Intranasal 15d-PGJ2 inhibits the growth of rat lactotroph pituitary neuroendocrine tumors by inducing PPARγ-dependent apoptotic and autophagic cell death

PPARγ agonists have been reported to induce cell death in pituitary neuroendocrine tumor (PitNET) cell cultures. However, the therapeutic effects of PPARγ agonists in vivo remain unclear. In the present study, we found that intranasal 15d-PGJ2, an endogenous PPARγ agonist, resulted in growth suppression of Fischer 344 rat lactotroph PitNETs induced by subcutaneous implantation with a mini-osmotic pump containing estradiol. Intranasal 15d-PGJ2 reduced the volume and weight of the pituitary gland and the level of serum prolactin (PRL) in rat lactotroph PitNETs. 15d-PGJ2 treatment attenuated pathological changes and significantly decreased the ratio of PRL/pituitary-specific transcription factor 1 (Pit-1) and estrogen receptor α (ERα)/Pit-1 double-positive cells. Moreover, 15d-PGJ2 treatment induced apoptosis in the pituitary gland characterized by an increased ratio of TUNEL-positive cells, cleavage of caspase-3, and elevated activity of caspase-3. 15d-PGJ2 treatment decreased the levels of cytokines, including TNF-α, IL-1β, and IL-6. Furthermore, 15d-PGJ2 treatment markedly increased the protein expression of PPARγ and blocked autophagic flux, as evidenced by the accumulation of LC3-II and SQSTM1/p62 and the decrease in LAMP-1 expression. Importantly, all these effects mediated by 15d-PGJ2 were abolished by cotreatment with the PPARγ antagonist GW9662. In conclusion, intranasal 15d-PGJ2 suppressed the growth of rat lactotroph PitNETs by inducing PPARγ-dependent apoptotic and autophagic cell death. Therefore, 15d-PGJ2 may be a potential new drug for lactotroph PitNETs.

Low 15d-PGJ2 status is associated with oxidative stress in chronic obstructive pulmonary disease patients

BACKGROUND

Peroxisome proliferator-activated receptor γ (PPARγ) is a ligand-dependent nuclear receptor and highly expressed in human and rodent lungs. 15-Deoxy-delta-^12,14-prostaglandin J2 (15d-PGJ2), known for cyclopentenone prostaglandin, is the endogenous ligand of PPARγ. However, the associations among PPARγ, 15d-PGJ2 and chronic obstructive pulmonary disease (COPD) were unclear.

METHODS

All 130 fasting blood samples and 40 lung specimens were obtained from COPD patients and control subjects. Serum 15d-PGJ2 was detected by ELISA. The expressions of oxidative stress indicators were measured using western blotting and PPARγ nuclei were evaluated with immunohistochemistry in lungs. The associations among serum 15d-PGJ2, pulmonary PPARγ and oxidative stress indicators, and COPD were estimated.

RESULTS

Serum 15d-PGJ2 was reduced in COPD patients compared with healthy volunteers. Linear and logistic regression analysis indicated that serum 15d-PGJ2 was positively associated with pulmonary function in COPD patients. In addition, PPARγ-positive nuclei were reduced and oxidative stress indicators, included HO-1 and NOX-4, were increased in lungs of COPD patients. Further correlative analysis suggested that pulmonary function parameters was positively correlated with serum 15d-PGJ2 and pulmonary PPARγ-positive nuclei, inversely related to oxidative stress indicators in lungs of COPD patients. Pretreatment with 15d-PGJ2 obviously attenuated TNFα-induced oxidative stress in BEAS-2B cells.

CONCLUSIONS

Serum 15d-PGJ2 and pulmonary PPARγ are reduced, and oxidative stress is elevated in COPD patients. Serum 15d-PGJ2 is inversely associated with oxidative stress in COPD patients.

Involvement of FoxO1, Sp1, and Nrf2 in Upregulation of Negative Regulator of ROS by 15d-PGJ2 Attenuates H2O2-Induced IL-6 Expression in Rat Brain Astrocytes

Excessive production of reactive oxygen species (ROS) by NADPH oxidase (Nox) resulted in inflammation. The negative regulator of ROS (NRROS) dampens ROS generation during inflammatory responses. 15-Deoxy-∆12,14-prostaglandin J₂ (15d-PGJ₂) exhibits neuroprotective effects on central nervous system (CNS). However, whether 15d-PGJ₂-induced NRROS expression was unknown in rat brain astrocytes (RBA-1). NRROS expression was determined by Western blot, RT/real-time PCR, and promoter activity assays. The signaling components were investigated using pharmacological inhibitors or specific siRNAs. The interaction between transcription factors and the NRROS promoter was investigated by chromatin immunoprecipitation assay. Upregulation of NRROS on the hydrogen peroxide (H₂O₂)-mediated ROS generation and interleukin 6 (IL-6) secretion was measured. 15d-PGJ₂-induced NRROS expression was mediated through PI3K/Akt-dependent activation of Sp1 and FoxO1 and established the essential promoter regions. We demonstrated that 15d-PGJ₂ activated PI3K/Akt and following by cooperation between phosphorylated nuclear FoxO1 and Sp1 to initiate the NRROS transcription. In addition, Nrf2 played a key role in NRROS expression induced by 15d-PGJ₂ which was mediated through its phosphorylation. Finally, the NRROS stable clones attenuated the H₂O₂-induced ROS generation and expression of IL-6 through suppressing the Nox-2 activity. These results suggested that 15d-PGJ₂-induced NRROS expression is mediated through a PI3K/Akt-dependent FoxO1 and Sp1 phosphorylation, and Nrf2 cascade, which suppresses ROS generation through attenuating the p47^phox phosphorylation and gp91^phox formation and IL-6 expression in RBA-1 cells. These results confirmed the mechanisms underlying 15d-PGJ₂-induced NRROS expression which might be a potential strategy for prevention and management of brain inflammatory and neurodegenerative diseases.

