5,6-DiHETE attenuates vascular hyperpermeability by inhibiting Ca2+ elevation in endothelial cells

Transient receptor potential vanilloid 4 gene-deficiency attenuates the inhibitory effect of 5,6-dihydroxy-8Z,11Z,14Z,17Z-eicosatetraenoic acid on vascular permeability in mice

We investigated whether an anti-inflammatory lipid metabolite named 5,6-DiHETE reduces vascular permeability by inhibiting TRPV4 channels in vivo. In wild-type (WT) mice, histamine-induced dye extravasation was reduced by pre-administration of 5,6-DiHETE. In TRPV4-deficient mice, extravasation and histamine-induced edema were already reduced, and 5,6-DiHETE had no additional effect. In isolated WT aortas, 5,6-DiHETE attenuated acetylcholine-induced relaxation, but this effect was absent in TRPV4-deficient aortas. These findings suggest that 5,6-DiHETE reduces vascular permeability by inhibiting TRPV4 activity.

The unique metabolic and lipid profiles of patients with severe COVID-19 compared to severe community-acquired pneumonia: a potential prognostic and therapeutic target

BACKGROUND

Compare the changes and differences in metabolome and lipidome profiles among severe COVID-19 and CAP patients with ARF to identify biomarkers that could be used for personalized diagnosis, prognosis, and treatment.

RESEARCH DESIGN AND METHODS

Plasma samples were taken at hospital admission (baseline) and on the 5th day of hospitalization (follow-up) and examined by RP-LC-QTOF-MS and HILIC-LC-QTOF-MS.

RESULTS

127 patients, 17 with CAP and 110 with COVID-19, were included. The analysis revealed 87 altered metabolites, suggesting changes in the metabolism of arachidonic acid, glycerolipids, glycerophospholipids, linoleic acid, pyruvate, glycolysis, among others. Most of these metabolites are involved in inflammatory, hypoxic, and thrombotic processes. At baseline, the greatest differences were found in phosphatidylcholine (PC) 31:4 (p < 0.001), phosphoserine (PS) 34:3 (p < 0.001), and phosphatidylcholine (PC) 36:5 (p < 0.001), all of which were notably decreased in COVID-19 patients. At follow-up, the most dysregulated metabolites were monomethyl-phosphatidylethanolamine (PE-Nme) 40:5 (p < 0.001) and phosphatidylcholine (PC) 38:4 (p < 0.001).

CONCLUSIONS

Metabolic and lipidic alterations suggest inhibition of innate anti-inflammatory and anti-thrombotic mechanisms in COVID-19 patients, which might lead to increased viral proliferation, uncontrolled inflammation, and thrombi formation. Results provide novel targets for predictive biomarkers against CAP and COVID-19.

TRIAL REGISTRATION

Not applicable.

One-Year Effects of High-Intensity Statin on Bioactive Lipids: Findings From the JUPITER Trial

BACKGROUND

Statin effects extend beyond low-density lipoprotein cholesterol reduction, potentially modulating the metabolism of bioactive lipids (BALs), crucial for biological signaling and inflammation. These bioactive metabolites may serve as metabolic footprints, helping uncover underlying processes linked to pleiotropic effects of statins and yielding a better understanding of their cardioprotective properties. This study aimed to investigate the impact of high-intensity statin therapy versus placebo on plasma BALs in the JUPITER trial (Justification for the Use of Statins in Prevention: an Intervention Trial Evaluating Rosuvastatin; NCT00239681), a randomized primary prevention trial involving individuals with low-density lipoprotein cholesterol <130 mg/dL and high-sensitivity C-reactive protein ≥2 mg/L.

METHODS

Using a nontargeted mass spectrometry approach, over 11 000 lipid features were assayed from baseline and 1-year plasma samples from cardiovascular disease noncases from 2 nonoverlapping nested substudies: JUPITERdiscovery (n=589) and JUPITERvalidation (n=409). The effect of randomized allocation of rosuvastatin 20 mg versus placebo on BALs was examined by fitting a linear regression with delta values (∆=year 1-baseline) adjusted for age and baseline levels of each feature. Significant associations in discovery were analyzed in the validation cohort. Multiple comparisons were adjusted using 2-stage overall false discovery rate.

