The SOD Mimic, MnTE-2-PyP, Protects from Chronic Fibrosis and Inflammation in Irradiated Normal Pelvic Tissues

The role of Tyr34 in proton coupled electron transfer and product inhibition of manganese superoxide dismutase

Human manganese superoxide dismutase (MnSOD) plays a crucial role in controlling levels of reactive oxygen species (ROS) by converting superoxide (O 2 ∙ - ) to molecular oxygen (O2) and hydrogen peroxide (H2O2) with proton-coupled electron transfers (PCETs). A key catalytic residue, Tyr34, determines the activity of human MnSOD and also becomes post-translationally inactivated by nitration in various diseases associated with mitochondrial dysfunction. Tyr34 has an unusual pKa due to its proximity to the Mn metal and undergoes cyclic deprotonation and protonation events to promote the electron transfers of MnSOD. Neutron diffraction, X-ray spectroscopy, and quantum chemistry calculations in oxidized, reduced and product inhibited enzymatic states shed light on the role of Tyr34 in MnSOD catalysis. The data identify the contributions of Tyr34 in MnSOD activity that support mitochondrial function and give a thorough characterization of how a single tyrosine modulates PCET catalysis. Product inhibition occurs by an associative displacement mechanism.

Adipose Tissues Have Been Overlooked as Players in Prostate Cancer Progression

Obesity is a common risk factor in multiple tumor types, including prostate cancer. Obesity has been associated with driving metastasis, therapeutic resistance, and increased mortality. The effect of adipose tissue on the tumor microenvironment is still poorly understood. This review aims to highlight the work conducted in the field of obesity and prostate cancer and bring attention to areas where more research is needed. In this review, we have described key differences between healthy adipose tissues and obese adipose tissues, as they relate to the tumor microenvironment, focusing on mechanisms related to metabolic changes, abnormal adipokine secretion, altered immune cell presence, and heightened oxidative stress as drivers of prostate cancer formation and progression. Interestingly, common treatment options for prostate cancer ignore the adipose tissue located near the site of the tumor. Because of this, we have outlined how excess adipose tissue potentially affects therapeutics' efficacy, such as androgen deprivation, chemotherapy, and radiation treatment, and identified possible drug targets to increase prostate cancer responsiveness to clinical treatments. Understanding how obesity affects the tumor microenvironment will pave the way for understanding why some prostate cancers become metastatic or treatment-resistant, and why patients experience recurrence.

Balanced Duality: H2O2-Based Therapy in Cancer and Its Protective Effects on Non-Malignant Tissues

Conventional cancer therapy strategies, although centered around killing tumor cells, often lead to severe side effects on surrounding normal tissues, thus compromising the chronic quality of life in cancer survivors. Hydrogen peroxide (H2O2) is a secondary signaling molecule that has an array of functions in both tumor and normal cells, including the promotion of cell survival pathways and immune cell modulation in the tumor microenvironment. H2O2 is a reactive oxygen species (ROS) crucial in cellular homeostasis and signaling (at concentrations maintained under nM levels), with increased steady-state levels in tumors relative to their normal tissue counterparts. Increased steady-state levels of H2O2 in tumor cells, make them vulnerable to oxidative stress and ultimately, cell death. Recently, H2O2-producing therapies-namely, pharmacological ascorbate and superoxide dismutase mimetics-have emerged as compelling complementary treatment strategies in cancer. Both pharmacological ascorbate and superoxide dismutase mimetics can generate excess H2O2 to overwhelm the impaired H2O2 removal capacity of cancer cells. This review presents an overview of H2O2 metabolism in the physiological and malignant states, in addition to discussing the anti-tumor and normal tissue-sparing mechanism(s) of, and clinical evidence for, two H2O2-based therapies, pharmacological ascorbate and superoxide dismutase mimetics.

Radiation-induced fibrosis: Mechanisms and therapeutic strategies from an immune microenvironment perspective

Radiation-induced fibrosis (RIF) is a severe chronic complication of radiotherapy (RT) manifested by excessive extracellular matrix (ECM) components deposition within the irradiated area. The lung, heart, skin, jaw, pelvic organs and so on may be affected by RIF, which hampers body functions and quality of life. There is accumulating evidence suggesting that the immune microenvironment may play a key regulatory role in RIF. This article discussed the synergetic or antagonistic effects of immune cells and mediators in regulating RIF's development. Several potential preventative and therapeutic strategies for RIF were proposed based on the immunological mechanisms to provide clinicians with improved cognition and clinical treatment guidance.

