Suppression of inflammation by tumor-derived exosomes: a kind of natural liposome packaged with multifunctional proteins

Exosomes are small-membrane vesicles secreted by hematopoietic and malignant epithelial cells as well as trophoblasts. The composition of cancerous exosomes has been proven to play pivotal roles in the maintenance of the microenvironment that is beneficial for the progression of cancer, such as Fas-ligand-triggered lymphocyte apoptosis. We supposed that the immunosuppressive effect of cancerous exosomes might be helpful in the treatment of diseases characterized by overactivation of the immune system and subsequent tissue injury. The aim of this study was to evaluate the protective effect of tumor-derived exosomes in the mice model of lipopolysaccharide (LPS)-induced inflammation. Tetrazolium (MTT) and DNA electrophoresis were used to measure the cytotoxicity of exosomes on lymphocytes. Pathologic observation of tissue sections, serologic analysis of aspartate aminotransferase/alanine aminotransferase (AST/ALT), and urinary analysis of protein were used to assess the protection effect of exosomes in LPS-induced multiorgan damage. In vitro outcomes of MTT and DNA electrophoresis showed the cytotoxicity of exosomes on lymphocytes. Together with the alleviation of organ damages evaluated by urine protein, serum AST/ALT, and pathologic analysis, we confirmed the possibility that pretreatment of mice with exosomes, produced by H22 hepatic tumor cells, resulted in protection against LPS-induced tissue damage, which is caused by overactivation of the immune system and inflammation response. This therapeutic strategy will raise an interesting way to search new therapeutics in pairs of diseases with complementarities in etiology and pathology, namely, a strategy of taking advantage of the mutual complementarities between diseases.