Prostaglandin E2 downregulates TNF-α-induced production of matrix metalloproteinase-1 in HCS-2/8 chondrocytes by inhibiting Raf-1/MEK/ERK cascade through EP4 prostanoid receptor activation

Suppression of UVB-Induced MMP-1 Expression in Human Skin Fibroblasts Using Lysate of Lactobacillus iners Derived from Korean Women's Skin in Their Twenties

The process of skin aging is intricate, involving intrinsic aging, influenced by internal factors, and extrinsic aging, mainly caused by exposure to UV radiation, resulting in photoaging. Photoaging manifests as skin issues such as wrinkles and discoloration. The skin microbiome, a diverse community of microorganisms on the skin's surface, plays a crucial role in skin protection and can be affected by factors like humidity and pH. Probiotics, beneficial microorganisms, have been investigated for their potential to enhance skin health by regulating the skin microbiome. This can be accomplished through oral probiotics, impacting the gut-skin axis, or topical applications introducing live bacteria to the skin. Probiotics mitigate oxidative stress, suppress inflammation, and maintain the skin's extracellular matrix, ultimately averting skin aging. However, research on probiotics derived from human skin is limited, and there is no established product for preventing photoaging. The mechanism by which probiotics shield the skin microbiome and skin layers from UV radiation remains unclear. Recently, researchers have discovered Lactobacillus in the skin, with reports indicating a decrease in this microorganism with age. In a recent study, scientists isolated Lactobacillus iners KOLBM20 from the skin of individuals in their twenties and confirmed its effectiveness. A comparative analysis of genetic sequences revealed that strain KOLBM20 belongs to the Lactobacillus genus and closely relates to L. iners DSM13335(T) with a 99.20% similarity. Importantly, Lactobacillus iners KOLBM20 displayed anti-wrinkle properties by inhibiting MMP-1. This investigation demonstrated the inhibitory effect of KOLBM20 strain lysate on MMP-1 expression. Moreover, the data suggest that KOLBM20 strain lysate may prevent UVB-induced MMP-1 expression by inhibiting the activation of the ERK, JNK, and p38 signaling pathways induced by UVB. Consequently, KOLBM20 strain lysate holds promise as a potential therapeutic agent for preventing and treating skin photoaging.

β2-Adrenoceptor Agonists Promote ERK1/2 Dephosphorylation in Human Airway Epithelial Cells by Canonical, cAMP-driven Signaling Independently of β-Arrestin 2

Chronic use of β₂-adrenoceptor agonists as a monotherapy in asthma is associated with a loss of disease control and an increased risk of mortality. Herein, we tested the hypothesis that β₂-adrenoceptor agonists, including formoterol, promote biased, β-arrestin 2 (βArr2)-dependent activation of the mitogen-activated protein (MAP) kinases, ERK1/2, in human airway epithelial cells and, thereby, effect changes in gene expression that could contribute to their adverse clinical outcomes. Three airway epithelial cell models were used: the BEAS-2B cell line, human primary bronchial epithelial cells (HBEC) grown in submersion culture and HBEC that were highly differentiated at an air-liquid interface. Unexpectedly, treatment of all epithelial cell models with formoterol decreased basal ERK1/2 phosphorylation. This was mediated by cAMP-dependent protein kinase and involved the inactivation of C-rapidly-activated fibrosarcoma, which attenuated down-stream ERK1/2 activity, and the induction of dual-specificity phosphatase-1. Formoterol also inhibited the basal expression of early growth response-1, an ERK1/2-regulated gene that controls cell growth and repair in the airways. Neither carvedilol, a β₂-adrenoceptor agonist biased towards βArr2, nor formoterol promoted ERK1/2 phosphorylation in BEAS-2B cells although β₂-adrenoceptor desensitization was compromised in ARRB2-deficient cells. Collectively, these results contest the hypothesis that formoterol activates ERK1/2 in airway epithelia by nucleating a βArr2 signaling complex; instead, they indicate that β₂-adrenoceptor agonists inhibit constitutive ERK1/2 activity in a cAMP-dependent manner. These findings are the antithesis of results obtained using acutely challenged native and engineered HEK293 cells, which have been used extensively to study mechanisms of ERK1/2 activation, and highlight the cell-type-dependence of β₂-adrenoceptor-mediated signaling. Significance Statement It has been proposed that the adverse-effects of β₂-adrenoceptor agonist monotherapy in asthma are mediated by genomic mechanisms that occur principally in airway epithelial cells and are the result of β-arrestin 2-dependent activation of ERK1/2. This study shows that β₂-adrenoceptor agonists, paradoxically, reduced ERK1/2 phosphorylation in airway epithelia by disrupting upstream Ras-C-Raf complex formation and inducing DUSP1. Moreover, these effects were PKA-dependent suggesting that β₂-adrenoceptor agonists were not biased toward β-arrestin 2 and acted via canonical, cAMP-dependent signaling.