Exogenous APN protects normal tissues from radiation-induced oxidative damage and fibrosis in mice and prostate cancer patients with higher levels of APN have less radiation-induced toxicities

Radiation causes damage to normal tissues that leads to increased oxidative stress, inflammation, and fibrosis, highlighting the need for the selective radioprotection of healthy tissues without hindering radiotherapy effectiveness in cancer. This study shows that adiponectin, an adipokine secreted by adipocytes, protects normal tissues from radiation damage invitro and invivo. Specifically, adiponectin (APN) reduces chronic oxidative stress and fibrosis in irradiated mice. Importantly, APN also conferred no protection from radiation to prostate cancer cells. Adipose tissue is the primary source of circulating endogenous adiponectin. However, this study shows that adipose tissue is sensitive to radiation exposure exhibiting morphological changes and persistent oxidative damage. In addition, radiation results in a significant and chronic reduction in blood APN levels from adipose tissue in mice and human prostate cancer patients exposed to pelvic irradiation. APN levels negatively correlated with bowel toxicity and overall toxicities associated with radiotherapy in prostate cancer patients. Thus, protecting, or modulating APN signaling may improve outcomes for prostate cancer patients undergoing radiotherapy.

The role of Tyr34 in proton-coupled electron transfer of human manganese superoxide dismutase

Human manganese superoxide dismutase (MnSOD) plays a crucial role in controlling levels of reactive oxygen species (ROS) by converting superoxide (O 2 •- ) to molecular oxygen (O 2 ) and hydrogen peroxide (H 2 O 2 ) with proton-coupled electron transfers (PCETs). The reactivity of human MnSOD is determined by the state of a key catalytic residue, Tyr34, that becomes post-translationally inactivated by nitration in various diseases associated with mitochondrial dysfunction. We previously reported that Tyr34 has an unusual pK a due to its proximity to the Mn metal and undergoes cyclic deprotonation and protonation events to promote the electron transfers of MnSOD. To shed light on the role of Tyr34 MnSOD catalysis, we performed neutron diffraction, X-ray spectroscopy, and quantum chemistry calculations of Tyr34Phe MnSOD in various enzymatic states. The data identifies the contributions of Tyr34 in MnSOD activity that support mitochondrial function and presents a thorough characterization of how a single tyrosine modulates PCET catalysis.

[Essential trace elements, vitamins, and selected electrolytes in complementary medicine for cancer patients]

OBJECTIVE

Are there any evidence-based medicine (EBM)-supported treatment approaches of complementary and alternative medicine (CAM) methods for urological oncologists?

METHODS

We reviewed the actual German S3 guidelines "Supportive Care" and "Complementary Medicine" as well as the online-tool Onkopedia for recommendations about essential trace elements (Zn, Se, Mn, Fe), vitamins (A, B, C, D, E), and electrolytes (Mg, Ca). Furthermore, we added results of randomized trials to present potential future developments.

RESULTS

Each therapy with micronutrients should be based on laboratory observation of a deficit. There are selected guideline recommendations for selenium, iron and vitamin D. Potential indications were registered for manganese, vitamin A derivates, and vitamin C. No benefit was observed for vitamin B, zinc, and vitamin E.

CONCLUSION

Micronutrients should be substituted in the case of deficit. General supplementation of daily nutrition is not recommended for cancer patients.

NRF2: A crucial regulator for mitochondrial metabolic shift and prostate cancer progression

Metabolic alterations are a common survival mechanism for prostate cancer progression and therapy resistance. Oxidative stress in the cellular and tumor microenvironment dictates metabolic switching in the cancer cells to adopt, prosper and escape therapeutic stress. Therefore, regulation of oxidative stress in tumor cells and in the tumor-microenvironment may enhance the action of conventional anticancer therapies. NRF2 is the master regulator for oxidative stress management. However, the overall oxidative stress varies with PCa clinical stage, metabolic state and therapy used for the cancer. In agreement, the blanket use of NRF2 inducers or inhibitors along with anticancer therapies cause adverse effects in some preclinical cancer models. In this review, we have summarized the levels of oxidative stress, metabolic preferences and NRF2 activity in the different stages of prostate cancer. We also propose condition specific ways to use NRF2 inducers or inhibitors along with conventional prostate cancer therapies. The significance of this review is not only to provide a detailed understanding of the mechanism of action of NRF2 to regulate oxidative stress-mediated metabolic switching by prostate cancer cells to escape the radiation, chemo, or hormonal therapies, and to grow aggressively, but also to provide a potential therapeutic method to control aggressive prostate cancer growth by stage specific proper use of NRF2 regulators.

