Microglial reactivity and neuroinflammation-driven in motivational behaviors are regulated by Orai1 channels

Microglia are the primary immune cells of the central nervous system (CNS) and act as the first line of defense against disease and injury in the brain by releasing inflammatory molecules and clearing dead cells. Microglial functions are tightly regulated by dynamic transitions between homeostatic and reactive cell states, which can either exacerbate or resolve CNS inflammation. While Ca2+ signaling is known to regulate specific microglial functions such as phagocytosis, its role in controlling these critical state transitions remains poorly understood. Here, we identify the Orai1 Ca2+ channel as a key regulator of microglial plasticity and inflammation-induced behavioral dysfunction in mice. Transcriptomic and metabolomic analyses revealed that conditional Orai1 deletion in microglia suppressed proinflammatory programs linked to immunity and inflammation. Conversely, Orai1 knockout increased expression of growth factors and anti-inflammatory mediators, including BDNF, ARG1, and the mitochondrial metabolite, itaconate. In a model of CNS inflammation induced by peripheral inflammatory challenge with lipopolysaccharide (LPS), Orai1 deficiency attenuated microglial and astrocyte reactivity and reduced hippocampal levels of the cytokines IL-1ß and IL-6. Consistent with these cellular changes, microglial Orai1 knockout mice were protected against LPS-induced changes in motivational, depression-like behaviors, including impairments in reward-seeking and escape responses. These findings establish Orai1 channels as central regulators of microglial cell plasticity and neuroimmune responses, highlighting their therapeutic potential for neuroinflammatory disorders. Overall design: Primary microglia from Orai1fl/fl or Orai1fl/fl Cx3CR1-cre/ERT2 were cultured from neonates or FACS purified from adult animals and treated with Tg+PDBu, LPS, or vehicle control for 6h or 24h.