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.

Suppression of contractile activity in the small intestine by indomethacin and omeprazole.

Nonsteroidal anti-inflammatory drugs (NSAIDs) are widely used to treat a number of conditions, and proton pump inhibitors (PPIs) are often used to prevent NSAID-induced gastric mucosal damage; however, the effects of NSAIDs on intestinal motility are poorly understood. The purpose of the present study is to determine the effects of a prototypical NSAID, indomethacin, either alone or in conjunction with the PPI omeprazole, on intestinal motility. Rats were randomly divided into four groups treated with vehicle, omeprazole, indomethacin, or a combination of indomethacin and omeprazole. Intestinal motility and transit were measured along with inflammatory mediators in the intestinal smooth muscle, markers of mucosal damage, and bacterial counts in the intestinal wall. Indomethacin, but not omeprazole, caused mucosal injury indicated by lower gut bleeding; however, both omeprazole and indomethacin suppressed contractile activity and frequency in the distal part of the small intestine. Cotreatment with omeprazole did not reduce indomethacin-induced intestinal bleeding. Furthermore, although indomethacin caused increased inflammation as indicated by increased edema development and inflammatory mediators, cotreatment with omeprazole did not reduce inflammation in the intestinal smooth muscle or prevent the increased bacterial count in the intestinal wall induced by indomethacin. We conclude that both NSAID and PPI treatment suppressed contractile activity in the distal regions of the small intestine. The suppression of intestinal contractility was associated with increased inflammation in both cases; however, indomethacin and omeprazole appear to affect intestinal motility by different mechanisms.

Bile acids modulate signaling by functional perturbation of plasma membrane domains.

Eukaryotic cell membranes are organized into functional lipid and protein domains, the most widely studied being membrane rafts. Although rafts have been associated with numerous plasma membrane functions, the mechanisms by which these domains themselves are regulated remain undefined. Bile acids (BAs), whose primary function is the solubilization of dietary lipids for digestion and absorption, can affect cells by interacting directly with membranes. To investigate whether these interactions affected domain organization in biological membranes, we assayed the effects of BAs on biomimetic synthetic liposomes, isolated plasma membranes, and live cells. At cytotoxic concentrations, BAs dissolved synthetic and cell-derived membranes and disrupted live cell plasma membranes, implicating plasma membrane damage as the mechanism for BA cellular toxicity. At subtoxic concentrations, BAs dramatically stabilized domain separation in Giant Plasma Membrane Vesicles without affecting protein partitioning between coexisting domains. Domain stabilization was the result of BA binding to and disordering the nonraft domain, thus promoting separation by enhancing domain immiscibility. Consistent with the physical changes observed in synthetic and isolated biological membranes, BAs reorganized intact cell membranes, as evaluated by the spatial distribution of membrane-anchored Ras isoforms. Nanoclustering of K-Ras, related to nonraft membrane domains, was enhanced in intact plasma membranes, whereas the organization of H-Ras was unaffected. BA-induced changes in Ras lateral segregation potentiated EGF-induced signaling through MAPK, confirming the ability of BAs to influence cell signal transduction by altering the physical properties of the plasma membrane. These observations suggest general, membrane-mediated mechanisms by which biological amphiphiles can produce their cellular effects.

Aggregation behavior of ibuprofen, cholic acid and dodecylphosphocholine micelles.

Non-steroidal anti-inflammatory drugs (NSAIDs) are frequently used to treat chronic pain and inflammation. However, prolonged use of NSAIDs has been known to result in Gastrointestinal (GI) ulceration/bleeding, with a bile-mediated mechanism underlying their toxicity to the lower gut. Bile acids (BAs) and phosphatidylcholines (PCs), the major components of bile, form mixed micelles to reduce the membrane disruptive actions of monomeric BAs and simple BA micelles. NSAIDs are suspected to alter the BA/PC balance in the bile, but the molecular interactions of NSAID-BA or NSAID-BA-PC remain undetermined. In this work, we used a series of all-atom molecular dynamics simulations of cholic acid (CA), ibuprofen (IBU) and dodecylphosphocholine (DPC) mixtures to study the spontaneous aggregation of CA and IBU as well as their adsorption on a DPC micelle. We found that the size of CA-IBU mixed micelles varies with their molar ratio in a non-linear manner, and that micelles of different sizes adopt similar shapes but differ in composition and internal interactions. These observations are supported by NMR chemical shift changes, NMR ROESY crosspeaks between IBU and CA, and dynamic light scattering experiments. Smaller CA-IBU aggregates were formed in the presence of a DPC micelle due to the segregation of CA and IBU away from each other by the DPC micelle. While the larger CA-IBU aggregates arising from higher IBU concentrations might be responsible for NSAID-induced intestinal toxicity, the absence of larger CA-IBU aggregates in the presence of DPC micelles may explain the observed attenuation of NSAID toxicity by PCs.

