Antagonism of the thromboxane-prostanoid receptor is cardioprotective against right ventricular pressure overload.

Right ventricular (RV) failure is the primary cause of death in pulmonary arterial hypertension (PAH) and is a significant cause of morbidity and mortality in other forms of pulmonary hypertension. There are no approved therapies directed at preserving RV function. F-series and E-series isoprostanes are increased in heart failure and PAH, correlate to the severity of disease, and can signal through the thromboxane-prostanoid (TP) receptor, with effects from vasoconstriction to fibrosis. The goal of these studies was to determine whether blockade of the TP receptor with the antagonist CPI211 was beneficial therapeutically in PAH-induced RV dysfunction. Mice with RV dysfunction due to pressure overload by pulmonary artery banding (PAB) were given vehicle or CPI211. Two weeks after PAB, CPI211-treated mice were protected from fibrosis with pressure overload. Gene expression arrays and immunoblotting, quantitative histology and morphometry, and flow cytometric analysis were used to determine the mechanism of CPI211 protection. TP receptor inhibition caused a near normalization of fibrotic area, prevented cellular hypertrophy while allowing increased RV mass, increased expression of antifibrotic thrombospondin-4, and blocked induction of the profibrotic transforming growth factor ß (TGF-ß) pathway. A thromboxane synthase inhibitor or low-dose aspirin failed to replicate these results, which suggests that a ligand other than thromboxane mediates fibrosis through the TP receptor after pressure overload. This study suggests that TP receptor antagonism may improve RV adaptation in situations of pressure overload by decreasing fibrosis and TGF-ß signaling.

Pharmacokinetics of intravenous ibuprofen: implications of time of infusion in the treatment of pain and fever.

Intravenous NSAIDs are playing an increasingly large role in analgesia, anti-inflammation and antipyresis in the hospitalized setting. For many years, ketorolac was the only intravenous NSAID available in the US, but in 2009 intravenous ibuprofen was approved by the US FDA for the treatment of pain and fever in adults. In developing intravenous ibuprofen, a range of times of infusion and dosing levels have been utilized and compared with the oral route of administration. The earliest studies utilized a 60-minute infusion, and later a 30-minute infusion was used for the pivotal/registration studies demonstrating efficacy and safety. Another recent trial in healthy volunteers demonstrated a safe and tolerable rapid infusion (5-7 minute) of intravenous ibuprofen. The pharmacokinetic data from all of the clinical trials on 400 and 800 mg doses of intravenous ibuprofen were compiled, and pharmacokinetic modelling was utilized to simulate any data not acquired in the clinical studies. The pharmacokinetic profile of the following doses was modelled: 30-minute infusion of 800 mg intravenous ibuprofen, 5- to 7-minute infusion of 400 mg intravenous ibuprofen and 400 mg ibuprofen oral tablet. These pharmacokinetic analyses revealed that, in general, maximum plasma concentration (C(max)) decreases considerably as the length of the infusion increases and that an oral dose is not able to achieve the C(max) level of any intravenous dose. For the rapid infusion, C(max) was twice that of the oral dose and, as expected, time to C(max) (t(max)) was much more rapid than with the oral dose. However, the oral dose still maintained virtually 100% oral bioavailability. The efficacy of intravenous ibuprofen in terms of pain and fever has also been studied and this review found the drug to be efficacious for both indications. Future areas of study should include assessment of the analgesic and antipyretic efficacy of a rapid (5- to 10-minute) infusion and further assessment of pre-emptive administration of intravenous ibuprofen as part of a multimodal analgesic approach in the surgical setting.

A prospective, multicenter, randomized, double-blind trial of IV ibuprofen for treatment of fever and pain in burn patients.

This prospective study evaluated the efficacy and safety of IV ibuprofen for the reduction of fever and treatment of pain in patients with thermal burn injury. A total of 61 patients with second- and/or third-degree thermal burns covering >10% TBSA were randomly assigned in a 2:1 ratio to receive either 800 mg IV ibuprofen or placebo every 6 hours for 120 hours (5 days). Antipyretic medications were restricted during the first 24 hours of the study, but analgesics were allowed throughout. The primary efficacy endpoint was area under the curve for temperature (AUC-T°) within the first 24 hours of treatment. After 24 hours of dosing, there was a significant reduction in temperature in patients who received IV ibuprofen compared with those who received placebo (P = .008). The temperature remained reduced over the entire 120-hour dosing period in the patients who received IV ibuprofen, although the difference beyond 24 hours did not reach statistical significance. Because of enrollment of patients unable to perform self-assessments of pain, an inadequate number of patients were enrolled to detect differences in pain scores. There was no significant difference in the incidence of serious adverse events. Fever was reduced significantly by IV ibuprofen in burn patients over the initial 24-hour dosing period and remained reduced throughout the dosing period. Exposure to the maximum daily recommended dose of 3200 mg (800 mg every 6 hours) for a total of 120 hours (5 days) was well tolerated.

