Prostaglandin E2 induces cyclooxygenase-2 expression in human non-pigmented ciliary epithelial cells through activation of p38 and p42/44 mitogen-activated protein kinases

Human experience and efficacy of omidenepag isopropyl (Eybelis®; Omlonti®): Discovery to approval of the novel non-prostaglandin EP2-receptor-selective agonist ocular hypotensive drug

More than 75 million people worldwide suffer from ocular hypertension (OHT)-associated retinal and optic nerve degenerative diseases that cause visual impairment and can lead to blindness. In an effort to find novel pharmaceutical therapeutics to combat OHT with reduced side-effect potential, several emerging drug candidates have advanced to human proof-of-concept in recent years. One such compound is a nonprostaglandin (non-PG) EP2-receptor-selective agonist (omidenepag isopropyl ester). Omidenepag (OMD; free acid form) is a novel non-PG that selectively binds to and activates the human EP2-prostglandin receptor (EP2R) with a high affinity (Ki = 3.6 nM) and which potently generates intracellular cAMP in living cells (EC50 = 3.9-8.3 nM). OMD significantly downregulated COL12A1 and COL13A1 mRNAs in human trabecular meshwork (TM) cells, a tissue involved in the pathogenesis of OHT. Omidenepag isopropyl (OMDI) potently and efficaciously lowered intraocular pressure (IOP) in ocular normotensive rabbits, dogs, and monkeys, and also in ocular hypertension (OHT) Cynomolgus monkeys, after a single topical ocular (t.o.) instillation at doses of 0.0001-0.01%. No reduction in IOP-lowering response to OMDI was observed after repeated t.o. dosing with OMDI in dogs and monkeys. Additive IOP reduction to OMDI was noted with brinzolamide, timolol, and brimonidine in rabbits and monkeys. OMDI 0.002% t.o. decreased IOP by stimulating the conventional (TM) and uveoscleral (UVSC) outflow of aqueous humor (AQH) in OHT monkeys. In a Phase-III clinical investigation, 0.002% OMDI (once daily t.o.) reduced IOP by 5-6 mmHg in OHT/primary open-angle glaucoma (POAG) patients (22-34 mmHg baseline IOPs) that was maintained over 12-months. In an additional month-long clinical study, 0.002% OMDI induced IOP-lowering equivalent to that of latanoprost (0.005%), a prostanoid FP-receptor agonist, thus OMDI was noninferior to latanoprost. Additive IOPreduction was also noted in OHT/OAG patients when OMDI (0.002%, once daily t.o.) and timolol (0.05%, twice daily t.o.) were administered. Patients with OHT/POAG who were low responders or nonresponders to latanoprost (0.005%, q.d.; t.o.) experienced significant IOP-lowering (additional approximately 3 mmHg) when they were switched over to OMDI 0.002% (q.d.; t.o.). No systemic or ocular adverse reactions (e.g. iris color changes/deepening of the upper eyelid sulcus/abnormal eyelash growth) were noted after a year-long, once-daily t.o. dosing with 0.002 % OMDI in OHT/POAG patients. However, OMDI caused transient conjunctival hyperemia. These characteristics of OMDI render it a suitable new medication for treating OHT and various types of glaucoma, especially where elevated IOP is implicated.

Peroxisome proliferator-activated receptors as targets to treat metabolic diseases: Focus on the adipose tissue, liver, and pancreas

The world is experiencing reflections of the intersection of two pandemics: Obesity and coronavirus disease 2019. The prevalence of obesity has tripled since 1975 worldwide, representing substantial public health costs due to its comorbidities. The adipose tissue is the initial site of obesity impairments. During excessive energy intake, it undergoes hyperplasia and hypertrophy until overt inflammation and insulin resistance turn adipocytes into dysfunctional cells that send lipotoxic signals to other organs. The pancreas is one of the organs most affected by obesity. Once lipotoxicity becomes chronic, there is an increase in insulin secretion by pancreatic beta cells, a surrogate for type 2 diabetes mellitus (T2DM). These alterations threaten the survival of the pancreatic islets, which tend to become dysfunctional, reaching exhaustion in the long term. As for the liver, lipotoxicity favors lipogenesis and impairs beta-oxidation, resulting in hepatic steatosis. This silent disease affects around 30% of the worldwide population and can evolve into end-stage liver disease. Although therapy for hepatic steatosis remains to be defined, peroxisome proliferator-activated receptors (PPARs) activation copes with T2DM management. Peroxisome PPARs are transcription factors found at the intersection of several metabolic pathways, leading to insulin resistance relief, improved thermogenesis, and expressive hepatic steatosis mitigation by increasing mitochondrial beta-oxidation. This review aimed to update the potential of PPAR agonists as targets to treat metabolic diseases, focusing on adipose tissue plasticity and hepatic and pancreatic remodeling.

Recently Approved Drugs for Lowering and Controlling Intraocular Pressure to Reduce Vision Loss in Ocular Hypertensive and Glaucoma Patients

Serious vision loss occurs in patients affected by chronically raised intraocular pressure (IOP), a characteristic of many forms of glaucoma where damage to the optic nerve components causes progressive degeneration of retinal and brain neurons involved in visual perception. While many risk factors abound and have been validated for this glaucomatous optic neuropathy (GON), the major one is ocular hypertension (OHT), which results from the accumulation of excess aqueous humor (AQH) fluid in the anterior chamber of the eye. Millions around the world suffer from this asymptomatic and progressive degenerative eye disease. Since clinical evidence has revealed a strong correlation between the reduction in elevated IOP/OHT and GON progression, many drugs, devices, and surgical techniques have been developed to lower and control IOP. The constant quest for new pharmaceuticals and other modalities with superior therapeutic indices has recently yielded health authority-approved novel drugs with unique pharmacological signatures and mechanism(s) of action and AQH drainage microdevices for effectively and durably treating OHT. A unique nitric oxide-donating conjugate of latanoprost, an FP-receptor prostaglandin (PG; latanoprostene bunod), new rho kinase inhibitors (ripasudil; netarsudil), a novel non-PG EP2-receptor-selective agonist (omidenepag isopropyl), and a form of FP-receptor PG in a slow-release intracameral implant (Durysta) represent the additions to the pharmaceutical toolchest to mitigate the ravages of OHT. Despite these advances, early diagnosis of OHT and glaucoma still lags behind and would benefit from further concerted effort and attention.

