Phosphorylation of eIF2α suppresses cisplatin-induced p53 activation and apoptosis by attenuating oxidative stress via ATF4-mediated HO-1 expression in human renal proximal tubular cells

Sal003 alleviated intervertebral disc degeneration by inhibiting apoptosis and extracellular matrix degradation through suppressing endoplasmic reticulum stress pathway in rats

Apoptosis and extracellular matrix degradation of the nucleus pulposus are the main initiators of intervertebral disc degeneration (IVDD) and can be explained by endoplasmic reticulum (ER) stress. Thus, pharmacological therapy aimed at suppressing this pathway may be a promising approach for the management of intervertebral disc degeneration. In this study, we aimed to explore the protective effects of Sal003 against intervertebral disc degeneration and its underlying mechanisms. Thapsigargin (Tg)-stimulated rat nucleus pulposus cells and a needle puncture-induced intervertebral disc degeneration rat model were used to explore the protective effects of Sal003. Our results showed that Sal003 inhibited apoptosis and extracellular matrix degradation by suppressing the endoplasmic reticulum stress pathway. The therapeutic effects of Sal003 were also observed in the intervertebral disc degeneration rat model, as evidenced by improved degeneration along with decreased apoptosis and extracellular matrix degradation in intervertebral discs. Our results demonstrated Sal003 as a potential treatment for intervertebral disc degeneration.

Quantitative spectrofluorometric assay detecting nuclear condensation and fragmentation in intact cells

At present, nuclear condensation and fragmentation have been estimated also using Hoechst probes in fluorescence microscopy and flow cytometry. However, none of the methods used the Hoechst probes for quantitative spectrofluorometric assessment. Therefore, the aim of the present study was to develop a spectrofluorometric assay for detection of nuclear condensation and fragmentation in the intact cells. We used human hepatoma HepG2 and renal HK-2 cells cultured in 96-well plates treated with potent apoptotic inducers (i.e. cisplatin, staurosporine, camptothecin) for 6-48 h. Afterwards, the cells were incubated with Hoechst 33258 (2 µg/mL) and the increase of fluorescence after binding of the dye to DNA was measured. The developed spectrofluorometric assay was capable to detect nuclear changes caused by all tested apoptotic inducers. Then, we compared the outcomes of the spectrofluorometric assay with other methods detecting cell impairment and apoptosis (i.e. WST-1 and glutathione tests, TUNEL, DNA ladder, caspase activity, PARP-1 and JNKs expressions). We found that our developed spectrofluorometric assay provided results of the same sensitivity as the TUNEL assay but with the advantages of being fast processing, low-cost and a high throughput. Because nuclear condensation and fragmentation can be typical markers of cell death, especially in apoptosis, we suppose that the spectrofluorometric assay could become a routinely used method for characterizing cell death processes.

Crosstalk between endoplasmic reticulum stress and oxidative stress in the progression of diabetic nephropathy

Increasing evidence in substantiating the roles of endoplasmic reticulum stress, oxidative stress, and inflammatory responses and their interplay is evident in various diseases. However, an in-depth mechanistic understanding of the crosstalk between the intracellular stress signaling pathways and inflammatory responses and their participation in disease progression has not yet been explored. Progress has been made in our understanding of the cross talk and integrated stress signaling network between endoplasmic reticulum stress and oxidative stress towards the pathogenesis of diabetic nephropathy. In this present study, we studied the crosstalk between the endoplasmic reticulum stress and oxidative stress by understanding the role of protein disulfide isomerase and endoplasmic reticulum oxidase 1α, a key player in redox protein folding in the endoplasmic reticulum. We had recruited a total of 90 subjects and divided into three groups (control (n = 30), type 2 diabetes mellitus (n = 30), and diabetic nephropathy (n = 30)). We found that endoplasmic reticulum stress markers, activating transcription factor 6, inositol-requiring enzyme 1α, protein kinase RNA-like endoplasmic reticulum kinase, C/EBP homologous protein, and glucose-regulated protein-78; oxidative stress markers, thioredoxin-interacting protein and cytochrome b-245 light chain; and the crosstalk markers, protein disulfide isomerase and endoplasmic reticulum oxidase-1α, were progressively elevated in type 2 diabetes mellitus and diabetic nephropathy subjects. The association between the crosstalk markers showed a positive correlation with endoplasmic reticulum stress and oxidative stress markers. Further, the interplay between endoplasmic reticulum stress and oxidative stress was investigated in vitro using a human leukemic monocytic cell line under a hyperglycemic environment and examined the expression of protein disulfide isomerase and endoplasmic reticulum oxidase-1α. DCFH-DA assay and flow cytometry were performed to detect the production of free radicals. Further, phosphorylation of eIF2α in high glucose-exposed cells was studied using western blot. In conclusion, our results shed light on the crosstalk between endoplasmic reticulum stress and oxidative stress and significantly contribute to the onset and progression of diabetic nephropathy and therefore represent the major therapeutic targets for alleviating micro- and macrovascular complications associated with this metabolic disturbance. Graphical abstract.

tRNALys-Derived Fragment Alleviates Cisplatin-Induced Apoptosis in Prostate Cancer Cells

Cisplatin is a standard treatment for prostate cancer, which is the third leading cause of cancer-related deaths among men globally. However, patients who have undergone cisplatin can rxperience relapse. tRNA-derived fragments (tRFs) are small non-coding RNAs generated via tRNA cleavage; their physiological activities are linked to the development of human diseases. Specific tRFs, including tRF-315 derived from tRNA^Lys, are highly expressed in prostate cancer patients. However, whether tRF-315 regulates prostate cancer cell proliferation or apoptosis is unclear. Herein, we confirmed that tRF-315 expression was higher in prostate cancer cells (LNCaP, DU145, and PC3) than in normal prostate cells. tRF-315 prevented cisplatin-induced apoptosis and alleviated cisplatin-induced mitochondrial dysfunction in LNCaP and DU145 cells. Moreover, transfection of tRF-315 inhibitor increased the expression of apoptotic pathway-related proteins in LNCaP and DU145 cells. Furthermore, tRF-315 targeted the tumor suppressor gene GADD45A, thus regulating the cell cycle, which was altered by cisplatin in LNCaP and DU145 cells. Thus, tRF-315 protects prostate cancer cells from mitochondrion-dependent apoptosis induced by cisplatin treatment.

Cladribine Induces ATF4 Mediated Apoptosis and Synergizes with SAHA in Diffuse Large B-Cell Lymphoma Cells

Cladribine is a purine nucleoside analog used to treat B-cell chronic lymphocytic leukemia and hairy cell leukemia, also functions as an inhibitor of DNA synthesis to block the repair of the damaged DNA. The therapeutic role of cladribine against diffuse large B-cell lymphoma cells (DLBCL) is still undefined. In the present study, we demonstrated that cladribine inhibited cell proliferation and induced G₁ phase arrest in human DLBCL cells. Furthermore, we showed that cladribine induced apoptosis by decreasing the expression of c-FLIP_L and increasing the expression of DR4 and the cleaved form of caspase8. Cladribine also upregulated the expression of Bax, and downregulated the expression of Mcl-1 and Bcl-2 in a dose-dependent manner. It also activated endoplasmic reticulum (ER) stress, and ATF4 expression was required for cladribine induced apoptosis. Also, we showed that suberoylanilide hydroxamic acid (SAHA) enhanced the pro-apoptotic role of cladribine. Collectively, cladribine activated extrinsic and intrinsic apoptotic signaling pathways via stimulating ER stress signaling pathway and eliciting synergistic effect with SAHA in DLBCL cells.