Elevated Prostaglandin E2 Research Articles

Proliferative Diabetic Retinopathy Microenvironment Drives Microglial Polarization and Promotes Angiogenesis and Fibrosis via Cyclooxygenase-2/Prostaglandin E2 Signaling

Diabetic retinopathy (DR) is the leading cause of visual impairment, particularly in the proliferative form (proliferative DR [PDR]). The impact of the PDR microenvironment on microglia, which are the resident immune cells in the central nervous system, and the specific pathological changes it may induce remain unclear. This study aimed to investigate the role of microglia in the progression of PDR under hypoxic and inflammatory conditions. We performed a comprehensive gene expression analysis using human-induced pluripotent stem cell-derived microglia under different stimuli (dimethyloxalylglycine (DMOG), lipopolysaccharide (LPS), and DMOG + LPS) to mimic the hypoxic inflammatory environment characteristic of PDR. Principal component analysis revealed distinct gene expression profiles, with 76 genes synergistically upregulated under combined stimulation. Notably, prostaglandin-endoperoxide synthase 2 (encoding cyclooxygenase (COX)-2) exhibited the most pronounced increase, leading to elevated prostaglandin E2 (PGE2) levels and driving pathological angiogenesis and inflammation via the COX-2/PGE2/PGE receptor 2 signaling axis. Additionally, the upregulation of the fibrogenic genes snail family transcriptional repressor 1 and collagen type I alpha 1 chain suggested a role for microglia in fibrosis. These findings underscore the critical involvement of microglia in PDR and suggest that targeting both the angiogenic and fibrotic pathways may present new therapeutic strategies for managing this condition.

Spinster homolog 2/S1P signaling ameliorates macrophage inflammatory response to bacterial infections by balancing PGE2 production

BackgroundMitochondria play a crucial role in shaping the macrophage inflammatory response during bacterial infections. Spinster homolog 2 (Spns2), responsible for sphingosine-1-phosphate (S1P) secretion, acts as a key regulator of mitochondrial dynamics in macrophages. However, the link between Spns2/S1P signaling and mitochondrial functions remains unclear.MethodsPeritoneal macrophages were isolated from both wild-type and Spns2 knockout rats, followed by non-targeted metabolomics and RNA sequencing analysis to identify the potential mediators through which Spns2/S1P signaling influences the mitochondrial functions in macrophages. Various agonists and antagonists were used to modulate the activation of Spns2/S1P signaling and its downstream pathways, with the underlying mechanisms elucidated through western blotting. Mitochondrial functions were assessed using flow cytometry and oxygen consumption assays, as well as morphological analysis. The impact on inflammatory response was validated through both in vitro and in vivo sepsis models, with the specific role of macrophage-expressed Spns2 in sepsis evaluated using Spns2flox/floxLyz2-Cre mice. Additionally, the regulation of mitochondrial functions by Spns2/S1P signaling was confirmed using THP-1 cells, a human monocyte-derived macrophage model.ResultsIn this study, we unveil prostaglandin E2 (PGE2) as a pivotal mediator involved in Spns2/S1P-mitochondrial communication. Spns2/S1P signaling suppresses PGE2 production to support malate-aspartate shuttle activity. Conversely, excessive PGE2 resulting from Spns2 deficiency impairs mitochondrial respiration, leading to intracellular lactate accumulation and increased reactive oxygen species (ROS) generation through E-type prostanoid receptor 4 activation. The overactive lactate-ROS axis contributes to the early-phase hyperinflammation during infections. Prolonged exposure to elevated PGE2 due to Spns2 deficiency culminates in subsequent immunosuppression, underscoring the dual roles of PGE2 in inflammation throughout infections. The regulation of PGE2 production by Spns2/S1P signaling appears to depend on the coordinated activation of multiple S1P receptors rather than any single one.ConclusionsThese findings emphasize PGE2 as a key effector of Spns2/S1P signaling on mitochondrial dynamics in macrophages, elucidating the mechanisms through which Spns2/S1P signaling balances both early hyperinflammation and subsequent immunosuppression during bacterial infections.

Duloxetine-Induced Antidiuresis in Rats with Lithium-Induced Nephrogenic Diabetes Insipidus.

