Usefulness of oral administration of lipopolysaccharide for disease prevention through the induction of priming in macrophages.

Many publications show that macrophages are closely involved in etiology of diseases, such as cancer, diabetes, arteriosclerosis, and Alzheimer's disease. Recent studies show that waste products (e.g. dead cells, denatured proteins, oxidized lipids, and advanced glycation end-products) are the real causative agents of lifestyle-associated diseases. From the standpoint of health maintenance, macrophages eliminate foreign objects and waste products from an animal's body and appear to be quite important for maintaining homeostasis. There are two stages of activation of macrophages: one is priming and the other is the triggering stage with cytokine secretion. The priming stage of macrophages is an ostensibly functional stage without characteristic morphological changes and secretion of cytokines, but it functionally promotes clearance of waste products. In this review, we discuss the usefulness of oral administration of lipopolysaccharide (LPS) as a macrophage-priming agent for prevention/treatment of several diseases, including cancer. Moreover, the oral administration of LPS is safe. These observations suggest that LPS may be considered a vitamin-like substance with therapeutic properties.