Cyclooxygenase activity mediates colorectal cancer cell resistance to the omega-3 polyunsaturated fatty acid eicosapentaenoic acid

Purpose

The naturally-occurring omega-3 polyunsaturated fatty acid eicosapentaenoic acid (EPA) is safe, well-tolerated and inexpensive, making it an attractive anti-cancer intervention. However, EPA has only modest anti-colorectal cancer (CRC) activity, when used alone. Both cyclooxygenase (COX) isoforms metabolise EPA and are over-expressed in CRC cells. We investigated whether COX inhibition increases the sensitivity of CRC cells to growth inhibition by EPA.

Methods

A panel of 18 human and mouse CRC cell lines was used to characterize the differential sensitivity of CRC cells to the growth inhibitory effects of EPA. The effect of CRISPR-Cas9 genetic deletion and pharmacological inhibition of COX-1 and COX-2 on the anti-cancer activity of EPA was determined using in vitro and in vivo models.

Results

Genetic ablation of both COX isoforms increased sensitivity of CT26 mouse CRC cells to growth inhibition by EPA in vitro and in vivo. The non-selective COX inhibitor aspirin and the selective COX-2 inhibitor celecoxib increased sensitivity of several human and mouse CRC cell lines to EPA in vitro. However, in a MC38 mouse CRC cell tumour model, with dosing that mirrored low-dose aspirin use in humans, thereby producing significant platelet COX-1 inhibition, there was ineffective intra-tumoral COX-2 inhibition by aspirin and no effect on EPA sensitivity of MC38 cell tumours.

Conclusion

Cyclooxygenase inhibition by non-steroidal anti-inflammatory drugs represents a therapeutic opportunity to augment the modest anti-CRC activity of EPA. However, intra-tumoral COX inhibition is likely to be critical for this drug-nutrient interaction and careful tissue pharmacodynamic profiling is required in subsequent pre-clinical and human studies.

Electronic supplementary material

The online version of this article (10.1007/s00280-020-04157-2) contains supplementary material, which is available to authorized users.

Non-steroidal anti-inflammatory drugs (NSAIDs) and organ damage: A current perspective

Owing to the efficacy in reducing pain and inflammation, non-steroidal anti-inflammatory drugs (NSAIDs) are amongst the most popularly used medicines confirming their position in the WHO's Model List of Essential Medicines. With escalating musculoskeletal complications, as evident from 2016 Global Burden of Disease data, NSAID usage is evidently unavoidable. Apart from analgesic, anti-inflammatory and antipyretic efficacies, NSAIDs are further documented to offer protection against diverse critical disorders including cancer and heart attacks. However, data from multiple placebo-controlled trials and meta-analyses studies alarmingly signify the adverse effects of NSAIDs in gastrointestinal, cardiovascular, hepatic, renal, cerebral and pulmonary complications. Although extensive research has elucidated the mechanisms underlying the clinical hazards of NSAIDs, no review has extensively collated the outcomes on various multiorgan toxicities of these drugs together. In this regard, the present review provides a comprehensive insight of the existing knowledge and recent developments on NSAID-induced organ damage. It precisely encompasses the current understanding of structure, classification and mode of action of NSAIDs while reiterating on the emerging instances of NSAID drug repurposing along with pharmacophore modification aimed at safer usage of NSAIDs where toxic effects are tamed without compromising the clinical benefits. The review does not intend to vilify these 'wonder drugs'; rather provides a careful understanding of their side-effects which would be beneficial in evaluating the risk-benefit threshold while rationally using NSAIDs at safer dose and duration.

Regulation of arachidonic acid oxidation and metabolism by lipid electrophiles

Arachidonic acid (AA) is a precursor of enzymatic and non-enzymatic oxidized products such as prostaglandins, thromboxanes, leukotrienes, lipoxins, and isoprostanes. These products may exert signaling or damaging roles during physiological and pathological conditions, some of them being markers of oxidative stress linked to inflammation. Recent data support the concept that cyclooxygenases (COX), lipoxygenases (LOX), and cytochrome P450 (CYP450) followed by cytosolic and microsomal dehydrogenases can convert AA to lipid-derived electrophiles (LDE). Lipid-derived electrophiles are fatty acid derivatives bearing an electron-withdrawing group that can react with nucleophiles at proteins, DNA, and small antioxidant molecules exerting potent signaling properties. This review aims to describe the formation, sources, and electrophilic anti-inflammatory actions of key mammalian LDE.

