A new laboratory study from Brazil suggests that cannabigerol, a non-intoxicating cannabis compound increasingly sold as a dietary supplement, has an inconsistent effect on brain immune cells that depends heavily on dose. Conducted by a team led by Júlia Maiara dos Santos at the University of São Paulo and published in Toxicology, the work finds that low doses leave microglia largely intact while higher concentrations cause cellular stress and DNA damage in a cell-free test. The strongest concentration tested also killed many cells, while mid-range doses did not reliably quell an induced inflammatory response.
Cannabigerol (CBG) sits in the family of phytocannabinoids produced by Cannabis sativa. Unlike the main intoxicating component, tetrahydrocannabinol (THC), CBG does not cause intoxication or impair coordination, properties that have helped fuel interest in its role as a supplement and potential therapy. Earlier human studies have hinted at mood- and memory-related benefits; for example, a placebo-controlled trial reported that 20 milligrams of hemp-derived cannabigerol modestly reduced anxiety and stress and slightly improved verbal memory recall compared with a placebo.
The new in vitro work focused on whether CBG can protect brain tissue from neuroinflammation, a sustained immune response within the brain and spinal cord linked to neurodegenerative conditions. In microglia, the brain’s resident immune cells, prolonged activation can release harmful reactive chemicals and inflammatory proteins that damage nearby neurons. Previous experiments had suggested anti-inflammatory effects, including a 2018 cell-culture study showing protection for mouse motor neurons and a 2023 study noting reduced inflammatory chemical release in a microglial line after exposure to bacterial toxins.
In the current study, published in Toxicology, researchers designed a dish-based assessment to probe safety across a range of doses and to test whether non-toxic concentrations could dampen the inflammasome pathway in microglia without harming DNA. The team grew mouse-derived microglial cells and exposed them to five concentrations of purified CBG (0.01, 0.1, 1, 10 and 100 micromolar) for 24 hours, with appropriate untreated and solvent controls. They then evaluated cell survival, morphology, oxidative stress markers and inflammatory signals.
The investigators also performed genetic and DNA integrity tests. A cell-free assay exposed purified double-stranded DNA to CBG to gauge direct DNA-breaking potential, while a separate comet assay used human white blood cells to assess DNA damage in living cells. These results helped determine whether any observed cellular effects might reflect direct genetic toxicity rather than protective anti-inflammatory action.
When the microglial cells were challenged to simulate inflammation, the researchers primed the cultures with bacterial lipopolysaccharide, then applied CBG and finally activated the inflammasome with nigericin. A parallel group received a known inflammasome blocker for comparison. The team then re-assessed cell survival, reactive oxygen species, nitric oxide and messenger RNA for Caspase-1, a key enzyme in the inflammatory cascade.
In the 24-hour safety assessment, CBG up to 10 micromolar appeared well tolerated, with no measurable cell loss. Non-toxic doses modestly reduced nitric oxide levels to about 80 percent of untreated controls in unstimulated cells. By contrast, the highest concentration, 100 micromolar, reduced cell survival to roughly one-fifth of untreated levels and triggered marked chemical stress, elevating nitric oxide to around four times and reactive oxygen species to about ten times the baseline. The microglia also lost their characteristic branched shape and adopted a rounded, activated appearance at this dose.
The genetic toxicity tests yielded contrasting results. In the cell-free DNA test, all concentrations above 0.01 micromolar caused detectable strand breaks, with the 10 and 100 micromolar doses producing damage indices roughly two to three times greater than controls. For this reason, the authors excluded the 100 micromolar dose from inflammasome experiments conducted later.
However, in the comet assay using intact human white blood cells, DNA damage differences up to 10 micromolar were not statistically significant. The researchers suggest that living cells may shield their DNA through antioxidant defenses, metabolism, and DNA repair mechanisms, even though CBG can chemically break bare DNA in a test-tube setting.
When the two-step inflammasome challenge was applied, CBG at doses up to 10 micromolar helped partially restore microglial survival to levels comparable with a selective inflammasome blocker, albeit without dampening the rise in reactive oxygen species. Some doses actually increased nitric oxide production, though the overall inflammatory response in terms of cell viability still improved with CBG at certain concentrations.
Notably, at the 0.01 micromolar concentration — the one devoid of bare-DNA breaks — CBG unexpectedly raised Caspase-1 mRNA to about 375 percent of untreated levels, whereas the inflammasome blocker suppressed Caspase-1 expression under the same conditions. The authors interpret these mixed results as evidence that CBG does not act as a straightforward anti-inflammatory agent in microglia. They propose that moderate concentrations might activate protective nuclear receptors that limit nitric oxide production, while trace amounts could prime Caspase-1 transcription and very high doses may disrupt mitochondria and amplify oxidative stress.
The study’s external expert, Daniele Piomelli, a professor at the University of California, Irvine, said: “This intriguing in vitro study, conducted in a single cell line, encourages us to consider cannabigerol as a potential player in the neuroinflammation space, though the modest effect sizes and narrow therapeutic window suggest that considerable work remains before any translational conclusions can be drawn.”
The authors stress that a narrow therapeutic window exists, with 10 micromolar the only dose that reduced nitric oxide during inflammation and the same dose that also caused DNA breakage in the cell-free test. They caution that translating dish-based results to humans is difficult, noting that the immortalised mouse cell line differs from primary microglia and that plastic-well experiments cannot capture the complexities of a living system where digestion, metabolism, the blood proteins and the blood-brain barrier influence brain exposure to cannabinoids.
Limitations also include the measurement methods: the survival assay reflects mitochondrial enzyme activity rather than direct cell death, and Caspase-1 expression was assessed only at the mRNA level at a single low concentration. The authors call for future work using primary brain cell cultures, three-dimensional tissue models, animal studies and more detailed mutation analyses to determine whether these cellular shifts translate into real-world risks or benefits.
The study, “Could cannabigerol protect against neuroinflammation? Insights from an in vitro microglial study,” was authored by Júlia Maiara dos Santos, Amanda Kolinski Machado, Djenifer Leticia Ulrich Bick, Michele Rorato Sagrillo, Elaine Aparecida Del Bel, Alencar Kolinski Machado, and Antonio Cardozo dos Santos.
