The transcriptional response of Kupffer Cells to fat and cholesterol is non-canonical and distinct from bone-marrow derived macrophages

Abstract

Abstract Diets high in fat and cholesterol can cause hepatic lipid accumulation and inflammation known as non-alcoholic steatohepatitis (NASH). Liver macrophages putatively drive disease by responding to PAMPS/DAMPS and producing pro-inflammatory cytokines. However, recent studies show that there are two principle subsets of macrophages in a NASH liver: Tissue-resident macrophages that are embryonically derived (Kupffer Cells; KCs) and infiltrating macrophages that are adult-derived from bone marrow (IMs). Furthermore, the role that each subset plays in disease pathogenesis is unclear. We FACS sorted the KC (F4/80hiCD11blow) and IM subsets (F4/80lowCD11bhi) from mice fed a high fat/cholesterol (HFHC) diet as well as those from healthy controls. RNA was extracted and gene expression was analyzed using RNA sequencing techniques. HFHC mice had a prominent IM population that was absent in controls. IMs were the primary producers of cytokines and chemokines. KCs did not upregulate pro-inflammatory cytokines in response to dietary fat and cholesterol, yet upstream analysis revealed that lipid metabolism and bile acid signaling pathways were more active than IMs. 3,617 genes were differentially expressed KCs, while 3,421 genes were differentially expressed in IMs. Genes known to be expressed by restorative macrophages were enriched in KCs (CD163, MARCO, TIMD4, MMP12, MMP13), while pro-inflammatory and M1 genes predominated in the IM population (TNF, SPP1, CXCL2, CCL2, S100A8). In conclusion, bone marrow-derived macrophages have a transcriptional profile consistent with the previously reported role of liver macrophages in NASH pathogenesis. However, Kupffer Cells respond to dietary stress in a non-canonical manner.