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

Nonsteroidal anti-inflammatory drugs (NSAIDs) are one of the most widely consumed pharmaceuticals, yet both the mechanisms involved in their therapeutic actions and side-effects, notably gastrointestinal (GI) ulceration/bleeding, have not been clearly defined. In this study, we have used a number of biochemical, structural, computational and biological systems including; Fourier Transform InfraRed (FTIR). Nuclear Magnetic Resonance (NMR) and Surface Plasmon Resonance (SPR) spectroscopy, and cell culture using a specific fluorescent membrane probe, to demonstrate that NSAIDs have a strong affinity to form ionic and hydrophobic associations with zwitterionic phospholipids, and specifically phosphatidylcholine (PC), that are reversible and non-covalent in nature. We propose that the pH-dependent partition of these potent anti-inflammatory drugs into the phospholipid bilayer, and possibly extracellular mono/multilayers present on the luminal interface of the mucus gel layer, may result in profound changes in the hydrophobicity, fluidity, permeability, biomechanical properties and stability of these membranes and barriers. These changes may not only provide an explanation of how NSAIDs induce surface injury to the GI mucosa as a component in the pathogenic mechanism leading to peptic ulceration and bleeding, but potentially an explanation for a number of (COX-independent) biological actions of this family of pharmaceuticals. This insight also has proven useful in the design and development of a novel class of PC-associated NSAIDs that have reduced GI toxicity while maintaining their essential therapeutic efficacy to inhibit pain and inflammation.

Endotoxin-induced changes in phospholipid dynamics of the stomach.

BACKGROUND: The gastric mucosa is protected in part by a hydrophobic layer of phosphatidylcholine (PC) that overlies the mucus gel on the stomach. Endotoxin treatment (i.e., lipopolysaccharide [LPS]) results in an apparent disruption of this layer, as evidenced by a reduction in surface hydrophobicity and an increase in transmural permeability. The current studies compared PC and lyso-PC levels in mucus and gastric mucosa before and after LPS treatment, and examined potential mechanisms for surface phospholipid changes. METHODS: Rats were administered LPS (5 mg//kg, intraperitoneally) and samples were collected after 5 h for analysis of PC and its primary degradant, lyso-PC, in the loosely and firmly adherent mucus layers and the mucosa. The dependence of LPS-induced effects on gastric alkalinization, PC synthetic activity, and intestinal reflux material was assessed. RESULTS: The gastric contents after LPS, which also contained duodenal reflux material, had greatly increased amounts of PC and lyso-PC. The firmly adherent mucus layer was unchanged. The gastric mucosa after LPS revealed significant reductions of PC levels and no change in lyso-PC content. These phospholipid changes were not caused by alkalinization of the stomach or altered PC synthesis. Prevention of duodenogastric reflux by pylorus ligation blocked the LPS-induced increase in luminal lyso-PC and the reduction in mucosal PC. CONCLUSIONS: LPS appears to induce a release of PC from gastric mucosa into the lumen, along with degradation of PC to lyso-PC, without an effect on PC synthesis. Component(s) of intestinal reflux material appear to be required for these effects. The lowered PC levels in gastric mucosa after LPS may contribute to reduced barrier properties of this tissue.

In vitro and in vivo protection against indomethacin-induced small intestinal injury by proton pump inhibitors, acid pump antagonists, or indomethacin-phosphatidylcholine.

