Pharmacokinetics and Changes in Lipid Mediator Profiling after Consumption of Specialized Pro-Resolving Lipid-Mediator-Enriched Marine Oil in Healthy Subjects

Omega-3 polyunsaturated fatty acids (PUFAs) play a vital role in human health, well-being, and the management of inflammatory diseases. Insufficient intake of omega-3 is linked to disease development. Specialized pro-resolving mediators (SPMs) are derived from omega-3 PUFAs and expedite the resolution of inflammation. They fall into categories known as resolvins, maresins, protectins, and lipoxins. The actions of SPMs in the resolution of inflammation involve restricting neutrophil infiltration, facilitating the removal of apoptotic cells and cellular debris, promoting efferocytosis and phagocytosis, counteracting the production of pro-inflammatory molecules like chemokines and cytokines, and encouraging a pro-resolving macrophage phenotype. This is an experimental pilot study in which ten healthy subjects were enrolled and received a single dose of 6 g of an oral SPM-enriched marine oil emulsion. Peripheral blood was collected at baseline, 3, 6, 9, 12, and 24 h post-administration. Temporal increases in plasma and serum SPM levels were found by using LC-MS/MS lipid profiling. Additionally, we characterized the temporal increases in omega-3 levels and established fundamental pharmacokinetics in both aforementioned matrices. These findings provide substantial evidence of the time-dependent elevation of SPMs, reinforcing the notion that oral supplementation with SPM-enriched products represents a valuable source of essential bioactive SPMs.

PCOS: A Chronic Disease That Fails to Produce Adequately Specialized Pro-Resolving Lipid Mediators (SPMs)

Introduction: Polycystic ovary syndrome (PCOS) is an endocrinological disorder that affects 5–15% of women of their reproductive age and is a frequent cause of infertility. Major symptoms include hyperandrogenism, ovulatory dysfunction, and often obesity and/or insulin resistance. PCOS also represents a state of chronic low-grade inflammation that is closely interlinked with the metabolic features. “Classical” pro-inflammatory lipid mediators such as prostaglandins (PG), leukotrienes (LT), or thromboxanes (TX) are derived from arachidonic acid (AA) and are crucial for the initial response. Resolution processes are driven by four families of so-called specialized pro-resolving mediators (SPMs): resolvins, maresins, lipoxins, and protectins. The study aimed to establish lipid mediator profiles of PCOS patients compared to healthy women to identify differences in their resolutive and pro-inflammatory lipid parameters. Material and Methods: Fifteen female patients (18–45 years) were diagnosed with PCOS according to Rotterdam criteria, and five healthy women, as a comparator group, were recruited for the study. The main outcome measures were: pro-inflammatory lipid mediators (PG, LT, TX) and their precursor AA, SPMs (resolvins, maresins, protectins, lipoxins), their precursors EPA, DHA, DPA, and their active biosynthesis pathway intermediates (18-HEPE, 17-HDHA, 14-HDHA). Results: The level of pro-inflammatory parameters in serum was significantly higher in PCOS-affected women. The ratio (sum of pro-inflammatory molecules)/(sum of SPMs plus hydroxylated intermediates) reflecting the inflammatory state was significantly lower in the group of healthy women. Conclusion: There is a strong pro-inflammatory state in PCOS patients. Further research will clarify whether supplementation with SPMs or their precursors may improve this state.

Maresin 1 activates LGR6 receptor promoting phagocyte immunoresolvent functions

Resolution of acute inflammation is an active process orchestrated by endogenous mediators and mechanisms pivotal in host defense and homeostasis. The macrophage mediator in resolving inflammation, maresin 1 (MaR1), is a potent immunoresolvent, stimulating resolution of acute inflammation and organ protection. Using an unbiased screening of greater than 200 GPCRs, we identified MaR1 as a stereoselective activator for human leucine-rich repeat containing G protein-coupled receptor 6 (LGR6), expressed in phagocytes. MaR1 specificity for recombinant human LGR6 activation was established using reporter cells expressing LGR6 and functional impedance sensing. MaR1-specific binding to LGR6 was confirmed using 3H-labeled MaR1. With human and mouse phagocytes, MaR1 (0.01-10 nM) enhanced phagocytosis, efferocytosis, and phosphorylation of a panel of proteins including the ERK and cAMP response element-binding protein. These MaR1 actions were significantly amplified with LGR6 overexpression and diminished by gene silencing in phagocytes. Thus, we provide evidence for MaR1 as an endogenous activator of human LGR6 and a novel role of LGR6 in stimulating MaR1's key proresolving functions of phagocytes.