Molecular docking study and molecular dynamic simulation of human cyclooxygenase-2 (COX-2) with selected eutypoids

Inflammation is a key factor linked to almost all chronic and degenerative diseases implicit with certain levels of pain. In studies, over the past few years, it has been discovered that prostaglandins are the main cause of this inflammation and therefore could be blocked. Although no steroidal medications can be effective, natural compounds may offer a safer and often an effective alternative treatment for pain relief, especially for long-term use. Hence to find out natural anti-inflammatory compounds, we have highlighted five important butenolides that are eutypoid A, B, C, D and E with structure similar to that of rofecoxib, by ADMET and druglikeness analysis, followed by molecular docking with human COX-2 enzyme. Molecular docking studies revealed the importance of hydrophobic and hydrophilic amino acid residues for the stability of the ligands and that eutypoids C and E are the best candidates for the synthetic drugs with binding energy of -10.39 kcal/mol and -9.87 kcal/mol, respectively. The resulting complexes were then subject to 50 ns molecular dynamics (MD) simulation studies with the GROMACS package to analyze the stability of docked protein-ligand complexes and to assess the fluctuation and conformational changes during protein-ligand interaction. From the RMSD, RMSF, number of hydrogen bonds, SASA, PCA and MM/PBSA binding free energy analysis, we have found that out of five selected compounds eutypoid E showed good binding free energy of -174.45 kJ/mol, which is also good in other structural analyses. This compound displayed excellent pharmacological and structural properties to be drug candidates.Communicated by Ramaswamy H. Sarma.

Long-term nitric oxide synthase inhibition prevents 17β-estradiol-induced suppression of cyclooxygenase-dependent contractions and enhancement of endothelium-dependent hyperpolarization-like relaxation in mesenteric arteries of ovariectomized rats

Endothelial dysfunction is associated with a reduced bioavailability of nitric oxide (NO). In this study, the effects of 17β-estradiol supplement on endothelial function were examined in ovariectomized (OVX) rats following long-term inhibition of NO synthases with L-NAME. Female Sprague Dawley rats were ovariectomized at 12 weeks old. They were supplemented with 17β-estradiol (25 μg/kg/day, intramuscularly) or its vehicle (olive oil) until they were killed. At 18 weeks old, they were administered daily with NO synthase inhibitor L-NAME (60 mg/kg, by gavage) or its vehicle (distilled water) for 6 weeks. Rats were then anesthetized for blood pressure measurement and for isolation of mesenteric arteries and aortae for isometric tension measurement. Long-term L-NAME-treatment, without or with 17β-estradiol supplement, resulted in reduced plasma nitrite/nitrate level without causing an increase in blood pressure in OVX rats. Acute inhibition of cyclooxygenase (COX) with indomethacin improved relaxations of mesenteric arteries to the calcium ionophore A23187 in OVX rats, and in those with long-term L-NAME-treatment without or with 17β-estradiol supplement, but not in those with female hormone supplement only. 17β-estradiol supplement or long-term L-NAME-treatment resulted in a greater endothelium-dependent hyperpolarization-like relaxation in mesenteric arteries. In the quiescent aorta, 17β-estradiol supplement or long-term L-NAME-treatment unmasked the COX-dependent components of A23187-induced contractions, but prevented that of the smooth muscle contractions to U46619 in OVX rats. In summary, long-term 17β-estradiol-supplement results in differential effects in different blood vessel types, and its beneficial vascular effects are masked under the conditions with NO synthase inhibition.

In silico characterisation of olive phenolic compounds as potential cyclooxygenase modulators. Part 2

Non-steroidal anti-inflammatory drugs (NSAIDs) are commonly used to reduce pain, and function by targeting cyclooxygenase (COX) enzymes to inhibit the production of prostaglandins that facilitate inflammation. Since oleocanthal derived from Olea europaea is known to inhibit COX, we sought to characterise novel olive compounds with COX inhibitory activity using in silico techniques. Following on from part 1 of this study which identified 1-oleyltyrosol (1OL) and ligstroside derivative 2 (LG2) with COX inhibitory potential, the mechanisms of COX interactions by these selected compounds were further examined using molecular dynamics (MD) simulations. Classical MD simulations were carried out on COX-1 and COX-2 complexed with 1OL and LG2 to determine the stability and protein backbone fluctuation. Protein dynamics were examined using essential dynamics methods and network analysis, which identified that the N-terminal epidermal growth factor-like domain and membrane bound domains of COX-1 and -2 exhibited altered motions when ligands were bound. Distinct dynamical modules were identified, and that COX-2 inter-residue communications were more sensitive to ligand binding compared to COX-1. The use of various network metrics presents a novel approach in the characterisation of network behaviour of different ligands. It is proposed that inter-residue network metrics provide additional measures of the potential bioactivity of ligands, which may form a useful adjunct to conventional direct predictions of binding affinity, in determining the efficacy of potential small-molecule inhibitors. Overall, this two-part study characterises anti-inflammatory effects of low dosage dietary COX inhibitors, and provides a possible avenue for the development of therapeutics in inflammatory diseases.