15d-PGJ2 Promotes ROS-Dependent Activation of MAPK-Induced Early Apoptosis in Osteosarcoma Cell In Vitro and in an Ex Ovo CAM Assay

Osteosarcoma (OS) is the most common type of bone tumor, and has limited therapy options. 15-Deoxy-Δ^12,14-prostaglandin J₂ (15d-PGJ₂) has striking anti-tumor effects in various tumors. Here, we investigated molecular mechanisms that mediate anti-tumor effects of 15d-PGJ₂ in different OS cell lines. Human U2-OS and Saos-2 cells were treated with 15d-PGJ₂ and cell survival was measured by MTT assay. Cell proliferation and motility were investigated by scratch assay, the tumorigenic capacity by colony forming assay. Intracellular ROS was estimated by H₂DCFDA. Activation of MAPKs and cytoprotective proteins was detected by immunoblotting. Apoptosis was detected by immunoblotting and Annexin V/PI staining. The ex ovo CAM model was used to study growth capability of grafted 15d-PGJ₂-treated OS cells, followed by immunohistochemistry with hematoxylin/eosin and Ki-67. 15d-PGJ₂ substantially decreased cell viability, colony formation and wound closure capability of OS cells. Non-malignant human osteoblast was less affected by 15d-PGJ₂. 15d-PGJ₂ induced rapid intracellular ROS production and time-dependent activation of MAPKs (pERK1/2, pJNK and pp38). Tempol efficiently inhibited 15d-PGJ₂-induced ERK1/2 activation, while N-acetylcystein and pyrrolidine dithiocarbamate were less effective. Early but weak activation of cytoprotective proteins was overrun by induction of apoptosis. A structural analogue, 9,10-dihydro-15d-PGJ₂, did not show toxic effects in OS cells. In the CAM model, we grafted OS tumors with U2-OS, Saos-2 and MG-63 cells. 15d-PGJ₂ treatment resulted in significant growth inhibition, diminished tumor tissue density, and reduced tumor cell proliferation for all cell lines. Our in vitro and CAM data suggest 15d-PGJ₂ as a promising natural compound to interfere with OS tumor growth.

15-Deoxy-Δ-12,14-prostaglandin J2 effects in vascular smooth muscle cells: Implications in vascular smooth muscle cell proliferation and contractility

15-Deoxy-Δ-^12,14-prostaglandin J2 (15d-PGJ2) is an endogenous agonist of the ligand dependent transcriptional factor, peroxisome proliferator-activated receptor -gamma (PPAR-γ). Although PPAR-γ mediates some actions of 15d-PGJ2, many actions of 15d-PGJ2 are independent of PPAR-γ. The PPAR-γ signaling pathway has beneficial effects on tumor progression, inflammation, oxidative stress, and angiogenesis in numerous studies. In this review, various studies were analyzed to understand the effects of 15d-PGJ2 in vascular smooth muscle cells (VSMC)s. 15d-PGJ2 inhibits proliferation of VSMCs during vascular remodeling and it alters the expression of contractile proteins and inflammatory components within these cells as well. However, the effects of 15d-PGJ2 as well as its ability to induce PPAR-γ activation remains controversial as contradictory effects of this prostaglandin in VSMCs exist. Understanding the mechanisms by which 15d-PGJ2 elicit beneficial actions whether by PPAR-γ activation or independently, will aid in developing new therapeutic strategies for diseases such as hypertension with an inflammatory component. Although great advances are being made, more research is needed to reach definitive conclusions.

Oxylipin biosynthesis reinforces cellular senescence and allows detection of senolysis

Cellular senescence is a stress or damage response that causes a permanent proliferative arrest and secretion of numerous factors with potent biological activities. This senescence-associated secretory phenotype (SASP) has been characterized largely for secreted proteins that participate in embryogenesis, wound healing, inflammation, and many age-related pathologies. By contrast, lipid components of the SASP are understudied. We show that senescent cells activate the biosynthesis of several oxylipins that promote segments of the SASP and reinforce the proliferative arrest. Notably, senescent cells synthesize and accumulate an unstudied intracellular prostaglandin, 1a,1b-dihomo-15-deoxy-delta-12,14-prostaglandin J2. Released 15-deoxy-delta-12,14-prostaglandin J2 is a biomarker of senolysis in culture and in vivo. This and other prostaglandin D2-related lipids promote the senescence arrest and SASP by activating RAS signaling. These data identify an important aspect of cellular senescence and a method to detect senolysis.

