Biology and pharmacology of platelet-type 12-lipoxygenase in platelets, cancer cells, and their crosstalk

Functional lipid diversity and novel oxylipin identification for interspecies differentiation and nutritional assessment of commercial seahorse (Hippocampus) using untargeted and targeted lipidomics

Interspecific lipidological variations in seahorse (Hippocampus), as a functional food resource, profoundly influences its bioefficacy. This study employed untargeted and targeted lipidomics to comprehensively analyse and identify previously uncharacterized lipids in four commercial seahorses. A total of 41 lipid subclasses were discerned, encompassing 1114 and 1219 distinct lipid molecular species in positive and negative ion modes, respectively. Significant interspecific differences were observed in fatty acyls, glycerolipids, phospholipids, saccharolipids, sphingolipids, and sterol lipids across various detection modalities. Triacylglycerols and sphingolipids were dominant lipids in four seahorses. Additionally, 58 oxylipins derived from n-3/n-6 polyunsaturated fatty acids were identified and characterized within seahorses for the first time. Notably, the lined seahorse exhibited a remarkable enrichment in docosahexaenoic acid-derived oxylipins, underscoring its potential as valuable sources of functional lipids. Conclusively, these bioactive lipid profiles were proposed as potential biomarkers for distinguishing different seahorse species and substantiating nutritional values based on multivariate statistical analysis.

Immunoregulatory mechanisms of the arachidonic acid pathway in cancer

The arachidonic acid (AA) pathway promotes tumor progression by modulating the complex interactions between cancer and immune cells within the microenvironment. In this Review, we summarize the knowledge acquired thus far concerning the intricate mechanisms through which eicosanoids either promote or suppress the antitumor immune response. In addition, we will discuss the impact of eicosanoids on immune cells and how they affect responsiveness to immunotherapy, as well as potential strategies for manipulating the AA pathway to improve anticancer immunotherapy. Understanding the molecular pathways and mechanisms underlying the role played by AA and its metabolites in tumor progression may contribute to the development of more effective anticancer immunotherapies.

20-HETE induced platelet activation via a GPR75-independent pathway

BACKGROUND

Arachidonic acid (AA) metabolism is a critical regulator of platelet activation. The cytochrome P450 (CYP450) pathway represents a key metabolic route for AA, yet the precise roles of CYP450 enzymes and their primary product, 20-hydroxyeicosatetraenoic acid (20-HETE), in platelet activation and thrombosis remain incompletely elucidated.

METHODS

We assessed the impact of aspirin on AA-induced platelet aggregation in human platelets. We further explored the influence of 20-HETE on platelet aggregation, granule secretion, and integrin activation. To elucidate the underlying mechanisms of 20-HETE action, we employed the antagonist 20-hydroxyeicosa-6(Z),15(Z)-dienoic acid (20-HEDE) and G protein-coupled receptor 75 (GPR75) knockout mice. Additionally, we evaluated the antiplatelet potential of the CYP450 inhibitor 17-octadecynoic acid (17-ODYA).

RESULTS

Aspirin suppressed platelet aggregation induced by low dose of AA and has no effect on high dose AA-induced aggregation.20-HETE indirectly induced platelet aggregation, granule release, and integrin αIIbβ3 activation in a concentration-dependent manner, independent of GPR75. The effects of 20-HETE were mediated through Gαq-coupled GPCRs. The CYP450 inhibitor 17-ODYA potently suppressed platelet activation and thrombus formation.

CONCLUSIONS

Thromboxane A2 (TXA2) is not indispensable for AA induced platelet activation. Moreover, 20-HETE has been identified as a potent platelet activator that acts through Gαq-coupled GPCRs. Its effects are mediated by downstream metabolites rather than direct interaction with GPR75.

Ferroptosis-related genes as prognostic markers for survival and immunotherapy in triple-negative breast cancer: analysis of public databases and a single institution

Background

Ferroptosis plays a vital role in cancer development and treatment. The relationship between ferroptosis-related genes and breast cancer prognosis, as well as immunotherapy outcomes, remains unknown.

