Biomembrane Perturbation Induced by Xenobiotics in Model and Living Systems

This work reports on studies concerning with the interaction of important environmental contaminants, such as organotins, with model and biological systems. Organometallic compounds are synthesized and used for applications in industry and agriculture. Moreover, some organometallics can be directly formed in the environment by the action of microbial agents on inorganic precursors. Because of their wide diffusion and importance in a variety of anthropogenic activities, these compounds are present in significant concentrations in many ecosystems. Among the organometallic compounds, organotins have found many uses, e.g. as PVC stabilizers, industrial catalysts, biocides, surface disinfectants, marine antifouling agents, etc. For their ubiquitous presence in the environment, recent work has been devoted to the study of their effects on biological systems. It is known that organotin toxicity is related to the number and the nature of organic substituents on Sn(IV). In fact, toxicity decreases from tri-to mono-organotins and in the order ethyl>methyl>propyl>phenyl>hexyl>octyl for the type of organic ligand [1]. The evidence that organotin compounds interact with soluble [2,3] and membrane proteins [4,5] does not exclude the possibility that their toxicity could be related to their hydrophobicity, at least partially. Nowadays, organotins are considered among the most hazardous organic contaminants of marine and freshwater ecosystems [1,5]. Due to their lipid solubility, organotins undergo bioaccumulation and concentration in sediments, possibly causing accumulation in the food chain, which may also be important in the contamination of the human diet. The first reactions of organisms to toxic compounds take place at the molecular and cellular level, before the effects become visible at higher levels of biological organization [5]. It is recognized that the toxicity of organotin derivatives, in particular alkyltins, is dependent on their solubility and incorporation inside cells. The differences in their intracellular distribution is thought to be due to their degree of lipid solubility and/or their affinity with lipids and proteins of different intracellular compartments.