Biochemistry and Biophysics Reports (Sep 2022)
Polycationic peptide R7-G-Aβ25-35 selectively induces cell death in leukemia Jurkat T cells through speedy mitochondrial depolarization, and CASPASE-3 -independent mechanism
Abstract
Background: Acute lymphoblastic leukemia (ALL) is still incurable hematologic neoplasia in an important percentage of patients. Therefore, new therapeutic approaches need to be developed. Methods: To evaluate the cellular effect of cell-penetrating peptides (C-PP) on leukemia cells, Jurkat cells -a model of ALL were exposed to increasing concentration (50–500 μM) Aβ25–35, R7-G-Aβ25-35 and Aβ25–35-G-R7 peptide for 24 h. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, flow cytometry (FC), and fluorescent microscopy (FM) analysis were used to assess metabolic viability, cell cycle and proliferation, mitochondria functionality, oxidative stress, and cell death markers. Results: We report for the first time that the R7-G-Aβ25-35, but not Aβ25–35 peptide, induced selective cell death in Jurkat cells more efficiently than the Aβ25–35-G-R7 peptide. Indeed, R7-G-Aβ25-35 (200 μM) altered the metabolic activity (−25%), arrested the cell cycle in the G2/M-phase (15%), and induced a significant reduction of cellular proliferation (i.e., −74% reduction of Ki-67 nuclei reactivity). Moreover, R7-G-Aβ25-35 induced the dissipation of mitochondrial membrane potential (ΔΨm, 51%) and produced an important amount of reactive oxygen species (ROS, 75% at 8 h) in Jurkat cells. The exposure of cells to antioxidant/cytoprotectant N-acetylcysteine (NAC) did not prevent R7-G-Aβ25-35 from a loss of ΔΨm in Jurkat cells. The peptide was also unable to activate the executer CASPASE-3, thereby preserving the integrity of the cellular DNA corroborated by the fact that the caspase-3 inhibitor NSCI was unable to protect cells from R7-G-Aβ25-35 -induced cell damage. Further analysis showed that the R7-G-Aβ25-35 peptide is specifically localized at the outer mitochondria membrane (OMM) according to colocalization with the protein translocase TOMM20. Additionally, the cytotoxic effect of the poly-R7 peptide resembles the toxic action of the uncoupler FCCP, mitocan oligomycin, and rotenone in Jurkat cells. Importantly, the R7-G-Aβ25-35 peptide was innocuous to menstrual mesenchymal stromal cells (MenSC) –normal non-leukemia proliferative cells. Conclusion: Our findings demonstrated that the cationic Aβ peptide possesses specific anti-leukemia activity against Jurkat cells through oxidative stress (OS)- and CASPASE-3-independent mechanism but fast mitochondria depolarization.
