Longstanding Transcriptional Activation of APOA1 and PON1 in Human Hepatocytes by CRISPR/dCas9 Technology: Transcriptomic Profile and Crosstalk with Endothelial Cells

Apolipoprotein A1 (APOA1) and paraoxonase 1 (PON1) are key proteins of high-density lipoproteins (HDL). The aim of the present study was to obtain and characterize an in vitro model for endogenous APOA1 and PON1 longstanding upregulation in hepatocytes that can be further used to decipher the mechanisms of their protective action. Cultured human hepatocytes (HuH-7 cell line) were transfected with CRISPR/dCas9 activation plasmids targeting APOA1/PON1 genes. Following selection with specific antibiotics, RNA sequencing was used for the transcriptomic characterization of the transfected hepatocytes. The functionality of the secreted APOA1/PON1 was evaluated as the capacity of the conditioned medium (CM) from transfected HuH-7 to modulate the oxidative and inflammatory stress in TNFα-activated primary human umbilical endothelial cells (HUVEC). The results showed that: (1) a robust, longstanding upregulation (46 days) of endogenous APOA1/PON1 was obtained after CRISPR/dCas9 transfection and antibiotics selection; (2) APOA1/PON1 upregulation led to a modified transcriptomic profile and increased the expression of several antioxidant genes in transfected hepatocytes as demonstrated by RNAseq analysis; (3) secreted APOA1/PON1 were functional as demonstrated by the CM ability to reduce the levels of reactive oxygen species and inflammatory markers (VCAM-1, MCP-1) in TNFα-activated HUVEC. In conclusion, we achieved an experimental model of successful longstanding upregulation of endogenous APOA1 and PON1 in human hepatocytes. The targeted proteins are secreted in a functional form and can be used for deciphering their complex mechanism of protective action in various pathological conditions.