Introduction

Cirrhosis is a world-widely prevalent disease with a high global burden: approximately one million deaths worldwide are attributed to cirrhosis each year, and cirrhosis is the 11th leading cause of death¹. Fibrosis and cirrhosis develop after a long period of persistent inflammation, which can be caused by a variety of factors such as hepatitis B or C virus, obesity, high alcohol consumption, autoimmune diseases, cholestatic diseases, and so on². However, current clinical treatments for cirrhosis are mainly focused on improving complications such as portal hypertension. Although some patients with early-stage fibrosis may benefit from treatment to remove the cause of fibrosis, there is currently no effective treatment for advanced fibrosis or cirrhosis itself. Bortezomib (B) is a reversible inhibitor of the chymotrypsin-like site of the 20S proteolytic core within the 26S proteasome and is currently mainly used to treat multiple myeloma³. B has been shown to improve fibrosis of the skin, lungs and kidneys^{4, 5}.

Aims & Methods

We aimed to evaluate the efficacy of B to improve advanced parenchymal and biliary liver fibrosis in rats and potential underlying mechanisms. Advanced liver fibrosis was induced in 8-week-old rats by intraperitoneal injection of thioacetamide (TAA) for 12 weeks or bile duct ligation (BDL) for 3 weeks. Rats with advanced fibrosis were divided into 2 groups: intravenous injection of B at 0.1 mg/kg in PBS (B) or injection of PBS alone three times a week for 3 weeks (fibrotic controls, FC). Age matched rats with no intervention served as normal controls (NC). Portal vein pressure was measured after anesthesia before sacrifice. Liver and renal function parameters were determined to evaluate liver inflammation and potential toxicity of B. HE and Masson staining were used to evaluate liver inflammation and fibrosis. Liver collagen was quantified via hydroxyproline content. Fibrosis-related gene and protein expression were determined by RT-qPCR and Western blot. Liver samples were subjected to NGS analysis. LX-2 human hepatic stellate cells and LO2 human hepatocytes were cultured with different concentrations of B for 24 h. Cell apoptosis was quantified via flow cytometry.

Results

B treatment induced a decreased portal vein pressure (mmHg), though the p-values did not yet reach statistical significance in the two fibrosis models (B vs FC: TAA, 6.86 ± 0.76 vs 11.42 ± 2.37; BDL, 9.49 ± 2.92 vs 18.57 ± 16.83). On the other hand, B treatment decreased ALT and AST in both fibrosis models, while serum creatinine and bilirubin levels remained unchanged, indicating a beneficial effect of B on liver function with no apparent liver or renal toxicity. Morphometry and biochemical quantification showed a significant amelioration of fibrosis, as evidenced by liver hydroxyproline content and Masson-positive area. Gene set enrichment analysis indicated the upregulation of pro-inflammation-related Ugt2b7 and anti-proliferation-related gene Marvled1; while the key regulator in ubiquitin-mediated proteolysis and cell cycle pathways Cdc20 decreased after treatment with B, so did the Cdc20 protein. B-treated hepatic stellate cells but not hepatocytes showed prominent apoptosis.

Conclusion

Bortezomib induces activated hepatic stellate cell apoptosis and has a prominent antifibrotic potential in parenchymal and biliary fibrosis.

References

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