Prostaglandin D2 metabolites activate asthmatic patient-derived type 2 innate lymphoid cells and eosinophils via the DP2 receptor.

BACKGROUND: Prostaglandin D2 (PGD2) signaling via prostaglandin D2 receptor 2 (DP2) contributes to atopic and non-atopic asthma. Inhibiting DP2 has shown therapeutic benefit in certain subsets of asthma patients, improving eosinophilic airway inflammation. PGD2 metabolites prolong the inflammatory response in asthmatic patients via DP2 signaling. The role of PGD2 metabolites on eosinophil and ILC2 activity is not fully understood. METHODS: Eosinophils and ILC2s were isolated from peripheral blood of atopic asthmatic patients. Eosinophil shape change, ILC2 migration and IL-5/IL-13 cytokine secretion were measured after stimulation with seven PGD2 metabolites in presence or absence of the selective DP2 antagonist fevipiprant. RESULTS: Selected metabolites induced eosinophil shape change with similar nanomolar potencies except for 9α,11ß-PGF2. Maximal values in forward scatter of eosinophils were comparable between metabolites. ILC2s migrated dose-dependently in the presence of selected metabolites except for 9α,11ß-PGF2 with EC50 values ranging from 17.4 to 91.7 nM. Compared to PGD2, the absolute cell migration was enhanced in the presence of Δ12-PGD2, 15-deoxy-Δ12,14-PGD2, PGJ2, Δ12-PGJ2 and 15-deoxy-Δ12,14-PGJ2. ILC2 cytokine production was dose dependent as well but with an average sixfold reduced potency compared to cell migration (IL-5 range 108.1 to 526.9 nM, IL-13 range: 125.2 to 788.3 nM). Compared to PGD2, the absolute cytokine secretion was reduced in the presence of most metabolites. Fevipiprant dose-dependently inhibited eosinophil shape change, ILC2 migration and ILC2 cytokine secretion with (sub)-nanomolar potencies. CONCLUSION: Prostaglandin D2 metabolites initiate ILC2 migration and IL-5 and IL-13 cytokine secretion in a DP2 dependent manner. Our data indicate that metabolites may be important for in vivo eosinophil activation and ILC2 migration and to a lesser extent for ILC2 cytokine secretion.

Approaches to Potentiated Neuroprotective Treatment in the Rodent Model of Ischemic Optic Neuropathy.

Nonarteritic anterior ischemic optic neuropathy (NAION) commonly causes sudden optic nerve (ON)-related vision loss. The rodent NAION model (rAION) closely resembles NAION in presentation and physiological responses. We identified early rAION-associated optic nerve head (ONH) inflammatory gene expression responses and the anti-inflammatory prostaglandin PGJ2's effects on those responses. We hypothesized that blocking pro-inflammatory prostaglandin (PGE2) production by inhibiting monoacylglycerol lipase or cyclooxygenase activity and co-administering PGJ2 would potentiate RGC survival following ischemic neuropathy. Deep sequencing was performed on vehicle- and PGJ2-treated ONHs 3d post-rAION induction. Results were compared against responses from a retinal ischemia model. Animals were treated with PGJ2 and MAGL inhibitor KML29, or PGJ2 + COX inhibitor meloxicam. RGC survival was quantified by stereology. Tissue PG levels were quantified by ELISA. Gene expression was confirmed by qPCR. PGJ2 treatment nonselectively reduced inflammatory gene expression post-rAION. KML29 did not reduce PGE2 1d post-induction and KML29 alone increased RGC loss after rAION. Combined treatments did not improve ONH edema and RGC survival better than reported with PGJ2 alone. KML29's failure to suppress PGE2 ocular synthesis, despite its purported effects in other CNS tissues may result from alternative PG synthesis pathways. Neither KML29 nor meloxicam treatment significantly improved RGC survival compared with vehicle. While exogenous PGJ2 has been shown to be neuroprotective, treatments combining PGJ2 with these PG synthesis inhibitors do not enhance PGJ2's neuroprotection.

α-Ketoheterocycles Able to Inhibit the Generation of Prostaglandin E2 (PGE2) in Rat Mesangial Cells.

