiomyopathy and decreased lifespan in mice. We investigated whether cardiomyocyte-specific Bmal1 knockout (CBK) mice display early alterations in cardiac diastolic function, extracellular matrix (ECM) remodeling, and inflammation modulators by investigating CBK mice and littermate controls at 8 and 28 wk of age (i.e., prior to overt systolic dysfunction). Left ventricles of CBK mice exhibited (P < 0.05): 1) progressive abnormal diastolic septal annular wall motion and reduced pulmonary venous flow only at 28 wk of age; 2) progressive worsening of fibrosis in the interstitial and endocardial regions from 8 to 28 wk of age; 3) increased (>1.5 fold) expression of collagen I and III, as well as the matrix metalloproteinases MMP-9, MMP-13, and MMP-14 at 28 wk of age; 4) increased transcript levels of neutrophil chemotaxis and leukocyte migration genes (Ccl2, Ccl8, Cxcl2, Cxcl1, Cxcr2, Il1β) with no change in Il-10 and Il-13 genes expression; and 5) decreased levels of 5-LOX, HO-1 and COX-2, enzymes indicating impaired resolution of inflammation. In conclusion, genetic disruption of the cardiomyocyte circadian clock results in diastolic dysfunction, adverse ECM remodeling, and proinflammatory gene expression profiles in the mouse heart, indicating signs of early cardiac aging in CBK mice.

Interaction of 12/15-lipoxygenase with fatty acids alters the leukocyte kinetics leading to improved postmyocardial infarction healing

The metabolic transformation of fatty acids to form oxylipids using 12/15-lipoxygenase (LOX) can promote either resolving or nonresolving inflammation. However, the mechanism of how 12/15-LOX interacts with polyunsaturated fatty acids (PUFA) in postmyocardial infarction (post-MI) healing is unclear. Here, we reported the role of 12/15-LOX in post-MI cardiac remodeling in a PUFA [10% (wt/wt), 22 kcal]-enriched environment. Wild-type (WT; C57BL/6J) and 12/15-LOX-null (12/15-LOX-/-) male mice of 8-12 wk of age were fed a PUFA-enriched diet for 1 mo and subjected to permanent coronary artery ligation. Post-MI mice were monitored for day 1 or until day 5 along with standard diet-fed MI controls. No-MI surgery mice served as naïve controls. PUFA-fed WT and 12/15-LOX-/- mice improved ejection fraction and reduced lung edema greater than WT mice at day 5 post-MI (P < 0.05). Post-MI, neutrophil density was decreased in PUFA-fed WT and 12/15-LOX-/- mice at day 1 (P < 0.05). Deletion of 12/15-LOX in mice led to increased cytochrome P-450-derived bioactive lipid mediator epoxyeicosatrienoic acids (EETs), i.e., 11,12-EpETrE and 14,15-EpETrE, which were further enhanced by acute PUFA intake post-MI. Macrophage density was decreased in WT + PUFA and 12/15-LOX-/- mice compared with their respective standard diet-fed WT controls at day 5 post-MI. 12/15-LOX-/- + PUFA mice displayed an increased expression of chemokine (C-C motif) ligand 2 and reparative macrophages markers (Ym-1, Mrc-1, and Arg-1, all P < 0.05) in the infarcted area. Furthermore, 12/15-LOX-/- mice, with or without PUFA, showed reduced collagen deposition at day 5 post-MI compared with WT mice. In conclusion, deletion of 12/15-LOX and short-term exposure of PUFA promoted leukocyte clearance, thereby limiting cardiac remodeling and promoting an effective resolution of inflammation.NEW & NOTEWORTHY This study determined that 1) deletion of 12/15-lipoxygenase (LOX) promotes the generation of epoxyeicosatrienoic acids, the cytochrome P-450-derived metabolites in postmyocardial infarction (post-MI) healing; 2) acute exposure of fatty acids to 12/15-LOX-/- mice drives leukocyte (neutrophils and macrophages) clearance post-MI; and 3) metabolic transformation of fats is the significant contributor in leukocyte clearance to drive either resolving or nonresolving inflammation post-MI.