Recent Trends of microRNA Significance in Pediatric Population Glioblastoma and Current Knowledge of Micro RNA Function in Glioblastoma Multiforme

Central nervous system tumors are a significant problem for modern medicine because of their location. The explanation of the importance of microRNA (miRNA) in the development of cancerous changes plays an important role in this respect. The first papers describing the presence of miRNA were published in the 1990s. The role of miRNA has been pointed out in many medical conditions such as kidney disease, diabetes, neurodegenerative disorder, arthritis and cancer. There are several miRNAs responsible for invasiveness, apoptosis, resistance to treatment, angiogenesis, proliferation and immunology, and many others. The research conducted in recent years analyzing this group of tumors has shown the important role of miRNA in the course of gliomagenesis. These particles seem to participate in many stages of the development of cancer processes, such as proliferation, angiogenesis, regulation of apoptosis or cell resistance to cytostatics.

Oral administration of EP4-selective agonist KAG-308 suppresses mouse knee osteoarthritis development through reduction of chondrocyte hypertrophy and TNF secretion

Osteoarthritis (OA) is one of the world’s most common degenerative diseases, but there is no disease-modifying treatment available. Previous studies have shown that prostaglandin E2 (PGE₂) and PGE2 receptor 4 (EP₄) are involved in OA pathogenesis; however, their roles are not fully understood. Here, we examined the efficacy of oral administration of KAG-308, an EP₄-selective agonist, in surgically induced mouse knee OA. Cartilage degeneration and synovitis were significantly inhibited by the KAG-308 treatment. Chondrocyte hypertrophy and expression of tumor necrosis factor alpha (TNF) and matrix metalloproteinase 13 (Mmp13) in the synovium were suppressed in the KAG-308-treated mice. In cultured chondrocytes, hypertrophic differentiation was inhibited by KAG-308 and intranuclear translocation of histone deacetylase 4 (Hdac4) was enhanced. In cultured synoviocytes, lipopolysaccharide (LPS)-induced expression of TNF and Mmp13 was also suppressed by KAG-308. KAG-308 was detected in the synovium and cartilage of orally treated mice. TNF secretion from the synovia of KAG-308-treated mice was significantly lower than control mice. Thus, we conclude that oral administration of KAG-308 suppresses OA development through suppression of chondrocyte hypertrophy and synovitis. KAG-308 may be a potent candidate for OA drug development.

Anti‑apoptotic effects of glycosaminoglycans via inhibition of ERK/AP‑1 signaling in TNF‑α‑stimulated human dermal fibroblasts

It has been established that glycosaminoglycans (GAGs) serve an important role in protecting the skin against the effects of aging. A previous clinical trial by our group identified that a cream containing GAGs reduced wrinkles and increased skin elasticity, dermal density and skin tightening. However, the exact molecular mechanism underlying the anti‑aging effect of GAGs has not yet been fully elucidated. The present study assessed the influence of GAGs on cell viability, collagen synthesis and collagen synthesis‑associated signaling pathways in tumor necrosis factor‑α (TNF‑α)‑stimulated human dermal fibroblasts (HDFs); an in vitro model of aging. The results demonstrated that GAGs restored type I collagen synthesis and secretion by inhibiting extracellular signal‑regulated kinase (ERK) signaling in TNF‑α‑stimulated HDFs. However, GAGs did not activate c‑jun N‑terminal kinase or p38. It was determined that GAGs suppressed the phosphorylation of downstream transcription factors of ERK activation, activator protein‑1 (AP‑1; c‑fos and c‑jun), leading to a decrease in matrix metalloproteinase‑1 (MMP‑1) levels and the upregulation of tissue inhibitor of metalloproteinase‑1 in TNF‑α‑stimulated HDFs. In addition, GAGs attenuated the apoptosis of HDFs induced by TNF‑α. The current study revealed a novel mechanism: GAGs serve a crucial role in ameliorating TNF‑α‑induced MMP‑1 expression, which causes type I collagen degeneration via the inactivation of ERK/AP‑1 signaling in HDFs. The results of the present study indicate the potential application of GAGs as effective anti‑aging agents that induce wrinkle reduction.

