Non-Steroidal Anti-Inflammatory Drug Use and Genomic DNA Methylation in Blood

Background

Non-steroidal anti-inflammatory drug (NSAID) use is associated with decreased risk of some cancers. NSAID use modulates the epigenetic profile of normal colonic epithelium and may reduce risk of colon cancer through this pathway; however, the effect of NSAID use on the DNA methylation profile of other tissues including whole blood has not yet been examined.

Findings

Using the Sister Study cohort, we examined the association between NSAID usage and whole genome methylation patterns in blood DNA. Blood DNA methylation status across 27,589 CpG sites was evaluated for 871 women using the Illumina Infinium HumanMethylation27 Beadchip, and in a non-overlapping replication sample of 187 women at 485,512 CpG sites using the Infinium HumanMethylation450 Beadchip. We identified a number of CpG sites that were differentially methylated in regular, long-term users of NSAIDs in the discovery group, but none of these sites were statistically significant in our replication group.

Conclusions

We found no replicable methylation differences in blood related to NSAID usage. If NSAID use does effect blood DNA methylation patterns, differences are likely small.     

Modeling of Non-Steroidal Anti-Inflammatory Drug Effect within Signaling Pathways and miRNA-Regulation Pathways

To date, it is widely recognized that Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) can exert considerable anti-tumor effects regarding many types of cancers. The prolonged use of NSAIDs is highly associated with diverse side effects. Therefore, tailoring down the NSAID application onto individual patients has become a necessary and relevant step towards personalized medicine. This study conducts the systemsbiological approach to construct a molecular model (NSAID model) containing a cyclooxygenase (COX)-pathway and its related signaling pathways. Four cancer hallmarks are integrated into the model to reflect different developmental aspects of tumorigenesis. In addition, a Flux-Comparative-Analysis (FCA) based on Petri net is developed to transfer the dynamic properties (including drug responsiveness) of individual cellular system into the model. The gene expression profiles of different tumor-types with available drug-response information are applied to validate the predictive ability of the NSAID model. Moreover, two therapeutic developmental strategies, synthetic lethality and microRNA (miRNA) biomarker discovery, are investigated based on the COX-pathway. In conclusion, the result of this study demonstrates that the NSAID model involving gene expression, gene regulation, signal transduction, protein interaction and other cellular processes, is able to predict the individual cellular responses for different therapeutic interventions (such as NS-398 and COX-2 specific siRNA inhibition). This strongly indicates that this type of model is able to reflect the physiological, developmental and pathological processes of an individual. The approach of miRNA biomarker discovery is demonstrated for identifying miRNAs with oncogenic and tumor suppressive functions for individual cell lines of breast-, colon- and lung-tumor. The achieved results are in line with different independent studies that investigated miRNA biomarker related to diagnostics of cancer treatments, therefore it might shed light on the development of biomarker discovery at individual level. Particular results of this study might contribute to step further towards personalized medicine with the systemsbiological approach.     

RETRACTED ARTICLE: Anti-Inflammatory Effects of Chronic Aspirin on Brain Arachidonic Acid Metabolites

Pro-inflammatory and anti-inflammatory mediators derived from arachidonic acid (AA) modulate peripheral inflammation and its resolution. Aspirin (ASA) is a unique non-steroidal anti-inflammatory drug, which switches AA metabolism from prostaglandin E₂ (PGE₂) and thromboxane B₂ (TXB₂) to lipoxin A₄ (LXA₄) and 15-epi-LXA₄. However, it is unknown whether chronic therapeutic doses of ASA are anti-inflammatory in the brain. We hypothesized that ASA would dampen increases in brain concentrations of AA metabolites in a rat model of neuroinflammation, produced by a 6-day intracerebroventricular infusion of bacterial lipopolysaccharide (LPS). In rats infused with LPS (0.5 ng/h) and given ASA-free water to drink, concentrations in high-energy microwaved brain of PGE₂, TXB₂ and leukotriene B₄ (LTB₄) were elevated. In rats infused with artificial cerebrospinal fluid, 6 weeks of treatment with a low (10 mg/kg/day) or high (100 mg/kg/day) ASA dose in drinking water decreased brain PGE₂, but increased LTB₄, LXA₄ and 15-epi-LXA₄ concentrations. Both doses attenuated the LPS effects on PGE₂, and TXB₂. The increments in LXA₄ and 15-epi-LXA₄ caused by high-dose ASA were significantly greater in LPS-infused rats. The ability of ASA to increase anti-inflammatory LXA₄ and 15-epi-LXA₄ and reduce pro-inflammatory PGE₂ and TXB₂ suggests considering aspirin further for treating clinical neuroinflammation.     

