12/15-Lipoxygenase-Derived Electrophilic Lipid Modifications in Phagocytic Macrophages

Macrophages remove apoptotic cells via phagocytosis,
also known
as efferocytosis, during inflammation to maintain tissue homeostasis.
This process is accompanied by various metabolic changes in macrophages
including the production of lipid metabolites by fatty acid oxygenases.
Among these, highly reactive metabolites, called lipid-derived electrophiles
(LDEs), modify cysteines and other nucleophilic amino acids in intracellular
proteins. However, the landscape and functions of the modifications
by these electrophilic metabolites have been poorly characterized.
In this study, we used activity-based protein profiling to quantitatively
profile the cysteine reactivity landscape and identify the potential
targets of endogenous LDE modification during efferocytosis in mouse
peritoneal macrophages. Using this methodology, we identified multiple
cysteine sites that are highly likely to be modified by LDEs generated
by 12/15-lipoxygenase (12/15-LOX), an efferocytosis-related fatty
acid oxygenase that is highly expressed in peritoneal macrophages.
Among these, actin-depolymerizing protein Cofilin-1 was found to be
a target of 12/15-LOX-derived LDEs. In vitro Cofilin-1 activity was
attenuated by 12/15-LOX-derived LDEs, and intracellular actin stabilization
and efferocytosis were substantially enhanced by the LDE treatment
of mouse peritoneal macrophages. These results highlighted the role
of intracellular LDE modification during efferocytosis in macrophages.