In silico characterisation of olive phenolic compounds as potential cyclooxygenase modulators. Part 1

Non-steroidal anti-inflammatory drugs (NSAIDs) are widely used to reduce pain. These target cyclooxygenase (COX) enzymes which produce inflammatory mediators. Adverse effects associated with the use of traditional NSAIDs have led to a rise in the development of alternative therapies. Derived from Olea Europaea, olive oil is a main component of the Mediterranean diet, containing phenolic compounds that contribute to its antioxidant and anti-inflammatory properties. It has previously been found that oleocanthal, a phenolic compound derived from the olive, had similar effects to ibuprofen, a commonly used NSAID. There is an abundance of olive phenolic compounds that have yet to be investigated for their anti-inflammatory properties. In this study, it was sought to identify potential olive-derived compounds with the ability to inhibit COX enzymes, and study the mechanisms using in silico approaches. Molecular docking was employed to determine the COX inhibitory potential of an olive phenolic compound library. From docking, it was determined that 1-oleyltyrosol (1OL) and ligstroside derivative 2 (LG2) demonstrated the greatest binding affinity to both COX-1 and COX-2. Interactions with these compounds were further examined using molecular dynamics simulations. The residue contributions to binding free energy were computed using Molecular Mechanics-Poisson Boltzmann Surface Area (MM-PBSA) methods, revealing that residues Leu93, Val116, Leu352, and Ala527 in COX-1 and COX-2 were key determinants of potential inhibition. Along with part 2 of this study, this work aims to identify and characterise novel phenolic compounds which may possess COX inhibitory properties.

Vascular activity of infusion and fractions of Cymbopogon citratus (DC) Stapf. in human arteries

ETHNOPHARMACOLOGICAL RELEVANCE

Cymbopogon citratus (DC.) Stapf has been traditionally used mainly for inflammatory diseases and hypertension. However, the mechanisms underlying its vascular activity remain to be fully characterized and the fractions responsible for its cardiovascular activity are still unknown.

AIM OF THE STUDY

In this study, we aimed to assess the vascular activity of Cymbopogon citratus in human arteries and to study the role of cyclooxygenase in its vasorelaxant effects.

MATERIALS AND METHODS

Vascular effects of leaves infusion and three fractions (phenolic acids, flavonoids and tannins) were studied using distal segments of human internal thoracic arteries harvested from patients undergoing coronary revascularization, which were mounted as rings in tissue organ baths and maintained at 37 °C in Krebs Henseleit buffer. The effect on basal vascular tone, the effect on the noradrenaline-induced contraction and the vasorelaxant effects were assessed. The role of cyclooxygenase was evaluated with indomethacin.

RESULTS

Our results showed a mild effect on the basal vessel tone of the infusion. A significant inhibition on the adrenergic-mediated vasoconstriction was observed for the infusion (0.0002 mg/mL) and the flavonoid fraction (0.2 mg/mL), despite a potentiation was observed in some conditions. A vasorelaxant effect was observed for both the infusion (6.46% of maximal relaxation) and the tannin fraction (26.91% of maximal relaxation, P < 0.05 vs. infusion). Incubation with indomethacin (10 μM) elicited a decrease in the vasorelaxation to the infusion (P < 0.05).

CONCLUSIONS

These results suggest that cyclooxygenase may be involved in the vasorelaxation to the infusion of Cymbopogon citratus and that tannins are the compound fraction mainly responsible for this vasorelaxation.

Cycloarta-23-ene-3beta,25-diol a pentacyclic steroid from Euphorbia spinidens, as COX inhibitor with molecular docking, and in vivo study of its analgesic and anti-inflammatory activities in male swiss mice and wistar rats

BACKGROUND AND AIMS

Euphorbia is a large genus of flowering plants. In Iran, some plants of this family have been used in the treatment of inflammatory disorders and also to relieve back pain. Euphorbia spinidens is a rich source of Cycloarta-23-ene-3beta,25-diol. Cycloartane structures are the starting material for the synthesis of plant steroids, and the aim of this study is to demonstrate COX inhibitory activity, molecular docking and in vivo approach of anti-inflammatory activity of cycloartane compound isolated from Euphorbia spinidens.