Bacterial Microbiota Profiling in Gastritis without Helicobacter pylori Infection or Non-Steroidal Anti-Inflammatory Drug Use

Recent 16S ribosomal RNA gene (rRNA) molecular profiling of the stomach mucosa revealed a surprising complexity of microbiota. Helicobacter pylori infection and non-steroidal anti-inflammatory drug (NSAID) use are two main contributors to gastritis and peptic ulcer. However, little is known about the association between other members of the stomach microbiota and gastric diseases. In this study, cloning and sequencing of the 16S rRNA was used to profile the stomach microbiota from normal and gastritis patients. One hundred and thirty three phylotypes from eight bacterial phyla were identified. The stomach microbiota was found to be closely adhered to the mucosa. Eleven Streptococcus phylotypes were successfully cultivated from the biopsies. One to two genera represented a majority of clones within any of the identified phyla. We further developed two real-time quantitative PCR assays to quantify the relative abundance of the Firmicutes phylum and the Streptococcus genus. Significantly higher abundance of the Firmicutes phylum and the Streptococcus genus within the Firmicutes phylum was observed in patients with antral gastritis, compared with normal controls. This study suggests that the genus taxon level can largely represent much higher taxa such as the phylum. The clinical relevance and the mechanism underlying the altered microbiota composition in gastritis require further functional studies.     

Association of Individual Non-Steroidal Anti-Inflammatory Drugs and Chronic Kidney Disease: A Population-Based Case Control Study

Background

Non-steroidal anti-inflammatory agents (NSAIDs) are known to be associated with renal damage. No clear evidence exists regarding differential risk of chronic kidney disease (CKD), specifically, across various NSAIDs.

Aim

The aim of this population-based case-control study was to evaluate the association between use of individual NSAIDs and risk of CKD in a general population of Southern Italy.

Methods

A nested case-control study was carried out using the general practice Arianna database, identifying incident CKD patients as cases and matched controls from 2006 to 2011. The date of first CKD diagnosis was defined as the index date (ID). Conditional logistic regressions were performed to estimate the risk of CKD associated with NSAIDs by class and individual drugs as compared to non-use during different time windows (within one year, six or three months prior to ID), with the latter being defined as current users. Among current users, the effect of cumulative exposure to these drugs was evaluated.

Results

Overall, 1,989 CKD cases and 7,906 matched controls were identified. A statistically significant increase in the risk of CKD was found for current users of oxicams (adjusted OR: 1.68; 95% CI: 1.15-2.44) and concerning individual compounds, for ketorolac (adj. OR: 2.54; 95% CI: 1.45-4.44), meloxicam (adj. OR: 1.98; 95% CI: 1.01-3.87) and piroxicam (adj. OR: 1.95; 95% CI: 1.19-3.21).

Conclusions

The risk of CKD varies across individual NSAIDs. Increased risk has been found for ketorolac, which may precipitate subclinical CKD through acute renal damage, and long-term exposure to oxicams, especially meloxicam and piroxicam.     

