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Updated: Apr 25, 2026
Depletion and Reconstitution of Macrophages in Mice
Published on: August 1, 2012
Macrophage MERTK restrains GRAMD1A-driven mitochondrial oxysterol trafficking to limit colitis
Juanhan Liu1, Peizhao Liu1, Yangguang Li1
1Research Institute of General Surgery, Jinling Hospital, Affiliated Hospital of Medical School, Nanjing University, Nanjing, 210002, PR China; Department of General Surgery, BenQ Medical Center, Nanjing Medical University, Nanjing, 210002, PR China.
Abstract:
Impaired macrophage efferocytosis drives chronic inflammation, yet the underlying immunometabolic mechanisms remain poorly defined. In this study, we identify that impaired macrophage efferocytosis triggers excessive mitochondrial oxysterol accumulation, which drives mitochondrial ROS-associated inflammation in Crohn's disease (CD). We report an inverse correlation between CD activity and the abundance of MERTK+ macrophages. Mechanistically, MERTK loss enhances cholesterol biosynthesis in the endoplasmic reticulum (ER) and stabilizes the cholesterol transporter GRAMD1A. This promotes excessive cholesterol trafficking from the ER to mitochondria. Within mitochondria, this cholesterol is metabolized into specific oxysterols that, unlike other mevalonate pathway metabolites, directly impair the electron transport chain. This impairment triggers a burst of mitochondrial reactive oxygen species (ROS). Collectively, our findings define a pathogenic axis linking defective efferocytosis, dysregulated cholesterol metabolism, and oxysterol-induced mitochondrial damage.
Insights
Defective macrophage efferocytosis in Crohn's disease leads to excess mitochondrial oxysterols, causing inflammation. Restoring MERTK+ macrophage function may offer therapeutic potential for this chronic inflammatory condition.
Area of Science:
- Immunometabolism
- Cellular Biology
- Gastroenterology
Background:
- Macrophage efferocytosis is crucial for resolving inflammation.
- Defects in efferocytosis are implicated in chronic inflammatory diseases like Crohn's disease (CD).
- The immunometabolic drivers of impaired efferocytosis in CD are not well understood.
Purpose of the Study:
- To elucidate the immunometabolic mechanisms linking impaired macrophage efferocytosis to inflammation in Crohn's disease.
- To identify key molecular players in this pathogenic pathway.
Main Methods:
- Correlation analysis of CD activity and MERTK+ macrophage abundance.
- Investigation of cholesterol biosynthesis and trafficking pathways in macrophages.
- Assessment of mitochondrial function and reactive oxygen species (ROS) production.
Main Results:
- An inverse correlation was observed between Crohn's disease activity and MERTK+ macrophage levels.
- MERTK loss was found to enhance cholesterol biosynthesis and stabilize GRAMD1A, increasing ER-to-mitochondria cholesterol transport.
- Accumulated mitochondrial oxysterols impaired the electron transport chain, leading to increased mitochondrial ROS production.
Conclusions:
- Impaired macrophage efferocytosis in CD leads to excessive mitochondrial oxysterol accumulation.
- This oxysterol accumulation drives mitochondrial ROS-associated inflammation.
- A pathogenic axis involving defective efferocytosis, cholesterol dysregulation, and mitochondrial damage is defined.
