Doctor of Philosophy (PhD)
Biochemistry & Molecular Biology
Radiation therapy is frequently used as a treatment strategy for prostate cancer patients, which leads to several side effects due to damage to health tissue around the tumor and the development of radiation-induced fibrosis (RIF). Manganese (III) meso-tetrakis (N-ethylpyridinium-2-yl) porphyrin (MnTE-2-PyP or T2E or BMX-010) and other similar manganese porphyrin compounds that scavenge superoxide molecules have been demonstrated to be effective radioprotectors and prevent the development of RIF. However, understanding of the radioprotective molecular pathway associated with these compounds remains limited. Recent RNA-sequencing data from our laboratory revealed that MnTE-2-PyP treatment may activate the nuclear factor erythroid 2-related factor 2 (NRF2) signaling pathway. Therefore, we hypothesize that MnTE-2-PyP protects the prostate from RIF by activating the NRF2 signaling pathway. We identified that MnTE-2-PyP is a post-translational activator of NRF2 signaling in prostate fibroblast cells, which plays a major role in fibroblast activation and myofibroblast differentiation. The mechanism of NRF2 activation involves an increase in hydrogen peroxide and a corresponding decrease in kelch-like ECH-associated protein 1 (KEAP1) levels. Further, we identified some of the key downstream effects of NRF2 pathway activation by MnTE-2-PyP treatment in prostate fibroblast cells. The downstream changes identified include an increase in expression of NAD(P)H dehydrogenase [quinone] 1 (NQO1), increase in nicotinamide adenine dinucleotide (NAD+) levels, increase in sirtuin activity (nuclear and mitochondrial), and increase in superoxide dismutase 2 (SOD2) expression/activity. An increase in mitochondrial sirtuin activity correlates with a decrease in SOD2 (K122) acetylation. This decrease in SOD2 K122 acetylation correlates with an increase in SOD2 activity and mitochondrial superoxide scavenging capacity. Further, we identified changes in the consumption of mitochondrial substrates after radiation exposure that may correlate with mitochondrial health and protection mediated by MnTE-2-PyP. In the context of radiation exposure, MnTE-2-PyP fails to prevent fibroblast to myofibroblast transformation in the absence of NRF2 signaling. Collectively, our results indicate that the activation of the NRF2 signaling pathway by MnTE-2-PyP contributes to radioprotection in prostate fibroblast cells.
Shrishrimal, Shashank, "Molecular Mechanisms of Manganese Porphyrin Compounds in the Prevention of Radiation-Induced Fibrosis" (2020). Theses & Dissertations. 434.