Non-Steroidal Anti-Inflammatory Drugs Use Is Associated with Reduced Risk of Inflammation-Associated Cancers: NIH-AARP Study

Background

Chronic inflammation has been linked to cancers, and use of non-steroidal anti-inflammatory drugs (NSAIDs) has been associated with reduced risk of several cancers. To further refine the magnitude of NSAID-related associations, in particular for cancers related to inflammation, such as alcohol-, infection-, obesity-, and smoking-related cancers, as well as for less common cancers, we evaluated the use of NSAIDs and cancer risk in a very large cohort. We used propensity scores to account for potential selection bias and hypothesized that NSAID use is associated with decreased cancer incidence.

Methods

We conducted a prospective study among 314,522 participants in the NIH-AARP Diet and Health Study. Individuals who completed the lifestyle questionnaire, which included NSAID use, in 1996–1997 were followed through 2006. Information on cancer incidence was ascertained by linking to cancer registries and vital status databases.

Findings

During 2,715,994 person-years of follow-up (median 10.1 person-years), there were 51,894 incident cancers. Compared with non-users of NSAIDs, individuals who reported use in the 12 months prior to interview had a significantly lower risk of all inflammation-related cancer, alcohol-related, infection-related, obesity-related, and smoking-related cancers [hazard ratio (HR) (95% CI)) 0.90 (0.87–0.93), 0.80 (0.74–0.85), 0.82 (0.78–0.87), 0.88 (0.84–0.92), and 0.88 (0.85–0.92) respectively)].

Conclusions

After accounting for potential selection bias, our data showed an inverse association between NSAID use and alcohol-related, infection-related, obesity-related, and smoking-related cancers and support the hypothesis that inflammation is related to an increased risk of certain cancers.     

Org 214007-0: A Novel Non-Steroidal Selective Glucocorticoid Receptor Modulator with Full Anti-Inflammatory Properties and Improved Therapeutic Index

Glucocorticoids (GCs) such as prednisolone are potent immunosuppressive drugs but suffer from severe adverse effects, including the induction of insulin resistance. Therefore, development of so-called Selective Glucocorticoid Receptor Modulators (SGRM) is highly desirable. Here we describe a non-steroidal Glucocorticoid Receptor (GR)-selective compound (Org 214007-0) with a binding affinity to GR similar to that of prednisolone. Structural modelling of the GR-Org 214007-0 binding site shows disturbance of the loop between helix 11 and helix 12 of GR, confirmed by partial recruitment of the TIF2-3 peptide. Using various cell lines and primary human cells, we show here that Org 214007-0 acts as a partial GC agonist, since it repressed inflammatory genes and was less effective in induction of metabolic genes. More importantly, in vivo studies in mice indicated that Org 214007-0 retained full efficacy in acute inflammation models as well as in a chronic collagen-induced arthritis (CIA) model. Gene expression profiling of muscle tissue derived from arthritic mice showed a partial activity of Org 214007-0 at an equi-efficacious dosage of prednisolone, with an increased ratio in repression versus induction of genes. Finally, in mice Org 214007-0 did not induce elevated fasting glucose nor the shift in glucose/glycogen balance in the liver seen with an equi-efficacious dose of prednisolone. All together, our data demonstrate that Org 214007-0 is a novel SGRMs with an improved therapeutic index compared to prednisolone. This class of SGRMs can contribute to effective anti-inflammatory therapy with a lower risk for metabolic side effects.     

Hospital Physicians' Influence on Gastrointestinal Protection during Treatment with Non-Steroidal Anti-Inflammatory Drugs and Acetylsalicylic Acid and the Impact on Prescribing in Primary Care

Background

The aim of this study was to describe the use of gastrointestinal (GI) protection before, during and after hospitalisation for elderly patients using NSAID or low-dose ASA.

Methods

This study included all elderly patients (75+) admitted to hospital in the period of 1^st April 2010 to 31^st March 2011 at Odense University Hospital, Denmark, who were regular users of NSAID or low-dose ASA before hospital admission, or had one of these drugs initiated during hospital stay. By using pharmacy dispensing data and a hospital-based pharmacoepidemiological database, the treatment strategy for the individual patients was followed across hospital stay.

