Radioresistance in Prostate Cancer: Focus on the Interplay between NF-κB and SOD

Prostate cancer occurs frequently in men and can often lead to death. Many cancers, including prostate cancer, can be initiated by oxidative insult caused by free radicals and reactive oxygen species. The superoxide dismutase family removes the oxygen-derived reactive oxygen species, and increased superoxide dismutase activity can often be protective against prostate cancer. Prostate cancer can be treated in a variety of ways, including surgery, androgen deprivation therapy, radiation therapy, and chemotherapy. The clinical trajectory of prostate cancer varies from patient to patient, but more aggressive tumors often tend to be radioresistant. This is often due to the free-radical and reactive-oxygen-species-neutralizing effects of the superoxide dismutase family. Superoxide dismutase 2, which is especially important in this regard, can be induced by the NF-κB pathway, which is an important mechanism in radioresistance. This information has enabled the development of interventions that manipulate the NF-κB mechanism to treat prostate cancer.

Sirtuin-3 Protects Cochlear Hair Cells Against Noise-Induced Damage via the Superoxide Dismutase 2/Reactive Oxygen Species Signaling Pathway

Mitochondrial oxidative stress is involved in hair cell damage caused by noise-induced hearing loss (NIHL). Sirtuin-3 (SIRT3) plays an important role in hair cell survival by regulating mitochondrial function; however, the role of SIRT3 in NIHL is unknown. In this study, we used 3-TYP to inhibit SIRT3 and found that this inhibition aggravated oxidative damage in the hair cells of mice with NIHL. Moreover, 3-TYP reduced the enzymatic activity and deacetylation levels of superoxide dismutase 2 (SOD2). Subsequently, we administered adeno-associated virus-SIRT3 to the posterior semicircular canals and found that SIRT3 overexpression significantly attenuated hair cell injury and that this protective effect of SIRT3 could be blocked by 2-methoxyestradiol, a SOD2 inhibitor. These findings suggest that insufficient SIRT3/SOD2 signaling leads to mitochondrial oxidative damage resulting in hair cell injury in NIHL. Thus, ameliorating noise-induced mitochondrial redox imbalance by intervening in the SIRT3/SOD2 signaling pathway may be a new therapeutic target for hair cell injury.

The Role of Endothelial Superoxide Dismutase 2 in Modulating Sickle Pathology

Sickle cell disease (SCD) patients suffer from hemolysis in microcirculation. On the one hand, hemoglobin and heme released from sickled red blood cells catalyze reactive oxygen species (ROS) generation by Fenton chemistry. On the other hand, sickled red blood cells occlude capillaries, creating a hypoxic condition that exacerbates ROS production. As an essential antioxidant mechanism, superoxide dismutase 2 (SOD2) detoxifies superoxide by converting it to hydrogen peroxide (H 2O 2) in the mitochondria. In SCD patients, despite the elevated ROS production, we found that SOD2 expression is suppressed in the pulmonary endothelium (Figure 1A,B). Therefore, we hypothesize the depletion of endothelial SOD2 compromises endothelial function and exacerbates the progression of SCD. To examine the role of endothelial SOD2, we silenced SOD2 gene expression (SOD2 KD) with siRNA in primary human pulmonary microvascular endothelial cells (hPMVECs). Knocking down SOD2 in hPMVECs accelerated mitochondrial superoxide production and compromised mitochondrial potential. However, mitochondrial respiration, the activity of respiratory complexes, and the cellular ATP content were not affected by SOD2 KD. An important function of endothelial cells is to form a barrier and sequester cellular and molecular contents in the blood. SOD2 KD hPMVECs exhibited increased albumin leakage and decreased transendothelial resistance, indicating a disrupted endothelial barrier(Figure 1C). The defect in the endothelial barrier was rescued by adding 4 mM H 2O 2(Figure 1D), suggesting SOD2-derived H 2O 2 may serve as a critical signaling molecule. Moreover, cell migration or proliferation was inhibited in SOD2 KD hPMVECs, which was examined by a scratch assay. Since both cell migration and barrier maintenance require focal adhesion assembly, we next investigated the role of SOD2 in focal adhesion dynamics. In an attachment assay, SOD2 KD reduced cell attachment rate on uncoated plates, which was blunted by fibronectin precoating, indicating a fibronectin-dependent defect in cell adhesion(Figure 1E,F). Notably, although fibronectin protein expression in hPMVECs was not altered, SOD2 KD decreased the dimer/monomer ratio. Furthermore, confocal images showed that fibronectin was retained in SOD2 KD cells(Figure 1G), highlighting the importance of SOD2 in fibronectin assembly. In conclusion, we demonstrated for the first time that SOD2 expression is diminished in the pulmonary endothelium of SCD patients and that endothelial SOD2 is crucial for endothelial function by facilitating fibronectin assembly. The importance of SOD2 in endothelial function may prove therapeutic value in SCD patients, which requires further investigation. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.