BACKGROUND/AIMS: Proton pump inhibitors (PPIs) are widely used to prevent nonsteroidal anti-inflammatory drug (NSAID)-induced peptic ulcers. NSAIDs produce small intestinal injury and some PPIs have been reported to protect against NSAID-induced small bowel injury in rats. The aim of this study was to compare PPIs, revaprazan, and phosphatidylcholine-associated indomethacin (Indo-PC) for protection against indomethacin (Indo)-induced small bowel injury. METHODS: Rat intestinal epithelial cells (IEC-6) were pretreated with omeprazole, lansoprazole, or revaprazan prior to exposure to Indo or Indo-PC. Cell viability was assessed by methyl thiazolyl tetrazolium assay. Omeprazole, lansoprazole, or revaprazan was administered orally to rats prior to the vehicle or Indo. Indo-PC was administered alone. After 24 h, small intestinal erosions were counted; intestinal bleeding was assessed as the hemoglobin concentration of small intestinal fluid. RESULTS: Omeprazole, lansoprazole, and revaprazan did not protect against Indo-induced IEC-6 cell injury. Indo-PC was less damaging in vitro than Indo alone. In vivo, neither omeprazole nor lansoprazole protected against Indo-induced small bowel injury; however, revaprazan pretreatment and Indo-PC resulted in significantly fewer erosions (>50% reduction) or bleeding (>80% reduction). CONCLUSION: PPIs showed no small bowel protective effect in vitro or in vivo. Revaprazan showed a small bowel protective effect in vivo, whereas Indo-PC was protective both in vitro and in vivo.

Bile acids improve the antimicrobial effect of rifaximin.

Diarrhea is one of the most common infirmities affecting international travelers, occurring in 20 to 50% of persons from industrialized countries visiting developing regions. Enterotoxigenic Escherichia coli (ETEC) is the most common causative agent and is isolated from approximately half of the cases of traveler's diarrhea. Rifaximin, a largely water-insoluble, nonabsorbable (<0.4%) antibiotic that inhibits bacterial RNA synthesis, is approved for use for the treatment of traveler's diarrhea caused by diarrheagenic E. coli. However, the drug has minimal effect on the bacterial flora or the infecting E. coli strain in the aqueous environment of the colon. The purpose of the present study was to evaluate the antimicrobial effect and bioavailability of rifaximin in aqueous solution in the presence and absence of physiologic concentrations of bile acids. The methods used included growth measurement of ETEC (strain H10407), rifaximin solubility measurements, total bacterial protein determination, and assessment of the functional activity of rifaximin by monitoring inhibition of bacterial beta-galactosidase expression. Solubility studies showed rifaximin to be 70- to 120-fold more soluble in bile acids (approximately 30% in 4 mM bile acids) than in aqueous solution. Addition of both purified bile acids and human bile to rifaximin at subinhibitory and inhibitory concentrations significantly improved the drug's anti-ETEC effect by 71% and 73%, respectively, after 4 h. This observation was confirmed by showing a decrease in the overall amount of total bacterial protein expressed during incubation of rifaximin plus bile acids. Rifaximin-treated samples containing bile acids inhibited the expression of ETEC beta-galactosidase at a higher magnitude than samples that did not contain bile acids. The study provides data showing that bile acids solubilize rifaximin on a dose-response basis, increasing the drug's bioavailability and antimicrobial effect. These observations suggest that rifaximin may be more effective in the treatment of infections in the small intestine, due to the higher concentration of bile in this region of the gastrointestinal tract than in the colon. The water insolubility of rifaximin is the likely explanation for the drug's minimal effects on colonic flora and fecal pathogens, despite in vitro susceptibility.

Effect of indomethacin on bile acid-phospholipid interactions: implication for small intestinal injury induced by nonsteroidal anti-inflammatory drugs.

The injurious effect of nonsteroidal anti-inflammatory drugs (NSAIDs) in the small intestine was not appreciated until the widespread use of capsule endoscopy. Animal studies found that NSAID-induced small intestinal injury depends on the ability of these drugs to be secreted into the bile. Because the individual toxicity of amphiphilic bile acids and NSAIDs directly correlates with their interactions with phospholipid membranes, we propose that the presence of both NSAIDs and bile acids alters their individual physicochemical properties and enhances the disruptive effect on cell membranes and overall cytotoxicity. We utilized in vitro gastric AGS and intestinal IEC-6 cells and found that combinations of bile acid, deoxycholic acid (DC), taurodeoxycholic acid, glycodeoxycholic acid, and the NSAID indomethacin (Indo) significantly increased cell plasma membrane permeability and became more cytotoxic than these agents alone. We confirmed this finding by measuring liposome permeability and intramembrane packing in synthetic model membranes exposed to DC, Indo, or combinations of both agents. By measuring physicochemical parameters, such as fluorescence resonance energy transfer and membrane surface charge, we found that Indo associated with phosphatidylcholine and promoted the molecular aggregation of DC and potential formation of larger and isolated bile acid complexes within either biomembranes or bile acid-lipid mixed micelles, which leads to membrane disruption. In this study, we demonstrated increased cytotoxicity of combinations of bile acid and NSAID and provided a molecular mechanism for the observed toxicity. This mechanism potentially contributes to the NSAID-induced injury in the small bowel.