Prostaglandin E2 (PGE2) is a key mediator of inflammation, and consequently huge efforts have been devoted to the development of novel agents able to regulate its formation. In this work, we present the synthesis of various α-ketoheterocycles and a study of their ability to inhibit the formation of PGE2 at a cellular level. A series of α-ketobenzothiazoles, α-ketobenzoxazoles, α-ketobenzimidazoles, and α-keto-1,2,4-oxadiazoles were synthesized and chemically characterized. Evaluation of their ability to suppress the generation of PGE2 in interleukin-1ß plus forskolin-stimulated mesangial cells led to the identification of one α-ketobenzothiazole (GK181) and one α-ketobenzoxazole (GK491), which are able to suppress the PGE2 generation at a nanomolar level.

Isoprostanes evoke contraction of the murine and human detrusor muscle via activation of the thromboxane prostanoid TP receptor and Rho kinase.

Local or systemic inflammation can severely impair urinary bladder functions and contribute to the development of voiding disorders in millions of people worldwide. Isoprostanes are inflammatory lipid mediators that are upregulated in the blood and urine by oxidative stress and may potentially induce detrusor overactivity. The aim of the present study was to investigate the effects and signal transduction of isoprostanes in human and murine urinary bladders in order to provide potential pharmacological targets in detrusor overactivity. Contraction force was measured with a myograph in murine and human urinary bladder smooth muscle (UBSM) ex vivo. Isoprostane 8-iso-PGE2 and 8-iso-PGF2α evoked dose-dependent contraction in the murine UBSM, which was abolished in mice deficient in the thromboxane prostanoid (TP) receptor. The responses remained unaltered after removal of the mucosa or incubation with tetrodotoxin. Smooth muscle-specific deletion of Gα12/13 protein or inhibition of Rho kinase by Y-27632 decreased the contractions. In Gαq/11-knockout mice, responses were reduced and in the presence of Y-27632 abolished completely. In human UBSM, the TP agonist U-46619 evoked dose-dependent contractions. Neither atropine nor the purinergic receptor antagonist pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid decreased the effect, indicating that TP receptors directly mediate detrusor muscle contraction. 8-iso-PGE2 and 8-iso-PGF2α evoked dose-dependent contraction in the human UBSM, and these responses were abolished by the TP antagonist SQ-29548 and were decreased by Y-27632. Our results indicate that isoprostanes evoke contraction in murine and human urinary bladders, an effect mediated by the TP receptor. The G12/13-Rho-Rho kinase pathway plays a significant role in mediating the contraction and therefore may be a potential therapeutic target in detrusor overactivity.NEW & NOTEWORTHY Voiding disorders affect millions of people worldwide. Inflammation can impair urinary bladder functions and contribute to the development of detrusor overactivity. The effects and signal transduction of inflammatory lipid mediator isoprostanes were studied in human and murine urinary bladders ex vivo. We found that isoprostanes evoke contraction, an effect mediated by thromboxane prostanoid receptors. The G12/13-Rho-Rho kinase signaling pathway plays a significant role in mediating the contraction and therefore may be a potential therapeutic target.

A Novel Second-Generation EP2 Receptor Antagonist Reduces Neuroinflammation and Gliosis After Status Epilepticus in Rats.

Prostaglandin-E2 (PGE2), an important mediator of inflammation, achieves its functions via four different G protein-coupled receptors (EP1, EP2, EP3, and EP4). We previously demonstrated that the EP2 receptor plays a proinflammatory and neurodegenerative role after status epilepticus (SE). We recently developed TG8-260 as a second-generation highly potent and selective EP2 antagonist. Here, we investigate whether TG8-260 is anti-inflammatory and combats neuropathology caused by pilocarpine-induced SE in rats. Adult male Sprague-Dawley rats were injected subcutaneously with pilocarpine (380-400 mg/kg) to induce SE. Following 60 min of SE, the rats were administered three doses of TG8-260 or vehicle and were allowed to recover. Neurodegeneration, neuroinflammation, gliosis, and blood-brain barrier (BBB) integrity were examined 4 days after SE. The results confirmed that pilocarpine-induced SE results in hippocampal neurodegeneration and a robust inflammatory response that persists days after SE. Furthermore, inhibition of the EP2 receptor by TG8-260 administered beginning 2 h after SE significantly reduced hippocampal neuroinflammation and gliosis but, in distinction to the earlier generation EP2 antagonist, did not mitigate neuronal injury or BBB breakdown. Thus, attenuation of neuroinflammation and gliosis is a common feature of EP2 inhibition following SE.

Central Blockade of E-Prostanoid 3 Receptor Ameliorated Hypertension Partially by Attenuating Oxidative Stress and Inflammation in the Hypothalamic Paraventricular Nucleus of Spontaneously Hypertensive Rats.

