Articles by Dohyun Lee in JoVE
Synthesis of Multi-walled Carbon Nanotubes Modified with Silver Nanoparticles and Evaluation of Their Antibacterial Activities and Cytotoxic Properties Youngmin Seo*1, Chanhwi Park*2, Jaewoo Son2, Kyungwoo Lee2, Jangsun Hwang2, Yeonho Jo2, Dohyun Lee2, Muhammad Saad Khan2, Sachin Ganpat Chavan2, Yonghyun Choi2, Dasom Kim2, Assaf A Gilad3, Jonghoon Choi2 1Center for Biomaterials, Biomedical Research Institute, Korea Institute of Science and Technology, 2School of Integrative Engineering, Chung-Ang University, 3Division of Synthetic Biology and Regenerative Medicine, Institute for Quantitative Health Science and Engineering, Michigan State University In this study, antimicrobial nanomaterials were synthesized by acidic oxidation of multiwalled carbon nanotubes and subsequent reductive deposition of silver nanoparticles. Antimicrobial activity and cytotoxicity tests were performed with the as-prepared nanomaterials.
Other articles by Dohyun Lee on PubMed
Mixtures of Recombinant Growth Factors Inhibit the Production of Pro-inflammatory Mediators and Cytokines in LPS-stimulated RAW 264.7 Cells by Inactivating the ERK and NF-κB Pathways International Journal of Molecular Medicine. | Pubmed ID: 24888317 Growth factors are important for regulating a variety of cellular processes and typically act as signaling molecules between cells. In the present study, we examined the mechanisms underlying the inhibitory effects of mixtures of recombinant growth factors (MRGFs) on nitric oxide (NO) and pro-inflammatory cytokine production in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells. We also examined whether these effects are mediated through the mitogen‑activated protein kinase (MAPK) and nuclear factor-κB (NF-κB) signal transduction pathways. NO production was assessed by measuring nitrite acucmulation using the Greiss reaction. Cytokine concentrations were measured using respective ELISA kits for each cytokine. Our results revealed that the MRGFs significantly attenuated the LPS-induced production of pro-inflammatory cytokines and NO in a dose-dependent manner. To elucidate the mechanisms underlying the inhibitory effects of MRGFs, we examined the effects of the LPS-induced phosphorylation of MAPKs and the activation of the NF-κB signaling pathway on the stabilization of NF-κB nuclear translocation and inhibitory factor-κB (IκB) degradation. Western blot analysis was performed to determine the total and phosphorylated levels of ERK, as well as the nuclear translocation of NF-κB, and IκB phosphorylation and degradation. Our results demonstrated that treatment with MRGFs resulted in a reduction in the phosphorylation of the ERK and NF-κB signaling pathways, whereas the phosphorylation of JNK and p38 was not affected. Taken together, our results suggest that MRGFs inhibit the production of pro-inflammatory cytokines and NO by downregulating inducible NO synthase gene expression and blocking the phosphorylation of the ERK and NF-κB signaling pathways. These findings may provide direct evidence of the potential application of MRGFs in the prevention and treatment of inflammatory diseases.
A Ferroxidase, Cfo1, Regulates Diverse Environmental Stress Responses of Cryptococcus Neoformans Through the HOG Pathway Mycobiology. | Pubmed ID: 25071384 The iron uptake and utilization pathways play a critical role in allowing human pathogens, including Cryptococcus neoformans, the causative agent of fatal meningoencephalitis, to survive within the mammalian body by competing with the host for iron. Here we show that the iron regulon is also required for diverse environmental stress responses and that in C. neoformans, it is regulated by the high-osmolarity glycerol response (HOG) pathway. Between CFO1 and CFO2, two ferroxidase genes in the iron regulon, CFO1 but not CFO2 was induced during oxidative and osmotic stress. Interestingly, we found that the HOG pathway repressed basal expression of both CFO1 and CFO2. Furthermore, when the HOG pathway was blocked, CFO2 also responded to oxidative and osmotic stress and the response of CFO1 was increased. We also established that CFO1 plays a major role in responding and adapting to diverse environmental stresses, including oxidative and genotoxic damage, osmotic fluctuations, heavy metal stress, and stress induced by cell membrane destabilizers. Therefore, our findings indicate that in C. neoformans, the iron uptake and utilization pathways are not only required for iron acquisition and survival, but also play a significant role in the environmental stress response through crosstalk with the HOG pathway.
Superoxide Dismutase 1 Inhibits Alpha-melanocyte Stimulating Hormone and Ultraviolet B-induced Melanogenesis in Murine Skin Annals of Dermatology. | Pubmed ID: 25473218 Over the last decade, the incidence of ultraviolet B (UVB)-related skin problems has increased. Oxidative stress caused by UVB induces the secretion of melanocyte growth and activating factors from keratinocytes, which results in the formation of cutaneous hyperpigmentation. Therefore, increasing the antioxidant abilities of skin cells is thought to be a beneficial strategy for the development of sunscreen agents. Superoxide dismutase 1 (SOD1) is an antioxidant enzyme that is known to exhibit antioxidant properties.