Insight into NSAID-induced membrane alterations, pathogenesis and therapeutics: characterization of interaction of NSAIDs with phosphatidylcholine

Incorporation of aspirin modulates the dynamical and phase behavior of the phospholipid membrane

Effect of aspirin on the microscopic dynamics of a membrane has been investigated using quasielastic neutron scattering and neutron spin echo techniques.

Valdecoxib Recovers the Lipid Composition, Order and Dynamics in Colon Cancer Cell Lines Independent of COX-2 Expression: An ATR-FTIR Spectroscopy Study

Prostanoids play an important role in a variety of physiological and pathophysiological processes including inflammation and cancer. The rate-limiting step in the prostanoid biosynthesis pathway is catalyzed by cyclooxygenases (COXs). Aberrant expression of the inducible isoform COX-2 plays a significant role in colon cancer initiation and progression. In this study, we have hypothesized that COX-2 specific inhibitors such as Valdecoxib (VLX), being highly hydrophobic, may alter biophysical properties of cellular lipids. In this study, COX-2 expressing (HT29) and COX-2 non-expressing (SW620) colon cancer cell lines were treated with VLX and examined using attenuated total reflection infrared spectroscopy. The results revealed that VLX treatment decreased lipid fluidity in the cells irrespective of COX-2 expression status and affected order parameters of the lipids in both cell lines. Cluster analysis also indicated that the spectral differences between the two cell lines are profound and could be successfully differentiated. Valdecoxib treatment could enhance the composition, order and dynamics of the lipids of colon cancer cells independently of its COX-2 inhibitory mechanism. Valdecoxib has therapeutic effects upon colon cancer, therefore it can be used as an adjuvant and/or chemopreventive agent for colon cancer.

Antitumor and Antiangiogenic Effects of Aspirin-PC in Ovarian Cancer

To determine the efficacy of a novel and safer (for gastrointestinal tract) aspirin (aspirin-PC) in preclinical models of ovarian cancer, in vitro dose-response studies were performed to compare the growth-inhibitory effect of aspirin-PC versus aspirin on three human (A2780, SKOV3ip1, and HeyA8) and a mouse (ID8) ovarian cancer cell line over an 8-day culture period. In the in vivo studies, the aspirin test drugs were studied alone and in the presence of a VEGF-A inhibitor (bevacizumab or B20), due to an emerging role for platelets in tumor growth following antiangiogenic therapy, and we examined their underlying mechanisms. Aspirin-PC was more potent (vs. aspirin) in blocking the growth of both human and mouse ovarian cancer cells in monolayer culture. Using in vivo model systems of ovarian cancer, we found that aspirin-PC significantly reduced ovarian cancer growth by 50% to 90% (depending on the ovarian cell line). The efficacy was further enhanced in combination with Bevacizumab or B20. The growth-inhibitory effect on ovarian tumor mass and number of tumor nodules was evident, but less pronounced for aspirin and the VEGF inhibitors alone. There was no detectable gastrointestinal toxicity. Both aspirin and aspirin-PC also inhibited cell proliferation, angiogenesis, and increased apoptosis of ovarian cancer cells. In conclusion, PC-associated aspirin markedly inhibits the growth of ovarian cancer cells, which exceeds that of the parent drug, in both cell culture and in mouse model systems. We also found that both aspirin-PC and aspirin have robust antineoplastic action in the presence of VEGF-blocking drugs. Mol Cancer Ther; 15(12); 2894-904. ©2016 AACR.

Mitigation of indomethacin-induced gastrointestinal damages in fat-1 transgenic mice via gate-keeper action of ω-3-polyunsaturated fatty acids

Non-steroidal anti-inflammatory drugs (NSAIDs) damage the gastrointestinal (GI) epithelial cell membranes by inducing several signals through lipid raft organization after membrane incorporation, whereas ω-3 polyunsaturated fatty acids (PUFAs) relieve inflammation, reduce oxidative stress, and provide cytoprotection, consequent to lipid raft disorganization. Therefore, we hypothesized that ω-3 PUFAs can protect the GI from NSAID-induced damages by initiating the gatekeeper action of cell membranes, subsequent to anti-inflammatory and anti-oxidative actions. Administration of indomethacin (IND) leads to the formation of lipid rafts and activation of caveolin-1; however, no such observations were made upon co-administration of eicosapentaenoic acid (EPA) and IND. In addition, the EPA-induced lipid raft disorganization, caveolin-1 inactivation, and cellular cytotoxicity were inhibited when target cells were knocked-out using G-protein coupled receptor 120 (GPR 120). EPA significantly attenuated IND-induced oxidative damage and apoptosis. IND administration induced significant ulceration, bleeding, and oedema in the stomach or small intestine of wild-type (WT) mice; however, such severe damages to the GI significantly decreased in fat-1 transgenic (TG) mice (P < 0.001), which exhibited decreased cyclooxygenase-2 expression and apoptosis, decreased interleukin-1β and FAS concentrations, and increased heme oxygenase-1 concentration. Our study indicates that the gatekeeper function of ω-3 PUFAs improves GI safety when administered with NSAID.