CD69 Plays a Beneficial Role in Ischemic Stroke by Dampening Endothelial Activation

RATIONALE

CD69 is an immunomodulatory molecule induced during lymphocyte activation. Following stroke, T-lymphocytes upregulate CD69 but its function is unknown.

OBJECTIVE

We investigated whether CD69 was involved in brain damage following an ischemic stroke.

METHODS AND RESULTS

We used adult male mice on the C57BL/6 or BALB/c backgrounds, including wild-type mice and CD69^-/- mice, and CD69^+/+ and CD69^-/- lymphocyte-deficient Rag2^-/- mice, and generated chimeric mice. We induced ischemia by transient or permanent middle cerebral artery occlusion. We measured infarct volume, assessed neurological function, and studied CD69 expression, as well as platelet function, fibrin(ogen) deposition, and VWF (von Willebrand factor) expression in brain vessels and VWF content and activity in plasma, and performed the tail-vein bleeding test and the carotid artery ferric chloride-induced thrombosis model. We also performed primary glial cell cultures and sorted brain CD45^-CD11b^-CD31⁺ endothelial cells for mRNA expression studies. We blocked VWF by intravenous administration of anti-VWF antibodies. CD69^-/- mice showed larger infarct volumes and worse neurological deficits than the wild-type mice after ischemia. This worsening effect was not attributable to lymphocytes or other hematopoietic cells. CD69 deficiency lowered the time to thrombosis in the carotid artery despite platelet function not being affected. Ischemia upregulated Cd69 mRNA expression in brain endothelial cells. CD69-deficiency increased fibrin(ogen) accumulation in the ischemic tissue, and plasma VWF content and activity, and VWF expression in brain vessels. Blocking VWF reduced infarct volume and reverted the detrimental effect of CD69^-/- deficiency.

CONCLUSIONS

CD69 deficiency promotes a prothrombotic phenotype characterized by increased VWF and worse brain damage after ischemic stroke. The results suggest that CD69 acts as a downregulator of endothelial activation.

Cutting Edge: Human Vagus Produces Specialized Proresolving Mediators of Inflammation with Electrical Stimulation Reducing Proinflammatory Eicosanoids

Inflammatory resolution is a process that, when uncontrolled, impacts many organs and diseases. As an active, self-limited inflammatory process, resolution involves biosynthesis of specialized proresolving mediators (SPM) (e.g., lipoxins, resolvins [Rv], protectins, and maresins). Because vagal stimulation impacts inflammation, we examined human and mouse vagus ex vivo to determine if they produce lipid mediators. Using targeted lipid mediator metabololipidomics, we identified lipoxins, Rv, and protectins produced by both human and mouse vagus as well as PGs and leukotrienes. Human vagus produced SPM (e.g., RvE1, NPD1/PD1, MaR1, RvD5, and LXA₄) on stimulation that differed from mouse (RvD3, RvD6, and RvE3), demonstrating species-selective SPM. Electrical vagus stimulation increased SPM in both human and mouse vagus as did incubations with Escherichia coli. Electrical vagus stimulation increased SPM and decreased PGs and leukotrienes. These results provide direct evidence for vagus SPM and eicosanoids. Moreover, they suggest that this vagus SPM circuit contributes to a new proresolving vagal reflex.

Abstract 323: Metabolic Transformation of Fatty Acids Defines Resolving Versus Non-Resolving Inflammation in Obesity-Associated Heart Failure