Pharmacokinetics, safety, and tolerability of a rapid infusion of i.v. ibuprofen in healthy adults.

PURPOSE: The pharmacokinetics, safety, and tolerability of a rapid infusion of i.v. ibuprofen in healthy adults were evaluated. Methods In this randomized, double-blind, placebo-controlled, single-dose, crossover study, 12 healthy subjects age 18-65 years were randomized to receive a single dose of either 800 mg i.v. ibuprofen (infused over five to seven minutes) concomitantly with an oral placebo or 800 mg oral ibuprofen with concomitant i.v. placebo (0.9% sodium chloride injection). After a six-day washout period, subjects received the treatment not previously received. Blood samples were taken 1 hour before each dose of study medication was administered and throughout the 12 hours thereafter. Plasma ibuprofen concentrations were determined using validated liquid chromatography-tandem mass spectrometry methods. The frequency and severity of treatment-emergent adverse effects were monitored throughout the study. RESULTS: The maximum plasma concentration (C(max)) of i.v. ibuprofen was approximately twice that of oral ibuprofen, and the (t(max)) of i.v. ibuprofen was 0.11 hour, compared with 1.5 hours for oral ibuprofen. However, the elimination half-life of i.v. and oral ibuprofen did not differ, both of which were approximately 2 hours. Oral ibuprofen was 100% bioavailable; therefore, the area under the concentration-time curve did not differ between i.v. and oral ibuprofen. In addition, i.v. ibuprofen infused over five to seven minutes did not differ in terms of safety or tolerability when compared with oral ibuprofen. CONCLUSION: I.V. ibuprofen, when administered over five to seven minutes in healthy subjects, achieved a higher C(max) and a more-rapid t(max) than did oral ibuprofen and was found to be safe and well tolerated.

Efficacy and safety of ibuprofen and acetaminophen in children and adults: a meta-analysis and qualitative review.

OBJECTIVE: To evaluate the analgesic and antipyretic efficacy and safety of ibuprofen compared to acetaminophen in children and adults. DATA SOURCES: Literature searches were performed using PubMed/MEDLINE (through August 2009) and EMBASE (through January 2008) and were restricted to the English language. In PubMed/MEDLINE, search terms used were ibuprofen, acetaminophen, paracetamol, clinical trials, and randomized controlled trials. EMBASE search terms included ibuprofen and acetaminophen, restricted to human and clinical trials. STUDY SELECTION AND DATA EXTRACTION: All English-language articles identified from the data sources were reviewed. Multiple review articles were studied for any pertinent references and this yielded additional articles. Only articles that directly compared ibuprofen and acetaminophen were eligible for this review. DATA SYNTHESIS: Eighty-five studies that directly compared ibuprofen to acetaminophen were identified; 54 contained analgesic efficacy data, 35 contained antipyretic/temperature reduction data, and 66 contained safety data (some articles contained more than 1 type of data). Qualitative review of the literature revealed that, for the most part, ibuprofen was more efficacious than acetaminophen for the treatment of pain and fever in both pediatric and adult populations, and that these 2 drugs were equally safe. Meta-analyses on the subset of randomized clinical trial articles that reported sufficient quantitative information to calculate either an odds ratio (adverse event [AE]) or standardized mean difference (pain and fever) confirmed the qualitative results for adult (standardized mean difference [SMD] 0.69; 95% CI 0.57 to 0.81) and pediatric (SMD 0.28; 95% CI 0.10 to 0.46) pain at 2 hours postdose and pediatric fever (SMD 0.26; 95% CI 0.10 to 0.41) at 4 hours postdose. Conclusions regarding adult fever/temperature reduction could not be made due to a lack of evaluable data. The combined odds ratio for the proportion of adult subjects experiencing at least 1 AE slightly favored ibuprofen; however, the difference was not statistically significant (1.12; 95% CI 1.00 to 1.25). No significant difference between drugs in AE incidence was found for pediatric patients (0.82; 95% CI 0.60 to 1.12). CONCLUSIONS: Ibuprofen is as or more efficacious than acetaminophen for the treatment of pain and fever in adult and pediatric populations and is equally safe.

