Kyu Tae Chang

Gene expression defines natural changes in mammalian lifespan

Mammals differ more than 100‐fold in maximum lifespan, which can be altered in either direction during evolution, but the molecular basis for natural changes in longevity is not understood. Divergent evolution of mammals also led to extensive changes in gene expression within and between lineages. To understand the relationship between lifespan and variation in gene expression, we carried out RNA‐seq‐based gene expression analyses of liver, kidney, and brain of 33 diverse species of mammals. Our analysis uncovered parallel evolution of gene expression and lifespan, as well as the associated life‐history traits, and identified the processes and pathways involved. These findings provide direct insights into how nature reversibly adjusts lifespan and other traits during adaptive radiation of lineages.

Peroxiredoxin I is a ROS/p38 MAPK-dependent inducible antioxidant that regulates NF-κB-mediated iNOS induction and microglial activation

Reactive oxygen species (ROS) function as modulators of pro-inflammatory processes in microglia-associated neurodegenerative diseases. However, little is known about the involvement of specific antioxidants in regulating the microglial redox status. Here, we demonstrated that peroxiredoxin (Prx) I activity was induced by lipopolysaccharide (LPS), but not paraquat and hydrogen peroxide, through activation of the ROS/p38 MAPK signal pathway, and participated in alleviating the microglial activation and generation of nitric oxide (NO). Interestingly, a null mutation of Prx I accelerated NF-κB-mediated iNOS induction and subsequent NO secretion in LPS-stimulated microglia. Furthermore, F4/80 expression as microglial activation marker was notably up-regulated in primary cultures of microglia, hippocampal sections, and cerebral cortex of 15-month-old Prx I(-/-) mouse. Taken together, the results of our study indicated that Prx I is an antioxidant that is up-regulated in a ROS/p38 MAPK-dependent manner and governs the progression of neuroinflammation by suppressing microglial activation. In addition, Prx I deficiency increased the nuclear translocation of NF-κB mediated-iNOS induction as pro-inflammatory mediators. The findings of our work suggest possible strategies for developing novel therapies to treat inflammation-associated degenerative neurological diseases by targeting the induction of Prx I in microglial cells.

Melatonin plus exercise-based neurorehabilitative therapy for spinal cord injury.

Abstract:u2002 Spinal cord injury (SCI) is damage to the spinal cord caused by the trauma or disease that results in compromised or loss of body function. Subsequent to SCI in humans, many individuals have residual motor and sensory deficits that impair functional performance and quality of life. The available treatments for SCI are rehabilitation therapy, activity‐based therapies, and pharmacological treatment using antioxidants and their agonists. Among pharmacological treatments, the most efficient and commonly used antioxidant for experimental SCI treatment is melatonin, an indolamine secreted by pineal gland at night. Melatonin’s receptor‐independent free radical scavenging action and its broad‐spectrum antioxidant activity makes it an ideal antioxidant to protect tissue from oxidative stress‐induced secondary damage after SCI. Owing to the limitations of an activity‐based therapy and antioxidant treatment singly on the functional recovery and oxidative stress‐induced secondary damages after SCI, a melatonin plus exercise treatment may be a more effective therapy for SCI. As suggested herein, supplementation with melatonin in conjunction with exercise not only would improve the functional recovery by enhancing the beneficial effects of exercise but would reduce the secondary tissue damage simultaneously. Finally, melatonin may protect against exercise‐induced fatigue and impairments. In this review, based on the documented evidence regarding the beneficial effects of melatonin, activity‐based therapy and the combination of both on functional recovery, as well as reduction of secondary damage caused by oxidative stress after SCI, we suggest the melatonin combined with exercise would be a novel neurorehabilitative strategy for the faster recovery after SCI.

Organization of the Mammalian Metabolome according to Organ Function, Lineage Specialization, and Longevity

Biological diversity among mammals is remarkable. Mammalian body weights range seven orders of magnitude and lifespans differ more than 100-fold among species. While genetic, dietary, and pharmacological interventions can be used to modulate these traits in model organisms, it is unknown how they are determined by natural selection. By profiling metabolites in brain, heart, kidney, and liver tissues of 26 mammalian species representing ten taxonomical orders, we report metabolite patterns characteristic of organs, lineages, and species longevity. Our data suggest different rates of metabolite divergence across organs and reveal patterns representing organ-specific functions and lineage-specific physiologies. We identified metabolites that correlated with species lifespan, some of which were previously implicated in longevity control. We also compared the results with metabolite changes in five long-lived mouse models and observed some similar patterns. Overall, this study describes adjustments of the mammalian metabolome according to lifespan, phylogeny, and organ and lineage specialization.

Peroxiredoxin II preserves cognitive function against age-linked hippocampal oxidative damage

Reactive oxygen species (ROS), routinely produced in biological reactions, contribute to both normal aging and age-related decline in cognitive function. However, little is known regarding the involvement of specific antioxidants in the underlying mechanism(s). Here, we examined if peroxiredoxin II (Prx II) scavenges intracellular ROS that cause age-dependent mitochondrial decay in hippocampal CA1 pyramidal neurons and subsequent impairment of learning and memory. Age-dependent mitochondrial ROS generation and long-term potentiation (LTP) decline were more prominent in hippocampal neurons in Prx II(-/-) than in wild-type mice. Additionally, Prx II(-/-) mice failed to activate synaptic plasticity-related cellular signaling pathways involving CREB, CaMKII, and ERK, or to maintain functional integrity of their mitochondria. Dietary vitamin E alleviated Prx II deficiency-related deficits, including mitochondrial decay and CREB signaling, resulting in restoration of the abrupt cognitive decline in aged Prx II(-/-) mice. These results suggest that Prx II help maintain hippocampal synaptic plasticity against age-related oxidative damage.