Calculating the free energy of transfer of small solutes into a model lipid membrane: Comparison between metadynamics and umbrella sampling

We compare the performance of two well-established computational algorithms for the calculation of free-energy landscapes of biomolecular systems, umbrella sampling and metadynamics. We look at benchmark systems composed of polyethylene and polypropylene oligomers interacting with lipid (phosphatidylcholine) membranes, aiming at the calculation of the oligomer water-membrane free energy of transfer. We model our test systems at two different levels of description, united-atom and coarse-grained. We provide optimized parameters for the two methods at both resolutions. We devote special attention to the analysis of statistical errors in the two different methods and propose a general procedure for the error estimation in metadynamics simulations. Metadynamics and umbrella sampling yield the same estimates for the water-membrane free energy profile, but metadynamics can be more efficient, providing lower statistical uncertainties within the same simulation time.

In silico pharmacology: Drug membrane partitioning and crossing

Over the past decade, molecular dynamics (MD) simulations have become particularly powerful to rationalize drug insertion and partitioning in lipid bilayers. MD simulations efficiently support experimental evidences, with a comprehensive understanding of molecular interactions driving insertion and crossing. Prediction of drug partitioning is discussed with respect to drug families (anesthetics; β-blockers; non-steroidal anti-inflammatory drugs; antioxidants; antiviral drugs; antimicrobial peptides). To accurately evaluate passive permeation coefficients turned out to be a complex theoretical challenge; however the recent methodological developments based on biased MD simulations are particularly promising. Particular attention is paid to membrane composition (e.g., presence of cholesterol), which influences drug partitioning and permeation. Recent studies concerning in silico models of membrane proteins involved in drug transport (influx and efflux) are also reported here. These studies have allowed gaining insight in drug efflux by, e.g., ABC transporters at an atomic resolution, explicitly accounting for the mandatory forces induced by the surrounded lipid bilayer. Large-scale conformational changes were thoroughly analyzed.

The Anti-inflammatory Effect of the CXCR4 Antagonist-N15P Peptide and Its Modulation on Inflammation-Associated Mediators in LPS-Induced PBMC

Inflammation was the important pathological process of many disease developments, but current therapeutic means for inflammatory diseases are not satisfactory. Chemokines and their receptors represent valuable targets for anti-inflammatory drug discovery. The N15P polypeptide (sequence: LGASWHRPDKCCLGY) is independently developed by our research group, it is a new CXCR4 antagonist drug derived from viral macrophage inflammatory protein-II (vMIP-II). This study aims to clarify the anti-inflammatory potency of N15P polypeptide on the lipopolysaccharide (LPS)-induced inflammation in vitro. In this study, we evaluated the anti-inflammatory effects of N15P polypeptide by the LPS-induced peripheral blood mononuclear cell (PBMC) model and measured the level of inflammatory factors (tumor necrosis factor alpha (TNF-α), IL-6, IL-8, nuclear factor kappaB (NF-κB), cyclooxygenase-2 (COX-2), Toll-like receptor 4 (TLR4), MyD88, phosphoinositide 3-kinase (PI3K), and Akt). The messenger RNA (mRNA) expressions of inflammatory factors were analyzed by real-time PCR (RT-PCR) microarray analysis, and the production of inflammatory factors was measured further by enzyme-linked immunosorbent assay (ELISA) and Western blot. The results showed that the expression of inflammatory factors (TNF-α, IL-6, IL-8, NF-κB, COX-2, TLR4, MyD88, PI3K, and Akt) was downregulated by N15P peptide, suggesting that N15P peptide has a strong inhibitory effect on the inflammatory responses induced by LPS.

Synergistic growth inhibitory effect of deracoxib with doxorubicin against a canine mammary tumor cell line, CMT-U27

Cyclooxygenase (COX) inhibitors have been shown to exert anti-angiogenic and anti-tumor activities on many types of malignant tumors. These anticancer properties make it worthwhile to examine the possible benefit of combining COX inhibitors with other anti-cancer agents. In the present study, we evaluated the potential of deracoxib (DER) in potentiating antitumor activity of doxorubicin (DOX) in canine mammary carcinoma cells (CMT-U27). DER (50–250 µM) enhanced the antiproliferative activity of DOX by reducing the IC₅₀ (approximately 3- to 3.5 fold). Interaction analysis of the data showed that combinations of DOX at 0.9 µM with DER (100–250 µM) produced synergism in the CMT-U27 cell line, with a ratio index ranging from 1.98 to 2.33. In additional studies identifying the mechanism of observed synergistic effect, we found that DER strongly potentiated DOX-caused G₀/G₁ arrest in cell cycle progression. Also, DER (100–250 µM) augmented apoptosis induction with approximately 1.35- and 1.37- fold increases in apoptotic response caused by DOX in the cells. DER enhanced the antiproliferative effect of DOX in conjunction with induction of apoptosis by modulation of Bcl-2 expression and changes in the cell cycle of the CMT-U27 cell line. Although the exact molecular mechanism of the alterations in the cell cycle and apoptosis observed with DER and DOX combinations require further investigations, the results suggest that the synergistic effect of DOX and DER combinations in CMT therapy may be achieved at relatively lower doses of DOX with lesser side effects. Therefore, combining DER with DOX may prove beneficial in the clinical treatment of canine mammary cancer.