PGE2 /EP4 receptor attenuated mucosal injury via β-arrestin1/Src/EGFR-mediated proliferation in portal hypertensive gastropathy

BACKGROUND AND PURPOSE

Portal hypertensive gastropathy (PHG) is a serious complication of liver cirrhosis and a potential cause of bleeding in patients with cirrhosis. Suppressed mucosal epithelial proliferation is a crucial pathological characteristic of PHG. Our studies demonstrated an important role for PGE₂ and its EP₄ receptor in the promotion of mucosal proliferation. However, whether β-arrestin1 (β-arr1), a well-established mediator of GPCRs, is involved in the PGE₂ /EP₄ receptor-mediated mucosal proliferation complex in PHG remains unclear. The aim of the study was to investigate whether β-arr1 participated in PGE₂ /EP₄ receptor-mediated mucosal proliferation by recruiting the Src/EGF receptor (EGFR) complex to activate Akt/proliferating cell nuclear antigen (PCNA) signalling in PHG.

EXPERIMENTAL APPROACH

Gastric mucosal proliferation was examined in patients with PHG and the PHG model of β-arr1-knockout (β-arr1-KO) and β-arr1-wild type (β-arr1-WT) mice. The induction of β-arr1 and EP₄ receptor expression and the Src/EGFR signalling elements was investigated, and the mechanisms underlying PGE₂ -regulated gastric mucosal proliferation were analysed.

KEY RESULTS

Portal hypertension suppressed COX-1 but not COX-2, which was accompanied by a down-regulation of PGE₂ generation and EP₄ receptor levels in the mucosa of patients with PHG. PGE₂ administration markedly promoted mucosal proliferation in a mouse model of PHG. Targeted deletion of β-arr1 abolished PGE₂ /EP₄ receptor-mediated gastric proliferation in PHG by repressing the Src/EGFR/Akt/PCNA signalling network.

CONCLUSIONS AND IMPLICATIONS

These results indicate that β-arr1 regulates PGE₂ /EP₄ receptor-mediated mucosal proliferation by promoting activation of the Src/EGFR/Akt/PCNA signalling pathway, and thus, this network is a potential therapeutic target for PHG.

Compound K inhibits MMP-1 expression through suppression of c-Src-dependent ERK activation in TNF-α-stimulated dermal fibroblast

Compound K (CK) is one of the major metabolites of ginsenosides exhibiting a variety of pharmacological properties such as anti-ageing, anti-oxidation and anti-inflammatory activities. However, the protective efficacy of CK in abnormal skin conditions with inflammatory responses was not examined. Here, we investigated the effects of CK on matrix metalloproteinase-1 (MMP-1) and type I procollagen production in tumor necrosis factor-α (TNF-α)-stimulated human skin fibroblasts HS68 cells and human skin equivalents. We found that CK suppressed MMP-1 secretion and increased the level of reduced type I procollagen secretion, caused by the inhibition of extracellular signal-regulated kinase (ERK) activation, but not p38 and c-Jun N-terminal kinase (JNK) activation in TNF-α-stimulated HS68 cells. Then, we focused on the involvement of the c-Src and epidermal growth factor receptor (EGFR) as upstream signalling molecules for ERK activation by TNF-α in HS68 cells. CK suppressed the phosphorylation of c-Src/EGFR by TNF-α, which led to the inactivation of downstream signalling molecules including AKT and MEK. In addition, CK suppressed AP-1 (c-jun and c-fos) phosphorylation as downstream transcription factors of active ERK for MMP-1 expression in TNFα-stimulated HS68 cells. These results showed novel mechanisms by which CK inhibits TNF-α-induced MMP-1 expression through the inactivation of c-Src/EGFR-dependent ERK/AP-1 signalling pathway, resulting in the inhibition of collagen degradation in human fibroblast cells. Therefore, CK may be a promising protective agent for the treatment of inflammatory skin conditions such as skin ageing and atopic dermatitis.