Antidepressants, including duloxetine, are a significant cause of drug-induced hyponatremia, which can disrupt the continuation of medication. Tolvaptan is beneficial for correcting hyponatremia caused by the syndrome of inappropriate antidiuresis, but its impact on duloxetine-induced hyponatremia remains unknown. We used male Sprague-Dawley rats to examine the impact of duloxetine treatment on lithium-induced nephrogenic diabetes insipidus (Li-NDI) and to evaluate whether the results were reversed by co-treatment with tolvaptan. To induce Li-NDI, lithium chloride (40 mmol lithium/kg dry food) was administered for 2 weeks. Duloxetine (50 mg/kg/day) and tolvaptan (10 mg/kg/day) were also administered in food to assess their individual effects over the same period. At the end of each animal experiment, kidneys were harvested to measure levels of cAMP, vasopressin-2 receptor (V2R), cAMP-responsive element binding protein 1 (CREB-1), aquaporin-2 (AQP2), and prostaglandin E2 (PGE2). Water diuresis was induced in the Li-NDI rats, and duloxetine treatment reduced polyuria while increasing urine osmolality. Duloxetine treatment prevented the decrease in total AQP2, AQP2 phosphorylation at serine 256, and CREB-1 phosphorylation in Li-NDI rats. The V2R mRNA level was also reduced in Li-NDI rats and restored by duloxetine treatment. In the subsequent experiment, the decreased water diuresis in Li-NDI rats treated with duloxetine was reversed by co-treatment with tolvaptan. Tolvaptan co-treatment also reversed the changes in AQP2 protein and CREB-1 phosphorylation in the renal cortex and medulla. The decreased cAMP levels in Li-NDI rat kidneys were elevated by duloxetine treatment, and this elevation was reversed by co-treatment with tolvaptan. However, the elevated PGE2 levels in Li-NDI rat kidneys were not affected by either duloxetine alone or tolvaptan co-treatment. In conclusion, antidiuresis was induced by duloxetine in Li-NDI and reversed by tolvaptan co-treatment through alterations in the V2R-cAMP-AQP2 pathway. These findings could underlie the mechanism of duloxetine-induced hyponatremia and suggest the potential usefulness of tolvaptan in treating drug-induced hyponatremia.

Pathogenesis of chronic enteropathy associated with the SLCO2A1 gene: Hypotheses and conundrums.

Chronic enteropathy associated with the SLCO2A1 gene (CEAS) is a complex gastroenterological condition characterized by multiple ulcers in the small intestine with chronic bleeding and protein loss. This review explores the potential mechanisms underlying the pathogenesis of CEAS, focusing on the role of SLCO2A1-encoded prostaglandin transporter OATP2A1 and its impact on prostaglandin E2 (PGE2) levels. Studies have suggested that elevated PGE2 levels contribute to mucosal damage, inflammation, and disruption of the intestinal barrier. The effects of PGE2 on macrophage activation and Maxi-Cl channel functionality, as well as its interaction with nonsteroidal anti-inflammatory drugs play crucial roles in the progression of CEAS. Understanding the balance between its protective and pro-inflammatory effects and the complex interactions within the gastrointestinal tract can shed light on potential therapeutic targets for CEAS and guide the development of novel, targeted therapies.

Mechanically strained osteocyte-derived exosomes contained miR-3110-5p and miR-3058-3p and promoted osteoblastic differentiation

BackgroundOsteocytes are critical mechanosensory cells in bone, and mechanically stimulated osteocytes produce exosomes that can induce osteogenesis. MicroRNAs (miRNAs) are important constituents of exosomes, and some miRNAs in osteocytes regulate osteogenic differentiation; previous studies have indicated that some differentially expressed miRNAs in mechanically strained osteocytes likely influence osteoblastic differentiation. Therefore, screening and selection of miRNAs that regulate osteogenic differentiation in exosomes of mechanically stimulated osteocytes are important.ResultsA mechanical tensile strain of 2500 με at 0.5 Hz 1 h per day for 3 days, elevated prostaglandin E2 (PGE2) and insulin-like growth factor-1 (IGF-1) levels and nitric oxide synthase (NOS) activity of MLO-Y4 osteocytes, and promoted osteogenic differentiation of MC3T3-E1 osteoblasts. Fourteen miRNAs differentially expressed only in MLO-Y4 osteocytes which were stimulated with mechanical tensile strain, were screened, and the miRNAs related to osteogenesis were identified. Four differentially expressed miRNAs (miR-1930-3p, miR-3110-5p, miR-3090-3p, and miR-3058-3p) were found only in mechanically strained osteocytes, and the four miRNAs, eight targeted mRNAs which were differentially expressed only in mechanically strained osteoblasts, were also identified. In addition, the mechanically strained osteocyte-derived exosomes promoted the osteoblastic differentiation of MC3T3-E1 cells in vitro, the exosomes were internalized by osteoblasts, and the up-regulated miR-3110-5p and miR-3058-3p in mechanically strained osteocytes, were both increased in the exosomes, which was verified via reverse transcription quantitative polymerase chain reaction (RT-qPCR).ConclusionsIn osteocytes, a mechanical tensile strain of 2500 με at 0.5 Hz induced the fourteen differentially expressed miRNAs which probably were in exosomes of osteocytes and involved in osteogenesis. The mechanically strained osteocyte-derived exosomes which contained increased miR-3110-5p and miR-3058-3p (two of the 14 miRNAs), promoted osteoblastic differentiation.