Cyclopentenone Prostaglandins and Structurally Related Oxidized Lipid Species Instigate and Share Distinct Pro- and Anti-inflammatory Pathways

Oxidized lipids play a critical role in a variety of diseases with two faces: pro- and anti-inflammatory. The molecular mechanisms of this Janus-faced activity remain largely unknown. Here, we have identified that cyclopentenone-containing prostaglandins such as 15d-PGJ2 and structurally related oxidized phospholipid species possess a dual and opposing bioactivity in inflammation, depending on their concentration. Exposure of dendritic cells (DCs)/macrophages to low concentrations of such lipids before Toll-like receptor (TLR) stimulation instigates an anti-inflammatory response mediated by nuclear factor erythroid 2-related factor 2 (Nrf2)-dependent inhibition of nuclear factor κB (NF-κB) activation and downstream targets. By contrast, high concentrations of such lipids upon TLR activation of DCs/macrophages result in inflammatory apoptosis characterized by mitochondrial depolarization and caspase-8-mediated interleukin (IL)-1β maturation independently of Nrf2 and the classical inflammasome pathway. These results uncover unexpected pro- and anti-inflammatory activities of physiologically relevant lipid species generated by enzymatic and non-enzymatic oxidation dependent on their concentration, a phenomenon known as hormesis.

Oral administration of curcumin ameliorates pulmonary fibrosis in mice through 15d-PGJ2-mediated induction of hepatocyte growth factor in the colon

Oral administration of curcumin has been shown to inhibit pulmonary fibrosis (PF) despite its extremely low bioavailability. In this study, we investigated the mechanisms underlying the anti-PF effect of curcumin in focus on intestinal endocrine. In bleomycin- and SiO₂-treated mice, curcumin (75, 150 mg· kg^-1 per day) exerted dose-dependent anti-PF effect when administered orally or rectally but not intravenously, implying an intestinal route was involved in the action of curcumin. We speculated that curcumin might promote the generation of gut-derived factors and the latter acted as a mediator subsequently entering the lungs to ameliorate fibrosis. We showed that oral administration of curcumin indeed significantly increased the expression of gut-derived hepatocyte growth factor (HGF) in colon tissues. Furthermore, in bleomycin-treated mice, the upregulated protein level of HGF in lungs by oral curcumin was highly correlated with its anti-PF effect, which was further confirmed by coadministration of c-Met inhibitor SU11274. Curcumin (5-40 μM) dose-dependently increased HGF expression in primary mouse fibroblasts, macrophages, CCD-18Co cells (fibroblast cell line), and RAW264.7 cells (monocyte-macrophage cell line), but not in primary colonic epithelial cells. In CCD-18Co cells and RAW264.7 cells, curcumin dose-dependently activated PPARγ and CREB, whereas PPARγ antagonist GW9662 (1 μM) or cAMP response element (CREB) inhibitor KG-501 (10 μM) significantly decreased the boosting effect of curcumin on HGF expression. Finally, we revealed that curcumin dose-dependently increased the production of 15-deoxy-Δ^{12, 14}-prostaglandin J2 (15d-PGJ2) in CCD-18Co cells and RAW264.7 cells, which was a common upstream of the two transcription factors. Moreover, both the in vitro and in vivo effects of curcumin were diminished by coadministration of HPGDS-inhibitor-1, an inhibitor of 15d-PGJ2 generation. Together, curcumin promotes the expression of HGF in colonic fibroblasts and macrophages by activating PPARγ and CREB via an induction of 15d-PGJ2, and the HGF enters the lungs giving rise to an anti-PF effect.

Could Arachidonic Acid-Derived Pro-Resolving Mediators Be a New Therapeutic Strategy for Asthma Therapy?

Asthma represents one of the leading chronic diseases worldwide and causes a high global burden of death and disability. In asthmatic patients, the exacerbation and chronification of the inflammatory response are often related to a failure in the resolution phase of inflammation. We reviewed the role of the main arachidonic acid (AA) specialized pro-resolving mediators (SPMs) in the resolution of chronic lung inflammation of asthmatics. AA is metabolized by two classes of enzymes, cyclooxygenases (COX), which produce prostaglandins (PGs) and thromboxanes, and lypoxygenases (LOX), which form leukotrienes and lipoxins (LXs). In asthma, two primary pro-resolving derived mediators from COXs are PGE₂ and the cyclopentenone prostaglandin15-Deoxy-Delta-12,14-PGJ₂ (15d-PGJ₂) while from LOXs are the LXA₄ and LXB₄. In different models of asthma, PGE₂, 15d-PGJ₂, and LXs reduced lung inflammation and remodeling. Furthermore, these SPMs inhibited chemotaxis and function of several inflammatory cells involved in asthma pathogenesis, such as eosinophils, and presented an antiremodeling effect in airway epithelial, smooth muscle cells and fibroblasts in vitro. In addition, PGE₂, 15d-PGJ₂, and LXs are all able to induce macrophage reprogramming to an alternative M2 pro-resolving phenotype in vitro and in vivo. Although PGE₂ and LXA₄ showed some beneficial effects in asthmatic patients, there are limitations to their clinical use, since PGE₂ caused side effects, while LXA₄ presented low stability. Therefore, despite the strong evidence that these AA-derived SPMs induce resolution of both inflammatory response and tissue remodeling in asthma, safer and more stable analogs must be developed for further clinical investigation of their application in asthma treatment.

