Sweeping Up Dying Cells during Tissue Injury

Chimeric efferocytic receptors improve apoptotic cell clearance and alleviate inflammation

Our bodies turn over billions of cells daily via apoptosis and are in turn cleared by phagocytes via the process of "efferocytosis." Defects in efferocytosis are now linked to various inflammatory diseases. Here, we designed a strategy to boost efferocytosis, denoted "chimeric receptor for efferocytosis" (CHEF). We fused a specific signaling domain within the cytoplasmic adapter protein ELMO1 to the extracellular phosphatidylserine recognition domains of the efferocytic receptors BAI1 or TIM4, generating BELMO and TELMO, respectively. CHEF-expressing phagocytes display a striking increase in efferocytosis. In mouse models of inflammation, BELMO expression attenuates colitis, hepatotoxicity, and nephrotoxicity. In mechanistic studies, BELMO increases ER-resident enzymes and chaperones to overcome protein-folding-associated toxicity, which was further validated in a model of ER-stress-induced renal ischemia-reperfusion injury. Finally, TELMO introduction after onset of kidney injury significantly reduced fibrosis. Collectively, these data advance a concept of chimeric efferocytic receptors to boost efferocytosis and dampen inflammation.

The Pathophysiology of Sepsis-Associated AKI

Sepsis-associated AKI is a life-threatening complication that is associated with high morbidity and mortality in patients who are critically ill. Although it is clear early supportive interventions in sepsis reduce mortality, it is less clear that they prevent or ameliorate sepsis-associated AKI. This is likely because specific mechanisms underlying AKI attributable to sepsis are not fully understood. Understanding these mechanisms will form the foundation for the development of strategies for early diagnosis and treatment of sepsis-associated AKI. Here, we summarize recent laboratory and clinical studies, focusing on critical factors in the pathophysiology of sepsis-associated AKI: microcirculatory dysfunction, inflammation, NOD-like receptor protein 3 inflammasome, microRNAs, extracellular vesicles, autophagy and efferocytosis, inflammatory reflex pathway, vitamin D, and metabolic reprogramming. Lastly, identifying these molecular targets and defining clinical subphenotypes will permit precision approaches in the prevention and treatment of sepsis-associated AKI.