Elevated Prostaglandin E2 Synthesis Is Associated with Clinical and Radiological Disease Severity in Cystic Fibrosis.

Background: Previous studies found high but very variable levels of tetranor-PGEM and PGDM (urine metabolites of prostaglandin (PG) E2 and PGD2, respectively) in persons with cystic fibrosis (pwCF). This study aims to assess the role of cyclooxygenase COX-1 and COX-2 genetic polymorphisms in PG production and of PG metabolites as potential markers of symptoms' severity and imaging findings. Methods: A total of 30 healthy subjects and 103 pwCF were included in this study. Clinical and radiological CF severity was evaluated using clinical scoring methods and chest computed tomography (CT), respectively. Urine metabolites were measured using liquid chromatography/tandem mass spectrometry. Variants in the COX-1 gene (PTGS1 639 C>A, PTGS1 762+14delA and COX-2 gene: PTGS2-899G>C (-765G>C) and PTGS2 (8473T>C) were also analyzed. Results: PGE-M and PGD-M urine concentrations were significantly higher in pwCF than in controls. There were also statistically significant differences between clinically mild and moderate disease and severe disease. Patients with bronchiectasis and/or air trapping had higher PGE-M levels than patients without these complications. The four polymorphisms did not associate with clinical severity, air trapping, bronchiectasis, or urinary PG levels. Conclusions: These results suggest that urinary PG level testing can be used as a biomarker of CF severity. COX genetic polymorphisms are not involved in the variability of PG production.

Mechanical Stress Induces Sodium Entry and Osmoprotective Responses in Murine Synovial Fibroblasts.

Osteoarthritis (OA) is a multifactorial disease depending on molecular, genetic, and environmental factors like mechanical strain. Next to the cartilage and the subchondral bone, OA also affects the synovium, which is critically involved in the maintenance of joint homeostasis. As there is a correlation between the extracellular sodium content in the knee joint and OA, this study investigates the impact of sodium on OA-associated processes like inflammation and bone remodeling without and with mechanical loading in synovial fibroblasts. For that purpose, murine synovial fibroblasts from the knee joint were exposed to three different extracellular sodium chloride concentrations (-20 mM, ±0 mM and +50 mM NaCl) in the absence or presence of compressive or intermittent tensile strain. In addition to the intracellular Na+ content and gene expression of the osmoprotective transcription factor nuclear factor of activated T cells 5 (Nfat5), the gene and protein expression of inflammatory mediators (interleukin-6 (IL6), prostaglandin endoperoxide synthase-2 (Ptgs2)/prostaglandin E2 (PGE2)), and factors involved in bone metabolism (receptor activator of NF-κB ligand (RANKL), osteoprotegerin (OPG)) were analyzed by qPCR and ELISA. Mechanical strain already increased intracellular Na+ and Nfat5 gene expression at standard salt conditions to levels obtained by exposure to increased extracellular Na+ content. Both high salt and compressive strain resulted in elevated IL6 and PGE2 release. Intermittent tensile strain did not increase Il6 mRNA expression or IL6 protein secretion but triggered Ptgs2 expression and PGE2 production. Increased extracellular Na+ levels and compressive strain increased RANKL expression. In contrast, intermittent tension suppressed RANKL expression without this response being subject to modification by extracellular sodium availability. OPG expression was only induced by compressive strain. Changes in extracellular Na+ levels modified the inflammatory response and altered the expression of mediators involved in bone metabolism in cells exposed to mechanical strain. These findings indicate that Na+ balance and Nfat5 are important players in synovial fibroblast responses to mechanical stress. The integration of Na+ and Na+-dependent signaling will help to improve the understanding of the pathogenesis of osteoarthritis and could lead to the establishment of new therapeutic targets.

