Activation of EP4 alleviates AKI-to-CKD transition through inducing CPT2-mediated lipophagy in renal macrophages

Abstract

Acute kidney injury (AKI) is a common clinical syndrome with complex pathogenesis, characterized by a rapid decline in kidney function in the short term. Worse still, the incomplete recovery from AKI increases the risk of progression to chronic kidney disease (CKD). However, the pathogenesis and underlying mechanism remain largely unknown. Macrophages play an important role during kidney injury and tissue repair, but its role in AKI-to-CKD transition remains elusive. Herein, single nucleus RNA sequencing (snRNA-Seq) and flow cytometry validations showed that E-type prostaglandin receptor 4 (EP4) was selectively activated in renal macrophages, rather than proximal tubules, in ischemia-reperfusion injury (IRI)-induced AKI-to-CKD transition mouse model. EP4 inhibition aggravated AKI-to-CKD transition, while EP4 activation impeded the progression of AKI to CKD though regulating macrophage polarization. Mechanistically, network pharmacological analysis and subsequent experimental verifications revealed that the activated EP4 inhibited macrophage polarization through inducing Carnitine palmitoyltransferase 2 (CPT2)-mediated lipophagy in macrophages. Further, CPT2 inhibition abrogated the protective effect of EP4 on AKI-to-CKD transition. Taken together, our findings demonstrate that EP4-CPT2 signaling-mediated lipophagy in macrophages plays a pivotal role in the transition of AKI to CKD and targeting EP4-CPT2 axis could serve as a promising therapeutic approach for retarding AKI and its progression to CKD.

Proteomic characterisation of perhexiline treatment on THP-1 M1 macrophage differentiation

“…Using standard protocols to differentiate the human THP-1 cell line into macrophages ( 27 ), we have shown that the addition of PHX to M1 macrophage cultures resulted in more M1-like macrophages. Our findings are consistent with a recent report that PHX could shift murine bone marrow-derived M2 macrophages to an M1 macrophage profile ( 24 ) and that PHX delivery in vivo can suppress M2 polarisation in a mouse model of chronic kidney disease ( 50 ). However, our proteomic analysis of PHX treated M1 macrophages showed that in the treated cells, key proteins related to inflammation were downregulated.…”

“…Finally, it would also be valuable to know if the proteomic changes reported here are replicated in vivo by studying different macrophage-mediated in vivo disease models. PHX has been reported to influence macrophage function in mouse models of sepsis and kidney disease ( 26 , 50 ).…”