2A). Consistent with these data, alcohol-fed WT mice exposed to JWH-133

showed a lesser increase in liver/body weight ratio and in hepatic triglyceride accumulation (Fig. 2B). These findings demonstrate that endogenous and exogenous activation of CB2 receptors reduces the development of alcohol-induced fatty liver. Considering the predominant expression of CB2 receptors in immune cells, culture experiments were designed to evaluate the role of macrophage CB2 receptors in the regulation of macrophage polarization and hepatocyte steatogenesis. In a first series of experiments, we characterized the impact of CB2 Kupffer cells isolated from WT or CB2−/− mice and in the macrophage cell Carfilzomib purchase line, RAW264.7. M1 and M2 polarization was induced by incubation with LPS and IL-4, respectively. In keeping

with in vivo findings, CB2−/− Kupffer cells exhibited an enhanced M1 response to LPS, compared to WT Kupffer cells, as shown by a greater induction of TNF-α, IL-1β, and CCL4 induction and a tendency to increase IL-6 expression (Fig. 3A). In addition, the alternative response of CB2−/− Kupffer cells to IL-4 was reduced, as demonstrated by the lower induction of Mrc2, C-type lectin domain family 7 member A (Clec7A) and a tendency to decrease Mgl1 (Fig. 3B). In contrast, JWH-133 reduced M1 gene expression (Fig. 4A) and corresponding cytokine secretion (Fig. 4B) in RAW264.7 cells, without affecting the alternative M2 response elicited click here by IL-4 (Fig. 4C). There was no effect of JWH-133 on TLR4 mRNA expression (data not shown), suggesting that CB2 receptor activation does reduce the sensitivity of macrophages to LPS. Overall, these data indicate that activation of macrophage CB2 receptors reduces the proinflammatory M1 response to LPS and contributes to the alternative M2 response to IL-4, in keeping with results obtained from in vivo experiments. mafosfamide We next evaluated the impact of CB2 receptor activation in macrophages on fat accumulation in hepatocytes. To that aim, CM was collected from LPS-exposed RAW264.7 cells incubated in the absence or presence

of JWH-133. Hepatocytes cultured in the presence of the CM obtained from LPS-exposed RAW264.7 cells displayed enhanced lipid accumulation, as compared to control, as illustrated by Oil Red O staining quantification (Fig. 4D). Fat accumulation was reduced by 74% in hepatocytes exposed to CM prepared from JWH-133-treated, LPS-exposed RAW264.7 macrophages (Fig. 4D). LPS added directly to AML-12 cells had no effect on fat accumulation (Fig. 4D). Moreover, the addition of JWH-133 to AML-12 cells had no protective effects against steatosis elicited by the CM of LPS-treated RAW264.7 cells, therefore ruling out direct effects of the compounds on hepatocytes (Fig. 4D). Altogether, these data demonstrate that macrophage CB2 receptors reduce fat accumulation in hepatocytes via paracrine effects.