Ibuprofen regulates the expression and function of membrane-associated serine proteases prostasin and matriptase

BACKGROUND

The glycosylphosphatidylinositol-anchored extracellular membrane serine protease prostasin is expressed in normal bladder urothelial cells. Bladder inflammation reduces prostasin expression and a loss of prostasin expression is associated with epithelial-mesenchymal transition (EMT) in human bladder transitional cell carcinomas. Non-steroidal anti-inflammatory drugs (NSAIDs) decrease the incidence of various cancers including bladder cancer, but the molecular mechanisms underlying the anticancer effect of NSAIDs are not fully understood.

METHODS

The normal human bladder urothelial cell line UROtsa, the normal human trophoblast cell line B6Tert-1, human bladder transitional cell carcinoma cell lines UM-UC-5 and UM-UC-9, and the human breast cancer cell line JIMT-1 were used for the study. Expression changes of the serine proteases prostasin and matriptase, and cyclooxygenases (COX-1 and COX-2) in these cells following ibuprofen treatments were analyzed by means of reverse-transcription/quantitative polymerase chain reaction (RT-qPCR) and immunoblotting. The functional role of the ibuprofen-regulated prostasin in epithelial tight junction formation and maintenance was assessed by measuring the transepithelial electrical resistance (TEER) and epithelial permeability in the B6Tert-1 cells. Prostasin's effects on tight junctions were also evaluated in B6Tert-1 cells over-expressing a recombinant human prostasin, silenced for prostasin expression, or treated with a functionally-blocking prostasin antibody. Matriptase zymogen activation was examined in cells over-expressing prostasin.

RESULTS

Ibuprofen increased prostasin expression in the UROtsa and the B6Tert-1 cells. Cyclooxygenase-2 (COX-2) expression was up-regulated at both the mRNA and the protein levels in the UROtsa cells by ibuprofen in a dose-dependent manner, but was not a requisite for up-regulating prostasin expression. The ibuprofen-induced prostasin contributed to the formation and maintenance of the epithelial tight junctions in the B6Tert-1 cells. The matriptase zymogen was down-regulated in the UROtsa cells by ibuprofen possibly as a result of the increased prostasin expression because over-expressing prostasin leads to matriptase activation and zymogen down-regulation in the UROtsa, JIMT-1, and B6Tert-1 cells. The expression of prostasin and matriptase was differentially regulated by ibuprofen in the bladder cancer cells.

CONCLUSIONS

Ibuprofen has been suggested for use in treating bladder cancer. Our results bring the epithelial extracellular membrane serine proteases prostasin and matriptase into the potential molecular mechanisms of the anticancer effect of NSAIDs.

Structural Mechanism of the Interaction of Alzheimer Disease Aβ Fibrils with the Non-steroidal Anti-inflammatory Drug (NSAID) Sulindac Sulfide

Alzheimer disease is the most severe neurodegenerative disease worldwide. In the past years, a plethora of small molecules interfering with amyloid-β (Aβ) aggregation has been reported. However, their mode of interaction with amyloid fibers is not understood. Non-steroidal anti-inflammatory drugs (NSAIDs) are known γ-secretase modulators; they influence Aβ populations. It has been suggested that NSAIDs are pleiotrophic and can interact with more than one pathomechanism. Here we present a magic angle spinning solid-state NMR study demonstrating that the NSAID sulindac sulfide interacts specifically with Alzheimer disease Aβ fibrils. We find that sulindac sulfide does not induce drastic architectural changes in the fibrillar structure but intercalates between the two β-strands of the amyloid fibril and binds to hydrophobic cavities, which are found consistently in all analyzed structures. The characteristic Asp(23)-Lys(28) salt bridge is not affected upon interacting with sulindac sulfide. The primary binding site is located in the vicinity of residue Gly(33), a residue involved in Met(35) oxidation. The results presented here will assist the search for pharmacologically active molecules that can potentially be employed as lead structures to guide the design of small molecules for the treatment of Alzheimer disease.

Membrane Interactions of Phytochemicals as Their Molecular Mechanism Applicable to the Discovery of Drug Leads from Plants

In addition to interacting with functional proteins such as receptors, ion channels, and enzymes, a variety of drugs mechanistically act on membrane lipids to change the physicochemical properties of biomembranes as reported for anesthetic, adrenergic, cholinergic, non-steroidal anti-inflammatory, analgesic, antitumor, antiplatelet, antimicrobial, and antioxidant drugs. As well as these membrane-acting drugs, bioactive plant components, phytochemicals, with amphiphilic or hydrophobic structures, are presumed to interact with biological membranes and biomimetic membranes prepared with phospholipids and cholesterol, resulting in the modification of membrane fluidity, microviscosity, order, elasticity, and permeability with the potencies being consistent with their pharmacological effects. A novel mechanistic point of view of phytochemicals would lead to a better understanding of their bioactivities, an insight into their medicinal benefits, and a strategic implication for discovering drug leads from plants. This article reviews the membrane interactions of different classes of phytochemicals by highlighting their induced changes in membrane property. The phytochemicals to be reviewed include membrane-interactive flavonoids, terpenoids, stilbenoids, capsaicinoids, phloroglucinols, naphthodianthrones, organosulfur compounds, alkaloids, anthraquinonoids, ginsenosides, pentacyclic triterpene acids, and curcuminoids. The membrane interaction’s applicability to the discovery of phytochemical drug leads is also discussed while referring to previous screening and isolating studies.