Acellular Human Amniotic Membrane Scaffold with 15d-PGJ2 Nanoparticles in Postinfarct Rat Model

The difficulty in the regeneration of cardiomyocytes after myocardial infarction is a major cause of heart failure. Together, the amniotic membrane and 15-deoxy-Δ12,14-prostaglandin J2 (15d-PGJ₂) can help in the recovery of cardiomyocyte, as they present many growth factors and anti-inflammatory effect, respectively. The objective of this study is to compare the efficacy of Human Decellularized Amniotic Membrane Scaffold (AHAS) loaded with 15d-PGJ₂ in improving ventricular function in a rat model of postinfarct ventricular dysfunction. Myocardial infarction was induced in 24 rats by left coronary occlusion. After a week, the animals were subjected to echocardiography for evaluation of left ventricle ejection fraction (LVEF), left ventricle end diastolic volume (LVEDV), and left ventricle end systolic volume (LVESV). Animals with ejection fraction <40% were included in the study and were randomized into three groups: control (n = 8), AHAS (n = 8) and AHAS +15d-PGJ₂ (n = 8). In the AHAS group only the membrane was implanted, whereas in the AHAS +15d-PGJ₂ the membrane +15d-PGJ₂ was implanted on myocardial infarction. Echocardiographic evaluation was performed after 1 month. For histological analysis, heart tissue was stained with Gomori trichome, Sirius Red, the antibody against CD31 and connexin 43 (Cx43). There were no significant differences in the baseline LVEF, LVEDV, and LVESV in all groups. After 1 month, ejection fraction decreased in the control group but increased in the AHAS group and in the AHAS +15d-PGJ₂ group in comparison with the control group. The LVEDV and LVESV in the AHAS and AHAS +15d-PGJ₂ groups decreased compared with the control group, featuring a ventricular antiremodeling effect. Histopathology of the infarcted area identified the reduction of infarct size and collagen type 1 in the AHAS and AHAS +15d-PGJ₂ groups. New blood vessels and cardiomyocytes have been identified in an infarcted area by CD31 and Cx43. AHAS +15d-PGJ₂ provided an increase in the ejection fraction and prevented ventricular dilation in this postinfarction ventricular dysfunction model. Impact Statement Our study demonstrated reduction of myocardial fibrosis, proliferation of cardiomyocytes and increase in ejection fraction in rats after experimental acellular amniotic membrane scaffold (AHAS) carrying nanoparticles of 15d-PGJ2 scaffold engraftment in infarcted myocardium. AHAS grafts facilitated colonization of fibrotic myocardium regions with new contractile cells, in addition to preventing reduction of left ventricle wall thickness. This contribution is theoretically and practically relevant as current literature describes experimental studies performed on cardiac ischemic models which present conflicting results concerning cell types used in a research model.

Positive Reinforcing Mechanisms between GPR120 and PPARγ Modulate Insulin Sensitivity

G protein-coupled receptor 120 (GPR120) and PPARγ agonists each have insulin sensitizing effects. But whether these two pathways functionally interact and can be leveraged together to markedly improve insulin resistance has not been explored. Here, we show that treatment with the PPARγ agonist rosiglitazone (Rosi) plus the GPR120 agonist Compound A leads to additive effects to improve glucose tolerance and insulin sensitivity, but at lower doses of Rosi, thus avoiding its known side effects. Mechanistically, we show that GPR120 is a PPARγ target gene in adipocytes, while GPR120 augments PPARγ activity by inducing the endogenous ligand 15d-PGJ2 and by blocking ERK-mediated inhibition of PPARγ. Further, we used macrophage- (MKO) or adipocyte-specific GPR120 KO (AKO) mice to show that GRP120 has anti-inflammatory effects via macrophages while working with PPARγ in adipocytes to increase insulin sensitivity. These results raise the prospect of a safer way to increase insulin sensitization in the clinic.

Asiatic acid prevents renal fibrosis in UUO rats via promoting the production of 15d-PGJ2, an endogenous ligand of PPAR-γ

Renal fibrosis is an inevitable outcome of all kinds of progressive chronic kidney disease (CKD). Recently, asiatic acid (AA), a triterpenoid compound from Chinese medicine Centella asiatica, has been found to attenuate renal fibrosis. In the current study, we explored the mechanisms underlying antifibrotic effect of AA on UUO model. SD rats and ICR mice were subjected to unilateral ureteral occlusion (UUO) surgery. Prior the surgery, rats were administered AA (10 mg·kg^-1 per day, ig) for 7 days, whereas the mice received AA (15 mg·kg^-1 per day, ig) for 3 days. UUO group displayed significant degree of renal dysfunction, interstitial fibrosis, oxidative stress, and activation of the TGF-β/Smad and Wnt/β-catenin signaling pathway in the kidney, these pathological changes were greatly ameliorated by pretreatment with AA. In addition, we found that co-treatment with GW9662, a selective PPAR-γ antagonist (1 mg·kg^-1 per day, ip) for 7 days, abolished the protective effects of AA. We further revealed that AA pretreatment did not significantly change the expression levels of PPAR-γ in the kidney, but markedly increase the plasma levels of 15d-PGJ2, an endogenous ligand of PPAR-γ. In UUO mice, pretreatment with 15d-PGJ2 (24 μg·kg^-1 per day, ip, for 7 days) produced similar protective effect as AA. Moreover, AA pretreatment upregulated the expression levels of active, nuclear-localized SREBP-1 (nSREBP-1), whereas fatostatin, a specific inhibitor of SREBP-1, decreased the expression of nSREBP-1, as well as the level of 15d-PGJ2. These results provide new insight into the antifibrotic mechanism of AA and endogenous metabolites might become a new clue for investigation of drug mechanism.