Characterization of Heat Shock Protein 60 as an Interacting Partner of Superoxide Dismutase 2 in the Silkworm, Bombyx mori, and Its Response to the Molting Hormone, 20-Hydroxyecdysone

Oxidative stress promotes pupation in some holometabolous insects. The levels of superoxide, a reactive oxygen species (ROS), are increased and superoxide dismutase 1 (BmSod1) and superoxide dismutase 2 (BmSod2) are decreased during metamorphic events in silkworm (Bombyx mori). These observations strongly suggest that pupation is initiated by oxidative stress via the down-regulation of BmSod1 and BmSod2. However, the molecular mechanisms underlying ROS production during metamorphic events in silkworm remain unknown. To investigate these molecular mechanisms, the peripheral proteins of BmSod1 and BmSod2 were identified and characterized using dry and wet approaches in this study. Based on the results, silkworm heat shock protein 60 (BmHsp60) was identified as an interacting partner of BmSod2, which belongs to the Fe/MnSOD family. Furthermore, the present study results showed that BmHsp60 mRNA expression levels were increased in response to oxidative stress caused by ultraviolet radiation and that BmHsp60 protein levels (but not mRNA levels) were decreased during metamorphic events, which are regulated by the molting hormone 20-hydroxyecdysone. These findings improve our understanding of the mechanisms by which holometabolous insects control ROS during metamorphosis.

Anakinra Activates Superoxide Dismutase 2 to Mitigate Inflammasome Activity

Inflammasomes are powerful cytosolic sensors of environmental stressors and are critical for triggering interleukin-1 (IL-1)-mediated inflammatory responses. However, dysregulation of inflammasome activation may lead to pathological conditions, and the identification of negative regulators for therapeutic purposes is increasingly being recognized. Anakinra, the recombinant form of the IL-1 receptor antagonist, proved effective by preventing the binding of IL-1 to its receptor, IL-1R1, thus restoring autophagy and dampening NLR family pyrin domain containing 3 (NLRP3) activity. As the generation of mitochondrial reactive oxidative species (ROS) is a critical upstream event in the activation of NLRP3, we investigated whether anakinra would regulate mitochondrial ROS production. By profiling the activation of transcription factors induced in murine alveolar macrophages, we found a mitochondrial antioxidative pathway induced by anakinra involving the manganese-dependent superoxide dismutase (MnSOD) or SOD2. Molecularly, anakinra promotes the binding of SOD2 with the deubiquitinase Ubiquitin Specific Peptidase 36 (USP36) and Constitutive photomorphogenesis 9 (COP9) signalosome, thus increasing SOD2 protein longevity. Functionally, anakinra and SOD2 protects mice from pulmonary oxidative inflammation and infection. On a preclinical level, anakinra upregulates SOD2 in murine models of chronic granulomatous disease (CGD) and cystic fibrosis (CF). These data suggest that protection from mitochondrial oxidative stress may represent an additional mechanism underlying the clinical benefit of anakinra and identifies SOD2 as a potential therapeutic target.