Standardising the lactulose mannitol test of gut permeability to minimise error and promote comparability

BACKGROUND

Lactulose mannitol ratio tests are clinically useful for assessing disorders characterised by changes in gut permeability and for assessing mixing in the intestinal lumen. Variations between currently used test protocols preclude meaningful comparisons between studies. We determined the optimal sampling period and related this to intestinal residence.

METHODS

Half-hourly lactulose and mannitol urinary excretions were determined over 6 hours in 40 healthy female volunteers after administration of either 600 mg aspirin or placebo, in randomised order at weekly intervals. Gastric and small intestinal transit times were assessed by the SmartPill in 6 subjects from the same population. Half-hourly percentage recoveries of lactulose and mannitol were grouped on a basis of compartment transit time. The rate of increase or decrease of each sugar within each group was explored by simple linear regression to assess the optimal period of sampling.

KEY RESULTS

The between subject standard errors for each half-hourly lactulose and mannitol excretion were lowest, the correlation of the quantity of each sugar excreted with time was optimal and the difference between the two sugars in this temporal relationship maximal during the period from 2½-4 h after ingestion. Half-hourly lactulose excretions were generally increased after dosage with aspirin whilst those of mannitol were unchanged as was the temporal pattern and period of lowest between subject standard error for both sugars.

CONCLUSION

The results indicate that between subject variation in the percentage excretion of the two sugars would be minimised and the differences in the temporal patterns of excretion would be maximised if the period of collection of urine used in clinical tests of small intestinal permeability were restricted to 2½-4 h post dosage. This period corresponds to a period when the column of digesta column containing the probes is passing from the small to the large intestine.

Mechanisms of nonsteroidal anti-inflammatory drugs in cancer prevention

Various clinical and epidemiologic studies show that nonsteroidal anti-inflammatory drugs (NSAIDs), including aspirin and cyclooxygenase inhibitors (COXIBs) help prevent cancer. Since eicosanoid metabolism is the main inhibitory targets of these drugs the resulting molecular and biological impact is generally accepted. As our knowledge base and technology progress we are learning that additional targets may be involved. This review attempts to summarize these new developments in the field.

Protein-ligand and membrane-ligand interactions in pharmacology: the case of the translocator protein (TSPO)

The targets of many small molecule drugs are membrane proteins, and traditionally the focus of pharmacology is on the interaction between such receptors and their small molecule drug ligands. However, the lipid membranes of cells and organelles are increasingly appreciated as diverse and dynamic structures that also specifically interact with small molecule drugs and peptides, causing profound changes in the properties of these membranes, and modulating the function of the membrane and the proteins within it. Drug-membrane interactions are likely to have a role in both the therapeutic and toxic activity of a variety of compounds, and their role in the overall pharmacological effect of a drug needs to be understood more clearly. This is the case for the 18 kDa translocator protein (TSPO) and its ligands, where functions that were established based on pharmacological studies are being called into question. Re-examining the putative functions of the TSPO and the effects of its ligands reveals a need to consider in more detail the interplay between protein-ligand and membrane-ligand interactions, and the modulatory relationship between TSPO and the lipid membrane.

Differential Effect of Oxicam Non-Steroidal Anti-Inflammatory Drugs on Membranes and Their Consequence on Membrane Fusion

Non-steroidal anti-inflammatory drugs (NSAIDs) are the most commonly used analgesics and antipyretics, which form an interesting drug group because of their new and alternate functions. The ability of the NSAIDs belonging to the oxicam chemical group to induce membrane fusion at low physiologically relevant concentrations is a new function that has drawn considerable attention. Membrane fusion is dependent on the interplay of physicochemical properties of both drugs and membranes. Here, we have elucidated the effects of different oxicam drugs, Meloxicam, Piroxicam, Tenoxicam, Lornoxicam, and Isoxicam, on an identical membrane-mimetic system. This highlights only the differential effects of the drugs on drug-membrane interactions, which in turn modulate their role as membrane fusogens. The partitioning behavior and the location of the drugs in dimyristoylphosphatidylcholine vesicles have been studied using second-derivative absorption spectroscopy, fluorescence quenching, steady-state fluorescence anisotropy, and time-resolved fluorescence lifetime measurements. Fusion kinetics has been monitored by fluorescence assays and dynamic light scattering was used to provide a snapshot of the vesicle diameter distribution at different time points. The differential perturbing effect of the drugs on the membrane is dependent both on their partitioning and location. Although partitioning governs the extent of fusion, the location modulates the rates of each step.