Hypertension, as one of the major risk factors for cardiovascular disease, significantly affects human health. Prostaglandin E2 (PGE2) and the E3-class prostanoid (EP3) receptor have previously been demonstrated to modulate blood pressure and hemodynamics in various animal models of hypertension. The PGE2-evoked pressor and biochemical responses can be blocked with the EP3 receptor antagonist, L-798106 (N-[(5-bromo-2methoxyphenyl)sulfonyl]-3-[2-(2-naphthalenylmethyl) phenyl]-2-propenamide). In the hypothalamic paraventricular nucleus (PVN), sympathetic excitation can be introduced by PGE2, which can activate EP3 receptors located in the PVN. In such a case, the central knockdown of EP3 receptor can be considered as a potential therapeutic modality for hypertension management. The present study examined the efficacy of the PVN infusion of L-798106, by performing experiments on spontaneously hypertensive rats (SHRs) and normotensive Wistar-Kyoto rats (WKYs). The rats were administered with chronic bilateral PVN infusion of L-798106 (10 µg/day) or the vehicle for 28 days. The results indicated that the SHRs had a higher mean arterial pressure (MAP), an increased Fra-like (Fra-LI) activity in the PVN, as well as a higher expression of gp91phox, mitogen-activated protein kinase (MAPK), and proinflammatory cytokines in the PVN compared with the WKYs. Additionally, the expression of Cu/Zn-SOD in the PVN of the SHRs was reduced compared with the WKYs. The bilateral PVN infusion of L-798106 significantly reduced MAP, as well as plasma norepinephrine (NE) levels in the SHRs. It also inhibited Fra-LI activity and reduced the expression of gp91phox, proinflammatory cytokines, and MAPK, whereas it increased the expression of Cu/Zn-SOD in the PVN of SHRs. In addition, L-798106 restored the balance of the neurotransmitters in the PVN. On the whole, the findings of the present study demonstrate that the PVN blockade of EP3 receptor can ameliorate hypertension and cardiac hypertrophy partially by attenuating ROS and proinflammatory cytokines, and modulating neurotransmitters in the PVN.

Crosstalk between the COX2-PGE2-EP4 signaling pathway and primary cilia in osteoblasts after mechanical stimulation.

Primary cilia have been found to function as mechanosensors in low-magnitude high-frequency vibration (LMHFV)-induced osteogenesis. The PGE2 also regulates bone homeostasis and mechanical osteogenesis through its receptor EP4 signaling, but its involvement in LMHFV-induced or in primary cilia-induced osteogenesis has not been investigated. We hypothesized that LMHFV stimulates osteoblast (OB) differentiation by activating the COX2-PGE2-EP pathway in a manner dependent on primary cilia and that primary cilia are also affected by the PGE2 pathway. In this study, through western blot analysis, RNA interference, enzyme-linked immunosorbent assay, real-time quantitative polymerase chain reaction, and cytochemical staining, we observed that COX2, mPGES-1, and PGE2 levels were markedly elevated in cells treated with LMHFV and were greatly decreased in LMHFV-treated cells following IFT88 silencing. EP4 expression was significantly increased in OBs following LMHFV treatment, but IFT88 silencing significantly blocked this increase. EP4 localized to the bases of primary cilia. LMHFV reduced the length and abundance of primary cilia, but the cells could self-repair their primary cilia after mechanical damage. EP4 antagonism significantly blocked the LMHFV-induced increase in IFT88 expression and blocked the recovery of primary cilia length and the proportion of cells with primary cilia. In addition, COX2 or EP4 antagonism disrupted LMHFV-induced osteogenesis. These results demonstrate the integration of and crosstalk between primary cilia and the COX2-PGE2-EP4 signaling pathway under mechanical stimulation.

Druggable Prostanoid Pathway.