Whether and how fat intake contributes to persistent inflammation in obesity is unclear. Here, we report the differential metabolic transformation of fatty acids in heart failure (HF) pathology in the setting of obesity. We used permanent coronary ligation to induce myocardial infarction (MI) leading to acute (d1), healing phase (d5) and subsequent chronic HF phase (d28) in male C57BL/6J mice, while maintaining naïve controls at day (d)0. Prior to MI, 100 two month-old mice were subjected to n-6 fatty acids (safflower oil; SO; 22Kcal) for 3 months, with subsequent randomized allocation of 50 mice to docosahexaenoic acid (DHA; 22Kcal) enriched n-3 fatty acids for the next 2 months, while maintaining SO control in the remaining 50 mice. Both groups gained significant weight and fat mass independent of lean mass confirmed by magnetic resonance imaging. Post-MI survival and left ventricular (LV) function was decreased in SO-fed mice with downregulation of multiple inflammation resolution mechanisms in the spleen, infarcted LV, and kidney. DHA increased Ly6C low macrophages, MRC, Arg-1, YM1 and FFAR4 (GPR120) during the acute and resolving phase from d1 to d5 post-MI as compared with SO-fed mice. DHA-improved post-MI survival at d28, together with increased levels of D-series resolvins (RvD1, RvD2, RvD4, RvD5), maresin 1, and RvE3, and lower levels of prostaglandins (PGD 2 , PGE 2 , PGF2 α ), leukotriene B 4 (LTB 4 ), 20-OH-LTB 4 , thromboxane B2 and lipoxin A 4 in the resolving phase. During chronic HF at d28 post-MI, DHA increased CD4 + /CD127 - with increased expression of FOXp3 in the LV. DHA reduced FFAR1-3 , neprilysin activity and simultaneously increased FFAR4 in the kidney as compared with SO post-MI. In contrast, SO-induced overactivation of pro-inflammatory FFAR1 (GPR40) and reduction of anti-inflammatory FFAR4 tracked with increased serum creatinine and IL-1β, and decreased ALX/ FPR2 in kidney at d28 post-MI. Overall, DHA intake modulates the splenocardiac resolving phase with generation of proresolving mediators, augmentation of Ly6C low macrophages, and suppression of prostaglandins post-MI. Thus, the metabolic transformation of n-3 and -6 fatty acids can regulate resolution versus non-resolution of inflammation in HF post-MI in the setting of obesity.

Novel Resolvin D2 Receptor Axis in Infectious Inflammation

Resolution of acute inflammation is an active process governed by specialized proresolving mediators, including resolvin (Rv)D2, that activates a cell surface G protein-coupled receptor, GPR18/DRV2. In this study, we investigated RvD2-DRV2-dependent resolution mechanisms using DRV2-deficient mice (DRV2-knockout [KO]). In polymicrobial sepsis initiated by cecal ligation and puncture, RvD2 (∼2.7 nmol/mouse) significantly increased survival (>50%) of wild-type mice and reduced hypothermia and bacterial titers compared with vehicle-treated cecal ligation and puncture mice that succumbed at 48 h. Protection by RvD2 was abolished in DRV2-KO mice. Mass spectrometry-based lipid mediator metabololipidomics demonstrated that DRV2-KO infectious exudates gave higher proinflammatory leukotriene B₄ and procoagulating thromboxane B_2, as well as lower specialized proresolving mediators, including RvD1 and RvD3, compared with wild-type. RvD2-DRV2-initiated intracellular signals were investigated using mass cytometry (cytometry by time-of-flight), which demonstrated that RvD2 enhanced phosphorylation of CREB, ERK1/2, and STAT3 in WT but not DRV2-KO macrophages. Monitored by real-time imaging, RvD2-DRV2 interaction significantly enhanced phagocytosis of live Escherichia coli, an action dependent on protein kinase A and STAT3 in macrophages. Taken together, we identified an RvD2/DRV2 axis that activates intracellular signaling pathways that increase phagocytosis-mediated bacterial clearance, survival, and organ protection. Moreover, these results provide evidence for RvD2-DRV2 and their downstream pathways in pathophysiology of infectious inflammation.

Mannose-binding lectin promotes local microvascular thrombosis after transient brain ischemia in mice

BACKGROUND AND PURPOSE

Several lines of evidence support the involvement of mannose-binding lectin (MBL) in stroke brain damage. The lectin pathway of the complement system facilitates thrombin activation and clot formation under certain experimental conditions. In the present study, we examine whether MBL promotes thrombosis after ischemia/reperfusion and influences the course and prognosis of ischemic stroke.

METHODS

Middle cerebral artery occlusion/reperfusion was performed in MBL-deficient (n=85) and wild-type (WT; n=83) mice, and the brain lesion was assessed by MRI at days 1 and 7. Relative cerebral blood flow was monitored up to 6 hours after middle cerebral artery occlusion with laser speckle contrast imaging. Fibrin(ogen) was analyzed in the brain vasculature and plasma, and the effects of thrombin inhibitor argatroban were evaluated to assess the role of MBL in thrombin activation.