Cholesterol expels ibuprofen from the hydrophobic membrane core and stabilizes lamellar phases in lipid membranes containing ibuprofen

There is increasing evidence that common drugs, such as aspirin and ibuprofen, interact with lipid membranes. Ibuprofen is one of the most common over the counter drugs in the world, and is used for relief of pain and fever. It interacts with the cyclooxygenase pathway leading to inhibition of prostaglandin synthesis. From X-ray diffraction of highly oriented model membranes containing between 0 and 20 mol% ibuprofen, 20 mol% cholesterol, and dimyristoylphosphatidylcholine (DMPC), we present evidence for a non-specific interaction between ibuprofen and cholesterol in lipid bilayers. At a low ibuprofen concentrations of 2 mol%, three different populations of ibuprofen molecules were found: two in the lipid head group region and one in the hydrophobic membrane core. At higher ibuprofen concentrations of 10 and 20 mol%, the lamellar bilayer structure is disrupted and a lamellar to cubic phase transition was observed. In the presence of 20 mol% cholesterol, ibuprofen (at 5 mol%) was found to be expelled from the membrane core and reside solely in the head group region of the bilayers. 20 mol% cholesterol was found to stabilize lamellar membrane structure and the formation of a cubic phase at 10 and 20 mol% ibuprofen was suppressed. The results demonstrate that ibuprofen interacts with lipid membranes and that the interaction is strongly dependent on the presence of cholesterol.

Neutron Scattering at the Intersection of Heart Health Science and Biophysics

There is an urgent quest for improved heart health. Here, we review how neutron radiation can provide insight into the molecular basis of heart health. Lower cholesterol, a daily intake of aspirin and supplemental vitamin E are argued to all improve heart health. However, the mechanisms behind these common regimens, and others, are not entirely understood. It is not clear why a daily intake of aspirin can help some people with heart disease, and the benefits of vitamin E in the treatment of reperfusion injury have been heavily debated. The molecular impact of cholesterol in the body is still a hot topic. Neutron scattering experiments present a unique opportunity for biophysicists attempting to address these problems. We review some recently published studies that are advancing our understanding of how cholesterol, vitamin E and aspirin work at the molecular level, by studying the impact of these molecules on the cell membrane. These insights engage the broader health science community with new ways of thinking about these molecules.

Ascorbic Acid may Exacerbate Aspirin-Induced Increase in Intestinal Permeability

Ascorbic acid in combination with aspirin has been used to prevent aspirin-induced oxidative GI damage. We aimed to determine whether ascorbic acid reduces or prevents aspirin-induced changes in intestinal permeability over a 6-hr period using saccharidic probes mannitol and lactulose. The effects of administration of 600 mg aspirin alone, 500 mg ascorbic acid alone and simultaneous dosage of both agents were compared in a cross-over study in 28 healthy female volunteers. These effects were also compared with that of a placebo. The ability of ascorbic acid to mitigate the effects of aspirin when administered either half an hour before or after dosage with aspirin was also assessed in 19 healthy female volunteers. The excretion of lactulose over the 6-hr period was augmented after consumption of either aspirin or ascorbic acid compared with that after consumption of placebo. Dosage with ascorbic acid alone augmented the excretion of lactulose more than did aspirin alone. Simultaneous dosage with both agents augmented the excretion of lactulose in an additive manner. The timing of dosage with ascorbic acid in relation to that with aspirin had no significant effect on the excretion of the two sugars. These findings indicate that ascorbic acid does not prevent aspirin-induced increase in gut permeability rather that both agents augment it to a similar extent. The additive effect on simultaneous dosage with both agents in augmenting the absorption of lactulose suggests that each influences paracellular permeability by different pathways.

In vitro evidence that phosphatidylcholine protects against indomethacin/bile acid-induced injury to cells

Indomethacin is a powerful analgesic nonsteroidal anti-inflammatory drug (NSAID), but is limited in use by its primary side effect to cause gastrointestinal bleeding and serious injury. One factor important for exacerbating NSAID injury is the presence of bile acids, which may interact with indomethacin to form toxic mixed micelles in the gut. The development of a safer gastrointestinal formulation of indomethacin that is chemically complexed with phosphatidylcholine (PC-indomethacin) may offer an improved therapeutic agent, particularly in the presence of bile acid, but its potential protective mechanism is incompletely understood. Intestinal epithelial cells (IEC-6) were tested for injury with indomethacin (alone and plus various bile acids) compared with PC-indomethacin (alone and plus bile acids). To explore a role for bile acid uptake into cells as a requirement for NSAID injury, studies were performed using Madin-Darby canine kidney cells transfected with the apical sodium-dependent bile acid transporter (ASBT). Indomethacin, but not PC-indomethacin, was directly and dose-dependently injurious to IEC-6 cells. Similarly, the combination of any bile acid plus indomethacin, but not PC-indomethacin, induced cell injury. The expression of ASBT had a modest effect on the acute cytotoxicity of indomethacin in the presence of some conjugated bile acids. Complexing PC with indomethacin protected against the acute intestinal epithelial injury caused by indomethacin regardless of the presence of bile acids. The presence of luminal bile acid, but not its carrier-mediated uptake into the enterocyte, is required for acute indomethacin-induced cell injury. It is likely that initial cell damage induced by indomethacin occurs at or near the cell membrane, an effect exacerbated by bile acids and attenuated by PC.

