Cannabinoid receptor type 1 antagonist inhibits progression of obesity-associated nonalcoholic steatohepatitis in a mouse model by remodulating immune system disturbances

Scope: This study investigated whether AM251, a cannabinoid receptor type 1 (CB1) antagonist, ameliorates hepatic levels of metabolic abnormalities and inflammatory responses in a murine nonalcoholic steatohepatitis (NASH) model via reversal of disturbances in the immune system. Methods and Results: Fifteen-week-old male obesedb/dbmice were randomly assigned to the following two groups: no treatment and treatment with AM251 at 5 mg/kg for 15 days. C57BL/6J-Lean mice were utilized as the control group. Plasma parameters, liver histopathology, and hepatic status were measured. For the in vitro study, macrophage-derived RAW264.7 cells were cultured with AM251 or CB1 small interfering RNA (siRNA) before challenge with arachidonyl-2 '-chloroethylamide (ACEA) or a high concentration of fatty acids (HFFAs). Thedb/dbmice exhibited an increase in CB1 levels, lipid droplet accumulation, mitogen-activated protein kinase-related inflammatory responses, and macrophage and neutrophil infiltration in the liver tissues. Flow cytometry analysis revealed an elevation in macrophages and T helper cells, plus a decrease in natural killer T cells and regulatory T cells in the liver tissues of thedb/dbmice; treatment with 5 mg/kg AM251 reversed these changes. Moreover, in vitro experiments revealed that administration of 3.3 mu M AM251 or CB1 siRNA prevented 1 mM HFFA- and 1 mu M ACEA-induced inflammatory cytokine protein expression in the RAW264.7 cells. Conclusion: These findings suggested that a blockade caused by CB1 reduced obesity-associated NASH progression via correction of immune system dysregulations and elevated inflammatory responses in the liver tissues.