Prostanoids (prostaglandins, prostacyclin and thromboxane) belong to the oxylipin family of biologically active lipids generated from arachidonic acid (AA). Protanoids control numerous physiological and pathological processes. Cyclooxygenase (COX) is a rate-limiting enzyme involved in the conversion of AA into prostanoids. There are two COX isozymes: the constitutive COX-1 and the inducible COX-2. COX-1 and COX-2 have similar structures, catalytic activities, and subcellular localizations but differ in patterns of expression and biological functions. Non-selective COX-1/2 or traditional, non-steroidal anti-inflammatory drugs (tNSAIDs) target both COX isoforms and are widely used to relieve pain, fever and inflammation. However, the use of NSAIDs is associated with various side effects, particularly in the gastrointestinal tract. NSAIDs selective for COX-2 inhibition (coxibs) were purposefully designed to spare gastrointestinal toxicity, but predisposed patients to increased cardiovascular risks. These health complications from NSAIDs prompted interest in the downstream effectors of the COX enzymes as novel drug targets. This chapter describes various safety issues with tNSAIDs and coxibs, and discusses the current development of novel classes of drugs targeting the prostanoid pathway, including nitrogen oxide- and hydrogen sulfide-releasing NSAIDs, inhibitors of prostanoid synthases, dual inhibitors, and prostanoid receptor agonists and antagonists.

Crosstalk between EP2 and PPARα Modulates Hypoxic Signaling and Myopia Development in Guinea Pigs.

Purpose: Cyclic adenosine monophosphate (cAMP) and peroxisome proliferator-activated receptor alpha (PPARα) levels mediate extracellular matrix (ECM) changes by altering the levels of hypoxia-inducible factor 1-alpha (HIF-1α) in various tissues. We aimed to determine, in the sclera of guinea pigs, whether a prostanoid receptor (EP2)-linked cAMP modulation affects PPARα and HIF-1α signaling during myopia. Methods: Three-week-old guinea pigs (n = 20 in each group), were monocularly injected with either an EP2 agonist (butaprost 1 µmol/L/10 µmol/L), an antagonist (AH6809 10 µmol/L/30 µmol/L) or a vehicle solution for two weeks during normal ocular growth. Separate sets of animals received these injections and underwent form deprivation (FD) simultaneously. Refraction and axial length (AL) were measured at two weeks, followed by scleral tissue isolation for quantitative PCR (qPCR) analysis (n = 10) and cAMP detection (n = 10) using a radioimmunoassay. Results: Butaprost induced myopia development during normal ocular growth, with proportional increases in AL and cAMP levels. FD did not augment the magnitude of myopia or cAMP elevations in these agonist-injected eyes. AH6809 suppressed cAMP increases and myopia progression during FD, but had no effect in a normal visual environment. Of the diverse set of 27 genes related to cAMP, PPARα and HIF-1α signaling and ECM remodeling, butaprost differentially regulated 15 of them during myopia development. AH6809 injections during FD negated such differential gene expressions. Conclusion: EP2 agonism increased cAMP and HIF-1α signaling subsequent to declines in PPARα and RXR mRNA levels, which in turn decreased scleral fibrosis and promoted myopia. EP2 antagonism instead inhibited each of these responses. Our data suggest that EP2 suppression may sustain scleral ECM structure and inhibit myopia development.

Effect of selective inhibition or activation of PGE2 EP1 receptor on glomerulosclerosis.

Prostaglandin E2 (PGE2) is involved in numerous physiological and pathological processes of the kidney via its four receptors. A previous study has suggested that a defect in the PGE2 receptor 1 (EP1) gene markedly suppressed the transforming growth factor­ß1 (TGF­ß1)­induced mesangial cell (MC) proliferation and extracellular matrix aggregation. Therefore, the present study aimed to adopt a pharmacological method of specifically suppressing or activating the EP1 receptor to further verify and demonstrate these results. The EP1 receptor antagonist SC­19220 and EP1 receptor agonist 17­phenyl­trinor­PGE2 ethyl amide (17­pt­PGE2) were selectively used to treat five­sixths nephrectomy renal fibrosis model mice and TGF­ß1­stimulated MCs. An Alpha screen PGE2 assay kit, flow cytometry, western blotting and immunohistochemical techniques were adopted to perform in vivo and in vitro experiments. The present results suggested that compared with the control group, the selective EP1 receptor antagonist SC­19220 improved renal function, markedly reduced the plasma blood urea nitrogen and creatinine levels (P<0.05) and alleviated glomerulosclerosis (P<0.05). By contrast, the EP1 receptor agonist 17­pt­PGE2 aggravated renal dysfunction and glomerulosclerosis (P<0.05). To verify the renal protection mechanisms mediated by suppression of the EP1 receptor, the expression levels of endoplasmic reticulum stress (ERS)­related proteins, including chaperone glucose­regulated protein 78 (GRP78), transient receptor potential channel 1 (TRPC1) and protein kinase R­like endoplasmic reticulum kinase (PERK), were further evaluated histologically. The expression of GRP78, TRPC1 and PERK in the antagonist treatment group were markedly downregulated (P<0.05), whereas those in the agonist treatment group were upregulated (P<0.05). The present in vitro experiments demonstrated that, compared with the control group, the EP1 receptor antagonist suppressed the expression of GRP78, TRPC1 and PERK (P<0.05), reduced the production of PGE2 (P<0.05) and decreased the MC apoptosis rate (P<0.05), thus alleviating TGF­ß1­stimulated MC injury. Consequently, consistent with previous results, selectively antagonizing the EP1 receptor improved renal function and mitigated glomerulosclerosis, and its potential mechanism might be associated with the suppression of ERS.