Natural Antioxidant Evaluation: A Review of Detection Methods

Antioxidants have drawn the attention of the scientific community due to being related to the prevention of various degenerative diseases. The antioxidant capacity has been extensively studied in vitro, and different methods have been used to assess its activity. However, the main issues related to studying natural antioxidants are evaluating whether these antioxidants demonstrate a key role in the biological system and assessing their bioavailability in the organism. The majority of outcomes in the literature are controversial due to a lack of method standardization and their proper application. Therefore, this study aims to compile the main issues concerning the natural antioxidant field of study, comparing the most common in vitro methods to evaluate the antioxidant activity of natural compounds, demonstrating the antioxidant activity in biological systems and the role of the main antioxidant enzymes of redox cellular signaling and explaining how the bioavailability of bioactive compounds is evaluated in animal models and human clinical trials.

MnTE-2-PyP protects fibroblast mitochondria from hyperglycemia and radiation exposure

Radiation is a common anticancer therapy for prostate cancer, which transforms tumor-associated normal fibroblasts to myofibroblasts, resulting in fibrosis. Oxidative stress caused by radiation-mediated mitochondrial damage is one of the major contributors to fibrosis. As diabetics are oxidatively stressed, radiation-mediated reactive oxygen species cause severe treatment failure, treatment-related side effects, and significantly reduced survival for diabetic prostate cancer patients as compared to non-diabetic prostate cancer patients. Hyperglycemia and enhanced mitochondrial damage significantly contribute to oxidative damage and disease progression after radiation therapy among diabetic prostate cancer patients. Therefore, reduction of mitochondrial damage in normal prostate fibroblasts after radiation should improve the overall clinical state of diabetic prostate cancer patients. We previously reported that MnTE-2-PyP, a manganese porphyrin, reduces oxidative damage in irradiated hyperglycemic prostate fibroblasts by scavenging superoxide and activating NRF2. In the current study, we have investigated the potential role of MnTE-2-PyP to protect mitochondrial health in irradiated hyperglycemic prostate fibroblasts. This study revealed that hyperglycemia and radiation increased mitochondrial ROS via blocking the mitochondrial electron transport chain, altered mitochondrial dynamics, and reduced mitochondrial biogenesis. Increased mitochondrial damage preceeded an increase in myofibroblast differentiation. MnTE-2-PyP reduced myofibroblast differentiation, improved mitochondrial health by releasing the block on the mitochondrial electron transport chain, enhanced ATP production efficiency, and restored mitochondrial dynamics and metabolism in the irradiated-hyperglycemic prostate fibroblasts. Therefore, we are proposing that one of the mechanisms that MnTE-2-PyP protects prostate fibroblasts from irradiation and hyperglycemia-mediated damage is by protecting the mitochondrial health in diabetic prostate cancer patients.

Sympathoinhibition and Vasodilation Contribute to the Acute Hypotensive Response of the Superoxide Dismutase Mimic, MnTnBuOE-2-PyP5+, in Hypertensive Animals

The pathogenesis of hypertension has been linked to excessive levels of reactive oxygen species (ROS), particularly superoxide (O2•-), in multiple tissues and organ systems. Overexpression of superoxide dismutase (SOD) to scavenge O2•- has been shown to decrease blood pressure in hypertensive animals. We have previously shown that MnTnBuOE-2-PyP5+ (BuOE), a manganese porphyrin SOD mimic currently in clinical trials as a normal tissue protector for cancer patients undergoing radiation therapy, can scavenge O2•- and acutely decrease normotensive blood pressures. Herein, we hypothesized that BuOE decreases hypertensive blood pressures. Using angiotensin II (AngII)-hypertensive mice, we demonstrate that BuOE administered both intraperitoneally and intravenously (IV) acutely decreases elevated blood pressure. Further investigation using renal sympathetic nerve recordings in spontaneously hypertensive rats (SHRs) reveals that immediately following IV injection of BuOE, blood pressure and renal sympathetic nerve activity (RSNA) decrease. BuOE also induces dose-dependent vasodilation of femoral arteries from AngII-hypertensive mice, a response that is mediated, at least in part, by nitric oxide, as demonstrated by ex vivo video myography. We confirmed this vasodilation in vivo using doppler imaging of the superior mesenteric artery in AngII-hypertensive mice. Together, these data demonstrate that BuOE acutely decreases RSNA and induces vasodilation, which likely contribute to its ability to rapidly decrease hypertensive blood pressure.