Tempeh extract reduces cellular ROS levels and upregulates the expression of antioxidant enzymes

Tempeh is an Indonesian traditional food produced from soybeans through a mould fermentation involving Rhizopus oligosporus. It is rich in bioactive phytochemicals, including isoflavones that are known to exhibit antioxidant activities. This study aimed to investigate the ability of tempeh ethanol extract to reduce cellular reactive oxygen species (ROS) levels in HepG2 cells in vitro. Tempeh extract exhibited greater total phenolics, total flavonoids and free radical inhibition capacity than soybean extract. Both tempeh extract and soybean extract reduced the basal levels of cellular ROS in the cells, but tempeh extract induced higher expression of antioxidant enzymes [catalase, superoxide dismutase-2 (SOD2) and superoxide dismutase-3 (SOD3)] compared to soybean extract. This study provides novel evidence suggesting the ability of tempeh to tackle cellular oxidative stress by upregulating the expression of antioxidant enzymes. These findings would give an insight into the potential of tempeh to be developed as a functional food beneficial for human health.

Chewing Behavior Attenuates the Tumor Progression-Enhancing Effects of Psychological Stress in a Breast Cancer Model Mouse

We examined whether chewing behavior affects the tumor progression-enhancing impact of psychological stress. Human breast cancer cell line (MDA-MB-231) cells were inoculated into the mammary fat pads of athymic nude mice. The mice were assigned randomly to control, stress, and stress+chewing groups. Psychological stress was created by keeping mice in a transparent restraint cylinder for 45 min, three times a day, for 35 days after cell inoculation. Animals in the stress+chewing group were provided with a wooden stick for chewing on during the psychological stress period. Chewing behavior remarkably inhibited the tumor growth accelerated by the psychological stress. Immunohistochemical and Western blot findings revealed that chewing behavior during psychological stress markedly suppressed tumor angiogenesis and cell proliferation. In addition, chewing behavior decreased serum glucocorticoid levels and expressions of glucocorticoid and β2-adrenergic receptors in tumors. Chewing behavior decreased expressions of inducible nitric oxide synthase and 4-hydroxynonenal, and increased expression of superoxide dismutase 2 in tumors. Our findings suggest that chewing behavior could ameliorate the enhancing effects of psychological stress on the progression of breast cancer, at least partially, through modulating stress hormones and their receptors, and the subsequent signaling pathways involving reactive oxygen and nitrogen species.

Complexed trace mineral supplementation alters antioxidant activities and expression in response to trailer stress in yearling horses in training

To test the hypothesis that complexed trace mineral supplementation would increase antioxidant capacity and decrease muscle oxidative stress and damage in young horses entering an exercise training program, Quarter Horses (mean $$\pm$$ ± SD; 9.7 ± 0.7 mo) balanced by age, sex, and BW were assigned to receive complexed (CTM; n = 8) or inorganic (INORG; n = 8) trace minerals at -12 week relative to this study. Blood and muscle samples were collected before (week 0) and after 12 week of light exercise training surrounding a 1.5-h trailer stressor. Muscle glutathione peroxidase (GPx) activity was higher for CTM than INORG horses (P ≤ 0.0003) throughout the study. Following both trailer stressors, serum creatine kinase increased (P < 0.0001) and remained elevated through 24 h post-trailering (P < 0.0001). At week 0, muscle malondialdehyde, expression of superoxide dismutase 2, and whole blood GPx activity increased (P$$\le$$ ≤ 0.003) following trailering but trailering did not affect these measures at week 12. Young horses supplemented with CTM had higher muscle GPx activity than horses receiving INORG, but CTM did not affect damage markers following a stressor. Dietary CTM may be useful for improving antioxidant capacity during exercise training in young equine athletes.