MiR-7-5p is frequently downregulated in glioblastoma microvasculature and inhibits vascular endothelial cell proliferation by targeting RAF1

The aberrant expression of microRNAs (miRNAs) is always associated with tumor development and progression. Microvascular proliferation is one of the unique pathologic features of glioblastoma (GBM) . In this study, the microvasculature from GBM or normal brain tissue derived from neurosurgeries was purified and total RNA was isolated from purified microvasculature. The difference of miRNA expression profiles between glioblastoma microvasculature and normal brain capillaries was investigated. It was found that miR-7-5p in GBM microvessels was significantly reduced compared with that in normal brain capillaries. In the in vitro experiments, overexpression of miR-7-5p significantly inhibited human umbilical vein endothelial cell proliferation. Forced expression of miR-7-5p in human umbilical vein endothelial cells in vitro significantly reduced the protein level of RAF1 and repressed the activity of the luciferase, a reporter vector carrying the 3'-untranslated region of RAF1. These findings indicate that RAF1 is one of the miR-7-5p target genes. Furthermore, a significant inverse correlation between miR-7-5p expression and RAF1 protein level in GBM microvasculature was found. These data suggest that miR-7-5p functions as a tumor suppressor gene to regulate GBM microvascular endothelial cell proliferation potentially by targeting the RAF1 oncogene, implicating an important role for miR-7-5p in the pathogenesis of GBM. It may serve as a guide for the antitumor angiogenesis drug development.

Positive and negative effects of prostaglandins in Alzheimer's disease

The aim of this review was to clarify the role of prostaglandins and prostaglandin receptors in the immunopathology of Alzheimer's disease. A PubMed search was done using the key word, 'Alzheimer's disease' in combination with the term 'prostaglandins'. Articles from the past 10 years were preferentially selected but important ones from the past 20 years were also included according to the authors' judgment. Alzheimer's disease is characterized by pathological hallmarks such as extracellular deposition of the amyloid β-peptide, the appearance of intracellular neurofibrillary tangles, extensive neuronal loss and synaptic changes in the cerebral cortex and hippocampus. These processes induce inflammatory pathways by activating microglia, astrocytes and infiltrating leukocytes that produce inflammatory mediators including cytokines and prostaglandins.Prostaglandins are small lipid mediators derived from arachidonic acid by multi-enzymatic pathways in which cyclooxygenases and phospholipases are the rate-limiting enzymes. In the central nervous system, prostaglandins exhibit either neurotoxic or neuroprotective effects by acting on specific G-protein-coupled receptors that have different subfamilies and differences in their selective agonists, tissue distribution and signal transduction cascades. Further studies on the role of prostaglandins in Alzheimer's disease may contribute to clarification of their neuroprotective actions, which may lead to the development of successful therapeutic strategies.

Novel anti-tumor mechanism of galanin receptor type 2 in head and neck squamous cell carcinoma cells

Galanin and its receptors, GALR1 and GALR2, are known tumor suppressors and potential therapeutic targets in head and neck squamous cell carcinoma (HNSCC). Previously, we demonstrated that, in GALR1-expressing HNSCC cells, the addition of galanin suppressed tumor proliferation via upregulation of ERK1/2 and cyclin-dependent kinase inhibitors, whereas, in GALR2-expressing cells, the addition of galanin not only suppressed proliferation, but also induced apoptosis. In this study, we first transduced HEp-2 and KB cell lines using a recombinant adeno-associated virus (rAAV)-green fluorescent protein (GFP) vector and confirmed a high GFP expression rate (>90%) in both cell lines at the standard vector dose. Next, we demonstrated that GALR2 expression in the presence of galanin suppressed cell viability to 40-60% after 72 h in both cell lines. Additionally, the annexin V-positive rate and sub-G0/G1 phase population were significantly elevated in HEp-2 cells (mock vs GALR2: 12.3 vs 25.0% (P < 0.01) and 9.1 vs 32.0% (P < 0.05), respectively) after 48 h. These changes were also observed in KB cells, although to a lesser extent. Furthermore, in HEp-2 cells, GALR2-mediated apoptosis was caspase-independent, involving downregulation of ERK1/2, followed by induction of the pro-apoptotic Bcl-2 protein, Bim. These results illustrate that transient GALR2 expression in the presence of galanin induces apoptosis via diverse pathways and serves as a platform for suicide gene therapy against HNSCC.