FP and EP2 prostanoid receptor agonist drugs and aqueous humor outflow devices for treating ocular hypertension and glaucoma

Prostaglandin (PG) receptors represent important druggable targets due to the many diverse actions of PGs in the body. From an ocular perspective, the discovery, development, and health agency approvals of prostaglandin F (FP) receptor agonists (FPAs) have revolutionized the medical treatment of ocular hypertension (OHT) and glaucoma. FPAs, such as latanoprost, travoprost, bimatoprost, and tafluprost, powerfully lower and control intraocular pressure (IOP), and became first-line therapeutics to treat this leading cause of blindness in the late 1990s to early 2000s. More recently, a latanoprost-nitric oxide (NO) donor conjugate, latanoprostene bunod, and a novel FP/EP3 receptor dual agonist, sepetaprost (ONO-9054 or DE-126), have also demonstrated robust IOP-reducing activity. Moreover, a selective non-PG prostanoid EP2 receptor agonist, omidenepag isopropyl (OMDI), was discovered, characterized, and has been approved in the United States, Japan and several other Asian countries for treating OHT/glaucoma. FPAs primarily enhance uveoscleral (UVSC) outflow of aqueous humor (AQH) to reduce IOP, but cause darkening of the iris and periorbital skin, uneven thickening and elongation of eyelashes, and deepening of the upper eyelid sulcus during chronic treatment. In contrast, OMDI lowers and controls IOP by activation of both the UVSC and trabecular meshwork outflow pathways, and it has a lower propensity to induce the aforementioned FPA-induced ocular side effects. Another means to address OHT is to physically promote the drainage of the AQH from the anterior chamber of the eye of patients with OHT/glaucoma. This has successfully been achieved by the recent approval and introduction of miniature devices into the anterior chamber by minimally invasive glaucoma surgeries. This review covers the three major aspects mentioned above to highlight the etiology of OHT/glaucoma, and the pharmacotherapeutics and devices that can be used to combat this blinding ocular disease.

Phospholipase Signaling in Breast Cancer

Breast cancer progression results from subversion of multiple intra- or intercellular signaling pathways in normal mammary tissues and their microenvironment, which have an impact on cell differentiation, proliferation, migration, and angiogenesis. Phospholipases (PLC, PLD and PLA) are essential mediators of intra- and intercellular signaling. They hydrolyze phospholipids, which are major components of cell membrane that can generate many bioactive lipid mediators, such as diacylglycerol, phosphatidic acid, lysophosphatidic acid, and arachidonic acid. Enzymatic processing of phospholipids by phospholipases converts these molecules into lipid mediators that regulate multiple cellular processes, which in turn can promote breast cancer progression. Thus, dysregulation of phospholipases contributes to a number of human diseases, including cancer. This review describes how phospholipases regulate multiple cancer-associated cellular processes, and the interplay among different phospholipases in breast cancer. A thorough understanding of the breast cancer-associated signaling networks of phospholipases is necessary to determine whether these enzymes are potential targets for innovative therapeutic strategies.

Identification of 4'-Demethyltangeretin as a Major Urinary Metabolite of Tangeretin in Mice and Its Anti-inflammatory Activities

The present study showed that oral administration of tangeretin (TAN) in mice resulted in the production of 4'-demethyltangeretin (4DT) as a major urinary metabolite. The anti-inflammatory efficacy of TAN and 4DT was determined in RAW 264.7 macrophages stimulated by lipopolysaccharides (LPS). 4DT produced considerably stronger inhibition on the overproduction of prostaglandin E₂ and nitric oxide than TAN did at the same concentrations. Western blot and quantitative polymerase chain reaction analyses indicated that 4DT exerted more potent suppressive activity on the over-expression of interleukin-1β, inducible nitric oxide synthase, and cyclooxygenase-2 than TAN. Treatments with TAN and 4DT diminished LPS-stimulated nuclear factor κB (NFκB) translocation via suppressing the degradation of inhibitor κB (IκBα). Furthermore, both compounds attenuated mitogen-activated protein kinases (MAPKs) and Akt signaling upregulated by LPS. Overall, our findings showed that TAN and 4DT inhibited the LPS-stimulated inflammatory response in macrophages by suppressing Akt/MAPKs/NFκB proinflammatory pathways, while 4DT showed more potent activity than TAN, its parent compound.

LINC00461 Promoted Endometrial Carcinoma Growth and Migration by Targeting MicroRNA-219-5p/Cyclooxygenase-2 Signaling Axis

Endometrial carcinoma (EC) ranks as the most common female genital cancer in developed countries. Lately, more and more long noncoding RNAs (lncRNAs) have been identified as vital regulators in numerous physiological and pathological processes, including EC. However, the expression pattern and precise functions of different lncRNAs in EC remain unclear. In this study, we reported LINC00461 was upregulated in EC patient tissues and cell lines. In addition, LINC00461 knockdown could remarkably suppress cell proliferation, cell cycle progression, cell migration, and promote cell apoptosis in EC cells. We discovered LINC00461 could sponge microRNA-219-5p (miR-219-5p) and suppress its expression, thereby upregulating expression level of miR-219-5p’s target, cyclooxygenase-2 (COX-2). In vivo animal models, LINC00461 knockdown inhibited tumor growth by increasing miR-219-5p level and reducing COX-2 expression, thus confirming LINC00461 functions as an oncogene in EC. In this study, a novel regulatory role of LINC00461/miR-219-5p/COX-2 axis was systematically investigated in context of EC, with the aim to provide promising intervention targets for EC therapy from bench to clinic.

