Mechanisms mediating reduced responsiveness of neonatal neutrophils to lipoxin A4

Resolution of chronic inflammation and cancer

Chronic inflammation poses challenges to effective cancer treatment. Although anti-inflammatory therapies have shown short-term benefits, their long-term implications may be unfavorable because they fail to initiate the necessary inflammatory responses. Recent research underscores the promise of specialized pro-resolving mediators, which play a role in modulating the cancer microenvironment by promoting the resolution of initiated inflammatory processes and restoring tissue hemostasis. This review addresses current insights into how inflammation contributes to cancer pathogenesis and explores recent strategies to resolve inflammation associated with cancer.

Lipid droplets and lipid mediators in viral infection and immunity

Lipid droplets (LDs) contribute to key pathways important for the physiology and pathophysiology of cells. In a homeostatic view, LDs regulate the storage of neutral lipids, protein sequestration, removal of toxic lipids and cellular communication; however, recent advancements in the field show these organelles as essential for various cellular stress response mechanisms, including inflammation and immunity, with LDs acting as hubs that integrate metabolic and inflammatory processes. The accumulation of LDs has become a hallmark of infection, and is often thought to be virally driven; however, recent evidence is pointing to a role for the upregulation of LDs in the production of a successful immune response to viral infection. The fatty acids housed in LDs are also gaining interest due to the role that these lipid species play during viral infection, and their link to the synthesis of bioactive lipid mediators that have been found to have a very complex role in viral infection. This review explores the role of LDs and their subsequent lipid mediators during viral infections and poses a paradigm shift in thinking in the field, whereby LDs may play pivotal roles in protecting the host against viral infection.

Alzheimer's Disease and Specialized Pro-Resolving Lipid Mediators: Do MaR1, RvD1, and NPD1 Show Promise for Prevention and Treatment?

Alzheimer's disease (AD) is a common neurodegenerative disease and a major contributor to progressive cognitive impairment in an aging society. As the pathophysiology of AD involves chronic neuroinflammation, the resolution of inflammation and the group of lipid mediators that actively regulate it-i.e., specialized pro-resolving lipid mediators (SPMs)-attracted attention in recent years as therapeutic targets. This review focuses on the following three specific SPMs and summarizes their relationships to AD, as they were shown to effectively address and reduce the risk of AD-related neuroinflammation: maresin 1 (MaR1), resolvin D1 (RvD1), and neuroprotectin D1 (NPD1). These three SPMs are metabolites of docosahexaenoic acid (DHA), which is contained in fish oils and is thus easily available to the public. They are expected to become incorporated into promising avenues for preventing and treating AD in the future.

Proresolving Lipid Mediators: Endogenous Modulators of Oxidative Stress

Specialized proresolving mediators (SPMs) are a novel class of endogenous lipids, derived by ω-6 and ω-3 essential polyunsaturated fatty acids such as arachidonic acid (AA), docosahexaenoic acid (DHA), and eicosapentaenoic acid (EPA) that trigger and orchestrate the resolution of inflammation, which is the series of cellular and molecular events that leads to spontaneous regression of inflammatory processes and restoring of tissue homeostasis. These lipids are emerging as highly effective therapeutic agents that exert their immunoregulatory activity by activating the proresolving pathway, as reported by a consistent bulk of evidences gathered in the last two decades since their discovery. The production of reactive oxygen (ROS) and nitrogen (RNS) species by immune cells plays indeed an important role in the inflammatory mechanisms of host defence, and it is now clear that oxidative stress, viewed as an imbalance between such species and their elimination, can lead to many chronic inflammatory diseases. This review, the first of its kind, is aimed at exploring the manifold effects of SPMs on modulation of reactive species production, along with the mechanisms through which they either inhibit molecular signalling pathways that are activated by oxidative stress or induce the expression of endogenous antioxidant systems. Furthermore, the possible role of SPMs in oxidative stress-mediated chronic disorders is also summarized, suggesting not only that their anti-inflammatory and proresolving properties are strictly associated with their antioxidant role but also that these endogenous lipids might be exploited in the treatment of several pathologies in which uncontrolled production of ROS and RNS or impairment of the antioxidant machinery represents a main pathogenetic mechanism.