RESULTS

Infarct volumes and neurological deficits were smaller in MBL knockout mice than in WT mice. Relative cerebral blood flow values during middle cerebral artery occlusion and at reperfusion were similar in both groups, but decreased during the next 6 hours in the WT group only. Also, the WT mice showed more fibrin(ogen) in brain vessels and a better outcome after argatroban treatment. In contrast, argatroban did not improve the outcome in MBL knockout mice.

CONCLUSIONS

MBL promotes brain damage and functional impairment after brain ischemia/reperfusion in mice. These effects are secondary to intravascular thrombosis and impaired relative cerebral blood flow during reperfusion. Argatroban protects WT mice, but not MBL knockout mice, emphasizing a role of MBL in local thrombus formation in acute ischemia/reperfusion.

In vivo imaging of induction of heat-shock protein-70 gene expression with fluorescence reflectance imaging and intravital confocal microscopy following brain ischaemia in reporter mice

PURPOSE

Stroke induces strong expression of the 72-kDa heat-shock protein (HSP-70) in the ischaemic brain, and neuronal expression of HSP-70 is associated with the ischaemic penumbra. The aim of this study was to image induction of Hsp-70 gene expression in vivo after brain ischaemia using reporter mice.

METHODS

A genomic DNA sequence of the Hspa1b promoter was used to generate an Hsp70-mPlum far-red fluorescence reporter vector. The construct was tested in cellular systems (NIH3T3 mouse fibroblast cell line) by transient transfection and examining mPlum and Hsp-70 induction under a challenge. After construct validation, mPlum transgenic mice were generated. Focal brain ischaemia was induced by transient intraluminal occlusion of the middle cerebral artery and the mice were imaged in vivo with fluorescence reflectance imaging (FRI) with an intact skull, and with confocal microscopy after opening a cranial window.

RESULTS

Cells transfected with the Hsp70-mPlum construct showed mPlum fluorescence after stimulation. One day after induction of ischaemia, reporter mice showed a FRI signal located in the HSP-70-positive zone within the ipsilateral hemisphere, as validated by immunohistochemistry. Live confocal microscopy allowed brain tissue to be visualized at the cellular level. mPlum fluorescence was observed in vivo in the ipsilateral cortex 1 day after induction of ischaemia in neurons, where it is compatible with penumbra and neuronal viability, and in blood vessels in the core of the infarction.

CONCLUSION

This study showed in vivo induction of Hsp-70 gene expression in ischaemic brain using reporter mice. The fluorescence signal showed in vivo the induction of Hsp-70 in penumbra neurons and in the vasculature within the ischaemic core.

Group IVA phospholipase A2 is necessary for the biogenesis of lipid droplets

Lipid droplets (LD) are organelles present in all cell types, consisting of a hydrophobic core of triacylglycerols and cholesteryl esters, surrounded by a monolayer of phospholipids and cholesterol. This work shows that LD biogenesis induced by serum, by long-chain fatty acids, or the combination of both in CHO-K1 cells was prevented by phospholipase A(2) inhibitors with a pharmacological profile consistent with the implication of group IVA cytosolic phospholipase A(2) (cPLA(2)alpha). Knocking down cPLA(2)alpha expression with short interfering RNA was similar to pharmacological inhibition in terms of enzyme activity and LD biogenesis. A Chinese hamster ovary cell clone stably expressing an enhanced green fluorescent protein-cPLA(2)alpha fusion protein (EGFP-cPLA(2)) displayed higher LD occurrence under basal conditions and upon LD induction. Induction of LD took place with concurrent phosphorylation of cPLA(2)alpha at Ser(505). Transfection of a S505A mutant cPLA(2)alpha showed that phosphorylation at Ser(505) is key for enzyme activity and LD formation. cPLA(2)alpha contribution to LD biogenesis was not because of the generation of arachidonic acid, nor was it related to neutral lipid synthesis. cPLA(2)alpha inhibition in cells induced to form LD resulted in the appearance of tubulo-vesicular profiles of the smooth endoplasmic reticulum, compatible with a role of cPLA(2)alpha in the formation of nascent LD from the endoplasmic reticulum.