Constitutive KIT Activity and IL-6 Production in Mast Cells Alters Levels of Reactive Oxygen Species (ROS) and the Scavenger Protein DJ-1 in Mastocytosis

Abstract

RationaleMastocytosis is characterized by hyperproliferation of mast cells (MCs) which is mostly associated with activating mutations in KIT, the stem cell factor (SCF) receptor. DJ-1, a scavenger protein of ROS in MCs and other tissue cells, has been linked to oxidative damage in atopic dermatitis, cancer and neurogenerative diseases. We examined whether DJ-1 is dysregulated in indolent systemic mastocytosis (ISM) and the impact of KIT mutations on DJ-1 and ROS levels.MethodsSera was collected from patients with ISM with tryptase ranging from 1-1000 ng/ml. P815 cells were injected i.v. into DBA/2 mice to induce SM. DJ-1 levels were measured by ELISA and ROS by a fluorescent assay.ResultsPatients with ISM showed increased ROS and diminished DJ-1 levels in serum. DJ-1 but not ROS levels reverted towards normal values in patients with advanced ISM. Long-term exposure to SCF or expression of constitutively active mutant KIT in human MC cultures enhanced DJ-1 degradation. In contrast, IL-6, a cytokine which increases in serum with disease severity, induced DJ-1 transcription and promoted ROS release. Injection of mastocytoma cells harboring mutant KIT into mice reproduced the effects of human disease with biphasic changes in serum DJ-1 and increasing elevations in ROS and IL-6 as disease progressed. These effects and disease severity were reversed with anti-IL-6 receptor blocking antibody.ConclusionsThe link between IL-6 production in the context of aberrant KIT signaling to dysregulation of DJ-1 and ROS homeostasis suggests that IL-6 contributes to redox imbalance and worsening of ISM and provides potential targets for therapeutic intervention. RationaleMastocytosis is characterized by hyperproliferation of mast cells (MCs) which is mostly associated with activating mutations in KIT, the stem cell factor (SCF) receptor. DJ-1, a scavenger protein of ROS in MCs and other tissue cells, has been linked to oxidative damage in atopic dermatitis, cancer and neurogenerative diseases. We examined whether DJ-1 is dysregulated in indolent systemic mastocytosis (ISM) and the impact of KIT mutations on DJ-1 and ROS levels. Mastocytosis is characterized by hyperproliferation of mast cells (MCs) which is mostly associated with activating mutations in KIT, the stem cell factor (SCF) receptor. DJ-1, a scavenger protein of ROS in MCs and other tissue cells, has been linked to oxidative damage in atopic dermatitis, cancer and neurogenerative diseases. We examined whether DJ-1 is dysregulated in indolent systemic mastocytosis (ISM) and the impact of KIT mutations on DJ-1 and ROS levels. MethodsSera was collected from patients with ISM with tryptase ranging from 1-1000 ng/ml. P815 cells were injected i.v. into DBA/2 mice to induce SM. DJ-1 levels were measured by ELISA and ROS by a fluorescent assay. Sera was collected from patients with ISM with tryptase ranging from 1-1000 ng/ml. P815 cells were injected i.v. into DBA/2 mice to induce SM. DJ-1 levels were measured by ELISA and ROS by a fluorescent assay. ResultsPatients with ISM showed increased ROS and diminished DJ-1 levels in serum. DJ-1 but not ROS levels reverted towards normal values in patients with advanced ISM. Long-term exposure to SCF or expression of constitutively active mutant KIT in human MC cultures enhanced DJ-1 degradation. In contrast, IL-6, a cytokine which increases in serum with disease severity, induced DJ-1 transcription and promoted ROS release. Injection of mastocytoma cells harboring mutant KIT into mice reproduced the effects of human disease with biphasic changes in serum DJ-1 and increasing elevations in ROS and IL-6 as disease progressed. These effects and disease severity were reversed with anti-IL-6 receptor blocking antibody. Patients with ISM showed increased ROS and diminished DJ-1 levels in serum. DJ-1 but not ROS levels reverted towards normal values in patients with advanced ISM. Long-term exposure to SCF or expression of constitutively active mutant KIT in human MC cultures enhanced DJ-1 degradation. In contrast, IL-6, a cytokine which increases in serum with disease severity, induced DJ-1 transcription and promoted ROS release. Injection of mastocytoma cells harboring mutant KIT into mice reproduced the effects of human disease with biphasic changes in serum DJ-1 and increasing elevations in ROS and IL-6 as disease progressed. These effects and disease severity were reversed with anti-IL-6 receptor blocking antibody. ConclusionsThe link between IL-6 production in the context of aberrant KIT signaling to dysregulation of DJ-1 and ROS homeostasis suggests that IL-6 contributes to redox imbalance and worsening of ISM and provides potential targets for therapeutic intervention. The link between IL-6 production in the context of aberrant KIT signaling to dysregulation of DJ-1 and ROS homeostasis suggests that IL-6 contributes to redox imbalance and worsening of ISM and provides potential targets for therapeutic intervention.