MATERIAL AND METHODS

Plant material was extracted with acetone-chloroform and submitted to column chromatography for fractionation. Based on preliminary ¹H-NMR spectra, cycloartane fraction was selected and purified by repeated recycle HPLC system. The structure and purity of compound were determined by ¹H and ¹³C-NMR, HPTLC, and mass spectra. Inhibitory activities of the tested compounds on COX-1 and COX-2 were evaluated by a colorimetric COX (ovine) inhibitor screening method. Vero cells were used to assess the toxicity against the normal cells, and calculate the selectivity index. COX inhibitory activity results were evaluated and confirmed by molecular docking experiments. In the in vivo approach, analgesic activity was assessed by acetic acid-induced abdominal writhing and formalin tests. Croton oil-induced ear edema in mice and carrageenan-induced rat paw edema in rats were used to evaluate anti-inflammatory activity. Pain tests were carried out on male Swiss mice (25-35 g). Male Wistar rats (160-200 g) were used for the carrageenan test.

RESULTS

Cycloart-23-ene-3β,25-diol showedin vitro cyclooxygenase 1 and 2 inhibitory activities with more selectivity for COX-2. Molecular docking by predicting binding energies in COX protein receptors confirmed in vitro COX inhibitory results, and determined the best position for ligand in COX receptors along with its residue interactions in receptor pockets, which must be considered for designing of their inhibitors. In the in vivo studies, cycloartane inhibited significantly acetic acid-induced abdominal contractions and formalin-induced licking behavior at a dose of 200 mg/kg. The same dose reduced croton oil ear edema in mice and carrageenan-induced paw edema in rats.

CONCLUSION

Therefore, according to these findings, cycloart-23-ene-3beta,25-diol showed promising analgesic and anti-inflammatory effects with low toxicity against normal cells and can be suggested as a template lead for designing anti-inflammatory compounds with good selectivity index, and potency for COX-2 inhibitory activity.

Peripheral-to-central immune communication at the area postrema glial-barrier following bleomycin-induced sterile lung injury in adult rats

The pathways for peripheral-to-central immune communication (P → C I-comm) following sterile lung injury (SLI) are unknown. SLI evokes systemic and central inflammation, which alters central respiratory control and viscerosensory transmission in the nucleus tractus solitarii (nTS). These functional changes coincide with increased interleukin-1 beta (IL-1β) in the area postrema, a sensory circumventricular organ that connects P → C I-comm to brainstem circuits that control homeostasis. We hypothesize that IL-1β and its downstream transcriptional target, cyclooxygenase-2 (COX-2), mediate P → C I-comm in the nTS. In a rodent model of SLI induced by intratracheal bleomycin (Bleo), the sigh frequency and duration of post-sigh apnea increased in Bleo- compared to saline- treated rats one week after injury. This SLI-dependent change in respiratory control occurred concurrently with augmented IL-1β and COX-2 immunoreactivity (IR) in the funiculus separans (FS), a barrier between the AP and the brainstem. At this barrier, increases in IL-1β and COX-2 IR were confined to processes that stained for glial fibrillary acidic protein (GFAP) and that projected basolaterally to the nTS. Further, FS radial-glia did not express TNF-α or IL-6 following SLI. To test our hypothesis, we blocked central COX-1/2 activity by intracerebroventricular (ICV) infusion of Indomethacin (Ind). Continuous ICV Ind treatment prevented Bleo-dependent increases in GFAP + and IL-1β + IR, and restored characteristics of sighs that reset the rhythm. These data indicate that changes in sighs following SLI depend partially on activation of a central COX-dependent P → C I-comm via radial-glia of the FS.