RESULTS

We identified 610 lipid features associated with statin randomization with significant replication (overall false discovery rate, <0.05), including 26 with annotations. Statin therapy significantly increased levels of 276 features, including BALs with anti-inflammatory activity and arterial vasodilation properties. Concurrently, 334 features were significantly lowered by statin therapy, including arachidonic acid and proinflammatory and proplatelet aggregation BALs. By contrast, statin therapy reduced an eicosapentaenoic acid-derived hydroxyeicosapentaenoic acid metabolite, which may be related to impaired glucose metabolism. Additionally, we observed sex-related differences in 6 lipid metabolites and 6 unknown features.

CONCLUSIONS

Statin allocation was significantly associated with upregulation of BALs with anti-inflammatory, antiplatelet aggregation and antioxidant properties and downregulation of BALs with proinflammatory and proplatelet aggregation activity, supporting the pleiotropic effects of statins beyond low-density lipoprotein cholesterol reduction.

5,6-diHETE lactone (EPA-L) mediates hypertensive microvascular dilation by activating the endothelial GPR-PLC-IP3 signaling pathway

Endothelial microvascular dysfunction affects multi-organ pathologic processes that contribute to increased vascular tone and is at the base of impaired metabolic and cardiovascular diseases. The vascular dilation impaired by nitric oxide (NO) deficiency in such dysfunctional endothelium is often balanced by endothelial-derived hyperpolarizing factors (EDHFs), which play a critical role in managing vascular tone. Our latest research has uncovered a new group of lactone oxylipins produced in the polyunsaturated fatty acids (PUFAs) CYP450 epoxygenase pathway, significantly affecting vascular dilation. The lactone oxylipin, derived from arachidonic acid (5,6-diHET lactone, AA-L), has been previously shown to facilitate vasodilation dependent on the endothelium in isolated human microvessels. The administration of the lactone oxylipin derived from eicosapentaenoic acid (5,6-diHETE lactone, EPA-L) to hypertensive rats demonstrated a significant decrease in blood pressure and improvement in the relaxation of microvessels. However, the molecular signaling processes that underlie these observations were not fully understood. The current study delineates the molecular pathways through which EPA-L promotes endothelium-dependent vascular dilation. In microvessels from hypertensive individuals, it was found that EPA-L mediates endothelium-dependent vasodilation while the signaling pathway was not dependent on NO. In vitro studies on human endothelial cells showed that the hyperpolarization mediated by EPA-L relies on G-protein-coupled receptor (GPR)-phospholipase C (PLC)-IP3 signaling that further activates calcium-dependent potassium flux. The pathway was confirmed using a range of inhibitors and cells overexpressing GPR40, where a specific antagonist reduced the calcium levels and outward currents induced by EPA-L. The downstream AKT and endothelial NO synthase (eNOS) phosphorylations were non-significant. These findings show that the GPR-PLC-IP3 pathway is a key mediator in the EPA-L-triggered vasodilation of arterioles. Therefore, EPA-L is identified as a significant lactone-based PUFA metabolite that contributes to endothelial and vascular health.

LC-MS-based urine metabolomics analysis of chronic subdural hematoma for biomarker discovery

BACKGROUND

Chronic subdural hematoma (CSDH) is one of the most common neurosurgical diseases with atypical manifestations. The aim of this study was to utilize urine metabolomics to explore potential biomarkers for the diagnosis and prognosis of CSDH.

METHODS

Seventy-seven healthy controls and ninety-two patients with CSDH were enrolled in our study. In total, 261 urine samples divided into the discovery group and validation group were analyzed by LC-MS. The statistical analysis and functional annotation were applied to discover potential biomarker panels and altered metabolic pathways.

