Laboratory of Clinical Investigation, National Institute on Aging, National Institutes of Health, Baltimore, MD, USA.
Department of Nutritional Sciences, Oklahoma State University, Stillwater, OK, USA.
Cell Death Dis. 2020 Dec 9;11(12):1044. doi: 10.1038/s41419-020-03261-8.
Cannabinoid 1 receptor (CB1R) expression is upregulated in the liver with viral hepatitis, cirrhosis, and both alcoholic and non-alcoholic fatty liver disease (FLD), whereas its expression is muted under usual physiological conditions. Inhibiting CB1R has been shown to be beneficial in preserving hepatic function in FLD but it is unclear if inhibiting CB1R during an inflammatory response to an acute hepatic injury, such as toxin-induced injury, would also be beneficial. We found that intrinsic CB1R in hepatocytes regulated liver inflammation-related gene transcription. We tested if nullification of hepatocyte-specific CB1R (hCNR1) in mice protects against concanavalin A (Con A)-induced liver injury. We looked for evidence of liver damage and markers of inflammation in response to Con A by measuring liver enzyme levels and proinflammatory cytokines (e.g., TNF-α, IL-1β, IL-6, IL-17) in serum collected from hCNR1 and control mice. We observed a shift to the right in the dose-response curve for liver injury and inflammation in hCNR1 mice. We also found less inflammatory cell infiltration and focal necrosis in livers of hCNR1 mice compared to controls, resulting from downregulated apoptotic markers. This anti-apoptotic mechanism results from increased activation of nuclear factor kappa B (NF-κB), especially cAMP-dependent cannabinoid signaling and membrane-bound TNF-α, via downregulated TNF-α receptor 2 (TNFR2) transcription levels. Collectively, these findings provide insight into involvement of CB1R in the pathogenesis of acute liver injury.
大麻素 1 型受体(CB1R)在病毒性肝炎、肝硬化和酒精性及非酒精性脂肪性肝病(FLD)的肝脏中表达上调,而在正常生理条件下其表达受到抑制。抑制 CB1R 已被证明在 FLD 中对维持肝功能有益,但尚不清楚在急性肝损伤(如毒素诱导损伤)的炎症反应期间抑制 CB1R 是否也有益。我们发现肝细胞内源性 CB1R 调节肝脏炎症相关基因转录。我们测试了在小鼠中敲除肝细胞特异性 CB1R(hCNR1)是否可以预防伴刀豆球蛋白 A(Con A)诱导的肝损伤。我们通过测量从 hCNR1 和对照小鼠收集的血清中的肝酶水平和促炎细胞因子(例如 TNF-α、IL-1β、IL-6、IL-17)来寻找对 Con A 反应的肝损伤和炎症的证据。我们观察到 hCNR1 小鼠的肝损伤和炎症的剂量反应曲线向右偏移。与对照组相比,hCNR1 小鼠的肝脏炎症细胞浸润和局灶性坏死减少,这归因于凋亡标志物下调。这种抗凋亡机制是通过下调 TNF-α 受体 2(TNFR2)转录水平,导致核因子 kappa B(NF-κB)特别是 cAMP 依赖性大麻素信号和膜结合 TNF-α的激活增加。总之,这些发现提供了对 CB1R 在急性肝损伤发病机制中的作用的深入了解。