E-type prostanoid receptor 4 (EP4) in disease and therapy

The large variety of biological functions governed by prostaglandin (PG) E2 is mediated by signaling through four distinct E-type prostanoid (EP) receptors. The availability of mouse strains with genetic ablation of each EP receptor subtype and the development of selective EP agonists and antagonists have tremendously advanced our understanding of PGE2 as a physiologically and clinically relevant mediator. Moreover, studies using disease models revealed numerous conditions in which distinct EP receptors might be exploited therapeutically. In this context, the EP4 receptor is currently emerging as most versatile and promising among PGE2 receptors. Anti-inflammatory, anti-thrombotic and vasoprotective effects have been proposed for the EP4 receptor, along with its recently described unfavorable tumor-promoting and pro-angiogenic roles. A possible explanation for the diverse biological functions of EP4 might be the multiple signaling pathways switched on upon EP4 activation. The present review attempts to summarize the EP4 receptor-triggered signaling modules and the possible therapeutic applications of EP4-selective agonists and antagonists.

Thrombin-induced NF-κB activation and IL-8/CXCL8 release is mediated by c-Src-dependent Shc, Raf-1, and ERK pathways in lung epithelial cells

In addition to its functions in thrombosis and hemostasis, thrombin also plays an important role in lung inflammation. Our previous report showed that thrombin activates the protein kinase C (PKC)α/c-Src and Gβγ/Rac1/PI3K/Akt signaling pathways to induce IκB kinase α/β (IKKα/β) activation, NF-κB transactivation, and IL-8/CXCL8 expressions in human lung epithelial cells (ECs). In this study, we further investigated the mechanism of c-Src-dependent Shc, Raf-1, and extracellular signal-regulated kinase (ERK) signaling pathways involved in thrombin-induced NF-κB activation and IL-8/CXCL8 release. Thrombin-induced increases in IL-8/CXCL8 release and κB-luciferase activity were inhibited by the Shc small interfering RNA (siRNA), p66Shc siRNA, GW 5074 (a Raf-1 inhibitor), and PD98059 (a mitogen-activated protein kinase (MAPK) kinase (MEK) inhibitor). Treatment of A549 cells with thrombin increased p66Shc and p46/p52Shc phosphorylation at Tyr239/240 and Tyr317, which was inhibited by cell transfection with the dominant negative mutant of c-Src (c-Src DN). Thrombin caused time-dependent phosphorylation of Raf-1 and ERK, which was attenuated by the c-Src DN. Thrombin-induced IKKα/β phosphorylation was inhibited by GW 5074 and PD98059. Treatment of cells with thrombin induced Gβγ, c-Src, and p66Shc complex formation in a time-dependent manner. Taken together, these results show for the first time that thrombin activates Shc, Raf-1, and ERK through Gβγ, c-Src, and Shc complex formation to induce IKKα/β phosphorylation, NF-κB activation, and IL-8/CXCL8 release in human lung ECs.