NSAIDs: learning new tricks from old drugs

Nonsteroidal anti-inflammatory drugs (NSAIDs) comprise a heterogeneous group of pharmacological agents used for the symptomatic treatment of fever, pain, and inflammation. Although the main mechanism of action of NSAIDs consists of inhibiting prostaglandin synthesis by blocking the enzyme cyclooxygenase (COX), clinical, and experimental data strongly indicate the existence of additional mechanisms. Some of the COX-independent effects are related to the ability of NSAIDs to penetrate biological membranes and disrupt important molecular interactions necessary for a wide array of cellular functions, including cell adhesion. These effects, in particular those that interfere with L-selectin function in neutrophils during the inflammatory response, may contribute to the anti-inflammatory properties that NSAIDs exert in vivo. Recent contributions in this field have shown that the anti-L-selectin effect of NSAIDs is related to the NADPH-oxidase-dependent generation of superoxide anion at the plasma membrane. These findings might represent a novel approach for developing new and effective anti-inflammatory compounds with a better safety profile than the currently available NSAIDs.

Precision cut intestinal slices are an appropriate ex vivo model to study NSAID-induced intestinal toxicity in rats

Non-steroidal anti-inflammatory drugs (NSAIDs) are widely used therapeutic agents, however, they are associated with a high prevalence of intestinal side effects. In this investigation, rat precision cut intestinal slices (PCIS) were evaluated as an ex vivo model to study NSAID-induced intestinal toxicity. Firstly, PCIS were incubated with 0-200 μM diclofenac (DCF), one of the most intensively studied NSAIDs, to investigate whether they could correctly reflect the toxic mechanisms. DCF induced intestinal toxicity in PCIS was shown by morphological damage and ATP depletion. DCF induced endoplasmic-reticulum (ER) stress, mitochondrial injury and oxidative stress were reflected by up-regulated HSP-70 (heat shock protein 70) and BiP (binding immunoglobulin protein) gene expression, caspase 9 activation, GSH (glutathione) depletion and HO-1 (heme oxygenase 1) gene up-regulation respectively. Furthermore, DCF intestinal metabolites, which gave rise to protein adduct but not toxicity, were detected in PCIS. Secondly, PCIS were incubated with various concentrations of five NSAIDs. Typical NSAID-induced morphological changes were observed in PCIS. The ex vivo toxicity ranking (diflunisal> diclofenac = indomethacin > naproxen ≫ aspirin) showed good correlation with published in vitro and in vivo data, with diflunisal being the only exception. In conclusion, PCIS correctly reflect the various mechanisms of DCF-induced intestinal toxicity, and can serve as an ex vivo model for the prediction of NSAID-induced intestinal toxicity.

Acetylsalicylic acid (ASA) increases the solubility of cholesterol when incorporated in lipid membranes

Cholesterol has been well established as a mediator of cell membrane fluidity. By interacting with lipid tails, cholesterol causes the membrane tails to be constrained thereby reducing membrane fluidity, well known as the condensation effect. Acetylsalicylic acid (ASA), the main ingredient in aspirin, has recently been shown to increase fluidity in lipid bilayers by primarily interacting with lipid head groups. We used high-resolution X-ray diffraction to study both ASA and cholesterol coexisting in model membranes of dimyristoylphosphatidylcholine (DMPC). While a high cholesterol concentration of 40 mol% cholesterol leads to the formation of immiscible cholesterol bilayers, as was reported previously, increasing the amount of ASA in the membranes between 0 to 12.5 mol% was found to significantly increase the fluidity of the bilayers and dissolve the cholesterol plaques. We, therefore, present experimental evidence for an interaction between cholesterol and ASA on the level of the cell membrane at elevated levels of cholesterol and ASA.

Standardising the lactulose mannitol test of gut permeability to minimise error and promote comparability

BACKGROUND

Lactulose mannitol ratio tests are clinically useful for assessing disorders characterised by changes in gut permeability and for assessing mixing in the intestinal lumen. Variations between currently used test protocols preclude meaningful comparisons between studies. We determined the optimal sampling period and related this to intestinal residence.

METHODS

Half-hourly lactulose and mannitol urinary excretions were determined over 6 hours in 40 healthy female volunteers after administration of either 600 mg aspirin or placebo, in randomised order at weekly intervals. Gastric and small intestinal transit times were assessed by the SmartPill in 6 subjects from the same population. Half-hourly percentage recoveries of lactulose and mannitol were grouped on a basis of compartment transit time. The rate of increase or decrease of each sugar within each group was explored by simple linear regression to assess the optimal period of sampling.

KEY RESULTS

The between subject standard errors for each half-hourly lactulose and mannitol excretion were lowest, the correlation of the quantity of each sugar excreted with time was optimal and the difference between the two sugars in this temporal relationship maximal during the period from 2½-4 h after ingestion. Half-hourly lactulose excretions were generally increased after dosage with aspirin whilst those of mannitol were unchanged as was the temporal pattern and period of lowest between subject standard error for both sugars.