Comparison of preference and safety of powder and liquid lactulose in adult patients with chronic constipation.

BACKGROUND: Chronic constipation is an important clinical condition which can result in serious discomfort and even require hospitalization. Powder and liquid lactulose are designated as clinically equivalent for the treatment of constipation, but there are significant differences in the taste, consistency, and portability of the products, which may affect patient compliance and therefore clinical outcome. AIM: To evaluate patient preference between powder and liquid lactulose in terms of overall preference, taste, consistency, and portability, and safety in terms of adverse events. METHODS: Three sites randomized patients (total n = 50) to powder or liquid lactulose for seven days with crossover. Patient preference was assessed by a questionnaire, and the occurrence of adverse events was monitored. RESULTS: Of those expressing a preference, 44% and 57% more patients preferred the taste and consistency, respectively, of powder over liquid lactulose. More than six times as many patients preferred the portability of powder compared with liquid lactulose and, overall, 77% more patients preferred powder over liquid lactulose. There was no difference between treatment groups in terms of adverse events (P = 0.635). CONCLUSIONS: More patients preferred powder compared with liquid lactulose and the products were equally safe. These findings may impact patient compliance, and therefore may affect clinical outcome.

Suboptimal activation of protease-activated receptors enhances alpha2beta1 integrin-mediated platelet adhesion to collagen.

Thrombin and fibrillar collagen are potent activators of platelets at sites of vascular injury. Both agonists cause platelet shape change, granule secretion, and aggregation to form the primary hemostatic plug. Human platelets express two thrombin receptors, protease-activated receptors 1 and 4 (PAR1 and PAR4) and two collagen receptors, the alpha(2)beta(1) integrin (alpha(2)beta(1)) and the glycoprotein VI (GPVI)/FcRgamma chain complex. Although these receptors and their signaling mechanisms have been intensely studied, it is not known whether and how these receptors cooperate in the hemostatic function of platelets. This study examined cooperation between the thrombin and collagen receptors in platelet adhesion by utilizing a collagen-related peptide (alpha2-CRP) containing the alpha(2)beta(1)-specific binding motif, GFOGER, in conjunction with PAR-activating peptides. We demonstrate that platelet adhesion to alpha2-CRP is substantially enhanced by suboptimal PAR activation (agonist concentrations that do not stimulate platelet aggregation) using the PAR4 agonist peptide and thrombin. The enhanced adhesion induced by suboptimal PAR4 activation was alpha(2)beta(1)-dependent and GPVI/FcRgamma-independent as revealed in experiments with alpha(2)beta(1)- or FcRgamma-deficient mouse platelets. We further show that suboptimal activation of other platelet G(q)-linked G protein-coupled receptors (GPCRs) produces enhanced platelet adhesion to alpha2-CRP. The enhanced alpha(2)beta(1)-mediated platelet adhesion is controlled by phospholipase C (PLC), but is not dependent on granule secretion, activation of alpha(IIb)beta(3) integrin, or on phosphoinositol-3 kinase (PI3K) activity. In conclusion, we demonstrate a platelet priming mechanism initiated by suboptimal activation of PAR4 or other platelet G(q)-linked GPCRs through a PLC-dependent signaling cascade that promotes enhanced alpha(2)beta(1) binding to collagens containing GFOGER sites.

PAR1, but not PAR4, activates human platelets through a Gi/o/phosphoinositide-3 kinase signaling axis.

Thrombin-mediated activation of platelets is critical for hemostasis, but the signaling pathways responsible for this process are not completely understood. In addition, signaling within this cascade can also lead to thrombosis. In this study, we have defined a new signaling pathway for the thrombin receptor protease activated receptor-1 (PAR1) in human platelets. We show that PAR1 couples to G(i/o) in human platelets and activates phosphoinositide-3 kinase (PI3K). PI3K activation regulates platelet integrin alphaIIbbeta3 activation and platelet aggregation and potentiates the PAR1-mediated increase in intraplatelet calcium concentration. PI3K inhibitors eliminated these effects downstream of PAR1, but they had no effect on PAR4 signaling. This study has identified an important role for the direct activation of G(i/o) by PAR1 in human platelets. Given the efficacy of clopidogrel, which blocks the G(i/o)-coupled P2Y purinoceptor 12, as an antiplatelet/antithrombotic drug, our data suggest that specifically blocking only PAR1-mediated G(i/o) signaling could also be an effective therapeutic approach with the possibility of less unwanted bleeding.

