Effect of endoplasmic reticulum stress preconditioning on cytotoxicity of clinically relevant nephrotoxins in renal cell lines.

The cytoprotection of LLC-PK1 cells afforded by endoplasmic reticulum (ER) stress preconditioning suggests that the ER plays an important role during drug-induced renal toxicity. However, in vitro studies have been largely limited to LLC-PK1 cells and model toxins. Therefore, we tested the hypothesis that cytoprotection following ER stress preconditioning is a common property of renal cell lines (LLC-PK1 (pig), NRK-52E (rat), HEK293 (human), MDCK (dog)) and extends to clinically relevant nephrotoxins. ER stress inducers (tunicamycin, thapsigargin and oxidized dithiothreitol (DTTox)) resulted in a dose-dependent increase in GRP78 and GRP94 stress protein expression, but the magnitude of induction was cell line- and inducer-dependent. Toxicity of the model toxins iodoacetamide and tert-butylhydroperoxide was modified by preconditioning. DTTox was effective in decreasing the toxicity in all cell lines, but protection was variable with tunicamycin and thapsigargin. Toxicity of clinically relevant drugs (cisplatin, gentamicin, glyoxylate, cyclosporine A, p-aminophenol) was significantly decreased in cells preconditioned by tunicamycin or DTTox. These results demonstrate that ER stress preconditioning offers cytoprotection against clinically relevant nephrotoxins in renal cell lines from multiple species, although there were qualitative and quantitative differences between the cell lines. These results support the hypothesis that ER is involved in drug-induced renal toxicity.     

Calpain-Induced Endoplasmic Reticulum Stress and Cell Death following Cytotoxic Damage to Renal Cells

Calpains and endoplasmic reticulum (ER) stress have both beenimplicated in renal cell death following exposure to reactivechemical toxicants (RCTs). Therefore, we explored the link betweenER stress, calpain, and cell death in renal cell injury dueto model RCTs (iodoacetamide, menadione, tert-butyl hydroperoxide)and ER stress inducers (tunicamycin [TUN], thapsigargin [THAPS]).The calpain inhibitor, PD150606, significantly reduced the RCTand TUN-induced cell death in the renal cell line LLC-PK1, butnot death induced by THAPS. ER stress was confirmed by the significantinduction of GRP78 following exposure to RCTs and ER stressinducers. While GRP94 induction was observed following RCTsand TUN, it was not statistically significant because of variability.THAPS at 5µM significantly induced GRP94, while 20µMcaused a calpain-dependent cleavage of GRP94. Caspase-12 andm-calpain were variably induced and/or cleaved following exposureto all toxicants, supporting activation of these signaling pathways.Inhibition of calpain blocked the induction of GRP78 followingexposure to RCTs suggesting that calpain was contributing tothe observed ER stress following RCTs. In contrast, calpaininhibition did not block ER stress protein induction followingexposure to nontoxic concentrations of TUN or THAPS, indicatingthat calpain inhibition did not block the ER stress proteininduction pathways directly. These studies demonstrate a previouslyunappreciated link between calpain activation and ER stress–associatedcell death in renal cells. While further studies are requiredto clarify the molecular events involved, these results confirmthat calpain activation and the ER are important related playersin chemically induced renal cell damage.     

Tunicamycin induces resistance to camptothecin and etoposide in human hepatocellular carcinoma cells: role of cell-cycle arrest and GRP78