Inflammation and JNK's Role in Niacin-GPR109A Diminished Flushed Effect in Microglial and Neuronal Cells With Relevance to Schizophrenia

Schizophrenia is a neuropsychiatric illness with no single definitive aetiology, making its treatment difficult. Antipsychotics are not fully effective because they treat psychosis rather than the cognitive or negative symptoms. Antipsychotics fail to alleviate symptoms when patients enter the chronic stage of illness. Topical application of niacin showed diminished skin flush in the majority of patients with schizophrenia compared to the general population who showed flushing. The niacin skin flush test is useful for identifying patients with schizophrenia at their ultra-high-risk stage, and understanding this pathology may introduce an effective treatment. This review aims to understand the pathology behind the diminished skin flush response, while linking it back to neurons and microglia. First, it suggests that there are altered proteins in the GPR109A-COX-prostaglandin pathway, inflammatory imbalance, and kinase signalling pathway, c-Jun N-terminal kinase (JNK), which are associated with diminished flush. Second, genes from the GPR109A-COX-prostaglandin pathway were matched against the 128-loci genome wide association study (GWAS) for schizophrenia using GeneCards, suggesting that G-coupled receptor-109A (GPR109A) may have a genetic mutation, resulting in diminished flush. This review also suggests that there may be increased pro-inflammatory mediators in the GPR109A-COX-prostaglandin pathway, which contributes to the diminished flush pathology. Increased levels of pro-inflammatory markers may induce microglial-activated neuronal death. Lastly, this review explores the role of JNK on pro-inflammatory mediators, proteins in the GPR109A-COX-prostaglandin pathway, microglial activation, and neuronal death. Inhibiting JNK may reverse the changes observed in the diminished flush response, which might make it a good therapeutic target.

Self-regulation of the inflammatory response by peroxisome proliferator-activated receptors

The peroxisome proliferator-activated receptor (PPAR) family includes three transcription factors: PPARα, PPARβ/δ, and PPARγ. PPAR are nuclear receptors activated by oxidised and nitrated fatty acid derivatives as well as by cyclopentenone prostaglandins (PGA₂ and 15d-PGJ₂) during the inflammatory response. This results in the modulation of the pro-inflammatory response, preventing it from being excessively activated. Other activators of these receptors are nonsteroidal anti-inflammatory drug (NSAID) and fatty acids, especially polyunsaturated fatty acid (PUFA) (arachidonic acid, ALA, EPA, and DHA). The main function of PPAR during the inflammatory reaction is to promote the inactivation of NF-κB. Possible mechanisms of inactivation include direct binding and thus inactivation of p65 NF-κB or ubiquitination leading to proteolytic degradation of p65 NF-κB. PPAR also exert indirect effects on NF-κB. They promote the expression of antioxidant enzymes, such as catalase, superoxide dismutase, or heme oxygenase-1, resulting in a reduction in the concentration of reactive oxygen species (ROS), i.e., secondary transmitters in inflammatory reactions. PPAR also cause an increase in the expression of IκBα, SIRT1, and PTEN, which interferes with the activation and function of NF-κB in inflammatory reactions.

A RIPK3-PGE2 Circuit Mediates Myeloid-Derived Suppressor Cell-Potentiated Colorectal Carcinogenesis

Receptor-interacting protein kinase 3 (RIPK3) is essential for mucosal repair in inflammatory bowel diseases (IBD) and colorectal cancer. However, its role in tumor immunity is unknown. Here, we report that decreased RIPK3 in colorectal cancer correlates with the accumulation of myeloid-derived suppressor cells (MDSC). Deficiency of RIPK3 boosted tumorigenesis via accumulation and immunosuppressive activity of MDSCs. Reduction of RIPK3 in MDSC and colorectal cancer cells elicited NFκB-transcribed COX-2, which catalyzed the synthesis of prostaglandin E₂ (PGE₂). PGE₂ exacerbated the immunosuppressive activity of MDSCs and accelerated tumor growth. Moreover, PGE₂ suppressed RIPK3 expression while enhancing expression of NFκB and COX-2 in MDSCs and colorectal cancer cells. Inhibition of COX-2 or PGE₂ receptors reversed the immunosuppressive activity of MDSCs and dampened tumorigenesis. Patient databases also delineated the correlation of RIPK3 and COX-2 expression with colorectal cancer survival. Our findings demonstrate a novel signaling circuit by which RIPK3 and PGE₂ regulate tumor immunity, providing potential ideas for immunotherapy against colorectal cancer.Significance: A novel signaling circuit involving RIPK3 and PGE₂ enhances accumulation and immunosuppressive activity of MDSCs, implicating its potential as a therapeutic target in anticancer immunotherapy.Graphical Abstract: http://cancerres.aacrjournals.org/content/canres/78/19/5586/F1.large.jpg Cancer Res; 78(19); 5586-99. ©2018 AACR.