Pathophysiology of LPS-induced gastrointestinal injury in the rat: role of secretory phospholipase A2.

A hydrophobic layer of phosphatidylcholine (PC) overlies and protects the surface of the gastrointestinal (GI) tract, contributing to barrier integrity. During critical illness such as sepsis, gut barrier integrity is compromised, which could be related to degradation of PC. The purpose of this study was to investigate a role for luminal (secretory) phospholipase A2 (sPLA(2)) in LPS-induced GI injury. Rats were treated with LPS (5 mg/kg) or saline for 0.5, 1, 3, and 5 h. The gastric and ileal luminal contents were collected for determination of sPLA(2) activity, and the luminal lipids were analyzed using thin layer chromatography for lyso-PC content. The GI permeability was assessed in vivo with fluorescein-isothiocyanate dextran 4000 and rats were tested with or without a specific sPLA(2) inhibitor. LPS induced significant increases in sPLA(2) activity and lyso-PC content in the gastric and ileal lumens at 5 h. In addition, LPS treated rats showed a significant increase in GI permeability to fluorescein-isothiocyanate dextran in both the stomach and ileum at 5 h, which was prevented by pretreatment with the sPLA(2) inhibitor. In response to LPS, sPLA(2) activity increases in the GI tract lumen where it may degrade the extracellular protective phospholipid layer and membranes, producing injurious lyso-PC and increased GI permeability. Pretreatment with an orally active sPLA(2) inhibitor blocks the LPS-induced increase in GI permeability, and may suggest a new approach to fortify the GI mucosal barrier and prevent complications from endotoxin in trauma and other patients.

Importance of biliary excretion of indomethacin in gastrointestinal and hepatic injury.

BACKGROUND AND AIMS: A mechanism for protection of gastrointestinal (GI) and hepatic cells from damaging detergent actions of bile acids appears to involve the bile component, phosphatidylcholine (PC). Non-steroidal anti-inflammatory drugs (NSAIDs) induce intestinal injury in direct proportion to their ability to be excreted into bile, and are known to chemically associate with PC. We investigated the role of bile acids and PC in the mechanism of indomethacin-induced epithelial injury. METHODS: Rats were injected orally or intravenously with radiolabeled indomethacin and their bile was collected over time for determination of NSAID secretion. Bile from rats treated with or without indomethacin was used in studies of red blood cell (RBC) hemolysis as a measure of membrane cytotoxicity. The bile salt, sodium deoxycholate (SDC), and indomethacin were tested alone and in combination with PC on RBC and on hepatic HepG2 cells. RESULTS: Intravenously or orally given indomethacin was quantitatively excreted (approximately 50%) into bile over a 2-h study period. Bile from a rat treated with indomethacin or bile with exogenous indomethacin was cytotoxic to RBC, and the injury was prevented by the addition of PC. Hepatocytes exposed to SDC showed injury that could be dose-dependently prevented by PC, and reversed by indomethacin. CONCLUSIONS: Biliary PC plays an important physiological role in protecting GI and hepatic epithelia from the cytotoxic actions of bile salts. The ability of NSAIDs excreted into the bile to associate with mixed bile salt micelles and reduce the protective action of the PC may be a critical component in the drugs' pathogenic mechanism.

Role of phosphatidylcholine saturation in preventing bile salt toxicity to gastrointestinal epithelia and membranes.