CONCLUSION

The results indicate that between subject variation in the percentage excretion of the two sugars would be minimised and the differences in the temporal patterns of excretion would be maximised if the period of collection of urine used in clinical tests of small intestinal permeability were restricted to 2½-4 h post dosage. This period corresponds to a period when the column of digesta column containing the probes is passing from the small to the large intestine.

In vitro analysis of flufenamic acid activity against Candida albicans biofilms

In a recent high-throughput screen against specific Candida albicans drug targets, several compounds that exhibited non-specific antifungal activity were identified, including the non-steroidal anti-inflammatory drug flufenamic acid (FFA). This study sought to determine the effect of different doses of FFA, alone or in combination with fixed concentrations of the standard antifungal agents amphotericin B (AmB), caspofungin (CAS) or fluconazole (FLU), for the prevention and treatment of C. albicans biofilms. Biofilms were formed in a 96-well microplate followed by evaluation of antifungal activity using the XTT assay. FFA concentrations of ≥512mg/L demonstrated >80% prevention of biofilm formation. FFA concentrations of 1024mg/L demonstrated >85% reduction of mature biofilms. When FFA (≥8mg/L) was used in combination with FLU (32mg/L), antifungal activity increased to 99% for the prevention of biofilm formation. Similarly, when a FFA concentration of ≥8mg/L was used in combination with either AmB (0.25mg/L) or CAS (0.125mg/L), antifungal activity also increased up to 99% for the prevention of biofilm formation. The inhibitory effect of FFA on C. albicans biofilms has not been reported previously, therefore these findings suggest that FFA in combination with traditional antifungals might be useful for the treatment and prevention of C. albicans biofilms.

Recent Advances in NSAIDs-Induced Enteropathy Therapeutics: New Options, New Challenges

The injurious effects of NSAIDs on the small intestine were not fully appreciated until the widespread use of capsule endoscopy. It is estimated that over two-thirds of regular NSAID users develop injury in the small intestinal injuries and that these injuries are more common than gastroduodenal mucosal injuries. Recently, chronic low-dose aspirin consumption was found to be associated with injury to the lower gut and to be a significant contributing factor in small bowel ulceration, hemorrhage, and strictures. The ability of aspirin and NSAIDs to inhibit the activities of cyclooxygenase (COX) contributes to the cytotoxicity of these drugs in the gastrointestinal tract. However, many studies found that, in the small intestine, COX-independent mechanisms are the main contributors to NSAID cytotoxicity. Bile and Gram-negative bacteria are important factors in the pathogenesis of NSAID enteropathy. Here, we focus on a promising strategy to prevent NSAID-induced small intestine injury. Selective COX-2 inhibitors, prostaglandin derivatives, mucoprotective drugs, phosphatidylcholine-NSAIDs, and probiotics have potential protective effects on NSAID enteropathy.

Determination of nanostructure of liposomes containing two model drugs by X-ray scattering from a synchrotron source

Small-angle X-ray scattering has been employed to study how the introduction of paracetamol and acetylsalicylic acid into a liposome bilayer system affects the system's nanostructure. An X-ray scattering model, developed for multilamellar liposome systems [Pabst et al. (2000), Phys. Rev. E, 62, 4000-4009], has been used to fit the experimental data and to extract information on how structural parameters, such as the number and thickness of the bilayers of the liposomes, thickness of the water layer in between the bilayers, size and volume of the head and tail groups, are affected by the drugs and their concentration. Even though the experimental data reveal a complicated picture of the drug-bilayer interaction, they clearly show a correlation between nanostructure, drug and concentration in some aspects. The localization of the drugs in the bilayers is discussed.

Interaction of nonsteroidal anti-inflammatory drugs with membranes: in vitro assessment and relevance for their biological actions

Nonsteroidal anti-inflammatory drugs (NSAIDs) are among the most commonly used drugs in the world due to their anti-inflammatory, analgesic and antipyretic properties. Nevertheless, the consumption of these drugs is still associated with the occurrence of a wide spectrum of adverse effects. Regarding the major role of membranes in cellular events, the hypothesis that the biological actions of NSAIDs may be related to their effect at the membrane level has triggered the in vitro assessment of NSAIDs-membrane interactions. The use of membrane mimetic models, cell cultures, a wide range of experimental techniques and molecular dynamics simulations has been providing significant information about drugs partition and location within membranes and also about their effect on diverse membrane properties. These studies have indeed been providing evidences that the effect of NSAIDs at membrane level may be an additional mechanism of action and toxicity of NSAIDs. In fact, the pharmacokinetic properties of NSAIDs are closely related to the ability of these drugs to interact and overcome biological membranes. Moreover, the therapeutic actions of NSAIDs may also result from the indirect inhibition of cyclooxygenase due to the disturbing effect of NSAIDs on membrane properties. Furthermore, increasing evidences suggest that the disordering effects of these drugs on membranes may be in the basis of the NSAIDs-induced toxicity in diverse organ systems. Overall, the study of NSAIDs-membrane interactions has proved to be not only important for the better understanding of their pharmacological actions, but also for the rational development of new approaches to overcome NSAIDs adverse effects.

