Heme as a metabolic cell-fate switch.

Heme availability shapes mitochondrial function, redox balance, and innate immune signaling. Recent studies reveal threshold-dependent heme states that predispose cells to cuproptosis, ferroptosis, apoptosis, pyroptosis, or PANoptosis. Viewing heme as a metabolic rheostat provides a unifying framework for interpreting regulated cell death across cancer, infection, and metabolic disease.