Role of M1 Cytokines in the Progression of Chronic Kidney Disease

巨噬细胞可通过分泌巨噬细胞因子对慢性肾病（CKD）的进展产生深远影响。 促炎性“M1”细胞因子包括肿瘤坏死因子-β（TNF）和白细胞介素-1 β（IL-1 β）。在 上一个周期，我们确定巨噬细胞中的转录因子Krüppel样因子4限制了肾脏 通过抑制巨噬细胞TNF的表达而引起损伤和纤维化。然而，TNF和IL-1 β也产生， 我们的初步研究已经在肾小管细胞中鉴定出两种因子，A20和Porcupine （PORCN），其共同抑制局部TNF和IL-1 β产生并改善CKD。A20是一种泛素编辑 在骨髓细胞中下调NF-κ B B信号传导从而保护自身免疫的蛋白质。在我们 使用炎症和毒素诱导的肾损伤小鼠模型的初步研究，A20缺失 选择性地从RTC（A20 KKO）中释放可增强RTC中局部TNF和IL-1 β的表达， 损害因此，我们假设肾单位中的A20可以保护肾小管损伤， 通过抑制TNF和IL-1 β的局部产生来治疗CKD。为了测试这一点，我们将A20 KKO和同窝仔 慢性肾小管损伤模型对照组。我们最近报道，肿瘤坏死因子在RTCs诱导几个Wnt 配体同种型，并且O-酰基转移酶Porcupine所允许的Wnt配体的分泌夸大了 梗阻性肾纤维化相比之下，在以近端肾小管损伤为特征的其他模型中， 可以防止CKD的进展，在我们的初步研究中， PORCN上调肾TNF表达并加重肾毒性血清肾炎（NTS）。作为恢复- catenin信号可以保护近端小管，这是TNF诱导损伤的关键部位，我们证实PORCN在 近端肾小管细胞抑制TNF表达，从而限制CKD的严重程度。为了验证这个假设， 我们将使近端小管中缺乏PORCN的小鼠（PORCN PTKO）经受我们的肾小管损伤模型。我们 初步研究表明，从近端小管中删除TNF（TNF PTKO）可减轻毒素诱导的 肾小管损伤并阻止细胞周期停滞。因此，为了直接询问PORCN依赖性分泌是否 通过抑制TNF诱导的细胞毒性来限制CKD的严重程度，我们将比较 PORCN PTKO小鼠和携带PORCN和TNF双重缺失的小鼠对RTC损伤的易感性 仅限于近端小管（双重PTKO）。我们预测阻断近端小管中TNF的作用 将消除由近端小管中PORCN缺乏引起的对CKD的增加的易感性。与 我们的综合方法，我们将阐明TNF的上游和下游的肾单位特异性途径， 可用于改善CKD。

Macrophages can have profound effects on the progression of chronic kidney disease (CKD) via the secretion of pro-inflammatory “M1” cytokines including tumor necrosis factor- (TNF) and Interleukin-1 (IL-1). In the previous cycle, we established that the transcription factor Krüppel like factor 4 in macrophages limits kidney damage and fibrosis by suppressing macrophage TNF expression. However, TNF and IL-1 are also produced by renal tubular cells (RTCs), and our preliminary studies have identified 2 factors in RTCs, A20 and Porcupine (PORCN), that together constrain local TNF and IL-1 generation and ameliorate CKD. A20 is a ubiquitin editing protein that downregulates NF-b signaling in myeloid cells and thereby protects against autoimmunity. In our preliminary studies using murine models of inflammation- and toxin-induced renal injury, deletion of A20 selectively from RTCs (A20 KKO) permits enhanced local TNF and IL-1 expression and exacerbations in RTC damage. We therefore hypothesize that A20 in the nephron protects against tubular damage and subsequent CKD by constraining local generation of TNF and IL-1. To test this, we will subject A20 KKO and littermate controls to models of chronic renal tubular injury. We recently reported that TNF in RTCs induces several Wnt ligand isoforms and that the secretion of Wnt ligands permitted by the O-acyl transferase Porcupine exaggerates obstruction-induced renal fibrosis. By contrast, in other models featuring proximal tubular injury Wnt signaling can protect against CKD progression, and in our preliminary studies, inducible nephron-specific deletion of PORCN upregulates renal TNF expression and exacerbates nephrotoxic serum nephritis (NTS). As restoring - catenin signals can protect the proximal tubule, a key site of TNF-induced injury, we posit that PORCN in proximal tubular cells suppresses TNF expression and thereby limits the severity of CKD. To test this hypothesis, we will subject mice lacking PORCN in the proximal tubule (PORCN PTKO) to our tubular injury models. Our preliminary studies indicate that deleting TNF from the proximal tubule (TNF PTKO) mitigates toxin-induced tubular damage and prevents cell cycle arrest. Thus, to directly interrogate whether PORCN-dependent secretion in the proximal tubule limits CKD severity by suppressing TNF-induced cytotoxicity, we will compare the susceptibility to RTC damage of PORCN PTKO mice and mice harboring double PORCN and TNF deletion restricted to the proximal tubule (Dual PTKO). We predict that interrupting TNF’s actions in the proximal tubule will abrogate the augmented susceptibility to CKD accruing from PORCN deficiency in the proximal tubule. With our integrated approach, we will elucidate nephron-specific pathways upstream and downstream of TNF that can be targeted for the amelioration of CKD.