Macrophage responses to lipopolysaccharide are modulated by a feedback loop involving prostaglandin E2, dual specificity phosphatase 1 and tristetraprolin

In many different cell types, pro-inflammatory agonists induce the expression of cyclooxygenase 2 (COX-2), an enzyme that catalyzes rate-limiting steps in the conversion of arachidonic acid to a variety of lipid signaling molecules, including prostaglandin E₂ (PGE₂). PGE₂ has key roles in many early inflammatory events, such as the changes of vascular function that promote or facilitate leukocyte recruitment to sites of inflammation. Depending on context, it also exerts many important anti-inflammatory effects, for example increasing the expression of the anti-inflammatory cytokine interleukin 10 (IL-10), and decreasing that of the pro-inflammatory cytokine tumor necrosis factor (TNF). The tight control of both biosynthesis of, and cellular responses to, PGE₂ are critical for the precise orchestration of the initiation and resolution of inflammatory responses. Here we describe evidence of a negative feedback loop, in which PGE₂ augments the expression of dual specificity phosphatase 1, impairs the activity of mitogen-activated protein kinase p38, increases the activity of the mRNA-destabilizing factor tristetraprolin, and thereby inhibits the expression of COX-2. The same feedback mechanism contributes to PGE₂-mediated suppression of TNF release. Engagement of the DUSP1-TTP regulatory axis by PGE₂ is likely to contribute to the switch between initiation and resolution phases of inflammation.

The protective mechanism of QGC in feline esophageal epithelial cells by interleukin-1β treatment

In a previous study, Quercetin-3-O-β-D-glucuronopyranoside (QGC) has anti-oxidative and anti-inflammatory effects in vivo. QGC is a flavonoid glucoside extracted from Rumex Aquaticus. We investigated the downstream target proteins involved in IL-1β-stimulated ROS production and the ability of QGC to inhibit ROS production. Cell viability was determined using the MTT reduction assay. Western blot analysis was performed with antibodies to investigate the activation of three MAPKs, NF-κB, and phosphorylated IκB-α (pIB), and the expression of COX-2. 2',7'-dichlorofluorescin diacetate was used to detect the generation of intracellular ROS species. When the cells were exposed to media containing IL-1β for 18 h, cell viability was not affected. QGC did not reduce the COX-2 expression induced by IL-1β. However; QGC attenuated the production of intracellular ROS induced by IL-1β. IL-1β increased the expression of ERK, p38 MAPK, and pIB, and nuclear translocation of NF-κB were recovered by the ROS scavenger N-acetyl-L-cysteine (NAC) and QGC, but not by the NADPH oxidase inhibitor diphenylene iodonium. Pretreatment of cells with the ERK inhibitor PD98059, the p38 MAPK inhibitor SB202190, NAC, and QGC attenuated nuclear translocation of NF-κB and activation of pIB. QGC has a scavenging effect on cytokine-induced ROS production, thereby preventing its downstream effects, nuclear translocation of NF-κB, and activation of pIB is mediated by activation of ERK and p38 MAPK, although QGC does not inhibit IL-1β-stimulated COX-2 expression in feline esophageal epithelial cells. The data suggest that QGC exerts anti-oxidative effects and inhibitory effects against esophageal epithelial cells signals by the action of IL-1β treatment.

COX-2 inhibitors arrest prostate cancer cell cycle progression by down-regulation of kinetochore/centromere proteins

BACKGROUND

Previous studies have shown that COX-2 inhibitors inhibit cancer cell proliferation. However, the molecular mechanism remains elusive.

METHODS

Prostate cancer LNCaP, 22Rv1, and PC3 cells were cultured and treated with the COX-2 inhibitors celecoxib and CAY10404. Knockdown of COX-2 in LNCaP cells was carried out using lentiviral vector-loaded COX-2 shRNA. Cell cycle progression and cell proliferation were analyzed by flow cytometry, microscopy, cell counting, and the MTT assay. The antagonists of EP1, EP2, EP3, and EP4 were used to examine the effects of the PGE2 signaling. The effect of COX-2 inhibitors and COX-2 knockdown on expression of the kinetochore/centromere genes and proteins was determined by RT-PCR and immunoblotting.

RESULTS

Treatment with the COX-2 inhibitors celecoxib and CAY10404 or knockdown of COX-2 significantly inhibited prostate cancer cell proliferation. Flow-cytometric analysis and immunofluorescent staining confirmed the cell cycle arrested at the G2/M phase. Biochemical analysis showed that inhibition of COX-2 or suppression of COX-2 expression induced a dramatic down-regulation of key proteins in the kinetochore/centromere assembly, such as ZWINT, Cdc20, Ndc80, CENP-A, Bub1, and Plk1. Furthermore, the EP1 receptor antagonist SC51322, but not the EP2, EP3, and EP4 receptor antagonists, produced similar effects to the COX-2 inhibitors on cell proliferation and down-regulation of kinetochore/centromere proteins, suggesting that the effect of the COX-2 inhibition is through inactivation of the EP1 receptor signaling.

CONCLUSIONS

Our studies indicate that inhibition of COX-2 can arrest prostate cancer cell cycle progression through inactivation of the EP1 receptor signaling and down-regulation of kinetochore/centromere proteins.

Prostaglandin EP1 receptor down-regulates expression of cyclooxygenase-2 by facilitating its proteasomal degradation

The enzyme cyclooxygenase-2 (COX-2) is rapidly and transiently up-regulated by a large variety of signals and implicated in pathologies such as inflammation and tumorigenesis. Although many signals cause COX-2 up-regulation, much less is known about mechanisms that actively down-regulate its expression. Here we show that the G protein-coupled receptor prostaglandin E(1) (EP(1)) reduces the expression of COX-2 in a concentration-dependent manner through a mechanism that does not require receptor activation. The reduction in COX-2 protein is not due to decreased protein synthesis and occurs because of enhancement of substrate-independent COX-2 proteolysis. Although EP(1) does not interfere with the entry of COX-2 into the endoplasmic reticulum-associated degradation cascade, it facilitates COX-2 ubiquitination through complex formation. Blockade of proteasomal activity results in degradation of the receptor and concomitant recovery in the expression of COX-2, suggesting that EP(1) may scaffold an unknown E3 ligase that ubiquitinates COX-2. These findings propose a new role for the EP(1) receptor in resolving inflammation through down-regulation of COX-2.