Objectives

To evaluate the prognostic value of ferroptosis-related genes in breast cancer.

Methods

We conducted differential expressions and prognostic analysis for ferroptosis-related genes on public databases and breast cancer patients in our center and analyzed their predictive value for immunotherapy of breast cancer patients.

Results

We identified prognostic ferroptosis-related genes, constructed a nomogram, and validated key genes using patient data from our center. We also investigated ferroptosis-related genes significantly associated with immune infiltration and identified FTH1 as a promising biomarker for triple-negative breast cancer immunotherapy.

Conclusion

Ferroptosis-related genes had potential prognostic value and predictive value for breast cancer immunotherapy.

The Role of Hydroxyeicosatetraenoic Acids in the Regulation of Inflammation in Bronchial Asthma

Hydroperoxyeicosatetraenoic acids (HETEs) are metabolites of arachidonic acid that are oxidized by a family of enzymes including cyclooxygenase, lipoxygenase, and cytochrome P450 enzymes. These enzymes are widely present in various organs and tissues, and the HETEs they synthesize perform an important function in the regulation of immune reactions and haemostasis processes under physiological and pathophysiological conditions. More researchers confirm the role of these oxidized metabolites in modulating inflammation in asthma. The high production of HETEs in allergic and severe asthma indicates their involvement in the processes of an acute inflammatory response. On the other hand, disturbance of the metabolic transformation of arachidonic acid contributes to the development of chronic inflammation due to insufficient synthesis of mediators that resolve inflammatory processes. Several HETEs have both pro-inflammatory and anti-inflammatory effects, which underscores the ongoing interest in their involvement in the pathogenesis of asthma. At the same time, research results are scarce. Based on an analysis of the literature, the pathways of metabolic transformation of 5-HETE, 12-HETE, and 15-HETE with the participation of cyclooxygenases, lipoxygenases, and cytochrome P-450, as well as their role in asthma pathogenesis, were discussed. The PubMed database was searched for information covering the last five years using selected inclusion criteria. Information queries included the following set of keywords: "bronchial asthma, hydroxyeicosatetraenoic acids, 5-HETE, 12-HETE, 15-HETE." Literature data indicate that the role of HETEs in human physiology and pathology, including the modulation of inflammation in asthma, requires comprehensive study to selectively modulate the enzymatic pathways of arachidonic acid metabolism leading to the production of these mediators.

A sulfonimide derivative of bezafibrate as a dual inhibitor of cyclooxygenase-2 and PPARα

Background

PPARα and cyclooxygenase (COX)-2 are overexpressed in certain types of cancer. Thus, developing a dual inhibitor that targets both could be more effective as an anticancer agent than single inhibitors. We have previously shown that an analog of the bezafibrate named AA520 is a PPARα antagonist. Herein, we report the identification of AA520 as a potent COX-2 inhibitor using in silico approaches. In addition, we performed a thorough pharmacological characterization of AA520 towards COX-1 and COX-2 in different in vitro models.

Methods

AA520 was characterized for inhibiting platelet COX-1 and monocyte COX-2 activity in human whole blood (HWB) and for effects on lipidomics of eicosanoids using LC-MS/MS. The kinetics of the interaction of AA520 with COX-2 was assessed in the human colon cancer cell line, HCA-7, expressing only COX-2, by testing the COX-2 activity after extensive washing of the cells. The impact of AA520 on cancer cell viability, metabolic activity, and cytotoxicity was tested using the MTT reagent.

Results

In HWB, AA520 inhibited in a concentration-dependent fashion LPS-stimulated leukocyte prostaglandin (PG) E2 generation with an IC50 of 0.10 (95% CI: 0.05-0.263) μM while platelet COX-1 was not affected up to 300 μM. AA520 did not affect LPS-induced monocyte COX-2 expression, and other eicosanoids generated by enzymatic and nonenzymatic pathways. AA520 inhibited COX-2-dependent PGE2 generation in the colon cancer cell line HCA7. Comparison of the inhibition of COX-2 and its reversibility by AA520, indomethacin (a time-dependent inhibitor), acetylsalicylic acid (ASA) (an irreversible inhibitor), and ibuprofen (a reversible inhibitor) showed that the compound is acting by forming a tightly bound COX-2 interaction. This was confirmed by docking and molecular dynamics studies. Moreover, AA520 (1 μM) significantly reduced MTT in HCA7 cells.