Brain regulates weight bearing bone through PGE2 skeletal interoception: implication of ankle osteoarthritis and pain

Bone is a mechanosensitive tissue and undergoes constant remodeling to adapt to the mechanical loading environment. However, it is unclear whether the signals of bone cells in response to mechanical stress are processed and interpreted in the brain. In this study, we found that the hypothalamus of the brain regulates bone remodeling and structure by perceiving bone prostaglandin E2 (PGE2) concentration in response to mechanical loading. Bone PGE2 levels are in proportion to their weight bearing. When weight bearing changes in the tail-suspension mice, the PGE2 concentrations in bones change in line with their weight bearing changes. Deletion of cyclooxygenase-2 (COX2) in the osteoblast lineage cells or knockout of receptor 4 (EP4) in sensory nerve blunts bone formation in response to mechanical loading. Moreover, knockout of TrkA in sensory nerve also significantly reduces mechanical load-induced bone formation. Moreover, mechanical loading induces cAMP-response element binding protein (CREB) phosphorylation in the hypothalamic arcuate nucleus (ARC) to inhibit sympathetic tyrosine hydroxylase (TH) expression in the paraventricular nucleus (PVN) for osteogenesis. Finally, we show that elevated PGE2 is associated with ankle osteoarthritis (AOA) and pain. Together, our data demonstrate that in response to mechanical loading, skeletal interoception occurs in the form of hypothalamic processing of PGE2-driven peripheral signaling to maintain physiologic bone homeostasis, while chronically elevated PGE2 can be sensed as pain during AOA and implication of potential treatment.

Assessment of hepatic prostaglandin E2 level in carbamazepine induced liver injury.

Objective. Carbamazepine (CBZ), a widely used antiepileptic drug, is one major cause of the idiosyncratic liver injury along with immune reactions. Conversely, prostaglandin E2 (PGE2) demonstrates a hepatoprotective effect by regulating immune reactions and promoting liver repair in various types of liver injury. However, the amount of hepatic PGE2 during CBZ-induced liver injury remains elusive. In this study, we aimed to evaluate the hepatic PGE2 levels during CBZ-induced liver injury using a mouse model. Methods. Mice were orally administered with CBZ at a dose of 400 mg/kg for 4 days, and 800 mg/kg on the 5th day. Results. Plasma alanine transaminase (ALT) level increased in some of mice 24 h after the last CBZ administration. Although median value of hepatic PGE2 amount in the CBZ-treated mice showed same extent as vehicle-treated control mice, it exhibited significant elevated level in mice with severe liver injury presented by a plasma ALT level >1000 IU/L. According to these results, mice had a plasma ALT level >1000 IU/L were defined as responders and the others as non-responders in this study. Even though, the hepatic PGE2 levels increased in responders, the hepatic expression and enzyme activity related to PGE2 production were not upregulated when compared with vehicle-treated control mice. However, the hepatic 15-hydroxyprostaglandin dehydrogenase (15-PGDH) expression and activity decreased significantly in responders when compared with control mice. Conclusions. These results indicate that elevated hepatic PGE2 levels can be attributed to the downregulation of 15-PGDH expression under CBZ-induced liver injury.

Evaluation of Therapeutic Efficacy of Stigma and Petal Extracts of Crocus sativus L. on Acetic Acid-Induced Gastric Ulcer in Rats

Saffron (Crocus sativus L.) has long been considered a medicinal plant in Traditional Persian Medicine (TPM) due to its therapeutic properties. Despite this interest, its effects on gastrointestinal disorders have not been completely taken into consideration. Hence, this study aimed to evaluate the pharmacological activity of ethanolic extracts of saffron stigma (SS) and saffron petal (SP) in acetic acid-induced gastric ulcer in rats. The gastric ulcer model was imitated by the serosal application of acetic acid in male Wistar rats. Then, the animals were orally fed with 100 mg/kg and 200 mg/kg of ethanolic extracts of SS or SP, omeprazole (40 mg/kg), or saline for 12 days. The macroscopic and microscopic appearances of gastric ulcers and the levels of malondialdehyde (MDA), vascular endothelial growth factor (VEGF), and prostaglandin E2 (PGE2) in gastric tissues were assessed. The highest anti-ulcer activity was observed in the omeprazole-treated animals with the lowest ulcer size (4.29 ± 1.78 mm2). SS could not reduce gastric ulcer size in rats. Compared to the untreated rats, SP treatment significantly decreased ulcer indices in a dose-dependent manner. The gastric levels of PGE2, VEGF, and MDA were significantly elevated in the untreated animals with gastric ulcers compared to rats in the control group. The SS extract suppressed the elevated PGE2 and VEGF levels at both doses, while SP did not have a significant influence. Both SS and SP treatments significantly ameliorated MDA levels in rats with gastric ulcers. Omeprazole treatment enhanced the PGE2 level and suppressed MDA contents, but it did not influence the VEGF level. In conclusion, our findings demonstrated that the saffron stigma has no significant effects on the gastric ulcer healing process, while its petals accelerate the process. This discrepancy can be attributed to the difference in the main secondary metabolites between saffron stigma and petals.

