Intracellular ferriprotoporphyrin IX is a lytic agent

Area of Science:

• Hematology
• Biochemistry
• Toxicology

Background:

• Hemoglobin denaturation can lead to the release of ferriprotoporphyrin IX (ferriheme, FP).
• The interaction between ferriheme and drugs like chloroquine is of toxicological interest.

Purpose of the Study:

• To investigate the intracellular release of ferriheme (FP) from human erythrocytes induced by menadione.
• To determine the binding characteristics of chloroquine to menadione-induced intracellular FP.
• To assess the hemolytic activity associated with intracellular FP and its modulation by antimalarial drugs.

Main Methods:

• Human erythrocytes were treated with menadione to induce oxidative denaturation of hemoglobin.
• 14C-chloroquine binding assays were performed to quantify chloroquine affinity for treated erythrocytes.
• Hemolysis assays were conducted to evaluate the lytic effects of menadione and FP, with and without chloroquine, mefloquine, and quinine.

Main Results:

• Menadione-treated erythrocytes exhibited high-affinity binding of 14C-chloroquine (Kd = 10(-6)M), indicating intracellular FP release.
• Tween 80 confirmed the intracellular localization of menadione-induced FP, as it did not inhibit chloroquine binding.
• Menadione and extracellular FP induced similar hemolytic responses, potentiated by chloroquine and inhibited by mefloquine and quinine.

Conclusions:

• Menadione treatment effectively releases ferriheme (FP) intracellularly within erythrocytes.
• The released intracellular FP binds chloroquine with high affinity and contributes to red blood cell lysis.
• The findings suggest that intracellular FP shares similar toxicological properties with extracellular FP.