The nonsteroidal anti-inflammatory drug indomethacin induces heterogeneity in lipid membranes: potential implication for its diverse biological action.

BACKGROUND: The nonsteroidal anti-inflammatory drug (NSAID), indomethacin (Indo), has a large number of divergent biological effects, the molecular mechanism(s) for which have yet to be fully elucidated. Interestingly, Indo is highly amphiphilic and associates strongly with lipid membranes, which influence localization, structure and function of membrane-associating proteins and actively regulate cell signaling events. Thus, it is possible that Indo regulates diverse cell functions by altering micro-environments within the membrane. Here we explored the effect of Indo on the nature of the segregated domains in a mixed model membrane composed of dipalmitoyl phosphatidyl-choline (di16:0 PC, or DPPC) and dioleoyl phosphatidyl-choline (di18:1 PC or DOPC) and cholesterol that mimics biomembranes. METHODOLOGY/PRINCIPAL FINDINGS: Using a series of fluorescent probes in a fluorescence resonance energy transfer (FRET) study, we found that Indo induced separation between gel domains and fluid domains in the mixed model membrane, possibly by enhancing the formation of gel-phase domains. This effect originated from the ability of Indo to specifically target the ordered domains in the mixed membrane. These findings were further confirmed by measuring the ability of Indo to affect the fluidity-dependent fluorescence quenching and the level of detergent resistance of membranes. CONCLUSION/SIGNIFICANCE: Because the tested lipids are the main lipid constituents in cell membranes, the observed formation of gel phase domains induced by Indo potentially occurs in biomembranes. This marked Indo-induced change in phase behavior potentially alters membrane protein functions, which contribute to the wide variety of biological activities of Indo and other NSAIDs.

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.

Exposure to nonsteroidal anti-inflammatory drugs and weight loss and hospitalization in non-small cell lung cancer patients

Background. Cancer cachexia is a common syndrome complex in cancer, occurring in nearly 80% of patients with advanced cancer and responsible for at least 20% of all cancer deaths. Cachexia is due to increased resting energy expenditure, increased production of inflammatory mediators, and changes in lipid and protein metabolism. Non-steroidal anti-inflammatory drugs (NSAIDs), by virtue of their anti-inflammatory properties, are possibly protective against cancer-related cachexia. Since cachexia is also associated with increased hospitalizations, this outcome may also show improvement with NSAID exposure. ^ Design. In this retrospective study, computerized records from 700 non-small cell lung cancer patients (NSCLC) were reviewed, and 487 (69.57%) were included in the final analyses. Exclusion criteria were severe chronic obstructive pulmonary disease, significant peripheral edema, class III or IV congestive heart failure, liver failure, other reasons for weight loss, or use of research or anabolic medications. Information on medication history, body weight and hospitalizations was collected from one year pre-diagnosis until three years post-diagnosis. Exposure to NSAIDs was defined if a patient had a history of being treated with NSAIDs for at least 50% of any given year in the observation period. We used t-test and chi-square tests for statistical analyses. ^ Results. Neither the proportion of patients with cachexia (p=0.27) nor the number of hospitalizations (p=0.74) differed among those with a history of NSAID use (n=92) and those without (n=395). ^ Conclusions. In this study, NSAID exposure was not significantly associated with weight loss or hospital admissions in patients with NSCLC. Further studies may be needed to confirm these observations.^

A case comparison study of dietary factors and risk of colorectal polyps

Little is known about the etiology of colorectal adenomatous polyps, although they are generally considered to be precursor lesions to colorectal carcinoma. To investigate the associations of colorectal adenomatous polyps with dietary intake of calcium, total fat and fiber, a case comparison study was conducted among 98 persons who had first occurrences of adenomatous polyps and 408 persons who did not have colorectal polyps.^ The study population comprised Black, White and Hispanic males and females ages 35 to 80 inclusive, who underwent a sigmoidoscopy or total colonoscopy at collaborating clinics in the Texas Medical Center at Houston between September 1991 and November 1992, and met the eligibility criteria. Case participants were those who had a first-time diagnosis of adenomatous polyps. Comparison participants were individuals who underwent the same diagnostic procedure as the cases and met the same eligibility criteria but had no colorectal polyps. A food frequency questionnaire was administered by interview to obtain information about diet during the 28 days preceding the interview.^ Dietary intake of total fiber was inversely associated with risk of adenomatous polyps. An increment of 15 gm/day in energy-adjusted intake of fiber was associated with a relative odds of 0.39 with a 95% confidence interval of 0.20 to 0.79, after adjustment for age, sex, ethnicity, body mass index, cigarette smoking, family history of colorectal cancer and intake of nonsteroidal anti-inflammatory drugs. No association between dietary intake of total fat and risk of adenomatous polyps was observed. When total fat was analyzed as percent of energy, an increment of 15.3% in intake was associated with a relative odds of 0.98 with a 95% confidence interval of 0.53 to 1.80. However, few persons in the study group had intakes below 25% of energy from total fat. An inverse association was observed between energy-adjusted intake of dietary calcium and risk of adenomatous polyps, but this was not statistically significant; an increment of 638 mg/day was associated with a relative odds of 0.77 with a 95% confidence interval of 0.41 to 1.38. Intake of calcium did not appear to strongly modify the association between intake of fat and risk of adenomatous polyps, perhaps because the study group included few people with calcium intake below 400 mg/day.^ These results support the idea that dietary fiber decreases risk of adenomatous polyps. Further studies are needed on the association of dietary calcium and fat with risk of colorectal adenomatous polyps in populations where individuals vary widely in intake of these nutrients. ^