Cyclooxygenase-2 Induced the β-Amyloid Protein Deposition and Neuronal Apoptosis Via Upregulating the Synthesis of Prostaglandin E2 and 15-Deoxy-Δ12,14-prostaglandin J2

Elevated levels of cyclooxygenase-2 (COX-2) and prostaglandins (PGs) have been shown to be involved in the pathogenesis of Alzheimer's disease. Analysis of the underlying mechanisms elucidated a function of sequential PGE2 and PGD2 synthesis in regulating β-amyloid protein (Aβ) deposition by modulating tumor necrosis factor α (TNF-α)-dependent presenilin (PS)1/2 activity in COX-2 and APP/PS1 crossed mice. Specifically, COX-2 overexpression accelerates the expression of microsomal PGE synthase-1 (mPGES-1) and lipocalin-type prostaglandin D synthase (L-PGDS), leading to the synthesis of PGE2 and 15-deoxy-Δ12,14-prostaglandin J2 (15d-PGJ2) in 6-month-old APP/PS1 mice. Consequently, PGE2 has the ability to increase Aβ production by enhancing the expression of PS1/2 in a TNF-α-dependent manner, which accelerates the cognitive decline of COX-2/APP/PS1 mice. More interestingly, low concentrations of 15d-PGJ2 treatment facilitate the effects of PGE2 on the deposition of Aβ via TNF-α-dependent PS1/2 mechanisms. In contrast, high concentrations of 15d-PGJ2 treatment inhibit the deposition of Aβ via suppressing the expression of TNF-α-dependent PS1/2. In this regard, a high concentration of 15d-PGJ2 appears to be a therapeutic agent against Alzheimer's disease. However, the high 15d-PGJ2 concentration treatment induces neuronal apoptosis via increasing the protein levels of Bax, cleaved caspase-3, and DFF45, which further impairs the learning ability of APP/PS1 mice.

[Inflammatory metabolites of arahidonic acid in tear fluid in UV-induced corneal damage]

The ultraviolet (UV) B-induced damage of the eye surface of experimental animals (rabbits) includes loss of corneal epithelium, apoptosis of keratocytes and stromal edema. These changes are accompanied by clinically and histologically manifested corneal inflammation, neutrophil infiltration, and exudation of the anterior chamber of the eye. According to mass spectrometric analysis, UV-induced corneal damage is associated with pronounced changes in the lipid composition of tears, including a decrease in the amount of arachidonic acid and prostaglandin E2 and an increase in the concentrations of prostaglandin D2 and its derivative 15d-PGJ2. In addition, it is accompanied by an alteration in the levels of hydroxyeicosate tetraenic acid derivatives, namely upregulation of 12-HETE and downregulation of 5-HETE. The revealed changes indicate the activation of metabolic pathways involving 5-lipoxygenase, 12-lipoxygenase, cyclooxygenase 1 and 2, and prostaglandin-D-synthase. These findings contribute to understanding mechanisms of UV-induced keratitis and point on feasibility of selective anti-inflammatory therapy for improving corneal regeneration after iatrogenic UV damage.

An Algal Metabolite-Based PPAR-γ Agonist Displayed Anti-Inflammatory Effect via Inhibition of the NF-κB Pathway

In our previous study, a synthetic compound, (+)-(R,E)-6a1, that incorporated the key structures of anti-inflammatory algal metabolites and the endogenous peroxisome proliferator-activated receptor γ (PPAR-γ) ligand 15-deoxy-∆^12,14-prostaglandin J₂ (15d-PGJ₂), exerted significant PPAR-γ transcriptional activity. Because PPAR-γ expressed in macrophages has been postulated as a negative regulator of inflammation, this study was designed to investigate the anti-inflammatory effect of the PPAR-γ agonist, (+)-(R,E)-6a1. Compound (+)-(R,E)-6a1 displayed in vitro anti-inflammatory activity in lipopolysaccharides (LPS)-stimulated murine RAW264.7 macrophages. Compound (+)-(R,E)-6a1 suppressed the expression of proinflammatory factors, such as nitric oxide (NO), inducible NO synthase (iNOS), cyclooxygenase-2 (COX-2), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α), possibly by the inhibition of the nuclear factor-κB (NF-κB) pathway. In macrophages, (+)-(R,E)-6a1 suppressed LPS-induced phosphorylation of NF-κB, inhibitor of NF-κB α (IκBα), and IκB kinase (IKK). These results indicated that PPAR-γ agonist, (+)-(R,E)-6a1, exerts anti-inflammatory activity via inhibition of the NF-κB pathway.

The mechanistic insight of a specific interaction between 15d-Prostaglandin-J2 and eIF4A suggests an evolutionary conserved role across species

15-deoxy-delta 12,14-prostaglandin J2 (15d-PGJ2) is an anti-inflammatory/anti-neoplastic prostaglandin that functions through covalent binding to cysteine residues of various target proteins. We previously showed that 15d-PGJ2 mediated anti-inflammatory responses are dependent on the translational inhibition through its interaction with eIF4A (Kim et al., 2007). Binding of 15d-PGJ2 to eIF4A specifically blocks the interaction between eIF4G and eIF4A, which leads to the formation of stress granules (SGs), which then cluster mRNAs with inhibited translation. Here, we show that the binding between 15d-PGJ2 and eIF4A specifically blocks the interaction between the MIF4G domain of eIF4G and eIF4A. To reveal the mechanism of this interaction, we used computational simulation-based docking studies and identified that the carboxyl tail of 15d-PGJ2 could stabilize the binding of 15d-PGJ2 to eIF4A through arginine 295 of eIF4A, which is the first suggestion that the 15d-PGJ2 tail plays a physiological role. Interestingly, the putative 15d-PGJ2 binding site on eiF4A is conserved across many species, suggesting a biological role. Our data propose that studying 15d-PGJ2 and its targets may uncover new therapeutic approaches in anti-inflammatory drug discovery.

