Tyrosol attenuates NASH features by reprogramming the hepatic immune milieu

Area of Science:

• Hepatology and immunology
• Molecular and cellular biology
• Pharmacology

Background:

• Nonalcoholic steatohepatitis (NASH) is a progressive liver disease with no approved therapies.
• Plant-derived phenolic compounds, such as tyrosol (Tyr) from olive oil, exhibit potential hepatoprotective properties.
• Understanding the immunomodulatory effects of Tyr is crucial for developing novel NASH treatments.

Purpose of the Study:

• To investigate the therapeutic potential and underlying mechanisms of tyrosol (Tyr) in nonalcoholic steatohepatitis (NASH).
• To evaluate the impact of Tyr on the hepatic immune microenvironment and extrahepatic manifestations in NASH models.
• To assess Tyr's effects on cellular processes including fatty acid accumulation, inflammation, and immune cell differentiation.

Main Methods:

• In vitro: Co-culture of HepG2 cells (treated with fatty acids) with THP1-derived M1 macrophages and LX2 cells.
• In vivo: A mouse model of NASH induced by a high-fat, high-fructose diet combined with carbon tetrachloride (CCl4) administration.
• Analysis of hepatic steatosis, fibrosis, inflammatory markers, immune cell populations (macrophages, T cells), oxidative stress markers (NOX1), and behavioral changes.

Main Results:

• Tyrosol (Tyr) reduced fatty acid accumulation in HepG2 cells and modulated LX2 cell activation and macrophage differentiation in vitro.
• In vivo, Tyr treatment decreased hepatic steatosis, fibrosis, inflammation (reduced inflammatory foci, CD86+ macrophages, CD4+ T cells), and prooxidant enzyme NOX1 expression.
• Tyr significantly increased regulatory T cells (Treg, CD4+ FoxP3+) and attenuated fatigue and anxiety behaviors in NASH mice.

Conclusions:

• Tyrosol (Tyr) effectively ameliorates NASH-related steatosis, fibrosis, oxidative stress, and inflammation.
• Tyr demonstrates a beneficial effect on the hepatic immune infiltrate, promoting a shift towards regulatory immune responses.
• The multifaceted mechanisms of Tyr suggest its potential development as a therapeutic agent for nonalcoholic steatohepatitis (NASH).