p53 facilitates BH3-only BID nuclear export to induce apoptosis in the irrepairable DNA damage response

Protective Effects of Polydatin on Reproductive Injury Induced by Ionizing Radiation

The reproductive system is vulnerable to ionizing radiation, which is a hot research topic at present. We tested the effect of polydatin on spermatocytes(GC-1 cells) after X-ray irradiation. The reproductive damage model of C.elegans was established by 60Coγ-ray, and the protective effect of polydatin on reproductive damage caused by ionizing radiation was evaluated. We quantified the ROS levels of GC-1 cells and C.elegans after irradiation with polydatin and evaluated the anti-apoptosis effect of polydatin at proper concentration. Differential genes of C.elegans reproductive damage were screened out from transcriptome sequencing results and comparable GEO datasets. It was proved that 100μM polydatin significantly reduced the apoptosis of GC-1 cells induced by 2 Gy X-ray. In addition, the longevity, reproductive capacity, germ cell apoptosis and spawning and hatching capacity of polydatin were tested. The results showed that 100 μM polydatin content significantly increased the influence of 50 Gy 60Coγ-ray on reproductive capacity of C.elegans. Quantitative analysis of mRNA and protein levels of apoptosis-related genes and reproductive-related genes by qRT-PCR and Western blotcon firmed that polydatin with appropriate dosage had good protective effects on reproductive damage caused by radiation, which laid a foundation for the application research of polydatin in radiation protection.

Cisplatin Chemotherapy and Cochlear Damage: Otoprotective and Chemosensitization Properties of Polyphenols

Significance: Cisplatin is an important component of treatment regimens for different cancers. Notwithstanding that therapeutic success often results from partial efficacy or stabilizing the disease, chemotherapy failure is driven by resistance to drug treatment and occurrence of side effects, such as progressive irreversible ototoxicity. Cisplatin's side effects, including ototoxicity, are often dose limiting. Recent Advances: Cisplatin ototoxicity results from several mechanisms, including redox imbalance caused by reactive oxygen species production and lipid peroxidation, activation of inflammation, and p53 and its downstream pathways that culminate in apoptosis. Considerable efforts in research have targeted development of molecular interventions that can be concurrently administered with cisplatin or other chemotherapies to reduce side effect toxicities while preserving or enhancing the antineoplastic effects. Evidence from studies has indicated some polyphenols, such as curcumin, can help to regulate redox signaling and inflammatory effects. Furthermore, polyphenols can exert opposing effects in different types of tissues, that is, normal cells undergoing stressful conditions versus cancer cells. Critical Issues: This review article summarizes evidence of curcumin antioxidant effect against cisplatin-induced ototoxicity that is converted to a pro-oxidant activity in cisplatin-treated cancer cells, thus providing an ideal chemosensitivity combined with otoprotection. Polyphenols can modulate the adaptive responses to stress in the cisplatin-exposed cochlea. These adaptive effects can result from the interaction/cross talk between the cell's defenses, inflammatory molecules, and the key signaling molecules of signal transducers and activators of transcription 3 (STAT-3), nuclear factor κ-B (NF-κB), p53, and nuclear factor erythroid 2-related factor 2 (Nrf-2). Future Directions: We provide molecular evidence for alternative strategies for chemotherapy with cisplatin addressing the otoprotection and chemosensitization properties of polyphenols. Antioxid. Redox Signal. 36, 1229-1245.

Bcl-2 Inhibition to Overcome Resistance to Chemo- and Immunotherapy

Abstract: According to the World Health Organization (WHO), cancer is a leading cause of death worldwide. The identification of novel targets for cancer treatment is an area of intense work that has led Bcl-2 over-expression to be proposed as one of the hallmarks of cancer and Bcl-2 inhibition as a promising strategy for cancer treatment. In this review, we describe the different pathways related to programmed cell death, the role of Bcl-2 family members in apoptosis resistance to anti-cancer treatments, and the potential utility of Bcl-2 inhibitors to overcome resistance to chemo- and immunotherapy.

Induction of Huh‑7 cell apoptosis by HCV core proteins via CK1α‑p53‑Bid signaling pathway

Hepatitis C virus (HCV)-infected liver cells sensitize host cells to tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL)-induced cell apoptosis; however, the precise mechanisms are unknown. In the present study, flow cytometry demonstrated that the Annexin V-positive Huh-7 cell number was higher in groups transfected with core proteins when compared with the pcDNA3.1 group. The mRNA and protein expression levels of B-cell lymphoma 2 (Bcl-2) were negatively associated, while Bcl-2-associated X protein (Bax) were positively correlated, with cell apoptotic rate, which, were verified by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and western blotting. There were no significant differences in the expressions of casein kinase 1 (CK1)-ε, CK1γ or CK1δ; however, the mRNA and protein levels of CK1α were markedly higher in groups transfected with the T (those derived from the HCV-J6 strain), NT (those derived from non-tumor tissues) and C191 (those derived from tumor tissues) HCV core proteins than in mock group. When compared with the Mock and Negative Control (control known-down) groups, the mRNA and protein levels of CK1α were lower in the CK1α known-down group, and there were no marked Huh-7 cell morphological changes among the 3 groups. There was more sensitivity to cell apoptosis in CK1α-silenced, however, not in non-CK1α-silenced, Huh-7 cells. BH3 interacting-domain death agonist (Bid) protein levels in CK1α-silenced Huh-7 cells were higher when compared with non-CK1α-silenced Huh-7 cells, and the level of p53 that translocated to the nucleus increased. Chromatin immunoprecipitation-PCR demonstrated that p53 bound to human Bid gene promoter. The level of the Bid promoter in CK1α-silenced Huh-7 cells was significantly higher than in the non-CK1α-silenced Huh-7 cells. Electron microscopy indicated that p53 knockdown decreased HCV core protein and TRAIL-induced cell apoptosis. Bid/caspase-8 protein levels in CK1α-silenced Huh-7 cells that were transfected with p53 siRNA were lower than in the control group. The present study demonstrated that HCV core proteins sensitize host cells to TRAIL-induced cell apoptosis by activating the CK1α-p53-Bid dependent pathway.