Monocyte dysfunction in decompensated cirrhosis is mediated by the prostaglandin E2-EP4 pathway

Background & AimsInfection is a major problem in advanced liver disease secondary to monocyte dysfunction. Elevated prostaglandin (PG)E2 is a mediator of monocyte dysfunction in cirrhosis; thus, we examined PGE2 signalling in outpatients with ascites and in patients hospitalised with acute decompensation to identify potential therapeutic targets aimed at improving monocyte dysfunction.MethodsUsing samples from 11 outpatients with ascites and 28 patients hospitalised with decompensated cirrhosis, we assayed plasma levels of PGE2 and lipopolysaccharide (LPS); performed quantitative real-time PCR on monocytes; and examined peripheral blood monocyte function. We performed western blotting and immunohistochemistry for PG biosynthetic machinery expression in liver tissue. Finally, we investigated the effect of PGE2 antagonists in whole blood using polychromatic flow cytometry and cytokine production.ResultsWe show that hepatic production of PGE2 via the cyclo-oxygenase 1–microsomal PGE synthase 1 pathway, and circulating monocytes contributes to increased plasma PGE2 in decompensated cirrhosis. Transjugular intrahepatic sampling did not reveal whether hepatic or monocytic production was larger. Blood monocyte numbers increased, whereas individual monocyte function decreased as patients progressed from outpatients with ascites to patients hospitalised with acute decompensation, as assessed by Human Leukocyte Antigen (HLA)–DR isotype expression and tumour necrosis factor alpha and IL6 production. PGE2 mediated this dysfunction via its EP4 receptor.ConclusionsPGE2 mediates monocyte dysfunction in decompensated cirrhosis via its EP4 receptor and dysfunction was worse in hospitalised patients compared with outpatients with ascites. Our study identifies a potential drug target and therapeutic opportunity in these outpatients with ascites to reverse this process to prevent infection and hospital admission.Lay summaryPatients with decompensated cirrhosis (jaundice, fluid build-up, confusion, and vomiting blood) have high infection rates that lead to high mortality rates. A white blood cell subset, monocytes, function poorly in these patients, which is a key factor underlying their sensitivity to infection. We show that monocyte dysfunction in decompensated cirrhosis is mediated by a lipid hormone in the blood, prostaglandin E2, which is present at elevated levels, via its EP4 pathway. This dysfunction worsens when patients are hospitalised with complications of cirrhosis compared with those in the outpatients setting, which supports the EP4 pathway as a potential therapeutic target for patients to prevent infection and hospitalisation.

Does Compression Sensory Axonopathy in the Proximal Tibia Contribute to Noncontact Anterior Cruciate Ligament Injury in a Causative Way?-A New Theory for the Injury Mechanism.

Anterior cruciate ligament injury occurs when the ligament fibers are stretched, partially torn, or completely torn. The authors propose a new injury mechanism for non-contact anterior cruciate ligament injury of the knee. Accordingly, non-contact anterior cruciate ligament injury could not happen without the acute compression microinjury of the entrapped peripheral proprioceptive sensory axons of the proximal tibia. This would occur under an acute stress response when concomitant microcracks-fractures in the proximal tibia evolve due to the same excessive and repetitive compression forces. The primary damage may occur during eccentric contractions of the acceleration and deceleration moments of strenuous or unaccustomed fatiguing exercise bouts. This primary damage is suggested to be an acute compression/crush axonopathy of the proprioceptive sensory neurons in the proximal tibia. As a result, impaired proprioception could lead to injury of the anterior cruciate ligament as a secondary damage, which is suggested to occur during the deceleration phase. Elevated prostaglandin E2, nitric oxide and glutamate may have a critical neuro-modulatory role in the damage signaling in this dichotomous neuronal injury hypothesis that could lead to mechano-energetic failure, lesion and a cascade of inflammatory events. The presynaptic modulation of the primary sensory axons by the fatigued and microdamaged proprioceptive sensory fibers in the proximal tibia induces the activation of N-methyl-D-aspartate receptors in the dorsal horn of the spinal cord, through a process that could have long term relevance due to its contribution to synaptic plasticity. Luteinizing hormone, through interleukin-1β, stimulates the nerve growth factor-tropomyosin receptor kinase A axis in the ovarian cells and promotes tropomyosin receptor kinase A and nerve growth factor gene expression and prostaglandin E2 release. This luteinizing hormone induced mechanism could further elevate prostaglandin E2 in excess of the levels generated by osteocytes, due to mechanical stress during strenuous athletic moments in the pre-ovulatory phase. This may explain why non-contact anterior cruciate ligament injury is at least three-times more prevalent among female athletes.