Role of COX-2 in lymphangiogenesis and restoration of lymphatic flow in secondary lymphedema

The pathophysiology of secondary lymphedema remains poorly understood. To clarify the roles of cyclooxygenase (COX)-2 in enhancement of lymphangiogenesis during secondary lymphedema, we tested a mouse tail model and evaluated the recurrence of lymph flow. To induce lymphedema, a circumferential incision was made in the tail of anesthetized mice to sever the dermal lymphatic vessels. The maximum diameters of the tails were measured weekly. We found that the diameters of the tails around the wounds were markedly increased after surgery, and reached maximum size 2 weeks after wounding in mice without a COX-2 inhibitor, celecoxib (Celecoxib-). Expression of COX-2 in wound granulation tissues was markedly increased 1 week after surgery compared with unwounded naive control mice. In Celecoxib-, recurrence of lymphatic flow in the wound granulation tissues was detected 3 weeks after surgical treatment. In contrast, lymphatic flow was markedly suppressed in mice treated with celecoxib (Celecoxib+). Newly formed lymphatic structures were identified in the granulation tissues formed at wounded lesions in Celecoxib-, whereas those were markedly suppressed in Celecoxib+. Interstitial tissue pressures in the distal areas of the tail wounds were markedly increased in Celecoxib+ with reduced expression of vascular endothelial cell growth factor (VEGF)-C. F4/80-positive cells were accumulated to the wound granulation tissues in Celecoxib-, and the accumulation of these cells was suppressed in Celecoxib+. Prostaglandin E(2) (PGE(2)) upregulated the expressions of VEGF-A and VEGF-C in cultured macrophages, but not human lymphatic microvascular endothelial cells. The present study therefore suggests that lymphangiogenesis, together with recurrence of lymph flow after surgical induction of lymphedema, is upregulated by COX-2 possibly via generation of PGs.

Effect of PF-04217329 a prodrug of a selective prostaglandin EP(2) agonist on intraocular pressure in preclinical models of glaucoma

Better control of intraocular pressure (IOP) is the most effective way to preserve visual field function in glaucomatous patients. While prostaglandin FP analogs are leading the therapeutic intervention for glaucoma, new target classes also are being identified with new lead compounds being developed for IOP reduction. One target class currently being investigated includes the prostaglandin EP receptor agonists. Recently PF-04217329 (Taprenepag isopropyl), a prodrug of CP-544326 (active acid metabolite), a potent and selective EP(2) receptor agonist, was successfully evaluated for its ocular hypotensive activity in a clinical study involving patients with primary open angle glaucoma. In the current manuscript, the preclinical attributes of CP-544326 and PF-0421329 have been described. CP-544326 was found to be a potent and selective EP(2) agonist (IC(50) = 10 nM; EC(50) = 2.8 nM) whose corneal permeability and ocular bioavailability were significantly increased when the compound was dosed as the isopropyl ester prodrug, PF-04217329. Topical ocular dosing of PF-04217329 was well tolerated in preclinical species and caused an elevation of cAMP in aqueous humor/iris-ciliary body indicative of in vivo EP(2) target receptor activation. Topical ocular dosing of PF-04217329 resulted in ocular exposure of CP-544326 at levels greater than the EC(50) for the EP(2) receptor. PF-04217329 when dosed once daily caused between 30 and 50% IOP reduction in single day studies in normotensive Dutch-belted rabbits, normotensive dogs, and laser-induced ocular hypertensive cynomolgus monkeys and 20-40% IOP reduction in multiple day studies compared to vehicle-dosed eyes. IOP reduction was sustained from 6 h through 24 h following a single topical dose. In conclusion, preclinical data generated thus far appear to support the clinical development of PF-04217329 as a novel compound for the treatment of glaucoma.

Cigarette smoking, cyclooxygenase-2 pathway and cancer

Cigarette smoking is a major cause of mortality and morbidity worldwide. Cyclooxygenase (COX) and its derived prostanoids, mainly including prostaglandin E2 (PGE2), thromboxane A2 (TxA2) and prostacyclin (PGI2), have well-known roles in cardiovascular disease and cancer, both of which are associated with cigarette smoking. This article is focused on the role of COX-2 pathway in smoke-related pathologies and cancer. Cigarette smoke exposure can induce COX-2 expression and activity, increase PGE2 and TxA2 release, and lead to an imbalance in PGI2 and TxA2 production in favor of the latter. It exerts pro-inflammatory effects in a PGE2-dependent manner, which contributes to carcinogenesis and tumor progression. TxA2 mediates other diverse biologic effects of cigarette smoking, such as platelet activation, cell contraction and angiogenesis, which may facilitate tumor growth and metastasis in smokers. Among cigarette smoke components, nicotine and its derived nitrosamines 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) are the most potent carcinogens. COX-2 and PGE2 have been shown to play a pivotal role in many cancers associated with cigarette smoking, including cancers of lung, gastric and bladder, while the information for the role of TxA2 and PGI2 in smoke-associated cancers is limited. Recent findings from our group have revealed how NNK influences the TxA2 to promote the tumor growth. Better understanding in the above areas may help to generate new therapeutic protocols or to optimize the existing treatment strategy.