p53 and Ceramide as Collaborators in the Stress Response

The sphingolipid ceramide mediates various cellular processes in response to several extracellular stimuli. Some genotoxic stresses are able to induce p53-dependent ceramide accumulation leading to cell death. However, in other cases, in the absence of the tumor suppressor protein p53, apoptosis proceeds partly due to the activity of this "tumor suppressor lipid", ceramide. In the current review, we describe ceramide and its roles in signaling pathways such as cell cycle arrest, hypoxia, hyperoxia, cell death, and cancer. In a specific manner, we are elaborating on the role of ceramide in mitochondrial apoptotic cell death signaling. Furthermore, after highlighting the role and mechanism of action of p53 in apoptosis, we review the association of ceramide and p53 with respect to apoptosis. Strikingly, the hypothesis for a direct interaction between ceramide and p53 is less favored. Recent data suggest that ceramide can act either upstream or downstream of p53 protein through posttranscriptional regulation or through many potential mediators, respectively.

ER stress is involved in T17M rhodopsin-induced retinal degeneration

PURPOSE

The human rhodopsin (Rho) mutation T17M leads to autosomal dominant retinitis pigmentosa (adRP). The goal of our study was to elucidate the role of endoplasmic reticulum (ER) stress in retinal degeneration in hT17M Rho mice and identify potential candidates for adRP gene therapy.

METHODS

We used transgenic mice expressing the ER stress-activated indicator (ERAI) and hT17M Rho to evaluate the activation of ER stress responses. Quantitative reverse transcription PCR (qRT-PCR) was used to analyze changes in the expression of 30 unfolded protein response (UPR)-associated genes at P12, 15, 18, 21, and 25. The cytosolic fraction of hT17M Rho retinal cells was used to measure the release of cytochrome C and apoptotic inducing factor-1 (AIF1) by Western blotting. Optical coherence tomography (OCT) analysis was performed for 1-month-old hT17M Rho mice.

RESULTS

hT17M Rho was localized in the outer nuclear layer (ONL) of T17M(+/-)ERAI(+/-) photoreceptors as well as C57BL/6 retinas injected with AAV-hT17M Rho-GFP. In P15 hT17M Rho retinas, we observed an up-regulation of UPR genes (Atf4, Eif2α, Xbp1, Bip, Canx, and Hsp90), autophagy genes and proapoptotic Bcl2 genes. OCT, and the downregulation of Nrl and Crx gene expression confirmed that cell death occurs in 55% of photoreceptors via the up-regulation of caspase-3 and caspase-12, and the release of AIF1 from the mitochondria.

CONCLUSIONS

The ER stress response is involved in retinal degeneration in hT17M Rho mice. The final demise of photoreceptors occurs via apoptosis involving ER stress-associated and mitochondria-induced caspase activation. We identified Atg5, Atg7, Bax, Bid, Bik, and Noxa as potential therapeutic targets for adRP treatment.

Immune complex-mediated co-ligation of the BCR with FcγRIIB results in homeostatic apoptosis of B cells involving Fas signalling that is defective in the MRL/Lpr model of systemic lupus erythematosus

Negative regulation of B cell activation by cognate immune complexes plays an important homeostatic role in suppressing B cell hyperactivity and preventing consequent autoimmunity. Immune complexes co-ligate the BCR and FcγRIIB resulting in both growth arrest and apoptosis. We now show that such apoptotic signalling involves induction and activation of p53 and its target genes, the pro-apoptotic Bcl-2 family members, Bad and Bid, as well as nuclear export of p53. Collectively, these events result in destabilisation of the mitochondrial and lysosomal compartments with consequent activation and interplay of executioner caspases and endosomal-derived proteases. In addition, the upregulation of Fas and FasL with consequent activation of caspase 8-dependent death receptor signalling is required to facilitate efficient apoptosis of B cells. Consistent with this role for Fas death receptor signalling, apoptosis resulting from co-ligation of the BCR and FcγRIIB is defective in B cells from Fas-deficient MRL/MpJ-Fas(lpr) mice. As these mice develop spontaneous, immune complex-driven lupus-like glomerulonephritis, targeting this FcγRIIB-mediated apoptotic pathway may therefore have novel therapeutic implications for systemic autoimmune disease.