Prostaglandin EP4 receptor enhances BCR-induced apoptosis of immature B cells

Prostaglandin E2 (PGE2) is emerging as an important co-modulator of B cell responses. Using a pharmacological approach, we aimed to delineate the role of PGE2 in B cell receptor (BCR) induced apoptosis of immature B cells. Gene and protein expression analyses showed that, of the four PGE2 receptors subtypes, only EP4 receptor is upregulated upon BCR cross-linking, leading to sensitization of WEHI 231 cells towards PGE2 mediated inhibitory effects. EP4 receptor antagonist ONO-AE3-208, was able to completely revert the observed effects of PGE2. The engagement of EP4 receptor promotes BCR-induced G0/G1 arrest of WEHI 231 cells, resulting in enhanced caspase mediated, BCR-induced apoptosis. We addressed, mechanistically, the interplay between BCR and EP4 receptor signaling components. Prostaglandin1-alcohol (Pge1-OH), a selective EP4 receptor agonist inhibits BCR-induced activation of NF-κB by suppression of BCR-induced IκBα phosphorylation. Disruption of prosurvival pathways is a possible mechanism by which PGE2 enhances BCR-induced apoptosis in immature B lymphocytes.

PGE2 inhibits MMP expression by suppressing MKK4-JNK MAP kinase-c-JUN pathway via EP4 in human articular chondrocytes

Prostaglandin E2 (PGE2) is one of pro-inflammatory mediators. PGE2 maintains the homeostasis of many organs including articular cartilage, and a previous report showed that continuous inhibition of PGE2 accelerates the progression of osteoarthritis (OA). While PGE2 inhibits matrix metalloprotease (MMP) expression in several types of cells, little is known on direct effects of PGE2 on MMP expression in articular chondrocytes. The objective of this study was to investigate direct effects of PGE2 on IL-1beta-induced MMP-1 and MMP-13 expression and the intracellular signaling in articular chondrocytes. PGE2 showed inhibitory effects on IL-1beta-induced MMP-1 and MMP-13 expression demonstrated by immunoblotting both in OA and normal chondrocytes, which was further confirmed by enzyme-linked immunosorbent assay and immunohistochemistry of explant cultures of articular cartilages. An EP4 agonist, ONO-AE1-329, mimicked the inhibitory effect of PGE2, while an EP4 antagonist, ONO-AE3-208, blocked the effects. PGE2 suppressed the phosphorylation of JNK and ERK MAP kinases, but only knockdown of JNK by specific siRNA mimicked the effect of PGE2. PGE2 further inhibited the phosphorylation of MKK4 without suppression of MKK7 phosphorylation, and of c-JUN to decrease expression levels of MMP-1 and MMP-13. These results demonstrate that PGE2 inhibits IL-1beta-induced MMP-1 and MMP-13 productions via EP4 by suppressing MKK4-JNK MAP kinase-c-JUN pathway.

Mechanisms of non-opioid analgesics beyond cyclooxygenase enzyme inhibition

Non-opioid analgesics including both selective and non-selective cyclooxygenase (COX) inhibitors and acetaminophen are the most widely used treatments for pain. Inhibition of COX is thought to be largely responsible for both the therapeutic and adverse effects of this class of drugs. Accumulating evidence over the past two decades has demonstrated effects of non-opioids beyond the inhibition of COX and prostaglandin synthesis that might also explain their therapeutic and adverse effects. These include their interaction with endocannabinoids, nitric oxide, monoaminergic, and cholinergic systems. Moreover, the recent development of microarray technology that allows the study of human gene expression suggests multiple pathways that may be related to the analgesic and anti-inflammatory effects of non-opioids. The present review will discuss the multiple actions of non-opioids and their interactions with these systems during inflammation and pain, suggesting that COX inhibition is an incomplete explanation for the actions of non-opioids and proposes the involvement of multiple selective targets for their analgesic, as well as, their adverse effects.

Control of tight junctional sealing: roles of epidermal growth factor and prostaglandin E2

