In the female-specific systemic lupus erythematosus (SLE) model, activation of Gi protein-coupled receptor, GPR109A, in spinal microglia of female MRL lupus-prone mice (a well-established mouse model of human SLE) could attenuate thermal hyperalgesia via suppressing p38 activity and IL-18 production [91]. Here, HCAR2 is linked to systemic lupus erythematosus.