Disruption of adenosine 2A receptor exacerbates NAFLD through increasing inflammatory responses and SREBP1c activity

Adenosine 2A receptor (A_2A R) exerts protective roles in endotoxin- and/or ischemia-induced tissue damage. However, the role for A_2A R in nonalcoholic fatty liver disease (NAFLD) remains largely unknown. We sought to examine the effects of global and/or myeloid cell-specific A_2A R disruption on the aspects of obesity-associated NAFLD and to elucidate the underlying mechanisms. Global and/or myeloid cell-specific A_2A R-disrupted mice and control mice were fed a high-fat diet (HFD) to induce NAFLD. In addition, bone marrow-derived macrophages and primary mouse hepatocytes were examined for inflammatory and metabolic responses. Upon feeding an HFD, both global A_2A R-disrupted mice and myeloid cell-specific A_2A R-defcient mice revealed increased severity of HFD-induced hepatic steatosis and inflammation compared with their respective control mice. In in vitro experiments, A_2A R-deficient macrophages exhibited increased proinflammatory responses, and enhanced fat deposition of wild-type primary hepatocytes in macrophage-hepatocyte cocultures. In primary hepatocytes, A_2A R deficiency increased the proinflammatory responses and enhanced the effect of palmitate on stimulating fat deposition. Moreover, A_2A R deficiency significantly increased the abundance of sterol regulatory element-binding protein 1c (SREBP1c) in livers of fasted mice and in hepatocytes upon nutrient deprivation. In the absence of A_2A R, SREBP1c transcription activity was significantly increased in mouse hepatocytes.

Taken together, our results demonstrate that disruption of A_2A R in both macrophage and hepatocytes accounts for increased severity of NAFLD, likely through increasing inflammation and through elevating lipogenic events due to stimulation of SREBP1c expression and transcription activity. (Hepatology 2018;68:48-61).