RESULTS

A total of 53 differential metabolites were identified in this study. And the urinary metabolic profiles showed apparent separation between patients and controls. Further functional annotation showed that the differential metabolites were associated with lipid metabolism, fatty acid metabolism, amino acid metabolism, biotin metabolism, steroid hormone biosynthesis, and pentose and glucuronate interconversions. Moreover, one panel of Capryloylglycine, cis-5-Octenoic acid, Ethisterone, and 5,6-DiHETE showed good predictive performance in the diagnosis of CSDH, with an AUC of 0.89 in discovery group and an AUC of 0.822 in validation group. Another five metabolites (Trilobinol, 3'-Hydroxyropivacaine, Ethisterone, Arginyl-Proline, 5-alpha-Dihydrotestosterone glucuronide) showed the levels of them returned to a healthy state after surgery, showing good possibility to monitor the recovery of CSDH patients.

CONCLUSION AND CLINICAL RELEVANCE

The findings of the study revealed urine metabolomic differences between CSDH and controls. The potentially diagnostic and prognostic biomarker panels of urine metabolites were established, and functional analysis demonstrated deeper metabolic disorders of CSDH, which might conduce to improve early diagnose of CSDH clinically.

Alleviation of allergic conjunctivitis by (±)5(6)-dihydroxy-8Z,11Z,14Z,17Z-eicosatetraenoic acid in mice

Background: Allergic conjunctivitis (AC) is a common ophthalmologic disorder that causes symptoms that often reduces a patient's quality of life (QOL). We investigated the effects of the eicosapentaenoic acid metabolite (±)5(6)-dihydroxy-8Z,11Z,14Z,17Z-eicosatetraenoic acid ((±)5(6)-DiHETE) on AC using a mouse model. Methods: BALB/c mice were sensitized with two injections of short ragweed pollen in alum, challenged fifth with pollen in eyedrops. The clinical signs and tear volume were evaluated at 15 min after the final challenge. Histamine-induced ocular inflammation model was prepared by instilling histamine onto the surface of the eye. Fifteen minutes after histamine application, tear volume was measured using the Schirmer tear test. Miles assay was performed to investigate vascular permeability. To cause scratching behavior 10 μg of serotonin was injected in the cheek. Results: Repeated topical application of pollen induced conjunctivitis, accompanied by eyelid edema and tearing in mice. Pollen application typically degranulates mast cells and recruits eosinophils to the conjunctiva. Intraperitoneal administration of 300 μg/kg of (±)5(6)-DiHETE significantly inhibited pollen-induced symptoms. The administration of (±)5(6)-DiHETE also attenuated mast cell degranulation and eosinophil infiltration into the conjunctiva. To assess the effects of (±)5(6)-DiHETE on the downstream pathway of mast cell activation in AC, we used a histamine-induced ocular inflammation model. Topical application of 4 μg/eye histamine caused eyelid edema and tearing and increased vascular permeability, as indicated by Evans blue dye extravasation. Intraperitoneal administration of 300 μg/kg or topical administration of 1 μg/eye (±)5(6)-DiHETE inhibited histamine-induced manifestations. Finally, we assessed the effects of (±)5(6)-DiHETE on itching. An intradermal injection of 10 μg serotonin in the cheek caused scratching behavior in mice. Intraperitoneal administration of 300 μg/kg (±)5(6)-DiHETE significantly inhibited serotonin-induced scratching. Conclusion: Thus, (±)5(6)-DiHETE treatment broadly suppressed AC pathology and could be a novel treatment option for AC.

Detoxification Cytochrome P450s (CYPs) in Families 1-3 Produce Functional Oxylipins from Polyunsaturated Fatty Acids

This manuscript reviews the CYP-mediated production of oxylipins and the current known function of these diverse set of oxylipins with emphasis on the detoxification CYPs in families 1-3. Our knowledge of oxylipin function has greatly increased over the past 3-7 years with new theories on stability and function. This includes a significant amount of new information on oxylipins produced from linoleic acid (LA) and the omega-3 PUFA-derived oxylipins such as α-linolenic acid (ALA), docosahexaenoic acid (DHA), and eicosapentaenoic acid (EPA). However, there is still a lack of knowledge regarding the primary CYP responsible for producing specific oxylipins, and a lack of mechanistic insight for some clinical associations between outcomes and oxylipin levels. In addition, the role of CYPs in the production of oxylipins as signaling molecules for obesity, energy utilization, and development have increased greatly with potential interactions between diet, endocrinology, and pharmacology/toxicology due to nuclear receptor mediated CYP induction, CYP inhibition, and receptor interactions/crosstalk. The potential for diet-diet and diet-drug/chemical interactions is high given that these promiscuous CYPs metabolize a plethora of different endogenous and exogenous chemicals.