The indirubin derivative 6-bromoindirubin-3'-glycerol-oxime ether (6BIGOE) potently modulates inflammatory cytokine and prostaglandin release from human monocytes through GSK-3 interference.

Indirubin is a natural bis-indole alkaloid contained as active ingredient in the traditional Chinese remedy Danggui Longhui Wan. Indirubin and its 3'-oxime derivatives exhibit anti-cancer and anti-inflammatory properties and they inhibit glycogen synthase kinase (GSK)-3 in cell-free assays where 6-bromoindirubin-3'-oxime (6BIO) is among the most potent analogs. Here, we reveal 6-bromoindirubin-3'-glycerol-oxime ether (6BIGOE) as highly potent derivative able to inhibit pro-inflammatory cytokine, chemokine and prostaglandin (PG) release in human primary monocytes while increasing anti-inflammatory interleukin (IL)-10 levels. 6BIGOE suppressed lipopolysaccharide (LPS)-induced IL-1ß and PGE2 release with IC50 of 0.008 and 0.02 µM, respectively, being ≥ 12-fold more potent than 6BIO. The effects of 6BIGOE are mediated via intracellular inhibition of GSK-3, where 6BIGOE again surpassed the effectiveness of 6BIO despite the higher potency of the latter in cell-free GSK-3 activity assays. Side-by-side comparison of 6BIGOE (0.1 µM) with the selective GSK-3 inhibitor SB216763 (5 µM) revealed congruent properties such as enrichment of ß-catenin and suppression of cyclooxygenase (COX)-2 protein levels due to GSK-3 inhibition. Metabololipidomics using ultra-performance liquid chromatography-tandem mass spectrometry showed that 6BIGOE selectively decreases pro-inflammatory COX-derived product formation without marked modulation of other lipid mediators. In summary, 6BIGOE is a highly potent indirubin derivative in the cellular context that favorably modulates pro- and anti-inflammatory cytokines as well as COX-2-derived PG via interference with GSK-3.

Baicalein ameliorates pristane-induced lupus nephritis via activating Nrf2/HO-1 in myeloid-derived suppressor cells.

INTRODUCTION: Lupus nephritis (LN) is a representative manifestation in systemic lupus erythematosus (SLE). Some studies have shown that myeloid-derived suppressor cells (MDSCs) play a vital role in the regulation of the SLE process. MDSC infiltration in the kidney as well as inflammation and oxidative stress provokes the acceleration and deterioration of LN. Nuclear factor E2-related factor 2 (Nrf2) is thought to be a major regulator of the antioxidant response. Baicalein is a flavonoid with known anti-inflammatory effects and antioxidant response. However, the effects of baicalein on MDSCs, inflammation, and oxidative stress are not evaluated in the development of pristane-induced LN in mice. METHODS: The renoprotective effect of baicalein was detected in a pristane-induced lupus mice model. NLRP3 inflammasome activation and NF-κB phosphorylation as well as reactive oxygen species (ROS) production and Nrf2 activation were examined. The percentages and function changes of MDSCs were measured. The possible mechanisms of the underlying effects of baicalein on ROS production and signaling pathways of Nrf2/heme-oxygenase (HO)-1, NLRP3 inflammasome, and NF-κB phosphorylation in lipopolysaccharide (LPS)-primed MDSCs were analyzed. RESULTS: Baicalein reduced proteinuria and attenuated renal function impairment and renal histopathology including intrinsic cell proliferation, cellular crescents, and podocyte injury as well as glomerulonephritis activity in lupus mice. Moreover, baicalein downregulated the activation of NLRP3 inflammasome and levels of ROS or NF-κB phosphorylation, and it enhanced Nrf2 activation. Of note, baicalein inhibited the expansion of MDSCs and improved the function of MDSCs in lupus mice. Through analyzing LPS-primed MDSCs in vitro, baicalein was found to exhibit cytoprotective effects coincident with the induction of Nrf2/HO-1 signaling and the suppression of the NLRP3 inflammasome. CONCLUSION: The data show that baicalein alleviates the symptoms of pristane-induced LN and suggest that the alleviation may be attributed to inhibition of MDSC expansion and regulation of the balance of the Nrf2/HO-1 signal and NLRP3 expression in MDSCs.

