Mitochondria are key organelles involved in the mechanism of
Mitochondria are key organelles involved in the mechanism of apoptosis (Xiong et al., 2014), and loss of ΔΨm is an important marker associated with mitochondrial dysfunction and cell death. We found that Mino induced ΔΨm impairment and nuclear fragmentation in Jurkat PF-5274857 in a concentration-dependent manner. Furthermore, Mino/H2O2 up-regulates the PINK1/PARKIN (P/P) system (step 11). Interestingly, the P/P system has been demonstrated to be activated after loss of ΔΨm (Kondapalli et al., 2012). PINK1 accumulates at the surface of damaged mitochondria to recruit and activate PARKIN, an E3 ubiquitin ligase, which, in turn, elicits a signaling pathway that eventually leads to the removal of damaged organelles (Iguchi et al., 2013). Notably, P53 transcribes PARKIN (Zhang et al., 2011), and the latter can activate NF-κB (Sha et al., 2010). Therefore, a vicious cycle might occur wherein Mino/H2O2 indirectly triggers the P53 > P/P system > NF-κB > P53 (Fig. 9, red arrows). Taken together, these data suggest that mitochondrial depolarization and activation of the P/P system are related events responsive to Mino-induced OS and are actively involved in the functional maintenance of the mitochondria (Henn et al., 2007; Zhuang et al., 2016). Due to ΔΨm dissipation, several apoptogenic proteins (e.g., cytochrome c) are released into the cytoplasm and thereby activate executor proteins (Yuan and Akey, 2013). Our data reveal that Mino/H2O2 induces activation of two executor proteins CASPASE-3 (step 12) and AIF (step 13), two essential proteins involved in the dismantling of nuclei (Jimenez-Del-Rio and Velez-Pardo, 2012) (step 14).
Conclusion We have demonstrated that Mino specifically induces apoptosis in Jurkat cells through an OS-mediated mechanism. Moreover, we provide a mechanistic explanation for the most important molecular events in Mino/H2O2-induced apoptosis in Jurkat cells. The significance of the present investigation is twofold. First, Mino is a safe and specific- apoptosis-inducing drug against Jurkat cells in vitro. Furthermore, Mino is innocuous to hPBLCs, according to the cell viability assay, assessment of nuclear integrity, ΔΨm and normal display of protein expression of transcription factors and executor proteins involved in apoptosis. Second, minocycline is a pharmacologically well-characterized and widely available drug (Agwuh and MacGowan, 2006). However, no information is available to establish whether Mino might efficiently kill ALL cells in vivo. Interestingly, Mino has been found to be safe and well tolerated up to doses of 10 mg/kg (700 mg, Cmax ~ 48–36 μmol/l at 1 and 6 h, respectively) administered intravenously alone in stroke patients (Fagan et al., 2010). These Cmax values might be a sufficient concentration to reduce the viability of leukemia cells lines (e.g., Song et al., 2014 and this work). We therefore suggest that minocycline is a promising new chemotherapeutic agent for the treatment of ALL patients.
Acknowledgments This work was supported by the “Committee for Development and Research” (Comité para el Desarrollo y la Investigación-CODI, Universidad de Antioquia-UdeA) [grants #2014-935]. C Ruiz-Moreno is a master student from the Neuroscience program at the Basic Biomedical Sciences Academic Corporation-UdeA. The authors would like to thank the Flow Cytometry Unit (GICIG-SIU-UdeA) for the use of the instruments and technical assistance. The authors would also like to thank the Neuroscience Research Group at the UdeA for the use of the Odyssey Infrared Imaging System.
Introduction Currently, three main pathways of cell apoptosis exist: the first pathway involves cytochrome c release and caspase-3 activation, and described as the intrinsic mitochondrial pathway; the second pathway is mediated by the activation of caspase-8 and caspase-10, called the extrinsic death receptor pathway; and the third pathway, known as endoplasmic reticulum stress pathway, is mediated by the activation of caspase-12 (Gupta & Gollapudi, 2007). Mitochondria are important in regulating apoptosis. In particular, different pro-apoptotic proteins that are present in the inner membrane of the mitochondria are released to the cytoplasm and lead to apoptosis (Orrenius, 2004). Among intrinsic mitochondrial pathways, the broad-spectrum inhibitor of caspase could not completely prevent apoptosis in certain apoptosis models. Thus, another caspase-independent mitochondrial apoptosis pathway has been discovered, the apoptosis-inducing factor (AIF) pathway (Susin et al., 1999).