Microglial peroxiredoxin V acts as an inducible anti‐inflammatory antioxidant through cooperation with redox signaling cascades

J. Neurochem. (2010) 114, 39–50.

Therapeutic Implications for Overcoming Radiation Resistance in Cancer Therapy

Ionizing radiation (IR), such as X-rays and gamma (γ)-rays, mediates various forms of cancer cell death such as apoptosis, necrosis, autophagy, mitotic catastrophe, and senescence. Among them, apoptosis and mitotic catastrophe are the main mechanisms of IR action. DNA damage and genomic instability contribute to IR-induced cancer cell death. Although IR therapy may be curative in a number of cancer types, the resistance of cancer cells to radiation remains a major therapeutic problem. In this review, we describe the morphological and molecular aspects of various IR-induced types of cell death. We also discuss cytogenetic variations representative of IR-induced DNA damage and genomic instability. Most importantly, we focus on several pathways and their associated marker proteins responsible for cancer resistance and its therapeutic implications in terms of cancer cell death of various types and characteristics. Finally, we propose radiation-sensitization strategies, such as the modification of fractionation, inflammation, and hypoxia and the combined treatment, that can counteract the resistance of tumors to IR.

Prx I Suppresses K-ras-Driven Lung Tumorigenesis by Opposing Redox-Sensitive ERK/Cyclin D1 Pathway

AIMSnCoupled responses of mutated K-ras and oxidative stress are often an important etiological factor in non-small-cell lung cancer (NSCLC). However, relatively few studies have examined the control mechanism of oxidative stress in oncogenic K-ras-driven NSCLC progression. Here, we studied whether the redox signaling pathway governed by peroxiredoxin I (Prx I) is involved in K-ras(G12D)-mediated lung adenocarcinogenesis.nnnRESULTSnUsing human-lung adenocarcinoma tissues and lung-specific K-ras(G12D)-transgenic mice, we found that Prx I was significantly up-regulated in the tumor regions via activation of nuclear erythroid 2-related factor 2 (Nrf2) transcription. Interestingly, the increased reactive oxygen species (ROS) by null mutation of Prx I greatly promoted K-ras(G12D)-driven lung tumorigenesis in number and size, which appeared to require the activation of the ROS-dependent extracellular signal-regulated kinase (ERK)/cyclin D1 pathway.nnnINNOVATIONnTaken together, these results suggest that Prx I functions as an Nrf2-dependently inducible tumor suppressant in K-ras-driven lung adenocarcinogenesis by opposing ROS/ERK/cyclin D1 pathway activation.nnnCONCLUSIONnThese findings provide a better understanding of oxidative stress-mediated lung tumorigenesis.

Dominant Role of Peroxiredoxin/JNK Axis in Stemness Regulation during Neurogenesis from Embryonic Stem Cells

Redox balance has been suggested as an important determinant of “stemness” in embryonic stem cells (ESCs). In this study, we demonstrate that peroxiredoxin (Prx) plays a pivotal role in maintenance of ESC stemness during neurogenesis through suppression of reactive oxygen species (ROS)‐sensitive signaling. During neurogenesis, Prx I and Oct4 are expressed in a mutually dependent manner and their expression is abruptly downregulated by an excess of ROS. Thus, in Prx I−/− or Prx II−/− ESCs, rapid loss of stemness can occur due to spontaneous ROS overload, leading to their active commitment into neurons; however, stemness is restored by the addition of an antioxidant or an inhibitor of c‐Jun N‐terminal kinase (JNK). In addition, Prx I and Prx II appear to have a tight association with the mechanism underlying the protection of ESC stemness in developing teratomas. These results suggest that Prx functions as a protector of ESC stemness by opposing ROS/JNK cascades during neurogenesis. Therefore, our findings have important implications for understanding of maintenance of ESC stemness through involvement of antioxidant enzymes and may lead to development of an alternative stem cell‐based therapeutic strategy for production of high‐quality neurons in large quantity. Stem Cells 2014;32:998–1011

Adjuvant effect of bacterial outer membrane vesicles with penta-acylated lipopolysaccharide on antigen-specific T cell priming

Outer membrane vesicles (OMV) are nano-sized spherical blebs shed by Gram-negative bacteria and have been utilized in vaccine development. In the present study, we evaluated T cell adjuvant activity of OMV with strictly penta-acylated LPS produced by ΔmsbB/ΔpagP mutant of non-pathogenic Escherichia coli W3110 (mOMV) compared to OMV with hexa-acylated LPS produced by wild-type E. coli W3110 (wOMV). Penta-acylation of LPS renders mOMV less endotoxic than wOMV in in vitro and in vivo toxicity assays. In mice, mOMV has adjuvant activity on T cell priming not only in KLH protein immunization but also in SIINFEKL peptide immunization. The T-cell adjuvant activity of mOMV was comparable to that of wOMV and LPS and was abrogated in TLR4 K/O mice. In innate immunity, mOMV stimulated BMDCs to up-regulate co-stimulatory and antigen-presenting molecules and to produce pro-inflammatory cytokines in a TLR4-dependent manner. Of note, mOMV induced cytokine production at a significantly less extent compared with wOMV. Taken together, we propose that mOMV with penta-acylated LPS is a safe vaccine adjuvant for T cell priming and can be used in vaccine development against viral diseases and cancer.