Dendritic molecular transporters provide control of delivery to intracellular compartments.

Novel biocompatible macromolecular vectors were developed that not only enable transport of bioactive cargo across the cell membrane but also control the delivery into defined intracellular compartments. This work describes the synthesis and design of two non-peptidic fluorescently labeled Newkome-type dendrimers, differentiated over a varied alkyl spacer with guanidine end moieties. The internalization of the fluorescein-labeled molecular transporter into mammalian cells showed strong subcellular localizations, evident with both live cells and fixed cells costained with DAPI, a nuclear stain. We observed that the subcellular distribution of these vectors varied significantly, as one of the vectors concentrates in the nucleus (FD-1) while the other (FD-2) concentrates in the cytosol. All experiments performed with NIH-3T3 fibroblasts and human microvascular endothelial cells (HMEC) showed similar results. The differential localization patterns of the two molecular transporters can be controlled through the variation of alkyl spacer length at the terminal generation of the dendrimer. Intracellular delivery of bioactive entities into specific subcellular locations, utilizing this practical approach, might overcome limitations in drug delivery and pioneer future technologies in drug transport.

Protease-activated receptors differentially regulate human platelet activation through a phosphatidic acid-dependent pathway.

Pathological conditions such as coronary artery disease are clinically controlled via therapeutic regulation of platelet activity. Thrombin, through protease-activated receptor (PAR) 1 and PAR4, plays a central role in regulation of human platelet function in that it is known to be the most potent activator of human platelets. Currently, direct thrombin inhibitors used to block platelet activation result in unwanted side effects of excessive bleeding. An alternative therapeutic strategy would be to inhibit PAR-mediated intracellular platelet signaling pathways. To elucidate the best target, we are studying differences between the two platelet thrombin receptors, PAR1 and PAR4, in mediating thrombin's action. In this study, we show that platelet activation by PAR1-activating peptide (PAR1-AP) requires a phospholipase D (PLD)-mediated phosphatidic acid (PA) signaling pathway. We show that this PAR1-specific PA-mediated effect is not regulated through differential granule secretion after PAR-induced platelet activation. Perturbation of this signaling pathway via inhibition of lipid phosphate phosphatase-1 (LPP-1) by propranolol or inhibition of the phosphatidylcholine-derived phosphatidic acid (PA) formation by PLD with a primary alcohol significantly attenuated platelet activation by PAR1-AP. Platelet activation by thrombin or PAR4-AP was insensitive to these inhibitors. Furthermore, these inhibitors significantly attenuated activation of Rap1 after stimulation by PAR1-AP but not thrombin or PAR4-AP. Because PA metabolites such as diacylglycerol play an important role in intracellular signaling, identifying crucial differences in PA regulation of PAR-induced platelet activation may lead to a greater understanding of the role of PAR1 versus PAR4 in progression of thrombosis.

PAR4, but not PAR1, signals human platelet aggregation via Ca2+ mobilization and synergistic P2Y12 receptor activation.

Regulation of platelet activation plays a central role in hemostasis and pathophysiological processes such as coronary artery disease. Thrombin is the most potent activator of platelets. Human platelets express two thrombin receptors, PAR1 and PAR4, both of which signal platelet activation. Evidence is lacking on the mechanism by which PAR1 and PAR4 may differentially signal platelet aggregation. Here we show that at the relatively high concentration of agonist most likely found at the site of a local thrombus, dual inhibition of the P2Y12 receptor and calcium mobilization result in a complete inhibition of PAR4-induced aggregation, while having no effect on either thrombin or PAR1-mediated platelet aggregation. Both PAR1- and PAR4mediated aggregation are independent of calcium mobilization. Furthermore, we show that P2Y12 receptor activation is not required for protease-activated receptor-mediated aggregation at higher agonist concentrations and is only partially required for Rap1 as well as GPIIbIIIa activation. P2Y12 receptor inhibitors clinically in use such as clopidogrel are postulated to decrease platelet aggregation through partial inhibition of PAR1 signaling. Our data, however, indicate that at high local concentrations of thrombin, it is the signaling through PAR4 rather than PAR1 that may be regulated through purinergic feedback. Thus, our data identify an intra-platelet mechanism that may function as a future site for therapeutic intervention.