Hepatocellular carcinoma is chemoresistant to many anticancer drugs. Tunicamycin, an N-glycosylation inhibitor, causes unfolded protein response and is widely used as pharmacological inducer of endoplasmic reticulum stress. In this study, several designs were used to investigate the resistance mechanism to camptothecin and etoposide in hepatocellular carcinoma Hep3B cells. Tunicamycin significantly inhibited apoptosis induced by camptothecin or etoposide. Tunicamycin neither modified the topoisomerase levels nor inhibited the ATM activation caused by camptothecin and etoposide. The data suggest that tunicamycin-induced resistance may result from the downstream events of drug-trapped topoisomerase-DNA complexes and DNA double-strand breaks. Camptothecin and etoposide caused an increase of protein expression of several cell-cycle regulators and induced the cleavage of Bcl-2 family of proteins. These intracellular molecular events were abolished by tunicamycin. A design of postaddition of tunicamycin demonstrated that G1 checkpoint arrest contributed to the resistance mechanism. Curcumin, another G1 arrest-inducing agent in this study, was able to induce a similar resistant effect. Furthermore, the cells transfected with GRP78 siRNA were partly resistant to tunicamycin-induced apoptosis but not the inhibitory effect on cell-cycle regulators indicating that GRP78 and G1 arrest are two independent factors to tunicamycin-induced resistance mechanism. In conclusion, the data suggest that tunicamycin induces the resistance to topoisomerase inhibitors through GRP78 up-regulation and G1 arrest of the cell cycle. The findings also prompt the deliberation that the resistance can be caused during combined administration of chemotherapeutic drugs and Chinese herbal medicines, which induce endoplasmic reticulum stress and/or cell-cycle arrest in cancer cells.     

The regulatory mechanism of 4-phenylbutyric acid against ER stress-induced autophagy in human gingival fibroblasts

Endoplasmic reticulum (ER) stress is closely connected to autophagy. When cells are exposed to ER stress, cells exhibit enhanced protein degradation and form autophagosomes. In this study, we demonstrate that the chemical chaperone, 4-phenylbutyric acid (4-PBA), regulates ER stressinduced cell death and autophagy in human gingival fibroblasts. We found that 4-PBA protected cells against thapsigargin-induced apoptotic cell death but did not affect the reduced cell proliferation. ER stress induced by thapsigargin was alleviated by 4-PBA through the regulation of several ER stress-inducible, unfolded protein response related proteins including GRP78, GRP94, C/EBP homologous protein, phospho-eIF-2α, eIF-2α, phospho-JNK1 (p46) and phospho-JNK2/3 (p54), JNK1, IRE-1α, PERK, and sXBP-1. Compared with cells treated with thapsigargin alone, cells treated with both 4-PBA and thapsigargin showed lower levels of Beclin-1, LC-3II and autophagic vacuoles, indicating that 4-PBA also inhibited autophagy induced by ER stress. This study suggests that 4-PBA may be a potential therapeutic agent against ER stress-associated pathologic situations.     

抑制MEK对内质网应激诱导乳腺癌细胞凋亡的增敏作用

目的探讨抑制MEK/ERK信号通路对人乳腺癌细胞内质网(endoplasmic reticulum,ER)应激途径细胞凋亡的影响,以期为乳腺癌化疗提供新的靶点。方法不同浓度(0、1.5、3、6、9、12μmol.L-1)衣霉素(tunicamycin,TM)处理乳腺癌细胞SK-BR-3,48h后溴化丙啶(propidium iodide,PI)染色检测细胞凋亡率;TM(3μmol.L-1)处理SK-BR-3细胞不同时间(0、6、12、24、36h),Western blot检测葡萄糖调节蛋白78(glucose-regulated protein78,GRP78)、ERK1/2、pERK1/2的表达;MEK抑制剂U0126(20μmol.L-1)预处理1h后再给予TM(3μmol.L-1)同上处理,检测上述指标,比较U0126作用前后上述指标的变化。结果SK-BR-3细胞对TM诱导的细胞凋亡率<20%,且TM上调GRP78的表达;TM没有诱导ERK1/2的进一步激活;U0126明显增加TM诱导的细胞凋亡率(78%),同时下调GRP78的表达和阻断TM对GRP78的上调作用。结论MEK/ERK信号通路的抑制增强人乳腺癌细胞SK-BR-3对ER应激途径细胞凋亡的敏感性,抑制非折叠蛋白反应(unfolded protein response,UPR)的诱导。     