The fatty acid amide hydrolase and cyclooxygenase-inhibitory properties of novel amide derivatives of carprofen

In experimental animals, inhibition of fatty acid amide hydrolase (FAAH) reduces the gastrointestinal damage produced by non-steroidal anti-inflammatory agents that act by inhibition of cyclooxygenase (COX). This suggests that compounds able to inhibit both enzymes may be potentially useful therapeutic agents. In the present study, we have investigated eight novel amide analogues of carprofen, ketoprofen and fenoprofen as potential FAAH/COX dual action inhibitors. Carpro-AM1 (2-(6-Chloro-9H-carbazol-2-yl)-N-(3-methylpyridin-2-yl)propenamide) and Carpro-AM6 (2-(6-Chloro-9H-carbazol-2-yl)-N-(3-chloropyridin-2-yl)propenamide) were found to be fully reversible inhibitors of the hydrolysis of 0.5 µM [³H]anandamide in rat brain homogenates with IC₅₀ values of 94 and 23 nM, respectively, i.e. 2-3 orders of magnitude more potent than carprofen in this respect. Both compounds inhibited the cyclooxygenation of arachidonic acid by ovine COX-1, and were more potent inhibitors of human recombinant COX-2 when 2-arachidonoylglycerol was used as substrate than when arachidonic acid was used. It is concluded that Carpro-AM1 and Carpro-AM6 are dual-acting FAAH/substrate-selective COX inhibitors.

Prostanoids contribute to regulation of inwardly rectifying K+ channels in intrarenal arterial smooth muscle cells

AIM

The inward rectifier K⁺ (Kir) channels and prostanoids are important factors in regulating vascular tone, but the relationship between them has not been well studied. We aimed to study the involvement of prostanoids in regulating Kir activity in the rat intrarenal arteries (RIRAs).

MAIN METHODS

The vascular tone of isolated RIRAs was recorded with a wire myograph. The intracellular Ca²⁺ concentrations ([Ca²⁺]_i) and Kir currents were measured with a Ca²⁺-sensitive fluorescence probe and patch clamp, respectively, in the arterial smooth muscle cell (ASMC) freshly isolated from RIRAs. Kir2.1 expression in RIRAs was assayed by Western blotting.

KEY FINDINGS

At 0.03-1.0 mM, BaCl₂ (a specific Kir blocker) concentration-dependently contracted RIRAs and elevated [Ca²⁺]_i levels. Mild stimulations with various vasoconstrictors at low concentrations significantly potentiated RIRA contraction induced by Kir closure with BaCl₂. In both the quiescent and the stimulated RIRAs, cyclooxygenase inhibition and thromboxane-prostanoid receptor (TPR) antagonism depressed BaCl₂-induced RIRA contraction, while nitric oxide (NO) synthetase inhibition and endothelium-denudation enhanced the contraction. Kir2.1 expression was significantly more abundant in smaller RIRAs. Ba²⁺-sensitive Kir currents were depressed by TPR agonist U46619 while increased by NO donor sodium nitroprusside.

SIGNIFICANCE

The present results reveal that vasoconstrictor stimulation augments RIRA contraction induced by Kir closure with Ba⁺ and indicate that prostanoid synthesis followed by TPR activation is involved in the modulation of the myocyte Kir activity. This study suggests that prostanoid synthesis and TPR may be potential targets for dysfunctions in renal blood circulation.

Exposure to growth hormone is associated with hepatic up-regulation of cPLA2α and COX

Continuously elevated levels of growth hormone (GH) during life in mice are associated with hepatomegaly due to hepatocytes hypertrophy and hyperplasia, chronic liver inflammation, elevated levels of arachidonic acid (AA) at young ages and liver tumors development at old ages. In this work, the hepatic expression of enzymes involved in AA metabolism, cPLA2α, COX1 and COX2 enzymes, was evaluated in young and old GH-transgenic mice. Mice overexpressing GH exhibited higher hepatic expression of cPLA2α, COX1 and COX2 in comparison to controls at young and old ages and in both sexes. In old mice, when tumoral and non-tumoral tissue were compared, elevated expression of COX2 was observed in tumors. In contrast, exposure to continuous lower levels of hormone for a short period affected COX1 expression only in males. Considering the role of inflammation during liver tumorigenesis, these findings support a role of alterations in AA metabolism in GH-driven liver tumorigenesis.

Toll-like receptor signaling induces a temporal switch towards a resolving lipid profile in monocyte-derived macrophages

Inflammation is a tightly regulated process. During the past decade it has become clear that the resolution of inflammation is an active process and its dysregulation can contribute to chronic inflammation. Several cells and soluble mediators, including lipid mediators, regulate the course of inflammation and its resolution. It is, however, unclear which signals and cells are involved in initiating the resolution process. Macrophages are tissue resident cells and key players in regulating tissue inflammation through secretion of soluble mediators, including lipids. We hypothesize that persistent inflammatory stimuli can initiate resolution pathways in macrophages. In this study, we detected 21 lipids in LPS-stimulated human monocyte-derived macrophages by liquid chromatography coupled to tandem mass spectrometry. Cyclooxygenase-derived Prostaglandins were observed in the first six hours of stimulation. Interestingly, a switch towards 15-lipoxygenase products, such as the pro-resolving lipid precursors 15-HEPE and 17-HDHA was observed after 24 h. The RNA and protein expression of cyclooxygenase and 15-lipoxygenase were in line with this trend. Treatment with 17-HDHA increased IL-10 production of monocyte-derived macrophages and decreased LTB₄ production by neutrophils, indicating the anti-inflammatory property of this lipid. These data reveal that monocyte-derived macrophages contribute to the resolution of inflammation in time by the production of pro-resolving lipids after an initial inflammatory stimulus.

