Manganese Porphyrin, MnTE-2-PyP5+, Acts as a Pro-Oxidant to Potentiate Glucocorticoid-Induced Apoptosis in Lymphoma Cells

Abstract

Using current chemotherapy protocols, over 55% of lymphoma patients fail treatment. Novel agents are needed to improve lymphoma survival. The manganese porphyrin, MnTE-2-PyP5+, augments glucocorticoid-induced apoptosis in WEHI7.2 murine thymic lymphoma cells, suggesting that it may have potential as a lymphoma therapeutic. However, the mechanism by which MnTE-2-PyP5+ potentiates glucocorticoid-induced apoptosis is unknown. Previously, we showed that glucocorticoid treatment increases the steady state levels of hydrogen peroxide ([H2O2]ss) and oxidizes the redox environment in WEHI7.2 cells. In the current study, we found that when MnTE-2-PyP5+ is combined with glucocorticoids, it augments dexamethasone-induced oxidative stress however, it does not augment the [H2O2]ss levels. The combined treatment depletes GSH, oxidizes the 2GSH:GSSG ratio, and causes protein glutathionylation to a greater extent than glucocorticoid treatment alone. Removal of the glucocorticoid-generated H2O2 or depletion of glutathione by BSO prevents MnTE-2-PyP5+ from augmenting glucocorticoid-induced apoptosis. In combination with glucocorticoids, MnTE-2-PyP5+ glutathionylates p65 NF-κB and inhibits NF-κB activity. Inhibition of NF-κB with SN50, an NF-κB inhibitor, enhances glucocorticoid-induced apoptosis to the same extent as MnTE-2-PyP5+. Taken together, these findings indicate that: 1) H2O2 is important for MnTE-2-PyP5+ activity; 2) Mn-TE-2-PyP5+ cycles with GSH; and 3) MnTE-2-PyP5+ potentiates glucocorticoid-induced apoptosis by glutathionylating and inhibiting critical survival proteins, including NF-κB. In the clinic, over-expression of NF-κB is associated with a poor prognosis in lymphoma. MnTE-2-PyP5+ may therefore, synergize with glucocorticoids to inhibit NF-κB and improve current treatment.

Complex Chemistry and Biology of Redox-Active Compounds, Commonly Known as SOD Mimics, Affect Their Therapeutic Effects

“…In turn, this further supports the likelihood of the wide range of the reactivities of SOD mimics. We and others reported thus far on such reactivities (2,4,8,9). Yet, these reports have still made only modest impact on the field of Redox Biology and Drug Design.…”

“…Second, the experimental data show the differential impact of MnPs on normal versus cancer cells, which we understand now to be due to their differential redox environment: the cancer cell appears to be under high oxidative stress and produces higher peroxide levels that redox-active drugs can employ, as shown in lymphoma and leukemia studies by the Tome's group, to modify protein thiols and greatly affect proliferative and apoptotic processes. Eventually, such action would kill a cancer cell (7,8). At low levels of peroxide, the transient inhibition of NF-jB DNA binding would reduce secondary oxidative stress and, in turn, heal the normal cell, as indicated in Figure 1.…”

“…We have recently provided ample evidence that Mn porphyrins (in accord with their ability to act as prooxidants) interact with thiols. If that interaction occurs in the presence of peroxides, it produces an impact on the oxidation/ S-glutathionylation of signaling proteins (such as NF-jB) and components of the mitochondrial respiratory chain, suppressing ATP production (7,8 We have thus travelled a long way from identifying such redox-active drugs as SOD mimics to understand the key importance of their direct interactions with signaling protein thiols. In turn, we are offering here Figure 1 for the actions of cationic Mn N-substituted pyridylporphyrins and their impact on Redoxome (cellular redox-based pathways) in cancer and in normal cells.…”

The metabolites of glutamine prevent hydroxyl radical-induced apoptosis through inhibiting mitochondria and calcium ion involved pathways in fish erythrocytes

“…The activities of caspase-3, caspase-8 and caspase-9 were determined by measuring cleavage of the Ac-DEVD-pNA (caspase-3 substrate), Ac-IETD-pNA (caspase-8 substrate) and Ac-LEHD-pNA (caspase-9 substrate) to pNA using the detection kits (Beyotime, Nantong, China) as described previously [46,47]. The caspase activity in the samples was quantified with a Microplate reader (Thermo, Waltham, USA) at 405 nm.…”

Glyphosate, pathways to modern diseases IV: cancer and related pathologies

“…We mentioned earlier that Mn-SOD is protective against pancreatic cancer. Mn-SOD expression was also found to be anomalously low in erythrocytes of patients suffering from NHL [235]. In vitro studies have shown that an Mn-SOD mimetic had an anti-proliferation effect on human NHL Raji cells [236].…”