BACKGROUND AND AIM: The mechanism which protects the biliary and intestinal mucosa from the detergent properties of bile acids is not fully understood. We employed three contrasting in vitro model systems (human red blood cells, polarized intestinal [Caco-2] cells, and synthetic liposomes), to compare the efficacy of saturated and unsaturated phosphatidylcholine (PC) to protect cells and membranes from bile salt injury. METHODS: Hemolysis of red blood cells, electrical resistance across confluent monolayers of Caco-2 cells, and disruption of synthetic PC liposomes were assessed after incubation with varying concentrations of bile salt (sodium deoxycholate) alone or in the presence of saturated or unsaturated PC. RESULTS: The hemolytic activity of deoxycholate on red blood cells was observed at > or =2 mM, and could be blocked by equimolar concentration or greater of both saturated or unsaturated PC. In contrast, exposure of Caco-2 cells to deoxycholate at > or =0.8 mM induced a maximal decrease in resistance, which was reversed by > or =0.8 mM unsaturated PC or 5 mM saturated PC. Similarly, synthetic liposomes were permeabilized by 0.8 mM deoxycholate and were protected by a lower concentration of unsaturated PC (2 mM) than saturated (5 mM). CONCLUSIONS: Cells can show variable resistance to bile salt toxicity. Extracellular PC, especially in the unsaturated state, can directly protect cell and artificial membranes from bile salt injury. These findings support a role for biliary PC in the formation of mixed micelles that have low cytotoxic properties.

A report on associations among gastric pH, bleeding, duodenogastric reflux, and outcomes after trauma.

BACKGROUND: The pathogenesis of multiple organ failure (MOF) in trauma patients may involve the gastrointestinal tract, but its exact origins remain elusive. In a prospective study, the gastric fluid of major torso trauma patients was examined for evidence of duodenogastric reflux and potential gastric injury, and was compared with patient outcomes regarding MOF. METHODS: Patient samples were collected daily for 4 days by nasogastric tube and analyzed for pH, hemoglobin, and bile acid. Blood was collected for analysis of C-reactive protein (CRP). Outcomes were recorded for the presence or absence of MOF. RESULTS: The results showed that most patients exhibited alkaline gastric contents (pH >/=4.9) and elevated levels of hemoglobin immediately after the trauma. Although non-MOF patients demonstrated a decline of both mean gastric pH and bleeding by day 4, MOF patients maintained significant elevations in pH during this time period. Mean total bile acid levels were increased in all patients, signifying the presence of duodenogastric reflux. However, there were no clear differences in mean bile acid concentrations between MOF and non-MOF patients over time, although MOF patients tended to exhibit higher levels. All patients showed a progressive rise in serum CRP during the first 24 hours after trauma, which was maintained for 4 days. The initial rise in serum CRP in MOF patients was delayed compared with that in non-MOF patients. CONCLUSIONS: We conclude that duodenogastric reflux occurs in trauma patients in the first few days after trauma and may contribute to elevated gastric pH and bleeding. Further study is needed to verify whether monitoring the gastric juice of trauma patients during the first several days of hospitalization, for alkaline pH and excessive blood in the gastric lumen, could lead to better assessments of patient status.

Gastric alkalinization after major trauma.

BACKGROUND: Gastric function in trauma patients is poorly understood. In animals, shock causes gastric luminal alkalinization and bile reflux. In trauma patients, studies of stress gastritis prophylaxis demonstrated with continuous gastric pH monitoring that the stomach became alkaline even without antisecretory therapy. Therefore, we hypothesized that trauma patients have an alkaline gastric environment that may be because of bile reflux. METHODS: A prospective observational study at an urban Level I trauma center was performed. All major torso trauma patients (severe head injuries excluded) who met the criteria for standardized shock resuscitation were eligible for inclusion. A 12.5 Fr silastic pH probe (Sandhill Scientific) was placed in the stomach and the gastric pH continuously monitored for 7 days. Patients received no stress gastritis prophylaxis. Gastric samples were obtained each day and assayed for total bile acids and pH. RESULTS: Twelve patients were entered into the study. Mean age was 31 years +/- 4 years, 67% men, 75% blunt mechanism of injury, and mean Injury Severity Score 28 +/- 3. Three patients (25%) developed multiple organ failure and four acquired ventilator-associated pneumonia. During the first day of continuous pH monitoring, 9 of 12 patients had a gastric pH >4 for the majority of the day with 7 patients having essentially no acid production. During subsequent days, gastric pH began to drop and by the 4th day the majority of each day was spent at a pH <4. Additionally, gastric pH of patients with ventilator-associated pneumonia or multiple organ failure tended to be more alkaline. Bile acid was present in the gastric fluid of all patients in varying amounts. However, there was no significant correlation between gastric pH and bile acid concentration. CONCLUSIONS: Traumatic injury causes gastric luminal alkalinization that may be related, only in part, to bile acid reflux. Other alkalinizing factors remain to be elucidated.