Targeting biosynthetic networks of the proinflammatory and proresolving lipid metabolome.

Nonsteroidal anti-inflammatory drugs interfere with the metabolism of arachidonic acid to proinflammatory prostaglandins and leukotrienes by targeting cyclooxygenases (COXs), 5-lipoxygenase (LOX), or the 5-LOX-activating protein (FLAP). These and related enzymes act in conjunction with marked crosstalk within a complex lipid mediator (LM) network where also specialized proresolving LMs (SPMs) are formed. Here, we present how prominent LM pathways can be differentially modulated in human proinflammatory M1 and proresolving M2 macrophage phenotypes that, upon exposure to Escherichia coli, produce either abundant prostaglandins and leukotrienes (M1) or SPMs (M2). Targeted liquid chromatography-tandem mass spectrometry-based metabololipidomics was applied to analyze and quantify the specific LM profiles. Besides expected on-target actions, we found that: 1) COX or 15-LOX-1 inhibitors elevate inflammatory leukotriene levels, 2) FLAP and 5-LOX inhibitors reduce leukotrienes in M1 but less so in M2 macrophages, 3) zileuton blocks resolution-initiating SPM biosynthesis, whereas FLAP inhibition increases SPM levels, and 4) that the 15-LOX-1 inhibitor 3887 suppresses SPM formation in M2 macrophages. Conclusively, interference with discrete LM biosynthetic enzymes in different macrophage phenotypes considerably affects the LM metabolomes with potential consequences for inflammation-resolution pharmacotherapy. Our data may allow better appraisal of the therapeutic potential of these drugs to intervene with inflammatory disorders.-Werner, M., Jordan, P. M., Romp, E., Czapka, A., Rao, Z., Kretzer, C., Koeberle, A., Garscha, U., Pace, S., Claesson, H.-E., Serhan, C. N., Werz, O., Gerstmeier, J. Targeting biosynthetic networks of the proinflammatory and proresolving lipid metabolome.

Prostaglandin E2 facilitates Hepatitis B virus replication by impairing CTL function.

Reversal of T cell dysfunction is a novel and promising approach for the treatment of chronic diseases. PGE2, one of most studied Prostaglandins, exhibits strong and versatile immunoregulation activity on different immune cells including T cells, and has become a promising therapeutic target. Here we found that compared to healthy donors, patients with chronic Hepatitis B virus (HBV) infection had significantly elevated serum PGE2 level. Importantly, serum PGE2 concentration correlated with viral load and liver damage in Chronic hepatitis B(CHB)patients. In AAV-HBV1.2 mouse model, administration of PGE2 analogue promoted HBV replication, while antagonists for EP2 and EP4, two important receptors for PGE2, inhibited virus replication. However, PGE2 analogue had no significant effect on the growth and virus replication in cultured HBV-harboring hepatocyte cell line. Further analysis showed that high PGE2 level in CHB patients correlated with high Tim-3 expression and low level of perforin and granzme B in CD8 + T cells. In parallel, blockade of PGE2 signaling restored the function of CD8 + T cells and controls HBV infection. Depletion of CD8 + T cells almost abrogated the effects of PGE2 on HBV replication. These findings identify PGE2 as a negative regulator for CD8 + T cells contributing to HBV persistence and the intervention of PGE2 signaling might be of potentially translational significance.

A cyclic pathway of P2 × 7, bradykinin, and dopamine receptor activation induces a sustained articular hyperalgesia in the knee joint of rats.