Vesicular nucleotide transporter is a molecular target of eicosapentaenoic acid for neuropathic and inflammatory pain treatment

Eicosapentaenoic acid (EPA), an omega-3 (ω-3) polyunsaturated fatty acid, is an essential nutrient that exhibits antiinflammatory, neuroprotective, and cardiovascular-protective activities. Although EPA is used as a nutrient-based pharmaceutical agent or dietary supplement, its molecular target(s) is debatable. Here, we showed that EPA and its metabolites strongly and reversibly inhibit vesicular nucleotide transporter (VNUT), a key molecule for vesicular storage and release of adenosine triphosphate (ATP) in purinergic chemical transmission. In vitro analysis showed that EPA inhibits human VNUT-mediated ATP uptake at a half-maximal inhibitory concentration (IC₅₀) of 67 nM, acting as an allosteric modulator through competition with Cl^-. EPA impaired vesicular ATP release from neurons without affecting the vesicular release of other neurotransmitters. In vivo, VNUT^-/- mice showed a delay in the onset of neuropathic pain and resistance to both neuropathic and inflammatory pain. EPA potently attenuated neuropathic and inflammatory pain in wild-type mice but not in VNUT^-/- mice without affecting the basal nociception. The analgesic effect of EPA was canceled by the intrathecal injection of purinoceptor agonists and was stronger than that of existing drugs used for neuropathic pain treatment, with few side effects. Neuropathic pain impaired insulin sensitivity in previous studies, which was improved by EPA in the wild-type mice but not in the VNUT^-/- mice. Our results showed that VNUT is a molecular target of EPA that attenuates neuropathic and inflammatory pain and insulin resistance. EPA may represent a unique nutrient-based treatment and prevention strategy for neurological, immunological, and metabolic diseases by targeting purinergic chemical transmission.

Multi metabolomics-based analysis of application of Astragalus membranaceus in the treatment of hyperuricemia

Hyperuricemia (HUA) is a common metabolic disease that is an independent risk factor for comorbidities such as hypertension, chronic kidney disease, and coronary artery disease. The prevalence of HUA has increased over the last several decades with improved living standards and increased lifespans. Metabolites are considered the most direct reflection of individual physiological and pathological conditions, and represent attractive candidates to provide deep insights into disease phenotypes. Metabolomics, a technique used to profile metabolites in biofluids and tissues, is a powerful tool for identification of novel biomarkers, and can be used to provide valuable insights into the etiopathogenesis of metabolic diseases and to evaluate the efficacy of drugs. In this study, multi metabolomics-based analysis of the blood, urine, and feces of rats with HUA showed that HUA significantly altered metabolite profiles. Astragalus membranaceus (AM) and benbromomalone significantly mitigated these changes in blood and feces, but not in urine. Some crucial metabolic pathways including lipid metabolism, lipid signaling, hormones synthesis, unsaturated fatty acid (UFAs) absorption, and tryptophan metabolism, were seriously disrupted in HUA rats. In addition, AM administration exerted better treatment effects on HUA than benbromomalone. Furthermore, additional supplementation with UFAs and tryptophan may also induce therapeutic effects against HUA.

