Delta-9-tetrahydrocannabinol alleviates inflammation by modulating immune responses in LPS-induced murine...

Δ⁹-Tetrahydrocannabinol (THC), the primary psychoactive component of cannabis, has been reported to modulate immune responses; however, its effects on complex innate immune signaling pathways and inflammation remain incompletely understood. Here, we investigated the immunomodulatory effects of THC on lipopolysaccharide (LPS)-induced inflammation across cellular and in vivo models.

We integrated transcriptomic, cellular, and in vivo approaches to characterize the effects of THC on innate immune activation. Human THP-1 monocytic cells were treated with THC in the presence or absence of LPS, followed by transcriptomic and gene expression analyses to evaluate inflammatory, type I interferon, unfolded protein response (UPR), and autophagy pathways. Findings were validated in primary human monocytes by assessing immune activation markers. The effects of chronic THC exposure were further evaluated in a murine model of systemic inflammation by examining splenic myeloid and T-cell activation. RNA sequencing of brain tissue was performed to assess the effects of THC on neuroinflammatory and neuronal pathways.

THC induced a stress-adaptive transcriptional program in THP-1 cells, characterized by upregulation of genes associated with the UPR and autophagy pathways. In contrast, THC markedly suppressed LPS-induced type I interferon-stimulated genes (ISGs) and pro-inflammatory cytokines, including IL-1β and TNF-α. In primary human monocytes, THC significantly reduced the expression of activation markers CD80, CD83, and CD209. Consistent with these findings, chronic THC exposure attenuated the activation of splenic myeloid and T cells in mice subjected to systemic inflammation. Brain transcriptomic analysis further demonstrated reduced expression of neuroinflammatory pathways following THC exposure, accompanied by enrichment of pathways associated with neurogenesis and synaptic plasticity.

Our findings demonstrate that THC exerts broad immunomodulatory effects characterized by suppression of inflammatory and type I interferon responses while promoting cellular stress-adaptation pathways. These effects were observed across human monocytic cells, primary monocytes, and peripheral immune populations in vivo, and were accompanied by reduced neuroinflammatory signaling and increased neuronal plasticity-associated pathways in the brain. Together, these findings provide mechanistic insight into the immunomodulatory actions of THC and support further investigation of cannabinoid signaling as a potential regulator of chronic inflammatory and neuroimmune disorders.