Role of prostaglandins and specific place in therapy of bimatoprost in the treatment of elevated intraocular pressure and ocular hypertension: A closer look at the agonist properties of bimatoprost and the prostamides

Bimatoprost is the only representative of a novel class of prostaglandin ethanolamide (prostamide) compounds used therapeutically as an efficacious treatment for glaucoma. The pathways through which bimatoprost works to improve uveoscleral outflow to relieve elevated intraocular pressure are similar to those of the conventional prostaglandins used in glaucoma therapy, with some evidence of a preferential action at the trabecular meshwork. The pharmacology of bimatoprost is however, unclear. Pharmacological evidence supports a specific and distinct receptor-mediated agonist activity of bimatoprost at ‘prostamide’ receptors, which is selective to the prostamides as a class. However, other studies have reported either activity of bimatoprost at additional prostanoid and nonprostanoid receptors, or a conversion of bimatoprost to metabolites with agonist activity at prostaglandin FP receptors in the human eye. The formation of endogenous prostamides has been demonstrated in vivo, by a novel pathway involving the cyclooxygenase-2-mediated conversion of endogenous cannabinoid (endocannabinoid) substrates. Irrespective of the pharmacology of bimatoprost and the prostamides in general, further studies are needed to determine the biological role and biochemical pathology of prostamides in the human eye, particularly in glaucoma. Such studies may improve our understanding of uveoscleral flow and may offer new treatments for controlling intraocular pressure.

Prostaglandin pathway gene therapy for sustained reduction of intraocular pressure

Cyclooxygenase-2 (COX-2) is a rate-limiting enzyme in prostaglandin (PG) biosynthesis. In the eye, loss of COX-2 expression in aqueous humor-secreting cells has been associated with primary open-angle glaucoma (POAG). Reduction of intraocular pressure (IOP) is the main treatment goal in this disease. We used lentiviral vectors to stably express COX-2 and other PG biosynthesis and response transgenes in the ciliary body epithelium and trabecular meshwork (TM), the ocular suborgans that produce aqueous humor and regulate its outflow, respectively. We show that robust ectopic COX-2 expression and PG production require COX-2 complementary DNA (cDNA) sequence optimization. When COX-2 expression was coupled with a similarly optimized synthetic PGF2alpha receptor transgene to enable downstream signaling, gene therapy produced substantial and sustained reductions in IOP in a large animal model, the domestic cat. This study provides the first gene therapy for correcting the main cause of glaucoma.

Protective effects of DIDS against ethanol-induced gastric mucosal injury in rats

The compound 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) is an efficient anion exchanger inhibitor that can block the activities of anion exchanger 2 (AE2), which plays an indispensable role in gastric acid secretion. DIDS also has potent anti-oxidative and antiapoptosis activities. This study aimed to investigate the effect of DIDS on ethanol-induced mucosal damage in rats and to evaluate the underlying mechanisms that mediate the action of the compound. The rats received 1 ml of absolute ethanol or saline orally. DIDS [50 mg/kg intravenous (i.v.)] was given 5 min before ethanol administration. Gastric lesions were evaluated macroscopically, microscopically, and electron microscopically at 60 min after ethanol challenge. Gastric myeloperoxidase (MPO) activity, malonyldialdehyde (MDA) level, prostaglandin E2 (PGE2) synthesis, and cyclooxygenase-2 (COX-2) expression were assessed. For the evaluation of the effect of DIDS on gastric acid secretion, histamine-stimulatory gastric acid secretion was examined with or without pretreatment of DIDS (50 mg/kg; i.v.). Ethanol-induced gastric lesions were characterized by increasing gastric MDA level, MPO activity, and COX-2 expression, and decreasing PGE2 synthesis. It was found that DIDS significantly reduced the extent of gastric mucosal damage and reversed tissue MDA level and MPO activity. DIDS further enhanced the expression of COX-2 and reversed the decrease of PGE2. Our results suggested that DIDS is beneficial in rat model of gastric injury through mechanisms that involve inhibiting inflammatory cell infiltration and lipid peroxidation and up-regulating the COX-2/PGE2 pathway.

R(+)-methanandamide-induced apoptosis of human cervical carcinoma cells involves a cyclooxygenase-2-dependent pathway

PURPOSE

Cannabinoids have received renewed interest due to their antitumorigenic effects. Using human cervical carcinoma cells (HeLa), this study investigates the role of cyclooxygenase-2 (COX-2) in apoptosis elicited by the endocannabinoid analog R(+)-methanandamide (MA).

METHODS

COX-2 expression was assessed by RT-PCR and Western blotting. PGE2/PGD2 levels in cell culture supernatants and DNA fragmentation were measured by ELISA.

RESULTS

MA led to an induction of COX-2 expression, PGD2 and PGE2 synthesis. Cells were significantly less sensitive to MA-induced apoptosis when COX-2 was suppressed by siRNA or the selective COX-2 inhibitor NS-398. COX-2 expression and apoptosis by MA was also prevented by the ceramide synthase inhibitor fumonisin B1, but not by antagonists to cannabinoid receptors and TRPV1. In line with the established role of peroxisome proliferator-activated receptor gamma (PPARgamma) in the proapoptotic action of PGs of the D and J series, inhibition of MA-induced apoptosis was also achieved by siRNA targeting lipocalin-type PGD synthase (L-PGDS) or PPARgamma. A role of COX-2 and PPARgamma in MA-induced apoptosis was confirmed in another human cervical cancer cell line (C33A) and in human lung carcinoma cells (A549).

CONCLUSION

This study demonstrates COX-2 induction and synthesis of L-PGDS-derived, PPARgamma-activating PGs as a possible mechanism of apoptosis by MA.