Heart functional and structural compendium of cardiosplenic and cardiorenal networks in acute and chronic heart failure pathology

Heart failure (HF) secondary to myocardial infarction (MI) is linked to kidney complications that comprise cellular, structural, functional, and survival indicators. However, HF research is focused on left ventricular (LV) pathology. Here, we determined comprehensive functional analysis of the LV using echocardiography in transition from acute heart failure (AHF) to progressive chronic heart failure (CHF) pathology and developed a histological compendium of the cardiosplenic and cardiorenal networks in pathological remodeling. In surgically induced MI using permanent coronary ligation, the LV dysfunction is pronounced, with myocardium necrosis, wall thinning, and 20-30% LV rupture events that indicated AHF and CHF pathological remodeling in C57BL/6 male mice (2-4 mo old, n = 50). Temporal LV function analysis indicated that fractional shortening and strain are reduced from day 1 to day 5 in AHF and sustained to advance to CHF from day 28 to day 56 compared with naïve control mice ( n = 6). During the transition of AHF ( day 1 to day 5) to advanced CHF ( day 28 to day 56), histological and cellular changes in the spleen were definite, with bimodal inflammatory responses in kidney inflammatory biomarkers. Likewise, there was a unidirectional, progressive, and irreversible deposition of compact collagen in the LV along with dynamic changes in the cardiosplenic and cardiorenal networks post-MI. The renal histology and injury markers suggested that cardiac injury triggers irreversible dysregulation that actively alters the cardiosplenic and cardiorenal networks. In summary, the novel strategies or pathways that modulate comprehensive cardiosplenic and cardiorenal networks in AHF and CHF would be effective approaches to study either cardiac repair or cardiac pathology. NEW & NOTEWORTHY The present compendium shows irreversible ventricular dysfunction as assessed by temporal echocardiography while histological and structural measurements of the spleen and kidney added a novel direction to study cardiosplenic and cardiorenal networks in heart failure pathology. Therefore, the consideration of systems biology and integrative approach is essential to develop novel treatments.

Obesity and Cardiometabolic Defects in Heart Failure Pathology

Obesity is a major global epidemic that sets the stage for diverse multiple pathologies, including cardiovascular disease. The obesity-related low-grade chronic inflamed milieu is more pronounced in aging and responsive to cardiac dysfunction in heart failure pathology. Metabolic dysregulation of obesity integrates with immune reservoir in spleen and kidney network. Therefore, an integrative systems biology approach is necessary to delay progressive cardiac alternations. The purpose of this comprehensive review is to largely discuss the impact of obesity on the cardiovascular pathobiology in the context of problems and challenges, with major emphasis on the diversified models, and to study cardiac remodeling in obesity. The information in this article is immensely helpful in teaching advanced undergraduate, graduate, and medical students about the advancement and impact of obesity on cardiovascular health.

Resolution Agonist 15-epi-Lipoxin A 4 Programs Early Activation of Resolving Phase in Post-Myocardial Infarction Healing

Following myocardial infarction (MI), overactive inflammation remodels the left ventricle (LV) leading to heart failure coinciding with reduced levels of 15-epi-Lipoxin A4 (15-epi LXA4). However, the role of 15-epi LXA4 in post-MI acute inflammatory response and resolving phase is unclear. We hypothesize that liposomal fusion of 15-epi-LXA4 (Lipo-15-epi-LXA4) or free 15-epi-LXA4 will expedite the resolving phase in post-MI inflammation. 8 to 12-week-old male C57BL/6 mice were subjected to permanent coronary artery ligation. Lipo-15-epi-LXA4 or 15-epi-LXA4 (1 µg/kg/day) was injected 3 hours post-MI for (d)1 or continued daily till d5. 15-epi-LXA4 activated formyl peptide receptor (FPR2) and GPR120 on alternative macrophages but inhibited GPR40 on classical macrophages in-vitro. The 15-epi-LXA4 injected mice displayed reduced LV and lung mass to body weight ratios and improved ejection fraction at d5 post-MI. In the acute phase of inflammation-(d1), 15-epi-LXA4 primes neutrophil infiltration with a robust increase of Ccl2 and FPR2 expression. During the resolving phase-(d5), 15-epi-LXA4 initiated rapid neutrophils clearance with persistent activation of FPR2 in LV. Compared to MI-control, 15-epi-LXA4 injected mice showed reduced renal inflammation along with decreased levels of ngal and plasma creatinine. In summary, 15-epi-LXA4 initiates the resolving phase early to discontinue inflammation post-MI, thereby reducing LV dysfunction.