Chemoprevention with phosphatidylcholine non-steroidal anti-inflammatory drugs in vivo and in vitro.

The chemopreventive activity of non-steroidal anti-inflammatory drugs (NSAIDs), particularly aspirin, has been well demonstrated in preclinical and clinical studies. However, the primary side effect from this class of drug is gastrointestinal (GI) bleeding, which has limited the widespread use of NSAIDs for the prevention of cancer. The development of GI-safer NSAIDs, which are associated with phosphatidylcholine (PC) may provide a solution to this therapeutic problem. In the present study, the efficacy of two NSAIDs, aspirin and indomethacin, were compared using murine colon cancer cell line MC-26. Each NSAID was assessed alone and in combination with PC, using in vitro and in vivo systems. The results reveal that the PC-associated NSAIDs had a significantly higher degree of protection against cancer cell growth compared with the unmodified NSAIDs. It was also observed that Aspirin-PC and Indomethacin-PC prevented the metastatic spread of cancer cells in a syngeneic mouse model. These results support the potential use of PC-NSAIDs for the chemoprevention of colorectal cancer.

Unlocking Aspirin's Chemopreventive Activity: Role of Irreversibly Inhibiting Platelet Cyclooxygenase-1.

The mechanism by which aspirin consumption is linked to significant reductions in the incidence of multiple forms of cancer and metastatic spread to distant tissues, resulting in increased cancer patient survival is not well understood. In this study, using colon cancer as an example, we provide both in vitro (cell culture) and in vivo (chemically induced mouse model of colon cancer) evidence that this profound antineoplastic action may be associated with aspirin's ability to irreversibly inhibit COX-1-mediated platelet activation, thereby blocking platelet-cancer cell interactions, which promote cancer cell number and invasive potential. This process may be driven by platelet-induced epithelial-mesenchymal transition (EMT), as assessed using confocal microscopy, based upon changes in cell morphology, growth characteristics and fibronectin expression, and biochemical/molecular analysis by measuring changes in the expression of the EMT markers; vimentin, ß-catenin, and SNAIL. We also provide evidence that a novel, gastrointestinal-safe phosphatidylcholine (PC)-associated aspirin, PL2200 Aspirin, possesses the same or more pronounced actions versus unmodified aspirin with regard to antiplatelet effects (in vitro: reducing platelet activation as determined by measuring the release of thromboxane and VEGF in culture medium; in vivo: inhibiting platelet number/activation and extravasation into tumor tissue) and chemoprevention (in vitro: inhibiting colonic cell growth and invasive activity; in vivo: inhibiting colonic dysplasia, inflammation, and tumor mass). These results suggest that aspirin's chemopreventive effects may be due, in part, to the drug blocking the proneoplastic action of platelets, and the potential use of Aspirin-PC/PL2200 as an effective and safer chemopreventive agent for colorectal cancer and possibly other cancers. Cancer Prev Res; 10(2); 142-52. ©2016 AACR.

Phosphatidylcholine-associated nonsteroidal anti-inflammatory drugs (NSAIDs) inhibit DNA synthesis and the growth of colon cancer cells in vitro.