Efficient Attenuation of Dextran Sulfate Sodium-Induced Colitis by Oral Administration of 5,6-Dihydroxy-8Z,11Z,14Z,17Z-eicosatetraenoic Acid in Mice

5,6-dihydroxy-8Z,11Z,14Z,17Z-eicosatetraenoic acid (5,6-DiHETE) is an eicosapentaenoic acid-derived newly discovered bioactive anti-inflammatory lipid mediator having diverse functions. Here, we assessed the potential of orally administered 5,6-DiHETE in promoting healing of dextran sulfate sodium (DSS)-induced colitis in mice. We measured the plasma concentrations of 5,6-DiHETE in untreated mice before and 0.5, 1, 3, and 6 h after its oral administration (150 or 600 μg/kg) in mice. Mice developed colitis by DSS (2% in drinking water for 4 days), and 5,6-DiHETE (150 or 600 μg/kg/day) was orally administered from day 9 to 14. Next, the faecal hardness and bleeding were assessed, and the dissected colons on day 14 via H&E staining. The plasma concentration of 5,6-DiHETE reached 25.05 or 44.79 ng/mL 0.5 h after the administration of 150 or 600 μg/kg, respectively, followed by a gradual decrease. The half-life of 5,6-DiHETE was estimated to be 1.25-1.63 h. Diarrhoea deteriorated after day 3 and peaked on day 5, followed by a gradual recovery. Histological assessment on day 14 showed DSS-mediated granulocyte infiltration, mucosal erosion, submucosal edema, and cryptal abscesses in mice. Oral administration of 150 or 600 μg/kg/day of 5,6-DiHETE accelerated the recovery from the DSS-induced diarrhoea and significantly ameliorated colon inflammation. The therapeutic effect of 600 μg/kg/day 5,6-DiHETE was slightly stronger than that by 150 μg/kg/day. Our study reveals attenuation of DSS-induced colitis in mice by the oral administration of 5,6-DiHETE dose-dependently, thereby suggesting a therapeutic potential of 5,6-DiHETE for inflammatory bowel disease.

5,6-dihydroxy-8Z,11Z,14Z,17Z-eicosatetraenoic acid accelerates the healing of colitis by inhibiting transient receptor potential vanilloid 4-mediated signaling

5,6-dihydroxy-8Z,11Z,14Z,17Z-eicosatetraenoic acid (5,6-DiHETE) is an eicosapentaenoic acid-derived lipid metabolite, which we previously detected in inflamed mouse colon. In this study, we investigated the pathophysiological roles of 5,6-DiHETE in murine colitis and its underlying mechanisms of action, focusing on the effects on transient receptor potential vanilloid (TRPV) channel activity. Oral administration of dextran sodium sulfate (DSS, 2%, for 4 days) caused colon inflammation, which peaked on day 7 and gradually declined by day 18. 5,6-DiHETE concentration in colon tissue was significantly increased during the healing phase of colitis (days 9 to 18). In vitro study showed that pretreatment with 5,6-DiHETE (0.1-1 μM, 30 minutes) significantly inhibited endothelial barrier disruption induced by a TRPV4 agonist (GSK1016790A, 50 nM). Intracellular Ca²⁺ imaging also showed that pretreatment with 5,6-DiHETE (1 μM, 10 minutes) reduced GSK1016790A-induced intracellular Ca²⁺ increase in HEK293T cells overexpressing TRPV4. In vivo, intraperitoneal administration of 5,6-DiHETE (50 µg kg^-1  day^-1 ) during the healing phase accelerated the recovery from DSS-induced colitis. Pathological studies showed that the administration of 5,6-DiHETE inhibited edema formation and leukocyte infiltration in inflamed colon tissue. In conclusion, we identified 5,6-DiHETE as a novel endogenous TRPV4 antagonist, and we also demonstrated that its administration promotes the healing of colitis by inhibiting inflammatory responses.

Role of oxylipins generated from dietary PUFAs in the modulation of endothelial cell function

Oxylipins, which are circulating bioactive lipids generated from polyunsaturated fatty acids (PUFAs) by cyclooxygenase, lipooxygenase and cytochrome P450 enzymes, have diverse effects on endothelial cells. Although studies of the effects of oxylipins on endothelial cell function are accumulating, a review that provides a comprehensive compilation of current knowledge and recent advances in the context of vascular homeostasis is lacking. This is the first compilation of the various in vitro, ex vivo and in vivo reports to examine the effects and potential mechanisms of action of oxylipins on endothelial cells. The aggregate data indicate docosahexaenoic acid-derived oxylipins consistently show beneficial effects related to key endothelial cell functions, whereas oxylipins derived from other PUFAs exhibit both positive and negative effects. Furthermore, information is lacking for certain oxylipin classes, such as those derived from α-linolenic acid, which suggests additional studies are required to achieve a full understanding of how oxylipins affect endothelial cells.