OBJECTIVE: We investigated whether: (1) P2 × 7 receptor activation by its agonist (BzATP) induces articular hyperalgesia in the rat's knee joint via inflammatory mechanisms and (2) activation of P2 × 7 receptors by endogenous ATP contributes to the articular hyperalgesia induced by bradykinin, TNF-α, IL-1ß, CINC-1, PGE2, and dopamine. METHODS: The articular hyperalgesia was quantified using the rat knee joint incapacitation test. The knee joint inflammation, characterized by the concentration of pro-inflammatory cytokines and by neutrophil migration, was quantified in the synovial lavage fluid by ELISA and myeloperoxidase enzyme activity assay, respectively. RESULTS: BzATP induced a dose-dependent articular hyperalgesia in the rat's knee joint that was significantly reduced by the selective antagonists for P2 × 7, bradykinin B1 or B2 receptors, ß1 or ß2 adrenoceptors, and by pre-treatment with Indomethacin. BzATP induced a local increase of TNF-α, IL-1ß, IL-6, and CINC-1 concentration and neutrophil migration into the knee joint. The co-administration of the selective P2 × 7 receptor antagonist A-740003 significantly reduced the articular hyperalgesia induced by bradykinin and dopamine, but not by TNF-α, IL-1ß, CINC-1, and PGE2. CONCLUSIONS: P2 × 7 receptor activation induces articular hyperalgesia mediated by the previous inflammatory mediator release. P2 × 7 receptor-induced articular hyperalgesia is sustained by the involvement of this purinergic receptor in bradykinin and dopamine-induced hyperalgesia in the knee joint.

Wound healing.

Wound healing is an important physiological process to maintain the integrity of skin after trauma, either by accident or by intent procedure. The normal wound healing involves three successive but overlapping phases, including hemostasis/inflammatory phase, proliferative phase, and remodeling phase. Aberration of wound healing, such as excessive wound healing (hypertrophic scar and keloid) or chronic wound (ulcer) impairs the normal physical function. A large number of sophisticated experimental studies have provided insights into wound healing. This article highlights the information after 2010, and the main text includes (i) wound healing; (ii) wound healing in fetus and adult; (iii) prostaglandins and wound healing; (iv) the pathogenesis of excessive wound healing; (v) the epidemiology of excessive wound healing; (vi) in vitro and in vivo studies for excessive wound healing; (vii) stem cell therapy for excessive wound healing; and (viii) the prevention strategy for excessive wound healing.

Monoacylglycerol lipase inhibitor JZL184 prevents HIV-1 gp120-induced synapse loss by altering endocannabinoid signaling.

Monoacylglycerol lipase (MGL) hydrolyzes 2-arachidonoylglycerol to arachidonic acid and glycerol. Inhibition of MGL may attenuate neuroinflammation by enhancing endocannabinoid signaling and decreasing prostaglandin (PG) production. Almost half of HIV infected individuals are afflicted with HIV-associated neurocognitive disorder (HAND), a neuroinflammatory disease in which cognitive decline correlates with synapse loss. HIV infected cells shed the envelope protein gp120 which is a potent neurotoxin that induces synapse loss. Here, we tested whether inhibition of MGL, using the selective inhibitor JZL184, would prevent synapse loss induced by gp120. The number of synapses between rat hippocampal neurons in culture was quantified by imaging clusters of a GFP-tagged antibody-like protein that selectively binds to the postsynaptic scaffolding protein, PSD95. JZL184 completely blocked gp120-induced synapse loss. Inhibition of MGL decreased gp120-induced interleukin-1ß (IL-1ß) production and subsequent potentiation of NMDA receptor-mediated calcium influx. JZL184-mediated protection of synapses was reversed by a selective cannabinoid type 2 receptor (CB2R) inverse agonist/antagonist. JZL184 also reduced gp120-induced prostaglandin E2 (PGE2) production; PG signaling was required for gp120-induced IL-1ß expression and synapse loss. Inhibition of MGL prevented gp120-induced synapse loss by activating CB2R resulting in decreased production of the inflammatory cytokine IL-1ß. Because PG signaling was required for gp120-induced synapse loss, JZL184-induced decreases in PGE2 levels may also protect synapses. MGL presents a promising target for preventing synapse loss in neuroinflammatory conditions such as HAND.

PTGER2 activation induces PTGS-2 and growth factor gene expression in endometrial epithelial cells of cattle.