The use of NSAIDs or COX-2 inhibitors for chemoprevention of colorectal cancer has been suggested for patients at high risk for this disease. However, the gastrointestinal side effects of traditional NSAIDs which consist of bleeding and ulceration, and the cardiovascular effects of COX-2 inhibitors may limit their usefulness. In preclinical studies, our laboratory has shown that the addition of phosphatidylcholine (PC) to the NSAIDs aspirin (ASA) or ibuprofen (IBU) results in a NSAID-PC with fewer GI side effects and also maintained or enhanced analgesic, anti-pyretic and anti-inflammatory efficacy over the unmodified NSAID. Because NSAID-PCs have not been tested for anti-cancer activity, in the present study, ASA-PC and IBU-PC were tested on the SW-480 human colon cancer cell line. SW-480 cells were incubated in media containing 1-5 mM NSAID or NSAID-PC for 2 days. Measurements were made of cell number, cell proliferation (DNA synthesis), and manner of cell death (necrosis and apoptosis). ASA and IBU reduced cell number in a dose-dependent manner with IBU showing a greater potency than ASA. The association of PC to the NSAID resulted in greater reductions of cell number for both NSAIDs. Furthermore, the NSAID-PC formulation had significantly greater efficacy and potency to inhibit cellular DNA synthesis than the unmodified NSAID. PC alone at the doses and times used had no effect on cell number in this cell line, but did have a small effect to reduce DNA synthesis. None of the drugs had a clear effect on cell death by necrosis. Only IBU and IBU-PC caused cell death by apoptosis in SW-480 cells. We conclude that NSAID-PCs have activity to impede the growth of colon cancer cells in vitro, which is due, in major part, to a marked reduction in DNA synthetic activity of these cells. This growth inhibitory effect appears to be independent of COX-2 activity, since it is known that SW-480 cells do not have this inducible COX isoform. Due to its greater efficacy in this model system, IBU-PC should be further evaluated as a chemopreventive agent that is safer for the GI tract than unmodified NSAID.

NSAID injury to the gastrointestinal tract: evidence that NSAIDs interact with phospholipids to weaken the hydrophobic surface barrier and induce the formation of unstable pores in membranes.

In this review, we have discussed our current understanding of the barrier properties that are in place to protect the upper gastrointestinal mucosa from luminal acid, and the pathogenic mechanism by which nonsteroidal anti-inflammatory drugs (NSAIDs) induce injury to the gastrointestinal tract. The changes in our view of the importance of NSAID-induced cyclo-oxygenase (COX) inhibition on the pathogenesis and prevention of NSAID-induced gastrointestinal injury is presented. The focus of this paper has been placed on the effects of NSAIDs on the mucosal surface, and specifically the effect of these powerful drugs in inducing changes in the hydrophobicity, fluidity, biomechanical and permeability properties of extracellular and membrane phospholipids. Lastly, recent evidence is presented that salicylic acid and related NSAIDs may alter the stability of membranes, inducing the formation of unstable pores that may lead to back-diffusion of luminal acid and membrane rupture. This understanding of the interaction of NSAIDs with membrane phospholipids may prove valuable in the design of novel NSAID formulations with reduced gastrointestinal side-effects.

Indomethacin injury to the rat small intestine is dependent upon biliary secretion and is associated with overgrowth of enterococci.

NSAIDuse is limited due to the drugs' toxicity to the gastrointestinal mucosa, an action incompletely understood. Lower gut injury induced byNSAIDs is dependent on bile secretion and is reported to increase the growth of a number of bacterial species, including an enterococcal species,Enterococcus faecalis This study examined the relationships between indomethacin (INDO)-induced intestinal injury/bleeding, small bowel overgrowth (SBO) and dissemination of enterococci, and the contribution of bile secretion to these pathological responses. Rats received either a sham operation (SO) or bile duct ligation (BDL) prior to administration of two daily subcutaneous doses of saline orINDO, and 24 h later, biopsies of ileum and liver were collected for plating on selective bacterial media. Fecal hemoglobin (Hb) and blood hematocrit (Hct) were measured to assess intestinal bleeding. Of the four treatment groups, onlySO/INDOrats experienced a significant 10- to 30-fold increase in fecal Hb and reduction in Hct, indicating thatBDLattenuatedINDO-induced intestinal injury/bleeding. Ileal enterococcal colony-forming units were significantly increased (500- to 1000-fold) inSO/INDOrats. Of all groups, only theSO/INDOrats demonstrated gut injury, and this was associated with enterococcal overgrowth of the gut and dissemination to the liver. We also demonstrated thatINDO-induced intestinal injury andE. faecalisovergrowth was independent of the route of administration of the drug, as similar findings were observed in rats orally dosed with theNSAID Bile secretion plays an important role inINDO-induced gut injury and appears to support enterococcal overgrowth of the intestine.NSAID-induced enterococcalSBOmay be involved either as a compensatory response to gut injury or with the pathogenic process itself and the subsequent development of sepsis.

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.