Caffeine and its main targets of colorectal cancer

Figure 2 Modulation of intracellular calcium homeostasis by caffeine. Caffeine can modulate intracellular calcium homeostasis of inexcitable cells in two different ways. One way is by inhibiting the inositol 1,4,5-trisphosphate receptor through which Ca²⁺ released from the endoplasmic reticulum can be decreased, which results in a decrease in intracellular calcium levels. However, caffeine can increase the intracellular calcium levels by activating the ryanodine receptor, which causes an increase in Ca²⁺ being released from the endoplasmic reticulum. In this case, the store-operated Ca²⁺ entry, which was initiated from the depletion of Ca²⁺ from the endoplasmic reticulum can be activated and then result in an increase in extracellular Ca²⁺ getting into the intracellular compartment. IP3: 1,4,5-trisphosphate; IP3R: 1,4,5-trisphosphate receptor; ER: Endoplasmic reticulum; RyR: Ryanodine receptor; SOCE: Store-operated Ca²+ entry.