Tofacitinib suppresses mast cell degranulation and attenuates experimental allergic conjunctivitis

BACKGROUND

Allergic conjunctivitis (AC), a common eye inflammation that affects patients' health and quality of life, is still a therapeutic challenge for ophthalmologists. Tofacitinib, a new Janus kinase (JAK) inhibitor, has been successfully used in the treatment of several disorders. Nonetheless, its effect in AC and the potential anti-allergic mechanisms are still unclear. The objective of the current study was to explore the roles of tofacitinib in preventing AC and elucidate the potential underlying mechanisms.

METHODS

Tofacitinib was used topically in BALB/c mice with experimental allergic conjunctivitis (EAC). Ocular allergic symptoms and biological modifications were examined. To assess the anti-allergic mechanisms of tofacitinib, RBL-2H3 cells and HUVECs were cultured in vitro. The inhibitory effects and mechanisms of tofacitinib were studied and measured by real-time quantitative PCR, ELISA, western blot analysis, and flow cytometry.

RESULTS

Topical administration of tofacitinib reduced the clinical symptoms of OVA-induced EAC, with a substantial mitigation in inflammatory cell infiltration, histamine release, and TNF-α mRNA as well as IL-4 mRNA expression. In vitro, tofacitinib repressed the degranulation and cytokine production in RBL-2H3 cells and reduced histamine-induced vascular hyperpermeability. The underlying mechanism might involve the downregulation of phosphorylation of JAK3/STATs signaling molecules in RBL-2H3 cells and HUVECs.

CONCLUSIONS

Our findings provide evidence that tofacitinib prevented EAC by targeting the JAK3/STATs pathway. We recommend the use of tofacitinib as an innovative approach for the treatment of AC.

A novel eicosapentaenoic acid-derived anti-inflammatory lipid mediator 5,6-DiHETE is abundant in blue back fish intestines

Because omega-3 fatty acids, eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and their metabolites are known to possess anti-inflammatory and health-promoting functions in human and experimental animals, their intake is assumed to be beneficial for maintaining our health. We previously identified a cytochrome P450-metabolite of EPA, 5,6-dihydroxy-8Z,11Z,14Z,17Z-eicosatetraenoic acid (5,6-DiHETE), as a novel bioactive lipid, which inhibits vascular hyperpermeability in inflammation. Because blue back fishes including sardine, mackerel, and horse mackerel are reported to contain high concentrations of omega-3 fatty acids, we investigated which tissue of blue back fish is suitable as a source of 5,6-DiHETE. We measured the concentration of 5,6-DiHETE as well as major fatty acids in muscle, bone, heart, liver, and intestine of blue back fishes. Arachidonic acid was detected richer in intestines than other tissues of blue back fishes. The concentrations were between 4.45 and 5.62 µg/g tissue weight. EPA and DHA are also detected richer in intestines of blue back fishes. The concentrations were between 75.95 and 358.04 µg/g, and 203.09 and 464.88 µg/g, respectively. Especially, mackerel intestine contained the highest levels of both EPA and DHA. 5,6-DiHETE was present in greater amount in livers and intestines of blue back fishes. The livers contained 118.98 to 476.11 ng/g, whereas intestines contained 156.14 to 970.22 ng/g of 5,6-DiHETE. Of interest, sardine intestine contained much higher level of 5,6-DiHETE than the other fish tissues. These results suggest that visceral organs of blue back fishes, remarkably sardine intestine, can be a good source of 5,6-DiHETE. PRACTICAL APPLICATION: A novel anti-inflammatory lipid, 5,6-DiHETE, was detected in each tissues of blue back fishes. Especially their intestines contain the highest concentration of this lipid.