Conclusion

We have identified a highly selective COX-2 inhibitor with a unique scaffold. This inhibitor retains PPARα antagonism at the same concentration range. It has the potential to be effective in treating certain types of cancer, such as hepatocellular carcinoma (HCC) and renal cell carcinoma (RCC), where COX-2 and PPARα are overexpressed.

Enhancing insight into ferroptosis mechanisms in sepsis: A genomic and pharmacological approach integrating single-cell sequencing and Mendelian randomization

This research investigated the intricate relationship between ferroptosis and sepsis by utilizing advanced genomic and pharmacological methodologies. Specifically, we obtained expression quantitative trait loci (eQTLs) for 435 genes associated with ferroptosis from the eQTLGen Consortium and detected notable cis-eQTLs for 281 of these genes. Next, we conducted a detailed analysis to assess the impact of these eQTLs on susceptibility to sepsis using Mendelian randomization (MR) with data from a cohort of 10,154 sepsis patients and 452,764 controls sourced from the UK Biobank. MR analysis revealed 16 ferroptosis-related genes that exhibited significant associations with sepsis outcomes. To bolster the robustness of these findings, sensitivity analyses were performed to assess pleiotropy and heterogeneity, thus confirming the reliability of the causal inferences. Furthermore, single-cell RNA sequencing data from sepsis patients offered a detailed examination of gene expression profiles, demonstrating varying levels of ferroptosis marker expression across different cell types. Pathway enrichment analysis utilizing gene set enrichment analysis (GSEA) further revealed the key biological pathways involved in the progression of sepsis. Additionally, the use of computational molecular docking facilitated the prediction of interactions between identified genes and potential therapeutic compounds, highlighting novel drug targets. In conclusion, our integrated approach combining genomics and pharmacology offers valuable insights into the involvement of ferroptosis in sepsis, laying the groundwork for potential therapeutic strategies targeting this cell death pathway to enhance sepsis management.

Platelets and extracellular vesicles in disease promotion via cellular cross-talk and eicosanoid biosynthesis

New insights have been gained on the role of platelets beyond thrombosis. Platelets can accumulate in damaged and inflamed tissues, acting as a sentinel to detect and repair tissue damage. However, by releasing several soluble factors, including thromboxane A2 (TXA2) and 12-hydroxyeicosatetraenoic acid, and extracellular vesicles (EVs), platelets can activate vascular cells, stromal, such as fibroblasts, immune cells, and cancer cells, leading to atherosclerosis, vascular restenosis, tissue fibrosis, and tumor metastasis. Platelet-derived extracellular vesicles (PEVs) are released when platelets are activated and can transfer their cargo to other cell types, thus contributing to the development of diseases. Inhibitors of the internalization of PEVs can potentially represent novel therapeutic tools. Both platelets and PEVs contain a significant number of different types of molecules, and their omics assessment and integration with clinical data using computational approaches have the potential to detect early disease development and monitor drug treatments.

Glycoursodeoxycholic Acid Alleviates Arterial Thrombosis via Suppressing Diacylglycerol Kinases Activity in Platelet

BACKGROUND

Glycoursodeoxycholic acid (GUDCA) has been acknowledged for its ability to regulate lipid homeostasis and provide benefits for various metabolic disorders. However, the impact of GUDCA on arterial thrombotic events remains unexplored. The objective of this study is to examine the effects of GUDCA on thrombogenesis and elucidate its underlying mechanisms.

METHODS

Plasma samples from patients with arterial thrombotic events and diet-induced obese mice were collected to determine the GUDCA concentrations using mass spectrometry. Multiple in vivo murine thrombosis models and in vitro platelet functional assays were conducted to comprehensively evaluate the antithrombotic effects of GUDCA. Moreover, lipidomic analysis was performed to identify the alterations of intraplatelet lipid components following GUDCA treatment.