The prostaglandin E2 receptor 2 (PTGER2) is present in the endometrium and its gene expression is accompanied with endometrial growth, however, it is unknown whether there is endometrial repair through stimulation of growth factor gene expression that is promoted by PTGER2 activation in cattle. The aim of this study was to investigate whether PTGER2 activation can induce prostaglandin-endoperoxide synthase-2 (PTGS-2) and growth factor gene expression by activating PKA and ERK signaling pathways in endometrial epithelial cells of cattle. Results demonstrated that the PTGER2 agonist, butaprost, induced cAMP/PKA and ERK activation and up-regulated PTGS-2, VEGF, CTGF, TGF-ß1 and IL-8 gene expression. These activations were less after PTGER2 antagonist, AH6809, treatment. Data suggested that PTGS-2 gene expression was induced by PTGER2 activation through the PKA and ERK pathways. Furthermore, PTGER2 activation promoted several growth factor gene expressions in endometrial epithelial cells. One potential implication of this finding is that PTGER2 activation in the endometrium of cattle could induce endometrial repair by stimulating VEGF, CTGF, TGF-ß1 and IL-8 gene expression.

PGE2 upregulates renin through E-prostanoid receptor 1 via PKC/cAMP/CREB pathway in M-1 cells.

During the early phase of ANG II-dependent hypertension, tubular PGE2 is increased. Renin synthesis and secretion in the collecting duct (CD) are upregulated by ANG II, contributing to further intratubular ANG II formation. However, what happens first and whether the triggering mechanism is independent of tubular ANG II remain unknown. PGE2 stimulates renin synthesis in juxtaglomerular cells via E-prostanoid (EP) receptors through the cAMP/cAMP-responsive element-binding (CREB) pathway. EP receptors are also expressed in the CD. Here, we tested the hypothesis that renin is upregulated by PGE2 in CD cells. The M-1 CD cell line expressed EP1, EP3, and EP4 but not EP2. Dose-response experiments, in the presence of ANG II type 1 receptor blockade with candesartan, demonstrated that 10-6 M PGE2 maximally increases renin mRNA (approximately 4-fold) and prorenin/renin protein levels (approximately 2-fold). This response was prevented by micromolar doses of SC-19220 (EP1 antagonist), attenuated by the EP4 antagonist, L-161982, and exacerbated by the highly selective EP3 antagonist, L-798106 (~10-fold increase). To evaluate further the signaling pathway involved, we used the PKC inhibitor calphostin C and transfections with PKCα dominant negative. Both strategies blunted the PGE2-induced increases in cAMP levels, CREB phosphorylation, and augmentation of renin. Knockdown of the EP1 receptor and CREB also prevented renin upregulation. These results indicate that PGE2 increases CD renin expression through the EP1 receptor via the PKC/cAMP/CREB pathway. Therefore, we conclude that during the early stages of ANG II-dependent hypertension, there is augmentation of PGE2 that stimulates renin in the CD, resulting in increased tubular ANG II formation and further stimulation of renin.

The effect of nitric oxide synthase inhibition with and without inhibition of prostaglandins on blood flow in different human skeletal muscles.

PURPOSE: Animal studies suggest that the inhibition of nitric oxide synthase (NOS) affects blood flow differently in different skeletal muscles according to their muscle fibre type composition (oxidative vs glycolytic). Quadriceps femoris (QF) muscle consists of four different muscle parts: vastus intermedius (VI), rectus femoris (RF), vastus medialis (VM), and vastus lateralis (VL) of which VI is located deep within the muscle group and is generally regarded to consist mostly of oxidative muscle fibres. METHODS: We studied the effect of NOS inhibition on blood flow in these four different muscles by positron emission tomography in eight young healthy men at rest and during one-leg dynamic exercise, with and without combined blockade with prostaglandins. RESULTS: At rest blood flow in the VI (2.6 ± 1.1 ml/100 g/min) was significantly higher than in VL (1.9 ± 0.6 ml/100 g/min, p = 0.015) and RF (1.7 ± 0.6 ml/100 g/min, p = 0.0015), but comparable to VM (2.4 ± 1.1 ml/100 g/min). NOS inhibition alone or with prostaglandins reduced blood flow by almost 50% (p < 0.001), but decrements were similar in all four muscles (drug × muscle interaction, p = 0.43). During exercise blood flow was also the highest in VI (45.4 ± 5.5 ml/100 g/min) and higher compared to VL (35.0 ± 5.5 ml/100 g/min), RF (38.4 ± 7.4 ml/100 g/min), and VM (36.2 ± 6.8 ml/100 g/min). NOS inhibition alone did not reduce exercise hyperemia (p = 0.51), but combined NOS and prostaglandin inhibition reduced blood flow during exercise (p = 0.002), similarly in all muscles (drug × muscle interaction, p = 0.99). CONCLUSION: NOS inhibition, with or without prostaglandins inhibition, affects blood flow similarly in different human QF muscles both at rest and during low-to-moderate intensity exercise.