The Ability of the Nitric Oxide Synthases Inhibitor T1023 to Selectively Protect the Non-Malignant Tissues

Previously, we showed that a nitric oxide synthase (NOS) inhibitor, compound T1023, induces transient hypoxia and prevents acute radiation syndrome (ARS) in mice. Significant efficacy (according to various tests, dose modifying factor (DMF)-1.6-1.9 against H-ARS/G-ARS) and safety in radioprotective doses (1/5-1/4 LD10) became the reason for testing its ability to prevent complications of tumor radiation therapy (RT). Research methods included studying T1023 effects on skin acute radiation reactions (RSR) in rats and mice without tumors and in tumor-bearing animals. The effects were evaluated using clinical, morphological and histological techniques as well as RTOG classification. T1023 administration prior to irradiation significantly limited the severity of acute RSR. This was due to a decrease in radiation alteration of the skin and underlying tissues, and the preservation of the functional activity of cell populations that are critical in the pathogenesis of radiation burn. The DMF values for T1023 for skin protection were 1.4-1.7. Moreover, its radioprotective effect was fully selective to normal tissues in RT models of solid tumors-T1023 reduced the severity of acute RSR and did not modify the antitumor effects of γ-radiation. The results indicate that T1023 can selectively protect the non-malignant tissues against γ-radiation due to hypoxic mechanism of action and potentiate opportunities of NOS inhibitors in RT complications prevention.

Impact of EcSOD Perturbations in Cancer Progression

Reactive oxygen species (ROS) are a normal byproduct of cellular metabolism and are required components in cell signaling and immune responses. However, an imbalance of ROS can lead to oxidative stress in various pathological states. Increases in oxidative stress are one of the hallmarks in cancer cells, which display an altered metabolism when compared to corresponding normal cells. Extracellular superoxide dismutase (EcSOD) is an antioxidant enzyme that catalyzes the dismutation of superoxide anion (O₂⁻) in the extracellular environment. By doing so, this enzyme provides the cell with a defense against oxidative damage by contributing to redox balance. Interestingly, EcSOD expression has been found to be decreased in a variety of cancers, and this loss of expression may contribute to the development and progression of malignancies. In addition, recent compounds can increase EcSOD activity and expression, which has the potential for altering this redox signaling and cellular proliferation. This review will explore the role that EcSOD expression plays in cancer in order to better understand its potential as a tool for the detection, predicted outcomes and potential treatment of malignancies.

High serum superoxide dismutase activity improves radiation-related quality of life in patients with esophageal squamous cell carcinoma

OBJECTIVES

Esophageal squamous cell carcinoma (ESCC) is one of the most common malignant tumors in China. Intensity-modulated radiation therapy and volume-modulated arc therapy have become the main treatments for esophageal carcinoma; however, side effects caused by radiotherapy greatly impact the quality of life in these patients. This study aimed to explore the impact of serum superoxide dismutase (SOD) levels on the prognosis of patients with ESCC undergoing radiotherapy.

METHODS

Patients aged between 18 and 80 years with lower-middle ESCC who underwent radiotherapy were eligible for this assessment. Adverse events, responses, treatment outcomes, and overall survival (OS) were assessed. Between 2012 and 2014, 195 patients were enrolled, of which 65 were assigned to the low- and high-SOD groups based on their serum SOD values.

RESULTS

The baseline characteristics were similar between the two groups, except for the T staging. Adverse events in the low-SOD group were significantly higher than those in the high-SOD group (radiation esophagitis, p=0.007; radiation pneumonitis, p=0.032; leukopenia, p=0.023; thrombocytopenia, p=0.037; anemia, p=0.041). There were no significant differences in response, treatment outcomes, or OS.

CONCLUSION

In conclusion, high serum SOD activity improved post-radiotherapy quality of life but did not impact the prognosis of patients with ESCC. To the best of our knowledge, this study is the first to report that serum SOD activity is associated with radiation-induced toxicity and moderately increased radiotherapeutic response in patients with ESCC undergoing radiotherapy.