RESULTS

Plasma GUDCA level was significantly decreased in patients with arterial thrombotic events and negatively correlated with thrombotic propensity in diet-induced obese mice. GUDCA exhibited prominent suppressing effects on platelet reactivity as evidenced by the attenuation of platelet activation, secretion, aggregation, spreading, and retraction (P<0.05). In vivo, GUDCA administration robustly alleviated thrombogenesis (P<0.05) without affecting hemostasis. Mechanistically, GUDCA inhibited DGK (diacylglycerol kinase) activity, leading to the downregulation of the phosphatidic acid-mediated signaling pathway. Conversely, phosphatidic acid supplementation was sufficient to abolish the antithrombotic effects of GUDCA. More importantly, long-term oral administration of GUDCA normalized the enhanced DGK activity, thereby remarkably alleviating the platelet hyperreactivity as well as the heightened thrombotic tendency in diet-induced obese mice (P<0.05).

CONCLUSIONS

Our study implicated that GUDCA reduces platelet hyperreactivity and improves thrombotic propensity by inhibiting DGKs activity, which is a potentially effective prophylactic approach and promising therapeutic agent for arterial thrombotic events.

Pathological and pharmacological functions of the metabolites of polyunsaturated fatty acids mediated by cyclooxygenases, lipoxygenases, and cytochrome P450s in cancers

Oxylipins have garnered increasing attention because they were consistently shown to play pathological and/or pharmacological roles in the development of multiple cancers. Oxylipins are the metabolites of polyunsaturated fatty acids via both enzymatic and nonenzymatic pathways. The enzymes mediating the metabolism of PUFAs include but not limited to lipoxygenases (LOXs), cyclooxygenases (COXs), and cytochrome P450s (CYPs) pathways, as well as the down-stream enzymes. Here, we systematically summarized the pleiotropic effects of oxylipins in different cancers through pathological and pharmacological aspects, with specific reference to the enzyme-mediated oxylipins. We discussed the specific roles of oxylipins on cancer onset, growth, invasion, and metastasis, as well as the expression changes in the associated metabolic enzymes and the associated underlying mechanisms. In addition, we also discussed the clinical application and potential of oxylipins and related metabolic enzymes as the targets for cancer prevention and treatment. We found the specific function of most oxylipins in cancers, especially the underlying mechanisms and clinic applications, deserves and needs further investigation. We believe that research on oxylipins will provide not only more therapeutic targets for various cancers but also dietary guidance for both cancer patients and healthy humans.

Hirudin inhibits glioma growth through mTOR-regulated autophagy

Glioma is the most common primary malignant brain tumour, and survival is poor. Hirudin has anticancer pharmacological effects through suppression of glioma cell progression, but the molecular target and mechanism are poorly understood. In this study, we observed that hirudin dose- and time-dependently inhibited glioma invasion, migration and proliferation. Mechanistically, hirudin activated LC3-II but not Caspase-3 to induce the autophagic death of glioma cells by decreasing the phosphorylation of mTOR and its downstream substrates ULK1, P70S6K and 4EBP1. Furthermore, hirudin inhibited glioma growth and induced changes in autophagy in cell-derived xenograft (CDX) nude mice, with a decrease in mTOR activity and activation of LC3-II. Collectively, our results highlight a new anticancer mechanism of hirudin in which hirudin-induced inhibition of glioma progression through autophagy activation is likely achieved by inhibition of the mTOR signalling pathway, thus providing a molecular basis for hirudin as a potential and effective clinical drug for glioma therapy.

