Pulmonary inflammation caused by chitosan microparticles.

Chitosan is a cationic biopolymer derived from chitin with potential therapeutic applications such as controlled drug delivery to mucosal-epithelial surfaces in the body. Inhaled chitosan microparticles (CM), for example, are of potential interest in pulmonary pharmacotherapy. In this context, we examine some basic reactions of lung tissue to CM. Inhaled CM (2-10 mg/kg of particles) induce dose-dependent proinflammatory effects in rat lungs; these effects are documented in increases in bronchoalveolar lavage fluid protein (BALF-P) and lactate dehydrogenase activity (BALF-LDH) and increases in lung tissue myeloperoxidase (MPO) activity and leukocyte migration. Overall, the biochemical parameters (i.e., average of BALF-P, BALF-DH, and MPO) indicate that the inflammation response is 1.8-fold greater than controls without CM; the same inflammation parameters, however, are 1.9-fold lower with CM compared with the proinflammatory effects of lipopolysaccharide (LPS). Cytological examination of BALF shows a large infiltration of polymorphonuclear neutrophils to lung tissue: more than a sixfold increase in this population of inflammatory cells, after inhalation of CM relative to air inhalation controls. Thus, the results indicate that inhaled CM can have significant proinflammatory effects on lung tissues; these effects are mild relative to LPS but need to be considered in the context of therapeutic applications via pulmonary delivery if such concentrations of CM are used.