15d-PGJ2 is a new hope for controlling tumor growth

15-deoxy-Δ12,14-prostaglandin J2 (15d-PGJ2), a natural PPARγ agonist, has been investigated for over a decade. Studies have revealed that it has proapoptotic, anti-inflammatory, antiangiogenic, and anti-metastatic abilities, as well as a significant anticancer effect. However, the mechanisms underlying the actions of 15d-PGJ2 on various tumors are only partially known. In this review, we discuss the recent progress in elucidating these mechanisms. Understanding the various functions and mechanisms of 15d-PGJ2 are crucial for the development of new therapies for controlling tumor growth and providing the basis for further research.

M2 microglia promotes neurogenesis and oligodendrogenesis from neural stem/progenitor cells via the PPARγ signaling pathway

Neural stem/progenitor cells (NSPCs) are an important source of cells for cell replacement therapy after nerve injury. How to induce NSPCs differentiation towards neurons and oligodendrocytes is a challenging issue in neuroscience research. In the present study, we polarized microglia into M1 and M2 phenotype, used their supernatants to induce NSPCs differentiation, and investigated the effects of different microglia phenotypes on NSPCs differentiation and their mechanisms. We discovered that, after exposure to M1 phenotype supernatant, NSPCs differentiated into fewer Tuj-1+ and Olig2+ cells, but more GFAP+ cells. Meanwhile, a significantly increased number of Tuj-1+ and Olig2+ cells and smaller number of GFAP+ cells were generated by M2 microglia supernatant-induced NSPCs differentiation. We also observed that 15d-PGJ₂, an endogenous ligand of PPARγ, was elevated in M2 phenotype supernatant and could activate PPARγ expression in NSPCs, whereas use of the PPARγ inhibitor GW9662, could reduce the percentage of differentiated neurons and oligodendrocytes. Our study results confirm that M2 microglia supernatant can activate the PPARγ signaling pathway and promote neurogenesis and oligodendrogenesis from NSPCs differentiation. The present study provides a further theoretical basis for induction of NSPCs oriented differentiation.

15-Deoxy-Delta-12,14-Prostaglandin J2 Inhibits Lung Inflammation and Remodeling in Distinct Murine Models of Asthma

15-deoxy-Δ-12,14-prostaglandin J₂ (15d-PGJ₂) has been described as an anti-inflammatory lipid mediator in several in vitro and in vivo studies, but its effect on allergic pulmonary inflammation remains elusive. The aim of this study was to investigate the therapeutic potential of 15d-PGJ₂ based on distinct murine models of allergic asthma triggered by either ovalbumin (OVA) or house dust mite extract (HDM). Characteristics of lung inflammation, airway hyper-reactivity (AHR), mucus exacerbation, and lung remodeling in sensitized A/J mice treated or not with 15d-PGJ₂ were assessed. 15d-PGJ₂ treatments were carried out systemically or topically given via subcutaneous injection or intranasal instillation, respectively. Analyses were carried out 24 h after the last allergen provocation. Irrespective of the route of administration, 15d-PGJ₂ significantly inhibited the peribronchial accumulation of eosinophils and neutrophils, subepithelial fibrosis and also mucus exacerbation caused by either OVA or HDM challenge. The protective effect of 15d-PGJ₂ occurred in parallel with inhibition of allergen-induced AHR and lung tissue production of pro-inflammatory cytokines, such as interleukin (IL)-5, IL-13, IL-17, and TNF-α. Finally, 15d-PGJ₂ was found effective in inhibiting NF-κB phosphorylation upon HDM challenge as measured by Western blotting. In conclusion, our findings suggest that 15d-PGJ₂ can reduce crucial features of asthma, including AHR, lung inflammation, and remodeling in distinct murine models of the disease. These effects are associated with a decrease in lung tissue generation of pro-inflammatory cytokines by a mechanism related to downregulation of NF-κB phosphorylation.

15-Deoxy-Δ12,14-Prostaglandin J2 Modifies Components of the Proteasome and Inhibits Inflammatory Responses in Human Endothelial Cells

15-Deoxy-Δ^12,14-prostaglandin J₂ (15d-PGJ₂) is an electrophilic lipid mediator derived from PGD₂ with potent anti-inflammatory effects. These are likely to be due to the covalent modification of cellular proteins, via a reactive α,β-unsaturated carbonyl group in its cyclopentenone ring. This study was carried out to identify novel cellular target(s) for covalent modification by 15d-PGJ₂ and to investigate the anti-inflammatory effects of the prostaglandin on endothelial cells (EC). The data presented here show that 15d-PGJ₂ modifies and inhibits components of the proteasome and consequently inhibits the activation of the NF-κB pathway in response to TNF-α. This, in turn, inhibits the adhesion and migration of monocytes toward activated EC, by reducing the expression of adhesion molecules and chemokines in the EC. The effects are consistent with the covalent modification of 13 proteins in the 19S particle of the proteasome identified by mass spectrometry and the suppression of proteasome function, and were similar to the effects seen with a known proteasome inhibitor (MG132). The ubiquitin-proteasome system has been implicated in the regulation of several inflammatory processes and the observation that 15d-PGJ₂ profoundly affects the proteasome functions in human EC suggests that 15d-PGJ₂ may regulate the progression of inflammatory disorders such as atherosclerosis.