Pharmacological appraisal of ligustrazine based cyclohexanone analogs as inhibitors of inflammatory markers

The targeting of pro-inflammatory enzymes becomes a therapeutic intervention when acute inflammation is proliferating in pathological conditions. This research is intended to carry out an evaluation of inhibiting and inducing enzymes with inflammatory associations with 28 cyclohexanone analogs based on the ligustrazine. Tests were undertaken with inhibitor screening assay kits using a range of synthetic compounds to investigate how they could inhibit the activity of cyclooxygenase (COX) enzymes, secretory phospholipase A₂ (sPLA₂), and lipoxygenase (LOX) enzyme. Significant and similar inhibitory activities against sPLA₂ with were noted with synthetic compounds which included 1f and 1g (IC₅₀ = 2.2 μM). The optimal inhibitory activity regarding LOX enzyme was shown with compounds 1d (IC₅₀ = 8.1 μM) and 1e (IC₅₀ = 7.5 μM). Additionally, the compounds 1b, 1d, 1e, 2n, and 2o were shown to be significant inhibitors of COX-1 activity with IC₅₀ values 0.09 to 0.7 μM. The outcomes of assays for COX inhibition demonstrated that the same compounds had a further strong inhibitive influence on the COX-2 enzyme, and certain compounds such as 1d, 1e, and 2n demonstrated enhanced potency compared with positive controls.

Prostaglandin E2 stimulates COX-2 expression via mitogen-activated protein kinase p38 but not ERK in human follicular dendritic cell-like cells

Background

Prostaglandin E2 (PGE₂) is an endogenous lipid mediator of inflammation. Its production is regulated by the rate-limiting upstream enzyme cyclooxygenase-2 (COX-2). We have recently demonstrated that the major cell type expressing COX-2 in the germinal center is follicular dendritic cell (FDC). In this study, to elucidate the molecular mechanism of PGE₂ in COX-2 production, we asked whether mitogen-activated protein kinases ERK and p38 might regulate COX-2 expression.

Results

FDC-like cells were used to analyze the phosphorylation kinetics of ERK and p38 and the impact of genetic knockdown. PGE₂ stimulation gave rise to a rapid increase of p38 but not ERK phosphorylation. In contrast, IL-1β induced phosphorylation of both MAPKs. Knockdown of p38 resulted in a marked suppression of COX-2 expression induced by either PGE₂ or IL-1β. ERK knockdown did not significantly affect the effect of PGE₂ and IL-1β on COX-2 induction. The differential results of p38 and ERK siRNA transfection were reproduced in the production of prostaglandins and in experiments performed with pharmacologic inhibitors.

Conclusions

Our data indicate that p38 is essentially required for PGE₂ to induce COX-2 expression in FDC-like cells. The current study helps to expand our understanding of the biological function of FDC at the molecular level and provides a potential rationale for the pharmacologic or genetic approaches to regulate p38 MAPK in the treatment of various inflammatory disorders.

Intracerebroventricularly injected nesfatin-1 activates central cyclooxygenase and lipoxygenase pathways

Nesfatin-1 is a multifunctional neuropeptide having crucial autonomic roles. It is well known that nesfatin-1 collaborates with other central neuromodulatory systems, such as central corticotropin-releasing hormone, melanocortin, oxytocin, and cholinergic systems to show its autonomic effects. Central arachidonic acid cascade plays an important role to provide the homeostasis by exhibiting similar autonomic effects to nesfatin-1. Based on these similarities, the current study was designed to show the effects of intracerebroventricularly (ICV) injected nesfatin-1 on the hypothalamic arachidonic acid (AA) cascade. Immunochemistry and western blot approaches demonstrated that ICV administration of nesfatin-1 provokes an increase in the hypothalamic cyclooxygenase (COX) -1, -2 and lipoxygenase (LOX) protein expression. Moreover, the microdialysis study demonstrated that centrally injected nesfatin-1 increased the posterior hypothalamic extracellular AA products. In conclusion, these findings report that while nesfatin-1 is generating its autonomic effects, it also might be using central prostaglandins and leukotrienes by activating central COX and LOX pathways.

