Cellular copper overload mediates senescence-associated secretory phenotype induction in BV2 microglia following lead and copper exposure

Elevated levels of lead and copper dyshomeostasis are significant risk factors for cognitive dysfunction in older adults. During brain aging, microglia transition to a senescence-associated secretory phenotype (SASP), thereby contributing to cognitive decline. However, whether lead affects cognitive function by promoting microglial SASP transition remains unclear. In this study, we exposed BV2 microglial cells to lead or co-exposure to lead and copper to simulate severe copper dyshomeostasis. Lead exposure promoted the transition of BV2 cells to a SASP, characterized by enlarged cell bodies, increased M1 activation, and enhanced release of inflammatory cytokines. This promotion was more enhanced in the presence of copper and was attributed to intracellular copper overload. Mechanistically, copper overload triggered reactive oxygen species (ROS) production and mitochondrial DNA (mtDNA) release, activating the cGAS-STING-NLRP3 axis, driving M1 microglial activation, and sustaining neuroinflammation. Copper chelation following lead or lead and copper co-exposure reduced ROS, mtDNA release, and neuroinflammatory cytokine production. Our findings suggest that cellular copper overload, responsible for activating mtDNA-cGAS-STING-NLRP3 axis, plays a significant role in microglial transition following lead exposure.