Decoding the role of SOD2 in sickle cell disease

Sickle cell disease (SCD) is an inherited hemoglobinopathy caused by a single point mutation in the β-globin gene. As a consequence, deoxygenated hemoglobin polymerizes triggering red blood cell sickling and hemolysis, vaso-occlusion, and ischemia/reperfusion. Allied to these pathologies is the overproduction of reactive oxygen species driven by hemoglobin Fenton chemistry and peroxidase reactions as well as by secondary activation of vascular oxidases, including NAD(P)H oxidase and xanthine oxidase. In addition, hypoxia, produced by sickle red blood cell occlusion, disrupts mitochondrial metabolism and generates excess superoxide through electron leak from the mitochondrial respiratory chain. Superoxide dismutase 2 (SOD2) is a mitochondrial-specific antioxidant enzyme that dismutates superoxide to hydrogen peroxide, which is then converted to water by catalase and glutathione peroxidase. In SCD, the antioxidant defense system is significantly diminished through decreased expression and activity levels of antioxidant enzymes, including superoxide dismutase, catalase, and glutathione peroxidase. From a translational perspective, genetic variants including a missense variant in SOD2 (valine to alanine at position 16) are present in 45% of people with African ancestry and are associated with increased sickle complications. While it is known that there is an imbalance between oxidative species and antioxidant defenses in SCD, much more investigation is warranted. This review summarizes our current understanding of antioxidant defense systems in SCD, particularly focused on SOD2, and provides insight into challenges and opportunities as the field moves forward.

Pursuing the Elixir of Life: In Vivo Antioxidative Effects of Manganosalen Complexes

Manganosalen complexes are coordination compounds that possess a chelating salen-type ligand, a class of bis-Schiff bases obtained by condensation of salicylaldehyde and a diamine. They may act as catalytic antioxidants mimicking both the structure and the reactivity of the native antioxidant enzymes active site. Thus, manganosalen complexes have been shown to exhibit superoxide dismutase, catalase, and glutathione peroxidase activities, and they could potentially facilitate the scavenging of excess reactive oxygen species (ROS), thereby restoring the redox balance in damaged cells and organs. Initial catalytic studies compared the potency of these compounds as antioxidants in terms of rate constants of the chemical reactivity against ROS, giving catalytic values approaching and even exceeding that of the native antioxidative enzymes. Although most of these catalytic studies lack of biological relevance, subsequent in vitro studies have confirmed the efficiency of many manganosalen complexes in oxidative stress models. These synthetic catalytic scavengers, cheaper than natural antioxidants, have accordingly attracted intensive attention for the therapy of ROS-mediated injuries. The aim of this review is to focus on in vivo studies performed on manganosalen complexes and their activity on the treatment of several pathological disorders associated with oxidative damage. These disorders, ranging from the prevention of fetal malformations to the extension of lifespan, include neurodegenerative, inflammatory, and cardiovascular diseases; tissue injury; and other damages related to the liver, kidney, or lungs.

Adipocytes protect fibroblasts from radiation-induced damage by adiponectin secretion

Prostate and colon cancers are among the most common cancers diagnosed annually, and both often require treatment with radiation therapy. Advancement in radiation delivery techniques has led to highly accurate targeting of tumor and sparing of normal tissue; however, in the pelvic region it is anatomically difficult to avoid off-target radiation exposure to other organs. Chronically the effects of normal urogenital tissue exposure can lead to urinary frequency, urinary incontinence, proctitis, and erectile dysfunction. Most of these symptoms are caused by radiation-induced fibrosis and reduce the quality of life for cancer survivors. We have observed in animal models that the severity of radiation-induced fibrosis in normal tissue correlates to damaged fat reservoirs in the pelvic region. We hypothesize that adipocytes may secrete a factor that prevents the induction of radiation-associated fibrosis in normal tissues. In these studies we show that the adipokine, adiponectin, is secreted by primary mouse adipocytes and protects fibroblasts from radiation-induced cell death, myofibroblast formation, and senescence. Further, we demonstrated that adiponectin does not protect colorectal or prostate cancer cells from radiation-induced death. Thus, we propose that adiponectin, or its downstream pathway, would provide a novel target for adjuvant therapy when treating pelvic cancers with radiation therapy.

