Department of Cancer and Cell Biology, University of Cincinnati College of Medicine, Cincinnati, OH, USA.
Hepatology. 2011 May;53(5):1618-28. doi: 10.1002/hep.24239.
Previous studies demonstrated that targeted deletion of the Ron receptor tyrosine kinase (TK) domain in mice leads to marked hepatocyte protection in a well-characterized model of lipopolysaccharide (LPS)-induced acute liver failure in D-galactosamine (GalN)-sensitized mice. Hepatocyte protection in TK-/- mice was observed despite paradoxically elevated serum levels of tumor necrosis factor alpha (TNF-α). To understand the role of Ron in the liver, purified populations of Kupffer cells and hepatocytes from wildtype (TK+/+) and TK-/- mice were studied. Utilizing quantitative reverse-transcription polymerase chain reaction (RT-PCR), we demonstrated that Ron is expressed in these cell types. Moreover, we also recapitulated the protected hepatocyte phenotype and exaggerated cytokine production observed in the TK-/- mice in vivo through the use of purified cultured cells ex vivo. We show that isolated TK-/- Kupffer cells produce increased levels of TNF-α and select cytokines compared to TK+/+ cells following LPS stimulation. We also show that conditioned media from LPS-treated TK-/- Kupffer cells was more toxic to hepatocytes than control media, suggesting the exaggerated levels of cytokines produced from the TK-/- Kupffer cells are detrimental to wildtype hepatocytes. In addition, we observed that TK-/- hepatocytes were more resistant to cell death compared to TK+/+ hepatocytes, suggesting that Ron functions in both the epithelial and inflammatory cell compartments to regulate acute liver injury. These findings were confirmed in vivo in mice with hepatocyte and macrophage cell-type-specific conditional Ron deletions. Mice with Ron loss selectively in hepatocytes exhibited less liver damage and increased survival compared to mice with Ron loss in macrophages.
We dissected cell-type-specific roles for Ron such that this receptor modulates cytokine production from Kupffer cells and inhibits hepatocyte survival in response to injury.
先前的研究表明，在半乳糖胺（GalN）敏化的脂多糖（LPS）诱导的急性肝衰竭的典型模型中，靶向敲除 Ron 受体酪氨酸激酶（TK）结构域的小鼠，其肝细胞受到显著保护。尽管 TNF-α 血清水平升高，但 TK-/- 小鼠的肝细胞保护仍然存在。为了了解 Ron 在肝脏中的作用，我们研究了野生型（TK+/+）和 TK-/- 小鼠的纯化库普弗细胞和肝细胞。利用定量逆转录聚合酶链反应（RT-PCR），我们证明 Ron 在这些细胞类型中表达。此外，我们还通过体外培养细胞再现了体内观察到的 TK-/- 小鼠受保护的肝细胞表型和过度的细胞因子产生。我们表明，与 TK+/+ 细胞相比，分离的 TK-/- 库普弗细胞在 LPS 刺激后产生更高水平的 TNF-α 和选择细胞因子。我们还表明，LPS 处理的 TK-/- 库普弗细胞的条件培养基比对照培养基对肝细胞更具毒性，这表明 TK-/- 库普弗细胞产生的细胞因子水平过高对野生型肝细胞有害。此外，我们观察到与 TK+/+ 肝细胞相比，TK-/- 肝细胞对细胞死亡更具抗性，这表明 Ron 在上皮细胞和炎症细胞区室中都起作用，以调节急性肝损伤。这些发现通过具有肝细胞和巨噬细胞细胞类型特异性条件 Ron 删除的小鼠体内得到了证实。与巨噬细胞中 Ron 缺失相比，肝细胞中 Ron 缺失的小鼠肝损伤程度较低，存活率更高。
我们剖析了 Ron 的细胞类型特异性作用，即该受体调节库普弗细胞的细胞因子产生，并抑制肝细胞对损伤的存活反应。
