The effect of 5-aminolevulinic acid on canine peripheral blood mononuclear cells.

5-aminolevulinic acid (ALA) is a natural amino acid and a product of the first heme synthesis pathway in mitochondria. Its immunomodulatory effects have garnered recent attention for their potential application to cancer, inflammation, and autoimmune diseases in humans. A supplement containing ALA is now available in Japan to enhance ATP synthesis via mitochondrial activity. However, how ALA affects canine immunity is unclear. Here we studied the effects of ALA on peripheral blood mononuclear cells (PBMCs) from healthy dogs in vitro. Heme oxygenase-1 (HO-1) protein was expressed in Madin-Darby canine kidney (MDCK) cells and PBMCs treated with ALA and ferrous sodium citrate (SFC), which showed that ALA works in dogs as well as humans. ALA also induced concanavalin A (ConA)-stimulated PBMCs to produce significantly more interferon-gamma (IFN-γ). Next-generation RNA sequencing (RNA-seq) revealed that ALA enhanced T cell immunity among Th1, Th2, and Th17 subsets, especially the IL-17 signaling pathway. We then confirmed that ALA promoted interleukin (IL)- 17A production in ConA-stimulated PBMCs. Together, these findings indicate that ALA promotes heme synthesis in mitochondria and enhances ConA-induced T cell immune responses in canine PBMCs.