Nanoformulation of the superoxide dismutase mimic, MnTnBuOE-2-PyP5+, prevents its acute hypotensive response

Scavenging superoxide (O₂^•-) via overexpression of superoxide dismutase (SOD) or administration of SOD mimics improves outcomes in multiple experimental models of human disease including cardiovascular disease, neurodegeneration, and cancer. While few SOD mimics have transitioned to clinical trials, MnTnBuOE-2-PyP⁵⁺ (BuOE), a manganese porphyrin SOD mimic, is currently in clinical trials as a radioprotector for cancer patients; thus, providing hope for the use of SOD mimics in the clinical setting. However, BuOE transiently alters cardiovascular function including a significant and precipitous decrease in blood pressure. To limit BuOE's acute hypotensive action, we developed a mesoporous silica nanoparticle and lipid bilayer nanoformulation of BuOE (nanoBuOE) that allows for slow and sustained release of the drug. Herein, we tested the hypothesis that unlike native BuOE, nanoBuOE does not induce an acute hypotensive response, as the nanoformulation prevents BuOE from scavenging O₂^•- while the drug is still encapsulated in the formulation. We report that intact nanoBuOE does not effectively scavenge O₂^•-, whereas BuOE released from the nanoformulation does retain SOD-like activity. Further, in mice, native BuOE, but not nanoBuOE, rapidly, acutely, and significantly decreases blood pressure, as measured by radiotelemetry. To begin exploring the physiological mechanism by which native BuOE acutely decreases blood pressure, we recorded renal sympathetic nerve activity (RSNA) in rats. RSNA significantly decreased immediately following intravenous injection of BuOE, but not nanoBuOE. These data indicate that nanoformulation of BuOE, a SOD mimic currently in clinical trials in cancer patients, prevents BuOE's negative side effects on blood pressure homeostasis.

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MnTnBuOE-2-PyP⁵⁺ (BuOE) induces a rapid and significant decrease in blood pressure.

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BuOE's hypotensive response is concomitant with reduced sympathetic nerve activity.

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Nanoformulated BuOE (nanoBuOE) release of active drug is slow and sustained.

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nanoBuOE prevents the BuOE-induced hypotensive and sympathoinhibition responses.

MnTE-2-PyP Suppresses Prostate Cancer Cell Growth via H2O2 Production

Prostate cancer patients are often treated with radiotherapy. MnTE-2-PyP, a superoxide dismutase (SOD) mimic, is a known radioprotector of normal tissues. Our recent work demonstrated that MnTE-2-PyP also inhibits prostate cancer progression with radiotherapy; however, the mechanisms remain unclear. In this study, we identified that MnTE-2-PyP-induced intracellular H₂O₂ levels are critical in inhibiting the growth of PC3 and LNCaP cells, but the increased H₂O₂ levels affected the two cancer cells differently. In PC3 cells, many proteins were thiol oxidized with MnTE-2-PyP treatment, including Ser/Thr protein phosphatase 1 beta catalytic subunit (PP1CB). This resulted in reduced PP1CB activity; however, overall cell cycle progression was not altered, so this is not the main mechanism of PC3 cell growth inhibition. High H₂O₂ levels by MnTE-2-PyP treatment induced nuclear fragmentation, which could be synergistically enhanced with radiotherapy. In LNCaP cells, thiol oxidation by MnTE-2-PyP treatment was not observed previously and, similarly to PC3 cells, there was no effect of MnTE-2-PyP treatment on cell cycle progression. However, in LNCaP cells, MnTE-2-PyP caused an increase in low RNA population and sub-G₁ population of cells, which indicates that MnTE-2-PyP treatment may cause cellular quiescence or direct cancer cell death. The protein oxidative modifications and mitotic catastrophes caused by MnTE-2-PyP may be the major contributors to cell growth inhibition in PC3 cells, while in LNCaP cells, tumor cell quiescence or cell death appears to be major factors in MnTE-2-PyP-induced growth inhibition.

Manganese porphyrin, MnTE-2-PyP, treatment protects the prostate from radiation-induced fibrosis (RIF) by activating the NRF2 signaling pathway and enhancing SOD2 and sirtuin activity

Radiation therapy is a frequently used treatment for prostate cancer patients. 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 radiation-induced fibrosis (RIF). However, understanding the molecular pathway changes associated with these compounds remains limited for radioprotection. Recent RNA-sequencing data from our laboratory revealed that MnTE-2-PyP treatment activated 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. Activation of NRF2 signaling leads to an increase in expression of NAD(P)H dehydrogenase [quinone] 1 (NQO1), nicotinamide adenine dinucleotide (NAD+) levels, sirtuin activity (nuclear and mitochondrial), and superoxide dismutase 2 (SOD2) expression/activity. 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, in human primary prostate fibroblast cells, the NRF2 pathway plays a major role in the fibroblast to myofibroblast transformation, which is responsible for the fibrotic phenotype. In the context of radiation protection, 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 is at least a partial mechanism of radioprotection in prostate fibroblast cells.