Caffeic acid phenethyl ester analogues as selective inhibitors of 12-lipoxygenase product biosynthesis in human platelets

The inflammatory response is an essential process for the host defence against pathogens. Lipid mediators are important in coordinating the pro-inflammatory and pro-resolution phases of the inflammatory process. However, unregulated production of these mediators has been associated with chronic inflammatory diseases such as arthritis, asthma, cardiovascular diseases, and several types of cancer. Therefore, it is not surprising that enzymes implicated in the production of these lipid mediators have been targeted for potential therapeutic approaches. Amongst these inflammatory molecules, the 12-hydroxyeicosatetraenoic acid (12(S)-HETE) is abundantly produced in several diseases and is primarily biosynthesized via the platelet's 12-lipoxygenase (12-LO) pathway. To this day, very few compounds selectively inhibit the 12-LO pathway, and most importantly, none are currently used in the clinical settings. In this study, we investigated a series of polyphenol analogues of natural polyphenols that inhibit the 12-LO pathway in human platelets without affecting other normal functions of the cell. Using an ex vivo approach, we found one compound that selectively inhibited the 12-LO pathway, with IC50 values as low as 0.11 µM, with minimal inhibition of other lipoxygenase or cyclooxygenase pathways. More importantly, our data show that none of the compounds tested induced significant off-target effects on either the platelet's activation or its viability. In the continuous search for specific and better inhibitors targeting the regulation of inflammation, we characterized two novel inhibitors of the 12-LO pathway that could be promising for subsequent in vivo studies.

Cyclooxygenases and platelet functions

Cyclooxygenase (COX) isozymes, i.e., COX-1 and COX-2, are encoded by separate genes and are involved in the generation of the same products, prostaglandin (PG)G₂ and PGH₂ from arachidonic acid (AA) by the COX and peroxidase activities of the enzymes, respectively. PGH₂ is then transformed into prostanoids in a tissue-dependent fashion due to the different expression of downstream synthases. Platelets present almost exclusively COX-1, which generates large amounts of thromboxane (TX)A₂, a proaggregatory and vasoconstrictor mediator. This prostanoid plays a central role in atherothrombosis, as shown by the benefit of the antiplatelet agent low-dose aspirin, a preferential inhibitor of platelet COX-1. Recent findings have shown the relevant role played by platelets and TXA₂ in developing chronic inflammation associated with several diseases, including tissue fibrosis and cancer. COX-2 is induced in response to inflammatory and mitogenic stimuli to generate PGE₂ and PGI₂ (prostacyclin), in inflammatory cells. However, PGI₂ is constitutively expressed in vascular cells in vivo and plays a crucial role in protecting the cardiovascular systems due to its antiplatelet and vasodilator effects. Here, platelets' role in regulating COX-2 expression in cells of the inflammatory microenvironment is described. Thus, the selective inhibition of platelet COX-1-dependent TXA₂ by low-dose aspirin prevents COX-2 induction in stromal cells leading to antifibrotic and antitumor effects. The biosynthesis and functions of other prostanoids, such as PGD₂, and isoprostanes, are reported. In addition to aspirin, which inhibits platelet COX-1 activity, possible strategies to affect platelet functions by influencing platelet prostanoid receptors or synthases are discussed.

Hydroperoxidation of Docosahexaenoic Acid by Human ALOX12 and pigALOX15-mini-LOX

Human lipoxygenase 12 (hALOX12) catalyzes the conversion of docosahexaenoic acid (DHA) into mainly 14S-hydroperoxy-4Z,7Z,10Z,12E,16Z,19Z-docosahexaenoic acid (14S-H(p)DHA). This hydroperoxidation reaction is followed by an epoxidation and hydrolysis process that finally leads to maresin 1 (MaR1), a potent bioactive specialized pro-resolving mediator (SPM) in chronic inflammation resolution. By combining docking, molecular dynamics simulations, and quantum mechanics/molecular mechanics calculations, we have computed the potential energy profile of DHA hydroperoxidation in the active site of hALOX12. Our results describe the structural evolution of the molecular system at each step of this catalytic reaction pathway. Noteworthy, the required stereospecificity of the reaction leading to MaR1 is explained by the configurations adopted by DHA bound to hALOX12, along with the stereochemistry of the pentadienyl radical formed after the first step of the mechanism. In pig lipoxygenase 15 (pigALOX15-mini-LOX), our calculations suggest that 14S-H(p)DHA can be formed, but with a stereochemistry that is inadequate for MaR1 biosynthesis.