Exploring the Free Energy Landscape of Solutes Embedded in Lipid Bilayers

Free energy calculations are vital for our understanding of biological processes on an atomistic scale and can offer insight to various mechanisms. However, in some cases, degrees of freedom (DOFs) orthogonal to the reaction coordinate have high energy barriers and/or long equilibration times, which prohibit proper sampling. Here we identify these orthogonal DOFs when studying the transfer of a solute from water to a model membrane. Important DOFs are identified in bulk liquids of different dielectric nature with metadynamics simulations and are used as reaction coordinates for the translocation process, resulting in two- and three-dimensional space of reaction coordinates. The results are in good agreement with experiments and elucidate the pitfalls of using one-dimensional reaction coordinates. The calculations performed here offer the most detailed free energy landscape of solutes embedded in lipid bilayers to date and show that free energy calculations can be used to study complex membrane translocation phenomena.

Current perspectives in NSAID-induced gastropathy

Nonsteroidal anti-inflammatory drugs (NSAIDs) are the most highly prescribed drugs in the world. Their analgesic, anti-inflammatory, and antipyretic actions may be beneficial; however, they are associated with severe side effects including gastrointestinal injury and peptic ulceration. Though several approaches for limiting these side effects have been adopted, like the use of COX-2 specific drugs, comedication of acid suppressants like proton pump inhibitors and prostaglandin analogs, these alternatives have limitations in terms of efficacy and side effects. In this paper, the mechanism of action of NSAIDs and their critical gastrointestinal complications have been reviewed. This paper also provides the information on different preventive measures prescribed to minimize such adverse effects and analyses the new suggested strategies for development of novel drugs to maintain the anti-inflammatory functions of NSAIDs along with effective gastrointestinal protection.

Advent of novel phosphatidylcholine-associated nonsteroidal anti-inflammatory drugs with improved gastrointestinal safety

The mucosa of the gastrointestinal (GI) tract exhibits hydrophobic, nonwettable properties that protect the underlying epithelium from gastric acid and other luminal toxins. These biophysical characteristics appear to be attributable to the presence of an extracellular lining of surfactant-like phospholipids on the luminal aspects of the mucus gel layer. Phosphatidylcholine (PC) represents the most abundant and surface-active form of gastric phospholipids. PC protected experimental rats from a number of ulcerogenic agents and/or conditions including nonsteroidal anti-inflammatory drugs (NSAIDs), which are chemically associated with PC. Moreover, preassociating a number of the NSAIDs with exogenous PC prevented a decrease in the hydrophobic characteristics of the mucus gel layer and protected rats against the injurious GI side effects of NSAIDs while enhancing and/or maintaining their therapeutic activity. Bile plays an important role in the ability of NSAIDs to induce small intestinal injury. NSAIDs are rapidly absorbed from the GI tract and, in many cases, undergo enterohepatic circulation. Thus, NSAIDs with extensive enterohepatic cycling are more toxic to the GI tract and are capable of attenuating the surface hydrophobic properties of the mucosa of the lower GI tract. Biliary PC plays an essential role in the detoxification of bile salt micelles. NSAIDs that are secreted into the bile injure the intestinal mucosa via their ability to chemically associate with PC, which forms toxic mixed micelles and limits the concentration of biliary PC available to interact with and detoxify bile salts. We have worked to develop a family of PC-associated NSAIDs that appear to have improved GI safety profiles with equivalent or better therapeutic efficacy in both rodent model systems and pilot clinical trials.

Multiple NSAID-induced hits injure the small intestine: underlying mechanisms and novel strategies

Nonsteroidal anti-inflammatory drugs (NSAIDs) can cause serious gastrointestinal (GI) injury including jejunal/ileal mucosal ulceration, bleeding, and even perforation in susceptible patients. The underlying mechanisms are largely unknown, but they are distinct from those related to gastric injury. Based on recent insights from experimental models, including genetics and pharmacology in rodents typically exposed to diclofenac, indomethacin, or naproxen, we propose a multiple-hit pathogenesis of NSAID enteropathy. The multiple hits start with an initial pharmacokinetic determinant caused by vectorial hepatobiliary excretion and delivery of glucuronidated NSAID or oxidative metabolite conjugates to the distal small intestinal lumen, where bacterial β-glucuronidase produces critical aglycones. The released aglycones are then taken up by enterocytes and further metabolized by intestinal cytochrome P450s to potentially reactive intermediates. The "first hit" is caused by the NSAID and/or oxidative metabolites that induce severe endoplasmic reticulum stress or mitochondrial stress and lead to cell death. The "second hit" is created by the significant subsequent inflammatory response that would follow such a first-hit injury. Based on these putative mechanisms, strategies have been developed to protect the enterocytes from being exposed to the parent NSAID and/or oxidative metabolites. Among these, a novel strategy already demonstrated in a murine model is the selective disruption of bacteria-specific β-glucuronidases with a novel small molecule inhibitor that does not harm the bacteria and that alleviates NSAID-induced enteropathy. Such mechanism-based strategies require further investigation but provide potential avenues for the alleviation of the GI toxicity caused by multiple NSAID hits.