Induction of cystic ovarian follicles (COFs) in cattle by using an intrafollicular injection of indomethacin

The aim of this study was to establish a model to induce cystic ovarian follicles (COFs) in cattle using the cyclooxygenase inhibitor, indomethacin. Eighteen Holstein-Frisian cattle were synchronized with prostaglandin F2alpha (PGF2α) and gonadotropin-releasing hormone (GnRH). Ultrasound-guided transvaginal intrafollicular injections were performed in 23 preovulatory follicles with different concentrations of indomethacin 16 h after GnRH administration. An injection of 0.2 ml 35 µM indomethacin solution (resulting in a final concentration of 8 µg/ml in the follicular fluid) was the minimal dosage leading to COF formation. The induced COFs reached a maximum mean diameter of 36.9 ± 4.5 mm eleven days after injection. The estrous cycle was extended to 25-39 days. Luteinization was first observed 4 days after injection, accompanied by a slight increase in plasma progesterone concentration. The bioactivity of indomethacin was demonstrated by the decrease of prostaglandin E2 in the follicular fluid of three animals. The method presented here is minimally invasive and allows for the generation of defined COFs for further investigations.

Neuroblastoma SH-SY5Y cytotoxicity, anti-amyloidogenic activity and cyclooxygenase inhibition of Lasianthus trichophlebus (Rubiaceae)

The anti-amyloidogenic potential and cyclooxygenase anti-inflammatory activity of Lasianthus trichophlebus extracts were evaluated. The MeOH extract (LTM) and chloroform extract (LTC) exhibited significant cytotoxic inhibition against the neuroblastoma SH-SY5Y cell with an IC₅₀ of 17.52 μg/mL and 12.28 μg/mL, respectively. Thioflavin T assay indicated the LTC extract inhibition (70.56% at 50 μg/mL) to be statistically comparable (p < 0.05) to the positive control. Cyclooxygenase inhibition against COX-1 and COX-2 enzymes gave IC₅₀ values for the LTM extract to be 18.20 and 29.60 µg/mL, respectively; while, the LTC extract showed 4.11 and 2.78 µg/mL, respectively. LC-MS of the LTM extract identified 22 putative compounds, which may prove to be pharmacologically relevant. This study has provided potential insights into the utilization of L. trichophlebus to develop safer plant-based agents for anti-inflammatory or neurodegenerative diseases.

Structural modification of aspirin to design a new potential cyclooxygenase (COX-2) inhibitors

Aspirin (Asp) is one of the most important and ancient member of nonsteroidal anti-inflammatory drugs (NSAID), commonly used in medication of fever, pain and inflammation. It can inhibit the synthesis of prostaglandin by blocking the cyclooxygenase (COX). Attempts have been taken to analyze aspirin together with some of its modified derivatives applying quantum mechanical calculations in order to compare their physicochemical and biochemical properties. Density functional theory (DFT) with B3LYP/6-31G (d, p) basis set has been employed to elucidate their thermal, molecular orbital, equilibrium geometrical properties in gas phase. Molecular docking and nonbonding interactions have been performed against human cyclooxygenase-2 protein 5F1A to investigate the binding affinity and mode(s) of newly designed aspirin derivatives. ADMET prediction has been utilized to compare the absorption, metabolism, and carcinogenic properties of new derivatives with parent drug (Asp). Thermal and geometrical results support the thermochemical stability and equilibrium geometry of all the structures. From the molecular docking simulation, most of the derivatives exhibited better binding affinity than parent drug (Asp) with the receptor protein (5F1A). ADMET prediction disclosed the improved pharmacokinetic properties with lower acute oral toxicity of some derivatives. Based on quantum chemical, molecular docking and ADMET analysis, this investigation can be useful to understand the physicochemical and biochemical/biological activities of Asp and its modified derivatives to search a new antipyretic analgesic drug.

