Cheng Yu-Chi, Chang Jer-Ming, Chen Chien-An, Chen Hung-Chun
Graduate Institute of Medicine, Kaohsiung Medical University, Kaohsiung 80708, Taiwan.
Department of Internal Medicine, Kaohsiung Municipal Hsiao-Kang Hospital, Kaohsiung 80708, Taiwan Division of Nephrology, Kaohsiung Medical University Hospital, Kaohsiung 80708, Taiwan Faculty of Renal Care, College of Medicine, Kaohsiung Medical University, Kaohsiung 80708, Taiwan.
Exp Biol Med (Maywood). 2015 Apr;240(4):467-76. doi: 10.1177/1535370214553772. Epub 2014 Oct 15.
Endoplasmic reticulum stress occurs in a variety of patho-physiological mechanisms and there has been great interest in managing this pathway for the treatment of clinical diseases. Autophagy is closely interconnected with endoplasmic reticulum stress to counteract the possible injurious effects related with the impairment of protein folding. Studies have shown that glomerular podocytes exhibit high rate of autophagy to maintain as terminally differentiated cells. In this study, podocytes were exposed to tunicamycin and thapsigargin to induce endoplasmic reticulum stress. Thapsigargin/tunicamycin treatment induced a significant increase in endoplasmic reticulum stress and of cell death, represented by higher GADD153 and GRP78 expression and propidium iodide flow cytometry, respectively. However, thapsigargin/tunicamycin stimulation also enhanced autophagy development, demonstrated by monodansylcadaverine assay and LC3 conversion. To evaluate the regulatory effects of autophagy on endoplasmic reticulum stress-induced cell death, rapamycin (Rap) or 3-methyladenine (3-MA) was added to enhance or inhibit autophagosome formation. Endoplasmic reticulum stress-induced cell death was decreased at 6 h, but was not reduced at 24 h after Rap+TG or Rap+TM treatment. In contrast, endoplasmic reticulum stress-induced cell death increased at 6 and 24 h after 3-MA+TG or 3-MA+TM treatment. Our study demonstrated that thapsigargin/tunicamycin treatment induced endoplasmic reticulum stress which resulted in podocytes death. Autophagy, which counteracted the induced endoplasmic reticulum stress, was simultaneously enhanced. The salvational role of autophagy was supported by adding Rap/3-MA to mechanistically regulate the expression of autophagy and autophagosome formation. In summary, autophagy helps the podocytes from cell death and may contribute to sustain the longevity as a highly differentiated cell lineage.
内质网应激发生于多种病理生理机制中，人们对通过调控这一途径来治疗临床疾病有着浓厚兴趣。自噬与内质网应激紧密相连，以对抗与蛋白质折叠受损相关的潜在有害影响。研究表明，肾小球足细胞表现出较高的自噬率以维持其终末分化细胞的状态。在本研究中，足细胞暴露于衣霉素和毒胡萝卜素以诱导内质网应激。毒胡萝卜素/衣霉素处理分别导致内质网应激显著增加以及细胞死亡增加，表现为GADD153和GRP78表达升高以及碘化丙啶流式细胞术检测结果。然而，毒胡萝卜素/衣霉素刺激也增强了自噬的发展，单丹磺酰尸胺检测和LC3转化实验证明了这一点。为了评估自噬对内质网应激诱导的细胞死亡的调控作用，添加雷帕霉素（Rap）或3 - 甲基腺嘌呤（3 - MA）以增强或抑制自噬体形成。Rap + TG或Rap + TM处理后6小时内质网应激诱导的细胞死亡减少，但24小时未减少。相反，3 - MA + TG或3 - MA + TM处理后6小时和24小时内质网应激诱导的细胞死亡增加。我们的研究表明，毒胡萝卜素/衣霉素处理诱导内质网应激，导致足细胞死亡。同时，对抗诱导的内质网应激的自噬也增强。通过添加Rap/3 - MA来机械调控自噬表达和自噬体形成，支持了自噬的挽救作用。总之，自噬有助于足细胞避免细胞死亡，并可能有助于维持其作为高度分化细胞谱系的寿命。