Endocannabinoids in the retina: from marijuana to neuroprotection

The active component of the marijuana plant Cannabis sativa, Delta9-tetrahydrocannabinol (THC), produces numerous beneficial effects, including analgesia, appetite stimulation and nausea reduction, in addition to its psychotropic effects. THC mimics the action of endogenous fatty acid derivatives, referred to as endocannabinoids. The effects of THC and the endocannabinoids are mediated largely by metabotropic receptors that are distributed throughout the nervous and peripheral organ systems. There is great interest in endocannabinoids for their role in neuroplasticity as well as for therapeutic use in numerous conditions, including pain, stroke, cancer, obesity, osteoporosis, fertility, neurodegenerative diseases, multiple sclerosis, glaucoma and inflammatory diseases, among others. However, there has been relatively far less research on this topic in the eye and retina compared with the brain and other organ systems. The purpose of this review is to introduce the "cannabinergic" field to the retinal community. All of the fundamental works on cannabinoids have been performed in non-retinal preparations, necessitating extensive dependence on this literature for background. Happily, the retinal cannabinoid system has much in common with other regions of the central nervous system. For example, there is general agreement that cannabinoids suppress dopamine release and presynaptically reduce transmitter release from cones and bipolar cells. How these effects relate to light and dark adaptations, receptive field formation, temporal properties of ganglion cells or visual perception are unknown. The presence of multiple endocannabinoids, degradative enzymes with their bioactive metabolites, and receptors provides a broad spectrum of opportunities for basic research and to identify targets for therapeutic application to retinal diseases.

Molecular signaling in necrotizing enterocolitis: regulation of intestinal COX-2 expression

Necrotizing enterocolitis (NEC) is the most common surgical emergency in premature infants. The underlying etiology of NEC remains unknown, although bacterial colonization of the gut, formula feeding, and perinatal stress have been implicated as putative risk factors. The disease is characterized by exuberant gut inflammation leading to ischemia and coagulation necrosis of the intestinal epithelium. The molecular and cellular mechanisms responsible for these pathologic changes are poorly understood. It has been shown that various exogenous and endogenous mediators such as lipopolysaccharide, inflammatory cytokines, platelet activating factor, and nitric oxide may play a role in the pathogenesis of NEC. Recent studies in our laboratory and others have established a link between NEC and activation of cyclooxygenase-2, the enzyme that catalyzes the rate-limiting step in the biosynthesis of prostanoids. The challenge is in defining the molecular signaling pathways leading to accumulation of these mediators early in the disease progression, before the onset of tissue necrosis and systemic sepsis. Identification and characterization of these pathways could lead to the development of novel treatment strategies to alleviate the morbidity and mortality associated with NEC.

Prostaglandin E2 suppresses bacterial killing in alveolar macrophages by inhibiting NADPH oxidase

Prostaglandin E2 (PGE2) is a potent lipid mediator that effects changes in cell functions through ligation of four distinct G protein-coupled E prostanoid (EP) receptors (EP1-EP4). PGE2 inhibits bacterial killing and reactive oxygen intermediate (ROI) production by alveolar macrophages (AMs), although little is known about the operative molecular mechanisms. The aims of this study were to evaluate the molecular mechanisms and the specific EP receptors through which PGE2 inhibits killing of Klebsiella pneumoniae by AMs. The treatment of AMs with PGE2 suppressed the killing of K. pneumoniae, and this effect was blocked by an adenylyl cyclase inhibitor and mimicked by agonists for the stimulatory G protein (G(s))-coupled EP2 and EP4 receptors. Conversely, microbicidal activity was augmented by pretreatment with the cyclooxygenase inhibitor, indomethacin, and antagonists of EP2 and EP4. Similar results were found when ROI production was examined. PGE2 inhibition of killing and ROI generation was associated with its activation of the cAMP effectors, protein kinase A and exchange protein directly activated by cAMP-1, as well as attenuation of the phosphorylation and translocation of the reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase component, p47phox, to the phagosomal membrane. We conclude that PGE2 suppresses the microbicidal activity of AMs through the G(s)-coupled EP2/EP4 receptors, with increased cAMP inhibiting the assembly and activation of p47phox.

Activation of thromboxane receptor alpha induces expression of cyclooxygenase-2 through multiple signaling pathways in A549 human lung adenocarcinoma cells

Human lung adenocarcinoma A549 cells stably transfected with TPalpha (A549-TPalpha) were used to study agonist I-BOP-induced expression of cyclooxygenase-2 (COX-2) and the related mechanisms of induced expression. I-BOP, a TP agonist, induced a time- and dose-dependent expression of COX-2 in A549-TPalpha cells. The signaling pathways of I-BOP-induced COX-2 expression were elucidated by using various inhibitors of the signaling molecules. The effects of these inhibitors were assessed at protein level, enzyme activity and promoter activity of COX-2. Within MAPK family, both ERK and p38 MAPK but not JNK/SAPK pathways were involved in the induction. Other pathways such as JAK/Stat3 pathway and beta-catenin/TCF/LEF pathway also participated in the induction. The activation of key signaling molecules, ERK, p38 MAPK, CREB and NF-kappaB, involved in the COX-2 transcription was further studied at the phosphorylation step. Activation of ERK and p38 MAPK appeared to be mediated primarily by transactivation of EGFR, whereas activation of CREB and NF-kappaB was mediated by PKA, PKC and ERK. The role of CREB and NF-kappaB in I-BOP-induced COX-2 expression was further explored at the promoter level. Studies on promoter fragments and mutation of responsive motifs indicated that CRE and NF-kappaB sites are critical for the COX-2 induction. Distal NF-kappaB site is essential for the basal induction of the COX-2 transcription, whereas CRE and proximal NF-kappaB sites are important for the induced transcription. These results indicate that I-BOP-induced COX-2 expression through multiple signaling pathways.