Results

In total, 3,587 patients were included. Before hospital admission, 93 of 245 NSAID users (38.0%) and 597 of 1994 user of low-dose ASA (29.9%) had used GI protection. During hospital stay, use of GI protection increased to 75% and 33.9%, respectively. When hospital physicians initiated new treatment with NSAID or with low-dose ASA, 305 of 555 (55.0%) and 647 of 961 (67.3%) were initiated without concomitant use of GI protection. When hospital physicians initiated GI protection, 26.8–51.0% were continued in primary care after discharge.

Conclusions

During hospital stay, the use of GI protection increases, but when new treatment with NSAIDs or low-dose ASA is initiated in hospital, the use of gastrointestinal protection is low. The low use of GI protection is carried on in primary care after discharge.     

Long-Term Frequent Use of Non-Steroidal Anti-Inflammatory Drugs Might Protect Patients with Ankylosing Spondylitis from Cardiovascular Diseases: A Nationwide Case-Control Study

The objective of this case-control study was to investigate the risk of cardiovascular disease (CVD) following non-steroidal anti-inflammatory drug (NSAID) use in patients with ankylosing spondylitis (AS). A total of 10,763 new AS patients were identified from the National Taiwan Health Insurance claims database during the period from 1997 to 2008. In all, 421 AS patients with CVD were recruited as cases, and up to 2-fold as many sex- and age-matched controls were selected. Logistic regression models were used to estimate the odds ratio (OR) between NSAID use and CVD incidence. The medication possession rate (MPR) was used to evaluate NSAID exposure during the study period. AS patients had increased risk of CVD (OR, 1.68; 95% confidence interval (CI), 1.57 to 1.80). Among frequent (MPR≥80%) COX II users, the risks for all types of CVD were ten times lower than those among non-users at 24 months (OR, 0.08; 95% CI, 0.01 to 0.92). Among frequent NSAID users, the risks of major adverse cardiac event (MACE) were significantly lower at 12 months (OR, 0.23; 95% CI, 0.07 to 0.76)—a trend showing that longer exposure correlated with lower risk. Regarding non-frequent NSAID users (MPR<80%), short-term exposure did carry higher risk (for 6 months: OR, 1.41; 95% CI, 1.07 to 1.86), but after 12 months, the risk no longer existed. We conclude that long-term frequent use of NSAIDs might protect AS patients from CVD; however, NSAIDs still carried higher short-term risk in the non-frequent users.     

Protective Effect of Arachidonic Acid during Viral Infection: Synthesis of New Proteins by in vitroPotato Plants

The mechanisms of the protective, immunostimulating effects of arachidonic acid (AA) were studied, and its efficiency in the induction of defense reactions in the moderately virus-resistant potato cultivar Nevskii (Solanum tuberosumL.) was determined. Virus-free in vitropotato plants treated with AA and inoculated with phytopathogenic viruses were used as a model. The data on the X virus accumulation obtained by the enzyme-linked immunosorbent assay confirmed the immunizing effect of AA; the optimum concentration of the compound was 10^–8M. The antiviral effect of AA was maintained in infected in vitropotato plants for at least two or three weeks. The electrophoretic analysis of leaf proteins revealed a 33-kD polypeptide induced by the potato virus Y. Two weeks after inoculation with virus X, a 40-kD protein was identified in potato plants pretreated with AA. In addition, the relative content of the two groups of proteins consisting of two or three components with mol wts about 50 kD and above70 kD changed both upon viral infection and pretreatment with AA. Only small changes in the isozyme patterns of peroxidase in potato plants were observed during the development of systemic acquired resistance; they were manifested in some treatments in the band intensities. The existence of the alternative pathways of systemic acquired resistance in potato plants specifically activated by viral infection and AA was suggested.     