Immunoresolvents in asthma and allergic diseases: Review and update

Asthma and allergic diseases are inflammatory conditions developed by excessive reaction of the immune system against normally harmless environmental substances. Although acute inflammation is necessary to eradicate the damaging agents, shifting to chronic inflammation can be potentially detrimental. Essential fatty-acids-derived immunoresolvents, namely, lipoxins, resolvins, protectins, and maresins, are anti-inflammatory compounds that are believed to have protective and beneficial effects in inflammatory disorders, including asthma and allergies. Accordingly, impaired biosynthesis and defective production of immunoresolvents could be involved in the development of chronic inflammation. In this review, recent evidence on the anti-inflam]matory effects of immunoresolvents, their enzymatic biosynthesis routes, as well as their receptors are discussed.

Lipoxin A4 encapsulated in PLGA microparticles accelerates wound healing of skin ulcers

Lipoxin A₄ (LXA₄) is involved in the resolution of inflammation and wound healing; however, it is extremely unstable. Thus, to preserve its biological activities and confer stability, we encapsulated LXA₄ in poly-lactic-co-glycolic acid (PLGA) microparticles (LXA₄-MS) and assessed its application in treating dorsal rat skin lesions. Ulcers were sealed with fibrin adhesive and treated with either LXA₄-MS, unloaded microparticles (Un-MS), soluble LXA₄, or PBS/glue (vehicle). All groups were compared at 0, 2, 7, and 14 days post-lesions. Our results revealed that LXA₄-MS accelerated wound healing from day 7 and reduced initial ulcer diameters by 80%. Soluble LXA₄, Un-MS, or PBS closed wounds by 60%, 45%, and 39%, respectively. LXA₄-MS reduced IL-1β and TNF-α, but increased TGF-β, collagen deposition, and the number of blood vessels. Compared to other treatments, LXA₄-MS reduced inflammatory cell numbers, myeloperoxidase (MPO) concentration, and metalloproteinase-8 (MMP8) mRNA in scar tissue, indicating decreased neutrophil chemotaxis. In addition, LXA₄-MS treatment increased macrophages and IL-4, suggesting a positive impact on wound healing. Finally, we demonstrated that WRW4, a selective LXA₄ receptor (ALX) antagonist, reversed healing by 50%, indicating that LXA₄ must interact with ALX to induce wound healing. Our results show that LXA₄-MS could be used as a pharmaceutical formulation for the treatment of skin ulcers.

Signal transduction involved in lipoxin A4‑induced protection of tubular epithelial cells against hypoxia/reoxygenation injury

Previous studies have reported that lipoxin A₄ (LXA₄) may exert a renoprotective effect on ischemia/reperfusion injury in various animal models. The underlying mechanism of LXA₄-induced renoprotection during ischemia/reperfusion injury remains to be elucidated. The present study investigated LXA₄-induced protection on renal tubular cells subjected to hypoxia/reoxygenation (H/R) injury, and determined the effects of peroxisome proliferator-activated receptor-γ (PPARγ) and heme oxygenase-1 (HO-1) on LXA₄ treatment. HK-2 human tubular epithelial cells exposed to H/R injury were pretreated with LXA₄, signal molecule inhibitors or the HO-1 inhibitor zinc protoporphyrin-IX, or were transfected with PPARγ small interfering RNA (siRNA) or nuclear factor E2-related factor 2 (Nrf2) siRNA. The protein and mRNA expression levels of PPARγ and HO-1 were analyzed using western blotting and reverse transcription-quantitative polymerase chain reaction. Binding activity of Nrf2 to the HO-1 E1 enhancer was determined using chromatin immunoprecipitation. Nrf2 binding to the HO-1 antioxidant responsive element (ARE) was assessed using electrophoretic mobility shift assay. Preincubation of cells with LXA₄ exposed to H/R injury led to a decreased production of inducible nitrogen oxide synthase, malondialdehyde, γ-glutamyl transpeptidase, leucine aminopeptidase and N-acetyl-β-glucosaminidase. In addition, LXA₄ pretreatment increased cell viability, protein and mRNA expression levels of PPARγ and HO-1 and PPARγ and HO-1 promoter activity. SB20358 is a p38 mitogen-activated protein kinase (p38 MAPK) pathway inhibitor, which reduced LXA₄-induced PPARγ expression levels. LXA₄ treatment upregulated p38 MAPK activation, Nrf2 nuclear translocation and increased binding activity of Nrf2 to HO-1 ARE and E1 enhancer in cells exposed to H/R injury. Transfection of the cells with PPARγ siRNA reduced the LXA₄-induced Nrf2 translocation. Transfection of the cells with PPARγ siRNA or Nrf2 siRNA also reduced the LXA₄-induced increase in HO-1 expression. In conclusion, LXA₄-induced protection of renal tubular cells against H/R injury was associated with the induction of PPARγ and HO-1, via activation of the p38 MAPK pathway, as well as Nrf2 nuclear translocation and binding to HO-1 ARE and E1 enhancer. Therefore, LXA₄-induced renoprotection is associated with activation of the p38 MAPK/PPARγ/Nrf2-ARE/HO-1 pathway.

