Fig. 6: Proposed hypothetical mechanism of CBD-induced cell death.

TNF increases TRPA1 protein, which is located in intracellular compartments. CBD activates TRPA1 and Ca²⁺ is released into the cytosol. Elevations in cytosolic Ca²⁺ are reduced through uptake into mitochondria. In addition, increased cytosolic Ca²⁺ might enhance the activity of organic cation transporters (OCT) which might mediate the uptake of the fluorescent dye PoPo3. Additionally, OCT might mediate the uptake of CBD itself. By binding to VDAC1, CBD increases Ca²⁺ flux through the outer mitochondrial membrane. Ca²⁺ is then taken up into the matrix by the mitochondrial Ca²⁺ uniporter (MCU) and, if mitochondria are depolarized, by the Na⁺/Ca²⁺ exchanger (NCLX), which operates in reverse mode under these conditions. Ca²⁺ overload occurs, the mitochondrial permeability transition pore (mPTP) assembles and cell death occurs.