Probiotic-associated metabolites (PAMs) decrease silica-induced cytotoxicity and proinflammatory cytokine release in macrophages in vitro. PAMs must pass the intestinal epithelium (mimicked by Caco-2 cells) to produce the observed effects in vivo. SCFA, which are known to pass into circulation, were evaluated without Caco-2 cells, but the results showed they were not main contributors. As the first step toward establishing a co-culture model to investigate other active PAMs, the growth conditions of Caco-2 cells were optimized.