Combined Lycium barbarum polysaccharides and C-phycocyanin increase gastric Bifidobacterium relative abundance and protect against gastric ulcer caused by aspirin in rats

BackgroundNon-steroidal anti-inflammatory drugs such as aspirin are used for the treatment of cardiovascular disease. Chronic use of low-dose aspirin is associated with the occurrence of gastric ulcer. The aim of this study was to investigate the healing potential of Lycium barbarum polysaccharides (LBP) from Chinese Goji berry and C-phycocyanin (CPC) from Spirulina platensis on gastric ulcer in rats.MethodsMale Sprague–Dawley rats were divided into five groups: normal, aspirin (700 mg/kg bw), LBP (aspirin + 100 mg/kg bw/d LBP), CPC (aspirin + 50 mg/kg bw/d CPC), and MIX (aspirin + 50 mg/kg bw/d LBP + 25 mg/kg bw/d CPC) groups. Gastric ulcer was developed by daily oral feeding of aspirin for 8 weeks. Treatments were given orally a week before ulcer induction for 9 weeks.ResultsThe MIX group elevated gastric cyclooxygenase-1, prostaglandin E2, and total nitrite and nitrate levels by 139%, 86%, and 66%, respectively, compared with the aspirin group (p < 0.05). Moreover, the MIX group reduced lipid peroxides malondialdehyde levels by 78% (p < 0.05). The treatment of LBP and/or CPC increased gastric Bifidobacterium relative abundance by 2.5–4.0 times compared with the aspirin group (p < 0.05).ConclusionsWe conclude that combined LBP and CPC enhance gastroprotective factors, inhibit lipid peroxidation, and increase gastric Bifidobacterium relative abundance. Combined LBP and CPC have protective potential against gastric ulcer caused by aspirin in rats.

TRPV1 Channel Activated by the PGE2/EP4 Pathway Mediates Spinal Hypersensitivity in a Mouse Model of Vertebral Endplate Degeneration.

Low back pain (LBP) is the primary cause of disability globally. There is a close relationship between Modic changes or endplate defects and LBP. Endplates undergo ossification and become highly porous during intervertebral disc (IVD) degeneration. In our study, we used a mouse model of vertebral endplate degeneration by lumbar spine instability (LSI) surgery. Safranin O and fast green staining and μCT scan showed that LSI surgery led to endplate ossification and porosity, but the endplates in the sham group were cartilaginous and homogenous. Immunofluorescent staining demonstrated the innervation of calcitonin gene-related peptide- (CGRP-) positive nerve fibers in the porous endplate of LSI mice. Behavior test experiments showed an increased spinal hypersensitivity in LSI mice. Moreover, we found an increased cyclooxygenase 2 (COX2) expression and an elevated prostaglandin E2 (PGE2) concentration in the porous endplate of LSI mice. Immunofluorescent staining showed the colocalization of E-prostanoid 4 (EP4)/transient receptor potential vanilloid 1 (TRPV1) and CGRP in the nerve endings in the endplate and in the dorsal root ganglion (DRG) neurons, and western blotting analysis demonstrated that EP4 and TRPV1 expression significantly increased in the LSI group. Our patch clamp study further showed that LSI surgery significantly enhanced the current density of the TRPV1 channel in small-size DRG neurons. A selective EP4 receptor antagonist, L161982, reduced the spinal hypersensitivity of LSI mice by blocking the PGE2/EP4 pathway. In addition, TRPV1 current and neuronal excitability in DRG neurons were also significantly decreased by L161982 treatment. In summary, the PGE2/EP4 pathway in the porous endplate could activate the TRPV1 channel in DRG neurons to cause spinal hypersensitivity in LSI mice. L161982, a selective EP4 receptor antagonist, could turn down the TRPV1 current and decrease the neuronal excitability of DRG neurons to reduce spinal pain.