In vivo COX-2 modulation and metabolite profiling of Pandanus tectorius leaves extracts

The Pandanus tectorius methanolic (PTM) and P. tectorius aqueous (PTA) extracts were investigated for their potential in vivo anti-inflammatory activity using carrageenan-induced rat paw edema. Parameters including paw thickness measurement, histopathological, and immunohistochemical cyclooxygenase (COX)-2 expression analyses were measured and analyzed. PTA at 500 mg/kg significantly reduced inflammation after induction of carrageenan (Carr), with mean paw thickness change of 0.110 ± 0.024 mm at sixth hour post-induction and histopathological mean inflammatory grade of 1.80 ± 0.20. The reduced immunohistochemical COX-2 expression using PTA at 500 mg/kg was determined with mean final 3,3'-diaminobenzidine (DAB) intensity of 63.70 ± 2.08. The profiling of metabolites by liquid chromatography-mass spectrometry (LC-MS) revealed presence of ethyl caffeate and dihydroconiferyl alcohol as putative secondary metabolites of PTA which were the major peaks and have been reported to possess anti-inflammatory activities. This research has provided scientific insights of utilizing P. tectorius as a potential anti-inflammatory agent containing secondary metabolites which may be pharmacologically relevant.

Differential role of vacuolar (H+)-ATPase in the expression and activity of cyclooxygenase-2 in human monocytes

Monocytes are professional immune cells that produce abundant levels of pro-inflammatory eicosanoids including prostaglandins and leukotrienes during inflammation. Vacuolar (H⁺)-ATPase (V-ATPase) is critically involved in a variety of inflammatory processes including cytokine trafficking and lipid mediator biosynthesis. However, its role in eicosanoid biosynthetic pathways in monocytes remains elusive. Here, we present a differential role of V-ATPase in the expression and in the activity of cyclooxygenase (COX)-2 in human monocytes. Pharmacological targeting of V-ATPase increased the expression of COX-2 protein in lipopolysaccharide-stimulated primary monocytes, which was paralleled by enhanced phosphorylation of p38 MAPK and ERK-1/2, without impacting the NF-κB and SAPK/JNK pathways. Targeting of both p38 MAPK and ERK-1/2 pathways showed that the kinase pathways are crucial for COX-2 expression in human monocytes. Despite increased COX-2 protein levels, however, suppression of V-ATPase activity impaired the biosynthesis of COX- and also of 5-lipoxygenase (LOX)-derived lipid mediators in monocytes without affecting 12-/15-LOX products, assessed by a metabololipidomics approach using UPLC-MS-MS analysis. Our results indicate that changes in the intracellular pH may contribute to suppression of COX-2 and 5-LOX activities. We suggest that V-ATPase on one hand limits COX-2 protein levels via restricting p38 MAPK and ERK-1/2 activation, while on the other hand it governs the cellular activity of COX-2 through appropriate adjustment of the intracellular pH.

The Protective Effects of Up-Regulating Prostacyclin Biosynthesis on Neuron Survival in Hippocampus

Cellular arachidonic acid (AA), an unsaturated fatty acid found ubiquitously in plasma membranes, is metabolized to different prostanoids, such as prostacyclin (PGI₂) and prostaglandin E₂ (PGE₂), by the three-step reactions coupling the upstream cyclooxygenase (COX) isoforms (COX-1 and COX-2) with the corresponding individual downstream synthases. While the vascular actions of these prostanoids are well-characterized, their specific roles in the hippocampus, a major brain area for memory, are poorly understood. The major obstacle for its understanding in the brain was to mimic the biosynthesis of each prostanoid. To solve the problem, we utilized Single-Chain Hybrid Enzyme Complexes (SCHECs), which could successfully control cellular AA metabolites to the desired PGI₂ or PGE₂. Our in vitro studies suggested that neurons with higher PGI₂ content and lower PGE₂ content exhibited survival protection and resistance to Amyloid-β-induced neurotoxicity. Further extending to an in vivo model, the hybrid of PGI₂-producing transgenic mice and Alzheimer's disease (AD) mice showed restored long-term memory. These findings suggested that the vascular prostanoids, PGI₂ and PGE₂, exerted significant regulatory influences on neuronal protection (by PGI₂), or damage (by PGE₂) in the hippocampus, and raised a concern that the wide uses of aspirin in cardiovascular diseases may exert negative impacts on neurodegenerative protection. Graphic Abstract Our study intended to understand the crosstalk of prostanoids in the hippocampus, a major brain area impacted in AD, by using hybrid enzymes to redirect the synthesis of prostanoids to PGE₂ and PGI₂, respectively. Our data indicated that during inflammation, the vascular mediators, PGI₂ and PGE₂, exerted significant regulatory influences on neuronal protection (by PGI₂), or damage (by PGE₂) in the hippocampus. These findings also raised a concern that the widely uses of non-steroidal anti-inflammatory drugs in cardiovascular diseases may exert negative impacts on neurodegenerative protection.