Minor cannabinoids show promise in controlling brain inflammation

Neurological disorders affect over 40% of the global population and are driven in part by microglia-mediated neuroinflammation that depends on calcium (Ca²⁺) signaling. Cannabis-derived compounds (CBx) modulate microglial activation and cytokine release, however, the impact of understudied CBx on Ca2+ signaling pathways controlling inflammatory responses remains largely unknown. Here, we systematically examined the effects of over 22 CBx on key microglial Ca2+ signaling pathways. Using pharmacological modulators, live-cell Ca2+ imaging, immunofluorescence, and cytokine and nitric oxide assays, we characterized store-operated Ca2+ entry (SOCE) and purinergic signaling dynamics, inflammatory responses, and CBx effects in human (HMC3) and mouse (BV2) microglia under resting and activated conditions. We found that microglial SOCE in both mouse and human cell line models were potently inhibited by the same three, minor, acidic CBx - CBGA, CBGVA, CBDVA. In BV2, at least seven CBx (CBD, CBG, CBDVA, CBDA, CBGA, CBDV, CBNM) inhibited LPS-induced proinflammatory secretion of nitric oxide (NO) and TNF-α. Despite the profound SOCE inhibition in HMC3, CBx failed to inhibit downstream proinflammatory cytokine release in TNF-α - or IL-1β-activated cells. We found major differences in Ca2+ signaling between the models, including purinergic pathways, where HMC3 cells appear to express a more limited purinome with more subdued signaling responses. Purinergic Ca2+ responses to ATP in BV2, especially the delayed phase, was suppressed by at least eight CBx, and most prominently by CBDVA, CBGVA and CBGA. We observed partial, indirect involvement of P2X4, P2 X7, and P2Y13 purinoceptors and propose additional Ca2+ signaling targets mediating the anti-inflammatory properties of CBx. Additionally, we documented the pro-inflammatory potential of CBCA and CBNA that is likely facilitated by their ability to mobilize intracellular Ca2+ levels in both, human and mouse microglia. These findings provide a comprehensive qualitative and quantitative assessment of how individual CBx influence main Ca2+ signaling pathways in microglia and identify novel anti-inflammatory candidates with therapeutic potential for targeting microglial activation. Microglia are specialized immune cells that protect the brain from infection, injury, and other threats. To perform these functions, microglia rely on calcium signals inside the cell, which help control when and how strong they become activated. While this response is important for maintaining brain health, excessive activation of microglia can contribute to chronic inflammation and has been linked to several neurological disorders.Compounds found in cannabis have long been recognized for their anti-inflammatory properties, but their effects in calcium signaling in microglia are not well understood. In this study, we examined how 22 cannabis-derived compounds influence calcium signaling in human and mouse microglial cells. We focused on two important signaling systems involved in microglial activation: calcium entry pathways and ATP-mediated cell communication. We found that individual cannabis-derived compounds produced markedly different effects on microglial calcium signaling. Several understudied compounds strongly reduced calcium entry in both human and mouse microglia. However, these changes translated into reduced inflammatory responses only in mouse microglia, highlighting important differences between human and mouse models.Our findings further suggest that ATP-mediated signaling may play a greater role in regulating microglial inflammation than calcium entry alone. Together, these results show that cannabis-derived compounds can modify key signaling pathways in microglia, but their anti-inflammatory effects depend on the specific cellular mechanisms involved. This work improves our understanding of how phytocannabinoids influence brain immune cells and may help guide future studies aimed at controlling neuroinflammation.