Imbricaric Acid and Perlatolic Acid: Multi-Targeting Anti-Inflammatory Depsides from Cetrelia monachorum

In vitro screening of 17 Alpine lichen species for their inhibitory activity against 5-lipoxygenase, microsomal prostaglandin E₂ synthase-1 and nuclear factor kappa B revealed Cetrelia monachorum (Zahlbr.) W.L. Culb. & C.F. Culb. As conceivable source for novel anti-inflammatory compounds. Phytochemical investigation of the ethanolic crude extract resulted in the isolation and identification of 11 constituents, belonging to depsides and derivatives of orsellinic acid, olivetolic acid and olivetol. The two depsides imbricaric acid (4) and perlatolic acid (5) approved dual inhibitory activities on microsomal prostaglandin E₂ synthase-1 (IC₅₀ = 1.9 and 0.4 µM, resp.) and on 5-lipoxygenase tested in a cell-based assay (IC₅₀ = 5.3 and 1.8 µM, resp.) and on purified enzyme (IC₅₀ = 3.5 and 0.4 µM, resp.). Additionally, these two main constituents quantified in the extract with 15.22% (4) and 9.10% (5) showed significant inhibition of tumor necrosis factor alpha-induced nuclear factor kappa B activation in luciferase reporter cells with IC₅₀ values of 2.0 and 7.0 µM, respectively. In a murine in vivo model of inflammation, 5 impaired the inflammatory, thioglycollate-induced recruitment of leukocytes to the peritoneum. The potent inhibitory effects on the three identified targets attest 4 and 5 a pronounced multi-target anti-inflammatory profile which warrants further investigation on their pharmacokinetics and in vivo efficacy.     

2-Hydroxy Fatty Acid Enantiomers of Gb3 Impact Shiga Toxin Binding and Membrane Organization

Shiga toxin subunit B (STxB) binding to its cellular receptor Gb₃ leads to the formation of protein-lipid clusters and bending of the membrane. A newly developed synthetic route allowed synthesizing the biologically most relevant Gb₃-C24:1 2OH species with both, the natural (Gb₃-R) as well as the unnatural (Gb₃-S) configuration of the 2OH group. The derivatives bind STxB with identical nanomolar affinity, while the propensity to induce membrane tubules in giant unilamellar vesicles is more pronounced for Gb₃-S. Fluorescence and atomic force microscopy images of phase-separated supported membranes revealed differences in the lateral organization of the protein on the membrane. Gb₃-R favorably induces large and tightly packed protein clusters, while a lower protein density is found on Gb₃-S doped membranes.     

Melanocyte-Stimulating Properties of Arachidonic Acid Metabolites: Possible Role in Postinflammatory Pigmentation

Normal human epidermal melanocytes became swollen and more dendritic with an increase in the amount of tyrosinase and immunoreactive b-locus protein when they were cultured for 2 days with the following arachidonic acid metabolites: prostaglandin (PG) D₂, leukotriene (LT) B₄, LTC₄, LTD₄, LTE₄, thromboxane (TX) B₂ and 12-hydroxy eicosatetraenoic acid (12-HETE). The effect of LTC₄ was particularly strong compared to that of PGE₂, about which we have previously reported. On the other hand, PGE₁, PGF_2α and 6-ketoPGF_1α did not show any significant stimulatory effect. These data suggest that arachidonate-derived chemical mediators, especially LTC₄, may be responsible for the induction of post-inflammatory hyperpigmentation of the skin.     