Prostaglandin E2-EP4 receptor promotes endothelial cell migration via ERK activation and angiogenesis in vivo

Prostaglandin E2 (PGE(2)), a major product of cyclooxygenase, exerts its functions by binding to four G protein-coupled receptors (EP1-4) and has been implicated in modulating angiogenesis. The present study examined the role of the EP4 receptor in regulating endothelial cell proliferation, migration, and tubulogenesis. Primary pulmonary microvascular endothelial cells were isolated from EP4(flox/flox) mice and were rendered null for the EP4 receptor with adenoCre virus. Whereas treatment with PGE(2) or the EP4 selective agonists PGE(1)-OH and ONO-AE1-329 induced migration, tubulogenesis, ERK activation and cAMP production in control adenovirus-transduced endothelial EP4(flox/flox) cells, no effects were seen in adenoCre-transduced EP4(flox/flox) cells. The EP4 agonist-induced endothelial cell migration was inhibited by ERK, but not PKA inhibitors, defining a functional link between PGE(2)-induced endothelial cell migration and EP4-mediated ERK signaling. Finally, PGE(2), as well as PGE(1)-OH and ONO-AE1-329, also promoted angiogenesis in an in vivo sponge assay providing evidence that the EP4 receptor mediates de novo vascularization in vivo.

Synthetic prostacyclin analogs differentially regulate macrophage function via distinct analog-receptor binding specificities

PGI(2) (prostacyclin) is a lipid mediator with vasodilatory and antithrombotic effects used in the treatment of vasoconstrictive/ischemic diseases including pulmonary artery hypertension. However, emerging research supports a role for PGs, including PGI(2), in the regulation of both innate and acquired immunity. As PGI(2) is unstable, we sought to define the effects of various PGI(2) analogs on resident alveolar macrophage (AM) and peritoneal macrophage (PM) innate immune functions. The effects of iloprost, carbaprostacyclin, and treprostinil on the regulation of phagocytosis, bacterial killing, and inflammatory mediator production were determined in both macrophage populations from rats. Iloprost failed to suppress AM functions to the same degree that it did in PMs, a characteristic shared by carbaprostacyclin. This difference reflected greater expression of the G(alphas) protein-coupled I prostanoid receptor and greater cAMP generation in PMs than AMs. Treprostinil inhibited phagocytosis, bacterial killing, and cytokine generation in AMs to a much greater degree than the other PGI(2) analogs and more closely resembled the effects of PGE(2). Studies with the E prostanoid (EP) 2 receptor antagonist AH-6809 and EP2-null macrophages indicated that this was due in part to the previously unknown ability of treprostinil to stimulate the EP2 receptor. The present investigation for the first time identifies differences in immunoregulatory properties of clinically administered PGI(2) analogs. These studies are the first to explore the capacity of PGI(2) to regulate bacterial killing and phagocytosis in macrophages, and our findings may hold important consequences regarding the risk of infection for patients receiving such agents.

The role of the cylooxygenase pathway in nociception and pain

Cycloxygenase (COX) pathways have long been targeted for the treatment of inflammatory pain, initially through the use of NSAIDs. With the demonstration of two major COX isoforms, COX-1 and COX-2, involved in the production of prostanoids, but with different distribution and regulation, selective COX-2 inhibitors have been developed. This review covers factors influencing COX enzyme activity, the role of their products in the development and maintenance of pain and discusses recent safety concerns of COX-2 inhibitors.

Tangeretin suppresses IL-1beta-induced cyclooxygenase (COX)-2 expression through inhibition of p38 MAPK, JNK, and AKT activation in human lung carcinoma cells

Tangeretin (5,6,7,8,4'-pentamethoxyflavone) is a polymethoxylated flavonoid concentrated in the peel of citrus fruits. Recent studies have shown that tangeretin exhibits anti-proliferative, anti-invasive, anti-metastatic, and antioxidant activities. However, the anti-inflammatory properties of tangeretin are unclear. In this study, we examine the effects of tangeretin and its structure-related compound, nobiletin, on the expression of cyclooxygenases-2 (COX-2) in human lung epithelial carcinoma cells, A549, and human non-small cell lung carcinoma cells, H1299. Tangeretin exerts a much better inhibitory activity than nobiletin against IL-1beta-induced production of COX-2 in A549 cells, and it effectively represses the constitutively expressed COX-2 in H1299. RT-PCR was used to investigate the transcriptional inhibition of COX-2 by tangeretin. COX-2 mRNA was rapidly induced by IL-1beta in 3h and markedly suppressed by tangeretin. IL-1beta-induced the activation of ERK, p38 MAPK, JNK, and AKT in A549 cells. COX-2 expression in response to IL-1beta was attenuated by pretreatment with SB203580, SP600125, and LY294002, but not with PD98059, suggesting the involvement of p38 MAPK, JNK, and PI3K in this response. Pretreatment of cells with tangeretin inhibited IL-1beta-induced p38 MAPK, JNK, and AKT phosphorylation and the downstream activation of NF-kappaB. These results may reveal that the tangeretin inhibition of IL-1beta-induced COX-2 expression in A549 cells is, at least in part, mediated through suppression of NF-kappaB transcription factor as well as through suppression of the signaling proteins of p38 MAPK, JNK, and PI3K, but not of ERK.

Polyamine-mediated reduction in human airway epithelial migration in response to wounding is PGE2 dependent through decreases in COX-2 and cPLA2 protein levels

Both ornithine decarboxylase inhibition to deplete polyamines and cyclooxygenase inhibition diminish the migration response to injury of human airway epithelial cells in tissue culture monolayers by approximately 75%. Restoration of normal migration responses is achieved in the polyamine depleted system either by exogenous reconstitution of polyamines or the addition of prostaglandin E(2) (PGE(2)). However, only PGE(2) was able to restore migration in the cyclooxygenase-inhibited systems. Western blot for cyclooxygenase-2 and cytosolic phospholipase A(2) protein levels and ELISAs for PGE(2) secretion demonstrate dramatic increases over 24-48 h after monolayer wounding. These increases are completely abolished by polyamine depletion or cyclooxygenase inhibition. We conclude that polyamine inhibition decreases cellular migration in response to injury in airway epithelial cells at least in part through inhibiting normal PGE(2) production in response to injury. This may be brought about by decreases in cytosolic phospholipase A(2) and cyclooxygenase-2 protein levels.