TGF-β1-Licensed Murine MSCs Show Superior Therapeutic Efficacy in Modulating Corneal Allograft Immune Rejection In Vivo

Mesenchymal stromal cells (MSCs) are a promising therapeutic option for multiple immune diseases/disorders; however, efficacy of MSC treatments can vary significantly. We present a novel licensing strategy to improve the immunosuppressive capacity of MSCs. Licensing murine MSCs with transforming growth factor-β1 (TGF-β MSCs) significantly improved their ability to modulate both the phenotype and secretome of inflammatory bone marrow-derived macrophages and significantly increased the numbers of regulatory T lymphocytes following co-culture assays. These TGF-β MSC-expanded regulatory T lymphocytes also expressed significantly higher levels of PD-L1 and CD73, indicating enhanced suppressive potential. Detailed analysis of T lymphocyte co-cultures revealed modulation of secreted factors, most notably elevated prostaglandin E2 (PGE2). Furthermore, TGF-β MSCs could significantly prolong rejection-free survival (69.2% acceptance rate compared to 21.4% for unlicensed MSC-treated recipients) in a murine corneal allograft model. Mechanistic studies revealed that (1) therapeutic efficacy of TGF-β MSCs is Smad2/3-dependent, (2) the enhanced immunosuppressive capacity of TGF-β MSCs is contact-dependent, and (3) enhanced secretion of PGE2 (via prostaglandin EP4 [E-type prostanoid 4] receptor) by TGF-β MSCs is the predominant mediator of Treg expansion and T cell activation and is associated with corneal allograft survival. Collectively, we provide compelling evidence for the use of TGF-β1 licensing as an unconventional strategy for enhancing MSC immunosuppressive capacity.

Prostaglandin E2 stimulates the epithelial sodium channel (ENaC) in cultured mouse cortical collecting duct cells in an autocrine manner.

Prostaglandin E2 (PGE2) is the most abundant prostanoid in the kidney, affecting a wide range of renal functions. Conflicting data have been reported regarding the effects of PGE2 on tubular water and ion transport. The amiloride-sensitive epithelial sodium channel (ENaC) is rate limiting for transepithelial sodium transport in the aldosterone-sensitive distal nephron. The aim of the present study was to explore a potential role of PGE2 in regulating ENaC in cortical collecting duct (CCD) cells. Short-circuit current (ISC) measurements were performed using the murine mCCDcl1 cell line known to express characteristic properties of CCD principal cells and to be responsive to physiological concentrations of aldosterone and vasopressin. PGE2 stimulated amiloride-sensitive ISC via basolateral prostaglandin E receptors type 4 (EP4) with an EC50 of ∼7.1 nM. The rapid stimulatory effect of PGE2 on ISC resembled that of vasopressin. A maximum response was reached within minutes, coinciding with an increased abundance of β-ENaC at the apical plasma membrane and elevated cytosolic cAMP levels. The effects of PGE2 and vasopressin were nonadditive, indicating similar signaling cascades. Exposing mCCDcl1 cells to aldosterone caused a much slower (∼2 h) increase of the amiloride-sensitive ISC. Interestingly, the rapid effect of PGE2 was preserved even after aldosterone stimulation. Furthermore, application of arachidonic acid also increased the amiloride-sensitive ISC involving basolateral EP4 receptors. Exposure to arachidonic acid resulted in elevated PGE2 in the basolateral medium in a cyclooxygenase 1 (COX-1)-dependent manner. These data suggest that in the cortical collecting duct, locally produced and secreted PGE2 can stimulate ENaC-mediated transepithelial sodium transport.

Concerted EP2 and EP4 Receptor Signaling Stimulates Autocrine Prostaglandin E2 Activation in Human Podocytes.

Glomerular hyperfiltration is an important mechanism in the development of albuminuria. During hyperfiltration, podocytes are exposed to increased fluid flow shear stress (FFSS) in Bowman’s space. Elevated Prostaglandin E2 (PGE2) synthesis and upregulated cyclooxygenase 2 (Cox2) are associated with podocyte injury by FFSS. We aimed to elucidate a PGE2 autocrine/paracrine pathway in human podocytes (hPC). We developed a modified liquid chromatography tandem mass spectrometry (LC/ESI-MS/MS) protocol to quantify cellular PGE2, 15-keto-PGE2, and 13,14-dihydro-15-keto-PGE2 levels. hPC were treated with PGE2 with or without separate or combined blockade of prostaglandin E receptors (EP), EP2, and EP4. Furthermore, the effect of FFSS on COX2, PTGER2, and PTGER4 expression in hPC was quantified. In hPC, stimulation with PGE2 led to an EP2- and EP4-dependent increase in cyclic adenosine monophosphate (cAMP) and COX2, and induced cellular PGE2. PTGER4 was downregulated after PGE2 stimulation in hPC. In the corresponding LC/ESI-MS/MS in vivo analysis at the tissue level, increased PGE2 and 15-keto-PGE2 levels were observed in isolated glomeruli obtained from a well-established rat model with glomerular hyperfiltration, the Munich Wistar Frömter rat. COX2 and PTGER2 were upregulated by FFSS. Our data thus support an autocrine/paracrine COX2/PGE2 pathway in hPC linked to concerted EP2 and EP4 signaling.