Immunopathogenesis of HIV Infection in Cocaine Users: Role of Arachidonic Acid

Arachidonic acid (AA) is known to be increased in HIV infected patients and illicit drug users are linked with severity of viral replication, disease progression, and impaired immune functions. Studies have shown that cocaine accelerates HIV infection and disease progression mediated by immune cells. Dendritic cells (DC) are the first line of antigen presentation and defense against immune dysfunction. However, the role of cocaine use in HIV associated acceleration of AA secretion and its metabolites on immature dendritic cells (IDC) has not been elucidated yet. The aim of this study is to elucidate the mechanism of AA metabolites cyclooxygenase-2 (COX-2), prostaglandin E2 synthetase (PGE₂), thromboxane A2 receptor (TBXA₂R), cyclopentenone prostaglandins (CyPG), such as 15-deoxy-Δ12,14-PGJ2 (15d-PGJ2), 14-3-3 ζ/δ and 5-lipoxygenase (5-LOX) mediated induction of IDC immune dysfunctions in cocaine using HIV positive patients. The plasma levels of AA, PGE_2, 15d-PGJ2, 14-3-3 ζ/δ and IDC intracellular COX-2 and 5-LOX expression were assessed in cocaine users, HIV positive patients, HIV positive cocaine users and normal subjects. Results showed that plasma concentration levels of AA, PGE₂ and COX-2, TBXA₂R and 5-LOX in IDCs of HIV positive cocaine users were significantly higher whereas 15d-PGJ2 and 14-3-3 ζ/δ were significantly reduced compared to either HIV positive subjects or cocaine users alone. This report demonstrates that AA metabolites are capable of mediating the accelerative effects of cocaine on HIV infection and disease progression.     

Pathophysiology of Experimental Bovine Endotoxicosis: Endotoxin Induced Synthesis of Prostaglandins and Thromboxane and the Modulatory Effect of Some Non-Steroidal Anti-Inflammatory Drugs

Endotoxin-induced synthesis of thromboxane A2 (TXA2), prostacyclin (PGI2) and prostaglandin E2 (PGE2) was studied in 3 cows after intravenous E. coli endotoxin (055:B5–0.025 mg/kg b.w.) administration. Blood sampling and monitoring of clinical signs were performed from 2 h prior to until 6 h after endotoxin challenge. Blood samples were analyzed for stable hydrolysis products of TXA2 (TXB2), PGI2 (6-keto PGF) and PGE2 (bicyclic PGE2), biochemical and haematological parameters. In a similar experimental design the efficacy of the non-steroidal anti-inflammatory drugs (NSAID) flunixin meglumine (FM) and phenylbutazone (PB) in suppressing eicosanoid synthesis and clinical signs in response to endotoxin challenge was investigated. Two groups of cows, each comprising 2 animals, were treated with FM and PB prior to endotoxin challenge. It was observed that plasma concentrations of TXB2, 6-keto PGF and bicyclic PGE2 increased rapidly after endotoxin challenge. Concentrations were significantly elevated for hours and were correlated to the severity of clinical signs of endotoxicosis. Pretreatment with NSAID suppressed mediator production and alleviated clinical signs. The experiments suggest a certain pathophysiological role of TXA2, PGI2 and PGE2 for the early systemic ill-effects of bovine endotoxicosis.     

A New Brain Drug Delivery Strategy: Focused Ultrasound-Enhanced Intranasal Drug Delivery

Central nervous system (CNS) diseases are difficult to treat because of the blood-brain barrier (BBB), which prevents most drugs from entering into the brain. Intranasal (IN) administration is a promising approach for drug delivery to the brain, bypassing the BBB; however, its application has been restricted to particularly potent substances and it does not offer localized delivery to specific brain sites. Focused ultrasound (FUS) in combination with microbubbles can deliver drugs to the brain at targeted locations. The present study proposed to combine these two different platform techniques (FUS+IN) for enhancing the delivery efficiency of intranasally administered drugs at a targeted location. After IN administration of 40 kDa fluorescently-labeled dextran as the model drug, FUS targeted at one region within the caudate putamen of mouse brains was applied in the presence of systemically administered microbubbles. To compare with the conventional FUS technique, in which intravenous (IV) drug injection is employed, FUS was also applied after IV injection of the same amount of dextran in another group of mice. Dextran delivery outcomes were evaluated using fluorescence imaging of brain slices. The results showed that FUS+IN enhanced drug delivery within the targeted region compared with that achieved by IN only. Despite the fact that the IN route has limited drug absorption across the nasal mucosa, the delivery efficiency of FUS+IN was not significantly different from that of FUS+IV. As a new drug delivery platform, the FUS+IN technique is potentially useful for treating CNS diseases.     

