Drug-induced Phospholipidosis-Pathological Aspects and Its Prediction

Drug-induced phospholipidosis (PLDsis) is an excessive accumulation of polar phospholipids in cells or tissues/organs caused by xenobiotics. Numerous drugs and chemicals are capable of inducing the storage disorder in animals and humans; however, despite their diverse pharmacological activities, each of these drugs shares common physicochemical properties: a hydrophobic aromatic ring structure on the molecule and a hydrophilic side chain with a charged cationic amine group and therefore are in the group of cationic amphiphilic drugs. In affected cells the appearance of membrane-bound inclusions, primarily lysosomal in origin, with a lamellar structure (lamellar bodies) is a definitive morphologic hallmark. Massive accumulations can occur in animal tissues such as the lung with little effect on organ function. The inducing drug also accumulates in association with the excess phospholipid. Although these alterations are generally reversible after cessation of drug treatment, PLDsis is of regulatory concern and an issue for drug safety for pharmaceutical companies. Thus, the assessment of potential target organ dysfunction and the identification of clinical biomarkers are important objectives for new drug development. Recent advances in biotechnology such as metabonomics and toxicogenomics have been providing novel tools to elucidate the mechanisms of PLDsis and to establish biomarkers for screening tests in the preclinical stages and for monitoring in the clinical phases in addition to conventional approaches such as morphology (lamellar bodies) and biochemical methods including assays of specific metabolites and phospholipase inhibition. (J Toxicol Pathol 2008; 21: 9-24)