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

Abstract

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.

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

“…We have speculated that bile acid and indomethacin can form a toxic mixed micelle in the gut lumen, which is rendered less toxic in the presence of PC. This concept is supported by powerful NMR/MD techniques, which demonstrated that these two classes of amphipathic molecules (bile acids and NSAIDs) have a natural affinity to associate into mixed micelles that are further transformed in the presence of PC (3,11,16). This preassociation of PC and indomethacin may be even more important under in vivo conditions in the biliary tract system and/or intestinal lumen where indomethacin would have access to bile acid, both free and conjugated forms.…”

“…Thus we contend that a significant amount of unconjugated indomethacin may be available in the lower gut to associate with bile acids and form potentially toxic mixed micelles. Previously, we reported that cultured gastric (AGS) and intestinal (IEC-6) cells were injured by short-term incubation with indomethacin in the presence of bile acid (deoxycholate), and the concept that this greater cytotoxicity is due to the formation of toxic mixed micelles (23) is supported by physicochemical analysis [nuclear magnetic resonance (NMR)] and computational [molecular dynamics (MD)] modeling (3,11,16). This combination may resemble the in vivo situation, where bile acids and indomethacin are both secreted into bile via enterohepatic cycling.…”

“…The basis for this new formulation is that the NSAID can be noncovalently associated with the natural surfactant phosphatidylcholine (PC) (11) to reduce the associated gastrointestinal toxicity. In preclinical trials, PC-indomethacin has equivalent efficacy to inhibit pain and inflammation as traditional indomethacin, but with significantly less gastrointestinal bleeding and intestinal adhesions (9).…”

The Molecular Structure of Human Red Blood Cell Membranes From Highly Oriented, Solid Supported Multi-Lamellar Membranes

“…In particular, non-steroidal anti-inflammatory drugs (NSAID's) have been shown to disturb bilayer structures in native and model membranes 68,69 . Aspirin is the most common NSAID and is known to interact with membranes 15,68 . Aspirin strongly perturbs model membrane structure in a concentration dependent manner and also influences human erythrocyte shape 70 .…”

Role of Phospholipids in Protection of the GI Mucosa

“…Revisiting the Sippy diet approach, our lab demonstrated the importance of phospholipids in milk in ulcer protection and healing (overriding the effects of increased gastric acid secretion) [29], and also demonstrated that synthetic and soy lecithin-derived (PC) could protect against damaging agents or conditions (e.g., stress) [10]. This work led to reports by our lab and those of other investigators that NSAIDs can induce surface injury to the GI mucosa by chemically associating with PC present in mucus and cell membranes [30,31], thereby compromising these important barriers. These findings ultimately led to the development of a family of soy-derived PC-NSAIDs that have been demonstrated to have reduced GI toxicity in rodents [30] and in a number of clinical endoscopic trials, while fully maintaining the therapeutic activity of the NSAIDs [32,33].…”