BML-111 Attenuates Renal Ischemia/Reperfusion Injury Via Peroxisome Proliferator-Activated Receptor-α-Regulated Heme Oxygenase-1

We examine whether BML-111, a lipoxin receptor agonist, inhibits renal ischemia/reperfusion (I/R) injury, and whether peroxisome proliferator-activated receptor-α (PPARα) or heme oxygenase-1 (HO-1) is involved in protective effects of BML-111 on kidney against I/R injury. Rats subjected to renal I/R injury were treated with or without BML-111. Renal histological and immunohistochemical studies were performed. Expressions of phosphorylated p38 mitogen-activated protein kinase (pp38 MAPK), phosphorylated PPARα (pPPARα), and HO-1 were assessed in NRK-52E cells exposed to BML-111. The binding activity of PPARα to peroxisome proliferator-responsive element (PPRE) on HO-1 promoter in the cells was determined. BML-111 treatment resulted in a marked reduction in the severity of histological features of renal I/R injury, and attenuated the rise in renal myeloperoxidase and malondialdehyde, blood urea nitrogen and creatinine, urinary N-acetyl-β-glucosaminidase, and leucine aminopeptidase levels caused by I/R injury. BML-111 stimulated the renal expressions of pPPARα and HO-1, and cellular messenger RNA (mRNA) and protein expressions of pPPARα and HO-1 which were both blocked by GW6471, a selective PPARα antagonist, and ZnPP-IX, a specific inhibitor of HO-1 pretreatment. The pp38 MAPK inhibitor SB203580 blocked the BML-111-induced expressions of pp38 MAPK, pPPARα, and HO-1 in NRK-52E cells. The binding activity of PPARα to PPRE in nuclear extracts of NRK-52E cells was enhanced by treatment of the cells with BML-111, and was suppressed by GW6471 and SB203580. BML-111 protects the kidney against I/R injury via activation of p38 MAPK/PPARα/HO-1 pathway.

Pro-Resolving Lipid Mediators Improve Neuronal Survival and Increase Aβ42 Phagocytosis

Inflammation in the brain is a prominent feature in Alzheimer's disease (AD). Recent studies suggest that chronic inflammation can be a consequence of failure to resolve the inflammation. Resolution of inflammation is mediated by a family of lipid mediators (LMs), and the levels of these specialized pro-resolving mediators (SPMs) are reduced in the hippocampus of those with AD. In the present study, we combined analysis of LMs in the entorhinal cortex (ENT) from AD patients with in vitro analysis of their direct effects on neurons and microglia. We probed ENT, an area affected early in AD pathogenesis, by liquid chromatography-tandem mass spectrometry (LC-MS-MS), and found that the levels of the SPMs maresin 1 (MaR1), protectin D1 (PD1), and resolvin (Rv) D5, were lower in ENT of AD patients as compared to age-matched controls, while levels of the pro-inflammatory prostaglandin D2 (PGD2) were higher in AD. In vitro studies showed that lipoxin A4 (LXA4), MaR1, resolvin D1 (RvD1), and protectin DX (PDX) exerted neuroprotective activity, and that MaR1 and RvD1 down-regulated β-amyloid (Aβ)42-induced inflammation in human microglia. MaR1 exerted a stimulatory effect on microglial uptake of Aβ42. Our findings give further evidence for a disturbance of the resolution pathway in AD, and indicate that stimulating this pathway is a promising treatment strategy for AD.