Altered plasma prostaglandin E2 levels in epilepsy and in response to antiepileptic drug monotherapy

Prostaglandin E2 (PGE2), a physiologically active lipid compound, is increased in several diseases characterized by chronic inflammation. To determine its significance in epilepsy-associated inflammation and response to antiepileptic drug (AED), we evaluated the plasma PGE2 (median, pg/ml) levels in drug-free patients with epilepsy (N = 34) and patients receiving AED monotherapy (N = 55) in addition to that in healthy controls (N = 34). When compared to controls, plasma PGE2 levels were significantly elevated in all drug-free patients independent of the type of epilepsy (137.2 versus 475.7 pg/ml, p < 0.0001). Among the patients receiving AED monotherapy, only valproate responders showed a significant decrease compared to both drug-free patients (232.1 versus 475.7 pg/ml, p < 0.01) as well as valproate non-responders (232.1 versus 611.9 pg/ml, p < 0.0001). Both responders and non-responders on phenytoin or carbamazepine monotherapy had elevated PGE2 levels similar to drug-free patients. In addition, no difference was observed in plasma profiles of PGE2 precursor, arachidonic acid among the groups. Our work presents the clinical evidence of the association between plasma PGE2 levels and valproate efficacy in patients with epilepsy.

Anti-ulcerogenic activity of Gum Arabic in gastric mucosal injury induced by ethanol in male albino rats

The present study was performed to evaluate the anti-ulcerogenic activity of Acacia senegal (Gum Arabic) against ethanol-induced gastric mucosal injury in rats. Thirty-six adult male albino rats were divided into 4 groups: group 1 served as a control; group 2 consisted of rats that received 15% of gum in drinking water for 2 weeks; group 3 comprised ulcerated animals administered 5 mL of ethanol/kg body weight by gavage; and group 4 consisted of rats received 15% of gum in drinking water for 2 weeks before ethanol administration. Superoxide dismutase (SOD) glutathione peroxidase (GPx), malondialdehyde (MDA), prostaglandin E2 (PGE2), tumor necrosis factor alpha (TNF-α), interleukin (IL)-B1), alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), total protein, and albumin were assayed in addition to histological study. The results revealed that ethanol decreased SOD, GPx, and PGE2 in tissue and serum total protein and albumin, while increased MDA in tissue, serum TNF-α, IL-B1, PGE2, ALT, AST, and ALP. Histological findings showed less edema and leucocytes infiltration compared with ulcer group. Furthermore, gum administration elevated PGE2, SOD, and GPx and significantly reduced MDA, TNF-α, and IL-B2. In conclusion, Gum Arabic can enhance gastric protection and sustain the integrity of the gastric mucosa. Novelty The selected dose of Gum Arabic has the ability to decrease the pro-inflammatory cytokines in plasma and gastric tissue, thus enhancing gastric protection and maintaining the integrity of the gastric mucosa. Gum Arabic can compensate for the loss of antioxidants.

In vivo acute toxicity and anti-gastric evaluation of a novel dichloro Schiff base: Bax and HSP70 alteration.

Chlorine is shown to possess anti-gastric ulcer activity, since it can inactivate Helicobacter pylori, which is regarded as one of the most common risk factors for causing gastric problems. In the current study, the gastroprotective property of a novel dichloro-substituted Schiff base complex, 2, 2′- [−1, 2-cyclohexanediylbis(nitriloethylidyne)] bis(4-chlorophenol) (CNCP), against alcohol-induced gastric lesion in SD rats was assessed. SD rats were divided into four groups, i.e. normal, ulcer control, testing, and reference groups. Ulcer area, gastric wall mucus, and also gastric acidity of the animal stomachs were measured. In addition, antioxidant activity of CNCP was evaluated and its safe dose was identified. Immunohistochemistry staining was also carried to evaluate two important proteins, i.e. Bcl2-associated X protein (Bax) and heat shock protein 70 (HSP70). Moreover, the activities of super oxide dismutase and catalase, as well as the levels of prostaglandin E2 (PGE2) and malondialdehyde (MDA) were also measured. Antioxidant activity of CNCP was approved via the aforementioned experiments. Histological evaluations showed that the compound possesses stomach epithelial defense activity. Additionally, periodic acid-Schiff staining exhibited over-expression of HSP70 and down-expression of Bax protein in the CNCP-treated rats. Moreover, CNCP caused deceased MDA level and elevated PGE2 level, and at the same time increased the activities of the two enzymes.