GRP78与 CHOP在缺血再灌注损伤中的作用

缺血再灌注（ischemia-reperfusion ,IR）过程中多种因素可导致内质网应激（endoplasmic reticulum stress response,ERS）, ERS参与缺血再灌注（ ischemia-reperfusion injury,IRI）的发展过程。总结ERS抗凋亡标志物GRP78与促凋亡标志物CHOP在IRI中的作用。 IRI时GRP78与CHOP表达的变化及其作用。明晰GRP78与CHOP参与IRI的机制。     

Roscovitine在衣霉素诱导足细胞损伤中的保护作用

目的 应用衣霉素诱导内质网应激（ERS）, 观察 Roscovtine 对 ERS 导致足细胞损伤的保护作用。方法体外培养永生化小鼠足细胞, 取 37 ℃分化成熟细胞随机分组：（1）正常对照组、 DMSO 组及衣霉素 Tunicamycin（1.0 μmol/L, TM） 组, 各实验组分别刺激 3、 6、 12 h。（2） 正常对照组、 Tunicamycin （1.0 μmol/L, TM） 组及 Tunicamycin+Rosco⁃ vitine（20、 40 μmol/L, TM+ROS）组, 各实验组分别刺激 12 h。应用流式细胞术及 TUNEL 法检测足细胞凋亡情况; 应用 Western blot 检测细胞周期素依赖性蛋白激酶 5（Cdk5）及 ERS 标志蛋白 GRP78、 Caspase-12、 CHOP 的表达变化。结果 （1）与正常对照组和 DMSO 组相比, Tunicamycin 刺激 3、 6 及 12 h 后, TM 组足细胞凋亡率及 Cdk5、 GRP78、 Caspase-12 和 CHOP 蛋白的表达水平均呈明显的时间依赖性增高 （P < 0.05）;（2） 加入 Roscovitine 干预后, 与 TM 组相比, TM+ROS（20、 40 μmol/L）组足细胞凋亡率及 GRP78、 Caspase-12 和 CHOP 蛋白的表达水平均显著降低（P < 0.05）, 其干预作用呈现明显的剂量依赖性。结论 Cdk5 抑制剂 Roscovitine 能显著抑制衣霉素诱导的足细胞凋亡,从而发挥细胞保护作用。Roscovitine 的足细胞保护作用可能有助于糖尿病肾病的治疗。     

2-脱氧葡萄糖对脑缺血再灌注模型大鼠脑组织中葡萄糖调节蛋白78及天冬氨酸半胱氨酸蛋白酶-12的影响研究

目的:探讨2-脱氧葡萄糖(2-DG)对脑缺血再灌注(IR)模型大鼠脑组织中葡萄糖调节蛋白78(GRP78)及天冬氨酸半胱氨酸蛋白酶-12(caspase-12)的影响。方法:取大鼠随机分为假手术组、模型组和2-DG组(2-DG100mg·kg-1),每组60只,后2组建立局灶性脑IR模型,假手术组行手术但不插入线栓。建模前7d开始给药,每天1次,连续7d,考察建模后3、6、12、24、48h各组大鼠海马CA1区细胞凋亡情况(阳性细胞率)、GRP78和caspase-12蛋白及其mRNA的表达情况。结果:与假手术组比较,模型组和2-DG组阳性细胞率、GRP78和caspase-12蛋白及其mRNA表达均明显升高(P均<0.01);与模型组比较,2-DG组阳性细胞率、cas-pase-12蛋白及其mRNA表达明显降低,GRP78蛋白及其mRNA表达明显升高(P<0.05或P<0.01)。结论:2-DG可能通过上调GRP78和下调caspase-12的表达来预防脑IR损伤。     

Cisplatin, gentamicin, and p-aminophenol induce markers of endoplasmic reticulum stress in the rat kidneys.