MnTE-2-PyP, a manganese porphyrin, reduces cytotoxicity caused by irradiation in a diabetic environment through the induction of endogenous antioxidant defenses

Radiation is a common anticancer therapy for many cancer patients, including prostate cancer. Diabetic prostate cancer patients suffer from increased lymph node metastasis, tumor recurrence and decreased survival as compared to non-diabetic prostate cancer patients. These patients are also at increased risk for enhanced radiation-induced normal tissue damage such as proctitis. Diabetics are oxidatively stressed and radiation causes additional oxidative damage. We and others have reported that, MnTE-2-PyP, a manganese porphyrin, protects normal prostate tissue from radiation damage. We have also reported that, in an in vivo mouse model of prostate cancer, MnTE-2-PyP decreases tumor volume and increases survival of the mice. In addition, MnTE-2-PyP has also been shown to reduce blood glucose and inhibits pro-fibrotic signaling in a diabetic model. Therefore, to investigate the role of MnTE-2-PyP in normal tissue protection in an irradiated diabetic environment, we have treated human prostate fibroblast cells with MnTE-2-PyP in an irradiated hyperglycemic environment. This study revealed that hyperglycemia causes increased cell death after radiation as compared to normo-glycemia. MnTE-2-PyP protects against hyperglycemia-induced cell death after radiation. MnTE-2-PyP decreases expression of NOX4 and α-SMA, one of the major oxidative enzymes and pro-fibrotic molecules respectively. MnTE-2-PyP obstructs NF-κB activity by decreasing DNA binding of the p50-p50 homodimer in the irradiated hyperglycemic environment. MnTE-2-PyP increases NRF2 mediated cytoprotection by increasing NRF2 protein expression and DNA binding. Therefore, we are proposing that, MnTE-2-PyP protects fibroblasts from irradiation and hyperglycemia damage by enhancing the NRF2- mediated pathway in diabetic prostate cancer patients, undergoing radiotherapy.

Utilizing Superoxide Dismutase Mimetics to Enhance Radiation Therapy Response While Protecting Normal Tissues

Symptomatic normal tissue injury is a common side effect following definitive therapeutic radiation and chemotherapy treatment for a variety of malignancies. These cancer therapy related toxicities may occur acutely during treatment resulting in reduced or missed therapy agent administration or after the completion of therapy resulting in significant chronic morbidities that significantly diminish patient quality of life. Radiation and chemotherapy induce the formation of reactive oxygen species (ROS) both in normal tissues and tumor cells. One type of ROS common to both chemotherapy and radiation therapy is the formation of superoxide (O^2•-). Fortunately, due to metabolic differences between cancer and normal cell metabolism, as well as improved targeting techniques, ROS generation following radiation and chemotherapy is generally greater in cancer cells compared to normal tissues. However, the levels of ROS generated in normal tissues are capable of inducing significant toxicity. Thus, several groups are focusing on metabolism-based approaches to mitigate normal tissue effects occurring both during and following cancer therapy. This review will summarize the most current preclinical and clinical data available demonstrating the efficacy of small molecule, superoxide dismutase mimetics in minimizing radiation and chemotherapy-induced normal tissue injury, resulting in enhanced patient outcomes.

Reactive Oxygen Species Drive Epigenetic Changes in Radiation-Induced Fibrosis

Radiation-induced fibrosis (RIF) develops months to years after initial radiation exposure. RIF occurs when normal fibroblasts differentiate into myofibroblasts and lay down aberrant amounts of extracellular matrix proteins. One of the main drivers for developing RIF is reactive oxygen species (ROS) generated immediately after radiation exposure. Generation of ROS is known to induce epigenetic changes and cause differentiation of fibroblasts to myofibroblasts. Several antioxidant compounds have been shown to prevent radiation-induced epigenetic changes and the development of RIF. Therefore, reviewing the ROS-linked epigenetic changes in irradiated fibroblast cells is essential to understand the development and prevention of RIF.

