Downregulation of PCYT2 by increased portal pressure safeguards liver regeneration after partial hepatectomy.

Rationale: Metabolic remodeling occurs during partial hepatectomy (PHx)-induced liver regeneration. Phospholipid remodeling during this process and its subsequent impact on liver regeneration remain unknown. The remnant liver's ability to defend against injury is also essential for normal liver regeneration, although the underlying mechanisms remain unclear.

Methods

Phospholipidomics was performed to describe phospholipid remodeling after 70% PHx. Phosphate cytidylyltransferase 2, ethanolamine (PCYT2) was overexpressed in hepatocytes using adeno-associated virus under the thyroxine-binding globulin promoter. An ex vivo liver perfusion system was used to regulate portal pressure. GalNAc-conjugated PEG-PCL nano-particles (NPs) were developed to deliver the PCYT2 inhibitor, meclizine.

Results

We found a significant decrease in a series of phosphatidylethanolamine (PE) levels at 1 day after 70% PHx. PCYT2, an enzyme for PE synthesis, was downregulated by PHx. Higher portal pressure-induced shear stress is an early event after PHx. As a target gene of hepatocyte nuclear factor 4α, PCYT2 levels were decreased by higher portal pressure. Hepatocyte-specific PCYT2 overexpression aggravated liver damage after PHx by increasing reactive oxygen species levels, lipid peroxidation, and mitochondrial fragmentation. We observed higher hepatic PCYT2 levels in middle-aged mice than in young mice. PCYT2 inhibition by meclizine facilitates liver regeneration in middle-aged mice. Meclizine is also a blocker of the histamine H1 receptor, a membrane receptor. Therefore, we used NPs to deliver meclizine into cells to better target PCYT2 and prevent potential side effects. NP-meclizine improved liver regeneration in middle-aged mice, demonstrating higher therapeutic efficacy than carrier-free meclizine.

Conclusions

Decreased PCYT2 levels and PE content due to increased portal pressure protect hepatocytes from PHx-induced injury. Inhibiting PCYT2 with NP-meclizine promoted normal liver regeneration in middle-aged mice.