In vitro evidence of the involvement of the endoplasmic reticulum (ER) during drug-induced renal toxicity is accumulating. ER stress and ER-mediated cell death markers have been reported after exposure of renal cells to model toxicants and nephrotoxic drugs in various in vitro models, but in vivo experiments with clinically relevant nephrotoxic compounds are lacking. In order to determine the relevance of the in vitro findings, markers of ER stress (XBP1 messenger RNA processing and protein expression; GRP78 and GRP94 upregulation) and ER-mediated cell death (caspase-12 and calpain activation) were examined in kidney tissue of rats exposed to nephrotoxic doses of cisplatin (CIS), gentamicin (GEN), and p-aminophenol (PAP), a nephrotoxic metabolite of acetaminophen. XBP1 signaling was observed with all three drugs and was associated with increased expression of GRP94 and GRP78 in GEN- and PAP-treated animals, but surprisingly not after CIS exposure. m-Calpain expression was increased after 7 days of CIS treatment, whereas it was decreased in PAP-treated rats. Caspase-12 cleavage products were increased after CIS, GEN, and PAP administration. The results of this study demonstrate that three clinically relevant nephrotoxic drugs are all associated with changes in markers of ER stress and ER-mediated cell death in vivo. Further investigation is warranted to determine the role of the ER, the calpain system, and caspase-12 in drug-induced renal cell death.     

The nephroprotective effect of tauroursodeoxycholic acid on ischaemia/reperfusion-induced acute kidney injury by inhibiting endoplasmic reticulum stress

The incidence of acute kidney injury (AKI) is very high, and multiple physiopathological processes are involved, including endoplasmic reticulum stress (ERS). Tauroursodeoxycholic acid (TUDCA) is an endogenous bile acid derivative that has been reported to inhibit ERS. To determine whether TUDCA had a nephroprotective effect on AKI and to explore the exact mechanism, an ischaemia/reperfusion (I/R)-induced AKI mouse model and a tunicamycin-pre-treated TCMK-1 cell model were established. It was found that the renal tubular necrosis score and cell apoptosis index reached their peak 24 hr after I/R. GRP78 and C/EBP homologous protein (CHOP) expression and Caspase 12 activation were enhanced, reaching their peaks at 4 and 12 hr, respectively. TUDCA intervention not only decreased the renal tubular necrosis score and the cell apoptosis index but also down-regulated GRP78 and CHOP expression and Caspase 12 activation. The survival rate of TCMK-1 cells pre-treated with TUDCA was significantly higher than that of TCMK-1 cells without TUDCA pre-treatment. In conclusion, TUDCA had a nephroprotective effect on IR-induced AKI by inhibiting ERS and by blocking GRP78 and CHOP expression, reducing Caspase 12 activation and inhibiting cell apoptosis.     

GSK3beta and endoplasmic reticulum stress mediate rotenone-induced death of SK-N-MC neuroblastoma cells

Rotenone, an environmental toxin that inhibits mitochondrial complex I, has been used to induce experimental Parkinsonism in animals and cell cultures. We investigated the mechanism underlying rotenone-induced death of SK-N-MC neuroblastoma cells. Rotenone-induced cell death preceded intracellular accumulation of reactive oxygen species, and antioxidants failed to protect cells, indicating that oxidative stress was minimally involved in rotenone-induced death of SK-N-MC cells. Glycogen synthase kinase 3beta (GSK3beta), a multifunctional serine/threonine kinase, has been implicated in the pathogenesis of neurodegeneration. We showed that rotenone activated GSK3beta by enhancing its phosphorylation at tyrosine 216 while inhibiting phosphorylation at serine 9. Inhibitors of GSK3beta and dominant negative (kinase deficient) GSK3beta partially protected SK-N-MC cells against rotenone cytotoxicity. Rotenone also induced endoplasmic reticulum (ER) stress which was evident by an increase in phosphorylation of PERK, PKR, and eIF2alpha as well as the expression of GRP78. Rotenone had a modest effect on the expression of CHOP. An eIF2alpha siRNA significantly reduced rotenone cytotoxicity. ER stress was experimentally induced by tunicamycin and thapsigargin, but tunicamycin/thapsigargin did not activate GSK3beta in SK-N-MC cells. Down-regulation of eIF2alpha also offered partial protection against rotenone cytotoxicity. Combined treatment of GSK3beta inhibitors and eIF2alpha siRNA provided much greater protection than either treatment alone. Taken together, the results suggest that GSK3beta activation and ER stress contribute separately to rotenone cytotoxicity.     