Epithelia can adjust the permeability of the paracellular permeation route by regulating the degree of sealing of the tight junction. This is reflected by a transepithelial electrical resistance (TER) ranging from a few tenths to several thousand ohms times square centimeters, depending on the difference in composition between the fluid in the lumen and the interstitial fluid. Although teleologically sound, such correlation requires a physiological explanation. We have previously shown that urine extracts from different animal species increase the TER of Madin-Darby canine kidney (MDCK) monolayers and that these effects are mediated by epidermal growth factor (EGF) contained in the flowing intratubular fluid that eventually reaches the urine. This increase in TER is accompanied by an enhanced expression of claudin-4 (cln-4) and a decrement of cln-2. These changes are transient, peaking at approximately 16 h and returning to control values in approximately 24 h. In the present work we investigated how EGF provokes this transient response, and we found that the activation of extracellular-regulated kinases 1/2 (ERK1/2) by EGF is essential to increase TER and cln-4 content, but it does not appear to participate in cln-2 downregulation. On the other hand, prostaglandin synthesis, stimulated by EGF, functions as a negative feedback, turning off the signal initiated by EGF. Thus, PGE(2) blocks ERK1/2 by a mechanism that involves the G alpha(s) protein, adenylyl cyclase as well as protein kinase A in MDCK cells. In summary, the permeability of a given segment of the nephron depends on the expression of different claudin types, which may be modulated by EGF and prostaglandins.

Prostaglandin E2 differentially modulates proinflammatory/prodestructive effects of TNF-alpha on synovial fibroblasts via specific E prostanoid receptors/cAMP

The present study investigated the influence of PGE(2), E prostanoid (EP) receptors, and their signaling pathways on matrix metalloproteinase (MMP)-1 and IL-6 expression in synovial fibroblasts (SFs) from rheumatoid arthritis (RA) patients. RASFs expressed all four EP receptors, with selective induction of EP2 by TNF-alpha. TNF-alpha time-dependently increased intracellular cAMP/protein kinase A signaling (maximum, 6-12 h) and PGE(2) secretion (maximum, 24 h). PGE(2) and the EP2 agonists butaprost or ONO-AE1-259 ((16)-9-deoxy-9beta-chloro-15-deoxy-16-hydroxy-17,17-trimethylene-19,20-didehydro PGE(1)), in turn, induced a rapid, time-dependent (maximum, 15-30 min) increase of cAMP. Additionally, cyclooxygenase-2 inhibition by NS-398 (N-(2-cyclohexyloxy-4-nitrophenyl)-methanesulfonamide) reduced the TNF-alpha-induced increase in IL-6 mRNA/protein, which was restored by stimulation with PGE(2) or EP2, EP3, and EP4 agonists. In contrast, TNF-alpha-induced MMP-1 secretion was not influenced by NS-398 and diminished by PGE(2) via EP2. Finally, 3-isobutyl-1-methylxanthine enhanced the effects of PGE(2) on MMP-1, but not on IL-6 mRNA. In conclusion, PGE(2) differentially affects TNF-alpha-induced mRNA expression of proinflammatory IL-6 and prodestructive MMP-1 regarding the usage of EP receptors and the dependency on cAMP. Although specific blockade of EP2 receptors is considered a promising therapeutic strategy in RA, opposite regulation of proinflammatory IL-6 and prodestructive MMP-1 by PGE(2) via EP2 may require more complex approaches to successfully inhibit the cyclooxygenase-1/2 cAMP axis.

Emerging roles of PGE2 receptors in models of neurological disease

This review presents an overview of the emerging field of prostaglandin signaling in neurological diseases, focusing on PGE(2) signaling through its four E-prostanoid (EP) receptors. A large number of studies have demonstrated a neurotoxic function of the inducible cyclooxygenase COX-2 in a broad spectrum of neurological disease models in the central nervous system (CNS), from models of cerebral ischemia to models of neurodegeneration and inflammation. Since COX-1 and COX-2 catalyze the first committed step in prostaglandin synthesis, an effort is underway to identify the downstream prostaglandin signaling pathways that mediate the toxic effect of COX-2. Recent epidemiologic studies demonstrate that chronic COX-2 inhibition can produce adverse cerebrovascular and cardiovascular effects, indicating that some prostaglandin signaling pathways are beneficial. Consistent with this concept, recent studies demonstrate that in the CNS, specific prostaglandin receptor signaling pathways mediate toxic effects in brain but a larger number appear to mediate paradoxically protective effects. Further complexity is emerging, as exemplified by the PGE(2) EP2 receptor, where cerebroprotective or toxic effects of a particular prostaglandin signaling pathway can differ depending on the context of cerebral injury, for example, in excitotoxicity/hypoxia paradigms versus inflammatory-mediated secondary neurotoxicity. The divergent effects of prostaglandin receptor signaling will likely depend on distinct patterns and dynamics of receptor expression in neurons, endothelial cells, and glia and the specific ways in which these cell types participate in particular models of neurological injury.