Inhibitory effects of PPARγ ligands on TGF-β1-induced CTGF expression in cat corneal fibroblasts

Ligands of Peroxisome Proliferator Activated Receptor gamma (PPARγ) possess strong anti-fibrotic properties in the cornea and several other body tissues. In the cornea, we recently showed this class of molecules to prevent stromal myofibroblast differentiation partially by blocking the actions of p38 mitogen-activated protein kinase (MAPK). However, given the important role assigned to connective tissue growth factor (CTGF) in mediating corneal fibrosis, here we asked whether PPARγ ligands also act by affecting transforming growth factor-β (TGF-β) 1-induced expression of CTGF in cultured corneal fibroblasts. Corneal keratocytes were isolated from young, adult cats and early passage cells were exposed to TGF-β1 with or without the PPARγ ligands Rosiglitazone, Troglitazone and 15d-PGJ2. Western blots were used to assay levels of CTGF and alpha smooth muscle actin (αSMA), a marker of myofibroblast differentiation. CTGF siRNA demonstrated a critical role for CTGF in TGF-β1-mediated myofibroblast differentiation, while exogenously applied CTGF potentiated the pro-fibrogenic effects of TGF-β1. TGF-β1-mediated increases in CTGF and αSMA expression were strongly inhibited by all three PPARγ ligands tested, and by a c-jun N-terminal kinase (JNK) inhibitor. However, while extracellular signal-regulated kinase (ERK) 1/2, protein kinase B (AKT) and p38 MAPK inhibitors also blocked TGF-β1-induced αSMA induction, they did not dampen TGF-β1-induced increases in levels of CTGF. Thus, we conclude that PPARγ ligands block TGF-β1-induced increases in CTGF levels in cat corneal fibroblasts. They appear to do this in addition to their anti-fibrotic effect on p38 MAPK, providing a second intracellular pathway by which PPARγ ligands block αSMA induction.

A ground state of PPARγ activity and expression is required for appropriate neural differentiation of hESCs

BACKGROUND

Several evidences indicate stimulation of peroxisome proliferator activated receptor γ (PPARg), promotes neuronal differentiation. This study was conducted to testify the prominence of PPARγ during neural differentiation of human embryonic stem cells (hESCs).

METHODS

PPARγ expression level was assessed during neural differentiation of hESCs. Meanwhile, the level of endogenous miRNAs, which could be engaged in regulation of PPARγ expression, was measured. Next, natural and synthetic components of PPARγ agonists and antagonist were implemented on neural progenitor formation during neural differentiation of hESCs.

RESULTS

Data showed an increasing wave of PPARγ expression level when human neural progenitors (NPs) were formed upon retinoic acid treatment. Interestingly, there was no significant difference in the amount of PPARγ proteins during the differentiation of hESCs that is inconsistent with what we observed for RNA level. Our results indicated that miRNAs are not involved in the regulation of PPARγ expression, while proteasome-mediated degradation may to some degree be involved in this process. Among numerous treatments, PPARγ inactivation during NPs formation significantly decreased expression of NP markers.

CONCLUSIONS

We conclude that a ground state of PPARγ activity is required for NP formation of hESCs during early neural differentiation. However, high expression and activity of PPARγ could not enhance the required neural differentiation, whereas the PPARγ inactivation could negatively influence NP formation from hESCs by antagonist.

Possible involvement of 15-deoxy-Δ(12,14) -prostaglandin J2 in the development of leptin resistance

Obesity is a worldwide health problem that urgently needs to be solved. Leptin is an anti-obesity hormone that activates satiety signals to the brain. Evidence to suggest that leptin resistance is involved in the development of obesity is increasing; however, the molecular mechanisms involved remain unclear. We herein demonstrated that 15-deoxy-Δ(12,14) -prostaglandin J2 (15d-PGJ2 ) was involved in the development of leptin resistance. A treatment with 15d-PGJ2 inhibited the leptin-induced activation of signal transducer and activator of transcription 3 (STAT3) in neuronal cells (SH-SY5Y-Ob-Rb cells). Furthermore, the intracerebroventricular administration of 15d-PGJ2 reversed the inhibitory effects of leptin on food intake in rats. The peroxisome proliferator-activated receptor gamma (PPAR-γ) antagonist, GW9662, slightly reversed the inhibitory effects of 15d-PGJ2 on the leptin-induced activation of STAT3 in neuronal cells. The PPAR-γ agonist, rosiglitazone, also inhibited leptin-induced STAT3 phosphorylation. Therefore, the inhibitory effects of 15d-PGJ2 may be mediated through PPAR-γ. On the other hand, 15d-PGJ2 -induced leptin resistance may not be mediated by endoplasmic reticulum stress or suppressor of cytokine signaling 3. The results of the present study suggest that 15d-PGJ2 is a novel factor for the development of leptin resistance in obesity. Leptin resistance, an insensitivity to the actions of leptin, is involved in the development of obesity. Here, we found 15-deoxy-Δ(12,14) -prostaglandin J2 (15d-PGJ2 ) may be involved in the development of leptin resistance. The present results suggest that the 15d-PGJ2 may be a novel factor for the development of leptin resistance in obesity. 15d-PGJ2 , 15-Deoxy-Δ(12,14) -prostaglandin J2; STAT3, signal tranducer and activator of transcription 3.