Gingival crevicular fluid interleukin-8 and lipoxin A4 levels of smokers and nonsmokers with different periodontal status: a cross-sectional study

BACKGROUND AND OBJECTIVE

Smoking is an important risk factor for periodontal disease and effects the pathogenesis of the disease. This study evaluated the impact of smoking on gingival crevicular fluid interleukin-8 (IL-8) and lipoxin A4 (LxA4 ) levels in patients with and without periodontal disease.

MATERIAL AND METHODS

A total of 122 participants were grouped as follows: smokers with generalized aggressive periodontitis (S-GAgP, n = 15); smokers with chronic periodontitis (S-CP, n = 17); smokers with gingivitis (SG, n = 15); smokers classified as periodontally healthy (SH, n = 15); nonsmokers with generalized aggressive periodontitis (N-GAgP, n = 15); nonsmokers with chronic periodontitis (N-CP, n = 15); nonsmokers with gingivitis (NG, n = 15); and nonsmokers classified as periodontally healthy (NH, n = 15). Gingival index, plaque index, probing pocket depth and clinical attachment level were recorded. Gingival crevicular fluid IL-8 and LxA4 levels were analyzed by ELISA.

RESULTS

Gingival crevicular fluid IL-8 levels varied among groups, as follows: S-GAgP>S-CP>SG>SH and N-GAgP>N-CP>NG>NH. The gingival crevicular fluid IL-8 levels were significantly higher in the S-GAgP group compared with the N-GAgP group and in the S-CP group compared with the N-CP group (p < 0.05); differences between the SG and NG and the SH and NH groups were not statistically significant (p > 0.05). Gingival crevicular fluid LxA4 levels also varied among groups, but in an inverse direction when compared with the IL-8 levels, as follows: S-GAgP<S-CP<SG and N-GAgP<N-CP<NG. (The gingival crevicular fluid LxA4 levels in SH and NH groups were below the limits of detection.) The gingival crevicular fluid LxA4 levels were significantly lower in the S-GAgP group than in the N-GAgP group and in the S-CP group than in the N-CP group (p < 0.05); differences between the SG and NG groups were not statistically significant (p > 0.05).

CONCLUSION

The study findings suggest that the observed increases in gingival crevicular fluid IL-8 levels and decreases in gingival crevicular fluid LxA4 levels reflect changes in immune and inflammatory responses that occur as a result of smoking.

Lipoxins: nature's way to resolve inflammation

An effective host defense mechanism involves inflammation to eliminate pathogens from the site of infection, followed by the resolution of inflammation and the restoration of tissue homeostasis. Lipoxins are endogenous anti-inflammatory, pro-resolving molecules that play a vital role in reducing excessive tissue injury and chronic inflammation. In this review, the mechanisms of action of lipoxins at the site of inflammation and their interaction with other cellular signaling molecules and transcription factors are discussed. Emphasis has also been placed on immune modulatory role(s) of lipoxins. Lipoxins regulate components of both the innate and adaptive immune systems including neutrophils, macrophages, T-, and B-cells. Lipoxins also modulate levels of various transcription factors such as nuclear factor κB, activator protein-1, nerve growth factor-regulated factor 1A binding protein 1, and peroxisome proliferator activated receptor γ and control the expression of many inflammatory genes. Since lipoxins and aspirin-triggered lipoxins have clinical relevance, we discuss their important role in clinical research to treat a wide range of diseases like inflammatory disorders, renal fibrosis, cerebral ischemia, and cancer. A brief overview of lipoxins in viral malignancies and viral pathogenesis especially the unexplored role of lipoxins in Kaposi’s sarcoma-associated herpes virus biology is also presented.