Cytosolic Phospholipase A(2) alpha/Arachidonic Acid Signaling Mediates Depolarization-Induced Suppression of Excitation in the Cerebellum

Background

Depolarization-induced suppression of excitation (DSE) at parallel fiber-Purkinje cell synapse is an endocannabinoid-mediated short-term retrograde plasticity. Intracellular Ca²⁺ elevation is critical for the endocannabinoid production and DSE. Nevertheless, how elevated Ca²⁺ leads to DSE is unclear.

Methodology/Principal Findings

We utilized cytosolic phospholipase A₂ alpha (cPLA₂α) knock-out mice and whole-cell patch clamp in cerebellar slices to observed the action of cPLA₂α/arachidonic acid signaling on DSE at parallel fiber-Purkinje cell synapse. Our data showed that DSE was significantly inhibited in cPLA₂α knock-out mice, which was rescued by arachidonic acid. The degradation enzyme of 2-arachidonoylglycerol (2-AG), monoacylglycerol lipase (MAGL), blocked DSE, while another catabolism enzyme for N-arachidonoylethanolamine (AEA), fatty acid amide hydrolase (FAAH), did not affect DSE. These results suggested that 2-AG is responsible for DSE in Purkinje cells. Co-application of paxilline reversed the blockade of DSE by internal K⁺, indicating that large conductance Ca²⁺-activated potassium channel (BK) is sufficient to inhibit cPLA₂α/arachidonic acid-mediated DSE. In addition, we showed that the release of 2-AG was independent of soluble NSF attachment protein receptor (SNARE), protein kinase C and protein kinase A.

Conclusions/Significance

Our data first showed that cPLA₂α/arachidonic acid/2-AG signaling pathway mediates DSE at parallel fiber-Purkinje cell synapse.     

Regulation of Rat Intrapulmonary Arterial Tone by Arachidonic Acid and Prostaglandin E2 during Hypoxia

Aims

Arachidonic acid (AA) and its metabolites, prostaglandins (PG) are known to be involved in regulation of vascular homeostasis including vascular tone and vessel wall tension, but their potential role in Hypoxic pulmonary vasoconstriction (HPV) remains unclear. In this study, we examined the effects of AA and PGE2 on the hypoxic response in isolated rat intrapulmonary arteries (IPAs).

Methods and Results

We carried out the investigation on IPAs by vessel tension measurement. Isotetrandrine (20 µM) significantly inhibited phase I, phase IIb and phase IIc of hypoxic vasoconstriction. Both indomethacin (100 µM) and NS398 attenuated KPSS-induced vessel contraction and phase I, phase IIb and phase IIc of HPV, implying that COX-2 plays a primary role in the hypoxic response of rat IPAs. PGE2 alone caused a significant vasoconstriction in isolated rat IPAs. This constriction is mediated by EP4. Blockage of EP4 by L-161982 (1 µM) significantly inhibited phase I, phase IIb and phase IIc of hypoxic vasoconstriction. However, AH6809 (3 µM), an antagonist of EP1, EP2, EP3 and DP1 receptors, exerted no effect on KPSS or hypoxia induced vessel contraction. Increase of cellular cAMP by forskolin could significantly reduce KPSS-induced vessel contraction and abolish phase I, phase II b and phase II c of HPV.

Conclusion

Our results demonstrated a vasoconstrictive effect of PGE2 on rat IPAs and this effect is via activation of EP4. Furthermore, our results suggest that intracellular cAMP plays dual roles in regulation of vascular tone, depending on the spatial distribution of cAMP and its coupling with EP receptor and Ca²⁺ channels.