Modern management of osteoradionecrosis

PURPOSE OF REVIEW

Despite recent advances in radiotherapy, osteoradionecrosis (ORN) remains a common and difficult complication of radiation therapy in head and neck cancer patients. Available treatment options are complementary to its complex pathophysiology and the currently available theories of ORN development. The efficacy of hyperbaric oxygen therapy has recently been questioned, and therapies targeting the fibroatrophic process have become a focus of ORN treatment. The objective of this review is to evaluate the literature regarding ORN of the mandible, with a focus on available treatment options.

RECENT FINDINGS

The recently proposed fibroatrophic theory has challenged the traditional hypovascular-hypoxic-hypocellular theory as the mechanism of ORN. Medical management targeting this fibroatrophic process offers promising results, but has yet to be confirmed with robust clinical trials. The routine use of hyperbaric oxygen therapy is not substantiated in the literature, but may be justified for select patients. Systemic steroids may also have a role, though data are limited.

SUMMARY

The fibroatrophic process has gained acceptance as a main mechanism of ORN. No gold standard treatment or consensus guidelines exist, though a combination of therapeutic strategies should be considered, taking into account the severity of disease and individual patient characteristics.

Mn Porphyrin-Based Redox-Active Drugs: Differential Effects as Cancer Therapeutics and Protectors of Normal Tissue Against Oxidative Injury

SIGNIFICANCE

After approximatelty three decades of research, two Mn(III) porphyrins (MnPs), MnTE-2-PyP⁵⁺ (BMX-010, AEOL10113) and MnTnBuOE-2-PyP⁵⁺ (BMX-001), have progressed to five clinical trials. In parallel, another similarly potent metal-based superoxide dismutase (SOD) mimic-Mn(II)pentaaza macrocycle, GC4419-has been tested in clinical trial on application, identical to that of MnTnBuOE-2-PyP⁵⁺-radioprotection of normal tissue in head and neck cancer patients. This clearly indicates that Mn complexes that target cellular redox environment have reached sufficient maturity for clinical applications. Recent Advances: While originally developed as SOD mimics, MnPs undergo intricate interactions with numerous redox-sensitive pathways, such as those involving nuclear factor κB (NF-κB) and nuclear factor E2-related factor 2 (Nrf2), thereby impacting cellular transcriptional activity. An increasing amount of data support the notion that MnP/H₂O₂/glutathione (GSH)-driven catalysis of S-glutathionylation of protein cysteine, associated with modification of protein function, is a major action of MnPs on molecular level.

CRITICAL ISSUES

Differential effects of MnPs on normal versus tumor cells/tissues, which support their translation into clinic, arise from differences in their accumulation and redox environment of such tissues. This in turn results in different yields of MnP-driven modifications of proteins. Thus far, direct evidence for such modification of NF-κB, mitogen-activated protein kinases (MAPK), phosphatases, Nrf2, and endogenous antioxidative defenses was provided in tumor, while indirect evidence shows the modification of NF-κB and Nrf2 translational activities by MnPs in normal tissue.

FUTURE DIRECTIONS

Studies that simultaneously explore differential effects in same animal are lacking, while they are essential for understanding of extremely intricate interactions of metal-based drugs with complex cellular networks of normal and cancer cells/tissues.

A Review of the Catalytic Mechanism of Human Manganese Superoxide Dismutase

Superoxide dismutases (SODs) are necessary antioxidant enzymes that protect cells from reactive oxygen species (ROS). Decreased levels of SODs or mutations that affect their catalytic activity have serious phenotypic consequences. SODs perform their bio-protective role by converting superoxide into oxygen and hydrogen peroxide by cyclic oxidation and reduction reactions with the active site metal. Mutations of SODs can cause cancer of the lung, colon, and lymphatic system, as well as neurodegenerative diseases such as Parkinson's disease and amyotrophic lateral sclerosis. While SODs have proven to be of significant biological importance since their discovery in 1968, the mechanistic nature of their catalytic function remains elusive. Extensive investigations with a multitude of approaches have tried to unveil the catalytic workings of SODs, but experimental limitations have impeded direct observations of the mechanism. Here, we focus on human MnSOD, the most significant enzyme in protecting against ROS in the human body. Human MnSOD resides in the mitochondrial matrix, the location of up to 90% of cellular ROS generation. We review the current knowledge of the MnSOD enzymatic mechanism and ongoing studies into solving the remaining mysteries.