Effects of Lipoxin A4 on antimicrobial actions of neutrophils in sepsis

In sepsis, hyperactivation of neutrophils can lead to tissue injury. Later, neutrophil dysregulation with reduced levels of migration, decreased apoptosis and inadequate phagocytosis may impair the host׳s ability to clear infection. Lipoxin A4 (LXA4) is a pro-resolution lipid mediator which reduces neutrophil migration and inflammatory mediator expression. As neutrophil migration and activation are important in bacterial clearance, the role of LXA4 in regulating neutrophil function for bacterial clearance is unclear. Using the cecal ligation and puncture (CLP) rat model of sepsis, LXA4 given after 1h reduced blood bacterial load at 24h. LXA4 treatment decreased neutrophil migration to the peritoneum but augmented blood neutrophil phagocytic ability and promoted apoptosis without affecting free radical production. In contrast, LXA4 increased peritoneal neutrophil phagocytic ability without affecting apoptosis or free radical production suggesting that in vivo effects of LXA4 were compartment specific. To investigate if LXA4 acted directly on neutrophils, blood and peritoneal leukocytes were taken from CLP rats 1h after surgery and incubated ex vivo with and without LXA4. LXA4 (1nM) increased phagocytosis in blood neutrophils without affecting apoptosis or free radical production. Ex vivo LXA4 had no effect on peritoneal neutrophils which suggests that LXA4 enhanced peritoneal neutrophil phagocytic ability in vivo by an indirect mechanism. The results suggest that LXA4 reduced neutrophil migration, but increased neutrophil bacteria clearing function without excessive free radical production. This phenotype was associated with reduced blood bacteria load.

Control of myeloid cell trafficking in resolution

Following tissue injury or microbial invasion, neutrophils are robustly recruited to inflammatory loci, which is a hallmark of the host inflammatory response. This event initiates a series of processes required to activate resolution, including recruitment of monocytes, clearance of microbes, cellular debris and apoptotic neutrophils, the egress of phagocytes and, ultimately, regain of tissue homeostasis. Substantial evidence now signifies that resolution of inflammation is a highly coordinated, active process dictated by the spatial-temporal generation of proresolving mediators that act on specific receptors to modulate cell and tissue reactivity. This review will focus on the mediators, targets and pathways initiated to orchestrate resolution. Importantly, disruption of the key processes involved in inflammatory resolution could result in delayed restoration of tissue homeostasis, leading to fibrosis and/or persistent inflammation.

Decreased anti-inflammatory responses to vitamin D in neonatal neutrophils

Neutrophil activity is prolonged in newborns, suggesting decreased exposure and/or responses to immunosuppressive modulators, such as 1,25-hydroxyvitamin D(3) (1,25-vit D(3)). We hypothesized that 1,25-vit D(3) suppresses neutrophil activation and that this response is impaired in newborns. Consistent with this, 1,25-vit D(3) decreased LPS-induced expression of macrophage inflammatory protein-1β and VEGF in adult, but not neonatal, neutrophils. Expression of vitamin D receptor (VDR) and 25-hydroxyvitamin D(3)-1α-hydroxylase was reduced in neonatal, relative to adult neutrophils. Moreover, 1,25-vit D(3) induced VDR gene expression in activated adult, but not neonatal, neutrophils. 1,25-vit D(3) also suppressed expression of cyclooxygenase-2 and induced expression of 5-lipoxygenase in LPS-exposed adult neutrophils, while neonatal cells were not affected. 1,25-vit D(3) had no effect on respiratory burst in either adult or neonatal cells. Anti-inflammatory activity of vitamin D is impaired in neonatal neutrophils, and this may be due to decreased expression of VDR and 1α-hydroxylase. Insensitivity to 1,25-vit D(3) may contribute to chronic inflammation in neonates.

