A GPR55 Barrier Study Did Not Demonstrate THC-Induced Blood–Brain Barrier Injury
A study of GPR55 activation changed experimental barrier measurements, but its test substance was lysophosphatidylinositol, not THC. A cannabinoid-related receptor label cannot substitute for the actual exposure.
Cells and animals answered different questions
Researchers examined rat brain microvascular endothelial cells using calcium, electrical-resistance and junction-related measurements. Animal experiments also assessed barrier permeability with a dye method. These were preclinical endpoints, not measurements of cognitive injury in cannabis users.
The effects were pathway-specific
Lysophosphatidylinositol increased cellular calcium responses and altered barrier-related measures. Antagonist and channel-blocking experiments supported selected mechanistic steps. Repeated application also produced tachyphylaxis, so initial responsiveness did not necessarily describe later stimulation.
Relevance requires an exposure bridge
GPR55 has complex pharmacology and is often discussed alongside cannabinoid targets. That context does not establish that THC at a real-world concentration causes the same response. Transient permeability changes also are not automatically permanent structural damage or a diagnosis of brain disease. The study supplies a receptor-pathway hypothesis, while leaving cannabis formulation, concentration, duration and human functional consequences to separate research.
Related analysis: Cannabis Tolerance Claims: Questions to Ask Before Relying on Expert Testimony.
Primary research
GPR55-mediated effects on brain microvascular endothelial cells and the blood-brain barrier. Neuroscience (2019). DOI: 10.1016/j.neuroscience.2019.06.039.
