Chloroquine Interference with Hemoglobin Endocytic Trafficking Suppresses Adaptive Heme and Iron Homeostasis in Macrophages: The Paradox of an Antimalarial Agent

Abstract

The CD163 scavenger receptor pathway for Hb:Hp complexes is an essential mechanism of protection against the toxicity of extracellular hemoglobin (Hb), which can accumulate in the vasculature and within tissues during hemolysis. Chloroquine is a lysosomotropic agent, which has been extensively used as an antimalarial drug in the past, before parasite resistance started to limit its efficacy in most parts of the world. More recent use of chloroquine is related to its immunomodulatory activity in patients with autoimmune diseases, which may also involve hemolytic disease components. In this study we examined the effects of chloroquine on the human Hb clearance pathway. For this purpose we developed a new mass-spectrometry-based method to specifically quantify intracellular Hb peptides within the endosomal-lysosomal compartment by single reaction monitoring (SRM). We found that chloroquine exposure impairs trafficking of Hb:Hp complexes through the endosomal-lysosomal compartment after internalization by CD163. Relative quantification of intracellular Hb peptides by SRM confirmed that chloroquine blocked cellular Hb:Hp catabolism. This effect suppressed the cellular heme-oxygenase-1 (HO-1) response and shifted macrophage iron homeostasis towards inappropriately high expression of the transferrin receptor with concurrent inhibition of ferroportin expression. A functional deficiency of Hb detoxification and heme-iron recycling may therefore be an adverse consequence of chloroquine treatment during hemolysis.

Expression of Concern: The haptoglobin beta subunit sequesters HMGB1 toxicity in sterile and infectious inflammation

“…It might be a long journey to transform the experimental therapeutic results in animal models to bedside in patients. However, there is substantial clinical success in the use of plasma-purified haptoglobin to treat several inflammatory diseases [51, 52] in conjunction with extracorporeal detoxification, massive blood transfusions, and attenuation of thermal injury and hemoglobin-induced kidney toxicity (reviewed in [53]). It would thus be important to assess results of clinical trials with haptoglobin β protein to treat severe systemic inflammatory conditions caused by excessive systemic accumulation of HMGB1.…”

Haptoglobin, hemopexin, and related defense pathways—basic science, clinical perspectives, and drug development

“…Cumulatively, inflammation and glucocorticoids appear to enhance tolerance against extracellular Hb. In contrast, other drugs such as the antimalarial chloroquine can negatively affect Hb/heme detoxification in macrophages and potentially enhance free Hb toxicity (Schaer et al, 2013b ). The potential clinical relevance of these observations—for example, for the treatment of hemolytic anemias—remains to be resolved.…”

Alteration of redox status by commonly used antimalarial drugs in the north-western region of Nigeria

“…9,16 However, above the therapeutic dose, which may consistently induce ROS generation not only in the red blood cells but other lineages like macrophages and neutrophils, the ultimate results could be fatally characterized by molecular and cellular damages around the microenvironment and other distant vital tissues. [17][18][19] Overall, these biochemical events could further amplify the intensity of an oxidative burst leading to fatal consequences on macromolecules in both the host and parasite. Phagocytes respond to particulate or soluble stimuli by the oxidative burst associated with increased production of ROS.…”