Fluid shear stress-induced osteoarthritis: roles of cyclooxygenase-2 and its metabolic products in inducing the expression of proinflammatory cytokines and matrix metalloproteinases

The mechanical overloading of cartilage is involved in the pathophysiology of osteoarthritis (OA) by both biochemical and mechanical pathways. The application of fluid shear stress to chondrocytes recapitulates the earmarks of OA, as evidenced by the release of proinflammatory cytokines (PICs), matrix metalloproteinases (MMPs), and apoptotic factors. Dysregulations or mutations in these genes might directly cause OA in addition to determining the stage at which OA becomes apparent, the joint sites involved, and the severity of the disease and how rapidly it progresses. However, the underlying mechanisms remain unknown. In this review, we propose that the dysregulation of cyclooxygenase-2 (COX-2) is associated with fluid shear stress-induced OA via its metabolic products at different stages of the disease. Indeed, high fluid shear stress rapidly induces the production of PICs and MMPs via COX-2-derived prostaglandin (PG)E2 at the early stage of OA. In contrast, prolonged shear exposure (>12 h) aggravates the condition by concurrently up-regulating the expression of proapoptotic genes and down-regulating the expression of antiapoptotic genes in a 15-deoxy-Δ (12,14)-prostaglandin J2 (15d-PGJ2)-dependent manner at the late stage of disease. These observations may help to resolve long-standing questions in OA progression and provide insight for development of strategies to treat and combat OA.

15-Deoxy-Delta-Prostaglandin J(2) Upregulates the Expression of LPS-Induced IL-8/CXCL8 mRNA in Vascular Smooth Muscle Cells from Spontaneously Hypertensive Rats

Background

15d-PGJ₂ has been known to act as an anti-inflammatory agent and has anti-hypertensive effects. As a result of these properties, we examined the effect of 15d-PGJ₂ on the LPS-induced IL-8/CXCL8 mRNA expression in VSMCs from SHR.

Methods

Effect and action mechanism of 15d-PGJ₂ on the expression of LPS-induced IL-8/CXCL8 mRNA in VSMCs from SHR and WKY were examined by using real-time polymerase chain reaction, electrophoretic mobility shift assay for NF-κB avtivity, Western blotting analysis for ERK and p38 phosphorylation and flow cytometry for NAD(P)H oxidase activity.

Results

15d-PGJ₂ decreased the expression of LPS-induced IL-8/CXCL8 mRNA in WKY VSMCs, but increased the expression of LPS-induced IL-8/CXCL8 mRNA in SHR VSMCs. The upregulatory effect of 15d-PGJ₂ in SHR VSMCs was mediated through PPARγ, and dependent on NF-κB activation and ERK phosphorylation. However, inhibition of the p38 signaling pathway augmented the upregulatory effect of 15d-PGJ₂ on LPS-induced IL-8/CXCL8 mRNA. A NAD(P)H oxidase inhibitor inhibited the upregulatory effect of 15d-PGJ₂ on LPS-induced IL-8/CXCL8 mRNA expression in SHR VSMCs, and an increase in NAD(P)H oxidase activity was detected in SHR VSMCs treated with 15d-PGJ₂/LPS.

Conclusion

Our results indicate that the upregulatory effect of 15d-PGJ₂ on LPS-induced IL-8/CXCL8 expression in SHR VSMCs is mediated through the PPARγ and ERK pathway, and may be related to NAD(P)H oxidase activity. However, p38 inactivation may also play an important role in 15d-PGJ₂/LPS-induced IL-8/CXCL8 expression in SHR VSMCs.

Feedback Control of the Arachidonate Cascade in Osteoblastic Cells by 15-deoxy-Delta-Prostaglandin J(2)

15-deoxy-Δ^12,14-prostaglandin J₂ (15d-PGJ₂) and an anti-diabetic thiazolidinedione, troglitazone (TRO) are peroxisome proliferator-activated receptor (PPAR)-γ ligands, which regulate immuno-inflammatory reactions as well as adipocyte differentiation. We previously reported that 15d-PGJ₂ can suppress interleukin (IL)-1β-induced prostaglandin E₂ (PGE₂) synthesis in synoviocytes of rheumatoid arthritis (RA). IL-1 also stimulates PGE₂ synthesis in osteoblasts by regulation of cyclooxygenase (COX)-2 and regulates osteoclastic bone resorption in various diseases such as RA and osteoporosis. In this study, we investigated the feedback mechanism of the arachidonate cascade in mouse osteoblastic cells, MC3T3-E1 cells, which differentiate into mature osteoblasts. Treatment with 15d-PGJ₂ led to a significant increase in IL-1α-induced COX-2 expression and PGE₂ production in a dose dependent manner. The effect of 15d-PGJ₂ was stronger than that of TRO. However, it did not affect the expression of COX-1. In addition, cell viability of MC3T3-E1 cells was not changed in the condition we established. This means that 15d-PGJ₂ exerts a positive feedback regulation of the arachidonate cascade of PGE₂ in osteoblastic cells. These results may provide important information about the pathogenesis and treatment of bone resorption in a variety of diseases such as RA and osteoporosis.