Palmitate lipotoxicity is closely associated with the fatty acid-albumin complexes in BV-2 microglia

Abstract

Palmitic acid (PA) is considered a major contributor to the inflammation in many metabolic diseases; however, this role has been questioned recently for the complicated procedures in preparing PA-bovine serum albumin (BSA) complex. This study is aimed to evaluate the effect of PA-BSA complexing methods on cell viability and inflammatory responses of BV-2 cells. Three commercially available BSA brands and two types of solvents were compared for their effects on the expression of inflammatory cytokines. Three commonly used proportions of PA-BSA were tested for cell viability and inflammatory responses. We found that all the three types of BSA were proinflammatory. Both ethanol and isopropanol dampened inflammation except that 1% isopropanol treatment increased the IL-1β level by 26%. When reducing the BSA content in PA-BSA solutions from 3:1 to 5:1, a marked increase in cell viability (11%) was seen. To our surprise, reducing BSA content in PA-BSA solutions from 5:1 to 10:1 decreased cell viability by 11%. The 5:1 group exhibited the lowest inflammatory profile. Either PA-BSA or BSA alone increased the entry of LPS to the cytosol, which further caused pyroptosis. In summary, we found 5:1 (PA:BSA) to be the best binding ratio for studying inflammation in BV-2 microglia. The presence of LPS in the cytosol in the context of BSA might be the reason for confounding results from palmitate studies.