Inhibition of TNF-alpha-induced cyclooxygenase-2 expression by Mycobacterium bovis BCG in human alveolar epithelial A549 cells

Cyclooxygenase-2 (COX-2) is implicated in pathophysiological processes associated with the initiation or maintenance of host inflammatory responses to infection. Our results demonstrates that Mycobacterium bovis BCG (M. bovis BCG) downregulates tumour necrosis factor-alpha (TNF-alpha)-induced COX-2 gene expression in alveolar epithelial cells by inhibiting the phosphorylations of Raf-1 and p38 kinases. Further, M. bovis BCG-mediated inhibition of COX-2 or p38 mitogen-activated protein kinase could be reversed by Calyculin A, a selective inhibitor of Ser/Thr phosphatases. Moreover, M. bovis BCG inhibited the TNF-alpha-triggered NF-kappaB activation following IkappaB degradation. Taken together, these results suggest that the attenuation of COX-2 expression by vaccine strain, M. bovis BCG, represents a novel strategy to maintain robust host proinflammatory responses to subsequent challenges with virulent tuberculosis bacilli.

Growth and differentiation factors for cartilage healing and repair

Chondrocyte differentiation and the maintenance of function requires both transient and long-lasting control through humoral factors, particularly under stress, repair and regeneration in vivo or in vitro as in cell and tissue culture. To date, humoral factors from all major classes of molecules are known to contribute: ions (calcium), steroids (estrogens), terpenoids (retinoic acid), peptides (PTHRP, PTH, insulin, FGFs) and complex proteins (IGF-1, BMPs). They may act indirectly through membrane receptors and signal pathways or directly on transcriptional control elements. Those molecules may reach chondrocytes via free diffusion or may be bound to collagens or proteoglycans on extracellular matrix superstructures becoming available on metabolic processing of collagens and/or proteoglycans. Depending on their position in the metabolic cascade controlling chondrocyte development and homeostasis, they may be used in tissue engineering and regenerative approaches towards cartilage repair by direct application, carrier-mediated release or genetic delivery.

Prostaglandin E receptor type 4-associated protein interacts directly with NF-kappaB1 and attenuates macrophage activation

Macrophage activation participates pivotally in the pathophysiology of chronic inflammatory diseases, including atherosclerosis. Through the receptor EP4, prostaglandin E(2) (PGE(2)) exerts an anti-inflammatory action in macrophages, suppressing stimulus-induced expression of certain proinflammatory genes, including chemokines. We recently identified a novel EP4 receptor-associated protein (EPRAP), whose function in PGE(2)-mediated anti-inflammation remains undefined. Here we demonstrate that PGE(2) pretreatment selectively inhibits lipopolysaccharide (LPS)-induced nuclear factor kappaB1 (NF-kappaB1) p105 phosphorylation and degradation in mouse bone marrow-derived macrophages through EP4-dependent mechanisms. Similarly, directed EPRAP expression in RAW264.7 cells suppresses LPS-induced p105 phosphorylation and degradation, and subsequent activation of mitogen-activated protein kinase kinase 1/2. Forced expression of EPRAP also inhibits NF-kappaB activation induced by various proinflammatory stimuli in a concentration-dependent manner. In co-transfected cells, EPRAP, which contains multiple ankyrin repeat motifs, directly interacts with NF-kappaB1 p105/p50 and forms a complex with EP4. In EP4-overexpressing cells, PGE(2) enhances the protective action of EPRAP against stimulus-induced p105 phosphorylation, whereas EPRAP silencing in RAW264.7 cells impairs the inhibitory effect of PGE(2)-EP4 signaling on LPS-induced p105 phosphorylation. Additionally, EPRAP knockdown as well as deficiency of NF-kappaB1 in macrophages attenuates the inhibitory effect of PGE(2) on LPS-induced MIP-1beta production. Thus, PGE(2)-EP4 signaling augments NF-kappaB1 p105 protein stability through EPRAP after proinflammatory stimulation, limiting macrophage activation.