Ganoderma Lucidum polysaccharide peptides protect kidney from renal ischemia reperfusion injury via counteracting oxidative stress

OBJECTIVE Ganoderma lucidum polysaccharide peptides(GLPP)have an anti-oxidant activity.The oxidative stress implicates in the pathogenesis of renal ischemia-reperfusion injury(RIRI).The objective of this study was to determine whether GLPP could attenuate RIRI via counteracting the oxidative stress.METHODS Mice subjected to uninephrectomy with the right kidney ischemia for 35 min and reperfusion for 24 hwere used to explore the protective activity of GLPP against RIRI.In GLPP-treated group,100mg·kg-1·d-1 of GLPP were intraperitoneally injected for 7dbefore the procedure.In vitro,NRK-52 Ecells subjected to hypoxia-reoxygenation(H/R)and tunicamycin were used to explore the protective effect of GLPP against oxidative stress.The mechanisms in which GLPP protected kidney from RIRI were studied using a series of physiological and molecular biological methods.RESULTS Kidneys undergone ischemia-reperfusion showed renal dysfunction and characteristic morphological changes including cellular necrosis,brush border loss,cast formation,vacuolization and tubular dilatation while these damages were significantly attenuated by GLPP treatment.The abnormal levels of MPO,MDA and SOD caused by renal ischemia-reperfusion were significantly reversed by GLPP treatment.More apoptotic cells were found in the renal ischemia-reperfusion group than the sham group whereas GLPP reduced apoptotic cells in the ischemia-reperfusion mice by21.75%(P<0.01).The GLPPs(25-1μg·mL)alleviated H/R induced cell viability loss by 20.12%(P<0.01)andΔφm dissipation by 27.3%(P<0.01)in vitro as well and its pretreatment dramatically reduced H/R and tunicamycin induced cell injury.CONCLUSION Our study found that GLPP had a protective effect on RIRI via its anti-oxidative capacity,which suggests that GLPP may be developed as a candidate drug for preventing acute kidney injury.     

Modulating the endoplasmic reticulum stress response with trans-4,5-dihydroxy-1,2-dithiane prevents chemically induced renal injury in vivo.

Agents that disrupt functions of the endoplasmic reticulum (ER) induce expression of ER stress-response genes including ER chaperones. Increased expression of the major ER chaperone, Grp78, protects cells, including renal epithelial cells, from chemically induced injury and death in vitro. In this study, we determined if pharmacological manipulation of the ER stress-response gene is an effective strategy to protect the kidney from chemical stress in vivo. Treatment with trans-4,5-dihydroxy-1,2-dithiane (DTTox), a novel inducer of ER stress proteins, stimulated a time-and dose-dependent increase in Grp78 expression in the kidney, but it did not cause detectable injury. Furthermore, prior treatment with DTTox protected the proximal tubular epithelium against a subsequent challenge with the nephrotoxicant S-(1,1,2,2,-tetrafluoroethyl)-L-cysteine (TFEC). In contrast, activating a heat shock response did not have a protective effect. Prior treatment with DTTox did not reduce covalent binding of radiolabeled reactive metabolites of (35)S-TFEC to renal proteins, indicating that protection was not due to an effect on the metabolic activation of TFEC to the reactive metabolite(s) responsible for renal injury. Antisense grp78 expression in the renal epithelial cell line LLC-PK1 blocked the DTTox-induced Grp78 increase and ablated the protective effect against TFEC damage, indicating that the induction of grp78 expression and the ER stress response were critical for the protective effect of DTTox. These findings suggest that increased expression of Grp78 plays a major role in the protection of renal epithelial cells from reactive intermediate-induced chemical injury in vivo and that pharmacological manipulation is an effective strategy to prevent damage by some classes of nephrotoxicants.