Molecular regulators of resolution of inflammation: potential therapeutic targets in the reproductive system

Inflammatory processes are central to reproductive events including ovulation, menstruation, implantation and labour, while inflammatory dysregulation is a feature of numerous reproductive pathologies. In recent years, there has been much research into the endogenous mechanisms by which inflammatory reactions are terminated and tissue homoeostasis is restored, a process termed resolution. The identification and characterisation of naturally occurring pro-resolution mediators including lipoxins and annexin A1 has prompted a shift in the field of anti-inflammation whereby resolution is now observed as an active process, triggered as part of a normal inflammatory response. This review will address the process of resolution, discuss available evidence for expression of pro-resolution factors in the reproductive tract and explore possible roles for resolution in physiological reproductive processes and associated pathologies.

Serum levels of lipoxin A(4) do not predict the development of subsequent asthma among young children with acute bronchiolitis

BACKGROUND

Acute bronchiolitis frequently causes wheezing in infants and young children, although its relationship to asthma remains unclear. We hypothesized that serum lipoxin A(4) levels may be used as an early predictive biomarker of subsequent asthma in young children with acute bronchiolitis.

METHODS

We recruited 69 children who were divided into 3 groups: 47 children younger than 24 months with acute bronchiolitis as an experimental group (Group 1); 11 children aged 2-24 months with viral acute gastroenteritis as a non-allergic control group (Group 2); and 11 children older than 24 months with physician-diagnosed asthma exacerbations as an asthma control group (Group 3). We determined white blood cell counts, eosinophil counts, and serum levels of C-reactive protein, interleukin-4, interleukin-5, prostaglandin E(2), tumor necrosis factor-alpha, and lipoxin A(4).

RESULTS

The mean serum levels of lipoxin A(4) in the groups with acute bronchiolitis (1), acute gastroenteritis (2), and asthma (3) were 0.0430.028, 0.0540.015, and 0.0510.031 ng/ml, respectively. When compared by t-tests, there were no significant differences between Groups 1 and 2, or Groups 1 and 3 (p0.05), despite a significant difference between Groups 2 and 3 (p=0.0392). In a final regression model, serum lipoxin A(4) levels were positively correlated with age, female gender, white blood cell counts, and interleukin-5 levels in all patients, while asthma patients had lower serum lipoxin A(4) levels compared to the other two groups.

CONCLUSION

Serum levels of lipoxin A(4) cannot be used as an early predictive diagnostic marker for asthma in young children with acute bronchiolitis.

Vagal nerve stimulation in prevention and management of coronary heart disease

Coronary heart disease (CHD) that is due to atherosclerosis is associated with low-grade systemic inflammation. Congestive cardiac failure and arrhythmias that are responsible for mortality in CHD can be suppressed by appropriate vagal stimulation that is anti-inflammatory in nature. Acetylcholine, the principal vagal neurotransmitter, is a potent anti-inflammatory molecule. Polyunsaturated fatty acids (PUFAs) augment acetylcholine release, while acetylcholine can enhance the formation of prostacyclin, lipoxins, resolvins, protectins and maresins from PUFAs, which are anti-inflammatory and anti-arrhythmic molecules. Furthermore, plasma and tissue levels of PUFAs are low in those with CHD and atherosclerosis. Hence, vagal nerve stimulation is beneficial in the prevention of CHD and cardiac arrhythmias. Thus, measurement of catecholamines, acetylcholine, various PUFAs, and their products lipoxins, resolvins, protectins and maresins in the plasma and peripheral leukocytes, and vagal tone by heart rate variation could be useful in the prediction, prevention and management of CHD and cardiac arrhythmias.

PPAR-gamma activation as an anti-inflammatory therapy for respiratory virus infections

Newly emerged influenza viruses have attracted extensive attention due to their high infectivity, proinflammatory actions, and potential to induce worldwide pandemics. Frequent mutations and gene reassortments between viruses complicate the development of protective vaccines and antiviral therapeutics. In contrast, targeting the host response for the development of novel cost-effective, broad-based prophylactic or therapeutic agents holds greater promise. Since inflammation often parallels the development of productive immune responses, virus-induced pulmonary inflammation and injury represents an additional challenge to the development of broad-based immunotherapeutics. Excessive inflammatory responses to respiratory viruses, also known as "cytokine storm," are largely due to immune dysregulation that manifests as proinflammatory cytokine secretion. In addition to modulating lipid and glucose metabolism, peroxisome proliferator-activated receptors (PPAR) play important roles in antagonizing core inflammatory pathways such as NF-kappaB, AP1, and STAT. Their role in regulating inflammatory responses caused by pulmonary pathogens is receiving increasing attention, setting the stage for the discovery of novel applications for anti-diabetic and lipid-lowering drugs. This review focuses on the potential use of PPAR-gamma agonists to downregulate the inflammatory responses to respiratory virus-related pulmonary inflammation.

Lipoxin A4 may function as an endogenous anti-arrhythmic molecule

Cardiac arrhythmias cause significant morbidity and mortality in patients with coronary heart disease, hypertension, and congestive cardiac failure and in the elderly. Inflammation, oxidative injury, altered myocyte metabolism, extracellular matrix remodeling and fibrosis initiate and perpetuate cardiac arrhythmias, especially atrial fibrillation. Enhanced myeloperoxidase (MPO) activity by infiltrating activated leukocytes could bind to myocardial cells and cause fibrosis resulting in the initiation and progression of arrhythmias. Supplementation of eicosapentaenoic and docosahexaenoic acids (EPA and DHA, respectively) suppresses arrhythmias. EPA and DHA form precursors to anti-inflammatory lipid molecules: lipoxins, resolvins, protectins and maresins that are known to suppress inflammation, have anti-fibrotic actions and inhibit MPO activity. Hence, it is likely that leukocyte and/or myocardial deficiency of EPA and DHA and consequent reduced formation of lipoxins, resolvins, protectins and maresins enhance inflammation and MPO activity that leads to myocardial damage and fibrosis and initiation and progression of cardiac arrhythmias. Based on these evidences, I propose that lipoxins, resolvins and protectins function as endogenous anti-arrhythmic molecules and their stable synthetic analogs could be useful in the management of cardiac arrhythmias.

Hyperoxia-induced neonatal rat lung injury involves activation of TGF-{beta} and Wnt signaling and is protected by rosiglitazone

Despite tremendous technological and therapeutic advances, bronchopulmonary dysplasia (BPD) remains a leading cause of respiratory morbidity in very low birth weight infants, and there are no effective preventive and/or therapeutic options. We have previously reported that hyperoxia-induced neonatal rat lung injury might be prevented by rosiglitazone (RGZ). Here, we characterize 1) perturbations in wingless/Int (Wnt) and transforming growth factor (TGF)-beta signaling, and 2) structural aberrations in lung morphology following 7-day continuous in vivo hyperoxia exposure to neonatal rats. We also tested whether treatment of neonatal pups with RGZ, concomitant to hyperoxia, could prevent such aberrations. Our study revealed that hyperoxia caused significant upregulation of Wnt signaling protein markers lymphoid enhancer factor 1 (Lef-1) and beta-catenin and TGF-beta pathway transducers phosphorylated Smad3 and Smad7 proteins in whole rat lung extracts. These changes were also accompanied by upregulation of myogenic marker proteins alpha-smooth muscle actin (alpha-SMA) and calponin but significant downregulation of the lipogenic marker peroxisome proliferator-activated receptor-gamma (PPARgamma) expression. These molecular perturbations were associated with reduction in alveolar septal thickness, radial alveolar count, and larger alveoli in the hyperoxia-exposed lung. These hyperoxia-induced molecular and morphological changes were prevented by systemic administration of RGZ, with lung sections appearing near normal. This is the first evidence that in vivo hyperoxia induces activation of both Wnt and TGF-beta signal transduction pathways in lung and of its near complete prevention by RGZ. Hyperoxia-induced arrest in alveolar development, a hallmark of BPD, along with these molecular changes strongly implicates these proteins in hyperoxia-induced lung injury. Administration of PPARgamma agonists may thus be a potential strategy to attenuate hyperoxia-induced lung injury and subsequent BPD.